Patent Application
20240157999
The present disclosure relates generally to steer-by-wire systems in vehicles, and more specifically, embodiments are directed to applications for ball nut assembly angle sensor(s) within the steer-by-wire system.
Most conventional vehicles use a mechanical system boosted by hydraulic power for the mechanics of steering. Most vehicles also utilize power steering to reduce the amount of force it takes to turn the steering wheel. This was traditionally accomplished through hydraulic power, which is generated by a hydraulic actuator that assists the turning of the steering gear. A hydraulic pump can run off the rotation of the engine or can be driven by an electric motor (referred to as Electro-Hydraulic Power Steering). In addition, there is an electric power steering (hereinafter, referred to as “EPS”) system that may remove the hydraulic components as it uses an electric motor to drive traditional steering linkage (the pitman arm) within the mechanical system.
Conventional EPS systems assist a driver's steering operation by applying torque generated by a motor to a steering mechanism of a vehicle. For example, an EPS system includes a rack-and-pinion mechanism that serves as a steering mechanism. The rack-and-pinion mechanism changes the orientation of wheels by converting the rotation of a pinion caused by a steering operation into a liner motion of a rack shaft (steered shaft) meshed with the pinion. The rack shaft is provided with a ball screw profile that, when driven laterally by the circulating ball nut and contained ball bearings converts the rotational output from a motor via a belt drive system into a linear motion of the rack shaft. That is, the torque generated by the motor is converted into an axial force of the rack shaft in its axial direction, so that the steering operation is assisted. Generally, a front axle steering gear contains the pinion shaft and an angle sensor which are used to determine the absolute steer angle, in addition to the motor position angle sensor (MPS), so that accurate steer angle information is available in the steering gear's electronic power pack (EPP). The EPP is defined as the Assembly of the electronic control unit (ECU) and Motor. The steer angle being an important aspect of a vehicle's safety system as it transmits the steering wheels rate of turn, wheel angle, and other important information to the vehicles computer. If there is a fault in the signal, the computer can raise a diagnostic trouble code (DTC) warning to the driver and also disable the vehicle's stability control.
Conventional systems use sensors mounted to an input shaft and a harness that runs from the pinion shaft sensor directly back to the EPP, which means there is no monitoring of the ball nut assembly. Other example systems may remove the input shaft, which results in a pinion driven system. Such systems, effectively, are equivalent to a dual pinion system (commonly known as EPSdp). These systems are limited in terms of maximum load (e.g., less than 15 kN) due to the load capability of the worm gear arrangement and typically house the MPS and steer angle sensor in the EPP. Pinion driven systems also suffer from lower mechanical efficiency due to inefficiencies of the worm screw contact angle to worm gear's teeth.
While electric power steering removes the hydraulic components, they retain the traditional mechanical steering linkage (e.g., the pinion shaft). Improved steer-by-wire (SbW) technology may remove and/or reduce the requirement for steering linkage.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
Various embodiments disclosed herein relate to steer-by-wire systems in vehicles, and more specifically, embodiments directed to applications for ball nut assembly angle sensor(s) within the steer-by-wire system.
One embodiment of the present disclosure provides an EPS system comprising a housing secured to a vehicle body, wherein the housing is disposed such that a tubular housing extends across a vehicle. The housing comprising a rack bar extending through the tubular housing configured to move in a linear motion. The linear motion changes an angle of one or more wheels relative to the vehicle in which the one or more wheels are coupled. An electric power pack (EPP) supplies power which rotates an output motor shaft. In embodiments, a drive assembly may be coupled to the tubular body and the electric power pack. The drive assembly comprises a drive belt, a drive pulley and a ball nut assembly, which facilitates the conversion of rotary movement from the output motor shaft into lateral movement of the rack bar. In embodiments, a plurality of sensors is provided and configured to sense input signals based on characteristics of the vehicle. The drive belt may be coupled to the output motor shaft and ball nut assembly, wherein the drive belt transmits rotary motion to a cylindrical pulley coupled to the ball nut assembly and the tubular body. The rotary motion actuates the ball nut assembly based on an input of rotary motion of a steering wheel and the sensed input signals which is then converted to a torque or angle applied by the steering gear's motor. In response to ball nut assembly actuation, rack bar linear motion is actuated and therefore the angle of the one or more wheels is adjusted.
