JP2014096922A - Control method and control apparatus of stepping motor, and robot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method and control apparatus of stepping motor, and robot, capable of achieving complete driving with less electric power.SOLUTION: The control method of stepping motor includes a first difference detection process for applying a signal for rotating a rotor by a predetermined angle to a stepping motor, detecting a difference between a rotational angle of the rotor detected by a detector and the predetermined angle and increasing the intensity of the signal until the difference is not more than a predetermined value. The intensity of the signal is taken as a signal intensity for applying the intensity of the signal to the stepping motor when the difference is not more than the predetermined value.

Description

  The present invention relates to a stepping motor control method, a control device, and a robot.

  Conventionally, horizontal articulated robots and vertical articulated robots have been used as industrial robots. For example, a horizontal articulated robot has a base, a first arm that can rotate with respect to the base, and a second arm that can rotate with respect to the first arm. The first and second arms are driven by various motors. Various motor control methods for accurately driving the motor are also disclosed (see, for example, Patent Document 1).

  Patent Document 1 discloses a stepping motor control method capable of exhibiting stable starting characteristics. Specifically, in Patent Document 1, first, a stable point at the time of non-excitation unique to a stepping motor is set as a final target stop excitation position, and first rotation command energization is performed from a position offset with respect to this final target excitation position. Next, control is performed such that stop excitation is performed when the rotor rotates and moves to the final target stop excitation position. However, in such a control method, since the current value of the rotation command energization is constant, the following two problems occur.

  As a first problem, there is a problem that the power saving drive of the stepping motor cannot be performed because the current value cannot be adjusted. Further, as a second problem, since the current value cannot be adjusted, for example, when the rotational resistance of the rotor is increased due to deterioration of the stepping motor with time (for example, grease breakage) or the like, There is a problem that it cannot be driven.

Japanese Patent Laying-Open No. 2005-261023

  An object of the present invention is to provide a stepping motor control method, a control device, and a robot capable of reliably driving with less power.

Such an object is achieved by the present invention described below.
The stepping motor control method of the present invention is a stepping motor control method to which a detector for detecting the rotation angle of the rotor is connected,
A signal for rotating the rotor by a predetermined angle is applied to the stepping motor, a difference between the rotation angle of the rotor detected by the detector and the predetermined angle is detected, and the difference becomes a predetermined value or less. Until the first difference detection step to increase the intensity of the signal,
The signal strength applied to the stepping motor is the strength of the signal when the difference becomes equal to or less than the predetermined value.
Thereby, the stepping motor can be reliably driven with less electric power.

In the stepping motor control method of the present invention, the difference detection step further applies a signal for rotating the rotor by a predetermined angle in a direction opposite to the rotation direction to the stepping motor, and the detector detects the difference. A second difference detection step of detecting a difference between the rotation angle of the rotor and the predetermined angle, and increasing the intensity of the signal until the difference becomes a predetermined value or less,
It is preferable that the intensity of the signal when the difference becomes equal to or less than the predetermined value is a signal intensity applied to the stepping motor.
Thereby, since it is detected whether both normal rotation and reverse rotation are normal rotations, more reliable driving of the stepping motor can be ensured.

In the stepping motor control method of the present invention, an upper limit is set for the intensity of the signal,
If the difference does not fall below the predetermined value even when the upper limit signal is applied, it is preferable to notify that the stepping motor is in an abnormal state.
This promptly prompts the operator to repair or replace the stepping motor.

In the stepping motor control method of the present invention, it is preferable that the initial position for rotating the predetermined angle is a position at which the next driving is started after the stepping motor is applied with the signal intensity.
Thereby, after setting the driving conditions (current value, etc.) of the stepping motor, the stepping motor can be driven promptly.

In the stepping motor control method of the present invention, the predetermined angle is preferably an integer multiple of 360 ° (excluding 0).
Thereby, since the rotated rotor returns to a predetermined position, a difference detection process can be performed quickly and continuously.
In the stepping motor control method of the present invention, it is preferable to change the control gain of the stepping motor based on the reference signal strength.
Thereby, it is possible to cope with a change with time of mechanical characteristics of the stepping motor (for example, rotation resistance of the rotor), and it is possible to maintain the control characteristics of the stepping motor.

The control device of the present invention is a control device for a stepping motor to which a detector for detecting the rotation angle of the rotor is connected,
An application unit that applies a signal for rotating the rotor by a predetermined angle; a detection unit that detects a difference between the rotation angle of the rotor detected by the detector and the predetermined angle; and the difference is a predetermined value or less. A control unit that increases the signal intensity until the difference becomes equal to or smaller than the predetermined value, and sets the signal intensity to be applied to the stepping motor when the difference is equal to or less than the predetermined value.
Thereby, the control apparatus which can drive a stepping motor reliably with less electric power is obtained.

