Influence of signal delays and accuracy, on the performance of suspension control system and controller design

Abstract

Ride comfort, handling, and road holding are important vehicle dynamics characteristics, and at Volvo cars, these are actively controlled by Electronic dampers through software and control algorithm. The complexity of the software adds different sources of delays and errors within these controllers. And this presence of delays and errors leads to performance degradation, and in some cases, it could also result in system instability. Thus it’s important to consider the delays and errors when designing the controllers. So in the thesis work, we first focus on studying the influence of the delays and errors on the performance and stability of three different suspension control systems: Semi-active, Active and system with preview. Here we have modelled different mathematical delays and quantization error models, and they are used based on the test case and performance metrics. In the second part of the work, an LQG controller for the Active suspension system and Smith predictor compensator for both active and semi-active suspension system was implemented and evaluated, to compensate for the delays. This entire work is carried out in the simulation environment, using IPG Carmaker and Matlab/ Simulink. Finally, experimental tests were conducted on the current controller at Hällered Proving Ground to validate the trends, and perform a subjective and objective assessment for different sensor delays.