Feedback system with slug
Patent Information
- Authority / Receiving Office
- DE · DE
- Patent Type
- Patents
- Current Assignee / Owner
- SCANNER OPTICS CO LTD
- Filing Date
- 2019-04-23
- Publication Date
- 2026-07-23
Smart Images
Figure 00000000_0000_ABST
Abstract
Description
TECHNICAL AREA
[0001] The present invention relates to the field of galvanometers, in particular a line disk and a feedback system which are used for angle detection of galvanometer motors. BACKGROUND OF THE TECHNOLOGY
[0002] In laser processing and optical scanning, the guidance of laser and other scan signals is achieved by driving a mirror that moves back and forth within a specific range or enclosed angle via a rotary motor. This type of rotary motor, which drives the mirror to high-speed and high-precision oscillations, is commonly called a galvanometer motor. The galvanometer motor differs from a conventional motor in that it is not capable of rotating 360 degrees, but only of pivoting within a specific angle. Therefore, during a movement, the zero-position grating lines of the main gratings must appear in the sensor's field of view. Furthermore, extremely high demands are placed on precision and responsiveness, as the galvanometer motor controls the deflection angle of a lens used for light reflection.
[0003] Because light is reflected by a vibrating mirror and can only reach a surface to be processed or measured after traveling a relatively long distance, the positioning accuracy of the light or other signals on the surface is directly related to the precision of the mirror's vibration. The greater the path the light has to travel from the mirror to the surface, the greater the magnification of any mirror vibration error, and therefore the higher the demands on the mirror's positioning accuracy.
[0004] Generally, one end of the galvanometer motor's rotary shaft is directly connected to a reflector, and the other end is directly connected to rotary encoders located at a specific position on the feedback motor. To improve the reflector's positioning and repeatability accuracy, the encoder's precision should be enhanced.
[0005] In addition to the effects of the rotary encoders on the rotational precision of the reflector, shaking of the axis of rotation during its movement can also affect the rotational precision of the reflector.
[0006] In this way, it is necessary to provide a line disk and a feedback system that solves the problems of encoder precision and radial shaking of the rotary axis in order to improve the reflector's rotational precision. CONTENT OF THE INVENTION
[0007] One object of the present invention is to provide a reticle and a feedback system to overcome shortcomings of the prior art. This allows problems such as the influencing of reflector precision by shaking a rotating axis, or the influencing of reflector precision by drift of the rotating axis's center of rotation under different temperatures, vibrations, and environmental conditions.
[0008] To solve these technical problems, the present invention provides a reticle comprising main gratings and zero-position gratings. The main gratings are arranged at different diameter positions, and the zero-position gratings are arranged near the main gratings. The number of zero-position gratings is 2N, and the 2N zero-position gratings are distributed at equal angles with respect to the center of the reticle. N is a positive integer.
[0009] Furthermore, each of the main grids comprises a multitude of grid lines, and the grid lines have the same width and are arranged at equal intervals in an annular area / arc-shaped area of each of the main grids.
[0010] Furthermore, each of the zero-position grids comprises a multitude of grid lines, and the grid lines are arranged at unequal intervals in an arc-shaped area.
[0011] Furthermore, not all grid lines have the same width.
[0012] Furthermore, each of the zero-position grids comprises a multitude of grid lines. The grid lines are arranged within an arc-shaped region, and not all grid line widths are equal.
[0013] Furthermore, all zero-position grids are the same, or some or all zero-position grids are different from each other.
[0014] Furthermore, the zero-position grids include first zero-position grids and second zero-position grids, and the first zero-position grids and the second zero-position grids are arranged at different diameter positions.
[0015] The present invention further provides a feedback system to solve the aforementioned technical problems. The feedback system is applied to a rotating body and comprises a reed, encoders, and a processing unit. The reed is fixed to the rotating body, and the center of the reed and the axis of rotation of the rotating body are arranged coaxially. The number of encoders is 2N, and the 2N encoders are distributed at equal angles with respect to the center of the reed. The 2N encoders receive positions from corresponding zero-position grids for identifying zero positions and receive position changes from main grids for identifying rotation angles. N is a positive integer.The processing unit receives the zero positions reported back by all encoders to achieve the positioning of the corresponding encoders, and receives the rotation angles reported back by all encoders to calculate an average rotation angle in order to determine an actual rotation angle of the stroke disc.
