Patent Application
20250059989
A conventional hydraulic or pneumatic fluid power linear actuator includes a cylinder, a piston, and a piston rod. The cylinder restricts the piston to linear movement along a central axis defined by the cylinder. The piston rod allows mechanical connection from the piston to an external load.
The stoke of the piston within the cylinder (i.e., how far the piston and piston rod moves in the cylinder) depends on the magnitude of the external load, the fluid pressure and flow rate and the duration of the applied fluid pressure. For example, with a single acting cylinder, increasing the fluid pressure within the rear chamber extends the piston rod when the pressure times the cylinder bore area exceeds the external load. However, decreasing the fluid pressure within the rear chamber retracts the piston rod when the pressure times the cylinder bore area is less than the external load.
It should be understood that there are deficiencies to conventional fluid power actuators. Along these lines, the above-described conventional fluid power linear actuator typically provides imprecise position control, is susceptible to leaking/drifting over time, and may require external locking devices or redundant actuators to prevent loss of load control during a failure. Accordingly, the conventional fluid power actuator may not be ideal for certain precision material handling applications such as loading munitions onto an aircraft.
Unfortunately, conventional electric linear actuators are very expensive for high-force applications, routinely require lubrication, provide difficulties in manually moving loads during loss of electric power, and are not normally designed with high enough structural safety factors required by safety certification standards (e.g., American Society of Mechanical Engineers (ASME) standards for lifting devices or U.S. Air Force nuclear certification). Conventional electric linear actuators are also more difficult to package as the electric motor, brake, and drive train transmission must be packaged along with the linear actuator.
Similarly, conventional electro-hydraulic linear actuators have disadvantages of both fluid power actuators and electric linear actuators. Specifically, they are subject to the same disadvantages of fluid power linear actuators as described above and are more difficult to package inside compact areas, as an electric motor, a hydraulic fluid pump, reservoir and valve assemblies, etc. are all mounted directly to an electro-hydraulic linear actuator.
In contrast to the above-described conventional linear actuators, improved techniques involve a fluid power actuator that utilizes a screw and nut assembly. The screw and nut assembly enhances fluid power actuator performance such as by providing high precision positioning, simple mechanical locking, and convenient manual back-up operation. In some arrangements, the screw and nut assembly has a self-locking thread geometry (e.g., ACME threads). In some arrangements, the screw and nut assembly has a recirculating ball screw or roller screw geometry for low friction operation. Such techniques overcome various deficiencies of conventional fluid power, electric, and electro-hydraulic linear actuators.
One embodiment is directed to a fluid power actuator that includes:
In some arrangements, the motor controls rotation of the screw relative to a non-rotating nut.
In some arrangements, the motor controls rotation of the nut relative to a non-rotating screw.
In some arrangements, the screw is self-locking.
In some arrangements, the screw is non-self-locking and the motor contains a brake.
In some arrangements, the fluid power actuator further includes a load cell that measures an axial load on the screw or nut, and a controller that adjusts fluid pressure on at least one side of the piston to adjust the axial load.
In some arrangements, the fluid power actuator further includes an external position sensor that augments position actuator control logic using a closed-loop position control.
In some arrangements, motor and/or brake torque application and/or release is timed based on previously measured and recorded load command and response behavior.
In some arrangements, the fluid power actuator further includes a control system that uses an external load cell to measure axial load directly or indirectly, calculates fluid pressure, and controls fluid pressure with an open-loop control system.
In some arrangements, the fluid power actuator further includes a control system that uses an external load cell to measure axial load directly or indirectly, calculates the desired pressure, and controls fluid pressure with a closed-loop control system using at least one pressure transducer.
Another embodiment is directed to a fluid power actuator which includes:
In some arrangements, the brake controls rotation of the screw relative to a non-rotating nut.
In some arrangements, the brake controls rotation of the nut relative to a non-rotating screw.
In some arrangements, the screw is a non-self-locking recirculating ball screw, roller screw, or ACME screw.
In some arrangements, the fluid power actuator further includes a load cell that measures an axial load on the screw or nut, and a controller that adjusts fluid pressure on at least one side of the piston to adjust the axial load.
In some arrangements, the fluid power actuator further includes an external position sensor that augments position actuator control logic using a closed-loop position control.
In some arrangements, motor and/or brake torque application and/or release is timed based on previously measured and recorded load command and response behavior.
