FI120918B - A method for determining the dead area of a proportional control valve - Google Patents

Description

A method for determining the dead area of a proportional control valve

Background of the Invention

The invention relates to a method for determining the dead area of a proportional control valve used to control a rock drilling machine actuator, wherein the control valve is controlled by an electric P controller and the position of the actuator in a coordinate system representing its motion is measured.

Hydraulic rock drilling equipment controls actuators such as 10 boom feed beam cylinders using proportional directional valves. In practice, these have actuator control in both directions, so that when the valve is in the center position, i.e. in the 0 position, the actuator does not move and when moving the valve stem in either direction, the actuator moves at a speed proportional to works.

However, in current control systems, it has been found that when the valve operates on both sides of its 0-point, there is typically a so-called. dead area where the actuator does not flow with pressure fluid despite the control signal.

If this dead zone of the valve is known, it is possible to correct the control by taking into account the known dead zone and, for example, to make the electronic control signal start position deviation from the 0 position at departure so that the initial value of the control signal is equal to the required error.

However, this is not possible in practice because the dead region 25 varies from valve to valve. Further, the dead zone may be different in different directions of operation of the valve. Also, different valves have different dead areas in different directions of valves, so there is no single single value to correct this.

BRIEF DESCRIPTION OF THE INVENTION It is an object of the present invention to provide a method for further adjusting the hydraulic actuator actuator operation.

The method according to the invention is characterized in that the method comprises the steps of: 2 (a) setting the P controller for the control valve (8) to a first value of 0 gain or such a value that the actuator is not expected to move under its influence; a value whereby the difference between the current 5 position of the actuator and the target position determines a first difference, (b) adding a predetermined step value to the P controller for controlling the control valve, (c) waiting for a predetermined time to determine whether the actuator detects the position value provided by the position indicator after the actuator has started to move, (d) if the actuator has started to move based on the position value of the position indicator, proceeding to step (g), (e) repeating steps (b) - (c) until step (d). on the basis of which we move on n (g), 15 (f) waiting until the actuator motion based on the actuator position indicator has stopped and defining another difference as the difference value (g) between the target position and the stop position defining at least one offset value of (h) and / or (i) and (h) determining the first offset value as the product of the gain of the P controller according to (d) and (a) the first difference value, (i) defining the second offset value of step (d) as the product of the gain of the P-regulator 25 and the second difference in (f).

The essential idea of the invention is to determine for each control valve at least one control offset value corresponding to a dead area in the center of the spindle travel range, and always to control the dead area of its valve in that direction of motion.

According to one embodiment of the invention, for each control valve, at least one control offset value corresponding to a dead area in each of its two directions of motion is determined and controlled by said valve in each direction of motion using a corresponding offset value to compensate for the dead area of said valve.

An advantage of the invention is that a simple method defines in the control system the properties of each valve and the dead area specific to the valve in both directions of movement of the valve if desired, thus practically eliminating the dead area of the valve, whether purely valve or vir-5 he co-produced by control electronics.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail in the accompanying drawings in which

Fig. 1 schematically shows an actuator for a rock drilling device, Fig. 2 schematically shows an exemplary characteristic of a proportional directional valve and the value of the control signals it requires,

Fig. 3 is a schematic block diagram of a solution suitable for valve and actuator control.

Fig. 4 schematically shows a flow diagram for applying the method of the invention.

In the figures, some embodiments of the invention are shown in simplified form for clarity. Like parts are denoted by like reference numerals in the figures.

