JPS6362902A - Controlling method of hydraulic driving system - Google Patents

Abstract

PURPOSE:To effectively compensate a dead band regardless of the using condition by varying control signal values that control the hydraulic output of a hydraulic pump only by a set offset amount when the number of hydraulic pumps are to be changed. CONSTITUTION:When the number of hydraulic pumps being used are to be changed, a lifting and lowering drive control signal V is to vary only by a set offset amount DELTAV. By doing so, a dead band can be effectively compensated regardless of the using condition because the drive control signal value will jump from point P1 to point P2 on a characteristic line C0 and the range of its staying on the dead band R0 can be lessened.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for controlling a hydraulic drive system, such as one used for hoisting and lifting a crane for shipping, and particularly relates to a method for controlling a hydraulic drive system used for hoisting and lifting a crane for shipping. This invention relates to dead zone compensation control for a hydraulic drive system equipped with multiple pumps.

(Prior Art and its Problems) In a hydraulic drive system used for hoisting and lifting a suspended load of a crane, it is necessary to change the operating speed of the hydraulic actuator depending on the load condition and the operating conditions of the drive system. For this reason, the output capacity of the hydraulic pump for driving the hydraulic actuator must have a margin to be able to sufficiently cope with fluctuations in the operating speed of the hydraulic actuator.

However, hydraulic pumps with a large output capacity are generally large and expensive, so it is not appropriate to install such a large capacity hydraulic pump in a mobile crane or the like. Therefore, by installing multiple hydraulic pumps with normal capacity and changing the number of hydraulic pumps used,
Hydraulic drive systems that can drive hydraulic actuators over a wide range from low speeds to high speeds are often used.

However, in such a system, around the time when the number of hydraulic pumps used is changed,
Region where response sensitivity to drive control signals is significantly reduced (
A “dead zone”) will appear. Figure 12 is a graph illustrating such a situation, where ■ indicates an area where a hydraulic actuator is driven by one hydraulic pump (hereinafter referred to as "
1st speed region. ), and ■ indicates an area where driving is performed by two hydraulic pumps (hereinafter referred to as "second speed area").

In FIG. 12, when the drive 1III control signal U is continuously increased from 0, the hydraulic output of one hydraulic pump starts to increase after passing through a certain play area, and the hydraulic actuator is activated accordingly. The speed S also increases. Then, the saturation speed S corresponds to the capacity of one hydraulic pump. When reaching 1, the shift from the 1st speed area to the 2nd speed area ■
Then, the two hydraulic pumps start driving.

On the other hand, in order to change the drive by one hydraulic pump to two, it is necessary to change the connection of the hydraulic circuit using a switching valve or the like. In addition, a certain amount of delay tends to occur in the operation of such switching valves and the like. For this reason, even if you try to merge the pressure oil from the second hydraulic pump after the drive output of the first hydraulic pump is saturated, it will not be possible to perform this operation instantly, and as shown in Figure 12. The saturation region R8 is connected over a relatively wide range.

As is clear from the figure, this saturation region R8 forms a dead zone R8 in which the operating speed S of the hydraulic actuator does not change even if the drive control signal U changes. The existence of such a dead zone R8 makes the control of the hydraulic actuator unstable. For example, in the horizontal movement control of a suspended load in a crane, the first speed region I and the first speed awL
There is a problem in that the control deviation becomes large near the working radius corresponding to the boundary area with m.

To solve this problem, gradually start switching the output of the second hydraulic pump before the drive output of the first hydraulic pump becomes saturated, and then start switching the output of the second hydraulic pump immediately after the first hydraulic pump becomes saturated. An improvement is also conceivable in which pressure oil from a second hydraulic pump starts to be supplied to the hydraulic actuator. However, in a hydraulic drive system, its operating conditions (in the case of a crane, boom length, number of latches, workability, etc.) often change. Therefore, even if the above-mentioned adjustment or correction of the control gain is performed under specific conditions, it is usual that the device does not operate as intended under the specified conditions.

For example, when adjusting the hydraulic drive system of a crane under specific conditions, Shun explained, 11) When doubling the number of hydraulic drive systems, simply doubling the drive #I]a, +1t11 signal U will reduce the dead zone. It cannot be resolved.

As described above, the conventional control method has a problem in that it is not possible to effectively compensate for the dead zone regardless of the usage conditions.

