Sensor-less hill-assist using traction control in electric LCV

This paper describes the implementation of sensor-less hill-assist control system in electric Light Commercial Vehicle (LCV). In manual transmission vehicles without hill-assist, the restart at the slope can be done through skilled clutch control. For the vehicles not having clutch (auto transmission or fixed gear electric vehicles), the restart of the vehicle at hill is not possible with driver skills alone and needs the hill-assist functionality. It involves the costlier sensors and control mechanism for its implementation. The work aimed at implementing hill-assist functionality without the use of gradient sensor and brake actuators. In the absence of brake actuators the holding torque is provided by the traction motor. The PID controller with parameterized vehicle model in loop calculates the holding torque required. The precise vehicle model for the controller built through vehicle tests. As the PID gains are sensitive to the hill slope and vehicle load, they are indirectly estimated through controlled rollback and precise model of the vehicle implemented in vehicle controller. The estimation slope helps to change the PID parameters online to reduce the speed error as quickly as possible. The modeling, simulation of the hill-assist algorithm is presented. The algorithm is embedded with the existing traction control module of the electric LCV. Test results of the hill-assist operation are presented on comparison with the simulation results.