Position control system and position control method

Abstract

This enables precise positioning while suppressing vibrations of the controlled object. [Solution] The position control system comprises a command generation unit, a vibration damping control unit, and a drive unit. The command generation unit generates command coordinates C1 for controlling the position of the controlled object. The vibration damping control unit applies a vibration damping filter to the command coordinates C1 and outputs them as vibration damping coordinates C2. The drive unit controls the position of the controlled object. If the trigger condition is not met, the drive unit controls the position of the controlled object based on the vibration damping coordinates C2, while if the trigger condition is met, it controls the position of the controlled object based on the command coordinates C1. The trigger condition is that the velocity V2 corresponding to the vibration damping coordinates C2 is within a predetermined velocity range RV including zero, and the vibration damping coordinates C2 is within a predetermined coordinate range RC including the target value of the position of the controlled object.

Description

Technical Field

[0004] , , , , , , , , ,

[0005] , , , , , , , , <000...003><000...004>The present invention relates to a position control system and a position control method. <000...005>

Background Art

Prior Art Documents

Patent Documents

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] Furthermore, paragraph 0046 of Patent Document 2 describes an example of the effect of quantization error: when the calculation precision (number of bits) is reduced when performing calculations with a microcontroller, a value that would theoretically be 1.0 becomes, for example, 0.999...

[0007] Here, with reference to Figures 5 and 6, the configuration of the conventional position control system 100 will be briefly explained. Figure 5 is a block diagram showing the configuration of the position control system 100. Figure 6 is a graph showing the time change of the command coordinate C10 and the vibration damping coordinate C20 in the position control system 100. In this graph, the vertical axis represents the coordinates C10 and C20, and the horizontal axis represents time. Note that the conventional position control system 100 described here is a different system from the position control system in Patent Document 1.

[0008] The conventional position control system 100 is a system for controlling a loader 200 provided on a machine tool. The loader 200 is equipped with a transport head 210. A motor 140 generates a driving force to move the transport head 210. The position control system 100 controls the position of the transport head 210. As shown in Figure 5, this position control system 100 includes a command generation unit 110, a vibration damping control unit 120, and a motor 140. The command generation unit 110 generates command coordinates C10 for controlling the position of the transport head 210. The vibration damping control unit 120 applies a digital vibration damping filter 120a to the command coordinates C10 and outputs them as vibration damping coordinates C20. The motor 140 controls the position of the transport head 210 based on the vibration damping coordinates C20. With this configuration, vibration of the transport head 210 can be suppressed when controlling the position of the loader 200.

[0009] On the other hand, as shown in Figure 6, in the conventional position control system 100, if the convergence value of the command coordinate C10 (shown as a dashed line in Figure 6) is 1000 mm, the convergence value of the vibration damping coordinate C20 (shown as a solid line in Figure 6) may become 999.99999 mm due to quantization errors (e.g., rounding errors) occurring in the vibration damping control unit 120. In this case, although not shown in the graph, the position of the transport head 210 is controlled by the motor 140 to 999.99999 mm instead of 1000 mm. Note that the number of digits in the convergence value of the vibration damping coordinate C20 may change depending on the specifications and settings of the arithmetic unit provided in the vibration damping control unit 120.

[0010] This invention has been made in view of the above circumstances, and its purpose is to achieve precise positioning while suppressing vibrations of the controlled object. Means and effects for solving the problem

[0011] The problems that this invention aims to solve are as described above, and next, the means for solving these problems and their effects will be explained.

[0012] According to a first aspect of the present invention, a position control system is provided with the following configuration: the position control system comprises a command generation unit, a vibration damping control unit, and a drive unit. The command generation unit generates command coordinates for controlling the position of a control object. The vibration damping control unit applies a vibration damping filter to the command coordinates and outputs them as vibration damping coordinates. The drive unit controls the position of the control object. The drive unit controls the position of the control object based on the vibration damping coordinates when the trigger condition is not met, and controls the position of the control object based on the command coordinates when the trigger condition is met. The trigger condition is that the velocity corresponding to the vibration damping coordinates is within a predetermined velocity range including zero, and the vibration damping coordinates are within a predetermined coordinate range including a target value for the position of the control object.