[0016] Furthermore, a zero-position window group is arranged on one photoelectric receiving side of each transmitter. The zero-position window group comprises transparent and opaque windows. The transparent and opaque windows are arranged alternately, and the positions of the opaque windows correspond to the grid lines of the zero-position grids.
[0017] Furthermore, some or all of the zero-position grids are different, and each of the encoders is paired with a zero-position grid.
[0018] Furthermore, the feedback system also includes a signal processing circuit. This circuit comprises a filter module, a sampling module, a computation module, and a signal output module. These modules are arranged sequentially. The filter module is connected to the encoders, and the processing module is connected to the signal output module.
[0019] Furthermore, the rotating body is an axis of rotation of a galvanometer motor, and the center of the axis of rotation of the galvanometer motor and the center of the stroke disk are arranged coaxially.
[0020] By constructing a grating, using multiple sensors, and providing a feedback system, the present invention, compared to the prior art, particularly in a galvanometer motor system, increases the detection precision and stability of the grating and sensors and improves the eccentricity and drift tolerance of the galvanometer motor system, thus improving the compatibility and interference tolerance of the galvanometer motor with its environment. Furthermore, the difficulty of installation and adjustment is reduced, and it is also easier to identify unqualified products. List of characters Fig. Figure 1 is a schematic diagram of a concentricity error of a line disk of the present invention. Fig. Figure 2 is a schematic diagram of a drift error of a line disk of the present invention. Fig. Figure 3 is a schematic structure diagram of a line disk of the present invention. Fig. Figure 4 is an enlarged schematic structure diagram of Part A of Fig. 3. Fig. Figure 5 is a schematic structure diagram of a zero-position grid of a first scheme of the present invention. Fig. Figure 6 is a schematic structure diagram of a zero-position grid of a second scheme of the present invention. Fig. Figure 7 is a schematic structure diagram of a zero-position grid of a third scheme of the present invention. Fig. Figure 8 is a schematic structure diagram of a line disk based on four zero-position grids of the present invention. Fig. Figure 9 is a schematic structure diagram of a line disk based on eight zero-position grids of the present invention. Fig. Figure 10 is a schematic structure diagram of a feedback system of the present invention. Fig. Figure 11 is a schematic structure diagram of a feedback system based on a signal processing circuit of the present invention. Fig. Figure 12 is a schematic structure diagram of a feedback system based on four sensors of the present invention. Fig. Figure 13 is a schematic structure diagram of a feedback system based on eight sensors of the present invention. Fig. Figure 14 is a schematic diagram of a concentricity error compensation of a line disk of the present invention. Fig. Figure 15 is a schematic diagram of the drift error reduction of a line disk of the present invention. DETAILED DESCRIPTION
[0021] The embodiments of the present invention are described below with reference to the accompanying drawings.
[0022] The present invention provides a line disk and a feedback system that solves problems of precision of rotary encoders and radial shaking of a rotary axis.
[0023] Generally, there are two ways to improve the precision of rotary encoders. One way is to adjust the concentricity, end-of-travel error, and similar factors that are unsatisfactory in rotary encoders. This is achieved by adjusting the mounting so that an ideal center of rotation coincides as closely as possible with the actual center of rotation, and by fixing the relative distance between a main grid and a photoelectric sensor, thus improving positioning accuracy. However, given the requirements of certain adjustment devices, the precision of rotary encoders has an upper limit. Another way to improve the precision of rotary encoders is to increase the overall precision by increasing the number of grid lines in the encoder's circular grids, the resolution, and the electronic subdivision rate.Given a specific grid scribing process, increasing the number of grid lines necessitates larger diameters of the circular grids. Increasing the diameter of these grids leads to increased rotational inertia, which affects the maximum speed and acceleration of the galvanometer oscillation. The precision of the encoders also has an upper limit. Therefore, there is a limit and a bottleneck for methods to improve the overall precision of the galvanometer based on the encoder arrangement and the manufacturing accuracy. Further improving the precision of galvanometer motor products under specific assembly and manufacturing conditions presents a challenge.
