JPH04197099A - Step motor driving system - Google Patents

Abstract

PURPOSE:To prevent step-out of motor at the time of starting by utilizing one exciting coil as a coil for detecting the rotation of rotor at the time of starting the rotor and making a switch to next excitation when the rotor reaches a predetermined position. CONSTITUTION:Upon excitation of a coil 7a, a magnetic field is induced in a stator 11 to cause counterclockwise rotation of a rotor 10 and a voltage is induced in an unexcited coil 7b. At that time, the induced voltage is differentiated through a differentiating circuit 4b to detect a peak and when the output signal therefrom is fed through a zero level detector 5b to a microprocessor 1, the microprocessor 1 delivers a signal to a driving pulse generating circuit 2. The microprocessor 1 neglects output signals from zero level detectors 5a, 5b until a step motor 6 is stopped and delivers a driving pulse switching signal to the driving pulse generating circuit 2 according to a predetermined time table.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a step motor drive system.

[Prior Art] Conventionally, a step motor is driven in an oven loop, and a pulse train of a preset pulse width is applied to an excitation coil from the start of the motor to the stop of the motor.

[Problem to be solved by the invention]

However, in the conventional example described above, since a predetermined pulse train is applied, there are the following drawbacks.

(1) When the load on the motor becomes larger than expected or when the driving force decreases due to a drop in voltage, the rotor will step out.

(2) To solve the above problem, it is necessary to set a particularly sufficient pulse width at startup, which not only causes vibration and noise in the rotor, but also causes unnecessary current to flow, resulting in large power losses. .

SUMMARY OF THE INVENTION Therefore, in view of the above-mentioned points, an object of the present invention is to provide a step motor drive method that prevents step-out during startup of the motor and ensures reliable startup.

[Means to solve the problem]

In the present invention, when driving a multi-phase excitation type step motor having a plurality of excitation coils, at least one excitation coil is used to detect rotation of a rotor when the motor is started, and an output of the excitation coil used for the detection is provided. However, after detecting that the rotor has rotated to a predetermined position, it is operated as a normal excitation coil.

[For production]

In the present invention, when starting the rotor, one of the excitation coils is
Two coils are used as rotor rotation detection coils, and when the rotor reaches a predetermined position, switching to the next excitation is performed to prevent step-out when starting the motor.

[Example] Next, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of the invention. Here, 1 is a microprocessor that controls the step motor 6, 2 is a drive pulse generation circuit that drives the step motor 6, 3a,
3b, 3c, and 3d are diodes that detect and rectify the induced voltage generated in the exciting coils 7a and 7b;
4b is a differentiation circuit, and 5a and 5c are zero level detection circuits.

FIG. 2 is a diagram illustrating the principle of rotor rotation detection used in this embodiment, in which 10 is a permanent magnet rotor, and 11 and 12 are stators.

In the above configuration, the voltage shown in FIG. 3(a) is applied to the coil 7a to excite the coil 7a. At this time, the rotor lO is assumed to rotate counterclockwise due to the magnetic field generated in the stator 11. When the rotor lO starts rotating, a voltage as shown in FIG. 3(b) is generated in the unexcited coil 7b. If the rotation angle of the rotor 10 is expressed as θ with respect to the reference line 11 in FIG.
Φ=NΦ. Cosθ(Φ.

is the maximum magnetic flux interlinking with the coil 7b).

Since the induced voltage V generated in the coil 7b as the rotor rotates can be expressed as v=-dΦ/dt, from this, v=-
(dΦ/dθ) (dθ/dt) = NΦosinθ
-(dθ/dt) is obtained.

Therefore, θ= the switching point of the excitation coil
The induced voltage reaches a maximum near π/2.

This signal is differentiated by a differentiating circuit 4d to detect a peak, and the output signal is applied to a zero level detector 5b.

The output of the zero level detector 5b indicates that the rotor has reached the coil excitation switching point, and by inputting this signal to the microprocessor 1, the microprocessor 1 outputs a signal to the drive pulse generation circuit 2. .

After that, the microprocessor 1 ignores the signals from the zero level detectors 5a and 5b until the step motor 6 stops, and outputs a drive pulse switching signal to the drive pulse generation circuit 2 according to a predetermined timetable. do.

In the above embodiments, in order to make the explanation easier to understand, a four-pole structure was explained, but it goes without saying that the step motor drive method of the present invention can also be applied to a multi-pole step motor such as 24 poles or 48 poles. can be used.

〔Effect of the invention〕

As explained above, according to the present invention, by detecting the rotational position of the rotor and switching the coil excitation during startup when step-out is likely to occur, the motor can be started reliably without compromising control position accuracy. Not only can this be done, but it can also prevent the generation of vibration and noise.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram of rotation detection used in this embodiment, and FIG. 3 is a waveform diagram for explaining the operation of FIG. 2. DESCRIPTION OF SYMBOLS 1... Microprocessor, 2... Drive pulse generation circuit, 7... Coil, lO... Rotor.

Claims (1)

[Claims] 1) When driving a multiphase excitation type step motor having multiple excitation coils, at least one
Two excitation coils are used to detect the rotation of the rotor, and after the output of the excitation coil used for the detection detects that the rotor has rotated to a predetermined position, the excitation coil is operated as a normal excitation coil. Step motor drive method.