Patent Application
20220288731
The present invention belongs to the technical field of associative motion control mechanisms, and particularly, relates to a linkage turntable and a decoupling control method thereof.
The main application case of control method for linkage decoupling is a Chinese patent application whose application number is CN201810806333.1, applicant is KEDE CNC Co., Ltd., and name is a cradle turntable driven by ball screw, and the simplified motion process of the structure is shown in
According to the traditional control method, the axis movement in two directions is independently controlled. Assuming that the vertical direction is Z0-axis, the horizontal direction is X-axis, the horizontal sliding mechanism of the turntable is X′, and the swing mechanism of the turntable is A-axis, then, the grating scale of Z0-axis is mounted on the turntable base, with the direction parallel to the guide rail in the vertical direction of Z0-axis; the Z0-axis reading head is mounted on the Z-axis screw nut; the X-axis grating scale is mounted on the bed, with the direction parallel to the X-axis guide rail; and the X-axis reading head is mounted on the turntable base and displaces horizontally with the turntable machine tool. This traditional mounting method has the following defects when a control is exerted:
1. additional calculation is required to calculate the turntable horizontal displacement ΔX′ caused by Z0-axis when dragging the turntable;
2. the value calculated by the turntable horizontal instantaneous displacement usually has a certain delay and error, which are combined with the X-axis command, and the expression position is not accurate enough, causing an adverse effect on the accuracy;
3. the change is relatively large as compared with the control method of ordinary linear axis, and the application is more complicated; and the A-axis and X-axis have a mutual coupling relation in the control algorithm.
In order to solve the above-mentioned problems in the prior art, the present invention proposes a linkage turntable and a decoupling control method thereof, so that the dynamic performance requirements of the X-axis are reduced to some extent and there is no need to manually calculate the horizontal displacement ΔX′ of the turntable caused by the Z0-axis, thereby improving the control accuracy.
The technical solution is as follows.
A linkage turntable, including: a turntable column; a linkage turntable; an X-axis grating scale reading head; an X-axis grating scale; a turntable base; a sliding mechanism A; and a sliding mechanism B, wherein the turntable column is vertically mounted on the turntable base, the linkage turntable is slidably connected to the turntable column through the sliding mechanism A, the linkage turntable is slidably connected to the turntable base through the sliding mechanism B, the X-axis grating scale reading head is mounted on the sliding mechanism B, and the X-axis grating scale is mounted below the turntable base and arranged opposite to the X-axis grating scale reading head.
Further, the sliding mechanism A includes: a Z0-axis ball screw; a Z0-axis ram; a first rotation node of linkage mechanism; a linkage of linkage mechanism; and a Z0-axis guide rail, the Z0-axis guide rail is arranged on the turntable column, the Z0-axis ball screw is connected to the Z0-axis guide rail, the Z0-axis ram is slidably connected to the Z0-axis guide rail, one end of the linkage of linkage mechanism is rotatably connected to the Z0-axis ram through the first rotation node of linkage mechanism, and the other end of the linkage of linkage mechanism is connected to the linkage turntable.
Further, the sliding mechanism B includes: a horizontal guide rail; a second rotation node of linkage mechanism; and a horizontal ram, wherein the horizontal guide rail is arranged on the turntable base, the linkage turntable is rotatably connected to the horizontal ram through the second rotation node of linkage mechanism, the horizontal ram is slidably connected to the horizontal guide rail, and the X-axis grating scale reading head is mounted on the horizontal ram.
The linkage turntable further includes: a linkage turntable ram; a bed; a turntable guide rail; a turntable drag screw; and a turntable drag nut, wherein the bed is provided with the turntable guide rail, the turntable drag screw and the linkage turntable ram, the linkage turntable ram is slidably connected to the turntable guide rail, and the turntable drag nut is arranged on the turntable drag screw.
