CN109769096B - Servo motion control method for linear array CCD scanning process - Google Patents
Servo motion control method for linear array CCD scanning process Download PDFInfo
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Abstract
The invention discloses a servo motion control method for a linear array CCD scanning process, which comprises the steps of planning a scanning track of a linear array photoelectric coupling type imaging device CCD, setting parameters of a double-loop PID algorithm and an iterative learning feedforward plus PID feedback control algorithm, judging the current motion state of a shot object, and carrying out speed control according to switching and switching optimization among different motion states, thereby avoiding image distortion caused by unstable motion speed in the scanning process of a linear array CCD camera.
Description
Technical Field
The invention belongs to the technical field of precise motion control, and particularly relates to a servo motion control method for a linear array CCD scanning process.
Background
A ccd (charge Coupled device) is a photoelectric coupling type imaging device, and can directly convert an optical signal into an electrical signal, and obtain a digitized image after signal amplification and analog-to-digital conversion. The CCD devices are classified into linear array CCDs and planar array CCDs according to the arrangement of the light sensing units. The linear array CCD is widely applied because of simple structure and low cost. The image acquisition system different from the area array CCD can obtain an area image only by simple exposure, the linear array CCD scanning imaging system can obtain a two-dimensional area image only by continuous scanning at a motion speed, and the imaging characteristic of the imaging system is different from that of the area array CCD acquisition system to a certain extent.
The linear scanning imaging system is used for the scene that relative motion exists between a measured object and a camera, the linear array camera only acquires one line of pixels at a time, if a complete image is to be obtained, the measured object needs to move at a certain speed along the direction perpendicular to the linear array sensor, and after the linear array CCD collects one line of data, the measured object just moves to the next unit length to form continuous data acquisition.
The linear array CCD has a fixed line scanning period, when the linear array CCD acquires images only according to the scanning period of the linear array CCD and is asynchronous with the motion speed of a shot object, the situation of image blurring can occur, the acquired images are usually distorted, important data can be lost or repeated useless data can be added, and a compressed or stretched image of the shot object is presented, so that the realization of speed differential-free control in the scanning process is the key for acquiring correct and equal-proportion images.
The servo control in the existing linear array CCD scanning process mostly adopts a single control mode, and the accurate control of different motion states in the scanning process cannot be realized. Or the biaxial movement adopts a uniform control structure, and the difference of the functions realized by the biaxial movement in the scanning process is not considered. That is, the x-axis motion mainly realizes the movement of the subject during the scanning process, and it is required to realize the speed-free control. The Y-axis motion primarily performs the positioning function. Ignoring this point typically results in motion in the non-scanning direction still occurring during the scanning motion. Therefore, the pictures shot by the camera are stretched, compressed or even distorted, the difficulty of the obtained pictures in subsequent image processing is increased, and the detection efficiency of the system is reduced.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a servo motion control method for a linear array CCD scanning process, which avoids image distortion caused by unstable motion speed in the scanning process of a linear array CCD camera by carrying out no-difference control on the speed in the scanning process.
