ACTUATION SYSTEM FOR A BENT AXIS MOTOR

TECHNICAL FIELD

The present disclosure relates generally to electric motors used to control the displacement of variable displacement bent axis motor.

BACKGROUND AND SUMMARY

A hydraulic axial piston unit of the bent axis design (BAU) includes a rotary group (pistons, cylinder block and valve plate), whose pistons are arranged at an angle to a drive shaft of a hydraulic axial piston motor. In variable displacement units, the effective unit displacement can be varied and controlled during operation of the unit by adjusting an inclination angle of the cylinder block, thereby controlling a torque and/or speed of the drive shaft. The cylinder block inclination angle is typically adjusted by changing a linear position of a servo piston of the bent axis motor, by controlling a pressure in two chambers on either end of the servo piston. The pressure may be controlled by a dedicated regulator, which may be mechanical, hydraulic, or electro-hydraulic.

An electro-hydraulic control response may be dependent on maintaining an operating pressure of a hydraulic fluid used to control the servo piston within a desired range. Reliable control may rely on an operating pressure of at least 20 bar at a regulator inlet of the hydraulic axial piston motor (e.g., at one of the unit work-ports). If this pressure is not guaranteed, ensuring the reliable control may include applying an auxiliary pressure of 20 bar at the regulator inlet port.

In one embodiment, at least a portion of the abovementioned issues may be addressed by a variable displacement bent axis piston motor comprising a bent axis unit (BAU) rotary group including a cylinder block coupled to a drive shaft of the bent axis piston motor, and an electric actuator coupled to a servo piston of the bent axis piston motor, wherein a displacement of the BAU rotary group is controlled by an inclination angle between the drive shaft and a valve plate of the BAU rotary group coupled to the cylinder block, the inclination angle controlled by the servo piston, the servo piston controlled by the electric actuator. By actuating the servo piston via the electric actuator rather than via an electro-hydraulic regulator, a complexity of the variable displacement bent axis piston motor may be reduced, and a plurality of control strategies for the motor may be enabled based on a single configuration of the motor. The various control strategies may allow the servo piston, and the displacement of the BAU rotary group, to be controlled more precisely in response to a torque reference commanded by an operator, different feedback control signals, and/or changes in operating conditions.

For example, a first variable displacement bent axis piston motor may include a first electro-hydraulic regulator configured to control a position of the servo piston based on a pressure control strategy; a second variable displacement bent axis piston motor may include a second electro-hydraulic regulator configured to control the position of the servo piston based on a displacement control strategy; a third variable displacement bent axis piston motor may include a third electro-hydraulic regulator configured to control the position of the servo piston based on a velocity control strategy; and a fourth variable displacement bent axis piston motor may include a fourth electro-hydraulic regulator configured to control the position of the servo piston based on a torque control strategy. Each of the first, second, third, and fourth regulators may be constrained to control the position of the servo piston based on its corresponding configuration, and may not be configured to switch between the pressure, displacement, velocity, and torque control strategies. As a result, each of the first, second, third, and fourth variable displacement bent axis piston motors may be optimized to meet different performance standards based on a corresponding type of regulator. In contrast, a variable displacement bent axis piston motor with the disclosed electric servo-piston actuator may be configured to switch between the pressure, displacement, velocity, and torque control strategies to meet the different performance standards, based on a driving scenario.

For example, a first vehicle with a variable displacement bent axis piston motor actuated by the disclosed electric actuator may be operating on a flat road (e.g., a road with a grade of 0 degrees), where a velocity of the vehicle is maintained by a velocity control strategy (e.g., with a goal of maintaining a constant speed of the vehicle). A pressure of the hydraulic fluid may be 50 bar during operation on the flat road. The vehicle may then be operated up a hill. As the vehicle climbs uphill, a pressure of the hydraulic fluid may increase to 100 bar, 200 bar, or higher. When the pressure increases above a threshold pressure (e.g., 300 bar) an electronic control unit (ECU) of the vehicle may switch from the velocity control strategy to a pressure control strategy, to ensure that the pressure is maintained within a desired pressure range. In some embodiments, an operator of the first vehicle may manually switch the control strategies (e.g., via a button), for example in response to a message displayed by the ECU. In contrast, a second vehicle with a variable displacement bent axis piston motor including the third electro-hydraulic regulator configured to control the position of the servo piston based on a velocity control strategy may achieve a first performance on the flat road, but may achieve a second, lower performance on the hill. Similarly, a third vehicle with a variable displacement bent axis piston motor including the first electro-hydraulic regulator configured to control the position of the servo piston based on a pressure control strategy may achieve a first performance on the hill, but may achieve a second, lower performance on the flat road. Thus, an advantage of the electric actuator disclosed herein is that an overall performance of a vehicle or device including the electric actuator, over various operational scenarios, may be increased as a result of the plurality of different control strategies being enabled by the single configuration. Further, a variety of different variable displacement bent axis piston motors including different types of electro-hydraulic regulators optimized for different types of control strategies may not have to be maintained, reducing a cost for manufacturers.

Additionally, because the electric actuator does not rely on the operating pressure of a hydraulic fluid in a chamber of the servo piston, a leakage of the fluid and/or degradation of hydraulic components may be reduced, thus increasing an efficiency of the unit. Moreover, a pressure ripple at the work port may not impact the regulator, thereby improving an accuracy, consistency, and/or reaction of the servo piston, resulting in a more precise delivery of torque at the drive shaft.

It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings, in which:

FIG. 1 is a schematic representation of a bent axis piston motor system, in accordance with one or more embodiments of the present disclosure;

FIG. 2 is an electronic control diagram for operating a bent axis piston motor, in accordance with one or more embodiments of the present disclosure;

FIG. 3A is a schematic representation of a cross section of a bent axis piston motor including an electric actuator in a first position, in accordance with one or more embodiments of the present disclosure;

FIG. 3B is a schematic representation of a cross section of a bent axis piston motor including an electric actuator in a second position, in accordance with one or more embodiments of the present disclosure;

FIG. 4A is a schematic representation of a BAU rotary group positioned at a first angle with respect to a drive shaft, in accordance with one or more embodiments of the present disclosure;

FIG. 4B is a schematic representation of a BAU rotary group positioned at a second angle with respect to a drive shaft, in accordance with one or more embodiments of the present disclosure;

FIG. 4C is a schematic representation of a BAU rotary group positioned at a third angle with respect to a drive shaft, in accordance with one or more embodiments of the present disclosure; and

FIG. 5 is a flowchart illustrating an exemplary method controlling an inclination angle of a BAU rotary group, in accordance with one or more embodiments of the present disclosure.

DETAILED DESCRIPTION

One example of a hydraulic axial piston motor is a bent axis piston motor, including an electric motor and a bent axis unit (BAU). The BAU includes a rotary group of cylinders (also referred to herein as a BAU rotary group) housed within a cylinder block that is rotated by the electric motor. The BAU allows the cylinder block to be aligned at an angle of inclination with an output shaft of the BAU. As the inclination angle between the cylinder block and the output shaft is increased, a displacement of the BAU rotary group and the bent axis piston motor may be increased, which may result in more torque being delivered at the output shaft. As the inclination angle between the cylinder block and the output shaft is decreased, the displacement may be decreased, which may result in less torque being delivered at the output shaft.