In some arrangements, the fluid power actuator further includes a control system that uses an external load cell to measure axial load directly or indirectly, calculates fluid pressure, and controls fluid pressure with an open-loop control system.
In some arrangements, the fluid power actuator further includes a control system that uses an external load cell to measure axial load directly or indirectly, calculates the desired pressure, and controls fluid pressure with a closed-loop control system using at least one pressure transducer.
Other embodiments are directed to apparatus, devices, and related componentry. Some embodiments are directed to various vehicles, equipment, tools, systems, sub-systems, methods, and so on, which involve a fluid power actuator that utilizes a screw and nut assembly.
This Summary is provided merely for purposes of summarizing some example embodiments so as to provide a basic understanding of some aspects of the disclosure. Accordingly, it will be appreciated that the above-described example embodiments are merely examples and should not be construed to narrow the scope or spirit of the disclosure in any way. Other embodiments, aspects, and advantages will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the described embodiments.
The foregoing and other objects, features and advantages will be apparent from the following description of particular embodiments of the present disclosure, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of various embodiments of the present disclosure.
An improved technique involves a fluid power actuator that utilizes a screw and nut assembly. The screw and nut assembly enhances fluid power actuator performance by providing high precision positioning, offering mechanical locking, and lending to convenient manual back-up operation, among other features. In accordance with certain embodiments, the screw and nut assembly has a self-locking thread geometry (e.g., ACME thread with low efficiency) and is paired with a motor to actuate the screw or nut rotation. In accordance with certain embodiments, the screw and nut assembly has a recirculating ball screw or roller screw geometry for low friction operation and paired with a brake to prevent screw or nut rotation. Such techniques overcome a variety of deficiencies in conventional fluid power, electric and electro-hydraulic linear actuators.
The various individual features of the particular arrangements, configurations, and embodiments disclosed herein can be combined in any desired manner that makes technological sense. Additionally, such features are hereby combined in this manner to form all possible combinations, variants and permutations except to the extent that such combinations, variants and/or permutations have been expressly excluded or are impractical. Support for such combinations, variants and permutations is considered to exist in this document.
As best seen in
Also, as best seen in
In some arrangements, the piston 224 further defines other features such as a piston seal 228 that forms a fluid seal with the cylindrical barrel 210. That is, when the fluid power actuator 106 is assembled, the piston 224 and piston seal 228 divide the cylinder 212 into different sealed chambers thus enabling fluid pressure within the chambers to drive the piston rod assembly 142 in and/or out of the fluid power actuator housing 140.
Likewise, in some arrangements, the fluid power actuator housing 140 defines other features such as a piston rod seal 218 which forms a fluid seal between the piston rod 220 and the fluid power actuator housing 140.
In some arrangements, the piston rod 220 further has a piston rod end 226 at the end opposite to the piston 224 that enables coupling to a load. The piston rod end 226 enables the piston rod assembly 142 to easily couple (e.g., hinge or pivot) with the lift arm 104 (also see
As further shown in
In one embodiment, the screw 232 is allowed to rotate relative to the fluid power actuator housing 140 and about the actuator axis 150 under certain conditions. Such rotation enables the piston rod assembly 142 of the fluid power actuator 106 to move relative to the fluid power actuator housing 140 along the actuator axis 150 (e.g., to translate linearly along the actuator axis 150).
In certain arrangements, fluid pressure is used to extend or retract the piston and piston rod. For example, making the fluid pressure at the port 214 times the cylinder 212 bore area greater than the sum of the fluid pressure at the port 216 times the annular area (defined by bore area minus piston rod area) plus the force needed to overcome the load attached to the piston rod end 226 provides a force to extend the piston rod assembly 142 along the axis 150. Similarly, making the fluid pressure at the port 214 times the cylinder 212 bore area less than the sum of fluid pressure at the port 216 times the annular area plus the force needed to overcome the load attached to the piston rod end 226 provides a force to retract the piston 224 and piston rod 220 along the axis 150.
The fluid power actuator 106 includes additional devices such as a motor 260, a set of load sensors 270, and/or a brake 280. The motor 260 may be an electric, hydraulic or pneumatic powered motor. The motor 260 is constructed and arranged to rotate the screw 232 of the screw and nut assembly 144. The set of load sensors 270 is constructed and arranged to provide a set of load signals indicating axial loading on the screw 232 (e.g., a measurement of the current amount of axial load between the fluid power actuator housing 140 and the screw 232). In one embodiment, the fluid pressure on one or both fluid ports 214 and 216 are controlled in a closed-loop manner to make the load cell 270 read a near-zero load, thus enabling a low-torque, low-powered, and/or low-cost motor to turn the screw and extend or retract the actuator.
