CN113074630B - Imaging quality detection device and method for laser scanning system of laser printer - Google Patents
Imaging quality detection device and method for laser scanning system of laser printer Download PDFInfo
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Abstract
The invention relates to a laser scanning system imaging quality detection device of a laser printer and a detection method thereof, wherein the detection device comprises: the multi-face prism rotating mechanism adopts a sucker structure, a sucker sucks the upper surface of the multi-face prism to control the rotating angle of the multi-face prism, and the rotating mechanism is controlled by a Z-direction stepping motor; the CCD moving mechanism is a ball screw sliding table mechanism which is controlled in a closed loop mode by combining an X-direction servo motor with a grating ruler, the CCD is fixed on the sliding table, and the sliding table moves to drive the CCD to collect images at different positions of an image surface; and the control system is used for cross coupling and synchronously controlling the Z-direction stepping motor and the X-direction servo motor to complete the dual-motor motion control of the linear motion relation of the optical system to be detected. The invention collects the facula image at the image surface by a high-precision double-motor synchronous control system, obtains the shape and energy distribution condition of the facula after being processed by a computer, and realizes the high-precision automatic detection of the device to the laser scanning system.
Description
Technical Field
The invention belongs to the field of imaging optics, relates to an optical imaging quality detection technology of a laser scanning system, and particularly relates to an automatic high-precision detection device and method of the laser scanning system in a laser printer.
Background
With the development of information technology, laser scanning systems are increasingly widely used. The laser scanning system controls the laser beam to move in a translational motion mode, and realizes the movement of the laser beam on an image plane by virtue of a multi-face prism and an optical imaging system which rotate at a high speed. As shown in fig. 1, in a laser printer, a light source generates laser, which is imaged on a photosensitive drum after being corrected for distortion by an f-theta lens in a laser scanning system, thereby completing information transfer.
The imaging quality of the f-theta lens optical system in a laser scanning system directly affects the resolution and printing effect of the printed image, as shown in fig. 2 a-2 d. The f-theta lens is subjected to optical design and then is subjected to injection molding. In the injection molding process, the material undergoes the process from melt to solid solidification, the material solidification generates shrinkage, and although a certain compensation can be obtained in the processing process, the shrinkage compensation cannot reach the ideal precision due to the possibility of early solidification, uneven solidification, and correlated shrinkage and warping deformation of the surface layer of the plastic part, so that surface shape errors are generated, as shown in fig. 3. Such surface shape errors cause deviations between the actual optical performance and the designed optical performance, thereby affecting the image quality. The current detection process is as shown in fig. 4, and requires that an f- θ lens is installed in a laser scanning system, the system is installed on a printer, a gray image is printed, and optical quality judgment is performed through analysis of the gray image. The detection time is long, the detection efficiency is low, and efficient and high-precision detection cannot be carried out.
Disclosure of Invention
The invention aims to provide a high-precision detection device and a high-precision detection method of a laser scanning system aiming at the problems of long detection time, multiple detection process procedures and lower detection efficiency of the optical quality of the laser scanning system.
The technical scheme adopted by the invention for solving the technical problem is as follows:
the system to be detected is an imaging optical system, when the polygon prism rotates at a constant speed, light can be deflected into different angles to be incident on the lens group, the light passing through the f-theta lens in the optical system has the characteristic of linear imaging, and the requirements that when light beams move at a constant speed on an image surface, the image surface is a head-up field, pixel points on the image are not overlapped, and the distance between the pixel points is not changed are met.
According to the characteristics of the system, the detection method is determined by controlling two motors to respectively drive the CCD and the multi-surface prism to realize position change, and imaging at different positions of an image surface under different view field angles is simulated. In order to accurately and quickly acquire the spot information at the image point, the motion relationship of the two motors must satisfy the linear position relationship of the optical system. The system obtains accurate double-motor positions through a linear cross-coupling synchronous control strategy.
