Evaluation of on-off semi-active vehicle suspension systems by using the hardware-in-the-loop approach and the software-in-the-loop approach

Three controllers, namely the skyhook controller, the mixed-single-sensor controller and the groundhook controller, are compared using two validation approaches, namely the hardware-in-the-loop approach and the software-in-the-loop approach. The software-in-the-loop approach considers the dynamics (e.g. the body heave, the yaw, the roll, the pitch and the force) and the geometric parameters (the motion ratio of the suspension) without the real-time constraints. This allows an easier debugging and design procedure to be carried out for the control systems. The hardware-in-the-loop approach includes a commercial magnetorheological damper for testing the dynamic and transient responses in a control system. It is of interest to compare the conclusions generated under both approaches. The hardware-in-the-loop approach considers an on-off magnetorheological damper, and a quarter-vehicle model in a real-time embedded system. Two types of test were applied: chirp surface road tests and type F surface tests (ISO 8606:1995). For the software-in-the-loop approach the non-linearities and dynamics due to the geometric and physical component characteristics of a vehicle model were simulated by CarSim® software, while the non-linear magnetorheological damper model and the controller were running in MATLAB®/Simulink®. The classical tests for the vehicle, namely the dynamics bounce sine sweep test, the double-lane-change test and the fishhook test, were applied. In the hardware-in-the-loop approach, the best controller was the skyhook controller for comfort and the groundhook controller for road holding. In the software-in-the-loop approach, the mixed-single-sensor controller is the best for comfort, and the groundhook controller can be used in emergency driving conditions since it improves the stability, the road holding and the wheel tramp. The best controller in the hardware-in-the-loop approach and the best controller in the software-in-the-loop approach are not the same since the motion ratio of the automotive suspensions influences the performance of the semiactive control systems; the inclusion of this geometric parameter in further analysis and synthesis of semiactive suspension systems is recommended.