The bent axis piston motor may be a variable displacement bent axis piston motor, where a servo piston is used to dynamically adjust the inclination angle to vary an amount of the displacement during operation. By dynamically adjusting the inclination angle, an amount of torque generated on the output shaft may be varied in accordance with an operator demand for torque. For example, when the inclination angle is zero, the cylinder block is aligned in parallel to the output shaft, and a first torque is delivered to the output shaft. The operator may demand additional torque, whereby a controller of the bent axis piston motor may increase the inclination angle, thereby increasing a displacement of the bent axis piston motor. The increased displacement of the bent axis piston motor may generate a second torque to deliver at the output shaft, where the second torque is greater than the first torque. The controller may control the adjustment of the inclination angle via a servo piston coupled to a valve plate of the BAU rotary group. Variable displacement bent axis piston motors including a servo piston may use hydraulic or electro-hydraulic systems to adjust the position of the servo piston within servo piston chambers on either side of the servo piston. In some embodiments, a solenoid controls a set point force over a hydraulic spool valve. Electro-hydraulic control of the servo piston allows for a stepless and programmable adjustment of motor displacement proportional to a current strength supplied to a proportional solenoid valve. The proportional solenoid valve applies a force on a hydraulic spool proportional to a strength of a generated current, and the spool valve modulates a pressure in the piston chambers. The servo piston position varies until a force balance is restored by a feedback spring.

An electro-hydraulic control response may be dependent on an operating pressure within the piston chambers. The bent axis piston motor may include a dedicated regulator that monitors and modulates the pressure in the chambers at both ends of the servo piston. In various embodiments, the regulator may be coaxially aligned with a guide rod extending along a central axis of the feedback spring, where the regulator, the feedback spring, and the guide rod may be arranged on one side of the bent axis piston motor (e.g., a side opposite from the cylinder block). As such, hydraulic components responsible for providing the electro-hydraulic control response including the regulator, the feedback spring, and guide rod, displacement feedback sensors, etc. may increase a complexity of the bent axis piston motor.

Additionally, a reliable servo piston control response may rely on a threshold operating pressure (e.g., of at least 20 bar) at a working port of the piston chambers. If the operating pressure decreases below the threshold, for example, due to leakage of hydraulic fluid, an auxiliary pressure up to 20 bar may have to be applied at the working port of the chambers. As a result, the hydraulic or electro-hydraulic systems may include additional components for monitoring and maintaining the operating pressure and providing the auxiliary pressure. The additional components may further increase a size, complexity, and cost of the bent axis piston motor. The increased complexity may result in an increased amount of maintenance performed due to wear and tear on the additional components, further increasing the cost of the bent axis piston motor. Additionally, fluctuations and/or modulations of the pressure may result in imprecise movement of the servo piston, decreasing an efficiency of the bent axis piston motor.

To address this issue, the inventors herein propose a bent axis piston motor that relies on an electric actuator to control the position of the servo piston, rather than a hydraulic or electro-hydraulic system. The position of the servo piston may be more efficiently and/or reliably controlled by the electric actuator than by the hydraulic or electro-hydraulic system. Further, with the proposed bent axis piston motor, a single configuration may enable various control strategies for operating the hydraulic motor, where each of the various control strategies is based on a displacement of the servo piston by the electric actuator. The control strategies may be easily modified by a controller, without entailing changes to the configuration. For example, the inclination angle of the bent axis piston motor may be adjusted in accordance with a velocity control strategy, to maintain a vehicle at a constant velocity; the inclination angle may be adjusted in accordance with a pressure control strategy, to maintain a pressure of hydraulic fluid used by the bent axis piston motor at a desired pressure or within a desired pressure range; the inclination angle may be adjusted in accordance with a torque control strategy, to maintain a torque exerted on a drive shaft of the bent axis piston motor at a desired torque or within a desired torque range; and so on. An advantage of the systems proposed herein is that, unlike variable displacement bent axis piston motors that rely on electro-hydraulic actuators, the control strategies used to control the inclination angle may be changed during operation of the bent axis piston motor to increase a performance of the bent axis piston motor.

A bent axis piston motor system of a vehicle is schematically shown in FIG. 1, including a variable displacement bent axis piston motor. The bent axis piston motor may be controlled in accordance with an electronic control diagram of FIG. 2. FIG. 3A is a schematic representation of a cross section of the bent axis piston motor including an electric actuator in a first configuration, and FIG. 3B shows the electric actuator in a second, alternative configuration. An inclination angle of a BAU rotary group of the bent axis piston motor may be adjusted to vary a displacement of the BAU rotary group, where various inclination angles are depicted in FIGS. 4A, 4B, and 4C. The inclination angle may be adjusted by following one or more steps of a method shown in FIG. 5, which may be performed by a controller of the bent axis piston motor.

Referring now to FIG. 1, a schematic depiction of a bent axis motor system 100 of a vehicle 102 is shown, including a hydraulic bent axis piston motor 104 coupled to a controller 112, and to one or more wheels 110 of the vehicle via a drive shaft 120. It should be appreciated that while FIG. 1 refers to an embodiment within a vehicle, in other embodiments, bent axis motor system 100 may not be included in a vehicle, and may be included in a different machine that generates torque for a purpose other than propulsion.

Bent axis piston motor 104 includes a BAU rotary group 105. A cylinder block of BAU rotary group 105 is rotated by pressurized hydraulic fluid pumped into BAU rotary group 105 by a pump 150. As BAU rotary group 105 rotates, an amount of torque is generated on drive shaft 120. To increase or decrease the amount of torque, an inclination angle of BAU rotary group 105 with respect to drive shaft 120 may be adjusted. By adjusting the inclination angle, a displacement of BAU rotary group 105 may be increased, causing the amount of torque to increase, or the displacement of BAU rotary group 105 may be decreased, causing the amount of torque to decrease. Varying the amount of torque by adjusting the inclination angle is described in greater detail below in reference to FIGS. 3A-5.

Bent axis piston motor 104 may be powered by an energy storage device 106. Specifically, energy stored in energy storage device 106 may be used to power an actuator 124 of bent axis piston motor 104, where actuator 124 adjusts the inclination angle to vary the amount of torque delivered at drive shaft 120. Energy storage device 106 may be an energy storage device configured to deliver electrical power to various components of an electrical system of the vehicle 102 including supplying current to bent axis piston motor 104. Energy storage device 106 may be electrically coupled to bent axis piston motor 104, pump 150, and/or controller 112. Controller 112 may regulate the power supply provided by energy storage device 106 to bent axis piston motor 104 in order to increase or decrease a speed of the vehicle 102 via actuator 124.

Controller 112 may include a processor 140 and a memory 142. Memory 142 may hold instructions stored therein that when executed by the processor cause the controller 112 to perform various methods, control strategies, diagnostic techniques, etc. For example, the various methods may include adjusting the inclination angle of the cylinder block with respect to drive shaft 120, to vary the amount of torque applied to drive shaft 120 (e.g., in response to an operator input). Processor 140 may include a microprocessor unit and/or other types of circuits. Memory 142 may include known data storage mediums such as random access memory, read only memory, keep alive memory, combinations thereof, etc. Memory 142 may include non-transitory memory.

Controller 112 may receive vehicle data and various signals from sensors positioned in different locations in bent axis piston motor 104 and/or vehicle 102. The sensors may include an oil temperature sensor 170, an engine velocity sensor 172, one or more wheel velocity sensors 174, and/or other sensors of bent axis piston motor 104 (e.g., torque sensors, pressure sensors, valve plate angle sensor, etc.). Controller 112 may send control signals to one or more actuators of bent axis piston motor 104, in response to operator input and/or based on the received signals from the sensors. For example, controller 112 may adjust a speed and/or torque generated on drive shaft 120 in response to operator input and/or based on the received signals from the sensors.