One embodiment of the present disclosure provides a steering system including a steering feedback module (SFM) and an electric power steering (EPS) gear. In embodiments, the SFM may include an SFM motor, one or more sensors associated with the SFM (SFM sensor) which may include a torque and/or angle sensor and a first ECU to control the SFM and the one or more SFM input signals. The SFM sensors configured to sense one or more SFM input signals based on an input of rotary motion of a steering wheel. In embodiments, the electric power steering system (EPS) may include an EPS motor, one or more sensors associated with the EPS (EPS sensors), a ball nut assembly, a rack bar and a second ECU to control the one or more EPS. The one or more sensors configured to sense one or more EPS input signals based on vehicle characteristics. In embodiments, the one or more input signals may include a motor position sensed in the EPS motor or a ball nut angle sensed within the ball nut assembly. Thus, in response to the input of rotary motion of the steering wheel and based on SFM input signals and EPS input signals, the rack bar and angles of one or more wheels, coupled to the rack bar of a vehicle, are adjusted to a determined extent based on the SFM input signals and EPS input signals.
Another embodiment of the present disclosure includes a method for executing an EPS system. A plurality of sensors is included and configured to sense one or more input signals based on characteristics of a vehicle, which may be associated with a steer-by-wire system. In embodiments, a plurality of steering characteristics may be determined based on the one or more input signals and based on those steering characteristics, used to sufficiently adjust one or more road wheel angles of the vehicle, which are coupled to a rack bar. The one or more angles of the road wheels being adjusted by the rack bar's linear motion. This motion is generated by the drive mechanism based on the determined plurality of outputs from the SFM.
Another embodiment of the present disclosure includes a steering system comprising a vehicle control unit (VCU) configured to transmit and receive a first set of vehicle characteristics from one or more external sensors and calculate a required steer angle based on the first set of vehicle characteristics and an electric power steering system (EPS). The EPS comprising one or more EPS sensors associated with the EPS, wherein the EPS sensors are configured to sense one or more EPS input signals based on a second set of vehicle characteristics. An EPS motor may be configured to provide power to an output motor shaft for rotary movement and be integrated with at least one of the EPS sensors to sense an EPS motor position, wherein at least one of the EPS input signals includes the EPS motor position. A ball nut assembly may be integrated with at least one of the EPS sensors configured to sense a ball nut angle of the ball nut assembly, wherein at least one of the EPS input signals includes the ball nut angle. A rack bar may be included, wherein the rack bar moves about a linear axis actuated by a drive assembly. The drive assembly may include a drive belt coupled to the output motor shaft and the ball nut assembly such that the drive belt transmits rotary motion, by rotary movement of the output shaft, to a cylindrical pulley coupled to the ball nut assembly and further transmits rotary motion to the ball nut assembly and an ECU to control the EPS and the one or more EPS input signals, wherein the VCU and the ECU are communicatively coupled. The VCU may transmit the required steer angle to the ECU to activate the drive assembly, wherein the rack bar and angles of one or more wheels, coupled to the rack bar of the vehicle, are altered to a determined extent based on the first set of vehicle information and the EPS input signals.
The above summary is not intended to describe each illustrated embodiment or every implementation of the subject matter hereof. The figures and the detailed description that follow more particularly exemplify various embodiments.
Subject matter hereof may be more completely understood in consideration of the following detailed description of various embodiments in connection with the accompanying figures, in which:
While various embodiments are amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the claimed inventions to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the subject matter as defined by the claims.
While steer-by-wire (SbW) systems use electric motors to turn the road wheels and adjust the steering wheel, sensors to determine how much steering force to apply, and devices that provide tactile feedback to the driver, there is a present need for improved SbW technology and improved applications utilizing SbW technology.
Even with electric power steering, one of the biggest challenges is the limitations involving the mechanical component(s). Described herein is to create a new type of “SbW system with sensor devices” within a steer-by-wire system, which does not use a pinion, torsion bar, input shaft or rack preload yoke. Typically, in part, the pinion/input shaft is utilized in combination with an angle sensor to monitor the steer angle for vehicle steering operations. Replacing conventional steering components with SbW technology, described herein, removes the necessity for an input shaft assembly, which facilitates the removal of many other, otherwise necessary, components. For example, the components that may be removed include the input shaft, shaft bearings (upper and lower), the torsion bar, the pinion shaft, the sensor housing (including casting, cover plates fixings and seals), the rack preload yoke (including spring(s) fixings and seals), the requirement of complex forming processes such as rack teeth broaching, etc. The removal of such components offers numerous benefits, which include mass reduction (estimated at 2-3 Kg); piece cost reduction (estimated at 5-10%); build complexity reduction; reduced frictional variation (e.g., friction spikes) and system frictional losses (making the system more efficient in terms of energy usage); reduced operating noise; improved sustainability (e.g., significant reduction in use of steel (shaft, preload yoke and bearings) and aluminium (e.g. housing casting)); and more.
