Research On The Low Velocity Control Of The Direct Drive Volume Control Electro-hydraulic Servo System

The Direct Drive Volume Control (DDVC) Electro-hydraulic Servo System is a new Electro-hydraulic Servo System. From the view of energy, in the new type of the DDVC Electro-hydraulic Servo System, the motor drive a bidirectional fixed displacement pump to take the hydraulic system movement as the energy components. And also control the flow rate and cycle of the oil by controlling the flow rate and cycle of the motor to take the hydraulic system movement as the control components. It has the advantages of flexibility of AC servo motor control and high power of hydraulic servo system. Compared with the traditional electro-hydraulic servo system,the DDVC Electro-hydraulic Servo system is efficient,miniaturized integrated, convenient operated and economical. It has been used in many domains, and made great economic benefits. So it is widely considered to be one of the most important developing directions of the hydraulic control system. It will be widely used in more and more areas in the future. With the development of its application, how to improve the trajectory tracking precision of the DDVC Electro-hydraulic Servo system in low velocity motions becomes more important in the field. So that, the level of the low velocity characteristic impacted the system and how to compensate these factors become to an important subject.In this paper, the mathematical mode of AC asynchronism motor Direct Torque Control was established, and the simulation mode was built. In addition, the idealized model of the DDVC Electro-hydraulic Servo system which based on united simulation of AMEsim/Simulink was established, simulation was executed.In this paper, in order to make the research available, the low velocity characteristic of the DDVC Electro-hydraulic Servo system was also analyzed, and the low velocity characteristic simulation model was built. Computer simulation validated that the friction, the leakage and the mechanical losses are seriously influenced the system performance when the system working on the low velocity mode.In this paper, after analyzed the influence of the friction, the leakage and the mechanical losses,the mathematical mode and the simulation mode of the friction compensator was established. The availability of the compensator test and verify by the simulation. And also design a oil compensation installation,to compensate the volume loses by the gear pump.