The Love-Hate Relationship Between Hydraulics and Electricity

In 1998, “Fluid Power Transmission and Control” was removed from the university major catalog. It is said that this was because someone claimed that hydraulics would be replaced by electricity, and as a result, all “Fluid Power Transmission and Control” majors at that time were changed to “Mechatronics” majors.

More than 20 years have passed, and the hydraulic component manufacturing and application industry has made considerable progress worldwide, including in China. Important hydraulic components produced in China still have a considerable gap compared with the world’s advanced level. Hydraulic components are listed as key basic components in “Made in China 2025”; hydraulic major graduates are in high demand; hydraulic technicians who have received professional training, possess professional knowledge and professional skills, and can face, handle, and solve practical problems are extremely scarce. “Hydraulics has not been replaced to this day” is an indisputable fact.

In fact, the relationship between hydraulics and electricity is not simply a matter of whether one will or will not be replaced by the other, but should be examined and understood from three aspects: electrical control, electrification, and electric drive.

Before expanding the examination, let’s first sort out some concepts.

1) “Power” and “Information”

In modern science and technology, “power” and “information” have different meanings, different units, different pursuits, and follow different laws during transmission, so they should not be confused.

→ Sensor →← Electro-hydraulic Converter ←

However, the two are often closely connected in hydraulic systems. For example, sensors can extract information about power from the system’s operating conditions, such as pressure, flow rate, speed, etc., while electro-hydraulic converters regulate the transmission of power according to information sent by humans or computers.

2) “Drive” and “Control”

Related to “power” and “information”, the meanings of “drive” and “control” are also completely different.

Mechanical equipment can generally be divided into a drive part and a control part.

The control part handles the generation, transmission, reception, processing and sending of information, similar to human senses, brain and nerves. Due to the popularization of computers, in mechanical equipment, almost all electrical controls use computers (including PLCs), and electrical control is increasingly replacing manual control.

The drive part transmits power to make objects move or not move (braking), similar to human muscles.

Hydraulics, from the perspective of power conversion, is a transmission technology, and from the perspective of mechanical equipment, it undertakes the task of driving. In the following text, “hydraulic drive“ is abbreviated as “hydraulic drive”.

3) “Electrification” and “Electric Drive”

Driving loads always needs an energy source.

Hydraulic drive uses hydraulic cylinders or motors to drive loads, and the required hydraulic energy comes from hydraulic pumps.

To drive hydraulic pumps, for stationary equipment, electric motors are now almost universally used, because in modern society, electricity is almost “readily available”.

However, for mobile equipment, due to the inconvenience of connecting to electricity, internal combustion engines are still almost universally used to drive hydraulic pumps.

To reduce the harm to residents’ health caused by pollutants emitted by internal combustion engines, efforts are now being made to use electric motors to replace internal combustion engines. This is called “electrification”: the electric energy required by electric motors comes from batteries; fixed power sources or hydrogen fuel generators (fuel cells) are used to charge the batteries.

To avoid energy consumption caused by energy conversion in hydraulic drive, using electric motor + mechanical transmission, abbreviated as “electric drive”, to replace hydraulic drive has also been repeatedly put on the research and development agenda.

Electrical control is the well-deserved commander of hydraulic drive, electrification is a good backstage support for hydraulic drive, and electric drive has already begun to enter the market of hydraulic drive rotation.

In summary, hydraulic drive with electrical control is what we hydraulics professionals should have started developing yesterday; (for mobile equipment) hydraulic drive with electrification is what we must face today; and electric drive concerns what we hydraulics people will rely on for our livelihood tomorrow?!