JP5946359B2 - Motor control device and motor control method - Google Patents

Description

  The present invention relates to a technique for preventing step-out in motor advance angle control.

The stepping motor has features such as small size, high torque, and long life, and can easily realize digital positioning operation by open loop control. For this reason, they are widely used in devices such as imaging devices, optical disk devices, printers and projectors.
Patent Document 1 discloses a control device for a stepping motor that controls a winding excitation angle using a load torque current deviation. This device requires a current detection circuit for detecting a load torque current deviation.

  By the way, in the case of a motor having an encoder for detecting the rotor position, if the drive waveform is monitored, the advance angle can be measured based on the time ratio of the deviation of the drive waveform with respect to the rotor position. Further, the advance angle control becomes possible by controlling the time ratio of the deviation of the drive waveform with respect to the rotor position. In advance angle control, the torque can be maximized by matching the phases of the motor drive voltage waveform and the coil current waveform. If the target speed and target load of the motor are determined, the advance angle at which the required load torque is generated can be experimentally measured or grasped by simulation. Therefore, it is not necessary to use a current detection circuit by performing advance angle control with the advance angle set in advance according to the target speed and target load as the target advance angle.

Japanese Patent No. 4481262

  However, immediately after changing the target speed of the motor or at the time of recovery from speed fluctuation, the current speed has not reached the target speed, so the optimum measured lead angle, target speed and target load are optimal. There may be a large difference from the advance angle. Despite a large advance angle difference, if a drive waveform signal is applied to the motor to cancel the time lag corresponding to the optimum target advance angle at the target speed and load, the motor may step out. .

  An object of the present invention is to perform control so that step-out does not occur during motor drive control when a difference between a measured advance angle and a target advance angle is large.

  In order to solve the above-described problems, an apparatus according to the present invention is a motor control device that detects the position of a motor shaft and performs advance control, and outputs a signal corresponding to the position of the motor shaft. The phase value of the drive waveform of the motor in synchronization with the signal output by the position detection means, and the current output by the position detection means from the timing of the previous signal output by the position detection means Control means for measuring the time until the signal timing and changing the period of the drive waveform. The control means calculates a difference between the target phase value of the drive waveform in advance angle control and the phase value of the drive waveform acquired at the present time, and if the difference exceeds a threshold, the period of the drive waveform The phase change amount to be corrected is limited by the change of.

  According to the present invention, when the difference between the measured advance angle and the target advance angle is large, it is possible to perform control so that step-out does not occur during motor drive control.

FIG. 2 is a block diagram (A) showing a configuration example of a motor control device according to an embodiment of the present invention, and a perspective view (B) showing a configuration example of a motor. It is a figure explaining a sinusoidal drive waveform. It is a flowchart explaining the example of an update process regarding a drive waveform table. It is a time chart which illustrates the relationship between the position detection signal of a rotor shaft, and the drive waveform of a coil. It is a flowchart explaining the advance angle detection process at the present time. It is a time chart which illustrates the relationship between the position detection signal of a rotor shaft, and the drive waveform of a coil. It is a flowchart explaining advance angle control.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The motor control device and the motor control method will be described using a rotary drive motor as an example, but the present invention is also applicable to a linear drive motor in which the motor shaft moves linearly.
In the present embodiment, a control example will be described in which the advance angle that is the next control target is limited according to the advance angle measured this time in advance angle control.
FIG. 1A shows a configuration example of a motor control device 100 to which an embodiment of the present invention is applied. A CPU (Central Processing Unit) 101, ROM 102, and RAM 103 are connected to the internal bus 109. The ROM is a read-only memory, and the RAM is a random access memory. Furthermore, a drive waveform table storage unit 104, a PWM (pulse width modulation) unit 105, and an encoder input unit 108 are connected to the internal bus 109. Each unit transmits and receives data to and from each other via the internal bus 109. The ROM 102 stores various programs executed by the CPU 101. The CPU 101 as the control unit and the measurement unit controls each unit of the motor control device 100 using the RAM 103 as a work memory, for example, according to a program stored in the ROM 102. The drive waveform table storage unit 104 stores a drive waveform table having table values for 512 address divisions, and supplies a table value at a designated address to the PWM unit 105.

