JP2009268218A - Multi-shaft motor control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reconcile high control performance and low cost by enabling motor control in high speed and high acceleration with a multi-shaft even in case that the arithmetic capacity of CPU is not high. <P>SOLUTION: A multi-shaft motor control system, which performs control calculation of a plurality of motors 10 with one CPU 42, is equipped with a speed zone discriminator (a speed zone detector 42F and a position command operation part 50), which discriminates between a zone other than fall of speed and a fall zone, an compensation amount setter (a compensation amount operation part 42G and a compensation amount memory 42J), which sets the amount of current command compensation, and a current command compensator (a switch part 42H and a variable gain amplifier 42K), which adds the amount of current command compensation to a current command in the zone other than the fall of speed and does not add the amount of current command compensation to the current command in the fall zone of speed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a multi-axis motor control system used for industrial sewing machines, electronic component mounting apparatuses, machine tools, and the like.

  Motors are used to drive various industrial devices such as industrial sewing machines, chip mounters and machine tools. In particular, in recent years, the number of motor shafts used in the apparatus has been increasing for the purpose of improving efficiency and productivity.

  However, as the number of motor shafts increases, it is not preferable that the apparatus becomes larger or the cost increases. Therefore, as described in Patent Document 1, as illustrated in FIG. 1, controllers such as a controller and a driver that drive a motor shaft are combined so that a plurality of motor shafts can be controlled by one unit. In general, a multi-axis control system is used to reduce the size and cost. In the figure, 10 is a motor, 12 is an encoder provided for each motor, 20 is a motor drive unit including a power unit 22 and an I / F 24, 30 is a communication line, 40 is a CPU 42, a memory 44, and an I / F 46. , 48 includes a multi-axis controller.

JP 2006-262636 A

  In this multi-axis motor control system, a single CPU 42 performs control calculations for a plurality of (for example, 12 axes) motor axes. However, if the CPU performance is insufficient, the motor control gain is increased. In other words, the motor characteristics cannot be obtained sufficiently. That is, if the calculation speed of the current loop and the speed loop as shown in FIG. 2 is not sufficiently high, oscillation will occur when the control gain is raised high, so the control gain is limited to a low value, and the frequency As a result, the characteristics are suppressed. Specifically, in order to move the control target from the current position to the target position, as illustrated in FIG. 3, when trying to perform PTP driving at high speed and high acceleration / deceleration, the target speed is not reached, This causes a problem that the acceleration / deceleration cannot be obtained.

  In FIG. 2, 42A is a subtractor that calculates the difference between the position command and the position feedback signal from the encoder 12, 42B is a position deviation control calculation unit that calculates a speed command according to the output of the subtractor 42A, and 42C is A speed calculation unit 42D that calculates a speed from the output of the encoder 12 includes a subtractor 42E that calculates a difference between the speed command calculated by the position deviation control calculation unit 42B and the speed feedback signal calculated by the speed calculation unit 42C. Is a speed deviation control calculation unit that calculates a current command given to the power unit 22 by the output of the subtractor 42D.

  Furthermore, when the motor rotates at a high speed, the back electromotive voltage of the motor illustrated in FIG. 4 becomes a serious problem. That is, the voltage applied to the motor decreases due to the counter electromotive voltage generated when the motor rotates. This can be regarded in the same manner as the control gain decreasing according to the motor speed. That is, the control gain decreases at the time of rising speed toward the high speed (acceleration section I in FIG. 3) and at the constant speed driving at high speed (constant speed section II in FIG. 3). The control gain increases at the fall of the traveling speed (deceleration section III in FIG. 3).

  When the motor is driven by the PTP operation, the deviation between the position command and the actual position is largely accumulated in the acceleration section I and the constant speed section II due to the decrease in gain. On the other hand, when the gain is increased in the deceleration zone III, the motor current flows suddenly and an overcurrent error occurs because the deviation accumulated between the acceleration zone I and the constant speed zone II is converged at once. Problems arise.

  In order to solve this, it is necessary to increase the control gain. However, since the control gain is limited by the calculation speed of the CPU as described above, it is necessary to use a CPU having high calculation performance. However, in general, the CPU price increases as the computing performance increases.

  Although it is ideal to obtain high control performance using a cheap CPU, it has been difficult to achieve both high control performance and low cost in the conventional method.

  The present invention is for solving the above-described conventional problems, and an object thereof is to achieve both high control performance and low cost.

The present invention relates to a multi-axis motor control system in which a single CPU performs a control calculation of a plurality of motors, a speed section identifying means for identifying a section other than a speed falling and a falling section;
Compensation amount setting means for setting the current command compensation corresponding to the gain increase, and the current command compensation is added to the current command in the sections other than the speed falling, and the current command is used in the current command in the speed falling section. The above-mentioned problem is solved by providing a current command compensation means that does not add compensation.

