JPS63269212A - Servo device - Google Patents

Abstract

PURPOSE:To improve the following-up precision of a machine moving locus at the time of inverting the moving direction of a machine by changing the gain of an amplification control means based on a gain different from the gain for movement of the machine in a prescribed direction. CONSTITUTION:When the rotating direction of a driving motor 10 is inverted, a mobile base 14 is temporarily disconnected from the motor 10 because of backlash, and restrictions due to resonance of two inertia systems are removed. Consequently, respective gains of a position controller 2, a speed controller 3, and a current controller 4 are made higher than those for movement of the mobile base 14 in a prescribed direction, and quick response is realized. A gain setter 20 outputs the gain, which is designed most suitable for the load except the mobile base 14 when the moving direction of the mobile base 14 is changed. As the result, the response of a position l of the driving shaft of the motor 10 is quickened and a position lb of the mobile base 14 is returned to a normal locus.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a servo device that controls the position of a machine, and more particularly to a servo device that reduces errors in the movement trajectory of a machine that occur when the direction of movement of the machine is reversed. Regarding.

[Prior Art] FIG. 4 is a block diagram of a conventional servo device. In Fig. 4, (1) is a command value generator that outputs a command value g indicating the position of a machine whose position is controlled by a servo device, and (2) is a command value generator (13
) is a position controller that outputs a speed command value V such that the deviation from the position detection value g corresponding to the position of the machine detected by 12) A speed controller that outputs a current command value I such that the deviation from the speed detection value V corresponding to the speed of the machine detected by (11) is a current controller that outputs a drive voltage e such that the deviation from the current detection value I corresponding to the current flowing through the drive motor (10) detected by the drive motor (10) becomes zero; The drive motor to be driven (15) is a transmission mechanism such as a ball screw that converts the rotation of the drive motor (10) into linear motion; (14) is a transmission mechanism (
15) to which the rotation of the drive motor (lO) is transmitted, (30a), (30b), and (30c) are adders.

Next, the operation of the conventional servo device will be explained. First, the command value generator (1) generates a command value g corresponding to each drive axis necessary to realize a required tool trajectory such as a circular arc.
Output. Next, the position side controller (2) sets the speed command value V such that the deviation between the command value p and the detected position value g becomes zero.
Output. Next, the speed controller (3) sets the speed command value V
outputs a current command value l such that the deviation from the speed detection value V becomes zero.Furthermore, the current controller (4) outputs the current command value I
and the detected current value ■ Which deviation is the drive voltage e that makes it zero?
Output. The drive electric motor (lO) rotates by the drive pressure e, transmits the rotation to the movable base (14) via the transmission mechanism (15), and moves the movable base (14).

In addition, since the conventional servo device has backlash in the transmission mechanism (15), the position l1lb of the movable table (14) lags by I1 with respect to the position g of the drive shaft of the drive motor (lO). In order to correct this position lag gl, the command value g of the command value generator (1) includes a position advance correction (backlash) corresponding to the predetermined position lag gl.

[Problems to be Solved by the Invention] Figure 5 shows the position p of the drive shaft of the drive motor (10) and the position g of the movable base (14) when the rotation direction of the drive motor (10) is reversed. , which shows the relationship between . In FIG. 5, the vertical axis shows the position, and the horizontal axis shows the time t whose origin is when the rotation direction is reversed. Position g of movable platform (I4)
In order for b to reverse smoothly without being affected by backlash, the position p of the drive shaft of the drive motor (lO) needs to change as shown by the curve (40).

However, in reality, due to delays in the position control system, the position g of the drive shaft of the drive motor (lO) changes as shown by curve (41). Therefore, the position gb of the movable base (14)
changes like curve (51) and returns to the normal trajectory after time T1. This time T1 appears as a processing error. Specifically, as shown in FIG. 6, when a perfect circle machining command is issued and cutting is attempted along a perfect circle as shown by the curve (Go) in FIG. ), there is a delay of time T1 when the rotation direction is reversed, and the actual shape of the cut object has a bulge as shown in curve (61) at the quadrant switching part of circular arc cutting, which is a problem.

The present invention has been made to solve the above problems,
It is an object of the present invention to provide a servo device that can reduce trajectory errors caused by backlash when the rotation direction of a drive motor (lO) is reversed.

[Means for Solving the Problems] Therefore, the present invention includes a moving direction detecting means for detecting a change in the moving direction of a machine whose position is controlled based on a command value of a commanding means that commands the position of the machine, a gain setting device for setting a gain different from the gain of an amplification control means for feedback controlling a detection value outputted by a detection means for detecting the position of the machine so as to match a command value when the machine is moving in a predetermined direction; The servo device is configured to include gain changing means for changing the gain of the amplification control means based on the set gain when the moving direction detecting means detects a change in the moving direction of the machine.

[Function] The servo device having the above configuration performs 1. when the moving direction detecting means detects a change in the moving direction of the machine. The gain changing means changes the gain of the amplification control means based on a gain that is different from the gain set by the gain setting device when the machine is moving in a predetermined direction.

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

FIG. 1 is a block diagram of a servo device according to the present invention.

Note that in FIG. 1, parts that perform the same functions as those in FIG. 4 are designated by the same reference numerals, and their explanations will be omitted. Position controller (2), speed controller (3) and current controller (4)
) is adapted to change its gain depending on the setting value from the gain setting device (20).

Next, the operation of the servo device according to the present invention will be explained. When the movable base (14) is moving in a predetermined direction, the position controller (2), speed controller (3) and current controller (4) are activated.
) operates with the same predetermined gain as the conventional servo device.

