JPH0460764B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention connects a hydraulic cylinder or the like to a movable part of a machine tool that moves in the direction of gravity, and applies a force in the opposite direction to gravity. The present invention relates to position control of a movable part in a machine tool having a weight balance means for reducing the load weight on the movable part.

[Prior Art] A weight balance control device connects a hydraulic cylinder or the like to a movable part that moves in the direction of gravity, and applies a force in the opposite direction to gravity to the movable part in response to the load weight of the movable part. In addition to this, it also includes weight balance means to reduce the load on the drive motor, etc. In this case, a pressure detector is provided in the weight balance means 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 part. I'm trying to get it.

When moving a movable part equipped with such a weight 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 as follows.
Generally, each of them constitutes an independent control loop. In this case, one position feedback control is performed by servo control, while the other pressure control is performed by control of 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 parts, resulting in In other words, the response speed of the position feedback control system is reduced.

[Object of the Invention] The present invention has been made to overcome the above-mentioned disadvantages, and is to improve the response speed of the pressure control system, reduce disturbance to the position feedback control system, and improve the response of the entire position control system. Aims to improve time.

[Means for Achieving the Object] In order to achieve the above object, the present invention comprises: a movable part movable in the direction of gravity; a position/velocity command means for outputting a command position signal or a command speed signal; a calculation means for calculating and outputting a drive signal based on the position signal or the command speed signal; a servo drive means for driving the movable part based on the drive signal; and a servo drive means for detecting the position or speed of the movable part as a feedback signal. a feedback control section having a position/velocity detection means for outputting to the calculation means; a pressure control means for outputting a pressure control signal based on a command pressure corresponding to the weight of the movable part; A weight having a pressure control valve mechanism to control, a cylinder that applies a force in a direction opposite to gravity to the movable part based on the fluid pressure, and a pressure detection means for detecting the fluid pressure and outputting it as a feedback signal to the pressure control part. A weight balance control device comprising: a balance control unit; the weight balance control device calculates a command acceleration signal from a command position signal or a command speed signal obtained from the feedback control unit, and outputs the command acceleration signal as a feedback signal in the weight balance control unit. Compensation control means outputs to the pressure control means, the pressure control means outputting a command pressure corresponding to the weight of the movable part, a feedback signal from the pressure detection means, and a feedback signal from the compensation control means. The pressure control signal is output based on the word signal.

[Embodiments] Next, the weight balance control device according to the present invention will be described in detail below with reference to the accompanying drawings, citing preferred embodiments for implementing the same.

FIG. 1 is a diagram showing a device configuration for implementing a weight balance control device according to the present invention.

In the figure, reference numeral 2 is a movable part of a machine tool or robot, etc., to which a tool 8 is attached via a headstock 4 and a spindle 6, and a servo motor 1
0 (servo drive means) to be movable in the direction of gravity. 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, cancels the load weight of the movable part 2, and reduces the load on the servo motor 10. to work.

Reference numeral 16 is a feedback control section for positioning the movable section 2 at a predetermined position. This feedback control unit 16 includes a calculation unit 20 that creates a drive signal for the servo motor 10 based on a command position signal from a position command unit 18, a servo amplification unit 22, and a control unit that controls the rotation of the servo motor 10, the moving speed of the movable unit 2, and the position. It is composed of a speed detector 24 (position/speed detection means) for detecting the speed and the like. The detection signal of the speed detector 24 is transmitted to the calculation means 20.
The signal is fed back as a feedback signal, forming a so-called feedback control loop. Note that the position command means 18 can also be configured as a speed command means that outputs a command speed signal.

Reference numeral 26 is a weight balance control section that controls the pressure of the hydraulic cylinder 14, and generates a pressure control signal by the pressure control means 28 based on the command pressure Pc corresponding to the weight of the movable section 2, and controls the pressure control section 30. (pressure control valve mechanism) to control the fluid pressure of the hydraulic cylinder 14.
Reference numeral 32 is a pressure detection means, which connects the pressure control section 30 to the input/output port 3 of the hydraulic cylinder 14.
A feedback loop is formed which detects the pressure in the pipe leading to pressure 4 and returns it to the pressure control means 28 as a feedback signal.

