JP2012235612A - Dc motor drive control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC motor drive control device which can appropriately determine whether abnormality exists, even when its drive characteristics have degraded because of ambient environment fluctuations or aging deterioration, etc.SOLUTION: In a DC motor drive control device of the present invention, an average value p/N of drive voltage at the time of normal drive obtained by the (n-1) time is used to determine whether or not a drive voltage control value p(n) is abnormal (step B9). When the relationship |p(n)|≤α|p/N| is not satisfied, a possibility that abnormality might have occurred is assumed, and lock counts kare integrated (step B11). When the relationship |p(n)|≤α|p/N| is satisfied, kis reset to 0, and a drive voltage integrated value pand normal drive counts N are updated (step B12). If the determination in step B9 is not satisfied Ktimes in succession, occurrence of abnormality is assumed, and a motor drive flag is turned off, whereby motor drive is terminated (steps B13 and B14).

Description

  The present invention relates to a drive controller for a direct current motor that controls the drive of a direct current (DC) motor. The present invention can be suitably used for various analyzers such as a spectrophotometer.

  In a spectrophotometer, various driving mechanisms are used, for example, a mechanism for rotating a diffraction grating to perform wavelength scanning, a mechanism for automatically replacing a sample cell inserted in an optical path, and a method for exchanging a sample. ing. These drive mechanisms include a drive source such as a direct current motor or a stepping motor, an angle measurement means such as a rotary encoder, or a position measurement means such as a photo interrupter or a limit sensor such as a limit switch.

In a DC motor, since the applied drive voltage is proportional to the no-load rotational speed of the motor, the rotational speed can be controlled by adjusting the drive voltage. Patent Document 1 describes an example in which a direct current motor and a pulse encoder are used as a drive mechanism in an autosampler used in a chromatographic analyzer or the like. Here, the pulse encoder is attached to the rotating shaft of the DC motor, and its output is periodically fed back to the central processing unit (CPU). The CPU calculates the moving speed and the absolute position of the controlled object (movable part) based on the output from the pulse encoder, and controls the drive voltage so that each becomes the control target value.
Such a drive mechanism in which a DC motor and a pulse encoder are combined is often used in a spectrophotometer. For example, the sample holding drive unit and the wiping mechanism drive unit of Patent Document 2, the wiping unit and the pressing unit of Patent Document 3 are used. used.

Japanese Patent Laid-Open No. 10-90279 International Publication WO2008 / 044329 International Publication WO2007 / 113895 Publication

  In feedback control using a DC motor as a drive source, when the actual speed of the movable part falls below the target speed, the drive voltage is increased to make the actual speed follow the target speed. However, if the measured speed decreases due to the movable part reaching the movable limit or coming into contact with a foreign object, it acts to apply a larger driving voltage in an attempt to approach the target speed. May be damaged. In order to prevent such a situation, it is necessary to make some abnormality determination when performing feedback control.

For the abnormality determination, there may be used a time-out type determination method that determines whether the moving time of the movable part to a predetermined position (or within a predetermined range) is within an allowable range. However, in the determination of the timeout method, it can not be detected that an abnormality has occurred at the present time even though it has been detected that an abnormality has occurred in the past. Therefore, even if an abnormal state in which the drive voltage becomes high continues, the operation cannot be interrupted, resulting in damage to each part of the apparatus including the drive mechanism.
As a method for solving such a problem of the timeout method, the actual measurement speed of the movable part and / or the drive voltage (or drive current) applied to the DC motor, which is acquired or calculated periodically by the control part, are continuously repeated a certain number of times. A method of determining that an abnormality is outside the allowable range is adopted.

  However, when the characteristics of the drive mechanism are different due to individual differences between devices or changes in the surrounding environment, the optimum value of the drive voltage applied to the DC motor also differs. This optimum value also depends on the change in drive characteristics due to aging. It is difficult to obtain an optimum criterion value in consideration of individual differences, ambient environment fluctuations, and aging degradation of these devices.

  The problem to be solved by the present invention is to provide a drive control device for a direct current motor that can appropriately perform abnormality determination even if drive characteristics change.

The DC motor drive control device according to the first aspect of the present invention, which has been made to solve the above problems,
Conversion means for converting the rotational torque of the rotating shaft of the DC motor into a predetermined motion of the drive target, drive target measurement means for acquiring information including the position of the drive target, and information obtained by the drive target measurement means A DC motor drive control device comprising: a control means for periodically calculating a drive voltage to be applied to the DC motor based on the control value and controlling the drive voltage based on the calculated value;
The control means performs abnormality determination of the drive voltage value calculated this time, using an average of drive voltage values during normal driving calculated within a predetermined period as a determination criterion.