The present invention also includes a decoupling control method for linkage turntable, including the following steps:
S1. measure a length L of a hypotenuse of a triangular structure; and
S2. convert A-axis coordinates input to the system into Z0-axis coordinates according to
Z0=L*cos α
and input them on Z0-axis, wherein Z0 represents the length of the nut position of Z0-axis relative to the reference point of Z0-axis, and the reference point is located at the intersection of the extension lines of the displacement trajectories of the two rotation nodes of the linkage mechanism, and α represents the angle of the turntable, that is, the angle between the turntable normal and the positive direction of the X′-axis;
and in the case of a speed control method, convert the A-axis coordinates into a periodic displacement of Z0 according to
ΔZ0=L*(cos α1−cos α2)
and input the displacement to Z0-axis, wherein ΔZ0 indicates the displacement of Z0-axis, α1 indicates the angle of the turntable before moving, and α2 indicates the angle of the turntable after moving.
Further, the linkage turntable is assembled before measuring the length L of the hypotenuse of the triangular structure, and the assembly steps include:
S0.1. mount the X-axis grating scale parallel to the X-axis on the bed;
S0.2. align the X-axis grating scale reading head with the X-axis grating scale, fix the X-axis grating scale reading head on the horizontal ram, and repeatedly move the linkage turntable horizontally to check the readings; and
S0.3. mount the circular grating of the linkage turntable coaxially facing the A-axis rotation center.
Further, the steps of obtaining the length L of the hypotenuse of the triangular structure include:
moving Z0 to the first position, recording the Z0 coordinate Z01, the A-axis angle α1; moving Z0 to the second position, recording the Z0 coordinate Z02, the turntable angle α2, and using the following equation:
L*cos α1−L*cos α2=Z01−Z02
to obtain the length L of the hypotenuse of the triangular structure:
L=ΔZ0/(cos α1−cos α2).
Further, the detailed steps of step S2 are as follows:
S2.1. a command A0, that is, Δα, is sent to a Z0 controller; and a command X is sent to an X-axis controller;
S2.2. the Z0 controller calculates the distance Δα that the A-axis needs to travel in the next cycle according to the command and the feedback of the A-axis angle, and the command angle Δα sent out includes a tracking error and a speed feedforward;
and the A0-axis controller calculates the distance Δα that the A-axis needs to travel in the next cycle according to the command and the feedback of the A-axis angle, and the command angle Δα sent out includes a tracking error and a speed feedforward; and the X-axis performs the same process;
S2.3. before Δα is input to the Z0 actuator, Δα is converted into the current straight-line distance ΔZ0 to be traveled by Z0 according to the equation ΔZ0=L(cos α1−cos(α1+Δα)), and then a command is sent to the Z0 actuator; and ΔX is sent to the X-axis actuator;
S2.4, the Z0 actuator drives the turntable linkage mechanism to generate the A-axis swing angle change Δα′ and the X-axis direction horizontal displacement ΔX′, Δα′ is used to participate in the closed-loop operation of the next cycle; the X-axis actuator also generates a displacement ΔX0, ΔX0 and the horizontal displacement ΔX′ generated by the turntable linkage mechanism are combined to participate in the closed-loop operation of the next cycle; and S2.5. execute steps S2.1 to S2.4 periodically and cyclically.
The beneficial effect of the present invention is as follows.
The beneficial effects of the linkage turntable and the decoupling control method thereof described in the present invention are as follows. In the traditional control method, the closed-loop controls of Z0-axis and X-axis are irrelevant, and it is necessary to manually calculate the displacement in the horizontal direction, and then manually add the displacement in the horizontal direction to the X-axis command. In addition to the errors generated due to the calculation, there is also a large delay here. However, after changing the control algorithm, the horizontal displacement generated by the movement of the Z0-axis is directly integrated into the closed loop of the X-axis by means of measurement combination and the displacement directly calculated by grating scale has high precision and no delay, and it is possible to achieve a more effective control level on this mechanical structure.
