KR101567446B1 - Horsepower limiting device and horsepower limiting method - Google Patents

Abstract

The horsepower limitation device (101) of the present invention comprises: a pressure detector (5) for detecting a discharge pressure of a hydraulic pump unit; and a pressure sensor A parallel feed forward compensator (9) for outputting a compensation value for compensating the discharge pressure detected by the detector, and a controller for controlling the discharge pressure after compensation by the compensation value output by the parallel feedforward compensator, (11) for calculating a limit value of a discharge flow rate of the hydraulic pump unit in accordance with a horsepower limit value, and a flow rate limit value calculation unit (11) for determining a flow rate limit value calculated by the flow rate limit value calculation unit and a discharge flow rate of the hydraulic pump unit And a flow rate restricting portion (12) for outputting the flow rate instruction to the hydraulic pump unit after the horsepower limitation in accordance with the flow rate instruction.

Description

HORSEPOWER LIMITING DEVICE AND HORSEPOWER LIMITING METHOD [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a horsepower limiter and a horsepower limiting method for limiting a discharge flow rate of a hydraulic pump unit in accordance with a discharge pressure of a hydraulic pump unit.

)로부터 아래의 식으로 구해진다.Generally, in a system for performing hydraulic drive, a hydraulic pump uses a motor or an engine as a power source to discharge operating oil by rotational motion, and the discharged oil is supplied to a hydraulic actuator through a control valve. The horsepower (W [kW]) of the pump depends on the discharge flow rate Q [L / min], the discharge pressure P [MPa]

) From the following equation.

Incidentally, depending on the operating environment of the hydraulic actuator, there are cases where the hydraulic actuator temporarily stops due to an excessive load. In such a case, the discharge pressure of the hydraulic pump increases and the output of the pump increases. As a result, the load on the power source of the pump also increases, causing a trip in the motor and an engine stop in the case of an engine.

Conventionally, in the hydraulic pump, when the discharge pressure of the pump is increased, the horsepower is reduced to reduce the discharge flow rate of the pump in order to prevent the motor and the engine from being overloaded. (Qm [L / min]) for limiting the flow rate of the pump to the predetermined horsepower limit value (Wm [kW]) is set to a lower limit .

The flow rate command value indicating the discharge flow rate of the pump is made smaller than the flow rate limit value (Qm [L / min]) by limiting the discharge flow rate of the pump (for example, refer to Patent Document 1).

Japanese Patent Application Laid-Open No. 7-208403

However, in the horsepower limitation of the conventional hydraulic pump, since there is a response delay until the discharge pressure of the pump changes after the flow rate indication value changes, the flow rate limit value changes more than necessary during that period, ).

The present invention has been made to solve such a problem, and aims to reduce hunting due to response delay of discharge pressure of a hydraulic pump unit to a flow rate indication in a hydraulic pump unit under horsepower limitation.

In order to solve the above problems, an horsepower limitation apparatus according to an embodiment of the present invention includes: a pressure detector for detecting a discharge pressure of a hydraulic pump unit; A parallel feed forward compensator for outputting a compensation value for compensating the discharge pressure detected by the pressure detector in accordance with the compensation value outputted by the parallel feed forward compensator, A flow rate limit value calculation unit for calculating a limit value of the discharge flow rate of the hydraulic pump unit according to a set horsepower limit value of the hydraulic pump unit; To output the flow rate instruction after the horsepower limitation to the hydraulic pump unit It is comprising a flow restriction.

According to the above configuration, the discharge pressure of the hydraulic pump unit detected by the pressure detector is compensated in accordance with the compensation value output by the parallel feedforward compensator, and based on the discharge pressure after the compensation and the horsepower limit value of the hydraulic pump unit The limit value of the discharge flow rate of the hydraulic pump unit is calculated and the flow rate instruction is outputted to the hydraulic pump unit after the horsepower limitation in accordance with the calculated flow rate limit value and the flow rate instruction indicating the discharge flow rate of the hydraulic pump unit, It is possible to compensate for the response delay of the discharge pressure of the hydraulic pump unit to the flow rate instruction in the unit. As a result, hunting due to response delay can be reduced.

