JP2708928B2 - Motor positioning control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a motor positioning control device to which a frictional force is applied as a load.

[Conventional technology]

FIG. 3 is a control block diagram showing a conventional motor positioning control device similar to, for example, Japanese Patent Application Laid-Open No. 58-144202. FIG. 4 is a diagram showing a frictional force as a load using the motor positioning control device. It shows a current after positioning when a certain mechanism is subjected to positioning control. In FIG. 3, (1) is a movement command generation circuit for creating a movement distance command value P ^* to a target position, and (2) is a movement distance command value P ^*.
And a position control circuit for detecting the difference between the actual movement distance P and the speed command value ω ^* , and (3) the speed command value ω ^* output from the position control circuit and the actual speed ω speed control circuit for detecting a difference generates a current command value i ^*, the
(4) is a current control circuit for detecting the difference between the current command value i ^* output from the speed control circuit and the actual current i to generate a voltage v applied to the motor, and (5) is a motor control circuit for In the block diagram, (5a) is the reciprocal (1 / R _a ) of the armature resistance, (5b) is the torque constant (K _T ), and (5c) is the reciprocal (1) of the product of the moment of inertia J and the Laplace operator s. / Js), (5d) is the speed electromotive force constant (K _E), (6) represents the integration by the inverse of the Laplace operator s. In the drawing, V _C is the speed electromotive force, T _m is motor torque, T _L is the load torque (unbalanced torque; gravity when the vertical movement and the like), T _F is the frictional torque.

Next, the operation will be described. Consider a case where the motor (5) is to be stopped at a predetermined position. First, the difference between the current position and the target position is output by the movement command generation circuit (1) as a movement distance command value p ^* . The position control circuit (2) generates a speed command value ω ^* from the difference between the moving distance command value p ^* and the actual moving distance p. The speed control circuit (3) generates a current command value i ^* from a difference between the speed command value ω ^* and the actual speed ω. The current control circuit (4) obtains the applied voltage v to the motor from the difference between the current command i ^* and the actual current i, and applies it to the motor (5). When positioning is completed, the motor sum of the torque T _m of a (5), and the load torque T _L and the friction torque T _F (difference)
The motor (5) stops at a position where is balanced. Therefore, when the motor is stopped, a current flows to generate the sum (difference) of the load torque _TL and the friction torque _TF .

[Problems to be solved by the invention]

Incidentally, FIG. 4 is a graph showing a stopping current (hereinafter, a holding current) of a motor that drives a mechanism that moves in a vertical direction, in which the vertical axis indicates the motor holding current, the horizontal axis indicates the stop position, and a The b indicates the holding current when moving down and stopping, and b indicates the holding current when moving down and stopping. As can be seen from this graph, even when the vehicle stops at the same position, the current varies depending on the approaching direction.

That is, even if the motor is stopped at the same position as described above, a useless current is consumed in the approaching direction, and the motor and the drive circuit generate heat due to the useless holding current at the time of the stop and burn out. There was a point.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and it is possible to perform control so as to eliminate a useless current flowing against a frictional force after positioning is stopped and to minimize a current. An object of the present invention is to provide a motor positioning control device.

[Means for solving the problem]

A motor positioning control device according to the present invention generates a speed command value by detecting a difference between an output of the movement command generating circuit and an actual moving distance, the movement command generating circuit generating a moving distance to a target position. Control circuit for detecting the difference between the output of the position control circuit and the actual speed to generate a current command value, and detecting the difference between the output of the speed control circuit and the actual current A current control circuit for generating a voltage applied to the motor and controlling the position of the motor to which the frictional force is applied as a load. Inputting a gain change command output from the movement command generation circuit to change the gain of the position control circuit or the gain of the speed control circuit, When the difference between the actual moving distance and moving distance command value is equal to or larger than a predetermined value is characterized in that it comprises a gain change circuit for stopping the gain change.

