Grout pump control system

Abstract

The present invention provides a grout pump control system that enables the discharge rate of a grout pump to be controlled independently of the flow rate-frequency characteristics, allowing the grout pump's discharge rate to follow the flow rate command value appropriately and quickly adjust to the flow rate target value without causing overshoot or hunting. [Solution] A ramp control unit 1c is provided to ramp the flow rate target value CF* for the discharge rate control of the grout pump 10 so that it rises from near zero to the flow rate target value CF* over a predetermined time width Δt. The ramp-controlled flow rate command value CF is set as the flow rate command value CF in the PID control unit 1d. After the ramp control is completed, the flow rate command value CF = flow rate target value CF* is set as the flow rate command value CF in the PID control unit 1d.

Description

Technical Field

[0001] The present invention relates to a grout pump control system. More specifically, the present invention relates to a grout pump control system capable of quickly setting to a flow rate target value without causing overshoot or hunting, with the discharge amount control of the grout pump preferably following a flow rate command value without depending on the flow rate - frequency characteristics.

Background Art

[0002] In recent years, for the purposes of "support force strengthening", "settlement reduction", "liquefaction prevention", and "seismic reinforcement of existing structures" in soft ground, the number of ground improvement works that create a large number of cylindrical improvement bodies (ground improvement piles) in the ground by the mechanical agitation method (slurry - type mechanical agitation method) has been increasing. These ground improvement piles are formed in a cylindrical shape by a ground improvement machine equipped with a rotary drive device (swivel head) that rotates a casing rod at a predetermined torque and a feed device (leader device) that raises and lowers the rotary drive device at a predetermined feed pressure.

[0003] The casing rod is also called a stirring shaft, and a stirring device for creating a ground improvement pile is attached to the lower tip of the casing rod. This stirring device is composed of a "drilling blade" having a number of bits for excavating the ground, a "stirring blade" for mixing and stirring a cement - based solidifying agent and earth and sand, and a "back - rotation prevention blade" for preventing the earth and sand from rotating together with the stirring blade. A plurality of injection ports for injecting the solidifying agent are provided near the tip of the stirring blade.

[0004] Also, a grout hose is connected to the upper tip of the casing rod via a water swivel mechanism, and grout (cement - based solidifying agent) is pumped from a plant facility by a grout pump, flows through the inside of the casing rod, and is discharged into the ground from the injection ports. Therefore, the quality of the formed ground improvement pile is determined by, for example, the discharge flow rate (L) of the solidifying agent per interval depth (e.g., 1 m) and the number of blade rotations per interval depth (= the rotation speed of the casing rod × the number of blades of the stirring blade).

[0005] Incidentally, a columnar improvement pile construction system is known that can perform batch setting / modification, operational status confirmation, and grout level monitoring in a mixing plant, as well as operation / stop and discharge volume control in a grout pump, and rotation control of the rotary drive device and lifting / lowering control of the leader in a ground improvement machine, all in one unit (see, for example, Patent Document 1).

[0006] In the above-described columnar ground improvement pile construction system, an automatic operation setting unit is installed within the ground improvement machine, and an antenna and transceiver are installed in the mixing plant to receive control signals from the automatic operation setting unit. The control signals received by the transceiver are then transmitted via wire to the control devices of the mixing plant and the pump. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2016-65446 [Overview of the project] [Problems that the invention aims to solve]

[0008] Figure 8 is an explanatory diagram showing the flow rate-frequency characteristics and control responsiveness of the discharge rate (flow rate) for the grout pumps. Figure 8(a) shows the flow rate-frequency characteristics for grout pump 1 and grout pump 2. Figure 8(b) shows the control responsiveness of the discharge rate for grout pump 2. Figure 8(c) shows the control responsiveness of the discharge rate for grout pump 1. Here, "frequency" refers to the frequency of the power supply applied to the three-phase induction motor that drives the grout pump. Furthermore, since the rotational speed of the three-phase induction motor is proportional to the power supply frequency, "frequency" here corresponds to the rotational speed of the three-phase induction motor. Moreover, the rotational speed of the three-phase induction motor corresponds to the rotational speed of the grout pump. In short, "frequency" here corresponds to the rotational speed of the grout pump.

[0009] As shown in Figure 8(a), the frequency for grout pump 1 with respect to the flow rate target value CF* is f1 [Hz], and the frequency for grout pump 2 is f2 [Hz]. This indicates that in order to set the pump discharge rate to the flow rate target value CF*, the rotational speed of grout pump 2 must be set to a higher rotational speed than that of grout pump 1.

[0010] As shown in Figure 8(b), the grout pump 2 operates at a relatively high rotational speed, resulting in a large rise in the pump discharge rate. When the rise is large, the pump discharge rate is likely to exceed the flow rate target value CF* by a large amount (overshoot), or the pump discharge rate may fluctuate slightly up and down around the flow rate target value CF* (hunting), leading to problems such as unstable pump discharge rate.

[0011] On the other hand, as shown in Figure 8(c), the grout pump 1 operates at a relatively low rotational speed range, resulting in a small rise in pump discharge volume. A small rise in volume presents the problem that it takes time for the pump discharge volume to reach the target flow rate value CF*.

[0012] Thus, the control response of a grout pump regarding its discharge rate depends on the flow-frequency characteristics of the grout pump, that is, the magnitude of the frequency of the grout pump corresponding to the flow rate target value CF*. Therefore, selecting a grout pump with optimal control response (regarding discharge rate) for the construction of columnar improved piles was not easy.

[0013] Therefore, depending on the flow-frequency characteristics of the selected grout pump, automatic control of the grout pump's discharge volume may be difficult.

[0014] Incidentally, to simplify the columnar ground improvement pile construction system, a single control unit sometimes controls both the mixing plant and the grout pump. In this case, the control unit is installed in the larger mixing plant. The command values ​​for the mixing plant and the grout pump are transmitted wirelessly from the construction management device (computer device) installed in the ground improvement machine to the control unit.

[0015] The command values ​​for the mixing plant include the batch number (the proportions of cement, water, and admixtures). The command value for the grout pump is the flow rate target value CF* for the discharge volume.

[0016] However, even when a single control unit controls both the mixing plant and the grout pump, depending on the flow-frequency characteristics of the selected grout pump, it was sometimes impossible to control the grout pump's discharge rate to the target flow rate value CF*.