The device to be detected is a precision imaging laser scanning system. The precision of the optical system is high, so the precision index of the detection equipment is high, and in order to meet the precision requirement, the error of the control system needs to be small. The solution is to control the motion relationship of two motors in the system to be high-precision synchronous control. The synchronous control strategy of the control system adopts cross-coupling type synchronization. And a five-phase stepping motor is adopted in the Z direction, and the positioning precision is improved by optimizing an acceleration and deceleration curve. And a servo motor and a grating ruler linear displacement sensor are adopted in the X direction to form a mechanical full closed loop to reduce the positioning error.
The invention provides an imaging quality detection device of a laser scanning system of a laser printer, which comprises:
the multi-face prism rotating mechanism adopts a sucker structure, a sucker sucks the upper surface of the multi-face prism to control the rotating angle of the multi-face prism, and the rotating mechanism is controlled by a Z-direction stepping motor;
the CCD moving mechanism is a ball screw sliding table mechanism which is controlled in a closed loop mode by combining an X-direction servo motor with a grating ruler, the CCD is fixed on the sliding table, and the sliding table moves to drive the CCD to collect images at different positions of an image surface;
and the control system is used for cross coupling and synchronously controlling the Z-direction stepping motor and the X-direction servo motor.
Moreover, the Z-direction stepping motor is a five-phase differential speed stepping motor.
The invention provides a method for detecting imaging quality of a laser scanning system of a laser printer, which is characterized in that a plurality of sampling points are divided in an image surface H, the distance between the sampling points is L, light spot information of each sampling point corresponds to a position on an f-theta lens, and the quality of the lens can be obtained by analyzing the light spot information; the method comprises the following specific steps:
(1) Determining the number of image points to be detected of a system to be detected as n;
(2) Dividing a full view field of a laser scanning system into n sub view fields at equal intervals according to the number of points to be detected, and taking light spots of light at the edge of each sub view field as light spots to be detected;
(3) Determining the scanning length of the light rays in the image surface under each sub-field of view through optical simulation software;
(4) The Z-direction motor controls the multi-surface prism to rotate to complete the rotating scanning of the light beam in one sub-field, and the X-direction servo motor drives the CCD to collect light spots of marginal light rays of each sub-field on an image surface;
(5) After the light spots of one sub-field are collected, the Z-direction motor drives the rotary polygon mirror to scan the next adjacent sub-field, and the X-direction image surface CCD moves backwards by a scanning length until the collection of marginal light spots on all the sub-fields is completed;
(6) And analyzing the light spot information through a computer to obtain the final imaging quality of the system.
Also, the rotation angle of the Z-direction motor is determined by the field angle of the sub-field.
In addition, the Z-direction stepping motor is optimized through an acceleration and deceleration curve, and the acceleration and deceleration time is distributed according to the maximum pulse number when the acceleration and deceleration of the stepping motor is controlled, and the speed of the action is not greatly required when the action is executed, so that the trapezoidal acceleration and deceleration method is adopted for selecting the acceleration and deceleration method, the realization is simple and stable, the calculated amount is small, and the phenomena of motor desynchronization, locked rotor and the like can be reduced to the maximum extent. And (3) setting the total time required for executing a single complete action as T, the acceleration time as T1, the uniform speed time as T2 and the deceleration time as T3, and obtaining the motion change curves of the speed, the acceleration and the rotation angle during trapezoidal acceleration. Thereby ensuring the accurate positioning of the Z-direction rotating unit;
moreover, the X-direction servo motor and the grating ruler linear displacement sensor form a mechanical full closed loop, and the control flow is as follows: before starting, the parameters of the system need to be set. In the full closed-loop system, because the position resolution of the servo encoder is different from that of the external grating ruler, the relation between the command frequency division and multiplication equivalence needs to be set, and the system needs to set two command frequency division and multiplication D, namely between the command pulse and the motor encoder and between the grating ruler and the motor encoder. Wherein, the precision E of the encoder, the thread pitch L of the screw rod and the number of the instruction pulses are n, and the position resolution Delta M is as follows:
the instruction divide-and-multiply frequency D is:
and the control algorithm between the grating ruler and the servo motor driver is three-loop control. The input of the outermost ring position ring is the external pulse, namely the pulse number fed back by the grating ruler. The speed is controlled by the external pulse frequency, and the number of pulses controls the distance of movement. The external pulse is set as the position loop after being processed by smooth filtering and electronic gear calculation, and the setting and the calculated value of the pulse signal fed back from the encoder after being adjusted by the PID of the position loop and the sum of the output and the feedforward signal of the position setting form the setting of the speed loop. Feedback for the position loop also comes from the encoder.
