The difference between servo electric cylinder and ordinary hydraulic cylinder

The difference between servo electric cylinders and ordinary hydraulic cylinders lies in their design ideas and uses. Ordinary cylinders mainly perform reciprocating motion, some of which have positioning functions; Servo cylinders are designed for control and place greater emphasis on dynamic performance. In hydraulic systems, the control component is the valve, the power component is the pump, and the cylinder and motor are the executing components.

The core of servo hydraulic is control, not hydraulic. It is only because hydraulic is the method with the highest transmission power to volume ratio, which is more in line with the principle of strong force carrying small load (relative) and improving response that hydraulic transmission was chosen. In fact, servo hydraulic is similar to servo motors, and the focus is on control. The core issue of hydraulic systems today is to improve transmission efficiency and save energy, which is why load sensitive and closed systems have emerged. Servo systems, on the other hand, are typical low efficiency systems that trade efficiency for dynamic response. On the contrary, servo systems also hope for higher efficiency for better performance. Hydraulic and servo hydraulic are clearly two major components because their focus is completely different.

Servo cylinders need to consider friction, which affects the dynamic response, control accuracy, stability, and other aspects of the servo system. In the design of servo cylinders, low friction coefficient seals should be selected, and the moving surface should be more precise than ordinary ones.

Working principle of electro-hydraulic servo control system: An electro-hydraulic servo system is a feedback control system composed of an electrical signal processing device and a hydraulic power mechanism. The most common ones are electro-hydraulic position servo systems and electro-hydraulic (or torque) control systems. Hydraulic servo systems have been widely used in industrial control due to their unique advantages such as fast response speed, high load stiffness, and high control power. The electro-hydraulic servo system converts low-power electrical signals into high-power hydraulic power by using electro-hydraulic servo valves, thereby achieving servo control of some heavy machinery equipment.

The electro-hydraulic servo control system enables the output of the system, such as displacement, velocity, or force, to automatically, quickly, and accurately follow changes in the input quantity, while greatly amplifying the output power.

The composition of a hydraulic cylinder is mainly composed of five parts: cylinder barrel and cylinder head, piston and piston rod, sealing device, buffering device, and exhaust device.

Requirements for servo hydraulic cylinder:

Low friction, no crawling, and high frequency response. Low internal and external leakage. Usually, special treatment is applied to its friction pair.

Steel cylinder: The inner friction surface is plated with hard chromium and polished or precision polished.

Piston seal: an O-ring made of polyethylene filled with glass microspheres.

Piston rod seal: Pre added lip seals made of nitrile rubber, as well as static and dynamic pressure seals with a guide sleeve with a small cone inside.

Piston cylinder guide sleeve: made of high wear-resistant and high hardness Fe3N cast iron.

Dust ring: made of bimetallic material and pre ground into a blade shape.

Oil pipe: The oil pipe between the servo valve and the hydraulic cylinder is directly drilled through a transition block and pre installed thick walled rigid short pipe.