[0024] Besides the influence of the encoders on the rotational accuracy of the reflectors, the vibration of the axis of rotation during movement also affects the reflectors' accuracy. Generally, the rotation of the axis of rotation in the galvanometer motor is inextricably linked to bearings, and there is a certain distance between the balls and a track within the bearings. Therefore, a certain amount of radial vibration arises from the actual rotation of the axis of rotation, which also affects the rotational accuracy of the reflectors. In addition to vibration, the center of rotation of the axis of rotation drifts under the influence of varying temperatures, vibrations, and environmental conditions, and this drift ultimately affects the repeatability of the reflectors.
[0025] In particular, Fig. 1 on a shaking problem; Fig. Figure 1 is a schematic representation of a concentricity error between the reticle. 10and the center of rotation. Point A in Fig. 1 is an ideal center point of the reticle. 10 and an ideal center of rotation of the reticle 10 , which both coincide. Point A' is the actual center of rotation caused by the assembly and machining technologies. When the galvanometer motor rotates through a fixed angle Θ (set to 25°), the optical radius d is 10 mm. Ideally, the reticle rotates 10 around the ideal center of rotation A, and one from the transmitter 20 The read arc length L is calculated using the following formula: L = θ π d 180 = 25 × 3.14 × 10 180 ≈ 4.361
[0026] However, in actual measurements, the reticle rotates. 10 With respect to point A', whose concentricity differs from point A, and assuming that the optical radius d1 is 12 mm, the sensor 20 The measured arc length L1 is calculated as follows: L 1 = θ π d 1 180 = 25 × 3.14 × 12 180 ≈ 5.233
[0027] This shows that if there is an error in the concentricity between the reticle 10 and the center of rotation which is controlled by the transmitter 20 The read arc length is inaccurate, so that the final rotation angle of the galvanometer motor has a large deviation when the final rotation angle of the galvanometer motor is calculated by resetting the arc length formula.
[0028] Regarding a drift problem, further reference is made to... Fig. 2. Referenced. Fig. Figure 2 is a schematic representation of a drift error of the rotation center. Assuming that the center of a code channel of the reticle... 10Since the center of rotation coincides with the center of rotation, the ideal center of rotation is point A. However, because there is a gap between the bearings, the actual center of rotation drifts towards point A' under the influence of factors such as temperature, vibrations, and the like. If the galvanometer motor is not actually moving, the sensor reading changes. 20 due to the drift of the center of rotation. An arrow Q in Fig. 2 indicates an increasing direction of the sensor reading. 20 If the center of rotation shifts from point A to point A', the reading from the transmitter is 20 Compared to the ideal reading value, it is small; a value from a position feedback system drifts.
[0029] It will be on Fig. 3-4 referred. In Fig. 3-4 the present invention provides an embodiment of the line disk.
[0030] The reticle 200 includes main lattice 210 and zero-position grid 220The main gratings 210 are arranged at different diameter positions, and the zero-position grids 220 are near the main grids 210 arranged. The number of zero-position grids 220 is 2N, and the 2N zero-position grids 220 are at a uniform angle with respect to the center of the reticle 201 distributed. N is a positive integer. The main grids 210 and the zero-position grids 220 They do not overlap. A concept of grid lines described below refers to terms such as distance, interval, width, etc., which can be viewed as displacements or arc lengths between the grid line centers, as well as displacements or distances from other measurements.
