JP2012175730A - Driving method for stepping motor, driving system, and current pattern update device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving method for stepping motor, a driving system, and a current pattern update device such that a rotational angle reaches a target angle in a short time and vibration after the reaching can be suppressed.SOLUTION: Time variation in rotational angle of a shaft of a stepping motor is calculated based upon a mathematical model which represents operation of the stepping motor while considering dynamic characteristics of a fitted load part using a transition period needed to change the phase of a current flowing to a coil of the stepping motor. A transition time Td and a transition waveform of a current flowing to coils 13A, 13B, and dynamic characteristics of the load part 30 are taken into consideration, so the rotational angle θof the shaft can be simulated with high precision. Consequently, patterns of currents IA, IB can be optimized, the rotational angle θ(t) of the shaft reaches a target angle θin a short time, and the vibration after the reaching can be suppressed.

Description

  The present invention relates to a stepping motor drive system and a current pattern update device that rotate a rotor by switching excitation current phases.

  The stepping motor is a synchronous motor that operates in synchronization with pulse power, and its momentum (rotation angle) is proportional to the number of drive pulses. Therefore, compatibility with the digital control circuit is good, and accurate positioning can be realized with a simple circuit configuration.

  As a conventional stepping motor driving method, for example, test driving is performed by combining a plurality of patterns of speed, acceleration and deceleration, and among the combinations, the actual rotation angle of the stepping motor and a preset rotation command value A method for deriving a pulse pattern that minimizes the difference has been proposed (Patent Document 1). Further, there is a method in which a prohibited drive frequency corresponding to the resonance characteristic of the stepping motor is stored in advance, and the driving is performed at a frequency lower than the prohibited drive frequency when the drive frequency calculated at the time of driving the stepping motor is the prohibited drive frequency. It has been proposed (Patent Document 2).

JP 2006-211749 A JP 2008-113498 A

  Patent Document 1 is driven so as to follow a rotation command value by a pulse signal pattern of an excitation current composed of a plurality of pulses by a speed, acceleration, and deceleration pattern. However, since the relationship between the excitation current pulse signal pattern and the acceleration / deceleration state of the stepping motor is not always clear, the present invention is applied to a stepping motor driven by an excitation current pulse signal pattern composed of a short time and a small number of pulses. It is difficult.

  Further, in Patent Document 2, the resonance frequency of the primary vibration mode, which is the vibration of the mechanism of the stepping motor itself, is set as the prohibited drive frequency, and the primary vibration mode can be suppressed. However, in a stepping motor in which a high-order vibration mode such as a torsional vibration of a motor shaft that occurs when driving at high speed due to a large moment of inertia of the load, vibration may not be sufficiently suppressed.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a driving method and a driving system for a stepping motor capable of suppressing the vibration after the rotation angle reaches the target angle in a short time. And a current pattern updating apparatus.

  In the stepping motor driving method according to one aspect of the present invention, first, a transition period required for the phase of the current flowing through the coil of the stepping motor to be switched is measured. Next, parameters relating to the stepping motor in the mathematical model expressing the operation of the stepping motor in consideration of the dynamic characteristics of the attached load portion are identified. Next, a parameter related to the load unit in the mathematical model is identified. Next, using the measured transition period and the identified parameter, the time change of the rotation angle of the shaft of the stepping motor is calculated based on the mathematical model. Next, a pattern of current flowing in the coil based on the time required for the calculated rotation angle of the shaft to reach a predetermined target angle and the magnitude of vibration after reaching the target angle To decide. Then, the stepping motor is driven with the determined current pattern.

  In the stepping motor driving method according to one aspect of the present invention, first, the stepping motor is driven by passing a predetermined current pattern through the coil, and the vibration of the rotation angle of the shaft of the stepping motor is measured. Next, it is determined whether or not the measured vibration is within a predetermined allowable range. Next, if not within the allowable range, at least one of the parameters related to the load unit in the mathematical model expressing the operation of the stepping motor considering the dynamic characteristics of the attached load unit is applied to the coil measured in advance. Calculation is performed in consideration of the transition time required for the phase of the flowing current to change. Next, the current pattern is updated based on the calculated parameter. Then, the stepping motor is driven with the updated current pattern.

  According to one aspect of the present invention, a stepping motor drive system includes a comparison unit, a current pattern calculation unit, and a drive unit. The comparison unit determines whether the vibration of the rotation angle of the shaft of the stepping motor is within a predetermined allowable range. When the current pattern calculation unit is not within the allowable range, at least one of the parameters related to the load unit in the mathematical model expressing the operation of the stepping motor considering the dynamic characteristics of the attached load unit is measured in advance. The calculation is performed in consideration of the transition time required for the phase of the current flowing through the coil of the stepping motor to change, and the current pattern is updated based on the calculated parameter. The driving unit drives the stepping motor with the updated current pattern.