DETAILED DESCRIPTION OF THE INVENTION Fig. 1 schematically shows an actuator in a rock drilling apparatus. It schematically denotes a base 1 having a boom 3 pivotally connected by means of a joint 2. The boom 3 can be pivoted about the axis of the joint 2 by an actuator, i.e. a hydraulic cylinder 4 connected at one end pivotally. For controlling the hydraulic cylinder 4, pressure medium can be supplied to it from the pump 7 via a proportional control valve 8, whereby at one end of the hydraulic cylinder 4 the pressure fluid also flows through the valve 8 to the pressure fluid reservoir 9. The control unit 10 Further, the figure shows the feed beam 12 at the end of the boom 3 along which the drill machine 13 and the drill bar 14 connected thereto move as the hole is drilled into the rock 15. other actuators are generally known per se and, as they are not intrinsically related to the invention, they need not be shown in the drawings nor explained in the specification.

Fig. 2 schematically illustrates a typical valve characteristic, where line A represents the theoretical valve operating curve, i.e. the relationship between the incoming control signal of the valve and the flow rate of pressure fluid passing through the valve. The lines B1 and B2 respectively represent the actual control signals for valve operation and the volume flows of the pressure fluid passing through the valve, respectively.

As shown in the figure, in theory, the relationship between the control signal and the volume flow through the valve 10 is such that, when the control signal is 0, the volume flow is also 0 and depending on the value of the control signal, the order flow through the valve changes linearly from zero.

In practice, the operation of the valve, either as a property of the valve and as a result of the interaction of its control electronics, has a dead area which in Fig. 15 2 is + -20 units. Thus, the volume flow through the valve only begins when the value of the control signal is 20 units in one direction or another, and it is only up to this value that the volume flow of the pressure fluid through the valve follows the value of the control signal.

If such a situation were ideal for all control valves, this would be easily corrected by setting the control unit's offset 20 deadband to the valve control signal. In practice, however, this is not possible because the dead area of motion of each valve and each valve stem is unique.

Fig. 3 is a schematic block diagram of a solution suitable for adjusting the valve actuator. The controller 16 is connected to control the control valve 8 and the actuator assembly 17 by a control signal proportional to the difference between the measured actuator position and the desired position, herein control. The regulator 16 is a so-called. The P controller, i.e. it controls the valve and through it the actuator, is directly proportional to the incoming control signal. Further, there is schematically illustrated adder 18, which provides an offset value for control of the valve and a control signal provided by controller 16. In adder 18, a final control for the control valve is formed therefrom.

35 Calibration of valve and actuator operation is done by first setting the gain to the controller to 0, or a value at which control valve 5 does not yet begin to release the pressure fluid to the actuator. The offset value is of course 0. At this point, the target actuator is set to a target value, that is, a position value different from the current position so that a certain value 5 becomes the difference between the current actuator position and the desired position, such as 1 m. Of course, other numerical values for angular or linear motion are possible. The gain of the P controller can also be a value other than 0, as long as the control formed by it and the difference input does not cause the actuator to move. In practice, the gain value and the target value for determining the difference can be set in either order or even simultaneously. Thus, in claim 1 (a), when determining them, they are not referred to in the order in which they are listed, but may be any of the above.

When the P controller gain is 0, the valve control is 0. This is because the valve control at each time point is the controller gain times the actuator difference. When the regulator gain is low enough, the actuator will not move because the gain and difference value will not exceed the control value required by the valve.

Next, the gain of the P controller is increased. For example, a gain of 1 can be set for the gain, whereby the value of the valve control is the gain of the P-controller x difference value, i.e., by way of example, 1.

At this point, it will take some time, for example 0.5 seconds or longer depending on the device, to see, based on the signal from the actuator position sensor, whether this control supplied to the control valve causes the actuator to move, i.e., actuator position begins to change toward the target position. If this is not detected, the P controller gain is increased by predetermined increments, i.e. step by step, and is always waited for some time after the addition to detect any movement of the actuator before the P controller gain is increased again. When motion is detected in the 30 actuators, the first offset value is the same as the gain of the controller times the difference between the initial position of the actuator and the target position.

If, as a result of setting the first gain value, a displacement is detected in the actuator, there is no so-called offset in the control valve. dead zone 35 and the pressure flow volume resulting from the valve control, even with this minimum control, may be too large to achieve a good control result.