  The predetermined period is preferably from the time when the control to the DC motor is started to the time immediately before the abnormality determination is performed. Thereby, the determination reference can be updated during the control, and the abnormality determination more reflecting the drive characteristics can be performed.

  In the above invention, the abnormality determination is performed using the calculated value of the drive voltage. However, since the drive current is proportional to the torque in the DC motor, the drive current supplied to the DC motor is directly measured as shown below, Abnormality determination can also be performed using the measured value.

That is, the DC motor drive control device according to the second aspect of the present invention, which has been made to solve the above problems,
Conversion means for converting the rotational torque of the rotating shaft of the DC motor into a predetermined motion of the drive target, drive target measurement means for acquiring information including the position of the drive target, and information obtained by the drive target measurement means And a control means for controlling a drive voltage applied to the DC motor periodically, in a DC motor drive control device,
Drive current measuring means for measuring the drive current supplied to the DC motor;
The control means performs an abnormality determination of the drive current value measured this time, using an average of the drive current values during normal driving measured within a predetermined period as a determination criterion.

  In the DC motor drive control apparatus according to the present invention, the determination criterion is given based on the calculated value of the drive voltage or the actual value (measured value) of the drive current to be subjected to feedback control, and therefore the drive mechanism is actually used. It is possible to perform abnormality determination depending on the characteristics at the time. Accordingly, it is possible to cope with individual differences of devices including the drive mechanism and changes in the surrounding environment, and even if the drive characteristics change due to deterioration over time, it can be used appropriately over a long period of time.

1 is a schematic configuration diagram showing a drive mechanism provided with a first embodiment of a drive control apparatus according to the present invention. The flowchart which shows operation | movement of the control part of the drive control apparatus of 1st Example. The flowchart which shows operation | movement of the control part of the drive control apparatus of 1st Example. The flowchart which shows operation | movement of the control part of the drive control apparatus of 1st Example. The schematic block diagram which shows the drive mechanism provided with 2nd Example of the drive control apparatus which concerns on this invention. The flowchart which shows operation | movement of the control part of the drive control apparatus of 2nd Example. The flowchart which shows operation | movement of the control part of the drive control apparatus of 2nd Example. The flowchart which shows operation | movement of the control part of the drive control apparatus of 2nd Example.

  FIG. 1 shows a schematic configuration of a drive mechanism including a first embodiment of a DC motor drive control apparatus according to the present invention. The drive mechanism includes a CPU (control unit) 1, a drive voltage generation unit 2, a DC motor 3, a drive target measurement unit 4, a conversion unit 5, and a movable unit 6 that is a drive target.

  Here, the conversion unit 5 is composed of various mechanical elements such as a multi-stage gear and a ball screw, and these are connected to the rotation shaft of the DC motor 3 so that the rotational torque of the DC motor 3 is transferred to the movable unit 6. Convert to a predetermined motion.

  The drive target measurement unit 4 of the present embodiment includes a pulse encoder 11 and an up / down counter 12. Here, the pulse encoder 11 is attached to the rotating shaft of the DC motor 3 and outputs two rectangular wave signals having different phases to the up / down counter 12. The up / down counter 12 outputs a count value proportional to the rotation angle of the rotating shaft of the DC motor 3 based on the input signal from the pulse encoder 11. The CPU 1 can calculate the position of the movable unit 6 based on the output value (count value) of the up / down counter and the characteristics of the ball screw, gears, etc. in the conversion unit 5.

  In addition, the drive mechanism of FIG. 1 performs these controls (namely, control of a motor drive voltage) indirectly detecting the position and speed of the movable part 6 from the rotation angle and rotation speed of the rotating shaft of the DC motor 3. Although it is a mechanism using so-called semi-closed control, full-closed control in which the direct current motor 3 is controlled by directly measuring the position and speed of the movable portion 6 can also be used.