[0013] As a result, if the trigger condition is not met, the drive unit controls the position of the controlled object based on the damped coordinates output by applying a damping filter to the command coordinates, thereby suppressing vibrations of the controlled object. On the other hand, if the trigger condition is met, the drive unit controls the position of the controlled object based on the command coordinates, not the damped coordinates. In this case, the damping filter is effectively disabled, so there is no need to consider the effects of the quantization error mentioned above, and the position of the controlled object matches the command coordinates through position control based on the command coordinates. Here, when the trigger condition is met, the position of the controlled object is sufficiently close to its target value, and the speed of the controlled object is low, making vibrations less likely. Therefore, even if the control switches from position control based on damped coordinates to position control based on command coordinates, the controlled object will not vibrate significantly as a result.

[0014] Furthermore, by applying such trigger conditions, it is possible to switch position control at the appropriate timing in response to various situations arising from differences in the speed of the controlled object. For example, it is conceivable to predict in advance the time it takes for the vibration of the controlled object to subside and set a certain waiting time based on that predicted time. Here, the waiting time refers to the time from the time when the position of the controlled object first reaches its target value until the time when the position control is switched. However, in this case, in order to avoid the controlled object from vibrating excessively, it is necessary to set the waiting time assuming the case where it takes the longest time for the vibration to subside. In contrast, when the trigger conditions of the present invention are applied, if the time it takes for the vibration of the controlled object to subside to a certain extent is long, the waiting time will also be correspondingly long, and if the time it takes for the vibration of the controlled object to subside to a certain extent is short, the waiting time will also be correspondingly short, and this adjustment can be automatically performed.

[0015] In the position control system described above, the following configuration is preferable. That is, the position control system further comprises a movement amount calculation unit that calculates the amount of movement of the controlled object per unit time. The drive device controls the position of the controlled object based on the amount of movement per unit time. The movement amount calculation unit calculates the amount of movement per unit time based on the vibration damping coordinates when the trigger condition is not met, and calculates the amount of movement per unit time based on the command coordinates when the trigger condition is met.

[0016] This allows the drive unit to convert the damping coordinates into a unit of movement if the drive unit is of the type that inputs the amount of movement per unit time, and then input the converted amount of movement to the drive unit. Furthermore, if the amount of movement per unit time of the controlled object is calculated based solely on the damping coordinates, the amount of movement may become zero due to the quantization error mentioned above, even if the position of the controlled object does not match its target value. In contrast, here, when the trigger condition is met, the amount of movement per unit time of the controlled object is calculated based on the command coordinates, not the damping coordinates. Therefore, even if the integrated value of the amount of movement, i.e., the position of the controlled object, does not match its target value until just before the trigger condition is met, after the trigger condition is met, the difference between the integrated value of the amount of movement and the command coordinates is further integrated, causing the position of the controlled object to match its target value.

[0017] In the position control system described above, it is preferable that the vibration control unit outputs the command coordinates rather than the vibration control coordinates when the trigger condition is met.

[0018] As a result, when the trigger condition is met, the output of the vibration control unit is switched from vibration control coordinates to command coordinates. In that case, the drive unit controls the position of the controlled object based on the command coordinates, so that the position of the controlled object can be made to match its target value.

[0019] In the position control system described above, the object to be controlled is preferably a drive unit provided in a machine tool.

[0020] It is difficult to monitor the vibrations of the drive unit of a machine tool (for example, a loader that transports a workpiece) in real time. In such cases, the position control system of the present invention is particularly effective in that it can achieve high-speed and precise positioning while suppressing vibrations of the drive unit.

