The Research On The Servo Controller Of Pneumatic Linearity

Pneumatic technology, which has a series of obvious advantages, is applied widely in industry production more and more, and becomes a rigueur means of automation. Entering into 1990's, pneumatic technology is largely beyond the traditional blind area and comes through a quickly develop. As the leading study domain, pneumatic servo technique has a regard for the people. Pneumatic servo positioning technology can realize high accuracy arbitrarily point automatic positioning when cylinder moves in high velocity and break through the traditional pneumatic positioning method. Based on the requirement for engineering upgrading of pneumatic automatic equipment that has advantages such finer feasibility and higher ratio of property and price in middle and small enterprises, this paper introduced a low cost linear cylinder position control system based on a proportional directional valve. The emulation result indicated that it has a satisfactory control performance, thus, it can be expected to generalize and utilize in variously engineering regions.In this paper we take gas dynamics as a base, use some known theorems and laws such as law of thermodynamics, law of conservation of energy, second law of Newton and pass through several rational and necessary assumption and simplification, and take the basic status equation of controlled subject by deduced as the basic, by means of powerful Simulink nonlinear modeling function, built a firenew nonlinear model of straight line cylinder position control system based on the proportional directional valve. Thereinto, we have further perfected and improved former returns to build a cylinder nonlinear friction model and made it more close together to the active system. It afforded the basis and reference for the control strategy of system research. It also afforded a new thinking to study the modeling for others pneumatic servo systems. At the same time, in this paper we utilized linearization tools of Simulink to linearly treat at concreted operating point for the system model, and afforded reference to the parameters setup of PID controller.About the study of control strategy, for the slow "crawl" oscillating problem occurred nearby of target value when controlling the system withgeneral PID controller, we point it in the paper that this is the result of compressibility of gas bring a lag of gas pressure response and cylinder nonlinear friction interaction. Thereby, it determined the complex intelligent integral PID control strategy and obtained the satisfactory control effect. At the same time, for positive feed compensating control of the cylinder frictional force, because the cylinder frictional force can not directly rear time measure, it dissatisfies the fundamental demand of positive feed control. About this, the paper has indicated two methods to indirectly obtain real time measuring the cylinder frictional force. They are: the pressure of two cylinder cavities and acceleration of piston can be indirectly obtained with the second law of Newton; and it can be indirectly obtained by means of the velocity of piston to build the cylinder frictional force model.Finally, this paper sufficiently considered the nonlinearity and time changeability, utilized PID controller parameter optimizing tools of Simulink to assume the variation ranges of system parameter k (ratio of specific heat at constant pressure and specific heat at constant volume) and T (ambient temperature), obtained more optimized parameter values of complex intelligent integral PID controller. The emulated result shown that the system not only can control the cylinder at arbitrarily point, but it also has an excellent control effect.