Hydraulic Actuator System

• US 20150226234A1
• Filed: 08/27/2013
• Published: 08/13/2015
• Est. Priority Date: 08/27/2012
• Status: Active Grant

• Current Assignee: Ekso Bionics, Inc. (Ekso Bionics Holdings, Inc.)
• Original Assignee: Ekso Bionics, Inc. (Ekso Bionics Holdings, Inc.)
• Inventors: Amundson, Kurt Reed, Angold, Russdon, Scheinman, David, Swift, Tim, Norboe, Daniel P, Moore, Robert, Beard, Jonathan, Edelberg, Kyle
• Granted Patent: US 10,352,334 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61H 1/024 Knee A61H1/0255 takes precedence
• CPC Class Codes: A61H 1/0244 Hip A61H1/0255 takes precedence
• CPC Class Codes: A61H 1/0262 Walking movement; Appliances for aiding disabled persons to walk A61H3/00 takes precedence
• CPC Class Codes: A61H 2201/1238 with hydraulic or pneumatic drive
• CPC Class Codes: A61H 2201/1246 by piston-cylinder systems
• CPC Class Codes: A61H 2201/1409 Hydraulic or pneumatic means
• CPC Class Codes: A61H 2201/1614 Shoulder, e.g. for neck stretching
• CPC Class Codes: A61H 2201/1628 Pelvis
• CPC Class Codes: A61H 2201/164 Feet or leg, e.g. pedal
• CPC Class Codes: A61H 2201/165 Wearable interfaces
• CPC Class Codes: A61H 2201/5061 Force sensors
• CPC Class Codes: A61H 2201/5064 Position sensors
• CPC Class Codes: A61H 2201/5069 Angle sensors
• CPC Class Codes: A61H 2201/5071 Pressure sensors
• CPC Class Codes: A61H 2201/5079 Velocity sensors
• CPC Class Codes: A61H 2201/5092 Optical sensor
• CPC Class Codes: A61H 3/00 Appliances for aiding patients or disabled persons to walk about apparatus for helping babies to walk A47D13/04 ; applying electrical currents by contact electrodes for stimulating motor muscles, e.g. walking assistance A61N1/36003
• CPC Class Codes: F04C 14/22 by changing the eccentricity between cooperating members
• CPC Class Codes: F15B 11/028 for controlling the actuating force F15B11/024 takes precedence
• CPC Class Codes: F15B 11/04 for controlling the speed F15B11/024 takes precedence
• CPC Class Codes: F15B 15/08 : Characterised by the construction of the motor unit
• CPC Class Codes: F15B 2211/205 : Systems with pumps
• CPC Class Codes: F15B 2211/20515 : Electric motor
• CPC Class Codes: F15B 2211/20546 : variable capacity
• CPC Class Codes: F15B 2211/20561 : reversible
• CPC Class Codes: F15B 2211/20576 : with multiple pumps
• CPC Class Codes: F15B 2211/27 : Directional control by means of the pressure source
• CPC Class Codes: F15B 2211/6651 : Control of the prime mover, e.g. control of the output torque or rotational speed
• CPC Class Codes: F15B 2211/6652 : Control of the pressure source, e.g. control of the swash plate angle
• CPC Class Codes: F15B 2211/6654 : Flow rate control
• CPC Class Codes: F15B 2211/71 : Multiple output members, e.g. multiple hydraulic motors or cylinders
• CPC Class Codes: F15B 7/006 : Rotary pump input

Abstract

The invention is directed to controlling a hydraulic actuation system having at least one degree of freedom, a prime mover, at least one actuation module and a controller, with each actuation module including: an over-center variable displacement pump having a power input connection configured to power the pump from the prime mover and a displacement varying input for varying the displacement of the pump; a displacement varying actuator configured to modulate the displacement varying input of the pump; an output actuator in direct communication with the pump, the output actuator configured to drive a corresponding degree of freedom; and at least one sensor establishing a feedback measurement that represents a force or motion of the output actuator. Based on a value of each feedback measurement, the force or motion of the output actuator is regulated by controlling the prime mover and the displacement actuator for the output actuator.

Claims

1. A system for hydraulically actuating at least one degree of freedom, said system comprising:

a prime mover and at least one actuation module, each actuation module including;

(1) an over-center variable displacement pump, said pump having;

(a) a power input connection configured to power the pump from said prime mover; and

(b) a displacement varying input for varying the displacement of the pump; and

(2) a displacement varying actuator configured to modulate the displacement varying input of the pump;

(3) an output actuator in direct communication with the pump, said an output actuator being configured to drive a corresponding degree of freedom; and

(4) a feedback measurement that represents a force or motion of the output actuator, said feedback measurement being constructed from at least one sensor; and

a controller configured to control the prime mover and the displacement varying actuator, wherein said controller uses the feedback measurement to regulate the force or motion of the output actuator by controlling the displacement varying actuator.

2. The system of claim 1 wherein there are at least two actuation modules.

3. The system of claim 1 wherein there is one actuation module, said prime mover produces rotary motion, and said controller controls a speed of the rotary motion to maximize power transferred from said variable displacement pump wherein controlling the force or motion of the output actuator results in power being transferred from said variable displacement pump.

4. The system of claim 1 wherein the prime mover produces rotary motion and said controller further controls motion of the prime mover.

5. The system of claim 4 wherein the controller controls an angular speed of the prime mover to be generally constant.

6. The system of claim 1 wherein the output actuator has a limited travel.

7. The system of claim 4 wherein the prime mover is an electric motor.

8. The system of claim 7 wherein the controller controls the prime mover in three modes:

(1) producing power when an angular speed of the prime mover is generally below a low set point,

(2) producing no power when the angular speed of the prime mover is generally above said low set point but below a high set point, and

(3) absorbing power when the angular speed of the prime mover is generally above said high set point.

