Automatic flight control pilot assist system

• US 4,527,242 A
• Filed: 06/28/1982
• Issued: 07/02/1985
• Est. Priority Date: 06/28/1982
• Status: Expired due to Term

• Current Assignee: Rockwell International Corporation
• Original Assignee: Rockwell International Corporation
• Inventors: McElreath, Kenneth W., Fabian, Gordon R.
• Primary Examiner(s): Gruber, Felix D.
• Assistant Examiner(s): Black, Thomas G.
• Application Number:
  US06/392,917
• Time in Patent Office: 1,100 Days
• Field of Search: 364/432, 364/428, 364/433, 364/434, 364/440, 244/76 R, 244/184, 244/196, 244/197, 244/180, 244/182, 244/177, 244/194, 244/17.13, 244/223, 73/178 R
• US Class Current: 701/11
• CPC Class Codes: G05D 1/0061 for transition from automatic pilot to manual pilot and vice versa
• CPC Class Codes: G05D 1/0858 specially adapted for vertical take-off of aircraft

Abstract

Automatic flight control apparatus, preferably for use in a helicopter, comprises a parallel connected servosystem which allows the apparatus to discern manual input forces and to respond naturally to them. The manual forces are sensed internal the parallel servosystem by monitoring the corrective error drive signal to the parallel servomotor. A signal indicative of excess manual force is used to develop other signals, one of which aids in temporarily defeating the command signal generated by the autopilot in trying to do its job, and another of which temporarily contributes positive feedback within the parallel servosystem so as to cause the servomotor to aid the pilot'"'"'s manual input force. Another preferred embodiment includes a series connected servosystem.

Claims

1. For use in an aircraft having an autopilot for providing one or more flight command signals and further having a manually operable device mechanically coupled through appropriate linkages to a flight control surface so as to afford positioning of said surface, the apparatus comprising:

(i) signal combining first means for receiving a command signal S_at from the autopilot, and (b) a signal S_m, and for combining S_m and S_at in a predetermined phase relationship,

(ii) second means connected for receiving a control signal S_cp from said first means and comprising;

(a) servomotor means connected to said linkages so as to operate in parallel with said manually operable device;

(b) means for receiving S_cp and a feedback signal and producing therefrom a corrective error signal S_ep for causing the servomotor output position to change;

(c) sensing means comprising circuit means, responsive to S_ep, for providing a signal S_x indicative of the excess of S_ep over a predetermined reference R₁, said excess being caused by a sufficient manual force being applied through said manually operable device and through said linkages to said flight control surface,

(d) feedback circuit means for receiving the parallel servomotor output and signal S_x and in response thereto producing said feedback signal, said feedback circuit means responding to signal S_x and to the parallel servomotor output such that S_x and the parallel servomotor output evoke oppositely phased components of said feedback signal; and

(iii) third means, responsive to S_x, for producing a signal simulative of the changes in the autopilot command signal S_at which result from the aircraft responding to the manual force, the change-simulative signal provided by said third means being the signal S_m,

and said predetermined phase relationship in which S_m and S_at are combined by said first means being a phase relationship such that S_m and said changes in S_at tend to cancel one another.

2. Apparatus as defined in claim 1 wherein said sensing means further provides a signal S_td for indicating whether S_ep has exceeded the predetermined reference R₁, and the apparatus further includes switching means responsive to S_td for controlling the delivery S_m to said first means.

3. Apparatus as defined in claim 2 wherein said switching means comprises time delayed switching means.

4. Apparatus as defined in claim 1 wherein said first means comprises means for producing S_cp such that S_cp is indicative of the difference between S_at and S_m.

5. Apparatus as defined in claim 1 and further including a series servosystem fourth means connected for receiving a control signal S_cs from said first means and comprising:

(a) servomotor means connected to said linkages so as to operate in series with said manually operable device;

(b) means for receiving input and feedback signals and producing therefrom a corrective error signal S_es for causing said series servomotor output position to change;

(c) feedback circuit means connected to the series servomotor output for providing said feedback to the means producing S_es.

6. Apparatus as defined in claim 5 wherein said first means comprises means for producing S_cs and S_cp such that S_cs is indicative of the output of an amplitude limiter whose input is the difference S_D between S_at and S_m, and such that S_cp is indicative of the excess of S_D over a predetermined reference R₂.

7. Apparatus as defined in claim 6 wherein R₂ is S_cs.

8. Apparatus as defined in claim 1 wherein the feedback circuit means of the second means includes a washout circuit having input connected for receiving S_x and having output connected for contributing to net feedback signal.

9. Apparatus as defined in claim 1 wherein said third means comprises a variable gain circuit and a low-pass filter connected in cascade, said variable gain circuit comprising means for providing gain which varies as a function of a predetermined flight parameter.

10. Apparatus as defined in claim 9 wherein the filter characteristic of said low-pass filter is suitable to simulate the inertia of the aircraft.

11. Apparatus as defined in claim 9 wherein said predetermined flight parameter is airspeed.

12. Apparatus as defined in claim 11 wherein, over at least part of the gain range, the gain decreases as airspeed increases.

13. Apparatus as defined in claim 1 wherein said sensing means further provides a signal S_td for indicating whether S_ep has exceeded the predetermined reference R₁, and wherein there is further included switched synchronizer means responsive to S_td for synchronizing an autopilot generated heading hold signal in accordance with new aircraft heading resulting from the manual force.

14. Apparatus as defined in claim 1 wherein said predetermined reference R₁ comprises a signal S₀₁ indicative of the output of an amplitude limiter whose input is S_ep.

15. Apparatus as defined in claim 14 wherein said sensing means includes amplitude limiter means for providing the output signal S₀₁ in response to input signal S_ep according to the following:

S₀₁ is substantially equal to S_ep when -K₁ <

S_ep <

+K₂ ;

S₀₁ is substantially equal to (-K₁) when (-K₁)>

S_ep ; and

S₀₁ is substantially equal to (+K₂) when (+K₂)<

S_ep ;

where K₁ and K₂ are predetermined constants.

16. Apparatus as defined in claim 15 wherein K₁ =K₂.

17. Apparatus as defined in claim 16 wherein the feedback circuit means of the second means includes a washout circuit having input connected for receiving S_x and having output connected for contributing to net feedback signal.

18. Apparatus as defined in claim 16 or 17 wherein said third means comprises a variable gain circuit and a low-pass filter connected in cascade, said variable gain circuit comprising means for providing gain which varies as a function of a predetermined flight parameter.

19. Apparatus as defined in claim 18 wherein the filter characteristic of said low-pass filter is suitable to simulate the inertia of the aircraft.

20. Apparatus as defined in claim 19 wherein said predetermined flight parameter is airspeed.