[0017] Therefore, the present invention has been made in view of the problems of the above-mentioned prior art, and its objective is to provide a grout pump control system that enables the discharge rate control of the grout pump to be independent of the flow rate-frequency characteristics, and that allows the discharge rate of the grout pump to follow the flow rate command value suitably and quickly adjust to the flow rate target value without causing overshoot or hunting. [Means for solving the problem]

[0018] To achieve the above objective, the grout pump control system according to the present invention includes a pump control device (1) that controls the discharge amount of a grout pump (10) that discharges a solidifying agent for ground improvement piles, an inverter (2) that controls the frequency of the power supply applied to an induction motor (3) that rotates the grout pump (10), a flow meter (4) that measures the flow rate of the solidifying agent discharged from the grout pump (10), a construction management device (7) that controls a ground improvement machine (30) that constructs ground improvement piles underground, and a pump control device (1) that sets a flow rate target value (CF*) for the grout pump (10). A grout pump control system comprising a remote control device (8) that transmits to a pump control device (1), wherein the pump control device (1) comprises a ramp control unit (1c) that ramp controls and outputs a flow command value (CF) that "rises from near zero to the flow target value (CF*) in a predetermined time width (Δt)", and a PID control unit (1d) that adjusts the proportional gain (Kp), integral gain (Ki), or differential gain (Kd), respectively, so that the deviation (e) between the flow command value (CF) and the flow measurement value (FA) measured by the flow meter (4) becomes zero.

[0019] In the above configuration, the flow rate command value (CF) in the initial transient state of the grout pump (10) discharge rate control is ramp-controlled so that it rises from near zero to the flow rate target value (CF*) within a predetermined time width (Δt). As a result, the deviation (e) between the flow rate command value (CF) and the flow rate measurement value (FA) in the initial transient state of the grout pump (10) discharge rate control becomes significantly smaller compared to the case without ramp control. Consequently, the responsiveness of the grout pump (10) discharge rate (FA) to the flow rate command value (CF) in the initial transient state of the grout pump (10) discharge rate control is greatly improved, and the grout pump (10) discharge rate (FA) quickly reaches the flow rate target value (CF*) without causing an overshoot.

[0020] A second feature of the grout pump control system according to the present invention is that the ramp control unit (1c) sets the flow rate target value (CF*) as the flow rate command value (CF) to the PID control unit (1d) after the predetermined time width (Δt) has elapsed.

[0021] In the above configuration, after the flow rate measurement value (FA) stabilizes during the initial transient state of discharge rate control, the pump control device (1) sets the flow rate command value (CF) to the PID control unit (1d) as the flow rate target value (CF*). As a result, the flow rate measurement value (FA) settles to the flow rate target value (CF*) without hunting.

[0022] A third feature of the grout pump control system according to the present invention is that the ramp control unit (1c) changes the predetermined time width (Δt) according to the magnitude of the frequency corresponding to the flow rate target value (CF*) in the flow rate-frequency characteristics of the grout pump (10).

[0023] The above configuration focuses on the fact that the control responsiveness of the grout pump (10) regarding the discharge rate depends on the magnitude of the frequency corresponding to the flow rate target value (CF*) in the flow-frequency characteristics of the grout pump (10). That is, when the magnitude of the frequency corresponding to the flow rate target value (CF*) is relatively small, the ramp control unit (1c) shortens the ramp control time (Δt) in the initial transient state of discharge rate control. On the other hand, when the magnitude of the frequency corresponding to the flow rate target value (CF*) is relatively large, the pump control device (1) lengthens the ramp control time (Δt) in the initial transient state of discharge rate control. This makes it possible to quickly reach the flow rate target value (CF*) while making the discharge rate (FA) of the grout pump (10) follow the flow rate command value (CF), regardless of the magnitude of the frequency corresponding to the flow rate target value (CF*).

[0024] A fourth feature of the grout pump control system according to the present invention is that the remote control device (8) is capable of communicating with both the construction management device (7) and the pump control device (1).

[0025] In the above configuration, it is possible to interlock the grout pump (10) with an automatic operation program (for example, the automatic operation of the construction of ground improvement piles) by the construction management device (7). As a result, it is possible to automatically secure the sectional flow rate (L / m) and the integrated flow rate (L) of the cement milk required for the construction of the ground improvement piles via the grout pump (10).

[0026] Also, separately from the construction management device (7), an operator can transmit a flow rate target value (CF*) for the discharge amount (FA) of the grout pump (10) to the pump control device (1).

[0027] The fifth feature of the grout pump control system according to the present invention is that the remote control device (8) stores in advance a plurality of flow rate target values (CF*) for the discharge amount of the grout pump (10) set by the operator so that the operator can select them, and the flow rate target value (CF*) selected by the operator can be transmitted to the pump control device (1). It has a plurality of manual flow rate adjustment modes (A mode, B mode, C mode), and a construction machine interlock mode (M mode) in which the flow rate target value (CF*) for the discharge amount of the grout pump (10) stored in the construction management device (7) can be automatically transmitted to the pump control device (1).

[0028] In the above configuration, since a plurality of flow rate target values (CF*) are stored in advance so that the operator can select them, the operator does not need to reset the same flow rate target value (CF*) again. As a result, the operator's work related to resetting the flow rate target value (CF*) is significantly reduced. Also, the automatic operation program (for example, the automatic operation of the construction of ground improvement piles) by the construction management device (7) can be suitably performed in the construction machine interlock mode (M mode).

[0029] A sixth feature of the grout pump control system according to the present invention is that the remote control device (8) has a display unit (87) capable of displaying the target flow rate value (CF*) for at least the plurality of manual flow rate adjustment modes (A mode, B mode, C mode) and the construction machine interlocking mode (M mode), as well as the currently selected mode and the measured flow rate value (FA).

[0030] With the above configuration, it becomes possible to visually check the currently selected flow rate adjustment mode, its flow rate adjustment range, and the measured flow rate (FA).

[0031] A seventh feature of the grout pump control system according to the present invention is that the remote control device (8) has rotary flow adjustment volumes (83, 84, 85) for the operator to set the flow rate target value (CF*), and the rotary flow adjustment volumes (83, 84, 85) have a resolution that resolves the maximum discharge amount of the grout pump (10) by multiple rotations.

[0032] In the above configuration, it becomes possible to fine-tune the flow rate target value (CF*) for the discharge volume of the grout pump (10).

