Electro-rheological fluid damped actuator

Abstract

An electro-rheological fluid damped actuator having an actuator housing w a moveable element such as a piston and rod assembly disposed within the housing. The actuator further comprises a hydraulic circuit with an electro-rheological fluid disposed in the hydraulic circuit. The hydraulic circuit and rheological fluid provides an active and variable damping force on the moveable element. The damping force is controlled by the output of an electrical circuit which creates an electric field within the hydraulic circuit. The electric field will cause the viscosity of the electro-rheological fluid which is exposed to the electric field to increase or decrease in accordance with the magnitude of the electric field. The increase in viscosity of the electro-rheological fluid as it flows through the actuator provides an active damping force on the actuator which allows a more precise control of the output motions of the actuator.

What we claim as the invention is: 
     
       1. An electro-rheological fluid damped actuator comprising: a housing defining at least two chambers;   a moveable element disposed in each of said chambers further isolating and defining separate hydraulic chambers and pneumatic chambers;   a plurality of pneumatic inlet valves in communication with said pneumatic chambers and further adapted for accepting a supply of pressurized gases for moving said moveable element to a commanded position;   an electro-rheological fluid disposed in said hydraulic chambers;   an electro-rheological fluid valve disposed between the hydraulic chambers and in communication therewith, said electro-rheological fluid valve adapted for restricting the flow between said hydraulic chambers, said electro-rheological fluid valve in combination with said electro-rheological fluid provides an active and variable damping force on said moveable element; and   an electrical circuit an output of which creates an electric field within said electro-rheological fluid valve such that said electro-rheological fluid passing through said fluid control valve encounters said electric field whereby the viscosity of said electro-rheological fluid exposed to said electric field is varied in accordance with the magnitude of said electric field.   
     
     
       2. The electro-rheological fluid damped actuator of claim 1 wherein said moveable element is a piston and rod assembly. 
     
     
       3. The electro-rheological fluid damped actuator of claim 1 wherein said actuator further comprises a position sensor which generates a signal corresponding to the position of a control surface with respect to a control surface axis, said control surface operatively controlled by said actuator. 
     
     
       4. The electro-rheological fluid damped actuator of claim 3 wherein said electrical circuit further comprises: an inverter circuit having an position command signal corresponding to a commanded position of said actuator as input to said inverter circuit, said inverter circuit further reversing a sign of said position command signal thereby producing a reversed position command signal as an output;   a summer circuit adapted for receiving said reversed command signal as an input, said summer circuit adapted for scaling said reversed command signal and adding said scaled reversed command signal with said actual position signal to produce a summer circuit signal;   a comparitor circuit adapted for receiving said summer circuit signal and comparing said summer circuit signal resulting to a reference signal to determine if said actuator has moved to said commanded position, said comparitor circuit further adapted to forward a comparitor circuit signal as an output; and   an amplifier adapted for receiving said comparitor circuit signal and forwarding a high voltage output signal to said electro-rheological fluid valve.   
     
     
       5. An electro-rheological fluid damped actuator for controlling the orientation and displacement of a control surface with respect to a control surface axis, said actuator comprising: a cylindrical housing defining at least two interior chambers;   a piston and rod assembly movably disposed in said interior chambers further isolating and defining separate hydraulic chambers and pneumatic chambers, said piston and rod assembly further operatively connected to said control surface such that any movement of said piston and rod assembly causes a corresponding movement of said control surface to a commanded position with respect to said control surface axis;   a plurality of pneumatic inlet valves in communication with said pneumatic chambers and further adapted for accepting a supply of pressurized gases for moving said piston and rod assembly to a predetermined position;   a position sensor which generates a signal corresponding to the position of said control surface with respect to said control surface axis;   a electro-rheological fluid valve disposed between the hydraulic chambers and in communication therewith, said electro-rheological fluid valve adapted for restricting the flow between said hydraulic chambers;   an electro-rheological fluid disposed in said hydraulic chambers and in said electro-rheological fluid valve, said electro-rheological fluid flow further provides an active and variable damping force on said piston and rod assembly; and   an electrical circuit having a plurality of input signals and an output signal, said input signals include said position sensor signal and another signal corresponding to said commanded position to which said actuator is commanded, said output signal creates an electric field proximate said electro-rheological fluid valve whereby the viscosity of said electro-rheological fluid exposed to said electric field is varied in accordance with the magnitude of said electric field.   
     
     
       6. The electro-rheological fluid damped actuator of claim 5 wherein said electrical circuit further comprises: an inverter circuit having an position command signal corresponding to a commanded position of said actuator as input to said inverter circuit, said inverter circuit further reversing a sign of said position command signal thereby producing a reversed position command signal as an output;   a summer circuit adapted for receiving said reversed command signal as an input, said summer circuit adapted for scaling said reversed command signal and adding said scaled reversed command signal with said actual position signal to produce a summer circuit signal;   a comparitor circuit adapted for receiving said summer circuit signal and comparing said summer circuit signal resulting to a reference signal to determine if said actuator has moved to said commanded position, said comparitor circuit further adapted to forward a comparitor circuit signal as an output; and   an amplifier adapted for receiving said comparitor circuit signal and forwarding a high voltage output signal to said electro-rheological fluid valve.   
     
     
       7. A method for damping an actuator, said actuator comprising a cylindrical housing defining at least two interior chambers and further having moveable elements disposed in each said chamber further isolating and defining separate hydraulic chambers and pneumatic chambers, the movement of said moveable elements in response to pneumatic forces controls the orientation and displacement of a control surface with respect to a control surface axis, and method of damping comprising the steps of: placing a position sensor proximate said control surface which generates a signal corresponding to a position of said control surface with respect to said control surface axis;   inserting a electro-rheological fluid valve between the hydraulic chambers and in communication therewith, said electro-rheological fluid valve adapted for restricting the flow between said hydraulic chambers;   filling said hydraulic chambers and said electro-rheological fluid valve with an electro-rheological fluid whereby said electro-rheological fluid flow provides an active and variable damping force on said moveable elements; and   connecting an electrical circuit having a plurality of input signals and an output signal to said electro-rheological fluid valve, said input signals include said position sensor signal and another signal corresponding to a position to which said actuator is commanded, said output signal creates an electric field proximate said electro-rheological fluid valve whereby the viscosity of said electro-rheological fluid exposed to said electric field is varied in accordance with a magnitude of said electric field, which in turn restricts and hydraulic flow through said electro-rheological fluid valve to achieve a damping effect.