The parallel feedforward compensator may consist of a constant gain and a bandpass filter. According to the above arrangement, the response delay of the discharge pressure of the hydraulic pump unit to the flow rate indication can be appropriately compensated.

According to another aspect of the present invention, there is provided a method of limiting horsepower comprising the steps of: detecting a discharge pressure of a hydraulic pump unit; determining a horsepower limitation A step of outputting a compensation value for compensating for the detected discharge pressure in accordance with a flow rate indication of the hydraulic pump unit according to a discharge pressure after the compensation by the output compensation value, And outputting the flow rate instruction after the horsepower limitation to the hydraulic pump unit in accordance with the calculated flow rate limit value and a flow rate instruction indicating the discharge flow rate of the hydraulic pump unit do.

The step of outputting the compensation value may be a step of outputting by a parallel feedforward compensator composed of a constant gain and a band-pass filter.

The present invention has the above-described constitution and has the effect of reducing the hunting due to the response delay of the discharge pressure of the hydraulic pump unit to the flow rate indication in the hydraulic pump unit under the horsepower limitation.

These and other objects, features and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments with reference to the accompanying drawings.

1 is a block diagram showing a schematic configuration example of a hydraulic drive system using an horsepower limiting device according to a first embodiment of the present invention.
Fig. 2 is a block diagram showing an example of the configuration of the horsepower limitation device of Fig. 1. Fig.
3 is a graph showing the response waveform of the discharge pressure after compensation in the horsepower limiting controller.
4 is a graph showing the characteristics of a hydraulic pump based on horsepower limitation according to the first comparative example.
5 is a graph showing the characteristics of the hydraulic pump according to the first embodiment of the present invention.
6 is a graph showing the simulation result based on the horsepower limitation according to the first comparative example.
FIG. 7 is a graph showing the simulation result based on the horsepower limitation according to the first embodiment.
8 is a block diagram showing an example of the configuration of a series filter by horsepower limitation according to the second comparative example.
9 is a block diagram showing a configuration example of a parallel filter by horsepower limitation according to the first embodiment.
10 is a bode diagram showing the frequency characteristics of the series filter by the horsepower limitation according to the second comparative example.
11 is a board diagram showing frequency characteristics of a parallel filter by horsepower limitation according to the first embodiment.
12 is a block diagram of horsepower limitation of the hydraulic pump according to the third comparative example.
13 is a block diagram of a horsepower limiting apparatus according to a second embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. In the following description, the same reference numerals are assigned to the same or corresponding elements throughout the drawings, and redundant explanations are omitted.

(Embodiment 1)

1 is a block diagram showing a schematic configuration of a hydraulic drive system using an horsepower limiting device according to a first embodiment of the present invention. The hydraulic drive system 100 includes a hydraulic pump 1, a motor 2 as a power source of the hydraulic pump 1, a hydraulic actuator 3, a control valve 4, a pressure sensor 5, an actuator 6, A horsepower limitation controller 7, and a regulator 8. [ Here, the pressure sensor 5 and the horsepower limiting controller 7 constitute the horsepower limiting device 101. [ The hydraulic pump 1, the motor 2, and the regulator 8 constitute a hydraulic pump unit 102. In the following description, a configuration is described in which the discharge flow rate of the hydraulic pump 1 is controlled by inputting an instruction signal including a horsepower limited flow instruction value to the regulator 8, but for example, So that the discharge flow rate of the hydraulic pump 1 can be controlled (see other embodiments).