[0031] A type of reticle 200 It is generally circular, but not limited to that. For example, the serration disc can 200The grid lines should be rectangular. The grid lines are only visible within a certain swivel range of the reticle. 200 The code channel and a base plate of an area that cannot be read by an external encoder are removed. The base plate is a main body of the reticle. 200 , and the code channel is arranged on the base plate. And a ring-shaped or arc-shaped structure, which is formed by the main grids. 210 and the zero-position grids 220 The formation is linked to the center of the reticle. 201 arranged as the center point of a circle.
[0032] Furthermore, two embodiments of the serrated disc are described. 200 provided. In the first embodiment, the serration disc comprises 200A glass main body, a plurality of grid lines are engraved on a surface of the glass main body, the grid lines are an opaque part of the glass main body, and each smooth part of the glass main body located between each pair of grid lines is transparent. The grid lines can be a metal coating or other line traces. In the second embodiment, the grid disc comprises 200 A metal main body is formed, with several grid lines engraved on its surface. Each smooth metal surface positioned between two grid lines reflects light. The metal main body is also formed by coating the glass main body with a layer of metal.
[0033] Furthermore, preferred embodiments of the main grids 210 with reference to Fig. 4 provided. In the first embodiment, the main grid comprises 210The majority of grid lines are arranged with equal width and spacing in a ring-shaped area. The lateral spacing of the lines is a grid spacing, typically 20 µm or 40 µm, and can also be considered the arc length of a center line. Thus, a circle of the principal grids 210 on the reticle 200 arranged, and the center of the circle of the main grid 210 is the center of the reticle 201 In the second embodiment, the main grid comprises 210 The majority of grid lines are arranged with equal width and spacing in an arc-shaped area, as described above. They differ from those mentioned above only in that the lines are arranged in an arc. Preferably, the grid lines extend to two sides of a center point of the corresponding zero-position grid. 220with respect to the corresponding zero-position grid 220 extend. Furthermore, the length of the arc-shaped area depends on the application environment of the serration, i.e., on the angle of the forward and backward rotation.
[0034] Furthermore, embodiments of the zero-position grids are described with reference to Fig. 5- Fig. 7. In the first embodiment, each of the zero-position grids comprises the plurality of grid lines arranged at varying intervals within an arc-shaped area. The widths of the lines and the widths of the spaces between the lines together form a “code.” As long as the widths of the lines or the widths of the spaces between the lines are changed, a new “code” is formed. The “code” is a unique identification code that identifies the zero-position grids. 220 reflects, i.e., an identification number belonging to the "codes". With reference to Fig. 5 comprises each of the zero-position grids 220 Several grid lines are arranged at unequal intervals within the arc-shaped area, and the widths of the grid lines are equal. With reference to Fig. 6 comprises each of the zero-position grids 220 Several grid lines are arranged at unequal intervals in the arc-shaped area, and not all widths of the grid lines are the same, i.e., parts of the widths of the grid lines are the same or all widths of the grid lines are unequal.
[0035] With reference to Fig. In the second embodiment, 7 comprises each of the zero-position grids. 220Several grid lines are arranged in an arc-shaped area, and not all of the lines have the same width. There are two possibilities: the first is that the width of each grid line is the same, and the second is that not all of the grid lines have the same width.
[0036] In the third embodiment, the zero-position grids comprise 220 First zero-position grids and second zero-position grids. The first zero-position grids and the second zero-position grids are arranged at different diameter positions. The positioning accuracy of the encoders is further improved by the first zero-position grids and the second zero-position grids, thereby reducing external disturbances. The embodiments of the first zero-position grids and the second zero-position grids can refer to the first and second embodiments described above.
[0037] In this embodiment, the “code” is defined by the zero-position grids. 220 Formed, and various feasibility studies are conducted to address problems of the "code". Since the serif 200 When the present invention is applied in a special environment where a back-and-forth movement is achieved and the angle of rotation is small, different “codes” are generated on the reticle. 200 arranged to allow for a transitional rotation of the serration disc 200 to prevent this. For example, some or all of the zero-position grids 220 The differences lie in the fact that the "codes" are different. Optionally, the "codes" of adjacent zero-position grids are also possible. 220They differ if N is greater than 1. For example, all zero-position grids are the same, meaning that the "codes" of the zero-position grids are identical. Likewise, only two zero-position grids are 220 Present when N equals 1. The grating disc 200 rotates the zero-position grids 220 at an opposite angle, which is difficult and eliminates the need to apply different "coding" modes.
