| At present,the control theory for linear systems is more mature,and it has been widely used in production practice.However,the world is nonlinear in essence,strictly speaking,the reality of the system are nonlinear.We know that there are essential differences between linear systems and nonlinear systems,and there is no consensus control algorithm for nonlinear systems.During the moving process,the moving sprinkler is affected by many factors,such as soil texture,moisture content,terrain.It is difficult to ensure the steady running of the sprinkler along the predetermined route.Especially for the core components permanent magnet synchronous motor pump pressure regulating system and the truss brushless DC motor system,due to a variety of factors affected by water hammer effect,the soil texture,moisture content,obstacle,flow and pressure regulation,which will lead to the sudden increase or decrease of the output torque of the motor.The stator current and motor speed may produce nonlinear vibration or even burn out the motor,which seriously affects the stable and reliable operation of the sprinkler.Therefore,it is very important to design the advanced control strategy to ensure the stable and reliable operation of the translational sprinkler.The main work of this paper is as follows:(1)In this paper,the mathematical model of a kind of magnetic body system is given,and it is proved that the system has complex dynamic characteristics.The nonlinear dynamic characteristics of the system are obtained from the dissipation,the Poincare mapping and the Lyapunov exponent spectrum.Based on the variable structure control theory,a sliding mode controller is designed to control the system to the fixed point and the periodic orbit.Furthermore,a new wing-doubled fractional-order system as well as its physical realization is presented.Based on the fractional-order stability theorem,an effective sliding mode controller is designed for the complex wing-doubled fractional-order system.(2)A new class of square nonlinear system is proposed.By analyzing its unique parameter k,the topology of the system can be changed from the two wings to the four wings.The physical circuit is built,which is in agreement with the numerical simulation.With the help of the nonlinear dynamic analysis method,the stable,quasi periodic and chaotic transition process of the system is analyzed.According to the nonlinear characteristic of the stronger double wing system,based on the Takagi-Sugeno(T-S)fuzzy model and the linear matrix inequalities,the robust fuzzy controller is designed to stable the double wing system.(3)For a class of fractional-order nonlinear systems with uncertain parameters,the uncertainty of the system is described with the help of the fractional-order linear time invariant interval matrix theory.Based on the Generalized T-S fuzzy model and the fractional-order stability theory,a fractional-order T-S fuzzy controller is designed for the fractional-order nonlinear system for the first time.And the stability conditions are given in the form of linear matrix inequalities that is more practical and convenient.(4)As we all know,the Lyapunov stability based control method is on the basis of asymptotic stability theory,which considers less of the dynamic quality of the transient process.Considering the control quality requirements of the dynamic transition time,overshoot and oscillation frequency for the actual system,based on the finite-time stability theorem,a new terminal sliding mode surface is proposed.And the corresponding terminal sliding mode controller is designed to realize the finite time stability control of the nonlinear system.(5)A frequency distribution model based on time and frequency domain conversion is proposed.The fractional-order system is transformed into an equivalent integer-order system,and its stability is proved by the classical Lyapunov theorem.Based on the terminal sliding mode control method,the fractional-order terminal sliding surface and controller are proposed.Two typical examples including the three-dimensional fractional-order nonlinear Lorenz system and four-dimensional fractional-order nonlinear Chen system are presented to verify the effectiveness and robustness of the designed controller.(6)Fuzzy and predictive control are two independent development methods,and the combination of the two methods has good research and application prospects.A fuzzy predictive control scheme is designed for a class of constrained nonlinear systems.The fuzzy predictive controller can effectively control a class of nonlinear systems in the presence of constraints and disturbances.The simulation results show that the system can track the reference trajectory very well.The fuzzy predictive control method can be tried to apply to other similar nonlinear systems.(7)In non-rated operation,considering the requirements of the permanent magnet synchronous motor stator current and speed on the dynamic quality of transition time,overshoot and oscillation frequency of the irrigation pump pressure regulating system,the finite time sliding mode controller is designed for the permanent magnet synchronous motor on the basis of the finite time stability theory.Furthermore,based on the fractional-order stability theory and the generalized T-S fuzzy model,a new fractional-order finite time fuzzy controller is designed for the permanent magnet synchronous motor.The stability conditions of the system are given in the form of linear matrix inequalities,and also a detailed mathematical derivation and proof is presented.According to the soil texture,moisture content,topography and other factors caused the brushless DC motor output torque of the sudden change,which may lead to the nonlinear vibration of brushless DC motor stator current and speed of the truss.A nonlinear fuzzy generalized predictive controller is designed combining the fuzzy and generalized predictive control technologies.And it also provide a reference for the truss drive system control. |
PDF Full Text Request