JP5948165B2 - Horsepower limiting device and horsepower limiting method - Google Patents

Description

  The present invention relates to a horsepower limiting method and a horsepower limiting device for limiting the discharge flow rate of a hydraulic pump unit based on the discharge pressure of the hydraulic pump unit.

In general, in a system for performing hydraulic drive, a hydraulic pump discharges hydraulic oil by rotational movement using a motor or an engine as a power source, and the discharged oil is supplied to a hydraulic actuator via a control valve. The pump horsepower W [kW] is obtained from the discharge flow rate Q [L / min], the discharge pressure P [MPa], and the efficiency η by the following equation.
W = P · Q / (60 · η) (9)
By the way, depending on the operating environment of the hydraulic actuator, the hydraulic actuator may temporarily stop due to an excessive load. In such a case, the discharge pressure of the hydraulic pump increases and the pump output increases. As a result, the load applied to the power source of the pump also increases, causing the motor to trip and the engine to stop the engine.

Conventionally, in a hydraulic pump, when the discharge pressure of the pump becomes high, the horsepower restriction is performed to reduce the discharge flow rate of the pump in order to avoid overloading the motor and the engine. In the horsepower restriction that restricts the discharge flow rate of the pump based on the discharge pressure of the pump as described above, the flow rate restriction value Q _m [L / L] that restricts the pump flow rate with respect to the preset horsepower restriction value Wm [kW]. min] is calculated by the following formula.
Q _m = (60 · η) W _m / P (10)
The flow rate command value for commanding the pump discharge flow rate is made smaller than the flow rate limit value Q _m [L / min] to limit the pump discharge flow rate (see, for example, Patent Document 1).

JP 7-208403 A

  However, in the conventional horsepower limit of a hydraulic pump, there is a response delay between the change of the flow rate command value and the change of the pump discharge pressure, so the flow rate limit value changes more than necessary during that time, often hunting. There was a problem of waking up.

  The present invention has been made to solve such a problem, and aims to reduce hunting caused by a delay in response of the discharge pressure of the hydraulic pump unit to the flow rate command value in the hydraulic pump unit under a horsepower limit. To do.

  In order to solve the above problems, a horsepower limiting device according to an aspect of the present invention includes a pressure detector that detects a discharge pressure of a hydraulic pump unit, and commands a discharge flow rate that is horsepower limited to the hydraulic pump unit. A parallel feedforward compensator that outputs a compensation value for compensating the discharge pressure detected by the pressure detector based on a post-horsepower limiting flow command to be output, and a compensation value output by the parallel feedforward compensator Based on the compensated discharge pressure and the preset horsepower limit value of the hydraulic pump unit, the flow rate limit value calculation unit that calculates the discharge flow rate limit value of the hydraulic pump unit and the flow rate limit value calculation unit calculate The flow rate command after the horsepower limit is set to the hydraulic pressure based on the flow rate limit value and the flow rate command commanding the discharge flow rate of the hydraulic pump unit. Comprising a flow restriction to be output to the amplifier unit.

  According to the above configuration, the discharge pressure of the hydraulic pump unit detected by the pressure detector is compensated by the compensation value output by the parallel feedforward compensator, and the discharge pressure after the compensation and the preset hydraulic pump unit Based on the horsepower limit value, a limit value for the discharge flow rate of the hydraulic pump unit is calculated, and based on the calculated flow rate limit value and a flow rate command for commanding the discharge flow rate of the hydraulic pump unit, a flow rate command after the horsepower limit is set. Is output to the hydraulic pump unit, the response delay of the discharge pressure of the hydraulic pump unit to the flow rate command can be compensated for in the hydraulic pump unit under the horsepower limit. As a result, hunting caused by response delay can be reduced.

  The parallel feedforward compensator may be composed of a constant gain and a band pass filter. According to the above configuration, it is possible to suitably compensate for a response delay of the discharge pressure of the hydraulic pump unit with respect to the flow rate command.

