Electro-hydraulic servo actuator capable of implementing long-stroke and high-frequency loading, and control method

A control method of an electro-hydraulic servo actuator capable of implementing long-stroke and high frequency loading, wherein the electro-hydraulic servo actuator comprises:

• a long hydraulic cylinder with a piston;
• a short hydraulic cylinder with a piston;
• a fixed-end rod having one end connected to the piston of the long hydraulic cylinder, and the other end fixed;
• a low frequency electro-hydraulic servo valve and a high frequency electro-hydraulic servo valve, the low frequency electro-hydraulic servo valve and the high frequency electro-hydraulic servo valve being configured to convert electrical signals into hydraulic pressure flow control signals to control hydraulic pressure changes in left and right chambers of the hydraulic cylinders to implement corresponding piston movements;
• a left rod chamber and a right rod chamber;
• and
• a force applying end head and a force applying end rod, wherein the force applying end rod is connected to the piston of the short hydraulic cylinder and the force applying end head to output a movement of the piston of the short hydraulic cylinder to the force applying end head, the force applying end head has one end connected to the force applying end rod through a hinge joint, and the other end connected to a specimen under a load test, thereby applying a target large-displacement and high-frequency excitation to the specimen under the load test,
• the control method comprising:
• obtaining a target acceleration signal, and obtaining a low-frequency acceleration signal and a high-frequency acceleration signal based on the target acceleration signal through a frequency division algorithm;
• inputting reference signals to a long-stroke and low-frequency controller and a short-stroke and high-frequency controller, respectively, depending on a control strategy and a control algorithm that are adopted;
• controlling the long-stroke and low-frequency controller to output a first driving signal to a long-stroke electro-hydraulic servo system, and controlling the short-stroke and high-frequency controller to output a second driving signal to a short-stroke electro-hydraulic servo system, in such a manner that the long-stroke electro-hydraulic servo system and the short-stroke electro-hydraulic servo system generate respective output forces based on respective driving signals and push a load to move, wherein the long-stroke electro-hydraulic servo system comprises the long hydraulic cylinder with the piston and the low frequency electro-hydraulic servo valve, and the short-stroke electro-hydraulic servo system comprises the short hydraulic cylinder with the piston and the high frequency electro-hydraulic servo valve;
• and
• detecting a plurality of motion signals of pistons of the electro-hydraulic servo actuator relative to respective hydraulic cylinders of the electro-hydraulic servo actuator, and inputting, depending on a feedback strategy that is adopted, the motion signals as feedback signals to the controllers of the two electro-hydraulic servo systems, to further correct the driving signals of the electro-hydraulic servo systems.