JPH03198676A - Calculation of digital torque command value of motor - Google Patents

Abstract

PURPOSE:To obtain a torque command value having excellent control response by so composing a calculator as to obtain the command value of a digital amount by calculating directly from a position control loop. CONSTITUTION:In order to control a motor 1, a torque command T* of a digital amount is obtained from a position command value of a digital amount, a position detected value X of a digital amount fed back from the motor 1 and a speed detected value N. In this case, the command T* is calculated directly from input values by a torque command value calculator 5 without providing a speed control loop of a minor loop. Thus, the value T* of the digital amount having excellent control response is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a digital torque command (l! calculation method) for an electric motor for quickly calculating a torque command value for motor position control as a digital quantity.

[Prior Art] FIG. 3 is a block diagram showing a general example of electric motor control.

In FIG. 3, reference numeral 1 is a block diagram simulating an electric motor, and an integrator 2 integrates a speed detection value N obtained from the electric motor 1 to calculate a position detection value X. The torque command value calculation circuit 5 calculates the torque command value T1 from the speed detection value N1 position detection value X and the separately set position command value X''.On the other hand, the load torque estimation circuit 4 calculates the load torque The estimated value TL is calculated and output.

The adder 6 adds the torque command value T" and the estimated load torque value T, and sends the addition result to the torque control device 3.
The torque of the electric motor 1 is controlled by this torque control device 3. As a result, inside the electric motor 1, the remainder after subtracting the load torque TL from the generated torque T is used as acceleration torque to accelerate the load. Here, 1/S-J written inside the electric motor 1 is a transfer function from this acceleration torque to the speed N, and expresses the inertia of the electric motor including the load.

This speed detection value N of the electric motor 1 is integrated to obtain the device detection value X.
However, the specific means to obtain the position detection value X is as follows.
Of course, instead of the integrator 2, the position may be directly detected by a detection means attached to the rotating shaft of the electric motor 1, for example. Furthermore, the estimated load torque value T1 functions to offset the influence of the load 1 torque TL actually applied to the electric motor 1.

FIG. 4 is a circuit diagram showing a conventional example of a torque command value calculation circuit 5 for obtaining a digital torque command value in the electric motor control circuit shown in FIG.

In this FIG. 4, the digital quantity position command value X1,
The digital position detection value X and speed detection value N fed back from the electric motor 1 are each sent to the sampler 1.
1.12 or 13 are sampled separately.

The adder 14 calculates the deviation between the sampled position command value X'' and the position detected value
The output is manually input to the adder 15 as a speed command value, and since the sampled speed detection value N is also input to this adder 15, the adder 15 calculates the difference between the two inputs.

When this calculation result is input to the speed regulator 17, which is composed of a proportional-integral calculator, the speed regulator 17 outputs a control signal that makes the input deviation zero. This control signal is held in the sample holder 18, and the torque command value T1
1.

[Problem to be solved by the invention]

As shown in FIG. 4 above, conventionally, in order to obtain the torque command value T, a speed control loop is provided as a minor loop inside the position control loop, so in order to obtain a quick control response, , a processing device capable of extremely high-speed calculation is required. Conversely, if a microcomputer whose calculation speed is not very fast is used, the control response becomes slow and unstable.

Therefore, an object of the present invention is to obtain a digital torque command value with good control responsiveness without requiring a high-speed processing device.

[Means for Solving the Problems] In order to achieve the above object, the digital torque command value calculation method of the present invention adds a moment of inertia I that is the sum of the motor and the load to the sampled position command value of the electric motor.・
A first calculation result is obtained by multiplying the sampled position detection value of the motor by an amount proportional to and inversely proportional to the square of the sampling period. A second calculation result is obtained by multiplying the square by an amount inversely proportional to the square, and a third calculation result is obtained by multiplying the sampled speed detection value of the motor by an amount proportional to the total moment of inertia and inversely proportional to the sampling period. A calculation result is obtained, a second calculation result and a third calculation result are subtracted from the first calculation result, and the subtraction result is taken out as a torque command value for the electric motor via a sample holder, or the sampled The position command value of the nth motor is proportional to the moment of inertia that is the sum of the motor and the load,
and obtain a fourth calculation result by multiplying an amount inversely proportional to the square of the sampling period, and multiplying the n-th sampled position detection value of the motor by an amount proportional to the total moment of inertia,
and obtain a fifth calculation result by multiplying by an amount inversely proportional to the square of the sampling period, and multiplying the n-th sampled speed detection value of the motor by an amount proportional to the total moment of inertia,
Then, a sixth calculation result is obtained by multiplying the sampling period by a star that is inversely proportional to the sampling period, a seventh calculation result is obtained by multiplying the n-th sampled 1 to LK command values by a predetermined value, and a fifth calculation result is obtained from the fourth calculation result. The calculation result is subtracted from the sixth calculation result and the seventh calculation result, and the subtraction result is taken out as the n+1-th torque command value for the electric motor via the sample holder.

