JPH0279799A - Step motor - Google Patents

Abstract

PURPOSE:To apply damping simply when a two-phase chopper-driving step motor is stopped by removing a DC component from the output of a constant voltage circuit in one phase so as to obtain a speed signal, inverting the speed signal, and superimposing the signal on the other phase. CONSTITUTION:At the time of a constant speed rotation, a switch 4 is connected to a contact point (b). A current is made to flow into the inverter circuit of each driving circuit 1 through each constant voltage circuit 3. The gates of transistors(Tr) Q1 to Q4 are controlled with the output signals of chopper control circuits 2. Coils LA and LB are connected to the output terminals of the inverter circuits, and a two-phase pattern is obtained. When a motor is stopped, the switch 4 is switched to a low-voltage side contact point (a). The signal is inputted into a transient-signal detecting circuit 6 from the constant voltage circuit 3 in one phase (upper side in the Figure), and a DC component is removed. The speed signal obtained in this way is inverted and amplified 7 and inputted into the constant voltage circuit 3 in the other phase (lower side in the Figure). Thus, the motor is damped with the simple circuit, and the occurrence of vibration is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application in the TPE Industry 1 The present invention relates to a step motor that applies damping when the rotor is stopped.

1. Conventional technology] Step motors have the advantage of being able to accurately control position using an oven loop, so step motors are often used in equipment that requires positioning. However, with this step motor, there is a problem that vibration is large during stop F, it takes a long time to stop, and even if the rotation speed is increased, the total speed is slower than that of a servo motor or the like. Note that the time it takes for the rotor to stop is generally called settling time. Therefore, there is a need to shorten the opening time when the step motor is stopped.

In DC servo motors, etc., there is a circuit or mechanical method that detects the vibration of the rotor when it is stopped, obtains a speed signal, and feeds back this speed signal to suppress vibration and shorten the settling time. ing.

Therefore, in recent years, a method has been proposed in which a step motor is provided with a speed sensor and a braking effect is obtained through feedback control like a servo motor. Although this method provides a reasonable braking effect, it requires a speed sensor, which increases the cost, and it is desired to apply braking without a speed sensor.

As one method for achieving this, attempts have been made in the past to produce a braking effect while leaving the oven loop intact.

Methods for this include preparing two power sources and switching the voltages when stopped, generating one final pulse at an appropriate timing, and switching to constant voltage driving when stopped. However, in the open-loop control system, the braking effect was not so pronounced, and it was also susceptible to changes in load conditions and was extremely unstable. In other words, in terms of effectiveness, it is still preferable to apply braking by feedback of the speed signal.

[Problems to be Solved by the Invention] The present invention has been made in view of the above points, and its purpose is to provide a step motor that can obtain good braking effects without using a speed sensor. Our goal is to provide the following.

[Means for solving 9M 1 In order to achieve the above object, the present invention provides an analog switch that supplies drive power to the drive circuit when the rotor is rotating and lowers the voltage applied to the drive circuit when the rotor is stopped. and a constant voltage circuit that applies a constant voltage to the drive circuit when the rotor is stopped, and detects overcurrent and limits the current using a drive current detection resistor connected to the output, and A speed signal detection circuit detects a speed signal by removing the DC component from the output of the constant voltage circuit of the phase, and also inverts and amplifies this speed signal and outputs it, and the output of this speed signal detection circuit is connected to the phase current of the other phase. and an adder circuit that superimposes the signal and sends it to the excitation coil of the other phase.

(Function) By configuring as described above, the present invention detects the speed in the speed I1τ detection circuit from the voltage change that occurs in the output of the constant voltage circuit of either phase due to the back electromotive force of the rotor at the time of stop 1. The signal is detected, and the output obtained by inverting this speed signal is superimposed on the phase current of the other phase using an adder circuit. In other words, the speed signal obtained when the rotor is stopped F on the negative phase side is fed back to the other phase. It is designed to apply gunbing.

(Example) An embodiment of the present invention is shown in FIGS. 1 to 5.

The step motor of this embodiment is a two-phase step motor in which an alternating current is passed through the excitation coils LA and LR, respectively, by a drive circuit 1 composed of transistors Q, ~Q, in an H-brittle configuration, and driven by a chopper control circuit 2. The circuit 1 is driven by a chopper, and the coil current is detected by a coil current detection resistor R5A*RSR to cause a constant current to flow through the excitation coils LA and L.