  In order to solve the above-mentioned problem, a horsepower limiting method according to another aspect of the present invention is to detect a discharge pressure of a hydraulic pump unit and to discharge a horsepower limited to the hydraulic pump unit. Output a compensation value for compensating the detected discharge pressure based on the post-horsepower limited flow command for commanding, the discharge pressure after compensation by the output compensation value, and the preset hydraulic pressure Based on the horsepower limit value of the pump unit, calculating the limit value of the discharge flow rate of the hydraulic pump unit, and based on the flow rate command commanding the calculated flow rate limit value and the discharge flow rate of the hydraulic pump unit, Outputting the post-horsepower limited flow rate command to the hydraulic pump unit.

  The output of the compensation value may be output by a parallel feedforward compensator configured by a constant gain and a band pass filter.

  The present invention has the configuration described above, and has the effect of reducing hunting caused by a response delay of the discharge pressure of the hydraulic pump unit with respect to the flow rate command value in the hydraulic pump unit under the horsepower limit.

It is a block diagram which shows the schematic structural example of the hydraulic drive system using the horsepower limiting device which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structural example of the horsepower limitation apparatus of FIG. It is the graph which showed the response waveform of the discharge pressure after compensation in a horsepower limit controller. It is the graph which showed the characteristic of the hydraulic pump by the horsepower restriction concerning the 1st comparative example. 3 is a graph showing characteristics of a hydraulic pump by horsepower limitation according to Embodiment 1. FIG. It is the graph which showed the simulation result by the horsepower restriction concerning the 1st comparative example. 4 is a graph showing a simulation result by horsepower limitation according to the first embodiment. It is a block diagram which shows the structural example of the series filter by the horsepower restriction | limiting which concerns on a 2nd comparative example. 3 is a block diagram illustrating a configuration example of a parallel filter based on horsepower limitation according to Embodiment 1. FIG. It is the Bode diagram which showed the frequency characteristic of the series filter by the horsepower restriction | limiting which concerns on a 2nd comparative example. FIG. 3 is a Bode diagram showing frequency characteristics of a parallel filter based on horsepower limitation according to the first embodiment. It is a block diagram of horsepower restriction of a hydraulic pump concerning the 3rd comparative example. It is a block diagram of the horsepower limiting device concerning Embodiment 2 of the present invention.

  Embodiments of the present invention will be described with reference to the drawings. Below, the same code | symbol is attached | subjected to the element which is the same or it corresponds through all the drawings, and the overlapping description is abbreviate | omitted.

(Embodiment 1)
FIG. 1 is a block diagram showing a schematic configuration of a hydraulic drive system using a horsepower limiting device according to Embodiment 1 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 operating device 6, a horsepower limit controller 7, and a regulator 8. Here, the pressure sensor 5 and the horsepower limiting controller 7 constitute a horsepower limiting device 101. In addition, the hydraulic pump 1, the motor 2, and the regulator 8 constitute a hydraulic pump unit 102. In the following, a configuration in which the discharge flow rate of the hydraulic pump 1 is controlled by inputting a command signal including a flow rate command value limited in horsepower to the regulator 8 is exemplified. May be configured to control the discharge flow rate of the hydraulic pump 1 (see other embodiments).

  For example, the hydraulic pump 1 discharges hydraulic oil by rotational movement using the motor 2 as a power source. The discharged oil is supplied to the hydraulic actuator 3 via the control valve 4. A known pump can be used as the hydraulic pump 1. In the present embodiment, the hydraulic pump 1 is driven at a constant rotation by, for example, the motor 2 and can change the discharge flow rate of the hydraulic pump 1 (hereinafter sometimes simply referred to as a flow rate) by adjusting the swash plate tilt angle. It is a pump. The power source is not limited to the motor 2 and 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. An example of the hydraulic actuator 3 is a hydraulic cylinder.

  The control valve 4 controls the supply and discharge of the discharged oil to and from the hydraulic actuator 3, thereby controlling the operation of the hydraulic actuator 3. The control valve 4 operates in accordance with a control signal output by a controller (not shown) according to a user operation input (operation input for commanding the operation of the actuator 3). When the control valve 4 discharges the hydraulic oil from the actuator 3, the discharged hydraulic oil returns to the hydraulic pump 1 from the control valve 4 through an oil passage (not shown) as relief oil.

