Analysis of the Controllers for the Transitional Manoeuvres of Adaptive Cruise Control Systems DUR MUHAMMAD PATHAN*, ZEESHAN ALI MEMON* AND TANWEER HUSSAIN** RECEIVED ON 05.03.2012 ACCEPTED ON 21.06.2012 ABSTRACT PID (Proportional-Integral-Derivative) and MPC (Model Predictive Control) algorithms are used to synthesize the upper-level controller of a vehicle equipped with an ACC (Adaptive Cruise Control) system. Both controllers are analysed, with and without constraints, using a simple vehicle model under critical TM (Transitional Manoeuvres). A comparative analysis of both controllers’ results has been conducted. The comparison gives the suitability of MPC for ACC application over PID controller. The flaws of PID control approach for the given application are highlighted. This approach can be helpful for selecting the suitable controller for the given application. Key Words: Adaptive Cruise Control, PID Control, Model Predictive Control, Transitional Manoeuvres, Vehicle Control. * Assistant Professor, and ** Lecturer, Department of Mechanical Engineering, Mehran University of Engineering & Technology Jamshoro. 1. INTRODUCTION The longitudinal control of the ACC vehicle consists of two separate controllers as shown in Fig. 2. The ULC (Upper Level Controller) computes the required acceleration commands for the LLC (Lower Level Controller) to maintain the desired spacing behind the preceding vehicle. The LLC uses these required acceleration commands to generate the required throttle/ braking commands for the nonlinear ACC vehicle to follow the spacing-control laws computed by the ULC [3]. In the literature, different control techniques have been proposed for the ULC, e.g. PID control [5,6], sliding mode control [3,7-11], CTG (Constant Time Gap) [2,4], and MPC [2, 12-15]. Bageshwar, et al. [2] made a comparison of MPC and CTG methods using a first-order ACC vehicle model. He highlighted the flaws of CTG algorithm and suggested MPC algorithm for ACC system’s application. The comparison of MPC method with the other control methods T here are many different types of controllers being used in industrial processes, chemical process systems, mechanical systems, electrical systems, and economical processes. These controllers could be anything ranging from a simple classical PID controller to the most sophisticated non-linear controllers. The challenging task for a controller is to perform well in spite of uncertainties present in a system [1]. A two-vehicle model is proposed in this study, Fig. 1, which comprises of a preceding vehicle and an ACC vehicle. The aims for the ACC vehicle are to set up and retain a SIVD (Specified Inter-Vehicle Distance) with zero range-rate behind the preceding vehicle under steady- state and TM. ACC vehicle uses range, range-rate, and its velocity and acceleration to perform the required TM in order to maintain the SIVD and avoid a collision from the preceding vehicle. Mehran University Research Journal of Engineering & Technology, Volume 31, No. 3, July, 2012 [ISSN 0254-7821] 537