JPH03178590A - Controller for brushless synchronous motor - Google Patents

Abstract

PURPOSE:To improve the linearity of a required torque and output torque by providing a cogging torque compensator for compensating a cogging torque being the variation of a generated torque and not depending on the magnitude of the generated torque and a torque constant compensator for compensating a part depending on the magnitude of the generated torque. CONSTITUTION:In the controller of a brushless synchronous motor 1, a required torque T* from a host controller 6 is subtracted by cogging torque compensating data Tcog(theta) not depending on the magnitude of a generated torque read from a cogging torque compensator 4 by means of a rotation angle theta from a position transducer 2 as a parameter. The subtraction-compensated required torque T* is converted into a current command if* multiplied by the inverse number of a torque constant read from a torque constant compensator 5 by means of the rotation angle theta from the position transducer 2 as a parameter. The linearity of the obtained generated torque and required torque T* is considerably improved by the current command iT*.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for a brushless synchronous motor. −
Numerically speaking, a brushless synchronous motor is a rotating field type synchronous motor, and has features such as no consumable brushes and no commutator that requires maintenance, and has the same control ability as a conventional DC motor. Because of this, it is widely used as a control motor for robots, machine tools, etc.

In particular, the present invention relates to a device for controlling fluctuations in torque generated due to nonlinearity between the required torque and the output torque of a brushless synchronous motor.

[Conventional technology]

Conventional technology in this field is described in Japanese Patent Application Laid-Open No. 163591/1988, ``Control Device for Brushless Motor,'' which shows a control mechanism for a brushless motor and also discloses a method for correcting torque ripple.

The configuration will be explained below with reference to the drawings. FIG. 7 is a diagram showing a configuration for correcting torque fluctuations of a conventional brushless electric motor. This figure shows a three-phase brushless motor 21, a magnetic position detector 22 connected to the brushless motor to detect the rotation angle θ, and a memory that generates a three-phase signal using the rotation angle θ from the magnetic position detector 22 as a parameter. circuit 23
Then, the rotation angle θ and the torque command signal ETI given from the outside are used as human signals, and ΔET of the opposite polarity to the fluctuating torque (pulsating torque) Δτ of the generated torque τ of the electric motor TA 1 with the rotation angle θ as a parameter is calculated in advance. a torque correction circuit 24 that stores a torque command signal ETI using the rotation angle θ as a parameter, adds ΔET to it, corrects it to a corrected torque command signal ET2, and outputs the corrected torque command signal ET2; the corrected torque command signal T2; and the memory. A current command signal forming circuit 25 multiplies the output signal from the circuit 23 and outputs an analog current command signal, and the current command signal is used as a human power signal to generate an armature current proportional to the value of these human power signals to the motor. 1 armature winding.

Next, the operation of the torque correction circuit 24 will be explained. FIG. 8 is a diagram showing fluctuations in torque generated by a conventional brushless motor and correction thereof. In this figure, the horizontal axis indicates the rotation angle θ, and the vertical axis indicates the generated torque τ2 and the fluctuating torque Δr in FIG. 8(a). Even if the torque command signal ETI on the vertical axis in FIG. 8(b) is output as a control signal to the current command signal forming circuit 25 in order to obtain a uniform generated torque τ1, a −-like torque τ cannot be obtained. What can be obtained is a torque τ2 that varies depending on the pulsating torque Δτ. Therefore, the torque correction circuit 24 stores in advance a correction amount ΔET for canceling out this pulsation l and torque Δτ, using the rotation angle θ as a parameter. Thus, the torque command signal E is generated corresponding to the rotation angle θ.
ET corrected TI by pulsating torque Δτ and opposite polarity ΔBT
2, it was possible to set the generated torque to a constant value r1 and obtain stable generated torque with little fluctuation.

[Problem to be solved by the invention]

However, in the torque control of conventional permanent magnet type AC servo motors, when changing the magnitude of generated torque, Δ
Even if the armature current is changed in proportion to BT, the armature current, that is, the required torque and the output torque, do not become linear, and even if high-precision current control is performed, the motor output will not match the command even if the above correction mechanism is used. The problem is that the values do not match. Furthermore, by storing ΔET as dependent on the generated torque, reading ΔET for the required torque, and correcting ETI to ET2, it is possible to match the generated torque to the command value, but this requires a huge storage capacity. There is a cost issue.

Therefore, in view of the above problems, it is an object of the present invention to provide a highly accurate control device for a brushless synchronous motor by improving the linearity between the required torque and the output torque.