The hydraulic pump 1 uses, for example, the motor 2 as a power source, and discharges the working oil by rotational motion. The discharge oil is supplied to the hydraulic actuator 3 via the control valve 4. [ As the hydraulic pump 1, known ones can be used. In the present embodiment, the hydraulic pump 1 is driven at a constant speed by the motor 2, for example, and adjusts the discharge flow rate of the hydraulic pump 1 (hereinafter referred to simply as the flow rate Which may be referred to as a variable displacement pump. The power source is not limited to the motor 2 but may be, for example, an internal combustion engine.

The hydraulic actuator 3 drives a load (not shown) by the discharged oil discharged from the hydraulic pump 1. As the hydraulic actuator 3, for example, a hydraulic cylinder is exemplified.

The control valve 4 controls the supply and discharge of the discharged oil to the hydraulic actuator 3 and controls the operation of the hydraulic actuator 3 accordingly. The control valve 4 operates according to a control signal output by a controller (not shown) according to an operation input of a user (an operation input instructing the operation of the actuator 3). In addition, when the control valve 4 discharges the working oil from the actuator 3, the discharged working oil is discharged as relief oil to the hydraulic pump 1 through the flow path not shown in the control valve 4, .

The pressure sensor 5 detects the discharge pressure of the hydraulic pump 1 (hereinafter sometimes referred to simply as pressure). The pressure sensor 5 detects the pressure of the discharged oil supplied through the oil passage 20 in the oil passage 20 for supplying the oil discharged from the hydraulic pump 1 to the hydraulic actuator 3, And outputs the detected discharge pressure to the horsepower limiter 7.

The manipulator 6 is operated by the user to instruct the hydraulic pump 1 to discharge the fluid. Here, the operation device 6 generates an instruction signal of the discharge flow rate of the hydraulic pump 1 in accordance with the operation amount of the operation device 6, and outputs the instruction signal to the horsepower limitation controller 7.

The horsepower limitation controller 7 controls the horsepower limiting controller 7 based on the discharge pressure of the hydraulic pump 1 detected by the pressure sensor 5 and the discharge flow rate of the hydraulic pump 1 input by the actuator 6 Generates an instruction signal including the flow instruction value, and outputs it to the regulator 8. Here, the flow rate command value is a command value for controlling the swash plate of the hydraulic pump 1.

The regulator 8 adjusts the inclination angle of the swash plate of the hydraulic pump 1 to change the discharge flow rate of the driving hydraulic pump 1 in accordance with the sagittal angle instruction value included in the instruction signal of the discharge flow rate.

Next, the configuration of the horsepower limiting controller 7 will be described in detail with reference to Fig. 2 is a block diagram showing a configuration example of the horsepower limitation device 101. As shown in Fig. As shown in Fig. 2, the horsepower limiting device 101 is constituted by a pressure sensor 5 and a horsepower limiting controller 7. As shown in Fig.

The horsepower limitation controller 7 includes a parallel feed forward compensator 9, an adder 10, a flow rate limiting value calculator 11 and a flow rate limiter 12 . The horsepower limitation controller 7 is constituted by, for example, an arithmetic unit such as a micro controller or a programmable logic controller (PLC). The PFC 9, the adder 10, the flow rate limiting value calculator 11 and the flow rate limiter 12 are realized by the arithmetic unit executing the built-in operation program.

The PFC 9 calculates the actual value of the discharge pressure detected by the pressure sensor 5 in accordance with the flow rate command value Qc [L / min] after the horsepower limitation, which indicates the discharge flow rate with the horsepower limited to the regulator 8 (Pf [MPa]) for compensating the discharge pressure (output pressure).

The adder 10 adds the compensation value Pf [MPa] output by the PFC 9 and the actual value P [MPa] of the discharge pressure detected and output by the pressure sensor 5, And outputs the discharge pressure value P '[MPa].

The flow rate limit value calculation section 11 calculates the flow rate limit value Wm [kW] based on the discharge pressure value P '[MPa] after the compensation output by the adder 10 and the predetermined horsepower limit value Wm [kW] The limit value Qm [L / min] of the discharge flow rate of the pump 1 is calculated. The flow rate limit value Qm [L / min] is calculated by the following equation (1).

