Miniature Optical Joint Measurement Sensor for Robotic Application Using Curvature-Based Reflecting Surfaces

The miniaturization of robotic applications, such as flexible manipulators or robotic prosthetics, while maintaining high-precision closed-loop position control, faces the challenge of integrating all their mechanisms, sensors, and actuators within a limited space. For this reason, position sensors are usually installed outside the actuated joints, by for example using a wire (tendon)-driven system. In this case, high-precision position control may not be guaranteed due to wire slack or wire deformation caused by high tension. As such, this letter presents an optoelectronic-based joint measurement sensor capable of not only being integrated directly within joints of a versatile range of robotic applications, but also enhancing further miniaturization of these robot applications. Using a variable thickness reflecting surface for proximity-based intensity modulation, the proposed sensing system is shown to be able to measure a larger angular range of [0°–140°], with increased sensitivity (0–3.5 V) along with investigation of a light intensity model for estimation of sensor output.