[Means to solve the problem]

FIG. 1 is a diagram showing the basic configuration of the present invention. In order to solve the above problems, the present invention includes a cogging torque correction section 4 and a torque constant correction section 5 in a control device for a brushless synchronous motor 1. The cogging torque correction unit 4 uses cogging torque correction data Tco for correcting the cogging torque, which is a variation Δτ of the generated torque τ with the rotation angle θ as a parameter and does not depend on the magnitude of the generated torque τ.
g(θ) is stored in advance, and the cogging torque correction data Tcog(θ) is read out using the rotation angle θ as a parameter, and is subtracted from the required torque T'' for correction.

The torque constant correction unit 5 calculates torque constant correction data KT (θ) obtained by dividing the variation Δτ of the generated torque τ using the rotation angle θ as a parameter and the portion that depends on the magnitude of the generated torque r by the load current. 1 in advance, and furthermore, the rotation angle θ
The torque constant correction data KT (
θ) and multiplies the output of the cogging torque correction unit 4 by the reciprocal thereof, and outputs a current command to the drive control unit 3.

[For production]

In FIG. 1, according to the control device for the brushless synchronous motor 1 of the present invention, the required torque T'' from the host control device is generated by reading out the cogging torque correction 4 using the rotation angle θ from the position detector 2 as a parameter. Cogging torque correction data Tcog(θ) that does not depend on the magnitude of torque τ
will be subtracted.

This subtraction-corrected required torque T4 is a current command iT* multiplied by the reciprocal of the torque constant read from the torque constant correction unit 5 using the rotation angle θ from the position detector as a parameter.
is converted to This current command IT* includes a component for correcting the above fluctuation. The brushless synchronous motor 1 is driven by the current command iTI via the drive control section 3, and the linearity between the generated torque τ and the required torque TI is significantly improved.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a diagram showing a control device for a brushless synchronous motor according to an embodiment of the present invention. In this figure, the field poles made of permanent magnets are used as the rotor, the armature windings are used as the stator windings, and a three-phase AC armature current is passed through the stator windings, and the main magnetic flux of the field poles and this main Generates rotor (torque) in the rotor by the magnetomotive force of the armature current perpendicular to the magnetic flux,
A brushless synchronous motor 1 that rotates a rotor in synchronization with a rotating magnetic field generated by an armature current, and a magnetic motor that is connected to the brushless synchronous motor 1 and outputs a rotation angle θ of the rotor corresponding to a magnetic position as a digital signal. Position detector 2
Then, the rotation angle θ is stored in memory, each is read out manually at the rotation angle θ, and multiplied by the torque current command value l, * corresponding to the torque to be generated (output torque), and the motor applied voltage command is a current control section 3-1 that outputs a value υ9;
A constant voltage source power converter 3-2 that supplies current from a constant voltage source to the armature winding and supplies power to the motor 1 based on the applied voltage command value υ1 from the current control section 3-1, and the rotation angle θ. Storage 4 of cogging torque correction data Tcog(θ) tabulated with rotation angle θ as an address in order to correct the variation Δτ of the generated torque τ with the parameter Δτ that does not depend on the magnitude of the generated torque τ -1 and the rotation angle θ as the address, the cogging torque correction data Tcog(θ
) is read out and subtracted from the requested torque T'' from the host controller 6, a cogging torque correction section 4 corrects the requested torque T'', and a cogging torque correction section 4 that corrects the generated torque r using the rotation angle θ as a parameter. Fluctuation △τ and generated torque γ
The memory unit 5-1 stores torque constant correction data KT (θ) obtained by dividing the portion depending on the magnitude of the load current by the load current, and stores the torque constant correction data KT (θ) using the rotation angle θ as an address.
:? ! From 5-1, torque constant correction data KT (θ
) and multiplies the output of the cogging torque correction section 4 by the reciprocal thereof, and a torque constant correction section 5 that outputs the multiplied signal iT* to the current control section 3-1. .

Next, the cogging torque correction section 4 and the torque constant correction section 5, which are features of the present invention, will be explained in detail.