는 펌프의 효율이고, 마력 제한 값(Wm[kW])은, 예를 들어 미리 마력 제한 컨트롤러(7) 내부의 도시되지 않은 저장부에 저장되어 있다.here,

Is the efficiency of the pump, and the horsepower limit value Wm [kW] is stored, for example, in a storage unit (not shown) inside the horsepower limitation controller 7 in advance.

The flow rate limiting section 12 is configured to limit the flow rate limit value Qm [L / min] calculated by the flow rate limit value calculating section 11 and the flow rate instruction value Qd [L / min] indicating the discharge flow rate of the hydraulic pump 1, min] to the flow rate pump 1 after the horsepower limit is reached. More specifically, the flow rate limiting section 12 compares the flow rate command value Qd with the flow rate limit value Qm. When the flow rate command value Qd is smaller than the flow rate limit value Qm, The flow rate instruction value Qc outputted to the hydraulic pump is set to the flow rate instruction value Qd and the flow rate instruction value Qc outputted to the hydraulic pump when the flow rate instruction value Qd is larger than the flow rate restriction value Qm, (Qm). Here, the flow instruction value Qd [L / min] is indicated by the manipulator 6 in Fig. 1 and is temporarily stored in a storage unit (not shown) in the horsepower limitation controller 7. [ The storage unit in which the horsepower limit value Wm and the flow rate indication value Qd are stored includes an internal memory such as an arithmetic unit or an external memory such as a hard disc drive, Lt; / RTI > may be a storage device that can be accessed by a connected computer via a network.

Next, the configuration of the PFC 9 will be described. The PFC 9 receives the flow rate indication Qc after the horsepower limitation and outputs a compensation value Pf for compensating the discharge pressure of the hydraulic pump. In the present embodiment, for example, , A second-order high-pass filter, and a first-order low-pass filter. The transfer function Gf (s) of the PFC 9 is expressed by the following equation (2).

[Number 1]

[Number 2]

_H1,

_H2는, 2차 하이 패스 필터의 컷오프 주파수이고,

_L은 1차 로우 패스 필터의 컷오프 주파수이고, Kf는 상수 게인이다.here,

_H1 ,

_H2 is the cutoff frequency of the second-order high-pass filter,

_L is the cut-off frequency of the first-order low-pass filter, and Kf is a constant gain.

3 is a graph showing the response waveform of the discharge pressure after the compensation by the PFC 9. The vertical axis represents pressure, and the horizontal axis represents time. The solid line shows the pressure (P ') after the PFC compensation, the dotted line shows the pressure actual value (P), and the one-dot chain line shows the PFC compensation value (Pf). Here, the pressure response waveform is shown when the flow rate indication changes stepwise under certain load conditions.

In the pressure actual value P, the start of the response is delayed with respect to the change in the flow rate indication value (period td in the drawing). On the other hand, the PFC compensation value Pf generates a pseudo-output in the period td until the pressure actual value P changes. Thereby, the pressure P 'after PFC compensation appears to have no response delay.

As described above, since the pseudo-output can be generated during the timing from when the flow rate indication value changes by the PFC 9 to when the pressure performance value changes, the response delay of the pressure performance value can be compensated.

Next, specific horsepower limitation processing in the horsepower limiting controller 7 will be described. First, the continuous time transfer function Gf (s) of the PFC 9 shown in the equation (2) is converted into a discrete time transfer function Gf (z) such as the following equation (3) )).

[Number 3]

At this time, the output Pf (k) of the PFC 9 at the time k is calculated as follows.

[Number 4]

는 펌프의 효율을 고려한 것으로, 압력이나 유량에 따라 가변하게 함으로써 보다 정확하게 마력 제한을 하는 것이 가능하게 된다.The flow limit value calculation unit 11 then calculates the flow limit value Qm (k) at time k based on the pressure actual value P (k) at time k, PFC Is calculated using the output Pf (k) of the multiplier 9 as follows. here,

The efficiency of the pump is taken into consideration, and it is possible to more accurately limit the horsepower by varying the pressure or the flow rate.