[0033] An eighth feature of the grout pump control system according to the present invention is that, if the flow rate target value (CF*) is changed to a new flow rate target value (CF*') during discharge rate control, the ramp control unit (1c) ramp controls the new flow rate target value (CF*') to a flow rate command value (CF) that "rises from the previous flow rate target value (CF*) to the new flow rate target value (CF*') over a predetermined time width (Δt2)" and outputs it to the PID control unit (1d).

[0034] In the above configuration, even if the flow rate target value (CF*) is changed to a new flow rate target value (CF*') while the discharge rate of the grout pump (10) is being controlled by PID, ramp control is performed for the new flow rate target value (CF*'). This makes it possible to quickly adjust the discharge rate (FA) of the grout pump (10) from the previous flow rate target value (CF*) to the new flow rate target value (CF*') without causing overshoot or hunting. [Effects of the Invention]

[0035] According to the grout pump control system of the present invention, the discharge rate control for the grout pump (10) does not depend on the flow rate-frequency characteristics, and the discharge rate (FA) of the grout pump (10) can be suitably tracked to the flow rate command value (CF) and quickly adjusted to the flow rate target value (CF*) without causing overshoot or hunting. [Brief explanation of the drawing]

[0036] [Figure 1] This is a block diagram showing the configuration of a grout pump control system according to one embodiment of the present invention. [Figure 2] This is a skeletal diagram illustrating a grout pump according to the present invention. [Figure 3] This is an explanatory diagram showing a ground improvement machine according to the present invention. [Figure 4] This is a flowchart illustrating the discharge rate control for a grout pump using the pump control device of the present invention. [Figure 5] This is an explanatory diagram showing the lamp control unit and PID control unit of the pump control device of the present invention. [Figure 6] This is an explanatory diagram illustrating the effect of pump discharge rate control using the lamp control unit and PID control unit according to the present invention. [Figure 7] This is an explanatory diagram showing a remote control device according to the present invention. [Figure 8] This is an explanatory diagram showing the flow-frequency characteristics and control response of discharge volume (flow rate) for a conventional grout pump. [Figure 9] This is an explanatory diagram showing the construction pattern of automated operation related to the construction of ground improvement piles. [Figure 10] This is an explanatory diagram showing ramp control for the changed flow rate target value when the flow rate target value is changed during the discharge rate control process. [Modes for carrying out the invention]

[0037] Embodiments of the present invention will be described in detail below with reference to the attached drawings.

[0038] Figure 1 is a block diagram showing the configuration of a grout pump control system 100 according to one embodiment of the present invention.

[0039] This grout pump control system 100 is configured to quickly adjust the discharge rate FA of the grout pump 10 to an arbitrary flow rate target value* without causing overshoot or hunting. This makes it possible to link the grout pump 10 to the automatic operation (autopilot function) of the ground improvement machine 30 involved in the construction of ground improvement piles.

[0040] Therefore, the grout pump control system 100 is configured to include a pump control device 1 that receives a flow rate target value CF* and outputs a frequency command value Cf to the inverter 2 so that the flow rate measurement value FA becomes equal to the flow rate target value CF*, an inverter 2 that receives the frequency command value Cf and outputs a corresponding AC voltage Vf, a three-phase induction motor 3 that receives the AC voltage Vf and rotates the grout pump 10, a flow meter 4 that measures the discharge amount (flow rate measurement value) FA of the grout pump 10, a three-phase AC power supply 5 that supplies power to the inverter 2, a construction management device 7 that automatically controls the ground improvement machine 30 to automatically create ground improvement piles (columnar improvement bodies), and a remote control device 8 that modulates the flow rate target value CF* into an electromagnetic carrier wave and transmits it to the pump control device 1. Each of these components will be further explained below.

[0041] The pump control device 1 can be configured, for example, by a PLC (Programmable Logic Controller). The pump control device 1 is configured to have a pump-side antenna 1a that receives an electromagnetic carrier wave including a flow rate target value CF*, and a pump-side transceiver 1b that demodulates the electromagnetic carrier wave into an electrical signal of the flow rate target value CF* and extracts it, either built-in or externally. As the wireless communication standard for the electromagnetic carrier wave, for example, Bluetooth® or Wi-Fi® can be used.

[0042] The pump control device 1 includes a ramp control unit 1c that ramps and outputs a flow rate command value CF that rises from near zero to the target flow rate value CF* over a predetermined time width Δt. In the initial transient state, the flow rate command value CF of the PID control unit 1d is the ramp-controlled flow rate command value CF, not the target flow rate value CF* transmitted from the construction management device 7 or the remote control device 8. This ramp control will be described later with reference to Figures 4 and 5.

[0043] The pump control device 1 includes a PID control unit 1d that calculates the deviation e between the flow rate command value CF and the flow rate measurement value FA, and determines the frequency command value Cf for the inverter 2 so that the deviation e becomes zero. The frequency command value Cf for the inverter 2 can be obtained by summing a proportional term Kp·e obtained by multiplying the deviation e by the proportional gain Kp, an integral term Ki·∫edt obtained by multiplying the value obtained by integrating the deviation e by the integral gain Ki, and a differential term Kd·de / dt obtained by multiplying the value obtained by differentiating the value obtained by deriving the deviation e by the differential gain Kd. The PID control unit 1d is configured to adjust some or all of the proportional gain Kp, integral gain Ki, and differential gain Kd so that the deviation e becomes zero.

[0044] Inverter 2 generates an AC voltage Vf of a desired frequency f from a DC voltage. Inverter 2 is configured to communicate with the pump control device 1.

[0045] The three-phase induction motor 3 generates a rotating magnetic field by applying a three-phase AC voltage to the field coil wound around the stator, and this rotating magnetic field induces an electromotive force in the armature coil wound around the rotor. This induced electromotive force induces a current to flow through the armature coil, and the interaction between this induced current and the rotating magnetic field generates an electromagnetic force (Lorentz force) in the armature coil. By connecting the rotating shaft 3a (Figure 2) to the rotor of the three-phase induction motor 3, it becomes possible to extract rotational power (rotational torque, rotational energy) to rotate the grout pump 10.

