JPS63209491A - Speed controller for motor - Google Patents

Abstract

PURPOSE:To effect high-speed and stable speed control without being affected by the resonance frequency or the like of a mechanical system, by controlling an object based on a principle, considering the structure of the mechanical system. CONSTITUTION:A first speed control circuit 51 outputs a deviation TS' between a commanding speed omega and a load speed omegae. A torque control circuit 52 obtains another deviation omegam' between the deviation TS' and a transmitting torque TS from a motor to a load. A second speed control circuit 53 obtains the other deviation Tm between the deviation omegam' and a motor speed omegam while the deviation Tm is given to a power converter 6 as the torque command of the motor 1. The feedback control loop of a load speed omegal is provided in such a manner and the feedback control loop of the transmitting torque TS is provided as the minor loop of said feedback control loop of the load speed omegal while the feedback control loop of the motor speed omegam is provided as the minor loop of the feedback control loop of the transmitting torque TS.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention is a speed control device that performs feedback control of the rotational speed of an electric motor, and in particular, a transmission delay in a shaft system connecting the electric motor and a load, so-called shaft resonance. The present invention relates to a speed control device for an electric motor when a motor exists.

(Prior Art) FIG. 7 shows a schematic configuration of a general speed control device that feeds back motor speed. In FIG. 7, 1 is a motor, 2 is a load device driven by the motor 1, and 3 is a motor 1.
4 is a speed detector for detecting the rotational speed of the electric motor 1, and 5 is a speed detector g (the speed ω detected in 4 is the command value ω^). A speed control circuit 6 which amplifies the deviation so as to follow the speed control circuit 5 is a power conversion device which controls the supply current of the motor 1 so as to obtain a motor torque proportional to the output of the speed control circuit 5.

FIG. 8 is a block diagram showing the speed control system of FIG. 7, and S is a Laplace operator.

In this figure, 7 is a subtraction element, 8 is a deviation amplification transfer function Gs of the speed control circuit 5, 9 is a transfer function Ge of the power converter, IO is a subtraction element, 11 is a torque vs. speed transfer function of the electric motor 1, and 12 is a subtraction element, 13 is the speed difference (ω
, -ωJ), the transfer function of the torque generated on the shaft 3 is 1
4 is a transfer function representing the mechanical damping element of the shaft system, 15 is an addition element, and 16 is the speed ω□ of the load device 2 from the shaft torque Tg.
is the transfer function up to .

7 to 9 are the components of the speed control device, and 10 to 16 are the electric motors 1. This is a component representing the transmission characteristics of the mechanical system composed of the shaft system 3 and the load device 2.

The transfer function Gs of block 8 is usually composed of proportional + integral elements, and this gain is rs4! The speed response of the speed control device is determined by s.

The transfer function Gc of the block 9 is generally determined by the current control ability of the power converter 6 and can be approximated by a first-order or second-order lag element.

The actual power transmission system includes coupling devices, gears, etc.
Although it is often complicated, in most cases tti motive 1
moment of inertia J, and moment of inertia J of load device 2
1 can be approximated by a so-called two-mass system, which is connected by an axis with a spring constant Kg, and the block diagram 10 to 16 in FIG. 8 represents the transfer characteristics of this two-mass system.

From this block diagram, the open loop-circular transfer function 60 of the motor speed ω with respect to the speed command ω is calculated as follows.

FIG. 9 is a gain diagram of the transfer function 60 of equation 0) when G8 and G are the transfer functions of equation 2 and equation 0, respectively.

Gs'=Kp (with 1+) ・・・・・・・・・
・・・・・・・・・・・・・・・■１ ・・・
・・・・・・・・・・・・・・・・・・・・・■Gc=
1 ten guns. - S In Fig. 9, the intersection angular frequency ω of Go with the O(d[l) line. determines the response speed of speed control in closed loop, and ω.

The larger the value, the faster the response. However, in order to ensure stability (phase margin) during closed loop,
It is necessary to select a slope of 20 (dB/Dec) or less.

For this reason, the integral constant Kx in the equation 0 representing the transfer characteristic of the speed control circuit 5 is selected to be less than a fraction of ωG, and the corner point etc. due to the filter time constant rc&g of Ga in the equation 0 is ω. selected more than several times. This also applies when there is no transmission delay in the shaft system.

