Control method for variable-torque power output of excavator

Abstract

The invention relates to a control method for variable-torque power output of an excavator, which comprises the following steps that: a control unit acquires oil temperature, input rotating speed, output rotating speed and locking state of a torque converter according to a control period, compares a difference value between the input rotating speed and the output rotating speed with a rotating speed difference threshold value, judges a sliding or locking state in combination with the locking state, and accumulates corresponding state duration; the control unit is provided with a heat limit with an upper limit and a lower limit, the heat limit is deducted according to the duration and the oil temperature rising speed in the sliding state, the heat limit is supplemented according to the duration and the oil temperature falling speed in the locking state, and the oil temperature rising speed is determined by the oil temperature variation in the adjacent control period; when the control unit sets that the first threshold value is larger than the second threshold value and the heat limit is not higher than the second threshold value, the locking duty ratio is increased, and the continuous sliding duration is limited through periodic locking / unlocking; when the first threshold value is not lower than the first threshold value, the locking duty ratio is reduced; and when the current locking duty ratio is between the two threshold values, the current locking duty ratio is kept, and finally a locking control instruction is output.

Description

Technical Field

[0001] This invention relates to the field of power transmission control technology for engineering machinery, specifically a control method for torque converter power output of an excavator. Background Technology

[0002] Current technologies, such as the locking / unlocking method, locking / unlocking system, and hydraulic torque converter disclosed in CN115479120A, rely on setting lock-up conditions based on gear position and parameters such as speed difference, slip ratio, or speed ratio. When these preset conditions are met, the turbine lock-up clutch is controlled to lock up. Locking occurs when the gear reaches a preset position and the speed difference, slip ratio, or speed ratio meets the corresponding preset conditions. While this approach achieves automatic lock-up, it essentially remains at the level of static threshold control based on speed relationships. Its lock-up and unlocking decisions primarily depend on the comparison between instantaneous detection values ​​and pre-stored parameters, lacking systematic management of the torque converter's thermal state evolution, the cumulative effect of slip duration, and the oscillation behavior during locking / unlocking. Therefore, it still has significant shortcomings under complex operating conditions.

[0003] This method lacks a dynamic constraint mechanism between slip heating and lock-up recovery, and fails to quantitatively manage the heat accumulation caused by continuous slip. It only locks or unlocks when the required speed is met, failing to identify the impact of slip duration on torque converter oil temperature and clutch thermal load. This can easily lead to excessively long slip times and exacerbated temperature rise under high load and prolonged low-speed operation. The lock-up conditions in this scheme primarily revolve around gear position and speed difference or slip ratio, without utilizing oil temperature change trends or analyzing the rate of oil temperature rise or fall. Therefore, it cannot dynamically adjust the control strategy based on real-time thermal changes, causing the original preset parameters to become ineffective when ambient temperature or oil condition changes, thus affecting control performance. Although the document proposes multi-condition lock-up determination, its control logic remains a single-decision trigger structure. It does not consider the oscillation problem caused by repeated switching between lock-up and unlock near the threshold, and lacks a suppression mechanism for frequent lock-up and unlock behavior. Under load fluctuations or slight speed fluctuations, repeated engagement and disengagement of the lock-up clutch may occur, causing shocks, vibrations, and reduced comfort, while also increasing mechanical wear.

[0004] This technology lacks a historical memory mechanism, fails to accumulate statistics on multiple triggers of lockout restriction behavior, and does not adjust the control strategy in stages based on the number of repeated triggers. Therefore, it cannot identify long-term thermal shocks or continuous oscillation trends, and the control strategy lacks the ability to progressively strengthen or adjust in stages, making it difficult to maintain stable output in complex operating cycles. The shifting and lockout strategies in this document are primarily designed around engine speed. While the impact of throttle opening on shift points is considered, it still does not constrain slip behavior from a thermal management perspective, nor does it set up similar thermal allowance or thermal shock memory variables to coordinate slip energy consumption and lock-up recovery processes. Summary of the Invention

[0005] The purpose of this invention is to provide a control method for the torque converter power output of an excavator, thereby solving some of the drawbacks and shortcomings pointed out in the background art.

