JP6245808B2 - Position control device and position control method - Google Patents

Description

The present invention relates to a position control device.

Conventionally, there is an absolute encoder that simultaneously holds three incremental signals by three sample and hold circuits (see Patent Document 1).

JP-A-5-272988 (FIG. 1)

In the technique disclosed in Patent Document 1, it is necessary to connect three incremental signals to three sample and hold circuits, respectively. In such a position control device using an absolute encoder, the number of signal lines increases. In order to avoid this, the number of signal lines can be reduced by adopting a configuration in which a plurality of incremental signals having different pitches are output to the same signal line by pitch switching control. Here, when calculating the absolute position of the controlled object by combining a plurality of incremental signals having different pitches, the plurality of incremental signals must be acquired while the controlled object is stably stationary. This is because if the respective incremental signals are acquired in a state where the position of the control object is different, the absolute position of the control object cannot be calculated correctly.

In order to make the controlled object stand still, first, the relative position control is temporarily performed with the incremental signal of the start pitch. Next, acquire incremental signals with different pitches by pitch switching control, return to the starting pitch again by pitch switching control, calculate absolute position while continuing position control, and replace relative position information with absolute position information. good. However, when incremental signals with different pitches are output to the same signal line, the receiver's position encoding processing side seems to have changed the signal as if it moved, even though the control object did not move. May be visible. In other words, when an incremental signal with a different pitch is output to the place where the position encoding process is performed with the incremental signal of the starting pitch for the position control to be stopped, the position information as if it moved is output from the position encoding processing unit. The When the position control is performed by feeding back the position information, the stationary state may be unstable because the position control is erroneously performed even though the position information is not moved.

Accordingly, an object of the present invention is to provide a position control device capable of preventing position control from becoming unstable while switching to position detection signals having different pitches.

According to the position control device of the present invention, the output of the periodic waveform to the number of signal lines smaller than the number of the plurality of types of pitches is controlled by the switching control between the plurality of types of pitches from the outside. An encoder for switching between waveforms, position information generating means for generating position information from the output of each periodic waveform of the encoder, and position control means for performing position control of a controlled object by the output of the position information generating means. Prepare. After the position control unit enters a position control state in which the controlled object is controlled to be almost stationary, the position information generation unit stops generating position information, and the encoder pitch switching control is completed. from to, and switches the operating state of the position information generating means.

According to the present invention, when switching to a position detection signal with a different pitch, the position encoding calculation is stopped and then the pitch is switched. Therefore, position control is unstable while switching to a position detection signal with a different pitch. There is an effect of not becoming.

It is a block diagram of a position control device to which the present invention is applied. It is a conceptual diagram of the process of an incremental signal. It is a flowchart of an Example. It is a conceptual diagram of an incremental signal and a synthetic signal. It is a flowchart of an Example. It is a flowchart of an Example. It is a flowchart of an Example. It is a flowchart of an Example.

According to the present invention, after the position control state in which the control object is controlled to be stationary by the position control unit, the operation state of the position information generation unit is switched after the pitch switching control of the encoder is completed. According to the present invention, position encoding processing is performed with position detection signals even in a configuration in which a plurality of position detection signals are output to a smaller number of signal lines (for example, the same signal line) than the number of signal generation means. However, position detection signals with different pitches are not output. In addition, a plurality of position detection signals can be acquired in a state where the controlled object is stable and almost stationary. Accordingly, the absolute position of the control object can be correctly calculated.

Embodiments of the present invention will be described below.
Example 1
In the first embodiment, when switching from the minimum pitch to an incremental signal of a different pitch, an example in which the position encoding calculation is stopped and then the pitch is switched will be described.

Hereinafter, this embodiment will be described with reference to the drawings. FIG. 1 shows an exemplary configuration of a position control apparatus 100 to which each embodiment of the present invention can be applied. In FIG. 1, a CPU 101, ROM 102, RAM 103, control signal output unit 104, and AD (analog / digital) input unit 108 are connected to an internal bus 109. Each unit connected to the internal bus 109 can exchange data with each other via the internal bus 109. The ROM 102 stores various programs for the CPU 101 to operate. The CPU 101 as a control unit or a measurement unit controls each unit of the position control device 100 using the RAM 103 as a work memory according to a program stored in the ROM 102, for example. A control signal output unit 104 serving as a signal selection unit outputs a control signal instructed by the CPU 101 for driving the linear motor 106 serving as a driving unit to the motor driver 105. In addition, a control signal instructed by the CPU 101 for outputting incremental signals of different pitches to the linear encoder 107 which is a position signal generating means is output. The linear motor 106 moves the position of a control target (not shown) such as a lens, and the linear encoder 107 outputs an incremental signal according to the movement of the control target. An AD input unit 108 serving as a signal output unit AD converts the incremental signal output from the linear encoder 107 and supplies an AD converted data signal to the CPU 101. The CPU 101 calculates the current position of the control target from the incremental signal converted by the AD input unit 108 through incremental position encoding processing and absolute position encoding processing.