[0038] In the event that the number of encoders needs to be increased further, it is necessary to consider the relationship between the actual swivel angle of the galvanometer motor and the actual operating angle of each encoder. If the swivel angle of the galvanometer motor is too large, the same zero-position grid will appear to be affected. 220 to appear at different angles for two adjacent sensors, which requires the "code" of each zero-position grid. 220or two adjacent zero-position grids 220 to change.
[0039] With reference to Fig. 8 are four zero-position grids 220 on the reticle 200 arranged, i.e., N is 2 and the included angle of each zero-position grid 220 is 90 degrees. With reference to Fig. 9 are eight zero-position grids 220 on the reticle 200 arranged, i.e., N is 4 and the included angle of each zero-position grid 220 The temperature is 45 degrees.
[0040] With reference to Fig. 10 provides preferred embodiments of the feedback system of the present invention.
[0041] The feedback system is applied to the rotating body that controls the stroke. 200 , the donors 400 and a processing unit 500 includes the reticle. 200 is fixed to the rotating body. The center of the serration disc200 , which is the center of the reticle 201 is, and a rotation axis of the rotating body are arranged coaxially. The number of encoders 400 The value is 2N. The 2N transmitters 400 are at a uniform angle with respect to the center of the reticle 201 distributed. The 2N transmitters 400 positions of the corresponding zero-position grids are obtained. 220 to identify zero positions and obtain position changes of the main grids 210 for identifying rotation angles. N is a positive integer.
[0042] When the rotating body is ready to rotate, especially for the galvanometer motor, the center of the rotation axis of the galvanometer motor and the center 201 the reticle 200arranged coaxially. Since the galvanometer motor only pivots within an angle that is normally ± 12.5°, the galvanometer motor must pivot its axis of rotation back and forth to align the reticle. 200 among the donors 400 to swing and the transmitters 400 find their own zero positions. Then the transmitters can 400 first start normal operation and adjust the rotation angle of the serrated edge 200 capture.
[0043] In particular, an eccentricity of the reticle appears 200 one of two donors 400 of the same group, one large and one small. After averaging, the actual rotation angle of the reticle is determined. 200 compensates for the excessively high or low recorded value of the individual sensors. 400 is corrected. If the axis of rotation is shifted due to external factors, the values recorded by a sensor will appear. 400The reading is higher in one instance and lower in another. This is determined by averaging the recorded values from the two sensors. 400 The final value is balanced within the same group, thus greatly reducing the impact of the shift in the center of rotation on the result.
[0044] Furthermore, a zero-position window group is installed on a photoelectric receiving side of each of the transmitters. 400 The zero-position window group comprises transparent and opaque windows. The transparent and opaque windows are arranged alternately, and the positions of the opaque windows correspond to the grid lines of the zero-position grids. Due to the fact that the galvanometer motor only oscillates and does not rotate a full revolution, a separate zero-position signal must be provided at a location where each sensor 400 is arranged so that each donor 400After being switched on, it finds the zero positions. Of course, each of the sensors is located on the photoelectric receiving side. 400 A main grid window group is arranged. Similarly, the main grid window group also includes transparent windows and opaque windows. The transparent and opaque windows are arranged alternately, and the transparent and opaque windows are of equal width.
[0045] Furthermore, the arrangement direction of each sensor must be 400 relative to the reticle 200 be consistent to ensure that when the reticle is rotated 200 in a specific direction the readings of all sensors 400 change in the same direction, i.e., the readings of all sensors. 400 They rise or fall simultaneously. It is impossible for one sensor reading to increase while another sensor reading decreases.