Hereinafter, the so-called “SbW system with sensor devices” according to an embodiment of the invention will be described with reference to the accompanying drawings. A “SbW system with sensor devices” is an electric power steering system in which a steering assist motor is disposed such that the axis of the steering assist motor is parallel to a rack bar. The system uses an angle sensor in the gear housing to monitor the ball nut angle which will provide accurate steer angle information and the required redundancy when used in conjunction with the MPS information. Thus, removing the need for the pinion shaft also which, in turn, removes the need for rack bar preload because there is no interface or required mesh between a pinion shaft and rack bar teeth.
As illustrated in
Housing 102 comprises a drive assembly housing 110. In embodiments, the drive assembly housing 110 may be positioned near the left/right or center of the housing 102 depending on the vehicle's packaging requirements. In embodiments, an EPP 120, comprising an electric motor and electronic control unit (ECU) used as a motor controller may be secured to the upper portion (left or right side depending on vehicle packaging requirements) of the drive assembly housing 110. In embodiments, the EPP 120 may comprise an output motor shaft (OMS) 122 that extends along an axis parallel to the rack bar 104 and may be inserted into the drive assembly 110 through a side wall of the drive assembly housing 110. In embodiments, EPP 120 has a motor position angle sensor (not illustrated) to monitor and transmit MPS information, such as the angular position and velocity of the motor's rotor shaft. In embodiments, while various sensors are described herein in generality, for illustrative purposes, any sensor type may be utilized, such as hall effect sensors, magnetoresistive (MR) sensors, giant magnetoresistive (GMR) sensors, etc. and are not to be construed as limiting thereof.
The configuration of the drive assembly housing 110 will be described in detail below. As illustrated in
In embodiments, EPS systems may incorporate angle sensor(s) (e.g., ball nut angle sensor(s) 134) into the RBNA 130 housing of the housing 102. The BNA angle sensor(s) 134 monitors the ball nut angle and transmits accurate steer angle information. In embodiments, the BNA angle sensor 134 may be a type of sensor such as hall Effect sensor, magneto-resistance sensor or giant magneto-Resistance type sensor, but not limited thereto. In the case of use of a wired sensor, the sensor cable then runs directly back to the ECU (often referred to as the Power Steering Control Module (PSCM)) linking to one or multiple connections, depending on whether the ECU contains one or two ECU lanes based on system redundancy requirements. In embodiments, the connection between sensor and ECU may be wireless and intermediaries may be integrated for relaying sensor information to the ECU. Using this information in conjunction with the MPS information, gathered from the motor position angle sensor(s), the BNA angle sensor 134 provides sufficient redundancies in the event of failure of one or more of the sensors that may be required to determine the absolute steer angle so that accurate steer angle information is available (and provided) for adequate function of the vehicle's steering system.
In response to a steering operation (e.g., user's steering wheel input), ECUs 304 and 324 may process the available vehicle information (e.g., the available MPS information, sensor(s) information, a variety of angle information, torque(s), etc. as describe in greater detail with reference to
Embodiments of the EPS (base gear) steering system 320, as described herein, may include housing 322, an ECU 324 for control of the EPS steering system 320 and processing information between components which includes feedback information to the SFM's ECU 304 of the steer-by-wire system, an EPS motor 330, a rack bar 326 and RBNA 328. During axial movement and stationary positioning of rack bar 326, RBNA 328 may include ball nut angle sensor(s) (BNA sensor) 329 configured to monitor and transmit/make available ball nut angle information based on the ball nut's angular position which is relative to the rack bar's 326 lateral displacement within the vehicle. Said information may be transmitted between the ECU 304 and the ECU 320 for processing and steer operation/adjustment. The EPS motor 330 may include motor position sensor(s) 331 configured to monitor the EPS motor position 307 and may be configured to transmit/make available said information between ECU 304 and ECU 320 for processing and steer operation/adjustment.
