JPS6129230B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a speed control device that limits the torque of an electric motor according to the operating state and allows smooth operation.

(Prior Art) In controlling the speed of an electric motor, it is well known that current or torque is limited depending on the allowable current of the electric motor or the allowable torque of a load.

FIG. 7 is a block diagram of a speed control device with torque limitation for a DC motor. In this circuit, since the torque of the motor is proportional to its current, the motor current is limited to a constant value.

In FIG. 7, the speed of the electric motor 4 is detected by a speed generator 5, and its speed signal ω is input to a speed control amplifier 1.

The speed control amplifier 1 receives the speed command ωr and the speed signal ω.
The output signal Ir is given as a current command to the current control amplifier 2 at the next stage, the power converter 3 is controlled by the output, and the current of the motor 4 is set as the signal Ir.
control so that it is proportional to. 6 is a current detector,
The armature current I of the motor 4 is detected and given to the current control amplifier 2 as a feedback signal.

The output signal Ir of the speed control amplifier 1 is the speed command ωr
When the difference between and the speed signal ω is small, the difference ωr−
It is proportional to ω, but when this difference becomes large, the output signal Ir is limited to a constant value Irmax. As a result, the motor current I is limited to a value proportional to Irmax, and the torque of the motor is limited.

An example of this torque limiting circuit is shown in FIG. In FIG. 8, 8 is an operational amplifier which outputs a voltage signal Ir proportional to the difference ωr-ω between the speed command ωr and the speed signal ω. That is, when the signal Ir reaches the limit value Irmax, depending on its polarity, for example, in the case of forward rotation, transistor 1Q is energized, and in the case of reverse rotation, transistor 2Q is energized, and the signal Ir does not increase beyond the limit value - Irmax. It is something.

The above limit value Irmax can be adjusted by changing the ratio of resistors 4RS and 5RS or 6RS and 7RS. In addition, in Fig. 8, 1RS, 2RS, 3
RS is a resistor, and 1D, 2D, 3D, and 4D are diodes for determining polarity.

Next, the relationship between the current value, rotational speed, and time when starting and stopping the electric motor 4 will be explained using FIG. 3a. At startup, the current value I is the limit value
Instantly rises to the value equivalent to Irmax. For this reason,
The rotation speed N of the electric motor 4 rises rapidly, and starting is completed from time t ₀ to t ₁ . After this, operate at the rated rotation speed Nmax. The current value I at this time is
This value is significantly lower than the limit value Irmax. time
When the stop control is performed at t ₃ , the armature current I flows in the opposite direction, quickly reaches a value corresponding to the negative limit value −Irmax, and stops for a short time until time t ₄ . This operation is exactly the same for starting and stopping during reverse rotation.

However, short-time stop control using a large deceleration torque (large current value) as described above may have an adverse effect on the mechanical system of the driven device. For example, in a servo device where the inertia of the mechanical system is large and the power transmission system uses a gear mechanism, especially a worm gear, if a sudden deceleration is performed as described above, the impact on the gears will be large when the transition from high speed rotation to deceleration occurs. May cause damage to the system.

One possible means of preventing the sudden deceleration is to set the limit value Irmax to a low value, suppress the current value flowing during stop control to a low value, and bring the vehicle to a slow stop with a relatively weak deceleration torque. For example, as shown in FIG. 3b, the limit value Irmax' is set lower than the limit value Irmax. However, with this setting, the motor will come to a slow stop until time _t6 with a relatively weak deceleration torque, but on the other hand,
Since a sufficient accelerating current cannot be obtained, the startup time also becomes long from time t ₀ to t ₂ . In other words, it is generally desirable that the rotational speed of this type of electric motor 4 rises as quickly as possible when starting up, and as mentioned above, if the acceleration is low, the response time will be long when performing control such as angle difference response. Put it away.

(Problems to be Solved by the Invention) The problems to be solved by the present invention are that the mechanical system is subject to a large impact because the deceleration of high-speed tangles is performed rapidly by large torque, and in order to solve this problem, If the current value is limited to a low value, the speed rise at startup will be slow.

