Linear-acting controllable pneumatic motion control apparatus and control method therefor

Abstract

A controllable pneumatic apparatus including a pneumatic actuator coupled with a linear-acting brake including a field responsive medium. The pneumatic actuator has a housing with a gas cavity, a first piston slidably disposed in the gas cavity subdividing the gas cavity into first and second gas chambers, and an output member coupled to the first piston. The linear-acting controllable brake includes a medium containing cavity subdivided into a first and second chambers, and a second piston rigidly interconnected with, and longitudinally aligned with, the first piston. A passageway interconnects the first and the second chambers and a field responsive medium (e.g., a magnetic fluid) is contained in the passageway. A field generator produces a field to change a rheology of the medium and cause a braking force to be applied to the output member to control motion thereof. A preferable control method implements motion control based upon the kinetic energy and the braking force in the system.

What is claimed is:  
     
         1 . A controllable pneumatic apparatus, comprising: 
 (a) a pneumatic actuator including a housing with a gas cavity formed therein, a first piston slidably disposed in the gas cavity subdividing the gas cavity into first and a second gas chambers, and an output member coupled to the first piston;    (b) a controllable brake coupled to the actuator, the brake comprising a medium containing cavity subdivided into a first and second chambers, a second piston rigidly interconnected with, and longitudinally aligned with, the first piston and moveable in the cavity along an axial axis, a passageway interconnecting the first and the second chambers, a field responsive medium contained in the passageway, a field generator for producing a field to change a rheology of the medium upon exposure to the field causing a braking force to be applied to the output member to control motion thereof; and    (c) A control system, comprising a sensor for providing a signal representative of a motion of a moving component of the apparatus, and a motion control for processing the signal and providing a control signal to the brake thereby controlling at least one motion selected from a group consisting of a position, velocity and acceleration of the output member.    
     
     
         2 . The apparatus of  claim 1  wherein the motion comprises a position, velocity or acceleration.  
     
     
         3 . The apparatus of  claim 1  wherein the sensor comprises a position sensor.  
     
     
         4 . The apparatus of  claim 1  wherein said apparatus is controlled according to a method, comprising the steps of: 
 (a) inputting desired motion information for the output member to said pneumatic and motion controls from an input,  
 (b) measuring with a sensor an instantaneous motion of the output member and providing a measured motion signal, and  
 (c) processing the measured motion signal and the desired motion information within the pneumatic and motion controls and providing control signals to the pneumatic actuator to control the supply of differential pressure and to activate the controllable brake.  
 
     
     
         5 . The apparatus of  claim 4  wherein the pneumatic actuator is turned off and the controllable brake is activated within a tolerance band about a desired axial position.  
     
     
         6 . A controllable pneumatic apparatus, comprising: 
 (a) a pneumatic system, including a housing having a gas cavity formed therein, a first piston slidably disposed in the gas cavity subdividing the gas cavity into a first gas chamber and a second gas chambers, a pressure source providing a supply of pressurized gas, a pneumatic control which controls a pneumatic valve to apportion the supply of pressure to the first and second gas chambers thereby providing differential pneumatic pressure to move the first piston along an axial axis, and an output member coupled to the first piston,    (b) a controllable brake, including a medium containing cavity, a second piston subdividing the medium containing cavity into a first medium chamber and a second medium chamber, the second piston being longitudinally aligned with the first piston and rigidly interconnected by an interconnecting shaft to the first piston, the second piston moveable in the cavity along the axial axis, a passageway interconnecting the first and the second medium chambers, a magnetically controllable fluid contained in the passageway, a field generator further including a coil for producing a magnetic field to change a rheology of the fluid upon exposure to the magnetic field,    (c) a motion sensor for providing a motion signal representative of a motion of the output member, and    (d) a control system for processing the motion signal and providing a control signal to the controllable brake thereby controlling motion of the output member.    
     
     
         7 . A method of controlling a controllable pneumatic apparatus, comprising the steps of: 
 (a) providing a pneumatic actuator which causes motion of an output member,    (b) providing a controllable brake coupled to the output member,    (c) providing a control system for controlling the pneumatic actuator and the controllable brake,    (d) inputting system performance information to the control system,    (e) measuring a motion of the output member and providing a motion signal, and    (f) processing the motion signal and the desired motion information within the control system and providing control signals to control the pneumatic actuator and to activate the controllable brake, said processing being based upon a kinetic energy.    
     
