Detection element of open CNC system
1 Open controller matches multiple detection components Next page
The detection component is an important part of the servo control unit in the CNC system. It detects the displacement and speed of the actuator or servo motor rotor and feeds the detected signal back to the servo control unit to form a closed loop feedback. The quality of the detection component is directly related to the control accuracy of the system. Processing various signals from the motion mechanism through the detection component is an important manifestation of the openness of the open controller. PMAC can receive feedback from various detection components, including direct reception of incremental encoder feedback. Selecting accessories can receive tachogenerator, resolver, laser interferometer, absolute encoder, magnetostrictive sensor, inductive synchronizer, magnetic grid Feedback from components such as grating scales (straight and circular) and laser scales. Feedback types include orthogonal encoder feedback, parallel position feedback, linear displacement sensor feedback, analog position feedback, resolver feedback, and dual feedback. It can be seen that the openness of PMAC is very extensive.
2 Characteristics and applications of various detection components
Feedback components commonly used to measure rotational motion include rotary encoders (mainly photoelectric encoders), circular gratings, resolvers, and rotary inductive synchronizers. The feedback elements used to measure linear motion are straight gratings, laser scales, linear inductive synchronizers, and laser interferometers. Some of them can also be used for acceleration and speed feedback. Here, the commonly used detection components are briefly summarized in the following table for use in practical applications.
3 main detection component products
The following is a description of the most commonly used photoelectric encoders and scales, and a brief introduction to a new type of detector - laser scale.
Photoelectric encoder
The photoelectric encoder makes it easy to measure the angular displacement of the motor shaft and also the speed of the shaft. At present, the photoelectric encoder is often assembled directly with the servo motor through the cross coupling to form a closed loop or semi-closed loop servo system. For example, the SANYO coded disk DC and AC servo system, PANSONIC optional MINUS series AC servo system with incremental or absolute code.
Photoelectric encoder products, such as NEMICON's various types of code discs, are widely used in the control of multi-joint robots, the indexing of ATC work machines, the control of semiconductor shim mobile robots and the bed positioning of CT scanners. A wide range of manual encoders, absolute encoders, incremental multi-type absolute encoders, incremental encoders, hollow encoders and manual pulse generators, micro-miniature encoders are only 12mm in diameter. The resolution is 6 bits, 8 bits, 10 bits, etc., up to 25000 pulses / r, covering most control applications.
Scale
Metering gratings have been used as measuring elements for many years, especially as feedback elements for closed-loop control on CNC machine tools. The UK RENISHAW company opened the first non-contact steel strip grating system. The grating has a very high requirement for the installation and use environment, which makes the grating go out of the laboratory and enter a wide range of applications.
RENISHAW RG2 linear encoder consists of RGS steel strip grating and readhead. RGS steel strip is 0.2mm thick and 6mm wide. The length can be supplied from one meter to several tens of meters. The pitch is 20μm or 40μm, the grating accuracy is ±3μm/m, linear. Degree ± 3 μm / m or ± 1 μm / 60 mm. Double-sided gold plating protects the scale from dirt and deforms evenly on both sides. The reading head is divided into RGH22, RGH24 and RGH25 three dimensions, built-in subdivision circuit, available in 0.05μm, 0.1μm, 0.5μm, 1μm and 5μm resolution. The analog head has standard voltage output and current output options. Small size, light weight and easy adjustment. A built-in multi-color illuminated indicator light indicates the installation of the readhead without the need for tools such as an oscilloscope. Its special treatment ensures that the accuracy of the scratch of the scale is not affected.
RENISHAW also has RGH34 bare head grating system, RGH42 XY mesh grating, RGR circular grating, laser ruler and laser interferometer.
Laser ruler
RENISHAW The newly developed laser ruler RLE consists of RLU laser generator and RID probe. It is a high-precision, high-linear position feedback component specially developed for single or dual axes in the factory. The principle of laser interference is also used, but it is more suitable for industrial applications than laser interferometers than calibration. The measurable shaft length is up to 100m, the maximum feed rate is 5m/s, the accuracy is ±10nm, and the repeatability is 5~10nm. After subdivision compensation, a resolution of 0.077 nm is obtained. It is suitable for applications with high precision requirements such as semiconductors, gauges and machine tools.