In order to achieve the above object, the present invention provides a servo motion control method for linear array CCD scanning process, which is characterized by comprising the following steps:
(1) planning scanning track of linear array photoelectric coupling type imaging device CCD
(1.1) planning the motion trail in the scanning direction
Setting pixels of each line of the linear array CCD to be NrThe width of the linear array CCD is W0The scanning rate of the linear array CCD is VcThe moving speed of the object is V0，；
Then there are: accuracy of transverse scanning
Accuracy of longitudinal scanning
Ensuring that the acquired image is not distorted, and according to the principle that the horizontal resolution and the longitudinal resolution are equal, the optimal moving speed of the object to be shot and the scanning speed of the linear array CCD meet the following relation:
V0＝VC×W0/Nr
finally, according to the movement velocity V0Planning a motion track in a scanning direction;
(1.2) planning the motion trail in the non-scanning direction
Setting the motion stroke of the shot object as the single scanning width W of the linear array CCD0；
(1.3) optimizing the planned trajectory
A filtering module is added at the output end of the planned motion track to filter noise disturbance in the planned track;
(2) and parameter setting
(2.1) parameter tuning of double-loop PID algorithm
In the speed outer ring and the position inner ring, an expected acceleration curve A is obtained according to the optimized planning track respectivelyg(t), obtaining an actual acceleration curve A through a grating ruler sensorg0(t) then calculating an acceleration error curve eA(t)＝Ag(t)-Ag0(t), finally, adjusting the proportionality coefficient K according to a Ziegler-Nichols algorithmpAnd integral coefficient KiThereby finishingParameter setting of a double-loop PID algorithm;
(2.2) iteratively learning the parameter setting of the feedforward + PID feedback control algorithm;
(2.2.1) shielding off a speed outer ring of the system, and only keeping a position inner ring of the system; then, an expected speed curve V is obtained according to the optimized planning tracks(t) mixing Vs(t) Fourier transforming to obtain Vs(jw), and then Vs(jw) as system initial input and input to the velocity outer loop; reading out the actual speed curve V of the system according to the grating rulers0(t) mixing Vs0(t) Fourier transforming to obtain Vs0(jw), and then Vs0(jw) as system initial output;
finally, substituting the iterative learning control law into the system to obtain the first input of the system
Yd(jw) is the system desired output speed;
(2.2.2) reading out the first output Y of the system by means of the grating ruler sensor1(jw), then, the first output speed error curve DeltaY is calculated1(jw)＝Y1(jw)-Yd(jw)；
And calculating the second input U of the system according to the following formula through the iterative learning control law again2(jw)；
Wherein, Ur(jw) is the r-th input to the system, r is 2,3,4, …; y isr-1(jw) is the (r-1) th output of the system, and rho is a differential term proportionality coefficient;
simultaneously reading out the secondary output Y of the system through the grating ruler sensor2(jw), then, a second time output speed error curve DeltaY is calculated2(jw)＝Y2(jw)-Yd(jw)；
Judging whether the speed error curve obtained in the previous and subsequent times is oscillated or not, if the speed error curve is oscillated, taking the input obtained in the subsequent time as a feedforward input signal of the system, otherwise, calculating the next input of the system again through an iterative learning control law, and repeating the steps until the speed error curve is oscillated, and stopping iteration;
(2.2.3) inputting the feedforward input signal into the speed outer ring of the double-ring PID which is set in the step (2.1) to complete parameter setting of the iterative learning feedforward plus PID feedback control algorithm;
(3) judging the current motion state of the shot object
Velocity V of motion of object0Solving a first derivative to obtain the acceleration a of the shot object, comparing the acceleration a with a given threshold value epsilon, and when | a | is greater than epsilon, the shot object is in a variable speed motion state; when | a | ≦ epsilon, the object is in a uniform motion state;
(4) switching between different motion states and switching optimization
(4.1) when the shot object is in a variable speed motion state, switching to feedforward control and PID feedback control, wherein the specific control process is as follows:
(4.1.1) calculating the initial input U of the system in the motion state0；
U0＝Kp1*Kp2*Vs(0)+Ur(0)
Wherein, Kp1、Kp2Is the proportionality coefficient of the position inner ring and the velocity outer ring, Ur(0) For the value of the feed-forward input signal at the initial instant, Vs(0) Is the value of the desired speed profile at the initial time;
(4.1.2) reading the acceleration feedback signal A of the system in the motion state through the grating ruler0(t), then, substituting a feedforward control and PID feedback control law, and calculating an acceleration signal A (t) of the system in the motion state;
ev(t)＝A(t)-A0(t)
wherein the content of the first and second substances,Ki2is the integral coefficient of the velocity outer loop;
(4.1.3) repeating the steps (4.1.1) - (4.1.2), tracking the acceleration signal A (t) in real time, and enabling the speed curve output by the system in real time to reach the expected speed curve, thereby completing the control in the motion state;
(4.2) when the shot object is in a uniform motion state, switching to double-ring PID control, wherein the specific control process is as follows:
(4.2.1) calculating the initial input U of the system in the motion state0；
U0＝Kp1*Kp2*Vs(0)
(4.2.2) reading the acceleration feedback signal A of the system in the motion state through the grating ruler0(t), then, bringing into a double-loop PID control law, and calculating an acceleration signal A (t) of the system in the motion state;
ev(t)＝A(t)-A0(t)
wherein, Ki2Is the integral coefficient of the velocity outer loop;
(4.2.3) repeating the steps (4.2.1) - (4.2.2), tracking the acceleration signal A (t) in real time, and enabling the speed curve output by the system in real time to reach the expected speed curve, thereby completing the control in the motion state.
