Compact and robust load and moment sensor

Abstract

The present invention relates to a load and moment sensor for a prosthetic device detecting load in a single direction and moment in a single plane. The load and moment sensor includes a sensing element, and a plurality of strain gauges placed in specific locations of the sensing element. The plurality of strain gauges is part of a plurality of resistor circuits such as Wheatstone bridges. While the strain gauges can be located on a single sensing element, some resistive elements of the Wheatstone bridges can be located elsewhere on the prosthetic device. The combination of the location of the strain gauges and the use of the Wheatstone bridges allows for good side load rejection which is load and moment not in the single direction or the single plane.

What is claimed is: 
     
         1 . A load and moment sensor comprising:
 a sensing element;   a first resistor circuit including a first plurality of strain gauges located on the sensing element on a first plane, wherein the first resistor circuit detects a moment in a single plane; and   a second resistor circuit including a second plurality of strain gauges located on the sensing element on a second plane perpendicular to the first plane, wherein the second resistor circuit detects a load in a single direction.   
     
     
         2 . The sensor of  claim 1  wherein the first plurality of strain gauges includes a first strain gauge, a second strain gauge, a third strain gauge, and a fourth strain gauge. 
     
     
         3 . The sensor of  claim 2  wherein the first strain gauge, the second strain gauge, the third strain gauge, and the fourth strain gauge provide an output that represents a magnitude of a moment applied to the load and moment sensor. 
     
     
         4 . The sensor of  claim 2  wherein a first voltage is generated using the first strain gauge and the third strain gauge, a second voltage is generated using the second strain gauge and the fourth strain gauge, and a voltage differential between the first voltage and the second voltage is used to determine a moment applied to the load and moment sensor. 
     
     
         5 . The sensor of  claim 1  wherein the sensing element includes a mounting surface, and the first plane is parallel to the mounting surface. 
     
     
         6 . The sensor of  claim 1  wherein the sensing element includes a mounting surface, and the first plane is perpendicular to the mounting surface. 
     
     
         7 . The sensor of  claim 1  wherein the second plurality of strain gauges includes a first strain gauge, a second strain gauge, a third strain gauge, and a fourth strain gauge. 
     
     
         8 . The sensor of  claim 7  wherein the first strain gauge, the second strain gauge, the third strain gauge, and the fourth strain gauge provide an output that represents a magnitude of a load applied to the load and moment sensor. 
     
     
         9 . The sensor of  claim 7  wherein a first voltage is generated using the first strain gauge and the third strain gauge, a second voltage is generated using the second strain gauge and the fourth strain gauge, and a voltage differential between the first voltage and the second voltage is used to determine a load applied to the load and moment sensor. 
     
     
         10 . The sensor of  claim 1  wherein the first plurality of strain gauges and the second plurality of strain gauges include semiconductor strain gauges. 
     
     
         11 . A load and moment sensor comprising:
 a sensing element;   a first Wheatstone bridge including
 a first strain gauge, 
 a second strain gauge, 
 a third strain gauge, and 
 a fourth strain gauge, 
 wherein the first strain gauge, the second strain gauge, the third strain gauge, and the fourth strain gauge are located on the sensing element in a first plane, and the first Wheatstone bridge detects a moment in a single plane; and 
   a second Wheatstone bridge including
 a fifth strain gauge, 
 a sixth strain gauge, 
 a seventh strain gauge, and 
 an eighth strain gauge, 
 wherein the fifth strain gauge, the sixth strain gauge, the seventh strain gauge, and the eighth strain gauge are located on the sensing element in a second plane perpendicular to the first plane, and the second Wheatstone bridge detects a load in a single direction. 
   
     
     
         12 . The sensor of  claim 11  wherein the first strain gauge, the second strain gauge, the third strain gauge, and the fourth strain gauge provide an output that represents a magnitude of a moment applied to the load and moment sensor. 
     
     
         13 . The sensor of  claim 11  wherein a first voltage is generated using the first strain gauge and the third strain gauge, a second voltage is generated using the second strain gauge and the fourth strain gauge, and a first voltage differential between the first voltage and the second voltage is used to determine a moment applied to the load and moment sensor. 
     
     
         14 . The sensor of  claim 11  wherein the fifth strain gauge, the sixth strain gauge, the seventh strain gauge, and the eighth strain gauge provide an output that represents a magnitude of a load applied to the load and moment sensor. 
     
     
         15 . The sensor of  claim 11  wherein a third voltage is generated using the fifth strain gauge and the seventh strain gauge, a fourth voltage is generated using the sixth strain gauge and the eighth strain gauge, and a second voltage differential between the third voltage and the fourth voltage is used to determine a load applied to the load and moment sensor. 
     
     
         16 . The sensor of  claim 11  wherein the first strain gauge, the second strain gauge, the third strain gauge, the fourth strain gauge, the fifth strain gauge, the sixth strain gauge, the seventh strain gauge, and the eighth strain gauge are semiconductor strain gauges. 
     
     
         17 . A method for determining a load and a moment applied to a load and moment sensor comprising:
 using a first set of strain gauges located on a sensing element on a first plane to measure a moment applied to the load and moment sensor; and   using a second set of strain gauges located on the sensing element on a second plane perpendicular to the first plane to measure a load applied to the load and moment sensor.   
     
     
         18 . The method of  claim 17  wherein the moment is in a single plane, and the load is in a single direction. 
     
     
         19 . The method of  claim 17   wherein using the first set of strain gauges to measure the moment applied to the load and moment sensor includes using the first set of strain gauges to provide an output that represents the magnitude of the moment applied to the load and moment sensor, and   wherein using the second set of strain gauges to measure the load applied to the load and moment sensor includes using the second set of strain gauges to provide an output that represents the magnitude of the load applied to the load and moment sensor.   
     
     
         20 . The method of  claim 17   wherein using the first set of strain gauges to measure the moment applied to the load and moment sensor includes generating a first voltage and a second voltage from the first set of strain gauges, and generating a first voltage differential between the first voltage and the second voltage to determine the moment applied to the load and moment sensor, and   wherein using the second set of strain gauges to measure the load applied to the load and moment sensor includes generating a second voltage and a third voltage from the second set of strain gauges, and generating a second voltage differential between the third voltage and the fourth voltage to determine the load applied to the load and moment sensor.   
     
     
         21 . The sensor of  claim 11 , wherein the sensing element includes a mounting surface, and the first plane is parallel to the mounting surface.