In addition, the optimized control algorithm makes the X-axis have the motion characteristics of RTCP in the process of A-axis rotation, thereby reducing the requirements for the dynamic performance of the X-axis motor.
Description of reference signs: 1—turntable column; 2—Z0-axis ball screw; 3—Z0-axis ram; 4—the first rotation node of linkage mechanism; 5—linkage of linkage mechanism; 6—Z0-axis guide rail; 7—horizontal guide rail; 8—linkage turntable; 9—the second rotation node of linkage mechanism; 10—X-axis grating scale reading head; 11—horizontal ram; 12—linkage turntable ram; 13—X-axis grating scale; 14—turntable base; 15—bed; 16—turntable guide rail; 17—turntable drag screw; 18—turntable drag nut.
The linkage turntable and the decoupling control method thereof will be further described below with reference to
A linkage turntable, including: a turntable column 1; a linkage turntable 8; an X-axis grating scale reading head 10; an X-axis grating scale 13; a turntable base 14; a sliding mechanism A; and a sliding mechanism B, wherein the turntable column 1 is vertically mounted on the turntable base 14, the linkage turntable 8 is slidably connected to the turntable column 1 through the sliding mechanism A, the linkage turntable 8 is slidably connected to the turntable base 14 through the sliding mechanism B, the X-axis grating scale reading head 10 is mounted on the sliding mechanism B, and the X-axis grating scale 13 is mounted below the turntable base 14, fixed to the bed and arranged opposite to the X-axis grating scale reading head 10.
Further, the sliding mechanism A includes: a Z0-axis ball screw 2; a Z0-axis ram 3; a first rotation node of linkage mechanism 4; a linkage of linkage mechanism 5; and a Z0-axis guide rail 6, the Z0-axis guide rail 6 is arranged on the turntable column 1, the Z0-axis ball screw 2 is connected to the Z0-axis guide rail 6, the Z0-axis ram 3 is slidably connected to the Z0-axis guide rail 6, one end of the linkage of linkage mechanism 5 is rotatably connected to the Z0-axis ram 3 through the first rotation node of linkage mechanism 4, and the other end of the linkage of linkage mechanism 5 is connected to the linkage turntable 8.
Further, the sliding mechanism B includes: a horizontal guide rail 7; a second rotation node of linkage mechanism 9; and a horizontal ram 11, wherein the horizontal guide rail 7 is arranged on the turntable base 14, the linkage turntable 8 is rotatably connected to the horizontal ram 11 through the second rotation node of linkage mechanism 9, the horizontal ram 11 is slidably connected to the horizontal guide rail 7, and the X-axis grating scale reading head 10 is mounted on the horizontal ram 11.
The linkage turntable further includes: a linkage turntable ram 12; a bed 15; a turntable guide rail 16; a turntable drag screw 17; and a turntable drag nut 18, wherein the bed 15 is provided with the turntable guide rail 16, the turntable drag screw 17 and the linkage turntable ram 12, the linkage turntable ram 12 is slidably connected to the turntable guide rail 16, the turntable drag nut 18 is arranged on the turntable drag screw 17, and the linkage turntable ram 12 is fixed on the turntable base 14 and is then slidably connected to the turntable guide rail 16 on the bed 15.
A decoupling control method for linkage turntable, including:
S1. measure a length L of a hypotenuse of a triangular structure; and
S2. convert A-axis coordinates input to the system into Z0-axis coordinates according to
Z0=L*cos α
and input them on Z0-axis, wherein Z0 represents the length of the nut position of Z0-axis relative to the reference point of Z0-axis, and the reference point is located at the intersection of the extension lines of the displacement trajectories of the two rotation nodes of the linkage mechanism, and α represents the angle of the turntable, that is, the angle between the turntable normal and the positive direction of the X′-axis;
and in the case of a speed control method, convert the A-axis coordinates into a periodic displacement of Z0 according to
ΔZ0=L*(cos α1−cos α2)
and input the displacement to Z0-axis, wherein ΔZ0 indicates the displacement of Z0-axis, α1 indicates the angle of the turntable before moving, and α2 indicates the angle of the turntable after moving.
