ITEE Innovation Expo 2008 : Project Details

Embedded Controller for a VS-SEA

With a growing interest in the area of robotics that involves human-robot interaction, this field is currently challenged to find ways which allow close contact between human and robot, something which is, at present, prohibited due to safety issues. In order for technology to progress, and enable the dream of having robots help with everyday applications around the home, we must first improve the current safety measures seen in robotic actuation systems, and prove operation to be safe whilst around humans. Most robotic applications use a high impedance actuation system which means a motor is given a position or angle command. This creates problems if the robot’s surroundings are unknown and when it collides with an unfamiliar outer object. In this case, the robot’s control system sends a much larger force to the motor to compensate for the error in expected position. A method of overcoming this problem is the Series Elastic Actuator (SEA) which introduces a spring between the motor-gearbox and load which produces intrinsic low impedance, in the process creating a torque control loop. The Velocity Sourced Series Elastic Actuator (VS-SEA) introduces a tight velocity control loop, and inherently loses any problems associated with stiction and backlash. The aim of this thesis is to implement a new embedded controller system for the VS-SEA, then adapt existing control strategies to the new system. This thesis is working very closely with another thesis to implement the power electronics for the VS-SEA. When complete, these two theses will interact to form one complete robotic actuation and controller system to both drive the motor and to safely control its actions.