[0046] It is generally known that the rotational speed (rotational speed) N [rpm] of a three-phase induction motor 3 (rotor) can be expressed by the following equation 1. (Equation 1) N = 120f / P × (1-s), f: power supply frequency, P: number of poles, s: slip (value obtained by dividing the difference between synchronous speed Ns and rotational speed N by synchronous speed Ns) Therefore, when the number of poles P and slip s are constant, the rotational speed N [rpm] depends on the power supply frequency f. Consequently, by changing the power supply frequency f using the inverter 2, it is possible to change the rotational speed N [rpm] of the three-phase induction motor 3.

[0047] The flow meter 4 can be, for example, an electromagnetic flow meter. The flow rate measurement value FA is input to the PID control unit 1d of the pump control device 1 as the discharge volume of the grout pump 10.

[0048] Further details will be described later with reference to Figures 4-5, but the pump control device 1 is configured to feedback control the discharge amount of the grout pump 10 so that it becomes equal to the flow rate target value CF* by using a combination of ramp control and PID control, which brings the flow rate from near zero to the flow rate target value CF* within a predetermined time width Δt.

[0049] The three-phase AC power supply 5 is composed of, for example, an industrial generator powered by an internal combustion engine, and is capable of supplying three-phase AC power with a voltage of 200V and a frequency of 50Hz / 60Hz.

[0050] The construction management device 7 controls the rotary drive device 31 (Figure 3) and the leader device 32 (Figure 3) of the ground improvement machine 30 so that the ground improvement machine 30 automatically creates ground improvement piles (columnar improved bodies).

[0051] The remote control device 8 includes a transceiver 8b that modulates the flow rate target value CF* for the grout pump 10 into an electromagnetic carrier wave, and an antenna 8a that radiates the electromagnetic carrier wave into space, either internally or externally. The transceiver 8b also has the function of demodulating the received electromagnetic carrier wave back to the original signal. Details of this remote control device 8 will be described later with reference to Figure 7.

[0052] The grout pump 10 pumps cement grout (solidifying agent) transferred from a mixing plant (not shown) at a predetermined discharge pressure. The pumped cement grout flows through the inside of the stirring shaft 41 (Figure 3) via a water swivel mechanism 43 (Figure 3) and is injected into the ground from the surface of the stirring device 42 (Figure 3). The grout pump 10 will be described later with reference to Figure 2.

[0053] The ground improvement machine 30 is configured to stably perform ground improvement from the surface to deep layers (for example, to a depth of 25m) by appropriately gripping and changing the long-axis mixing shaft 41 (Figure 3) used in mechanical mixing methods (GI column method), etc. The ground improvement machine 30 rotates the mixing shaft 41 (Figure 3) with a rotary drive device 31 (Figure 3), and at the same time feeds the mixing shaft 41 (Figure 3) with a leader device 32 (Figure 3). The mixing device 42 (Figure 3) attached to the tip of the mixing shaft 41 (Figure 3) mixes the cement milk (solidifying agent) pumped from the grout pump 10 with the ground, creating ground improvement piles (columnar improved bodies) in the ground. The ground improvement machine 30 will be described later with reference to Figure 3.

[0054] Figure 2 is a skeletal diagram illustrating the grout pump 10 according to the present invention. This grout pump 10 includes a drive shaft 11 that rotates the crankshaft 12 by receiving rotational power from a three-phase induction motor 3, a crankshaft 12 that causes the crosshead 14 to reciprocate along its longitudinal direction (horizontal direction), a connecting rod 13 that connects the crosshead 14 and the crankshaft 12, a crosshead 14 and a crosshead rod 15 that transmit the pushing force (axial force) of the connecting rod 13 to the plunger 16, a plunger 16 that pressurizes and pumps the sucked-in cement grout, a plunger case 17 in which the plunger 16 reciprocates and slides, a packing 18 that seals the gap between the plunger 16 and the plunger case 17, a compression block 19 that compresses the cement grout sucked in by the plunger 16, and a suction block that temporarily stores the sucked-in cement grout. The system includes a lock 20, a discharge block 21 that pumps compressed cement grout from a discharge port 21a, a suction valve 22 that allows only the flow of cement grout from the suction block 20 to the compression block 19, a discharge valve 23 that allows only the flow of cement grout from the compression block 19 to the discharge block 21, a crankshaft case 24 that houses the crankshaft 12 and drive shaft 11, a driven pulley 25 that is rotationally driven by a belt 27, a drive pulley 26 that extracts the rotational power of the three-phase induction motor 3, a belt 27 that transmits the rotational power of the three-phase induction motor 3 to the driven pulley 25, a safety valve 28 that discharges cement grout corresponding to the pressure excess exceeding the set pressure for discharge pressure to maintain the discharge pressure at the set pressure, and a pressure sensor 29 that measures the pressure of the cement grout. Each component will be described in more detail below.

[0055] A drive gear 11a, which meshes with the driven gear 12a of the crankshaft 12, is fixed to the outer surface of the drive shaft 11. The drive shaft 11 is also rotatably supported by a bearing 11b.

[0056] A driven gear 12a, which meshes with the drive gear 11a of the drive shaft 11, is fixed to the outer surface of the crankshaft 12. The crankshaft 12 is also rotatably supported by a bearing 12b.

[0057] The meshing portions of gears 11a and 11b, and the bearing portions 11b and 12b, are lubricated with oil.

[0058] The connecting rod 13 and the crosshead 14 are connected by a pin (not shown) from a direction perpendicular to the longitudinal direction of the connecting rod 13, so as to be able to rotate relative to each other around the pin.

[0059] Furthermore, the crosshead 14 is configured to reciprocate within the cylindrical portion 24a of the crankshaft case 24 in synchronization with the rotation of the crankshaft 12.

[0060] The sliding portion of the cylindrical section 24a with the crosshead rod 15 is sealed by an oil seal (not shown) to prevent oil from leaking into the plunger case 17.

[0061] The plunger 16 is designed to reciprocate within the plunger case, penetrating deeply into the compression block 19. As the plunger 16 penetrates deeply into the compression block 19, the pressure of the cement grout inside the compression block 19 increases. This causes the discharge valve 23 to open, and the cement grout inside the compression block 19 is pumped into the discharge block 21. As a result, the cement grout inside the protruding block 21 is pumped to the outside through the discharge port 21a.

[0062] On the other hand, when the plunger 16 retracts from the compression block 19, a negative pressure is created inside the compression block 19. This causes the suction valve 22 to open, and the cement grout in the suction block 20 is drawn into the compression block 19. As the plunger 16 retracts deeper into the compression block 19, the discharge valve 23 opens, and the cement grout in the compression block 19 is pumped into the discharge block 21. This causes the cement grout in the protruding block 21 to be pumped out through the discharge port 21a.

