Servo Hydraulic and Pneumatic Drive

Abstract

Among the various drives available, the hydraulic drive ranks at the forefront in terms of application history. The history of hydraulic power dated to the beginning of civilization, where artefacts show the applications of water turbines in power generation (Wikander, Handbook of Ancient Water Technology: Technology and Change in History, Brill, Leiden, 2000). However, more significant progress in this field is generally achieved following Pascal’s pioneering work which was later known as Pascal’s law of hydrostatic. Bernoulli’s discovery of the hydrodynamic law in 1750, and the Industrial Revolution in 1850 further catalysed the development of servo hydraulic drives. They led to the first applications of hydraulic equipment as a power source to power industrial machines such as the press, the crane, and the jack, as they also contributed to the development of hydraulic pumps, driven by steam engines, which produce hydraulic energy to run hydraulic systems. In the early 20th century, a revolutionary design of hydraulic drives used the oil, instead of water, as the hydraulic liquid, which greatly expanded the applications of hydraulic drives to more devices. World War II also contributed to the development of hydraulic drives, especially in the development of submarine control systems, radar/sonar drives, and military cargo transportation.

Hydraulic drives are still being used today, and, in fact, their applications are expanding to loads of increasing mass and power requirements, yet with higher speed and control precision. The main attraction of a hydraulic drive is its high power-to-weight ratio, rendering it the natural servo drive to use for heavy applications found in the aircraft and space shuttle. Moreover, it possesses several desirable characteristics such as accuracy, flexibility in applications, and simplicity of operations, as it also allows for fast, smooth, and precise start, stop, and reversal actions.