FIG. 2 is a conceptual diagram of incremental signal processing. FIG. 3 is a flowchart of the incremental position encoding process of the CPU 101. Incremental position encoding will be described with reference to FIGS. In FIG. 2A, the vertical axis represents the 10-bit AD conversion value, the horizontal axis represents the position of the controlled object, and 201 and 202 are output as a sine wave and a cosine wave according to the movement of the controlled object, respectively. It is an image of a two-phase incremental signal. In FIG. 2B, the vertical axis represents angle radians, and the horizontal axis represents position. 203 is an image of an arc tangent function result that is normalized and calculated from 0 to 2π as an arc tangent function between the signal 201 and the signal 202 in accordance with the movement of the controlled object. In FIG. 2C, the vertical axis is the incremental position encoded value, the horizontal axis is the position, and when the arctangent function result 203 crosses 0, the LSB is an incremental position encoded value that increases or decreases the upper digits corresponding to 2π. It is an image.

In s301 of the flowchart of FIG. 3, the CPU 101 determines whether or not the permission flag for the incremental position encoding process is set. If the permission flag is not set, the CPU 101 ends the process. If the permission flag is set, the process proceeds to s302. In s302, the CPU 101 acquires AD conversion values of two-phase signals such as 201 and 202 in FIG. Then, after performing the offset removal calculation and the gain adjustment calculation, the result of calculating the arctangent function such as 203 in FIG. 2B is stored in the RAM 103, and the process proceeds to s303. In s303, the CPU 101 determines whether or not the difference between the previous arc tangent function calculation result and the current arc tangent function calculation result is 3π / 8 or less, the process proceeds to s304 if not, and the process proceeds to s310 if not. Move processing to. The value of this difference is determined from the viewpoint of determining whether the change is normal or not, and is not limited to 3π / 8.

In s304, the CPU 101 determines whether or not the value of the previous arctangent function calculation result and the current arctangent function calculation result has crossed 0, and if so, the process moves to s305, and if not, the process moves to s308. . In s305, the CPU 101 determines whether or not the current arc tangent function calculation result is equal to or less than the previous arc tangent function calculation result, and if not, the process proceeds to s306, and if not, the process proceeds to s307. In s306, since the moving direction is considered to be an increasing direction, the CPU 101 adds 1 to the upper digit, which is 2π units, and shifts the processing to s308. The upper digit is a digit of 2π or more of the incremental position encoded value. On the other hand, in s307, since the movement direction is considered to be a decreasing direction, the CPU 101 subtracts 1 from the upper digit, which is 2π units, and shifts the processing to s308.

In s308, the CPU 101 adds the upper digit of 2π and the current result to obtain a new incremental position encoded value as indicated by 204 in FIG. 2C, and shifts the processing to s309. In s309, since the current and previous movements are 3π / 8 or less and the movement direction is correctly determined, the CPU 101 ends the process with no movement direction determination error warning. On the other hand, in s310, the CPU 101 moves 3π / 8 or more due to an increase in the movement direction of the movement amount that is 3π / 8 or more this time or the previous time, or 3π / 8 or more due to a decrease. It is difficult to determine whether Therefore, the process ends with a moving direction determination error warning. Thereby, an incremental position encoded value can be generated from the incremental signal and used for position control. As described above, relative position control is performed with the normal position detection pitch, and the absolute position detection pitch is switched only when the absolute position is obtained as described later.

