Modelling, dynamic stability analysis and control of an omni-directional road vehicle

In a modern society, traffic congestion is a major problem in every metropolis. To solve the problem of traffic congestion an innovative omni-directional vehicle is proposed. The most important advantage of an omni-directional vehicle is that by steering all four wheels it can turn in a small radius. This means that a smaller area is required for turning or parking. Lots of researches have focused on the use of an omni-directional vehicle for in-door situations, but less research has focussed on its use as an on road vehicle. Therefore, this research has mainly focussed on developing the comprehensive vehicle dynamics model for an omni-directional road vehicle for high velocity conditions, transferring loads and the effect of traction and braking. This research consists of the following three parts: A model was developed for an omni-directional vehicle that mainly focussed on vehicle dynamics in the yaw plane because the side slip angle and yaw rate are the two most important outputs of a dynamics system and determine its total stability. An innovative four wheel, independent steering system was incorporated into this vehicle dynamics model and the effect of roll motion on the yaw plane was examined. Secondly, the stability of the vehicle in the yaw plane was analysed based on the response of the side slip angle, as first suggested. Then in the actual simulation, and based on the stability criterions, vehicle stability was determined under different scenarios. The first scenario was large and small radius turning, followed by simulating a combination of turning, braking, and traction. This was followed by an analysis of the disturbance of vehicle stability, including the bank angle, the effect of a lateral wind and the coefficient of friction. Finally, the effect of roll motion such as load transfer and roll steer, and how an independent driving system would affect vehicle stability is presented. An active steering PID controller was suggested and which, according to the results of the simulation, improved the yaw plane stability (side slip angle)