In embodiments, the EPS steering system may include an inner tie rod left portion 352A (comprising a tie rod force transducer 353A); an inner tie rod right portion 352B (comprising a tie rod force transducer 353B); an outer tie rod left portion 354A; an outer tie rod right portion 354B; a suspension knuckle left portion 356A; a suspension portion right portion 356B; a road wheel left portion 358A; and a road wheel right portion 358B. Inner tie rod left portion 352A; outer tie rod left portion 354A; suspension knuckle left portion 356A; and road wheel left portion 358A may be coupled to (e.g., to distribute the transfer of energy) and configured to facilitate transferring a user's (e.g., driver's) application of torque and angle of the steering wheel 312 into moving the rack bar 326 in the appropriate, calculated axial displacement (described in greater detail with reference to
With additional reference to
At step S400, the steering wheel angle 311 may be utilized to determine the required axial rack bar movement (e.g., based on the amount of steering wheel rotation input by the user, the rack bar is required to move a certain amount of distance in order to make appropriate road wheel 358A/B angle adjustments). Steering wheel torque 313 may be monitored by the steering wheel torque sensor(s) 309 of the torque/angle sensor(s) 308 and provided to the SFM's ECU 304. Steering wheel angle 311 and steering wheel torque 313 may be provided, by the ECU 304, as input signals from the SFM sensor(s) 308 to relay the signal(s)/information to the EPS 320.
At step S402, the steering wheel angle 311 may be used to determine the amount of axial rack bar movement that is required based on the amount of steering wheel rotation input by the user (e.g., determining the amount of distance the rack bar needs to move in order to make appropriate road wheel 358A/B angle adjustments based on the information monitored on the steering wheel). At step S404, the steering wheel torque 313 may be utilized along with other data provided to the EPS's ECU 324 to determine the required torque from the EPS motor 330.
From the EPS 320, input signals such as the ball nut angle 332 (monitored by ball nut angle sensor(s) 329 integrated with RBNA 328), motor position (monitored by motor position sensor(s) 333 integrated with the EPS motor 330), motor current 334, tie rod force of the left position 336A (monitored by tie rod force transducer 353A integrated with the inner tie rod left position 352A) and tie rod force of the right position 336B (monitored by tie rod force transducer 353B integrated with the inner tie rod right position 352B) may be utilized for road wheel 358A/B angle adjustments based on a user's steering wheel 312 input. At step S406, the ball nut angle 332 and motor position 333 signals/information are used to determine the amount of rack bar 326 movement. Utilizing the ball nut angle 332 (within RBNA) to facilitate rack bar movement enables the replacement and removal of conventional components normally required for monitoring and making such information available, as described herein.
At step S408, the calculated rack bar movement of step 406 is utilized with motor current 334, tie rod force left position 336, tie rod force right position 336B and vehicle speed 337 (monitored by wheel speed sensor(s) 361 integrated with wheel speed sensor assembly 360) to calculate the rack load and therefore the amount of motor torque necessary to appropriately move the rack bar 326.
At step S410, ball nut angle 332 and motor position 333 signals/information may also be utilized to determine steering speed (e.g., the speed at which the road wheels 358A/B adjusts their angle relative to the vehicle), which would otherwise be monitored and provided from conventional pinion angle(s) 341 (monitored by pinion shaft angle sensor(s) 340). Thus, eliminating the otherwise, necessary conventional pinion angle(s) 341 information (monitored by pinion shaft angle sensor(s) 340). At step S412, the determined rack bar movement (calculated at step S402), torque (calculated at step S404), rack bar force (calculated at step S408) and steering speed (calculated at step S410) is utilized to determine the required torque from the EPS motor 330 in order to generate sufficient rack bar movement to fulfill the user's steering wheel operation(s)/input and the system's required output. At step S420, based on the calculated information as described herein, the EPS may output, for application in rack bar 326 and road wheel 358A/B adjustment(s), appropriate EPS motor torque 422, implementation signal(s) to the SFM regarding the amount of rack bar 326 movement 424 and the amount of rack bar force 426. At step S428, the implementation signal(s) from the EPS's ECU 324 are output from the EPS 320 to the SFM 302 (via ECUs 304 and 324) to convert the rack bar force and rack bar movement into the requisite SFM motor torque necessary for user feedback. At step S432, the rack bar 326 is adjusted to fulfill the steering request from the user's steering wheel rotation operation/input (based on output from the EPS 320 at step S420).
At step S430, the SFM motor torque is applied to the steering wheel 312. Thus, at step S432, the steering wheel's 312 angle is adjusted to complete step S434 based on feedback from the EPS 320.