[Number 5]

Assuming that the flow rate restriction value Qm (k) is smaller than the flow rate command value Qd (k) at time k and the flow rate is limited, Qc (k) = Qm (k). Therefore, the flow rate limit value Qm (k) at the time k is calculated by the following equation (6).

[Number 6]

Then, when the flow rate restriction value Qm (k) is actually smaller than the flow rate instruction value Qd (k) by the flow rate restriction section 12, Qc (k) = Qm do.

Thus, by calculating the flow rate restriction value using the compensated pressure, it is possible to suppress the hunting in the horsepower limitation because it is not necessary to change the flow rate indication value more than necessary.

(Comparative Example 1)

Next, the effect of horsepower limitation according to this embodiment using the PFC 9 will be described in comparison with a comparative example. First, the horsepower limitation employed in the prior art will be described as a first comparative example.

In the horsepower limitation according to the first comparative example, the actual value (output horsepower) W of the horsepower is calculated from the flow rate of the hydraulic pump and the discharge pressure of the hydraulic pump according to the equation (9). The flow rate limiting value Qm [L / min] for limiting the flow rate of the hydraulic pump to the preset horsepower limit value Wm [kW] is calculated by the following equation.

When the actual horsepower value W exceeds the horsepower limit value Wm, the flow rate command value indicating the discharge flow rate of the hydraulic pump is limited to the flow rate limit value Qm [L / min] Thereby limiting the horsepower of the hydraulic pump.

4 is a graph showing the characteristics of a hydraulic pump based on horsepower limitation according to the first comparative example. The vertical axis represents the discharge flow rate of the hydraulic pump, and the horizontal axis represents the discharge pressure of the hydraulic pump. The curve Wm of this graph shows the horsepower limiting curve connecting the points of the flow rate and the pressure which become the horsepower Wm. The locus P indicated by the solid line is obtained by plotting the position of the flow rate and the pressure at a certain time in a time series at a constant time (points (a) to (i) in the drawing). In the horsepower limitation according to the first comparative example, when the horsepower exceeds Wm at the time indicated by the point (a) due to an increase in pressure, the flow rate indicated by the dotted line indicates the horsepower Wm). Similarly, if the pressure also increases at the next time (b), the flow rate indication value is limited to the flow rate at which the horsepower Wm at the pressure of the point b. Here, if the pressure changes with respect to the change of the flow rate indication value without a response delay, the locus P by this operation will converge on the horsepower limiting curve Wm immediately. However, since there is actually a response delay, if the flow rate which becomes the horsepower Wm according to the current pressure is indicated, the flow rate is reduced too much from point (b) to point (c) If the horsepower exceeds the Wm or the horsepower exceeds the Wm at the point (f) by excessively increasing the flow rate from the point (d) to the point (e), the fluctuation is repeated as exceeding the horsepower limitation curve. That is, hunting occurs.

On the contrary, FIG. 5 is a graph showing the characteristics of the hydraulic pump due to the horsepower limitation according to the first embodiment. Here, the vertical axis represents the discharge flow rate of the hydraulic pump, and the horizontal axis represents the discharge pressure of the hydraulic pump. The curve Wm of this graph shows the horsepower limiting curve connecting the points of the flow rate and the pressure which become the horsepower Wm. The locus P indicated by the dotted line is obtained by plotting the position of the flow rate and the pressure at a certain time in a time series at a predetermined time (points (a) to (d) in the drawing). The locus P 'indicated by the solid line is obtained by plotting the flow rate at a certain time and the position of the pressure after the compensation by the PFC in a time series at predetermined time intervals (points a' to d '). In the horsepower limitation according to the first embodiment, when the horsepower exceeds Wm at the time indicated by the point (a) due to an increase in pressure, the flow rate indication value is represented by a point (a ')) Is limited to the flow rate which becomes the horsepower (Wm). Then, if the pressure also increases at the next time (b), the flow rate indication value is limited to the flow rate which becomes the horsepower Wm at the pressure after the compensation of the point b ', as indicated by the dotted line. Here, since the response delay to the flow rate indicated by the PFC is compensated by the PFC and the delay is very small, the locus P 'by this operation is immediately converged on the horsepower limiting curve Wm. Further, when the pressure after the compensation is converged, the actual pressure locus P also converges on the horsepower limiting curve Wm. That is, hunting is reduced.

