Patent US 5,487,437

A turning control system for an electric vehicle includes a differential filter which receives a signal indicative of a desired vehicle steer angle and generates a pair of signals representative of proportional speed and direction at a left and a right drive wheel of the vehicle. Speed limit factors generated by an angular speed limit filter and an operator set throttle control are applied to the signals indicative of proportional speeds to generate desired proportional speed signals. The desired proportional speed signals are applied to a motor coupling controller along with signals indicating the actual motor speeds. Error signals representative of the difference between the desired speed and the actual speed of each motor are scaled and integrated to generate lag signals (representative of accumulated error) and the lag signal of one motor is applied to the desired proportional speed signal of the other motor to generate coupled control signals which are applied to respective left and right motor control circuits.