Servo Hydraulics – Definition, Structure & Advantages

Servo hydraulics is a sub-area of hydraulic technology. It encompasses all approaches that utilize controlled and regulated volumetric flows. The particular advantage of servo hydraulics lies in its energy efficiency. It can save up to 80% energy compared to unregulated hydraulics.

Structure of Servo Hydraulic Systems

Like conventional hydraulic systems, servo hydraulics consists of the following components:

• Pump with Drive
• Lines
• Valves
• Actuators
• Tank

Advantages and Differences of Servo Hydraulics Compared to Unregulated Hydraulics

The essential difference between servo hydraulics and unregulated hydraulics lies in the drive system. In unregulated systems, the motor driving the servo pump runs at a constant speed. This only allows for uniform movements without demand matching. The only control option in these systems is to switch the motor on or off. A typical application is a hydraulic lift platform. Due to the short-term use of a few seconds to raise the platform, regulation is not required. However, the situation is different for construction vehicles, for example. Here, different actuators are constantly in use, which should be supplied with varying pressures and volumetric flows to operate efficiently. In these cases, the use of servo hydraulics is advisable. It ensures that the actuators always move at optimal speed and force development, and that the motor’s power is regulated down accordingly when demand is lower. This can significantly reduce the demand for electrical energy and fuel.

Disadvantages of Servo Hydraulics

The main disadvantage of servo hydraulics is the higher cost. A device for controlling the speed of an electric motor – the so-called frequency converter – is already a very expensive component. In addition, there is a significant need for sensors that monitor volumetric flow and internal pressure. The data from these sensors must then be monitored and evaluated in a programmable controller. This further drives up the costs for servo hydraulic systems. In summary, this results in a specification sheet that should be used for planning a servo hydraulic system:

• Size and complexity of the hydraulic system
• Base, peak, and continuous load
• Operating time

Servo Hydraulics Extends Beyond the Frequency Converter

The frequency converter for controlling the speed of the pump drive is only the beginning of servo hydraulics. It can be supplemented with a variety of additional components to increase performance and capacity. In addition to electrical components such as the frequency converter or sensors, several solutions are also available on the hydraulic side. These include, for example, proportional valves, which maintain the volumetric flow under all circumstances. Furthermore, as electro-hydraulically designed proportional valves, they can significantly increase the efficiency and precision of a servo hydraulic system. For professional hydraulics in medium and large formats, proportional valves are therefore gradually becoming the new standard, displacing older, manual valves.