The robot of the present invention includes a base,
An arm connected to the base and rotatable relative to the base;
A stepping motor for rotating the arm with respect to the base;
And a control device according to claim 7 for controlling driving of the stepping motor.
Thereby, a highly reliable robot can be obtained.

It is a block diagram which shows the control apparatus which concerns on suitable embodiment of this invention. It is a flowchart explaining the control method of the control apparatus shown in FIG. It is a perspective view which shows an example of the robot of this invention. It is a perspective view which shows an example of the robot of this invention.

Hereinafter, a control method, a control device, and a robot of a stepping motor of the present invention will be described in detail based on preferred embodiments shown in the drawings.
FIG. 1 is a block diagram showing a control device according to a preferred embodiment of the present invention, FIG. 2 is a flowchart for explaining a control method of the control device shown in FIG. 1, and FIG. 3 and FIG. It is a perspective view which shows an example of a robot.

1. Control Device First, the control device of the present invention (the stepping motor control method of the present invention) will be described.
A control device 1 shown in FIG. 1 is a device that controls driving of a stepping motor 3 to which an encoder (detector) 2 is connected.

  In the present embodiment, a two-phase stepping motor is used, but the configuration of the stepping motor 3 is not limited to this. For example, the number of phases of the stepping motor 3 is not limited to two phases, and may be single phase, three phases, four phases, five phases, or the like. Also, the type of rotor (rotor) is not particularly limited, and a PM (Permanent Magnet) type, a VR (Variable Reluctance) type, an HB (Hybrid) type, and the like can be used.

  The encoder 2 is not particularly limited as long as the rotation angle (position) of the rotor (rotor) can be detected. For example, a known encoder such as a magnetic encoder or an optical encoder may be used. it can. In this embodiment, an encoder is used as a detector. However, the detector is not particularly limited as long as the rotation angle (position) of the rotor can be detected. For example, a known resolver or the like is used. Also good.

  The control device 1 includes an integrated control unit 101, a subtractor 102, a position control unit 103, a subtractor 104, an angular velocity control unit 105, an inverse park conversion unit 106, an electrical angle initialization operation control unit 107, Control mode switching unit 108, A phase current control unit 109, B phase current control unit 110, electrical angle calculation unit 111, angular velocity calculation unit 112, rotation angle calculation unit 113, and initialization motion creation rejection determination unit 114 And have. In the following description, “value is input and output” or the like is used, which means “a signal corresponding to the value is input or output”. Further, “the stepping motor rotates” means “the rotor (rotor) rotates relative to the stator”.

  In such a control device 1, the control mode switching unit 108 can switch between an operation confirmation mode for confirming the operation of the stepping motor 3 and a normal drive mode for performing normal driving of the stepping motor 3. . The control mode switching unit 108 receives the A-phase current command and the B-phase current command generated by the electrical angle initialization operation control unit 107 according to the command from the integrated control unit 101, and the A-phase current control unit 109 and the B-phase current control unit 110 and a second state in which the A-phase current command and the B-phase current command generated by the reverse park conversion unit 106 are output to the A-phase current control unit 109 and the B-phase current control unit 110, respectively. Switch. The control mode switching unit 108 is in the first state in the operation confirmation mode, and is in the second state in the normal drive mode.

Hereinafter, the normal drive mode and the operation confirmation mode will be sequentially described.
≪Normal drive mode≫
A position command Pc of the stepping motor 3 is input to the subtracter 102 from the integrated control unit 101, and a position feedback value Pfb, which will be described later, is input from the rotation angle calculation unit 113. The rotation angle calculation unit 113 counts the number of pulses input from the encoder 2 and outputs the rotation angle of the stepping motor 3 corresponding to the count value to the subtracter 102 as the position feedback value Pfb. The subtractor 102 outputs a deviation between the position command Pc and the position feedback value Pfb (a value obtained by subtracting the position feedback value Pfb from the target value of the rotation angle of the stepping motor 3) to the position control unit 103.

  The position control unit 103 performs a predetermined calculation process using the deviation input from the subtractor 102 and a position proportional gain, which is a predetermined coefficient, so that the angular velocity of the stepping motor 3 corresponding to the deviation is calculated. Calculate the target value. The position control unit 103 outputs a signal indicating the target value (command value) of the angular velocity of the stepping motor 3 to the subtracter 104 as the angular velocity command ωc. In addition, although proportional control (P control) is used as feedback control, it is not limited to this. Further, the position proportional gain can be appropriately changed based on the result of the operation confirmation mode.