[0063] The suction valve 22 is biased downwards by a spring (not shown) in the figure, and the discharge valve 23 is biased upwards by a spring (not shown) in the figure. Therefore, when the pressure inside the compression block 19 exceeds the elastic force of the spring, only the discharge valve 23 will open. On the other hand, when the pressure inside the compression block 19 exceeds the elastic force of the spring, only the suction valve 22 will open.

[0064] Furthermore, a safety valve 28 is attached to the discharge pipe 21a. In the safety valve 28, a roller 28b is biased by a spring 28c and fitted into the circumferential groove of the piston 28a from the lateral direction (a direction perpendicular to the longitudinal direction). Therefore, when the discharge pressure of the cement milk is below the set pressure, the piston 28a rotates along the roller 28b due to the discharge pressure of the cement milk. When the discharge pressure of the cement milk exceeds the set pressure, the piston 28a separates from the roller 28b and rises. As a result, the vent port 28d opens, and the cement milk corresponding to the pressure excess exceeding the set pressure is discharged from the vent port 28d. When the discharge pressure of the cement milk returns to the set pressure, the piston 28a descends and closes the vent port 28d, and the roller 28b is fitted back into the circumferential groove of the piston 28a, maintaining a constant height position for the piston 28a.

[0065] The pressure measurement value PA of the cement grout measured by the pressure sensor 29 is taken into the pump control device 1 (Figure 1) as the discharge pressure of the grout pump 10. The taken-in cement grout pressure measurement value PA is transmitted by the pump control device 1 (Figure 1) to the remote control device 8 (Figure 1). The cement grout pressure measurement value PA is displayed on the display unit 87 (Figure 7) of the remote control device 8 (Figure 1) and is also taken into the construction management device 7.

[0066] Figure 3 is an explanatory diagram showing the ground improvement machine 30 according to the present invention. This ground improvement machine 30 includes a rotary drive device 31 that rotates the stirring shaft 41, a leader device 32 that raises and lowers the rotary drive device 31 along the axial direction, a hydraulic chuck mechanism 33 that fixes the position of the stirring shaft 41 while rotating it together with the rotary drive device 31, a shaft clamp mechanism 34 that fixes the position of the stirring shaft 41, a shaft guide mechanism 35 that prevents the stirring shaft 41 from shaking, a leader tilting cylinder 36 that swings the leader device 32 in the front-rear direction, a vehicle body 37 that houses a hydraulic pump and oil tank, a hydraulic control circuit that controls the flow of oil, an engine that drives the hydraulic pump and a fuel tank, etc., and a mechanism that allows the ground improvement machine 30 to travel in the front-rear, left-right, and right directions. The ground improvement machine 30 comprises a crawler device 38, outriggers 39 that press the four corners of the ground improvement machine 30 against the ground to stabilize its posture, a counterweight 40 that cancels out the tipping moment that would cause the ground improvement machine 30 to tip over when the leader device 32 rotates and penetrates the stirring shaft 41 into the ground, a stirring shaft 41 that transmits the rotational force of the rotary drive device 31 to the stirring device 42, a stirring device 42 that mixes and stirs the solidifying agent in the ground, a water swivel mechanism 43 that connects a non-rotatable grout hose (not shown) that pumps cement milk (solidifying agent) to the rotatable stirring shaft 41, and a guide rod 44 that supports the water swivel mechanism 43.

[0067] The stirring shaft 41 consists of multiple hollow casing rods connected in series. The lowest casing rod is connected to a stirring device 42, and the highest casing rod is connected to a water swivel mechanism 43.

[0068] The stirring device 42 consists of an excavation blade 42a equipped with numerous bits, a stirring blade 42b for mixing and stirring soil and solidifying agent, and an anti-rotation blade 42c for preventing soil from rotating together with the stirring blade 42b. The outer surface of the excavation blade 42a is provided with multiple nozzles from which cement grout is injected.

[0069] The water swivel mechanism 43 has a bearing (not shown) in the gap between an outer pipe (not shown) to which a grout hose (not shown) is connected and an inner pipe (not shown) to which the stirring shaft 41 is connected. A packing (not shown) is provided at the joint between the outer pipe flow path (not shown) and the inner pipe flow path (not shown) to prevent cement grout from leaking from the joint between the outer pipe flow path (not shown) and the inner pipe flow path (not shown). This makes it possible to supply cement grout into the rotating stirring shaft 41 via the water swivel mechanism 43.

[0070] The guide rod 44 supports the outer tube (not shown) of the water swivel mechanism 43. As a result, the outer tube (not shown) is unable to rotate. The guide rod 44 is also configured to be telescopic, forming a so-called telescopic mechanism, allowing the rod to extend and retract. Therefore, when the hydraulic chuck mechanism 33 changes its grip on the lower part of the stirring shaft 41, the guide rod 44 extends. Conversely, when the hydraulic chuck mechanism 33 changes its grip on the upper part of the stirring shaft 41, the guide rod 44 retracts.

[0071] Figure 4 is a flow chart showing the discharge rate control for the grout pump 10 by the pump control device 1 of the present invention. Steps S1 through S3 are performed manually by the operator. From step S4 onwards, the system is automatically controlled by the construction management device 7 or the pump control device 1.

[0072] In step S1, you input the pump characteristic parameters. For example, you input the pump flow rate-frequency characteristics.

[0073] In step S2, select the pump to be used. For example, select a pump whose maximum discharge rate is 50% greater than the standard discharge rate [L / min] of cement grout required for ground improvement work (construction of ground improvement piles).

[0074] In step S3, the start of the automated pile construction operation is selected. The automated pile construction operation has pre-set and patterned necessary parameters. As shown in Figure 9, the necessary parameters include the drilling distance [m] of the agitator 42 (Figure 3), the pile top mixing return distance [m], the length of the ground improvement pile [m], the bottom mixing return distance [m], the number of blade cuts per 1m [times / m], and the section flow rate of cement grout per 1m [L / m].

[0075] In step S4, the construction management device 7 determines whether or not the excavation depth for injecting cement grout has been reached. The excavation depth for injecting cement grout into the ground is measured by a linear encoder (not shown) attached to the leader device 32.