[0021] A second aspect of the present invention provides a position control method as follows: This position control method comprises a command generation step, a vibration damping control step, and a drive step. The command generation step generates command coordinates for controlling the position of a control object. The vibration damping control step applies a vibration damping filter to the command coordinates and outputs them as vibration damping coordinates. The drive step controls the position of the control object. In the drive step, if the trigger condition is not met, the position of the control object is controlled based on the vibration damping coordinates, while if the trigger condition is met, the position of the control object is controlled based on the command coordinates. The trigger condition is that the velocity corresponding to the vibration damping coordinates is within a predetermined velocity range including zero, and the vibration damping coordinates are within a predetermined coordinate range including a target value for the position of the control object.

[0022] As a result, in the drive process, if the trigger condition is not met, the position of the controlled object is controlled based on the damped coordinates output by applying a damping filter to the command coordinates, thereby suppressing vibration of the controlled object. On the other hand, if the trigger condition is met, in the drive process, the position of the controlled object is controlled based on the command coordinates, not the damped coordinates. In this case, the damping filter is effectively disabled, so there is no need to consider the effects of the quantization error mentioned above, and the position of the controlled object matches the command coordinates through position control based on the command coordinates. Here, when the trigger condition is met, the position of the controlled object is sufficiently close to its target value, and the speed of the controlled object is low, making vibration less likely. Therefore, even if the control switches from position control based on damped coordinates to position control based on command coordinates, the controlled object will not vibrate significantly as a result.

[0023] Also, by applying such trigger conditions, it is possible to switch the position control at an appropriate timing for various situations caused by differences such as the speed of the control target. For example, it is conceivable to predict in advance the time when the vibration of the control target converges and provide a certain waiting time based on the predicted time. Here, the waiting time refers to the time from the point when the position of the control target first reaches its target value to the point when the position control is switched. However, in this case, in order to avoid large vibrations of the control target, it is necessary to set the waiting time assuming the case where the time required for the vibration to converge is the longest. On the other hand, when the trigger conditions of the present invention are applied, when the time until the vibration of the control target converges to a certain extent is long, the waiting time also becomes correspondingly long, and when the time until the vibration of the control target converges to a certain extent is short, the waiting time also becomes correspondingly short, and such adjustment can be automatically performed.

Brief Description of the Drawings

[0024] [Figure 1] Front view showing the configuration of a lathe to which a position control system is applied. [Figure 2] Block diagram showing the configuration of a position control system according to the first embodiment. [Figure 3] Graph showing the time changes of the command coordinates, vibration control coordinates, and integrated movement amount, as well as the time changes of the command speed, vibration control speed, and movement amount. [Figure 4] Block diagram showing the configuration of a position control system according to the second embodiment. [Figure 5] Block diagram showing the configuration of a position control system according to the prior art. [Figure 6] Graph showing the time changes of the command coordinates and vibration control coordinates in a position control system according to the prior art.

Modes for Carrying Out the Invention

[0025] Next, a first embodiment of the present invention will be described with reference to the drawings. Figure 1 is a front view showing the configuration of a lathe 50 to which the position control system 10 is applied. Figure 2 is a block diagram showing the configuration of the position control system 10 according to this embodiment. Figure 3 is a graph showing the time change of command coordinate C1, vibration damping coordinate C2, and integrated displacement value MA, as well as the time change of command speed V1, vibration damping speed V2, and displacement amount M per unit time. In the graph of Figure 3, the command coordinate C1 and command speed V1 are shown by dashed lines, the vibration damping coordinate C2 and vibration damping speed V2 are shown by dashed lines, and the integrated displacement value MA and displacement amount M per unit time are shown by thick lines.

[0026] The lathe 50 shown in Figure 1 is a type of machine tool. The lathe 50 processes a workpiece 70 by rotating the workpiece 70 and bringing a tool 60 into contact with the workpiece 70. The lathe 50 comprises a support section 51, a spindle section 52, a tool 60, a tool rest 53, a loader 20, and a display 55.