(Object of the Invention) The present invention is intended to overcome the above-mentioned problems in the prior art, and is a control method capable of effectively compensating for dead zones in a hydraulic drive system equipped with a plurality of hydraulic pumps, regardless of usage conditions. The purpose is to provide

(Means for Achieving the Object) In order to achieve the above-mentioned object, the present invention includes a plurality of hydraulic pumps that drive a predetermined hydraulic actuator, and the number of hydraulic pumps used and the hydraulic output of the hydraulic pumps are adjusted. A method for controlling a hydraulic drive system that changes the operating speed of the hydraulic actuator by changing the number of hydraulic pumps used, the value of the control signal that controls the hydraulic output of the hydraulic pump is set to a predetermined value. change by the offset amount.

(Example) Hereinafter, as an example of the present invention, a method of controlling a hoisting and vertical hydraulic drive system in horizontal movement of a suspended load by a crane will be described. However, this explanation does not include the ``overview of mechanical configuration'', ``configuration of hydraulic drive system'', r.
a. II. 12g Device Configuration and Operation".

Finally, a modification of this invention will be mentioned.

A. Fig. 1 of the internal structure of the crane mechanism is shown in Fig. 1 according to an embodiment of the present invention. 1 is a schematic external view showing an overview of the mechanical configuration of a crane incorporating a hydraulic drive system controlled by an IJ. In FIG. 1, this crane 1 includes a crane main body 2 and a crane main body 2.
The boom 3 is attached to the end of the boom 3 so as to be able to rise and fall freely. One end of a boom elevating lobe 4 is fixed to the tip of the boom 3, and the other end of the boom elevating lobe 4 is wound around a boom elevating drum 5 provided within the crane body 2. There is. Therefore, by rotating this boom elevating drum 5, the boom elevating row 14 is wound up/feeded out, whereby the boom 3 is elevated as shown by arrows α and (-α), and its tip is raised. The height H changes.

On the other hand, a hook 7 is suspended from the tip of the boom 3 by a hoisting and lowering row 16. This winding and lowering row 76
is wound around a hoisting and lifting drum 8 provided within the crane body 2. Therefore, by rotating the winding/lowering drum 8, the winding/I of the winding/lowering lobe 6 is
I! As a result, the hook 7 descends four times in the vertical direction (seven directions in the figure). By simultaneously performing the lifting and raising movements of the boom 3 and the hoisting and lifting movements of the hook 7, the load 9 suspended from the hook 7 can be horizontally maintained while maintaining the height h from the horizontal plane. (in the X direction shown in the figure).

On the other hand, the crane main body 2 is provided with an engine EG as a power source for the crane, and an i/H1l, which will be described later.
A control device 10 for performing operations 1 and an operation panel 11 for inputting operations by an operator are also installed. Further, a boom elevation angle detector 12 is provided near the boom foot of the boom 3 to detect an elevation angle θ of the boom 3 from a horizontal plane. As the boom elevation angle detector 12, an inclinometer type detector (for example, one equipped with a freely movable part and an oil damper) for detecting the angle with respect to the ground is used. A rope winding/feeding amount detector 13 is attached to an idler sheave provided near the tip of the boom 3 and guiding the hoisting/up-down winding 0-16. This rope winding/1!4 rope winding amount detector 13 is constituted by a rotary encoder or the like, and is for detecting the winding/winding amount of the winding/lowering row 76 from the rotation angle of the idler sheave.

B. Horizontal 1 of Hydraulic Drive System FIG. 2 is a hydraulic circuit diagram showing the configuration of a hydraulic drive system for raising and raising the boom 3 and hoisting and raising the hook 7. In FIG. 2, this hydraulic drive system includes the engine EG
(not shown in FIG. 2)
and second main hydraulic pumps 21a and 21b. Of these, hydraulic pressure from the first main hydraulic pump 21a is applied to the boom elevation hydraulic motor 23a via the boom elevation direction control valve 22a. This boom elevating hydraulic motor 23a is for rotationally driving the boom elevating drum 5 shown in FIG. Further, the respective hydraulic pressures from the first and second main hydraulic pumps 21a and 21b rotate the hoisting and up-and-down drum 8 in FIG. It is also provided to a hydraulic motor 23b for hoisting and lifting for driving.

Among these control valves 22a=22c, the pilot part of the boom elevation control valve 22a includes a boom-raising proportional electromagnetic pressure reducing valve 26a and a boom-lowering electromagnetic proportional pressure reducing valve 27a.
and the respective secondary side circuits 248.25a are connected. Similarly, the hoisting/uploading directional control valves 22b, 22
Secondary side circuits 24b and 25b of the hoisting electromagnetic proportional pressure reducing valve 26b and the hoisting electromagnetic proportional pressure reducing valve 27b are connected to the pilot section c, respectively.

