Modeling And Control Tehnology Research For Networked Motion Control System Of Wavemaker

As one of the important branch of automatic control field, motion control technology has been widely used in modern industrial production, design, manufacture, and so on. However, with the complexity of control tasks and diversification of control devices, the traditional point-to-point control mode cannot cope with a large, distributed, and more collaborative axis control requirements. Introducing communication network into motion control field to build distributed motion control system can not only solve the above mentioned problems but also simplify the design of the software and hardware system and reduce the cost of system. Taking into account the application of networked motion control technology for large-scale experimental equipment named Wavemaker in ocean engineering field, the paper will try to solve the key technical problems which the absorption Wavemaker is controlled with high accuracy and high real-time performance. The model is established aiming at the delay time and data packets drop over network. And a series of intelligent control technologies are researched. The paper is outlined as follows:First of all, in view of the characteristics of Wavemaker, the hierarchical system structure of networked control Wavemaker is proposed. The system mathematical model is given based on analyzing one of control units of the subsystem. And the all closed loop system model is proposed under certain condition. The system trigger mode should be clearly defined in the framework of four application trigger modes. Considering the characteristics of networked motion control systems, the paper presents a unified mathematical model of networked motion control system for Wavemaker. In the model, the constraint condition is relaxed. The system with interference signal and disordered data packets is analyzed. The system stability conditions are proposed for the above mentioned mathematical model. The conditions are proved by the method of linear matrix inequalities.Second, to revise the target spectrum and cope with the experimental requirements, the wave parameters must be timely tested and sent to the upper computer under the bounded delay time. Taking advantage of the characteristic which the timestamp can be carried by the data packets in the networked motion control system with hierarchical structure, the observer prediction model based neural network is presented according to the recorded end-to-end communication delay in the upper computer. The model is used to predict the next communication delay time to determine the required control instructions. The specific method is to record the past delay time sequence values before the data sampling time K. The values are entered into the neural network and trained by the neural network model. After the training process is finished, the new control instructions are generated by the predicted delay time values before the data sampling time K+l. The proposed method includes two key aspects:the neural network topology selection for the predicted model. Moreover, taking into communication delay and data packets drop, the system based the model should be stable and the effectiveness of model must be verified through the simulation method.Third, the PID(Proportional-Integral-Derivative) parameters of networked motion control system should be optimized under different types of delay time. At the same time, the variation of parameters by cost standard function is given according to different sample time and system time constant. To achieve the online PID parameters of the subsystem automatic adjustment, the intelligent networked PID adjustment methods are proposed based on the analysis of the different types of delay time. Two methods are put forward named PID control method based on binary coded genetic algorithm and PID control method based on fuzzy theory, respectively. The system simulation model is established to evaluate the difference between the conventional adjustment method and the intelligent PID regulation method under Pre-set delay time.Finally, the composition of Industrial Ethernet delay time is analyzed by space-time diagram. We compare the delay time difference of the system including different number of slave stations using three mainstream Industrial Ethernet protocols, respectively. And we focus on verifying the EtherCAT protocol performance from the perspective of the protocol theory. And clock synchronization scheme based on EtherCAT protocol is put forward and the new clock dynamic drift compensation algorithm is set forth. Next, the design scheme of networked motion control system for Wavemaker is proposed. In the scheme, the EtherCAT protocol is proposed to construct the field devices control network and these devices communicate with the upper computer through standard Ethernet. The experimental platform is set up based on above scheme. The whole system structure consists of two parts named master station and slave station. To ensure the realization of the real-time performance, the function of EtherCAT master station protocol stack should be achieved on the Windows system platform which is extended the INtime real time core. The paper gives the hardware design diagrams of EtherCAT slave station experiment platform based on DSP controller and EtherCAT network interface chip. In addition, the software achieves the function of EtherCAT slave station protocol stack and the flow chart of each program module is presented. The system should be able to achieve the following goals:(1) The high-speed and high bandwidth data acquisition system should be constructed, and the master station of subsystem can finish real-time synchronization of data acquisition less than1millisecond.(2) To control synchronously the wave making boards, the closed-loop Wavemaker networked communication control system with better robustness should be set up. (3) The system must be able to control synchronously all of wave making boards through the communication network. And the real-time control function should be achieved under multi-tasking operating system.To verify the effectiveness and reliability of the designed experimental platform, the system performance must be evaluated. We test the stability, repeatability and accuracy of the designed system through making repeatedly wave in the experimental pool. On the other hand, the cycle and synchronization performance indexes of the subsystem should be tested.