Moreover, the optical system to be detected meets the condition that the emergent angle of the light ray and the position of the image surface are in a linear relation. In order to enable each detection position to detect light spots, a control system is required to ensure that a position rotation angle and a moving distance accurately meet the linear relation of the system, and the position rotation angle and the moving distance have certain coupling. The positioning of the dual motors in the motor control system should provide coupling. The cross-coupling synchronous control is to feed back the following error of two motors to the control loop of the other side through proportional control aiming at the control system of the double motors, thereby realizing the closed loop of the synchronous error. The method mainly comprises the steps of feeding errors on positions into a system in a feedforward mode, compensating and eliminating synchronous errors, and selecting compensation points to perform position compensation on a position ring to meet the positioning accuracy of the system.
The invention has the advantages and positive effects that:
the invention collects the facula image at the image surface by a high-precision double-motor synchronous control system, obtains the shape and energy distribution condition of the facula after being processed by a computer, and realizes the high-precision automatic detection of the device to the laser scanning system. The efficiency of manual detection is low and detection errors are avoided, and the detection quality and the detection efficiency of the laser scanning system are improved.
Drawings
FIG. 1 is a schematic diagram of a laser scanning system;
FIG. 2a is a schematic diagram of a non-uniform spot; FIG. 2b is a printed gray scale image of non-uniform light spots; FIG. 2c is a schematic view of a uniform spot; FIG. 2d is a printed gray scale image of uniform spots;
FIG. 3 is a lens profile measurement;
FIG. 4 is a flow chart of a prior art laser scanning system inspection;
FIG. 5 is a simulation diagram of parameters of a laser scanning system;
FIG. 6 is a diagram of a multi-configuration simulation;
FIG. 7 is a schematic view of a detection apparatus;
in the figure: 1 is a Z-axis motor; 2 is a sucker; 3 is a polygon prism; 4 is a lifting bracket; 5 is an X-axis motor; 6 is a laser scanning system; 7 is CCD;8 is a ball screw sliding table; 9 is a ball screw; and 10 is a grating ruler.
FIG. 8 is a schematic view of the detection principle;
FIG. 9 is a schematic diagram of a scanning sampling;
FIG. 10 is a graph showing the variation of displacement, velocity and acceleration of trapezoidal acceleration and deceleration;
FIG. 11 is a setting of stepper motor control unit parameters;
FIG. 12 is a block diagram of a full closed loop control mode;
FIG. 13 is a flow chart of a fully closed loop control implementation;
FIG. 14 is a photograph of a detection device;
fig. 15 is a diagram showing an actual detection sample of the detection device.
Detailed Description
The present invention is further illustrated by the following specific examples, which are intended to be illustrative, not limiting and are not intended to limit the scope of the invention.
The principle of the laser scanning system is shown in fig. 1, and two actions must be realized to complete scanning, namely, the polygon prism rotates to complete the deflection of the laser beam, and the laser beam moves on an image plane after passing through the optical system to complete scanning. Therefore, the structure of the detection device is divided into two parts, namely driving the rotation of the multi-surface prism and the movement of the image acquisition system on a straight line. The structure of the device is shown in figure 7 and comprises an optical system to be measured, an electromechanical system and an image acquisition system. The detection principle is shown in fig. 8, and a motor 1 and a laser scanning system 6 fixing table for controlling the rotation of the multi-facet prism in the electromechanical system are positioned on a lifting support 4 vertical to the base. The motor 5 and the ball screw device are arranged in the horizontal direction. The CCD7 of the image acquisition system is arranged on a sliding platform 8 of a ball screw and moves along with the platform to complete scanning on an image surface.
