Multi-sensor integration and fusion for control of Multi-DOF spherical motion platform

Abstract

This paper presents to develop multi-sensor integration and fusion for controlling a multi-degree-of-freedom (DOF) spherical motion platform (SMP) by utilizing four compliant spherical wheels. A cockpit sphere is not directly connected to a motion basis but spherical spheres with the compliant mechanism. The compliant wheel enables the SMP to achieve not only six-DOF motion, including unlimited rotational motion, but also reliable contact. However, it is difficult to measure the orientation of the cockpit without mechanical joints, unlike other existing platforms. Optical sensors and an inertial measurement unit (IMU) offer contact-free measurements, and sensor fusion is applied to compensate for accumulated errors of the IMU and data loss of the optical sensor, where a compliant mechanism helps contact distance between the cockpit and optical sensor to be maintained uniformly. A set of loadcell sensors enables to measure an unbalanced weight distribution incurring slipping and a further decline in control performance. Moreover, a control system with a multi-sensing system is designed to deal with disturbances and uncertainties, including coupled rotation. The experimental results of sensing and control operations validate that SMP can be applied to the virtual reality industry as motion simulators.