The subtractor 104 receives an angular velocity command ωc and an angular velocity feedback value ωfb described later. The subtractor 104 outputs a deviation (a value obtained by subtracting the angular velocity feedback value ωfb from the target angular velocity value of the stepping motor 3) between the angular velocity command ωc and the angular velocity feedback value ωfb to the angular velocity control unit 105.
The angular velocity control unit 105 uses a deviation input from the subtractor 104 and a predetermined coefficient, such as an angular velocity proportional gain, an angular velocity integral gain, and the like, and performs a predetermined calculation process including integration to respond to the deviation. The stepping motor 3 drive signal (torque current command, field current command) is generated and output to the reverse park converter 106. In addition, although PI control is used as feedback control, it is not limited to this. Further, the angular velocity proportional gain and the angular velocity integral gain can be appropriately changed based on the result of the operation confirmation mode.

  The reverse park conversion unit 106 generates an A-phase current command and a B-phase current command based on a drive signal (torque current command, excitation current command) input from the angular velocity control unit 105 and an electrical angle feedback value afb described later. Is generated. Then, the A phase current command is output to the A phase current control unit 109 and the B phase current command is output to the B phase current control unit 110 via the control mode switching unit 108. The A and B phase current control units 109 and 110 supply the stepping motor 3 with the A phase current and the B phase current corresponding to the input A and B phase current commands. Thereby, the stepping motor 3 rotates according to the A and B phase currents. In this way, feedback control is performed so that the position feedback value Pfb is as equal as possible to the position command Pc, and the angular velocity feedback value ωfb is as equal as possible to the angular velocity command ωc. The drive current is controlled.

≪Operation check mode≫
The operation confirmation mode is a mode in which the magnitude of the current (A phase current and B phase current) that drives the stepping motor 3 is determined according to the state of the stepping motor 3. By having such a mode, as will be described later, since the minimum current value necessary for driving the stepping motor 3 can be detected, the stepping motor 3 can be driven reliably, and the stepping motor 3 power saving drive can be achieved.
In the operation confirmation mode, the integrated control unit (control unit) 101, the electrical angle initialization operation control unit 107, the control mode switching unit 108, the A phase current control unit (application unit) 109, and the B phase current control unit ( An application unit 110, a rotation angle calculation unit 113, and an initialization motion creation rejection determination unit (detection unit) 114 are used.

A drive command for the stepping motor 3 is input from the integrated control unit 101 to the electrical angle initialization operation control unit 107. The electrical angle initialization operation control unit 107 generates an A-phase current command and a B-phase current command based on the input drive command, and sends the A-phase current command to the A-phase current control unit via the control mode switching unit 108. 109, and a B-phase current command is output to the B-phase current control unit 110. The A and B phase current control units 109 and 110 supply the stepping motor 3 with the A phase current and the B phase current corresponding to the input A and B phase current commands. Thereby, the stepping motor 3 rotates according to the A and B phase currents.
The rotation angle calculation unit 113 counts the number of pulses input from the encoder 2 according to the rotation of the stepping motor 3 and calculates the rotation angle of the stepping motor 3. Then, the calculated rotation angle of the stepping motor 3 (measured rotation angle θ ′) is output to the initialization motion creation rejection determination unit 114.

The initialization motion creation rejection determination unit 114 receives the measured rotation angle θ ′ from the rotation angle calculation unit 113 and the theoretical value of the stepping motor 3 when the drive currents A and B are supplied from the integrated control unit 101. A rotation angle (theoretical rotation angle θ) is input. The initialization motion creation rejection determination unit 114 obtains a difference S (S = | θ−θ ′ |) between the theoretical rotation angle θ and the measured rotation angle θ ′, and whether the obtained difference is within a predetermined range set in advance. Judge whether or not. The initialization motion creation rejection determination unit 114 determines that the stepping motor 3 is normally driven if the difference S is within the predetermined range, and conversely, if the difference S is outside the predetermined range, the stepping motor. 3 is determined not to be driven normally. Then, the initialization motion creation rejection determination unit 114 outputs the determination result to the integrated control unit 101.
The integrated control unit 101 to which the determination result is input outputs a different command depending on the determination result.