Next, simulation results of the first embodiment and the first comparative example are compared with each other. The simulation conditions are as follows: the flow rate command value Qd is 800 L / min; the horsepower limit value Wm is 200 kW; the hydraulic cylinder volume is 10 L; the relief flow rate is 800 L / min ] To 250 [L / min] for 30 seconds.

6 is a graph showing the simulation result based on the horsepower limitation according to the first comparative example.

6 (a) shows the time response waveform of the horsepower actual value, and Fig. 6 (b) shows the characteristics of the hydraulic pump due to horsepower limitation. From the simulation results, in the first comparative example, considerable hunting occurs in the vicinity of 20 seconds after the elapse of 15 seconds from the start.

On the other hand, FIG. 7 is a graph showing a simulation result by horsepower limitation according to the first embodiment. 7 (a) shows the time response waveform of the horsepower performance value, and Fig. 7 (b) shows the characteristics of the hydraulic pump due to horsepower limitation. From the simulation results, hunting is reduced in this embodiment compared to the first comparative example.

(Comparative Example 2)

Next, the effect of horsepower limitation according to this embodiment using the PFC 9 will be described in comparison with the second comparative example. The second comparative example is configured to include a compensating circuit in the first comparative example.

8 is a block diagram of a compensation circuit in the second comparative example. 8, G denotes a control object (hydraulic pump, etc.), u denotes an operation amount (flow instruction value), y denotes output (pressure after compensation (pressure performance)) and F denotes a serial filter . The second comparative example includes a filter in series with respect to the control target (hydraulic pump) in order to compensate for the response delay.

On the other hand, Fig. 9 is a block diagram of the compensation circuit in the first embodiment. G is the control object (hydraulic pump, etc.), u is the manipulated variable (flow indication value), y is the output (pressure after compensation) and H is the parallel filter (PFC). As shown in Fig. 9A, in this embodiment, a parallel filter is provided for the hydraulic pump in order to compensate for the response delay. Here, if the block diagram of FIG. 9A is equivalently converted, it is expressed as a serial filter of FIG. 9B. Therefore, when the series filter of the second comparative example is set to F = 1 + G ^-1 H, the same effect as that of the parallel filter (PFC) of the present embodiment can be obtained. However, since G ^-1 generally includes higher order differential terms, it is practically impossible to use such a filter. Therefore, the second comparative example using a serial filter as a compensation element and the present embodiment employing a parallel filter as a compensation element have an essential difference in configuration.

The effects of the serial filter of the second comparative example and the parallel filter of this embodiment will be described. 10 is a board diagram showing the frequency characteristics of the series filter according to the second comparative example. Fig. 10 (a) shows a gain diagram, and Fig. 10 (b) shows a phase diagram. The solid line represents the characteristic after compensation, H (s) represents the characteristic of the series filter, and G (s) represents the characteristic of the controlled object. The delay of the control object G (s) is large in the high frequency range, and the phase delay can hardly be improved.

On the other hand, FIG. 11 is a board diagram showing frequency characteristics of the parallel filter according to the first embodiment. Fig. 11 (a) shows a gain diagram, and Fig. 11 (b) shows a phase diagram. The solid line represents the characteristic after compensation, H (s) represents the characteristic of the series filter, and G (s) represents the characteristic of the controlled object. 11, the characteristic after compensation is almost equal to the characteristic G (s) of the controlled object while the characteristic after compensation is substantially equal to the characteristic H (s) of the parallel filter in the high frequency range Phase delay can be eliminated.