  The pressure sensor 5 detects the discharge pressure of the hydraulic pump 1 (hereinafter sometimes simply referred to as pressure). Here, the pressure sensor 5 is installed in the oil passage 20 that supplies the discharge oil from the hydraulic pump 1 to the hydraulic actuator 3, detects the pressure of the discharge oil supplied through the oil passage 20, and the detected discharge pressure. Is output to the horsepower limit controller 7.

  The operation device 6 is operated by the user to instruct the hydraulic pump 1 to discharge the flow rate. Here, the operation device 6 generates a command signal for the discharge flow rate of the hydraulic pump 1 in accordance with the operation amount of the operation device 6, and outputs the command signal to the horsepower limit controller 7.

  The horsepower limit controller 7 includes a flow rate command value limited in horsepower based on the discharge pressure of the hydraulic pump 1 detected by the pressure sensor 5 and the discharge flow rate command signal of the hydraulic pump 1 input by the operating device 6. A command signal is generated and output to the regulator 8. Here, the flow rate command value is a tilt angle command value for controlling the swash plate of the hydraulic pump 1.

  The regulator 8 adjusts the tilt angle of the swash plate of the hydraulic pump 1 in accordance with the tilt angle command value included in the discharge flow rate command signal, and changes the discharge flow rate of the hydraulic pump 1 being driven.

  Next, the configuration of the horsepower limiting controller 7 will be specifically described with reference to FIG.

  The horsepower limit controller 7 includes a parallel feed forward compensator (hereinafter referred to as PFC) 9, an adder 10, a flow rate limit value calculation unit 11, and a flow rate limiter 12. The horsepower limit controller 7 is composed of a computing unit such as a microcontroller or PLC (Programmable Logic Controller), for example. The PFC 9, the adder 10, the flow rate limit value calculation unit 11, and the flow rate limit unit 12 are realized by the calculation unit executing the built-in operation program.

  The PFC 9 is based on the flow rate command value Qc [L / min] after the horsepower limit commanding the regulator 8 for the discharge flow rate limited to the horsepower, and the actual value (output) of the discharge pressure detected by the pressure sensor 5 A compensation value Pf [MPa] for compensating the discharge pressure) is output.

  The adder 10 adds the compensation value Pf [MPa] outputted by the PFC 9 and the actual value P [MPa] of the discharge pressure detected and outputted by the pressure sensor 5, and the compensated discharge pressure value P ′ [ MPa] is output.

  Based on the compensated discharge pressure value P ′ [MPa] output from the adder 10 and the preset horsepower limit value Wm [kW] of the hydraulic pump 1, the flow rate limit value calculation unit 11 The discharge flow rate limit value Qm [L / min] is calculated. The flow rate limit value Qm [L / min] is calculated based on the following equation (1).

Qm = (60η) · Wm / P ′ (1)
Here, η is the efficiency of the pump, and the horsepower limit value Wm [kW] is stored in a storage unit (not shown) in the horsepower limit controller 7 in advance, for example.

  The flow restriction unit 12 is based on the flow restriction value Qm [L / min] calculated by the flow restriction value calculator 11 and the flow command value Qd [L / min] that instructs the discharge flow rate of the hydraulic pump 1. The subsequent flow rate command value Qc [L / min] is output to the hydraulic pump 1. Specifically, the flow restriction unit 12 compares the flow command value Qd with the flow restriction value Qm, and when the flow command value Qd is smaller than the flow restriction value Qm, the flow command value Qc output to the hydraulic pump 1 is flowed. When the command value Qd is set and the flow rate command value Qd is larger than the flow rate limit value Qm, the flow rate command value Qc output to the hydraulic pump is set as the flow rate limit value Qm. Here, the flow rate command value Qd [L / min] is commanded from the operating device 6 in FIG. 1 and temporarily stored in a storage unit (not shown) inside the horsepower limiting controller 7. The storage unit for storing the horsepower limit value Wm and the flow rate command value Qd is a memory inside the arithmetic unit, an external memory such as a hard disk drive, or any other storage device accessible by a computer connected via a network. It may be.

