Proportional Control Steering Study Of Seven-axle Vehicle

In the wake of the mushroom growth of inland industry and carrying trade,especially the class of highway has escalated,and along with the special vehicle leasing business's politically progressive,the requirement of large heavy-duty special vehicle in our country is escalating. Those vehicle wherewith higher economical efficiency, more powerful, and higher intensity than medium-sized and pint-sized special vehicles which can't compare with, has already seized about 80% of overseas special vehicle throughput and tenure amount. But in our country, by the reason of the extortionate import price and the bottleneck of inland production technology, large heavy-duty special vehicles have not been applied widely.In a general way, all terrain wheel undercarriages have application in large heavy-duty special vehicle, their steering performance directly influence to vehicle controllability and stability, agility and efficiency. As a result, it is necessary to make deeply research on steering characteristics of all terrain wheel undercarriages in order to enhance special vehicle various parameter and active safety.At present, the research on multi-steering mainly focus on four-wheel car's multi-wheel steering, and the study is rather deeply, but as to the large heavy-duty special vehicle which have more than 3-axles the study on the control of multi-steering has not been very deep, and basically has not applied in production.Firstly, according to standards of SAE, the paper defined a reference frame on bodywork, and then predigested vehicle model which with 2-DOF, yaw rate and lateral rate, and regulate longitudinal velocity is invariant, and elicited primitive vehicle control model by Newton's second law, established general formula and state space relation of single track vehicle 2-DOF control model by stress analysis of tyre. With vehicle dynamic model for underlay, according to vehicle steering Ackerman's geometrical law the paper analyzed vehicle steering characteristic and computed turning radius and turning center elementarily with proportional control tactics of homostasis centerofgravity zeroth yaw angle, and then examined steady state response briefly. Proportional control tactics of homostasis centerofgravity zeroth yaw angle, being one of open loop proportional control tactics, have the excellence of little controls parameter and easy actualize etc. Vehicle with Proportional control tactics of homostasis centerofgravity zeroth yaw angle behave better agility and response characteristic than the vehicle with front wheel steering. Yet, when the heavy-duty special vehicle working it almost can't accord with Ackerman's geometrical law, which mean that all tyres only be rolling, but take different control medium to content different work environment according to diverse control objectives. The paper took the technique of sectionalization optimization and overall fit to resolve the question of agility and stability, and optimized angle value of every tyre and vehicle response characteristic. The ways and means of hardware realization of all terrain wheel undercarriage multi-wheel steering control has been introduced in the paper, and it content all terrain wheel undercarriage multi-wheel steering control implementation requirement.There was a long history, about 80 years, of studying on vehicle controllability and stability, in the wake of the development of computer and lucubrating of tyre characteristics, it's possible to making comprehensive simulation study on vehicle dynamic response. A lot of scholars produce vehicle dynamics model with more and more DOF, and different evaluating indicators of vehicle controllability and stability. But, there is a question of open loop research technique of vehicle controllability and stability, that is different evaluating indicators always give out different results, even to the extent that mutual contravention. There is an obstacle when producing and using vehicle dynamics model, that is the open loop research technique ignore drivers'go-aheadism. Based on this realization, researchers raised studying of vehicle controllability and stability with Driver-Vehicle-Road closed loop system from the 80s of last century. This kind of systems makes driver and vehicle integrative, include the feedback mechanism of drivers'operation such as analysis, judgment and modifiability etc. The closed loop research on controllability and stability applied to four wheel vehicles deeply in China, but has not been applied to large heavy-duty special vehicles especially to which with all terrain wheel undercarriage. The all terrain wheel undercarriage is expensive and has a long production cycle, our technology and development tools drop behind the overseas country. According to the theory of"Preview-Follower", which established by K.H.Guo, the paper established driver model of large heavy-duty special vehicles, and have a preferable performance in doing vehicle controllability and stability closed loop simulation experiment, such as S-shaped experiment and hurriedly move experiment. Simulation experiment can shorten production cycle and enhanced products'quality with it's virtue of high economical efficiency and low fatalness. The simulation experiments in this paper testify the conclusions worked out before are accurate, and the subjective opinion of vehicle controllability and stability has directionless significance to manufacture of all terrain wheel undercarriage.The works upon indicate that, the steering angle value, which got from the technique of sectionalization optimization and overall fit, content control objectives in data integrity of large heavy-duty special vehicles that working in diverse environment. The simulation experiments in this paper, contraposed certain large heavy-duty special vehicle's multi-wheel steering controllability and stability, supply active foundation for shortening production cycle and enhancing products'quality, and supply subjective opinion reference standards of physical experiments.