The CPU 1 calculates the position and speed of the movable unit 6 using the count value input from the up / down counter 12, and periodically supplies the drive voltage generation unit 2 with the control target value given in advance. Interrupt processing is performed to control the drive voltage applied to the DC motor 3. Various control methods of feedback control can be used for controlling the drive voltage. In this embodiment, the drive voltage is controlled by PID control represented by the following equation.
p _set (n) = g _p × (v _set -v _act (n)) + g _i × Σ _{j = 0 to n} (v _set -v _act (j))
+ g _d × (v _act (n-1) -v _act (n))… (1)
Here, v _set , g _p , g _i , and g _d are a target speed of the movable portion 6, a P-term gain, an I-term gain, and a D-term gain, which are set values given in advance. Further, v _act is an actual measurement speed of the movable unit 6 determined from a measurement value of the drive target measurement unit 4. In the PID control, the control value p _set (n) of the drive voltage in the n-th interrupt process is calculated from the equation (1) based on these set values and measured values.

The actually measured speed v _act (n) of the movable part 6 is, for example, the position x _act (n) of the movable part 6 at the present time (nth) and the previous position x _act (n−1) of the movable part 6. However, when the moving speed of the movable part 6 is directly measured by a speed sensor or the like, the measured value can be used.

As described above, in the PID control, the drive voltage in the interrupt processing this time (n-th) is calculated from the actual measured speed v _act , the target speed v _set given in advance, and the gains g _p , g _i , and g _d . The control value p _set (n) can be calculated. The drive voltage generator 2 receives the control value p _set (n) of the drive voltage calculated by the CPU 1 as a PWM signal, and generates a drive voltage to be applied to the DC motor 3 based on the PWM signal.

Next, a specific processing procedure in the CPU 1 will be described with reference to the flowcharts of FIGS.
FIG. 2 shows a rough processing procedure of the CPU 1. Before the DC motor 3 is driven, the CPU 1 sets or initializes various parameter values used for the periodic interrupt processing and turns on the motor drive flag (steps A1 and A2). Periodic interrupt processing is performed (step A3). This is continued until the motor drive flag is turned off in the periodic interrupt processing (steps A4 and A5). When the motor drive flag is turned off, it is assumed that the movable part 6 has reached the target position or that an abnormality has occurred. The operation of the entire drive mechanism is finished.

Note that x _set , x _start , x _dev , v _set , v _stp , K _stl , K _stp , K _loc , p _limit , and α in step A1 are the target position, start position, and arrival determination position deviation of the movable part 6, respectively. , Target speed, stop determination reference speed, arrival determination reference count, stop determination reference count, lock determination reference count, drive voltage upper limit value, lock determination coefficient.
Further, N, p _int , k _stl , k _stp , and k _loc in step A2 indicate the number of times of normal driving, the driving voltage integrated value during normal driving, the number of times reached, the number of stops, and the number of locks, respectively. Note that x _act (-1) is used when v _act (0) is calculated from the difference. Also, v _act (-1) is necessary when calculating p _set (0).

3 and 4 show a specific procedure of the periodic interrupt process in the flowchart of FIG. In this periodic interrupt process, first, the count value is acquired from the up / down counter 12 (step B1), and based on this, the position x _act (n) and speed v of the movable part 6 at the present time (during the n-th interrupt process) are obtained. _Act (n) is calculated, and the control value p _set (n) of the drive voltage applied to the DC motor 3 until the next interruption processing is calculated using the equation (1) (step B2).

Steps B <b> 3 to B <b> 7 show determination of arrival of the movable unit 6 to the target position x _set , determination of abnormality with respect to the actually measured speed v _act (n), and various processes associated with these determinations. These determinations and processes can be the same as those of a conventional drive mechanism. In this embodiment, these determinations and processing are performed as follows.

[Arrival judgment]
Step B3 is a determination as to whether the movable part 6 reaches the target position _xset . In this step, it is determined whether or not the current position x _act (n) of the movable part 6 is approaching the target position x _set . Here, if it is sufficiently close (if | x _act (n) −x _set | <x _dev ), the number of arrivals k _stl is accumulated one by one (step B4). When k _stl reaches the arrival determination reference count K _stl (step B13), it is considered that the movable portion 6 has reached the target position x _set , and the motor drive flag is turned off (step B14). Note that K _stl is normally set to 1 in order to _{minimize the} travel time and prevent overrun.