  Next, the configuration of the PFC 9 will be described. The PFC 9 receives the flow rate command value Qc after the horsepower limit and outputs a compensation value Pf for compensating the discharge pressure of the hydraulic pump. In this embodiment, for example, a constant gain and a secondary A band-pass filter having a 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).

Here, ω _H1 and ω _H2 are cutoff frequencies of the secondary high-pass filter, ω _L is the cutoff frequency of the primary low-pass filter, and Kf is a constant gain.

  FIG. 3 is a graph showing a response waveform of the discharge pressure after compensation by the PFC 9. The vertical axis represents pressure, and the horizontal axis represents time. The solid line indicates the pressure P ′ after PFC compensation, the broken line indicates the actual pressure value P, and the alternate long and short dash line indicates the PFC compensation value Pf. Here, the response waveform of the pressure when the flow rate command value changes stepwise under a certain load condition is shown.

  The rise in response of the actual pressure value P is delayed with respect to the change in the flow rate command value (period td in the figure). On the other hand, the PFC compensation value Pf generates a pseudo output during a period td until the actual pressure value P changes. As a result, the pressure P ′ after PFC compensation does not appear to have a response delay.

  In this way, the PFC 9 can generate a pseudo output during the time lag from when the flow rate command value changes until the actual pressure value changes, so that the response delay of the actual pressure value can be compensated. .

  Next, a specific horsepower restriction process in the horsepower restriction controller 7 will be described. First, the continuous-time transfer function Gf (s) of the PFC 9 shown in Expression (2) is converted into a discrete-time transfer function Gf (z) like the following Expression (3) using a technique such as bilinear conversion. .

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

  Next, the flow rate limit value calculation unit 11 calculates the flow rate limit value Qm (k) at time k using the actual pressure value P (k) at time k and the output Pf (k) of PFC 9 as follows. The Here, η takes into account the efficiency of the pump, and it is possible to limit the horsepower more accurately by making it variable according to the pressure and flow rate.

Here, assuming that the flow rate limit 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 time k is calculated by the following equation (6).

  Next, if the flow restriction value Qm (k) is actually smaller than the flow instruction value Qd (k), the flow restriction is performed by setting Qc (k) = Qm (k).

  Thus, by calculating the flow rate limit value using the compensated pressure, the flow rate command value is not changed more than necessary, so that hunting in the horsepower limit can be suppressed.

(First comparative example)
Next, the effect of the horsepower limitation according to the present 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 horsepower is calculated from the flow rate of the hydraulic pump and the discharge pressure of the hydraulic pump based on the equation (9). In addition, a flow rate limit value Qm [L / min] for limiting the flow rate of the hydraulic pump is calculated from the following equation with respect to a preset horsepower limit value Wm [kW].
Qm = (60 · η) Wm / P (7)
When the actual horsepower value W exceeds the horsepower limit value Wm, the flow rate command value for commanding the discharge flow rate of the hydraulic pump is limited to the flow rate limit value Qm [L / min] to limit the discharge flow rate of the hydraulic pump. , Thereby limiting the horsepower of the hydraulic pump.

  FIG. 4 is a graph showing characteristics of the hydraulic pump due to the 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. A curve Wm in the graph indicates a horsepower limit curve connecting the points of flow rate and pressure to be horsepower Wm. A trajectory P indicated by a solid line is a plot of the flow rate and pressure position at a certain time in a time series at regular intervals (point a to point i in the figure). In the horsepower restriction according to the first comparative example, when the pressure increases and the horsepower exceeds Wm at the time indicated by the point a, the flow rate command value becomes a flow rate at which the horsepower Wm is obtained at the pressure at the point a as indicated by the dotted line. Limited. Similarly, at the next time b, if the pressure increases, the flow rate command value is limited to a flow rate at which the horsepower Wm is obtained at the pressure at the point b. Here, if the pressure changes without delay in response to the change in the flow rate command value, the locus P by this operation should immediately converge on the horsepower limit curve Wm. However, since there is actually a response delay, if a flow rate that gives a horsepower Wm is commanded based on the current pressure, the flow rate is excessively lowered from point b to point c as shown in FIG. 4, and the horsepower falls below Wm at point d. Or, conversely, when the flow rate is increased excessively from point d to point e and the horsepower exceeds Wm at point f, the variation is repeated across the horsepower limit curve. That is, hunting occurs.