In this embodiment, in addition to the basic step motor circuit described above, the following configuration is provided. In other words, when the rotor is rotating, the drive circuit 1 is supplied with the drive source V ++n, and when the rotor is stopped, the analog switch 4 lowers the voltage applied to the drive circuit 1, and when the rotor is stopped, the drive circuit 1 is supplied with a constant voltage. and a constant voltage circuit 3 that limits the current by detecting an overcurrent with a drive current detection resistor R1 connected to the output, and a drive current of the constant voltage circuit 3 of either phase when the rotor is stopped. a speed signal detection circuit 6 that detects a speed signal by removing a DC component from the voltage across the detection resistor R, and also inverts and amplifies this speed signal and outputs it;
An adder circuit 7 is provided which superimposes the output of the speed signal detection circuit 6 on the phase current of the other phase and flows it to the excitation coil of the other phase.

The output voltage of the analog switch 4 when the rotor is stopped is set by the volume VR, and the set voltage value when the rotor is stopped is determined by the current of the constant voltage circuit 3, taking into account the resistance value of the FaJiI coil L Decide so that it is approximately equal to the limit value.

In addition, a puff 7r is provided in the constant voltage circuit 3 of the upper phase in FIG.
The analog switch 4 output is input via 5. Hereinafter, the upper part in FIG. 1 will be referred to as A phase, and the lower part will be referred to as B phase.

When the rotor is rotating, the drive power VDrl is applied to the drive circuit 1 via the analog switch 4, and the chicopper control circuit 2 performs constant current drive. When the rotor is stopped, the analog switch 4 is used to control the voltage setting volume VR.
A low voltage set in is applied to the drive circuit 1, and the drive circuit 1 is driven at a constant voltage. When the rotor is stopped, the counter electromotive force generated by the rotor magnet is superimposed on the output of the constant voltage circuit 3 (the output of the drive current detection resistor R1 on the drive circuit 1 side).

In other words, since the voltage is constant during original constant voltage driving,
The back electromotive force caused by the rotor magnets is canceled out, and there should be no change in the output voltage of the constant voltage circuit 3.However, this current limiting circuit 3 limits the current value, and the rotor stops 1-
Due to the back electromotive force at the time, a current exceeding the set current limit value flows into the drive circuit 1, so the constant voltage circuit 3 operates to limit the current, and the back electromotive voltage component becomes a voltage change, causing the constant voltage circuit 3 to Appears in the output. In other words, since this back electromotive voltage component does not correspond to the rotor speed, the speed signal detection circuit 6 detects the speed signal by removing the DC voltage from the output of the constant voltage circuit. The detection circuit 6 inverts and amplifies the output, and adds it to the polynym VR't' output of the analog switch 4 and the adder circuit 7. In other words, the adder circuit 7 adds the phase current of the B phase to the speed of the A phase. Damping is applied to the B phase by subtracting the signal, that is, applying feedback.

Here, the principle of shortening the settling time by feeding back the speed signal will be explained. Note that this principle will be explained using a speed sensor.

First, when damping control is not performed, the speed signal detected by the speed sensor in each phase is proportional to the rotational speed of the rotor, and is expressed by the following equation.

E＾=-to ω5sin(θs) −(1)EB=
ω43 cos(θs) ” (2) The equation of motion of the two-phase step motor is simplified as follows.

T=J"-19-'+Bzu-q-9...(3) dt
dj Next, when defining the motor torque formula, the rotor is A, B
There are two phases, each magnetic flux distribution is sin-like, and the phase difference is 9.
Since the phase angle of the rotor is 09 and the torque constant is 0, the torque of each phase is calculated by the following formula. The peak value of the current is I2. Then i^=
I, cos(θE)...(6)iB"
I, 5in(θE)...(7), and by substituting equations (6) and (7) into equations (4) and (5), respectively, the following torque equation is obtained.

TA=-, I, 5in(θ5)eos(θE)
・=(8)TR=K,1. cos(θ5)si
n(θF) − (9) Therefore, the total torque is T = T A + T B = K o I os + n (
θF−〇s) = 410). Here, the current phase angle and the rotor phase angle are almost equal near the stopping point, so 5in(θE-θs)#θε-θS...(11
) can be approximated as After applying this to equation (10), (
3) By substituting into the equation and performing Laplace transform, the following transfer function is obtained. However, K=1. The vibration frequency fss damping ratio ξ and settling time t5 in equation (12), which is the binding, are expressed as f fi = EK7] - ξ = B/(2ff Otcho), which shows a typical second-order lag response. . Above (12)
If the formula is expressed in a block diagram, it will be as shown in FIG.

In this second-order lag response, in order to suppress vibration and shorten the settling time tS, the viscosity coefficient B may be controlled to become equivalently large.