[0006] The present invention addresses the aforementioned technical problems by employing the following technical solution: a control method for torque converter power output of an excavator, comprising: applicable to a power transmission system having a torque converter and a lock-up unit, executed by a control unit, wherein the control unit collects torque converter oil temperature, input speed, output speed, and lock-up status according to a control cycle; compares the difference between the input speed and the output speed with a speed difference threshold, and determines whether the torque converter is in a slip state or a lock-up state in conjunction with the lock-up status, and accumulates the duration of the corresponding state;

[0007] The control unit sets a thermal limit, which has an upper and lower limit. In the sliding state, the thermal limit is deducted based on the duration and the rate of oil temperature rise. In the locked state, the thermal limit is replenished based on the duration and the rate of oil temperature fall. The rate of oil temperature rise and the rate of oil temperature fall are determined by the amount of oil temperature change in adjacent control cycles.

[0008] The control unit sets a first threshold greater than a second threshold. When the thermal load is not higher than the second threshold, it increases the locking duty cycle and periodically locks / unlocks to limit the duration of continuous sliding. When the thermal load is not lower than the first threshold, it decreases the locking duty cycle. When the thermal load is between the two thresholds, it maintains the current locking duty cycle. The control unit outputs a locking control command.

[0009] Furthermore, when the thermal rating is not lower than the first threshold and the torque converter is continuously locked for a preset stable duration, the control unit releases the lock and resumes locking after a preset pulse duration; and adjusts the thermal rating deduction intensity in the subsequent slip state or the thermal rating recovery intensity in the locked state according to the oil temperature change amplitude before and after the pulse.

[0010] Furthermore, the control unit counts the number of times the sliding state and the locking state are switched within a preset time window; when the number of switching reaches a preset entry threshold, vibration suppression control is entered, so that the locking duty cycle remains unchanged, and the duration of the sliding state is not less than a preset sliding duration threshold and the duration of the locking state is not less than a preset locking duration threshold, while temporarily increasing the interval between the first threshold and the second threshold; when the number of switching drops to a preset exit threshold, vibration suppression control is exited, wherein the locking duty cycle adjustment based on thermal load is paused during vibration suppression control, and is resumed after exiting.

[0011] Furthermore, the control unit sets a thermal shock memory value; when the thermal rating is not higher than the second threshold and triggers an increase in the lock-up duty cycle and periodic lock / unlock, the thermal shock memory value is accumulated; when the thermal shock memory value reaches a preset value, the upper limit of the thermal rating is temporarily lowered and the first threshold and the second threshold are lowered simultaneously; when the cumulative lock-up duration reaches the preset recovery time and the oil temperature meets the cooling criterion, the thermal shock memory value is cleared and the upper limit of the thermal rating and the threshold are restored.

[0012] Furthermore, when entering the vibration suppression control, the threshold interval increase is selected as one of the preset levels based on the peak number of switching times during the preset backtracking period before entering; if the entry condition is met again during the vibration suppression control period, the threshold interval increase is switched to the next preset level and the interval between the first threshold and the second threshold is updated; when the preset backtracking condition is met, backtracking to the previous preset level is allowed.

[0013] Furthermore, the control unit sets release conditions for state switching during vibration suppression control: switching from sliding state to locked state requires that the sliding holding time is not less than a preset sliding holding time threshold and the number of switching is not greater than a preset fall-off threshold; switching from locked state to sliding state requires that the locking holding time is not less than a preset locking holding time threshold and the number of switching is not greater than the preset fall-off threshold.

[0014] Furthermore, the preset gears are mapped according to the interval to which the peak number of switching times belongs, and each preset gear corresponds to a threshold interval increment; when entering vibration suppression control, the interval to which the peak belongs is first determined, then the corresponding preset gear is selected and the interval between the first threshold and the second threshold is updated.

[0015] Furthermore, the conditions for re-entering during the vibration suppression control include continuously satisfying the entry threshold a preset number of times within a preset time window; when satisfied, the threshold interval is increased and switched to the next preset level, and a preset holding time is set, during which it is prohibited to revert to the previous preset level.