However, in the horsepower limitation, the flow rate limit value Qm is obtained by dividing the horsepower limit value Wm by the pressure P as in the expression (7), but this equation 7 is linearized around the operating point (pressure P ₀ ) , It can be expressed as the following expression (8).

[Numeral 7]

)Wm/P₀ ² 는 피드백 게인에 해당하며, 동작점의 압력(P₀)이 낮은 경우는 매우 큰 게인이 된다는 것을 알 수 있다. 피드백 제어의 이론에서는, 위상 지연 180도 이상의 응답 지연이 되는 주파수 영역이 있으면, 일정 이상 크기의 게인으로 피드백을 했을 때 불안정해진다.Assuming that the equation (8) is feedback control of the pressure,

) Wm / P ₀ ² Corresponds to the feedback gain, and it can be seen that when the operating point pressure (P ₀ ) is low, it becomes a very large gain. In the feedback control theory, if there is a frequency range where the response delay is 180 degrees or more, the feedback becomes unstable when feedback is performed with a gain of a predetermined magnitude or more.

In the compensation by the series filter of the second comparative example, hunting may occur because it is inevitable that the phase delay becomes 180 degrees or more in the high frequency range. On the other hand, in the compensation by the PFC of the present embodiment, since the phase delay can be reduced over the entire frequency range, hunting can be made difficult.

(Comparative Example 3)

Next, the effect of the horsepower limitation according to the present embodiment using the PFC 9 will be described in comparison with the third comparative example. The third comparative example describes the configuration of the horsepower limit applying the PFC to the feedback control of the horsepower.

Generally, the PFC is applied to a control such that the control amount (output) is fed back (negative feedback) by inverting its phase. The configuration of the horsepower limitation when this PFC is simply applied becomes like the block diagram of Fig.

However, since the horsepower of the hydraulic pump generally becomes the product of the discharge flow rate and the discharge pressure, the control target (flow rate → horsepower) of the block diagram of FIG. 12 becomes nonlinear, I can not.

Therefore, in the present embodiment, the hydraulic pump has the same structure as the block of FIG. 2 by using the one that can change the pressure by operating the flow rate and measure the changed pressure.

As a result, the control object (flow rate → pressure) becomes a characteristic that can basically linearly approximate, and the concept of PFC compensation can be applied. Further, a compensation element such as a PID controller is also unnecessary, and the horsepower limitation can be realized with a very simple configuration.

The configuration of the horsepower limitation according to the present embodiment is such that, as shown in the block diagram of Fig. 2, the feedback actual pressure value and the indication value (horsepower) are different in dimension and the phase of the pressure actual value to be fed back is not reversed Do not. And it is designed to use PFC by feeding back this pressure performance value in the form of division. In this respect, the control of the horsepower limitation of this embodiment is essentially unique to the general feedback control, and is also unique to the hydraulic pump, which can be expressed as "horsepower = flow rate x pressure ".

(Second Embodiment)

Next, a second embodiment of the present invention will be described with reference to Fig. The description of the configuration common to that of the first embodiment will be omitted, and only the other configurations will be described.

13 is a block diagram of a horsepower limiting apparatus according to a second embodiment of the present invention. The present embodiment is different from the first embodiment in that the horsepower limiting controller 7 further includes an adder-subtractor 13. The adder-subtractor 13 subtracts the flow rate instruction value Qc from the flow rate instruction value Qc after horsepower limitation, (Qd) is subtracted from the input of the PFC (9).

Since the PFC 9 basically corrects the response in the high frequency range, when the variation of the flow instruction value Qd is not in such a high frequency range (in general, the flow instruction value Qd is constant), the PFC 9 The effect of the PFC 9 is not impaired even if the component of the flow instruction value Qd is subtracted from the input of the flow instruction value Qd. With such a configuration, for example, when the flow rate indication value is elevated from zero to the specified value in a stepwise manner in a state where there is no load, for example, when the hydraulic pump 1 is started, the actual pressure does not rise but the compensation value of the PFC 9 It is possible to prevent the increased horsepower limitation from being activated.