When the control system is designed, the rotation angle is different and the corresponding image surface position is different due to the linear imaging relation of the optical system. The resolution that determines the image quality in a transverse scan range is determined by the size and shape of the spot. The detection principle of the detection device is shown in fig. 9, a plurality of sampling points are divided in an image plane H, the distance between the sampling points is L, light spot information of each sampling point corresponds to a position on the f-theta lens, and the quality of the lens can be obtained by analyzing the light spot information to complete detection. Precise position shifting is therefore achieved by the control system. The experiment shows that when the rotation angle of the polygon prism is determined, the maximum allowable positioning error of the CCD on the image surface is +/-1 mm. In order to enable the CCD to accurately move to an image point to acquire light spot information, the motion relation of the two motors needs to be controlled in a high-precision linear synchronization mode through a control system. The device control system adopts a double-motor synchronous control strategy of cross-coupling synchronous control. And a five-phase stepping motor is adopted in the Z direction, and the positioning precision is improved by optimizing an acceleration and deceleration curve. The positioning error is reduced by adopting a mechanical full closed loop form formed by the servo motor and the linear displacement sensor 10 of the grating ruler in the X direction.
And finally, building an experimental platform, and obtaining linear relation parameters of the double motors by adopting a model simulation method. The laser scanning system parameters are shown in fig. 5. The exit angle of the rotating polygon prism is set to be a multi-configuration structure in the optical simulation software, as shown in fig. 6, so as to simulate the exit position of the light beam when the polygon prism rotates by different angles. The corresponding parameters of the rotation angle and the imaging position of the multi-face prism can be obtained, and the device is adopted to verify the light spot detection effect.
The laser scanning system has the following remarkable characteristics:
(1) the linear imaging characteristics are as follows: according to the relative position relation of the rotary polygon prism and the f-theta lens, the laser scanning system to be detected is in front of the lens for scanning, namely the rotary polygon prism is positioned in front of the f-theta lens. Assuming that the focal length of the f-theta lens is f, the total scan angle is 2 theta, and the scan coverage length is H, for a normal lens with distortion corrected, the image height is:
H＝f·tanθ (1)
differentiating the time yields:
it can be seen that the scanning speed of an incident beam deflected at equal angular velocities over the focal plane is not constant. However, for an f- θ lens, in order to obtain a certain scanning speed, the image height after introducing negative distortion to the lens is:
H＝f·θ (3)
this is done:
omega is the angular velocity of the rotating polygon prism, so that constant-speed scanning in the range of an image plane with H = f.theta.can be realized, and the minimum resolution information in the transferred image can be ensured not to generate overlapping and disconnection, which is the linear imaging characteristic.
(2) The center point brightness. The imaging quality of the optical system is expressed by the ratio S.D of the central brightness of the diffraction spot imaged by the optical system to the central brightness of the diffraction spot in the absence of aberration. When S.D is more than or equal to 0.8, the imaging quality of the optical system is considered to be perfect, which is based on the Stratel criterion;
according to the imaging characteristics of the system, in order to enable the printer to print high-quality images, the laser scanning system needs to achieve the consistency of the required resolution of the whole scanning coverage area, namely the requirements of the size specification, the spot intensity and the like of the image points outside the shaft on the shaft are consistent. The scanning sampling principle is shown in fig. 9, where H is the image plane scanning length, X is the transverse scanning direction, Y is the longitudinal information printing direction, and σ is the system resolution, i.e., the emergent spot size. Under the action of the rotating polygon mirror, scanning sampling points are in the X direction, and T is a sampling period. L is the sampling resolution within the scan length. The sweep sampling frequency f is then:
and the imaging quality of the laser scanning system is judged by analyzing the light spot information of all sampling points.
