Brake Position Control of Electric Mover Based on the Disturbance Force Observer

Although the heavy non-powered trailer can be easily moved and driven by the prime traction vehicle, positioning and parking are not easy. This is because it requires highly skilled driving skills. The electric mover system can drive the heavy non-powered trailer itself without a prime vehicle using the electric driven roller at the trailer wheel. During the driving mode, the mover roller is detached from the trailer wheel to reduce the traction vehicle load. The roller is solid-firmed to the trailer tire and then rotates the trailer wheel by the electric motor to adjust the parking position during the parking mode.

To suppress the proper friction between the mover roller and trailer tire, the actuator motor has to be stopped at the proper braking point of the roller. And, this can be implemented by the actuator motor current detection. A simple over-current with the holding time is generally used to determine the actuator braking point between the roller and the tire. The conventional over-current detection is very simple and powerful, but the actual frictions at each tire are not similar due to the load and operating conditions of each side mover. The different frictions at each side tire increase the motion and moving errors at the actual positioning and parking motion.

To balance the friction between the mover rollers and each tire, the non-linear disturbance force observer based on the sensorless speed estimation of the actuator motor is proposed. To keep the same friction force, the actuator motors are stopped at the same pre-fixed friction level using the estimated disturbance force and estimated actuator motor speed.

Compared to the conventional over-current holding time method, the proposed method shows improved friction control performance at each wheel and mover roller. And, the moving torques are improved due to the balanced friction.