  Further, according to one aspect of the present invention, the current pattern update device includes a stepping motor that takes into account the dynamic characteristics of the attached load portion when the vibration of the rotation angle of the shaft of the stepping motor exceeds a predetermined allowable range. Calculating at least one of the parameters related to the load section in the mathematical model expressing the operation of the above in consideration of the transition time required for the phase of the current flowing in the coil of the stepping motor measured in advance to be changed, and A current pattern calculation unit that updates a current pattern based on the calculated parameters is provided.

  According to the present invention, in order to consider the transition period required for the phase of the current flowing through the coil to switch and the dynamic characteristics of the attached load section, the rotation angle reaches the target angle in a short time and reaches the target angle. Later vibrations can be suppressed.

The figure which shows typically the stepping motor 10 and the load part 30 attached to this. 1 is a block diagram showing a schematic configuration of a drive system for a stepping motor 10 according to a first embodiment of the present invention. The timing diagram which shows an example of the pattern of the 1st-4th pulse and electric current IA, IB which the pulse generation part 21 produces | generates. The flowchart which shows the procedure which calculates | requires each parameter. The graph which shows rotation angle (theta) _M (t) of the shaft 12. FIG. The graph which shows rotation angle (theta) _M (t) of the shaft 12. FIG. The graph which shows rotation angle (theta) _M (t) of the shaft at the time of driving the motor 10 using the obtained current pattern. Graph showing the rotation angle of the shaft theta _{M (t)} which is driven by the optimized current pattern using the moment of inertia J _L obtained by the method of the first embodiment. The block diagram which shows schematic structure of the drive system of the stepping motor 10 which concerns on the 2nd Embodiment of this invention. The flowchart which shows the procedure which updates period T1-T3. Graph showing the measurement result of the rotation angle of the shaft 12 θ _{M (t),} and a simulation result of the operation of the motor 10 using the moment of inertia J _L newly identified. It shows an example of the relationship between the moment of inertia _{J L} and duration T1~T3 stored in the table 52. Graph showing the rotation angle θ _M (t) before updating the period T1 to T3, the rotation angle of the updated theta _M and (t).

  Embodiments of a stepping motor driving method and a driving apparatus according to the present invention will be specifically described below with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram schematically showing a stepping motor (hereinafter simply referred to as a motor) 10 and a load portion 30 attached thereto. FIG. 2 is a block diagram showing a schematic configuration of the drive system of the motor 10 according to the first embodiment of the present invention. The motor 10 is used for positioning a conveyance table of a taping device that taps a chip-type electronic component such as a capacitor.

  The motor 10 includes a rotor 11, a shaft 12, and coils 13A and 13B. The shaft 12 is provided so as to penetrate the rotor 11, and the shaft 12 rotates as the rotor 11 rotates. The coil 13A is wound around a stator (not shown) arranged to face the rotor 11, and the coil 13B is wound to another stator (not shown) arranged to face the rotor 11. The load 32 is attached to the shaft 12 via the coupling 31. The coupling 31 and the load 32 constitute a load portion 30, and the load portion 30 rotates when the shaft 12 rotates. An encoder 40 is attached to the shaft 12 so that the rotation angle of the shaft can be measured.

  The driving device 20 that drives the motor 10 includes a pulse generation unit 21 and a current control unit 22. These constitute a drive unit. The pulse generator 21 generates the first to fourth pulses at a predetermined timing. In synchronization with these, the current control unit 22 controls the currents IA and IB supplied to the coils 13A and 13B of the motor 10. This current IA includes an A-phase excitation current Ia flowing from the first end 14A of the coil 13A to the common terminal COMA and an A'-phase excitation current Ia 'flowing from the second end 14A' of the coil 13A to the common terminal COMA. Similarly, the current IB includes a B-phase excitation current Ib and a B′-phase excitation current Ib ′.

  FIG. 3 is a timing diagram showing an example of patterns of the first to fourth pulses and currents IA and IB generated by the pulse generator 21. 3A to 3C, the vertical axis represents the presence / absence of a pulse, currents IA and IB, and the horizontal axis represents time t. The current I0 on the vertical axis represents the rated current, the current IA = I0 corresponds to the A-phase excitation current Ia, and the current IA = −I0 corresponds to the A′-phase excitation current Ia ′. The same applies to the current IB.

