Sensorless control of the suspension preload in motorcycles

This paper describes the sensorless control of a motorcycle suspension preload. The aim of the system is to make the suspension work around its optimal operating point, making the vehicle height independent of the load carried. This improves the safety and comfort of the vehicle. The electronic system described here reveals load changes and automatically adjusts the motorcycle suspension preload in order to compensate the load variation, without expensive sensors. The preload is set by means of a DC motor and a worm gear that in its turn regulates the preload hydraulic piston. The basic idea is to monitor the DC motor current during activations and calculate the load torque, which carries information on the actual vehicle load. This allows the feedback chain to be sensorless. Laboratory experiments carried out on a benchmark demonstrate that the system is able to guarantee the same correct functionalities as the sensored prototype, but with a great cost saving.