Theoretical Analysis And Experiment Of Electric Control Bent Axial Piston Hydraulic Transformer

Hydraulic transformer is an important unit which can transform pressure in hydraulic transmission. It corresponds to a hydraulic pressure transformer, by which hydraulic performance unit (fixed displacement hydraulic motor and hydraulic cylinder)can gain energy without throttling losses from hydraulic constant pressure rail system. The hydraulic transformer expands the application scope of secondary regulation of hydrostatic transmission. The working principle of secondary regulation of hydrostatic transmission determines that its load must be variable unit. For the piston area of hydraulic cylinder can't be varied, hydraulic valves are usually adopted to this system. Not only this method brings throttling loss but also causes low efficiency. As a result, the application of traditional hydraulic transformer is restraint. An optimum method to solve this problem is to adopt new hydraulic transformer, which has the advantages not only without throttling losses but also recuperation and reuse energy. It also provides with an effective method to improve the efficiency of hydraulic constant pressure rail system. So it has great valve to research on the new hydraulic transformer.After synthesizing numerous related literatures and reference materials at home and abroad, this research not only summarizes the current study status and development trend of hydraulic transformer and analyses the characteristics of the hydraulic transformer, but also expatiates on the key technology and study status of the hydraulic transformer. It also introduces the applications of the hydraulic transformer. For the low transformation and the limited transformation scope of manual operating new hydraulic transformer, the electric control bent axial piston hydraulic transformer is developed.According to the working principle of hydraulic transformer, the characteristic of hydraulic transformer is analyzed and deduced the formula of flow, torque and pressure transformation factor, which provide with theoretical basis for hydraulic transformer construction design and simulation analysis.The electric control bent axial piston hydraulic transformer driving linear system consists of three subsystems which are computer control system, alternating synchronous servo motor system and hydraulic transformer controlling hydraulic cylinder power mechanism. This study also builds mathematical models of the three subsystems.In order to analyze the working principle of the hydraulic transformer, the balance angle of hydraulic transformer is defined and built its formula. Combining with the mathematical models of three subsystems, the mathematical model of hydraulic transformer control angle is built and the hydraulic transformer driving linear load system mathematical model is also built.In order to meet the demand of new servo system, adopting optimum design method to mechanism construction, the mechanism construction design of electric control bent axial piston hydraulic transformer is completed. Also the assembly and debug of the hydraulic transformer is done. As a result the electric control bent axial piston hydraulic transformer is developed which transformation factor scope is from zero to two.By introduction"driving load"to analyze on hydraulic transformer four-quardant characteristics, simulation and experiment study are made including pressure of hydraulic constant pressure rail system, flow of hydraulic accumulator, control angle of hydraulic transformer and efficiency of energy recuperation and reuse under working condition of hydraulic transformer"load driving"and"driving load"in driving linear load system. In view of the complex nonlinear characteristic of new servo hydraulic transformer, the fuzzy adaptive tuning PID control strategy is applied to the experiment system. Simulation study is done on the new servo hydraulic transformer driving linear load position servo system. Simulation results prove that application of the fuzzy adaptive tuning PID control strategy can compensate the nonlinear characteristic of the hydraulic transformer and improve the resistibility of load disturbance and the ability of fast response to the system.Based on the developed electric control bent axial piston hydraulic transformer prototype, the hydraulic transformer driving linear load system experiment test-bed, the hardware circuit design for the system and the computer control system are built. And the control software is programmed to control the experiment prototype. Not only the characteristic of the developed hydraulic transformer is tested by experiment but also the two control strategies including PID and fuzzy adaptive tuning PID are applied to the system. The experiment result shows that not only the expatiated theory is correct and the adopted control strategy is feasible but also the prototype of hydraulic transformer driving linear system for hydraulic constant pressure rail system is successful.