Research On Trajectory Planning And Tracking Control Of Electric Mobile Platform For Spacecraft Motion Ground Simulation

With the progress of science and technology,the aerospace industry has been developed rapidly.In order to reduce the cost and development period of spacecraft space experiment,the ground simulation of spacecraft space motion using the electric mobile platform has become an effective method,namely transforming the motion control of spacecraft space into equivalent ground motion control of electric mobile platform considering specific requirements based on similarity transformation.For the orbital motion of the spacecraft,the speed of each point on its orbit is determined,so that the corresponding motion control of electric mobile platform should satisfy the given position and speed requirements simultaneously.At present,for the traditional applications of electric mobile platform in the industry,logistics and other fields,only the location is considered,and the given velocity requirement for the planning and tracking control problem has never been considered.In this paper,the ground simulation of spacecraft space motion is described as the trajectory planning and tracking control problem of electric mobile platform satisfying the given position and speed requirements simultaneously.The trajectory planning,trajectory tracking control and actuator motor control problems of electric mobile platform satisfying the given speed requirements are studied respectively.The main innovations and achievements are as follows:A trajectory planning method based on virtual path points and B-spline functions are proposed for the position and velocity requirements of electric mobile platforms.Firstly,in order to avoiding the Runge phenomenon caused by the velocity equality constraint,the virtual way points are used for modeling the reference trajectory,which can be generated low order B spline functions.Secondly,in order to avoiding the big bulges,sharp peaks and loops for the reference trajectory,the non-uniform space method is proposed for designing of the interval time between these wanypoints.On this basis,the constraint conditions are quantified.Then,the entire running time is used as the optimization variable,which reduces the optimization parameters,and improves the speed of solving the trajectory planning problem.Finally,the optimal trajectory planning problem can be transformed into the parameter optimization problem,and the feasible output trajectory is obtained by optimizing the parameters.For the nonlinear underactuated kinematic equation of the electric mobile platform,an error dynamics equation with a similar affine form for the error variable is established by using a trigonometric function transformation,and a nonlinear trajectory tracking control method combining feedforward and feedback control is proposed.Firstly,the feedforward controller is designed based on inverse dynamics.Secondly,in order to reduce the difficulty of controller design for nonlinear underactuated system,the trigonometric function transformation is constructed,and an error dynamics equation with a similar affine form for the error variable is established.Secondly,a trajectory tracking controller with asymptotical stability is designed by using the Lyapunov method.The whole design process is clear and the controller structure is explicit.Then,an error correction algorithm based on the neural dynamic model is designed for the velocity jumping problem caused by the initial tracking error,which avoiding the acceleration saturation problem and improving the transient performance of the system.Finally,the asymptotic stability of the closed-loop system is analyzed under the Lyapunov framework,and the effectiveness of the control method is verified by Pionner3-DX mobile robot experiment platform.Aiming at the compensating of cogging torque,friction force and load torque disturbance under non-periodic variable speed condition,an extended state observer based adaptive robust nonlinear motor control method is proposed.Firstly,by transforming of the cogging torque model equivalently and simplifying of the non-linear frictional force,the model expressions with affine forms of unknown parameters are obtained.On this basis,the modeling errors and load disturbances are unified into system disturbances,and a control-oriented model of DC motor is obtained.The model has the advantages of online identification of unknown parameters and system disturbances when the motor speed varies arbitrarily.Secondly,the adaptive algorithm is used to identify the uncertain parameters of cogging torque and frictional force,and extended state observer is used to estimate the disturbance uncertainty.Then,under the frame of triple-step nonlinear method control,a steady state controller is designed to update the model parameters and disturbance uncertainties,and a robust feedback controller considering the estimation error is designed.Finally,the anti-jamming and robustness of the method is verified by J60LYS05 motor experiment.