Design Of Automobile’s CAN Modules Function Test System And Study Of It’s Real-time

At the present, the CAN bus is used widely in the automobile electronicproducts, and the core of many automobiles’ control system are compose of thecontrol unit of the network of CAN bus, this unit is called CAN module. How totake effective means of CAN module have strict test before delivery is a problem forthe automotive electronics manufacturers. At present domestic the CAN modulefunction test system have already had some preliminary development, they end thestate of the manual testing, but the existing technology was designed for only onespecific CAN module, they did not have generality and relate no instantaneity of testsystem, which had affect the performance of test system. So at the basic ondesigning the CAN module function test system which have stronger generality, thisthesis have researched the instantaneity of test system, and improved theperformance of test system.The thesis first abstract CAN module test system as an communication networksystem of aperiodic real-time tasks, then applied the queuing theory to the CAN buscommunication network system and put forward response time model of CAN busbasing on the queuing theory. This model does not only consider the fillingmechanism of bit of CAN bus and the influence of bus load factor on the responsetime but also consider the rising of time cost which is cause by retransmissionbecause of environmental disturbance. Taking a function test system of CANnetwork modele as an example, simulation of the proposed model is conducted.Relationship diagram between mean value of message response time of differentpriority and load rate, error arrival rate is obtained. According to the simulationresult, the lower the priority of the message is, the greater the influence of load rateand error arrival rate on the mean value of message response time. It’s a non-linearrelationship.An improved DM algorithm is proposed. The CAN bus network task model isestablished. Using MATLAB, respectively, for improved DM algorithm and EDFalgorithm and LSF algorithm from the transient load rate, response time andscheduling success rate of this a few aspects to compare. From final comprehensiveanalysis came to a conclude that improved DM algorithm is batter than other twoalgorithm at the aspects of transient load rate, response time and scheduling successrate, thus more suitable for CAN module function test system.Function test requirement of CAN module was got by analyzing the function ofCAN module, then put forward the total design plan.The test system hardware wasdesigned in detail. Finally the implement method of improved scheduling algorithm and thesystem hardware debugging results was put forward.