Bent axis motor system 100 may include one or more input devices 114. For example, input devices 114 may include a pedal of the vehicle (e.g., an accelerator pedal), a control stick (e.g., a forward-neutral-reverse (FNR) lever), one or more buttons, or similar types of control, or combinations thereof. In one example, a FNR lever is used to operate the vehicle in a forward direction or a reverse direction, and an accelerator pedal is used to increase or decrease a speed of the vehicle. The input devices 114, responsive to driver input, may generate a torque reference to which bent axis motor system 100 may be controlled, and a desired drive direction (a forward or reverse drive direction). For instance, when a speed adjustment requested is received by the controller, an output speed of the bent axis piston motor 104 may be correspondingly increased.

Bent axis motor system 100 may automatically switch between drive modes when demanded. For example, the operator may request a forward or reverse drive mode speed change, and controller 112 may command bent axis piston motor 104 to increase speed and automatically transition between one or more drive ranges associated with the different drive modes, as needed.

Referring now to FIG. 2, a electronic control diagram 200 shows a control system 202 for operating a hydraulic bent axis piston motor 204, which may be a non-limiting example of bent axis piston motor 104 of FIG. 1. Control system 202 includes a drive shaft 206, where torque is delivered at drive shaft 206 by bent axis piston motor 204.

As described in greater detail below, operating bent axis piston motor 204 includes adjusting an inclination angle of a cylinder block of bent axis piston motor 204 to vary an amount of the torque delivered at drive shaft 206. The cylinder block houses a plurality of cylinders within a BAU rotary group, which is rotated by an electric motor 226 (e.g., actuator 124 of FIG. 1). As the inclination angle increases or decreases, a displacement of the BAU rotary group increases or decreases correspondingly, increasing or decreasing the amount of torque, respectively. In various embodiments, the inclination angle is determined by a position of a servo piston 210, where the servo piston 210 may be controlled by an electronic control unit (ECU) 212 of hydraulic bent axis piston motor 204 (e.g., controller 112 of FIG. 1). Specifically, the servo piston 210 may be controlled by ECU 212 via an actuator powered by electric motor 226. A processor of ECU 212 (e.g., the processor 140 of the controller 112) may execute instructions stored on a memory of the ECU (e.g., the memory 142 of the controller 112 of FIG. 1) to control the servo piston 210 in accordance with electronic control diagram 200.

Electronic control diagram 200 includes a pump 240 (e.g., pump 150 of FIG. 1), which may pump a hydraulic fluid into bent axis piston motor 204 via a first port 230 and a first conduit 234, and/or a second port 232 and a second conduit 236. The hydraulic fluid may enter bent axis piston motor 204 via a third port 235 (e.g., from first conduit 234) and/or a fourth port 237 (e.g., from second conduit 236). The hydraulic fluid may circulate through the plurality of chambers of the BAU rotary group due to a hydrostatic pressure acting on pistons of the BAU rotary group, exiting via first port 230 or second port 232. A drain port 208 is further provided. Electronic control diagram also includes a sump 222.

During operation of bent axis piston motor 204, ECU 212 may adjust the position of a servo piston of bent axis piston motor 204, to adjust an inclination angle of the BAU rotary group to increase or decrease the displacement of bent axis piston motor 204. ECU 212 may receive a feedback signal from a pressure sensor 214, which may indicate a pressure of the hydraulic fluid at third port 235 and fourth port 237. Based on the feedback signal, ECU 212 may adjust a position of servo piston 210 to control the displacement of the BAU rotary group in accordance with a pressure control strategy. ECU 212 may also receive a second feedback signal from a speed sensor 245, such as a wheel speed sensor of a vehicle, which may indicate a rotational velocity of the drive shaft 206. Based on the second feedback signal, ECU 212 may adjust a position of servo piston 210 to control the displacement of the BAU rotary group in accordance with a velocity control strategy. Similarly, ECU 212 may receive a third feedback signal from a torque sensor 246, which may indicate a torque exerted on drive shaft 206. Based on the third feedback signal, ECU 212 may adjust the position of servo piston 210 to control the displacement of the BAU rotary group in accordance with a torque control strategy. It should be appreciated that the sensors and strategies described herein are for illustrative purposes, and other sensors and control strategies may be used to control the displacement of the BAU rotary group without departing from the scope of this disclosure.

Electronic control diagram 200 advantageously does not include components of an electro-hydraulic system typically used for controlling the servo piston, such as a regulator, a proportional hydraulic valve and an on/off hydraulic valve, a solenoid, displacement feedback spring, guide rod, sensors, ports and conduits, and the like, which may increase a complexity and cost of control system 202.

Referring now to FIG. 3A, a detailed schematic drawing of a bent axis piston motor 300 is shown, which may be a non-limiting example bent axis piston motor 104 described above in reference to FIG. 1. Bent axis piston motor 300 includes a BAU rotary group 302, housed within a housing 301 of bent axis piston motor 300. BAU rotary group 302 includes a cylinder block 303, which houses a plurality of pistons 306 that slide within a corresponding plurality of respective chambers 317 of cylinder block 303. The plurality of pistons 306 may rotate around a guide piston 340. Guide piston 340 may not slide within a respective chamber, which may be directly connected to an external environment of BAU rotary group 302. The external environment may be separated from housing 301 by a sealing ring. The guide piston 340 may include a holding spring 313, which helps maintain cylinder block 303 in a desired position. A flange 307 may be rotated by pistons 306 via hydraulic pressure as BAU rotary group 302 is rotated by a hydraulic fluid pressure force acting on the pistons 306, where the hydraulic fluid pressure is generated by a pump (e.g., pump 150 of FIG. 1).

BAU rotary group 302 functions as a variator that provides a variable output torque on a drive shaft 304 based on an inclination angle of cylinder block 303 with respect to drive shaft 304. The equal number of respective chambers 317 may ride on a variable angle valve plate 308, such that a range of movement of the pistons 306 is set by an adjustable the inclination angle between valve plate 308 of BAU rotary group 302 and drive shaft 304. Pistons 306 may be coupled to flange 307 via a universal or ball joint 305, which may allow flange 307 to be rotated by pistons 306 as the inclination angle is adjusted.

Flange 307 may be mechanically coupled to drive shaft 304 via a plurality of roller bearings 309 housed within a respective plurality of bearing housings 311, such that as flange 307 is rotated by rotating pistons 306, a rotation of flange 307 is transferred to drive shaft 304. Bent axis piston motor 200 may include a timing gear 315, which may provide a speed feedback signal used by one or more control strategies for controlling the inclination of BAU rotary group 302. For example, the speed feedback signal may be used to control a shifting of a vehicle and/or a displacement of BAU rotary group 302 based on the vehicle speed, or may be used to control a speed of the payload lifting and dropping of a winch of a vehicle. In more complex systems, the speed feedback signal may be used to manage an efficiency of a transmission of a vehicle. Housing 301 may include a shaft seal 342, which may seal bent axis piston motor 104 around a surface of drive shaft 304.

Chambers 317 are in fluid communication with a hydraulic system (not depicted in FIG. 3A), where a hydraulic fluid fills chambers 317 and intervening conduits. Chambers 317 may be coupled by hydraulic conduits through which the hydraulic fluid circulates between the hydraulic system and chambers 317. For example, during operation of bent axis piston motor 200, the hydraulic system may flow the hydraulic fluid to chambers 317 via a first hydraulic conduit, and receive the hydraulic fluid back from chambers 317 via a second hydraulic conduit.