In response to a steering operation (e.g., sensed signals from the ADAS and determining the requirement of a steering maneuver), similarly described with reference to the EPS's ECU 320 and the SFM's ECU 304 of
In embodiments, beyond the SFM/ECU being exchanged for the VCU 402, the remaining components provide the same functionality of those described in reference to
With additional reference to
From the EPS 520, input signals such as the ball nut angle 532 (monitored by ball nut angle sensor(s) 529 integrated with RBNA 528), motor position (monitored by motor position sensor(s) 533 integrated with the EPS motor 530), motor current 534, tie rod force of the left position 536A (monitored by tie rod force transducer 553A integrated with the inner tie rod left position 552A) and tie rod force of the right position 536B (monitored by tie rod force transducer 553B integrated with the inner tie rod right position 552B) may be utilized for road wheel 558A/B angle adjustments. At step S602, the ball nut angle 532 and motor position 533 signals/information are used to determine the amount of rack bar 526 travel. Utilizing the ball nut angle 532 (via ball nut angle senor(s) 529 within RBNA 528) to facilitate rack bar movement enables the replacement and removal of conventional components normally required for monitoring and making such information available, as described herein.
At step S604, the calculated rack bar movement of step S602 is utilized with motor current 534, tie rod force left position 536, tie rod force right position 536B and vehicle speed 537 (monitored by wheel speed sensor(s) 561 integrated with wheel speed sensor assembly 560) to calculate the rack load and therefore the amount of motor torque necessary to appropriately move the rack bar 326.
At step S606, the ball nut angle 532 and motor position 353 signals/information may also be utilized to determine steering speed (e.g., the speed at which the road wheels 358A/B adjusts their angle relative to the vehicle), which would otherwise be monitored and provided from conventional pinion angle(s) (monitored by pinion shaft angle sensor(s) 540). Thus, the otherwise, necessary conventional pinion angle(s) information (monitored by pinion shaft angle sensor(s) 540) may be eliminated.
At step S608, the determined required steer angle (determined at step S600), calculated rack bar movement (determined at step S602), rack bar force (calculated at step S604) and steering speed (calculated at step S606) is utilized to determine the required torque from the EPS motor 530 in order to generate sufficient rack bar movement based on the steer angle request from the VCU 530 of step S600.
At step S610, based on the calculated information as described herein, the EPS may output, for application in rack bar 526 and road wheel 558A/B adjustment(s), appropriate EPS motor torque 522 and a generated steer angle feedback signal 525. At step S612, the VCU 530 may combine the steer angle data (calculated through steps S600-S608) with the VCU's other stability control/ADAS signals to calculate and adjust the feedback signal to the EPS 520. At step S614, the VCU 502 may transmit the updated required steer angle feedback signal (i.e., in part an updated required steer angle), based on the combined information in step S612, to the EPS 520.
Thus, at step S616, the rack bar movement is adjusted to fulfill the steering request from the VCU 502 (based on output from the EPS 520 at step S610).
Various embodiments of systems, devices, and methods have been described herein. These embodiments are given only by way of example and are not intended to limit the scope of the claimed inventions. It should be appreciated, moreover, that the various features of the embodiments that have been described may be combined in various ways to produce numerous additional embodiments. Moreover, while various materials, dimensions, shapes, configurations, and locations, etc. have been described for use with disclosed embodiments, others besides those disclosed may be utilized without exceeding the scope of the claimed inventions.
Persons of ordinary skill in the relevant arts will recognize that the subject matter hereof may comprise fewer features than illustrated in any individual embodiment described above. The embodiments described herein are not meant to be an exhaustive presentation of the ways in which the various features of the subject matter hereof may be combined. Accordingly, the embodiments are not mutually exclusive combinations of features; rather, the various embodiments can comprise a combination of different individual features selected from different individual embodiments, as understood by persons of ordinary skill in the art. Moreover, elements described with respect to one embodiment can be implemented in other embodiments even when not described in such embodiments unless otherwise noted.
Although a dependent claim may refer in the claims to a specific combination with one or more other claims, other embodiments can also include a combination of the dependent claim with the subject matter of each other dependent claim or a combination of one or more features with other dependent or independent claims. Such combinations are proposed herein unless it is stated that a specific combination is not intended.
Any incorporation by reference of documents above is limited such that no subject matter is incorporated that is contrary to the explicit disclosure herein. Any incorporation by reference of documents above is further limited such that no claims included in the documents are incorporated by reference herein. Any incorporation by reference of documents above is yet further limited such that any definitions provided in the documents are not incorporated by reference herein unless expressly included herein.
For purposes of interpreting the claims, it is expressly intended that the provisions of 35 U.S.C. § 112(f) are not to be invoked unless the specific terms “means for” or “step for” are recited in a claim.
