Research Of Scheduling Algorithm And Simulation Based On Hybrid Trigger CAN Bus

CAN bus has been widely used in industrial control field with those advantages that make up of a simple structure, high reliability, strong anti-interference, low cost, good fault tolerance, transfer short frame. But CAN bus protocol using the rule of non-destructive by bitwise to assign the priority in CAN bus, and making network utilization is low, and the real-time processing capabilities to emergency is not high. In the network bandwidth is limited, in order to improve CAN bus fairness, timeliness and bus bandwidth utilization, dispatching reasonable packet of each node, and reducing delay of transmission of packet, to meet the transport needs of all types of packets on the bus, so the research focus of CAN is how reasonably dispatch messages and make it effective transmission. To this end, the paper propose to mix-trigger scheduling algorithm that name is TMSA based on TTCAN.On the basis of a detailed description of the main characteristics of CAN bus technology, the hierarchical structure of the agreement, conflict arbitration mechanisms of link layer, packet types and the frame format. Discussing the existing CAN bus scheduling policy type, applications and problems, and clearing the main differences and similarities between two trigger way(triggers of event-based and trigger of time-based) and based on the principle of the similarities and differences between static and dynamic event-triggered scheduling algorithm strengths and weaknesses, analyze RM scheduling algorithms and TTCAN protocol, elaborated the theory and gray GM(1,1) to establish a method to predict the model. Then put forward the basic principles of mixing triggered scheduling strategy to build, improve and construct a mixed schedule TTCAN static scheduling algorithm triggered design, build aperiodic message time behavior analysis and forecasting model, matrix model cycle and base period, with time aperiodic packet arbitration mechanism, describing TMSA hybrid scheduling algorithm from the worst response time can be tripartite scheduling and bus utilization face TMSA hybrid scheduling algorithm effectiveness analysis. Finally, using MATLAB software Stateflow and Simulink toolbox to build CAN bus communication model and scheduling algorithm model, the RM scheduling algorithm, TTCAN scheduling algorithm and TMSA hybrid scheduling algorithm simulation.Simulation results show that TMSA hybrid scheduling algorithm improves network utilization, reduce the non-periodic packet delay and improve the aperiodic packets in real time.