CN113541406B - High-precision galvanometer motor feedback system and design method thereof - Google Patents
High-precision galvanometer motor feedback system and design method thereof Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K11/00—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection
- H02K11/20—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection for measuring, monitoring, testing, protecting or switching
- H02K11/21—Devices for sensing speed or position, or actuated thereby
- H02K11/22—Optical devices
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
- G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
- G02B26/0816—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
- G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
- G02B26/10—Scanning systems
- G02B26/105—Scanning systems with one or more pivoting mirrors or galvano-mirrors
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K29/00—Motors or generators having non-mechanical commutating devices, e.g. discharge tubes or semiconductor devices
- H02K29/06—Motors or generators having non-mechanical commutating devices, e.g. discharge tubes or semiconductor devices with position sensing devices
- H02K29/10—Motors or generators having non-mechanical commutating devices, e.g. discharge tubes or semiconductor devices with position sensing devices using light effect devices
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P25/00—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details
- H02P25/02—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details characterised by the kind of motor
- H02P25/032—Reciprocating, oscillating or vibrating motors
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
- H02P6/14—Electronic commutators
- H02P6/16—Circuit arrangements for detecting position
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P90/00—Enabling technologies with a potential contribution to greenhouse gas [GHG] emissions mitigation
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Abstract
The embodiment of the application belongs to the technical field of high-precision scanning galvanometer motors, and relates to a high-precision galvanometer motor feedback system and a design method thereof. The technical scheme provided by the application comprises the following steps: arranging at least one group of encoders at two symmetrical ends of the center of the grating disk according to the diameter direction of the grating; the positions of the grating zero position score lines are in one-to-one correspondence with the positions of the optical center points of the encoder; the output signal of the encoder is connected to a signal processing circuit board. Through the joint work of multiple encoders, the special grating disk for multiple encoding of the vibrating mirror motor is redesigned, so that each encoder can correctly identify the zero position under the swinging condition, then the encoders are placed on the same grating disk according to the specific positions, and a specific algorithm is assisted, so that the position error in the final output is reduced, and the influences on the aspects of eccentricity, radial shaking drift and the like are reduced. The precision and the stability of the vibrating mirror motor system are improved, and the eccentric and drifting resistance of the vibrating mirror motor system is improved.
Description
Technical Field
The application relates to a high-precision scanning galvanometer motor technology, in particular to a high-precision galvanometer motor feedback system and a design method thereof.
Background
In the current laser processing field and the light scanning field, the guiding control of laser or other scanning signals is mainly realized by driving a mirror through a rotating motor capable of reciprocating in a certain range or included angle. Such a motor that can drive the mirror to oscillate at high speed and high precision is commonly referred to as a galvanometer motor. Unlike conventional motors, which cannot rotate one revolution but only oscillate at an angle, the zero-position scribe line of the main grating must appear in the encoder field of view during motion. And because it controls the deflection angle of the lens for reflecting light, there is a very high requirement for accuracy and response capability.
The light beam, after being reflected by the oscillating mirror, propagates a considerable distance to reach the surface to be treated or inspected. Thus, the positioning accuracy of the final light or other signal at the surface being measured or processed has a direct relationship with the accuracy of the mirror wobble. The longer the distance from the mirror to the surface to be treated, the larger the magnification of the mirror wobble error, and therefore the higher the positioning accuracy of the mirror.
In general, one end of a rotating shaft of the vibrating mirror motor is directly connected with the reflecting mirror, and the other end of the rotating shaft is directly connected with an encoder for feeding back the position of the motor. To improve the positioning accuracy and repetition accuracy of the mirror, the accuracy of the encoder is improved. Generally, two methods for improving the precision of the encoder are adopted, one is to adjust the concentricity of the encoder, end jump and other non-ideal conditions through assembly, so that an ideal rotation center and an actual rotation center are overlapped as much as possible, the relative distance between the main grating and the photoelectric receiver is fixed, and the positioning precision can be improved. However, on the premise of a certain adjustment device, the accuracy improvement has an upper limit. The second is to increase the resolution and the electronic subdivision ratio to improve the overall accuracy by increasing the number of lines of the encoder grating. However, on the premise of a certain grating ruling process, increasing the number of ruling means that the grating diameter must be increased, and the increase of the grating diameter brings about an increase of moment of inertia, so that the highest speed and acceleration and deceleration capability of the oscillating mirror are affected, and therefore, an upper limit exists.
