JPS62239881A - Control of dc motor - Google Patents

Abstract

PURPOSE:To enable a DC motor to deccelerate and stop without hunting even under the load of large inertia, by using the residual travel of a motor multiplied by a constant value as a command speed at which the motor should run. CONSTITUTION:A control means 2 contained in a digital control unit u receives the command data from outside and outputs a control signal to a drive circuit 3. A control means 2 acquires a signal of an encoder 5 that detects the rotation of a DC motor 4 as a feedback signal and outputs a control signal so as to stop the DC motor at the target stopping position. In soft-stopping the, command speed given to the motor 4 is changed over in the middle from a pattern wherein the speed is determined by decrementing by a constant value an externally inputted command speed at every specified time down to zero to a pattern wherein it is determined by the residual travel multiplied by a constant value.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method of controlling a DC motor that is equipped with an encoder for detecting position and speed, performs soft start and stop, and performs a position system @ seven steps. The present invention relates to a digital control method for a surface flow motor suitable for positioning a large inertial load with a soft stop.

[Conventional technology]

Conventionally, as a DC motor equipped with a soft stop function, as described in Japanese Utility Model Application Publication No. 59-109296,
A known method is to perform a soft stop by subtracting a command speed that the motor should follow during deceleration from an externally input command speed by a constant value at regular intervals until it reaches zero.

[Problem that the invention seeks to solve]

In the conventional technology described above, if the load inertia is small and the load speed can follow the command speed well when performing a soft stop in a short time, a clean soft stop can be performed, but if the load inertia is large, the load speed However, there is a problem in that the motor cannot be decelerated to follow the command speed, and the motor ends up passing the stop position. When the stop position is exceeded, reverse rotation and forward rotation are repeated to stop at the target stop position, but such a hunting phenomenon and a long stop time are required. An object of the present invention is to provide a digital control method for a DC motor, which performs a soft stop without overshooting when starting and stopping a load with large inertia in a short time.

[Means for solving problems]

The object of the present invention is to determine the command speed given to the motor during a soft stop by multiplying the remaining travel distance by a certain value from a pattern in which the command speed given to the motor is determined by decelerating by a certain value at certain time intervals from the externally input command speed to zero. and then switch to a pattern that uses that value as the command speed (achieved from C).

[Effect]

By multiplying the motor's remaining travel distance by a constant value and setting the motor's command speed to a power of 9, the command speed decreases exponentially. That is, it decreases rapidly at the start of deceleration, but gradually decreases as it approaches the stop position, so even a large inertial load can be decelerated and stopped without hunting.

〔Example〕

The following describes a motor deceleration method according to an embodiment of the present invention.
As shown in the figure. Further, the configuration of the apparatus of the embodiment is shown in FIG.

In FIG. 2, U indicates a digital control device, and 1 indicates command data. Then, upon receiving command data 1t from the outside, the control means 2 included in the digital control device U outputs a control signal to the drive circuit 3 to control the DC motor 4. The control means 2 receives a signal from an encoder 5 that detects the rotation of the DC motor 4 as a feedback signal, and outputs a control signal to stop the DC motor 4 at a target stop position. or,
The drive circuit receives the output signal of the control means 2 and digitally controls the DC motor 4.

A method of performing soft stop positioning and stopping in such a control Q position will be explained.

The principle of soft stop will be explained with reference to FIG.

The command speed to be followed by the motor is set from zero to the externally input command speed ns using direct current, and the motor is started from the beginning until it reaches the externally input command speed. Measure the distance ta that the DC motor has moved, and measure the remaining distance traveled so that it is equal to this distance. The starting point of the soft stop is a point Q at which the areas of the shaded area shown in (which shows the rotational speed waveform of the motor when the motor is rotated) and the area of the shaded area S are equal to each other.

The positioning control method of the present invention based on the above-mentioned soft stop principle is a deceleration method in which a deceleration curve A is obtained after the start of deceleration as shown in FIG. From the method in which the speed is determined by subtracting a fixed value from the speed to zero at fixed intervals, P
At point B, the deceleration method is switched to a deceleration method (method in which the command speed to be followed by the DC motor M is determined by multiplying the remaining travel distance by a constant value to obtain the running value) and deceleration is performed. A flowchart of this procedure is shown in FIG. As shown in Figure 3, first, an externally inputted finger <? The commanded speed a is calculated by subtracting a fixed value from the speed to zero at fixed time intervals, and then the commanded speed a is calculated by multiplying the remaining travel distance by a fixed value to obtain the commanded speed. Then, it is determined whether the deceleration method has been established or not, that is, whether it is after point P in FIG. Also, before switching,
Next, determine whether a) b, and if a>b, then
a) If not b, let a be the commanded speed that the motor should follow.

As described above, according to this embodiment, when position control is performed using a short-time soft stop, the soft stop can be performed without overshooting even for a large inertial load. Also, compared to the case where the command speed calculated from the remaining travel distance alone is enough for the deceleration, the speed change at the start of deceleration can be made smaller.
This has the effect of reducing the shock given to the load during deceleration.

So far, we have described a soft stop in which the soft stop start point is determined by the travel distance at the soft start, but the same applies to the case where the soft stop is started when a predetermined fixed remaining travel distance is reached. be.

〔Effect of the invention〕

As described above, according to the present invention, even when the inertia of the load is large, multiple soft stop patterns are controlled by switching between both patterns, so that the DC motor can be positioned and stopped in a short time without... It is.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of a deceleration method showing an embodiment of the present invention;
3 is a block diagram of an embodiment of the present invention, FIG. 3 is a flowchart showing the procedure of an embodiment of the present invention, and FIG. 4 is an explanatory diagram showing a conventional deceleration method. A...Deceleration curve due to constant deceleration at fixed time intervals, B...
...Deceleration curve due to remaining travel distance, P...Intersection of A and B, U...Digital control device, 1...Command data, 2...Control means, 3...Drive circuit, 4. ...DC motor, 5...encoder. Agent: Patent Attorney Katsuo Ogawa - 7th ward in 1st map

Claims (1)

[Claims] 1. A DC motor, an encoder that detects the rotation of this DC motor, a drive circuit that drives this DC motor, a speed command given from the outside, and an actual DC current obtained by the encoder. and control means for digitally processing and controlling the rotation of the DC motor based on a speed signal of the motor, the control means changing the command speed given to the DC motor from zero to a command input externally. A DC motor that calculates according to the speed, performs a soft start according to a pattern based on this calculation result, calculates from an externally input command speed to zero, and performs a soft stop according to a pattern based on this calculation result. In the control method, when the soft stop is started, the deceleration is performed according to the latter pattern, and on the way, calculation is performed according to the distance to be moved to the stop position, and the pattern is switched to a pattern based on the calculation result, and the DC A DC motor control method characterized by decelerating the motor and stopping it at a target position.