Acceptance testing of actuators using backlash and stiction measurements

• US 20060060078A1
• Filed: 07/27/2005
• Published: 03/23/2006
• Est. Priority Date: 07/28/2004
• Status: Active Grant

• Current Assignee: HR Textron, Inc.
• Original Assignee: HR Textron, Inc.
• Inventors: Deller, Robert W., Lee, Joon H.
• Granted Patent: US 7,292,954 B2
• Time in Patent Office: Days
• US Class Current: 91/1
• CPC Class Codes: B64F 5/60 Testing or inspecting aircraft components or systems
• CPC Class Codes: F15B 19/005 Fault detection or monitoring
• CPC Class Codes: G01R 31/2829 Testing of circuits in sensor or actuator systems testing of apparatus for measuring electric or magnetic variables G01R35/00; testing of indicating or recording apparatus G01D; in airbag systems B60R21/0173; checking gas analysers G01N33/007; monitoring or fail-safe circuits for electromagnets H01F7/1844
• CPC Class Codes: G01R 31/343 in operation
• CPC Class Codes: G05B 19/4063 Monitoring general control system G05B19/4062 takes precedence
• CPC Class Codes: G05B 2219/42298 Measure backlash, time difference between point A to point B and from B to A, if too large
• CPC Class Codes: G05B 2219/45071 Aircraft, airplane, ship cleaning manipulator, paint stripping
• CPC Class Codes: G05B 23/0254 based on a quantitative model, e.g. mathematical relationships between inputs and outputs; functions: observer, Kalman filter, residual calculation, Neural Networks

Abstract

Aspects of the present invention are directed to systems, methods, and computer-readable media for measuring certain actuator system parameters of an actuator, e.g., an EMA in its working environment. Stiction and backlash are examples of such parameters, and these indicate the impending failure of an actuator system than conventional approaches of measuring the elapsed time of operation. When the measured backlash and/or stiction parameters exhibit a deleterious increase over time, e.g., by exceeding a preset threshold, imminent failure or the need for service/repair of the system is indicated.

Claims

1. An actuation system, comprising:

a base;

an actuator coupled to the base, the actuator being configured to move a load relative to the base; and

a test subsystem coupled to the actuator, the test subsystem being configured to acceptance test the actuator, the test subsystem including (i) a sensing circuit, (ii) a controller, and (iii) a communications medium connecting the sensing circuit and the controller, the controller being configured to;

obtain a first rate of change of an operating characteristic of the actuator, the first rate of change being based on previous measurements of actuator movement,

generate a second rate of change of the operating characteristic of the actuator from current measurements of actuator movement and at least some of the previous measurements of actuator movement, and

electronically indicate whether the actuator is in acceptable condition based on a comparison of the second rate of change and the first rate of change.

2. An actuation system as in claim 1 wherein the base is a portion of an aircraft, the actuator being installed at an operating location of the portion of the aircraft;

and

wherein the controller is configured to obtain the first rate of change, generate the second rate of change, and electronically indicate whether the actuator is in acceptable condition while the actuator remains installed at the operating location of the portion of the aircraft and while the aircraft is on ground.

3. A test system to acceptance test an actuator, the test system comprising:

a sensing circuit;

a controller; and

a communications medium connecting the sensing circuit and the controller, the controller being configured to;

obtain a first rate of change of an operating characteristic of the actuator, the first rate of change being based on previous measurements of actuator movement,

generate a second rate of change of the operating characteristic of the actuator from current measurements of actuator movement and at least some of the previous measurements of actuator movement, and

electronically indicate whether the actuator is in acceptable condition based on a comparison of the second rate of change and the first rate of change.

4. A test system as in claim 3 wherein the actuator is configured to install at an operating location of an aircraft;

and

wherein the controller is configured to obtain the first rate of change, generate the second rate of change, and electronically indicate whether the actuator is in acceptable condition while the actuator remains installed at the operating location of the aircraft and while the aircraft is on ground.

5. A test system as in claim 4 wherein the operating characteristic of the actuator is backlash of the actuator;

wherein the first rate of change is based on actuator movement over a first operating interval; and

wherein the controller, when electronically indicating whether the actuator is in acceptable condition includes, is configured to;

provide a result signal indicating whether the backlash of the actuator has substantially increased over a second operating interval, the second operating interval being substantially equal to the first operating interval.

6. A test system as in claim 5 wherein the actuator includes a motor and an output element coupled to the motor;

and wherein the controller, when generating the second rate of change, is configured to;

provide a set of motor signals to the motor of the actuator to move the output element,

measure motor positions of the motor and corresponding output element positions of the output element in response to the provided set of motor signals, and

output a current backlash measurement based on the measured motor positions and the measured corresponding output element positions.

7. A test system as in claim 6 wherein the controller, when outputting the current backlash measurement, is configured to:

determine a series of differences between the measured motor positions and the measured corresponding output elements positions; and

select a peak difference from the series of differences, the selected peak difference being the current backlash measurement.