Therefore, there are upper limits and bottlenecks on the method for improving the overall precision of the vibrating mirror from the aspects of encoder adjustment and design precision, and how to further improve the precision of the vibrating mirror motor product on the premise of a certain assembly process and a certain processing process becomes a difficult problem.
In addition, besides the influence of the encoder on the rotation precision of the reflecting mirror, the rotation precision of the reflecting mirror can be influenced by the shaking of the rotating shaft in the moving process. Normally, the rotation of the rotating shaft in the motor is not separated from the matching of the bearing, and a certain gap exists between the ball inside the bearing and the matching of the track. This results in a certain radial wobble of the final actual rotation of the spindle. These oscillations also affect the accuracy of the rotation of the mirror. Besides shaking, under the influence of different temperatures, vibration and environment, the rotation center of the rotating shaft can drift, and the drift can finally cause the influence on the repeated precision of the reflecting mirror. Therefore, it is also one of the aspects requiring improvement.
In summary, to improve the rotation accuracy of the mirror, the encoder accuracy and radial wobble need to be solved simultaneously.
Disclosure of Invention
The application aims to provide a high-precision vibrating mirror motor feedback system and a design method thereof, which can solve the problems of encoder precision and radial shaking, and realize the reduction of position errors during final output and the reduction of the influence of eccentricity, radial shaking drift and the like through the joint work of a plurality of encoders.
In order to solve the above-mentioned problems, the embodiment of the present application provides the following technical solutions:
a design method of a high-precision galvanometer motor feedback system comprises the following steps:
arranging at least one group of encoders at two symmetrical ends of the center of the grating disk according to the diameter direction of the grating;
the positions of the grating zero position score lines are in one-to-one correspondence with the positions of the optical center points of the encoder;
the output signal of the encoder is connected to a signal processing circuit board.
Further, the encoder includes at least one of a transmissive encoder and a reflective encoder.
Further, in the step of arranging at least one group of encoders at both ends of the center symmetry of the grating disk in the grating diameter direction, the light source used includes at least one of a light emitting diode LED and a laser diode LD.
Further, the angles between adjacent different sets of encoders are the same.
Further, the placement direction of each encoder relative to the grating disk is consistent to ensure that the readings of all encoders remain the same as the grating disk rotates in one direction.
Further, the output signal of the encoder includes at least one of an analog quantity signal, a digital protocol signal, and a square wave signal of ABZ.
Further, the data type received by the signal processing board comprises at least one of an analog sine-cosine signal, a square wave ABZ signal, a pulse signal and a digital protocol signal.
Further, the grating includes a main code track and a zero code track.
Further, the grating is circular or square.
In order to solve the technical problems set forth above, the embodiment of the application also provides a high-precision galvanometer motor feedback system, which adopts the following technical scheme:
the utility model provides a high accuracy galvanometer motor feedback system, includes at least a set of encoder, grating and signal processing circuit board, the encoder is arranged in grating disk central symmetry's both ends according to grating diameter direction, grating zero position dividing line position with the position one-to-one of the optical center point of encoder, the output signal of encoder is connected to a signal processing circuit board.
Compared with the prior art, the embodiment of the application has the following main beneficial effects:
a high-precision galvanometer motor feedback system and a design method thereof are provided, wherein a plurality of encoders work together, a special grating disk for the galvanometer motor is redesigned, so that each encoder can correctly identify a zero position under the swinging condition, then the encoder is placed on the same grating disk according to a specific position, and a specific algorithm is assisted, so that the effects of reducing position errors during final output, weakening eccentricity, radial shaking drift and the like are realized. The precision and the stability of the vibrating mirror motor system are improved, and the eccentric and drifting resistance of the vibrating mirror motor system is improved, so that the environment tolerance and the interference resistance of the vibrating mirror motor are improved, the adjustment difficulty can be reduced, and the products with unqualified adjustment are easier to detect.