In another embodiment, the brake 280 is paired with a non-self-locking screw and constructed and arranged to prevent the screw 232 from turning relative to the fluid power actuator housing 140 when the brake is engaged (or applied) and allows the screw 232 to turn relative to the fluid power actuator housing 140 when the brake is disengaged (or released).
In some embodiments, the fluid power actuator assembly 106 is implemented in equipment that includes a base and a lift arm. Such equipment advantageously enjoys high precision positioning, offers mechanical locking, and lends to convenient manual back-up operation, among other advantages.
By way of example only, the equipment may take the form of a loading apparatus such as a munitions loader. However, it should be understood that the equipment may have different shapes, sizes, configurations, arrangements, structures, etc. combinations thereof, other than that shown. Other suitable types of equipment include road vehicles, watercraft, aircraft, industrial machinery, heavy duty robotics, combinations thereof, and so on.
In some embodiments, the base is constructed and arranged to serve as a structural foundation and provide support for the equipment. The base may be configured to reside at a fixed location and/or move among different locations as a vehicle chassis. In some arrangements, the base may be provisioned with a set of vehicle components (e.g., tires, tracks, propellers, combinations thereof, etc.), a set of motors for propulsion/mobility (e.g., combustion engines, electric motors, combinations thereof, etc.), a power source for powering the set of motors, and so on.
In some embodiments, the lift arm is constructed and arranged to manage (or carry) a set of loads while providing linkage with the base. Along these lines, the lift arm may have a first end that couples with the base and a second end that interfaces with the set of loads.
In some embodiments, the fluid power actuator 106 is constructed and arranged to maneuver a lift arm. Recall that the fluid power actuator 106 includes the fluid power actuator housing 140, the piston rod assembly 142, and the screw and nut assembly 144. The fluid power actuator housing 140 may mechanically couple with a base (e.g., at a first hinge or pivot location), and the piston rod assembly 142 may mechanically couple with a lift arm (e.g., at a second hinge or pivot location). The piston rod assembly 142 may be restrained (e.g., internally, externally, etc.) to prevent rotation relative to the fluid power actuator housing 140.
In some embodiments, the screw and nut assembly 144 mechanically couples with both the fluid power actuator housing 140 and the piston rod assembly 142. The screw and nut assembly 144 works in conjunction with a fluid power source and control system to operate the fluid power actuator 106 to selectively enable the piston rod assembly 142 to move along the actuator axis 150 and lock/hold the piston rod assembly 142 in place relative to the fluid power actuator housing 140. The fluid power source and a control system can be directly mounted to the fluid power actuator 106, or be located within a base or located at a remote location relative to the equipment.
As will be explained in further detail shortly, the fluid power actuator 106 may precisely control positing of a lift arm (e.g., during loading, during unloading, etc.), provides stability (e.g., locking in place to eliminate drift and maintain positing), and enables convenient and simple manual backup operation (e.g., to enable operation even without power). Accordingly, the fluid power actuator 106 is well-suited for various tasks in which factors such as accuracy, reliability, and safety are critical.
It should be understood that the lift arm may include multiple joints, hinges, arms, etc., and that the equipment may include other mechanisms such as an additional set of actuators to operate the lift arm at various points. One or more of the additional set of actuators may be provisioned with one or more respective screw and nut assemblies 144 in the same manner as that for the fluid power actuator 106.
Further, it should be appreciated that fluid power actuator 106 may take a variety of different embodiments. Depending on the particular embodiment, one or more of these above-described devices may be present (or may be optional). Various details for particular embodiments of the fluid power actuator 106 will now be provided in further detail.
The actuator axis 150 defined by the fluid power actuator housing 140 is also shown in
It should be appreciated that, in certain arrangements in which hydraulic fluid power is used, the hydraulic fluid within the fluid power actuator 106 lubricates the nut 502 and the screw 504. Moreover, in certain arrangements in which pneumatic fluid power being used, an air compressor lubricator may lubricate the screw and nut assembly. In either case, there is no need for other periodic maintenance action to lubricate the set of screw and nut assembly components 500.
It should be further understood that the nut 502 and the screw 504 use a complementary thread geometry which enables self-locking. In some arrangements, the screw and nut assembly 144 uses a self-locking ACME screw whose mechanical efficiency is 35% or less. However, other self-locking screw arrangements use other thread shapes, angles, pitches, depths, etc.