  It is assumed that the current control unit 22 generates a current IA = I0 and a current IB = I0 at time t0. In this state, an A-phase excitation current Ia and a B-phase excitation current Ib (hereinafter referred to as “excitation current AB”. The same applies to other excitation currents).

  At time t1, the pulse generator 21 generates a first pulse. In synchronization with this, the current control unit 22 switches the current IB from the rated current I0 to -I0, that is, from the B-phase excitation current Ib to the B'-phase excitation current Ib '. However, the current IB does not instantly switch from the rated current I0 to -I0, but reaches the rated current -I0 at time t2 when the transition period Td has elapsed. After time t2, the current control unit 22 generates an excitation current AB '.

  Similarly, at time t3 when the period T1 has elapsed from time t1, the pulse generator 21 generates the second pulse, and the current controller 22 generates the excitation current A'B '. Further, at time t5 when the period T2 has elapsed from time t3, the pulse generator 21 generates a third pulse, and the current controller 22 generates an excitation current A'B. Further, at time t7 when the period T3 has elapsed from time t5, the pulse generator 21 generates the fourth pulse, and the current controller 22 generates the excitation current AB again.

  As described above, by switching the current phase flowing through the coils 13A and 13B in the order of the excitation currents AB, AB ', A'B', and A'B, for example, the magnetic poles excited in the respective stators are changed. The rotor 11 has a plurality of teeth magnetized to the N pole or the S pole, and the rotor 11 rotates as the stator and the stator repel each other or attract each other.

The current waveform in the transition period Td can be assumed to be a straight line, and the patterns of currents IA and IB in FIGS. 3B and 3C are expressed by the following equations (1) and (2), respectively.

When these are set to time t1 = 0 and the current patterns for one cycle are rewritten using the periods T1 to T3 and the transition period Td, the following equations (1 ′) and (2 ′) are obtained.

  In the present embodiment, based on a mathematical model of the motor 10 described later, the rotation angle of the shaft 12 is simulated in consideration of the transition period Td and the transition waveform of the excitation current, and the shaft 12 of the motor 10 is set to the target angle in a short time. The periods T1 to T3 are optimized so that the vibration of the shaft 12 is suppressed.

  Hereinafter, the mathematical model of the motor 10 will be described.

When the load unit 30 is not attached to the motor 10, the operation of the motor 10 is expressed by the following equation (3).

Here, J _M , D _M , T _M , and θ _M (t) are the moment of inertia [kg · m ² ], damping constant [kg · m · s], generated torque [N · m], This is the rotation angle [rad] of the shaft 12. The above expression (3) means that when the torque T _M is applied to the motor 10 having the moment of inertia J _M and the damping constant D _M , the shaft 12 rotates at the rotation angle θ _M (t). The torque _TM is generated by the excitation currents IA and IB, which will be described in detail later.

On the other hand, torque T _L [N · m] expressed by the following equation (4) is generated in the load section 30.

Here, J _L , K _L , and θ _L (t) are the inertia moment [kg · m ² ], the spring constant [Nm / rad], and the rotation angle [rad] of the load unit 30, respectively. The above equation (4) means that a torque proportional to the difference between the rotation angle θ _M (t) of the shaft 12 and the rotation angle θ _L (t) of the load portion 30, that is, the twist of the shaft 12 is generated. .

  The above expression (4) expresses the load unit 30 with a so-called two-inertia model. Since the operation of the motor 10 is greatly affected by the dynamic characteristics of the load unit 30, the operation of the motor 10 can be accurately simulated by expressing the load unit 30 using a two-inertia system model.

The torque _{T L} acts on the generated torque _{T M} in the opposite direction from the motor 10. Therefore, the operation of the motor 10 when the load unit 30 is attached is expressed by the following equation (5).

From the above equations (3) to (5), the operation of the motor 10 to which the load unit 30 is attached is represented by the mathematical model of the following equation (6).

Then, to calculate the torque _{T M} of the motor 10. Of the current IA flowing through the coil 13A, the torque due to the A-phase exciting current Ia (hereinafter, torque generated by the A phase) _{T A} is represented by the following equation (7).

Here, _KT is a torque constant [Nm / A], and _NR is the number of teeth of the rotor. Meanwhile, because of the current IB flowing through the coil 13B, the torque due to the B-phase exciting current Ib (hereinafter, torque generated by the B-phase) T _B is the A phase and the phases are disposed so as delayed by [pi / 2, It is represented by the following formula (8).

Further, as shown in FIG. 3B, the A-phase excitation current and the A′-phase excitation current have the same magnitude and opposite directions, so that the A-phase generated torque T _A = A ′ phase is generated. Torque TA _′ . Similarly, B-phase torque _T B = a B 'phase of the generated torque T _B'. Therefore, the generated torque T _M of the motor 10 is the sum of the A-phase generated torque T _A and the B-phase generated torque T _B and is expressed by the following equation (9).

