Actuator hardover monitor

Patent metadata

Field	Value
Publication number	US-10486792-B2
Application number	US-201715662773-A
Country	US
Kind code	B2
Filing date	Jul 28, 2017
Priority date	Aug 1, 2016
Publication date	Nov 26, 2019
Grant date	Nov 26, 2019

Abstract

An actuator hardover monitor for a control surface includes an actuator sensor for detecting an actuator position, a command model of an expected position of the actuator based on an input command, and a monitor to determine whether a difference between the actuator position and the expected position exceeds a threshold for a predetermined duration. A method of preventing a hardover event for a control surface includes commanding an actuator valve to a commanded position, determining continuously when the commanded position, or an actuator valve position, or a control-surface position, or a modeled actuator valve position exceeds a predetermined limit to provide an exceedance. The method may further include filtering a signal of the exceedance based on a time constant to provide a filtered exceedance, and switching to a backup control-surface actuator when the filtered exceedance exceeds the predetermined limit for a predetermined duration.

First claim

The invention claimed is:

1. An actuator hardover monitor for a control surface, comprising:
an actuator sensor for detecting an actuator position of a first control-surface actuator configured to control the control surface;
a computer having a processor for executing software instructions stored in non-transitory memory, the software instructions comprising:
a command model of an expected position of the control-surface actuator based on an input command;
a command delay for delaying the input command by a time lag to synchronize the command model with a deflection of the control surface; and
a monitor to determine whether a difference between the actuator position and the expected position exceeds a threshold for a predetermined duration; and

a switch for switching to a second control-surface actuator configured to control the control surface when the difference exceeds the threshold for at least the predetermined duration.

2. The actuator hardover monitor of claim 1 , further comprising a controller to adjust the actuator position of the first control-surface actuator to reduce the difference between the actuator position and the expected position.

3. The actuator hardover monitor of claim 1 , wherein the threshold comprises a softstop limit corresponding to a deflection range based on an aircraft parameter that is within a physical capability of the control surface.

4. The actuator hardover monitor of claim 1 , further comprising a control surface sensor for detecting a control-surface position such that the monitor determines whether a difference between the control-surface position and the expected position exceeds the threshold for the predetermined duration.

5. The actuator hardover monitor of claim 1 , wherein the monitor determines whether a difference between the control-surface position and the actuator position exceeds the threshold for the predetermined duration.

6. A method of mitigating unintended deflection of a control surface, comprising:
providing, from a sensor, a position signal indicative of a position of the control surface;
providing a softstop limit corresponding to a deflection range of the control surface based on an aircraft parameter;
determining when the position signal exceeds the softstop limit;
monitoring the position signal for a first duration; and
switching from a primary control-surface actuator to a backup control-surface actuator for driving the control surface, when the position signal persists for at least the first duration.

7. The method of claim 6 , further comprising, prior to the step of switching, preparing a switch by delaying the switching step to enable the backup control-surface actuator time to establish control over the control surface for providing a smooth transition from the primary control-surface actuator to the backup control-surface actuator.

8. The method of claim 6 , further comprising filtering the position signal based on a first time constant to provide a first filtered position signal.

9. The method of claim 8 , further comprising:
filtering the position signal based on a second time constant, different than the first time constant, to provide a second filtered position signal;
monitoring the second filtered position signal for a second duration, different than the first duration; and
switching from the primary control-surface actuator to the backup control-surface actuator when the first filtered position signal persists for at least the first duration and the second filtered position signal persists for at least the second duration.

10. A method of anticipating and mitigating unintended deflections of a control surface, comprising:
commanding an actuator valve to a commanded position, wherein the actuator valve is configured to control the control surface;
determining continuously when the commanded position exceeds an actuator valve limit to provide an exceedance; and
switching to a backup control-surface actuator when the exceedance exceeds the actuator valve limit for a predetermined duration.

11. The method of claim 10 , further comprising filtering the exceedance based on a time constant to provide a filtered exceedance.

12. The method of claim 10 , further comprising modeling the actuator valve position based on a physics-based computational model of the actuator valve and the commanded position.

13. The method of claim 10 , wherein the step of determining comprises evaluating the commanded position as a binary state such that the exceedance is determined to be any absolute value above the actuator valve limit.

14. The method of claim 10 , wherein the step of determining comprises evaluating the commanded position as a range such that the exceedance is determined to be any value outside a predetermined range.

15. The method of claim 10 , wherein the step of determining comprises evaluating the commanded position as a range with a correct sign such that exceedance is determined to be any value outside the predetermined range in a predetermined direction.

16. The method of claim 10 , wherein the step of determining comprises evaluating the commanded position by dynamically tracking the actuator valve position within a predetermined tolerance using a sensor.

17. The method of claim 10 , further comprising modifying the actuator valve limit by a scaled factor to determine a threshold, and determining continuously when the commanded position exceeds the threshold to provide the exceedance.

18. A method of correcting uncommanded motion of a control surface of an aircraft, comprising:
providing an actual position of the control surface from a position sensor;
modeling an expected position of the control surface based on a control input;
determining a difference between the actual position and the expected position;
providing a limit for the control surface position based on an aircraft parameter;
determining whether the difference exceeds the limit for a predetermined duration; and
switching to a backup control surface actuator when the difference exceeds the limit for at least the predetermined duration.

19. The method of claim 18 , further comprising filtering a signal of the difference based on a time constant.

20. The method of claim 18 , wherein the difference is due to an incorrect direction of motion.

21. The method of claim 18 , wherein the difference is an overshoot of the actual position above the expected position.

22. The method of claim 18 , wherein the difference is an undershoot of the actual position below the expected position.

23. The method of claim 18 , wherein the aircraft parameter is from the group consisting of airspeed, estimated airspeed, stabilizer trim position, and flap position.

24. The method of claim 18 , further comprising resetting the expected position to equal the actual position such that the difference is zero prior to the step of switching to a backup control surface actuator.

25. A method of mitigating unintended deflection of a control surface, comprising:
providing a measured position of the control surface based on a control-surface sensor;
deriving a control surface rate based on the measured position of the control surface;
providing an expected position of the control surface based on a position of an actuator valve from an actuator-valve sensor, wherein the actuator valve is configured to control the control surface;
deriving an actuator rate based on the position of the a

Assignees

• Textron Aviation Inc
• Textron Innovations Inc

Inventors

• Hagerott Steven G
• Peters Russell
• Eddy Stephen M

Classifications

• B64C9/14

  forming slots · CPC title

• B64C5/02

  Tailplanes · CPC title

• B64C9/00 Primary

  Adjustable control surfaces or members, e.g. rudders (trimming stabilising surfaces B64C5/10) · CPC title

• B64D45/0005

  Devices specially adapted to indicate the position of a movable element of the aircraft, e.g. landing gear · CPC title

• B64C5/10

  adjustable · CPC title