The variable angle valve plate 308 may be coupled to a servo piston 316 of bent axis piston motor 300 within a servo piston housing 322 (e.g., a portcover). Servo piston 316 may be actuated by an actuator 324 to adjust an inclination angle between valve plate 308 and drive shaft 304. Actuator 324 may be electric actuator, including an electric motor 370. Electric motor 370 may be powered by an energy storage device (e.g., energy storage device 106 of FIG. 1), such as a battery. The energy storage device may be a dedicated energy storage device that is used to power actuator 324 and electric motor 370 and not used to power other devices or components, for example, of a vehicle including the bent axes piston motor, or the energy storage device may be used to power the other devices or components in addition to actuator 324 and electric motor 370.

In one example, the variable angle valve plate 308 is coupled to the servo piston 316 via a cam joint 318, where the inclination angle is adjusted as servo piston 316 slides within a servo piston chamber 320 of servo piston housing 322. The inclination angle is depicted in greater detail in FIGS. 4A, 4B, and 4C. Servo piston 316 may slide in a first direction indicated by an upward arrow 382, or a second direction indicated by a downward arrow 384 (e.g., in a Z dimension as indicated in reference coordinates 390). In various embodiments, valve plate 308 may be slid along a curved, slidable surface 314 of servo piston housing 322 in response to a movement of servo piston 316. For example, valve plate 308 may be slid in a first rotational direction indicated by arrow 385 (e.g., counterclockwise) by actuating servo piston 316 within servo piston chamber 320 in the first direction indicated by upward arrow 382, and valve plate 308 may be slid in a second rotational direction indicated by arrow 386 (e.g., clockwise) by actuating servo piston 316 within servo piston chamber 320 in the second direction indicated by downward arrow 384.

In response to the movement of servo piston 316, valve plate 308 may be slid over a range of positions corresponding to different inclination angles. For example, servo piston 316 may be actuated to a first end 325 of servo piston chamber 320. When servo piston 360 is actuated to the first end 325 of servo piston chamber 320, valve plate 308 may be slid into a position that minimizes a displacement of chambers 317 of BAU rotary group 302 where the inclination angle is zero, and pistons 306 are aligned with drive shaft 304. Bent axis piston motor 300 may include a minimum displacement limiter 321, where a counterclockwise motion of valve plate 308 may be stopped by minimum displacement limiter 321 as servo piston 316 reaches first end 325 of servo piston chamber 320. Alternatively, servo piston 316 may be actuated to a second end 327 of servo piston chamber 320. When servo piston 360 is actuated to the second end 325 of servo piston chamber 320, valve plate 308 may be slid into a position that maximizes the displacement of chambers 317 of BAU rotary group 302, where the inclination angle reaches a predefined maximum inclination angle for BAU rotary group 302. For example, in an embodiment, the predefined maximum inclination angle for BAU rotary group 302 may be 28 degrees. Bent axis piston motor 300 may include a maximum displacement limiter 323, where a clockwise motion of valve plate 308 may be stopped by minimum displacement limiter 323 as servo piston 316 reaches second end 327 of servo piston chamber 320. An inclination angle between zero and the predefined maximum inclination angle may therefore be achieved by actuating servo piston 316 to a position between first end 325 of servo piston chamber 320 and second end 327 of servo piston chamber 320.

Bent axis piston motor 300 may include various sensors which may be used by a controller of bent axis piston motor 300 (e.g., controller 112 of FIG. 1 and/or ECU 212 of FIG. 2) to adjust the position of servo piston 316 via actuator 324. For example, servo piston housing 322 may include a piston position sensor 326, which may indicate the position of servo piston 316 within servo piston chamber 320. Bent axis piston motor 300 may also include one or more pressure sensors 344 (e.g., pressure sensor 214 of FIG. 2), which may measure an operating pressure of the hydraulic fluid circulating through BAU rotary group 302. Bent axis piston motor 300 may also include a valve plate angle sensor 328, which may estimate the inclination angle, a wheel speed sensor 345 (e.g., speed sensor 245), a drive shaft torque sensor 346 (e.g., torque sensor 246), and/or other sensors. It should be appreciated that the sensors included herein are for illustrative purposes, and in other embodiments, bent axis piston motor 300 may include a greater or fewer number of sensors or different sensors without departing from the scope of this disclosure.

As the inclination angle varies, a greater or lesser volume of hydraulic fluid is received or taken from the chambers of the pistons 306. If a greater volume of hydraulic fluid is received from the chambers of the pistons 306, an output speed of drive shaft 304 is increased, while if a lesser volume of hydraulic fluid received from the chambers of the pistons 316, the output speed of drive shaft 304 is decreased. Thus, the output speed of bent axis piston motor 200 varies with and is controlled by the angle of valve plate 308. In this way, the controller can control the output speed of bent axis piston motor 300 by adjusting the position of servo piston 316 within servo piston chamber 320 via actuator 324.

The position of servo piston 316 may be controlled using actuator 324 in accordance with various open-loop or close-loop control strategies. Thus, a single displacement control system may advantageously support a plurality of servo piston control strategies which may be employed in different circumstances or in response to different inputs. For example, a first control strategy could be based on controlling a maximum operating pressure on the hydraulic fluid, which may be measured using the one or more pressure sensors 327. In response to the operating pressure increasing above a threshold operating pressure, actuator 324 may adjust the position of servo piston 316 within chamber 320 to decrease the inclination angle and the displacement of bent axis piston motor to decrease the operating pressure. A second control strategy could be based on controlling a torque delivered at drive shaft 304, which may be measured using the torque sensor 346. In response to the torque increasing above a threshold torque, actuator 324 may adjust the position of servo piston 316 within chamber 320 to decrease the inclination angle and the displacement of bent axis piston motor to deliver the torque without increasing the pressure. A third control strategy could be based on controlling a rotational velocity of drive shaft 304, which may be measured using the speed sensor 345. In response to the velocity increasing above a threshold velocity, actuator 324 may adjust the position of servo piston 316 within chamber 320 to decrease the inclination angle and the displacement of bent axis piston motor to deliver more velocity without increasing the pressure. Other sensors may also be used to facilitate additional control strategies.

Typically, bent axis piston motors including a servo piston use hydraulic or electro-hydraulic systems to adjust the position of the servo piston within the servo piston chamber. One advantage of bent axis piston motor 300 over other bent axis piston motors with an alternative electro-hydraulic system is that the position of servo piston 316 within servo piston chamber 320 is adjusted via (electric) actuator 324, whereby no hydraulic or electro-hydraulic systems may be relied on to control the position of servo piston 316.

For example, an alternative electro-hydraulic system may include at least components such as a proportional hydraulic valve; an on/off hydraulic valve; a displacement feedback spring mounted on a guide rod, which may provide a force counteracting forces generated by hydraulic fluid on servo piston 316 to control a position of servo piston 316; one or more ports and corresponding conduits through which hydraulic fluid is flowed into and out of servo piston chamber 320; a hydraulic spool valve that controls a pressure of the hydraulic fluid in the servo piston chamber 320; and a dedicated regulator (e.g., solenoid) to control a set point force over the hydraulic spool valve. The hydraulic valves, guide rod and displacement feedback spring, regulator/solenoid, and/or other components included in the alternative electro-hydraulic system may be advantageously eliminated from bent axis piston motor 300, reducing a cost and complexity of bent axis piston motor 300.