  The control device 1 specifically performs the following control using the function of each unit. That is, the control device 1 applies the A and B phase currents (signals) for rotating the rotor at an arbitrary position in the positive direction (first direction) by a predetermined angle (theoretical rotation angle θ1) to the stepping motor 3, and the encoder The first step of detecting the difference S1 (S1 = | θ1-θ1 ′ |) between the rotation angle (measured rotation angle θ1 ′) of the stepping motor 3 detected by 2 and the theoretical rotation angle θ1 and the rotor at an arbitrary position The A and B phase currents (signals) for rotating a predetermined angle (theoretical rotation angle θ2) in the reverse direction (second direction) are applied to the stepping motor 3, and the rotation angle of the stepping motor 3 detected by the encoder 2 (actual rotation) Difference detection step including a second step of detecting the difference S2 (S2 = | θ2-θ2 ′ |) between the angle θ2 ′) and the theoretical rotation angle θ2 until both the differences S1 and S2 are equal to or less than a predetermined threshold value. A, Sequentially strengthen repeated the amplitude of the phase current, set A of when the difference S1, S2 are both equal to or less than the predetermined value, the intensity of the B-phase current as a reference current intensity (signal intensity to be applied to the stepping motor 3). In addition, it is preferable that an upper limit value is set for the intensity of the A and B phase currents, and even when the upper limit values are supplied as the A and B phase currents, the differences S1 and S2 are not less than the predetermined values. Determines that this is a failure of the stepping motor 3 (not normal) and notifies (warns) the operator.

Hereinafter, this control will be described based on the flowchart shown in FIG. In the integrated control unit 101, the initial position of the rotor with respect to the position information and the currents of the A and B phase currents with respect to the current information, depending on the device in which the stepping motor 3 is incorporated (for example, robots 7 and 8 described later) It has an initial value (current lower limit value) I ₀ , a current increase amount ΔI, and a current upper limit value I _max .

First, the integrated control unit 101 issues a command to set the rotor to the initial position (arbitrary position) according to the conditions [rotation direction: forward rotation] and [current values of currents A and B: current initial value I ₀ ] as an electrical angle. The data is output to the initialization operation control unit 107. The electrical angle initialization operation control unit 107 outputs A and B phase current commands corresponding to the input commands to the A and B phase current control units 109 and 110. The A and B phase current control units 109 and 110 supply the A and B phase currents corresponding to the input A and B phase current commands to the stepping motor 3. Accordingly, theoretically, the rotor rotates in the positive direction and moves to the initial position, and the electrical angle is initialized (STEP 1).

Next, the integrated control unit 101 instructs the rotor to rotate 360 ° (theoretical rotation angle θ1) according to the conditions of [rotation direction: forward rotation] and [current values of currents A and B: current initial value I ₀ ]. Is output to the electrical angle initialization operation control unit 107. The electrical angle initialization operation control unit 107 outputs A and B phase current commands corresponding to the input commands to the A and B phase current control units 109 and 110. The A and B phase current control units 109 and 110 supply the A and B phase currents corresponding to the input A and B phase current commands to the stepping motor 3. This theoretically causes the rotor to rotate 360 ° in the positive direction (STEP 2).

Next, the integrated control unit 101 electrically issues a command to set the rotor to the initial position (predetermined position) according to the conditions [rotation direction: reverse rotation] and [current values of currents A and B: current initial value I ₀ ]. Output to the angle initialization operation control unit 107. The electrical angle initialization operation control unit 107 outputs A and B phase current commands corresponding to the input commands to the A and B phase current control units 109 and 110. The A and B phase current control units 109 and 110 supply the A and B phase currents corresponding to the input A and B phase current commands to the stepping motor 3. Thereby, theoretically, the rotor rotates in the reverse direction and moves to the initial position, and the electrical angle is initialized (STEP 3).

Next, the integrated control unit 101 instructs the rotor to rotate 360 ° (theoretical rotation angle θ2) according to the conditions of [rotation direction: reverse rotation] and [current values of currents A and B: current initial value I ₀ ]. Is output to the electrical angle initialization operation control unit 107. The electrical angle initialization operation control unit 107 outputs A and B phase current commands corresponding to the input commands to the A and B phase current control units 109 and 110. The A and B phase current control units 109 and 110 supply the A and B phase currents corresponding to the input A and B phase current commands to the stepping motor 3. This theoretically causes the rotor to rotate 360 ° in the reverse direction (STEP 4).

  Next, the initialization motion creation rejection determination unit 114 determines the difference S1 (S1 = S1) between the measured rotation angle θ1 ′ in STEP2 output from the rotation angle calculation unit 113 and the theoretical rotation angle θ1 output from the integrated control unit 101. | Θ1-θ1 ′ |) is obtained. The initialization motion creation rejection determination unit 114 also determines the difference S2 (S2 = |) between the actual rotation angle θ2 ′ in STEP 4 output from the rotation angle calculation unit 113 and the theoretical rotation angle θ2 output from the integrated control unit 101. θ2-θ2 ′ |) is obtained.

  Then, the initialization motion creation rejection determination unit 114 determines that the initialization operation is normal if both of the differences S1 and S2 are within a predetermined value, and either of the differences S1 and S2 must be within the predetermined value. In this case, it is determined that the initialization operation is abnormal (STEP 5). Here, the predetermined value is not particularly limited and may be set as appropriate according to the characteristics required of the stepping motor 3. However, the smaller the value, the more accurately the success or failure of the initialization operation can be determined. it can. Specifically, the predetermined range is preferably, for example, a range of S1, S2 ≦ 1 °, and more preferably, S1, S2 = 0 °.

