Retroreflective multi-axis force torque sensor

A method comprising:

• causing a light emitter to project light toward a curved reflector, wherein the curved reflector is fixed to a surface of a first rigid structure and the light emitter is fixed to a surface of a second rigid structure, and further wherein the first rigid structure is elastically coupled to the second rigid structure by a flexure element such that the first rigid structure is movable in six degrees of freedom relative to the second rigid structure;
• measuring, by three or more photodetectors fixed to the surface of the second rigid structure, three or more illuminances of light incident on the respective three or more photodetectors, wherein each illuminance represents an intensity of a portion of the projected light that reflects off the curved reflector and is incident on a respective photodetector;
• determining, based on the three or more measured illuminances, a displacement of the first rigid structure or the second rigid structure in one or more degrees of freedom with respect to a reference position of either the first rigid structure or the second rigid structure respectively, wherein the reference position is based on a spatial location of the curved reflector when the flexure is at equilibrium;
• determining, based on the determined displacement and a relationship between displacement and force, a force vector of a force applied against at least one of the first rigid structure or the second rigid structure, wherein the force vector comprises a magnitude and a direction of the applied force;
• and
• providing an output signal indicative of the force vector.

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 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;
• 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 one 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;
• and
• at least one processor configured to perform operations comprising:
• measuring, by each optical sensor assembly of the plurality of optical sensor assemblies, an illuminance of the respective portion of projected light incident on the three or more photodetectors of each optical sensor assembly;
• after a force is applied against at least one of the first rigid structure or the second rigid structure, determining, based on an illuminance distribution, a displacement of the first rigid structure or the second rigid structure in one or more degrees of freedom with respect to a reference position of either the first rigid structure or the second rigid structure respectively, wherein the illuminance distribution comprises each of the measured illuminances of each optical sensor assembly;
• determining, based on the determined displacement and a relationship between displacement and force, a force vector of the applied force, wherein the force vector comprises a magnitude and a direction of the applied force;
• and
• adjusting operation of the robotic system based on the determined force vector.