Another advantage of including actuator 324 in bent axis piston motor 300 is that servo piston 316 may be more accurately and/or reliably positioned within servo piston chamber 320 by actuator 324 than by the alternative electro-hydraulic system. Because controlling the servo piston relies on an operating pressure of at least 20 bar in servo piston chamber 320 in the electro-hydraulic system, a reduction in the operating pressure (e.g., due to wear on components and/or leakage) may result in the servo piston not being precisely and/or consistently controlled to a desired position. To compensate for the reduction in operating pressure, auxiliary pressure may be delivered, which may entail additional components and control routines, which may increase a complexity of bent axis piston motor 300, resulting in additional maintenance and repairs. Further, the additional components and control routines may increase a cost of bent axis piston motor 300 and an overall cost of the bent axis piston motor. In contrast, the proposed solution in not dependent on the effective operative pressure, and control features typical of electro-hydraulic systems are performed with via pressure and position sensors.

In the embodiment depicted in FIG. 3A, actuator 324 is a linear actuator aligned in a first inline configuration with servo piston 316 and servo piston chamber 320. In the first inline configuration, actuator 324 may be aligned in parallel with a central axis of servo piston 316. In some embodiments, actuator 324 may be aligned coaxially with the central axis, while in other embodiments, actuator 324 may be aligned in an offset position from the central axis. In various embodiments, the servo piston 316 may be coupled to the linear actuator via a mechanical joint. In other embodiments, actuator 324 may not be aligned in parallel with servo piston 316 and servo piston chamber 320, and may be located in a different position than indicated in FIG. 3A.

FIG. 3B shows a cross-sectional view 350 of bent axis piston motor 300, including an actuator 352, which may be a non-limiting example of actuator 324 of FIG. 3A. Actuator 352 is shown in a second, parallel configuration with servo piston 316 and servo piston chamber 320. In the second configuration, actuator 352 is a rotary electric actuator, where the position of servo piston 316 within servo piston chamber 320 is controlled via a dedicated transmission gear 354 between a rotary motor of actuator 324 and servo piston 316. An advantage of the rotary actuator over the linear actuator is that the rotary actuator may be more compact, saving space and reducing an overall size of the bent axis piston motor. Alternatively, an advantage of the linear actuator over the rotary actuator is that the rotary actuator may be more complex, due to the addition of components such as dedicated transmission gear 354.

Referring now to FIG. 4A, a first BAU alignment diagram 400 illustrates a first configuration of a BAU rotary group 402 of a BAU of a bent axis piston motor, such as bent axis piston motor 300 of FIG. 3A. BAU rotary group 402 is coupled to a valve plate 408 (e.g., valve plate 308). Valve plate 408 is mechanically coupled to a servo piston 416 (e.g., servo piston 416) of the bent axis piston motor via a cam joint 418. Servo piston 416 may be positioned within a servo piston chamber 420. Servo piston 416 may be configured to slide within servo piston chamber 420 in either a first direction 482, or a second, opposite direction 484, between a first end 425 of servo piston chamber 420 and a second end 427 of servo piston chamber 420. As described above in relation to FIG. 3A, a movement and a position of servo piston 416 may be controlled by an actuator 424, which may be a non-limiting example of actuator 324 of FIG. 3A.

BAU rotary group 402 includes a plurality of pistons 406 housed within a cylinder block 403. The plurality of pistons 406 may be arranged in parallel around a central axis 490 of BAU rotary group 402. In the first configuration of BAU rotary group 402 shown in FIG. 4A, servo piston 416 is in a first position at second end 427 of servo piston chamber 420, such that servo piston 416 is at a lower bound of a range of motion of servo piston 416. At the lower bound of the range of motion, valve plate 408 may be in contact with a maximum displacement limiter 423 (e.g., maximum displacement limiter 323 of FIG. 3A), which may prevent valve plate 408 from continuing to slide in a direction 486. In the first position, central axis 490 of BAU rotary group 402 is offset from a central axis 492 of a drive shaft of the bent axis piston motor (e.g., drive shaft 304 of FIG. 3A) by a first inclination angle 480. Because servo piston 416 is at the lower bound of its range of motion, inclination angle 480 may be an angle at which a displacement of the bent axis piston motor is maximized. When the displacement of the bent axis piston motor is maximized, an amount of torque delivered at the driveshaft may be maximized.

Servo piston 416 may be actuated upward (e.g., in the Z dimension indicated by reference coordinate axes 390) in direction 482 by actuator 424. As servo piston 416 is actuated upward by actuator 424, inclination angle 480 may decrease as central axis 490 of BAU rotary group 402 becomes increasingly aligned with central axis 492 of the drive shaft. As inclination angle 480 decreases, the displacement of the bent axis piston motor decreases, and the amount of torque delivered at the drive shaft decreases.

FIG. 4B shows a second BAU alignment diagram 430 illustrating a second configuration of BAU rotary group 402. In the second configuration, servo piston 416 is in a second position at a midpoint of servo piston chamber 420, where a first amount of space at first end 425 of servo piston chamber 420 is equal to a second amount of space at second end 427 of servo piston chamber 420. Valve plate 408 is positioned at a midpoint between maximum displacement limiter 423 and a minimum displacement limiter 421 (e.g., maximum displacement limiter 323 of FIG. 3A), at a center of a range of motion of valve plate 408. In the second configuration, central axis 490 of BAU rotary group 402 is offset from central axis 492 of the drive shaft by a second inclination angle 488. Second inclination angle 488 is less than first inclination angle 480, whereby the amount of torque delivered at the drive shaft in the second configuration of BAU rotary group 402 may be less than the amount of torque delivered at the driveshaft in the first configuration of BAU rotary group 402.

FIG. 4C shows a third BAU alignment diagram 460 illustrating a third configuration of BAU rotary group 402. In the third configuration of BAU rotary group 402, servo piston 416 is in a third position at first end 425 of servo piston chamber 420. In the third position, servo piston 416 is at an upper bound of the range of motion of servo piston 416. At the upper bound of the range of motion, valve plate 408 may be in contact with the minimum displacement limiter 421, which may prevent valve plate 408 from continuing to slide in a direction 485.

In the third position, central axis 490 of BAU rotary group 402 is aligned with central axis 492 of the drive shaft of the bent axis piston motor, where an inclination angle between central axis 490 of BAU rotary group 402 and central axis 492 of the drive shaft is zero. When servo piston 416 is at the upper bound of its range of motion and the inclination angle is zero, the displacement of the bent axis piston motor may be minimized. When the displacement of the bent axis piston motor is minimized, the amount of torque delivered at the driveshaft may be minimized.

Thus, the amount of torque delivered at the drive shaft may be varied by adjusting the position of servo piston 416 within servo piston chamber 420. As actuator 424 adjusts the position of servo piston 416 in the first direction 482, the amount of torque delivered at the drive shaft decreases. As actuator 424 adjusts the position of servo piston 416 in the second direction 484, the amount of torque delivered at the drive shaft increases.

For example, the bent axis piston motor may generate traction in a vehicle, such as vehicle 102 of FIG. 1. An operator of the vehicle may command an increase in the amount of torque delivered at one or more wheels of the vehicle (e.g., wheels 110), for example, via an accelerator pedal of the vehicle. In response to the operator commanding the increase in the amount of torque, a controller of the bent axis piston motor (e.g., controller 112 of FIG. 1) may command actuator 424 to actuate servo piston 416 in the second direction 484. As actuator 424 moves in direction 482 within servo piston chamber 420, valve plate 408 slides towards maximum displacement limiter 423 in direction 486, and the inclination angle (e.g., inclination angle 480 or 488) between central axis 490 of BAU rotary group 402 and central axis 492 of the drive shaft increases. As the inclination angle increases, the displacement of BAU rotary group 402 increases, generating an increase in torque at the drive shaft.