The invention aims to realize the following steps:
the invention relates to a servo motion control method for a linear array CCD scanning process, which comprises the steps of planning a scanning track of a linear array photoelectric coupling type imaging device CCD, setting parameters of a double-loop PID algorithm and an iterative learning feedforward plus PID feedback control algorithm, judging the current motion state of a shot object, and carrying out speed control according to switching and switching optimization among different motion states, thereby avoiding image distortion caused by unstable motion speed in the scanning process of a linear array CCD camera.
Meanwhile, the servo motion control method for the linear array CCD scanning process also has the following beneficial effects:
(1) the differential model-free iterative learning algorithm adopted by the acceleration feedforward can avoid errors caused by system modeling errors, and the dynamic iterative process can continuously correct output errors caused by disturbance, so that the differential-free control of the acceleration stage is realized; in the algorithm adopted by the invention, the difference term not only considers the influence of the system states of the previous two times of the current state on the system, but also considers the influence of the system state on the system residue in the initial iteration process, and introduces a proportionality coefficient rho to distribute the influence coefficient of each iteration on the system;
(2) the two control models designed by the invention are switched and controlled, so that the system is subjected to double-loop PID control in a constant speed scanning stage, and the acceleration feedforward control is used in the system in an acceleration motion stage and a deceleration motion stage, and the control structure enables the system to have the advantages of a double-loop PID control structure and avoids the defect that the system is in a single-mode control state;
(3) and a switching optimization signal is introduced in the switching process, so that the disturbance of the system caused by the sudden switching of the model is avoided, and the switching time of the system between two control modes is also reduced.
Drawings
FIG. 1 is a flow chart of a servo motion control method for a linear array CCD scanning process according to the present invention;
FIG. 2 is a schematic diagram of a linear array CCD scanning process;
FIG. 3 is a graph of a filtered planned motion trajectory;
FIG. 4 is a block diagram of a switch module switch motion state;
FIG. 5 is a schematic diagram of a handover optimization signal;
FIG. 6 is a graph comparing feed forward input signals before and after optimization;
FIG. 7 is a block diagram of a feed forward input module;
FIG. 8 is a block diagram of a servo motion control system;
FIG. 9 is a graph comparing a conventional PID control with the speed profile of the present invention;
FIG. 10 is a graph comparing the speed error curves of the conventional PID control and the present invention.
Detailed Description
The following description of the embodiments of the present invention is provided in order to better understand the present invention for those skilled in the art with reference to the accompanying drawings. It is to be expressly noted that in the following description, a detailed description of known functions and designs will be omitted when it may obscure the subject matter of the present invention.
Examples
Fig. 1 is a flow chart of a servo motion control method for a linear array CCD scanning process of the present invention.
In this embodiment, as shown in fig. 1, the servo motion control method for a linear array CCD scanning process of the present invention includes the following steps:
s1 planning scanning track of linear array photoelectric coupling type imaging device CCD
S1.1, planning the motion trail of the scanning direction
The line scanning imaging system must include motion control to normally capture images, the most important link of the motion control is to determine the relationship between the line frequency and the motion speed of the line scanning camera, and a correct and undistorted image can be obtained only if the scanning frequency and the motion speed are in a correct matching relationship, and the specific scanning process is shown in fig. 2.
To ensure that the acquired image is not stretched or compressed, one must follow a point: the resolution of the object in the lateral and longitudinal directions is equal, i.e. the distance the object moves in one line synchronization period is the same as the actual size of the pixel sample.
Setting pixels of each line of the linear array CCD to be NrThe width of the linear array CCD is W0The scanning rate of the linear array CCD is VcThe moving speed of the object is V0，；
Then there are: accuracy of transverse scanning
Accuracy of longitudinal scanning
Ensuring that the acquired image is not distorted, and according to the principle that the horizontal resolution and the longitudinal resolution are equal, the optimal moving speed of the object to be shot and the scanning speed of the linear array CCD meet the following relation:
V0＝VC×W0/Nr
when the lens and camera are selected, the lateral accuracy is a fixed value, and the longitudinal accuracy of the image varies with the moving speed of the object under the condition that the line frequency of the linear array scanning camera is not changed. When the object moving speed is too fast, the actual image is compressed, some data segments are lost, and when the object moving speed is too slow, the actual image is stretched, and repeated useless data can be brought. In the application of a machine vision system, in order to obtain clear images of moving objects and avoid image blurring, a line scanning image must be locked with longitudinal precision: the longitudinal accuracy is always equal to the transverse accuracy.