Therefore, it is an object of the present invention to provide a speed control device that alleviates sudden deceleration from high speed without reducing the rise speed at startup, and reduces shock to the mechanical system. .

[Structure of the invention]

(Means for Solving the Problems) The speed control device of the present invention inputs from a speed generator a speed signal ω having a polarity corresponding to the direction of rotation of the motor and a magnitude proportional to the rotation speed. The value of the limit value Irmax with the polarity opposite to the speed signal ω
The above problem was solved by providing a limit value adjuster that lowers the limit value according to the magnitude of the limit value.

(Function) In the present invention, during stop control of the motor, the value of the armature current flowing in the opposite direction to that during operation is suppressed to a value lower than a preset control value Irmax, and the deceleration torque from high speed is reduced. This prevents strong shock from being applied to the mechanical system.

(Example) Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an example of a speed control device according to the present invention. In FIG. 1, numeral 7 is a limit value adjuster for limiting torque, and the other parts are the same as in FIG. That is, the limit value of speed control amplifier 1
Irmax was a constant value in the conventional figure 7, but in figure 1 according to the present invention, the limit value Irmax is automatically set by inputting the speed signal ω and the current signal I to the limit value adjuster 7. Changes to An example of a circuit including this torque limiting regulator 7 is shown in FIG.

In FIG. 2, diodes 6D and 8D provided in the limit value regulator 7 are used to determine the polarity of the output of the speed generator 5, that is, the direction of rotation of the electric motor 4. For example, the diode 6D is for determining reverse rotation, and its anode is connected to the illustrated lower terminal side of the speed generator 5, which becomes the positive electrode when the motor 4 is reversed. Further, its cathode is connected via a variable resistor 9VR to the base side of a transistor 1Q constituting the torque limiting circuit of the speed control amplifier 1 configured in the same manner as before, that is, to the connection point between resistors 4RS and 5RS. On the other hand, the diode 8D is for normal rotation determination, and its cathode is connected to the illustrated lower terminal side of the speed generator 5, which becomes a negative electrode when the motor 4 rotates in the normal rotation. Moreover, the anode is a variable resistor 11
The base side of the transistor 2Q constituting the above-mentioned torque limiting circuit via VR, that is, the resistor 6RS
Connect to the connection point between and 7RS. In addition, resistance 13
RS generates a voltage according to the output of the speed generator 5.

In FIG. 2, transistor 1Q limits the output signal Ir of speed control amplifier 1 to a positive control value Irmax by turning on the transistor 1Q, and limits the output signal Ir to a negative limit value by turning on transistor 2Q. -Limited to Irmax.

In the above configuration, when starting the electric motor 4 in the forward rotation direction, the current value I changes at the time as shown in FIG. 3c.
At _t0 , it instantly rises to a value corresponding to a preset positive limit value Irmax. During this startup, a negative potential is generated on the lower terminal side of the speed generator 5 shown in the figure, but the base side of the transistor 1Q is not affected by the diode 6D, and the positive limit value Irmax set by the resistors 4RS and 5RS is maintained. is output as the output signal of the speed control amplifier 1. Therefore, the start-up speed of the electric motor 4 at the time of starting does not decrease, and the starting is completed at time _t1 .

On the other hand, when the stop control is performed at time _t3 , the armature current I flows in the opposite direction. At this time, electric motor 4
Since the rotation direction of is the normal rotation direction as mentioned above,
A negative potential is generated on the lower terminal side of the speed generator 5 as shown in the figure, and is connected to the transistor 2 via the diode 8D.
Joins the base side of Q. Therefore, the negative limit value -
Irmax is significantly lower than the value set by the resistors 6RS and 7RS, and the reverse current value I at time _t3 is limited by the lowered negative limit value -Irmax'. Therefore, the deceleration torque from high speed is relaxed, and no large impact is applied to the mechanical system. Furthermore, when the rotational speed of the electric motor 4 decreases due to the above-mentioned stop control, the output of the speed generator 5 also decreases.
The negative potential applied to the base of transistor 2Q also decreases, and the negative limit value -Irmax' increases, eventually returning to the original set limit value -Irmax. Therefore, the deceleration in the high speed range where the impact of the mechanical system is large is gradual, but the deceleration in the low speed range where the impact of the mechanical system is small is rapid, resulting in a weak impact and a stop in a relatively short time. Control is complete.