[Effect]

This invention is based on the fact that the presence of a speed control loop as a minor loop inside the position control loop is the cause of not being able to improve control responsiveness or the need for a processing device capable of high-speed data processing. By configuring the calculation circuit so that the digital torque command value can be calculated directly from the position control loop,
The objective is to obtain a torque command value with good control responsiveness without using a high-speed processing device.

〔Example〕

First, the principle of the present invention will be explained below.

As mentioned above, when trying to obtain the torque command value T1 by direct calculation in the position control loop without using the speed control minor loop, the N number ratio model of the controlled object can be expressed by the following equation (1). However, if x+=X , the torque command value T11 can be calculated backwards from the following equation (2).

T.

Here, if we set "Z-x + -X", the position command value X1
The torque command value T8 required to follow can be calculated by (3) 2.

Therefore, it is sufficient to construct a circuit that calculates this equation (3).

FIG. 1 is a circuit diagram showing a first embodiment of the present invention, and this circuit allows the calculation of equation (3) to be executed.

In this FIG. 1, the digital quantity position command value X1 is
After being sampled by the sampler 11, it is input to the proportional gain 2I.
Since it has a gain that is proportional to twice the sampling period T5 and inversely proportional to the square of the sampling period T5, the output of the proportional gain 21 becomes the first term on the right side of the above-mentioned equation (3), that is, the first calculation result.

The position detection value X fed back from the electric motor 1 is
After being sampled by the sampler 12, it is input to the proportional gain 22. This proportional gain 22 is 2 of the understanding moment J.
Since it has a negative polarity gain that is proportional to the sampling period T, and inversely proportional to the square of the sampling period T, the proportional gain
The output becomes the operation of the second term on the right side of equation (3), that is, the second operation result.

Further, the speed detection value N fed back from the electric motor 1 is sampled by a sampler 13 and then input to a proportional gain 23 . This proportional gain 23 has a negative polarity gain that is proportional to twice the moment of inertia J and inversely proportional to the sampling period T, so the output of this proportional gain 23 is calculated by the third term on the right side of equation (3). In other words, it becomes the third calculation result.

The first calculation result, the second calculation result, and the third calculation result are added in the adder 24, and the calculation result is held in the sample holder 18 and taken out as the 1.] O torque command value T1.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention.

The discretized model of the controlled object can be expressed by equation (1) as described above, where T = T" + Tt, TL = T, and the total moment of inertia of the motor and its load J is known, and considering the calculation time of the arithmetic processing unit that performs digital calculations, the torque command value calculated based on the n-th sampling point value X + tn+, It has to be output as T9°.1 at the sampling point.Therefore, the calculation at the nth sampling point is n
+ Value at the second sampling point X + tn*t)
The torque command value T1, . . . required to match the position command value X'' (nl) is determined.

Then, equation (1) can be replaced by equation (7) below.

Z−X−8・x + b・T1−−−−− (7
) By multiplying both sides of this equation (7) by Z or by 8, the following equation (8) can be obtained.

Z2・X=A −Z −XIb・Z−T“−82・X1
8.1)-T"1-1)-Z-T"-(8) For position control, only the relationships in the upper half of the matrix are needed. Therefore, this relationship is extracted from equations (4), (5), (6) and (8) 2 and written as the following equation (9). The solution is 00) Formula Z2 ・By replacing XI with the position command value X0, n
In order to make xl at the +2nd sampling point coincide with X11, the n+1st torque command value T''1° can be found. Therefore, the following equation (11) is written by replacing Z with n. It is.

T.

That is, this equation (11) makes it possible to directly calculate the torque command value T'' for performing position control.