Next, when the initialization operation creation rejection determination unit 114 determines that the initialization operation is normal, the integrated control unit 101 determines the current value (I _{0 in} this case) at the time when the initialization operation is determined normal as the reference current intensity ( The signal gain applied to the stepping motor 3) is set, and the control gain is changed according to the set reference current intensity (STEP 6). Then, the integrated control unit 101 switches the control mode switching unit 108 to the normal drive mode, and then performs normal drive of the stepping motor 3 using the changed reference current intensity and control gain (STEP 7).

  On the other hand, when the initialization motion creation rejection determination unit 114 determines that the initialization operation is abnormal, the integrated control unit 101 increases the current value by one step (ΔI) based on the stored information, and the above STEPs 1 to 5 are performed. Repeat the same process. In the following, a case where the current value is increased by one level and reconfirmed will be described. However, the current value may be increased by a plurality of levels (for example, 2ΔI, 3ΔI, etc.) at a time. For example, in the case where the differences S1 and S2 are both greatly protruded from a predetermined value or less in STEP5 described above, as in the latter case, the current value is increased at a plurality of stages at a time, thereby improving work efficiency (repetition count). (Reduction) may be achieved.

First, the integrated control unit 101 issues a command to set the rotor to the initial position according to the conditions [rotation direction: forward rotation] and [current values of A and B phase currents: I ₀ + ΔI]. Output to. Accordingly, theoretically, the rotor rotates in the positive direction and moves to the initial position, and the electrical angle is initialized (STEP 8). Next, the integrated control unit 101 electrically issues a command to rotate the rotor 360 ° (theoretical rotation angle θ1) according to the conditions of [rotation direction: forward rotation] and [current values of A and B phase currents: I ₀ + ΔI]. Output to the angle initialization operation control unit 107. This theoretically causes the rotor to rotate 360 ° in the positive direction (STEP 9).

Next, the integrated control unit 101 gives a command to set the rotor to the initial position according to the conditions [rotation direction: reverse rotation] and [current values of A and B phase currents: I ₀ + ΔI]. It outputs to 107. Accordingly, theoretically, the rotor rotates in the reverse direction and moves to the initial position, and the electrical angle is initialized (STEP 10). Next, the integrated control unit 101 electrically issues a command to rotate the rotor 360 ° (theoretical rotation angle θ2) according to the conditions [rotation direction: reverse rotation] and [current values of A and B phase currents: I ₀ + ΔI]. Output to the angle initialization operation control unit 107. This theoretically causes the rotor to rotate 360 ° in the reverse direction (STEP 11).

  Next, the initialization motion creation rejection determination unit 114 obtains a difference S1 between the actually measured rotation angle θ1 ′ output in STEP9 output from the rotation angle calculation unit 113 and the theoretical rotation angle θ1 output from the integrated control unit 101. Further, the initialization motion creation rejection determination unit 114 obtains a difference S2 between the actually measured rotation angle θ2 ′ output in STEP11 output from the rotation angle calculation unit 113 and the theoretical rotation angle θ2 output from the integrated control unit 101. Then, the initialization motion creation rejection determination unit 114 determines that the initialization operation is normal if both the differences S1 and S2 are within the predetermined range, and one of the differences S1 and S2 must be within the predetermined range. In this case, it is determined that the initialization operation is abnormal (STEP 12).

Next, when the initialization motion creation rejection determination unit 114 determines that the initialization operation is normal, the integrated control unit 101 sets the current value (I ₀ + nΔI) at the time when the initialization operation is determined normal as the reference current intensity. The process proceeds to STEP 6 described above.
On the other hand, when the initialization motion creation rejection determination unit 114 determines that the initialization operation is abnormal, the integrated control unit 101 first determines that the current value (I ₀ + nΔI) when the initialization operation is abnormally detected immediately before is the current upper limit value. It is determined whether or not it is less than I _max (STEP 13). Then, when the current value immediately before is less than the maximum current _{I max} is increased a current value one step, again implementing STEP8～12. Conversely, if the current value immediately before is the maximum current I _max or more, it determines that the stepping motor 3 is faulty, it notifies this fact to the operator (STEP 14). The notification method is not particularly limited, and examples thereof include warning sound, warning lighting, and display on an operation screen.