FIG. 2 shows details of a sinusoidal drive waveform table. The table numbers from 0 to 511 correspond to the phase value of the sine waveform and correspond to the address value on a one-to-one basis. Table number 0 corresponds to the 0 degree phase of the sine wave, and table number 256 corresponds to the 180 degree phase of the sine wave. A value of 50% duty ratio is stored in table number 0, and a duty ratio value of PWM output is stored in accordance with the phase for the subsequent table numbers. In the following description, it is assumed that the table number and the address value match for convenience.
The PWM unit 105 shown in FIG. 1A outputs a PWM signal to the motor driver 106. The PWM signal has a duty ratio corresponding to the table value received from the drive waveform table storage unit 104 in order to drive the stepping motor with encoder 107. For example, the value of the drive waveform table corresponding to the address value designated by the CPU 101 according to the program is supplied to the PWM unit 105 at a constant cycle. If the specified address interval is changed, such as sending address values one by one with 0, 1, 2,..., Or sending every fourth with 0, 4, 8,. A waveform is obtained.

  The stepping motor with encoder 107 includes an encoder that detects a rotor position by a two-phase photo interrupter, and outputs a position signal of the rotor shaft in accordance with the rotation angle. The encoder input unit 108 detects the rotor position from the position signal output by the stepping motor with encoder 107 and outputs the detection signal to the CPU 101. The CPU 101 detects the phase between the detection signal detected by the encoder input unit 108 and the drive waveform currently being output from the drive waveform table storage unit 104, and calculates a new address interval according to the program. Based on the address interval calculated by the CPU 101 according to the program, the table value is read from the drive waveform table storage unit 104 and supplied to the PWM unit 105.

  FIG. 1B is a perspective view showing an appearance of the stepping motor with encoder 107. A slit rotating plate 205 is attached to the rotor shaft 202 of the stepping motor 201 as a detected portion. The slit rotating plate 205 is designed so that the ratio of the bright area to the dark area is 50:50. A ch0 photointerrupter 203 and a ch1 photointerrupter 204 are arranged on the slit rotating plate 205, respectively. As the slit rotating plate 205 rotates with the rotation of the rotor shaft 202, the output signal of each photo interrupter changes. A comparator (not shown) outputs a binarized signal by comparing each analog input signal from the ch0 photointerrupter 203 and the ch1 photointerrupter 204 with a set threshold voltage. This signal is encoded to obtain a detection signal corresponding to the position of the motor shaft. It is assumed that the phase relationship between the signal change of the two-phase photo interrupter constituting the detection unit and the rotation angle of the rotor shaft is known.

FIG. 3 is a flowchart for explaining an example of update processing related to the drive waveform table executed by the CPU 101.
In S301, the CPU 101 determines whether or not it is a drive waveform update time. If it is not the update time, the CPU 101 ends the process. If it is the update time, the process proceeds to S302. In S302, the CPU 101 updates the address of the table value supplied from the drive waveform table storage unit 104 to the PWM unit 105 according to the specified address interval, and ends the process.
FIG. 4 is a time chart illustrating the relationship between the position detection signal of the rotor shaft and the drive waveform of the coil. FIG. 5 is a flowchart for explaining processing for detecting the current advance angle (hereinafter referred to as current advance angle) by the CPU 101. Hereinafter, measurement of the current advance angle will be described with reference to FIGS. 4 and 5.

  4A shows the first detection signal of the two phases detected by the encoder input unit 108, and FIG. 4B shows the other second detection signal. T1 to t5 shown on the horizontal axis are times indicating the rising and falling timings of the respective detection signals. When the repetition period of the detection signal is normalized to 360 degrees, the first detection signal shown in FIG. 4A has a relationship that is 90 degrees ahead of the second detection signal shown in FIG. FIG. 4C shows a drive waveform example 1 of one of the two phases supplied from the drive waveform table storage unit 104 according to the control of the CPU 101 with respect to the detected rotor position. The vertical axis represents the duty ratio, and table numbers 0, 128, 256, and 384 shown on the horizontal axis correspond to address values. p1 represents an address value that is being output at the rising point t5 of the first detection signal shown in FIG. The center of the amplitude of the output data is at a position where the duty ratio indicates 50%, and the direction of the current flowing through the coil changes at the position where the duty ratio is 50% depending on the specification of the motor driver 106. After returning to the address value corresponding to 0 after the address value shown in the range of 0 to 511, the repeated amplitude waveform is output. The period or frequency of the drive waveform can be controlled by changing the designated address interval. For example, compared to the case where the address value is advanced by 1 such as 0, 1, 2,..., If the address value is advanced by 2 such as 0, 2, 4,. Become. The frequency of the drive waveform is changed by the control for changing the designated address interval from 0 to 511.