8. A test system as in claim 7 wherein the controller, when providing the result signal, is configured to:

provide the result signal with (i) a first value when the second rate of change is less than 10% to indicate that the actuator is in acceptable condition, and (ii) a second value when the second rate of change is greater than or equal to 10% to indicate that the actuator is no longer in acceptable condition, the first value being different that the second value.

9. A test system as in claim 4 wherein the operating characteristic of the actuator is stiction of the actuator;

wherein the first rate of change is based on actuator movement over a first operating interval; and

wherein the controller, when electronically indicating whether the actuator is in acceptable condition, is configured to;

provide a result signal indicating whether the stiction of the actuator has substantially increased over a second operating interval, the second operating interval being substantially equal to the first operating interval.

10. A test system as in claim 9 wherein the actuator includes a motor and an output element coupled to the motor;

and wherein the controller, when generating the second rate of change, is configured to;

provide a set of motor signals to the motor of the actuator to move the output element over multiple small displacements and over a large displacement,

measure response velocities of the output element in response to movements of the output element over the multiple small displacements and over the large displacement, and

output a current stiction measurement based on the measured response velocities of the output element.

11. A test system as in claim 10 wherein the controller, when outputting the current stiction measurement, is configured to:

determine a series of velocity deviations, each velocity deviation being a difference between a particular response velocity measured during movement of the output element over a particular one of the multiple small displacements and a response velocity measured during movement of the output element over the large displacement; and

select a peak velocity deviation from the series of velocity deviations, the peak velocity deviation being the current stiction measurement.

12. A test system as in claim 11 wherein the controller, when providing the result signal, is configured to:

provide the result signal with (i) a first value when the second rate of change is less than 10% to indicate that the actuator is in acceptable condition, and (ii) a second value when the second rate of change is greater than or equal to 10% to indicate that the actuator is no longer in acceptable condition, the first value being different that the second value.

13. A method of acceptance testing an actuator, the method comprising:

obtaining a first rate of change of an operating characteristic of the actuator, the first rate of change being based on previous measurements of actuator movement;

generating a second rate of change of the operating characteristic of the actuator from current measurements of actuator movement and at least some of the previous measurements of actuator movement; and

electronically indicating whether the actuator is in acceptable condition based on a comparison of the second rate of change and the first rate of change.

14. A method as in claim 13, further comprising:

installing the actuator at an operating location of an aircraft; and

wherein obtaining, generating, and electronically indicating occur while the actuator remains installed at the operating location of the aircraft and while the aircraft is on ground.

15. A method as in claim 14 wherein the operating characteristic of the actuator is backlash of the actuator;

wherein the first rate of change is based on actuator movement over a first operating interval; and

wherein electronically indicating whether the actuator is in acceptable condition includes;

providing a result signal indicating whether the backlash of the actuator has substantially increased over a second operating interval, the second operating interval being substantially equal to the first operating interval.

16. A method as in claim 15 wherein the actuator includes a motor and an output element coupled to the motor;

and wherein generating the second rate of change includes;

providing a set of motor signals to the motor of the actuator to move the output element,

measuring motor positions of the motor and corresponding output element positions of the output element in response to the provided set of motor signals, and

outputting a current backlash measurement based on the measured motor positions and the measured corresponding output element positions.

17. A method as in claim 16 wherein outputting the current backlash measurement includes:

determining a series of differences between the measured motor positions and the measured corresponding output elements positions; and

selecting a peak difference from the series of differences, the selected peak difference being the current backlash measurement.

18. A method as in claim 17 wherein providing the result signal includes:

providing the result signal with (i) a first value when the second rate of change is less than 10% to indicate that the actuator is in acceptable condition, and (ii) a second value when the second rate of change is greater than or equal to 10% to indicate that the actuator is no longer in acceptable condition, the first value being different that the second value.

19. A method as in claim 14 wherein the operating characteristic of the actuator is stiction of the actuator;

wherein the first rate of change is based on actuator movement over a first operating interval; and

wherein electronically indicating whether the actuator is in acceptable condition includes;

providing a result signal indicating whether the stiction of the actuator has substantially increased over a second operating interval, the second operating interval being substantially equal to the first operating interval.

20. A method as in claim 19 wherein the actuator includes a motor and an output element coupled to the motor;

and wherein generating the second rate of change includes;

providing a set of motor signals to the motor of the actuator to move the output element over multiple small displacements and over a large displacement,

measuring response velocities of the output element in response to movements of the output element over the multiple small displacements and over the large displacement, and

outputting a current stiction measurement based on the measured response velocities of the output element.

21. A method as in claim 20 wherein outputting the current stiction measurement includes:

determining a series of velocity deviations, each velocity deviation being a difference between a particular response velocity measured during movement of the output element over a particular one of the multiple small displacements and a response velocity measured during movement of the output element over the large displacement; and

selecting a peak velocity deviation from the series of velocity deviations, the peak velocity deviation being the current stiction measurement.

22. A method as in claim 21 wherein providing the result signal includes:

providing the result signal with (i) a first value when the second rate of change is less than 10% to indicate that the actuator is in acceptable condition, and (ii) a second value when the second rate of change is greater than or equal to 10% to indicate that the actuator is no longer in acceptable condition, the first value being different that the second value.