JPS63251108A - Weight balance control system for moving part of industrial machine - Google Patents

Abstract

PURPOSE:To improve the response speed of a pressure control system, by a method wherein a compensating means is located between control parts for feedback and weight balance to calculate compensation control data, and the result is fed to a pressure control means together with on output from a pressure detecting means to control the pressure of a hydraulic cylinder. CONSTITUTION:A compensation control means 36 is situated between a position feedback control part 16 to control positioning of a moving part 2 and a pressure control part 30, e.g. a hydraulic cylinder 14 coupled to the moving part 2 for well balancing. Based on a command speed signal for the moving part 2 provided from the position feedback control part 16, compensation control data is calculated. A feedforward control element is added to the pressure control part 30 to perform feedback control by adding the calculating result. This constitution enables improvement of the response speed of the pressure control part 30, reduction of production of the disturbance to the position feedback control part 16, and improvement of the response time of a whole position control system.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a technology for controlling the position of a movable part in an industrial machine, and more specifically, the present invention relates to a technology for controlling the position of a movable part in an industrial machine. This is for controlling the position of a movable part in an industrial machine having a weight balance means for reducing the load weight of the movable part by coupling a hydraulic cylinder or the like to apply a force in the opposite direction to gravity, The present invention relates to a control method that improves the responsiveness of a weight balance means performed by large flow rate hydraulic control with a slow response speed to position control of a movable part controlled by a feedback control system.

[Background of the Invention] With the recent development of electronic technology, the development of NC machine tools and various industrial machines is also remarkable, and along with the demand for abbreviation, automation of various manufacturing equipment is progressing. Generally, when positioning a movable part that grips a tool in an NC machine tool, etc., a speed detector is provided for the drive source such as a servo motor, and the position and speed of the movable part are detected, and the detection signal is This is done through so-called feedback control, in which the output is fed back to the servo motor.

By the way, the movable part moves in the direction of gravity,
In other words, when displacing in the vertical direction, a hydraulic cylinder or the like is connected to the movable part, and a force in the opposite direction to gravity is applied to the movable part in accordance with the load weight of the movable part, and the drive motor etc. It is common practice to provide weight balancing means to reduce the load. In this case, the weight balance means is also equipped with a pressure detector to detect the pressure of the hydraulic cylinder, and this detected pressure is fed back to the pressure control unit to control it to a command pressure, and the balance force is adjusted according to the movement of the movable parts. is configured to obtain.

When moving and positioning a movable part equipped with such a balance means to a predetermined position in response to a position command, position feedback control for controlling the positioning of the movable part and pressure control of the weight balance means are performed in independent control loops. Generally, it consists of . In this case, one position feedback control is performed electronically using servo control, while the other pressure control is controlled by a large flow rate hydraulic system. Therefore, there is a large difference in response speed between the two, and the delay in the response time of the pressure control of the hydraulic system cannot be ignored, and this response delay of the hydraulic system adds as a disturbance to the position feedback control system of the moving part, resulting in Another disadvantage is that the response speed of the position feedback control system decreases.

[Object of the Invention] The present invention has been made to overcome the above-mentioned disadvantages, and includes a position feedback control system for controlling the positioning of a movable part of an industrial machine, and a position feedback control system that is coupled to the movable part and balances the weight. A compensation control means is provided between the pressure control system such as a hydraulic cylinder for the purpose of the invention, and the compensation control data is calculated by the compensation control means based on the command speed signal to the movable part obtained from the position feedback control system. The purpose is to improve the response speed of the pressure control system by applying this to the pressure control system together with the pressure detection signal and adding a feedforward control element.

[Means for Achieving the Object] In order to achieve the above object, the present invention includes a movable part that is movable in the direction of gravity, and a weight that is coupled to the movable part and applies a force in the opposite direction to gravity to the movable part. a balance means, a feedback control section for setting the movable part to a commanded position, which is composed of a position command means, a calculation means, a servo amplification means, a servo drive means, and a speed detection means; a pressure control means;
A weight balance control system for movable parts in an industrial machine, comprising a pressure control section, a hydraulic cylinder, and a pressure detection means, and a weight balance control section for controlling a balancing force of the weight balance means, the feedback control method A compensation control means is provided between the part and the weight balance control part, and the compensation control means calculates compensation control data based on the command value of the speed detection means of the movable part, and calculates the compensation control data together with the output of the pressure detection means. It is characterized in that the pressure control means is applied to the hydraulic cylinder to control the pressure of the hydraulic cylinder.

