Research On CAN-Bus Based Electronic Control Multi-axle Dynamic Steering System

All Terrain Crane is a new kind of high-efficient hoist apparatus , its has some advantages of truck crane and rough terrain crane , such main characteristics as moves fast and goes with load on rough terrain. Compared with general truck crane, it has more superior jack-up performance and stronger cross-country ability. In addition, it can meet the needs of different working environment. Experts in the field think that all terrain-crane will be an important species of engineering crane in the future.Multi-axle steering is one of the key technologies of all terrain-crane. At a lower speed it can substantially reduce the turning radius of vehicles, flexibility of vehicles were increased, made vehicles work in the narrow space operations easily. On the other hand, at a high-speed it can improve the handling and stability, and enhance the safety performance of vehicles. Multi-axle electronic control technology can improve the excessive steering or less steering, enhanced vehicle dynamic stability so that vehicles running safer, avoid the loss of control of vehicle caused by excessive steering or less steering.Along with the constant development of computer network technology, the technology can be applied to the automobile growing quickly, and its functions have become increasingly powerful. Network route greatly reduce the number of network wires on the vehicles, narrow the beam diameter. At the same time network technology made the computer network and the entire vehicle system together, speeding up the development of intelligent vehicles. In modern vehicle design, the CAN bus has become a trend of the technology network.In this paper, based on reading more extensive data give a summarization for the actuality of the research of multi-axle inland and outland. Multi-axle can be divided into four classification for different execute patterns, mechanical, hydraulic, hydraulic-electric and control, electric power and control. According to the working environment of all-terrain crane, as well as to the steering feature, we chose hydraulic-electric control pattern. Due to the rapid and stable response requirements of multi-axle steering system, all bridges were to achieve the target value in the shortest possible time. Therefore, a method based on CAN bus structure was brought forward. The main ECU obtained signals of the front-wheelsteering angle and speed of the vehicle, computed each angle value for rear axles. Then the values were sent to the came to implementation ECU by the bus. The implementation ECU drive hydraulic cylinder to move until the wheel at the fit angle. The synchronization between each bridge ensures a rapid response for the system.In order to have a deep understanding of the CAN bus technology, detailed technical specifications and the CAN bus communication were depicted. Some network criterion such as the CAN hierarchical structure and the data forms of transmission and error handling were analyzed. Laying a foundation for the hardware architecture based on CAN bus communication.Electro-hydraulic executing agency is a typical model of the electro-hydraulic position control. According to the actual parameters of the vehicle's hydraulic implementation system, the transfer function from the electro-hydraulic proportional valve cylinder displacement to the PWM signal was deduced. Incremental PID control algorithm was used for the control of the implementing agencies. Using the MATLAB software got the simulation and analysis of implementing agencies, from the response curve of the step input, it was able to meet the rapid speed and stable property of the hydraulic cylinder.The hardware part of the electro-hydraulic control Multi-axle steering system was studied. Multi-axle steering system demand the vehicle speed and front wheel angle value as the input value. After analyzing by ECU, the PWM signal was put out to drive the hydraulic cylinder. According to the actual, choice of the sensor, electro-hydraulic proportional valve and hydraulic cylinder were selected. The MCU P89C52 were selected as the ECU for the control system. Some hardware structures such as signal disposal circuit, clock circuit, reset Circuit were built. Based on the analysis of the traditional ratio amplifier, designed a switch-driven amplifier circuit using the single chip to generate PWM signal. The amplifier circuit is simple in structure and good amplify effect. Discussed the hardware interfere technology, made a detailed analysis of the interference sources note.The software of control system was written in assembly language. Based on CAN bus the multi-axle steering control system software, mainly divided into two parts: the main control ECU software and the implement ECU software. The software included signal acquisition and processing module, steering execution module and the output module. It also includes the design of anti-interference software. The modular program could be applicable to more complex controlsystem. The control algorithm was the zero lateral angle proportional control from my laboratory research.With development of the electronic design automation (EDA) technology, new experimental methods were created, using "virtual machines" "virtual device" on the computer for electronic circuit design. At present, such simulation software, the "virtual electronic bench"—MultiSim8 was more outstanding, gradually promote its application. This new type of virtual electronics technology in the creation of experimental circuits, components and test equipment can be selected directly from the screen graphics. The testing equipment and graphics software were with similar physical appearance. In order to save hardware resources, Multisim8 software was used for the external circuit simulation. A simple device of test table for CAN bus communication was set up. WAVE 2000 was used for CAN communication modules of the control system hardware and software debugging.Finally, the conclusions, innovations, defects and research prospect of the research work are identified. The work above provides a reference to the research of multi-wheel steering system for multi-axle vehicle.