Among these, the negative side of the electromagnetic proportional pressure reducing valves 26a and 27a is the secondary side circuit 30a of the boom elevation remote control valve 32a.
, 31a, respectively. The boom elevation remote control valve 32a is equipped with a pair of variable pressure reducing valves (not shown), and controls the secondary pressure to be applied to the secondary circuit 30a or 31a according to the operating direction and operating amount of the boom operating lever 33a. It has the function of controlling.

Further, boom lever pilot pressure detectors 36 and 37 for detecting the respective secondary pressures are provided in the secondary side circuits 30a and 31a of the boom elevation remote control valve 32a. This boom lever pilot pressure detector 36,37 allows the boom operating lever 33 to
The operation direction and operation amount of a can be detected.

On the other hand, the electromagnetic proportional pressure reducing valves 26b and 2 for hoisting and lowering
The primary sides of 7b are connected to the secondary sides of electromagnetic switching valves 28 and 29, respectively. And these electromagnetic switching valves 28
．． On the primary side of 29, a corresponding one of the secondary side circuits 30b and 31b of the remote control valve 32b for hoisting and lowering, and a secondary side circuit 35 of the pilot hydraulic pump 34 driven by the engine EG can be freely switched. It is connected. The remote control valve 32b for hoisting and lowering is the same as the remote control valve 3 for raising and lowering the boom.
2a, it is equipped with a pair of variable pressure reducing valves (not shown), and is used to control the secondary pressure applied to the secondary circuit 30b or 31b according to the operating direction and operating amount of the hoisting/lowering operation lever 33b. belongs to. In addition, in the figure, C
■ indicates a check valve.

An outline of the drive operation of the hydraulic drive system having such a configuration during horizontal movement is as follows. That is, when horizontally moving the hanging load 9 in FIG. 1, first, a mode changeover switch (not shown) provided on the operation panel 11 in FIG. 1 is switched to the horizontal movement control mode. Then, the second
The electromagnetic switching valves 28 and 29 in the figure are urged upward in the figure, and hydraulic pressure from the secondary circuit 35 of the pilot hydraulic pump 34 is applied to the primary side of the electromagnetic proportional pressure reducing valves 25b and 27b.

Therefore, at this time, the winding/lowering operation lever 33b
The operation becomes independent of drive control.

When the operator operates the boom operation lever 33a, hydraulic pressure is applied in accordance with the direction and amount of operation from the boom elevation remote control valve 32a to the electromagnetic proportional pressure reducing valve 26a,
27a on the primary side.

Electromagnetic proportional pressure reducing valves 26a, 27a and 26b.

27b is a drive control signal (2) from a control system, which will be described later.

U (not shown in FIG. 2) and thereby the secondary circuits 24a, 25a, 24b.

The oil pressure in 25b changes. These oil pressures are applied to respective pilot portions of the boom elevation directional control valve 22a and the first and second hoisting/up/down directional control valves 22b and 22C.

Then, the boom elevation direction control valve 22a is gradually turned to the boom up (or boom down) position, and the pressure oil from the main hydraulic pump 21a is transferred to the boom elevation hydraulic motor 23a.
supplied to As a result, the pressure oil motor 23a rotationally accelerates due to this pressure oil, and the boom elevation drum 5 shown in FIG. 1 rotates.

As a result, the boom elevating rope 4 shown in FIG. 1 is wound up or let out, and the boom 3 is raised or lowered.

On the other hand, among the hoisting/up/down directional control valves 22b, 22C in FIG. It is set smaller than the spring constant of the spring. For this reason, the electromagnetic proportional pressure reducing valve 26b.

When the control signal U applied to 26c is small, the first
Only the hoisting/lowering directional control valve 22b is switched to the hoisting (or hoisting) position, whereby the main hydraulic pump 21
Pressure oil from a is supplied to the hoisting/lowering hydraulic motor 23b. As a result, this hydraulic motor 23b rotates and accelerates, and the hoisting/lowering drum 8 shown in FIG.
Winding or unwinding is performed. The binding is performed, and the hook 7 is raised or lowered.

On the other hand, when the control signal U applied to the electromagnetic proportional pressure reducing valves 26b, 26c is larger than a certain level, the first hoisting/up/down directional control valve 22b is turned on fully, and the second hoisting/up/down directional control valve 22c is turned on. Switching begins.

