1.2 New development of pneumatic technology
(1) Cylinder with magnetic proximity switch
The cylinder with magnetic proximity switch is equipped with a permanent magnet on the piston, so when the piston moves to the preset position of the proximity switch, the magnet on the piston will close the contact and send an electric signal to indicate the travel position or control the action of a certain element. The mechanical positioning stopper and the additional position sensor are omitted.
(2) Gas liquid shift actuator
In some applications, not only the actuator is required to have sufficient driving force, but also the feed speed is required to be uniform, adjustable and stable when the load changes. The common cylinder is characterized by fast action, but the speed is not easy to control, and the phenomenon of “crawling” and “self walking” will occur, which is difficult to meet these requirements; The hydraulic cylinder is characterized by slow action, high load rigidity and good speed stability. The combination of the two can give full play to their respective advantages, that is, they become the pneumatic hydraulic damping cylinder commonly used in the pneumatic (or hydraulic) control system. The gas-liquid conversion actuator unit can realize accurate constant speed, low-speed feed, inching and intermediate stop by using the gas source as power, and can meet the needs of special users.
(3) Cylinder with displacement measurement and braking (locking) function
The cylinder with displacement sensor can measure the displacement in real time during the movement of the piston by using the principle of magnetic grating ruler, with a resolution of 0.1mm. It integrates driving and measuring functions and can be used as a position servo actuator with accurate positioning.
For example, the ml2b series produced by SMC is a cylinder with integrated functions of position measurement, feedback, Rodless and braking. With spring and air pressure double locking device, when the piston speed is below 500mm / s, there is no need for any correction control circuit, and its stop accuracy can be below 0.5mm. The brake (locking) device is set in the brake (locking) cylinder, which can stop the piston at a certain position of the stroke according to the needs, with high positioning accuracy.
(4) Proportional control technology (electric proportional control valve)
Electric proportional control valve (abbreviated as pneumatic proportional valve) is a new pneumatic control element developed on the basis of on-off electromagnetic pneumatic valve. Unlike on-off electromagnetic pneumatic valves, the electric proportional control valve can linearly control the output gas flow or output gas pressure of the valve depending on the magnitude of the proportional electric signal (voltage or current) to meet the requirements of force or speed control.
Because the pressure sensor is used to detect the controlled pressure and form a small closed loop, the accuracy of pressure control is high. The repetition accuracy is within 0.5% of the full scale. In addition, a novel electromagnetic switch type pneumatic proportional control valve and digital valve are also applied. Pressure proportional valves with analog input of current or voltage have been introduced. However, in many applications, it is not necessary to continuously control the pressure, but only to set a few points of pressure in advance. At this time, the pressure preset pressure proportional valve controlled by the switching value can be selected. Not only the pressure setting is accurate, but also the A / D and D / a conversion modules are not required. Another feature of this series of pressure proportional valves is that the exhaust volume is large to ensure that there is no pressure overshoot.
Select the pressure preset pressure proportional valve controlled by the switch value. As long as you press the button, you can easily and accurately set 16 preset pressure points. The real-time pressure can be displayed by the bright and easy to read led. It has the characteristics of high sensitivity and good performance.
(5) Electric servo technology
In the field of pneumatic technology, the traditional regulating elements are often based on the working principle of mechanical feedback, such as the classical pressure reducing valve. At present, the industrialized pneumatic closed-loop control system, i.e. servo pneumatic system, is realized on the basis of the latest development of sensing technology, electronic technology, modern control technology and software technology. Servo pneumatic realizes the continuous control of the output physical quantity of the pneumatic system, which is mainly used for the startup (acceleration) and braking of the pneumatic drive mechanism, speed control, force control (such as the grasping force control of the manipulator) and precise arbitrary positioning.
1.2.2 high speed
The high-speed development of the cylinder is of great significance to improving the production efficiency of the device. In recent years, it has attracted much attention. The rod less cylinder developed by the world famous companies such as SMC, CKD, Taiyo, origa, Norgren and mecmen
The maximum speed has reached more than 2m / s, other types of high-speed cylinders have even reached the speed of 3 ~ 4m / s, and FESTO has even produced 17m / s high-speed cylinders. The development of high-speed cylinder has corresponding technical problems to be solved. In addition to considering the sealing material and shape, the driving mode of the cylinder and how to absorb the impact inertia for buffering are very important. For example, the sinusoidal cylinder developed by SMC can run at a maximum speed of 500mm / s, which effectively solves the contradiction between high speed and low impact.
(1) Stylus cylinder
The cylinder diameter of needle pen type cylinder is as small as d = 2.5 ~ 15mm, which can be used for small and micro mechanical equipment.
(2) Thin cylinder
The thin cylinder is a type of cylinder that saves installation space and can be installed and fixed in multiple directions. The axial thin cylinder is suitable for short stroke and high thrust occasions. The radial ultra-thin cylinder adopts elliptical piston, and its thickness is only half of that of ordinary cylinder under the same thrust.