FIG. 4 is a conceptual diagram of three types of incremental signals and synthesized signals having different pitches. FIG. 5 is a flowchart of the absolute position encoding process of the CPU 101. Absolute position encoding will be described with reference to FIGS. In FIG. 4A, the vertical axis is the angle radians, the horizontal axis is the position, and 401 is the arctangent of the minimum pitch that is normalized and calculated from 0 to 2π as an arctangent function according to the movement of the controlled object. It is an image of the function result. 21 cycles appear in all strokes. In FIG. 4B, the vertical axis is the angle radians, the horizontal axis is the position, and 402 is the arc tangent function result of the intermediate pitch that is normalized and calculated from 0 to 2π as the arc tangent function according to the movement. It is an image. Appears 10 cycles in all strokes. In FIG. 4C, the vertical axis is the angle radians, the horizontal axis is the position, and 403 is the arc tangent function result of the maximum pitch that is normalized and calculated from 0 to 2π as the arc tangent function according to the movement. It is an image. Appears in 4 cycles in all strokes.

In FIG. 4D, the vertical axis is angle radians, the horizontal axis is the position, and 404 is normalized from 0 to 2π as a result of the following expression (1) of s504 in FIG. 5 according to the movement. Is the resulting image. As described above, p1 appears in 21 cycles and p2 appears in all cycles as described above, so doubling p2 and p1 have a difference of one cycle in all strokes, so ph1 appears in one cycle in all strokes To do. In FIG. 4E, the vertical axis is angle radians, the horizontal axis is position, and 405 is normalized from 0 to 2π as a result of the following expression (2) of s504 in FIG. 5 according to the movement. Is the resulting image. Since it is the difference between 10 cycles and 4 cycles, 6 cycles appear in all strokes. In FIG. 4F, the vertical axis is angle radians, the horizontal axis is position, and 406 is normalized from 0 to 2π as a result of the following expression (3) of s504 in FIG. 5 according to the movement. Is the resulting image. Since it is the difference between 21 cycles and twice the 4 cycles, 13 cycles appear in all strokes.

Formula (1) ph1 = p1-2 * p2
Formula (2) ph6 = p2-p3
Formula (3) ph13 = p1-2 * p3

In s <b> 501 of the flowchart of FIG. 5, which is a flowchart of the absolute position encoding process of the CPU 101, the CPU 101 acquires the AD conversion value of the two-phase signal with the minimum pitch stored in the RAM 103. Then, after performing the offset removal calculation and the gain adjustment calculation, the result of the arctangent function calculation as 401 in FIG. 4A is stored in the RAM 103 as p1, and the process proceeds to s502. In step S <b> 502, the CPU 101 acquires the AD conversion value of the two-phase signal having the intermediate pitch stored in the RAM 103. Then, after performing the offset removal calculation and the gain adjustment calculation, the result of the arctangent function calculation such as 402 in FIG. 4B is stored in the RAM 103 as p2, and the process proceeds to s503. In s503, the CPU 101 acquires the AD conversion value of the two-phase signal with the maximum pitch stored in the RAM 103. Then, after performing the offset removal calculation and the gain adjustment calculation, the result of the arctangent function calculation such as 403 in FIG. 4C is stored in the RAM 103 as p3, and the process proceeds to s504.

In s <b> 504, the CPU 101 calculates the value ph <b> 1 using p <b> 1 and p <b> 2 stored in the RAM 103 to obtain ph <b> 1 and stores it in the RAM 103. ph1 appears for one cycle for every stroke. In addition, the CPU 101 calculates the value ph6 using p2 and p3 stored in the RAM 103, and stores them in the RAM 103. ph6 appears 6 cycles in all strokes. The CPU 101 uses p1 and p3 stored in the RAM 103 to perform an operation using Equation (3), obtains ph13, and stores it in the RAM 103. ph13 appears for 13 cycles in all strokes. The CPU 101 stores p1 stored in the RAM 103 as ph21 in the RAM 103, and shifts the processing to s505. ph21 appears 21 cycles in all strokes.

In s505, the CPU 101 calculates the following expression (4) using ph1 stored in the RAM 103, calculates in which cycle the control target is present in 6 cycles in all strokes, and stores the RAM 103 as abs6. Save to Further, the CPU 101 calculates the following expression (5) using abs6 and ph6 stored in the RAM 103, calculates which cycle among the 13 cycles appearing in all strokes is present, and sets the RAM 103 as abs13. Save to Further, the CPU 101 calculates the following expression (6) using abs 13 and ph 13 stored in the RAM 103, calculates which cycle of 21 cycles appears in all strokes, and sets the RAM 103 as abs 21. Save to Further, the CPU 101 calculates the following equation (7) using the abs 21 and ph 21 stored in the RAM 103, calculates in which cycle the control target exists with the resolution of the minimum pitch, and stores it in the RAM 103 as FullABS. Finish the process.