  On the other hand, 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. A curve Wm in the graph indicates a horsepower limit curve connecting the points of flow rate and pressure to be horsepower Wm. A trajectory P indicated by a broken line is a plot of the flow rate and pressure position at a certain time in a time series at regular intervals (points a to d in the figure). A trajectory P ′ indicated by a solid line is a plot of the flow rate at a certain time and the position of the pressure after compensation by the PFC at a certain time interval (points a ′ to d ′ in the figure). In the horsepower limitation according to the first embodiment, when the pressure increases and the horsepower exceeds Wm at the time indicated by point a, the flow rate command value is the pressure at point a (= point a ′) as indicated by the dotted line. The flow rate is limited to a horsepower Wm. Next, at the next time b, if the pressure increases, the flow rate command value is limited to a flow rate at which the horsepower Wm is obtained at the pressure after compensation at the point b ', as indicated by the dotted line. Here, in the compensated pressure, the response delay with respect to the flow rate command value is compensated by the PFC, and the delay is very small. Therefore, the locus P ′ due to this operation immediately converges on the horsepower limit curve Wm. Furthermore, if the compensated pressure converges, the actual pressure locus P also converges to the horsepower limit curve Wm. That is, hunting is reduced.

  Next, the simulation results of the first embodiment and the first comparative example are compared. The simulation condition is that the flow rate command value Qd is 800 [L / min], the horsepower limit value Wm is 200 [kW], the volume of the hydraulic cylinder is 10 [L], and the relief flow rate is 800 [L / min] to 250 [L]. / Min] is assumed to be changed in 30 seconds.

  FIG. 6 is a graph showing a simulation result by the horsepower limitation according to the first comparative example. FIG. 6A shows a time response waveform of the actual horsepower value, and FIG. 6B shows the characteristics of the hydraulic pump due to the horsepower limitation. From the simulation result, in the first comparative example, significant hunting occurs in the vicinity of 20 seconds after 15 seconds from the start.

  On the other hand, FIG. 7 is a graph showing a simulation result by the horsepower limitation according to the first embodiment. FIG. 7A shows the time response waveform of the horsepower actual value, and FIG. 7B shows the characteristics of the hydraulic pump due to the horsepower limitation. From the simulation result, in this embodiment, hunting is reduced as compared with the first comparative example.

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

  FIG. 8 is a block diagram of a compensation circuit in the second comparative example. In FIG. 8, G is a control target (hydraulic pump or the like), u is an operation amount (flow command value), y is an output (pressure after compensation (actual pressure)), and F is a series filter (phase advance filter) as a compensation element. ). The second comparative example includes a filter in series with the controlled object (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 a control target (hydraulic pump or the like), u is an operation amount (flow rate command value), y is an output (pressure after compensation), and H is a parallel filter (PFC). As shown to Fig.9 (a), in this embodiment, in order to compensate a response delay, a parallel filter is provided with respect to a hydraulic pump. Here, when equivalently converting the block diagram of FIG. 9A, it is expressed as a series filter of FIG. 9B. Therefore, if the series filter of the second comparative example is F = 1 + G ⁻¹ H, the same effect as the parallel filter (PFC) of this embodiment can be obtained. However, since G ^-1 generally includes higher-order differential terms, it is impossible to use such a filter in practice. Accordingly, there is an essential difference in configuration between the second comparative example using a series filter as a compensation element and the present embodiment in which a parallel filter is applied as a compensation element.