[Embodiments] Next, preferred embodiments for carrying out the weight balance control method of a movable part in an industrial machine according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a diagram showing a device configuration for implementing a weight balance control method for movable parts in an industrial machine according to the present invention.

In the figure, reference numeral 2 is a movable part of an industrial machine or a robot, on which a tool 8 is attached via a headstock 4 and a spindle 6, and is configured to be movable in the direction of gravity by a servo motor IO.

In this case, the tool 8 performs a predetermined process on the workpiece 12 by displacing in the direction of the arrow. In addition, in the figure, only the configuration related to the vertical axis is shown, and the configuration of the drive device in the horizontal axis and rotational axis directions is omitted.

Reference numeral 14 indicates a hydraulic cylinder, and this hydraulic cylinder 14 applies a force to the movable part 2 in a direction opposite to the direction of gravity, so as to cancel the load weight of the movable part 2 and reduce the load on the servo motor 10. It constitutes a weight balance means that works. Reference numeral 16 is a feedback control section for positioning the movable section 2 at a predetermined position. This feed pack control unit 16 includes a calculation unit 20 that creates a drive signal for the servo motor 10 based on a position command from a position command unit 18, a servo amplification unit 22, and a movement speed of the movable unit 2 based on the rotation of the servo motor 10; It is composed of a speed detector 24 for detecting position and the like. Note that the detection signal of the speed detector 24 is fed back to the calculation means 20, forming a so-called feedback control loop.

Reference numeral 26 is a weight balance control section, which controls the pressure of the hydraulic cylinder 14, which is a weight balance means, and controls the pressure control means 2 based on the command pressure PC.
8 to generate a pressure control signal and control the pressure control unit 30 to control the pressure of the hydraulic cylinder 14. Reference numeral 32 is a pressure detection means, and the pressure sensor 3
A feedback loop is formed in which the pressure is detected from the pressure sensor signal of the hydraulic cylinder 14 by 4 and fed back to the pressure control means 28.

Reference numeral 36 is provided between the position feed bank control section 16 and the weight balance control section 26 which is a pressure control system,
This is a compensation control means that combines the two. A command speed signal and the like are inputted to the compensation control means 36 via the calculation means 20, compensating control data is calculated, and this data is applied to the pressure control means 28 of the weight balance control section 26, which is a pressure control system.

Here, the compensation control data is, for example, an acceleration signal obtained by differentiating a speed signal, and the pressure control means 28 includes data generated by the compensation control means 36 in addition to the pressure signal detected by the pressure detection means 32. Since the acceleration signal of the movable part 2 is given, the response speed of the hydraulic cylinder 14 can be accelerated.

The apparatus for carrying out the weight balance control method for movable parts in industrial machinery according to the present invention is roughly configured as described above, and the operation and effects regarding weight balance control will be explained in more detail next.

When moving and positioning the movable part 2 to a predetermined position with respect to the workpiece 12 and performing desired processing using the tool 8 or the like, the calculation means 20, based on command data from the position command means 18,
The servo motor 10 is driven via the servo amplifying means 22, and the movable part 2 moves.

When the movable part 2 moves, the position and speed are detected by the speed detector 24, and the detection output of the speed detector 24 is fed to the calculation means 20 to perform position feedback control.

Weight balance control is also performed in parallel with this position feedback control. That is, when the movable part 2 moves, the pressure inside the hydraulic cylinder 14 changes, the pressure change is detected by the pressure detection means 32 via the pressure sensor 34, and the pressure change is detected by the pressure detection means 32 via the pressure control means 28 and the pressure control section 30. The internal pressure is controlled to match the command pressure P.

