Electromechanical actuator and method of use

Abstract

Electromechanical actuators for use in a MWD tool in a downhole environment, including actuators having a servo valve, comprising: a rotary actuator having a rotary actuator shaft; and a spring positioned in the servo valve such that movement of the rotary actuator shaft causes the spring to be changed between a first state and a second state, wherein gaps in the structure of the spring vary in size as the spring is changed between the first state and a second state, wherein the gaps act as fluid vents for fluid flow through the servo valve, such that movement of the rotary actuator shaft causes the fluid vents to vary in size and thereby change an amount of fluid flow through the servo valve; and an electronic control assembly configured to detect change in load within the servo valve based on the change in the amount of fluid flow.

What is claimed is: 
     
         1 . An electromechanical actuator for use in a measurement-while-drilling tool in a downhole environment, comprising:
 a servo valve, comprising:
 a rotary actuator having a rotary actuator shaft; and 
 a spring positioned in the servo valve such that movement of the rotary actuator shaft by the rotary actuator causes the spring to be changed between a first state and a second state, wherein gaps in the structure of the spring vary in size as the spring is changed between the first state and a second state, wherein the gaps act as fluid vents for fluid flow through the servo valve, such that movement of the rotary actuator shaft causes the fluid vents to vary in size and thereby change an amount of fluid flow through the servo valve; 
   a valve housing having a wall surrounding the servo valve; and   an electronic control assembly positioned within the valve housing and configured to detect change in load within the servo valve based on the change in the amount of fluid flow caused by the rotary actuator shaft causing the spring to be changed between the first state and the second state.   
     
     
         2 . The electromechanical actuator of  claim 1 , wherein the wall of the valve housing has an exterior surface and an interior surface, and wherein the valve housing has at least one wall fluid vent extending from the exterior surface of the wall to the interior surface of the wall, and wherein one or more of the gaps in the structure of the spring when the spring is in the first state overlap with the at least one wall fluid vent, thereby creating a fluid passage. 
     
     
         3 . The electromechanical actuator of  claim 1 , wherein the wall of the valve housing has an exterior surface and an interior surface, and wherein the valve housing has at least one wall fluid vent extending from the exterior surface of the wall to the interior surface of the wall, and wherein one or more of the gaps in the structure of the spring has a varying overlap area with the at least one wall fluid vent as the spring changes between the first state and the second state, thereby creating a fluid passage with varying flow area as the spring changes between the first state to the second state. 
     
     
         4 . The electromechanical actuator of  claim 3 , wherein the wall of the valve housing has an exterior surface and an interior surface, and wherein the valve housing has at least one wall fluid vent extending from the exterior surface of the wall to the interior surface of the wall, and wherein one or more of the gaps in the structure of the spring has no overlap area with the at least one wall fluid vent when the spring is in the second state, thereby blocking the fluid passage. 
     
     
         5 . The electromechanical actuator of  claim 1 , wherein the spring is linearly in line with the rotary actuator shaft, the electromechanical actuator further comprising:
 a screw attached to the rotary actuator shaft; and   a nut configured to reciprocate linearly along the screw, wherein the spring has a first end that is coupled to the nut.   
     
     
         6 . The electromechanical actuator of  claim 1 , wherein the valve housing has a first end at an upstream end of the valve housing and a second end at a downstream end of the valve housing with the servo valve positioned between the first end and the second end, the valve housing comprising:
 at least one debris vent extending from an exterior surface of the wall to an interior surface of the wall and positioned between the servo valve and the first end of the valve housing.   
     
     
         7 . The electromechanical actuator of  claim 1 , further comprising:
 an electronic control assembly comprising:
 drive circuitry configured to generate drive signals to drive the rotary actuator; and 
 a non-transitory ferroelectric random access memory having a ferroelectric layer configured to store one or more of diagnostic data regarding the servo valve and logging data regarding the servo valve. 
   
     
     
         8 . A method of operating an electromechanical actuator in a measurement-while-drilling pulser in a downhole environment, comprising:
 actuating a servo valve of an electromechanical actuator, the servo valve comprising a spring and a rotary actuator having a rotary actuator shaft, wherein actuating the servo valve causes the rotary actuator to move the rotary actuator shaft which causes the spring to be changed between a first state and a second state, thereby causing gaps in the structure of the spring to vary in size as the spring is changed between the first state and a second state, wherein the gaps act as fluid vents for fluid flow through the servo valve, such that movement of the rotary actuator shaft causes the fluid vents to vary in size and thereby change an amount of fluid flow through the servo valve; and   detect, with an electronic control assembly of the electromechanical actuator, change in load within the servo valve based on the change in the amount of fluid flow caused by the rotary actuator shaft causing the spring to be changed between the first state and the second state.   
     
     
         9 . The method of  claim 8 , wherein the servo valve is located in a valve housing having a wall, and wherein the wall of the valve housing has an exterior surface and an interior surface, and wherein the valve housing has at least one wall fluid vent extending from the exterior surface of the wall to the interior surface of the wall, and wherein one or more of the gaps in the structure of the spring when the spring is in the first state overlap with the at least one wall fluid vent, thereby creating a fluid passage. 
     
     
         10 . The method of  claim 8 , wherein the servo valve is located in a valve housing having a wall, wherein the wall of the valve housing has an exterior surface and an interior surface, and wherein the valve housing has at least one wall fluid vent extending from the exterior surface of the wall to the interior surface of the wall, and wherein one or more of the gaps in the structure of the spring has a varying overlap area with the at least one wall fluid vent as the spring changes between the first state and the second state, thereby creating a fluid passage with varying flow area as the spring changes between the first state to the second state. 
     
     
         11 . The method of  claim 10 , wherein the wall of the valve housing has an exterior surface and an interior surface, and wherein the valve housing has at least one wall fluid vent extending from the exterior surface of the wall to the interior surface of the wall, and wherein one or more of the gaps in the structure of the spring has no overlap area with the at least one wall fluid vent when the spring is in the second state, thereby blocking the fluid passage. 
     
     
         12 . The method of  claim 8 , wherein the spring is linearly in line with the rotary actuator shaft, the electromechanical actuator further comprising:
 a screw attached to the rotary actuator shaft; and   a nut rotatably connected to the screw, wherein the spring has a first end that is coupled to the nut, such that when the rotary actuator shaft moves, the nut reciprocates linearly along the screw, thereby causing the spring to be changed between the first state and the second state.   
     
     
         13 . The method of  claim 8 , wherein the servo valve is located in a valve housing having a wall, wherein the valve housing has a first end at an upstream end of the valve housing and a second end at a downstream end of the valve housing with the servo valve positioned between the first end and the second end, the valve housing comprising:
 at least one debris vent extending from an exterior surface of the wall to an interior surface of the wall and positioned between the servo valve and the first end of the valve housing.   
     
     
         14 . The method of  claim 8 , wherein the electromechanical actuator comprises an electronic control assembly, comprising drive circuitry and a non-transitory ferroelectric random access memory having a ferroelectric layer, the method comprising:
 generating, with the drive circuitry, drive signals to drive the rotary actuator; and   storing, in the non-transitory ferroelectric random access memory, one or more of diagnostic data regarding the servo valve and logging data regarding the servo valve.   
     
     
         15 . An electromechanical actuator, comprising:
 a rotary actuator; and   an electronic control assembly comprising:
 drive circuitry configured to generate drive signals to drive the rotary actuator; and 
 a non-transitory ferroelectric random access memory having a ferroelectric layer configured to store one or more of diagnostic data regarding the rotary actuator and logging data regarding the rotary actuator.