9. The system of claim 2 wherein the controller controls the prime mover to a rotational speed, with said rotational speed being chosen by the following steps:

(1) the controller divides the flow required by each said output actuator by a maximum displacement of its corresponding variable displacement pump producing a required prime mover speed for that actuation module,

(2) the controller computes a maximum speed that is the maximum of an absolute value of each of the said required prime mover speeds, and

(3) the controller establishes said rotational speed to be slightly larger than said maximum speed.

10. The system of claim 4 wherein the system is incorporated into a device, the controller controls a rotational speed of the prime mover and receives an external signal from the device, and, based on the external signal, the controller changes the rotational speed of the prime mover between at least two different values wherein lower values correspond to the device being in a rest state and higher values correspond to the device being in an active state.

11. The system of claim 4 wherein the controller controls the prime mover to a rotational speed, the controller includes a model of power loss in the actuation system, and said controller establishes the rotational speed to minimize power loss.

12. The system of claim 4 wherein the controller controls the prime mover to a rotational speed and said controller establishes the rotational speed to maximize a life of the pump.

13. The system of claim 4 wherein the controller controls the prime mover to a rotational speed and said controller establishes the rotational speed to minimize acoustic volume.

14. The system of claim 13 wherein the acoustic volume is minimized over a specific range of frequencies.

15. The system of claim 4 wherein the controller controls the prime mover to a rotational speed and the controller establishes the rotational speed to maximize performance in regulating the force or motion of the output actuator.

16. The system of claim 4 wherein the controller controls the prime mover to a rotational speed and the controller establishes the rotational speed to minimize an amount of power consumed in regulating the force or motion of the output actuator.

17. The system of claim 4 wherein the controller controls the prime mover to a rotational speed, the system is incorporated into a device, and said device signals said controller which of several modes of optimization the controller should use in order to choose the rational speed of the prime mover, said modes including at least two of the following:

minimizing power loss, maximizing efficiency, maximizing pump life, minimizing acoustic volume, maximizing actuation performance, and minimizing system temperatures.

18. The system of claim 17 wherein the device involves a human operator and the human operator provides input on which of said modes of optimization should be chosen.

19. The system of claim 9 wherein the system is incorporated in a device, with the device estimating future flow requirements and signaling this the future flow requirements to the controller, said controller utilizing the future flow requirements in place of a flow presently required by the output actuator.

20. The system of claim 1 wherein the displacement varying actuator is backdrivable.

21. The system of claim 2 wherein the variable displacement hydraulic pump includes a rotating core that holds pistons or vanes, a translating housing, and a stationary body, said rotating core being driven by said prime mover to rotate within said housing, said housing being translated by the displacement varying actuator, and said housing being constrained to translate with respect to the stationary body with a flexural connection.

22. The system of claim 1 wherein moving parts of said variable displacement pump are submersed in working hydraulic fluid.

23. The system of claim 4 wherein the variable displacement pump comprises two rotating cores that hold pistons or vanes, and a translating housing.

24. The system of claim 23 wherein said two rotating cores are rotatably coupled to said prime mover to rotate in opposite directions within said translating housing, and hydraulic fluid is ported to and from the two rotating cores approximately in phase, whereby forces from the two rotating cores onto the translating housing are generally neutralized.

25. The system of claim 23 wherein said two rotating cores are rotatably coupled to said prime mover to rotate in the same direction within said translating housing, and hydraulic fluid is ported to and from the two rotating cores approximately out of phase, whereby forces from the two rotating cores onto the translating housing are generally neutralized.

26. The system of claim 1 wherein the variable displacement pump comprises two rotating cores that hold pistons or vanes, two translating housings, a housing connection, and a pump body, and wherein each said core is located coaxially along a common shaft and rotates within one of the two translating housings, and the housing connection couples said two translating housings so that the displacement varying actuator moves both translating housings in opposite directions.

27. A method for controlling a hydraulic actuation system having at least one degree of freedom, a prime mover, at least one actuation module and a controller, with each actuation module including:

an over-center variable displacement pump having a power input connection configured to power the pump from said prime mover and a displacement varying input for varying the displacement of the pump;

a displacement varying actuator configured to modulate the displacement varying input of the pump;

an output actuator in direct communication with the pump, said output actuator configured to drive a corresponding degree of freedom; and

at least one sensor establishing a feedback measurement that represents a force or motion of the output actuator, said method comprising;

reading a value of each feedback measurement; and

controlling the force or motion of the output actuator by controlling the prime mover and the displacement actuator for the output actuator.

28. A system for hydraulically actuating one degree of freedom within a device, said system comprising:

a prime mover and one actuation module, said module including;

(1) an over-center variable displacement pump, said pump having;

(a) a power input connection configured to power the pump from said prime mover,

(b) a displacement varying input for varying a displacement of the pump,

(2) a displacement varying actuator configured to modulate the displacement varying input of the pump,

(3) an output actuator in direct communication with the pump, said output actuator configured to drive a corresponding degree of freedom, and

(4) at least one sensor for constructing a feedback measurement that represents a force or motion of the output actuator, and

a controller configured to control the prime mover and the displacement actuator wherein, when said output actuator is absorbing power from said device, said controller controls the prime mover and displacement actuator to achieve two goals;

(1) regulate the force or motion of said output actuator, and

(2) maximize power absorbed by said prime mover.