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On the other hand, once the actuator has begun to move, the first offset value corresponding to the gain and difference input set to the motion controller P that caused the motion is stored in memory and can be used in the future to control that valve and thereby the actuator.

5 Once the actuator has begun to operate as a result of the control valve opening, the valve control begins to decrease as it is the product of the P controller gain and the residual difference. The difference here is the distance between the target position and the current instantaneous position. As the actuator continues to move, the valve control value decreases and at some point the actuator 10 stops moving because the control valve control value decreases as the difference decreases so much that the control valve stops releasing pressure to the actuator or closes. Of course, the actuator movement may stop because the actuator reaches the target position, resulting in a difference of 0. The second offset value of the control valve at which the closure occurred is obtained by multiplying the gain set by the P controller with the difference the second offset value is stored in memory. This product of the gain and difference of the P regulator formed at the end of the actuator movement is another offset value with respect to the control valve control, which describes the dead zone 20 in the middle of its operation. In fact, in this way both the first offset value of the valve control, which represents the offset required to start the valve control operation, and the second offset value of the valve control, which represents the offset remaining at the end of the valve control operation. The two values are different, and when the valve is subsequently controlled, both values can be used, only one value or something in between to compensate for the dead area of the valve. Similarly, since these values are generally different for different directions of motion of the valve stem, only one offset value may be used for each direction of travel, or theirs in each direction. In embodiments that require extreme precision, of course, both offset values can be used in both directions of motion.

This determination of the dead area of the control valve result is schematically illustrated in the diagram in Fig. 4, where an exemplary offset value, i.e., the determination of the dead area when both first and second offset values are determined, is illustrated.

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In Fig. 4, in the flowchart in the first step 21, the gain of the P controller is set to Kp, i.e. the control value 0, which prevents the control valve from being controlled and consequently the actuator cannot move.

Next, in step 22, the reference value Ref is set to position 1 and the desired direction of motion relative to the current position of the actuator 5 in question. This value 1 may be, for example, 1 0 at an angle of rotation, 1 m in linear motion, or any other suitable value, exemplified as 1.

Then, in step 23, the current gain value Kp plus one, Kp = Kp + 1, is set to the gain of the P controller 10. Similarly, here, one means one predetermined step size, exemplified by 1.

Once this is done, it is expected in step 24 as a result of this manufacturing value whether it causes movement in the actuator. This motion, if sel-15 occurs, is detected based on the position value provided by the actuator position detector.

In step 25, a selection is made based on the position value given by the position detector whether the actuator has started to move. If no motion is detected, return to step 23 and add a predetermined gain step Kp to the P controller gain. The loop between steps 23 to 25 is repeated until step 25 determines that the actuator has begun to move. Then, according to step 26, the current control value, i.e. the first offset value, formed by the P controller input value and the difference input Ref set in step 22, is stored in offset 1 for future use to control the actuator control valve.

Once motion of the actuator has been detected, step 27 is expected without making any changes to the control valve control.

In the next step 28, the actuator position detector checks whether the actuator is still moving, i.e., whether the position value 30 provided by the position detector changes. As long as this value continues to change, return to step 27, and after a predetermined time, move to step 28 again to check if the actuator is still moving.

When it has been established in step 28 that the position value of the actuator position detector no longer changes, proceed to step 29, where the difference between the target position set on the actuator and the position at the time of stopping is determined. Hereby a second offset 8 value of the control valve, offset 2, i.e. the amount of dead area in its center region from the O position to the measured direction of motion, is obtained by multiplying the difference value by the gain of the P controller. This second offset value is stored in memory and can be used in the schematic representation of Fig. 3 by adding the resulting offset value 5 to the control value of the valve, whether analog or digital control system is used and also when using manually operated control such as joystick control.