Drawings
In order to more clearly illustrate the solution of the present application, a brief description will be given below of the drawings required for the description of the embodiments, it being apparent that the drawings in the following description are some embodiments of the present application and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a block flow diagram of a method for designing a feedback system of a high-precision galvanometer motor according to an embodiment of the application;
FIG. 2 is a schematic diagram illustrating an assembly of a galvanometer position feedback system for a set of encoders in accordance with an embodiment of the application;
FIG. 3 is a schematic diagram of an assembly of the galvanometer position feedback system of the two encoders in other embodiments;
FIG. 4 is a schematic diagram of a grating of a galvanometer motor position feedback system of a set of encoders according to an embodiment of the application;
FIG. 5 is a schematic diagram of a grating of a galvanometer motor position feedback system of two encoders in other embodiments;
FIG. 6 is a schematic diagram of concentricity error compensation of a grating disk according to an embodiment of the present application;
FIG. 7 is a schematic diagram of center of rotation drift compensation according to an embodiment of the present application.
Reference numerals illustrate:
1. a motor; 2. an encoder; 3. a grating disk; 4. a motor shaft; 5. a signal transmission cable; 6. a signal processing circuit board; 8. a zero signal portion; 9. zero bit code channel; 10. a main code channel; 11. a grating disk main body.
Detailed Description
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The terms "comprising" and "having" and any variations thereof in the description of the application and the claims and the foregoing description of the drawings are intended to cover non-exclusive inclusions. The terms first, second and the like in the description and in the claims or in the above-described figures, are used for distinguishing between different objects and not necessarily for describing a sequential or chronological order.
Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those of skill in the art will explicitly and implicitly appreciate that the embodiments described herein may be combined with other embodiments.
In order to enable those skilled in the art to better understand the present application, a technical solution of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.
Examples
The embodiment of the application provides a high-precision galvanometer motor feedback system which comprises at least one group of encoders, gratings and a signal processing circuit board, wherein the encoders are arranged at two symmetrical ends of the center of a grating disk according to the diameter direction of the gratings, the positions of zero position dividing lines of the gratings are in one-to-one correspondence with the positions of optical center points of the encoders, and output signals of the encoders are connected to the signal processing circuit board.
The embodiment of the application also provides a design method of the feedback system of the high-precision galvanometer motor.
As shown in fig. 1, a design method of a feedback system of a high-precision galvanometer motor includes:
s100, arranging at least one group of encoders at two symmetrical ends of the center of the grating disk according to the diameter direction of the grating;
s200, the positions of the zero position score lines of the grating are in one-to-one correspondence with the positions of the optical center points of the encoder;
s300, connecting the output signal of the encoder to a signal processing circuit board.
In the step S100, one set of encoders includes two encoders, one or two sets of encoders may be disposed, or three, four, five or more sets of encoders may be disposed according to the accuracy requirement.
In the step S100, the light source includes at least one of a light emitting diode LED and a laser diode LD.
The included angle of the two encoders of each group is 180 degrees, the paired angular lines of the two encoders of each group are opposite, and the included angle formed by the paired angular lines and the connecting lines of the circle centers is 180 degrees.
If N groups of encoders are provided, the included angles between adjacent different groups of encoders are the same, and the included angle θ between each group of encoders satisfies the formula:
when the grating disk is eccentric, the readings of two encoders in the same group are larger than each other, and after the readings are averaged, the actual rotation angle of the grating disk is compensated, so that the condition that the readings caused by a single encoder are larger or smaller is corrected.
When the rotation center is displaced due to external reasons, the readings of the group of encoders which are perpendicular to the displacement direction can generate a condition that one reading is increased and the other reading is reduced, and after the readings of the two encoders in the same group are averaged, the final reading can be reset to zero, so that the influence of the rotation center offset on the result is greatly weakened.