Alternatively, the operator may command a decrease in the amount of torque delivered at the one or more wheels via the accelerator pedal. In response to the operator commanding the decrease in the amount of torque, the controller may command actuator 424 to actuate servo piston 416 in the first direction 482. As actuator 424 moves in direction 482 within servo piston chamber 420, valve plate 408 slides towards minimum displacement limiter 421 in direction 485, and the inclination angle decreases. As the inclination angle decreases, the displacement of BAU rotary group 402 decreases, generating a decrease in torque at the drive shaft.

Referring now to FIG. 5, a flowchart of an exemplary method 500 is shown for controlling an operation of a vehicle by controlling an inclination angle of a BAU rotary group of a variable displacement bent axis piston motor of the vehicle. The inclination angle may be controlled by controlling a position of a servo piston within a servo piston chamber of the bent axis piston motor via an electric actuator, where the servo piston, servo piston chamber, and other components of the bent axis piston motor described herein may be non-limiting examples of servo piston 316, servo piston chamber 320, and other components of bent axis piston motor 300 of FIG. 3A. In an embodiment, operations of method 500 may be stored in non-transitory memory and executed by a processor of an ECU of the vehicle, such as memory 142 and processor 140 of controller 112 of FIG. 1, respectively, during operation of the vehicle.

Method 500 is described with respect to a specific driving scenario, during which a control strategy for controlling an inclination angle of a BAU rotary group is advantageously switched from a first control strategy to a second control strategy. It should be appreciated that the specific driving scenario is one of many possible driving scenarios involving one or more control strategies, and in other scenarios or embodiments, different control strategies may be used.

At 502, method 500 includes estimating and/or measuring vehicle operating conditions. Vehicle operating conditions may be estimated based on one or more outputs of various sensors of the vehicle (e.g., such as an oil temperature sensor, engine velocity or wheel velocity sensor, torque sensor, valve plate angle sensor, pressure sensor, etc., as described above in reference to vehicle 102 of FIG. 1 and bent axis piston motor 300 of FIG. 3A. Vehicle operating conditions may include engine velocity and load, vehicle velocity, oil temperature, exhaust gas flow rate, coolant temperature, coolant flow rate, electric motor velocity, battery charge, engine torque output, vehicle wheel torque, etc.

At 504, method 500 includes receiving a request for torque or speed (e.g., a torque/speed reference) from a driver of the vehicle. The request for torque/speed may be received via an input device of the vehicle (e.g., an input device 114 of FIG. 1), such as an accelerator pedal of the vehicle. For example, the driver may be operating the vehicle in a torque control mode or a speed control mode, and may increase a pressure on the accelerator pedal to request increased torque/speed, Alternatively, the driver may release the pressure on the accelerator pedal to request less torque/speed.

At 506, method 500 includes setting an inclination angle of the BAU rotary group based on the torque/speed request. Setting the inclination angle of the BAU rotary group includes actuating the servo piston either in a first linear direction (e.g., direction 484 of FIG. 4A) within the servo piston chamber of the BAU, or in a second linear direction (e.g., direction 482 of FIG. 4A) to achieve a desired position of the servo piston. The desired position of the servo piston may be determined from a reference table, based on the speed/torque request. As the servo piston is actuated in the first or second linear direction, a valve plate (e.g., valve plate 408 of FIG. 4A) coupled to the servo piston may slide along a curved surface (e.g., curved slidable surface 314 of FIG. 3A) of a housing of the servo piston in a first rotational direction (e.g., direction 486 of FIG. 4A) or a second rotational direction (e.g., direction 485 of FIG. 4C), thereby increasing or decreasing the inclination angle between the cylinders of the BAU rotary group and a drive shaft of the vehicle, respectively. If the inclination angle increases, a displacement of the BAU rotary group increases, generating increased torque at the drive shaft (e.g., at one or more wheels of the vehicle). If the inclination angle decreases, the displacement of the BAU rotary group decreases, reducing the torque at the drive shaft.

At 508, method 500 includes selecting and applying a control strategy for controlling the inclination angle based on maintaining the speed/torque of the vehicle. If the vehicle is operating in a torque control mode, the control strategy may be a torque control strategy, where applying the torque control strategy may include measuring a torque delivered at the drive shaft via a torque sensor, and adjusting the inclination angle based on a difference between the torque request and the measured torque. If the vehicle is operating in a speed control mode, the control strategy may be a speed control strategy, where applying the speed control strategy may include measuring a speed of the drive shaft via a speed sensor (e.g., a wheel speed sensor), and adjusting the inclination angle based on a difference between the speed request and the measured speed. In one embodiment, a default control strategy is the speed control strategy. The control strategy may be implemented in a logic of a software component installed in an ECU of the vehicle, such as ECU 212 of FIG. 2.

In various embodiments, a plurality of control strategies for controlling the position of the servo piston may be stored in a memory of the ECU (e.g., memory 142). For example, the plurality of control strategies may include one or more speed control strategies that control the inclination angle to meet a desired speed reference; one or more torque control strategies that control the inclination angle to meet a desired torque reference; one or more pressure control strategies that control the inclination angle to meet a desired pressure reference; or a different type of control strategy. Each control strategy may include independent logic, and may rely on feedback from different sensors. For example, the speed control strategies may rely on feedback signals from a speed sensor (e.g., speed sensor 245 and/or 345); the torque control strategies may rely on feedback signals from a torque sensor (e.g., torque sensor 246 and/or 346); the pressure control strategies may rely on feedback signals from a pressure sensor (e.g., pressure sensor 214); and so on. In some embodiments, different control strategies of a same type of control strategy may be selected based on a type of vehicle, use, or application, or for a different reason. For example, a first vehicle may use a first pressure control strategy, and a second vehicle may use a second pressure control strategy, where the first and second pressure control strategies are based on a size of a bent axis piston motor of the vehicle. Alternatively, a vehicle may use a first speed control strategy in a first driving scenario, and a second speed control strategy in a second driving scenario. In some embodiments, the first speed control strategy may rely on a feedback signal from a first speed sensor, and the second speed control strategy may rely on a feedback signal from a second speed sensor.

At 510, method 500 includes determining whether an operating pressure of hydraulic fluid used to power the variable displacement bent axis piston motor has increased above a threshold pressure. If at 510 it is determined that operating pressure has increased above the threshold pressure, method 500 proceeds to 512.

At 512, method 500 includes switching from the speed/torque control strategy to a pressure control strategy. For example, the threshold pressure may be a pressure at which a performance of the vehicle decreases, or a pressure at which a component of the BAU rotary group may become degraded. By switching to the pressure control strategy, the ECU may control the inclination angle of the BAU rotary group.

At 513, method 500 includes adjusting the inclination angle of the BAU rotary group in accordance with the pressure control strategy. Adjusting the inclination angle of the BAU rotary group in accordance with the pressure control strategy may include maintaining the pressure within a desired pressure range (e.g., a pressure range below the threshold pressure), based on a difference between a measured pressure and the threshold pressure. In various embodiments, the pressure may be measured via a pressure sensor of the BAU rotary group, such as pressure sensor 214 of FIG. 2.