Formula (4) abs6 = ph1 / (2π / 6)
Formula (5) abs13 = (2π * abs6 + ph6) / (2π * 6/13)
Formula (6) abs21 = (2π * abs13 + ph13) / (2π * 13/21)
Formula (7) Full ABS = (2π * abs21 + ph21)

As described above, it is possible to synthesize incremental signals having different pitches by synthesizing three types of incremental signals having different pitches. The absolute position encoding process is performed by synthesizing incremental signals with different pitches acquired while the control object is stationary, and the absolute position of the control object can be obtained with the minimum pitch resolution.

FIG. 6 is a flowchart of the CPU 101 pitch switching control and encoding process switching. FIG. 7 is a flowchart of the position control process of the CPU 101. 4, 6, and 7, encoding process switching synchronized with pitch switching control (that is, control to switch the pitch at a predetermined timing after stopping the position encoding calculation when switching the pitch) I will explain. In s601 of FIG. 6, the CPU 101 instructs the control signal output unit 104 to output a control signal for setting the pitch of the incremental signal to the minimum pitch as shown in FIG. 4A, and the incremental position encoding process permission flag. Set. Thereafter, the CPU 101 initializes the upper digit of the incremental position encoding, sets the servo target position to the current value of the incremental position encoding, sets the servo ON flag, and shifts the processing to s602. As a result, an incremental signal with the minimum pitch is output from the linear encoder 107, and the CPU 101 performs an incremental position encoding process according to the flowchart of FIG. Further, the CPU 101 applies position control to try to stay at the target position in accordance with the flowchart of FIG.

In s602, the CPU 101 determines whether the servo stability flag is set. If it is set, the process proceeds to s603, and if not, the process proceeds to s602. In s603, the CPU 101 stores the two-phase AD conversion value with the minimum pitch in the RAM 103, and clears the servo ON flag. After that, the CPU 101 clears the incremental position encoding permission flag, and then instructs the control signal output unit 104 to output a control signal for setting the incremental signal pitch to an intermediate pitch as shown in FIG. To do. Then, the switching timer count is started and the process proceeds to s604. The switching timer count is, for example, that the CPU 101 counts the processing clock. As a result, an intermediate pitch incremental signal is output from the linear encoder 107, but since incremental position encoding processing by the CPU 101 is not performed, position information that has moved even though the control target is not moving is output. Not.

In s604, the CPU 101 determines whether or not the switching timer has elapsed a predetermined count. If the count has elapsed, the process proceeds to s605, and if not, the process proceeds to s604. In step s605, the CPU 101 stores the two-phase AD conversion value of the intermediate pitch in the RAM 103, and instructs the control signal output unit 104 to output a control signal that sets the incremental signal pitch setting to the minimum pitch. Then, the switching timer count is started and the process proceeds to s606. In s606, the CPU 101 determines whether or not a predetermined count has elapsed for the switching timer. If the count has elapsed, the process proceeds to s607, and if not, the process proceeds to s606. In s607, the CPU 101 sets a permission flag for incremental position encoding processing, sets a servo ON flag, and shifts the processing to s608. As a result, the incremental signal with the minimum pitch is output again from the linear encoder 107, and the CPU 101 performs the incremental position encoding process according to the flowchart of FIG. If the control object is not moving, the position information indicating that it is not moving is output. If the control object is moving, the position information indicating that it is moving is output. Therefore, the CPU 101 stays at the target position according to the flowchart of FIG. Apply the position control to try.

In s608, the CPU 101 determines whether the servo stability flag is set. If it is set, the process proceeds to s609, and if not, the process proceeds to s608. In s609, the CPU 101 clears the servo ON flag and clears the permission flag for the incremental position encoding process. Then, the control signal output unit 104 is instructed to output a control signal that sets the pitch of the incremental signal to the maximum pitch as shown in FIG. Thereafter, the CPU 101 starts the switching timer count and shifts the processing to s610. As a result, although the incremental signal of the maximum pitch is output from the linear encoder 107, since the incremental position encoding processing by the CPU 101 is not performed, position information that has moved even though the control target is not moving is output. Not. In s610, the CPU 101 determines whether or not the switching timer has passed a predetermined count. If the count has elapsed, the process proceeds to s611, and if not, the process proceeds to s610. In s611, the CPU 101 saves the two-phase AD conversion value of the maximum pitch in the RAM 103, and instructs the control signal output unit 104 to output a control signal that sets the incremental signal pitch setting to the minimum pitch. Then, the switching timer count is started and the process proceeds to s612.