As a result, the pressure oil from the first and second main hydraulic pumps 21a, 21b is combined and applied to the hoisting/lowering hydraulic motor 23b.

Therefore, in this case, the winding up/down drum 8 in FIG. 1 rotates at high speed, and the suspended load 9 is hoisted up or lowered at high speed. However, at this time, as will be understood from the explanation of the control system to be described later, the raising and raising motion of the boom 3 is also performed at high speed.

Stable horizontal movement of the suspended load 9 is realized by adjusting and controlling the relationship between the elevating motion of the boom 3 and the hoisting and hoisting motion of the hook 7 using a υ1ull device, which will be described later.

Structure and operation of C1 control device FIG. 3 is a block diagram showing the structure of a control device for controlling the hydraulic drive of the crane.

This control system includes a boom elevation control system and a hoisting hoist up/down control system, of which the shipping hoist up/down υ1111 system is
It has a feedforward control system and a feedback control system. Further, this control system is provided with means for compensating for a dead zone in the load hoist vertical drive system, corresponding to the features of the present invention. Below, these configurations and operations will be emphasized.

(C-1) Boom elevation control system First, in the boom elevation control system, the detection 1111D1 of the boom lever pilot pressure detector 36, 37 explained in FIG. 2 is used as a control input, and this input is applied to the multiplier shown in FIG. Give to 42. Other inputs to the multiplier 42 include boom elevation suppression pattern data D2 (described later) stored in the boom elevation suppression pattern storage device 41.

) is given. Then, a boom elevation signal D3 obtained by multiplying the detection value D1 and this suppression pattern data D2 is given to the boom elevation electromagnetic proportional pressure reducing valve 43 as an elevation drive control signal V. However, this boom elevation proportional electromagnetic pressure reducing valve 43 corresponds to the boom raising proportional electromagnetic pressure reducing valve 26a and the boom lowering proportional electromagnetic pressure reducing valve 27a shown in FIG.

By giving such an elevation drive control signal (2) to the boom elevation electromagnetic proportional pressure reducing valve 43, the boom elevation drive control valve 2!2a and the boom elevation hydraulic motor 2 shown in FIG.
A boom elevation drive system 44 shown in FIG. 3, which is constituted by components such as 3a, operates based on the driving force of the engine EG.

As a result, the boom 3 starts to move up and down depending on the direction and amount of operation of the boom operation lever 33a shown in FIG.

Here, the boom elevation suppression pattern data D2 shown in FIG. 3 mentioned above will be explained. During the horizontal movement of the suspended load 9, hunting is most likely to occur during the period immediately after the horizontal movement is started.

Therefore, in this embodiment, pattern data as shown in FIG. 4 is provided as the boom elevation suppression R11 pattern data D2 in which the elapsed time t from the start of horizontal movement is used as a parameter. Then, even if the operator suddenly operates the boom operation lever 33a at the start of horizontal movement and the detection value D1 of the boom lever pilot pressure detector 36.37 becomes a large value, the suppression pattern data D2 in FIG.
By multiplying this detected value D1 by the value of the rising portion R (<1), the boom elevation signal D3 becomes the detected value D1.
will be a smaller value. Therefore, within the period corresponding to the rising portion R1 in FIG. 4, the direction ill control valve 22a,
Since the switching of 22b is performed gradually, the upward and downward movements of the boom 3 are slow, and hunting at the start of horizontal movement is prevented.

Then, after the horizontal movement starts, a certain amount of time t.

In the steady portion R2 after (FIG. 4) has elapsed, the pattern data D2 becomes "1", and the detected value D1 corresponding to the operation amount of the boom operating lever 33a becomes the elevation drive control signal V as it is.

Therefore, at the start of horizontal movement, hunting is prevented by a slow boom elevation movement, and as time passes, the boom elevation is accelerated, and in a steady state, the boom elevation movement is realized as intended by the operator. It turns out.

(C-2) Shipping hoisting system MT system Next, the hoisting hoisting vertical control system will be explained. As described above, this hoisting vertical control system has a feedforward control system and a feedback control system. this house,
In the feedforward control system, first, the detected value D1 detected by the boom lever pilot pressure detector 36, 37 in FIG. 3 is given to the multiplier 45. As another input of this multiplier 45, feedforward rising pattern data D4 stored in a feedforward rising pattern storage 46 is applied.

This feedforward rising pattern data D4 is data prepared in order to prevent sudden changes in operation at the start of horizontal movement, similar to the boom elevation suppression pattern D2 described above, and is data prepared as described above for time t. It has a pattern as shown in FIG. Then, data D obtained by multiplying these data D and D4 by the power IW45
is given to the arithmetic unit 47.