During operation of the fluid power actuator 106, the control system receives, from the set of load sensors 270, a set of load signals indicating how much axial loading currently exists between the screw 504 and the fluid power actuator housing 140. Such axial loading is the load that is parallel to the centerline of the screw shaft, and affects how easily the screw 504 is able to turn within the nut 502.
To extend the fluid power actuator 106, the control system turns the motor 260 so that the screw 504 rotates in a first direction (e.g., counterclockwise) to move the nut 502 in a direction away from the motor 260 (i.e., left to right in
It should be understood that similar operation occurs to retract the fluid power actuator 106. In particular, the control system turns the motor 260 so that the screw 504 rotates in a second direction (e.g., clockwise) to move the nut 502 in a direction toward the motor 260 (i.e., right to left in
Furthermore, when power is removed and fluid power pressure is released, the set of screw and nut assembly components 500 self-lock, i.e., the friction between the nut 502 and the screw 504 is sufficiently high so that the fluid power actuator 106 remains in its current position and no drifting occurs. Along these lines, due to the self-locking thread geometry, the set of screw and nut assembly components 500 provides, among other things, increased stopping speed, drift-proof mechanical locking during power loss, and repeatable and reliable operation. Accordingly, the fluid power actuator 106 is well suited for a variety of equipment in which precision, stability, and reliability are critical.
In some arrangements, the screw 504 connects to or changes to a smooth shaft allowing a shaft to exit the rear of the cylinder through a shaft seal 219 (see
In some arrangements, the motor 260 is mounted to the rear end of the fluid power actuator housing 140 on the set of load sensors 270 (e.g., load cells which measure the axial load from the screw shaft). The axial load may be reacted by the motor 260 or a separate axial bearing between the motor 260 and fluid power actuator housing 140 (not shown).
In some arrangements, the motor 260 is an electric, servo, or stepper motor. In other arrangements, the motor 260 is a hydraulic or pneumatic fluid power motor.
In some arrangements the motor shaft passes through the rear or the motor, allowing access for back-up manual operation during a power loss (e.g., using a hand crank or hand power tool to turn the screw 504).
The actuator axis 150 defined by the fluid power actuator housing 140 is also shown in
The brake 280 may be mechanically, hydraulically, pneumatically or electronically actuated and released as controlled by the control system. Accordingly, the brake 280 is operatively coupled with the screw 604 (
In some arrangements, the brake 280 includes a set of springs that biases the brake 280 from a disengaged state to an engaged state. Such spring biasing of the brake 280 into the engaged state prevents the screw 604 from rotating (e.g., actuator locking) when power to the control system is removed.
In some arrangements, the brake 280 is disengaged in response to activity initiated by control system. Along these lines, the brake 280 may be spring applied and released hydraulically, pneumatically, and/or electrically. For example, the brake 280 may take the form of a wet disc hydraulic brake assembly or spring applied electrically released brake.
During operation, the control system governs the position of the piston rod assembly 142 relative to the fluid power actuator housing 140 by managing fluid pressure and timing of the brake release and brake application. By adding position feedback using an external position sensor and using accurately controlling brake actuation timing using known time delays precision actuator positioning can be achieved. Accordingly, the control system is able to provide appropriate timing for brake release, brake re-application, including learning from prior position cycle events, and so on.
In some embodiments, control logic algorithms for the control system enable operation from the control system to be based either solely on actuator position and velocity using brake control timing, or based on measurements of the apparent system inertia from an acceleration profile (e.g., using that information to adjust the brake-application timing for a more precise position control).
It should be appreciated that, in the ball screw embodiments, loading sensors become optional to assist with the timing of the brake release without unwanted load motion, or using other fluid pressure sensors or switches and control logic to determine the safe timing/conditions for brake release without unwanted motion.
It should be further appreciated that back-up manual operation to lower a load without power (e.g., by gravity) simply involves gradual/proportional release of the brake 280 to safely lower the load and operation of the brake 280. Additionally, manual operation to raise a load without power involves manual rotation of the screw 604 coordinated with brake release or use of a one-way sprag clutch allowing rotation in one direction with the brake still engaged.