  Here, the current command compensation means can subtract a current command compensation amount corresponding to an increase in gain accumulated in a section other than the speed fall in the speed fall section.

  In the present invention, in a control system for a multi-axis motor, in a section other than the speed fall (for example, acceleration section I and constant speed section II), a current command compensation equivalent to the gain reduction is added to the current command. . On the other hand, in the speed fall section (deceleration section III), the current command compensation is not added, or the current command compensation corresponding to the gain increase accumulated in the sections other than the speed fall from the current command Subtract minutes.

  As a result, since a substantially high control gain can be maintained in a section other than the falling, multi-axis control can be performed at high speed and high acceleration / deceleration as instructed. In addition, since a large deviation does not accumulate in a section other than the falling edge, it is possible to prevent a current error from occurring in the falling section.

  Accordingly, even when the CPU's computing power is not high, it is possible to drive the motor with multiple axes at high speed and high acceleration / deceleration, and it is possible to achieve both high control performance and low cost.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 5 is a block diagram showing the overall configuration of the first embodiment of the present invention. In the figure, only one motor axis is shown for explanation.

  Positioning control of the motor shaft is performed according to a position command signal output from a position command unit (not shown).

  Specifically, the subtraction unit 42A compares the position feedback value output from the encoder 12 attached to the motor end with the position command value, and calculates the position deviation. Based on this position deviation, a speed command value is calculated by the position deviation control calculation unit 42B. Further, a deviation between the speed command value and the speed feedback value calculated by the speed calculation unit 42C from the output value of the encoder 12 is calculated by the subtractor 42D. Based on this deviation, the current command is calculated by the speed deviation control calculation unit 42E. Calculate the value. The calculated current command value is output to a power unit (for example, a servo amplifier) 22, and a motor current is given to the motor 10 to drive the shaft.

  When calculating the speed command value and the current command value, the control gain is multiplied. Increasing the control gain high affects the control performance, but is limited because it is affected by the rigidity of the load, CPU computing power, sensor resolution, data communication speed, and the like. When the control gain is low, it is difficult to perform driving at high speed and high acceleration / deceleration and positioning and setting at high speed and high accuracy.

  As an example, the case of positioning driving at high speed and high acceleration / deceleration is taken up.

When the motor rotates, a counter electromotive voltage Ei is generated. As the counter electromotive voltage Ei is shown in FIG. 4, in proportion to the rotation speed omega _r of the motor can be expressed by the following equation.

E _i = K _e × ω _r (1)
(K _e : Back electromotive force constant)

  This means that the voltage applied to the motor becomes lower by the counter electromotive voltage in proportion to the rotational speed of the motor. In other words, since the actual current does not flow in response to the current command, when viewed from the control gain, it can be considered that the control gain decreases and decreases as the motor speed increases. .

  When PTP driving is performed in such a state, the decrease in the control gain increases in the acceleration section I and the constant speed section II, so that the actual current does not flow with respect to the current command, and the position deviation is largely accumulated. On the other hand, when the drive of the motor is shifted to the deceleration zone III, the decrease in control gain is eliminated and the gain is increased as the speed is reduced, so that a phenomenon occurs in which a current flows suddenly to converge the accumulated deviation.

  A motor control system generally has a function of setting a maximum current value for protection and stopping the motor as an overcurrent error when a current exceeding the set value flows. As a result, an overcurrent error occurs in the deceleration zone III, causing a problem that the motor stops.

  In order to solve this problem, it is necessary to increase the control gain in the acceleration section I and the constant speed section II. Therefore, in the present embodiment, compensation is performed by adding a command corresponding to the gain reduction to the current command value in the acceleration section I and the constant speed section II.

  Specifically, the speed section detector 42F monitors the speed and detects the acceleration section I and the constant speed section II. A section where the speed is increasing is determined as an acceleration section I, a section where the speed is constant is determined as a constant speed section II, and a section where the speed is decreasing is determined as a deceleration section III.

When the acceleration section I and the constant speed section II are detected, the switch section 42H is turned on, and the current command compensation amount ΔI _cmd calculated by the compensation amount calculation section 42G is added to the current command I _cmd by the accelerator 42I. The current command compensation amount ΔI _cmd is proportional to the motor speed,
ΔI _cmd = K _comp × ω _r (2)
(K _comp : current command compensation coefficient)
It becomes.