Finally, according to the movement velocity V0Planning a motion track in a scanning direction; the planning result is shown in fig. 3, and the motion process is divided into an acceleration stage, a uniform motion stage, and a deceleration stage. In the stage of uniform motion, the stages of R1 and R2 are reserved, and the scanning process is started after the speed is completely uniform.
S1.2, planning the motion trail in the non-scanning direction
The motion in the non-scanning direction is in an idle stroke stage, and the CCD linear array camera does not work at the moment. In order to reduce the idle travel time, the working area of the nonlinear array camera is increased in speed as much as possible, but the positioning precision needs to be ensured. In order to save the idle travel time, the motion of the scanned object is divided into an acceleration section and a deceleration section. The whole moving stroke is just to set the moving stroke of the shot object as the single scanning width W of the linear array CCD0；
S1.3, optimizing the planned track
To avoid sudden changes in velocity and acceleration during the scanning process. The movement process is as smooth and stable as possible. The planned trajectory is required to be as smooth as possible, free of high frequency components. In order to make the planned track smoother, the invention adopts the filtering module added at the track planning output end. The filtering module adopts a Kalman filter, so that noise disturbance in the planned track can be filtered, namely the unsmooth track stage between accelerated motion and uniform motion, and optimization of the planned track is realized.
The planned trajectory after the trajectory optimization by adding the filter is shown in fig. 3, and the abrupt change of the speed between the accelerated motion stage and the uniform motion stage is eliminated after the filter is added.
S2, parameter setting
S2.1 parameter setting of double-loop PID algorithm
In the speed outer ring and the position inner ring, an expected acceleration curve A is obtained according to the optimized planning track respectivelyg(t), obtaining an actual acceleration curve A through a grating ruler sensorg0(t) then calculating an acceleration error curve eA(t)＝Ag(t)-Ag0(t), finally, adjusting the proportionality coefficient K according to a Ziegler-Nichols algorithmpAnd integral coefficient KiThereby completing the parameter setting of the double-loop PID algorithm;
the parameter setting of the double-ring PID algorithm comprises parameter setting of a speed outer ring PID algorithm and parameter setting of a position inner ring PID algorithm, the setting processes are completely the same, the parameter setting of the speed outer ring PID algorithm is taken as an example for explanation, and the specific process is as follows:
1) accessing the proportional controller into the system;
2) setting a proportional gain K of a proportional controller, inputting a unit step signal to the proportional controller, and observing an acceleration response curve A of the motor to the unit step signals0(t)；
3) Changing the proportional gain K from small to large until the system oscillates;
4) when the system generates continuous constant amplitude oscillation, recording the gain and the oscillation period at the moment, and respectively marking as critical gain KuAnd a critical period Tu；
5) Calculating the proportionality coefficient K of the speed outer ringp2And integral coefficient Ki2；
S2.2, setting parameters of an iterative learning feedforward + PID feedback control algorithm;
s2.2.1, shielding off the outer ring of the speed of the system and only keeping the inner ring of the position of the system; then, an expected speed curve V is obtained according to the optimized planning tracks(t) mixing Vs(t) Fourier transforming to obtain Vs(jw), and then Vs(jw) as system initial input and input to the velocity outer loop; reading out the actual speed curve V of the system according to the grating rulers0(t) mixing Vs0(t) Fourier transforming to obtain Vs0(jw), and then Vs0(jw) as system initial output;
finally, substituting the iterative learning control law into the system to obtain the first input of the system
Yd(jw) is the system desired output speed;
s2.2.2 first time output Y of reading system by grating ruler sensor1(jw), then, the first output speed error curve DeltaY is calculated1(jw)＝Y1(jw)-Yd(jw)；
And calculating the second input U of the system according to the following formula through the iterative learning control law again2(jw)；
Wherein, Ur(jw) is the r-th input to the system, r is 2,3,4, …; y isr-1(jw) is the (r-1) th output of the system, and rho is a differential term proportionality coefficient;
simultaneously reading out the secondary output Y of the system through the grating ruler sensor2(jw), then, a second time output speed error curve DeltaY is calculated2(jw)＝Y2(jw)-Yd(jw)；