[0046] Regarding the processing unit 500 The values of the output signals from the sensors will be 400 Digitally summed and averaged. The sum of all sensor readings. 400 is A and is determined by the total number of donors 400 , i.e., 2N, divided to obtain the final rotation angle ϕ A of the galvanometer motor. The formula is as follows: Φ = A 2 N .
[0047] Furthermore, the zero position windows of the encoders 400 directly above / below the zero-position grids 220 arranged.
[0048] In this embodiment, the serration disc comprises 200 The main glass body has a multitude of grid lines engraved on its surface. These grid lines are opaque parts of the main glass body, and the smooth portion of the main glass body between each pair of grid lines is transparent. The transmitter 400are transmissive transmitters. The reticle 200 It comprises a metal main body, the multiple grid lines of which are engraved on a surface of the metal main body, the grid lines being opaque parts of the metal main body, and the smooth part of the metal main body between each pair of grid lines reflecting light. The transmitter 400These are reflective sensors. Specifically, in the case of transmassive sensors, the sensors emit parallel light of a specific wavelength band from a light source. This parallel light is transmitted vertically and then captured by a photoelectric receiver on the opposite side of the light source. The parallel light then forms a moiré pattern and is converted into an electrical signal. In the case of reflective sensors, the sensors emit parallel light of a specific wavelength band from the light source. This parallel light enters a smooth metal surface at a specific angle, is then reflected by the smooth metal surface at a specific angle, and is finally captured by a photoelectric receiver on the same side of the light source to form the electrical signal.Furthermore, the light source of the transmissive transmitters is a light-emitting diode (LED), and the light source of the reflective transmitters is a laser diode (LD).
[0049] In this embodiment, the rotating body is a rotational axis of the galvanometer motor.
[0050] In laser processing or optical signal scanning, swiveling the reflectors changes the direction of light propagation, which then reaches the surface of the object being processed or detected. The precision of the sensor installation 400 of the galvanometer motor, the precision of the processing and manufacturing of the sensors 400 , the reticle 200The photoelectric receiving component, as well as the radial vibration and drift generated by the rotating shaft of the galvanometer motor, affect the rotational accuracy of the reflectors. Furthermore, a rotational error of the reflectors is amplified by the path of the reflected light, causing the light to strike the surface of the object being processed or measured at a position other than the predetermined one.
[0051] Through the interaction of several transmitters 400 , the redesign of a special reticle 200 for the multiple coding of the galvanometer motor to ensure that each sensor 400 The zero positions were correctly identified, and the arrangement of the sensors was correct. 400 at certain positions of the same reticle 200Using a specific algorithm, the positional deviation occurring at the final output is reduced, and the effects of deviation of the center point, radial shaking, drift, and similar phenomena are mitigated.
[0052] As in Fig. As shown in Figure 11, the present invention provides an embodiment of a signal processing circuit.
[0053] The feedback system also includes a signal processing circuit. 600 The signal processing circuit 600 includes a filter module 610 , a scanning module 620 , a calculation module 630 and a signal output module 640 The filter module 610 , the scanning module 620 , the calculation module 630 and the signal output module 640 are arranged one after the other. The filter module 610 is with the donors 400 connected, and the processing unit 500 is with the signal output module640 tied together.
[0054] The output signals of the sensors 400 These can be analog sine-cosine signals, square-wave ABZ signals, pulse signals, digital protocol signals, etc. In the signal processing circuit 600 The signals are filtered, sampled, and calculated. Then a final position is determined via the signal output module. 640 Output signals can include analog signals, square wave ABZ signals, digital protocol signals, and other types of signals. A final signal is transmitted via signal transmission cables to a back-end processing device, such as a driver.
[0055] Furthermore, with regard to the addition method for analog quantities, an output quantity of the transmitter is specified. 400 converted into an analog quantity, and the modulation accuracy of the transmitters 400 is strictly controlled, so that the phases of the process are controlled by all donors 400The signals output by all transmitters are the same. Then the signals from all transmitters are 400 The output signals are stacked in parallel. Finally, the signals from all groups of transmitters are processed. 400 simultaneously connected to the signal processing circuit 600 The data was transmitted, filtered and sampled, and then the final position was calculated.
