Fractional-order PI~λD~u Control Of Hybrid Mechanism For Automobile Electro-coating Conveying Based On The Optimization Of Genetic Algorithm

The conventional automobile electro-coating conveying systems,such as RoDip and Vario Shuttle which adopt the cantilever structures,have the poor ability to withstand heavy and large payloads and the low flexibility.Supported by National Natural Science Foundation of China(Grant No.51375210),a novel hybrid mechanism for automobile electro-coating conveying has been developed based on the hybrid mechanism.The hybrid mechanism has the characteristics of the serial mechanism and the parallel mechanism,which has simple structure,strong payload,high flexibility and wide applicability.The novel conveying hybrid mechanism is mainly composed of the parallel mechanism,which consists of multiple kinematic chains,and the motion control of which is more complex result from its highly nonlinear,strong coupling,time-varying parameters and unknown disturbances.The classical motion control strategies such as PID control,which is operated and implemented easily,is widely used in the actual engineering and production equipment result from its simple structure.However,when model uncertainties,nonlinear and multivariable exist in the controlled plant,high control performance cannot be obtained by PID usually.The tuning range of the controller parameters can be increased by introducing the integral order l and the differential order μ,so that a better control performance can be obtained by the fractional-orderPI~λD~u(FOPID).In addition,FOPID is insensitive to the changes of its parameters and the parameters of the controlled plant system.As long as these relevant parameters change within a limited range,the good control performance can be obtained by FOPID.However,FOPID only can be used for the individual control loop of the novel conveying hybrid mechanism,which means the couplings among kinematic chains are not taken into consideration.Therefore,it is necessary to consider the couplings among kinematic chains of the novel conveying hybrid mechanism further.Moreover,the additional parameters l and μ are introduced into the controller,it is also necessary to consider parameters optimization.According to the above analysis,in order to solve the problem of couplings among kinematic chains of the conveying hybrid mechanism,the fractional-order PI~λD~ucontrol integrated with feed-forward compensation(FOPID + FFC)control strategy is proposed in this paper,and the genetic algorithm(GA)is also adopted to optimize the parameters of the FOPID.Firstly,the automobile electro-coating conveying equipments and the motion control strategy of hybrid mechanism are summarized.The characteristics and the development application of FOPID and the development status of GA are expounded in this paper.Secondly,the inverse kinematics,the forward kinematics and the Jacobi matrix are built for the novel conveying hybrid mechanism.The kinematics of the mechanism is simulated by MATLAB,and the simulation results show the correctness of the kinematics analysis.Thirdly,the dynamic model of the novel conveying hybrid mechanism is established by the Lagrange method,and the coupling characteristics of the mechanism are further analyzed based on the established dynamic model.The MATLAB simulation results show the reliability of the model.There are couplings among kinematic chains of the mechanism by the MATLAB.Then,in order to solve the problem of couplings among kinematic chains of the conveying hybrid mechanism,the FOPID + FFC control strategy is proposed,which can be used for the individual control loop of the novel conveying hybrid mechanism respectively.At the same time,the coupling effect among branches is obtained by further analyzing the established dynamic model,which is eliminated by feed-forward compensation.Then GA is adopted to optimize the parameters of the controller.The MATLAB simulation results show that FOPID + FFC controller has stronger robustness for external disturbance,and it has better tracking performance comparing with FOPID controller and PID controller without feed-forward compensation.Finally,the experimental platform of the control system is established by adopting the distributed structure of "PC and UMAC" for the novel conveying hybrid mechanism.Then the motion control experiments are completed based on the experimental platform.The feasibility and effectiveness of the designed FOPID + FFC controller is further verified from the experiment results.