Judging whether the speed error curve obtained in the previous and subsequent times is oscillated or not, if the speed error curve is oscillated, taking the input obtained in the subsequent time as a feedforward input signal of the system, otherwise, calculating the next input of the system again through an iterative learning control law, and repeating the steps until the speed error curve is oscillated, and stopping iteration;
s2.2.3, inputting the feedforward input signal into the speed outer ring of the double-ring PID which has been set in the step S2.1, and completing the parameter setting of the iterative learning feedforward + PID feedback control algorithm;
s3, judging the current motion state of the shot object
The function of the motion state judgment module is realized by the switch module, as shown in fig. 4, the motion speed V of the object is judged0Calculating a first derivative to obtain the acceleration a of the shot object, comparing the acceleration a with a given threshold epsilon, and when | a | > epsilon, the scanned object has an error outside an allowable error range, and the shot object is in a variable speed motion state; when | a | ≦ epsilon, the acceleration of the scanned object drifts near the zero point, and the object to be shot is in a uniform motion state at the moment;
s4 switching between different motion states and switching optimization
In order to ensure that the stability of the system is not influenced by the switching process of the control model of the system, the invention designs a switching optimization module. The design of the switching optimization signal is shown in fig. 5, so as to avoid sudden zero setting of the feedforward signal when the switching critical point is reached, which leads to sudden change of the system model, thereby affecting the stability of the system. Trajectory optimization must be performed at the initial stage of handover. Two basic requirements for switching the optimization signal are considered: 1. a smooth transition from the switching critical point to zero is achieved. 2. The transition time is reduced as much as possible, and the switching time of the system between the two models is reduced.
Therefore, the invention selects the steepest descent line, namely the cycloid line, at the initial switching stage of the switch module down-switch optimization signal. The steepest descent line can well meet the requirement of switching optimization signals. The problem of system disturbance caused in the switching process of the system control structure can be well solved by designing the mutual switching state between the system critical state epsilon and 0 into the steepest descent line. The output of the acceleration feedforward module with the added switching optimization signal is shown in fig. 6, and when the system reaches a critical switching state epsilon, the feedforward signal drops to zero along the steepest descent line until the scanning process is finished. At this time, the acceleration feedforward signal output is zero. The system realizes smooth switching from acceleration feedforward control to double-loop PID control.
Next, we describe a specific procedure of the handover control.
S4.1, when the shot object is in a variable-speed motion state, switching to feedforward control and PID feedback control, wherein a structural block diagram of a feedforward input module is shown in FIG. 7, and the basic idea is that the input quantity of the (k + 1) th iteration is adjusted by using data obtained by the previous k iterations in the iteration process, and the specific control process is as follows:
s4.1.1, calculating initial input U of the system in the motion state0；
U0＝Kp1*Kp2*Vs(0)+Ur(0)
Wherein, Kp1、Kp2Is the proportionality coefficient of the position inner ring and the velocity outer ring, Ur(0) For the value of the feed-forward input signal at the initial instant, Vs(0) Is the value of the desired speed profile at the initial time;
s4.1.2, reading the acceleration feedback signal A of the system in motion state by the grating ruler0(t), then, substituting a feedforward control and PID feedback control law, and calculating an acceleration signal A (t) of the system in the motion state;
ev(t)＝A(t)-A0(t)
wherein, Ki2Is the integral coefficient of the velocity outer loop;
s4.1.3, repeating the steps S4.1.1-S4.1.2, and tracking the acceleration signal A (t) in real time to enable the speed curve output by the system in real time to reach the expected speed curve, thereby completing the control in the motion state;
s4.2, when the shot object is in a uniform motion state, switching to double-ring PID control, wherein the specific control process is as follows:
s4.2.1, calculating the initial input U of the system in the motion state0；
U0＝Kp1*Kp2*Vs(0)
S4.2.2, reading the acceleration feedback signal A of the system in motion state by the grating ruler0(t), then, bringing into a double-loop PID control law, and calculating an acceleration signal A (t) of the system in the motion state;
ev(t)＝A(t)-A0(t)
wherein, Ki2Is the integral coefficient of the velocity outer loop;
s4.2.3, repeating the steps S4.2.1-S4.2.2, tracking the acceleration signal A (t) in real time, and making the speed curve output by the system in real time reach the expected speed curve, thereby completing the control in the motion state.