If there is a transmission delay in the shaft system, there will be further restrictions on the selection of ωC, and in order to stably control the speed ω□ of the load device W12, ω is required. must be less than or equal to the individual angular frequency JKs/J* on the load side, because ω. When R! is increased, the speed change of the motor 1 becomes faster, and the load equipment r! 12 and the shaft system 3, the speed ω□ of the load device [2 vibrates at g/JJ with an individual angular frequency of 1, and the vibration is caused by the damping element of the mechanical system. Since it is attenuated only by the change in force, the settling time becomes longer, and as a result, the speed response of the load device 2, which is the object of control, is reduced. For this reason.

It is common to select a value smaller than the load-side individual angular frequency 4/Kg/JJ so as not to cause an excitation force.

Therefore, in applications where high-speed response speed control is required, the stiffness of the shaft (spring constant m) can be increased by increasing the angular frequency 4.
Measures are being taken to increase Km/Jt.

(Problem that R-mei is trying to solve) However, in recent years, it has become difficult to increase the natural angular frequency of many mechanical devices with complex structures, mainly robots, due to constraints such as installation surface precision. Some have a single cage frequency of several Hz.

In such cases, it is impossible to increase the response speed of the speed control system as described above, and in order to improve followability and machining accuracy, the speed must be operated without sudden changes. Therefore, the problem arises that the processing time becomes longer.

On the other hand, even in applications where high-speed response is not required, problems different from those described above occur.For example, in elevators, etc., in order to improve ride comfort, the response speed of the speed control system of the hoisting motor is lowered to prevent steep speed fluctuations. I'm trying to prevent it from happening. In an elevator, a resonant system is created between the hoisting motor shaft and the car chamber by the expansion and contraction of the lobe that suspends the car.Since the response speed of the speed control system is set low, the electric motor becomes an excitation source and the car is damaged. Normally, vibrations do not occur, but if a single resonance vibration occurs due to some disturbance, there is no vibration suppression force due to the slow response of the speed control system, and it takes time for the vibration to decay. Makes the coming experience worse. As described above, in applications where high-speed response is not required, there is a problem in that there is almost no force to suppress resonance vibrations on the load side caused by disturbances.

The present invention has been made in view of the above problem, and even when shaft resonance exists between the motor and the load, it is possible to realize a high-speed response without being restricted by the unique angular frequency of the load side. It is an object of the present invention to provide a speed control device for an electric motor that can suppress vibrations on the load side due to external disturbances even when the response is set to be slow.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object of the invention, in the present invention, as shown in FIG. 1, the first speed control circuit 51 amplifies the deviation between the command speed ω and the load speed ω□. Then, the deviation between the output TsI'I and the transmission torque T8 between the motor and the load is amplified by the torque control circuit 52, and the deviation between the output ω- and the motor speed ω is amplified by the second speed control circuit 53. The amplified signal T- is given to the power conversion device 6 as a torque command for the electric motor 1. That is, the present invention is a feedback control loop of load speed ω1.

It has a feedback control loop for the transmission torque T8 as its minor loop, and a feedback control loop for the motor speed ω as its minor loop.

However, even when the motor speed ω is used as a feedback signal in the outermost control loop instead of the load speed ω, the object of the present invention can be achieved as described later.

(Function) The speed ω□ of the load 2 is determined by the torque Ts of the shaft 3. Therefore, the shaft torque T, When ω changes, the load speed ω is controlled to follow the command speed ω. The shaft torque T8 is feedback-controlled by the torque control circuit 52 so that the shaft torque T8 follows the shaft torque command T-, which is the output of the first speed control circuit 51. Since the shaft torque τ8 is generated by the speed difference between the motor speed ω and the load speed ω, in order for the shaft torque T11 to be controlled quickly and stably, the motor speed ω must be adjusted to follow the output ω- of the torque control circuit 52. , needs to change. The second speed control circuit 53 acts so that the motor speed ω follows the motor speed command ω-, which is the output of the torque control circuit 52.