  The control method of the control device 1 (the stepping motor control method of the present invention) has been described above. According to such a control device 1, it is necessary to drive the stepping motor 3, and a smaller current value can be reliably detected, and the normal driving of the stepping motor 3 is based on the current value. Therefore, it is possible to realize power-saving driving of the stepping motor 3 while assuring reliable driving of the stepping motor 3. Specifically, the mechanical characteristics (rotational resistance, etc.) of the stepping motor 3 change due to the use environment of the stepping motor 3, aging deterioration, and the like. For example, the higher the environmental temperature, the softer the grease and the lower the rotational resistance, and the longer the use time, the lower the grease and the higher the rotational resistance. Therefore, the minimum current value that can drive the stepping motor 3 changes. Therefore, by performing the above-described operation confirmation mode before the normal drive mode and detecting a smaller current value that can drive the current stepping motor 3, the stepping motor 3 is not affected by the use environment or aging deterioration. Can be reliably driven with smaller electric power.

In particular, in the present embodiment, in the operation confirmation mode, an upper limit value I _max is set for the current value, and when the current value exceeds the upper limit value I _max , it is determined that the stepping motor 3 has failed and is notified. It is configured as follows. With such a configuration, the abnormality of the stepping motor 3 can be reliably detected, and the stepping motor 3 can be quickly repaired and replaced.

  In the present embodiment, the rotor is positioned at the initial position as in STEP 1 and 3. Here, the initial position means a position where the next normal driving (normal driving mode) of the stepping motor 3 is started. That is, it is a position when the next driving is started after the operation confirmation mode ends. Starting from such an initial position, it is possible to start the next normal driving of the stepping motor 3 more reliably by determining whether or not the initialization operation of the stepping motor 3 is successful as in STEPs 2 and 4. However, in STEP 1, 3, etc., the position of the rotor is not limited to the initial position, and may be an arbitrary position different from the initial position. Further, the stop position of the rotor at STEP 1 and the stop position of the rotor at STEP 3 may be the same or different.

  Further, in this embodiment, when the success or failure of the initialization operation of the stepping motor 3 is determined in STEP 2, 4, etc., the theoretical rotation angle of the rotor is set to 360 °. That is, it is set so that it returns to the original position (initial position) even if the rotor rotates once. In this way, by rotating the rotor one or more times, it is possible to take into account the difference in rotational resistance over the entire circumference of the rotor in the rotational direction, so that the reference current intensity can be set more accurately. If the theoretical rotation angle of the rotor is 360 °, the rotor theoretically returns to the initial position. Therefore, for example, STEP3 can be omitted after STEP2 and STEP4 can be performed. Therefore, it is possible to shorten the time for performing the operation confirmation mode (a similar effect can be achieved if the rotation angle is an integer (except 0) of 360 °). However, the theoretical rotation angle is not limited to 360 °, and may be any angle such as 90 °, 180 °, 270 °, and the like.

  In this embodiment, the control gain is changed in STEP 6 according to the set reference current intensity. Thus, by changing the control gain in accordance with the reference current intensity, the stepping motor 3 can be reliably driven with smaller electric power. Examples of the control gain to be changed include the above-described position proportional gain, angular velocity proportional gain, angular velocity integral gain, and the like. Among these, it is preferable to change the angular velocity proportional gain. Thereby, the effect mentioned above can be exhibited more. Further, when changing the angular velocity proportional gain, it is preferable to change the angular velocity proportional gain in proportion to the increase amount (decrease amount) of the reference current intensity. That is, when the reference current intensity is doubled from the previous value, the angular velocity proportional gain is doubled from the previous value, and when the reference current intensity is four times from the previous value, the angular velocity proportional gain is also increased from the previous value. It is preferable to make it 4 times.

  Here, the timing of performing the operation confirmation mode is not particularly limited, but it is preferable to perform the operation confirmation mode every time before starting the driving of the stepping motor 3 in the normal driving mode (immediately before). Thereby, since the control gain can be appropriately changed so as to follow the change in the mechanical characteristics of the stepping motor 3, it is possible to ensure accurate driving of the stepping motor 3 every time. However, the operation confirmation mode may be performed, for example, when the use environment of the stepping motor 3 has changed from the previous normal drive mode or when a certain time (one day, one month, etc.) has passed.

In the second and subsequent operation confirmation modes, the initial current value I ₀ may be used as the current value to be set first in STEPs ₁ to 4 or the previous value (that is, the current confirmation value was set in the previous operation confirmation mode). Current reference value) may be used. Also, the current initial value I ₀ may be a value that is not the previous value.
When the current initial value I ₀ is used as the current value to be set first, the current value is increased in order from the current minimum value, so that the optimum reference current intensity can be reliably detected. For example, use environment or change of the stepping motor 3 from the previous operation confirmation mode, if or not to drive the stepping motor 3 for an extended period, it is preferable to use a current initial value I _0.

