A three degree-of-freedom optical orientation measurement method for spherical actuator applications

The advance of robotics, actuators and manufacturing technology motivates the research on measurement of multiple degree-of-freedom (DOF) rotational motions. A novel laser-based noncontact high-precision spherical displacement measurement methodology has been proposed for spherical actuator applications in this paper. The laser detector is utilized to measure the distance from the target to the detector on several light spots, and thus to calculate the rotation angle of the rigid body in three directions. As there is no physical contact between the laser detector and the moving body, additional mass/moment of inertia and friction on the rotor are avoided, and thus the working efficiency of moving body can be improved. The algorithm of orientation angles has been derived. Experimental apparatuses have been developed to evaluate the working performance of the measurement method. Comparison between experimental and analytical results shows that the proposed method can achieve high-precision measurement for multi-DOF rotational motions. Precision of the laser-based angular displacement measurement method can be improved further by increasing the slot density on the rigid body or using new models of laser detectors.