[0027] The support section 51 rotatably supports the spindle section 52. A workpiece 70 can be detachably attached to the spindle section 52. The spindle section 52 rotates due to the driving force of a motor (not shown). A tool 60 can be mounted on the tool rest 53. The tool rest 53 can move forward and backward relative to the spindle section 52 due to the driving force of a motor (not shown). The workpiece 70 can be machined by rotating the workpiece 70 together with the spindle section 52 and bringing the tool 60 into contact with the workpiece 70. The tool rest 53 also functions as an automatic tool changer, allowing the tool 60 used to machine the workpiece 70 to be replaced. The lathe 50 in this embodiment is configured as a parallel twin-spindle lathe, with two spindle sections 52, two tool rests 53, etc.

[0028] The loader 20 is a conveying device for transporting workpieces 70. The loader 20 is equipped with a conveying head 21 configured to detachably hold the workpieces 70. The loader 20 is equipped with multiple motors 14 for moving the conveying head 21 in the three axes of X, Y, and Z. The motors 14 are a type of drive device. The loader 20 can transport workpieces 70 supplied from outside the device to the spindle section 52, or transport workpieces 70 that have been processed in the spindle section 52 to the outside of the device. The loader 20 can also transport workpieces 70 between two spindle sections 52.

[0029] The display 55 shows various information indicating the status of the lathe 50.

[0030] In this embodiment, the position control system 10 controls the position of the transport head 21 that transports the workpiece 70 in the lathe 50 using a feedforward method. As shown in Figure 2, the position control system 10 comprises a command generation unit 11, a vibration damping control unit 12, a movement amount calculation unit 13, and a motor 14. The transport head 21 is an example of a controlled object and an example of a drive unit.

[0031] The command generation unit 11, the vibration damping control unit 12, and the displacement calculation unit 13 can be implemented by a known computer equipped with a CPU, ROM, RAM, etc. A program for implementing the position control method of the present invention is pre-installed on the computer. Through the cooperation of this hardware and software, the computer can function as the command generation unit 11, the vibration damping control unit 12, and the displacement calculation unit 13. In this example, these elements are implemented by a single computer, but they may be implemented by multiple computers.

[0032] The command generation unit 11 generates command coordinates C1 for controlling the position of the transport head 21 (command generation step). The command coordinates C1 are determined corresponding to three or fewer coordinate axes, and in this example, they are determined three-dimensionally corresponding to three coordinate axes. However, for simplicity, in the description herein, only one coordinate axis will be mentioned. As shown in Figure 3, the command generation unit 11 of this embodiment operates so that when a target value for the position of the transport head 21 (1000 mm in this example) is determined, the output command coordinates C1 change smoothly and converge to the target value. The command coordinates C1 output by the command generation unit 11 are input to the vibration control unit 12 and to the movement amount calculation unit 13.

[0033] The vibration control unit 12 applies a digital vibration control filter 12a (which may consist of, for example, a known notch filter or low-pass filter) to the input command coordinate C1 and outputs it as vibration control coordinate C2 (vibration control process). The vibration control unit 12 in this embodiment has a mathematical model that expresses the motion of the transport head 21 in mathematical terms, and calculates and outputs vibration control coordinate C2 based on this mathematical model to suppress vibrations when the transport head 21 moves. The vibration control coordinate C2 output by the vibration control unit 12 is input to the movement amount calculation unit 13.

[0034] If the trigger condition is not met, the movement amount calculation unit 13 calculates the amount of movement M of the transport head 21 per unit time (1 millisecond in this example) based on the vibration damping coordinate C2. The trigger condition will be described later. For example, if the value of the vibration damping coordinate C2 at a certain point in time is 1 mm, and the value of the vibration damping coordinate C2 1 millisecond later is 2 mm, the movement amount calculation unit 13 calculates and outputs the difference of 1 mm as the amount of movement M of the transport head 21 per unit time. The amount of movement M output by the movement amount calculation unit 13 is input to the motor 14.