FIG. 4D shows a driving waveform of the other coil that is 90 degrees out of phase with the waveform shown in FIG. The vertical axis represents the duty ratio, and table numbers 0, 128, 256, and 384 shown on the horizontal axis correspond to address values.
FIG. 4E shows a drive waveform example 2 of one of the two phases supplied from the drive waveform table to the detected rotor position. p2 represents the address value that is being output at the rise time t5 of the first detection signal shown in FIG. FIG. 4F shows a driving waveform of the other coil that is 90 degrees out of phase with the waveform shown in FIG. 4E and 4F, the drive waveforms shown in FIGS. 4C and 4D are compared with the drive waveforms shown in FIGS. 4C and 4D when one cycle shown in the range of 0 to 511 is normalized to 360 degrees. The relationship is 45 degrees ahead.

Next, the current advance angle detection that is processed in a fixed cycle will be described with reference to the flowchart of FIG.
In S501 of FIG. 5, the CPU 101 determines whether or not a detection signal is supplied from the encoder input unit. If the detection signal is not supplied, the process ends. If the detection signal is supplied, the process proceeds to S502. In step S <b> 502, the CPU 101 acquires the current address value during data supply from the drive waveform table storage unit 104 to the PWM unit 105. In next step S503, the CPU 101 determines which of the two phases the detection signal from the encoder input unit 108 is and the type of edge. Four types of signal discrimination are performed by discriminating between two phases and edge discrimination between rising edge and falling edge. For example, four types of signals shown at time points t1, t2, t3, and t4 in FIG. In the next step S504, the CPU 101 acquires a planned address value to which data is to be supplied from the drive waveform table storage unit 104 to the PWM unit 105 when the advance angle is desired to be zero at the edge timing at which the type has been determined. This can be acquired from a program stored in the ROM 102 or the RAM 103.

  In step S505, the CPU 101 calculates a difference between the current address value during data supply and the planned address value to which data is to be supplied when the advance angle is zero. That is, the value of the current advance angle with respect to the advance angle 0 is calculated, and the process ends. For example, when the drive waveform shown in FIG. 4C is output at the rising edge shown at time t5 in FIG. 4A, the current address value p1 being driven is zero. In this case, the advance angle at time t5 is measured to be zero. 4A is output at the rising edge shown at time t5 in FIG. 4A, the current address value p2 during driving is 64. In this case, at the rising edge of FIG. 4A, when the advance address is 0, if the planned address value to which data is to be supplied is zero, the advance angle at time t5 is measured to be an angle corresponding to 64. Is done. When one cycle of the address range from 0 to 511 is normalized to 360 degrees, the states shown in FIGS. 4E and 4F are the states shown in FIGS. 4C and 4D where the advance angle is 0. Compared to the advanced angle state advanced by 45 degrees. This can be calculated from (64/512) × 360 = 45 degrees.

  As described above, if the planned address value related to the output of the drive waveform data at each edge in the state of the advance angle 0 is known, this value and the current address value acquired in synchronization with the position detection signal The current advance angle state can be measured from the difference.

FIG. 6 is a time chart showing the relationship between the rotor position detection signal and the coil drive waveform. FIG. 7 is a flowchart for explaining advance angle control by the CPU 101, which is executed subsequent to the processing shown in FIG.
6A shows the first detection signal of the two phases detected by the encoder input unit 108, and FIG. 6B shows the other second detection signal. T1 to t6 shown on the horizontal axis are times indicating each timing. When the repetition period of the detection signal is normalized to 360 degrees, the first detection signal in FIG. 6A has a relationship that is 90 degrees ahead of the second detection signal in FIG. 6B. 6C and 6D show a coil drive waveform example 1 supplied from the drive waveform table storage unit 104 in accordance with the control of the CPU 101 with respect to the detected rotor position. The vertical axis represents the duty ratio, and table numbers 0, 128, 256, and 384 shown on the horizontal axis correspond to address values.

  When the driving waveform with the address value 384 is output in FIG. 6C, the phase state in which the rising edge of the first detection signal in FIG. 6A is detected is the target state. . The current address value p1 is an address value that is being output at time t5 in the first detection signal of FIG. Since the drive waveform data corresponding to the address value 384 is being output, the target phase state is obtained. For the second detection signal that comes next, the target address value is zero. The time point t6 at which the rising edge of the second detection signal shown in FIG. 6B is detected is a delayed phase of 90 degrees with respect to the first detection signal in FIG. For this reason, the planned address value of the drive waveform shown in FIG. 6C is also delayed by 90 degrees, and 384 + 128 = 512, that is, the address value zero becomes the target value. The period of the latest detection signal, that is, the time from the previous timing of the position detection signal to the timing of the current position detection signal (current time t5) is the time indicated by t5-t1, and is a quarter of the period. The timing after elapses is time t6. At this time, the designated address interval is determined so that the address value p3 becomes zero, and the cycle of the drive waveform is changed. That is, the designated address interval is determined as an interval in which the address advances by the change amount 128 within the transition time of (t5−t1) / 4 and stored in the RAM 103. Thereafter, until the time t6, the CPU 101 reads the table value of the drive waveform table storage unit 104 based on the specified address interval calculated according to the program and stored in the RAM 103, and stores it in the PWM unit 105. Supplied. In the other drive waveform shown in FIG. 6D, the designated address interval at the time of update is the same as that in the case of the drive waveform shown in FIG. 6C, but an angle of 90 degrees when converted into a phase angle. It only needs to be shifted. If the motor is driven in the target advance angle state, the drive waveform does not greatly expand and contract in time.