In the step S200, the positions of the zero position score lines of the grating are in one-to-one correspondence with the positions of the optical center points of the arranged encoders. Because the galvanometer motor has the characteristic that the galvanometer motor only swings and can not rotate for one circle, a zero signal is independently arranged at the installation position of each encoder, so that the zero position can be found after each encoder is electrified.
It should be noted that, when the N sets of encoders are provided, if the oscillation angle of the oscillating mirror is greater than 360/2N, there may be a risk that two zero positions occur in the oscillation range. Therefore, the zero pseudo-random code at each position is required to be converted to distinguish the zero signals at different positions, so that the problem of multiple zero positions in the swinging range is prevented.
The encoder includes at least one of a transmissive encoder and a reflective encoder. Encoders include, but are not limited to, the following two types: the first type is a transmission type encoder, which emits parallel light rays with a certain wave band by a light source, and the parallel light rays vertically penetrate through a main grating and are captured by a photoelectric receiver at the other side of the main grating. And finally forms interference fringes and converts them into an electrical signal. The second type is a reflective encoder, which emits parallel light rays of a certain wave band from a light source, and after the parallel light rays are incident to a main grating at a certain angle, the parallel light rays are reflected by the main grating at a certain angle, and finally, the parallel light rays are captured by a photoelectric receiver positioned on the same side of the light source to form an electric signal.
In the step S300, the signal processing circuit is divided into an analog quantity adding method and a digital quantity adding method. For the digital sum, the algorithm of the signal processing circuit board is responsible for accumulating the sum a of all encoder readings and dividing by the total number N of encoders to obtain the final galvanometer motor rotation angle Φ. The formula is as follows:
for the analog quantity addition method, the output quantity of the encoder is changed into analog quantity, and the adjustment precision of the encoder is strictly controlled. The signals output by all the encoders are identical in phase, the encoders are overlapped in parallel, and finally all the encoders are input into the signal acquisition circuit board at the same time, and the final positions are calculated after signal filtering and acquisition.
As shown in fig. 2, the embodiment of the application is a high-precision galvanometer motor feedback system formed by a group of encoders (shown in a top view, mainly showing an image of one end of a motor related to the galvanometer motor feedback system, and other related smaller parts are not shown). The device comprises a motor 1, an encoder 2, a grating disk 3, a motor rotating shaft 4, a signal transmission cable 5 and a signal processing circuit board 6. All optical components are positioned inside the motor 1, and the encoder 2 or the reading head are arranged at 180-degree diagonal relative to the motor rotating shaft 4.
The signal processing circuit board 6 includes a filtering module, a sampling module, an operation module, and a signal output module.
The encoder 2 may be a reflective encoder in which a light source and a photoelectric receiver are combined, or may be a transmissive encoder in which the light source and the photoelectric receiver are separately disposed, and in this embodiment, the encoder 2 is a reflective encoder.
The placement direction of each encoder 2 relative to the grating disk 3 is kept consistent, so that when the grating disk 3 rotates along a certain direction, the readings of all the encoders 2 keep the same direction change, namely increase or decrease simultaneously, and the situation of increase and decrease cannot occur. As shown in fig. 2, it can be determined whether or not its orientation is correct based on the small black dot direction above the encoder 2.
The grating disk 3 is marked with a code track for identifying the position, and for an incremental encoder, the code track at least comprises a main code track 10 and a zero code track 9. And the windows of zero pulses are located directly below the two encoders 2, respectively. When the motor 1 is powered up to start ready operation, the mirror motor can only oscillate within an angle, typically + -12.5 deg.. Therefore, the motor 1 needs to swing the rotating shaft back and forth to drive the grating disk 3 to swing below the encoder 2, so that the encoder 2 can find the zero positions of the encoder 2 respectively, and then the encoder 2 can start to work normally.
The output signal of the encoder 2 comprises at least one of an analog signal, a digital protocol signal and a square wave signal of ABZ.
The data type received by the signal processing board comprises at least one of an analog sine and cosine signal, a square wave ABZ signal, a pulse signal and a digital protocol signal.
The signal processing circuit board 6 may be a separate circuit board or it may be integrated in the circuit board of the encoder 2 or in the circuit board of the driver.