At 514, method 500 includes determining whether a minimum inclination angle (e.g., an angle of 0) has been reached. At the minimum inclination angle, the BAU rotary group may be aligned with a drive shaft of the vehicle. The minimum inclination angle may be reached when a valve plate of the BAU rotary group comes in contact with a minimum displacement limiter of the BAU rotary group, as depicted in FIG. 4C (e.g., minimum displacement limiter 421). When the valve plate of the BAU rotary group comes in contact with the minimum displacement limiter, the inclination angle of the BAU rotary group may not be adjusted further to reduce the pressure.

If at 514 it is determined that the minimum inclination angle has been reached, method 500 proceeds to 516. At 516, method 500 includes displaying a message to the driver to reduce the speed/torque of the vehicle, to reduce the pressure (e.g., that the pressure control strategy may no longer control the pressure, whereby the pressure may continue to increase above the threshold pressure if the speed/torque is not reduced). Method 500 proceeds back to 504, where method 500 includes receiving a new torque/speed request from the driver.

Returning to 510, it is determined that operating pressure has not increased above the threshold pressure, method 500 proceeds to 518. At 518, method 500 includes maintaining the speed/torque control strategy, and continuing to control the inclination angle of the BAU rotary group based on a speed or torque reference. Method 500 ends.

Thus, systems and methods are disclosed herein to adjust an inclination angle of a BAU rotary group of a bent axis piston motor via a servo piston coupled to a valve plate of the BAU rotary group, where a position and/or a movement of the servo piston within a corresponding servo piston chamber is controlled by an electric actuator. The electric actuator may be a linear actuator positioned along a central axis of the servo piston, or the electric actuator may be a rotary actuator aligned in parallel with the servo piston. By using the electric actuator to adjust the position of the servo piston, an adjustment of the position of the valve plate and the BAU rotary group may be performed via a more simplified and efficient procedure than an alternative electro-hydraulic control mechanism. The alternative electro-hydraulic control mechanism may rely on a pressure of hydraulic fluid to control the servo piston, where a reduction in the pressure of the hydraulic fluid caused by leakage and/or a degradation of one or more components of the alternative electro-hydraulic control mechanism may reduce an accuracy and/or a precision of a positioning of the servo piston, reducing an efficiency of the bent axis piston motor. Further, the alternative electro-hydraulic control mechanism may rely on additional components to measure and monitor the pressure of the hydraulic fluid, which may increase a complexity and cost of the bent axis piston motor. By using the electric actuator rather than the alternative electro-hydraulic control mechanism, and by operating the electric actuator in accordance with the methods disclosed herein, the accuracy and/or precision of the positioning of the servo piston may be increased, with a less costly and less complex bent axis piston motor. A further advantage of the electric actuator is that the servo piston may be controlled in a more stable manner. For example, with the alternative electro-hydraulic control mechanism, fluctuations in pressure in a hydraulic line (e.g., pressure ripples) may cause an oscillation of the BAU rotary group, which may result in an undesired oscillation of the system (e.g. wheels, winch, etc . . . ) and/or undesired resonances.

Additionally, by actuating the servo piston via the electric actuator rather than via an electro-hydraulic regulator, a plurality of control strategies for the motor may be enabled. A desired control strategy may be switched during operation to the servo piston and the displacement of the BAU rotary group to be controlled in response to a desired feedback control signal, while alternative electro-hydraulic control mechanisms may be configured to adjust a position of the servo piston based on a single control strategy and a single feedback control signal. Thus, an advantage of the electric actuator disclosed herein is that an overall performance of a vehicle or device including the electric actuator, over various operational scenarios, may be increased as a result of being able to switch between different control strategies being enabled by a single actuator configuration. Further, a first number of different types of vehicles and/or devices manufactured with the electric actuator may be less than a second number of different types of vehicles and/or devices manufactured with different actuator configurations, reducing manufacturing and maintenance costs. The technical effect of operating a bent axis piston motor using an electric actuator rather than an electro-hydraulic actuator is that an efficiency of adjusting an inclination angle of a BAU rotary group of a BAU of the bent axis piston motor may be increased, while a complexity of the BAU may be reduced, and a number of strategies for controlling a displacement of the bent axis piston motor may be increased.

The disclosure also provides support for a variable displacement bent axis piston motor comprising a bent axis unit (BAU) rotary group including a cylinder block coupled to a drive shaft of the bent axis piston motor, and an electric actuator coupled to a servo piston of the bent axis piston motor, wherein a displacement of the BAU rotary group is controlled by an inclination angle between the drive shaft and a valve plate of the BAU rotary group coupled to the cylinder block, the inclination angle controlled by the servo piston, the servo piston controlled by the electric actuator. In a first example of the system, the electric actuator is positioned along a central axis of the servo piston in an inline configuration. In a second example of the system, optionally including the first example, the electric actuator is positioned to one side of the servo piston, and the servo piston is controlled by the electric actuator via a dedicated transmission gear. In a third example of the system, optionally including one or both of the first and second examples, the servo piston is controlled by the electric actuator based a feedback control system of the variable displacement bent axis piston motor. In a fourth example of the system, optionally including one or more or each of the first through third examples, the feedback control system includes: one or more pressure sensors that measure an operating pressure of a hydraulic fluid circulating through the BAU rotary group, one or more speed sensors that measure a rotational speed of the drive shaft, one or more torque sensors that measure an amount of torque delivered at the drive shaft, a valve plate angle sensor that measures the inclination angle, and a piston position sensor that indicates a position of the servo piston within a servo piston chamber of the BAU rotary group. In a fifth example of the system, optionally including one or more or each of the first through fourth examples, controlling the electric actuator based on the feedback control system of the BAU rotary group further comprises actuating the servo piston to a desired position based on a selected control strategy for adjusting the inclination angle of the BAU rotary group, the selected control strategy stored in a memory of a controller of the variable displacement bent axis piston motor, the selected control strategy selected based on one of: a speed reference and an output of a speed sensor of the one or more speed sensors, a torque reference and an output of a torque sensor of the one or more torque sensors, and a pressure reference and an output of a pressure sensor of the one or more pressure sensors. In a sixth example of the system, optionally including one or more or each of the first through fifth examples, controlling the electric actuator based on the feedback control system further comprises selecting a first control strategy in response to a first driving scenario, and switching to a second control strategy in response to a second driving scenario. In a seventh example of the system, optionally including one or more or each of the first through sixth examples, first control strategy is a speed control strategy, the second control strategy is a pressure control strategy, and the second control strategy is selected in response to the output of the pressure sensor increasing above a threshold pressure. In a eighth example of the system, optionally including one or more or each of the first through seventh examples, the valve plate may be adjusted to a range of inclination angles, each inclination angle of the range of inclination angles corresponding to a location of the servo piston within the servo piston chamber. In a ninth example of the system, optionally including one or more or each of the first through eighth examples, the range of inclination angles extends from an inclination angle of zero, where a plurality of pistons of the cylinder block are aligned with the drive shaft and the displacement of the BAU rotary group is minimized, to a predefined maximum inclination angle where the displacement of the BAU rotary group is maximized. In a tenth example of the system, optionally including one or more or each of the first through ninth examples, the system further comprises: a minimum displacement limiter that stops the valve plate at the inclination angle of zero when the servo piston reaches a first end of the servo piston chamber, and a maximum displacement limiter that stops the valve plate at the predefined maximum inclination angle when the servo piston reaches a second, opposite end of the servo piston chamber. In a eleventh example of the system, optionally including one or more or each of the first through tenth examples, a hydraulic or electro-hydraulic actuator is not used to control the servo piston.