The value of the boom elevation angle θ detected by the boom elevation angle detector 12 is also input to the calculator 47 . Then, the calculator 47 calculates K F = K (fCOSθ - (
The value of 1) is calculated and obtained, and this value is multiplied by the data D5 to obtain the feedforward ωU.

In addition, the reason why the 7 actors of "CO3θ" are included in the above equation (1) is that the amount of elevation of the tip of the boom 3 when the boom elevation angle θ changes to (θ + 8) is COSθ
Therefore, in order to compensate for this and realize horizontal movement, the winding/feeding amount of the winding/lowering row 16 must also be COS.
This is due to the fact that it must be proportional to θ.

The feedforward mu (obtained in this manner) is added to the feedback amount ub in the adder 48 to form the winding/up/down signal U.Then, this winding/up/down signal U is subjected to dead zone compensation in the compensation device 56 (described later). This signal U becomes the hoisting/up/down control signal U, and this signal U is given to the hoisting up/down electromagnetic pressure reducing valve 49 as a pressure reducing control signal. This corresponds to the proportional pressure reducing valve 26b and the lowering electromagnetic proportional area pressure changer 271).

The hoisting hoist up/down drive system 50 shown in FIG. 3, which is constituted by the hoisting/up/down directional control valve 22b in FIG. 2, the hoisting/up/down hydraulic motor 23b, etc. Based on this, the winding/lowering row 76 shown in FIG. 1 is caused to wind up/unwind.

The above is the configuration and operation of the feedforward control system.

Next, the feedback control system will be explained.

In this feedback control system, first, the actual winding/n unwinding/retracting l of the winding/lowering lobe 6 is detected by the lobe winding/unwinding detector 13 shown in FIG. on the other hand,
The value of the boom elevation angle θ detected by the boom elevation angle detector 12 described above is also given to the calculator 51. In this performance 0351, the target value 1' of the winding/feeding distance of the winding/lowering row 76 required to maintain the suspended load 9 at a predetermined height h is calculated for the value of the boom elevation angle θ. Calculate using the formula: % formula %). However, l is the length of the boom 3, and θ0 is the boom elevation angle at the start of horizontal movement.

The target 'til' obtained in this way and the actual winding/unwinding Nl detected as described above are applied to a subtractor 52, in which the deviation between them is calculated as follows: Δh= l'-1...(3) is obtained.

This deviation Δh is input to the arithmetic unit 53, and the arithmetic unit 53
Then, the sum of the proportional control component: Δh and the integral III control component IfΔhdt=KlΔh/s is determined. However, S represents a Laplace operator. The feedback obtained in this way ffi
As described above, ub is added to the feedforward suspension u'' in the adder 48, and the hoisting/up-down control is executed based on the sum U.

That is, here, feedback control is performed based on the deviation of the target value l' of lobe winding/feeding agitation from the actual value l, and by combining the feed forward till l described above and this feedback control, the boom The winding/I unwinding of the winding/lowering row 76 is performed in response to the elevation/elevation motion of step 3. As a result, the suspended load 9 is moved horizontally.

(C-3) Dead zone compensation Next, dead zone compensation in this embodiment will be explained. As already explained, the plurality of hydraulic pumps 21a, 2
1b to control the speed of the hoisting/up-down drum 8, the hoisting/up-down drum 8 is
The dependence of the rotational speed S on the rotational speed S is as shown in FIG. 5 by a characteristic line C8. Therefore, the winding up and down drive in Figure 3! , II When the control signal U is directly applied to the electromagnetic proportional pressure reducing valve 49 for lifting and lowering the load, the saturation speed S is determined by the capacity of the first main hydraulic pump 21a. There is a dead zone Ro in the speed portion corresponding to 1.
(Figure 5) occurs.

Therefore, in this embodiment, when changing the number of hydraulic pumps used, the hoisting/up/down drive υJall signal U is changed by a predetermined offset amount ΔU to substantially reduce the range of the dead zone R0. That is, when the winding/up/down drive control signal U is sequentially changed, the points P and P2 on the characteristic aC in FIG.
The aim is to reduce the range that remains on the dead zone Ro by making a jump between the two. In addition, in this embodiment, the dead zone E of the starting part due to mechanical play etc.
Also compensate for o. This compensation is for the origin O and point P. This is done by jumping between the two.