  Furthermore, effects of the series filter of the second comparative example and the parallel filter of the present embodiment will be described. FIG. 10 is a Bode diagram showing the frequency characteristics of the series filter according to the second comparative example. FIG. 10A shows a gain diagram, and FIG. 10B shows a phase diagram. The solid line indicates the characteristic after compensation, H (s) indicates the characteristic of the series filter, and G (s) indicates the characteristic to be controlled. In the high frequency region, the delay of the control object G (s) is large, indicating that the phase delay can hardly be improved.

  In contrast, FIG. 11 is a Bode diagram showing the frequency characteristics of the parallel filter according to the first embodiment. FIG. 11A shows a gain diagram, and FIG. 11B shows a phase diagram. The solid line indicates the characteristic after compensation, H (s) indicates the characteristic of the series filter, and G (s) indicates the characteristic to be controlled. In FIG. 11, in the low frequency region, the compensated characteristic is substantially equal to the control target characteristic G (s), while in the high frequency region, the compensated characteristic is substantially equal to the parallel filter characteristic H (s). The phase delay can be eliminated.

By the way, in the horsepower limit, the flow rate limit value Qm is obtained by dividing the horsepower limit value Wm by the pressure P as shown in the equation (7). The equation (7) is expressed around the operating point (pressure P ₀ ). When linearized, it can be expressed as the following equation (8).

If equation (8) is regarded as pressure feedback control, it can be seen that (60η) Wm / P ₀ ² corresponds to the feedback gain, and that the gain becomes very large when the pressure P ₀ at the operating point is low. In the theory of feedback control, if there is a frequency region in which a response delay is 180 degrees or more in phase delay, it becomes unstable when feedback is performed with a gain larger than a certain level.

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

(Third comparative example)
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. In the third comparative example, a configuration of horsepower limitation in which PFC is applied to feedback control of horsepower will be described.

  Usually, PFC is applied to control in which a control amount (output) is fed back by inverting its phase (negative feedback). The configuration of the horsepower limit when this PFC is simply applied is as shown in the block diagram of FIG.

  However, since the horsepower of a hydraulic pump is generally the product of the discharge flow rate and the discharge pressure, the control target (flow rate → horsepower) in the block diagram of FIG. 12 has a non-linear characteristic. It cannot be applied as it is.

  Therefore, in the present embodiment, the hydraulic pump is configured as shown in the block diagram of FIG. 2 using the fact that the pressure can be changed by operating the flow rate and the changed pressure can be measured.

  As a result, the controlled object (flow rate → pressure) basically has a characteristic that can be linearly approximated, and the concept of PFC compensation can be applied. Further, no compensation element such as a PID controller is required, and the horsepower limit can be realized with a very simple configuration.

  Further, as shown in the block diagram of FIG. 2, the configuration of the horsepower restriction according to the present embodiment is different in the dimension of the feedback actual pressure value and the command value (horsepower), and the actual feedback pressure value is fed back. The phase of is not reversed. And it is devised so that PFC can be used by feeding back such pressure actual value in the form of division. In this respect, the horsepower limit control according to the present embodiment is essentially different from normal feedback control, and an original configuration unique to a hydraulic pump that can be expressed by “horsepower = flow rate × pressure”. It is.

(Embodiment 2)
Next, Embodiment 2 of the present invention will be described with reference to FIG. The description of the configuration common to the first embodiment is omitted, and only the configuration that is different will be described.

  FIG. 13 is a block diagram of a horsepower limiting device according to Embodiment 2 of the present invention. Compared with Embodiment 1, this embodiment further includes an adder / subtractor 13 in which the horsepower limit controller 7 subtracts a value obtained by subtracting the flow rate command value Qd from the flow rate command value Qc after the horsepower limit. The difference is that the input is PFC9.

  Here, since the PFC 9 basically corrects the response in the high frequency region, when there is no fluctuation in the flow rate command value Qd in such a high frequency region (typically when the flow rate command value Qd is constant), the PFC 9 Even if the component of the flow rate command value Qd is subtracted from the input to, the effect of the PFC 9 is not impaired. With this configuration, for example, when the flow rate command value is raised in steps from 0 to a specified value when there is no load when the hydraulic pump 1 is started, the actual pressure does not increase, but the compensation of the PFC 9 It can prevent the value from increasing and the horsepower limit from working.