  In the above equation (9), in order to excite each phase in sequence, π / 4, which is an intermediate phase between the A phase and the B phase, is set as an initial value. The currents IA and IB of the same formula are expressed by the above formulas (1 ') and (2').

As described above, the mathematical model of the motor 10 is expressed by the above expressions (1 ′), (2 ′), (4), (6), and (9). Therefore, if the value of the parameter in each equation is known, the rotation angle θ _M (t) that is the operation of the motor 10 can be simulated. In particular, in this embodiment, since the transition period Td and the dynamic characteristics of the load unit 30 are taken into consideration, simulation can be performed with high accuracy.

  Next, a method for obtaining each parameter in the mathematical model will be described. FIG. 4 is a flowchart showing a procedure for obtaining each parameter.

First, with the load unit 30 removed, the pulse generation unit 21 generates one pulse. As a result, the currents IA and IB change from the rated current I0 to -I0 (or -I0 to I0). At this time, the time change of the rotation angle θ _M (t) of the shaft 12 and the currents IA and IB are measured (step S1). The rotation angle θ _M (t) of the shaft can be measured by the encoder 40 in FIG. The currents IA and IB can measure transition waveforms with an oscilloscope using a current probe, for example.

FIG. 5 is a graph showing the rotation angle θ _M (t) of the shaft 12. The vertical axis is the rotation angle θ _M (t), and the horizontal axis is time. The broken line in the figure shows the measured rotation angle θ _M (t).

  Then, from the measurement results of the currents IA and IB, the transition period Td required for the currents IA and IB to transition from the rated current I0 to -I0 (or -I0 to I0) is identified (step S2). The value of the obtained transition period Td is, for example, 500 [μs]. Since the transition period Td differs depending on the motor 10, it is desirable to perform measurement for each motor 10 to identify the transition period Td.

Furthermore, using the measured rotation angle θ _M (t), the parameters relating to the motor 10, that is, the moment of inertia J _M , the damping constant D _M, and the torque constant K _T are identified from the equations (6) and (9). (Step S3). In the above equation (6), since the load portion 30 is not attached, the shaft 12 is not twisted, and the rotation angle θ _M (t) of the shaft 12 may be set to the rotation angle θ _L (t) of the load portion 30. .

More specifically, for example, the following is performed using the Nelder-Mead method. First, arbitrary initial values are given to the parameters J _M , D _M , and K _T, and the rotation angle θ _M (t) of the shaft 12 that satisfies the above equation (6) is calculated. In the following, the rotation angle calculated by solving the above equation (6) is θ _MS (t), and the rotation angle measured in step S1 is θ _ME (t). Then, the rotation angles θ _MS (t) and θ _ME (t) are compared. Next, the parameters J _M , D _M , and K _T are changed little by little to calculate the rotation angle θ _MS (t), and further comparison is performed. This operation is repeated, and parameters J _M , D _M , and K _T that minimize the difference between the rotation angles θ _MS (t) and θ _ME (t) among the tried parameters J _M , D _M , and K _T are selected. .

For comparison between the rotation angles θ _MS (t) and θ _ME (t), for example, an objective function F1 (J _M , D _M , K _T ) of the following equation (10) can be used. It is only necessary to identify parameters J _M , D _M , and K _T that reduce F1 (J _M , D _M , and K _T ).

The value of each parameter to be identified is, for example, J _M = 8.5 * 10 ⁻⁶ [kg · m ² ], D _M = 9.8 * 10 ⁻⁴ [kg · m · s], K _T = 2 .8 * 10 ⁻¹ [Nm / A]. When the rotation angle θ _MS (t) is simulated using these parameters, the result is as shown by a solid line in FIG. 5, which substantially coincides with the measured rotation angle θ _MS (t). In order to identify the parameters J _M , D _M , and K _T as described above, for example, numerical calculation software MATLAB (registered trademark) can be used.

Since the parameters relating to the motor 10 have been identified as described above, the parameters J _L and K _L relating to the load section 30 are next identified.

With the load unit 30 attached, the pulse generation unit 21 generates the first to fourth pulses in FIG. 3, and measures the change over time of the rotation angle θ _M (t) of the shaft at this time (step S4). 6 is a graph showing the rotation angle θ _M (t) of the shaft 12, and the vertical axis and the horizontal axis are the same as those in FIG. The broken line in the figure shows the measured rotation angle θ _M (t).

