Ethernet is becoming an increasingly important network in industrial applications. As far as motion control is concerned, Ethernet, fieldbus, and other technologies (such as the interconnection of peripheral components) have always competed with each other to gain control in industrial automation and control systems. Processing permissions for some of the most demanding workloads. Motion control applications require determinism (to ensure that the network can deliver the workload to a predetermined node in time), which is necessary to ensure position retention, which in turn will ensure accurate stopping of the drive, proper acceleration/deceleration, and other tasks.
The standard IEEE 802.3 Ethernet has never met this requirement. Even if the full-duplex switching and isolating the collision domain eliminate the outdated CSMA/CD data link layer, it still lacks predictability. In addition, the high complexity of TCP/IP in a typical stack is not optimized for reliable delivery of real-time traffic. Therefore, fieldbus and PC control architecture with ASIC-based PCI cards have always been common motion control solutions.
The Ethernet solution from EtherNet/IP® to EtherCAT® overcomes these shortcomings in a unique way. Although Industrial Ethernet has some other advantages over other alternative technologies, it is far from dominating in motion control. Let's take a look at three reasons why it can and will be more and more accepted in the competition in the next few years.
1. Converge rather than increase complexity
Over time, the interconnection between enterprise IT and factories has increased, resulting in more complex systems, often mixing standard Ethernet and industrial Ethernet with fieldbus. For example, the machine might use:
* SERCOS1 for communication with the server * PROFIBUS® for networked variable frequency drives * SafetyBUS p for fail-safe fieldbus communication * DeviceNet for connection to sensors * Suitable for sending data to end users, access via gateway Ethernet
Such a network is complicated, and it is expensive to build and maintain. Each agreement requires its own implementation procedures, installation personnel, and training. In contrast, Ethernet offers the possibility of converging different networks suitable for sports, security, etc., onto a cost-effective infrastructure that is easier to wire, has extensive support from suppliers, and can adapt to future requirements.
Ethernet provides the possibility of convergence of different networks
The EtherNet/IP protocol embodies how to give full play to the role of integration in practice. By using standard Ethernet technologies such as TCP/IP and UDP/IP, supplemented by features such as CIP Sync (used to achieve distributed clock IEEE 1588 precise time protocol synchronization), the integrated switching system can adapt to both commercial and industrial applications.
2. Determinism is suitable for motion control applications
Motion control relies on precise communication. This accuracy is supported by the use of slot-based scheduling, and each device has a schedule for communicating with other devices in the scheduling strategy. These servo drives and controllers calculate their respective timings, from which the ∆T value of the control function can be calculated. However, if the data transmission becomes unpredictable, the results may be lost, so determinism is required to ensure the stability of the loop.
Ethernet can support demanding motion control applications in factories. In some cases, the implementation of IEEE 1588 in EtherNet/IP through accelerator circuits directly integrated in Intel® chips is just one of the Ethernet solutions used to enforce determinism Common mechanism. EtherCAT's high-speed real-time processing is another example of how to achieve consistent predictive performance in motion control applications. EtherCAT breaks through the strict physical limitations of PCI-based centralized communication, which requires fast communication between the machine processing unit and the servo processor but requires a short distance.
Jason Goerges explained in an article published in Machine Design in 2010: "The distributed processor architecture based on EtherCAT has wide bandwidth, synchronization and physical flexibility, comparable to the functions of centralized control and both distributed. Advantages of the Type Network".
"In fact, some processors in this way can control up to 64 highly coordinated axes (including position, velocity, current loop and commutation), with a sampling rate and update rate of 20 kHz."
3. Long-term feasibility for IIoT
Since the advent of Ethernet as a local area network technology, it has undergone a series of developments. Given that traditional fieldbus components are currently manufactured on a small scale, and PCI is facing the risk of becoming an outdated industry standard architecture, Ethernet has been continuously developed and is now fully capable of providing services for the IP-centric industrial Internet of Things.
Upcoming improvements (such as time-sensitive networks that will improve IEEE 1588 and support the possibility of network convergence) also make Ethernet an ideal choice for current and future motion control. This is not to say that fieldbus and PCI will die out, but that as the automation industry moves towards IIoT, the advantages of Ethernet will continue to increase.
According to the different backlight sources, LCDs can be divided into two types: CCFL displays and LED displays.
Misunderstanding:
Many users believe that liquid crystal displays can be divided into LEDs and LCDs. To some extent, this understanding is misguided by advertisements.
The LED display on the market is not a true LED display. To be precise, it is an LED-backlit Liquid Crystal Display. The liquid crystal panel is still a traditional LCD display. In a sense, this is somewhat fraudulent. nature! South Korea`s Samsung was once convicted by the British Advertising Association as violating the country`s advertising laws because its [LEDTV" LCD TVs were suspected of misleading consumers. For liquid crystal displays, the most important key is its LCD panel and backlight type, while the LCD panels of displays on the market generally use TFT panels, which are the same. The difference between LEDs and LCDs is only their backlight types: LED The backlight and CCFL backlight (that is, fluorescent lamps) are diodes and cold cathode lamps, respectively.
LCD is the acronym for Liquid Crystal Display, which means "liquid crystal display", that is, liquid crystal display. The LED display refers to a type of liquid crystal display (LCD), that is, a liquid crystal display (LCD) with LED (light emitting diode) as the backlight source. It can be seen that LCD includes LEDs. Corresponding to the LED display is actually a CCFL display.
(1) CCFL
Refers to a liquid crystal display (LCD) with CCFL (cold cathode fluorescent lamp) as the backlight source.
The advantage of CCFL display is good color performance, but the disadvantage is higher power consumption.
(2) LED
Refers to a liquid crystal display (LCD) that uses LEDs (light emitting diodes) as a backlight source, and generally refers to WLEDs (white light LEDs).
The advantages of LED displays are small size and low power consumption. Therefore, using LEDs as a backlight source can achieve high brightness while taking into account lightness and thinness. The main disadvantage is that the color performance is worse than that of CCFL monitors, so most professional graphics LCDs still use traditional CCFL as the backlight source.
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