The above method can be implemented automatically in computer controlled hardware, whereby the adjustment can be made by anyone and no special control professionals are required. In rock drilling equipment with several different actuators, this calibration can be performed automatically for all control valves and their controlled actuators, providing their own offset values. Adjustment can also be made in both directions of movement, whereby, if desired, different offset values in different directions of movement can be stored for each valve and actuator. In some cases, sufficient control accuracy is obtained by selecting an offset value between the measured start and stop offset values and using that value to correct the control. If desired, the same value can be used for both directions of movement.

The invention is described in the description and drawings only by way of example-20 and is not limited in any way to the description thereof. It is essential that the dead area in the proportional control valve operation where the valve does not actually control the actuator is defined as described in the claim and the error value thus obtained is used to compensate for this dead area of the valve during operation and control of the valve. Once the offset-25 value or values are stored in memory, they can be used to control the actuator regardless of the actual control mode and controller mode used. Thus, the values can be used with P, D and / or I controllers as well as control systems that use analog and digital control signals to control the valves. Likewise, when manual controls are used for control, offset values can be taken into account in the control system as desired.

In some cases, the features set forth in this application may be used as such, despite other features. On the other hand, the features disclosed in this application may be combined, if necessary, to form various combinations.

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The drawings and the description related thereto are intended only to illustrate the idea of the invention. The details of the invention may vary within the scope of the claims.

Claims (8)

1. A method for determining a dead zone for a proportional control valve (8) used for controlling a rock drilling rig, in which method the control valve is controlled by an electric P regulator and the position of the actuator in a coordinate system describing its movement is measured. with a separate position indicator, characterized by the method encompassing steps: (a) installed for the P controller for controlling the control valve (8) the gain of the controller as a first value 0 or such value that the actuator is not expected to move through its effect, and for the actuator, a value for the target position deviating from its actual position is installed, the difference between the actuator's current position and the grinding position determining a first difference magnitude, (b) being added to the P controller for controlling the control valve (8). to the value for the gain of the controller an addition of a value equal to one a predetermined step, (c) a predetermined time is expected to guarantee whether the position value that the actuator's position detector detects that the actuator has started to move, (d) if the actuator has started to move, based on the position detector's position value if one is transferred to step (f), (e) points (b) - (d) are repeated until on the basis of step (d) transfer to step (f), (f) is expected until the movement of the actuator on the basis of the position detector of the actuator has ceased and defined a second difference quantity as the difference value between the target position and the stop instant position, (g) at least one offset value is defined in accordance with points (h) and / or (i) and it is stored in memory to be used to compensate the dead zone of the control valve (8) when controlling the control valve (8), (h) a first offset value is defined as the product of the gain of the P controller according to point (d) and the first difference quantity according to point (a), (i) a second offset value is defined as the product of the gain of the P controller according to point (d) and the second difference quantity according to point (f). Method according to claim 1, characterized in that both the first and the second offset values are defined in at least one direction of movement of the control valve (8) and they are stored in memory to be used to compensate (8) the dead zone when controlling the control valve. (8). 3. A method according to claim 1 or 2, characterized in that the offset values are defined in the operating directions of the control valve (8). 5 4. A method according to claim 3, characterized in that the offset values for each direction of movement are used to compensate the dead zone of the control valve (8) only in the direction of movement in which it was measured. 5. A method according to claim 3, characterized in that of the offset values is formed between their values a value, preferably a value corresponding to the average value used to compensate the dead zone of the control valve (8) when controlling the control valve (8) at least in its other direction of movement. 6. A method according to claim 5, characterized in that the value formed between the offset values is used to compensate the dead zone of the control valve (8) in controlling the control valve (8) in its two directions of movement. 15 The method according to any of claims 1-4, characterized in that the first offset value is used to compensate for the control zone (8) dead zone. Method according to any of claims 1-4, characterized in that the second offset value is used to compensate for the dead zone of the control valve (8).