Further, using the measured rotation angle θ _M (t), the parameters related to the load unit 30 from the above formulas (1 ′), (2 ′), (4), (6), (9), that is, the load unit 30 inertia moments J _L and spring constants K _L are identified (step S5). More specifically, for example, using the Nelder-Mead method, the identification is performed as follows, similarly to the parameters of the motor 10.

First, by giving arbitrary initial values to the parameters J _L and K _L , the rotation angle θ _M (t) of the shaft 12 and the rotation angle θ _L (t) of the load section 30 satisfying the above equations (4) and (6) are set. calculate. Hereinafter, the rotation angle calculated by solving the above equations (4) and (6) is θ _MS (t), and the rotation angle measured in step S4 is θ _ME (t). Then, the rotation angles θ _MS (t) and θ _ME (t) are compared. Next, the parameters J _L and K _L are changed little by little to calculate the rotation angle θ _MS (t), and further comparison is performed. For comparison, an objective function similar to the above equation (10) can be used. Repeat this procedure, parameter _J L of attempts, _K rotation angles theta _MS (t) and theta parameter difference is smallest between _ME (t) _J L of the _L, selects the _{K L.}

The value of each parameter to be identified is, for example, J _L = 8.1 * 10 ⁻⁶ [kg · m ² ], K _L = 1.1 * 10 ² [Nm / rad]. When the rotation angle θ _MS (t) is simulated using these parameters, it becomes as shown by the solid line in FIG. 6 and substantially coincides with the measured rotation angle θ _MS (t).

As described above, each parameter in the mathematical model can be identified. Steps S3 and S5 can be executed by, for example, one computer different from the drive device 20. The shaft rotation angle θ _M (t) can be simulated for any current IA, IB using the identified parameters.

Subsequently, when the motor is driven, the pattern of the currents IA and IB that the shaft rotation angle θ _M (t) reaches the target angle θ _tg [rad] in a short time and can suppress the vibration after the rotation is calculated. . More specifically, the periods T1 to T3 in the above equations (1 ′) and (2 ′) are calculated as follows.

First, an objective function F2 (T1, T2, T3) is defined as in the following equation (11).

The objective function F2 (T1, T2, T3) is the maximum value of the vibration of the shaft 12 after the time T1 + T2 + T3 + Td has elapsed, that is, after the motor 10 is driven with a current pattern for one cycle (after time t8 in FIG. 3). To express. Further, if the periods T1 to T3 are too short, the motor 10 may step out. Therefore, the periods T1 to T3 are set to predetermined constants C1 to C3 or more, respectively. Each of the constants C1 to C3 is set to 500 μs, for example.

In general, the shorter the period T1 to T3, the shorter the time required to reach the target angle θ _tg , but the greater the vibration after reaching. On the other hand, the longer the periods T1 to T3, the smaller the vibration after reaching the target angle θ _tg , but the longer it takes to reach the target angle θ _tg .

  Therefore, for example, the objective function F2 (T1, T2, T3) is calculated for various T1 to T3 using the Nelder-Mead method. Since the objective function F2 (T1, T2, T3) may not have unimodality, it is desirable to try several initial values. Then, periods T1 to T3 in which the objective function F2 (T1, T2, T3) is smaller than a predetermined value and the time T1 + T2 + T3 is within the predetermined time are calculated. When there are a plurality of sets of periods T1 to T3 that satisfy these conditions, for example, priority is given to either the objective function F2 being as small as possible or the time T1 + T2 + T3 being as short as possible. T3 is calculated.

  In this way, a pattern of currents IA and IB, for example, T1 = 1678 μs, T2 = 653 μs, and T3 = 1716 μs is obtained.

FIG. 7 is a graph showing the rotation angle θ _M (t) of the shaft when the motor 10 is driven using the obtained current pattern. The vertical axis and the horizontal axis are the same as those in FIG. In the figure, the target angle θ _tg is 3.6 [deg], and the value measured by the encoder 40 is indicated by a broken line. In the figure, the simulation results based on the mathematical model are also shown by solid lines for reference. Parameters such as J _M is the above values. FIG. 7B is an enlarged view of the vicinity of the target angle 3.6 [deg] in FIG. 7A, and a low-pass filter is applied to the measurement value for easy viewing.

As shown in FIGS. 7A and 7B, the operation of the motor 10 substantially coincides with the simulation result, reaches the target angle θ _tg in only about 5 ms, and the vibration after the arrival is small.

Thus, in the first embodiment, in the mathematical model of the motor 10, the transition period Td and transition waveform of the current flowing through the coils 13A and 13B and the dynamic characteristics of the load unit 30 are also taken into consideration. The rotation angle θ _M can be simulated with high accuracy. As a result, the patterns of the currents IA and IB can be optimized, the shaft rotation angle θ _M (t) can reach the target angle θ _tg in a short time, and vibration after reaching can be suppressed.

