Comparison of electric, pneumatic, and hydraulic actuators

Thread Content

Comparison of electric, pneumatic, and hydraulic actuators – Actuator comparison: Hydraulic actuators provide the greatest thrust. Nowadays, they are usually combined with mechanical components to form mechatronic systems, but they are relatively bulky; as a result, they are used less frequently these days. For example, hydraulic actuators are used in the valve systems of the Three Gorges project. Electric actuators have poor safety and explosion-proof capabilities; their motors do not operate quickly enough, and the motors are prone to damage when the movement is obstructed or the valve stem gets stuck. Although electric actuators have been continuously improving and seeing an increasing trend in their application in recent years, overall they are not as widely used as pneumatic actuators. The actuator and the control mechanism of a pneumatic actuator form a unified unit, with the actuator types including diaphragm type and piston type. Pistons have a long stroke, making them suitable for applications that require high thrust ； The membrane type has a smaller stroke and can only directly drive the valve stem. Due to their advantages such as simple structure, high output thrust, stable and reliable operation, as well as safety and explosion-proof properties, pneumatic actuators are widely used in production processes with high safety requirements, such as in the chemical and petroleum industries. Working principles and characteristics of hydraulic and pneumatic mechanisms 1. Hydraulic mechanism A hydraulic mechanism is a mechanism that uses hydraulic oil as a power source to fulfill specified motion requirements and enable various mechanical functions. Compared with purely mechanical mechanisms and electrically driven mechanisms, hydraulic mechanisms have the following advantages: (1) Under the condition of delivering the same power, they feature a compact structure, small size, light weight, and low inertia. (2) It operates smoothly, with low levels of shock, vibration, and noise; it is easy to start and reverse frequently, and it can perform rotational movements as well as various reciprocating motions. (3) It is simple to operate and easy to adjust the speed; it enables stepless speed control over a wide range, with a speed ratio of up to 5000. (4) It enables low-speed, high-torque transmission without the need for a reduction gear. The drawback of hydraulic mechanisms is that the viscosity of the oil is greatly affected by temperature changes, making them unsuitable for use in low- and high-temperature environments ； The machining and fitting of hydraulic components require high precision; the manufacturing process is difficult and the costs are high. 2. Pneumatic mechanism A pneumatic mechanism is a mechanism that uses compressed air as the working medium to transmit power and control signals. Compared to hydraulic mechanisms, it has the following advantages: (1) It uses air as the working medium, which can be directly discharged into the atmosphere after use, making disposal straightforward. (2) Fast operation, quick response, simple maintenance, and clean working medium; there is no issue of medium degradation. (3) It has good adaptability to working environments, especially in harsh conditions such as those with flammability, explosiveness, high dust levels, strong magnetic fields, severe vibrations, humidity, radiation, and large temperature fluctuations; its safety and reliability are superior to those of hydraulic, electronic, and electrical mechanisms. The drawback of pneumatic mechanisms is that, due to the compressibility of air, the stability of their operating speed is somewhat poor; however, the use of gas-liquid actuation systems can yield satisfactory results ； The working pressure is low (usually 0.3–1.0 MPa), making it difficult to achieve high output force ； There is a lot of noise; a silencer must be installed during high-speed exhaust. Pneumatic actuation mechanism 1. Advantages of pneumatic actuation 1) Air is used as the working medium, which is easy to obtain; the used air can be discharged into the atmosphere, making treatment straightforward. Compared to hydraulic actuation, there is no need for oil tanks or pipelines for oil recovery. 2) Since the viscosity of air is very low (about one ten-thousandth of that of hydraulic oil), its losses are also minimal, which makes it convenient for centralized air supply and long-distance transmission. External leaks do not contaminate the environment as severely as in hydraulic transmission. 3) Compared with hydraulic transmission, pneumatic transmission features rapid action, fast response, simple maintenance, and a clean working medium, without issues such as medium degradation. 4) It has good adaptability to working environments, and is superior to hydraulic, electronic, and electrical controls in harsh working conditions such as those with flammability, explosiveness, high dust levels, strong magnetic fields, radiation, or vibration. 5) Low cost, with automatic overload protection. 2. Disadvantages of pneumatic actuation 1