Therefore, the speed signal is fed back as shown in the block diagram of FIG. Here, the speed signal is (IL(2
), and if these equations are multiplied by the dein a and the motor current equations (6) and (7) are respectively destroyed, then iA= lo oc
os(θp)-QEs = I ucos(θ,)-1-Q KωS s i
n (θ5) = I 0(eos(θ'') ten βωssi
++(θ1)) −(11) Similarly, iB= 1, (sin(θF)−βω5 cO5(θ
ji)) ・(14). In addition, β== (!
It/i. It is defined as.

Therefore, if the total torque of the motor is calculated by substituting the currents shown in the above equations (13) and (14) into the torque equations (4)1(5), then T=TA+T.

”K, I.(sin(θF-θS)-βωs)
・,・(15) Here, as in the case without gunbing control, [5] 5 inches (θE-05
)#θ, −05 to obtain the transfer function, and the settling time t9 becomes. However, K=, I, and so. Above (17)
As is clear from the equation, the viscous friction coefficient B increases only by β, and therefore the settling time becomes shorter.

The above explanation was based on the case where a speed sensor was used, but in the case of this embodiment, a speed signal is detected without using a speed sensor, and this speed signal is fed back to the B phase. Braking can be applied in the same way as when using a speed sensor. FIG. 3 is a diagram showing the effect of this embodiment, and A in the diagram shows no damping control;
The rotor is stopped after driving 9 pulses. In this case, it vibrates as shown in Fig. 3, and the settling time is 4.
0 n5ee Kagaru. However, in the case of this example, the settling time is 10 n5ec as shown at the opening in the figure.
It ended in a shortened time. In other words, according to this embodiment, the same effect as when using a speed sensor can be obtained. Moreover, if the speed signal is detected circuit-wise in this way, it becomes possible to integrate it with the chopper control circuit 2 and the like into an IC, thereby reducing the cost.

[Effect of the Invention 1] As described above, the present invention includes an analog switch that supplies drive power to the drive circuit when the rotor is rotating and lowers the voltage applied to the drive circuit when the rotor is stopped; A constant voltage circuit that applies voltage and limits the current by detecting overcurrent using a drive current detection resistor connected to the output, and a DC component from the output of the constant voltage circuit of either phase when the rotor is stopped. A speed signal detection circuit that detects a speed signal by removing it, inverts and amplifies this speed signal, and outputs it, and a speed signal detection circuit that superimposes the output of this speed signal detection circuit on the phase current of the other phase and sends it to the excitation coil of the other phase. The speed signal detection circuit detects the speed signal from the voltage change that occurs in the drive current detection resistor of the constant voltage circuit of either phase due to the back electromotive force generated by the rotor when the rotor is stopped. Speed (By superimposing the inverted output of No. 1 on the phase current of the other phase using an adder circuit, the speed signal obtained on the negative phase side when the rotor is stopped can be fed back to the other phase and damping can be applied. It is effective.Moreover, if the speed signal is detected by a circuit without using a speed sensor etc., it will be possible to integrate it with a chip control circuit etc. and make it into an IC, which will reduce the cost.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a one-sentence embodiment of the present invention, and Figures 2 (a) to (
c) is an explanatory diagram of the operation when stopped, and the same figure (dL+(e) is an explanatory diagram of the operation during normal operation, Fig. 3 is an explanatory diagram showing the measurement results with and without damping control, and Fig. 4 is an explanatory diagram with damping applied. Figure 5 is a block diagram for the case where damping is not applied. 1 is the drive circuit, 2 is the a'7 chaperer control 5iJ path, 3 is the constant voltage circuit, 4 is the analog switch, 6 is a speed signal detection circuit, 7 is an addition circuit, and L^wLB is an excitation coil. Agent Patent Attorney Ishi 1) Ai 7 Figure 2-4-T Figure 5 Procedural Amendment (Spontaneous) 1988 November 2nd

Claims (1)

[Claims] (1) The rotor is equipped with magnets and two-phase excitation coils through which excitation currents with a phase angle of 90° differ are passed, and the drive circuit that causes excitation currents to flow through these excitation coils is driven in a chopper manner, and the excitation currents flow into the rotor. In a chopper-driven step motor that maintains a constant current, an analog switch supplies drive power to the drive circuit when the rotor is rotating, and lowers the voltage applied to the drive circuit when the rotor is stopped. A constant voltage circuit that applies a constant voltage to the output and limits the current by detecting overcurrent using a drive current detection resistor connected to the output, and from the output of the constant voltage circuit of either phase when the rotor is stopped. A speed signal detection circuit that removes the DC component and detects the speed signal, inverts and amplifies this speed signal, and outputs it, and the output of this speed signal detection circuit is superimposed on the phase current of the other phase to excite the other phase. A step motor characterized by comprising an adder circuit for supplying current to a coil.