JPH02219500A - Rorational speed changing method for open-loop control pulse motor - Google Patents

Abstract

PURPOSE:To suppress vibration and to prevent the step-out of a pulse motor by making the rate of change of a pulse frequency constant in spite of a set rate of change for the period while said pulse frequency passes the resonance frequency range of a mechanical system carrying said pulse motor. CONSTITUTION:At the time t0, a pulse frequency (f) is changed from 0 to a starting pulse frequency f0. Then, said pulse frequency (f) is caused to rise at a certain set rate to the lower limit value fa of a resonance frequency range f. Simultaneously when the pulse frequency (f) reaches the lower limit value fa of f at the time t1, the rate of change of (f) is changed and a large frequency increasing rate is maintained for the period t1 from said time t1 until the pulse frequency reaches the upper limit value fb of f (until the time t2A). Simultaneously when the pulse frequency f reaches the upper limit value fb of f, the rate of in crease of f returns to the original one. After the pulse frequency reached the maximum frequency fmax corresponding to the maximum set speed at the time t3a, said frequency fmax is maintained until the time t4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for changing the rotational speed of an open-loop controlled pulse motor.

[Prior art and problems to be solved by the invention] For example, an article transfer robot is equipped with two translational axes, an X-axis and a Y-axis, and the handling head is moved in the can be moved in each direction.

These X.

The Y-axis arms are usually driven by pulse motors to position the head.

When changing the position of the handling head, the rotational speed of the pulse motor is usually increased with a constant acceleration, the head is moved at a constant maximum speed, and then the rotational speed of the pulse motor is increased with a constant negative acceleration. lower to stop the head. The speed of the pulse motor is changed by increasing or decreasing the frequency of a pulse train for generating energizing signals for each phase winding of the motor. However, especially when controlling a pulse motor in an open loop, when increasing or decreasing the pulse frequency, if this frequency passes through a resonant frequency region with a certain width, the vibrations of the mechanical system are amplified and the pulse motor becomes easily out of step.

Now, in some cases, not only the maximum moving speed of the handling head but also its acceleration/deceleration time can be arbitrarily changed by setting. In other words, the time rate of change of the pulse frequency is arbitrarily set or changed, and the vibration of the mechanical system increases when passing through the resonance frequency region, and the frequency of motor adjustment may increase.

In view of the above points, the present invention changes the rotation speed of the pulse motor by increasing or decreasing the pulse frequency for generating the energization signal for each phase winding of the open-loop control pulse motor at an arbitrary set rate of change. The purpose of the method is to suppress vibrations in a mechanical system in which a pulse motor is mounted and to prevent tax adjustment of the pulse motor.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the method for changing the rotational speed of a pulse motor according to the present invention uses pulses for generating energization signals for each phase winding of an open-loop control pulse motor. When increasing or decreasing the frequency, the pulse frequency change rate is kept constant regardless of the set change rate during the period during which this frequency passes through the resonance frequency region of the mechanical system in which the pulse motor is mounted.

[Function] Outside the resonance frequency region, the pulse frequency is increased or decreased at an arbitrarily changeable setting change rate, and the rotation speed of the pulse motor is changed. However, during the period in which the pulse frequency passes through the resonant frequency region, the pulse frequency increases or decreases at an appropriate constant rate of change that is different from the set rate of change.

[Embodiment] FIG. 1 is a block diagram showing the configuration of an article transfer robot that is an application example of a method for changing the rotational speed of an open-loop control pulse motor according to an embodiment of the present invention.

This robot, which performs so-called palletizing work, has two translational axes, an X-axis 2 and a Y-axis 4, which are orthogonal to each other. Reference numeral 6 is the X arm that constitutes the X axis 2, and reference numeral 8 is the Y arm.
This is a Y-axis arm that constitutes the axis 4. A handling head 10 for gripping articles is attached to the Y-axis arm 8. X-axis arm 6 and Y-axis arm 8 each have built-in open-loop control pulse monitors for positioning.
The Y-axis arm 8 can be translated in the X-axis direction with respect to the axis arm 6, and the handling head 1o can be translated in the Y-axis direction with respect to the Y-axis arm 8. Therefore, the handling head IO is movable in both axial directions by driving both pulse motors. The handling head 10 includes, for example, an air chuck and an air cylinder, and can grip and release an article by opening and closing the air chuck, and can move up and down by operating the air cylinder.

