Research On E/P Positioner Control System With Long Tube

The positioner system has been an important application field of modern pneumatic technology. At the work site, thinking of the intrinsically safety and explosion-proof, normally the electrical pneumatic device is not allowed to set up. In addition, due to the adverse working conditions especially in chemical and metallurgical industry, the operator is not allowed to stay. Last, limited by the installation size, the positioner can’t be installed besides the pneumatic actuators. Thus, the positioner is usually separated from the cylinder with long tube, working as a remote control system. However, the join of long tube will affect the control of system. Focus on the phenomenon; this paper aims to improve the control performance of long-tube positioner system by the fuzzy adaptive PID controller based on the theoretical derivation, simulation proof and experiments.This paper targets the improvement of the control performance of long-tube positioner system under different working conditions. For different actuators and load, the fuzzy adaptive PID controller proposed can make the adjust time reduced to three times as long as the positioner works at full operation, together with a overshoot less than 5.5% and a steady-state error less than 1%.The first chapter of this paper introduces the development of the positioning system, together with the meaning and main contents of the research.The second chapter deduces the continuity equation and the momentum equation of transient flow in tubes based on the basic principle of hydromechanics. The partial differential equations of pressure and flow are deduced finally and solved by the finite volume method. Through the simulation and experiment, the delays, impedance and capacitance characteristics of tube is understood quantitatively. A basis for the subsequent development of the corresponding fuzzy rules is provided. The third chapter mainly introduces the model and simulation of the torque motor, the nozzle and flapper and the main valve based on electric equations, fluid equations and mechanical equations. The dynamic and static characteristics of the valve used in this paper are fully understood, which lays a good foundation for the design of control system and the realization of the control algorithm.According to the dynamic and static characteristics of the valve and in the spite of the serious nonlinearity of the pneumatic system, which is more serious under long tube condition, the fourth chapter proposes the long tube positioner control algorithm based on fuzzy adaptive PID controller and the specific implementation process is given. The implementation process of the algorithm is also given.In the fifth chapter, the long-tube pneumatic positioner system is built with the PC as the hardware and the Lab VIEW as the software. The experiments are excuted under different actuators and loads, which affords the validity of the control algorithm.