[0016] Furthermore, the control unit sets a one-way holding duration during vibration suppression control, and the one-way holding duration is one of a plurality of preset holding duration levels; after the switch from sliding state to locked state is completed, the switch from locked state to sliding state is prohibited from being triggered within the one-way holding duration; after the switch from locked state to sliding state is completed, the switch from sliding state to locked state is prohibited from being triggered within the one-way holding duration.

[0017] Furthermore, the one-way holding duration is dynamically adjusted based on the number of times the sliding state and the locked state switch within the first time window after the one-way holding duration expires; when the number of switching is still greater than the preset adjustment threshold, the one-way holding duration is switched to the next preset holding duration; when the number of switching is not greater than the preset adjustment threshold, the one-way holding duration is switched to the previous preset holding duration or remains unchanged.

[0018] The beneficial effects of this invention are as follows: It constructs a hierarchical control mechanism centered on thermal allowance, directly linking torque converter slip heating with lock-up adjustment, thus achieving dynamic thermal constraint control of the torque converter's power output. By deducting thermal allowance based on duration and oil temperature rise rate during slip, and replenishing thermal allowance based on duration and oil temperature drop rate during lock-up, the control strategy aligns with actual thermal change trends, thereby avoiding excessive slip or heat accumulation problems caused by relying solely on speed or load changes in traditional control methods. Simultaneously, the zoned adjustment logic formed by the first and second thresholds provides a clear hierarchy for lock-up duty cycle adjustment, ensuring the required torque amplification capability during operation while effectively limiting continuous slip duration, reducing the risk of torque converter overheating, and improving the reliability and durability of the transmission system.

[0019] The introduction of calibration slip pulses, thermal shock memory, and multi-level vibration suppression control mechanisms enables the system to have adaptive correction and oscillation suppression capabilities. By adjusting the thermal allowance deduction and compensation intensity based on the actual oil temperature change, thermal management accuracy can be improved; by adjusting the threshold range in conjunction with the thermal shock memory, repetitive thermal shocks can be identified and suppressed; and by adjusting the threshold intervals in different gears, limiting the duration of unidirectional holding, and dynamically adjusting the gears, frequent switching between slip and lock-up can be effectively suppressed, improving the smoothness of power output. Attached Figure Description

[0020] Figure 1 This is a logic diagram for torque converter output based on thermal zoning in this invention.

[0021] Figure 2 This is a graph showing the changes of key variables over time in Embodiment 1 of the present invention.

[0022] Figure 3 This is a comparison diagram before and after the control strategy is enabled in Embodiment 1 of the present invention.

[0023] Figure 4 This is a diagram illustrating the linkage mechanism between thermal power, oil temperature, and thermal rating in Embodiment 1 of the present invention.

[0024] Figure 5 This is a schematic diagram of the sliding window switching count and release threshold in Embodiment 2 of the present invention.

[0025] Figure 6 This is a comparison chart of statistical indicators before and after the vibration suppression control is enabled in Embodiment 2 of the present invention.

[0026] Figure 7 This is a window evolution diagram of the vibration suppression level and unidirectional holding time in Embodiment 2 of the present invention. Detailed Implementation

[0027] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0028] Combined with appendix Figure 1 This invention discloses a control method for the torque converter power output of an excavator. The control cycle is a fixed time interval, which can meet the real-time requirements of the power transmission system. Within each control cycle, the control unit collects the torque converter oil temperature signal, the torque converter input speed signal, the torque converter output speed signal, and the current status signal of the lock-up unit. The torque converter oil temperature reflects the internal thermal state of the torque converter; the input speed is the engine-side speed or the torque converter pump wheel speed; the output speed is the torque converter turbine-side speed or the transmission mechanism input speed; and the lock-up status indicates whether the lock-up unit is engaged or disengaged.

[0029] The control unit calculates the difference between the acquired input and output speeds to obtain the current speed difference. The control unit compares this speed difference with a preset speed difference threshold. When the speed difference is greater than the threshold and the locking unit is disengaged, the torque converter is determined to be in a slip state; when the speed difference is not greater than the threshold or the locking unit is engaged, the torque converter is determined to be in a locked state. By combining the speed difference and the locking unit status for judgment, misjudgments based solely on the speed difference can be avoided, thereby improving the accuracy of state identification.

