Intelligent Electric Drive System - A Mechatronics Approach

Drive efficiency is an important consideration in most robotic applications. A hybrid controller for permanent magnet DC motors has been developed to control the current, and hence the output torque of the motor. An H bridge is used to provide the basic PWM voltage to the motor, and the controller switches the bridge between bipolar and unipolar modes in order to minimise the switching losses within the bridge and motor, and also to minimise the electromagnetic interference. The first application presented is for a walking robot, and the second is for a dexterous robotic hand. In both cases, control is obtained from a voltage sourced inverter by means of a tight control loop that uses position readings to infer velocity so that a full DC motor model can be utilised in the control computer. For the dexterous hand, current control is by model prediction to avoid the need for direct measurement. The controller and communications are contained within a small programmable system on a chip which together with a dual H bridge driver is integrated into small circuit board that is used for distributed control within the hand.