[0076] If the agitator 42 (Figure 3) reaches the excavation depth at which cement grout injection begins (YES), step S5 is executed. On the other hand, if the agitator 42 (Figure 3) has not yet reached the excavation depth at which cement grout injection begins (NO), step S4 is executed again.

[0077] In step S5, pump operation is started. Specifically, the construction management device 7 transmits the flow rate target value CF* for the grout pump 10 to the pump control device 1 via the remote control device 8. Upon receiving the flow rate target value CF*, the pump control device 1 transmits an inverter ON signal to the inverter 2, which energizes the inverter 2 (turns it on). This energizes the three-phase induction motor 3 that rotates the grout pump 10 (turns it on).

[0078] In step S6, the pump control device 1 performs ramp control for the flow rate target value CF* and PID control for the flow rate command value CF. Ramp control for the flow rate target value CF* means changing the flow rate target value CF* to a flow rate command value CF that "reaches the flow rate target value CF* from zero with a constant time width Δt (slope)".

[0079] On the other hand, PID control for the flow rate command value CF means calculating the deviation e between the flow rate command value CF and the measured flow rate value FA, and determining the frequency command value Cf for the inverter 2 so that the deviation e becomes zero (the discharge amount of the grout pump 10 becomes equal to the flow rate command value CF). The frequency command value Cf for the inverter 2 can be, for example, the sum of the deviation e multiplied by the proportional gain Kp (Kp·e), the integral of the deviation e (∫edt) multiplied by the integral gain Ki (Ki·∫edt), and the derivative of the deviation e (de / dt) multiplied by the differential gain Kd (Kd·de / dt) (Kp·e+Ki·∫edt+Kd·de / dt). Therefore, the pump flow rate control device 1 will sequentially update the frequency command value Cf for the inverter 2 while taking in the measured flow rate value FA until the deviation e between the flow rate command value CF and the measured flow rate value FA becomes zero.

[0080] In step S7, the pump control device 1 determines whether the lamp control time Δt (Figure 5) has elapsed. If the lamp control time Δt has elapsed (YES), step S8 is executed. On the other hand, if the lamp control time Δt has not elapsed (NO), step S6 is executed again.

[0081] In step S8, the pump control device 1 terminates ramp control for the flow rate target value CF*. As a result, the pump control device 1 sets the flow rate command value CF = flow rate target value CF*.

[0082] In step S9, the pump control device 1 performs PID control for the flow rate target value CF*.

[0083] In step S10, the construction management device 7 determines whether the excavation depth has reached the excavation depth at which cement grout injection is completed. If the excavation depth has reached the depth at which cement grout injection is completed (YES), the process proceeds to step S11 and the operation of the grout pump 10 is terminated. On the other hand, if the excavation depth has not reached the depth at which cement grout injection is completed (NO), step S10 is executed again.

[0084] In step S11, the construction management device 7 terminates the operation of the pump. Specifically, the construction management device 7 transmits a pump stop signal to the pump control device 1 via the remote control device 8. Upon receiving the pump stop signal, the pump control device 1 transmits an inverter OFF signal to the inverter 2, which puts the inverter 2 into an unpowered (off) state. As a result, the inverter 2 becomes unpowered (off), which also causes the three-phase induction motor 3 to become unpowered (off), and the grout pump 10 stops operating.

[0085] Figure 5 is an explanatory diagram showing the lamp control unit 1c and PID control unit 1d of the pump control device 1 of the present invention. Figure 5(a) shows the lamp control unit 1c of the pump control device 1, and Figure 5(b) shows the PID control unit 1d of the pump control device 1.

[0086] As shown in Figure 5(a), the ramp control unit 1c controls the flow rate command value CF for the PID control unit 1d by ramping the flow rate command value CF so that it reaches the flow rate target value CF* from zero at a constant slope for a period of time width Δt from the start of control (t=t0), and outputs the ramp-controlled flow rate command value CF to the PID control unit 1d. That is, for 0≦t≦t1, the ramp control unit 1c sets the flow rate command value CF to CF=CF* / t1×t. This completes the ramp control, and for t≧t1, the ramp control unit 1c sets the flow rate command value CF to CF=CF* (a constant value).

[0087] Therefore, as shown in Figure 5(b), the flow rate command value CF input to the PID control unit 1d is the ramp-controlled flow rate command value CF = CF* / t1 × t when 0 ≤ t ≤ t1. On the other hand, when t ≥ t1, the flow rate command value CF input to the PID control unit 1d is the flow rate command value CF = CF*.

[0088] The PID control unit 1d calculates the deviation e (=CF-FA) between the flow rate command value CF input from the lamp control unit 1c and the flow rate measurement value FA of the grout pump 10 measured by the flow meter 4. The deviation e is multiplied by the differential gain Kd, proportional gain Kp, and integral gain Ki, respectively, to obtain Kd·e, Kp·e, and Ki·e. Of these, Kd·e is further differentiated to obtain Kd·de / dt, and Ki·e is further integrated to obtain Ki·∫edt. The sum of all these, Kd·de / dt + Kp·e + Ki·∫edt, is used as the manipulated variable (frequency command value) Cf input to the inverter 2.

[0089] The inverter 2, upon receiving the manipulated variable Cf, generates an AC voltage Vf corresponding to the manipulated variable Cf and applies it to the three-phase induction motor 3. The three-phase induction motor 3 rotates at a speed corresponding to the AC voltage Vf, causing the grout pump 10 to suck in cement grout, compress it, and discharge it into the grout hose.

[0090] The cement grout discharged from the grout pump 10 is measured by the flow meter 4, and the flow rate measurement value FA is fed back to the PID control unit 1d. The fed-back flow rate measurement value FA is used to calculate the deviation e between it and the flow rate command value CF. The calculated deviation e is subjected to gain processing, differential processing, or integral processing and used to calculate the manipulated variable Cf for the inverter 2. The above feedback process continues until the deviation e becomes zero.

[0091] Figure 6 is an explanatory diagram illustrating the effect of pump discharge rate control by the ramp control unit 1c and PID control unit 1d according to the present invention. Figure 6(a) shows the ramp control for the flow rate target value CF*, the flow rate target value CF*+Δ increased by Δ, and the flow rate target value CF*-Δ decreased by Δ, respectively. Figure 6(b) shows the discharge rate (flow rate measurement value FA) of the grout pump 10 for each of the flow rate target values ​​CF*, CF*+Δ, and CF*-Δ when the ramp control and PID control are being performed.