At this time, in general, the response of the weight balance control section 26 to the response speed of the position feedback control section 16 is a response by hydraulic control of a large flow rate, and there is a large time delay, and the pressure change of the hydraulic cylinder 14 is directly fed back to the position. This is added to the control unit 16 as a disturbance (increase in load weight), and as a result becomes a factor that reduces the response speed of the position feedback control unit 16.

Figure 2 shows an example of this position response waveform.
The horizontal axis shows the time t, the vertical axis shows the change This is the response waveform in the case of only part 16,
Curve C indicates the hydraulic cylinder 14 and the weight balance control section 2.
6 shows a response waveform when 6 is added.

Such a delay in response speed indicates that when a movable part is controlled with multiple axes, the response speed of only the vertical axis is delayed relative to the response speed of other axes, causing errors in the movement path of tools, etc. This causes a decrease in machining accuracy.

In the weight balance control method according to the present invention, a compensation control means 36 is provided between the position feedback control section 16 and the weight balance control section 26 which is a pressure control system, and the command speed signal etc. to the movable section 2 are calculated. It is input via means 20. The compensation control means 36 converts this command speed signal into an acceleration signal by performing differential processing, for example, and applies this acceleration data to the pressure control means 28 as compensation control data.

Therefore, the pressure control means 28 is given not only the detection data of the pressure detection means 32 that detects the pressure change of the hydraulic cylinder 14, but also the acceleration data obtained by differentiating the speed signal of the movable part 2, so that the pressure control means 28 is not limited to a simple feedback loop. Since not only pressure control but also a kind of feedforward control element is taken into consideration, the response speed of the weight balance control section 26 can be increased accordingly.

That is, by causing the pressure fluctuation correction operation of the weight balance control section 26 to precede the movement of the movable section 2, pressure fluctuations in the hydraulic cylinder 14 are kept to an extremely minimum level, and disturbances to the position feedback control section 16 are minimized and the entire system is adjusted. This improves the response characteristics.

In the above description, the compensation control means 36 was explained as calculating compensation control data based on the speed signal from the speed detector 24, but the present invention is not limited to this, and the compensation control means 36 calculates the compensation control data based on the speed signal from the speed detector 24. Compensation data may be calculated based on this.

[Effects of the Invention] As explained in detail above, the weight balance control system for a movable part in an industrial machine according to the present invention includes a position feedback control system that performs positioning control of the movable part, and a position feedback control system that is coupled to the movable part to balance the weight. A compensation control means is provided between the pressure control system such as a hydraulic cylinder, and compensation control data is calculated based on the command speed signal of the movable part obtained from the position feedback control system, and this is transmitted to the pressure control system. By adding a feedforward control element to the pressure control system that performs feedback control, this improves the response speed of the pressure control system, reduces disturbances to the position feedback control system, and improves the response of the entire position control system. This produces the effect that time can be improved.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments.
Of course, various improvements and changes in design are possible without departing from the gist of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a device configuration for implementing a weight balance control method for a movable part in an industrial machine according to the present invention, and FIG. 2 is an explanatory diagram of response characteristics of position control of a movable part. 2...Movable part 8...Tool 10...
・Servo motor 12... Workpiece 14...
- Hydraulic cylinder 16...Position feedback control section 18...Position command means 20...Calculation means 22...Servo amplification means 24...Speed detector 26...Weight balance control section 28... Pressure control means 30...pressure control section 32...pressure detection means 36...compensation control means

Claims (1)

[Claims] (1) A movable part movable in the direction of gravity, weight balance means coupled to the movable part and applying a force in the opposite direction to gravity to the movable part, position command means, calculation means, servo amplification means, and servo drive means and a feedback control section for setting the movable part to a commanded position, which is composed of a speed detection means, a pressure control means, a pressure control section, a hydraulic cylinder, and a pressure detection means to control the balance force of the weight balance means. A method for controlling the weight balance of a movable part in an industrial machine, comprising a weight balance control section for controlling the weight, wherein a compensation control means is provided between the feedback control section and the weight balance control section, and the compensation control means detects the speed. Compensation control data is calculated based on a command signal from the means, and this data is applied to the pressure control means together with the output of the pressure detection means to control the pressure of the hydraulic cylinder. Weight balance control method.