  FIG. 6E shows a coil drive waveform example 2 supplied from the drive waveform table storage unit 104 according to the control of the CPU 101 with respect to the detected rotor position. As shown in FIG. 6C, the target is a state in which the rising edge of the first detection signal in FIG. 6A is detected when the drive waveform at the address value 384 is output. However, the address value p2 being output at time t5 shown in FIG. 6A is zero. In this case, the motor is driven with a waveform delayed by 384 (270 degrees in phase angle) as an address value from the target advance angle. Regarding the target value at time t6 when the rising edge of the second incoming detection signal (see FIG. 4B) is detected next, it is necessary to recover the phase delay corresponding to 384. For this reason, 384 is added to the address value 128, and the 512 advance interval is set. In other words, in order to catch up with the target advance angle within the period from p2 to p3, it is necessary to set the address to an interval of 512 advancement. Since the address 512 to be corrected by the next time corresponds to the amount of phase change for one cycle, the drive waveform read from the reference table must be greatly reduced in time and output. In advance control with the advance set in advance according to the target speed and target load as the target advance, the drive waveform is reduced in time even though the current advance and the target advance are different. If you try to make it coincide with the target advance angle, the motor may step out. Therefore, under such conditions, that is, when the current advance angle is greatly deviated from the target value, it is an object of the present invention to control the drive waveform so as not to shrink too much in time to avoid step-out. One.

  FIG. 6F shows a coil drive waveform example 3 supplied from the drive waveform table storage unit 104 in accordance with the control of the CPU 101 with respect to the detected rotor position. The drive waveform shown in FIG. 6F is the same delay as the drive waveform shown in FIG. 6E until time t5. The necessary address interval is the 512 advance interval similar to that shown in FIG. However, in this example, in order not to shrink the drive waveform too much, in this example, the address value is not advanced at a time by 512 minutes and the phase difference is made zero, but the half of 256 is advanced within the period from p2 to p4. There is a limit. That is, the address value (phase change amount) for recovering the phase delay is limited to 128 with respect to the original target address value. Since the time scaling operation for the drive waveform data does not work excessively, the drive waveform can be gradually reduced in time by limiting the drive waveform cycle changing operation within a predetermined range. A step-out prevention effect is obtained. In this example, the amount of phase change is limited according to the transition time for adjustment, but when changing the drive waveform cycle or frequency in advance control, the motor load, target speed, current speed, etc. Within the setting range according to the limit value of phase change is controlled according to the situation.

Next, the advance angle control with the above restrictions taken into account will be described with reference to the flowchart of FIG.
In step S701, the CPU 101 acquires the current address value of the drive waveform table when the current detection signal measured according to the flowchart of FIG. 5 is input. In next step S702, the CPU 101 acquires the scheduled address value (control target phase value) of the drive waveform table from the RAM 103, and moves the process to step S703. In step S <b> 703, the CPU 101 calculates a difference between the scheduled address value and the current address value to obtain a phase shift amount. In next step S704, the CPU 101 determines whether the shift amount of the address value calculated in step S703 is greater than the first threshold value or less than the first threshold value. The first threshold is 128. If the deviation amount is 128 or less, the process proceeds to S706. If the deviation amount exceeds 128, the process proceeds to S705.

  In S705, the CPU 101 sets the correction amount (correction address) for the address value to 128, and advances the process to S709. In step S <b> 706, the CPU 101 determines whether the address value shift amount calculated in step S <b> 703 is smaller than the second threshold value. The second threshold is −128. If the deviation amount is −128 or more, the process proceeds to S708. If the deviation amount is less than −128, the process proceeds to S707. In S707, the CPU 101 sets the correction address to −128, and the process proceeds to S709. In step S708, the CPU 101 sets the correction address to the shift amount obtained in step S703, and the process proceeds to step S709.