(3) Low power consumption and microelectronics
At present, the power consumption of the solenoid valve electromagnet is mostly below 1.8W, the power of the small pneumatic reversing valve is only 0.1W, the width is 10mm, and the power of the direct acting valve is generally less than 4W, which truly realizes the miniaturization of the components. SMC adds a new power-saving circuit for VJ series valves. When the energization time of the coil exceeds 30ms, the power consumption of the coil can be reduced by 30% on the premise of ensuring the necessary attraction of the iron core. The significance of low power consumption of the electromagnet is not only to save electric energy consumption and improve the reliability of the electromagnet, but also to create necessary conditions for the combination of pneumatic technology and microelectronics technology. Pneumatic systems in automatic production devices are mostly sequential control circuits. The signals of low-power pneumatic components can be directly processed as the signals of programmable controllers in time-sharing. The signals driving dozens of solenoid valves can be transmitted to the remote integrated valve block through one wire. This technology not only greatly saves wiring work, but also reduces faults caused by complex wiring. At present, this technology is not only applied to the transmission of drive signals, but also applied to the transmission of various sensor signals monitored by field actuators and mechanisms, which makes the configuration of the whole system more concise and lively.
Another development trend of cylinders is compounding. In order to facilitate users and shorten the time of mechanical design, various companies have developed cylinder components with compounding concept. The actuator not only has various installation forms, but also has developed various air cylinders and swing cylinders with guide mechanisms and connecting structures, which are suitable for special series of pneumatic actuators, ultra high speed and low speed components in various environments (such as corrosion resistance, pollution resistance, high and low temperature resistance, vibration resistance, etc.). The structure is also diversified, such as piston rod, non piston rod, double piston rod, magnetic piston, elliptical piston, cylinder with valve, cylinder with travel switch or sensor, proportional servo cylinder, etc. For example, SMC’s MRQ series linear and shaking compound cylinders have two degrees of freedom of motion, and are equipped with two flexible air claws to form a useful manipulator. NOK’s FPT Series platform bearing cylinder integrates the guide rail, platform and cylinder. The cylinder platform directly supports 780kg and can be directly used as a mobile base under a small press.
(1) Integrated development
The fundamental purpose of the integration of various functions on components is to reduce the workload of design, installation and debugging, and save the space required by components. This requirement and trend is manifested in all aspects of the industrial automation field, for the production of every pneumatic product.
Manufacturers are the key to maintaining competitiveness. With the development of computer technology, microelectronic technology and IC technology, electromechanical integration has a broader development space. Some electronic components or devices are installed on the original pneumatic control valve and pneumatic actuator, such as D / a conversion, signal amplification, modulation, decoding, measurement and signal feedback, so as to realize the integration of electronic and pneumatic control valve and even the pneumatic device directly integrated with the actuator, which greatly improves the system reliability and maintenance performance. Rotation, loading and unloading and indexing device of FESTO; The complete set of single coordinate manipulator of Matong company, including cylinder, manipulator, controller and measuring device; All kinds of small manipulators and robots of SMC, xiaojinjing, CKD and other companies, feed devices with guide mechanisms, indexing and positioning devices, and composite cylinders that can realize rotation and displacement have been produced as finalized products. In fact, this is an extremely important development direction and an inevitable trend of the development of pneumatic technology
(2) Integration of control valve and controller (one valve island)
The word “valve island” is translated from “ventilinsel” in German and “valve terminal” in English. The air control unit realized in the conventional way is characterized by a large number of discrete components in the system, and these discrete components are connected through a large number of pipe fittings and connectors. Complicated interconnection leads to high failure rate, and brings inconvenience to equipment management and maintenance. The air supply branch of the control valve and the air flow channel such as the exhaust port are integrated, and the wiring of the sensor input electric signal is integrated into a socket to form a modular and small integrated block, which is called the valve island. For example, FESTO’s valve island has integrated various functions such as pneumatic valves, sensors, bus interfaces and programming control.
On the valve island, the output signal and input signal of the programmable controller are connected to the valve island through a multi strand cable with a multi pin plug, and the signal output by the sensor is connected to the electrical signal input port of the valve island through a cable. Therefore, the interface between the programmable controller and the input electric signals of the pneumatic valve and the sensor is simplified to only one multi pin plug and one multi strand cable. Compared with the conventional control system, it can be seen that the system does not need a junction box after the valve island with multi pin interface is adopted. At the same time, all electrical signal processing and protection functions (such as polarity protection, photoelectric isolation, waterproof, etc.) have been realized on the valve island. Obviously, the design, manufacturing and maintenance process of the system is greatly simplified by adopting the valve island with multiple external interfaces.