The signal processing circuit board 6 calculates the average change value of all the encoders 2 through an algorithm to compensate the influence of eccentricity, shaking, drift and other factors.
The algorithm of the signal processing circuit board 6 can be calculated by a single chip, or can be calculated by a main control chip of the motor 1 driving board, or can be calculated by a chip built in the encoder 2.
The signal processing mode includes digital mode and analog mode. Digital averaging is to add all encoder 2 readings and to count the number of encoders 2 to obtain an average. The analog average needs to strictly control the installation positions of the encoders 2 in the same group, so that the analog sine and cosine signals obtained by the photoelectric receivers of the encoders 2 have the same phase and direction, and the superposition can be completely formed. Finally, the superimposed signals of each group are input to the signal processing circuit board 6.
When both encoders 2 enter normal operation, position information is output. The signals are supplied to the signal processing circuit board 6 via respective signal transmission cables 5. The type of signal transmitted by the signal transmission cable 5 includes an analog signal, a digital protocol signal, a square wave ABZ signal, and the like. In the signal processing circuit board 6, the signals are filtered, sampled, and the final position is output through the signal output module after operation, and the output signals also comprise analog, digital protocol, square wave ABZ and other types of signals. The final signal is transmitted to a back-end processing device such as a driver via a signal transmission cable 5. The signal processing circuit board 6 may be a single circuit board disposed outside the motor 1, or may be integrated with the circuit board of the encoder 2 disposed inside the motor 1 and disposed inside the motor 1. Or integrated with the driver signal processing circuitry, placed inside the driver.
In other embodiments, as shown in fig. 3, two or more sets of encoders 2 may be used, with the same included angle between adjacent different sets of encoders 2. Fig. 3 shows a high-precision galvanometer motor feedback system formed by two groups of encoders, wherein the number of the encoders 2 is expanded to 4, and the encoders are respectively arranged at 90 degrees. Correspondingly, the grating disk 3 is correspondingly set to 4 zero positions from 2 zero positions, namely, the redesigned 4 zero position grating disk 3 is matched to provide zero position information to different encoders 2. The back-end processing circuit is identical to the scheme in fig. 2.
As shown in fig. 4, fig. 4 is a grating disk of a galvanometer motor feedback system based on a set of encoders, corresponding to the scheme of fig. 2. The grating disk 3 comprises a grating disk main body 11, a main code channel 10 and a zero code channel 9, wherein the part shown as 8 in fig. 4 is a zero signal part, and a plurality of tracks of the zero signal part 8 are shown in an enlarged mode in the figure.
The grating disk body 11 is made of glass or metal. For the grating disk body 11 made of glass, the track is usually completed by a metal plating film coated on the glass. For the metal grating disk main body 11, a blazed grating pattern code track is engraved by a scoring or machining process.
The zero bit track 9 is formed by a zero bit score line with different sequence widths. The sequence of zero-position reticles of this column needs to be in one-to-one correspondence with the zero-position windows of the photo-receiver of the encoder 2. When the grating disk 3 is zero rotated to a position just below the encoder 2, the reticle thereof is perfectly aligned with the zero position of the photo receiver of the encoder 2, a zero pulse signal is generated. Normally, the zero code channel 9 is composed of two sub code channels, i.e., index+ and index-, respectively, and the black and white lines of the two code channels are completely opposite.
The main track 10 is usually only one, and is composed of light and dark stripes with equivalent widths, and the grid pitch is usually 20um or 40um.
It should be noted that the shape of the main grating is circular, but not limited to circular. For a multi-encoder feedback system using only one set, i.e. two encoders, the main grating may be arranged in a rectangular shape, with the scribe lines only being provided in the wobble area, and for areas not readable by the encoder 2, the grating and the glass substrate may be removed together with the code tracks.
The zero position is usually a window with different light and shade widths, and is full black or full white except the window.
For a vibrating mirror motor with a large swinging angle, zero positions of each encoder 2 or any two adjacent encoders 2 need to be distinguished. Correspondingly, the zero bit codes of the corresponding photo receivers also need to be distinguished.