The mechanical system mainly comprises a grabbing mechanism of the reflecting prism device and a ball screw feeding mechanism, and is shown in fig. 7.
(1) The function of the ball screw feeding system is to convert the rotary motion of the motor into the linear motion of the worktable. The system structure comprises a servo motor 5, a coupler, a ball screw 9, a nut, a support bearing, a guide rail, a workbench and the like. The ball screw feeding system is fixed on the workbench of the detection device, and the transmission mode is an indirect driving mode in which a servo motor drives a ball screw;
(2) The grabbing mechanism is used for grabbing the multi-face prism to complete rotation. The grabbing mechanism is connected with a shaft of the stepping motor 1. Since the torque required for the rotation of the polygon mirror 3 is very small, a suction cup structure is adopted. The sucking disc 2 directly sucks the upper surface of the rotating polygon prism to complete the grabbing. The stepping motor, the gripping device and the laser scanning system 6 are arranged on a lifting support 4 vertical to the workbench.
The detection function of the detection device of the laser scanning system is mainly controlled by the double motors and the corresponding sensors. The specific implementation includes system hardware and control system software.
(1) And (4) selecting system hardware. The hardware of the control system comprises a main controller, two motors and corresponding driver linear displacement sensors. The master control system adopts Siemens S7-1200PLC, can control the output of two shafts, and meets the control of two motors of the device. The Z-axis motor selects a five-phase differential speed stepping motor, and compared with a common two-phase stepping motor, the Z-axis motor realizes low vibration and low noise, and has good micro-step driving performance, and the precision can not be deteriorated even if micro-step is stopped through electronic subdivision. The X-axis motor selects a servo motor, the precision of the servo motor is determined by an encoder of the servo motor, and the precision of the encoder selected by the device is 23bit. Selecting a grating ruler with the resolution ratio of 5um as an actual external sensor to realize high-precision positioning of the device;
(2) The control strategy and the parameters are determined, because the image plane and the rotation angle need to be positioned at a plurality of points, the positioning accuracy and the position synchronism of the system have high requirements, and a simple open-loop control mode may not meet the requirements. Because the rotation angle and the image plane spot position satisfy a linear relation, the corresponding position relation of the two motors in a motor control system has coupling, and a cross-coupling double-motor synchronous control strategy is selected. The advantage is that the speed or position signals of the two motors are compared to obtain a difference as an additional feedback signal. This additional feedback signal is used as a tracking signal from which the control system can adjust to the load change of any one of the motors to achieve good synchronous control accuracy.
The control parameters of the control system are obtained by adopting a model simulation method. The laser scanning system parameters are shown in fig. 5. The exit angle of the rotating polygon prism is set to be a multi-configuration structure in the optical simulation software, as shown in fig. 6, and the exit positions of the light beams under different angles of the rotating polygon prism are simulated. Corresponding data of the rotation angle and the imaging position of the multi-face prism can be obtained;
(3) The Z-direction stepping motor control unit selects 20 speed-reducing stepping motors in consideration of device structures, the stepping angle is 0.72 degrees, the stopping precision is +/-0.05 degrees, the maximum subdivision number is 250 degrees, the minimum stepping angle can reach 0.00288 degrees, and the micro-step stopping precision cannot be deteriorated due to good micro-step driving performance and electronic subdivision. The motor adopts a harmonic reducer with a reduction ratio of 1. The maximum subdivision number of the driver is 250, and the maximum pulse number required for one rotation of the output shaft after the motor is decelerated is 6250000. In order to reduce the phenomena of motor step loss, locked rotor and the like, accurate positioning is realized. The stepping motor is controlled by adopting trapezoidal acceleration and deceleration, and as shown in fig. 10, the stepping motor is simple and stable to realize, small in calculated amount and remarkable in effect. When the acceleration and deceleration control of the stepping motor is carried out, the acceleration and deceleration time needs to be reasonably distributed according to the maximum pulse number, and generally the acceleration and deceleration time needs to be more than 300 ms. Let the total time required to execute a single complete action be T, the acceleration time be 1, the uniform velocity time be 2, the deceleration time be 3, and the parameter settings be as shown in fig. 11. The motion change curves of speed, acceleration and rotation angle during trapezoidal acceleration can be obtained according to the formula. Thereby ensuring the accurate positioning of the Z-direction rotating unit;