In this embodiment, the overall control block diagram of the present invention is shown in fig. 8. The method of the invention is compared with a group of well-debugged common double-ring PID servo motion control methods. FIG. 9 is a graph comparing the speed curves of the conventional PID control and the present invention, and FIG. 10 is a graph comparing the speed error curves of the conventional PID control and the present invention. As shown in fig. 9 and 10. In the variable speed motion stage, the tracking error of the control method adopted by the invention is obviously smaller than that of the traditional PID control, the response speed is greatly improved, and the problem of time lag of the traditional PID control is solved. In the stage of uniform motion, the tracking precision of the control method adopted by the invention is obviously improved compared with the traditional PID control. The experimental results show that: through the design, the dynamic performance of the motion servo system is obviously improved, the steady-state tracking error is reduced, meanwhile, the modeling difficulty of the motion servo system is greatly reduced, model uncertainty caused by disturbance is tracked, and the tracking precision is improved, so that the motion servo system can ensure the stability and the corresponding rapidity, and the output speed of the motion servo system can reproduce the planning speed to the maximum extent at any moment.
Although illustrative embodiments of the present invention have been described above to facilitate the understanding of the present invention by those skilled in the art, it should be understood that the present invention is not limited to the scope of the embodiments, and various changes may be made apparent to those skilled in the art as long as they are within the spirit and scope of the present invention as defined and defined by the appended claims, and all matters of the invention which utilize the inventive concepts are protected.
Claims (2)
1. A servo motion control method for a linear array CCD scanning process is characterized by comprising the following steps:
(1) planning scanning track of linear array photoelectric coupling type imaging device CCD
(1.1) planning the motion trail in the scanning direction
Setting pixels of each line of the linear array CCD to be NrThe width of the linear array CCD is W0The scanning rate of the linear array CCD is VcThe moving speed of the object is V0；
Then there are: accuracy of transverse scanning
Accuracy of longitudinal scanning
Ensuring that the acquired image is not distorted, and according to the principle that the horizontal resolution and the longitudinal resolution are equal, the optimal moving speed of the object to be shot and the scanning speed of the linear array CCD meet the following relation:
V0＝VC×W0/Nr
finally, according to the movement velocity V0Planning a motion track in a scanning direction;
(1.2) planning the motion trail in the non-scanning direction
Setting the motion stroke of the shot object as the single scanning width W of the linear array CCD0；
(1.3) optimizing the planned trajectory
A filtering module is added at the output end of the planned motion track to filter noise disturbance in the planned track;
(2) and parameter setting
(2.1) parameter tuning of double-loop PID algorithm
In the speed outer ring and the position inner ring, an expected acceleration curve A is obtained according to the optimized planning track respectivelyg(t), obtaining an actual acceleration curve A through a grating ruler sensorg0(t) then calculating an acceleration error curve eA(t)＝Ag(t)-Ag0(t), finally, adjusting the proportionality coefficient K according to a Ziegler-Nichols algorithmpAnd integral coefficient KiThereby completing the parameter setting of the double-loop PID algorithm;
(2.2) iteratively learning the parameter setting of the feedforward + PID feedback control algorithm;
(2.2.1) shielding off a speed outer ring of the system, and only keeping a position inner ring of the system; then, an expected speed curve V is obtained according to the optimized planning tracks(t) mixing Vs(t) Fourier transforming to obtain Vs(jw), and then Vs(jw) as system initial input and input to the velocity outer loop; reading out the actual speed curve of the system according to the grating ruler
Will be provided with
Fourier transform to obtain
Then use
As the system initial output;
finally, substituting the iterative learning control law into the system to obtain the first input of the system
Yd(jw) is the system desired output speed;
(2.2.2) reading out the first output Y of the system by means of the grating ruler sensor1(jw), then, the first output speed error curve DeltaY is calculated1(jw)＝Y1(jw)-Yd(jw)；
And calculating the second input U of the system according to the following formula through the iterative learning control law again2(jw)；