Further, the linkage turntable is assembled before measuring the length L of the hypotenuse of the triangular structure, and the assembly steps include:
S0.1. mount the X-axis grating scale parallel to the X-axis on the bed;
S0.2. align the X-axis grating scale reading head with the X-axis grating scale, fix the X-axis grating scale reading head on the horizontal ram, and repeatedly move the linkage turntable horizontally to check the readings; and
S0.3. mount the circular grating of the linkage turntable coaxially facing the A-axis rotation center.
Further, the steps of obtaining the length L of the hypotenuse of the triangular structure include:
moving Z0 to the first position, recording the Z0 coordinate Z01, the A-axis angle α1; moving Z0 to the second position, recording the Z0 coordinate Z02, the turntable angle α2, and using the following equation:
L*cos α1−L*cos α2=Z01−Z02
to obtain the length L of the hypotenuse of the triangular structure:
L=ΔZ0/(cos α1−cos α2).
Further, the detailed steps of step S2 are as follows:
S2.1. a command A0, that is, Δα, is sent to a Z0 controller; and a command X is sent to an X-axis controller;
S2.2. the Z0 controller calculates the distance Δα that the A-axis needs to travel in the next cycle according to the command and the feedback of the A-axis angle, and the command angle Δα sent out includes a tracking error and a speed feedforward;
and the A0-axis controller calculates the distance Δα that the A-axis needs to travel in the next cycle according to the command and the feedback of the A-axis angle, and the command angle Δα sent out includes a tracking error and a speed feedforward; and the X-axis performs the same process;
S2.3. before Δα is input to the Z0 actuator, Δα is converted into the current straight-line distance ΔZ0 to be traveled by Z0 according to the equation ΔZ0=L(cos α1−cos(α1+Δα)), and then a command is sent to the Z0 actuator; and ΔX is sent to the X-axis actuator;
S2.4, the Z0 actuator drives the turntable linkage mechanism to generate the A-axis swing angle change Δα′ and the X-axis direction horizontal displacement ΔX′, Δα′ is used to participate in the closed-loop operation of the next cycle; the X-axis actuator also generates a displacement ΔX0, ΔX0 and the horizontal displacement ΔX′ generated by the turntable linkage mechanism are combined to participate in the closed-loop operation of the next cycle; and
S2.5. execute steps S2.1 to S2.4 periodically and cyclically.
Compared with the traditional control scheme, the modification is convenient and fast in the control method proposed in the present application, with low cost and obvious effect. The implementation of the technical solution described in this application only needs to refit the reading head of the X-axis from the turntable base to a turntable support slider.
The traditional control method is expressed on the algorithm schematic diagram shown in
The schematic diagram of the control scheme mentioned in this application is shown in
It should be noted that the dotted line part in the figure does not require additional implementation, only the mounting position of the X-axis reading head needs to be changed, and the X-axis control algorithm does not need to be changed.
In the traditional control algorithm, the displacement in the horizontal direction needs to be calculated according to Z0 and added to the command X, but here, since the reading head is mounted on the turntable support slider, for the horizontal displacement of the turntable caused by the movement of the Z0-axis, the real-time feedback displacement can be fed back to the closed loop of the X-axis through the grating scale (or other measuring device) in real time.
Assuming that the command X of the X-axis remains unchanged, it can be automatically realized that the horizontal center of the turntable remains unchanged during the Z0-axis dragging the turntable, that is, the left side of the X of the A-axis rotation center is always X1 in
The unique advantages of this control structure are summarized as follows:
1. Since the horizontal displacement of the turntable is measured by the grating scale, the part of calculating the horizontal displacement is omitted and manpower is saved.