The position of the zero position needs to correspond to the position of the encoder 2, and the included angle of the adjacent zero position needs to be consistent with the included angle of the adjacent encoder 2.
As shown in FIG. 5, FIG. 5 is a diagram of a grating design of a galvanometer motor feedback system of two sets of encoders. It is used in combination with the encoder placement scheme of fig. 3, with four zero signals. For the case where the number of encoders 2 needs to be further increased, the relationship between the actual swing angle of the motor 1 and the actual operation angle of each encoder 2 needs to be considered. If the motor 1 swings too far, it may happen that the same zero position may appear on two adjacent encoders 2 at different angles. For this case the constituent sequence of the zero signals of the grating disk 3 of each or of the adjacent two encoders 2 needs to be modified. I.e., a pseudo-random code that alters the zero-bit score line. The zero window layout on the photo receiver of the encoder 2 should be modified accordingly, corresponding to the zero score line of the grating disk 3, so that each zero can only be recognized by the encoder 2 in a specific position.
As shown in fig. 6, fig. 6 is a schematic diagram of concentricity error compensation of the grating disk. In the figure, the point A is an ideal main grating center point and a rotation center, which are coincident, and the point A' is an actual rotation center caused by an assembly or machining process. When the motor 1 is rotated by a fixed angle θ (25 °), the optical radius d is 10mm, and in an ideal case the grating disk 3 rotates around the ideal rotation center a, the arc length L read by the encoder 2 (1) is calculated by the following formula:
when the grating disk 3 rotates around the point a' with different concentricity, assuming that the optical radius d1 is 12mm, the arc length L1 read by the encoder 2 (1) is:
therefore, if the concentricity of the grating disk 3 and the rotation center is in error, the error of the distance read by the encoder 2 is caused, and the rotation angle of the final measuring motor 1 is caused to have larger deviation by continuing to reversely push according to the ideal rotation center.
The situation changes after adding the diagonal encoder 2. According to the formula, the arc length L2 measured by the encoder 2 is:
by averaging L1 with L2, the final arc length L' is as follows:
therefore, the scheme has a good inhibition effect on errors generated by the galvanometer motor due to the concentricity problem of the grating disk.
As shown in fig. 7, fig. 7 is a schematic diagram of center of rotation drift compensation. Under the condition that the center of the grating disk code channel and the rotating shaft are ideal concentricity, the ideal rotating center is the point A, but due to the fact that gaps exist in cooperation between the bearings, the actual rotating center drifts to the point A' due to the influences of factors such as temperature, vibration and the like. The motor, when in fact not moving, causes a variation in the readings of both encoders due to a drift in the centre of rotation. Arrows a and B in the figure are the increasing directions of the two coded readings, respectively. Then one encoder reading will get smaller and the other encoder reading will get larger when the center of rotation shifts from a to a', thus shifting the value of the position feedback system when only one encoder is installed. However, if the values of the two encoders are averaged, the effects of the increase and decrease cancel each other out, leaving the final position data unchanged. This is related to two encoder positions being specifically arranged in the diameter direction. For drift in a particular direction, only the two encoders of the set of diagonals perpendicular to this direction vector may play a maximum role. Multiple sets of encoders are therefore required to support if multiple directional drift needs to be eliminated. Because of the particularity of the vibrating mirror motion, the vibrating mirror can swing continuously only within a fixed certain angle (commonly +/-12.5 degrees) and cannot rotate in a whole circle, and therefore drift errors can be reduced approximately by a minimum of two encoders.
The technical scheme adopted by the application is completed by combining optics, hardware and software, and firstly, a unique multi-zero-position main grating is designed, so that accurate signals can be provided for a plurality of encoders at the same time. And secondly, the adverse effects caused by the eccentricity of the code wheel or the rotating shaft, the shaking of the rotating shaft and the drifting of the rotating center are greatly weakened by utilizing a unique encoder arrangement and combination mode. And thirdly, processing the encoder data by using a uniquely designed software algorithm to obtain the final more stable and more real position feedback data.