[0035] On the other hand, if the trigger condition is met, the movement amount calculation unit 13 calculates the amount of movement M of the transport head 21 per unit time based on the command coordinate C1 input from the command generation unit 11. For example, if the value of the vibration damping coordinate C2 was 999.99999 mm just before the trigger condition was met, the movement amount calculation unit 13 calculates and outputs the difference between this value and the command coordinate C1, which is 1000 mm, which is 0.00001 mm, as the amount of movement M of the transport head 21 per unit time immediately after the trigger condition is met. Subsequently, the command coordinate C1 input to the movement amount calculation unit 13 becomes constant at 1000 mm, so the amount of movement M of the transport head 21 per unit time becomes constant at 0 mm.

[0036] Here, the trigger condition is that the vibration damping speed V2 is within a predetermined speed range RV including zero, and the vibration damping coordinate C2 is within a predetermined coordinate range RC including the target value of the position of the transport head 21 (1000 mm in this example). When the trigger condition is met, the position of the transport head 21 is sufficiently close to its target position, and the speed of the transport head 21 is sufficiently low, making it unlikely that large vibrations will occur even with some step-like positional fluctuations. In the example in Figure 3, the trigger condition is met at time t1. In Figure 2, the switching function from vibration damping coordinate C2 to command coordinate C1 provided by the movement amount calculation unit 13 is conceptually represented by a switch symbol used in electrical circuit diagrams.

[0037] The integrated displacement value MA shown in the upper graph of Figure 3 can be calculated as the integral of the displacement M per unit time shown in the lower graph of the same figure. The command velocity V1 and damping velocity V2 shown in the lower graph of Figure 3 can be calculated as the derivatives of the command coordinate C1 and damping coordinate C2 shown in the upper graph of the same figure. Although the position of the transport head 21 is not shown in the graph of Figure 3, this position basically coincides with the integrated displacement value MA with a small time delay.

[0038] In this embodiment, the motor 14 is configured as a servo motor. The motor 14 controls the position of the transport head 21 based on the input amount of movement M (more broadly, based on the command coordinate C1 or vibration damping coordinate C2 used to calculate the amount of movement M) (driving process). That is, if the trigger condition is not met, the motor 14 controls the position of the transport head 21 based on the amount of movement M calculated from the vibration damping coordinate C2, while if the trigger condition is met, the motor 14 controls the position of the transport head 21 based on the amount of movement M calculated from the command coordinate C1. Therefore, after the trigger condition is met, the position of the transport head 21 is controlled to coincide with the command coordinate C1.

[0039] In the calculation of the vibration damping coordinate C2 in the vibration damping control unit 12 of this embodiment, the coordinate is handled in the form of an 8-byte floating-point number. Since computers perform numerical calculations internally using finite-digit binary numbers, it is sometimes necessary to represent and handle real numbers with approximate values. Hereinafter, the difference between the real number and the approximate value will be called the rounding error. Since the rounding error is an error that occurs when representing a real number as a binary digital value, it can also be called the quantization error. Due to this rounding error, even if the command coordinate C1 input to the vibration damping control unit 12 is a constant value, a situation may occur where the vibration damping coordinate C2 calculated and output by the vibration damping control unit 12 converges to a value that is slightly different from the command coordinate C1. Consequently, if the motor 14 is controlled based solely on the vibration damping coordinate C2, the positional accuracy of the transport head 21 will decrease.

[0040] In this embodiment, when the need for vibration damping control has sufficiently decreased, the motor 14 is controlled using the command coordinate C1 output by the command generation unit 11, rather than the vibration damping coordinate C2. This prevents a decrease in the positional accuracy of the transport head 21.

[0041] As described above, the position control system 10 of this embodiment comprises a command generation unit 11, a vibration damping control unit 12, and a motor 14. The command generation unit 11 generates command coordinates C1 for controlling the position of the transport head 21 of the loader 20. The vibration damping control unit 12 applies a vibration damping filter 12a to the command coordinates C1 and outputs them as vibration damping coordinates C2. The motor 14 controls the position of the transport head 21. If the trigger condition is not met, the motor 14 controls the position of the transport head 21 based on the vibration damping coordinates C2, while if the trigger condition is met, the motor 14 controls the position of the transport head 21 based on the command coordinates C1. The trigger condition is that the speed corresponding to the vibration damping coordinates C2 is within a predetermined speed range RV including zero, and the vibration damping coordinates C2 is within a predetermined coordinate range RC including the target value of the position of the transport head 21.