2. Since the horizontal displacement of the turntable is measured by the grating scale, it is possible to ensure the real-time and accuracy of the value, and ensure the accuracy of the control.
3. In practical applications, since the reading head is mounted on the turntable support slider, the horizontal displacement generated by the turntable will be automatically added to the horizontal displacement feedback of the X-axis, and there is no need to make any changes to the control algorithm of the X-axis, thereby also saving manpower.
Steps of implementation
Assembly:
1. mount the grating scale parallel to the X-axis on the bed, and proceed to Step 2 after checking that there is no mistake;
2. align the X-axis grating scale reading head with the grating scale, fix it on the support slider of the horizontal turntable, and move the turntable horizontally repeatedly to check that the reading is normal and then proceed to Step 3; and
3. mount the circular grating of the turntable coaxially facing the A-axis rotation center, and proceed to Step 4 after checking that there is no mistake repeatedly.
Measurement:
4. measure the length of the hypotenuse of the triangular structure, move Z0 repeatedly after measuring the length, and verify whether the length of the hypotenuse, the A-axis angle and the Z0 coordinate can be perfectly matched to form a triangle, and proceed to Step 6 after completing the measurement, and if there are large differences among the triangles calculated at each position, the assembly should be rechecked and the implement should be restarted from Step 1, and if there is no accurate measuring device, proceed to Step 5;
5. move Z0 to the first position, record the Z0 coordinate Z01, the A-axis angle α1, and move Z0 to the second position, record the Z0 coordinate Z02, the turntable angle α2, and since the turntable mechanical structure is mounted at a right angle, the length of the hypotenuse can be calculated according to the following equations, assuming that the length of the hypotenuse is L:
L*cos α1−L*cos α2=Z01−Z02
L=ΔZ0/(cos α1−cos α2)
and when calculating the result, a few more positions should be obtained to verify whether the calculated L is correct, and if the L values of repeated calculations are quite different, it means that the result of the mechanical assembly is not a right angle, and then the mechanical assembly should be checked carefully, and the implementation should be restarted from Step 1, and if it is considered that the calculated hypotenuse length is accurate enough, proceed to Step 6.
Algorithm:
6. change the A-axis control method of the system, convert A-axis coordinates input to the system into Z0-axis coordinates according to the following Z0=L*sin α, and input them on the Z0-axis, and in the case of a speed control method, convert the A-axis coordinates into a periodic displacement (that is, speed) of Z0 according to
ΔZ0=L*(cos α1−cos α2)
and input the displacement to the Z0-axis, and other axes do not need to be changed,
and the flowchart of linkage decoupling control is shown in
1. a command A0, that is, Δα, is sent to a Z0 controller; and a command X is sent to an X-axis controller;
2. the A0 controller calculates the distance Δα that the A-axis needs to travel in the next cycle according to the command and the feedback of the A-axis angle, and the command angle Δα sent out includes a tracking error and a speed feedforward; and the same applies to ΔX;
3. before Δα is input to the Z0 actuator, Δα is converted into the current straight-line distance ΔZ0 to be traveled by Z0 according to the equation, and then a command is sent to the Z0 actuator, which is generally a servo motor, a frequency converter, or other actuator; and ΔX is also sent to the X-axis actuator;
4. the Z0 actuator drives the turntable linkage mechanism to generate the A-axis swing angle change Δα′ and the X-axis direction horizontal displacement ΔX′, Δα′ is used to participate in the closed-loop operation of the next cycle; the X-axis actuator also generates a displacement ΔX0, ΔX0 and the horizontal displacement ΔX′ generated by the turntable linkage mechanism are combined to participate in the closed-loop operation of the next cycle; and
5. execute the steps above periodically and cyclically.
The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. Any equivalent replacements or changes made by a person skilled in the art within the technical scope disclosed by the present invention according to the technical solution of the present invention and the inventive concept thereof should be within the protection scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201910754540.1 | Aug 2019 | CN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2020/109114 | 8/14/2020 | WO |
