| The powder metallurgy hydraulic press, as the key equipment producing powder metallurgy parts, its control system performance directly affects the quality of powder product. With the rapid growth of demand for powder metallurgy parts of high strength, high precision and complex shape, ordinary powder hydraulic press has been difficult in meeting requirements of production, developing powder metallurgy hydraulic press equipped with CNC control system is an urgent problem of powder metallurgy industry’s development in our country.Usually, CNC powder hydraulic machine adopts PID control, with regard to electro-hydraulic servo system which is time-varying and vulnerable to interference, Control ability of PID controller is poor, and achieving the ideal control effect is difficult. In this paper, the fuzzy control and PID control are combined organically, and the fuzzy PID controller is designed to control the electro-hydraulic servo control system of CNC powder hydraulic press. Aiming at the application of fuzzy PID control in the electro-hydraulic servo control system of CNC powder hydraulic press, the research work of this paper is mainly carried out from the following aspects:1、According to the working principle of electro-hydraulic servo system, and combined with real work conditions of CNC PM hydraulic press, the position and velocity control’s mathematical models are established.2、In order to tune the fuzzy PID control’s initial PID parameters, this paper improves the traditional genetic algorithm and puts forward adaptive genetic algorithm to set PID parameters. Then, the paper adopts the adaptive genetic algorithm proposed and applies Visual Basic6.0to develop the general software of setting PID parameters, and uses this software to separately set initial PID parameters of position and velocity of CNC powder hydraulic machine’s fuzzy-PID controller.3、The fuzzy-PID controller is designed to control CNC powder hydraulic machine. For checking the control effect of the fuzzy-PID controller designed, assuming that electro-hydraulic servo system of CNC powder hydraulic machine is in three different working conditions that the system is normal, exists interference and its damping ratio is changed, inputting the unit step signal, the simulation analysis on Conventional PID and fuzzy-PID control on electro-hydraulic servo system of CNC powder hydraulic machine is respectively carried out. The simulation results show that compared with conventional PID control, the control performance of the fuzzy-PID control is better.4、This paper takes suppressing a multi-step part as an example to explore the control performance of the fuzzy-PID controller to suppress multi-step parts. Firstly, input signals of punches’displacement and velocity are set. Then, the fuzzy-PID and conventional PID are separately applied to control the displacement and velocity of punches. Finally, simulation results of the fuzzy-PID is compared with conventional PID control, and simulation results show that the fuzzy-PID control can track displacement and velocity signals of punches very well, but the conventional PID control appears oscillation, overshoot and signal distortion.In this paper, the fuzzy-PID control is applied to the electro-hydraulic servo control system of CNC powder hydraulic machine, which not only provides a new control method to improve the control performance of CNC powder hydraulic machine, also establishes a theoretical foundation for the development of intelligent powder hydraulic machine. |
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