[Action]

According to the present invention, the gain of the position or speed control circuit is lowered by the gain changing circuit after the positioning is stopped, and the gain is fixed when the movement is started even by a small amount, thereby reducing the holding current at the time of stopping.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1 in which the same parts as those in FIG. In FIG. 1, as a new configuration, (7) designates a gain change command and a movement distance command value p from a movement command generation circuit (1).
^This is a gain changing circuit for changing the gain of the speed control circuit (3) by inputting the difference between ^* and the actual moving distance p.

Next, the operation will be described. The operation is the same as that of the conventional example until the positioning is stopped. However, when a gain change command is received from the movement command generation circuit (1) after a lapse of a fixed time after the positioning is stopped, the gain changing circuit (7) performs speed control. Start lowering the gain of circuit (3). Then, the current command i
^* Decreases, and the current i flowing through the motor decreases. That is, in FIG. 2, if the position is at the point A when the positioning is stopped, the current decreases with the gain change, and the current changes as indicated by a broken line. The current can be reduced without changing the position up to the point B. If the point B is slightly exceeded, the position cannot be held and the position starts to change. The change in position is determined by the movement distance command value p ^*.
Since the difference can be determined by observing the difference between the distance and the actual moving distance p, when the difference is equal to or more than a predetermined value, the gain changing circuit (7)
Stops the gain reduction at that point and fixes the gain to that value. Alternatively, it is configured to work so as to slightly increase the gain just to undo the change in position.

Before the movement command generation circuit (1) issues the next movement command, the movement command generation circuit (1) drops the gain change command. At that time, the gain returns to the normal state, and the motor is turned off. It does not affect the operation.

In the above embodiment, the gain changing circuit (7)
Controls the gain of the speed control circuit (3), but may control the gain of the position control circuit (2).

[Effect of the Invention] As described above, after the positioning of the motor to which the frictional force of the motor according to the present invention is applied as a load, the gain change command output from the movement command generation circuit is input until the next motor start-up. A gain change circuit that changes the gain of the position control circuit or the speed control circuit and stops the gain change when the difference between the movement distance command value from the movement command generation circuit and the actual movement distance exceeds a predetermined value. With this configuration, it is possible to reduce heat generated by the motor and heat generated by the motor drive circuit by reducing the current flowing to the motor in accordance with the gain change when positioning is stopped and eliminating unnecessary current flowing against the frictional force. Therefore, it is possible to use a motor or a drive circuit with a smaller capacity, and the current flowing through the motor decreases with a change in the gain. In the case of lowering, by immediately stopping and fixing the gain change, it is possible to prevent the movement of the minute displacement amount and secure the fixed position stop at the time of the positioning control of the motor to which the frictional force is applied as a load. .

[Brief description of the drawings]

1 and 2 are block diagrams according to one embodiment of the present invention, and waveform diagrams of a motor holding current for explaining the operation during positioning stop control. FIGS. 3 and 4 are FIGS. 1 and 2. FIG. 2 is a block diagram and a current waveform diagram of a conventional example corresponding to FIG. (1) a movement command generation circuit, (2) a position control circuit, (3) a speed control circuit, (4) a current control circuit, and (7) a gain change circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-76380 (JP, A) JP-A-59-44995 (JP, A) JP-A-1-94878 (JP, A) JP-A-2- 294290 (JP, A) JP-A-60-40577 (JP, A) JP-A-59-228233 (JP, A)

Claims (1)

(57) [Claims] A moving command generating circuit for generating a moving distance to a target position, a position control circuit for detecting a difference between an output of the moving command generating circuit and an actual moving distance and generating a speed command value; A speed control circuit for detecting the difference between the output of the position control circuit and the actual speed to generate a current command value, detecting the difference between the output of the speed control circuit and the actual current and applying the difference to the motor In a motor positioning control device that includes a current control circuit for generating a voltage and that controls the positioning of a motor to which a frictional force is applied as a load, the movement command generation circuit is provided from the completion of motor positioning to the start of the next motor. The gain change command output from the controller is input to change the gain of the position control circuit or the gain of the speed control circuit, and the travel distance command value from the travel command generation circuit and the actual travel distance Positioning the motor control device characterized by comprising a gain changing circuit for stopping the gain changes when the difference exceeds a predetermined value of.