In s612, the CPU 101 determines whether or not a predetermined count has elapsed for the switching timer. If the count has elapsed, the process proceeds to s613, and if not, the process proceeds to s612. In s613, the CPU 101 sets a permission flag for incremental position encoding processing, sets a servo ON flag, and shifts the processing to s614. As a result, the incremental signal with the minimum pitch is output again from the linear encoder 107, and the CPU 101 performs the incremental position encoding process according to the flowchart of FIG. If the control object is not moving, the position information indicating that it is not moving is output. If the control object is moving, the position information indicating that it is moving is output. Therefore, the CPU 101 stays at the target position according to the flowchart of FIG. Apply the position control to try.

In s614, the CPU 101 performs an absolute position encoding process according to the flowchart of FIG. 5, and moves the process to s615. As described above, since the incremental signals with different pitches can be acquired in a state where the linear motor 106 is stationary and subjected to position control with the minimum pitch resolution, the absolute position can be correctly detected.

In s615, the CPU 101 clears the servo ON flag, clears the incremental position encoding processing permission flag, and then overwrites the absolute position encoding result obtained in s614 to the upper digit of the incremental position encoding. Thereafter, the CPU 101 sets a permission flag for the incremental position encoding process, sets the servo target position to the current value of the incremental position encoding, sets the servo ON flag, and ends the process. As a result, the position information can be obtained only by the incremental position encoding process with the minimum pitch, while taking over the absolute position encoding result.

FIG. 7 of a flowchart for applying the position control to stay at the target position will be described. In s701, the CPU 101 determines whether the servo ON flag is set. If it is set, the process proceeds to s702, and if not, the process proceeds to s709. In s702, the CPU 101 acquires the servo target position, acquires the current value of the incremental position encoding, and moves the process to s703. In s703, the CPU 101 calculates a control error from the servo target position and the current value of the incremental position encoding, and proceeds to s704.

In s704, the CPU 101 determines whether or not the control error is within a predetermined range. If it is within the range, the process proceeds to s705, and if not within the range, the process proceeds to s706. In s705, the CPU 101 sets a servo stability flag and shifts the processing to s707. In s706, the CPU 101 clears the servo stability flag and shifts the processing to s707. In s707, the CPU 101 calculates a control signal necessary for compensation from the control error, and shifts the processing to s708. In S <b> 708, the CPU 101 updates the control signal that the control signal output unit 104 wants to output to drive the linear motor 106 to the motor driver 105, and ends the process. In step s709, the CPU 101 finishes the processing by setting the control signal that the control signal output unit 104 wants to output to drive the linear motor 106 to the motor driver 105 as non-updated.

As described above, the position control is performed using the incremental signal with the minimum pitch, and after the servo becomes stable, the incremental position encoding process is temporarily stopped before switching to the incremental signal with a different pitch. As a result, the positional information that appears to have moved despite the fact that the control target is not moving is output, which can prevent the stationary state from becoming unstable due to erroneous position control. is there.

(Example 2)
Next, Example 2 will be described. Here, an example will be described in which the pitch is switched after switching to the position encoding calculation for individual pitches while switching from the minimum pitch to the incremental signals of different pitches. For example, in a lens barrel, since it is necessary to perform a plurality of position controls such as a focus lens position control, a zoom lens position control, an anti-vibration lens position control, etc., the incremental position encoding process can also be performed in parallel with a plurality of systems. May be. Therefore, when only one linear motor is mounted, the redundant second and third incremental position encoding processes can be combined. That is, in the second embodiment, a plurality of position information generating means are provided, and switching to individual position information generating means determined for each pitch is performed in synchronization with encoder pitch switching control.

