JPS6280710A - Method for controlling digital servo - Google Patents

Abstract

PURPOSE:To attain positioning more rapidly by increasing acceleration gain especially in an instantaneous acceleration changing part in addition to the increase of position gain and speed gain to control a servo amplifier. CONSTITUTION:A control device 1 consists of a microprocessor as a main body, sets up and processes respective command values relating to a moving distance of an object 4 to be positioned, moving speeds including start, deceleration, stop, etc., and acceleration at the time of acceleration/deceleration and supplies respective gain data such as a position command value, a speed command value and an acceleration command value to the servo amplifier 2 as k1-k3 respectively. In this case, the acceleration gain k3, the speed gain k2 and the position gain k1 successively contribute to the improvement of characteristics in order from a time close to a starting time. Consequently, more efficient control can be attained by changing how to increase respective gain properly in accordance with the position of the object to be positioned on a speed curve drawn by the object.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method of extracting a feedback signal as a digital value and performing servo control based on the digital value.

[Conventional technology]

In recent years, with the progress of so-called mechatronics technology, there has been a demand for the development of high-speed and ultra-precise positioning control technology, and in order to meet this demand.

The prerequisite is the establishment of rapid acceleration and deceleration control technology.

Servo control in conventional numerical control is generally an analog control method in which, for example, a power transistor in a servo amplifier is controlled using the PWM (pulse width modulation) method based on position data of the controlled object. It is.

[Problem that the invention seeks to solve]

However, with the conventional servo control method, there is a sudden increase.

It is considered virtually impossible to perform deceleration control with good follow-up characteristics and without causing vibrations.

For this reason, in the conventional numerical control having the above-mentioned servo control system, creating acceleration data on a digital value basis or feeding back a feedback signal for actual acceleration detection is not performed at all.

[Means for solving problems]

The present invention provides a servo control method that executes control by supplying a control signal to the power transistor of a servo amplifier using digital acceleration data in addition to position data and velocity data used in conventional servo control. It was created with the purpose of is within a predetermined range, forming a speed curve of the controlled object using a digital value indicating acceleration or speed per unit time formed from the database for positioning;
Control all or part of the gain data regarding the position, velocity, and acceleration so that the digital value of the feedback data regarding the position, velocity, and acceleration formed when the controlled object moves approximates the speed curve. It is characterized by this.

[Action of the invention]

Forms an acceleration value per unit time in the movement section of the controlled object from a database for positioning by numerical control, processes this acceleration value, and applies the above to the servo amplifier that controls the servo motor that is the drive source of the controlled object. A planned speed curve of the controlled object is formed together with each planned gain data of the acceleration command, speed command, and position command supplied in the moving section.

On the other hand, the position feedback value fed back as the amount of movement per unit time from the controlled object moving in the movement section is processed to form gain data regarding the current position, velocity, and acceleration appearing on the controlled object. .

The deviation between the two gain data is processed and the gain data supplied to the servo amplifier is controlled so that the current speed curve of the controlled object approximates or coincides with the planned speed curve.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

The figure is a block diagram showing the essential parts of an example of a control system for carrying out the control method of the present invention, in which the block surrounded by broken lines represents the control device 1, and 2 represents the servo control system mainly composed of PWM type power transistors. Amplifier.

3 is a servo motor, 4 is a positioning object driven by the motor 3, 3a is a pulse encoder attached to a rotating system such as a motor shaft or a feed screw, and 4a is 4fLti! This is a pulse length measuring device installed on the target.

The control device 1 is mainly formed with a microprocessor, and controls the amount of movement of the positioning object 4, the movement speed including start, deceleration and stop, etc., as well as acceleration.

Each command value related to acceleration during deceleration etc. is set and processed,
The gain data of the position command value, speed command value, and acceleration command value are supplied to the servo amplifier 2 as , , , and .

