With the expansion of human activities into space, deep sea, and the deepening of exploration into natural phenomena, sensors and actuators have become a new field where basic research and modern technology are integrated. They incorporate multidisciplinary research achievements and have become one of the most dynamic areas for human exploration of nature and the development of social productivity. As applied technologies that utilize various functional materials to realize information detection and output, sensor and actuator technologies constitute one of the three pillars of modern information technology systems.
In the field of opto-mechatronics integration, sensors can be classified by measured parameters into non-electric sensors for dimensional and shape parameters (width, thickness, crown, flatness, curvature, diameter, etc.), position (level, valve opening, height, inclination angle, etc.), temperature, velocity (rotational speed, linear velocity), force (gravity, pressure, tension, rolling force, etc.), vibration, acceleration, flow, humidity, viscosity, color, illumination, visual images, and so on. Classified by measuring principles, they are mainly based on physical and chemical principles, including electrical parameter type, magnetoelectric type, magnetostrictive type, piezoelectric type, semiconductor type, etc.
Actuators are required to have high-precision control and fast response capabilities according to control system requirements. They mainly include electric actuators (servo motors, linear motors, stepper motors, variable-speed motors, etc.), pneumatic actuators, hydraulic actuators (proportional control valves, servo valve closed-loop control), piezoelectric ceramic actuators, LV/HV nano-actuators, etc.
The integration of electrical control and instrument control has become the basic automation system. Sensors (transmitters), measuring instruments and actuators serve as input and output devices for PLC, PAC or IPC. Most applications of sensors and actuators involve complex control systems with high speed, high precision and multiple control loops, realizing functions such as regulation, correction, deviation rectification and compensation.
They are mainly used in the mechanical and electrical industry for machining equipment (high-speed machining, laser machining, precision die-casting, precision processing, plastic processing, rapid prototyping, etc.), CNC equipment, parallel machine tools, printing and packaging equipment (synchronization, deviation correction, compensation devices, etc.), transportation equipment (conveyors, elevators, cranes, automated warehouses, etc.), semiconductor manufacturing and testing and IT industry equipment (precision positioning, micro-cutting, die bonders, bonders, SMT production lines, etc.), pharmaceutical/consumer goods production lines (batching, weighing, counting, inkjet coding, labeling, color recognition, etc.), automotive manufacturing (welding robots, tire pressure detection, process monitoring, etc.), automatic mail sorting lines and office equipment.
With the integration of digital and information technologies with mechanical devices, sensors and actuators have begun to realize data sharing, coordinated integration of control functions and control parameters, and connection with external systems via fieldbuses. With the redistribution of basic automation control functions, many computer control functions have been decentralized to sensors and actuators, such as parameter detection, control, diagnosis and maintenance management.
Functional safety of mechanical equipment specified by the IEC-62061 standard has become a popular concept and an unavoidable issue. For sensors and actuators, MTBF (Mean Time Between Failures) was conventionally used to evaluate reliability. With the integration of hardware, software and network communication, reliability must be described by an overall indicator, namely the functional safety specification. During operation, under the individual or combined effects of external factors (mechanical vibration, shock, temperature, electrical noise, surge, lightning, etc.), the devices must be protected against hazards caused by functional failures while maintaining reliable operation, without abandoning the established reliability theory based on rigorous probability theory.
The development trend of sensors and actuators is toward integration, miniaturization, intelligence, networking and multi-functionality. New principles and materials such as nanotechnology, advanced piezoelectric and ceramic materials, and tunnel barrier effects are being used to develop sensing and actuation systems for aerospace, deep-sea and genetic engineering applications.
In the industrial field, sensors (transmitters) and actuators with fieldbus capabilities can generally provide device status information along with measurement data, and enhance self-diagnosis functions with dedicated software—for example, differential pressure/pressure transmitters can diagnose blockages in impulse lines and orifice erosion. In recent years, fieldbus technology has focused on the development of Field Device Tool (FDT) technology, aiming to standardize field device interfaces so that manufacturers can develop parameter setting and fault diagnosis software integrated in the form of Device Type Managers (DTMs). In most cases, the new FDT interface can be applied in a “soft adapter” manner for both RS-232C and fieldbus connections.
With the acceleration of digital and information technology transformation of traditional industries and the advancement of opto-mechatronics integration, the prospects for R&D and application of new high-performance-cost-ratio sensors and actuators in China will be even broader.