     
         8 . A method of  claim 7  wherein said measuring step further comprises measuring an axial position of said output member.  
     
     
         9 . A method of  claim 7  further comprising an additional step of obtaining a velocity.  
     
     
         10 . A method of  claim 9  wherein the velocity is obtained based upon the axial position.  
     
     
         11 . A method of  claim 7  wherein the system performance information comprises desired motion information of the output member.  
     
     
         12 . A method of  claim 11  wherein the desired motion information further comprises a desired stopping position.  
     
     
         13 . A method of  claim 11  wherein the desired motion information further comprises a desired accuracy.  
     
     
         14 . A method of  claim 11  wherein the desired motion information further comprises a desired velocity.  
     
     
         15 . A method of  claim 11  wherein the desired motion information further comprises a desired velocity profile.  
     
     
         16 . A method of  claim 11  wherein the desired motion information further comprises a desired acceleration profile.  
     
     
         17 . A method of  claim 7  wherein the system performance information comprises a mass of moving system elements.  
     
     
         18 . A method of  claim 7  wherein the system performance information comprises a braking force available from the controllable brake.  
     
     
         19 . A method of  claim 7  wherein the system performance information comprises a braking force available from the controllable brake, a mass of any moving system components and desired motion information of the output member.  
     
     
         20 . A method of  claim 7  wherein the system performance information comprises a braking force available from the controllable brake, a mass of all moving system components, a desired stopping position of the output member and a desired accuracy.  
     
     
         21 . A method of  claim 7  wherein the system performance information comprises a braking force available from the controllable brake, a mass of all moving system components, a desired stopping position of the output member and a desired accuracy.  
     
     
         22 . A method of  claim 7  wherein the processing is further based upon an available braking force.  
     
     
         23 . A method of  claim 7  wherein a shut down point is determined based upon the kinetic energy and the available braking force.  
     
     
         24 . A method of  claim 7  wherein a shut down point for activation of the brake and shut down of the pneumatic actuator to stop the output member at the desired stopping position is determined based upon the equation:  
       
         
           
             
               
                 
                   Δ 
                    
                   
                       
                   
                    
                   x 
                 
                 = 
                 
                   
                     mv 
                     2 
                   
                   
                     2 
                      
                     
                       F 
                       mr 
                     
                   
                 
               
               , 
             
           
           
           
               
           
         
       
       where Δx is the distance from the shut down point to the desired stopping position, m is the mass of any moving system components, v is the velocity at the stopping point and F mr  is the available braking force.  
     
     
         25 . A method of  claim 7  wherein the controllable brake contains a field responsive fluid.  
     
     
         26 . A method of controlling a controllable pneumatic system, comprising the steps of: 
 (a) providing a pneumatic actuator which, when provided with a supply of differential pressure, moves a position of an output member,    (b) providing a controllable brake coupled to the output member,    (c) providing a control system to control the pneumatic actuator and the controllable brake,    (d) inputting desired motion information for the output member to the control system from a input,    (e) measuring with a sensor a motion of the output member and providing a measured motion signal, and    (f) processing the measured motion signal and the desired motion information within the control system and providing control signals to control the pneumatic actuator and to activate the controllable brake, the processing being based upon a kinetic energy.    
     
     
         27 . A motion control apparatus, comprising: 
 (a) a pneumatically controlled actuator including a housing with a gas cavity formed therein, a first piston slidably disposed in the gas cavity, the first piston subdividing the gas cavity into first and a second gas chambers, and an output member coupled to the first piston, the output member being movable in response to movement of the first piston, the first piston being movable along an axial axis of the housing as a result of a differential pressure between the first and second chambers; and    (b) a controllable brake for controlling the motion of the output member, the brake being coupled to the pneumatically controlled actuator, the brake including a medium containing cavity subdivided into a first and second chambers, a second piston rigidly interconnected with the first piston and moveable in the medium containing cavity along said axial axis, a passageway interconnecting the first and the second chambers, a field responsive medium contained in the chambers and passageway, a field generator for producing a field to change the rheology of the field responsive medium in the passageway upon exposure to the field causing a braking force to be applied to the output member to control motion thereof.