FIG. 3 is a diagram showing the relationship between the magnitude and fluctuation of generated torque. The inventor of this application has discovered that in the conventional torque correction method, the armature current and output torque do not become linear, and that there is a limit to highly accurate current control. There is no particular problem during operation, but when operating with varying magnitude of generated torque, torque control characteristics may deteriorate if correction torque ΔET for correcting fluctuating torque is used in proportion to the magnitude of generated torque. I noticed that. Furthermore, in order to solve this problem, it was discovered that the fluctuation of the generated torque has the following characteristics. In FIG. 3, the horizontal axis is the rotation angle θ and the vertical axis is the magnitude of the generated torque. In the third (b), the generated torque τ when no correction is made for the requested torque T'' = T from the upper control unit 6 is the rotation as shown by the solid line (1) around the desired generated torque τ for the requested torque. It changes with respect to the angle θ and does not match τ.This variation is a combination of short and long periods as shown in Figure 3(a).Next, double the required torque. When trying to obtain the desired generated torque 2τ, the short-period fluctuation part centered around 2τ is shown in Fig. 3(a) in the same way as above.
As shown in Figure 3(b), there is no change in amplitude but the period is long.

A change in amplitude can be seen as shown by the dotted line (2) in (C). Torque fluctuations in this short-period portion are called "cogging torque." It is known that this cogging torque is determined by the magnet shape, iron core shape, and their positional relationship.
. . , (θ).

On the other hand, the factors that cause torque fluctuations in the long period part are:
It is called the "torque constant". It has been found that this torque constant is mainly due to core magnetic saturation, and is expressed as τk(θ). Torque τ due to torque constant variation. , (θ), let τ, (θ) be the generated torque of the solid lines in the third (b) and (c), then τ, (θ)=τ. , (θ) tenτ.

. , (θ) becomes τcr (θ)τ, (θ)−d. 09
It has been confirmed from the experimental results and simulations that (θ)-1°·τ3(θ) holds true and is proportional to the load current of 1°. Therefore, τ, (θ) = [τ, (θ) − r.

09(θ)]/1°...(1).

Here, Io is the load current flowing to the armature winding. To summarize, fluctuations in generated torque consist of cogging torque that does not depend on load current and torque due to torque constant fluctuation that depends on load current. Conventionally, the cogging torque, which does not depend on the load current, was forcibly corrected using the load current, which resulted in the correction causing the torque control characteristics to deteriorate. Therefore, it can be easily assumed that if these fluctuations can be taken into account and corrected separately, the correction accuracy will be improved.

Next, data Tcog(θ) for correcting cogging torque,
A method of creating data KT (θ) for correcting the torque constant will be explained.

FIG. 4 is a diagram showing creation of a cogging torque correction table according to the present invention. In this figure, components that are different from those in FIG. 2 are a torque detector 10 and an analog/digital A/D converter 11. Torque detector 10 is electric motor 1
It is installed on the shaft of the motor and calculates torque by converting the torsion of the shaft into an electrical signal. The A/D converter 11 converts the analog electrical signal from the torque detector 10 into a digital signal. Next, when the brushless synchronous motor 1 is operated under no load,
Data on the rotation angle θ is obtained by the position detector 2 and used for addressing the cogging torque correction data storage unit 4-1. The torque detector 10 detects the cogging torque (1
) τ in Eq. . 9(θ) (kg-m) is detected and A/D
Cogging torque correction data Tcog(θ), which is sent to the cogging torque correction data storage unit 4-1 via the converter 11 and uses the rotation angle θ as a parameter, is generated for one rotation.

FIG. 5 is a diagram showing the creation of torque constant correction data according to the present invention. In this figure, the components that are different from those in FIGS. 2 and 4 are a subtracter 13 and a divider 14. Next, when the brushless synchronous motor 1 is operated with a constant load, the position detector 2 obtains data on the rotation angle θ, which is used for addressing the torque constant correction data storage unit 5-1. The torque detector 10 detects τ and (θ) in equation (1) and outputs them to the subtracter 13 via the A/D converter 11.

In the cogging torque correction data storage section 4-1, cogging torque correction data Tcog(θ) is read based on the address of the rotation angle θ from the position detector 2.
is subtracted from the above in (θ) to obtain τ, (θ)−τ. . 9
(θ) is formed. On the other hand, the armature current■. corresponds to the load current, which is converted into a digital signal by the A/D converter, and the divider 14 converts the output of the subtracter 13 into the load current ■. divided by to form the following equation: τ5(O) is stored in the torque constant correction data storage unit 5-1 using the rotation angle θ as an address. ! Section 5-1 contains torque constant correction data KT (θ)
is created. Note that the cogging torque correction data storage section 4-1 and the torque constant correction data storage section 5-1 are constituted by a ROM (Read Memory).

Next, a series of operations according to the present invention will be explained. FIG. 6 is a flowchart for correcting torque fluctuations in a brushless synchronous motor according to an embodiment of the present invention.

