Modelling and control of an electro-mechanical drum parking brake system for vehicle rollaway prevention

Abstract

The main function of parking brake system is to hold the vehicle stationary on flat or sloped roads. A fully mechanical parking brake (MPB) system seems to have a few drawbacks and rollaway is one of them. A vehicle rolls unintentionally in parking mode when the torque produced by the brake is less than the torque required to hold the vehicle. Rollaway occurs on a MPB-equipped vehicle if the gradient of the road is more than 11.3 degrees and the friction coefficient is less than 0.3. Furthermore, the driver and four passengers on-board also experiences a rollaway if the handbrake force applied is less than 220N when the vehicle in an upward direction and less than 200N when the vehicle in a downward direction. The aim of this research is to evaluate the performance of an electro-mechanical parking brake (EMPB) system. A mathematical modelling of the parking brake assembly based on the drum brake design was firstly developed. Then, an electronic control unit (ECU) model with different controller schemes such as proportional controller (P), and Proportional-Derivative (PD) controller was considered and simulated using MATLAB/SIMULINK to enhance its response performances. The parking brake model and ECU model have been validated using experimental works and it shows a good correlation. From the experimental results, the PD controller of the EMPB performs satisfactorily with engagement time of 1.05s, the steady state error, Ess of 1.66% and percentage overshoot, POS of 5.8%. In conclusion, the performance of the EMPB is within one second engagement time and the error percentage is less than 10%. The results were as good as other electric parking brake (EPB) mechanisms that has been accepted by many researchers. Furthermore, validated mechanical parking brake (MPB) and electro-mechanical parking brake (EMPB) models have been established and rollaway issue has been completely solved.