Therefore, a method for specifically performing such compensation will be described below with reference to the flowchart shown in FIG. 6. This compensation operation is performed when the compensation device 56 in FIG. 3 is configured by a microcomputer or the like. In addition, in this operation, (1) hysteresis is provided in the compensation, and (2) the offset amount ΔU corresponding to the compensation amount is set smaller than the width of the dead zone R8, resulting in "incomplete compensation." The reason for performing such processing will be described later.

First, in step S1 of FIG. 6, the flag F is set to "0". Then, in the next step S2, the engine speed N of the engine EG is detected by the engine speed detector 54 shown in FIG. Then, in step S3, data representing the engine rotational speed N is transferred to the offset amount setting device 5 in FIG.
5, thereby determining the offset amount ΔU.

This is because the width of the dead zone R6 changes depending on the rotation speed N of the engine EG, as illustrated in FIG.
This is a process for setting the offset amount ΔU according to. However, the vertical axis in FIG. 7 indicates the drum rotational speed normalized by the maximum rotational speed 5lax of each of the hoisting and lowering drums 8 at the angular rotational speed N of the engine EG.

For this purpose, the offset ffl determiner 55 of FIG.
The internal memory (not shown) is pre-loaded with a table expressing the correspondence between the engine speed N and the offset amount ΔU. As can be seen from FIG. 7, as the engine speed N increases, the width of the dead zone R6 becomes narrower. Therefore, the relationship between N and ΔU is set as shown in FIG. 8, for example.

Returning to FIG. 6, in the next step S4, the value of the winding/up/down drive control signal U before compensation is read from the filter 53 of FIG. In the next step S5, it is determined whether F=0, but at this point it is F-〇, so step S5
6, the value of the winding/up/down drive control signal U and the predetermined fa
The magnitude relationship with uo is determined. This U. The value of
As shown in the figure, the rising position P of the characteristic line C0. It corresponds to the width in the horizontal axis direction from the point P3 set near the left end of the dead zone R0. As will be explained later, this value U. is related to the jump position of the winding/up/down drive control signal U. Therefore, U depends on the engine speed N. If you also want to change the value of , enter N and U in the offset ff1l regulator 55 in FIG.

Which correspondence table should be set up?

Returning to FIG. 6, considering the case where the winding/up/down drive $ control signal U is raised from Ohl to Ohl, initially U<U.

Therefore, the process moves from step S6 to step S87, and the offset amount ΔUO is added to the winding/up/down drive control signal U to generate the winding/up/down drive control signal U after compensation. However, this offset amount ΔUO is the section width from the origin O to the point Po in FIG. Therefore, as shown in FIG. 9, U=O
is converted to U=Δuo. After setting the flag F to '1' in step S7, the hoisting/up/down drive control signal U is outputted to the hoisting/up/down electromagnetic proportional control valve 49 shown in FIG. 3 in step S8.

In the next processing cycle, since it is F-1, the process goes from steps S4 to S9 through 85. Then, in this step S9, the winding/up/down drive control signal U before compensation and (Δu
□ + W) is compared.

However, W is a predetermined hysteresis width.

In a period in which U<(ΔU O+ W ), the process moves to step S10, where the above-mentioned Δuo is added to the winding/vertical drive control signal U to generate the winding/vertical drive control signal U, which is output in step S8. These steps S4.35. S9
．． The process of 810.38 is repeated until U≧(ΔU0+W).

When U≧(Δu □ + W), the process moves from step S9 to step 811, where two types of offset amounts ΔU and ΔU are added to the winding/up/down drive control signal U to generate the compensated winding/up/down drive control signal U. . And after setting it to F-0,
In step S8, the winding/up/down drive control signal @U is output. Therefore, as shown in FIG. 9, a jump occurs in the relationship between the winding and vertical drive control signals u and U before and after compensation when U=Uo+W.

Thereafter, when the winding/up/down drive control signal U increases further, the process starts from step S4, passes through 85, 86, and 812, and then goes to S8. In step 812, as in step 811, two types of offset amounts ΔU and ΔU are added to U.

Therefore, as the winding/vertical drive control signal U increases from O, the value of the winding/vertical drive control signal U after compensation changes along the locus of FIG. 9: Hl, R2, R3, H4. become. Therefore, in the interval 0≦U≦(uo+w), the actual winding/up/down drive control signal U is (U
+ΔUo) is given, and the characteristic line C is shown in Figure 5.
As shown, processing equivalent to shifting the section from P to Pl of the original characteristic line C8 toward the origin O by ΔUo is performed. However, point Q -02
is point P. -P2O respectively. Also, from point P1 in Figure 5 to R
The section up to 2 is effectively short-circuited by the jump in trajectory H3 in FIG. Then, point P on the characteristic line Co
For the part to the right from 2, it is equivalent to shifting to the left by (ΔU□+ΔU). As a result, the illustrated characteristic lIC is obtained.

