ACTIVE FLUID ISOLATION SYSTEM

• US 3,701,499 A
• Filed: 04/08/1968
• Issued: 10/31/1972
• Est. Priority Date: 04/08/1968
• Status: Expired due to Term

• Current Assignee: Dale W. Schubert, Frederick D. Ezekiel
• Original Assignee: Dale W. Schubert, Frederick D. Ezekiel
• Inventors: Schubert, Dale W., Ezekiel, Frederick D.
• Primary Examiner(s): Milton Buchler
• Assistant Examiner(s): Paul E. Sauberer
• Application Number:
  US04/719,472
• Time in Patent Office: 1,667 Days
• Field of Search: 244/118,776,80,83,8,122,17.27 188/1B,181A 248/20,358
• US Class Current: 244/17.27
• CPC Class Codes: B64C 2027/004 using actuators, e.g. active systems
• CPC Class Codes: B64C 27/001 Vibration damping devices
• CPC Class Codes: B64D 11/0689 specially adapted for pilots
• CPC Class Codes: F16F 15/027 comprising control arrangements F16F15/0237 takes precedence
• CPC Class Codes: Y02T 50/40 Weight reduction

Abstract

A body to be stabilized, such as an aircraft pilot seat includes means, such as an accelerometer, for providing an acceleration signal representative of the acceleration of the body. This acceleration signal is used to control the action of a servovalve-controlled hydraulic actuator, to reduce the force applied to the body tending to reduce the acceleration sensed by the accelerometer to a substantially zero value. There is also a position transducer for providing a signal representative of the displacement of the body relative to the supporting structure position to provide a displacement control signal that controls the actuator so that the mass position is normally in a predetermined rest position, typically at the hydraulic actuator midposition.

Claims

1. Active fluid isolation apparatus comprising, means defining a body to be isolated and remain in a stationary position relative to a reference, acceleration-responsive means placed on and attached to said body for providing an acceleration signal representative of the acceleration of said body, controllable actuating means outside said body responsive at least to said acceleration signal for acting upon said body so as to reduce the acceleration of said body, support means for carrying said controllable actuating means, position-responsive means for providing a displacement signal representative of the displacement of said body from said stationary position, and means for coupling said displacement signal to said controllable actuating means, said controllable actuating means also responding to said displacement signal for maintaining said body substantially in said stationary position.

2. Active fluid isolation apparatus in accordance with claim 1 wherein said reference is said support means.

3. Active fluid isolation apparatus in accordance with claim 1 wherein said controllable actuating means comprises, servovalve means having an actuator coupled to said body, power source means for providing fluid through said servovalve means to said actuator, servoamplifier means for processing at least said acceleRation signal to provide a control signal, means for coupling said control signal to said servovalve to regulate the flow of said fluid through said servovalve for controlling said actuator at least in accordance with a predetermined function of said acceleration signal, said servoamplifier having means for establishing said predetermined function.

4. Active fluid isolation apparatus in accordance with claim 3 and further comprising, means including a flexible coupling for coupling said actuator to said body.

5. Active fluid isolation apparatus in accordance with claim 3 and further comprising, means for coupling said displacement signal to said servoamplifier means, said servoamplifier means having means for also processing said deflection signal in accordance with a predetermined weighting function to provide a component of said control signal.

6. Active fluid isolation apparatus in accordance with claim 3 and further comprising, means associated with said servoamplifier means for establishing the resonant frequency of said apparatus many times lower than the open-loop resonant frequency of said apparatus with said servoamplifier means disconnected from said apparatus.

7. Active fluid isolation apparatus in accordance with claim 5 and further comprising, means associated with said servoamplifier means for establishing the resonant frequency of said apparatus many times lower than the open-loop resonant frequency of said apparatus with said servoamplifier means disconnected from said apparatus.

8. Active fluid isolation apparatus in accordance with claim 5 and further comprising, means including a flexible coupling for coupling said actuator to said body.

9. Active fluid isolation apparatus in accordance with claim 6 and further comprising, means including a flexible coupling for coupling said actuator to said body.

10. Active fluid isolation apparatus in accordance with claim 3 wherein said means for establishing said predetermined function is characterized by a frequency response having at least one notch centered about a first notch frequency whereby signals of frequency very close to said first notch frequency applied to said servoamplifier means exercise much more influence on said control signal than signals of frequency further from said first notch frequency.

11. Active fluid isolation apparatus in accordance with claim 10 wherein said means for establishing said predetermined function is characterized by a frequency response having a plurality of notches centered about a corresponding plurality of respective harmonically related notch frequencies.

12. Active fluid isolation apparatus in accordance with claim 5 wherein at least one of said means for establishing said predetermined function and said means for processing said deflection signal is characterized by a frequency response having at least one notch centered about a first notch frequency whereby signals applied to said servoamplifier means of frequency very close to said first notch frequency exercise much more influence on said control signal than signals of frequency further from said first notch frequency.

13. Active fluid isolation apparatus in accordance with claim 12 wherein at least one of said means for establishing said predetermined function and said means for processing said deflection signal is characterized by a frequency response having a plurality of notches centered about a corresponding plurality of respective harmonically related notch frequencies.

14. Active fluid isolation apparatus in accordance with claim 13 wherein said support means comprises a rotor of a helicopter, said mass comprises a fuselage of said helicopter, and said notch frequencies are harmonically related to the frequency of rotation of said rotor.

15. Active fluid isolation apparatus in accordance with claim 5 and further comprising, means including said controllable actuating means, said acceleration-responsive means and said servoamplifier means for establishing unilateral dynamic stiffness between said body and said support means for appreciably resisting relative displacement between said body and said support means caused by dynamic forces on said body while hardly resisting such relative displacement caused by dynamic forces on said support means.

16. Active fluid isolation apparatus in accordance with claim 3 wherein said acceleration-responsive means comprises a load cell, said load cell, said servoamplifier means and said controllable actuating means comprising means for isolating said support means from vibration and shock produced by said body.

17. Active fluid isolation apparatus in accordance with claim 1 wherein said isolated body comprises a vehicle seat.

18. Active fluid isolation apparatus in accordance with claim 1 wherein said acceleration includes a rotational component.

19. Active fluid isolation apparatus in accordance with claim 1 wherein said acceleration includes a plurality of orthogonal components and further comprising, means for independently reducing each of said components.

20. An isolator system to isolate a flexible body from disturbances causing objectionable movement of said flexible body comprising:

actuator means having a movable member connected to said flexible body mass, control means causing said actuator movable member to move to oppose responsive movement of said flexible body to disturbances;

said control means including means for applying a force to said movable member and including sensor means producing a signal corresponding to the movement of said mass member when said mass member responds to a disturbance and also including means for applying said force in response to said signal and in a manner indicated by said signal to oppose said movement; and

compensation means eliminating the response of said movable member to sensor signals corresponding to steady and very low frequency mass member response.

21. An isolator system to isolate a flexible body from disturbances causing objectionable movement of said flexible body comprising:

actuator means having a movable member connected to said flexible body mass, control means causing said actuator movable member to move to oppose responsive movement of said flexible body to disturbances;

said control means including means for applying a force to said movable member and including sensor means producing a signal corresponding to the movement of said mass member when said mass member responds to a disturbance and also including means for applying said force in response to said signal and in a manner indicated by said signal to oppose said movement; and

control loop means limiting the travel of said movable member to a predetermined constant maximum value.