Development of Electronics and Control for Servo Actuators in Robotic Applications

Abstract

Servo actuators are integrated mechatronic drives for applications with high demands in dynamic response and positioning accuracy. In robotic applications, servo actuators are applied for fast and precise positioning of joint axes, manipulators or sensors. The drives have to be able to move to the desired positions without any overshoot and need to provide high stead-state accuracy despite fast changes in load torque and disturbances. In the course of this thesis, improved electronics and advanced control for the widely used RX-28 and RX-64 servo actuators of the Dynamixel series produced by Robotis were developed and evaluated. The enhanced electronic setup improves the operating characteristics and eliminates design related deficiencies of the original servo actuators. The essential improvements comprise increased measurement accuracy, computational capability and power efficiency. The advanced control concept introduces a tracking control with a highly adjustable desired trajectory for an individual control of the angular position and speed. The used trajectory generation allows to customize the desired actuator motion and the applied state observer provides an accurate estimation of relevant actuator values. For the implementation of the tracking control, a novel model predictive control strategy was proposed and compared to a loop-shaping control with a conditional anti-windup scheme. By applying the designed electronic setup and control concept, the enhanced DD-28 and DD-64 servo actuators become universal and capable drives for small and medium scaled robotic applications with an increased performance and durability.