Next, consider a case where the winding/up/down drive control signal U decreases from a large value toward zero. In this case, as can be seen by following the flowchart of FIG. 6 in the same manner as above, U≧u.

In the section, two types of offset amounts ΔU and ΔU are added to the winding/up/down drive control signal U. And LJ < u
.

Then, the winding/up/down drive υ control signal U has an offset amount Δ
Only UOs are added.

Therefore, in this case, the characteristic line C8 in FIG. A point located on the right side by ΔU is a point that indicates the apparent relationship between the winding/up/down drive control signal U and the rotational speed S.

Therefore, even when the winding/up/down drive control signal U decreases from a large value toward 0, the apparent characteristic line coincides with the characteristic line C described above.

As is clear from the figure, the characteristic line C obtained in this way has a shape obtained by truncating the section R0 in the dead zone R6 of the original characteristic line C8. This process is executed regardless of the usage conditions of the hydraulic drive system. Therefore, the dead zone R8 is effectively compensated, and stable hydraulic system control can be performed.

Next, the effects of hysteresis and incomplete compensation will be explained.

■Hysteresis As can be seen from the flowchart in Figure 6, when the winding vertical drive control signal U increases, a jump occurs at U = (Uo + W), and when the winding vertical drive control signal U decreases, a jump occurs at U. A jump occurs at u 6. Therefore, in the latter case, the relationship between the winding up/down drive control signals u and U before and after compensation changes along the locus of Fig. 9: H, R5, 86, Hl. However, hysteresis as shown occurs.

However, since this hysteresis generating operation occurs in the dead zone R8 in FIG. 5, no hysteresis appears in the characteristic IIC.

The reason for providing such hysteresis is as follows. That is, first, if hysteresis is not provided (
W=O), the winding/up/down drive control signal U is U. When there are fluctuations in the vicinity, jumps by the offset amount ΔU frequently occur in the control system.

Then, the control signal level fluctuates rapidly, and the operating state of the electromagnetic proportional pressure reducing valve 49 for lifting and lowering the load shown in FIG. 3 becomes unstable. As a result, the operation of the hoisting vertical drive system 50 also becomes unstable, and there is a possibility that the drive responsiveness, which should originally have the characteristics as shown in FIG. 5, collapses. For this reason, u
It is also possible that hunting of the suspended load 9 occurs near the point ``uo''.

On the other hand, when hysteresis is provided as described above, the movement of the winding/up/down drive control signal U and the drive system does not become unstable, and stable control can be performed.

■Five Brother Emperor 11 In the embodiment described above, the magnitude of the offset amount ΔU in FIG. 5 is made smaller than the width of the dead zone R8 to some extent. Therefore, some dead zone remains in the apparent characteristic line C.

On the other hand, if the offset amount ΔU is made equal to the width of the dead zone R8, the dead zone can be completely compensated for, but in this case, the following situation may occur. That is, the characteristic line C1 as shown in FIG. 10(a) is obtained by completely performing dead zone compensation.
Even if the shape of the original characteristic line C (Fig. 5) is shifted due to the following reasons, as a result, the connection boundary between the first speed region ■ and the second speed region ■ will be distorted. , 10th
There is a possibility that a jump ΔS in the speed S as exemplified by the characteristic line C2 in FIG. Examples of reasons why such a situation occurs are as follows.

(a) Individual differences in the hydraulic system and drive system (b) Individual differences in the N magnetic ratio side pressure reducing valve and the electric circuit for driving it (C) Characteristic changes due to differences in the weight of the suspended load (d) Characteristic changes due to differences in engine speed (However, if the size of the offset amount ΔU is changed according to the engine speed N as in the above embodiment, this effect becomes smaller.) When the step change ΔS occurs, there is a possibility that an overshoot will occur in the output of the electromagnetic proportional pressure reducing valve or in the position change of the main spool of the directional control valve.

In this way, complete compensation may lead to control instability, but in the above embodiment, the offset amount ΔU is set to be smaller than the dead zone R8 to some extent.
There is a margin for characteristic fluctuations, and jumps like the one shown in FIG. 10(b) do not occur.

Therefore, in this embodiment, preferable dead zone compensation is performed.