In this case, the main components are the drive motor (lO) and the movable base (14
) are connected by a transmission mechanism (15) with lower rigidity than this, due to resonance due to the so-called two-inertial system, the response frequency of the servo device is limited, and the gain of the controller cannot be set sufficiently high.

However, when the direction of movement changes, i.e. the drive motor (l
When the rotational direction of O) is reversed, the movable base (14) is temporarily separated from the drive motor (lO) due to a crash, so there is no restriction due to the resonance of the two-inertial system. , the position controller (2), the speed controller (3), and the current controller (4).
) can be higher than when moving in a predetermined direction, and high-speed response can be realized.

The gain setting device (20) outputs the same gain as before when the movable base (14) is moving in a predetermined direction, and outputs the same gain as the conventional one when the movable base (14) is moving in a predetermined direction, and outputs the same gain as the conventional one when the movable base (14) is moving in a predetermined direction. 1
4) Output the optimally designed gain for the load except for. In this case, the time at which the direction of movement changes is given by the speed command value {circle around (2)} which is the output of the position controller (2). Also, the time at which the reversal ends is determined by a position detector connected to the drive motor (lO) that indicates movement by a predetermined amount of backlash.
13) You can learn more.

As a result, as shown in FIG. 5, the response of the position g of the drive shaft of the drive motor (10) becomes faster as shown by the curve (51).
The position g of the movable platform (14) changes like a curve (52), and returns to the normal trajectory after time T2.

In addition, in this embodiment, a gain setter (20
), but a movable stand (14) was used for the gain setting device (20).
The position detector (13) when changing the moving direction of
) is provided, and based on the position detection value g stored in the storage circuit,
The set value may be changed.

Next, FIG. 2 is a block diagram showing another embodiment of the servo device according to the present invention. Note that in FIG. 2, parts that perform the same functions as those in FIG. 1 are designated by the same reference numerals, and their explanations are omitted.

The servo device shown in FIG. 2 includes a feedforward compensator (5). Also in the servo device including this feedforward compensator (5), the movable base (14)
When the direction of movement changes, the feedforward compensator (5
) Position controller including feedforward compensation gain (
2) By setting each gain of the speed controller (3) and current controller (4) to optimal gains, a faster response can be achieved.

Next, FIG. 3 is a block diagram showing another embodiment of the servo device according to the present invention. Note that in FIG. 2, parts that perform the same functions as those in FIG. 1 are designated by the same reference numerals, and their explanations are omitted.

In the above embodiment, the optimum gain when the moving direction of the movable base (14) changes is determined in advance, but in this embodiment, the current detector (11) connected to the drive motor (lO) , speed detector (12) and position detector (13)
Determine using the output of For example, the current controller (11)
The response frequency of W (12) is set sufficiently high, and the gain of the speed control W (12) is subjected to model-based adaptive control.

The state equation of the speed control system of the servo device when the moving direction of the movable table (14) is reversed is *−−av + b I,
(1), and the state equation of the desired model is *--a
*+b v (2)ffl
Here, a and b are unknown constants, and a1 and b are constants corresponding to the desired model.
``If we construct a speed controller that becomes
“The control system converges to the response of the model. Here, kl, k2
is a proper positive number and is e*−■.

Note that the gain of the position controller (2) when the moving direction of the movable table (14) is reversed may be determined according to the second equation of the model equation of the speed control system.

[Effects of the Invention] As explained above, according to the present invention, when the moving direction detecting means detects a change in the moving direction of the machine, the gain changing means moves the machine set by the gain setting device in a predetermined direction. Since the gain of the amplification control means is changed based on a gain that is different from the gain when the machine is moving, the tracking accuracy of the machine's movement trajectory is improved when the machine's movement direction is reversed in a circular arc, etc., and the machining accuracy is improved. A servo device with high performance can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a servo device according to the present invention, FIGS. 2 and 3 are block diagrams showing other embodiments of the servo device according to the present invention, and FIG. 4 is a block diagram of a conventional servo device. FIG. 5 is an explanatory diagram showing an example of the positional response when the rotation direction is reversed, and FIG. 6 is an explanatory diagram of the locus when a perfect circle cutting command is issued. In each figure, 1 is a command value generator, 2 is a position controller, 3 is a speed controller, 4 is a current controller, 5 is a feedforward compensator, 10 is a drive motor, 11 is a current detector, and 12 is a speed Detector, 13 is a position detector, 14 is a drive stand, 15 is a transmission mechanism, 20 is a gain setting device, 30a130b, 30c
is an adder. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (5)

[Claims] (1) having a command means for outputting a command value corresponding to the position of the machine, a detection means for outputting a detected value corresponding to the position of the machine whose position is controlled based on the command value, and a predetermined gain; A servo device comprising: an amplification control means for feedback controlling the detected value to match a command value; a moving direction detecting means for detecting a change in the moving direction of the machine; a gain setting device that sets a gain different from a gain when the machine is in use; and a gain change that changes the gain of the amplification control means based on the set gain when the moving direction detection means detects a change in the moving direction of the machine. A servo device comprising means. (2) The servo device according to claim 1, wherein the servo device performs current control, speed control, and position control. (3) The servo device according to claim 1, wherein the gain setting device sets a predetermined value. (4) The servo device according to claim 1, wherein the gain setter changes the set value based on the detection output of the detection means. (5) A claim in which the gain setting device has a storage means for storing the detection output of the detection means when the moving direction of the machine is changed, and the set value is changed based on the stored detection output. The servo device according to item 1.