FIG. 8 is a flowchart of the CPU 101 pitch switching control and encoding process switching. The description will be made with reference to FIG. 8, and FIGS. 1, 3, 4, 5, and 7, which are the same as those in the first embodiment. In s801 in FIG. 8, the CPU 101 instructs the control signal output unit 104 in FIG. 1 to output a control signal that sets the pitch of the incremental signal to the minimum pitch as shown in FIG. Then, the first permission flag for the incremental position encoding process is set, and the second and third permission flags are cleared. Incremental position encoding processing No. 1, No. 2, and No. 3 are images in which three flowcharts of FIG. 3 are independently processed. Thereafter, the CPU 101 initializes the upper digit of the first incremental position encoding, sets the servo target position to the current value of the first incremental position encoding, sets the servo ON flag, and shifts the processing to s802. As a result, an incremental signal with the minimum pitch is output from the linear encoder 107, and the CPU 101 performs the first incremental position encoding process according to the flowchart of FIG. In addition, the CPU 101 performs position control so as to stay at the target position according to the flowchart of FIG.

In s802, the CPU 101 determines whether the servo stability flag is set. If it is set, the process proceeds to s803, and if not, the process proceeds to s802. In s803, the CPU 101 stores the arctangent function value with the minimum pitch as 401 in FIG. 4A in the RAM 103, and clears the servo ON flag. After that, the CPU 101 clears the first incremental position encoding process permission flag, and then instructs the control signal output unit 104 to output a control signal with the pitch setting of the incremental signal as an intermediate pitch. Then, the switching timer count is started and the process proceeds to s804. As a result, an intermediate pitch incremental signal is output from the linear encoder 107, but the first incremental position encoding process by the CPU 101 is not performed. Therefore, from the first incremental position encoding process, position information that is moved is not output even though the control target is not moved.

In s804, the CPU 101 determines whether or not the switching timer has reached a predetermined count. If the count has elapsed, the process proceeds to s805, and if not, the process proceeds to s804. In s805, the permission flag for the second incremental position encoding process is set, the servo target position is set to the current value of the second incremental position encoding, the servo ON flag is set, and the process proceeds to s806. As a result, an intermediate pitch incremental signal is output from the linear encoder 107, and the CPU 101 performs the second incremental position encoding process according to the flowchart of FIG. Since the CPU 101 uses the servo target value as the current value of the incremental position encoding process No. 2, the CPU 101 changes the position from the minimum pitch to the intermediate pitch in a stationary state and tries to stay at the target position according to the flowchart of FIG. You can continue to apply.

In s806, the CPU 101 determines whether the servo stability flag is set. If it is set, the process proceeds to s807, and if it is not set, the process proceeds to s806. In s807, the CPU 101 saves the arc tangent function value of the intermediate pitch as indicated by 402 in FIG. 4B in the RAM 103, and clears the servo ON flag. Thereafter, the CPU 101 clears the second incremental position encoding processing permission flag, and then instructs the control signal output unit 104 to output a control signal with the maximum pitch setting of the incremental signal, and the switching timer count. And the process proceeds to s808.

In s808, the CPU 101 determines whether or not a predetermined count has elapsed for the switching timer. If the count has elapsed, the process proceeds to s809, and if not, the process proceeds to s808. In s809, the permission flag for the third incremental position encoding process is set, the servo target position is set to the current value of the third incremental position encoding, the servo ON flag is set, and the process proceeds to s810. As a result, an incremental signal with the maximum pitch is output from the linear encoder 107, and the CPU 101 performs the third incremental position encoding process according to the flowchart of FIG.

Since the CPU 101 uses the servo target value as the current value of the incremental position encoding process No. 3, the CPU 101 switches from the intermediate pitch to the maximum pitch in a stationary state and attempts to stay at the target position according to the flowchart of FIG. You can continue to apply. In s810, the CPU 101 determines whether the servo stability flag is set. If it is set, the process proceeds to s811, and if not, the process proceeds to s810. In s811, the CPU 101 stores the arc tangent function value of the maximum pitch as indicated by 403 in FIG. 4C in the RAM 103, and clears the servo ON flag. Thereafter, the CPU 101 clears the No. 3 incremental position encoding processing permission flag, and then instructs the control signal output unit 104 to output a control signal that sets the pitch setting of the incremental signal to the minimum pitch. And the process proceeds to s812.

In s812, the CPU 101 determines whether or not a predetermined count has elapsed for the switching timer. If the count has elapsed, the process proceeds to s813, and if not, the process proceeds to s812. In s813, the 1st incremental position encoding process permission flag is set, the servo target position is set to the same value as the previous minimum pitch switching, the servo ON flag is set, and the process proceeds to s814. As a result, the incremental signal having the minimum pitch is output again from the linear encoder 107, and the CPU 101 performs the first incremental position encoding process according to the flowchart of FIG.