FIGS. 11(a) and 11(b) show the changes in the hoisting vertical deviation and the hoisting/vertical drive control signal U (current) over time t, respectively, compared to the conventional control method without dead zone compensation (dashed line). It is a figure shown by the above-mentioned example (solid line). As can be seen from this figure, by performing the dead band compensation, the deviation near the transition from the first speed range work to the second speed range (3) is significantly reduced, and stable control is performed.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and for example, the following modifications are possible.

■ In the above embodiment, a case is considered in which changes in the individual hydraulic outputs of the two main hydraulic pumps 21a and 21b and changes in the number of main hydraulic pumps used are controlled based on one control signal U. However, the present invention can also be applied to a case where the output of each hydraulic pump and the number of hydraulic pumps to be used are changed using separate II-- TLL signals.

(2) The effects can be further improved by employing the above-mentioned hysteresis and incomplete compensation, but these do not need to be employed in hydraulic drive systems that do not require much consideration of changes in characteristics. Further, when the engine rotational speed (generally the rotational speed of a power source that provides rotational power to a hydraulic pump) is constant, there is no need to change the offset amount according to a change in the rotational speed.

(2) The hydraulic actuator in this invention may be a direct-acting actuator (such as a hydraulic cylinder), and any number of hydraulic pumps may be used as long as they are plural. The present invention can be applied to a wide range of applications such as hydraulic drive systems for cranes, various transportation equipment, processing wire machines, and hydraulic drive systems for large robots.

(Effects of the Invention) As explained above, according to the present invention, when changing the number of hydraulic pumps that drive a hydraulic actuator, the value of the control signal for controlling the hydraulic output of the hydraulic pumps is adjusted by a predetermined offset port. Since the dead zone is varied, it is possible to effectively compensate for the dead zone in a hydraulic drive system including a plurality of hydraulic pumps, regardless of the usage conditions.

[Brief explanation of drawings]

Fig. 1 is a schematic external view of a crane to which an embodiment of the present invention is applied, Fig. 2 is a hydraulic circuit diagram of the hydraulic drive system of the crane shown in Fig. 1, and Fig. 3 is a control used in the embodiment. A block diagram of the system, FIG. 4 is a diagram showing an example of suppression pattern data, FIG. 5 is a diagram showing characteristic changes of the winding/up/down drive control signal U and rotational speed S in the embodiment, and FIG. 6 is a diagram showing an example of the suppression pattern data. A flowchart showing the operation, Fig. 7 is an explanatory diagram of characteristic changes depending on engine speed, Fig. 8 is a diagram showing the relationship between engine speed and offset amount, and Fig. 9 is a graph showing compensation of the winding/up/down drive control signal. , FIG. 10 is an explanatory diagram of incomplete compensation, FIG. 11 is an explanatory diagram of the effect of the embodiment, and FIG. 12 is an explanatory diagram of dead zone. 1... Crane, 2... Crane body, 3...
...Boom, 4...Boom elevation rope, 6
... Lobe for hoisting and lifting, 9... Hanging load, 12... Boom elevation angle detector, 21a, 21b... Main hydraulic pump, 22a... Boom elevation directional control valve, 22b, 22c
... Directional control valve for winding up and down, 26a, 26b, 27a,
27b-...'\f magnetic proportional pressure reducing valve, 32a, 32b... remote control valve, 33a... boom operation lever, 33b... winding/up/down operation lever, 36.37... boom lever pilot pressure detection 54...Engine rotation speed detector, 55...Offset setting device, 56...Compensation device

Claims (3)

[Claims] (1) A hydraulic drive system that includes a plurality of hydraulic pumps that drive a predetermined hydraulic actuator and changes the operating speed of the hydraulic actuator by changing the number of hydraulic pumps used and the hydraulic output of the hydraulic pumps. A method for controlling a hydraulic drive system, characterized in that when changing the number of hydraulic pumps used, the value of a control signal that controls the hydraulic output of the hydraulic pump is changed by a predetermined offset amount. (2) The control signal is a control signal that is commonly used to control the output change of the hydraulic pump and the control to change the number of hydraulic pumps used, and the offset amount is a power source that provides rotational power to the hydraulic pump. Claim 1, which changes depending on the rotational speed of
A method for controlling a hydraulic drive system as described in Section 1. (3) The method of controlling a hydraulic drive system according to claim 1 or 2, wherein the hydraulic drive system is a system that drives up and down a rope-shaped body on which a suspended load is suspended in a crane.