In this way, in the present invention, the frequency of the object is controlled based on a principle that takes into account the structure of the mechanical system, so high-speed and stable speed control can be achieved without being affected by the resonance frequency of the mechanical system.

(Example) (Configuration of Example) FIG. 1 is a configuration diagram showing an example of the present invention, in which 1 is an electric motor, 2 is a load device driven by the electric motor 1, and 3 is a load device 2 from the electric motor 4a1. !2, 41 is a speed detector for detecting the rotational speed ω1 of the electric motor 1, 42 is a speed detector for detecting the speed ω□ of the load device 2, 43 is a shaft system 51 is a first speed control circuit that amplifies the deviation between the speed ω1 of the load device 2 detected by the speed detector 43 and its command value ω, 52; is the torque detector 43
A torque control circuit 53 amplifies the deviation between the shaft torque T detected by the speed detector 41 and the output of the first speed control circuit 51; 6 is a power conversion device that controls the current supplied to the motor 1 so as to obtain a motor torque T1 proportional to the output T- of the second speed control circuit 53; be.

(Operation of the embodiment) The first speed control circuit 51 outputs a shaft torque command T? as a signal obtained by amplifying the deviation of the load speed ω1 from the speed command ω.
Output. Since the shaft torque Ts is the driving force of the load device 2, if the shaft torque TIl changes following the command 7s%, the load speed ω□ will be increased by the action of the first speed control circuit 51.
is controlled to follow the command speed ω decrease.

The torque control circuit 52 determines whether the shaft torque is the command value T? The purpose is to control it so that it follows.

The deviation between the command element - and the detected value T8 is amplified and outputted as a speed command ω- for the electric motor 1. That is, the shaft torque T8
is proportional to the rotation angle difference between the motor 1 and the load device 2, so
In order for the shaft torque T8 to follow the command TsM, the motor speed ω needs to change according to the torque deviation 8-T8.

The second speed control circuit 53 is a circuit for changing the motor speed ω1 according to the torque deviation. It is amplified and output to the power conversion device 6 as the generated torque command τ- of the electric 1F11 machine 1.

The power conversion device 6 controls the current supplied to the electric motor 1 according to the torque command T-, and the electric motor 1 generates a torque T that is approximately proportional to the torque command T-.

Therefore, the motor torque T, is approximately proportional to the output T- of the second speed control circuit 53, and the motor speed ω1 is controlled to follow the output ω♂ of the torque control circuit 52. Then, due to the action of the torque control circuit 52, the shaft torque T8 becomes the first
The speed control circuit 51 is controlled to follow the output T1114 of the speed control circuit 51. As a result, the load speed ω□ is controlled to follow the command speed ω by the action of the first speed control circuit 51.

FIG. 2 shows a transfer function block diagram of the embodiment having the configuration shown in FIG. Since this element is the same as the block with , the explanation will be omitted. 71.72.73 is a subtraction element, 81.82.
83 are blocks representing the deviation amplification transfer functions of the first speed control circuit 51, the torque control circuit 52, and the second speed control circuit 53, respectively.

Each deviation amplification transfer function is Gtt1+ GTI G
Let it be sz.

As is clear from FIG. 2, the embodiment shown in FIG. 1 provides feedback control of the outputs of three integral elements 11, 13, and 16 included in the mechanical system.

By feeding back the motor speed ω, the output of the torque control circuit 52, f′I! Motivation speed command ω
, and the motor speed ω1 can be approximated by a first-order lag. The response angular frequency ωc2 of the loop expressed as the reciprocal of the time constant of this first-order delay can be determined by the gain IGa*I of the second speed control circuit 53, and if the control delay of the power conversion device 6 is ignored, ωet
can be selected arbitrarily. However, in reality, the power conversion bag v
In addition to the control delay of 16, there is a detection delay of the speed detector 41, which is omitted in Fig. 2, so if the response angular frequency ωc2 is chosen too high, it is impossible to approximate it with a first-order delay. This results in an unstable system. In this way ωe2
Although there is an upper limit, it can be arbitrarily selected as long as it is below the response angular frequency obtained as a speed control system when the motor is alone with the load 2 disconnected.