[0042] As a result, if the trigger condition is not met, the motor 14 controls the position of the transport head 21 based on the damped coordinate C2 output by applying the damped filter 12a to the command coordinate C1, thereby suppressing vibration of the transport head 21. On the other hand, if the trigger condition is met, the motor 14 controls the position of the transport head 21 based on the command coordinate C1 instead of the damped coordinate C2. In this case, since the damped filter 12a is effectively disabled, there is no need to consider the effects of the quantization error mentioned above, and the position of the transport head 21 matches the command coordinate C1 through position control based on the command coordinate C1. Here, when the trigger condition is met, the position of the transport head 21 is sufficiently close to its target value, and the speed of the transport head 21 is low, making vibration less likely. Therefore, even if the position control is switched from based on the damped coordinate C2 to based on the command coordinate C1, the transport head 21 will not vibrate significantly as a result.

[0043] Furthermore, by applying such trigger conditions, position control can be switched at the appropriate timing in response to various situations arising from differences in the speed of the transport head 21. For example, it is conceivable to predict in advance the time it takes for the vibration of the transport head 21 to subside and set a certain waiting time based on that predicted time. Here, the waiting time refers to the time from the time when the position of the transport head 21 first reaches its target value until the time when the position control is switched. However, in this case, in order to avoid the transport head 21 from vibrating excessively, it is necessary to set the waiting time assuming the case where it takes the longest time for the vibration to subside. In contrast, when the trigger conditions of this embodiment are applied, if the time it takes for the vibration of the transport head 21 to subside to a certain extent is long, the waiting time will also be correspondingly long, and if the time it takes for the vibration of the transport head 21 to subside to a certain extent is short, the waiting time will also be correspondingly short. This adjustment can be performed automatically. Therefore, vibration suppression and improved position accuracy can be achieved simultaneously while avoiding a prolonged cycle time.

[0044] Furthermore, the position control system 10 of this embodiment further includes a movement amount calculation unit 13 that calculates the amount of movement M of the transport head 21 per unit time. The motor 14 controls the position of the transport head 21 based on the amount of movement M per unit time. The movement amount calculation unit 13 calculates the amount of movement M per unit time based on the vibration damping coordinate C2 when the trigger condition is not met, and calculates the amount of movement M per unit time based on the command coordinate C1 when the trigger condition is met.

[0045] As a result, if the motor 14 is of a type that inputs a movement amount M per unit time, the movement amount calculation unit 13 can convert the vibration damping coordinate C2 into a movement amount M per unit time, and the converted movement amount M can be input to the motor 14. Furthermore, if the movement amount M of the transport head 21 per unit time is calculated based only on the vibration damping coordinate C2, there is a risk that the movement amount M will be zero when the position of the transport head 21 does not match its target value due to the quantization error mentioned above. In contrast, here, when the trigger condition is met, the movement amount M of the transport head 21 per unit time is calculated based on the command coordinate C1 instead of the vibration damping coordinate C2. Therefore, even if the integrated value of the movement amount M, i.e., the position of the transport head 21, does not match its target value until just before the trigger condition is met, after the trigger condition is met, the difference between the integrated value of the movement amount M and the command coordinate C1 is further integrated, so that the position of the transport head 21 matches its target value.

[0046] Furthermore, in the position control system 10 of this embodiment, the control target is the transport head 21 of the loader 20 provided on the machine tool.

[0047] It is difficult to monitor the vibration of the transport head 21 in real time. In such cases, the position control system 10 of this embodiment is particularly effective in that it can achieve high-speed and precise positioning while suppressing the vibration of the transport head 21.