(4) The X-direction motor unit control system adopts an indirect drive mode in the X direction, and only adopts a servo motor closed loop. The motor can only be ensured to reach the position to be positioned, the actual position of the mechanical structure is not clear, and high-precision positioning is difficult to ensure due to the problems of machining and mounting precision of the mechanical structure. So the device adopts a mechanical full closed loop. And a grating ruler displacement sensor is additionally arranged on the moving sliding table on the load side of the motor. The control principle is shown in fig. 12, the PLC performs open-loop control on the servo driver, and the actual position of the mechanical structure is fed back by the external displacement sensor to complete a full closed loop for the servo driver, so that the positioning accuracy is high, and the positioning accuracy of the μ level can be realized.
The control flow chart is shown in fig. 13, and before starting, the parameters of the system need to be set. In the full closed-loop system, because the position resolution of the servo encoder is different from that of the external grating ruler, the relation between the command frequency division and multiplication equivalence needs to be set, and the system needs to set two command frequency division and multiplication D, namely between the command pulse and the motor encoder and between the grating ruler and the motor encoder. Wherein, the precision E of the encoder, the thread pitch L of the screw rod and the number of the instruction pulses are n, and the position resolution Delta M is as follows:
the instruction divide-and-multiply frequency D is:
the specific implementation steps of image acquisition and experimental verification are as follows:
(1) The image acquisition system acquires light spots on an image surface by using the CCD, fixes the CCD on a sliding table of a ball screw, and drives the CCD to acquire images at different positions of the image surface by moving the platform. The feasibility of the method is verified, and a device detection experiment is designed, as shown in fig. 7. Setting parameters as the corner of a multi-surface prism to be 30 degrees, taking sampling points every 5 degrees, totaling 6 sampling points, and acquiring the light spot information of each point through a CCD (charge coupled device) according to the distance L =18.324mm between the sampling points of the linear imaging relation image plane;
(2) The experimental results are shown in fig. 15, which are based on acceleration and deceleration control and a mechanical fully closed-loop control system. The feedback pulse is 3665 after each movement, the resolution of the grating ruler is 5um, namely the CCD actually moves 18.325mm, and the control precision of the control system is met within an error allowable range. The size of the facula at each point can be known to be 2 +/-0.2 mm and the shape is regular through the image acquisition system on the computer, and the energy distribution of the facula is concentrated, so that the qualification of the laser scanning system can be judged.
The experiment for the actual detection of the device is shown in FIG. 14. In the device, the pitch of a ball screw is 5mm, the rotation angle of a multi-face prism is 30 degrees, a sampling point is taken every 5 degrees, 6 sampling points are counted, and according to the linear imaging relation, the distance L =18.324mm between image surface sampling points is obtained through a CCD (charge coupled device). The experimental result is shown in fig. 15, the resolution of the grating ruler is 5um through a mechanical full closed loop, the feedback pulse is 3665 after each movement, namely the CCD actually moves 18.325mm, and the control accuracy of the control system is satisfied within the error allowable range. The image acquisition system can know that the size of the light spot at each point is 2 +/-0.2 mm, the shape is regular, the energy distribution of the light spot is concentrated, and the quality of the laser scanning system to be detected can be determined to be qualified.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various changes and modifications can be made without departing from the inventive concept, and these changes and modifications are all within the scope of the present invention.
