Retroreflective Multi-Axis Force Torque Sensor

Abstract

The present application discloses implementations that relate to devices and techniques for sensing position, force, and torque. Devices described herein may include a light emitter, photodetectors, and a curved reflector. The light emitter may project light onto the curved reflector, which may reflect portions of that projected light onto one or more of the photodetectors. Based on the illuminances measured at the photodetectors, the position of the curved reflector may be determined. In some implementations, the curved reflector and the light emitter may be elastically coupled via one or more spring elements; in these implementations, a force vector representing a magnitude and direction of a force applied against the curved reflector may be determined based on the position of the curved reflector.

1 . A device comprising:
 a first rigid structure;   a second rigid structure elastically coupled to the first rigid structure by a spring element such that the first rigid structure is moveable in six degrees of freedom relative to the second rigid structure;   a curved reflector fixed to a surface of the first rigid structure;   three or more photodetectors each operable to measure an illuminance of light incident on the photodetector, wherein each of the three or more photodetectors is fixed to a surface of the second rigid structure; and   a light emitter operable to project light toward the curved reflector, wherein the curved reflector reflects respective portions of the projected light onto the three or more photodetectors, wherein the light emitter and the three or more photodetectors are fixed with respect to each other, and wherein the first rigid structure is movable in six degrees of freedom with respect to the light emitter and the three or more photodetectors.   
     
     
         2 . The device of  claim 1 , comprising three or more curved reflectors fixed to the surface of the first rigid structure. 
     
     
         3 . The device of  claim 1 , wherein the first rigid structure is composed of substantially nonreflective material. 
     
     
         4 . The device of  claim 1 , wherein the second rigid structure is a printed circuit board. 
     
     
         5 . The device of  claim 1 , wherein the three or more photodetectors and the light emitter are substantially coplanar. 
     
     
         6 . The device of  claim 1 , further comprising:
 a fourth photodetector operable to measure a calibration illuminance indicative of a luminance of the light emitter, wherein the calibration illuminance is not affected by a position of the first rigid structure relative to the second rigid structure.   
     
     
         7 . A robotic system comprising a sensor located within the robotic system, the sensor comprising:
 a first rigid structure;   a second rigid structure elastically coupled to the first rigid structure by a spring element such that the first rigid structure is moveable in six degrees of freedom relative to the second rigid structure;   a curved reflector fixed to a surface of the first rigid structure;   three or more photodetectors each operable to measure an illuminance of light incident on the photodetector, wherein each of the three or more photodetectors is fixed to a surface of the second rigid structure; and   a light emitter operable to project light toward the curved reflector, wherein the curved reflector reflects respective portions of the projected light onto the three or more photodetectors, wherein the light emitter and the three or more photodetectors are fixed with respect to each other, and wherein the first rigid structure is movable in six degrees of freedom with respect to the light emitter and the three or more photodetectors.   
     
     
         8 . The robotic system of  claim 7 , wherein the sensor comprises three curved reflectors spaced out on the surface of the first rigid structure. 
     
     
         9 . The robotic system of  claim 7 , further comprising a robotic arm, wherein the robotic system is configured to control the robotic arm based on force information from the sensor. 
     
     
         10 . The robotic system of  claim 7 , wherein the first rigid structure is composed of substantially nonreflective material. 
     
     
         11 . The robotic system of  claim 7 , wherein the second rigid structure is a printed circuit board. 
     
     
         12 . The robotic system of  claim 7 , wherein the three or more photodetectors and the light emitter are substantially coplanar. 
     
     
         13 . The robotic system of  claim 7 , wherein the sensor further comprises:
 a fourth photodetector operable to measure a calibration illuminance indicative of a luminance of the light emitter, wherein the calibration illuminance is not affected by a position of the first rigid structure relative to the second rigid structure.   
     
     
         14 . A device comprising:
 a first rigid structure;   a second rigid structure elastically coupled to the first rigid structure by a spring element such that the first rigid structure is movable in six degrees of freedom relative to the second rigid structure;   a plurality of curved reflectors coupled to a surface of the first rigid structure; and   a plurality of optical sensor assemblies coupled to a surface of the second rigid structure, wherein each optical sensor assembly of the plurality of optical sensor assemblies is aligned with a respective curved reflector of the plurality of curved reflectors, and further wherein each of the optical sensor assemblies comprises:
 three or more photodetectors each operable to measure an illuminance of light incident on the photodetector; and 
 a light emitter operable to project light towards the respective curved reflector aligned with the respective sensor assembly, wherein the curved reflector reflects respective portions of the projected light onto the three or more photodetectors. 
   
     
     
         15 . The device of  claim 14 , wherein the plurality of curved reflectors comprises three curved reflectors spaced out on the surface of the first rigid structure, and further wherein the plurality of optical sensor assemblies comprises three optical sensor assemblies, wherein each of the three optical sensor assemblies is aligned with one of the three curved reflectors. 
     
     
         16 . The device of  claim 14 , wherein the first rigid structure is composed of substantially nonreflective material. 
     
     
         17 . The device of  claim 14 , wherein the second rigid structure is a printed circuit board. 
     
     
         18 . The device of  claim 14 , wherein, for each of the plurality of optical sensor assemblies, the three or more photodetectors and the light emitter are substantially coplanar. 
     
     
         19 . The device of  claim 14 , wherein at least one of the plurality of optical sensor assemblies further comprises:
 a fourth photodetector operable to measure a calibration illuminance indicative of a luminance of the light emitter, wherein the calibration illuminance is not affected by a position of the first rigid structure relative to the second rigid structure.   
     
     
         20 . The device of  claim 14 , wherein the device is integrated into a robotic arm.