Research On Controller Area Network Bus Communication Of Automobile Electronic Mechanical Braking System

Electro mechanical braking system is a new type of brake system which is widely usedin aircraft braking system in recent years, mainly consists of electro brake pedal, sensorsignal acquisition module, a central controller, a brake actuator and bus communicationmodule. Compared with the electro mechanical braking system and the hydraulic orpneumatic braking system in structure, the biggest difference lies in type of actuator, thebrake actuator of the electro mechanical braking system is composed of motor, slow downand increase torque mechanism, the motion conversion mechanism, the brake caliper andbrake disc; hydraulic or pneumatic brake system is composed of a brake wheel cylinder,brake caliper and the brake disc. The working principle of electro mechanical braking systemis that the central control module collect electro brake pedal signal and the sensor signal andcalculate the target braking force by the control algorithm，transfer to the wheel brakeactuator motor controller by bus，which control the operation of the brake actuator. Electromechanical braking system has the advantage of fast response speed, compact structure andhigh brake efficiency. Domestic and foreign scholars have begun the application of electromechanical braking system on vehicle braking system. Research direction of the electronicmechanical braking system application in automobile braking system mainly includedresearch on control algorithm, on the brake actuator and on the bus communication. Thispaper mainly researched on bus communication of electronic mechanical brake system.Compared to the performance of communication bus used on electronic and mechanicalbraking system of aircraft（MIL-STD-1553B）and automobile（CAN）, the paper draw aconclusion that the Control Area Network bus can be used in electronic mechanical brakesystem communication instead of the1553B bus, and finally selected CAN bus which has rich application experience in automotive applications as the bus communication protocol ofelectronic and mechanical brake system for automobile.This paper uses CAN bus application development process as the research method,mainly completed the following contents：First, we formulate the application scheme of CAN bus in automobile braking system,which included determining the CAN network node of electromechanical brake system，building the network topology，distributing each node address, name, and packet transmission.On the basis of the analysis and realization of automobile braking system ABS and anti-skidbraking function, this paper determined automobile electronic mechanical brake CANnetwork consists of nodes, engine electronic throttle node, ABS&ASR (anti lock and anti slip)the central control node, four wheel brake actuator controller node, and established a networktopology structure; according to CAN Senior Application Protocol SAE J1939networkmanagement standards, this paper distributed each node address and name; according to theparameters of electromechanical brake system function and SAE J1939managementapproach, each node is assigned specific message.Second, the automobile braking system of CAN network simulation. After establishingthe CAN network topology and the address, send and receive message of each node,considering the cost and development cycle perspective, offline simulation using simulationsoftware to verify the feasibility of CAN network is necessary. We use CANoe software tocarry on the off-line simulation, mainly consists of three steps, the first step is theestablishment of automobile braking system of network database, and the second step is theestablishment of the automobile braking system simulation model, finally we write controlprocedures to the node simulation model in order to the whole simulation model of operation.The simulation results show that the CAN network nodes of electromechanical brake systemcan send and receive data by the function, the bus load less than1%，the normal bus load ofthe vehicle system At about30%，thus the CAN network bus load of the automobile brakingsystem is low, the bus has good real-time performance and Extended properties.Third, the automobile braking system of the CAN node hardware circuit design. According to the principle of coordination and structure optimization of the systemperformance coordination, this paper completed the selection of the ABS&ASR centralcontrol chip, the chip for motor control, motor drive chip and CAN transceiver chip, thencomplete the design and draw of a central control node, the wheel brake actuator controllernode and motor drive circuit in the Altium designer software.Fourth, this paper design CAN node software of Automobile braking system mainlyincludes the software design of the initialization module of the MSCAN controller and datatransceiver module. In the process of designing the initialization module, according to theCAN communication baud rate and bus frequency, we calculated bit time parameters, andthen complete the bus timing register configuration; in transmitting data module, we firstintroduced the situation of data transmission register, and then completed the transmittingprogramming as the calculation of the engine torque message of ABS&ASR central controllersending as an example; in the data receiving module, this paper first introduced the situationof using the data receive register, and then completed configuration of filter register and thedata receiving program as the state information of the four motor controller of ABS&ASRcentral controller receiving as an example.