The precision and the stability of the vibrating mirror motor system are improved, and the eccentric and drifting resistance of the vibrating mirror motor system is improved, so that the environment tolerance and the anti-interference capacity of the vibrating mirror motor are improved. The difficulty of assembly and adjustment can be reduced, and products which are unqualified in assembly and adjustment are easier to detect.
Through the joint work of multiple encoders, the special grating disk for multiple encoding of the vibrating mirror motor is redesigned, so that each encoder can correctly identify the zero position under the swinging condition, then the encoders are placed on the same grating disk according to the specific positions, and a specific algorithm is assisted, so that the position error in the final output is reduced, and the influences on the aspects of eccentricity, radial shaking drift and the like are reduced.
It is apparent that the above-described embodiments are only some embodiments of the present application, but not all embodiments, and the preferred embodiments of the present application are shown in the drawings, which do not limit the scope of the patent claims. This application may be embodied in many different forms, but rather, embodiments are provided in order to provide a thorough and complete understanding of the present disclosure. Although the application has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments described in the foregoing description, or equivalents may be substituted for elements thereof. All equivalent structures made by the content of the specification and the drawings of the application are directly or indirectly applied to other related technical fields, and are also within the scope of the application.
Claims (10)
1. A design method of a high-precision galvanometer motor feedback system is characterized by comprising the following steps:
arranging at least one group of encoders at two symmetrical ends of the center of the grating disk according to the diameter direction of the grating;
the positions of the grating zero position score lines are in one-to-one correspondence with the positions of the optical center points of the encoder; setting zero signals at the installation positions of the encoders independently, and converting zero pseudo-random codes at each position; the zero window on the encoder photoelectric receiver corresponds to the zero score line of the grating disk, so that each zero is identified by the encoder at a specific position;
the output signal of the encoder is connected to a signal processing circuit board.
2. The method for designing a feedback system of a high-precision galvanometer motor according to claim 1, wherein,
the encoder includes at least one of a transmissive encoder and a reflective encoder.
3. The method for designing a feedback system of a high-precision galvanometer motor according to claim 1, wherein,
in the step of arranging at least one group of encoders at both ends of the grating disk which are symmetrical in the center in the grating diameter direction, the light source used includes at least one of a Light Emitting Diode (LED) and a Laser Diode (LD).
4. The method for designing a feedback system of a high-precision galvanometer motor according to claim 1, wherein,
the angles between adjacent different sets of encoders are the same.
5. The method for designing a feedback system of a high-precision galvanometer motor according to claim 1, wherein,
the placement direction of each encoder relative to the grating disk is consistent to ensure that the readings of all encoders remain the same as the grating disk rotates in one direction.
6. The method for designing a feedback system of a high-precision galvanometer motor according to claim 1, wherein,
the output signal of the encoder includes at least one of an analog signal, a digital protocol signal, and a square wave signal of ABZ.
7. The method for designing a feedback system of a high-precision galvanometer motor according to claim 1, wherein,
the data type received by the signal processing circuit board comprises at least one of an analog sine and cosine signal, a square wave ABZ signal, a pulse signal and a digital protocol signal.
8. The method for designing a feedback system of a high-precision galvanometer motor according to claim 1, wherein,
the grating comprises a main code channel and a zero code channel.
9. The method for designing a feedback system of a high-precision galvanometer motor according to claim 1, wherein,
the grating is round or square.
10. A high-precision galvanometer motor feedback system is characterized in that,
the system comprises at least one group of encoders, gratings and a signal processing circuit board, wherein the encoders are arranged at two symmetrical ends of the center of a grating disk in the diameter direction of the gratings, the positions of zero position dividing lines of the gratings are in one-to-one correspondence with the positions of optical center points of the encoders, zero position signals are independently arranged at the installation positions of each encoder, and zero position pseudo-random codes corresponding to each position are required to be transformed; the zero window on the encoder photoelectric receiver corresponds to the zero score line of the grating disk, so that each zero is identified by the encoder at a specific position; the output signal of the encoder is connected to a signal processing circuit board.
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