Development And HIL Validation Of ABS ECU For Commercial Vehicle

The vehicle's Anti-Lock Brake System (namely ABS) can effectively prevent the car's slippage due to the wheel's lock-up during the braking process of the vehicle, heavy-duty commercial vehicle and large passenger car that equipped with ABS can reduce the occurrence rate of traffic accidents to a large extent. ABS has been as standard equipment for automobile abroad, now domestic regulation also obliges all homemade heavy-duty commercial vehicles and large passenger cars must equipped with ABS.Electronic Control Unit (namely ECU) is the key component of commercial vehicle ABS, which also the primary part weighs the performance and function rating of ABS, its performance determines the control effect of whole ABS directly. Whatever how well the other components of brake system are, once there some problems happened to ECU, the anti-lock function of ABS will invalid, sometimes would make the brake effect worse. ABS ECU is the extremely secret technology to the foreign ABS manufacturers, the key control algorithm and the internal detailed structure are rarely mentioned in public literatures, the research that how to complete the ECU is hardly seen, too. So develop a mature ECU has very significant and practical meaning in the process of ABS production.This paper aim at air-pressure ABS of commercial vehicle, on the basis oftheory and practice of commercial vehicle ABS that belonged to the lab, we gives lots of emphasis on developing the air-pressure ABS ECU. Mainly complete the overall design scheme of ECU, design and develop the hardware circuit and software program of ECU, then make an intensive research on control strategy of ABS, finally we carry out the ABS ECU embedded Hardware-in-the-Loop test on the single wheel ABS test bench that devised by the lab, through the tests validate the function of ECU we developed and the control strategy we adopted.The paper mainly completes the following research:(1) Accomplish the hardware circuit design of ECU through the analyses of input signal characteristic and control object. Choose the Micro Controller Unit (namely MCU) of ABS ECU after a series of selection job, then choose the develop mode of MCU. Design the minimum system that set Motorola 16 bit MCU MC9S12DP256 as the core, make sure that the system runs normally; design the wheel speed sensor signal processing circuit, which can collect the signal from the sensor precisely; design the solenoid valves drive circuit, adopt the chip that especially designed to drive inductive loads, which can improve anti-jamming of the system, the circuit can offer five brake chamber pressure mode that make use of MCU's PWM module, include increase pressure, main pressure, decrease pressure, step-up pressure, step-down pressure; design the V/F (voltage-to-frequency) convert circuit, which convert the ladder wheel speed signal that sent out from the data collecting card to the corresponding wheel speed in frequency form, then send it to ECU, it's the necessary circuit in the ABS ECU embedded Hardware-in-the-Loop test, the test data indicate the circuit up to the test request.(2) Make an intensive discussion and analysis on control strategy of ABS, which based on logic threshold value, give lots of emphasis on several difficult questions of the control strategy, on the basis of above research we devise a suit of control algorithm that based on logic threshold value, then make it to the software program format, which include main program, wheel speed compute program,slippage compute program, control logic program and solenoid valve act program etc. After successfully debug the program we download it to MCU via BDM (Background Debug Mode) interface, it establish stable foundation for ECU embedded Hardware-in-the-Loop test and the function validation of ABS ECU.(3) ABS ECU embedded Hardware-in-the-Loop test. Embed the developed ECU in the ABS Hardware-in-the-Loop test bench that devised by the lab, which based on the system of xPC Target, then do some tests in high and low adhesion coefficient road conditions. The tests results indicate that the developed hardware circuit of ECU is right and reasonable, the developed control strategy that software adopted is right and effective, the ABS system runs stably and reliably, achieve the purpose and requirement of anti-lock brake control. It's proved that the developed ABS ECU has got basic anti-lock brake function, which establish a good foundation in the mass manufacture process of ABS product.