Similarly, the shaft torque feedback loop can be approximated by a first-order lag, and the response angular frequency ωeT of the loop can be selected by the control gain IGTI of the torque control circuit 52. However, since the first-order delay can be approximated in a region where the delay of the control loop of the motor speed ω can be ignored, it is necessary to select 00 to be less than ωc2 in order to ensure stability.

Furthermore, regarding the feedback loop of the load speed ω□, ωC is similarly controlled by the gain of the first speed control circuit 51.
The loop response angular frequency ωC can be selected within a range of T or less.

(Effects of Example) FIG. 3 shows the deviation amplification transfer function G of the first speed control circuit 51.
Speed command ω when g□ is proportional/integral controlled using formula 0
This figure shows a gain diagram of the open-loop-circular transfer function 60 of the load speed ω with respect to 0. In this figure, the transfer function G of the shaft torque control loop, which is a minor loop, is shown. , transfer function G of the motor speed control loop. Also shown is the gain diagram.

As is clear from the comparison of FIG. 3 with FIG.

The gain diagram of the speed control system of the present invention is a curve that monotonically decreases as the angular frequency ω increases, and there is no point affected by mechanical constants.In other words, according to the present invention, regardless of the resonance frequency of the mechanical system, there is no point affected by the mechanical constant.・Response angular frequency ω as a speed control system. can be selected, and the control response required of the device can be realized.

In addition, even if the control response is set low, the operation of the minor ft1 motor speed control loop and shaft torque control loop will not cause vibrations due to external disturbances.
This is because when the load speed ω changes due to disturbance or the like, the shaft torque T8 and the motor speed ω1 also change. Due to the low control response, changes in the load speed ω□ are not reflected much in the output of the first speed control circuit 51, but the shaft torque T
Since changes in s and motor speed ω are reflected in the control output of the minor loop, the mechanical system does not vibrate by ε.

(Other Embodiments) In the block diagram of FIG. 2, the shaft torque Tli and the load speed ω1 subtracted through the two subtraction elements 10 and 12 can be treated as disturbance elements within the loop.

As with conventional speed control systems, disturbances do not cause the system to become unstable and are not much of a problem; however, in the present invention, the influence of disturbances can be reduced by 1F! if necessary. Reduced configurations are also possible.

FIG. 4 shows another embodiment of the present invention configured to reduce the influence of disturbances. The embodiment of FIG. 4 has the configuration of the embodiment of FIG. It was added. The adder circuit 54 outputs a signal obtained by adding the load speed ω to the output of the torque control port N52 as a motor speed command ω−.
It is given to the second speed control circuit 53 as a signal. Addition circuit 55
is a signal obtained by adding the shaft torque T to the output of the second speed control circuit 53 and outputs the signal to the power converter 6 as a motor torque command T-.
give to

FIG. 5 is a transfer function block diagram of the embodiment shown in FIG. 4, and the double-door arithmetic circuits 54 and 55 are represented by addition elements having the same number.

By superimposing the shaft torque Tg on the electric motor torque command T- in the addition element 55, 1! Although there is a difference due to the transfer function 60 of the t-power conversion device 6, the delay in Go is small, so that the shaft torque applied via the subtraction element 10 can be canceled. As a result, ω in the motor speed control loop
The followability of the motor speed ω relative to - is ensured even when the shaft torque T8 fluctuates.

Similarly, by using the signal on which the load speed ωJ is superimposed in the addition element 54 as the motor speed command ω-, the subtraction element 1
The load speed ω applied through 2.

can be removed from the torque control loop.

As described above, according to the configuration of the embodiment shown in FIG. 4, it is possible to realize a speed control system in which disturbance factors are eliminated. In the embodiment shown in FIG. 4, the rain detection signal of shaft torque Tg and load speed ω□ is used to perform disturbance correction, but it is clear that disturbance correction for either one alone is effective.

In the embodiments of FIGS. 1 and 4, the first speed control circuit 5
Although the load speed ω□ is used as the feedback speed for 1, it is also possible to use π and the motive speed ωyo instead of the load speed ω1 as in another embodiment of the present invention shown in FIG. Through the operation of the minor motor speed control loop and shaft torque control loop, the shaft torque T8 is controlled to stably follow the command 7314. If stability is ensured, there will be almost no difference between the motor speed ω and the load speed ω□, so it is clear that a stable and fast-responsive speed control device can also be realized by the embodiment shown in Fig. 6. It is.