However, with the complexity of the control circuit, the cables of the programmable controller output, transmission and valve island will be thicker and longer as the distance between the valve island and the programmable controller increases. In order to overcome this shortcoming, a new type of valve island with field bus has appeared. Two objects that use fieldbus for information exchange need only be connected by a two strand or four segment wire. In this way, the cable connection can be simplified, the anti-interference is stronger, and the reliability of data transmission is higher.
With the rapid development of computer network technology, the process control and monitoring technology of manufacturing industry is in the ascendant. The field bus and LAN technology make the integrated manufacturing information and integrated manufacturing process become a general trend. The development of pneumatic technology is also reflected in the intellectualization of its products
It is required to have the ability of judgment and reasoning, logical thinking and independent decision-making.
The application of modern interface technology in the field of industrial automation is mainly embodied in three forms: Fieldbus (Fieldbus), Ethernet (Ethernet) and ASI (axis and sensor interface). Its common feature is to realize signal transmission in serial mode. The main advantages are the simple connection between each action unit, the substantial reduction of installation and commissioning costs and the convenience of fault diagnosis.
Fieldbus is developed to meet the requirements of PLC peripheral interface system and components in practical applications. These requirements mainly include signal transmission distance, speed and reliability in industrial field application. At present, all automatic control component manufacturers, including major pneumatic component manufacturers, provide products with bus interface to the market. Programmable controller and field bus are the mainstream of industrial automation control recently. The most outstanding advantage of as is that it can use the same two-core cable for transmission
The transmission rate of control and feedback signals and control signals required for reversing of pneumatic components is high, which has been increased from the original 10MB / s to 10Gb / s, and can fully meet the requirements of field control. Meanwhile, based on TCP / IP communication protocol, Ethernet can
It is very convenient to combine with Internet and open the door for CIM production technology. These will inevitably have a profound impact on the pneumatic technology. At present, industrial control computer (IPC) with Ethernet connection has begun to partially replace programmable controller with field bus interface.
1.2.7 pneumatic robot and pneumatic manipulator
Since the pneumatic components can complete linear, rotating, sucking, grasping and other actions, and have a variety of specifications to choose from, they are particularly suitable for assembling into a modular work robot or manipulator. For example, it is composed of a column type pneumatic manipulator, a gantry type pneumatic manipulator, a slider type pneumatic manipulator, and other types of pneumatic manipulators. In the process of combination and expansion, each part of the pneumatic manipulator (including bracket, support, fittings,screw and nut) is listed in the product sample of the pneumatic supplier, and the designer does not need to redesign, manufacture or purchase another small part.
1.2.8 vacuum technology
Vacuum technology is an important branch in the field of pneumatic technology. In industrial production, as a sucker manipulator, it is widely used. Therefore, many pneumatic enterprises attach great importance to the development of vacuum components. For the general vacuum circuit, it is unnecessary to set an independent vacuum source when using the jet vacuum generator. A usable vacuum system can be easily formed by using only the suction cup and the vacuum circuit unit module. The unit module contains a vacuum valve, a vacuum pressure switch, a filter, a muffler, etc., and has a compact structure. SMC’s ZX and ZM series vacuum circuit units have a width of only 15.5mm. In order to improve the suction flow rate of the vacuum generator, SMC has developed a jet type vacuum generator with two-stage nozzle structure. Under the same air consumption, the suction flow rate can be increased by 40%, and the maximum vacuum pressure can reach – 83.99kpa. The nozzle and shell of ZH series vacuum generator are integrally formed resin materials, which are very light and practical. There are two types of square box type (built-in muffler) and three-way joint type.
1.2.9 energy saving, environmental protection and green development
Economic development has brought a series of problems to the ecological environment and energy situation of the earth. Environmental protection and energy conservation have now become an important symbol to measure whether a country can achieve sustainable development.
As human beings have higher and higher requirements on the environment, they do not want the exhaust gas emitted by pneumatic components to pollute the environment with oil mist, so oil-free lubricating pneumatic components will be popularized. There are also some special industries, such as food, beverage, pharmaceutical and electronics, which have stricter requirements for air. In addition to oil-free, they also require tasteless and sterile filters. Such filters with special requirements will be continuously developed. Maeda Commercial Service Co., Ltd. has developed antibacterial and sterilization air filters with zero water drop, 99.99% oil mist and 0.1um filtration precision, which are widely used in food factories.
The general industrial pneumatic system is composed of two parts: the air source system and the air consumption system. The efficiency of the pneumatic system is low and the energy loss is large. How to achieve energy saving is an important research topic.
The compressed air used in the pneumatic system is produced by the air compressor. Reducing the air consumption will reduce the power consumption of the compressor, which will undoubtedly increase the energy saving effect. The way to reduce the air consumption is to use the piston area difference of the differential cylinder to control and control the air flow in the pneumatic system to the minimum according to the use purpose and conditions.