[0048] Furthermore, the position control method of this embodiment comprises a command generation step, a vibration damping control step, and a drive step. In the command generation step, command coordinates C1 for controlling the position of the transport head 21 of the loader 20 are generated. In the vibration damping control step, a vibration damping filter 12a is applied to the command coordinates C1 and output as vibration damping coordinates C2. In the drive step, the position of the transport head 21 of the loader 20 is controlled. In the drive step, if the trigger condition is not met, the position of the transport head 21 is controlled based on the vibration damping coordinates C2, while if the trigger condition is met, the position of the transport head 21 is controlled based on the command coordinates C1. The trigger condition is that the speed corresponding to the vibration damping coordinates C2 is within a predetermined speed range RV including zero, and the vibration damping coordinates C2 is within a predetermined coordinate range RC including the target value of the position of the transport head 21.

[0049] As a result, in the drive process, if the trigger condition is not met, the position of the transport head 21 is controlled based on the damped coordinate C2 output by applying the damped filter 12a to the command coordinate C1, thereby suppressing vibration of the transport head 21. On the other hand, if the trigger condition is met, in the drive process, the position of the transport head 21 is controlled based on the command coordinate C1 instead of the damped coordinate C2. In this case, the damped filter 12a is effectively disabled, so there is no need to consider the effects of the quantization error mentioned above, and the position of the transport head 21 matches the command coordinate C1 through position control based on the command coordinate C1. Here, when the trigger condition is met, the position of the transport head 21 is sufficiently close to its target value, and the speed of the transport head 21 is low, making vibration less likely. Therefore, even if the position control is switched from based on the damped coordinate C2 to based on the command coordinate C1, the transport head 21 will not vibrate significantly as a result.

[0050] Furthermore, by applying such trigger conditions, position control can be switched at the appropriate timing in response to various situations arising from differences in the speed of the transport head 21. For example, it is conceivable to predict in advance the time it takes for the vibration of the transport head 21 to subside and set a certain waiting time based on that predicted time. Here, the waiting time refers to the time from the time when the position of the transport head 21 first reaches its target value until the time when the position control is switched. However, in this case, in order to avoid the transport head 21 from vibrating excessively, it is necessary to set the waiting time assuming the case where it takes the longest time for the vibration to subside. In contrast, when the trigger conditions of this embodiment are applied, if the time it takes for the vibration of the transport head 21 to subside to a certain extent is long, the waiting time will also be correspondingly long, and if the time it takes for the vibration of the transport head 21 to subside to a certain extent is short, the waiting time will also be correspondingly short. This adjustment can be performed automatically. Therefore, vibration suppression and improved position accuracy can be achieved simultaneously while avoiding a prolonged cycle time.

[0051] Next, a second embodiment will be described. Figure 4 is a block diagram showing the configuration of the position control system 10 according to this embodiment. In the description of this embodiment, components that are the same as or similar to those in the previously described embodiment will be denoted by the same reference numerals in the drawings, and their descriptions may be omitted.

[0052] As shown in Figure 4, the position control system 10 of this embodiment includes a vibration damping control unit 12 that has a function to switch its output between vibration damping coordinates C2 and command coordinates C1. Specifically, if the trigger condition is not met, the vibration damping control unit 12 applies a vibration damping filter 12a to the command coordinates C1 input from the command generation unit 11 and outputs it as vibration damping coordinates C2. On the other hand, if the trigger condition is met, it outputs the command coordinates C1 input from the command generation unit 11 as is. The vibration damping coordinates C2 or command coordinates C1 output by the vibration damping control unit 12 are input to the movement amount calculation unit 13. Therefore, if the trigger condition is not met, the movement amount calculation unit 13 calculates the amount of movement M of the transport head 21 per unit time based on the vibration damping coordinates C2. On the other hand, if the trigger condition is met, it calculates the amount of movement M of the transport head 21 per unit time based on the command coordinates C1.