Reference numeral 36 is compensation control means provided between the feedback control section 16 and the weight balance control section 26, which is a pressure control system, and coupling the two. This compensation control means 36 calculates a command acceleration signal from a command position signal, a command speed signal, etc. input via the calculation means 20, and sends this signal to the pressure control means 28 of the weight balance control section 26, which is a pressure control system. give to Here, since the command acceleration signal is given to the pressure control means 28 together with a feedback signal which is the fluid pressure detected by the pressure detection means 32, the response speed of the hydraulic cylinder 14 can be accelerated.

The apparatus for carrying out the weight balance control apparatus according to the present invention is roughly constructed as described above, and the operation and effects related to weight balance control will now be described in more detail.

When moving the movable part 2 to a predetermined position with respect to the workpiece 12 and performing desired processing with the tool 8 or the like,
Based on the position command signal from the position command means 18, the servo motor 10 is driven via the calculation means 20 and the servo amplification 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.
The detection output No. 4 is fed back to the calculation means 20, and position feedback control is performed.

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 change in pressure is detected by the pressure detection means 32 via the input/output port 34, and the hydraulic pressure is detected by the pressure control means 28 and the pressure control section 30. The pressure inside the cylinder 14 is controlled to match the command pressure Pc.

At this time, generally the feedback control section 16
The response of the weight balance control unit 26 to the response speed of As a result, this becomes a factor that reduces the response speed of the feedback control section 16. FIG. 2 shows an example of this position response waveform, where the horizontal axis shows time t, the vertical axis shows change x in the movable part 2, straight line a shows the position command, and curve b shows the position command.
is the case where there is no influence of the weight balance means (hydraulic cylinder 14), that is, the feedback control section 1
The curve c shows the response waveform when the hydraulic cylinder 14 and the weight balance control section 26 are added.

Such a delay in the response speed indicates that when the movable part 2 is multi-axis controlled, the response speed of only the vertical axis is delayed relative to the response speed of the other axes, causing a movement path error of the tool 8, etc. This, in turn, causes a reduction in machining accuracy.

In contrast, in the weight balance control device according to the present invention, a compensation control means 36 is provided between the feedback control section 16 and the weight balance control section 26 which is a pressure control system, and a compensation control means 36 is provided between the feedback control section 16 and the weight balance control section 26 which is a pressure control system. A position signal or a command speed signal, etc. is the calculation means 20
Input via . The compensation control means 36 differentially processes this command position signal or speed signal to convert it into a command acceleration signal, and this signal is sent to the pressure control means 28.
Add to. Therefore, the pressure control means 28 includes a pressure detection means 32 for detecting pressure changes in the hydraulic cylinder 14.
Not only the feedback signal from the movable part 2
Since the command acceleration signal for the weight balance controller 26 is also given as a feed-forward signal, not only pressure control by a simple feedback loop but also the element of feed-forward control is taken into account, and the response speed of the weight balance control section 26 is increased accordingly. It can only be done faster.

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 minimized, and disturbances to the feedback control section 16 are minimized. It is possible to improve the response characteristics of

[Effects of the Invention] As explained above, the weight balance control device according to the present invention improves the response speed of the pressure control system,
Reduces disturbances to the position feedback control system,
The response time of the entire position control system can be improved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a device configuration for implementing a weight balance control device 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... Feedback control unit, 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, a position/speed command means for outputting a command position signal or a command speed signal, and a drive signal calculated based on the command position signal or the command speed signal. Feedback control comprising a calculation means for outputting an output, a servo drive means for driving the movable part based on the drive signal, and a position/speed detection means for detecting the position or speed of the movable part and outputting it as a feedback signal to the calculation means. a pressure control means that outputs a pressure control signal based on a command pressure corresponding to the weight of the movable part; a pressure control valve mechanism that controls fluid pressure based on the pressure control signal; and a pressure control valve mechanism that controls fluid pressure based on the fluid pressure. A weight balance control device comprising: a cylinder that applies a force in a direction opposite to gravity; and a weight balance control section having pressure detection means for detecting the fluid pressure and outputting it as a feedback signal to the pressure control section. , comprising compensation control means for calculating a command acceleration signal from the command position signal or command speed signal obtained from the feedback control section and outputting it as a feedback signal to the pressure control means in the weight balance control section, The control means outputs the pressure control signal based on a command pressure corresponding to the weight of the movable part, a feedback signal from the pressure detection means, and a feedback signal from the compensation control means. Weight balance control device.