To borrow the words of Dr. Zhang Haiping of China's hydraulics industry:
"The two fundamentals on which hydraulic technology is based - higher energy density than electrical drives and more flexibility than mechanical drives - are not so easy to break through."
Characteristics of hydraulic transmission
Characteristics of hydraulic transmission: Hydraulic transmission has many characteristics such as small size but high power, high speed and high power density, strong and firm shock resistance, strong environmental resistance and long life. Comparing hydraulic motors with electric motors and other transforming electromagnetic transmission actuators, the power density is about 10 times higher, and the power ratio is more than 20 times higher than the responsiveness standard.
In this regard, piezoelectric or super-magnetostrictive actuators, although you can get a larger thrust, but can move the stroke and hydraulic cylinders, the stroke is super short and not comparable. Therefore, the use of engineering machinery, such as hydraulic cylinders and other linear transmission, the use of electromagnetic substitution is inconceivable.
In addition, the advantage of hydraulic power transmission is that it is more flexible in terms of the configuration of the realized components than the mechanical power transmission such as gears or connecting rods. Since the configuration of the composition between a power source such as a pump and an actuating element such as a control valve, a hydraulic cylinder, a motor, etc. is realized by piping, the configuration between them is not a problem even if they are far away from each other, and there is a greater degree of freedom in the shape or spatial design of the transmission system. Moreover, it is possible to realize a high-performance and high-strength adjustable power transmission system by adopting the hydraulic base parts in conjunction with the hydraulic base parts without being limited by the mechanical and structural constraints of the structure.
Fixed equipment hydraulics is now beginning to be partially sidelined by electrical drives - servo motors, etc., that is, because electrical energy can generally be obtained directly, and the use of hydraulics can also be one more energy conversion, one more energy loss. But that only happens on low-power stationary equipment, on those thousands to tens of thousands of tons of hydraulic presses, in another twenty years hydraulics will not have a rival." "Currently the aerospace industry, robots (e.g., Boston Dynamics' Atlas with a battery on its back), still use a lot of hydraulic drives. The fundamental reason for this is the high force density of hydraulic drives. To obtain linear motion, hydraulic cylinders have a simple structure and can achieve thrusts that electric drives can't hope to achieve. Small thrust, dozens of hundreds of kilograms of force, electric drive can be. But the large thrust, not to mention the tens of thousands of tons, or thousands of tons, electric drive is very difficult to do, this is because, the electromagnetic force is limited by the current. All currently available materials have resistance: the higher the current, the worse the heating." Of course, in the future, if fuel cells, superconductivity technology, etc. have industrialization breakthroughs, perhaps hydraulic drive will be replaced to a certain extent, but in terms of the current industrial development, hydraulics in many areas is still very important.
As far as I know, the hydraulic system has been embracing intelligence in recent years, adding more digital, intelligent control and data acquisition and analysis, the future development prospects are still very broad.