In some arrangements, a non-self-locking ACME screw is used as the set of screw and nut assembly components 600 rather than a recirculating ball screw system shown in
As shown in
The set of screw assembly components 700 includes a nut 702, a screw 704 (only a portion of which is shown in
At 802, the controller applies fluid pressure to one or more of the actuator ports to counter balance the external load applied to the actuator. This may involve using the axial load cell 270 (see
At 804, the controller initiates screw rotation to effectuate high precision fluid power actuator movement. For example, the controller may direct the motor 260 to rotate the screw. In some embodiments, the controller maintains minimal loading on the screw thus enabling the motor to turn the screw using very low torque. In some embodiments, the controller partially or fully releases the brake 280 and further increases or decreases the fluid pressure in the ports 214 and/or 216 to extend or retract the actuator.
At 806, the controller prevents the screw from rotating further. As a result, the fluid power actuator remains in place. In some embodiments, the controller maintains appropriate fluid power pressure in response to axial loading feedback to provide precision and stability. In some embodiments, the controller applies precise braking (e.g., using acceleration, inertia, etc. as factors) for smooth response behavior.
At 808, the controller removes power. As a result, the fluid power actuator automatically enters a self-locking state. In some embodiments, the screw is a self-locking type screw. In some embodiments, a brake automatically returns to an engaged state to hold the screw in place.
As mentioned above, improved techniques involve a fluid power actuator 106 that utilizes a screw and nut assembly 144. The screw and nut assembly 144 enhances fluid power actuator performance such as by providing high precision positioning, simple mechanical locking, and convenient manual back-up operation. In some arrangements, the screw and nut assembly 144 has a self-locking thread geometry. In some arrangements, the screw and nut assembly 144 has a recirculating ball screw or roller screw geometry for low friction operation. Such techniques overcome various deficiencies of conventional fluid power, electric and electro-hydraulic linear actuators.
While various embodiments of the present disclosure have been particularly shown and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims.
It should be appreciated that conventional actuators to lift heavy payloads or equipment (such as loading munitions on an aircraft) are typically either fluid power, electric or electro-hydraulic linear actuators. Conventional fluid power actuators have lower position precision, susceptible to leaking/drifting over time, require frequent maintenance to repair leaks, and may need redundant actuators to ensure no failure mode results in loss of load control, required by some agency safety certifications (e.g., U.S. Air Force nuclear certification). Conventional electric actuators are very expensive for high force applications, require periodic lubrication, are difficult to manually move the load in case of loss of power, require internal load holding brakes to prevent unwanted motion when not powered and are not normally designed with high enough safety factors required by nuclear certification standards. Conventional electro-hydraulic actuators have elements of both disadvantages plus are more difficult to package inside compact areas as the motor, pump, reservoir & valve assemblies are all mounted directly to the actuator.
In accordance with certain embodiments, a servo/stepper motor driven self-locking ACME screw and load cell are provided to either a fluid power cylinder or electro-hydraulic actuator. Precision positioning can be accomplished with a very small low torque motor, mechanical locking in any position and manual back-up operation can be provided which counters many of the negative aspect of using a fluid power actuator. Alternatively, by using a non-self-locking lead screw or ball screw and a spring applied, hydraulically, pneumatically or electrically released rotary brake assembly (with or without the servo/stepper motor & load cell), similar advantages can be provided with even fewer components.
In some embodiments, a blind end of the actuator forms a pivot mount (e.g. clevis or trunnion) to an external structure. In some embodiments, a rod end of the piston rod includes a connection to a movable arm with a munitions carrier to position and carry munitions.
In some embodiments, a self-locking ACME screw and nut is added inside a piston rod assembly of a fluid power actuator. The piston rod assembly is externally restrained by other means to prevent the piston rod assembly from rotating. The ACME screw connects to or changes to a smooth shaft allowing a shaft to exit the rear of the cylinder through a shaft seal. A servo or stepper motor is connected to the shaft with the option for the shaft to pass through and exit the rear or the servo motor, allowing access for back-up manual operation using a hand crank or hand power tool. The servo motor is mounted to the rear end of the cylinder on load cells which measure the axial load of the screw shaft. The axial load is either reacted by the servo motor or a separate axial bearing between the servo motor and cylinder. Either a proportional pressure control valve or a variable pressure-controlled pump is used to achieve the proper fluid power pressure differential across the fluid power actuator such that the load cell value is close-to-zero load (e.g., no axial load on the screw). This allows a very low motor torque required to rotate the screw for fine positioning of the load attached to the actuator. Either hydraulic fluid or compressed air lubricators may lubricate the screw and nut, preventing the need for periotic maintenance action to lubricate the screw. When power is removed, the pressure is released and the self-locking ACME screw will lock the actuator in position.