[0092] As shown in Figure 6(a), ramp control was performed similarly for the flow rate target value CF* of the grout pump 10, which is the target of control, for both the flow rate target value CF*+Δ, which is increased by ΔCF compared to the flow rate target value CF*, and the flow rate target value CF*-Δ, which is decreased by Δ compared to the flow rate target value CF*. Although the ramp control time Δt is kept the same, it is also possible to set the ramp control time Δt to be longer, for example, depending on the magnitude of the flow rate target value.

[0093] As shown in Figure 6(b), it can be seen that the discharge rate (flow rate measurement value FA) of the grout pump follows the flow rate command value CF favorably, regardless of the magnitude of the flow rate target value. In particular, in the initial transient state immediately after the start of discharge rate control, the discharge rate (flow rate measurement value FA) of the grout pump comes to follow the flow rate command value CF favorably. As a result, it can be seen that the pump discharge rate (flow rate measurement value FA) settles to the flow rate target value in a short time without causing an overshoot that significantly exceeds the flow rate target value or a hunting that oscillates up and down around the flow rate target value.

[0094] Furthermore, the results shown in Figure 6(b) indicate that even when the operator changes the flow rate target value CF* of the grout pump 10's discharge volume using the remote control device 8, the pump control device 1 can control the grout pump 10's discharge volume to the changed flow rate target value CF*.

[0095] Similarly, the results shown in Figure 6(b) indicate that even when the construction management device 7 changes the flow rate target value CF* of the grout pump 10's discharge volume, the pump control device 1 can control the grout pump 10's discharge volume to the changed flow rate target value CF*. At the same time, this indicates that, according to the grout pump control system 100, the grout pump 10 can be linked to the automatic operation (autopilot function) of the construction of ground improvement piles, regardless of the flow rate-frequency characteristics.

[0096] Figure 7 is an explanatory diagram showing the remote control device 8 according to the present invention. The remote control device 8 is configured to form a computer communication network with the construction management device 7 and the pump control device 1. Therefore, the remote control device 8 receives the flow rate target value CF* for the discharge volume of the grout pump 10 from the construction management device 7, modulates it into an electromagnetic carrier wave, and transmits it to the pump control device 1. At the same time, it receives an electromagnetic carrier wave from the pump control device 1 that includes the flow rate measurement value FA and the pressure measurement value PA for the discharge volume of the grout pump 10, demodulates it, and extracts the flow rate measurement value FA and the pressure measurement value PA. The extracted flow rate measurement value FA and pressure measurement value PA are displayed on the display unit 87.

[0097] The user interface of the remote control device 8 includes a pump operation switch 81, a mode selection switch 82, an A-mode flow rate adjustment volume 83, a B-mode flow rate adjustment volume 84, a C-mode flow rate adjustment volume 85, and a display unit 87. Note that the antenna 8a (Figure 1) and the transceiver 8b (Figure 1) are built into the remote control device 8 and are not shown in the user interface. Each component will be further described below.

[0098] The pump operation switch 81 is configured as a toggle switch. By flipping the toggle switch upwards (to the ON position), the mode (flow rate target value CF*) selected by the operator in the mode selection switch 82 described later is transmitted to the pump control device 1. As a result, the pump control device 1 operates the inverter 2 (Figure 1) to control the three-phase induction motor 3 (Figure 1) so that the discharge amount of the grout pump 10 becomes equal to the flow rate target value CF*. On the other hand, by flipping the toggle switch downwards (to the OFF position), an inverter OFF signal is transmitted to the pump control device 1, which de-energizes the inverter 2 (Figure 1) (turns it off). As a result, the three-phase induction motor 3 (Figure 1) is de-energized (turns off), and the grout pump 10 stops.

[0099] The mode selector switch 82 is a rotary switch for the operator to select one of the following modes: A mode, B mode, C mode, and M mode. Modes A, B, and C are preset values ​​for the flow rate target value CF* of the grout pump 10's discharge volume (flow rate measurement value FA). In other words, the A mode flow rate adjustment volume 83, B mode flow rate adjustment volume 84, or C mode flow rate adjustment volume 85 described later have been manually set by the operator and are pre-stored in the remote control device 8 as A mode, B mode, and C mode. This eliminates the need for the operator to reset the flow rate target value CF* by operating the flow rate adjustment volume, as they only need to select a mode. When the pump operation switch 81 is turned ON, the preset value of the selected mode is transmitted to the pump control device 1 as the flow rate target value CF* for the grout pump 10.

[0100] In contrast, the M mode is a construction machine interlocking mode that automatically transmits the flow rate target value CF* corresponding to the automatic operation (autopilot function) of the ground improvement pile construction by the construction management device 7 to the pump control device 1. Therefore, the flow rate target value CF* that is pre-stored in the construction management device 7 is automatically transmitted to the pump control device 1 as the flow rate target value CF*.

[0101] In this embodiment, mode A sets the flow rate target value CF* to 50% of the maximum discharge volume of the grout pump 10. Similarly, mode B sets the flow rate target value CF* to 75% of the maximum discharge volume of the grout pump 10. Similarly, mode C sets the flow rate target value CF* to 90% of the maximum discharge volume of the grout pump 10. mode M sets the flow rate target value CF* to 50% of the maximum discharge volume of the grout pump 10.

[0102] The A-mode flow rate adjustment volume 83, B-mode flow rate adjustment volume 84, and C-mode flow rate adjustment volume 85 are all 5-turn dial switches. In this way, each flow rate adjustment volume decomposes the maximum discharge rate (100%) of the grout pump 10 into 5 rotations (360° x 5), so the resolution of the flow rate value with respect to the rotation angle of the volume is 5 times higher than that of 1 rotation (360°). As a result, fine adjustment of the flow rate target value CF* becomes possible.

[0103] The display unit 87 is composed of liquid crystal or organic EL. It displays the flow rate adjustment range for each mode, the currently selected mode, the discharge volume (flow rate measurement value FA) and discharge pressure (pressure measurement value PA) of the grout pump 10, the remaining battery level, and the radio wave strength.