For starting and stopping operations when the motor 4 is reversed, the output polarity of the speed generator 5 is reversed, and the reduction of the limit value Irmax for deceleration is controlled by the transistor 1Q via the diode 6D and the variable resistor 9VR. However, all other operations are the same as described above.

Control value Irmax (-Irmax) during the above deceleration
The amount of decrease varies depending on the magnitude of the corresponding variable resistor 9VR or 11VR, as shown in FIG.

In addition, if you want to limit the torque at the time of starting the electric motor 4 for some reason, as shown by the line in FIG. Just connect 10VR. With this configuration, when starting in the forward direction, the transistor 1Q is connected via the diode 5D and variable resistor 8VR.
can be controlled and the positive control value Irmax can be reduced to limit the torque at the start of forward rotation. Also, when starting in the reverse direction, transistor 2Q is controlled via diode 7D and variable resistor 10VR, and the negative control value -
It is possible to limit the torque when starting in reverse by lowering Irmax.

In the circuit of FIG. 5, a series circuit of a variable resistor 16VR and a switching element 9 is connected in parallel to a resistor 5RS for setting an operating value of a transistor 1Q that determines a positive limit value Irmax. This switching element 9 is always on, and is configured to lower the limit value Irmax by turning it off. Also, the negative limit value - Irmax
Similarly, a series circuit of a variable resistor 17VR and a switching element 10 is connected in parallel to a resistor 7RS for setting the operating value of a transistor 2Q, which determines the
By turning off the switching element 10, the value of the negative limit value -Irmax is lowered. These switching elements 9 and 10 are provided with corresponding logic elements 11 and 12 for turning off the switching elements. For these logic elements 11 and 12, the direction of the armature current I of the electric motor 4 and the rotational direction and rotational speed of the electric motor 4 are added as input conditions. That is, the armature current I is detected by the current detector 6
, and after reaching a predetermined voltage at resistors 14RS and 15RS, the corresponding logic elements 11 and 15 are connected via corresponding diodes 11D and 9D.
12. Furthermore, after the output of the speed generator 5 reaches a predetermined voltage through the resistors 12RS and 13RS, the Zener diodes 1ZD and 2
ZD and corresponding logic elements 11, 12 through corresponding diodes 10D, 12D.
is applied to the other input terminal of

For the sake of explanation, the input points of each logic element 11 and 12 are labeled a, b, c, and d, and the output points thereof are labeled e and f. A NAND circuit is used for each of the logic elements 11 and 12, and only when the input points a, b or c, d are "1", the corresponding output points e, f become "0", and under other conditions Output points e and f become "1". The switching elements 9, 10 are turned on when the output points e, f of the corresponding logic elements 11, 12 are "1", and are turned off when they are "0".

Next, input points a, b, and
The relationship between the "1" and "0" levels of c and d will be explained.
When the electric motor 4 rotates in the normal direction, the input point b becomes "0", and the input point d becomes "1" if the rotation speed is equal to or higher than the planned value (set by the Zener diode 2ZD), and "0" if it is less than the planned value. . When the motor 4 is in reverse rotation, the input point d becomes "0", the input point b becomes "1" if the rotational speed is equal to or higher than the predetermined value (set by the Zener diode 1ZD), and "0" if it is less than the predetermined value. In addition, if the motor 4 enters deceleration during normal rotation, the armature current I will be in the opposite direction, so input point c becomes "1" and input point a becomes "0". , input point a becomes "1" and input point c becomes "0".