[0056] In this embodiment, the signal processing circuit 600 It can be a separate circuit board, but it can also be integrated into a circuit board of the sensor. 400 It may be integrated or a circuit board of an integrated driver. Furthermore, an algorithm for the signal processing board is required for the signal processing circuit. 600 by a separate chip, or by a main control chip of an external motor drive board, or by one integrated into the encoder 400 The built-in chip is calculated.
[0057] Signal processing methods include, for example, digital and analog methods. In digital averaging, all sensor readings are processed. 400 The measured values are added together, and a sum of the measured values is determined by the sensor. 400 The values are divided to obtain an average. When calculating the average using analog methods, the mounting position of the sensors must be taken into account. 400 the same group are strictly controlled, so that the analog sine-cosine signals that pass through the photoelectric receiver of the transmitter 400 The signals must have the same phase and direction and be stacked completely in parallel. The stacked signals of each group are then fed to the signal processing circuit. 600 transmitted.
[0058] As in Fig. 12 and Fig. As shown in Figure 13, the present invention provides an embodiment of the encoders. Generally, one or two groups of encoders are required. 400arranged, and each group has two donors 400 , arranged symmetrically at 180 degrees. And more than two groups or even more transmitters. 400 They can be arranged according to precision requirements. An angle between each group of the two sensors. 400 must meet a requirement of 180°. If there are a total of 2N sensors... 400 There is an angle θ that satisfies 360 between each transmitter 400 a formula: θ = 360 2 N .
[0059] If there are multiple transmitters 400 If the galvanometer is arranged in a specific configuration and its swivel angle is greater than 360 / 4N, there is a risk of two zero positions occurring within the same swivel range. Therefore, the zero signals at different positions are differentiated by corresponding zero grids at each position to prevent multiple zero positions from occurring within the swivel range.
[0060] As in Fig. As shown in Figure 14, the present invention provides an embodiment of a concentricity error compensation for the reticle. Point A is an ideal center point of the reticle. 200 and the ideal center of rotation of the reticle 200 , which both normally coincide. Point A' is the actual center of rotation caused by the assembly and machining technologies. When the galvanometer motor rotates through the fixed angle θ (set to 25°), the optical radius d is 10 mm. When the reticle 200 If the optical radius d1 is assumed to be 12 mm and rotates around point A', whose concentricity deviates, then the sensor 400 The recorded arc length L1 is calculated as follows: L 1 = θ π d 1 180 = 25 × 3.14 × 12 180 ≈ 5.233
[0061] While the optical radius d2 is 8 mm, the one from the transmitter 420The measured arc length L2 of an opposite angle is calculated as follows: L 2 = θ π d2 180 = 25 × 3.14 × 8 180 ≈ 3.489
[0062] By averaging L1 and L2, a final arc length L' is calculated as follows: L ' = L 1 + L 2 2 = 4.367
[0063] Ideally, the reticle rotates 200 , when the center of the reticle 200 which coincides with the center of rotation around the ideal center of rotation A, and the arc length L detected by the sensors is calculated according to the following formula: L = θ π d 180 = 25 × 3.14 × 10 180 ≈ 4.361
[0064] It can be seen that for the galvanometer motor 300 the concentricity problem of the serration 200 The errors caused experience a good inhibitory effect.
[0065] As in Fig. As shown in Figure 15, the present invention provides an embodiment of the drift error reduction of the reticle.
[0066] Assuming that the center of the code channel is the serif 200 Since the center of rotation coincides with the axis of rotation, the ideal center of rotation is point A, but because there is a gap between the bearings, the actual center of rotation drifts to point A' under factors such as temperature, vibrations, and the like.
