Research Of Electro-hydraulic Position Closed-loop Sampled-data Control System

In electro-hydraulic servo control system or electro-hydraulic proportion control system's routine application, generally connect the sensor to the port of electrical amplifier, constitute continuous time closed-loop control system. And this systematic command input is analog signal, the signal which sensor input electrical amplifier is also analog signal, therefore, this kind of system is regarded as analog closed-loop control system, this adjustment of system is also fairly simple, but modern high-level intelligent controls is difficult to come true under this form linking up. With the quick developing of computer technology, the computer control technology is extended application gradually, especially PLC, as one kind of controlling computer, getting extensive use in the industrial automation. Modern PLC has already the complicated calculation function, but in modern actual application, many PLC are only as the simple tool which provides the command signal and carry out the general logic control. Through correct programming at present, PLC has already being able to carry out closed-loop PID adjustment by the subroutine has been called. But the form can only limit the PID adjusting and not apply high-level intelligent control.Be going to base on the available equipment, applying the modern high-level various control method being on the rise, improves the control accuracy of control system, only insert the sensor's feedback interface into PLC, constitute an actual computer control system, this control system has obvious superiority when comparing with the continuous control system. But this computer control system can only receive and handle binary code, use these binary code to express some one kind of physics amount size or some numerical valve (digital signal so-called). Therefore, in this system it is first sampling and dispersing to continuous amount in actual system, becoming disperse control system of modern control, more accurate speaking it is sampled-data control system. However, according to actual control system model that is composed of PLC, how to carry out correct building model, simulation and analysis on sampled-data closed-loop control system and apply it to actual control system is the job that current auto control system researchers are carrying out, and being able to apply high-level various control such as intelligent control to actual control system after correct building model and analysis on actual system. Therefore, not only do my research establish theory foundation for the future relevant system research and development, but also do the sampled-data period T range method and the guiding significance to practice deserve being extend and being applying to practice.Based on former theory research in this field, PLC applying Siemens's is a controller, proportional valve and hydraulic cylinder are member controlled, and the laser sensor as feedback component designed electro-hydraulic position closed-loop sampled-data control system by self. Owe controller PLC CPU226 in system only receive and handle digital form's signal, the so-called digital signal is relative to continuous signal, it's signal duplication chooses only limited discrete valve, while the controlled member proportional valve and hydraulic cylinder is continuous, therefore, studying system is a closed-loop sampled-data control system.Study process is: first, carry out conscientious examination on electricity part and hydraulic part of electro-hydraulic position closed-loop sampled-data control system, avoid electricity part short circuit and hydraulic part leakage or block, ensure the system's service behavior is stable. Second, analyze each segments of control system seriously, such as proportional valve, hydraulic cylinder and sensor, give them out respective transfer function under relevant reference theory knowledge, analysis having been especially detailed to PLC, not only analyses the PLC treatment process to the signal, moreover give out transfer function of zero-order hold in PLC. Third, have drawn the block diagram of the actual sampled-data control system, since the Z operator and time have being more direct relation, can be directly apply to the computer sampled-data control system calculation, therefore, this paper reach the Z transfer function of opened-loop and closed-loop sampled-data control system by applying sampled-data control system theory, and as the basis mathematic model analyzing entire sampled-data control system. Fourth, carry out simulating to sampled-data control system under the different sampling period by applying SIMULINK, simulated result is able to ensure that system stable and oscillating does not come into being when choosing the sampling period within 0