A hydraulic power tong fluid excess pressure recovery control system and method thereof

Abstract

The application provides a hydraulic power tong fluid residual pressure recovery control system and method, relates to the technical field of recovery control, and realizes real-time collection and comparison of initial pressure values of pressure relief of clamping cylinders and motor brake return oil pressure values, preferential on-off control of a recovery control valve group, continuous monitoring of real-time rising gas back pressure values in an accumulator, calculation of available recovery time windows of the accumulator, accounting of effective releasable hydraulic energy actually stored in the accumulator through actual safe recovery cutoff pressure values and back pressure influence data, supply-demand difference calculation in combination with hydraulic pump initial output pressure values at the start of the next cycle, acquisition of an auxiliary energy compensation start pressure threshold, and advanced control of the opening time of an energy supply valve at the accumulator outlet, so as to obtain actual effective output power utilization rate values of the hydraulic pump after insufficient compensation recovery, and the application can recover multiple residual pressure sources in a systematic way and take into account operation safety and rhythm.

Description

Technical Field

[0001] This invention proposes a fluid residual pressure recovery control system and method for hydraulic power clamps, which relates to the field of recovery control technology, specifically to the field of fluid residual pressure recovery control technology for hydraulic power clamps. Background Technology

[0002] Hydraulic power tongs are key equipment used for threading and unthreading tubing in oilfield workover operations. Their clamping cylinder and rotary motor frequently undergo high-pressure clamping and depressurization, high-speed rotation, and braking / reversing operations. In existing hydraulic systems, when the clamping cylinder depressurizes after clamping, the high-pressure oil typically flows directly back to the tank via the reversing valve, with the pressure energy completely converted into heat energy and dissipated. Simultaneously, during braking or reversing, the high-pressure oil generated on the return side of the hydraulic motor also flows directly back to the tank, resulting in a significant waste of hydraulic energy. The pressure energy lost during these depressurization and braking processes accounts for a considerable proportion of the system's total input energy, leading not only to low energy utilization but also to a continuous increase in oil temperature, accelerating seal aging and shortening the lifespan of hydraulic components. Some existing solutions use accumulators to recover residual pressure from a single source, but these are insufficient to simultaneously address the residual pressure recovery needs under both clamping cylinder depressurization and motor braking conditions. Furthermore, the back pressure generated during accumulator recovery can interfere with the clamping force of the clamping cylinder, posing a safety risk of tubing slippage. Summary of the Invention

[0003] This invention provides a fluid residual pressure recovery control system and method for hydraulic power clamps, to solve the above-mentioned problems: This invention proposes a fluid residual pressure recovery control system and method for hydraulic power clamps, the method comprising: S1. By real-time acquisition and comparison of the initial pressure value of the clamping cylinder and the return oil pressure value of the motor brake, the priority level of the current residual pressure source is obtained, and the recovery control valve group is preferentially controlled to obtain the initial accumulator charging pressure value. S2. By continuously monitoring the real-time rising gas back pressure value in the accumulator and dynamically comparing it with the current actual clamping and maintaining pressure value of the clamping cylinder, the equivalent pressure value of the reverse thrust generated by the back pressure on the piston of the clamping cylinder is obtained, and the proportional throttle valve is adjusted by narrowing the opening to obtain the corrected actual effective recovery pressure rise slope value of the accumulator. S3. By using the pressure rise slope value and the initial accumulator filling pressure value, the available recovery time window of the accumulator is calculated and matched with the maximum allowable release delay time of the clamping cylinder to obtain the actual safe recovery cutoff pressure value. The recovery control valve group is then switched in stages to obtain the actual release action completion time value that meets the operation cycle requirements. S4. By using the actual safe recovery cutoff pressure value and back pressure impact data, calculate the effective releaseable hydraulic energy actually stored in the accumulator, and calculate the supply and demand difference by combining the initial output pressure value of the hydraulic pump when starting the next cycle, obtain the auxiliary energy replenishment starting pressure threshold, and advance the opening timing of the accumulator outlet energy supply valve to obtain the actual effective output power utilization rate value of the hydraulic pump after insufficient compensation and recovery.

[0004] Furthermore, the system includes: The conduction control module is used to obtain the priority level of the current residual pressure source by real-time acquisition and comparison of the initial pressure value of the clamping cylinder and the return oil pressure value of the motor brake, and to perform priority conduction control on the recovery control valve group to obtain the initial accumulator charging pressure value. The dynamic comparison module is used to continuously monitor the real-time rising gas back pressure value in the accumulator and dynamically compare it with the current actual clamping and maintaining pressure value of the clamping cylinder to obtain the equivalent pressure value of the reverse thrust generated by the back pressure on the piston of the clamping cylinder, and to adjust the proportional throttle valve to obtain the corrected actual effective recovery pressure rise slope value of the accumulator. The comparison control module is used to calculate the available recovery time window of the accumulator by using the pressure rise slope value and the initial accumulator filling pressure value, and to match and compare it with the maximum allowable release delay time of the clamping cylinder to obtain the actual safe recovery cutoff pressure value. It also performs graded switching control of the recovery control valve group to obtain the actual release action completion time value that meets the operation cycle requirements. The calculation and control module is used to calculate the effective releaseable hydraulic energy actually stored in the accumulator by using the actual safe recovery cutoff pressure value and back pressure influence data. It also calculates the supply and demand difference by combining the initial output pressure value of the hydraulic pump at the start of the next cycle, obtains the auxiliary energy replenishment starting pressure threshold, and controls the opening timing of the accumulator outlet energy supply valve in advance to obtain the actual effective output power utilization rate value of the hydraulic pump after insufficient compensation and recovery.

[0005] The beneficial effects of this invention are as follows: This invention solves a series of problems such as competition for recovery channels when two residual pressure sources occur simultaneously, dynamic interference of accumulator back pressure on clamping force, timing conflicts between recovery actions and actuator release actions, and ineffective reuse of recovered energy; it achieves automatic identification and priority recovery of residual pressure sources, real-time tracking and adjustment of recovery flow rate to clamping safety status, dynamic matching of recovery time window and allowable delay time, and early release of recovered energy during standby phase; it avoids energy loss caused by incorrect channel allocation, the risk of tubing slippage due to excessive back pressure, delays in operation cycle due to excessive recovery, and system pressure fluctuations due to improper timing of energy replenishment; it improves the effectiveness of energy recovery selection, the safety of the recovery process, the system's adaptability to changing operating conditions, and the overall energy utilization efficiency. Attached Figure Description

[0006] Figure 1 This is a schematic diagram of a fluid residual pressure recovery control method for a hydraulic power clamp. Detailed Implementation

[0007] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0008] In one embodiment of the present invention, a fluid residual pressure recovery control system and method for hydraulic power clamps are provided, the method comprising: S1. By real-time acquisition and comparison of the initial pressure value of the clamping cylinder and the return oil pressure value of the motor brake, the priority level of the current residual pressure source is obtained, and the recovery control valve group is preferentially controlled to obtain the initial accumulator charging pressure value. S2. By continuously monitoring the real-time rising gas back pressure value in the accumulator and dynamically comparing it with the current actual clamping and maintaining pressure value of the clamping cylinder, the equivalent pressure value of the reverse thrust generated by the back pressure on the piston of the clamping cylinder is obtained, and the proportional throttle valve is adjusted by narrowing the opening to obtain the corrected actual effective recovery pressure rise slope value of the accumulator. S3. By using the pressure rise slope value and the initial accumulator filling pressure value, the available recovery time window of the accumulator is calculated and matched with the maximum allowable release delay time of the clamping cylinder to obtain the actual safe recovery cutoff pressure value. The recovery control valve group is then switched in stages to obtain the actual release action completion time value that meets the operation cycle requirements. S4. By analyzing the actual safe recovery cutoff pressure and back pressure impact data, the effective releaseable hydraulic energy actually stored in the accumulator is calculated. Combined with the initial output pressure of the hydraulic pump at the start of the next cycle, the supply-demand difference is calculated to obtain the auxiliary energy replenishment starting pressure threshold. Furthermore, the opening timing of the accumulator outlet energy supply valve is advanced to obtain the actual effective output power utilization rate of the hydraulic pump after insufficient recovery compensation. Figure 1 As shown.

[0009] The initial pressure value of the clamping cylinder refers specifically to the actual oil pressure value in the rodless chamber of the clamping cylinder at the instant the clamping cylinder on the main clamp of the hydraulic power clamp completes the clamping or unclamping operation and the solenoid directional valve switches to the neutral or pressure relief position to begin pressure relief. The value range is usually 60% to 90% of the nominal system pressure. For example, when the nominal system pressure is 25 MPa, the initial pressure value is usually in the range of 15 to 22.5 MPa.

[0010] The motor braking return oil pressure value specifically refers to the high-pressure oil pressure value generated by the return oil circuit due to the motor inertia and load inertia when the hydraulic motor driving the main clamp needs to stop rotating or change the direction of rotation. This pressure value can reach 50% to 80% of the system's nominal pressure at the moment of braking.

[0011] The priority level of the residual pressure source refers to the controller's comparison of the initial pressure values ​​of the clamping cylinder and the motor braking action when they occur simultaneously or almost simultaneously. The controller determines the side with the higher pressure value as the priority recovery target, while the other side waits for the high-pressure side to finish recovering or directly releases pressure through the auxiliary relief valve.

[0012] The recovery control valve group is an integrated valve block consisting of one or more solenoid directional valves and proportional throttle valves. Its oil inlet is connected to the rodless chamber oil circuit of the clamping cylinder and the return oil circuit of the motor, respectively, and its oil outlet is connected to the accumulator and the oil tank, respectively. The solenoid directional valve is used to switch the oil flow direction, and the proportional throttle valve is used to adjust the recovery flow rate.

[0013] The initial accumulator filling pressure refers to the stable pressure value measured at the accumulator port when the high-pressure oil first flows into the accumulator through the recovery branch, compressing the gas inside the accumulator (usually nitrogen) to reduce the gas volume and increase the pressure, and the gas pressure inside the accumulator reaches equilibrium with the pressure of the flowing oil.

[0014] The real-time rising gas back pressure value inside the accumulator refers to the gas back pressure value, which is the value that rises non-linearly as the recovered oil is continuously injected into the accumulator and the pre-charged gas inside the accumulator is continuously compressed. The rate of increase is related to the inflow rate and the volume of the accumulator.

[0015] The equivalent pressure value of reverse thrust refers to the equivalent hydraulic pressure value converted from the reverse force generated by the accumulator back pressure on the clamping cylinder piston. This value is equal to the current back pressure value of the accumulator multiplied by the ratio of the accumulator port area to the clamping cylinder piston area. For example, when the accumulator back pressure is 10 MPa, the accumulator port area is 50 square centimeters, and the clamping cylinder piston area is 200 square centimeters, the equivalent pressure value is 10 multiplied by 50 divided by 200 equals 2.5 MPa.

[0016] A proportional throttle valve is a flow control valve in which the valve core opening can change continuously and linearly with the magnitude of the input electrical signal. Its valve port flow area is determined by the displacement of the valve core driven by an electromagnet. When the input current changes from four milliamps to twenty milliamps, the valve port opening changes continuously from fully closed to fully open.

[0017] Narrowing regulation refers to dynamically reducing or increasing the flow area of ​​the proportional throttle valve based on the real-time calculated equivalent pressure value of the reverse thrust during the recovery process. When the equivalent pressure value increases, the flow area is reduced to limit the flow rate and reduce the rate of back pressure rise. When the equivalent pressure value decreases, the flow area is increased to increase the flow rate and improve the recovery speed.

[0018] The pressure rise slope value refers to the increase in gas pressure inside the accumulator per unit time. The calculation formula is the accumulator inlet flow rate divided by the effective volume of the accumulator gas chamber and then multiplied by the reciprocal of the gas bulk elastic modulus. The unit is megapascals per second. For example, when the flow rate is 5 liters per minute, the accumulator volume is 10 liters, and the pressure rise rate is 0.5 megapascals per minute, the slope value is 0.0083 megapascals per second.

[0019] The available recovery time window for an accumulator refers to the theoretically longest time required for the accumulator to rise from the current pressure to the maximum allowable working pressure, starting from the initial filling pressure and ending at the accumulator's maximum allowable working pressure, at the currently measured pressure rise slope. For example, if the initial pressure is 8 MPa, the maximum allowable working pressure is 20 MPa, and the rise slope is 2 MPa per minute, the time window is (20 minus 8) divided by 2, which equals 6 minutes.

[0020] The maximum allowable release delay time of the clamping cylinder refers to the longest time allowed by the operation process from when the controller issues the release command until the clamping cylinder is completely released and no longer in contact with the tube string surface. For example, if the single up-and-down cycle is ten seconds, the clamping cylinder action must be completed within this time to ensure timely alignment of the next tube string.

[0021] The actual safe recovery cutoff pressure value refers to the highest actual pressure value that the accumulator pressure is allowed to rise to under the conditions of taking into account both energy recovery efficiency and clamping cylinder release time constraints. This value is less than or equal to the accumulator's maximum allowable working pressure, and its selection is based on the comparison between the available recovery time window and the maximum release delay time.

[0022] The graded switching control refers to a two-stage control mode in which the solenoid directional valve in the recovery control valve group switches from the recovery position to the pressure relief position based on the comparison between the current pressure of the accumulator and the cutoff pressure value. When the pressure has not reached the cutoff value, the recovery position is maintained and the pressure relief position is switched when the pressure reaches the cutoff value.

[0023] The pressure relief characteristic curve of the clamping cylinder refers to the functional relationship curve of the pressure in the rodless chamber of the clamping cylinder changing with time. During the pressure relief process, the pressure drops exponentially or linearly from the initial value to close to the oil tank pressure. This curve reflects the combined influence of pressure relief flow rate, oil viscosity and pipeline resistance on the pressure relief speed.

[0024] The lookup table refers to using the current recovery flow rate and the final pressure value when the accumulator terminates recovery as input parameters to look up the corresponding time required to empty the oil in the clamping cylinder in a data table pre-stored in the controller. This data table is obtained through experimental calibration or simulation calculation.

[0025] The equation of state for a gas is a physical equation that describes the relationship between the pressure, volume, and temperature of a gas inside an accumulator. It is a constant that equals the absolute pressure multiplied by the gas volume raised to the power of a constant. It is used to calculate the energy stored in an accumulator under different pressures.

[0026] Effective releasable hydraulic energy refers to the net energy value that can actually be output to do work after deducting the basic energy corresponding to the pre-charge gas pressure of the accumulator from the total hydraulic energy stored at the end of the recovery.

[0027] The auxiliary energy replenishment starting pressure threshold refers to the critical pressure value at which the accumulator's current pressure reaches the threshold, allowing the standby energy replenishment action to be initiated. This value is derived by calculating the difference between the total energy required to start the system in the next cycle and the energy that the accumulator can provide. For example, if the system needs to absorb 1,000 joules of energy to start up, and the energy provided by the pressure and volume relationship inside the accumulator is 2,000 joules, the threshold is set to a lower value to allow energy replenishment to begin earlier. If the accumulator only provides 800 joules, the threshold is set to a higher value to ensure that the energy is released at the correct time.

[0028] The standby phase refers to the intermittent period between the completion of the clamping cylinder's release action and the switching of the main directional valve to the neutral position, and the operator pressing the start button to trigger the clamping action in the next cycle. During this period, the hydraulic pump may still be running, but the main actuator will not move.

[0029] The power supply valve refers to an electromagnetically controlled check valve or cartridge valve installed between the accumulator outlet and the main oil circuit. Its opening is controlled by the output signal of the controller and is used to release the high-pressure oil stored in the accumulator to the main oil circuit during the standby phase.

[0030] The actual advance opening time point refers to the time difference between the moment when the power supply valve starts to be energized and opens and the moment when the clamping action of the next cycle is triggered. A negative value indicates advance opening. For example, if the power supply valve opens 0.8 seconds before the clamping trigger, the advance opening time point is -0.8 seconds.

[0031] The actual effective output power utilization rate refers to the ratio of the effective power output of the hydraulic pump to its input power. The improvement effect of the system's energy utilization level is evaluated by calculating the degree of compensation of the load during the hydraulic pump start-up phase by the energy released in advance by the energy supply valve.

[0032] An analog-to-digital converter (ADC) is an electronic circuit unit that converts continuously changing analog voltage signals (such as four to twenty milliamps or zero to ten volts) output by a sensor into discrete digital signals (such as twelve-bit or sixteen-bit binary numbers). The conversion resolution is typically 0.1% to 0.01% of the full scale.

[0033] The comparison register is a dedicated register unit inside the controller used to store two digital values ​​and compare their values. Its built-in high-speed comparator can determine the size of two binary numbers and output the comparison result within one clock cycle.

[0034] The binary comparison result flag bit refers to a single binary bit output by the comparison register. A logical 1 indicates that the first digital pressure value is greater than or equal to the second digital pressure value, and a logical 0 indicates that the first digital pressure value is less than the second digital pressure value. This flag bit is directly used as the basis for subsequent logical judgments.

[0035] A high-speed comparator is a voltage comparison circuit with a response time in the nanosecond range. It can quickly compare the voltage signals at two input terminals and output the difference signal. Its response time is usually less than one hundred nanoseconds.

[0036] A Schmitt trigger is a level-shaping circuit with hysteresis characteristics. Its forward threshold voltage is higher than its reverse threshold voltage. For example, the forward threshold voltage is 3.0 volts and the reverse threshold voltage is 1.5 volts. The output flips to a high level only when the input voltage exceeds 3.0 volts and to a low level only when it is below 1.5 volts, thereby eliminating noise jitter of the input signal near the threshold.

[0037] The output latch unit refers to a digital circuit that latches the input level signal at the effective edge of the controller clock signal and keeps the output stable. The latched level signal remains unchanged throughout the entire clock cycle until the next effective edge arrives, ensuring a stable output of the comparison result throughout the complete control cycle.

[0038] The linear inverse proportional function mapping unit refers to the software function module within the controller that performs an operation in the form of y equal to k divided by x plus c, where x is the input equivalent pressure value, y is the output opening control value, k is the fixed proportional coefficient, and c is the minimum denominator limit value, and is used to realize the continuous mapping calculation of the inverse proportional relationship.

[0039] The fixed proportional coefficient is a constant obtained by multiplying the maximum clamping pressure value by the minimum opening value of the proportional throttle valve. For example, when the maximum clamping pressure is 20 MPa and the minimum opening value is 1 square millimeter, the fixed proportional coefficient is 20 multiplied by 1, which equals 20 MPa square millimeter.

[0040] A limiter is a software function module that limits the input signal to a preset upper and lower limit range. When the input value exceeds the upper limit, the output is clamped to the upper limit. When the input value is lower than the lower limit, the output is raised to the lower limit to prevent the output from exceeding the physical executable range of the actuator.

[0041] A subtractor is a digital logic unit inside a controller that performs a subtraction operation between two values. Its output includes the magnitude and sign information of the value.

[0042] A selector is a digital switching circuit that selects one of multiple input channels to connect to the output terminal based on the level of the input signal at the channel control terminal. It is usually composed of an analog switch array.

[0043] Analog switch arrays refer to integrated circuits composed of multiple field-effect transistor switches, which achieve switching connections between different signal channels by controlling the on and off states of each switch.

[0044] The proportional calculation module refers to the software functional unit inside the controller that performs multiplication operations. It is used to multiply the ratio of the maximum delay time to the available recovery time window by the maximum allowable operating pressure of the accumulator to obtain the scaled cutoff pressure value.

[0045] A logic AND gate is a digital logic circuit that performs a logic AND operation. It outputs a high level only when all inputs are high, and outputs a low level otherwise.

[0046] High-speed transistor switching circuits refer to fast switching circuits based on bipolar transistors or field-effect transistors, used for overlapping detection of input level signals, and their switching response time is typically on the order of microseconds.

[0047] The enable terminal of the drive circuit refers to the input terminal on the drive circuit specifically used to receive the enable control signal. When the level is high, the power supply circuit of the drive circuit is turned on, enabling it to trigger the output capability. When the level is low, the power supply circuit is turned off, locking the drive circuit in the off state.

[0048] An electromagnetic coil refers to the winding coil in a powered valve used to generate electromagnetic force to drive the valve core. When energized, it generates a magnetic field that attracts the valve core to move, thus opening the valve.

[0049] A check valve is a directional control valve that allows oil to flow only from the accumulator side to the main oil circuit and prevents oil from flowing back from the main oil circuit to the accumulator, ensuring that the oil released from the accumulator will not flow backward.

[0050] The system pressure sensor is a pressure sensor installed on the main oil line to monitor the overall pressure level of the system. Its measurement range is usually from zero to 1.3 times the nominal system pressure, and the output signal is an analog signal of four to twenty milliamps or zero to ten volts.

[0051] The time difference calculation unit refers to the timer module inside the controller used to calculate the time interval between two time signals. It can accurately measure the difference in milliseconds or microseconds between the reference time point and the clamping action trigger time.

[0052] The first pressure sensor refers to the pressure sensing element installed at the oil port of the rodless chamber of the clamping cylinder. Its range is usually 1.5 times the nominal pressure of the system, and the output signal is proportional to the measured pressure. It is used to provide real-time feedback on the internal pressure value of the clamping cylinder.

[0053] The second pressure sensor refers to the pressure sensing element installed at the return port of the hydraulic motor. Its range is usually one to one and two times the nominal pressure of the system, and it is used to collect the pressure value on the return side of the motor in real time during braking or reversing.

[0054] The third pressure sensor refers to the pressure sensing element installed at the outlet of the accumulator. Its range must cover more than 1.2 times the maximum allowable working pressure of the accumulator and be used to continuously monitor the real-time changes in the back pressure of the gas inside the accumulator.

[0055] The logic judgment unit refers to the logic circuit module inside the controller that is responsible for decoding the level of the binary comparison result flag bit, decoding the high level as high priority on the clamping cylinder side and the low level as high priority on the motor return oil side.

[0056] An electromagnetic directional valve is a type of valve that uses an electromagnet to generate electromagnetic force to drive the valve core to move and change the direction of oil flow. The position of the valve core is determined by the energized or de-energized state, and it is used to control the connection and disconnection between the recovery branch and the accumulator or oil tank.

[0057] The electromagnetic drive end refers to the input port on the proportional throttle valve that receives the control current signal. The magnitude of the input current is proportional to the displacement of the valve core. Typically, the input current is four to twenty milliamps, corresponding to the valve opening from fully closed to fully open.

[0058] A flow meter is a flow measurement element installed at the inlet of an accumulator. It is used to continuously measure the volume of oil flowing into the accumulator per unit time. Its output signal is an analog electrical signal or pulse signal that is proportional to the flow rate.

[0059] The controller storage unit refers to the non-volatile memory inside the controller, which is used to store the preset maximum allowable working pressure value of the accumulator, the maximum allowable delay time value of the clamping cylinder, the clamping cylinder pressure relief characteristic curve data table, and various threshold parameters.

[0060] The proportional calculation module refers to the software functional unit inside the controller that performs multiplication operations. It is used to multiply the ratio of the maximum delay time to the available recovery time window by the maximum allowable operating pressure of the accumulator to obtain the scaled cutoff pressure value.

[0061] A logic AND gate is a digital logic circuit that performs a logic AND operation. It outputs a high level only when all inputs are high, and outputs a low level otherwise.

[0062] The power supply circuit of the drive circuit refers to the power circuit path that provides electrical energy to the electromagnetic coil of the power supply valve. Its on / off state is controlled by the enable terminal of the drive circuit. When the enable terminal is at a high level, the circuit is connected and has the ability to supply power. When the enable terminal is at a low level, the circuit is cut off and locked.

[0063] The main directional valve is the main control directional valve that controls the flow of hydraulic pump output oil to the rodless chamber of the clamping cylinder or the oil inlet of the hydraulic motor. When switched to the neutral position, it cuts off the connection between the clamping cylinder and the hydraulic pump, causing the clamping cylinder to enter the depressurization state.

[0064] The auxiliary overflow valve is a safety valve connected in parallel on the recovery branch. It is used to overflow excess high-pressure oil back to the oil tank when the accumulator reaches the maximum allowable working pressure or when the recovery valve group fails, so as to prevent the system pressure from exceeding the limit.

[0065] Seals refer to elastic sealing elements installed between the piston and cylinder barrel of a hydraulic cylinder, and between the valve core and valve body, to prevent high-pressure oil leakage. Their service life is significantly affected by the rise in oil temperature.

[0066] Tubing refers to the tubular metal components that need to be threaded or unthreaded during well workover operations in oilfields, including tubing, drill pipe, and casing. The quality of their threaded connections directly affects operational safety.

[0067] The upper buckle refers to the process of connecting and fastening two tubing columns by rotating them with threads. The clamping cylinder needs to continuously provide sufficient clamping force during the rotation to prevent the tubing columns from slipping.

[0068] The shackle refers to the process of separating two connected tubing strings by rotating them in opposite directions. The clamping cylinder also needs to provide sufficient clamping force to overcome the resistance when the threads come off.

[0069] The nominal pressure of the system refers to the highest working pressure value specified in the design of the hydraulic power clamp system. It is usually determined by the rated output pressure of the hydraulic pump and the pressure resistance rating of each component in the system, such as 25 MPa or 31.5 MPa.

[0070] Precharge gas pressure refers to the initial pressure value of gas (usually nitrogen) that is precharged into the accumulator before it is filled with oil. This value is usually set to 50% to 60% of the system's nominal pressure to ensure that the accumulator can still effectively store and release energy at the lowest operating pressure.

[0071] The working principle and technical effect of the above technical solution are as follows: The residual pressure values ​​at the instant of pressure relief of the clamping cylinder and the instant of braking of the motor are collected by the first and second pressure sensors respectively. These values ​​are input to the controller for amplitude comparison to determine the high-priority residual pressure source. The controller then controls the recovery valve group to open, allowing high-pressure side oil to flow preferentially into the accumulator to complete the initial filling. During the recovery process, the accumulator gas back pressure is continuously monitored by the third pressure sensor. The difference between this back pressure and the current clamping and maintaining pressure of the clamping cylinder is compared to obtain the equivalent value of the reverse thrust. Based on this, the opening of the proportional throttle valve is adjusted inversely to limit the recovery flow rate, obtaining the corrected pressure rise slope value. Based on this slope value and the initial filling pressure value, the pressure rise slope is calculated... The available recovery time window of the accumulator is calculated and compared with the maximum allowable release delay time of the clamping cylinder to determine the safe recovery cutoff pressure value. The recovery valve group is controlled by stage switching. When the accumulator pressure reaches the cutoff value, it switches to the pressure relief position to obtain the actual release action completion time value. Finally, based on the cutoff pressure value and back pressure influence data, the effective releaseable hydraulic energy actually stored in the accumulator is calculated. The difference between this and the initial output pressure value of the hydraulic pump at the start of the next cycle is calculated to obtain the auxiliary energy replenishment starting pressure threshold. During the standby stage, the energy supply valve is opened in advance to release high-pressure oil to the main oil circuit to obtain the actual effective output power utilization rate value of the hydraulic pump after insufficient recovery.

[0072] This system resolves a series of issues, including competition for recovery channels when two residual pressure sources exist simultaneously, dynamic interference of accumulator back pressure on clamping force, timing conflicts between recovery actions and actuator release actions, and the ineffective reuse of recovered energy. It achieves automatic priority identification and priority recovery of residual pressure sources, real-time adjustment of recovery flow rate to clamping safety status, dynamic matching of recovery time window and allowable operation delay time, and early release of recovered energy during standby phases. This avoids energy losses due to incorrect channel allocation, the risk of tubing slippage due to excessive back pressure, operation cycle delays due to over-recovery, and system pressure fluctuations due to improper energy replenishment timing. It also improves the effectiveness of energy recovery selection, the safety of the recovery process, the system's adaptability to changing operating conditions, and overall energy utilization efficiency.

[0073] In one embodiment of the present invention, S1 includes: By using a first pressure sensor installed at the oil port of the rodless chamber of the clamping cylinder, the initial pressure value of the rodless chamber at the moment of depressurization after the clamping cylinder completes the clamping or unclamping operation is collected in real time, and the initial pressure value of the clamping cylinder depressurization is obtained. By using a second pressure sensor installed at the return port of the hydraulic motor, the initial pressure value of the return side of the motor is collected in real time at the moment when the motor needs to brake or reverse, and the motor braking return pressure value is obtained. By comparing the initial pressure value of the clamping cylinder depressurization with the motor brake return oil pressure value input to the controller, the side with the higher pressure value is determined as the current high-priority residual pressure source, and the priority level of the current residual pressure source is obtained. By applying a priority level, a conduction signal is applied to the solenoid directional valve corresponding to the high-pressure side in the recovery control valve group, so that the high-pressure side oil flows into the accumulator preferentially through the recovery branch, thereby obtaining the initial accumulator charging pressure value.

[0074] The working principle and technical effect of the above technical solution are as follows: A first pressure sensor installed at the rodless chamber oil port of the clamping cylinder collects the initial pressure value of the rodless chamber at the moment of depressurization after the clamping cylinder completes the clamping or unclamping operation, thus obtaining the initial pressure value of the clamping cylinder depressurization; a second pressure sensor installed at the hydraulic motor return oil port collects the initial pressure value of the return oil side at the moment the motor needs to brake or reverse, thus obtaining the motor braking return oil pressure value; the initial pressure value of the clamping cylinder depressurization and the motor braking return oil pressure value are compared with the amplitude of the input controller, and the side with the higher pressure value is determined as the current high-priority residual pressure source, thus obtaining the priority level of the current residual pressure source; based on the priority level, a conduction signal is applied to the solenoid directional valve corresponding to the high-pressure side in the recovery control valve group, causing the high-pressure side oil to preferentially flow into the accumulator through the recovery branch, thus obtaining the initial accumulator charging pressure value.

[0075] It solves the channel conflict and energy competition problem caused by the competition of recovery branches when two residual pressure sources appear at the same time; realizes automatic identification and priority recovery control of high-pressure side residual pressure sources; avoids energy loss and system pressure shock caused by incorrect allocation of recovery channels; and improves the selection effectiveness of energy recovery and system response speed.

[0076] In one embodiment of the present invention, the step of comparing the initial pressure value of the clamping cylinder depressurization with the motor brake return oil pressure value input to the controller, determining the one with the higher pressure value as the current high-priority residual pressure source, and obtaining the priority level of the current residual pressure source includes: The first analog electrical signal corresponding to the initial pressure value of the clamping cylinder and the second analog electrical signal corresponding to the return oil pressure value of the motor brake are respectively input into the analog-to-digital converter module built into the controller for digital conversion to obtain the first digital pressure value and the second digital pressure value. By inputting the first digital pressure value and the second digital pressure value into the comparison register built into the controller for numerical comparison, if the first digital pressure value is greater than or equal to the second digital pressure value, the comparison register outputs a high-level logic signal, otherwise it outputs a low-level logic signal, thereby obtaining a binary comparison result flag bit that represents the magnitude relationship between the two values. By inputting the comparison result flag bit into the logic judgment unit of the controller for high and low level decoding, when the flag bit is high, the clamping cylinder side is determined to be a high priority residual pressure source, and when the flag bit is low, the motor oil return side is determined to be a high priority residual pressure source, thus obtaining the priority level of the current residual pressure source.

[0077] Specifically, by inputting the first digital pressure value and the second digital pressure value into a built-in comparison register of the controller for numerical comparison, if the first digital pressure value is greater than or equal to the second digital pressure value, the comparison register outputs a high-level logic signal; otherwise, it outputs a low-level logic signal. This yields a binary comparison result flag bit representing the magnitude relationship between the two values, including: By loading the binary data corresponding to the first digital pressure value into the first input terminal of the comparison register, and loading the binary data corresponding to the second digital pressure value into the second input terminal of the comparison register, the high-speed comparator inside the comparison register compares the level amplitude of the two input terminals bit by bit to obtain the original analog comparison voltage output by the comparator. By shaping the original analog comparison voltage input to the Schmitt trigger built into the comparison register, the positive feedback characteristic of the Schmitt trigger is used to perform threshold judgment and waveform trimming on the original voltage. When the voltage is higher than the first threshold, a high level is output, and when it is lower than the second threshold, a low level is output, thus obtaining a stable digital level signal after shaping. By inputting a stable digital level signal into the output latch unit of the comparator register, the latch unit latches and holds the level signal at the rising edge of the controller clock signal, keeping the level signal stable throughout the entire control cycle until refreshed in the next clock cycle, thus obtaining a binary comparison result flag bit that represents the magnitude relationship between the two.

[0078] The working principle and technical effect of the above technical solution are as follows: The first analog electrical signal corresponding to the initial pressure value of the clamping cylinder and the second analog electrical signal corresponding to the motor brake return oil pressure value are respectively input into the analog-to-digital conversion module built into the controller for digital conversion to obtain the first digital pressure value and the second digital pressure value; The first digital pressure value and the second digital pressure value are input into the comparison register built into the controller for numerical comparison. If the first digital pressure value is greater than or equal to the second digital pressure value, the comparison register outputs a high-level logic signal, otherwise it outputs a low-level logic signal to obtain a binary comparison result flag bit representing the magnitude relationship between the two; The comparison result flag bit is input into the logic judgment unit of the controller for high and low level decoding. When the flag bit is high, the clamping cylinder side is determined to be a high-priority residual pressure source; when the flag bit is low, the motor return oil side is determined to be a high-priority residual pressure source to obtain the priority level of the current residual pressure source.

[0079] It solves the problem that direct comparison of analog signals is easily misjudged due to line noise and environmental interference; it realizes the digital conversion of pressure signals and accurate amplitude comparison; it eliminates the negative impact of noise interference during signal transmission on the comparison results; and it improves the accuracy of priority determination and the system's anti-interference capability under harsh working conditions.

[0080] In one embodiment of the present invention, S2 includes: By using a third pressure sensor installed at the accumulator outlet, the gas compression back pressure value inside the accumulator that continues to rise as the recovered oil is continuously injected is continuously monitored, and the current real-time gas back pressure value of the accumulator is obtained. By comparing the current real-time gas back pressure value of the accumulator with the current actual clamping and maintaining pressure value of the rodless chamber of the clamping cylinder, the difference is used to characterize the magnitude of the reverse force generated by the back pressure of the accumulator on the piston of the clamping cylinder, and the equivalent pressure value of the reverse thrust generated by the back pressure on the piston of the clamping cylinder is obtained. Based on the equivalent pressure value, the controller adjusts the proportional throttle valve in the recovery branch in real time according to the rule that the larger the equivalent pressure value, the smaller the opening, and the smaller the equivalent pressure value, the larger the opening, so as to obtain the actual pressure rise of the accumulator per unit time after flow limitation. The corrected effective recovery pressure rise slope of the accumulator is obtained by dividing the actual pressure rise per unit time by the corresponding time step.

[0081] The working principle and technical effect of the above technical solution are as follows: A third pressure sensor installed at the accumulator outlet continuously monitors the rising back pressure of the gas compression within the accumulator as the recovered oil is continuously injected, obtaining the current real-time gas back pressure value of the accumulator. This real-time gas back pressure value is compared with the current actual clamping and maintaining pressure value of the rodless chamber of the clamping cylinder. This difference characterizes the magnitude of the reverse force generated by the accumulator back pressure on the piston of the clamping cylinder, obtaining the equivalent pressure value of the reverse thrust generated by the back pressure on the piston of the clamping cylinder. Based on the equivalent pressure value, the controller adjusts the proportional throttle valve in the recovery branch in real-time according to the rule that a larger equivalent pressure value results in a smaller opening, and a smaller equivalent pressure value results in a larger opening, obtaining the actual pressure rise per unit time of the accumulator after flow limitation. By dividing the actual pressure rise per unit time by the corresponding time step, the corrected actual effective recovery pressure rise slope value of the accumulator is obtained.

[0082] It solves the safety hazard of dynamic interference caused by the continuous rise of accumulator back pressure on the clamping force of the clamping cylinder; realizes real-time tracking and adjustment of the recovery flow rate to the clamping safety state; reduces the clamping force loss and tubing slippage risk caused by the reverse thrust of back pressure on the clamping cylinder piston; and improves the safety of the recovery process and the dynamic adaptability to changes in operating conditions.

[0083] In one embodiment of the present invention, the controller adjusts the proportional throttle valve in the recovery branch in real time according to the rule that the larger the equivalent pressure value, the smaller the opening, and the smaller the equivalent pressure value, the larger the opening, to obtain the actual pressure rise of the accumulator per unit time after flow limitation, based on the equivalent pressure value. This includes: By inputting the equivalent pressure value of the reverse thrust into the linear inverse proportional function mapping unit built into the controller, the target opening area control quantity of the proportional throttle valve is obtained by continuously mapping and calculating according to the inverse proportional relationship between the equivalent pressure value from zero to the highest clamping pressure and the opening of the proportional throttle valve from the maximum opening to the minimum opening. By outputting the target opening area control quantity to the electromagnetic drive end of the proportional throttle valve, the valve core displacement changes linearly with the magnitude of the control current to change the flow cross-sectional area of ​​the valve orifice, thereby obtaining the actual flow area of ​​the valve orifice after real-time adjustment. The flow meter installed at the accumulator inlet continuously measures the volume of oil flowing into the accumulator per unit time after the actual valve port flow area is limited, thus obtaining the actual pressure rise of the accumulator per unit time after the flow limit.

[0084] Specifically, by inputting the equivalent pressure value of the reverse thrust into the linear inverse proportional function mapping unit built into the controller, continuous mapping calculations are performed according to the inverse proportional relationship between the equivalent pressure value from zero to the maximum clamping pressure and the proportional throttle valve opening from the maximum opening to the minimum opening, to obtain the target opening area control quantity of the proportional throttle valve, including: By inputting the digital quantity corresponding to the equivalent pressure value into the input terminal of the linear inverse proportional function mapping unit, the mapping unit calls the linear function coefficient stored internally. This linear function coefficient is predetermined by the product of the highest clamping pressure value and the minimum opening value of the proportional throttle valve, thus obtaining the fixed proportional coefficient required for the mapping operation. By dividing a fixed proportional coefficient by the sum of the current input equivalent pressure value and the preset minimum denominator limit value, the output approaches the maximum opening when the equivalent pressure value approaches zero and the output approaches the minimum opening when the equivalent pressure value approaches the highest clamping pressure, thus obtaining the intermediate opening control quantity calculated according to the inverse proportional continuous mapping relationship. By inputting the intermediate opening control quantity into the limiter built into the mapping unit, when the intermediate opening control quantity exceeds the maximum opening limit value physically allowed by the proportional throttle valve, the output will be clamped to the maximum opening limit value; when the intermediate opening control quantity is lower than the minimum opening limit value physically allowed by the proportional throttle valve, the output will be raised to the minimum opening limit value, thereby obtaining the target opening area control quantity of the proportional throttle valve.

[0085] The working principle and technical effect of the above technical solution are as follows: The equivalent pressure value of the reverse thrust is input into the linear inverse proportional function mapping unit built into the controller. According to the inverse proportional relationship between the equivalent pressure value from zero to the highest clamping pressure and the proportional throttle valve opening from the maximum opening to the minimum opening, the target opening area control quantity of the proportional throttle valve is obtained. The target opening area control quantity is output to the electromagnetic drive end of the proportional throttle valve, so that the valve core displacement changes linearly with the magnitude of the control current to change the flow cross-sectional area of ​​the valve port, thereby obtaining the actual valve port flow area after real-time adjustment. The flow meter installed at the accumulator inlet continuously measures the volume of oil flowing into the accumulator per unit time after the actual valve port flow area is limited, thereby obtaining the actual pressure rise of the accumulator per unit time after the flow limit.

[0086] It solves the problem that a fixed throttling orifice cannot adapt to dynamic changes in accumulator back pressure; it achieves continuous linear mapping adjustment between the equivalent pressure value and the opening area; it reduces safety risks or recovery efficiency losses caused by lag or over-throttling adjustment; and it improves the response speed and control accuracy of the proportional throttling valve.

[0087] In one embodiment of the present invention, S3 includes: By inputting the pressure rise slope value in step S2 and the initial accumulator filling pressure value in step S1 into the controller, and combining it with the maximum allowable working pressure value of the accumulator, the theoretical shortest recovery time required for the accumulator to rise from the initial filling pressure to the maximum allowable working pressure is calculated, and the available recovery time window of the accumulator is obtained. By matching and comparing the available recovery time window with the maximum allowable delay time during the clamping cylinder release phase input controller, if the available recovery time window is less than or equal to the maximum delay time, the highest allowable working pressure is taken as the cutoff pressure; if it is greater than the maximum delay time, the corresponding pressure value is calculated by reverse calculation according to the ratio of the time window to the maximum delay time to obtain the actual safe recovery cutoff pressure value. Based on the actual safe recovery cutoff pressure value, the controller executes a graded switching command on the recovery control valve group. When the accumulator pressure has not reached the cutoff pressure value, the recovery position is kept open to recover energy. When the cutoff pressure value is reached, the controller immediately switches to the pressure relief position to bypass the remaining low-pressure oil in the clamping cylinder to the oil tank, thereby obtaining the final pressure value when the accumulator actually terminates recovery. By substituting the final pressure value of the accumulator when it actually terminates recovery into the pressure relief characteristic curve of the clamping cylinder, and combining it with the time required for the oil in the clamping cylinder to be emptied under the current recovery flow rate, the actual release action completion time value that meets the operation cycle requirements is obtained.

[0088] The working principle and technical effect of the above technical solution are as follows: The pressure rise slope and initial accumulator filling pressure are input into the controller. Combined with the accumulator's maximum allowable working pressure, the theoretical shortest recovery time required for the accumulator to rise from the initial filling pressure to the maximum allowable working pressure is calculated, thus obtaining the accumulator's usable recovery time window. The usable recovery time window is compared with the maximum allowable delay time during the clamping cylinder's release phase. If the usable recovery time window is less than or equal to the maximum delay time, the maximum allowable working pressure is taken as the cutoff pressure. If it is greater than the maximum delay time, the corresponding pressure is calculated by reverse calculation based on the ratio between the time window and the maximum delay time. The pressure value is used to obtain the actual safe recovery cutoff pressure value. Based on the actual safe recovery cutoff pressure value, the controller executes a graded switching command on the recovery control valve group. When the accumulator pressure has not reached the cutoff pressure value, the recovery position is kept open for energy recovery. When the cutoff pressure value is reached, the controller immediately switches to the pressure relief position to bypass the remaining low-pressure oil in the clamping cylinder to the oil tank, thus obtaining the final pressure value when the accumulator actually terminates recovery. The final pressure value when the accumulator actually terminates recovery is substituted into the pressure relief characteristic curve of the clamping cylinder, and combined with the time required to empty the oil in the clamping cylinder under the current recovery flow rate, a table is consulted to obtain the actual release action completion time value that meets the operation cycle requirements.

[0089] It resolves the timing conflict between the recovery action and the release action of the actuator; achieves dynamic matching decision between the recovery time window and the allowable delay time of the operation; reduces the operation cycle delay caused by excessive recovery or the energy waste caused by premature depressurization; and improves the system's adaptability and overall energy efficiency under varying operating conditions.

[0090] In one embodiment of the present invention, the step of matching and comparing the available recovery time window with the maximum allowable delay time during the clamping cylinder release phase input to the controller, and if the available recovery time window is less than or equal to the maximum delay time, then the highest allowable working pressure is taken as the cutoff pressure; if it is greater than the maximum delay time, then the corresponding pressure value is calculated by reverse calculation according to the ratio of the time window to the maximum delay time to obtain the actual safe recovery cutoff pressure value, includes: The difference between the value of the available recovery time window and the value of the maximum allowable delay time during the clamping cylinder release phase is calculated by inputting the value of the subtractor built into the controller. If the difference is less than or equal to zero, it is determined that the window is sufficient. If the difference is greater than zero, it is determined that the window is insufficient. The result of the difference sign determination is obtained by matching comparison. By inputting the difference sign determination result into the controller's selector, if the window is sufficient, the selector directly selects the maximum allowable working pressure of the accumulator as the output cutoff pressure; if the window is insufficient, the selector switches to the proportional calculation module to obtain the cutoff pressure selection path determination signal. In cases of insufficient window conditions, the ratio of the maximum delay time to the available recovery time window is input into the proportional calculation module. This ratio is then multiplied by the maximum allowable operating pressure of the accumulator to obtain the time-scaled cutoff pressure value, which is then used to calculate the scaled cutoff pressure value. The selector selects the path determination signal based on the cutoff pressure, and outputs the maximum allowable working pressure under sufficient window conditions or the scaling cutoff pressure value under insufficient window conditions as the final result to the controller storage unit to obtain the actual safe recovery cutoff pressure value.

[0091] Specifically, by inputting the difference sign determination result into the controller's selector, if the window is sufficient, the selector directly selects the accumulator's maximum allowable operating pressure as the output cutoff pressure; if the window is insufficient, the selector switches to the proportional calculation module to obtain the cutoff pressure selection path determination signal, including: By inputting the binary level signal corresponding to the difference sign determination result into the channel control terminal of the selector, the two input channels inside the selector are associated one-to-one with the two logic states of the difference sign determination result, thus obtaining the initial configuration state of the channel switching path inside the selector. By loading the digital quantity corresponding to the maximum allowable working pressure of the accumulator into the first input channel of the selector, and electrically connecting the second input channel of the selector to the output terminal of the proportional calculation module, the output path of the first input channel corresponds to the window when it is sufficient, and the output path of the second input channel corresponds to the window when it is insufficient, thus obtaining the path allocation status of the two input channels inside the selector. The analog switch array inside the selector is controlled by the difference sign determination result level signal received by the channel control terminal. When the determination result is that the window is sufficient, the analog switch connects the first input channel and the output terminal. When the determination result is that the window is insufficient, the analog switch connects the second input channel and the output terminal to obtain the cutoff pressure selection path determination signal.

[0092] The working principle and technical effect of the above technical solution are as follows: The value of the available recovery time window and the value of the maximum allowable delay time during the clamping cylinder release stage are input into the subtractor built into the controller for difference calculation. If the difference is less than or equal to zero, it is determined that the window is sufficient; if the difference is greater than zero, it is determined that the window is insufficient, and the sign of the difference is obtained by matching comparison. The sign of the difference is input into the selector of the controller. If the window is sufficient, the selector directly selects the maximum allowable working pressure of the accumulator as the output cutoff pressure. If the window is insufficient, the selector switches to the proportional calculation module to obtain the cutoff pressure selection path determination signal. In the case of insufficient window, the ratio of the maximum delay time to the available recovery time window is input into the proportional calculation module. This ratio is multiplied by the maximum allowable working pressure of the accumulator to obtain the cutoff pressure value scaled by the time ratio, and the scaled cutoff pressure value after back calculation is obtained. The selector outputs the maximum allowable working pressure in the case of sufficient window or the scaled cutoff pressure value in the case of insufficient window as the final result to the controller storage unit to obtain the actual safe recovery cutoff pressure value.

[0093] It solves the problem of insufficient time or energy waste caused by setting a fixed cutoff pressure based on experience, which cannot adapt to different working conditions; it realizes differentiated decision-making by making full use of the accumulator capacity for maximum recovery when the window is sufficient, and automatically compressing the recovery depth according to the time ratio when the window is insufficient; it reduces the decrease in operational safety or energy efficiency loss caused by improper cutoff pressure setting; and it improves the scientific nature of cutoff pressure setting and its adaptability to the work rhythm.

[0094] In one embodiment of the present invention, S4 includes: By inputting the actual safe recovery cutoff pressure value and the corresponding current gas volume change of the accumulator into the controller, the total hydraulic energy stored in the accumulator at the time of recovery termination is calculated using the gas state equation, and then the basic energy corresponding to the accumulator's own charging pressure is deducted to obtain the effective releaseable hydraulic energy actually stored in the accumulator. By inputting the effective releaseable hydraulic energy of the accumulator and the initial output pressure value of the hydraulic pump at the start of the next work cycle into the controller, the difference between the total energy required by the system at the start of the next cycle and the energy that the accumulator can provide is calculated. If the energy of the accumulator is higher than the demand, the energy difference is zero; if it is lower than the demand, the difference is taken as the additional energy demand value, and the auxiliary energy replenishment starting pressure threshold is obtained. By using the auxiliary energy replenishment starting pressure threshold, the controller applies an early opening signal to the accumulator outlet energy supply valve during the standby phase before the clamping cylinder starts to move in the next cycle. This allows the accumulator to release high-pressure oil into the main oil circuit before the hydraulic pump starts, thereby reducing the peak load pressure at the moment the pump starts and obtaining the actual early opening time of the energy supply valve. The actual effective output power utilization rate of the hydraulic pump is obtained by inputting the ratio of the energy released at the actual early opening time of the power supply valve to the actual output energy of the hydraulic pump during the startup phase into the controller. That is, the actual output power utilization rate is equal to the ratio of the effective working power to the input power.

[0095] The working principle and technical effect of the above technical solution are as follows: The actual safe recovery cutoff pressure value and the corresponding current gas volume change of the accumulator are input into the controller. The total hydraulic energy stored in the accumulator at the time of recovery termination is calculated using the gas state equation. Then, the basic energy corresponding to the accumulator's own charging pressure is subtracted to obtain the effective releaseable hydraulic energy actually stored in the accumulator. The effective releaseable hydraulic energy of the accumulator and the initial output pressure value of the hydraulic pump at the start of the next working cycle are input into the controller. The difference between the total energy required by the system at the instant of the start of the next cycle and the energy that the accumulator can provide is calculated. If the energy of the accumulator is higher than the demand, the energy difference is zero; if it is lower than the demand, the difference is taken as the additional energy demand value. The auxiliary energy replenishment starting pressure threshold is obtained. Based on the auxiliary energy replenishment starting pressure threshold, the controller applies an early opening signal to the accumulator outlet energy supply valve during the standby phase before the clamping cylinder starts operating in the next cycle. This causes the accumulator to release high-pressure oil into the main oil circuit before the hydraulic pump starts, thereby reducing the peak load pressure at the moment of pump start-up. The actual early opening time of the energy supply valve is obtained. The released energy value corresponding to the actual early opening time of the energy supply valve is compared with the actual output energy value of the hydraulic pump during the startup phase. The ratio is calculated by inputting the data into the controller. That is, the actual output power utilization rate is equal to the ratio of the effective working power to the input power. The actual effective output power utilization rate of the hydraulic pump after insufficient compensation and recovery is obtained.

[0096] It solves the problems of inaccurate energy recovery calculation leading to inappropriate energy replenishment strategies and large load impact at the moment of pump start-up; it realizes accurate calculation of recovered energy and early release of replenishment energy during standby; it reduces the load pressure and high-pressure overflow loss at the moment of hydraulic pump start-up; and it improves the reuse rate of recovered energy and the overall energy utilization efficiency of the system.

[0097] In one embodiment of the present invention, by using an auxiliary energy replenishment starting pressure threshold, the controller applies an early opening signal to the accumulator outlet energy supply valve during the standby phase before the clamping cylinder starts operating in the next cycle. This causes the accumulator to pre-release high-pressure oil into the main oil circuit before the hydraulic pump starts, thereby reducing the peak load pressure at the moment of pump startup. The actual early opening time of the energy supply valve is obtained by: By continuously comparing the auxiliary energy replenishment start pressure threshold input controller with the current pressure value of the accumulator monitored in real time by the third pressure sensor, the standby energy replenishment permission condition is triggered when the current pressure value of the accumulator is greater than or equal to the auxiliary energy replenishment start pressure threshold, and the energy replenishment permission trigger signal is obtained. By performing a logical AND operation between the energy replenishment enable trigger signal and the current work cycle end time signal generated by the controller's internal timer, the outlet energy supply valve drive circuit is enabled during the standby phase after the clamping cylinder completes the release action and the main directional valve switches to the neutral position, thereby obtaining the standby phase opening enable signal for the energy supply valve. By outputting the standby phase enable signal to the solenoid coil of the accumulator outlet power supply valve, the power supply valve opens first during the standby period before the hydraulic pump starts, allowing the high-pressure oil in the accumulator to flow into the main oil circuit through the check valve. At the same time, the system pressure sensor installed on the main oil circuit monitors the starting time of the system pressure rise caused by this release process, and obtains the reference time point when the accumulator actually begins to release energy. By inputting the reference time point and the time signal at which the operator presses the start button to trigger the clamping action in the next cycle into the time difference calculation unit built into the controller, the advance amount of the reference time point relative to the clamping action triggering time is calculated, and the actual advance opening time of the power supply valve is obtained.

[0098] Specifically, by performing a logical AND operation between the replenishment enable trigger signal and the current work cycle end time signal generated by the controller's internal timer, the outlet power supply valve drive circuit is enabled during the standby phase after the clamping cylinder completes its release action and the main directional valve switches to the neutral position, thereby obtaining the standby phase opening enable signal for the power supply valve, including: By inputting the first level signal corresponding to the power replenishment enable trigger signal and the second level signal corresponding to the current work cycle end time signal into the first and second input terminals of the logic AND gate built into the controller, the logic AND gate is prepared to output a high level when both input signals are high, thus obtaining the input condition ready state of the logic AND operation; The first and second level signals are detected by the high-speed transistor switching circuit inside the logic AND gate. When both the first and second level signals are high, the transistor switch is turned on and outputs a high-level signal. When either input is low, the transistor switch is turned off and outputs a low-level signal, thus obtaining the logic AND result level signal after level overlap detection. By inputting the logic and result level signals into the enable terminal of the drive circuit built into the controller, when the enable terminal receives a high-level signal, the power supply circuit of the output power supply valve drive circuit is turned on, putting the drive circuit into a standby trigger state. When the enable terminal receives a low-level signal, the power supply circuit is turned off, keeping the drive circuit in a locked off state, thus obtaining the standby stage enable signal of the power supply valve.

[0099] The working principle and technical effect of the above technical solution are as follows: By continuously comparing the auxiliary energy replenishment starting pressure threshold input to the controller with the current pressure value of the accumulator monitored in real time by the third pressure sensor, when the current pressure value of the accumulator is greater than or equal to the auxiliary energy replenishment starting pressure threshold, the standby energy replenishment permission condition is triggered, and an energy replenishment permission trigger signal is obtained; by performing a logical AND operation between the energy replenishment permission trigger signal and the current work cycle end time signal generated by the controller's internal timer, the outlet energy supply valve drive circuit is enabled during the standby stage after the clamping cylinder completes the release action and the main reversing valve switches to the neutral position, and the standby stage opening enable signal of the energy supply valve is obtained; by performing a logical AND operation between the standby stage input and the output pressure threshold input to the controller, the standby stage opening enable signal of the energy supply valve is obtained; by performing a logical AND operation between the output pressure threshold input to the controller and the current pressure value of the accumulator monitored in real time by the third pressure sensor, the standby energy replenishment enable signal ... The stage-opening enable signal is output to the solenoid coil of the accumulator outlet power supply valve. During the standby period before the hydraulic pump starts, the power supply valve opens first, allowing the high-pressure oil in the accumulator to flow into the main oil circuit through the check valve. At the same time, the system pressure sensor installed on the main oil circuit monitors the start time of the system pressure rise caused by this release process, obtaining the reference time point when the accumulator actually begins to release energy. By inputting the reference time point and the time signal when the operator presses the start button to trigger the clamping action in the next cycle into the time difference calculation unit built into the controller, the advance amount of the reference time point relative to the clamping action triggering time is calculated, obtaining the actual advance opening time point of the power supply valve.

[0100] It solves the problem of potential timing conflicts between the energy replenishment action and the main actuator action; it achieves time constraint control that the energy replenishment action is executed only during the standby window period between operations; it reduces system pressure fluctuations and execution interference caused by the overlap of the energy replenishment action and the main action; and it improves the timing safety of the accumulator energy replenishment action and the coordination of system operation.

[0101] According to one embodiment of the present invention, the system includes: The conduction control module is used to obtain the priority level of the current residual pressure source by real-time acquisition and comparison of the initial pressure value of the clamping cylinder and the return oil pressure value of the motor brake, and to perform priority conduction control on the recovery control valve group to obtain the initial accumulator charging pressure value. The dynamic comparison module is used to continuously monitor the real-time rising gas back pressure value in the accumulator and dynamically compare it with the current actual clamping and maintaining pressure value of the clamping cylinder to obtain the equivalent pressure value of the reverse thrust generated by the back pressure on the piston of the clamping cylinder, and to adjust the proportional throttle valve to obtain the corrected actual effective recovery pressure rise slope value of the accumulator. The comparison control module is used to calculate the available recovery time window of the accumulator by using the pressure rise slope value and the initial accumulator filling pressure value, and to match and compare it with the maximum allowable release delay time of the clamping cylinder to obtain the actual safe recovery cutoff pressure value. It also performs graded switching control of the recovery control valve group to obtain the actual release action completion time value that meets the operation cycle requirements. The calculation and control module is used to calculate the effective releaseable hydraulic energy actually stored in the accumulator by using the actual safe recovery cutoff pressure value and back pressure influence data. It also calculates the supply and demand difference by combining the initial output pressure value of the hydraulic pump at the start of the next cycle, obtains the auxiliary energy replenishment starting pressure threshold, and controls the opening timing of the accumulator outlet energy supply valve in advance to obtain the actual effective output power utilization rate value of the hydraulic pump after insufficient compensation and recovery.

[0102] The working principle and technical effect of the above technical solution are as follows: The residual pressure values ​​at the instant of pressure relief of the clamping cylinder and the instant of braking of the motor are collected by the first and second pressure sensors respectively. These values ​​are input to the controller for amplitude comparison to determine the high-priority residual pressure source. The controller then controls the recovery valve group to open, allowing high-pressure side oil to flow preferentially into the accumulator to complete the initial filling. During the recovery process, the accumulator gas back pressure is continuously monitored by the third pressure sensor. The difference between this back pressure and the current clamping and maintaining pressure of the clamping cylinder is compared to obtain the equivalent value of the reverse thrust. Based on this, the opening of the proportional throttle valve is adjusted inversely to limit the recovery flow rate, obtaining the corrected pressure rise slope value. Based on this slope value and the initial filling pressure value, the pressure rise slope is calculated... The available recovery time window of the accumulator is calculated and compared with the maximum allowable release delay time of the clamping cylinder to determine the safe recovery cutoff pressure value. The recovery valve group is controlled by stage switching. When the accumulator pressure reaches the cutoff value, it switches to the pressure relief position to obtain the actual release action completion time value. Finally, based on the cutoff pressure value and back pressure influence data, the effective releaseable hydraulic energy actually stored in the accumulator is calculated. The difference between this and the initial output pressure value of the hydraulic pump at the start of the next cycle is calculated to obtain the auxiliary energy replenishment starting pressure threshold. During the standby stage, the energy supply valve is opened in advance to release high-pressure oil to the main oil circuit to obtain the actual effective output power utilization rate value of the hydraulic pump after insufficient recovery.

[0103] This system resolves a series of issues, including competition for recovery channels when two residual pressure sources exist simultaneously, dynamic interference of accumulator back pressure on clamping force, timing conflicts between recovery and actuator release actions, and ineffective reuse of recovered energy. It achieves automatic priority identification and recovery of residual pressure sources, real-time adjustment of recovery flow rate to clamping safety status, dynamic matching of recovery time window and allowable operation delay time, and early release of recovered energy during standby. This avoids energy loss due to incorrect channel allocation, the risk of tubing slippage due to excessive back pressure, operation cycle delays due to over-recovery, and system pressure fluctuations due to improper energy replenishment timing. It also improves the effectiveness of energy recovery selection, the safety of the recovery process, the system's adaptability to varying operating conditions, and overall energy utilization efficiency. Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for controlling fluid residual pressure recovery in a hydraulic power clamp, characterized in that, The method includes: S1. By real-time acquisition and comparison of the initial pressure value of the clamping cylinder depressurization and the return oil pressure value of the motor brake, the priority level is obtained, and the recovery control valve group is preferentially controlled to obtain the initial accumulator charging pressure value. S2. By continuously monitoring the real-time rising gas back pressure value in the accumulator and dynamically comparing it with the current actual clamping and maintaining pressure value of the clamping cylinder, the equivalent pressure value of the reverse thrust is obtained, and the proportional throttle valve is adjusted by narrowing the opening to obtain the pressure rise slope value. S3. By using the pressure rise slope value and the initial accumulator filling pressure value, the available recovery time window of the accumulator is calculated and matched with the maximum allowable release delay time of the clamping cylinder to obtain the actual safe recovery cutoff pressure value. The recovery control valve group is then subjected to graded switching control to obtain the actual release action completion time value. S4. By using the actual safe recovery cutoff pressure value and back pressure impact data, the effective releaseable hydraulic energy actually stored in the accumulator is calculated. Combined with the initial output pressure value of the hydraulic pump when starting the next cycle, the supply and demand difference is calculated to obtain the auxiliary energy replenishment starting pressure threshold. The opening timing of the accumulator outlet energy supply valve is advanced to obtain the actual effective output power utilization rate value.

2. The method for controlling fluid residual pressure recovery in a hydraulic power clamp according to claim 1, characterized in that, S1 includes: By using a first pressure sensor installed at the oil port of the rodless chamber of the clamping cylinder, the initial pressure value of the rodless chamber is collected in real time to obtain the initial pressure value of the clamping cylinder for depressurization. By using a second pressure sensor installed at the return port of the hydraulic motor, the initial pressure value on the return side is collected in real time to obtain the motor braking return pressure value. By comparing the initial pressure value of the clamping cylinder depressurization with the motor brake return oil pressure value input to the controller, the side with the higher pressure value is determined as the current high-priority residual pressure source, and the priority level of the current residual pressure source is obtained. By applying a conduction signal to the solenoid directional valve corresponding to the high-pressure side in the recovery control valve group according to the priority level, the high-pressure side oil flows into the accumulator preferentially through the recovery branch to obtain the initial accumulator charging pressure value.

3. The method for controlling fluid residual pressure recovery in a hydraulic power clamp according to claim 2, characterized in that, The method involves comparing the initial pressure value of the clamping cylinder depressurization with the motor brake return oil pressure value input to the controller, determining the one with the higher pressure value as the current high-priority residual pressure source, and obtaining the priority level of the current residual pressure source, including: By inputting the first analog electrical signal corresponding to the initial pressure value of the clamping cylinder depressurization and the second analog electrical signal corresponding to the motor brake return oil pressure value into the analog-to-digital converter module built into the controller for digital conversion, the first digital pressure value and the second digital pressure value are obtained. The first digital pressure value and the second digital pressure value are input into the comparison register built into the controller for numerical comparison operation to obtain the binary comparison result flag bit; By inputting the binary comparison result flag bit into the logic judgment unit of the controller for high and low level decoding, when the flag bit is high, the clamping cylinder side is determined to be a high priority residual pressure source, and when the flag bit is low, the motor oil return side is determined to be a high priority residual pressure source, thus obtaining the priority level of the current residual pressure source.

4. The method for controlling fluid residual pressure recovery in a hydraulic power clamp according to claim 1, characterized in that, S2 includes: By continuously monitoring the gas compression back pressure value through a third pressure sensor installed at the accumulator outlet, the current real-time gas back pressure value of the accumulator can be obtained. By inputting the difference between the current real-time gas back pressure value of the accumulator and the current actual clamping and maintaining pressure value of the rodless chamber of the clamping cylinder into the controller, the difference is used to characterize the magnitude of the reverse force generated by the back pressure of the accumulator on the piston of the clamping cylinder, and the equivalent pressure value of the reverse thrust is obtained. The controller adjusts the proportional throttle valve in the recovery branch in real time according to the rule that the larger the equivalent pressure value of the reverse thrust, the smaller the opening, and the smaller the equivalent pressure value of the reverse thrust, the larger the opening, so as to obtain the actual pressure rise per unit time. The actual effective recovery pressure rise slope of the accumulator is obtained by dividing the actual pressure rise per unit time by the corresponding time step.

5. The method for controlling fluid residual pressure recovery in a hydraulic power clamp according to claim 4, characterized in that, The controller adjusts the proportional throttle valve in the recovery branch in real time according to the rule that the larger the equivalent pressure value of the reverse thrust, the smaller the opening, and the smaller the equivalent pressure value of the reverse thrust, the larger the opening, to obtain the actual pressure rise per unit time, including: By inputting the equivalent pressure value of the reverse thrust into the linear inverse proportional function mapping unit built into the controller, the target opening area control quantity of the proportional throttle valve is obtained by continuously mapping and calculating according to the inverse proportional relationship between the equivalent pressure value from zero to the highest clamping pressure and the opening of the proportional throttle valve from the maximum opening to the minimum opening. By outputting the target opening area control quantity to the electromagnetic drive end of the proportional throttle valve, the valve core displacement changes linearly with the magnitude of the control current to change the flow cross-sectional area of ​​the valve orifice, thereby obtaining the actual flow area of ​​the valve orifice. The flow meter installed at the accumulator inlet continuously measures the volume of oil flowing into the accumulator per unit time after being limited by the actual valve port flow area, thus obtaining the actual pressure rise of the accumulator per unit time.

6. The method for controlling fluid residual pressure recovery in a hydraulic power clamp according to claim 1, characterized in that, S3 includes: By inputting the pressure rise slope value and the initial accumulator filling pressure value into the controller, and combining them with the maximum allowable working pressure value of the accumulator, the theoretical shortest recovery time required for the accumulator to rise from the initial filling pressure to the maximum allowable working pressure is calculated, and the available recovery time window of the accumulator is obtained. By matching and comparing the available recovery time window of the accumulator with the maximum allowable delay time during the clamping cylinder release phase, the controller is matched. If the available recovery time window is less than or equal to the maximum delay time, the highest allowable working pressure is taken as the cutoff pressure. If it is greater than the maximum delay time, the corresponding pressure value is calculated by reverse calculation according to the ratio of the time window to the maximum delay time to obtain the actual safe recovery cutoff pressure value. Based on the actual safe recovery cutoff pressure value, the controller executes a graded switching command on the recovery control valve group. When the accumulator pressure has not reached the cutoff pressure value, the recovery position is kept open to recover energy. When the cutoff pressure value is reached, the controller switches to the pressure relief position to bypass the remaining low-pressure oil in the clamping cylinder to the oil tank, thereby obtaining the final pressure value when the accumulator actually terminates recovery. By substituting the final pressure value into the pressure relief characteristic curve of the clamping cylinder and combining it with the time required for the oil in the clamping cylinder to be emptied under the current recovery flow rate, the actual release action completion time value is obtained by referring to a table.

7. The method for controlling fluid residual pressure recovery in a hydraulic power clamp according to claim 6, characterized in that, The process involves matching and comparing the available recovery time window of the accumulator with the maximum allowable delay time during the clamping cylinder's release phase, inputting this value to the controller. If the available recovery time window is less than or equal to the maximum delay time, the highest allowable working pressure is taken as the cutoff pressure. If it is greater than the maximum delay time, the corresponding pressure value is calculated by reverse calculation based on the ratio of the time window to the maximum delay time to obtain the actual safe recovery cutoff pressure value, including: The difference between the value of the available recovery time window and the value of the maximum allowable delay time during the clamping cylinder release phase is calculated by inputting the value of the subtractor built into the controller. If the difference is less than or equal to zero, it is determined that the window is sufficient. If the difference is greater than zero, it is determined that the window is insufficient, and the sign of the difference is obtained. By inputting the difference sign determination result into the controller's selector, if the window is sufficient, the selector directly selects the maximum allowable working pressure of the accumulator as the output cutoff pressure; if the window is insufficient, the selector switches to the proportional calculation module to obtain the cutoff pressure selection path determination signal. In cases where the window is insufficient, the ratio of the maximum delay time to the available recovery time window is input into the proportional calculation module. This ratio is then multiplied by the maximum allowable operating pressure of the accumulator to obtain the time-scaled cutoff pressure value, thus obtaining the scaled cutoff pressure value. The selector selects the path determination signal based on the scaling cutoff pressure value, and outputs the maximum allowable working pressure under sufficient window conditions or the scaling cutoff pressure value under insufficient window conditions as the final result to the controller storage unit to obtain the actual safe recovery cutoff pressure value.

8. The method for controlling fluid residual pressure recovery in a hydraulic power clamp according to claim 1, characterized in that, S4 includes: By inputting the actual safe recovery cutoff pressure value and the corresponding current gas volume change of the accumulator into the controller, the total hydraulic energy stored in the accumulator at the time of recovery termination is calculated using the gas state equation, and then the basic energy corresponding to the accumulator's own charging pressure is deducted to obtain the effective releasable hydraulic energy. By inputting the effective releasable hydraulic energy and the initial output pressure value of the hydraulic pump at the start of the next work cycle into the controller, the difference between the total energy required by the system at the start of the next cycle and the energy provided by the accumulator is calculated. If the energy of the accumulator is higher than the demand, the energy replenishment difference is zero; if it is lower than the demand, the difference is taken as the additional energy replenishment demand value, and the auxiliary energy replenishment starting pressure threshold is obtained. By using the auxiliary energy replenishment starting pressure threshold, the controller applies an early opening signal to the accumulator outlet energy supply valve during the standby phase before the clamping cylinder starts to move in the next cycle, so that the accumulator releases high-pressure oil to the main oil circuit in advance before the hydraulic pump starts, thus obtaining the actual early opening time of the energy supply valve. The actual effective output power utilization rate is obtained by calculating the ratio between the energy released at the actual early start time and the actual output energy of the hydraulic pump during the start-up phase.

9. The method for controlling fluid residual pressure recovery in a hydraulic power clamp according to claim 8, characterized in that, The controller, through the auxiliary energy replenishment starting pressure threshold, applies an early opening signal to the accumulator outlet energy supply valve during the standby phase before the clamping cylinder starts operating in the next cycle. This causes the accumulator to release high-pressure oil into the main oil circuit before the hydraulic pump starts, thus obtaining the actual early opening time of the energy supply valve, including: By continuously comparing the auxiliary energy replenishment start pressure threshold input controller with the current pressure value of the accumulator monitored in real time by the third pressure sensor, the standby energy replenishment permission condition is triggered when the current pressure value of the accumulator is greater than or equal to the auxiliary energy replenishment start pressure threshold, and the energy replenishment permission trigger signal is obtained. By performing a logical AND operation between the energy replenishment enable trigger signal and the current work cycle end time signal generated by the controller's internal timer, the outlet energy supply valve drive circuit is enabled during the standby phase after the clamping cylinder completes the release action and the main directional valve switches to the neutral position, thereby obtaining the standby phase enable signal. By outputting the standby phase enable signal to the solenoid coil of the accumulator outlet power supply valve, the power supply valve opens first during the standby period before the hydraulic pump starts, allowing the high-pressure oil in the accumulator to flow into the main oil circuit through the check valve. At the same time, the system pressure sensor installed on the main oil circuit monitors the start time of the system pressure rise caused by this release process to obtain the reference time point. By inputting the reference time point and the signal at which the operator presses the start button to trigger the clamping action in the next cycle into the time difference calculation unit built into the controller, the advance amount of the reference time point relative to the clamping action triggering time is calculated to obtain the actual advance opening time point.

10. A fluid residual pressure recovery control system for a hydraulic power clamp, characterized in that, The system includes: The conduction control module is used to obtain the priority level of the current residual pressure source by real-time acquisition and comparison of the initial pressure value of the clamping cylinder and the return oil pressure value of the motor brake, and to perform priority conduction control on the recovery control valve group to obtain the initial accumulator charging pressure value. The dynamic comparison module is used to continuously monitor the real-time rising gas back pressure value in the accumulator and dynamically compare it with the current actual clamping and maintaining pressure value of the clamping cylinder to obtain the equivalent pressure value of the reverse thrust generated by the back pressure on the piston of the clamping cylinder, and to adjust the proportional throttle valve to obtain the corrected actual effective recovery pressure rise slope value of the accumulator. The comparison control module is used to calculate the available recovery time window of the accumulator by using the pressure rise slope value and the initial accumulator filling pressure value, and to match and compare it with the maximum allowable release delay time of the clamping cylinder to obtain the actual safe recovery cutoff pressure value. It also performs graded switching control of the recovery control valve group to obtain the actual release action completion time value that meets the operation cycle requirements. The calculation and control module is used to calculate the effective releaseable hydraulic energy actually stored in the accumulator by using the actual safe recovery cutoff pressure value and back pressure influence data. It also calculates the supply and demand difference by combining the initial output pressure value of the hydraulic pump at the start of the next cycle, obtains the auxiliary energy replenishment starting pressure threshold, and controls the opening timing of the accumulator outlet energy supply valve in advance to obtain the actual effective output power utilization rate value of the hydraulic pump after insufficient compensation and recovery.

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