  The counter electromotive voltage Ei is expressed by the equation (1).

or,
_{V a -E i = L a (} di a / dt) + R a × i a ... (3)
(V _a : Motor applied voltage, i _a : Motor current, L _a : Motor inductance, R _a : Motor resistance)
Therefore, the current command compensation amount ΔI _cmd for compensating the counter electromotive voltage E _i is obtained from the equations (1) to (3):
_{ΔI cmd = K e / (L} a s + R a) × ω r ... (4)
It can be.

In other words, you do it by adding the current command compensation amount to the current command as _{K comp = K e / (L} a s + R a), it is possible to compensate for eroded gain by the counter electromotive voltage.

  Since the decrease in gain at high speed becomes a problem in the acceleration section I and the constant speed section II, the switch section 42H is turned off in the deceleration section III.

  By the above compensation, since a substantially high control gain can be maintained in the acceleration section I and the constant speed section II, multi-axis control with high speed and high acceleration / deceleration as commanded becomes possible. Further, since a large deviation does not accumulate between the acceleration section I and the constant speed section II, it is possible to prevent a current error from occurring in the deceleration section III.

  In this embodiment, the case where the rotation direction of the motor is the forward direction is taken as an example. However, when the rotation direction of the motor is the reverse direction, it can be read as the output direction of each signal is reversed. It ’s fine.

  In the embodiment, the speed section detection unit 42F is provided to detect the sections I, II, and III. However, as in the second embodiment shown in FIG. It is also possible to switch on / off for current command compensation by outputting II and III switching signals. Further, the constant speed section II may not be required for short-distance movement.

Further, in the embodiment has been turned off the current command compensation amount in the deceleration zone III, it is also possible to'll subtracting the current command compensation amount [Delta] I _cmd.

Further, in the above embodiment uses the _{K comp = K e / (L} a s + R a) as a current command compensation coefficient, for performing the compensation which has been subjected to optimum adjustment for each motor, and any constant K _comp It is also possible to do. It is also possible to use different K _comps in the sections I, II and III.

In the above embodiment, a linear function proportional to the motor speed represented by the equation ΔI _cmd = K _comp × ω _r is used as the current command compensation, but as in the third embodiment shown in FIG. It is also possible to store or set the current command compensation determined based on the data measured in advance in the replenishment amount storage unit 42J and perform more complicated correction.

  In the above embodiment, the switch unit 42H is used to perform on / off switching. However, as in the fourth embodiment shown in FIG. 8, the gain is changed to, for example, 0 to 1 times instead of the switch unit. It is also possible to use a variable gain amplifier 42K that can

  In addition, as in the fifth embodiment shown in FIG. 9, the disturbance observer 42L is provided in the embodiment, so that robust control that is not affected by friction, parameter fluctuations, or the like can be performed.

  In addition, the calculation in each control unit can apply integral control, differential control, etc. in addition to proportional control.

  Further, not only a rotary motor but also a linear motor can be applied.

  Moreover, although the said embodiment is a structure which made the multi-axis controller part and the motor drive part a separate block, it is also possible to integrate. Also, it is possible to employ a configuration in which only the position loop and the velocity loop are calculated by one CPU and the current loop is calculated by another CPU, and the configuration of the embodiment is not necessarily limited.

Block diagram showing a configuration example of a conventional multi-axis motor control system The figure which similarly shows an example of a motor control loop The figure which shows the example of the change state of the motor speed in PTP drive Diagram showing an example of the relationship between motor speed and back electromotive force The block diagram which shows 1st Embodiment of this invention. Similarly, a block diagram showing the second embodiment Similarly, a block diagram showing the third embodiment Similarly, a block diagram showing the fourth embodiment Similarly, a block diagram showing a fifth embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Motor 12 ... Encoder 20 ... Motor drive part 22 ... Power part 40 ... Multi-axis controller 42 ... CPU
42B ... Position deviation control calculation unit 42C ... Speed calculation unit 42E ... Speed deviation control calculation unit 42F ... Speed section detection unit 42G ... Compensation amount calculation unit 42H ... Switch unit 42J ... Compensation amount storage unit 42K ... Variable gain amplifier 50 ... Position command Calculation unit

Claims (2)

In a multi-axis motor control system in which a single CPU performs a control operation of a plurality of motors,
Speed section identifying means for identifying a section other than the speed falling and a falling section;
Compensation amount setting means for setting a current command compensation amount corresponding to an increase in gain;
Current command compensation means for adding the current command compensation to the current command in a section other than the speed falling, and not adding the current command compensation to the current command in the speed falling section;
A multi-axis motor control system comprising:   2. The current command compensation means subtracts a current command compensation amount corresponding to an increase in gain accumulated in a section other than the speed fall in the speed fall section. Axis motor control system.

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