(Second Embodiment)
First embodiment described above, by using the initial moment of inertia J _L of the load unit 30, it was to optimize the period T1 to T3. On the other hand, in the second embodiment described below, the periods T1 to T3 are dynamically optimized in consideration of the fluctuation of the load unit 30.

FIG. 8 is a graph showing the rotation angle θ _M (t) of the shaft driven by the current pattern optimized using the moment of inertia J _L obtained by the method of the first embodiment. The broken line in the figure is the rotation angle θ _M (t) at the initial stage of rotation, and the solid line is the rotation angle θ _M (t) when a certain amount of time has passed. As shown in the figure, the vibration can be suppressed at the initial stage of rotation, but the vibration increases as time elapses. This, when actually using the motor 10, the load 30 fluctuates, along with this, the moment of inertia J _L is considered to be because it had fluctuated.

Therefore, in this embodiment, by dynamically update period T1~T3 in accordance with the variation of the moment of inertia J _L of the load unit 30, achieving the suppression of vibration.
FIG. 9 is a block diagram showing a schematic configuration of a drive system of the motor 10 according to the second embodiment of the present invention. In FIG. 9, the same components as those in FIG. 2 are denoted by the same reference numerals, and different points will be mainly described below.

The drive device 20 in FIG. 9 further includes a comparison unit 23. The comparison unit 23 determines whether or not the maximum error between the motor rotation angle θ _M (t) measured by the encoder 40 and the target angle θ _tg is less than or equal to the allowable range θ _al .

The drive system also includes a current pattern update device 50. The current pattern update device 50 includes a current pattern calculation unit 51 and a table 52. Current pattern calculation section 51 identifies the moment of inertia J _L of the load unit 30 after fluctuations, and supplies the optimal duration T1~T3 depending on the identified moment of inertia J _L to the drive device 20. Table 52 stores in advance calculated, the relationship between the moment of inertia _{J L} and duration T1~T3 the load section 30. The current pattern update device 50 is built in, for example, one or a plurality of computers.

FIG. 10 is a flowchart showing a procedure for updating the periods T1 to T3. The drive device 20 drives the motor 10 for one cycle, that is, from time t1 to time t8 in FIG. 3 with the current pattern before update (step S11). Then, the encoder 40 measures the rotation angle θ _M (t) of the shaft 12 after being driven for one cycle (step S12). Further, the comparison unit 23 in the driving device 20 determines whether the maximum error between the rotation angle θ _M (t) and the target angle θ _tg is equal to or less than the allowable range θ _{al based on the} following equation (12) (step) S13).

If an unacceptable theta _al (NO in step S13), and since the moment of inertia J _L of the load unit 30 is considered to be varied, the current pattern calculation section 51 is newly identified moment of inertia J _L of the load unit 30 To do. More specifically, the inertia moment J _L is identified based on the measured rotation angle θ _M (t) of the motor and the mathematical model of the motor 10 as in step S5 (FIG. 4) of the first embodiment. To do. Moment of inertia _{J L} is initially what was as above ^{8.1 * 10 -6 [kg · m} 2] is, for ^example, varies ^{8.5 * 10 -6 [kg · m} 2].

Figure 11 is a graph showing the measurement result of the rotation angle of the shaft 12 θ _{M (t),} and a simulation result of the operation of the motor 10 using the moment of inertia J _L newly identified. As shown in the figure, the simulation result is close to the measurement result. This means that one of the causes that the rotation angle θ _M (t) changes over time as shown in FIG. 8 is a change in the moment of inertia J _L of the load section 30.

Thereafter, a current pattern calculation section 51, in response to the identified moment of inertia _{J L,} using the table 52 to calculate a new optimum period T1 to T3, and updates the current pattern (step S15). Figure 12 is a diagram showing an example of the relationship between the moment of inertia _{J L} and duration T1~T3 stored in the table 52. In the first embodiment, to calculate the optimal duration T1~T3 if the moment of inertia _{J L} is ^{8.1 * 10 -6 [kg · m} 2], in the present embodiment, in advance the moment of inertia _{J L} Is calculated in the vicinity of 8.1 * 10 ⁻⁶ [kg · m ² ], for example, 7.0 * 10 ⁻⁶ to 10 * 10 ⁻⁶ [kg · m ² ]. Set to 52. Then, the current pattern calculation section 51 reads out the optimum duration T1~T3 from the table 52 with respect to identified moment of inertia _{J L,} and supplies to the pulse generator 21.