[0067] If the galvanometer motor is not actually moving, the sensor readings will be invalid. 410 and the giver 420 changed due to the drift of the center of rotation. Arrow Q1 and arrow Q2 in Fig. The 15 represent the ascending directions of the sensor readings. When the center of rotation shifts from point A to point A', the sensor reading changes. 410 small compared to the ideal value, and the measured value of the transmitter 420 becomes large. Therefore, if only one sensor is installed, the value of the position feedback system drifts. By averaging the values of the two sensors (410 , 420 However, the increases and decreases in the measured value cancel each other out, so the final position data remains unchanged. This is due to the positions of the two sensors, which are specifically arranged in the diameter direction.
[0068] For drift in a specific direction, only two sensors on diagonals perpendicular to a vector of that direction play a maximum role. Therefore, if it is necessary to counteract drift in multiple directions, several groups of sensors are required for support. This is due to a peculiarity of the movement of the galvanometer motor. 300 The galvanometer motor oscillates 300 within a certain angle, which is normally ± 12.5°, but never rotates a full circle, so that at least a group of two sensors can essentially cancel out any drift error.
[0069] It should be understood that the specific embodiments described herein are used only to illustrate the present invention and not to limit it. Equivalent changes or modifications made in any area of the present invention are covered by the present invention.
Claims
[1] Grid disk with main gratings arranged at different diameter positions and zero-position gratings arranged close to the main gratings, characterized by , that the number of zero-position grids is 2N and the 2N zero-position grids are distributed at equal angles with respect to a reticle center, where N is a positive integer. [2] Line disc according to claim 1, characterized by , that each of the principal grids comprises a plurality of grid lines, and the grid lines have the same width and are arranged at equal intervals in an annular area of each of the principal grids / an arc-shaped area of each of the principal grids. [3] Line disc according to claim 1, characterized by , that each of the zero-position grids comprises a plurality of grid lines and the grid lines are arranged at unequal intervals in an arc-shaped region of each of the zero-position grids. [4] Stroke disc according to claim 3, characterized by that not all widths of the grid lines are the same. [5] Line disc according to claim 1, characterized by , that each of the zero-position grids comprises a plurality of grid lines, the grid lines are arranged in an arc-shaped area of each of the zero-position grids, and not all widths of the grid lines are the same. [6] Line disc according to one of claims 1-5, characterized by that all zero-position grids are the same; or that some or all zero-position grids are different from each other. [7] Line disc according to one of claims 1-5, characterized by , that the zero-position grids comprise first zero-position grids and second zero-position grids, wherein the first zero-position grids and the second zero-position grids are arranged at different diameter positions. [8] Feedback system applied to a rotating body, characterized by , that it includes: a line disk according to one of claims 1-7, which is fixedly arranged on the rotating body, wherein a center of the line disk and an axis of rotation of the rotating body are arranged coaxially; 2N encoders, wherein the 2N encoders are distributed at equal angles with respect to the center of the grating; and the 2N encoders are assigned positions of the corresponding zero-position gratings, to identify zero positions, and obtain position changes of the main grids to identify rotation angles; where N is a positive integer; and a processing unit that receives the zero positions returned by all encoders to achieve the positioning of the corresponding encoders, and that receives the rotation angles returned by all encoders to calculate an average rotation angle in order to determine an actual rotation angle of the stroke disc. [9] Feedback system according to claim 8, characterized by , that a zero-position window group is arranged on a photoelectric receiving end of each of the transmitters; the zero-position window group includes transparent windows and opaque windows; the transparent windows and the opaque windows are arranged alternately; and the positions of the opaque windows correspond to grid lines of the zero-position grids. [10] Feedback system according to claim 9, characterized by that some or all of the zero-position grids are different and each of the encoders is paired with a zero-position grid. [11] Feedback system according to claim 8, characterized by, that the feedback system further comprises a signal processing circuit; wherein the signal processing circuit comprises a filter module, a sampling module, a computation module and a signal output module; the filter module, the sampling module, the computation module and the signal output module are arranged sequentially; the filter module is connected to the encoders and the processing unit is connected to the signal output module. [12] Feedback system according to claim 8, characterized by that the rotating body is an axis of rotation of a galvanometer motor and that the center of the axis of rotation of the galvanometer motor and the center of the stroke disk are arranged coaxially.