[0104] As described above, according to the grout pump control system 100 of one embodiment of the present invention, the flow rate target value CF* for the discharge amount of the grout pump 10 is ramp-controlled to a flow rate command value CF that "reaches the flow rate target value CF* from near zero in a predetermined time width Δt", and this is set as the flow rate command value CF in the PID control unit 1d. On the other hand, after the ramp control is completed, the flow rate target value CF* is set as the flow rate command value CF in the PID control unit 1d. As a result, the deviation e between the discharge amount FA of the grout pump 10 and the flow rate command value CF becomes significantly smaller compared to the case without ramp control. As a result, the discharge amount of the grout pump 10 in the initial transient state from the start of control follows the flow rate command value CF favorably and quickly settles to the flow rate target value CF* without causing overshoot or hunting.

[0105] Furthermore, the remote control device 8 according to the present invention is configured to form a computer communication network with the construction management device 7 and the pump control device 1. This makes it possible to automatically transmit the flow rate target value CF* to the pump control device 1, while automatically receiving the flow rate measurement value FA for the discharge amount of the grout pump 10 from the pump control device 1.

[0106] While a grout pump control system 100 according to one embodiment of the present invention has been described with reference to the drawings, the embodiments of the present invention are not limited to those described above. That is, various modifications and changes can be made without departing from the technical features of the present invention.

[0107] For example, the grout pump 10 described above is a plunger-type pump. However, the grout pump 10 is not limited to a plunger-type pump. In other words, any type of pump capable of pumping grout is acceptable. For example, it could be a tube-type pump in which grout is continuously pumped by repeatedly compressing a tube on the inner surface of the case from the inlet (suction port) to the outlet (discharge port) using a rotating body (roller).

[0108] Furthermore, as shown in Figure 10, ramp control may be performed not only at the start of pump operation but also during the PID control of the discharge rate. In this case, the ramp control unit 1c of the pump control device 1 will perform ramp control to a flow rate command value CF that "rises from the previous flow rate target value CF* to the new flow rate target value CF*' over a predetermined time width Δt2." [Explanation of Symbols]

[0109] 1. Pump control device 1a Pump-side antenna 1b Pump-side transceiver 1c Lamp control unit 1d PID control unit 2 Inverters 3. Three-phase induction motor 4 Flowmeter 5 Three-phase AC power supply 7 Construction management device 8 Remote control device 8a antenna 8b Transmitter / Receiver 10 Grout pumps 30 Ground improvement machine 31 Rotary drive device 32. Reader device 33 Hydraulic chuck mechanism 34 Axis clamping mechanism 35 Axis guide mechanism 36 Leader tilting cylinder 37 Body section 38 Crawler device 39 Outrigger 40 counterweights 41 Stirring shaft 42 Stirring device 43 Water swivel mechanism 44 Guide Rod 81 Pump operation switch 82 Mode selector switch 83 A-mode flow rate adjustment volume 84 B-mode flow rate adjustment volume 85 C mode flow rate adjustment volume 87 Display section 100 Grout Pump Control System CF* Flow rate target value CF*' New flow rate target value CF flow rate command value Cf frequency command value (manipulated variable) FA flow rate measurement value (discharge volume) PA pressure measurement value Vf AC voltage

Claims

1. A pump control device (1) controls the discharge amount of a grout pump (10) that discharges a solidifying agent for ground improvement piles, An inverter (2) controls the frequency of the power supply applied to the induction motor (3) that rotates the grout pump (10), A flow meter (4) measures the flow rate of the solidifying agent discharged from the grout pump (10), A construction management device (7) that controls a ground improvement machine (30) that constructs ground improvement piles underground, A grout pump control system comprising a remote control device (8) that transmits a flow rate target value (CF*) for the grout pump (10) to the pump control device (1), The pump control device (1) includes a ramp control unit (1c) that controls the ramp to output a flow rate command value (CF) that "rises from near zero to the flow rate target value (CF*) within a predetermined time width (Δt)", The system includes a PID control unit (1d) that adjusts the proportional gain (Kp), integral gain (Ki), or differential gain (Kd) respectively so that the deviation (e) between the flow command value (CF) and the flow measurement value (FA) measured by the flow meter (4) becomes zero. A grout pump control system characterized by the following features.

2. In the grout pump control system according to claim 1, The lamp control unit (1c) sets the flow rate target value (CF*) as the flow rate command value (CF) to the PID control unit (1d) after the predetermined time width (Δt) has elapsed. A grout pump control system characterized by the following features.

3. In the grout pump control system according to claim 1, The lamp control unit (1c) changes the predetermined time width (Δt) according to the magnitude of the frequency corresponding to the flow rate target value (CF*) in the flow rate-frequency characteristics of the grout pump (10). A grout pump control system characterized by the following features.

4. In the grout pump control system according to claim 1, The remote control device (8) is capable of communicating with both the construction management device (7) and the pump control device (1). A grout pump control system characterized by the following features.

5. In the grout pump control system according to claim 1, The remote control device (8) has multiple manual flow rate adjustment modes (A mode, B mode, C mode) that allow the operator to select and store multiple flow rate target values ​​(CF*) for the discharge volume of the grout pump (10) set by the operator, and transmit the flow rate target value (CF*) selected by the operator to the pump control device (1), and a construction machine interlocking mode (M mode) that allows the flow rate target value (CF*) for the discharge volume of the grout pump (10) stored in the construction management device (7) to be automatically transmitted to the pump control device (1). A grout pump control system characterized by the following features.

6. In the grout pump control system according to claim 1, The remote control device (8) has a display unit (87) that can display the target flow rate value (CF*) for at least the plurality of manual flow rate adjustment modes (A mode, B mode, C mode) and the construction machine interlocking mode (M mode), as well as the currently selected mode and the measured flow rate value (FA). A grout pump control system characterized by the following features.

7. In the grout pump control system according to claim 1, The remote control device (8) has rotary flow rate adjustment potentiometers (83, 84, 85) for the operator to set the flow rate target value (CF*), The rotary flow rate adjustment volume (83, 84, 85) has a resolution that resolves the maximum discharge amount of the grout pump (10) through multiple rotations. A grout pump control system characterized by the following features.

8. In the grout pump control system according to claim 1, If the aforementioned flow rate target value (CF*) is changed to a new flow rate target value (CF*') during discharge rate control, the lamp control unit (1c) controls the lamp to set the new flow rate target value (CF*') to a flow rate command value (CF) that "rises from the previous flow rate target value (CF*) to the new flow rate target value (CF*') over a predetermined time interval (Δt2)" and outputs it to the PID control unit (1d). A grout pump control system characterized by the following features.

Images