[0053] As described above, in the position control system 10 of this embodiment, the vibration control unit 12 outputs the command coordinate C1 instead of the vibration control coordinate C2 when the trigger condition is met.

[0054] As a result, when the trigger condition is met, the output of the vibration control unit 12 is switched from vibration control coordinate C2 to command coordinate C1. In that case, the motor 14 controls the position of the transport head 21 based on the command coordinate C1, so that the position of the transport head 21 can be matched to its target value.

[0055] Preferred embodiments of the present invention have been described above, but the above configuration can be modified as follows, for example. Modifications may be made individually, or multiple modifications may be made in any combination.

[0056] In the above embodiment, the transport head 21 of the loader 20 provided on the machine tool constitutes the controlled object, but the controlled object is not limited to this. For example, the controlled object may be the traveling or lifting section of a crane, or the traveling section or lateral mechanism of an OHT (Overhead Hoist Transport).

[0057] The displacement calculation unit 13 may be omitted. In this case, the command coordinate C1 or vibration damping coordinate C2 can be input directly to the motor 14. This configuration is useful when the motor 14 is of a type that takes target coordinates as input.

[0058] The vibration damping coordinate C2 may be calculated in a floating-point format with a number of bytes different from 8 bytes. The vibration damping coordinate C2 may also be calculated in an integer format with a sufficiently short unit length.

[0059] The coordinate values ​​of the X, Y, and Z axes indicating the position of the transport head 21 may be displayed on the display 55, respectively. The coordinate values ​​can be calculated based on the detection values ​​of sensors (e.g., encoders) not shown, which are provided on the motors 14 of each axis. [Explanation of symbols]

[0060] 10 Position control system 11 Command generation section 12 Vibration control unit 12a Vibration damping filter 13 Travel amount calculation section 14. Motor (drive device) 20 Loader 21. Transport head (controlled object, drive unit) C1 command coordinate C2 Vibration control coordinates MA (Multiple Absorption) Displacement Sum of Values V1 command speed V2 vibration damping speed M Travel amount RC coordinate range RV speed range

Claims

1. A command generation unit that generates command coordinates for controlling the position of the controlled object, A vibration control unit that applies a vibration damping filter to the command coordinates and outputs them as vibration damped coordinates, A drive device for controlling the position of the object to be controlled, Equipped with, The drive unit controls the position of the controlled object based on the vibration-damping coordinates when the trigger condition is not met, namely that the speed corresponding to the vibration-damping coordinates is within a predetermined speed range including zero, and the vibration-damping coordinates are within a predetermined coordinate range including a target value for the position of the controlled object; on the other hand, when the trigger condition is met, the drive unit controls the position of the controlled object based on the command coordinates.

2. A position control system according to claim 1, The system further includes a movement amount calculation unit that calculates the amount of movement of the controlled object per unit time, The drive device controls the position of the controlled object based on the amount of movement per unit time. The position control system is characterized in that the movement amount calculation unit calculates the amount of movement per unit time based on the vibration damping coordinates when the trigger condition is not met, and calculates the amount of movement per unit time based on the command coordinates when the trigger condition is met.

3. A position control system according to claim 1, The vibration damping control unit is characterized in that, when the trigger condition is met, it outputs the command coordinates instead of the vibration damping coordinates.

4. A position control system according to any one of claims 1 to 3, The position control system is characterized in that the controlled object is a drive unit provided in a machine tool.

5. A command generation process for generating command coordinates to control the position of the controlled object, A vibration control process that applies a vibration damping filter to the command coordinates and outputs them as vibration damped coordinates, A drive step for controlling the position of the controlled object, Equipped with, In the drive step, if the trigger condition that the speed corresponding to the vibration damping coordinate is within a predetermined speed range including zero, and the vibration damping coordinate is within a predetermined coordinate range including a target value for the position of the controlled object is not met, the position of the controlled object is controlled based on the vibration damping coordinate; on the other hand, if the trigger condition is met, the position of the controlled object is controlled based on the command coordinate.

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