Then, the pulse generator 21 generates the first to fourth pulses with a current pattern based on the new periods T1 to T3, and drives the motor 10. By repeating each cycle the above processing operation example, even the moment of inertia J _L of the load section 30 is changed, to update the duration T1~T3 to follow this variation, as a result, the motor 10 while suppressing the vibration Can be driven.

FIG. 13 is a graph showing the rotation angle θ _M (t) before the period T1 to T3 is updated and the rotation angle θ _M (t) after the update, and FIG. 13B is a graph illustrating the rotation angle θ _M (t). It is an enlarged view near target angle 3.6 [deg]. As shown in the figure, the vibration can be suppressed by updating the periods T1 to T3.

As described above, in the second embodiment, the vibration of the shaft 12 is measured while the motor 10 is being driven, and the periods T1 to T3 are updated when the vibration exceeds the allowable range. Therefore, even if the moment of inertia J _L of the load section 30 is changed in a short time the shaft rotational angle θ _{M (t)} reaches the target angle theta _tg, and can suppress the vibration mode after arrival.

In step S15 of FIG. 10, the periods T1 to T3 may be calculated by the same method as in the first embodiment without using the table 52. Moreover, although the example in which the current pattern update device 50 is built in the computer has been shown, it may be built in the drive device 20. Furthermore, in the present embodiment has shown an example of calculating the moment of inertia J _L of the load unit 30 with a current pattern calculation section calculates the other of the at least one parameter relating to the load unit 30 updates the current pattern May be.

  At least a part of the motor drive system described in the above-described embodiment may be configured by hardware or software. When configured by software, a program for realizing at least part of the functions of the motor drive system may be stored in a recording medium such as a flexible disk or a CD-ROM, and read and executed by a computer. The recording medium is not limited to a removable medium such as a magnetic disk or an optical disk, but may be a fixed recording medium such as a hard disk device or a memory.

  Further, a program for realizing at least a part of the functions of the motor drive system may be distributed via a communication line (including wireless communication) such as the Internet. Further, the program may be distributed in a state where the program is encrypted, modulated or compressed, and stored in a recording medium via a wired line such as the Internet or a wireless line.

  Based on the above description, those skilled in the art may be able to conceive additional effects and various modifications of the present invention, but the aspects of the present invention are not limited to the individual embodiments described above. Absent. Various additions, modifications, and partial deletions can be made without departing from the concept and spirit of the present invention derived from the contents defined in the claims and equivalents thereof.

DESCRIPTION OF SYMBOLS 10 Stepping motor 11 Rotor 12 Shaft 13A, 13B Coil 20 Drive apparatus 21 Pulse generation part 22 Current control part 23 Comparison part 30 Load part 31 Coupling 32 Load 40 Encoder 50 Current pattern update apparatus 51 Current pattern calculation part 52 Table

Claims (18)

Measuring a transition period required for the phase of the current flowing in the coil of the stepping motor to switch; and
Identifying a parameter relating to the stepping motor in a mathematical model representing the operation of the stepping motor in consideration of the dynamic characteristics of the attached load section;
Identifying a parameter related to the load in the mathematical model;
Using the measured transition period and the identified parameter, and calculating a time change of the rotation angle of the shaft of the stepping motor based on the mathematical model;
A pattern of current flowing in the coil is determined based on the time required for the calculated rotation angle of the shaft to reach a predetermined target angle and the magnitude of vibration after reaching the target angle. Steps,
And a step of driving the stepping motor with the determined current pattern. The coil of the stepping motor includes first and second coils,
The stepping motor driving method according to claim 1, wherein the mathematical model is expressed by the following equations (1) to (3).

Here, J _L is the moment of inertia of the load section, t is time, θ _L (t) is the rotation angle of the load section, K _L is the torsion spring constant of the shaft, and θ _M (t) is the stepping motor. rotation angle of the shaft, J _M is the moment of inertia of the stepping motor, D _M is the attenuation constant of the stepping motor, K _L is the spring constant of the load unit, T _M is the stepping motor generator torque, IA, IB is the first currents flowing through the first and second coils, K _T is a torque constant, N _R is the number of teeth of the rotor of the stepping motor. One period of the currents IA and IB flowing through the first and second coils is expressed by the following equations (4) and (5):
3. The stepping motor driving method according to claim 2, wherein in the step of calculating the pattern of the current flowing through the coil, T1 to T3 in the equations (4) and (5) are calculated.