Note that the above commands are not independent of each other, and here, the differential value of the position command W is the speed command, and the differential value of the speed command is the acceleration command. Alternatively, the acceleration command may be subjected to integral processing to form the speed command and the position command.

On the other hand, in the control device 1, 1s is an adder/subtractor inserted on the position command supply system, 1v is an accelerator also inserted on the speed command supply system, and 1a is also on the acceleration command supply system. This is an added/subtractor inserted.

Here, the feedback pulse from the pulse length measuring device 4a is fed back to the adder/subtractor 1s of the position command system path.

Further, a feedback pulse from the pulse encoder 3a is fed back to the adder/subtractor 1v of the speed command path. Further, the adder/subtractor 1a of the acceleration/deceleration command path is supplied with a feedback pulse obtained by differentiating the feedback pulse from the pulse encoder 3a in a differentiator 11a.

Therefore, during operation of the machine, each command value and each feedback signal are sent to each adder/subtractor is, lv,
1 to each gain data formed based on the numerical values after addition and subtraction in la. ,,・k, is.

After being added and subtracted by the gain data adder/subtractor 1k, the gain data is supplied to the servo amplifier 2.

Thus, for each gain data regarding each command value, the ratio between each gain is known in advance, and the total sum of gains is also within a predetermined range based on the capacity of the motor 3, etc.

Therefore, each gain data cannot be changed to an arbitrary S limit for the motor, and the way each gain is applied is also different.

When we actually performed a simulation using the control system shown in the figure, we obtained the following results.

Here, each constant is a ==0.1. b = 1t
c = 10 td = 10, and each designation signal is 5 intp for position command, cost for speed command, - - for acceleration command.
It was set to 5 int.

The experiment was conducted while varying the values of , k, , k, for each gain.

If 3 is set to zero for acceleration gain, 2 is set for velocity gain.
When the value was increased, the following characteristics of the first peak at one position command of 5 int improved.

However, in order to improve the tracking characteristics of peaks and valleys after this, it was possible to obtain better tracking characteristics by increasing the position gain by 1.

On the other hand, even if the above gains were increased by □9 and 2, the tracking characteristics at the time of starting were not significantly improved.

Next, in addition to the above control, we performed a simulation while gradually increasing the acceleration gain, and found that kl was 2.
By increasing , and increasing , the follow-up characteristics at the time of starting are improved and at the same time.

Results showed that the tracking characteristics at subsequent peaks and valleys were also good.

As a result of these experiments, it was found that the acceleration gain k, 31 speed gain, 2e position gain, and □ contribute to the improvement of characteristics in the order of starting from the point closest to the start.

Therefore, in the present invention, more efficient control is achieved by appropriately changing how each gain is applied depending on the position on the speed curve drawn by the positioning object.

In fact, for positioning targets such as machine tool tables, the speed command often becomes a trapezoidal step function.

In such a speed curve, the change in acceleration is rapid, so the present invention provides position gain, speed gain, and
In particular, if the servo amplifier is controlled by making use of the acceleration gain in such a rapid acceleration change portion, it becomes possible to perform positioning control at higher speed.

As described above, the present invention is particularly capable of performing positioning control that involves rapid changes in speed and acceleration with good follow-up characteristics.

Suitable for highly precise positioning control.

[Brief explanation of drawings]

The figure is a control block showing an example of implementing the method of the present invention. 1...Control device, 2...Servo amplifier, 3...Servo motor, 4...Positioning target

Claims (1)

[Claims] In positioning control of a controlled object, when the sum of each gain data for the servo amplifier formed based on the position data, velocity data, and acceleration data and the ratio between each gain are within a predetermined range, from the database for positioning. The speed curve of the controlled object is formed using digital values indicating acceleration or speed per unit time, while the digital values of feedback data regarding the position, speed, and acceleration formed when the controlled object moves are used to form the speed curve. A digital servo control method characterized by controlling all or part of the gain data regarding the position, velocity, and acceleration described above so that the gain data approximates the above.