A teaching pendant 30 has various keys such as a numeric keypad and a display window, and is connected to a microprocessor 34 via an I10 port 32. A memory 36 is connected to this microprocessor 34. Furthermore, the microprocessor 34! Signals are exchanged with the X-axis arm 6 through the 10 port 32, and the X-axis arm 6 exchanges some signals with the Y-axis arm 8.

A case in which the handling head 10 is moved from the starting point S to the ending point E will be described below. However, the coordinates of the starting point S and the ending point E are input to the microprocessor 34 through the numeric keypad of the teaching pendant 30 and stored in the memory 36. In addition, the maximum speed of movement and acceleration/deceleration time between these points S and E are also set and input in the same way, and are stored in the memory 3.
6 is stored. The pulse motors built into the X-axis arm 6 and Y Idl arm 8 are driven by the microprocessor 34 via the I10 port 32 based on this information.

FIG. 2 is a flowchart showing the operation of the microprocessor 34.

First, the pulse rate at startup, that is, the period of the pulse train for generating the energization signal for each phase winding of the pulse motor, is set in a software timer (step 1). This starting pulse rate is determined in consideration of the self-starting characteristics of the open-loop control pulse motor, and is determined by the starting pulse frequency f. corresponds to

The software timer outputs one pulse to the pulse motor each time the time measurement is completed (step 2). This pulse is converted into an energization signal for each phase winding through a logic circuit consisting of a flip-flop, etc., and is applied to the pulse motor. A pulse motor that is given sequential energization signals is
Rotate one step at a time.

In step 3, it is determined whether the pulse rate currently set in the software timer has reached a value corresponding to the maximum moving speed of the handling head 10, which is manually set in advance in the memory 3G. If it has not been reached,
In step 4, it is checked whether the pulse frequency f is within the resonance frequency region Δf specific to the shaft. If it is not within the resonance range, set the set acceleration pulse rate in the software timer according to the set acceleration time (Step 5)
However, if it is within the resonance region, a predetermined acceleration rate for the resonance region that is different from this set acceleration pulse rate is set (step 6).

After the processing in step 5 or 7, the process returns to step 2.

Therefore, when adopting an acceleration rate for the resonance region that is larger than the set acceleration pulse rate, the handling head I
During the period until the moving speed of O reaches the set maximum speed, the rate of change of the pulse frequency f becomes large only within the resonance frequency region Δf, and this region can be passed through in a short time.

Once the pulse rate reaches a value corresponding to the maximum speed of movement of the handling rod 10, the process proceeds to step 7, where it is determined whether or not to start deceleration. If deceleration is not to be performed, the process returns to step 2 while maintaining the current pulse rate in step 8. When decelerating, it is checked again whether the step pulse frequency f is within the resonance frequency range Δf unique to the shaft. If it is not within the resonance region, a set deceleration pulse rate corresponding to the set deceleration time is set in the software timer (step 10), but if it is within the resonance region, a predetermined deceleration rate for creating resonance that is different from this set deceleration pulse rate is set. Set (Step 11)
. After the processing in step 10 or 11, the process advances to step 12 to determine whether the starting pulse rate has been decelerated or not, that is, the pulse frequency f is f.

It is determined whether or not the speed has decreased to 100. If further deceleration is required, the process returns to step 2. Conversely, the pulse frequency f is fo
If the pulse train output to the pulse motor is reached, the rotation of the motor is stopped (step 13).
. Therefore, when adopting a deceleration rate for resonance formation that is larger than the set deceleration pulse rate, the period until the moving speed of the handling head 10 decreases from the set maximum speed to a constant speed is in the resonance frequency region Δf, similar to the time of acceleration. The rate of change of the pulse frequency f becomes large only within this range, and it is possible to pass through this range in a short time.

