The grating is an optical element that uses the phenomenon of light transmission and diffraction to work. There are many applications of grating detection devices, and its measurement accuracy can reach plus or minus μm, and it has the advantages of high accuracy, fast response speed, and wide range.https://www.wondercopper.com/ There are linear gratings and circular gratings, which are used to measure linear displacement and angular displacement, respectively.
1. Structure of grating detection device
The structure of the grating device is composed of a scale grating and an indicating grating. There are many of the same density on the scale grating and the indicating grating, which are called grating fringes. The amperage of the grating fringes is generally 25, 50, 100, 250 per millimeter. https://sandcasting.org/For transmission gratings, this line is not self (for reflective gratings, this line does not reflect light), and the light is transmitted (or reflected back) from the narrow surface between the two lines.
2. Working principle of grating measuring device
Place the indicating grating parallel to the side of the ruler grating, and make their lines relatively inclined at a small angle θ, and place the light on the other side of the ruler grating (take the heading mimeograph as an example). When light passes through them, bandits are produced on the mimeograph.https://lasercutting-service.com Moiré fringes are stripes of light and dark. When the mimeograph is instructed to move, the bandit fringe moves, and the direction of movement is almost perpendicular to the direction of the grating. The mimeograph is instructed to move a distance between the scribe lines relative to the scale grating, and the bandit fringe is also called a moiré interval. The relationship between moiré spacing and line spacing is W≈P/θ where W is the moiré spacing; P is the spacing between two engraved lines; θ is the relative inclination angle between two feet (rad).https://cncmachining.jp
The Moyun fringe has an amplification effect. If P=0.01mm and θ=0.001, then W=10mm, which is equivalent to magnifying the distance of the two-foot marking line by 1000 places. The photoelectric element moves together with the indicating mimeograph. When moving, the light received by the photoelectric component changes sinusoidally under the influence of the moiré fringe, so the photoelectric element generates a current that changes according to the sinusoidal law (voltage 0. The change law of the current or voltage can be analyzed to measure the displacement of the moving part , Speed and direction of movement.
The structure of the DC servo motor mainly includes three parts.https://ptjcnc.com
Stator: The magnetic field is generated by the magnetic poles. According to the way of generating the magnetic field, the DC servo motor can be divided into permanent magnet type and separately excited type. Permanent magnet poles are made of permanent magnet materials. Separately excited poles are made of stamped silicon steel sheets, and the coils are wound on the outside to generate a constant magnetic field through direct current.
Rotor: The rotor is made of silicon steel laminated with coils embedded on the surface. When direct current is applied, the electromagnetic torque that drives the load to rotate is generated under the action of the stator’s magnetic field.https://numerical-control.com/
Brushes and commutator segments: In order to keep the electromagnetic torque generated in a constant direction, the rotor can rotate uniformly and continuously in a predetermined direction, the brushes are connected to an external DC power supply, and the commutator segments are connected to the armature conductor.
Considering the actual operation, the DC servo motor has introduced a mechanical commutation device. Three highs] There are many failures and difficult maintenance. The sparks generated by the carbon brushes often affect production and cause electromagnetic interference to other equipment. http://plastic-mold.cn/At the same time, the commutation capability of the mechanical delimiter limits the capacity and speed of the motor. The armature of the motor is on the rotor, which makes the motor low efficiency and poor heat dissipation. In order to change the commutation ability and reduce the leakage inductance of the armature, it is short and thick, which affects the dynamic performance of the system.