First, the brushless synchronous motor 1 at the rated speed with the load zero.
The torque detector 10 calculates the cogging torque τ using the rotation angle θ as a parameter. . , (θ) is measured (Sl
). Next, with current flowing through the armature winding under a constant load, the generated torque τ(θ) is measured using a torque detector using the rotation angle θ as a parameter (S2). Steps 1 and 2
τ obtained by , (θ) and γ, (θ), the torque constant Kt (θ) is determined using the following equation (S3). Kt (θ)
=(τ, (θ)−τc09 (θ))/I0 where work.

is the load current. The cogging torque correction data TCOg(O) is stored using the cogging torque rcag (θ) obtained in step 1, and the torque constant correction data KT (θ) obtained in step 3 is stored in a storage unit 4-
1.5-1 (S4). Once the above preparations have been completed, the device will go into operation. Requested torque T0 from the upper control unit 6
The current command iTI for is calculated according to the following formula via the cogging torque correction data storage section 4 and the torque constant correction data storage 5 (S5) o iT'' =
(T"-Tcog(θ)) and □, )・Final (° elbow y 7'5"'') 911.f: Current The generated torque τ
Since the electric motor 1 is driven by the current command iTI from which fluctuation components have been removed in advance with respect to the required torque T''', the linearity with the required torque TI is significantly improved. Capacity increase can be suppressed as much as possible, and when applied to motors as actuators for automation equipment, robots, etc. (1) Highly accurate torque measurement function, stable extremely low speed drive required for DD motors, etc. It is possible to improve the performance and functionality of equipment automation.In addition, it is an element that enables highly accurate trajectory control in robot drive.

〔Effect of the invention〕

As explained above, according to the present invention, a cogging torque correction section for correcting the cogging torque which is a fluctuation in the generated torque and does not depend on the magnitude of the generated torque, and a portion that depends on the magnitude of the generated torque are corrected. Since the torque constant correction section is provided, it is expected that the linearity between the required torque and the output torque can be improved, and the control of the brushless synchronous motor can be made more precise while suppressing an increase in the storage capacity of the correction section. .

[Brief explanation of drawings]

Fig. 1 is a diagram showing the principle configuration of the present invention, Fig. 2 is a diagram showing a control device for a brushless synchronous motor according to an embodiment of the present invention, and Fig. 3 is a diagram showing the relationship between the magnitude and fluctuation of generated torque. , Fig. 4 is a diagram showing the creation of cogging torque correction data according to the present invention, Fig. 5 is a diagram showing the creation of torque constant correction data according to the invention, and Fig. 6 is a diagram showing the creation of the cogging torque correction data according to the present invention. A flowchart for correcting torque fluctuations of a synchronous motor, FIG. 7 is a diagram showing a configuration for correcting torque fluctuations of a conventional brushless motor, and FIG. 8 is a diagram showing torque fluctuations and correction of a conventional brushless motor. In the figure, 1... Brushless synchronous motor, 2... Position detector, 3... Drive control section, 4... Cogging torque correction section, 5... Torque constant correction section. Rotation Angle O Figure 5 is a flowchart for correcting torque fluctuations in a brushless synchronous motor according to an embodiment of the present invention. Figure 6 is a diagram showing a configuration for correcting torque fluctuations in a conventional brushless motor.

Claims (1)

[Claims] 1. Rotation angle (θ) of the rotor of the brushless synchronous motor (1)
) and corrects the required torque (T^*) so as to offset the variation (Δτ) of the generated torque (τ) with the rotation angle (θ) as a parameter. A brushless synchronous motor control device comprising a drive control unit (3) that drives and controls a synchronous motor (1), the generated torque (τ) having the rotation angle (θ) as a parameter.
Cogging torque correction data (Tcog(θ)) for correcting the cogging torque which is a variation (Δτ) and does not depend on the magnitude of the generated torque (τ) is stored in advance, and the rotation angle (θ) is A cogging torque correction unit (4) that reads out the cogging torque correction data (Tcog (θ)) as a parameter and subtracts it from the required torque (T^*) for correction, and uses the rotation angle (θ) as a parameter. Fluctuation (Δτ) of the generated torque (τ), which is the generated torque (
Torque constant correction data (KT(θ)) obtained by dividing the portion depending on the magnitude of τ) by the load current is stored in advance, and the torque constant correction data (KT(θ)) is further stored using the rotation angle (θ) as a parameter. θ)) and outputs a current command obtained by multiplying the output of the cogging torque correction unit (4) by its reciprocal to the drive control unit (3).
) A control device for a brushless synchronous motor, comprising: