| Pneumatic technology is spreading very fast in China, and has made remarkable achievements in the development of conventional pneumatic components. The quality of some products has even come up to the leading level in the world. However, the development of the pneumatic proportional pressure valve (PPPV for short) is quite slow and remains mainly in theory and laboratory stage, the commercial PPPV made in China are still rarely seen until now. The PPPV is famous with its good dynamic performance, precision and easy electrical integration, thus it is widely used in the control field of pressure regulation, position control, velocity control, force control and so on. Unfortunately, the PPPV manufacturing technology is proprietary to several foreign companies, such as FESTO, SMC, and relies on imports mostly. Therefore, it is of great importance to achieve the pneumatic proportional components autonomy and promote the pneumatic technology development in China by studying the key technonlogy of the PPPV and developing our products with independent intellectual property rights.A poppet type PPPV driven by a proportional solenoid was proposed on the background, which was capable of adjusting the output air flow pressure continuously in the range of 0 to 600 kPa. The theoretical analysis, numerical simulation and experiments were carefully involved. The design process of the PPPV and its digital proportional controller were introduced at first, the key parameters and their influence to the valve’s static and dynamic characteristics were well analyzed by combining FEM analysis with lumped parameter modelling next. Based on different requirements of the pressure regulation speed and accuracy, the Novel Robust Fuzzy PD control algorithm (NRFPD for short) and the Active Disturbance Rejection PI control (ADRPI for short) were proposed respectively. The designed PPPV prototype was adopted in the application of the cylinder trajectory tracking control to test the real performance finally. This paper is divided into seven chapters as follows.In chapter 1, the researching background related to the PPPV was reviewed firstly. Current research status was illustrated based on the structure and applications in detail next. Work progress in numerical simulation, proportional controller, control strategies and applications were explained respectively then. At last, research significance, challenges and main contents of this dissertation were declared.In chapter 2, the design theory of the PPPV, which was mainly consisting of a proportional solenoid, a poppet assembly, a pressure sensor and a proportional controller, was well introduced. The influence of the output load was studied, and the necessity of the closed loop pressure control was annouced. The proportional controller was designed with a power supply module, a signal conditioning module, a current detect module and a drive module, and the PID plus anti-windup algorithm was adopted to control the coil current. Experiment workbench was outlined in the following section, and the open loop test of the PPPV prototype was carried out at last.In chapter 3, a complete nonlinear numerical model was developed, which described the PPPV’s every work progress from the air-in to the air out. A lumped parameter model of the proportional solenoid, whose parameters were obtained by FEM analysis, was created. The movements of the poppet assembly and the pneumatic subsystems were studied respectively. Several experiments were designed to verify the proposed model, and key parameters were analyzed by the simulation. Last not the least, a simple PI control algorithm is applied to study the PPPV’s close loop characteristics.In chapter 4, a novel robust fuzzy PD controller was proposed to achieve the fast pressure regulation and pressure recovery on the sudden disturbance of the PPPV by combining the linear tracking differentiator (LTD for short) with robust compensation and fuzzy PD control. The LTD term was adopted to filter and differentiate the feedback pressure signal, the fuzzy PD term was used to track the reference signal, and the robust compensation term was applied to minimize the tracking error to the tolerance limits. The NRFPD algorithm was verified by both the numerical simulation and the experiments, and the performance of the NRFPD was analyzed in real time carefully.In chapter 5, due to the poor controllability of the PPPV, the idea of combining the pressure control loop with the current control loop was proposed. The current control loop was accomplished by a special designed analog proportional amplify circuit. The pressure control loop was designed with active disturbance rejection PI control algorithm to achieve precision pressure control, which was divided into two parts:active disturbance rejection control was adopted to drive the output pressure tracking the command signal when the feedback error was big; the nonlinear PI controller was switched on to enhance both the accuracy and the stability when error was small. The reference signal profile planning was further involved to improve the performance of the valve. Experiment results proved that the proposed PPPV can achieve a continuously variable pressure adjustment, and also robust to the downstream disturbance.In chapter 6, a single rod cylinder controlled by a pair of the PPPVs was established to study the precision trajectory tracking control subject. The state-space model of the system was created. Due to the parameters’ uncertainties and unknown external disturbance in the model, an adaptive robust control algorithm was proposed, which employed online least square algorithm with forget factors as the parameters adaptive law and the back-stepping algorithm to design the nonlinear robust controller. Reference trajectory planning was also involved to improve the tracking performance. The proposed adaptive robust control algorithm was assessed by experiments finally.In chapter 7, the conclusions of the dissertation are illustrated. The main contributions and innovative points are summarized, and the recommendations of future study are proposed. |
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