Note that even if the set acceleration/deceleration pulse rate regarding the pulse frequency f is changed, the acceleration/deceleration rate for the resonance region is not changed.

FIG. 3 is a time chart showing temporal changes in the pulse frequency f for the pulse motor due to the operation of the microprocessor 84 described above.

At time 10, the pulse frequency f is suddenly changed from O to the starting pulse frequency fo. Subsequently, the pulse frequency f is increased to the lower limit value f 2 of the resonant frequency region Δf at a set constant rate. Pulse frequency f at time t1
As soon as Δf reaches the lower limit fa, the rate of change of f is changed, and during the period Δt (until time t2a) from time t1 until Δf reaches the upper limit fb, a large frequency increase rate is maintained, for example. . pulse frequency f
At the same time that Δf reaches the upper limit value f, the rate of increase in f returns to the original value. After the pulse frequency f reaches the maximum frequency f corresponding to the set maximum speed at time t3a, at time t4
Up to this frequency ff1a! Maintain f.

The aX pulse frequency f maintains the highest frequency f for a predetermined time, then decreases at a rate of 18X for a constant time from time t4, and returns to the resonant frequency region Δ at time t5.
The upper limit value fb of f is reached. As soon as the pulse frequency f reaches the upper limit value fb of Δf, its rate of decrease is changed, and the period Δt (until time t8a) from time t5 until the pulse frequency f reaches the lower limit value f of Δf has a large frequency decrease rate, for example. maintain. Then, as soon as the pulse frequency f reaches the lower limit value f 2 of Δf, the decreasing rate of f returns to the original value. Thereafter, when the pulse frequency f reaches the starting pulse frequency fo at time t7a, f is suddenly decreased to O and the pulse motor is stopped.

In the case of the conventional method of changing the rotational speed of a pulse motor, the pulse frequency f changes as shown by the two-dot chain line in the figure.

That is, starting pulse frequency f reaches the maximum frequency f from time t 0 0
A constant frequency increase rate is maintained over the entire period until time tab when the pulse starts waxing, and a constant frequency decrease rate is maintained over the entire period from time t when the maximum frequency f is reached to time t7b when the starting pulse frequency fo is reached. In other words, when passing through the resonance frequency region Δf, the time t1
It takes a time Δt from time t2b to time t2b, and a time Δt4 from time t5 to time t6b, respectively. In this example, the transit times Δt and Δt3 are respectively Δt2
and Δt4.

Note that the pulse rate may be set in a hardware timer instead of the software timer.

[Effects of the Invention] As explained above, the method for changing the rotational speed of a pulse motor according to the present invention is effective when increasing or decreasing the pulse frequency for generating the energization signal for each phase winding of an open-loop control pulse motor. , during the period during which this frequency passes through the resonance frequency region of the mechanical system in which the pulse motor is mounted, the pulse frequency change rate is kept constant regardless of the set change rate.According to the present invention, the vibration of the mechanical system is reduced. It is possible to suppress the noise of the pulse motor and prevent the tax adjustment of the pulse motor.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an article transfer robot that is an application example of the method for changing the rotation speed of an open-loop control pulse motor according to an embodiment of the present invention, and FIG. FIG. 3 is a time chart showing temporal changes in pulse frequency for the pulse motors that drive each axis of the article transfer robot shown in FIG. 1. Explanation of symbols 2...X-axis, 4...Y-axis, 6...X-axis arm, 8
... Y-axis arm, 10 ... Handling head, 3
0...Teaching pendant, 34...Microprocessor. Patent applicant: Shibaura Seisakusho Co., Ltd.

Claims (1)

[Claims] 1. In a method of changing the rotational speed of the pulse motor by increasing or decreasing the pulse frequency for generating the energization signal for each phase winding of an open-loop control pulse motor at a set arbitrary rate of change, the pulse frequency is changed. When increasing or decreasing the frequency, the rate of change is kept constant regardless of the setting during a period during which the frequency passes through a resonance frequency region of a mechanical system in which the pulse motor is mounted. How to change speed.