[Speed abnormality judgment (stop judgment)]
Step B5 is an abnormality determination for the actually measured speed v _act (n) of the movable part 6. In this step, it is determined whether or not the measured speed v _act (n) is smaller than the stop judgment reference speed v _stp, but if it is less than v _stp continuously K _stp times, an abnormality has occurred. As a matter of fact, the motor drive flag is turned off (steps B13 and B14). Therefore, in step B5, if the actually measured speed v _act (n) is smaller than the stop determination reference speed v _stp, it is assumed that an abnormality has occurred and the stop count k _stp is accumulated one by one (step B6 ), V _stp or more, k _stp is reset to 0 (step B7).

Next, abnormality determination of the drive voltage control value p _set (n) and processing accompanying it, which are characteristic of the present invention, will be described using steps B8 to B12.

[Driving voltage abnormality judgment (lock judgment)]
In the present invention, as shown in step B9, the drive voltage control value p _set (n) calculated in step B2 is used as a criterion for the average value p _int / N of the normal drive voltage so far. To determine the abnormality. Thereby, the reference value according to the environment and driving characteristics when using the driving mechanism can be used for abnormality determination.

However, the reference value used for abnormality determination is not obtained immediately after the DC motor 3 is driven. Therefore, as shown in step B8, the abnormality determination is not performed until the movable part 6 reaches a predetermined position (position where | x _act (n) −x _start | ≧ x _dev ), and the drive voltage integrated value p Only integration of _int and normal driving frequency N is performed (step B12). Since a large driving voltage is often applied to the DC motor 3 immediately after driving to obtain the initial speed, until the driving voltage is stabilized (that is, until | p _set (n) | ≦ p _limit ), driving voltage control value p _{the set} of (n) is not integrated into p _int (step B10).

After the movable part 6 reaches a predetermined position, the drive voltage control value p _set (n) is obtained by using the average value p _int / N of the drive voltage at the normal drive obtained up to (n-1) th. Is determined (step B9).

Even in this lock determination, as in the case of the stop determination described above, it is assumed that an abnormality has occurred when the determination of step B9 is not satisfied continuously for K _loc times, and the motor drive flag is turned off. (Steps B13 and B14). Therefore, if | p _set (n) | ≦ α | p _int / N | is not satisfied, the lock count k _loc is accumulated (step B11), assuming that an abnormality may have occurred. _{If set} (n) | ≦ α | p _int / N |, k _loc is reset to 0 (step B12). In step B12, the drive voltage integrated value _pint and the normal drive count N are further updated.

When all the above determinations are completed, it is determined in step B13 whether or not k _stl , k _stp , k _loc has reached the reference number. If any of these has reached the reference number, it is assumed that the position of the movable portion 6 has reached the target position or an abnormality has occurred, the motor drive flag is turned off, and p _set (n) is _set. Set to 0 (step B14).

Also, if the absolute value of p _set (n) is greater than the drive voltage upper limit p _limit , _set p _set (n)
p _set (n) ← sgn (p _set (n)) × p _limit
(Steps B15 and B16). Note that sgn (•) indicates a sign function.

Finally, the drive voltage control value p _set (n) is transmitted as a PWM signal to the drive voltage generation unit 2, and the periodic interrupt process ends.

In equation (1), if the state of large speed deviation (difference between measured speed v _act (n) and target speed v _set ) continues, the I term (second term on the right side) becomes dominant, and accordingly The absolute value of p _set (n) increases. Therefore, even if the stop determination is set to be loose by decreasing the stop determination reference speed v _stp or increasing the stop determination reference count K _stp , an abnormality can be reliably detected by the lock determination. Moreover, since the stop determination can be set loosely, even if the operation immediately after driving, when the moving distance of the movable part 6 is long, or when the operation of each part of the device including the driving mechanism is slow in a low temperature environment, the stop is stopped. It is possible to make it difficult to cause erroneous determination.

  Next, FIG. 5 shows a schematic configuration of a drive mechanism including a second embodiment of the DC motor drive control device according to the present invention. The drive control apparatus of this embodiment is obtained by adding a drive current measuring unit 7 to the configuration of FIG. In the drive mechanism of this embodiment, instead of the drive voltage abnormality determination shown in the first embodiment, abnormality determination is performed on the measured value of the drive current.

  The flowchart of FIGS. 6-8 shows the procedure of the process of CPU1 of a present Example. Steps C1 to C5 and steps D1 to D17 in these flowcharts substantially correspond to steps A1 to A5 and steps B1 to B17 of the first embodiment. Hereinafter, only steps for performing processing different from the first embodiment will be described.

