Dual-Laser Goniometer: A Flexible Optical Angular Sensor for Joint Angle Measurement

This article presents a flexible optical goniometer for the measurement of single-axis joint angular displacement. The design philosophy behind the apparatus lies that the agent's angular displacement is converted to the laser's distance measurement thanks to geometric conversion. We propose a dual-laser ranging model for joint angle measurement with the aid of a reference plane. This model converts the agent's rotational angle to the distance of laser range measurements under triangular constraints. Compared with the commonly used rotary encoders, the proposed sensor shows its competence in easy installation and flexible deployment. Furthermore, a model parameter calibration approach is introduced to decrease the angular measurement error. Extensive validation experiments with a prototype sensor on a robot arm prove the aforementioned claims and show that the prototype sensor can reach an angular precision of 0.3° with a measurement range of -30°-30°.