(Other embodiments)
In each of the above embodiments, the PFC 9 is composed of a constant gain and a bandpass filter having a secondary high-pass filter and a primary low-pass filter, but is not limited to this. As long as the response delay of the discharge pressure of the hydraulic pump with respect to the flow rate command can be compensated, the PFC 9 may be configured by, for example, a constant gain and other band pass filters, or may be configured only by the constant gain. Also good.

  In each of the above embodiments, the rotational speed of the motor 2 in the hydraulic pump 1 is constant, and the command to the hydraulic pump 1 is performed by converting the flow rate command value into a command for the tilt angle of the pump. However, the present invention is not limited to this, and the tilt angle of the hydraulic pump may be fixed, and the command to the hydraulic pump may be performed by converting the flow rate command value into a command for the rotational speed of the motor.

  From the foregoing description, many modifications and other embodiments of the present invention are obvious to one skilled in the art. Accordingly, the foregoing description should 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 details of the structure and / or function may be substantially changed without departing from the spirit of the invention.

  The present invention can be used in the field of hydraulic pumps that limit the discharge flow rate of a pump based on the discharge pressure of the hydraulic pump.

DESCRIPTION OF SYMBOLS 1 Hydraulic pump 2 Motor 3 Hydraulic actuator 4 Control valve 5 Pressure sensor 6 Actuator 7, 70 Horsepower limit controller 8 Regulator 9 PFC (parallel feedforward compensator)
10 Adder 11 Flow Limit Value Calculation Unit 12 Flow Limit Unit 13 Adder / Subtractor 20 Oil Path 100 Hydraulic Drive System 101 Horse Power Limiting Device 102 Hydraulic Pump Unit

Claims (6)

A pressure detector for detecting the discharge pressure of the hydraulic pump unit;
A parallel feedforward compensator that outputs a compensation value for compensating the discharge pressure detected by the pressure detector based on a post-horsepower limited flow command that commands a discharge flow limited in horsepower to the hydraulic pump unit When,
A flow rate limit for calculating a discharge flow rate limit value of the hydraulic pump unit based on the compensated discharge pressure by the compensation value output by the parallel feedforward compensator and a preset horsepower limit value of the hydraulic pump unit A value calculator,
Based on the flow rate limit value calculated by the flow rate limit value calculation unit and the flow rate command that commands the discharge flow rate of the hydraulic pump unit, the flow rate limiting unit that outputs the post-horsepower limited flow rate command to the hydraulic pump unit;
A horsepower limiting device comprising:   The horsepower limiting device according to claim 1, wherein the parallel feedforward compensator is configured by one or both of a constant gain and a band pass filter.   The horsepower limiting device according to claim 1 or 2, wherein the input to the parallel feedforward compensator is configured by subtracting a flow rate command value from an operating device from a flow rate command to the hydraulic pump unit. Detecting the discharge pressure of the hydraulic pump unit;
Outputting a compensation value for compensating the detected discharge pressure on the basis of a post-horsepower limited flow command that commands a horsepower-limited discharge flow rate to the hydraulic pump unit;
Calculating a discharge flow rate limit value of the hydraulic pump unit based on a discharge pressure after compensation by the output compensation value and a preset horsepower limit value of the hydraulic pump unit;
Based on the calculated flow rate limit value and a flow rate command that commands the discharge flow rate of the hydraulic pump unit, outputting the post-horsepower limited flow rate command to the hydraulic pump unit;
A horsepower limiting method comprising:   The horsepower limiting method according to claim 4, wherein outputting the compensation value is outputting by a parallel feedforward compensator configured by one or both of a constant gain and a band pass filter.   6. The horsepower limiting method according to claim 4, wherein the input to the parallel feedforward compensator is to subtract a flow rate command value from an operating unit from a flow rate command to the hydraulic pump unit.

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