(Other Embodiments)

In each of the above embodiments, the PFC 9 is composed of a band-pass filter having a constant gain, a second-order high-pass filter, and a first-order low-pass filter, but is not limited thereto. If the response delay of the discharge pressure of the hydraulic pump to the flow instruction is compensated for, the PFC 9 may be constituted by, for example, a constant gain, other band-pass filters, have.

In each of the above embodiments, the number of revolutions of the motor 2 in the hydraulic pump 1 is made constant, and the instruction to the hydraulic pump 1 is converted into the instruction of the angle of inclination of the pump However, the present invention is not limited to this, but the angle of inclination of the hydraulic pump can be made constant, and the instruction to the hydraulic pump can be made by converting the flow rate indication into an indication of the number of revolutions of the motor.

From the above description, many modifications and other embodiments of the invention will be apparent to those skilled in the art. Accordingly, the above description is to be construed as illustrative only, and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The structure and / or function thereof can be substantially changed without departing from the spirit of the present invention.

INDUSTRIAL APPLICABILITY The present invention can be used in the field of a hydraulic pump which limits the discharge flow rate of the pump in accordance with the discharge pressure of the hydraulic pump.

1: Hydraulic pump
2: Motor
3: Hydraulic actuator
4: Control valve
5: Pressure sensor
6: Actuator
7,70: Power limit controller
8: Regulator
9: PFC (Parallel Feed Forward Compensator)
10: adder
11: Flow limit value calculation section
12:
13: adder and subtracter
20: Euro
100: Hydraulic drive system
101: Power limiter
102: Hydraulic pump unit

Claims (6)

A pressure detector for detecting a discharge pressure of the hydraulic pump unit,
A parallel feedforward compensator for outputting a compensation value for compensating a discharge pressure detected by the pressure detector in accordance with a flow rate instruction after a horsepower limitation indicating a discharge flow rate with a limited horsepower to the hydraulic pump unit;
A flow rate limiting value calculation unit for calculating a limiting value of the discharge flow rate of the hydraulic pump unit according to a discharge pressure after compensation by the compensation value output by the parallel feed forward compensator and a predetermined horsepower limit value of the hydraulic pump unit,
And a flow rate restricting portion for outputting the flow rate restriction after the horsepower limitation to the hydraulic pump unit according to a flow rate limit value calculated by the flow rate limit value calculation portion and a flow rate instruction for indicating a discharge flow rate of the hydraulic pump unit Power limiter.
The apparatus of claim 1, wherein the parallel feedforward compensator is configured by either or both of a constant gain and a bandpass filter.
3. The horsepower limiter according to claim 1 or 2, wherein the input of the parallel feedforward compensator is configured by subtracting the flow rate indication value from the controller in the flow rate instruction to the hydraulic pump unit.
Detecting a discharge pressure of the hydraulic pump unit,
Outputting a compensation value for compensating for the detected discharge pressure in accordance with a flow rate instruction after limiting the horsepower that indicates a discharge flow rate limited by the hydraulic pump unit;
Calculating a limit value of a discharge flow rate of the hydraulic pump unit according to a discharge pressure after compensation by the output compensation value and a predetermined horsepower limit value of the hydraulic pump unit,
And outputting the flow rate instruction after the horsepower limitation to the hydraulic pump unit according to a flow rate instruction indicating the calculated flow rate limit value and a discharge flow rate of the hydraulic pump unit.
5. The method of claim 4, wherein outputting the compensation value is output by a parallel feedforward compensator configured by either or both of a constant gain and a bandpass filter.
6. The method of claim 5, wherein the input of the parallel feed forward compensator subtracts a flow rate indication from the actuator in a flow rate indication to the hydraulic pump unit.

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