A circuit according to a second embodiment of the present invention shown in FIG. 2 is a circuit that executes the calculation of equation (11). In FIG. 2, the n-th digital position command value X'' is input to the proportional gain 21 via the sampler 11, but this proportional gain 21 is proportional to twice the moment of inertia LJ, and the sampling period Ts is Since it has a gain inversely proportional to the square, the output of this proportional gain 21 is the first term on the right side of equation (11), that is, the result of the 34th calculation.

The n-th position detection value X fed back from the electric motor 1 is input to the proportional gain 22 via the sampler 12, but this proportional gain 22 is proportional to twice the moment of inertia J and has a sampling period T.

Since the output of the proportional gain 22 is the second term on the right side of equation (11), that is, the fifth calculation result.

Furthermore, the n-th speed detection value N fed back from the motor 1 is input to the proportional gain 31 via the sampler 13, but this proportional gain 31 is proportional to four times the moment of inertia J, and is proportional to the sampling period T. Since it has a negative polarity gain that is inversely proportional, the output of this proportional gain 31 is the third term on the right side of equation (II), that is, the sixth calculation result.

Further, the fourth term on the right side of equation (11), that is, the seventh calculation result, is obtained by the previous value holding circuit 30 that outputs the n-th torque command value T'' and the proportional gain 32 that multiplies this by -3. .

The results of the fourth calculation, the fifth calculation, the sixth calculation 4, and the seventh calculation are added in the adder 24, and the addition result is held in the sample holder 18, so that the n→-1st torque command is The value T'' will be extracted.

〔Effect of the invention〕

According to this invention, in order to control the electric motor, in determining the digital torque command value from the digital position command value and the digital position detection value and speed detection value fed back from the electric motor, Since the torque command value is calculated directly from each of the above input values without providing a speed control loop, which is a minor loop, it is possible to obtain a digital torque command value with good control response by using data at high speeds. Since an expensive processing device for processing is not required, the cost of the device can be reduced.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing the first embodiment of the present invention;
The figure is a circuit diagram showing a second embodiment of the present invention, Figure 3 is a block diagram showing a general example of motor control, and Figure 4 is a block diagram showing a general example of motor control.
FIG. 2 is a circuit diagram showing a conventional example of a torque command value calculation circuit 5 for obtaining a digital torque command value in the motor control circuit shown in the figure. ■...Electric motor, 2...Integrator, 3...Torque control device, 4...Load torque estimation circuit, 5...Torque command value calculation circuit, 6, 14.15.24... adder,
11. , 12.13... Sampler, 16... Position adjuster, 17... Speed adjuster, 18... Sample holder, 21.22.23. , 31.32...proportional gay diagram kudzu

Claims (1)

[Claims] 1) The first calculation result is obtained by multiplying the sampled position command value of the motor by an amount that is proportional to the total moment of inertia of the motor and the load and inversely proportional to the square of the sampling period. is calculated, and the sampled position detection value of the motor is given as
A second calculation result is obtained by multiplying the total moment of inertia by an amount that is inversely proportional to the square of the sampling period, and the sampled speed detection value of the electric motor is proportional to the total moment of inertia, A third calculation result is obtained by multiplying the sampling period by an amount inversely proportional to the sampling period, the second calculation result and the third calculation result are subtracted from the first calculation result, and this subtraction result is sent to the electric motor via a sample holder. A method for calculating a digital torque command value for an electric motor, characterized in that the torque command value is extracted as a torque command value. 2) The position command value of the nth motor sampled is proportional to the moment of inertia that is the sum of the motor and the load,
and obtain a fourth calculation result by multiplying an amount inversely proportional to the square of the sampling period, and multiplying the n-th sampled position detection value of the motor by an amount proportional to the total moment of inertia,
and obtain a fifth calculation result by multiplying by an amount inversely proportional to the square of the sampling period, and multiplying the n-th sampled speed detection value of the motor by an amount proportional to the total moment of inertia,
A sixth calculation result is obtained by multiplying the sampling period by an amount inversely proportional to the sampling period, a seventh calculation result is obtained by multiplying the n-th sampled torque command value by a predetermined amount, and a fifth calculation result is obtained from the fourth calculation result. A digital torque command value calculation method for an electric motor, characterized in that the result of subtraction is subtracted from the sixth calculation result and the seventh calculation result, and the subtraction result is taken out as the (n+1)th torque command value of the electric motor through a sample holder.