Wherein, Ur(jw) is the r-th input to the system, r is 2,3,4, …; y isr-1(jw) is the (r-1) th output of the system, and rho is a differential term proportionality coefficient; u shape0(jw) and Y0(jw) is an initial value set by the iterative learning control law in the iterative process;
simultaneously reading out the secondary output Y of the system through the grating ruler sensor2(jw), then, a second time output speed error curve DeltaY is calculated2(jw)＝Y2(jw)-Yd(jw)；
Judging whether the speed error curve obtained in the previous and subsequent times is oscillated or not, if the speed error curve is oscillated, taking the input obtained in the subsequent time as a feedforward input signal of the system, otherwise, calculating the next input of the system again through an iterative learning control law, and repeating the steps until the speed error curve is oscillated, and stopping iteration;
(2.2.3) inputting the feedforward input signal into the speed outer ring of the double-ring PID which is set in the step (2.1) to complete parameter setting of the iterative learning feedforward plus PID feedback control algorithm;
(3) judging the current motion state of the shot object
Velocity V of motion of object0Solving a first derivative to obtain the acceleration a of the shot object, comparing the acceleration a with a given threshold value epsilon, and when | a | is greater than epsilon, the shot object is in a variable speed motion state; when | a | ≦ epsilon, the object is in a uniform motion state;
(4) switching between different motion states and switching optimization
(4.1) when the shot object is in a variable speed motion state, switching to an iterative learning feedforward + PID feedback control algorithm, wherein the specific control process is as follows:
(4.1.1) calculating the initial input U of the system in the motion state0；
U0＝Kp1*Kp2*Vs(0)+Ur(0)
Wherein, Kp1、Kp2Is the proportionality coefficient of the position inner ring and the velocity outer ring, Ur(0) For the value of the feed-forward input signal at the initial instant, Vs(0) Is the value of the desired speed profile at the initial time;
(4.1.2) reading the acceleration feedback signal A of the system in the motion state through the grating ruler0(t), then, substituting an iterative learning feedforward + PID feedback control algorithm to calculate an acceleration signal A (t) of the system in the motion state;
ev(t)＝A(t)-A0(t)
wherein, Ki2Is the integral coefficient of the velocity outer loop;
(4.1.3) repeating the steps (4.1.1) - (4.1.2), tracking the acceleration signal A (t) in real time, and enabling the speed curve output by the system in real time to reach the expected speed curve, thereby completing the control in the motion state;
(4.2) when the shot object is in a uniform motion state, switching to double-ring PID control, wherein the specific control process is as follows:
(4.2.1) calculating the initial input U of the system in the motion state0；
U0＝Kp1*Kp2*Vs(0)
(4.2.2) reading the acceleration feedback signal A of the system in the motion state through the grating ruler0(t), then, bringing into a double-loop PID control law, and calculating an acceleration signal A (t) of the system in the motion state;
ev(t)＝A(t)-A0(t)
wherein, Ki2Is the integral coefficient of the velocity outer loop;
(4.2.3) repeating the steps (4.2.1) - (4.2.2), tracking the acceleration signal A (t) in real time, and enabling the speed curve output by the system in real time to reach the expected speed curve, thereby completing the control in the motion state.
2. The servo motion control method for the linear array CCD scanning process as recited in claim 1, wherein in the step (2.1), the parameter setting of the double loop PID algorithm comprises the parameter setting of a velocity outer loop PID algorithm and the parameter setting of a position inner loop PID algorithm;
the specific process of parameter setting of the speed outer ring PID algorithm is as follows:
1) accessing the proportional controller into the system;
2) setting a proportional gain K of a proportional controller, inputting a unit step signal to the proportional controller, and observing an acceleration response curve of the motor to the unit step signal
3) Changing the proportional gain K from small to large until the system oscillates;
4) when inWhen the system has continuous constant amplitude oscillation, recording the gain and the oscillation period at the moment, and respectively marking as critical gain KuAnd a critical period Tu；
5) Calculating the proportionality coefficient K of the speed outer ringp2And integral coefficient Ki2；
Kp2＝λ*Ku，
Wherein λ and η are constants;
the specific process of the parameter setting of the PID algorithm of the position inner ring comprises the following steps:
according to the method of the steps 1) -5), completing the parameter setting of the PID algorithm of the position inner ring to obtain the proportionality coefficient K of the position inner ringp1And integral coefficient Ki1。
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