Here, I0 is the rated current, and Td is the transition period. Determining the current pattern comprises:
Each of the plurality of periods T1 to T3 is set in the equations (4) and (5), and calculated based on the equations (1) to (3) until the shaft reaches the target angle. Calculating the time required for and the magnitude of vibration after reaching the target angle;
Of the plurality of periods T1 to T3, the time required to reach the target angle is within a predetermined time, and the magnitude of vibration after reaching the target angle is equal to or less than a predetermined value. The stepping motor driving method according to claim 3, further comprising: selecting a period T1 to T3.   5. The stepping motor driving method according to claim 3, wherein the periods T <b> 1 to T <b> 3 are set longer than a predetermined period so that the stepping motor does not step out. Identifying the parameters for the stepping motor comprises:
Passing a current through the first and second coils with the load section removed, and measuring a rotation angle of the shaft;
6. The step of identifying the J _M , D _M, and K _T based on the equation (2) and the measured rotation angle of the shaft is provided. A driving method of the stepping motor described. Identifying said J _M , D _M and K _T comprises:
Setting each of a plurality of types of J _M , D _M and K _{T in} the equation (2), and calculating a rotation angle θ _M (t) of the shaft;
Among the plurality of types of J _M , D _M and K _T , the difference between the calculated rotation angle θ _M (t) and the measured rotation angle of the shaft becomes the smallest J _M , D _M And a step of selecting _KT . 7. The stepping motor driving method according to claim 6, further comprising: Identifying a parameter relating to the load section,
Passing a current of one cycle through the first and second coils with the load portion attached, and measuring a rotation angle of the shaft;
Wherein (1), based on the rotation angle of the shaft is measured (2) and any of claims 2 to 7, characterized in that it has the steps of: identifying the J _L and the K _L A stepping motor driving method described in 1. Identifying the J _L and the K _L comprises:
Setting each of the plurality of J _L and K _{L in} the equations (1) and (2), and calculating the rotation angle θ _M (t) of the shaft;
Among the J _L and K _L of the plural kinds, selecting with the calculated rotation angle θ _{M (t),} the rotation angle of the measured shaft, the difference of the smallest J _L and K _L of And a stepping motor driving method according to claim 8. Driving the stepping motor to measure vibration of the rotation angle of the shaft;
Determining whether the measured vibration is within a predetermined tolerance;
If not within the tolerance, calculating at least one of the parameters for the load section;
The stepping motor driving method according to claim 2, further comprising a step of updating the current pattern based on the calculated parameter. Wherein the at least one parameter relating to the load unit, the driving method of the stepping motor according to claim 10, characterized in that the said J _L. Updating the pattern of current of said coil based on the calculated parameters, calculated in advance, by using a table showing the relationship between the pattern of the J _L and the current, updating the pattern of the current The method for driving a stepping motor according to claim 11.   The stepping motor driving method according to claim 10, wherein the current pattern is updated every time a current of one cycle is supplied to the coil. Driving a stepping motor by passing a predetermined current pattern through a coil, and measuring vibration of a rotation angle of a shaft of the stepping motor;
Determining whether the measured vibration is within a predetermined tolerance;
If not within the allowable range, at least one of the parameters related to the load unit in the mathematical model expressing the operation of the stepping motor in consideration of the dynamic characteristics of the attached load unit is a pre-measured current of the coil. Calculating taking into account the transition time required for the phase to change;
Updating a current pattern based on the calculated parameters;
And a step of driving the stepping motor with the updated current pattern. A comparison unit for determining whether the vibration of the rotation angle of the shaft of the stepping motor is within a predetermined allowable range;
If it is not within the allowable range, at least one of the parameters related to the load unit in the mathematical model expressing the operation of the stepping motor in consideration of the dynamic characteristics of the attached load unit is stored in the coil of the stepping motor measured in advance. A current pattern calculation unit that calculates the transition time required for the phase of the flowing current to change and updates the current pattern based on the calculated parameter;
A drive unit for driving the stepping motor with the updated current pattern. A table showing a relationship between at least one of the parameters related to the load section and the current pattern;
The stepping motor drive system according to claim 15, wherein the current pattern calculation unit updates the current pattern using the table.   When the vibration of the rotation angle of the shaft of the stepping motor exceeds a predetermined allowable range, at least one of the parameters related to the load unit in the mathematical model expressing the operation of the stepping motor considering the dynamic characteristics of the attached load unit Is calculated in consideration of the transition time required for the phase of the current flowing through the coil of the stepping motor to be measured in advance, and the current pattern is updated based on the calculated parameter. An apparatus for updating a current pattern of a stepping motor. A table showing a relationship between at least one of the parameters related to the load section and the current pattern;
The current pattern update device according to claim 17, wherein the current pattern calculation unit updates the current pattern using the table.

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