Hydraulic actuator with pressure-based piston position feedback

Abstract

A hydraulic actuator includes a piston housing having a head end and a base end opposite the head end and a drive piston movable between a first piston position proximate to the head end and a second piston position proximate to the base end. The hydraulic actuator further includes a control valve positionable between a first control valve position, in which the control valve directs fluid into the base end, and a second control valve position, in which the control valve directs fluid into the head end. A pressure-based position feedback system configured to facilitate transition of the control valve between the first control valve position and the second control valve position in response to predetermined head end and base end pressures.

What is claimed is: 
     
         1 . A hydraulic actuator comprising:
 a piston housing having a head end and a base end opposite said head end;   a drive piston disposed within said piston housing and movable between a first piston position proximate to said head end and a second piston position proximate to said base end;   a control valve positionable between a first control valve position and a second control valve position, wherein:
 in the first control valve position, said control valve is configured to direct fluid into said base end; and 
 in the second control valve position, said control valve is configured to direct fluid into said head end; and 
   a pressure-based position feedback system comprising:
 a first pressure actuated valve coupled in fluid communication with said head end, said first pressure actuated valve configured to facilitate transition of said control valve from the first control valve position to the second control valve position in response to a predetermined head end pressure; and 
 a second pressure actuated valve coupled in fluid communication with said base end, said second pressure actuated valve configured to facilitate transition of said control valve from the second control valve position to the first control valve position in response to a predetermined base end pressure. 
   
     
     
         2 . The actuator in accordance with  claim 1 , wherein at least one of said first pressure actuated valve and said second pressure actuated valve is a pilot-operated pressure sequence valve. 
     
     
         3 . The actuator in accordance with  claim 1  further comprising at least one deceleration feature proximate to at least one of said first piston position and said second piston position. 
     
     
         4 . The actuator in accordance with  claim 3 , wherein said at least one deceleration feature comprises at least one of a groove defined by said piston housing, a spring, a hydraulic cushion, and a bumper. 
     
     
         5 . The actuator in accordance with  claim 1 , wherein said control valve comprises at least one of a two-position, detented, four-way directional control valve and a three-position, detented, four-way directional control valve. 
     
     
         6 . The actuator in accordance with  claim 1  further comprising a unitary valve manifold comprising each of said control valve, said first pressure actuated valve, and said second pressure actuated valve. 
     
     
         7 . A downhole pump system comprising:
 a piston rod pump assembly; and   a hydraulic actuator coupled to said piston rod pump assembly, said hydraulic actuator comprising:
 a piston housing having a head end and a base end opposite said head end; 
 a drive piston disposed within said piston housing and movable between a first piston position proximate to said head end and a second piston position proximate to said base end; 
 a control valve positionable between a first control valve position and a second control valve position, wherein:
 in the first control valve position, said control valve is configured to direct fluid into said base end; and 
 in the second control valve position, said control valve is configured to direct fluid into said head end; and 
 
 a pressure-based position feedback system comprising:
 a first pressure actuated valve coupled in fluid communication with said head end, said first pressure actuated valve configured to facilitate transition of said control valve from the first control valve position to the second control valve position in response to a predetermined head end pressure; and 
 a second pressure actuated valve coupled in fluid communication with said base end, said second pressure actuated valve configured to facilitate transition of said control valve from the second control valve position to the first control valve position in response to a predetermined base end pressure. 
 
   
     
     
         8 . The downhole pump system in accordance with  claim 7  further comprising:
 an actuator pump configured to provide fluid to said piston housing through said control valve; and 
 an actuator motor coupled to said actuator pump and configured to drive said actuator pump. 
 
     
     
         9 . The downhole pump system in accordance with  claim 8  further comprising at least one of an accumulator and a compensator bag, coupled in fluid communication with said actuator pump. 
     
     
         10 . The downhole pump system in accordance with  claim 8 , wherein said actuator pump is a positive displacement pump. 
     
     
         11 . The downhole pump system in accordance with  claim 7 , wherein at least one of said first pressure actuated valve and said second pressure actuated valve is a pilot-operated pressure sequence valve. 
     
     
         12 . The downhole pump system in accordance with  claim 7  further comprising at least one deceleration feature proximate to at least one of the first piston position and the second piston position. 
     
     
         13 . The downhole pump system in accordance with  claim 12 , wherein said at least one deceleration feature comprises at least one of a groove defined by said piston housing, a spring, a hydraulic cushion, and a bumper. 
     
     
         14 . The downhole pump system in accordance with  claim 7 , wherein said control valve comprises at least one of a two-position, detented, four-way directional control valve and a three-position, detented, four-way directional control valve. 
     
     
         15 . The downhole pump system in accordance with  claim 7  further comprising a unitary valve manifold comprising each of said control valve, said first pressure actuated valve, and said second pressure actuated valve. 
     
     
         16 . The downhole pump system in accordance with  claim 7 , further comprising a piston rod extending from said drive piston, said piston rod coupling said drive piston to said piston rod pump assembly. 
     
     
         17 . A method of controlling a hydraulic actuator, the hydraulic actuator including a piston housing having a head end and a base end opposite the head end, a drive piston disposed within the piston housing and movable between a first piston position proximate to the head end and a second piston position proximate to the base end, and a control valve positionable between a first control valve position and a second control valve position, said method comprising:
 determining, using a first pressure actuated valve coupled in fluid communication with the head end, a head end pressure exceeds a predetermined head end pressure threshold;   transitioning, in response to determining the head end pressure exceeds the predetermined head end pressure threshold, the control valve into the second control valve position;   determining, using a second pressure actuated valve coupled in fluid communication with the base end, a base end pressure exceeds a predetermined base end pressure threshold; and   transitioning, in response to determining the base end pressure exceeds the predetermined base end pressure threshold, the control valve into the first control valve position.   
     
     
         18 . The method in accordance with  claim 17  further comprising latching the control valve in at least one of the first control valve position and the second control valve position after translating the control valve into the first control valve position and second control valve position, respectively. 
     
     
         19 . The method in accordance with  claim 17 , wherein at least one of the first pressure actuated valve and the second pressure actuated valve is a pilot-operated pressure sequence valve. 
     
     
         20 . The method in accordance with  claim 17 , wherein the first predetermined fluid pressure corresponds to a fluid pressure within the head end when the drive piston is substantially in the first piston position, and the second predetermined fluid pressure corresponds to a fluid within the base end when the drive piston is substantially in the second piston position.