| Multi-axis steering vehicles have advantages of :high flexibility, high carrying capacity and big power. It also have its weakness that once the steering-wheels turn uncoordinate, it will cause abnormal damage of the tire and even affect the safety of the vehicle, thus, the steering control technology of the multi-axis vehicle has become the key of multi-axis vehicles. Based on the zero sideslip angle of mass-center control strategy, combined with electro-hydraulic proportional steering technology, theoretical analysis and control simulation have implemented on the steady-state performance and transient characteristics of the multi-axis vehicle.With some simplifications to the mathematical model of the multi-axis vehicle, we obtained the 2-dof model. Based on the 2-dof model , we do a lot analysis about the steady-state characteristics and transient response characteristics. By analog with the two-axis vehicle, we derived the turning radius of the multi-axis vehicle, the critical speed and boundary conditions of stability. Futhermore the factors that affect the stability of multi-axis vehicles were discussed.By simplifying the proportional valve and hydraulic cylinder, we obtained the transfer function model of the valve controlled cylinder system, and used the Rolls stability criteria for some stability analysis, and also analysised the dynamic characteristics of the Hydraulic power steering system.By combination of the traditional PID control and modern control theory, on the basis of MATLAB / Simulink design environment, by using the fuzzy logic control toolbox,a adaptive fuzzy PID controller was designed. The responses of the hydraulic power steering system to the angle step signal were analysised.In MATLAB / Simulink environment, we establish a 2-dof model of a five- axis all terrain crane. The data obtained from the test are used to verify the simulation model, some analysis about the steady state performance and the transient characteristics are carried out. |
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