In this embodiment, as shown in FIG. 6, a current upper limit value qlimit is added as a parameter to be set in step C1. In step C2, the drive current integrated value q _int is initialized instead of the drive voltage integrated value p _{int in} step A1 in FIG. 2 (p _int is not used).

  Further, in the periodic interrupt process of FIG. 7, in addition to the count value of the up / down counter 12 in step D1, the drive current measurement value q (n) of the drive current measuring unit 7 is acquired. Further, in steps D8 to D12 in FIG. 8, an abnormality determination (lock determination) is performed on the drive current measurement value instead of the abnormality determination on the drive voltage performed in steps B8 to B12 in FIG. Note that the drive mechanism of this embodiment is a characteristic process different from the first embodiment and the conventional one in that the average of drive current measurement values during normal drive is used as a determination criterion in this lock determination. Except for these steps, the same processing as in the first embodiment can be used.

  The DC motor drive control device according to the present invention has been described with reference to the embodiments. However, it is obvious that the above is only an example, and changes, modifications, or additions are appropriately made within the scope of the present invention. You may do.

For example, in the above embodiment, the period for calculating the average value is from the time when | x _act (n) −x _start | ≧ x _dev until immediately before the abnormality determination (specifically, (n−1) th). However, it may be an average value in the latest periodic interrupt processing over a predetermined number of times. In addition, data obtained when normal operation in the past (before starting control) can be used. Further, any of these may be selected by the user.

台形駆動方式では、図２のステップＡ１又は図６のステップＣ１において加減速距離x_accの設定を追加し、さらに図３のステップＢ２又は図７のステップＤ２における駆動電圧値p_set(n)の算出の際に、v_setの代わりに上記のv_set ^*(n)を用いれば良い。また、上記の台形駆動方式では目標速度が直線的に変化するようにしているが、例えば加速度が一定となるように変化させても良い。 In the above embodiment, the constant speed driving method (the target speed is constant at v _set ) has been described. However, the present invention can also be applied to a trapezoidal driving method. The trapezoidal drive system is a system that adjusts the target speed so as to accelerate at start-up, at a constant speed before the target position, and to decelerate before the target position. Here, if the target speed at the n-th interrupt processing is v _set ^* (n) and the acceleration / deceleration distance is x _acc , the target speed v _set ^* (n) is based on the measured position x _act (n). Is expressed by the following equation.

In the trapezoidal driving method, the setting of the acceleration / deceleration distance x _acc is added in step A1 in FIG. 2 or step C1 in FIG. 6, and the drive voltage value p _set (n) in step B2 in FIG. 3 or step D2 in FIG. during calculation, v above v _set ^* (n) may be used instead of _{the set.} Further, in the trapezoidal driving method described above, the target speed is linearly changed. However, for example, the target speed may be changed to be constant.

1 ... CPU
DESCRIPTION OF SYMBOLS 2 ... Drive voltage generation part 3 ... DC motor 4 ... Drive object measurement part 5 ... Conversion part 6 ... Movable part 7 ... Drive current measurement part 11 ... Pulse encoder 12 ... Up / down counter

Claims (4)

Conversion means for converting the rotational torque of the rotating shaft of the DC motor into a predetermined motion of the drive target, drive target measurement means for acquiring information including the position of the drive target, and information obtained by the drive target measurement means A DC motor drive control device comprising: a control means for periodically calculating a drive voltage to be applied to the DC motor based on the control value and controlling the drive voltage based on the calculated value;
The control means performs an abnormality determination of the drive voltage value calculated this time, using an average of drive voltage values during normal driving calculated within a predetermined period as a determination criterion. . Conversion means for converting the rotational torque of the rotating shaft of the DC motor into a predetermined motion of the drive target, drive target measurement means for acquiring information including the position of the drive target, and information obtained by the drive target measurement means And a control means for controlling a drive voltage applied to the DC motor periodically, in a DC motor drive control device,
Drive current measuring means for measuring the drive current supplied to the DC motor;
The control means performs an abnormality determination of the drive current value measured this time, using an average of drive current values during normal driving measured within a predetermined period as a determination criterion. .   3. The direct current according to claim 1, wherein the drive target measuring unit includes an encoder attached to a rotating shaft of the direct current motor and a counter that counts an output signal of the encoder. Motor drive control device.   The DC motor drive control device according to any one of claims 1 to 3, wherein the predetermined period is from a time point when control to the DC motor is started to a time point immediately before performing the abnormality determination. .

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