Embedded System Development of an Electric Power Assisted Steering System Using MATLAB/SIMULINK/Real-Time Workshop 2004-01-0711
Electronic Control has been widely used in automotive systems, such as Vehicle Dynamics Control, Anti-Lock Braking Systems, Active Suspension and Steering System control, etc. The rapid prototyping development of an embedded controller for an electronic power assisted steering system (EPAS) will be presented in this paper. A steering model is established in MATLAB/SIMULINK to verify the proposed EPAS in this paper. This model includes the effects of kingpin inclination, caster, camber and lateral offset to calculate the total steering torque. The EPAS control strategy has considered the driver commands and vehicle speed to provide multiple stages of steering torque assistance. TMS320F240 DSP is used as the embedded controller of EPAS. EPAS Control algorithms have been designed using MATLAB/SIMULINK/Real-Time Workshop and Input/Output of Blocksets of TMS320F240 DSP have been developed in SIMULINK. Owing to the controller design, done by drag-and-drop blocks in SIMULINK, it can avoid the risk of hand-coding error. This process allows automotive engineers to develop EPAS control strategies easily under the GUI environment in SIMULINK. Auto-Code generation techniques are introduced to transform the SIMULINK model into ANSI C code. The machine code is loaded into TMS320F240 DSP after compiling the C code. TMS320F240 DSP would operate as a standalone embedded system for controlling the EPAS. This “Model to Chip” technique can greatly reduce the effort of control strategy development, and achieve the goal of rapid prototyping.