JPH0681537B2 - State observer for motor load torque estimation - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement of a state observer for estimating a motor load torque from an output torque current signal and a speed signal of an electric motor.

[Conventional technology]

Conventionally, when driving an electric motor at a variable speed, it is known to provide a state observer 1 as shown in FIG. 6 to estimate the electric motor load torque τ _L and compensate the output torque of the electric motor. In addition,
In the figure, 2 is a control circuit, 3 is a power converter, 4 is an electric motor, 5 is a load, and 6 is a speed detector. By the way, as such a state observing device 1, as shown in FIG. 7, an integrator 11A simulating a mechanical system of an electric motor (1 / S
T _M , S are Laplace operators, T _M is the starting time constant), integrator 11
B, a proportional amplifier 12A, adder / subtractors 13A, 13B, 13C, an output torque calculator 15, etc., and is detected via a speed detector 6 and a motor torque component current signal I _a equivalent to the output of the power converter 3. It is known that the load torque is estimated from the speed signal n.

[Problems to be Solved by the Invention]

However, it is difficult for the speed detector to accurately detect fluctuations of high frequency components included in the speed detection value, and therefore the speed estimation value calculated by the state observer 1 Is attached to indicate an estimated value, and the same applies hereinafter. ) Cannot be canceled out, and as a result, the pulsation component of the output torque due to the pulsation of the torque component current resulting from the switching operation of the power converter 3 and the imbalance of the AC power supply becomes the load torque estimated value. Will appear in _L. Therefore, to realize a stable control of the motor 4, so that the transfer characteristic predetermined attenuation amount A is obtained at the fundamental frequency component omega _S of the pulsation components as Figure 8, with respect to omega _S Cutoff frequency ω
Must be set _{and C,} as a result, the response characteristic of the load torque estimate for step changes in such load torque of FIG. 9, there is a problem that the response time increases as the dotted line in FIG.

Therefore, it is an object of the present invention to provide a state observing device capable of estimating a motor load torque at high speed and stably.

[Means for Solving the Problems]

In order to achieve the above object, in the present invention, at least one of the input side or the output side of the state observer for estimating the motor load torque, a moving average filter having a transfer characteristic that attenuates the pulsating component of the output torque. Provided.

[Action]

By setting the transfer characteristic of the smoothing filter so that the output torque pulsation component due to the switching operation of the power converter and the imbalance of the AC power source is sufficiently attenuated, the response of the load torque estimation calculation circuit is made faster, The influence of the output torque pulsation on the estimated load torque output is eliminated to speed up the response.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention. As is apparent from the figure, this embodiment is characterized in that the moving average filter 14 is provided at the subsequent stage of the conventional circuit shown in FIG. The state observer 1 shown in FIG. 1 is applied, for example, as shown in FIG. 2. However, since FIG. 2 is basically the same as that in FIG. 6, its explanation is omitted.

The function of the filter 14 will be described below. Now, the gain of the integrator 11A is 1 / T _M , and the gain of the proportional amplifier 12A is 2ζω.
_C T _M, the gain of the integrator ^{_{11B ω C 2 T M (ω}} C: natural frequency of the state observers, zeta: damping off actor), and the output torque τ _a = φI _a [phi: motor constant, I _a: Armature current (current of output torque)] and load torque τ _L ,
Speed n When expressed as Is expressed by the following equation.

Assuming that the high frequency speed change due to the torque pulsation component is not detected by the speed detector, n in equation (2) is used.
Since (S) is n (S) = 0, the expression (2) is substituted by substituting this. Becomes

Next, the moving average filter 14 moves from time (tT) to t. If you output (T: averaging time), Is. From the above equations (1), (2) and (5) Is obtained.

On the other hand, the pulsating component of the output torque τ _a is mainly 6ω _S , 12ω _S , 18ω _S , ... due to the switching of the power converter 3.
2ω due to three-phase unbalance with the component of (ω _S : power source angular frequency)
2 mω _S (m = 1,2, consisting of components of _S , 4ω _S , 6ω _S , ...
3, ...) component, and if T = π / ω _S for these, the above equation (6) becomes Becomes Substituting this into equation (7), from _L , H ₁
The 2mω _S component is removed regardless of the transfer characteristic of (S).

If it is difficult to detect the 2mω _S component by the velocity detector, by substituting n (j2mω _S ) ≈0 into equation (4), Can be obtained by the following equation.

Here, In order not to be too large, (output) ≤ (input)
From the relationship Under these conditions, ω _C becomes a value within the range represented by the following equation.

FIG. 3 shows another embodiment of the present invention.

This is because the filters 14A and 14B are provided on the input side so as to realize the same transfer characteristic as the expression (5). In this case, the output torque ripple components of the speed signal n and the signal I _a are
Since the transfer characteristic is removed by the moving average filters 14A and 14B of H ₂ (S), H ₁ (S) can be set freely.

Although the filters are provided on the input side or the output side in the above, they may be provided on both sides.

FIG. 4 and FIG. 5 show the above two embodiments, FIG. 7 is a characteristic diagram showing an example of transient response of the load torque estimated output with respect to the transfer characteristic | H ₁ (jω) · H ₂ (jω) | From Figure 4,
It can be seen that the transfer characteristic has an infinite amount of attenuation with respect to the torque ripple component of 2 mΩ _S , and the response time of the load torque average estimated value is π / ω _S (1/1 of the AC power supply as shown by the dotted line in Fig. 5).
2 cycles), and it can be seen that the response becomes faster than in the conventional method of FIG.

〔The invention's effect〕

According to the present invention, the moving average filter is provided on at least one of the input side and the output side of the state observing device to eliminate the output torque pulsation, so that the load torque irrespective of the response characteristic of the state observing device. Since the output torque pulsation component is not mixed in the estimated output, the transient response of the load torque estimation output is speeded up by improving the response of the load torque estimation calculation, which brings the advantage that stable and high-speed load torque estimation is possible. .

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing an electric motor variable speed drive device to which the present invention is applied, and FIG. 3 is a block diagram showing another embodiment of the present invention. FIG. 4 is a characteristic diagram showing a transfer characteristic of the state observing device according to the present invention, and FIG. 5 is a characteristic diagram showing an estimated output response characteristic with respect to a load torque unit step change according to the present invention.
The figure is a block diagram showing a conventional example of a motor variable speed drive device,
FIG. 7 is a block diagram showing an example of a general state observer, FIG. 8 is a characteristic diagram showing the transfer characteristic of the state observer shown in FIG. 7, and FIG. 9 is a characteristic diagram showing the state observer shown in FIG. It is a characteristic view which shows the response characteristic of the estimated value with respect to a load torque unit step change. Description of symbols 1 ... State observer, 2 ... Control circuit, 3 ... Power converter, 4 ... Electric motor, 5 ... Load, 6 ... Speed detector, 7
...... Moment of inertia, 11A, 11B …… Integrator, 12A, 12B ……
Proportional amplifier, 13A, 13B, 13C ... Adder / subtractor, 14, 14A, 14B ...
… Filter, 15… Output torque calculator.

Claims (1)

[Claims] 1. A state observing device for estimating a motor load torque from a current signal corresponding to an output torque of a motor and a speed signal, wherein a transfer characteristic for attenuating a pulsating component of the output torque to at least one of an input side and an output side thereof. A state observer for estimating a motor load torque, comprising a moving average filter having: