Construction machine hoist system and control unit therefor

Abstract

An engineering machinery hoisting system includes: a closed-loop hydraulic system comprising a pump and a motor connected via a closed-loop hydraulic circuit; a hoist driven by the motor to lift or lower a load; a main hoist handle configured to be operable to input hoisting action commands; a braking mechanism configured to lock and release the hoist; and a control unit configured to perform a load holding function in two control phases during the hoist's transition from motion to static state, wherein the first control phase is from the start of the load holding function triggering until the load reaches a static state, and the second control phase is from the start of the load reaching a static state until the braking mechanism closes.

Description

Technical Field

[0001] This application relates to a control scheme for a winch system for engineering machinery such as rotary drilling rigs, for maintaining the load during winch switching between moving and stationary states. Background Technology

[0002] In construction machinery with a winch system, the main winch motor drives the winch to lift and lower the load. The winch system is equipped with a closed hydraulic system containing a closed pump-motor. After the winch completes the lifting or lowering of the load, a braking mechanism is used to close the winch. Due to inherent leakage in the closed hydraulic system, during the braking process, the load drags the winch and motor, causing the load to slowly descend a short distance and resulting in wear on the brake mechanism. On the other hand, before the winch starts lifting or lowering the load from a stationary state, the brake mechanism needs to be opened. However, when the winch is stationary, the pressure at both ends of the motor is relatively low (e.g., approximately 30 bar). During the opening of the brake mechanism, the load also drags the winch and motor, causing the load to slowly descend and resulting in wear on the brake mechanism, while also causing hydraulic vibration on the high-pressure side of the closed hydraulic system.

[0003] In existing technologies, the aforementioned problems during hoisting switching between moving and stationary states can be mitigated by using explosion-proof valves on the high-pressure side of closed hydraulic systems. However, during hoisting switching, leakage still exists at hardware points (such as explosion-proof valves and motors) on the high-pressure side, and there are still issues with load reduction and brake mechanism wear. Summary of the Invention

[0004] The purpose of this application is to provide a control scheme that is executed during the switching between moving and stationary operation of a winch in construction machinery, which can at least partially avoid the problems of load drop and brake mechanism wear during the switching between moving and stationary operation.

[0005] Therefore, this application provides, in one aspect, a control unit for a hoisting system of construction machinery, the hoisting system comprising:

[0006] A closed-loop hydraulic system, which includes a pump and a motor connected via a closed-loop hydraulic circuit;

[0007] A hoist, driven by the motor, lifts or lowers the load;

[0008] The main winch handle is configured to be controlled to input winch action commands;

[0009] A braking mechanism configured to lock and release the winch;

[0010] The control unit is configured to control the operation of the closed hydraulic system and the braking mechanism based on the hoisting action command from the main hoist handle;

[0011] During the switching process of the winch from moving to stationary, the control unit is configured to perform the load holding function in two control phases. The first control phase is from the start of the load holding function triggering until the load reaches a static state, and the second control phase is from the start of the load reaching a static state until the brake mechanism closes.

[0012] In the first control phase, the control unit is configured to:

[0013] Real-time acquisition of the pressure difference across the motor;

[0014] The pump output is controlled by PID based on the real-time pressure difference across the motor, which reduces the motor speed until the load reaches a static state.

[0015] In the second control phase, the control unit is configured to:

[0016] Issue a brake mechanism closing command and simultaneously record the actual pressure difference across the motor or the actual swing angle of the pump at the moment the closing command is issued;

[0017] Based on the actual pressure difference across the motor or the actual swing angle of the pump at the moment the shutdown command is issued, PID control is applied to the pump output to reduce the motor speed to 0.

[0018] After the braking mechanism is closed, the control pump's swing angle returns to the neutral position.

[0019] In one implementation, the control unit is configured to trigger the load holding function when both of the following conditions are met:

[0020] The main hoist handle was returned to the neutral position; and

[0021] The motor speed is equal to or less than the set trigger speed threshold.

[0022] In one implementation, the control unit is configured to determine that the load has reached a static state based on the motor speed being equal to or less than a set static speed threshold.

[0023] In one implementation, during the first control phase, the control unit is configured to: perform PID control on the pump's output pressure based on real-time acquired pressure difference across the motor; and

[0024] In the second control phase, the control unit is configured to: perform PID control on the pump's output pressure based on the actual pressure difference across the motor at the time the shutdown command is issued; or perform PID control on the pump's displacement based on the pump's actual swing angle at the time the shutdown command is issued.

[0025] In one implementation, during the first control phase, performing PID control on the pump's output pressure based on the real-time acquired pressure difference across the motor includes:

[0026] The target pressure difference, obtained by adding the real-time pressure difference across the motor to the PID pressure regulation value calculated based on the motor speed feedforward control, is sent to the pump's pressure control module.

[0027] In one implementation, during the second control phase, performing PID control on the pump's output pressure based on the actual pressure difference across the motor at the moment the shutdown command is issued includes:

[0028] The target pressure difference, obtained by adding the actual pressure difference across the motor at the moment the shutdown command is issued to the PID pressure regulation value calculated based on the motor speed feedforward control, is sent to the pump's pressure control module.

[0029] In one implementation, during the second control phase, performing PID control on the pump's displacement based on the actual pump swing angle at the moment the shutdown command is issued includes:

[0030] The target swing angle, obtained by adding the actual swing angle of the pump at the moment the shutdown command is issued to the PID swing angle adjustment value calculated based on the motor speed feedback, is sent to the pump's displacement control module.

[0031] In one implementation, during the first control phase, the control unit is configured to: perform PID control on the pump's displacement based on real-time acquired pressure differential across the motor; and

[0032] In the second control phase, the control unit is configured to perform PID control on the pump's displacement based on the pump's actual swing angle at the moment the shutdown command is issued.

[0033] In one implementation, during the first control phase, performing PID control on the pump's displacement based on the real-time acquired pressure difference across the motor includes:

[0034] The target pressure difference across the motor is determined by adding the PID pressure regulation value calculated from the real-time acquired pressure difference across the motor speed feedforward control. The leakage of the closed hydraulic system is then sent as the target flow rate to the pump's displacement control module.

[0035] In one implementation, during the second control phase, performing PID control on the pump's displacement based on the actual pump swing angle at the moment the shutdown command is issued includes:

[0036] The target swing angle, obtained by adding the actual swing angle of the pump at the moment the shutdown command is issued to the PID swing angle adjustment value calculated based on the motor speed feedback, is sent to the pump's displacement control module.

[0037] In one embodiment, during the switching process from stationary to moving of the winch, the control unit is configured to:

[0038] The output pressure of the pump is controlled based on the target differential pressure predicted by the load, so that the real-time pressure difference across the motor is within the target differential pressure threshold range.

[0039] Then, a command is issued to open the braking mechanism.

[0040] In one embodiment, during the switching process from stationary to moving of the winch, the control unit is configured to:

[0041] The pump displacement is controlled based on the target differential pressure based on the load estimate, so that the real-time differential pressure across the motor is within the target differential pressure threshold range.

[0042] Then, a command is issued to open the braking mechanism.

[0043] In one implementation, controlling the pump displacement based on the target differential pressure estimated by the load includes:

[0044] The leakage of the closed hydraulic system is determined based on the target pressure difference estimated by the load. The determined leakage of the closed hydraulic system is multiplied by a flow gain coefficient and sent to the pump's displacement control module as the target flow rate.

[0045] In one embodiment, during the switching process from stationary to moving of the winch, the control unit is configured to:

[0046] After issuing the brake mechanism opening command, the determined leakage of the closed hydraulic system is sent as the target flow rate to the pump's displacement control module.

[0047] In another aspect, this application provides a hoisting system for engineering machinery, comprising:

[0048] A closed-loop hydraulic system, which includes a pump and a motor connected via a closed-loop hydraulic circuit;

[0049] A hoist, driven by the motor, lifts or lowers the load;

[0050] The main winch handle is configured to be controlled to input winch action commands;

[0051] A braking mechanism configured to lock and release the winch;

[0052] The control unit of this application is configured to control the operation of the closed hydraulic system and the braking mechanism based on the hoisting action command from the main hoist handle.

[0053] According to this application, in the closed hydraulic system of construction machinery with a hoisting system, during the switching between moving and stationary states of the hoist, leakage in the closed hydraulic system is compensated by preloading the motor and a motor pressure differential required to keep the load stationary is established, thereby reducing or avoiding load drop and wear of the braking mechanism. Attached Figure Description

[0054] The foregoing and other aspects of this application will be more fully understood and appreciated through the following detailed description with reference to the accompanying drawings, in which:

[0055] Figure 1 This is a schematic diagram of an engineering machinery winch system to which the solution of this application is applicable;

[0056] Figure 2 , Figure 3 The control logic and corresponding control flow of an exemplary control scheme executed by the hoisting system according to this application when the brake mechanism is closed are shown respectively.

[0057] Figures 4-8 This is for testing Figure 2 , Figure 3 The graph shows the experimental results of the control scheme shown, where... Figure 4 The curve S1 represents the change in the position signal of the main hoist handle over time. Figure 5 Curve S2 represents the change of the pump's control current over time. Figure 6 Curve S3 represents the change of the motor's control current over time. Figure 7 Curve S4 represents the change of motor speed over time, and curve S5 represents the change of the control signal of the braking mechanism over time. Figure 8 Curve S6 in the diagram represents the change of high-pressure side pressure over time, and curve S7 represents the change of low-pressure side pressure over time.

[0058] Figure 9 , Figure 10 The control logic and corresponding control flow of another exemplary control scheme executed by the hoisting system according to this application when the brake mechanism is closed are shown respectively;

[0059] Figure 11 , Figure 12 The control logic and corresponding control flow of another exemplary control scheme executed by the hoisting system according to this application when the brake mechanism is closed are shown respectively;

[0060] Figure 13 , Figure 14 The control flow of an exemplary control scheme executed by the hoisting system according to this application when the brake mechanism is opened is shown respectively, wherein, Figure 13 The control flow under pressure control mode is shown. Figure 14 The control flow under displacement control mode is shown. Detailed Implementation

[0061] This application generally relates to a control scheme for engineering machinery (such as rotary drilling rigs) with a hoisting system during the switching between moving and stationary hoisting.

[0062] A portion of the hoisting system suitable for engineering machinery employing the scheme of this application, such as Figure 1 This schematic representation shows that the hoisting system is powered by an engine 1, which serves as the power source for the construction machinery. The output of engine 1 is typically connected to a transfer case (not shown), and the outputs of the transfer case distribute the power of engine 1 to the hoisting system and other working devices of the construction machinery.

[0063] The hoisting system includes a closed-loop hydraulic system comprising a closed-loop pump 2 and a motor 3 connected via a closed-loop hydraulic circuit. Both the closed-loop pump 2 and the motor 3 have adjustable swing angles (openings). The closed-loop pump 2 is driven by an engine 1 (e.g., via a transfer case), and the closed-loop pump 2 drives the motor 3 via the closed-loop hydraulic circuit.

[0064] The motor shaft of motor 3 is connected to winch (main winch) 5 via reducer 4. The wire rope 6 on winch 5 is wound around a set of pulleys, with the load 7 at its end. The motor shaft is equipped with a braking mechanism 8. When closed, the braking mechanism 8 locks the motor shaft via brake pads, stopping the rotation of motor 3 and winch 5. When opened, the brake pads release the motor shaft, allowing motor 3 and winch 5 to rotate. It is understood that the braking mechanism 8 can also be located in other parts of the winch system (such as integrated into reducer 4), as long as it enables locking and releasing of winch 5.

[0065] The braking mechanism 8 can be hydraulically driven, for example, driven by a brake hydraulic pump (not shown) driven by the engine 1 via a brake valve. The braking mechanism 8 can also be of other forms, such as electrically driven, electrically-hydraulic combined driven, etc.

[0066] The operating commands for the hoisting system originate from the main hoist handle 9, which can be controlled by an operator. The main hoist handle 9 has a neutral position, a forward maximum position, and a reverse maximum position, and can be moved to these three positions and any position in between. In the neutral position of the main hoist handle 9, the corresponding command signal is that the hoisting system is stationary. In the forward and reverse positions of the main hoist handle 9 (as a ratio of the forward and reverse maximum positions, such as a percentage or per mille), the corresponding command signal is that the hoisting system raises or lowers the load 7 at the corresponding speed.

[0067] The operation of the hoisting system is controlled by the control unit 10. The control unit 10 can be the main controller of the construction machinery, or it can be a control unit specifically equipped for the hoisting system, and it can communicate with the main controller of the construction machinery or be integrated into the main controller of the construction machinery.

[0068] The control unit 10 is configured to receive signals from the main winch handle 9 and to control the operation of the pump 2, motor 3, and brake mechanism 8 (mainly controlling their swing angles). Furthermore, the control unit 10 monitors various sensors in the winch system, including the swing angle sensor of the pump 2, pressure sensors on both sides (high-pressure side and low-pressure side) of the closed hydraulic circuit, the speed sensor of the motor 3, etc., and adjusts the operation of the winch system based on the detection values ​​of these sensors.

[0069] After the hoist 5 completes its lifting or lowering of the load 7, the brake mechanism 8 is used to close the hoist 5. Due to leakage in the closed hydraulic system, especially in the high-pressure side hydraulic circuit, during the closing of the brake mechanism 8, the load 7 applies torque to the hoist 5 and motor 3 via the wire rope 6, tending to drag them to rotate. To minimize the dragging of the hoist 5 and motor 3 by the load 7 during the closing of the brake mechanism 8, this application proposes a control scheme for the process of the hoist system changing from motion to stillness (i.e., the hoist switching from moving to stationary). This control scheme is executed by the control unit 10, which controls the pump 2 to establish the pressure difference required to keep the load 7 stationary across the motor 3 before the brake is closed. This control scheme applicable to the hoist switching from moving to stationary can be implemented in three modes: pressure control mode, displacement control mode, and pressure plus displacement control mode.

[0070] First refer to Figure 2 , Figure 3 This describes the pressure control mode during the hoist's transition from moving to stationary. This pressure control mode is applicable to a closed-loop pump 2 with pressure closed-loop control. This pressure closed-loop control function of the closed-loop pump 2 can be implemented through its built-in pressure control module (whether via hardware or software). This pressure control module... Figure 2 China and Israel M P express.

[0071] This pressure control mode controls the output pressure of pump 2. This pressure control mode includes two control phases: the first control phase is from the start of the load holding function triggering until the load reaches a static state, and the second control phase is from the start of the load reaching a static state until the brake mechanism closes.

[0072] The load holding function is triggered only if the following two conditions are met simultaneously: (a) the main winch handle 9 is operated back to the neutral position, and (b) the speed of motor 3 is equal to or less than the set trigger speed threshold. Since the control unit 10 can directly obtain the detection signal from the speed sensor of motor 3, the motor speed detected by the speed sensor of motor 3 can be used to determine whether the above condition (b) is met.

[0073] With n act This represents the current motor speed (i.e., the actual motor speed), expressed in n.th This indicates the trigger speed threshold. Therefore, when... When the condition is met, it is determined that condition (b) above is satisfied.

[0074] If both conditions (a) and (b) above are met, the load holding function will be triggered; if either condition is not met, the load holding function will not be triggered.

[0075] Similarly, the load can be determined to be static by using the motor speed sensor of motor 3 to detect that the motor speed is equal to or less than the set static speed threshold.

[0076] With n stab Representing the static speed threshold, then, when When the load reaches a static state, it is considered to have reached a static state. At this time, the load has reached a static state, but for the hoisting system, it is actually in a quasi-static state, that is, although the load 7 has stopped moving, the motor 3 has not completely stopped rotating (the speed is already very low).

[0077] Trigger speed threshold n th and static velocity threshold n stab All are preset values ​​(n) th >>n stab For example, the motor speed n when the main hoist handle 9 is operated back to the neutral position can be taken as the value. act A ratio (e.g., 1 / n, n≥3, preferably n≥5) is used as the trigger speed threshold n th Static velocity threshold n stab Set it to a value slightly greater than 0. For example, the static velocity threshold n stab It can be set to approximately 5 rpm.

[0078] Next, let ΔP represent the pressure difference across motor 3. Assume that port A of motor 3 is the high-pressure oil port, port B is the low-pressure oil port, and the pressure at port A is P. A The pressure at port B is P. B Then ΔP = P A -P B .

[0079] After the hoisting system reaches the load holding function trigger condition, in the first control phase, the control unit 10 triggers the load holding function and uses PID (Proportional Integral Derivative) to control the pressure of pump 2, causing the speed of motor 3 to decrease rapidly until it reaches the static speed threshold n. stab The PID input setpoint is motor zero speed, and the PID control feedback signal is the motor speed n. act The control unit 10 obtains the current pressure difference ΔP across the motor 2 in real time from the motor speed sensor, and calculates the PID pressure regulation value PID(n) based on the motor speed feedforward control. act), and to the pressure control module M built into pump 2. P The target pressure difference ΔP of the transmitting motor 3 dem ΔP dem =ΔP+PID(n act ), through pressure control module M P Control the output pressure of pump 2 so that the speed of motor 3 decreases rapidly.

[0080] After the load reaches a static state, the second control phase begins. The control unit 10 issues a braking command, and the braking mechanism 8 begins to perform the braking operation. At the same time, the actual pressure difference ΔP across the motor 3 is recorded when the braking command is issued. brk Next, the control unit 10 regulates the pressure of pump 2 using a PID controller, causing the speed of motor 3 to gradually decrease towards zero, thereby suppressing pressure oscillations on the high-pressure side of the closed hydraulic circuit. The PID input setpoint is the motor speed zero, and the feedback signal for PID control is the motor speed n. act The control unit 10 calculates the PID pressure regulation value PID(n) based on the motor speed feedforward control. act ), and to the pressure control module M built into pump 2. P The target pressure difference ΔP of the transmitting motor 3 dem ΔP dem =ΔP brk +PID(n act ), through pressure control module M P The output pressure of pump 2 is controlled to gradually reduce the speed of motor 3 to 0 and stabilize it at 0. In the second control phase, the pressure difference ΔP across motor 2 is no longer monitored in real time; instead, the actual pressure difference ΔP across motor 3 recorded when the braking command is issued is used. brk This fixed value (which is very close to the pressure difference required to keep the load stationary) reduces the amount of calculation and increases the calculation speed. Furthermore, the speed reduction of motor 3 in the second control stage is much smaller than that in the first control stage (i.e., the amplification factor of the PID proportional controller in the second control stage is smaller than that in the first control stage), which easily suppresses pressure fluctuations in the closed hydraulic system (especially on the high-pressure side).

[0081] The control logic executed by control unit 10 in the first control phase is as follows: Figure 2 The upper part of the diagram schematically represents the control logic executed in the second control phase. Figure 2 The lower half of the diagram is shown schematically. See below for reference. Figure 3 The flowchart in the document describes an exemplary control flow that can be used to implement the pressure control mode. Figure 2 The control logic shown is shown below.

[0082] See Figure 3 In step S11, the control flow is started.

[0083] Next, in step S12, the position of the main winch handle is monitored during the hoisting or lowering operation.

[0084] Next, in step S13, it is determined whether the following two conditions are met simultaneously: the main hoist handle is returned to the neutral position, and the motor speed meets the requirements. If either of these two conditions is not met, the process returns to step S12; if both conditions are met, the process proceeds to step S14.

[0085] In step S14, the pressure difference ΔP across the motor is detected in real time, and the target pressure difference (ΔP) calculated based on the motor speed feedforward control is used. dem =ΔP+PID(n act Send to pressure control module M P .

[0086] Next, in step S15, the actual motor speed n is detected. act .

[0087] Next, in step S16, it is determined whether the motor speed meets the requirements. If the condition is not met, the process returns to step S14; if the condition is met, the process proceeds to step S17.

[0088] In step S17, a brake mechanism closing command is issued, and the actual pressure difference ΔP across the motor at this moment is recorded. brk .

[0089] Next, in step S18, during the braking mechanism closing process, the target pressure difference (ΔP) calculated based on the motor speed feedforward control is applied. dem =ΔP brk +PID(n act Send to pressure control module M P .

[0090] Next, in step S19, after the brake mechanism has closed (possibly with a short delay), the control pump's swing angle returns to the neutral position.

[0091] To verify the actual effectiveness of the pressure control mode, the applicant conducted a specific experiment. The results of one of the experiments are as follows: Figures 4-8 It is displayed in the middle.

[0092] Figures 4-8 In the middle, the horizontal axis represents time.

[0093] exist Figure 4In the middle, the vertical axis represents the position signal of the main hoist handle 9, where 0 represents the neutral position, 1 represents the maximum forward position, and -1 represents the maximum reverse position. Figure 4 The curve S1 represents the change of the position signal of the main hoist handle 9 over time.

[0094] exist Figure 5 In the diagram, the vertical axis represents the control current of pump 2 in the closed hydraulic system. The swing angle of pump 2 is mainly affected by its control current value. Figure 5 The curve S2 represents the change of the control current of pump 2 over time.

[0095] exist Figure 6 In the diagram, the vertical axis represents the control current of motor 3 in the closed hydraulic system. The swing angle of motor 3 depends on its control current value. The smaller the control current value, the larger the motor displacement; the larger the control current value, the smaller the motor displacement. Figure 6 The curve S3 represents the change of the control current of motor 3 over time.

[0096] exist Figure 7 In the diagram, the vertical axis represents the rotational speed of motor 3 and the control signal of braking mechanism 8. Figure 7 Curve S4 in the figure represents the change of motor 3 speed over time, and curve S5 represents the change of control signal of brake mechanism 8 over time.

[0097] exist Figure 8 In the middle, the vertical axis represents the pressure sensor signals on the high and low pressure sides of the closed hydraulic circuit. Figure 8 Curve S6 in the diagram represents the change of pressure on the high-pressure side over time, and curve S7 represents the change of pressure on the low-pressure side over time.

[0098] As can be seen from curve S1, the position signal of the main winch handle 9 is initially -1, indicating that the winch is being lowered. Afterwards, the position signal of the main winch handle 9 switches from -1 to 0, indicating that the operator has pushed the main winch handle back to the neutral position. Then, the position signal of the main winch handle 9 remains at 0.

[0099] As can be seen from curves S2-S7, in response to the position signal of the main winch handle 9 switching from -1 to 0, the control current value of pump 2 decreases, the control current value of motor 3 rapidly decreases to the minimum control current, and the speed of motor 3 and the high-pressure side pressure of the closed hydraulic system both decrease. The control signal of brake mechanism 8 indicates that the brake mechanism is in the open state.

[0100] When the speed of motor 3 decreases to the set trigger speed threshold n th When the speed of motor 3 is reduced to the set static speed threshold n, the first control phase is initiated. stabAfterwards, the first control phase ends, the second control phase begins, and the control signal of the braking mechanism 8 switches to the off state, initiating braking. In the second control phase, the speed of motor 3 decreases to 0, and after a set delay after the speed of motor 3 stabilizes at 0, the control current of pump 2 decreases to 0, causing the swing angle of pump 2 to return to the neutral position, ending the second control phase. Subsequently, the pressure difference across motor 3 decreases to approximately 0, meaning the pressure on both sides of the closed hydraulic circuit is at a substantially equal low pressure (e.g., approximately 30 bar).

[0101] As can be seen from these figures, in the first control stage, the pressure difference across motor 3 is rapidly adjusted using PID control to reduce the speed of motor 3 to a static speed threshold n close to zero. stab In the first control phase, the actual pressure difference across motor 3 fluctuates significantly. In the second control phase, based on the actual pressure difference across motor 3 recorded at the end of the first control phase (no longer monitored in real time), a slower PID adjustment is performed to reduce the speed of motor 3 to 0 and maintain it at 0. Throughout the second control phase, the fluctuation of the actual pressure difference across motor 3 is minimal. In the latter part of the second control phase, the pressure difference required to keep the hoisting system stationary has been established across motor 3. In this state, brake mechanism 8 is closed. After brake mechanism 8 closes, the second control phase ends, the swing angle of pump 2 returns to the neutral position, and the load is kept stationary entirely by brake mechanism 8. Because the hoisting system remains stationary when brake mechanism 8 closes, the slow descent of load 7 and wear on the brake mechanism (especially brake pads) during the brake closure operation are avoided.

[0102] Next, refer to Figure 9 , Figure 10 This describes the displacement control mode during the hoist's transition from moving to stationary. This displacement control mode is applicable to a closed-loop pump 2 with a swing angle closed-loop control function. This swing angle closed-loop control function of the closed-loop pump 2 can be implemented through its built-in displacement (swing angle) control module (whether via hardware or software). This displacement (swing angle) control module... Figure 9 China and Israel M V express.

[0103] This displacement control mode controls the displacement of pump 2. This mode also includes two control phases: the first phase is from the start of the load holding function until the load reaches a static state, and the second phase is from the start of the load reaching a static state until the braking mechanism closes. The definitions of these two control phases can be found in the previous description of the pressure control mode.

[0104] After the hoisting system reaches the load holding function trigger condition, in the first control phase, the control unit 10 triggers the load holding function and uses PID control to control the displacement of pump 2, causing the speed of motor 3 to decrease rapidly until it reaches the static speed threshold n. stab The PID input setpoint is motor zero speed, and the PID control feedback signal is the motor speed n. act The control unit 10 monitors the pressure difference ΔP across the motor 3 in real time and calculates the PID pressure regulation value PID(n) based on the motor speed feedforward control. act ), thereby determining the target pressure difference ΔP dem ΔP dem =ΔP+PID(n act Then, the control unit 10, based on the target pressure difference ΔP, dem Determine the leakage Q of a closed hydraulic system leak Leakage amount Q leak This can be obtained based on testing or experience. Then, the control unit 10 determines the target flow rate Q. dem =Q leak And to the pump 2's built-in displacement (swing angle) control module M V Send target traffic Q dem Through displacement (swing angle) control module M V Control the displacement of pump 2 so that the speed of motor 3 decreases rapidly.

[0105] After the load reaches a static state, the second control phase begins. The control unit 10 issues a braking command, and the braking mechanism 8 begins to perform the braking operation. Simultaneously, the actual swing angle V of the pump 2 at the time the braking command is issued is recorded. gbrk Next, the control unit 10 adjusts the sway angle of pump 2 using a PID controller, causing the speed of motor 3 to gradually change towards zero, thereby suppressing pressure oscillations on the high-pressure side of the closed hydraulic circuit. The PID input setpoint is the motor speed zero, and the feedback signal for PID control is the motor speed n. act The control unit 10 calculates the PID swing angle adjustment value PIDV based on the motor speed feedback. g (n) act ), and to the pump 2's built-in displacement (swing angle) control module M V The target swing angle V of the sending pump 2 gdem V gdem =V gbrk +PIDV g (n) act ), through displacement (swing angle) control module M PThe displacement of pump 2 is controlled so that the speed of motor 3 gradually decreases to 0 and stabilizes at 0. In the second control phase, the pressure difference ΔP across motor 2 or the actual swing angle of pump 2 is no longer monitored in real time; instead, the actual swing angle V of pump 2 recorded when the braking command is issued is used. gbrk This fixed value reduces the amount of computation and increases the computation speed. Furthermore, the speed reduction of motor 3 in the second control stage is much smaller than that in the first control stage, which makes it easier to suppress pressure fluctuations in the closed hydraulic system (especially on the high-pressure side).

[0106] The control logic executed by control unit 10 in the first control phase is as follows: Figure 9 The upper part of the diagram schematically represents the control logic executed in the second control phase. Figure 9 The lower half of the diagram is shown schematically. See below for reference. Figure 10 The flowchart in the document describes an exemplary control flow that can be used to implement the displacement control mode. Figure 9 The control logic shown is shown below.

[0107] See Figure 10 In step S21, the control flow is started.

[0108] Next, in step S22, the position of the main winch handle is monitored during the hoisting or lowering operation.

[0109] Next, in step S23, it is determined whether the following two conditions are met simultaneously: the main hoist handle is returned to the neutral position, and the motor speed meets the requirements. If either of these two conditions is not met, the process returns to step S22; if both conditions are met, the process proceeds to step S24.

[0110] In step S24, the pressure difference ΔP across the motor is detected in real time, and the target pressure difference (ΔP) is calculated based on the motor speed feedforward control. dem =ΔP+PID(n act The leakage Q of the closed hydraulic system under the target pressure differential is obtained. leak , target traffic Q dem =Q leak Send to displacement (swing angle) control module M V .

[0111] Next, in step S25, the actual motor speed n is detected. act .

[0112] Next, in step S26, it is determined whether the motor speed meets the requirements. If the condition is not met, the process returns to step S24; if the condition is met, the process proceeds to step S27.

[0113] In step S27, a brake mechanism closing command is issued, and the actual swing angle V of pump 2 at this moment is recorded. gbrk .

[0114] Next, in step S28, during the braking mechanism closing process, the target swing angle (V) of the pump calculated based on the motor speed feedback is... gdem =V gbrk +PIDV g (n) act Send to displacement (swing angle) control module M V .

[0115] Next, in step S29, after the brake mechanism has closed (possibly with a short delay), the control pump's swing angle returns to the neutral position.

[0116] Similarly, to verify the actual effect of the displacement control mode, the applicant conducted a specific experiment. The experimental results show that similar technical effects to those described earlier for the pressure control mode can be achieved. Furthermore, the pressure fluctuation of the closed-loop hydraulic system exhibited by the displacement control mode in the second control stage is superior to that exhibited by the pressure control mode in the second control stage.

[0117] Next, refer to Figure 11 , Figure 12 This describes the pressure-displacement control mode during the hoist's transition from moving to stationary. This pressure-displacement control mode is applicable to a closed-loop pump 2 with both pressure and swing angle closed-loop control functions. These pressure and swing angle closed-loop control functions of the closed-loop pump 2 can be implemented through its built-in pressure control module (whether hardware or software) and displacement (swing angle) control module (whether hardware or software). Figure 11 In this pressure control module, M P This indicates that the displacement (sway angle) control module uses M V express.

[0118] This pressure-displacement control mode controls the pressure and displacement of pump 2 in two separate control phases: the first control phase is from the start of the load holding function triggering until the load reaches a static state, and the second control phase is from the start of the load reaching a static state until the brake mechanism closes. The definitions of the two control phases can be found in the previous description of the pressure control mode.

[0119] After the hoisting system reaches the load holding function trigger condition, in the first control phase, the control unit 10 triggers the load holding function and uses PID control to control the pressure of pump 2, causing the speed of motor 3 to decrease rapidly until it reaches the static speed threshold n. stabThe PID input setpoint is motor zero speed, and the PID control feedback signal is the motor speed n. act The control unit 10 monitors the pressure difference ΔP across the motor 3 in real time and calculates the PID pressure regulation value PID(n) based on the motor speed feedforward control. act ), to the pressure control module M built into pump 2 P The target pressure difference ΔP of the transmitting motor 3 dem ΔP dem =ΔP+PID(n act ), through pressure control module M P Control the output pressure of pump 2 so that the speed of motor 3 decreases rapidly.

[0120] After the load reaches a static state, the second control phase begins. The control unit 10 issues a braking command, and the braking mechanism 8 begins to perform the braking operation. Simultaneously, the actual swing angle V of the pump 2 at the time the braking command is issued is recorded. gbrk Next, the control unit 10 adjusts the sway angle of pump 2 using a PID controller, causing the speed of motor 3 to gradually change towards zero, thereby suppressing pressure oscillations on the high-pressure side of the closed hydraulic circuit. The PID input setpoint is the motor speed zero, and the feedback signal for PID control is the motor speed n. act The control unit 10 calculates the PID swing angle adjustment value PIDV based on the motor speed feedback. g (n) act ), and to the pump 2's built-in displacement (swing angle) control module M V The target swing angle V of the sending pump 2 gdem V gdem =V gbrk +PIDV g (n) act ), through displacement (swing angle) control module M V The displacement of pump 2 is controlled so that the speed of motor 3 gradually decreases to 0 and stabilizes at 0. In the second control phase, the pressure difference ΔP across motor 2 or the actual swing angle of pump 2 is no longer monitored in real time; instead, the actual swing angle V of pump 2 recorded when the braking command is issued is used. gbrk This fixed value reduces the amount of computation and increases the computation speed. Furthermore, the speed reduction of motor 3 in the second control stage is much smaller than that in the first control stage, which makes it easier to suppress pressure fluctuations in the closed hydraulic system (especially on the high-pressure side).

[0121] The control logic executed by control unit 10 in the first control phase is as follows: Figure 11 The upper part of the diagram schematically represents the control logic executed in the second control phase. Figure 11 The lower half of the diagram is shown schematically. See below for reference. Figure 12The flowchart in the document describes an exemplary control flow that can be used to implement the displacement control mode. Figure 11 The control logic shown is shown below.

[0122] See Figure 12 In step S31, the control flow is started.

[0123] Next, in step S32, the position of the main winch handle is monitored during the hoisting or lowering operation.

[0124] Next, in step S33, it is determined whether the following two conditions are met simultaneously: the main hoist handle is returned to the neutral position, and the motor speed meets the requirements. If either of these two conditions is not met, the process returns to step S32; if both conditions are met, the process proceeds to step S34.

[0125] In step S34, the pressure difference ΔP across the motor is detected in real time, and the target pressure difference (ΔP) calculated based on the motor speed feedforward control is used. dem =ΔP+PID(n act Send to pressure control module M P .

[0126] Next, in step S35, the actual motor speed n is detected. act .

[0127] Next, in step S36, it is determined whether the motor speed meets the requirements. If the condition is not met, the process returns to step S34; if the condition is met, the process proceeds to step S37.

[0128] In step S37, a brake mechanism closing command is issued, and the actual swing angle V of pump 2 at this moment is recorded. gbrk .

[0129] Next, in step S38, during the braking mechanism closing process, the target swing angle (V) of the pump calculated based on the motor speed feedback is... gdem =V gbrk +PIDV g (n) act Send to displacement (swing angle) control module M V .

[0130] Next, in step S39, after the brake mechanism has closed (possibly with a short delay), the control pump's swing angle returns to the neutral position.

[0131] Similarly, to verify the actual effect of the pressure plus displacement control mode, the applicant conducted a specific experiment. The experimental results show that similar technical effects to those described above for the pressure control mode can be achieved. Furthermore, the pressure fluctuation of the closed-loop hydraulic system exhibited by the pressure plus displacement control mode in the second control stage is superior to that exhibited by the pressure control mode in the second control stage.

[0132] In summary, in the control scheme described above for the switching process of the winch from moving to stationary, any one of the control modes—pressure control mode, displacement control mode, or pressure plus displacement control mode—can establish the pressure difference required to keep the load 7 stationary across the motor 3 by controlling the pump 2, thus preventing the load 7 from slowly decreasing and the brake mechanism (especially the brake pads) from wearing out. Simultaneously, it can maintain the pressure stability of the closed hydraulic system when the brake is closed, avoiding pressure fluctuations in the closed hydraulic system (especially on the high-pressure side).

[0133] Next, the control scheme of this application also focuses on the process of the hoisting system changing from static to dynamic (i.e., the hoisting switching process from static to dynamic). Specifically, when the brake mechanism 8 is in the closed state, the hoisting system is in a static state. If the hoisting system is to perform the action of lifting or lowering the load 7 at this time, the brake mechanism 8 needs to be opened first. When the brake mechanism 8 is in the closed state, the pressure at both ends of the motor 3 is at a low pressure (e.g., about 30 bar). If the brake mechanism 8 is opened without taking measures to establish a differential pressure at both ends of the motor 3, the load 7 will act on the hoisting 5 and the motor 3 through the wire rope 6, causing the pressure at the high-pressure port of the motor 3 to increase sharply. At this time, the high pressure will cause the closed hydraulic system to leak on the high-pressure side. The hoisting 5 and the motor 3 will be dragged down slowly by the load 7, and the brake mechanism 8 (especially the brake pads) will wear. It will also cause the driver to feel a sudden vibration when the brake is opened. At the same time, it will also cause pressure oscillation in the closed hydraulic system (especially the high-pressure side). To avoid this problem, this application further proposes a control scheme for the process of a hoisting system changing from a stationary state to a moving state (i.e., the hoisting switching process from stationary to moving). This control scheme is executed by the control unit 10, which controls the pump 2 to establish the pressure difference required to keep the load 7 stationary across the motor 3 before the brake mechanism is opened. This control scheme applicable to the hoisting switching process from stationary to moving can be implemented in two modes: pressure control mode and displacement control mode.

[0134] First, the pressure control mode during the hoist's transition from stationary to moving state is described. This pressure control mode is applicable to the closed-loop pump 2, which has a pressure closed-loop control function. This pressure closed-loop control function of the closed-loop pump 2 can be implemented through its built-in pressure control module (whether through hardware or software).

[0135] In this pressure control mode, the pressure difference required to be established across motor 3 to keep load 7 stationary is determined, i.e., the target pressure difference ΔP. dem Target pressure difference ΔP dem It can be roughly calculated (estimated) based mainly on the size of the load 7, the transmission ratio of the reducer 4, the pressure-torque relationship of the motor 3, etc., or determined by the recorded values ​​of the previous working cycle, or it can also be determined by experience.

[0136] In this pressure control mode, the following parameters need to be set:

[0137] ΔP thl Target differential pressure lower limit parameter;

[0138] ΔP thu Target differential pressure upper limit parameter;

[0139] t brk Braking mechanism response time;

[0140] t Joy Anti-rebound time used to determine whether the main winch handle has actually been operated;

[0141] t pre : The anti-rebound time used to determine whether the required differential pressure has been reached.

[0142] All of the above parameters are variable parameters.

[0143] The core of the pressure control mode during the hoist's transition from stationary to moving state lies in: before the brake mechanism 8 opens, by controlling the output pressure of pump 2, establishing the necessary pressure difference across motor 3 to keep load 7 stationary. The following section combines... Figure 13 This paper introduces an exemplary control process for implementing pressure control mode during the switching process of a hoist from stationary to moving.

[0144] like Figure 13 As shown, in step S41, the control flow is started.

[0145] Next, in step S42, the position of the main winch handle is monitored while the winch system is in standby mode.

[0146] Next, in step S43, it is determined whether the main hoist handle has been manipulated away from the neutral position; if it is determined that the handle has not been manipulated away from the neutral position, the process returns to step S42; if it is determined that the handle has been manipulated away from the neutral position, the process proceeds to step S44. It should be noted that in step S43, after receiving the signal that the main hoist handle has left the neutral position, the process can proceed after a waiting anti-bounce time t. Joy After confirming that the main winch handle had not returned to the center position, it was determined that the handle had indeed been manipulated away from the center position.

[0147] In step S44, the target pressure difference ΔP based on the load forecast is... dem The pressure is sent to the pump's pressure control module to perform the load holding function.

[0148] Next, in step S45, the actual pressure difference ΔP across the motor is detected.

[0149] Next, in step S46, it is determined whether the actual pressure difference ΔP across the motor is within the target pressure difference threshold range, i.e., whether it meets the ΔP threshold. dem -ΔP thl ≤ΔP≤ΔP dem +ΔP thu (That is, the target differential pressure threshold range is (ΔP) dem -ΔP thl ) to (ΔP dem +ΔP thu If this condition is not met, the process returns to step S44; if this condition is met, the process waits for the anti-rebound time t. pre The process then proceeds to step S47.

[0150] In step S47, a command to open the brake mechanism is issued.

[0151] Next, in step S48, wait for the braking mechanism response time t. brk Then, the load holding function is released, allowing the pump to perform the corresponding functions in the hoisting or lowering operation.

[0152] Based on the pressure control mode during the hoist's transition from stationary to moving state, before the brake mechanism opens, the load holding function is performed by controlling the pressure of pump 2, thereby establishing the pressure difference across motor 3 required to keep load 7 stationary before the brake mechanism opens. The established pressure difference can be within a preset range (ΔP). dem -ΔP thl ≤ΔP≤ΔP dem +ΔP thu This prevents the load 7 from moving up or down during the brake mechanism's opening action, thus avoiding wear on the brake mechanism (especially the brake pads).

[0153] The following describes the displacement control mode during the hoist's transition from stationary to moving state. This displacement control mode is applicable to the closed-loop pump 2, which has a displacement (swing angle) closed-loop control function. This displacement (swing angle) closed-loop control function of the closed-loop pump 2 can be implemented through its built-in displacement (swing angle) control module (whether through hardware or software).

[0154] In this displacement control mode, the pressure difference required to be established across motor 3 to keep load 7 stationary is determined, i.e., the target pressure difference ΔP. dem Target pressure difference ΔP demIt can be roughly calculated (estimated) based mainly on the size of the load 7, the transmission ratio of the reducer 4, the pressure-torque relationship of the motor 3, etc., or determined by the recorded values ​​of the previous working cycle, or it can also be determined by experience.

[0155] In this displacement control mode, in addition to setting the previously described parameter ΔP, it is also necessary to... thl ΔP thu t brk t Joy t pre The following parameters also need to be set:

[0156] k pbld The flow gain coefficient required for pressure buildup affects the pressure buildup rate and is a variable parameter with a value ≥1.

[0157] The core of the displacement control mode during the hoist's transition from stationary to moving state lies in: before the brake mechanism 8 is opened, by controlling the displacement (swing angle) of pump 2, the necessary pressure difference to keep the load 7 stationary is first established across motor 3. The following section combines... Figure 14 This paper introduces an exemplary control process for implementing displacement control mode during the switching process of a hoist from stationary to moving.

[0158] like Figure 13 As shown, in step S51, the control flow is started.

[0159] Next, in step S52, the position of the main winch handle is monitored while the winch system is in standby mode.

[0160] Next, in step S53, it is determined whether the main hoist handle has been manipulated away from the neutral position; if it is determined that the handle has not been manipulated away from the neutral position, the process returns to step S52; if it is determined that the handle has been manipulated away from the neutral position, the process proceeds to step S54. It should be noted that in step S53, after receiving the signal that the main hoist handle has left the neutral position, the process can proceed after a waiting anti-bounce time t. Joy After confirming that the main winch handle had not returned to the center position, it was determined that the handle had indeed been manipulated away from the center position.

[0161] In step S54, based on the target pressure difference ΔP estimated by the load... dem The leakage Q of the closed hydraulic system under the target pressure differential is obtained. leak , target traffic Q dem =k pbld ×Q leak The displacement (swing angle) control module of the pump is sent to perform the load holding function.

[0162] Next, in step S55, the actual pressure difference ΔP across the motor is detected.

[0163] Next, in step S56, it is determined whether ΔP is satisfied. dem -ΔP thl ≤ΔP≤ΔP dem +ΔP thu If this condition is not met, the process returns to step S54; if this condition is met, the process waits for the anti-rebound time t. pre The process then proceeds to step S57.

[0164] In step S57, a brake mechanism opening command is issued, and the target flow rate Q is... dem = Q leak The displacement (swing angle) control module of the pump is sent.

[0165] Next, in step S58, wait for the braking mechanism response time t. brk Then, the load holding function is released, allowing the pump to perform the corresponding functions in the hoisting or lowering operation.

[0166] The various control modes in the control scheme applicable to the hoisting switching process from moving to stationary can be combined with the various control modes in the control scheme applicable to the hoisting switching process from stationary to moving in the same hoisting control scheme, and can be executed by the control unit 10.

[0167] It is understandable that, for specific application scenarios, the steps in the various exemplary processes described above can be adapted.

[0168] According to this application, when the winch switches from moving to stationary and from stationary to moving, before the brake mechanism is operated, the pump of the closed hydraulic system of the winch system is controlled to establish the pressure difference required to keep the load stationary at both ends of the motor of the closed hydraulic system, thereby compensating for leakage in the closed hydraulic system and reducing or avoiding load drop and brake mechanism wear.

[0169] While this application has been described herein with reference to specific embodiments, the scope of this application is not limited to the details shown. Various modifications may be made to these details without departing from the basic principles of this application.

Claims

1. A control unit for a hoist system of a working machine, characterized in that, The engineering machinery hoisting system includes: A closed hydraulic system, comprising a pump (2) and a motor (3) connected via a closed hydraulic circuit. The hoist (5) is driven by the motor (3) to lift or lower the load (7); The main winch handle (9) is configured to be controlled to input winch action commands; Braking mechanism (8), configured to lock and release the winch (5); The control unit is configured to control the operation of the closed hydraulic system and the brake mechanism (8) based on the hoisting action command from the main hoist handle (9); During the switching process of the hoist (5) from moving to static, the control unit is configured to perform the load holding function in two control phases, wherein the first control phase is from the start of the load holding function triggering to the load reaching static, and the second control phase is from the start of the load reaching static to the completion of the brake mechanism closing action; In the first control phase, the control unit is configured to: Real-time acquisition of the pressure difference across the motor; The pump output is controlled by PID based on the real-time pressure difference across the motor, which reduces the motor speed until the load reaches a static state. In the second control phase, the control unit is configured to: Issue a brake mechanism closing command and simultaneously record the actual pressure difference across the motor or the actual swing angle of the pump at the moment the closing command is issued; Based on the actual pressure difference across the motor or the actual swing angle of the pump at the moment the shutdown command is issued, PID control is applied to the pump output to reduce the motor speed to 0. After the braking mechanism is closed, the control pump's swing angle returns to the neutral position.

2. The control unit as claimed in claim 1, wherein, The control unit is configured to trigger the load holding function when both of the following conditions are met: The main hoist handle (9) is operated back to the neutral position; and The rotational speed of the motor (3) is equal to or less than the set trigger speed threshold.

3. The control unit as described in claim 1 or 2, wherein, The control unit is configured to determine when the load reaches a static state based on the motor speed being equal to or less than a set static speed threshold.

4. The control unit as claimed in claim 1 or 2, wherein, In the first control phase, the control unit is configured to: perform PID control on the pump's output pressure based on the real-time acquired pressure difference across the motor; and In the second control phase, the control unit is configured to: perform PID control on the pump's output pressure based on the actual pressure difference across the motor at the time the shutdown command is issued; or perform PID control on the pump's displacement based on the pump's actual swing angle at the time the shutdown command is issued.

5. The control unit as claimed in claim 4, wherein, In the first control phase, the PID control of the pump's output pressure based on the real-time acquired pressure difference across the motor includes: The target pressure difference, obtained by adding the real-time pressure difference across the motor to the PID pressure regulation value calculated based on the motor speed feedforward control, is sent to the pump's pressure control module.

6. The control unit as claimed in claim 4, wherein, In the second control phase, PID control of the pump's output pressure based on the actual pressure difference across the motor at the moment the shutdown command is issued includes: The target pressure difference, obtained by adding the actual pressure difference across the motor at the moment the shutdown command is issued to the PID pressure regulation value calculated based on the motor speed feedforward control, is sent to the pump's pressure control module.

7. The control unit as claimed in claim 4, wherein, In the second control phase, PID control of the pump's displacement is performed based on the actual pump swing angle at the moment the shutdown command is issued, including: The target swing angle, obtained by adding the actual swing angle of the pump at the moment the shutdown command is issued to the PID swing angle adjustment value calculated based on the motor speed feedback, is sent to the pump's displacement control module.

8. The control unit as claimed in claim 1 or 2, wherein, In the first control phase, the control unit is configured to: perform PID control on the pump's displacement based on the real-time acquired pressure difference across the motor; and In the second control phase, the control unit is configured to perform PID control on the pump's displacement based on the actual pump swing angle at the moment the shutdown command is issued.

9. The control unit as claimed in claim 8, wherein, In the first control phase, PID control of the pump's displacement based on the real-time acquired pressure difference across the motor includes: The target pressure difference across the motor is determined by adding the PID pressure regulation value calculated from the real-time acquired pressure difference across the motor speed feedforward control. The leakage of the closed hydraulic system is then sent as the target flow rate to the pump's displacement control module.

10. The control unit as claimed in claim 8, wherein, In the second control phase, PID control of the pump's displacement is performed based on the actual pump swing angle at the moment the shutdown command is issued, including: The target swing angle, obtained by adding the actual swing angle of the pump at the moment the shutdown command is issued to the PID swing angle adjustment value calculated based on the motor speed feedback, is sent to the pump's displacement control module.

11. The control unit as claimed in claim 1 or 2, wherein, During the switching process of the hoist (5) from stationary to moving, the control unit is configured to: The output pressure of the pump is controlled based on the target differential pressure predicted by the load, so that the real-time pressure difference across the motor is within the target differential pressure threshold range. Then, a command is issued to open the braking mechanism.

12. The control unit as claimed in claim 1 or 2, wherein, During the switching process of the hoist (5) from stationary to moving, the control unit is configured to: The pump displacement is controlled based on the target differential pressure based on the load estimate, so that the real-time differential pressure across the motor is within the target differential pressure threshold range. Then, a command is issued to open the braking mechanism.

13. The control unit as claimed in claim 12, wherein, The target differential pressure control pump displacement based on load forecasting includes: The leakage of the closed hydraulic system is determined based on the target pressure difference estimated by the load. The determined leakage of the closed hydraulic system is multiplied by a flow gain coefficient and sent to the pump's displacement control module as the target flow rate.

14. The control unit as claimed in claim 13, wherein, During the switching process of the hoist (5) from stationary to moving, the control unit is configured to: After issuing the brake mechanism opening command, the determined leakage of the closed hydraulic system is sent as the target flow rate to the pump's displacement control module.

15. A hoisting system for engineering machinery, characterized in that, include: A closed hydraulic system, comprising a pump (2) and a motor (3) connected via a closed hydraulic circuit. The hoist (5) is driven by the motor (3) to lift or lower the load (7); The main winch handle (9) is configured to be controlled to input winch action commands; Braking mechanism (8), configured to lock and release the winch (5); and The control unit as described in any one of claims 1 to 14.

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