  In step S709, the CPU 101 calculates a planned address value corresponding to the planned advance angle when the next detection signal is input. This is a value obtained by adding 128 and the correction address to the current scheduled address value, and is stored in the RAM 103. 128 corresponds to an address value for an electrical angle of 90 degrees. In next step S710, the CPU 101 calculates the number of moving addresses until the next detection signal is input as a difference from the next scheduled address value and the current address value, and shifts the processing to step S711. In step S <b> 711, the CPU 101 calculates an address update interval until the next detection signal is input. The address update interval is calculated by dividing the number of moving addresses up to the next time obtained in S710 by the moving time up to the next time and the update frequency of the drive waveform. The moving time until the next time is “t6-t5” shown in FIG. In the present embodiment, in FIG. 6A, one-fourth of one cycle “t5-t1” of the detection signal nearest to t5 is set as the transition time, and the time when this time has passed is set as the timing of t6. However, the present invention is not limited to this, and can be set arbitrarily, such as one-half or one-third of one cycle. Further, the update frequency of the drive waveform may be any frequency that can achieve the necessary drive waveform resolution at the target maximum speed. Specifically, for example, when one cycle of the drive waveform corresponds to 100 Hz and a resolution of 512 divisions is required, the update frequency may be 51.2 kHz or more.

  As described above, in the present embodiment, the address value of the current drive waveform table is acquired in synchronization with the rotor position detection signal, and the difference between the current address value and the planned address value in the target advance state is calculated. calculate. The advance angle control is performed by setting the address update interval so that the difference amount is corrected or reduced within the adjustment transition period. At that time, by limiting the amount of change in the address to be corrected until the next position detection within a predetermined range, the drive waveform can be gradually changed over time. Therefore, an effect of preventing the motor from stepping out during acceleration or speed fluctuation can be obtained.

100 Motor control device 101 CPU
104 Drive waveform table storage unit 105 PWM unit 106 Motor driver 107 Stepping motor with encoder

Claims (8)

A motor control device that detects the position of a motor shaft and performs advance angle control,
Position detecting means for outputting a signal corresponding to the position of the motor shaft;
A phase value of the driving waveform of the motor is acquired in synchronization with the signal output by the position detection means, and the current signal output by the position detection means from the timing of the previous signal output by the position detection means Control means for measuring the time until the timing of and changing the period of the drive waveform,
The control means calculates a difference between the target phase value of the drive waveform in advance angle control and the phase value of the drive waveform acquired at the present time, and if the difference exceeds a threshold, the period of the drive waveform A motor control device that limits the amount of phase change to be corrected by changing the value. Drive waveform table storage means for dividing and storing the drive waveform data,
The said control means changes the period of the said drive waveform by controlling the address space | interval which reads data from the said drive waveform table memory | storage means, when the said difference is below a threshold value. Motor control device. The control means includes
When the difference is less than or equal to a threshold value, a control is performed to change the cycle so that the phase value of the drive waveform coincides with the target phase value at the time when the transition time corresponding to the phase value for adjustment has elapsed from the present time,
When the difference exceeds a threshold, the period of the drive waveform is changed within a predetermined range, and the difference between the phase values calculated when the transition time has elapsed from the present time has already been calculated. The motor control device according to claim 2, wherein control is performed to make the difference smaller than the difference.   4. The motor control device according to claim 2, wherein the control unit obtains a phase value of the drive waveform of the motor from an address value of the drive waveform output from the drive waveform table storage unit.   The said control means determines the target phase value of the said drive waveform using the address value of the drive waveform which the said drive waveform table memory | storage means memorize | stores, The any one of Claim 2 to 4 characterized by the above-mentioned. Motor control device.   6. The motor control device according to claim 2, wherein the drive waveform table storage unit stores sine waveform data, and outputs the data according to an address interval specified by the control unit. . The position detecting means includes
A detection unit for detecting the position of the detection unit provided on the motor shaft;
Comparison means for comparing the output of the detection unit with a threshold;
The motor control device according to claim 1, further comprising an encoding unit that measures a change in the signal binarized by the comparison unit and outputs the change to the control unit. A motor control method executed by a motor control device that detects the position of a motor shaft and performs advance angle control,
A position detecting step for outputting a signal corresponding to the position of the motor shaft;
The current signal output in the position detection step from the timing of the previous signal output in the position detection step is acquired in synchronization with the signal output in the position detection step. A control step of measuring the time until the timing of and changing the period of the drive waveform,
The control step includes a step of calculating a difference between a target phase value of the drive waveform in advance angle control and a phase value of the drive waveform currently acquired, and when the calculated difference exceeds a threshold value, A motor control method comprising a step of limiting a phase change amount to be corrected by changing a cycle of a drive waveform.

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