In other embodiments, a non-self-locking ACME screw, a recirculating ball screw, or a roller screw is used and the servo/stepper motor is replaced with a spring applied, hydraulically/pneumatically/electrically released rotary brake (such as a wet disc hydraulic brake assembly or spring applied electric motor brake). This also provides actuator locking in any position when power is removed. Use of the load cells may be used to assist with the timing of the brake release without unwanted load motion. Use of other fluid pressure sensors or switches and control logic may also be used to determine safe timing and conditions for brake release without unwanted load motion. Precision positioning may be achieved using an external position sensor and the appropriate timing of the brake release and brake re-application. Such control logic algorithms can be based on actuator position and velocity using brake control timing. Additionally or alternatively, such control logic algorithms can measure apparent system inertia from the acceleration profile and use that information to adjust the brake-application timing for a more precise position control. Optional back-up manual operation enables gradual or proportional release of the brake to safely lower the load. Manual operation of the screw further enables the completion of back-up lifting operations.
In some embodiments, the screw is constructed and arranged to rotate relative to the fluid power actuator housing and the piston and nut are constrained to not rotate where their translation is controlled by the rotation angle of the screw, and screw rotation is controlled with an actuator or brake.
In some embodiments, the screw is constructed to be non-rotating relative to the fluid power actuator housing, and the piston and nut are constructed to rotate and translate relative to the screw, where the piston translation is controlled by the rotation angle of the nut and the nut rotation is controlled with an actuator or brake.
In some embodiments, the fluid power actuator is single acting where fluid pressure is used on one side of the piston and gravity or a spring is used for motion in the opposite direction.
In some embodiments, the fluid power actuator is double acting where fluid pressure is used on both sides of the piston for motion in either direction.
In some embodiments, the nut and the screw define threads with lead angles and/or material properties that are self-locking between the nut and the screw. An example of a nut and a screw with a self-locking feature is an ACME screw where mechanical efficiency is below 35 percent. With a self-locking screw, a rotational actuator (e.g., electrical, hydraulic, or pneumatic motor) is used to control the angular position of the screw or nut which in turn controls the position of the piston.
In some embodiments, the nut and the screw define threads with lead angles and/or material properties that are not self-locking between the nut and the screw. An example of a nut and a screw that is not self-locking is a recirculating ball nut or roller screw nut where mechanical efficiencies are over 90%. With a non-self-locking screw, a rotational brake (e.g., electrical, hydraulic, pneumatic or mechanical brake) is used to control the angular position of the screw or nut which in turn controls the position of the piston.
In some embodiments, the fluid power actuator further includes a load sensor coupled with the fluid power actuator housing and the screw or nut, a fluid power pressure-controlled system (e.g., pressure-controlled pump or valves) coupled with one or both of the fluid power cylinder pressures on either side of the piston, and an electronic controller coupled with the load sensor and the fluid power pressure control system. The electronic controller is constructed and arranged to receive a sensor signal from the load sensor and operate the fluid power pressure control system to provide changes in the fluid pressure based on the sensor signal.
In some embodiments, the load sensor includes a load cell constructed and arranged to indicate, within the sensor signal, an amount of loading between the fluid power actuator housing and the screw or nut. Additionally, the electronic controller, when providing the changes in the fluid pressure based on the sensor signal, is constructed and arranged to minimize loading between the fluid power actuator housing and the screw or nut, thereby allowing a very small, low torque, low power motor to be used for the application.
In some embodiments, the fluid power actuator further includes an electronic controller coupled with the electrically controlled motor or brake. The electronic controller is constructed and arranged to coordinate motor or brake operation with movement between the fluid power actuator housing and the piston to provide precision positioning.
In some embodiments, the brake includes a set of springs that biases the brake from a disengaged state to an engaged state to provide actuator locking when power to the electronic controller is removed. Such a brake may be controlled in various ways such as hydraulically, pneumatically, or electrically.
It should be understood that the various actuator embodiments disclosed herein may be well-suited for certain specialized applications such as munitions handling equipment, aircraft munitions loading, and so on. Other applications include commercial and/or military material handling applications, lift trucks, belt loaders or de-icers and/or washer vehicles, and so on. Such modifications and enhancements that are disclosed herein are intended to belong to various embodiments of the disclosure.