Also, in the embodiment shown in FIG. 6, as in the embodiment shown in FIG. ! Disturbance correction for the l14il speed control loop can also be performed.

In the embodiment of the present invention described above, the shaft torque Tll to be fed back to the torque control circuit 52 is detected by the torque detector 43 attached to the shaft system 3. In addition to this means of mounting torque detector 43, there are many other ways to obtain a torque feedback signal.

From the block diagrams shown in FIGS. 2, 4, and 8,
The following equations for calculating the shaft torques T and l are obtained. However, the following formula ignores the attenuation factor. Since the shaft torque control loop is for the purpose of stabilizing the system, the feedback torque signal does not need to be accurate, and the purpose can be achieved as long as it is a signal that changes in the same way as the shaft torque T8. Therefore, there is no problem even if the attenuation factor is ignored.

rs= Tl1-Jli・Genko ・・・・・・・・・
・・・・・・・・・・・・・・・ 0t If the load speed ω1 can be detected, the shaft torque T can be obtained using a circuit that calculates the formula.

Furthermore, in places where it is easy to install an accelerometer, such as inside an elevator car, the detected acceleration can be multiplied by a coefficient to obtain the acceleration.

If the motor speed ω and the load speed ω□ can be detected, the shaft torque Ts can also be calculated using equation (c).

■To calculate the equation, we need the motor torque T, but since the motor torque T and its command T- are almost equal, we use the command torque T- in place of equation 11 in the calculation. Even if the torque is fed back, the object of the present invention can be sufficiently achieved. By using the torque command T-,
(The only detection signal required to calculate Equation 60 is the motor speed ω.

It becomes possible to realize a speed control device with a simple configuration.

〔Effect of the invention〕

As explained above, according to the present invention, even when shaft resonance exists between the motor and the load, it is possible to realize a speed control device with high-speed response without being affected by the two-machine resonance system. becomes. Furthermore, even in applications where the speed flil+control response is slow, the speed on the load side can be stably controlled without causing load side vibration due to external disturbances or the like.

For convenience of explanation, the power transmission system from the electric motor to the load device is treated as the axis, but the present invention is applicable to all mechanical systems in which the power transmission system includes a spring element, such as the hanging lobe of an elevator. Therefore, the speed control device of the present invention can be applied to many fields.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
Figure 3 is a transfer function block diagram of the speed control system in the embodiment shown in Figure 1. Figure 3 is a gain diagram of the Louvous circular transfer function between the speed control systems of the embodiment in Figure 1. Figure 4 is a configuration showing another embodiment of the present invention. Figure, 5th
The figures are a transfer function block diagram of the speed control system shown in FIG. 4, FIG. 6 is a block diagram showing still another embodiment of the present invention, FIG. 7 is a block diagram of a conventional general speed control device, and 9 is a transfer function block diagram of the speed control system shown in FIG. 7, and FIG. 9 is a gain diagram of the loop-circular transfer function of the speed control system shown in FIG. 1...Electric motor, 2...Load device. 3... Axis system, 4, 41.42... Speed detector. 51, 53...speed control circuit, 52...torque control circuit, 54.55...addition circuit. 6...Power conversion device. Agent Patent Attorney Noriyuki Chika Yudo Hirofumi Mitsumata Figure 7

Claims (1)

[Scope of Claims] In order to control the speed of an electric motor that drives a load device, a speed control device for an electric motor is configured to determine a command value of a motor generated torque according to a deviation between a detected speed value and a command value, a first speed control circuit that controls the speed of the electric motor or the load device by feedback in response to a speed command value; and a transmission torque between the electric motor and the load device using the output of the first speed control circuit as the command value. a torque control circuit that performs feedback control; and a second speed control circuit that performs feedback control of the speed of the electric motor using the output of the torque control circuit as a command value, and uses the output of the second speed control circuit to generate the electric motor. A speed control device for an electric motor, characterized in that it is used as a torque command value.