Since the first incremental position encoding process is performed even at the previous minimum pitch, if the control object is not moving, position information indicating that it is not moving, and if the control object is moving, position information indicating that it is moving Is output. Subsequently, the CPU 101 applies position control to stay at the target position according to the flowchart of FIG. In s814, the CPU 101 performs an absolute position encoding process according to the flowchart of FIG. 5, and moves the process to s815.

As described above, the incremental signals having different pitches can be acquired while the linear motor 106 is stationary and subjected to position control with the resolution of each pitch, so that the absolute position can be correctly detected. In s815, the CPU 101 clears the servo ON flag, and clears the permission flag for the first incremental position encoding process. Then, the absolute position encoding result obtained in s814 is overwritten on the first incremental position encoding upper digit. Thereafter, the CPU 101 sets again the permission flag for the first incremental position encoding process, sets the servo target position to the current value of the first incremental position encoding, sets the servo ON flag, and ends the process. As a result, the position information can be obtained only by the first incremental position encoding process while taking over the absolute position encoding result.

As described above, after the position is controlled using the incremental signal of each pitch, and after the servo becomes stable, before switching to the incremental signal having a different pitch, the system is switched to the incremental position encoding process of a predetermined system. did. As a result, the positional information that appears to have moved despite the fact that the control target is not moving is output, which can prevent the stationary state from becoming unstable due to erroneous position control. is there.

100..Position control device, 101..CPU (position information generating means, position control means), 102..ROM, 103..RAM, 104..Control signal output unit, 107..Linear encoder (encoder), 108 ..AD input section

Claims (10)

By switching control between multiple types of pitches from the outside, an encoder that switches the output of periodic waveforms to a number of signal lines less than the number of multiple types of pitches between cyclic waveforms of multiple types of pitches with different pitches, and
Position information generating means for generating position information from the output of each periodic waveform of the encoder;
Position control means for controlling the position of the control object by the output of the position information generating means;
With
After the position control unit enters a position control state in which the controlled object is controlled to be substantially stationary, the position information generation unit stops generating position information, and the encoder pitch switching control is completed. To switch the operating state of the position information generating means. The position control device according to claim 1, wherein generation of position information by the position information generation unit that has switched the operation state is started, and position information is generated from an output of a periodic waveform of the switched pitch. 2. The operation state of the position information generating means is switched in synchronization with the pitch switching control of the encoder after the position control means enters a position control state of a controlled object within a predetermined error. Or the position control apparatus of 2. A plurality of position information generating means;
4. The position control device according to claim 1, wherein the position control device switches to individual position information generating means determined for each pitch in synchronization with the pitch switching control of the encoder. 5. 5. The position control means performs relative position control at a normal position detection pitch of the encoder, and switches to the absolute position detection pitch of the encoder only when an absolute position is obtained. The position control device according to any one of the above. By switching control between multiple types of pitches from the outside, the output of periodic waveforms to a number of signal lines less than the number of multiple types of pitches is switched between the periodic waveforms of multiple types of pitches of encoders with different pitches . Switching control process;
A position information generation step of generating position information from the output of each periodic waveform of the encoder;
A position control step for controlling the position of the control object by the output in the position information generation step,
After entering the position control state in which the control object is controlled to be substantially stationary in the position control step, the generation of the position information in the position information generation step is stopped, and further, the plurality of pitches in the switching control step are A position control method characterized by switching an operation state in the position information generating step after switching between periodic waveforms is completed. The position control method according to claim 6, wherein generation of position information in the position information generation step in which the operation state is switched is started, and position information is generated from an output of a periodic waveform of the switched pitch. The operation in the position information generation step is performed in synchronization with the switching between the periodic waveforms of a plurality of types of pitches in the switching control step after the position control state of the controlled object within the predetermined error in the position control step. The position control method according to claim 6 or 7, wherein the state is switched. 7. A position information generation step by individual position information generation means determined for each pitch is performed in synchronization with switching between periodic waveforms of a plurality of types of pitches in the switching control step. The position control method according to claim 1. 10. The position control step performs relative position control at a normal position detection pitch of the encoder, and switches to the absolute position detection pitch of the encoder only when an absolute position is obtained. The position control method according to any one of the above.

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