On the other hand, when the previous value is used as the current value to be set first, the execution time of the operation confirmation mode can be shortened because the previous value is taken into consideration. For example, if the usage environment of the stepping motor 3 has not changed from the previous operation confirmation mode or if the time has not passed since the driving of the stepping motor 3 in the previous normal driving mode, the previous value is set. It is preferable to use it. Note that if the previous value is a value relatively close to the upper limit value I _max as the current value to be set initially, may be used a lower current value than the previous value. According to such a method, the mechanical malfunction of the stepping motor 3 can be confirmed. That is, in the previous time, it can be confirmed whether the reference current intensity has happened to be high or whether the reference current intensity has increased due to aged deterioration.

2. Robot Next, a robot (the robot of the present invention) to which the control device 1 and the stepping motor 3 described above are applied will be described. As examples of the robot, a horizontal articulated robot and a vertical articulated robot are shown below, but the robot is not limited to these, and may be a double-armed robot or other other-axis robot.

The robot 7 shown in FIG. 3 is a horizontal articulated robot. Such a robot 7 has a base 71, a first arm 72, a second arm 73, a work head 74, and an end effector 75.
The base 71 is fixed to a floor surface (not shown) with bolts or the like, for example. A first arm 72 is connected to the upper end of the base 71. The first arm 72 is rotatable around a rotation axis along the vertical direction with respect to the base 71. In the base 71, a stepping motor 3A for rotating the first arm 72, an encoder 2A connected to the stepping motor 3A, and a control device 1A for controlling the stepping motor 3A are installed.

  A second arm 73 is connected to the tip of the first arm 72. The second arm 73 is rotatable about a rotation axis along the vertical direction with respect to the first arm 72. In the second arm 73, a stepping motor 3B for rotating the second arm 73, an encoder 2B connected to the stepping motor 3B, and a control device 1B for controlling the stepping motor 3B are installed.

  A work head 74 is disposed at the tip of the second arm 73. The working head 74 includes a spline nut 741 and a ball screw nut 742 that are coaxially disposed at the tip of the second arm 73, and a spline shaft 743 inserted through the spline nut 741 and the ball screw nut 742. The spline shaft 743 can rotate about its axis with respect to the second arm 73 and can move (elevate) in the vertical direction.

In the second arm 73, a stepping motor 3C, an encoder 2C connected to the stepping motor 3C and a control device 1C for controlling the stepping motor 3C, a stepping motor 3D, an encoder 2D connected to the stepping motor 3D, and a stepping motor A control device 1D that performs 3D control is disposed. The driving force of the stepping motor 3C is transmitted to the spline nut 741 by a driving force transmission mechanism (not shown), and when the spline nut 741 rotates forward and backward, the spline shaft 743 rotates forward and backward around the rotation axis along the vertical direction. On the other hand, the driving force of the stepping motor 3D is transmitted to the ball screw nut 742 by a driving force transmission mechanism (not shown), and when the ball screw nut 742 rotates forward and backward, the spline shaft 743 moves up and down.
An end effector 75 is connected to the tip (lower end) of the spline shaft 743. The end effector 75 is not particularly limited, and examples thereof include one that grips the object to be conveyed and one that processes the object to be processed.

The robot 8 shown in FIG. 4 is a vertical articulated (six axis) robot. Such a robot 8 includes a base 81, four arms 82, 83, 84, 85, and a wrist 86, which are sequentially connected.
The base 81 is fixed to a floor surface (not shown) with bolts or the like, for example. The arm 82 is connected to the upper end portion of the base 81 in a posture inclined with respect to the horizontal direction, and the arm 82 can rotate about a rotation axis along the vertical direction with respect to the base 81. It has become. In the base 81, a stepping motor 3E that rotates the arm 82, an encoder 2E connected to the stepping motor 3E, and a control device 1E that controls the stepping motor 3E are arranged.

  An arm 83 is connected to the distal end portion of the arm 82, and the arm 83 is rotatable about a rotation axis along the horizontal direction with respect to the arm 82. Also, in the arm 83, a stepping motor 3F that rotates the arm 83 with respect to the arm 82, an encoder 2F that is connected to the stepping motor 3F, and a control device 1F that controls the stepping motor 3F are installed.

  An arm 84 is connected to the tip of the arm 83, and the arm 84 can rotate about a rotation axis along the horizontal direction with respect to the arm 83. Also, in the arm 84, a stepping motor 3G that rotates the arm 84 with respect to the arm 83, an encoder 2G connected to the stepping motor 3G, and a control device 1G that controls the stepping motor 3G are installed.

  An arm 85 is connected to the distal end portion of the arm 84, and the arm 85 can be rotated around a rotation axis along the central axis of the arm 84 with respect to the arm 84. Further, in the arm 85, a stepping motor 3H that rotates the arm 85 with respect to the arm 84, an encoder 2H that is connected to the stepping motor 3H, and a control device 1H that controls the stepping motor 3H are installed.