The disclosure also provides support for a method for controlling an inclination angle of a bent axis unit (BAU) rotary group of a variable displacement bent axis piston motor, the method comprising: receiving one a torque request from an operator of the variable displacement bent axis piston motor, setting the inclination angle of the BAU rotary group based on the torque request, selecting and applying a torque control strategy for controlling the inclination angle based on the torque request, in response to a pressure of a hydraulic fluid circulating through the BAU rotary group increasing above a threshold pressure: selecting a pressure control strategy for controlling the inclination angle based on a pressure reference, switching from the torque control strategy to the pressure control strategy, and adjusting the inclination angle in accordance with the pressure control strategy, and in response to the pressure being maintained below the threshold pressure, continuing to control the inclination angle using the torque control strategy. In a first example of the method, applying the torque control strategy for controlling the inclination angle further comprises receiving a torque measurement from a torque sensor of the variable displacement bent axis piston motor, and adjusting the inclination angle based on a difference between the torque request and the torque measurement, and adjusting the inclination angle in accordance with the pressure control strategy further comprises receiving a pressure measurement from a pressure sensor of the variable displacement bent axis piston motor, and adjusting the inclination angle based on a difference between the pressure reference and the pressure measurement. In a second example of the method, optionally including the first example, the method further comprises, in response to the inclination angle achieving a minimum inclination angle and the pressure being maintained above the threshold pressure, notifying the operator. In a third example of the method, optionally including one or both of the first and second examples, the torque control strategy and the pressure control strategy are selected from a plurality of control strategies stored in a memory of a controller of the variable displacement bent axis piston motor.

The disclosure also provides support for a control system for a variable displacement bent axis piston motor, the control system comprising: a servo piston coupled to a valve plate of a bent axis unit (BAU) rotary group of the variable displacement bent axis piston motor, the valve plate configured to slide between a first position where a displacement of the BAU rotary group is maximized and a second position where the displacement is minimized, based on a position of the servo piston within a corresponding piston chamber, a piston position sensor that indicates a position of the servo piston within the corresponding piston chamber, a pressure sensor that measures an operating pressure of a hydraulic fluid circulating through the BAU rotary group, a speed sensor that measures a rotational speed of a drive shaft coupled to the BAU rotary group, a torque sensor that measures an amount of torque delivered at the drive shaft, an electric actuator configured to adjust the position of the servo piston within the corresponding piston chamber, the electric actuator not including hydraulic components, and a controller including a processor and instructions stored in a non-transitory memory of the controller that when executed cause the controller to: adjust the position of the servo piston based on one of a torque reference, a speed reference, and a pressure reference, and a feedback signal from one of the torque sensor, the speed sensor, and the pressure sensor. In a first example of the system, further instructions are stored in the non-transitory memory that when executed, cause the controller to: in a first condition, in response to a first speed reference provided by an operator of the bent axis piston motor, actuate the servo piston based on the first speed reference and a first feedback signal from the speed sensor, and in a second condition, in response to a second feedback signal from the pressure sensor increasing above a threshold pressure, actuate the servo piston based on the second feedback signal and a desired pressure range. In a second example of the system, optionally including the first example, the operator is a driver of a vehicle including the of the bent axis piston motor, the first condition includes the vehicle being operated at a speed on a road with a grade of 0 degrees, and the second condition includes the vehicle being operated at the speed on a road with a grade greater than 0 degrees. In a third example of the system, optionally including one or both of the first and second examples, further instructions are stored in the non-transitory memory that when executed, cause the controller to: in the second condition, in response to the servo piston being actuated to a minimum inclination angle and the feedback signal from the pressure sensor being maintained above the threshold pressure, notify the operator to reduce a speed of the bent axis piston motor.

In another representation, a method for controlling an inclination angle of a cylinder block of a bent axis unit (BAU) of a hydraulic bent axis piston motor with respect to a drive shaft of the hydraulic bent axis piston motor comprises receiving a torque request from an input device coupled to the bent axis piston motor; calculating a desired position of a servo piston coupled to a valve plate of the cylinder block based on the torque request; determining a current position of the servo piston via a feedback control system of the BAU; and actuating the servo piston to the desired position via an electric actuator. In response to actuating the servo piston to the desired position via the electric actuator, the inclination angle is adjusted to increase or decrease a displacement of the hydraulic bent axis piston motor.

While various embodiments have been described above, it should be understood that they have been presented by way of example, and not limitation. It will be apparent to persons skilled in the relevant arts that the disclosed subject matter may be embodied in other specific forms without departing from the spirit of the subject matter. The embodiments described above are therefore to be considered in all respects as illustrative, not restrictive.

Note that the example control and estimation routines included herein can be used with various powertrain and/or vehicle system configurations. The control methods and routines disclosed herein may be stored as executable instructions in non-transitory memory and may be carried out by the control system including the controller in combination with the various sensors, actuators, and other transmission and/or vehicle hardware. Further, portions of the methods may be physical actions taken in the real world to change a state of a device. The specific routines described herein may represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various actions, operations, and/or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the example examples described herein, but is provided for ease of illustration and description. One or more of the illustrated actions, operations and/or functions may be repeatedly performed depending on the particular strategy being used. Further, the described actions, operations and/or functions may graphically represent code to be programmed into non-transitory memory of the computer readable storage medium in the vehicle and/or transmission control system, where the described actions are carried out by executing the instructions in a system including the various hardware components in combination with the electronic controller. One or more of the method steps described herein may be omitted if desired.

It will be appreciated that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural of said elements or steps, unless such exclusion is explicitly stated. Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising,” “including,” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property. The terms “including” and “in which” are used as the plain-language equivalents of the respective terms “comprising” and “wherein.” Moreover, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements or a particular positional order on their objects.

FIGS. 2, 3A, 3B, 4A, 4B, and 4C show example configurations with relative positioning of various components. If shown directly contacting each other, or directly coupled, then such elements may be referred to as directly contacting or directly coupled, respectively, at least in one example. Similarly, elements shown contiguous or adjacent to one another may be contiguous or adjacent to each other, respectively, at least in one example. As an example, components laying in face-sharing contact with each other may be referred to as in face-sharing contact. As another example, elements positioned apart from each other with only a space there-between and no other components may be referred to as such, in at least one example. As yet another example, elements shown above/below one another, at opposite sides to one another, or to the left/right of one another may be referred to as such, relative to one another. Further, as shown in the figures, a topmost element or point of element may be referred to as a “top” of the component and a bottommost element or point of the element may be referred to as a “bottom” of the component, in at least one example. As used herein, top/bottom, upper/lower, above/below, may be relative to a vertical axis of the figures and used to describe positioning of elements of the figures relative to one another. As such, elements shown above other elements are positioned vertically above the other elements, in one example. As yet another example, shapes of the elements depicted within the figures may be referred to as having those shapes (e.g., such as being circular, straight, planar, curved, rounded, chamfered, angled, or the like). Further, elements shown intersecting one another may be referred to as intersecting elements or intersecting one another, in at least one example. Further still, an element shown within another element or shown outside of another element may be referred as such, in one example.

This written description uses examples to disclose the invention, including the best mode, and also to enable a person of ordinary skill in the relevant art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those of ordinary skill in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

ACTUATION SYSTEM FOR A BENT AXIS MOTOR

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