In the field of industrial automation, machines require sensors to provide essential information to correctly perform related operations. Most industrial intelligent robots have begun to utilize sensors to improve their adaptability. Sensors for intelligent robots can be broadly categorized into tactile sensors, proximity sensors, force sensors, and various other types such as vision, slip, and thermal sensors. For example, many collaborative robots integrate torque sensors and cameras to ensure a better field of view during operation and to guarantee the safety of the work area. Today, the TalkControl.com editor will share the application of displacement sensors in the field of industrial automation.
Introduction to the principle of displacement sensor
Displacement sensors, also known as linear sensors, are linear devices that utilize metal induction. Their function is to convert various measured physical quantities into electrical quantities. The most commonly used type is the magnetostrictive displacement sensor.
Magnetostrictive displacement sensors measure the actual displacement of a product by accurately detecting the absolute position of a movable magnetic ring using non-contact measurement and control technology. The sensor utilizes the principle of magnetostriction, generating a strain pulse signal through the intersection of two different magnetic fields to accurately measure position. The measuring element is a waveguide, and the sensitive element inside is made of a special magnetostrictive material. The measurement process involves a current pulse generated in the sensor's electronic chamber. This pulse propagates within the waveguide, creating a circular magnetic field outside the waveguide. When this magnetic field intersects with the magnetic field generated by the movable magnetic ring, which represents positional change, a strain mechanical wave pulse signal is generated within the waveguide due to magnetostriction. This strain mechanical wave pulse signal travels at a fixed speed of sound and is quickly detected by the electronic chamber.
Displacement sensors are mainly used in the following fields
1. Electronics and automotive industries
As times change, people are becoming increasingly reliant on automobiles and electronic products. Displacement sensors are used for online inspection on production lines in the electronics and automotive industries, significantly improving equipment automation and production efficiency, making them an indispensable part of automated production lines. Sensors are also used for dimensional measurement and assembly positioning of various automotive parts and electronic components, enhancing the quality of processed products.
2. Pharmaceutical equipment and petrochemical industry
In specialized applications such as the pharmaceutical and petrochemical industries, displacement sensors must possess explosion-proof and corrosion-resistant properties. Explosion-proof magnetostrictive displacement sensors are available in intrinsically safe, flameproof, and intrinsically safe flameproof types, suitable for displacement and level measurement in flammable and explosive environments. Corrosion-resistant magnetostrictive displacement sensors, protected by an external PTFE (polytetrafluoroethylene) protective layer, can be used for measurement and control in corrosive media such as acids, alkalis, and salts.
3. Rubber and plastic machinery, die-casting machinery
The plastics and metal casting industries are pillar industries of my country's economy, producing a wide range of products, including consumer goods, automobiles, industrial equipment, agricultural machinery, and scientific research instruments. Displacement sensors are used in CNC machinery such as injection molding machines, rubber molding machines, and die-casting machines to measure displacement and locate positions. The quality of the sensor directly determines the control effect of the CNC machinery. Resistive linear displacement sensors are commonly used in rubber and plastics machinery and die-casting machinery. However, with the continuous improvement of equipment performance, the market demand for magnetostrictive displacement sensors, which offer better vibration resistance, anti-interference performance, and service life, is constantly increasing, gradually replacing resistive linear displacement sensors as a trend.
4. Food machinery
The food industry has much higher cleanliness requirements than other industries, making the replacement of traditional semi-automatic or manual machinery with highly automated CNC machines an inevitable trend. Displacement sensors enable automated operation and online monitoring of food processing machinery. Furthermore, the processing environment in the food industry is typically humid, placing relatively high demands on the protective performance of displacement sensors for on-site applications.
5. Electrical equipment
Displacement sensors are used in gate control and turbine control in the power industry. Commonly used sensors include resistive linear displacement sensors and LVDT (Low Voltage Detector) displacement sensors. LVDT sensors, in particular, have become standard components in some power sectors due to their high accuracy, good protection performance, and long service life. Eddy current displacement sensors are commonly used for online detection of turbine eccentricity, differential pressure, and rotational speed. In the hydropower industry, rope displacement sensors and magnetostrictive displacement sensors are commonly used for reservoir level monitoring.
6. Textile machinery
Resistive linear displacement sensors, magnetostrictive displacement sensors, LVDT displacement sensors, and angle sensors are used in textile machinery to achieve displacement measurement (including linear and angular displacement) and precision control of equipment. Resistive linear displacement sensors are widely used in textile machinery due to their cost-effectiveness. LVDT displacement sensors, with their high protection level, strong anti-interference performance, and long service life, are gradually replacing resistive linear displacement sensors and becoming a best-selling product.
7. Hydraulic machinery
Hydraulic machinery is widely used in automated control systems due to its high power and control precision. Displacement sensors enable precise measurement and feedback of the position of hydraulic cylinders in hydraulic machinery. Commonly used products include potentiometer-based linear displacement sensors, draw-wire displacement sensors, or magnetostrictive displacement sensors. Among these, magnetostrictive displacement sensors offer better shock resistance and a longer service life. Built-in magnetostrictive displacement sensors can also withstand higher pressures within the hydraulic cylinder, making installation and use more convenient. For some hydraulic machinery with large cylinder strokes and rigid push rods requiring very high parallelism during installation, manufacturing potentiometer-based linear displacement sensors or magnetostrictive displacement sensors is challenging. Draw-wire displacement sensors effectively solve these problems.
8. Medical equipment
Modern medical equipment places stringent requirements on the size and performance of sensors. Displacement sensors are mainly used in small to medium-sized equipment such as X-ray machines, fully automated operating tables, spiral CT scanners, or dual-source CT scanners to achieve precise displacement measurement and position positioning. Pull-wire displacement sensors have a small installation size, making them particularly suitable for the measurement needs of such equipment. Multiple pull-wire displacement sensors can also achieve multi-dimensional precision movement of platforms or columns.
The above are just a small part of the applications of magnetostriction. There are many other applications in work automation, which we will share in more detail later.
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