  A wrist 86 is connected to the tip of the arm 85. The wrist 86 includes a ring-shaped support ring 861 connected to the arm 85, and a cylindrical wrist body 862 supported at the tip of the support ring 861. The front end surface of the wrist body 862 is a flat surface, and is, for example, a mounting surface on which a manipulator that holds a precision device such as a wristwatch is mounted.

The support ring 861 can be rotated around a rotation axis along the horizontal direction with respect to the arm 85. The wrist main body 862 is rotatable about a rotation axis along the central axis of the wrist main body 862 with respect to the support ring 861. Further, in the arm 85, there are a stepping motor 3I for rotating the support ring 861 with respect to the arm 85, an encoder 2I connected to the stepping motor 3I, a control device 1I for controlling the stepping motor 3I, and a wrist body 862. A stepping motor 3J that rotates with respect to the support ring 861, an encoder 2J connected to the stepping motor 3J, and a control device 1J that controls the stepping motor 3J are arranged. The driving forces of the stepping motors 3I and 3J are transmitted to the support ring 861 and the wrist body 862 by a driving force transmission mechanism (not shown), respectively.
As described above, the stepping motor control method, the control device, and the robot have been described based on the illustrated embodiment. However, the present invention is not limited to this, and the configuration of each unit may be any arbitrary function having the same function. It can be replaced with that of the configuration. In addition, any other component may be added to the present invention.

  DESCRIPTION OF SYMBOLS 1, 1A-1J ... Control apparatus 101 ... Integrated control part 102 ... Subtractor 103 ... Position control part 104 ... Subtractor 105 ... Angular velocity control part 106 ... Inverse park conversion part 107 ... Electric angle initialization operation control part 108 ... Control mode Switching unit 109 ... A phase current control unit 110 ... B phase current control unit 111 ... Electrical angle calculation unit 112 ... Angular velocity calculation unit 113 ... Rotation angle calculation unit 114 ... Initialization motion creation rejection determination unit 2, 2A-2J ... Encoder 3, 3A to 3J: Stepping motor 7: Robot 71 ... Base 72 ... Arm 73 ... Arm 74 ... Working head 741 ... Spline nut 742 ... Ball screw nut 743 ... Spline shaft 75 ... End effector 8 ... Robot 81 ... Base 82-85 ... Arm 86 ... List 861 ... Support ring 862 ... Squirrel A body

Claims (8)

A stepping motor control method to which a detector for detecting a rotation angle of a rotor is connected,
A signal for rotating the rotor by a predetermined angle is applied to the stepping motor, a difference between the rotation angle of the rotor detected by the detector and the predetermined angle is detected, and the difference becomes a predetermined value or less. Until the first difference detection step to increase the intensity of the signal,
A stepping motor control method, wherein the signal strength applied to the stepping motor is the strength of the signal when the difference becomes equal to or less than the predetermined value. In the difference detection step, a signal for rotating the rotor by a predetermined angle in a direction opposite to the rotation direction is applied to the stepping motor, and the rotation angle of the rotor detected by the detector and the predetermined rotation are detected. A second difference detecting step of detecting a difference from an angle and increasing the intensity of the signal until the difference becomes a predetermined value or less;
2. The stepping motor control method according to claim 1, wherein the intensity of the signal when the difference becomes equal to or less than the predetermined value is a signal intensity applied to the stepping motor. An upper limit is set for the intensity of the signal,
3. The stepping motor control method according to claim 1, wherein when the difference is not less than or equal to the predetermined value even when the signal of the upper limit value is applied, the stepping motor is notified that the stepping motor is in an abnormal state.   4. The stepping motor control according to claim 1, wherein the initial position for rotating the predetermined angle is a position when starting the next driving after applying the stepping motor with the signal intensity. 5. Method.   5. The stepping motor control method according to claim 1, wherein the predetermined angle is an integer multiple of 360 ° (excluding 0). 6.   6. The stepping motor control method according to claim 1, wherein a control gain of the stepping motor is changed based on the reference signal strength. A control device for a stepping motor to which a detector for detecting a rotation angle of a rotor is connected,
An application unit that applies a signal for rotating the rotor by a predetermined angle; a detection unit that detects a difference between the rotation angle of the rotor detected by the detector and the predetermined angle; and the difference is a predetermined value or less. A control unit that increases the signal strength until the difference becomes equal to or less than the predetermined value, and sets the signal strength to be applied to the stepping motor. . The base,
An arm connected to the base and rotatable relative to the base;
A stepping motor for rotating the arm with respect to the base;
A control device according to claim 7, which controls driving of the stepping motor.

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