Claims (3)
1. A method for detecting imaging quality of a laser scanning system of a laser printer is characterized by comprising the following steps: dividing a plurality of sampling points in an image plane H, wherein the distance between the sampling points is L, the light spot information of each sampling point corresponds to a position on the f-theta lens, and the quality of the lens can be obtained by analyzing the light spot information; the method comprises the following specific steps:
(1) Determining the number of image points to be detected of a system to be detected as n;
(2) Dividing a full view field of a laser scanning system into n sub view fields at equal intervals according to the number of points to be detected, and taking light spots of light at the edge of each sub view field as light spots to be detected;
(3) Determining the scanning length of the light rays in the image surface under each sub-field of view through optical simulation software;
(4) The Z-direction motor controls the multi-surface prism to rotate to complete the rotating scanning of the light beam in one sub-field, and the X-direction servo motor drives the CCD to collect light spots of marginal light rays of each sub-field on an image surface;
(5) After the light spots of one sub-field are collected, the Z-direction motor drives the rotary polygon mirror to scan the next adjacent sub-field, and the X-direction image surface CCD moves backwards by a scanning length until the collection of marginal light spots on all the sub-fields is completed;
(6) Analyzing the light spot information through a computer to obtain the final imaging quality of the system;
the detection system for realizing the detection method comprises the following steps:
the polygon prism rotating mechanism adopts a sucker structure, a sucker sucks the upper surface of the polygon prism to control the rotating angle of the polygon prism, the rotating angle is determined by the field angle of a sub-field of view, the rotating mechanism is controlled by a Z-direction stepping motor, the Z-direction stepping motor is optimized by a trapezoidal acceleration and deceleration curve, and the acceleration and deceleration time is distributed according to the maximum pulse number when the acceleration and deceleration control of the stepping motor is carried out;
the CCD moving mechanism is a ball screw sliding table mechanism which is controlled by an X-direction servo motor in combination with a grating ruler in a closed loop manner, the CCD is fixed on the sliding table and is driven to collect images at different positions of an image surface by the movement of the sliding table,
the control system is used for cross coupling and synchronously controlling the Z-direction stepping motor and the X-direction servo motor, wherein the cross coupling and synchronous control is to feed back the following errors of the two motors to a control loop of the other party through proportional control to realize the closed loop of synchronous errors, feed forward the errors on the positions to the system to compensate and eliminate the synchronous errors, and select a compensation point on a position loop to compensate the positions;
the X-direction servo motor and the grating ruler form a mechanical full closed loop, and the control flow is as follows: before starting, setting parameters of a system, in a full closed-loop system, setting position resolution of a servo encoder and an external grating ruler to be different, setting a relation between instruction frequency division and frequency multiplication equivalence and setting two instruction frequency division and frequency multiplication D between an instruction pulse and a motor encoder and between the grating ruler and the motor encoder respectively, wherein the encoder precision E, the screw pitch L of a lead screw and the instruction pulse number are n, and then the position resolution Delta M is as follows:
the instruction divide-and-multiply frequency D is:
the control algorithm between the grating ruler and the servo motor driver is three-loop control, the input of the outermost loop position loop is external pulse, the speed is controlled by the external pulse frequency, the moving distance is controlled by the pulse number, the external pulse is set as the position loop after being processed by smooth filtering and electronic gear calculation, the set value and the calculated value of the pulse signal fed back from the encoder after being adjusted by the PID of the position loop and the resultant value of the feedforward signal given by the position form the given of the speed loop, and the feedback of the position loop is also from the encoder.
2. The detection method according to claim 1, characterized in that: the Z-direction stepping motor is a five-phase differential speed stepping motor.
3. The detection method according to claim 2, characterized in that: the speed or position signals of the Z-direction stepping motor and the X-direction servo motor are compared to obtain a difference value as an additional feedback signal, the additional feedback signal is used as a tracking signal, and according to the tracking signal, a control system adjusts according to the load change of any motor, so that good synchronous control precision is obtained.
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