In the above configuration, regardless of whether the electric motor 4 is rotating in the forward or reverse direction, if it has not entered deceleration, the input points a and b of the logic element 11 and the input points c and d of the logic element 12 are None of them are "1", and these output points e and f are each "1", and switching elements 9 and 10 are in an on state. Therefore, the base of transistor 1Q includes resistors 5RS and 16VR connected in parallel with each other, and resistor 4 connected in series with them.
The divided voltage with RS is added, and the positive limit value Irmax becomes the value set by these. The same goes for transistor 2Q, as the divided voltage of resistors 7RS, 17VR and resistor 6RS is applied to the base.
Negative limit value - Irmax will be the value set by these. Next, when stop control is performed from the high-speed normal rotation state, the armature current I is reversed and the input point c becomes "1". Also, since it is in a high speed state of forward rotation,
The input point d maintains "1", and as a result, the output point f of the logic element 12 becomes "0", turning off the switching element 10. On the other hand, since the speed command ωr of the speed control amplifier 1 becomes "0" due to the stop control, a negative output signal -Ir is generated in accordance with this difference by comparison with the speed signal ω in the high speed state. This output signal -Ir is limited by the transistor 2Q and becomes -Irmax, but the base potential of the transistor 2Q is lowered (approximately 0V) due to the off operation of the switching element 10, and the negative reduced value -Irmax has decreased to -Irmax' as shown in Figure 6. Therefore, the armature current I is suppressed to a low value, and the speed is decelerated from high speed with relatively low torque. The speed of the electric motor 4 is reduced by the above-mentioned stop control, and the sixth
When ω in the figure becomes less than ₁ , the input point d is inverted to "0", and the output point f of the logic element 12 is set to the "1" level, turning on the switching element 10.
Therefore, the base potential of the transistor 2Q rises to its original value, the negative limit value also rises to its original value -Irmax, a relatively large armature current I flows, and deceleration is performed with strong torque. In other words, in high speed ranges, a relatively high torque is used to gently decelerate to weaken the mechanical impact, while in low speed ranges, high torque is used to quickly decelerate.
Stopping time is shortened.

Regarding the stop control during reverse rotation, the basic operation is the same although the polarity of each part is different, and the explanation will be omitted.

〔Effect of the invention〕

As described above, according to the present invention, when controlling the stop of an electric motor running at high speed, it is decelerated with relatively low torque in the high speed range, so that the shock applied to the mechanical system is alleviated and the motor is smoothly operated. can be stopped.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the speed control device according to the present invention, Fig. 2 is a circuit diagram showing the main part configuration in Fig. 1, and Fig. 3 compares the operation of the present invention with the conventional operation. FIG. 4 is a characteristic diagram showing the change in the limit value with respect to speed in FIG. 1 in relation to the value of the variable resistor. FIG. This figure is a characteristic diagram showing the relationship between the limit value and speed in FIG. 5, and FIGS. 7 and 8 are a block diagram and a main circuit diagram of the conventional device. 1... Speed control amplifier, 2... Current control amplifier, 3... Power converter, 4... Electric motor, 5... Speed generator, 6... Current detector, 7... Limit value regulator, 8 ...Operation amplifier, 9,10...Switching element.

Claims (1)

[Scope of Claims] 1. A speed generator that outputs a speed signal ω with a polarity corresponding to the rotational direction of the motor and a magnitude proportional to the rotational speed, and a speed signal ω and a speed command ω from the speed generator.
a speed control amplifier that outputs a signal Ir with a polarity and magnitude corresponding to the difference between the speed control amplifier and r, and limits the signal Ir to a predetermined control value Irmax for each of the positive and negative polarities when the difference exceeds a predetermined value; a current control amplifier that controls the motor current according to the output signal Ir of the speed control amplifier; A speed control device comprising: a limit value adjuster that lowers the limit value according to the size; and a speed control device. 2. A speed generator that outputs a speed signal ω with a polarity that corresponds to the rotation direction of the motor and a magnitude that is proportional to the rotation speed, and a speed signal ω and a speed command ω from this speed generator.
a speed control amplifier that outputs a signal Ir with a polarity and magnitude corresponding to the difference between the speed control amplifier and r, and limits the signal Ir to a predetermined control value Irmax for each of the positive and negative polarities when the difference exceeds a predetermined value; a current control amplifier that controls the motor current according to the output signal Ir of the speed control amplifier; and inputs a speed signal ω from the speed generator and a polarity signal corresponding to the direction of the armature current I of the motor; Based on the magnitude and polarity of A speed control device comprising: a limit value adjuster that reduces the limit value Irmax of polarity opposite to the polarity of the speed signal to a predetermined level.