[0030] After determining the state, the control unit accumulates the duration of the currently determined slip or lock-up state. When the torque converter is continuously in the same state, the duration increases with the control cycle; when a state transition occurs, the current state duration is reset to zero, and the accumulation of the new state duration begins. The duration is used to characterize the length of time slip or lock-up is maintained, providing a time basis for subsequent control strategies.

[0031] The control unit records the torque converter oil temperature in each control cycle and compares it with the oil temperature recorded in the previous control cycle to obtain the oil temperature change. The oil temperature change is divided by the control cycle length to determine the oil temperature change rate. When the oil temperature change is positive, it is determined that the oil temperature is rising, and the corresponding rate of change is taken as the oil temperature rise rate; when the oil temperature change is negative, it is determined that the oil temperature is falling, and the corresponding rate of change is taken as the oil temperature fall rate. By using the oil temperature change between adjacent control cycles to determine the oil temperature rise rate and oil temperature fall rate, the instantaneous thermal change trend of the torque converter can be reflected.

[0032] When the control unit determines that the torque converter is in a slipping state, it deducts the heat allowance based on the duration of the slipping state and the rate of oil temperature rise. The longer the slipping duration or the greater the rate of oil temperature rise, the greater the corresponding heat allowance deduction. After completing the deduction, the control unit checks whether the heat allowance is below a preset lower limit. If it is below the lower limit, the heat allowance is set to the lower limit value to prevent invalid heat allowance values.

[0033] When the control unit determines that the torque converter is in a lock-up state, it replenishes the thermal allowance according to the duration of the current lock-up state and the rate of oil temperature drop. The longer the lock-up duration or the greater the rate of oil temperature drop, the greater the corresponding thermal allowance replenishment. After completing the replenishment, the control unit checks whether the thermal allowance exceeds a preset upper limit. If it does, the thermal allowance is limited to the upper limit value.

[0034] The control unit reads the current thermal margin in each control cycle and compares it with a first threshold and a second threshold. When the thermal margin is not higher than the second threshold, it is determined that the current thermal margin is insufficient, and slip heating needs to be limited. The control unit increases the lock-up duty cycle, increasing the proportion of time the lock-up unit remains engaged. To avoid overheating caused by continuous slip, the control unit performs alternating lock-up and unlock control according to a preset cycle, causing the torque converter to periodically switch between slip and lock-up, thereby limiting the maximum duration of continuous slip.

[0035] When the heat margin is not lower than the first threshold, the current heat margin is determined to be sufficient. The control unit reduces the lock-up duty cycle, thereby reducing the engagement ratio of the lock-up unit per unit time, which allows the torque converter to maintain a certain degree of slip to meet the requirements of power amplification and smooth operation.

[0036] When the heat load is between the first and second thresholds, the system is determined to be in the thermal management transition zone. To avoid frequent changes in the control strategy, the control unit maintains the current lock-up duty cycle without making any additional adjustments, thus ensuring the continuity and stability of the system's operation.

[0037] After completing the above judgment and duty cycle adjustment, the control unit generates the corresponding locking control command based on the currently determined locking duty cycle and the periodic locking and unlocking control strategy, and outputs the locking control command to the locking unit actuator.

[0038] When the above conditions are met, the control unit outputs a release control command to the lock-up unit, causing the torque converter to enter a short-term slip state. After this slip is maintained for a preset pulse duration, the control unit outputs a lock-up restoration control command again, causing the torque converter to re-enter the lock-up state. The preset pulse duration is pre-set according to the system response characteristics; its length is sufficient to cause a detectable change in oil temperature, but insufficient to cause significant heat accumulation or power fluctuations.

[0039] During the calibration slip pulse execution, the control unit records the oil temperature before the pulse and the oil temperature value during the preset observation period after the pulse ends, and calculates the change range between the two. The oil temperature change range is used to reflect the actual impact of short-term slip on the thermal state of the torque converter under the current operating conditions and oil fluid conditions.

[0040] When the oil temperature change exceeds a preset threshold, the system is deemed to have a high sensitivity to heat generation during slippage. The control unit increases the thermal deduction intensity during subsequent slippage states or decreases the thermal compensation intensity during lockup states to make thermal consumption more stringent, thereby limiting slippage behavior in advance. If the oil temperature change is below the preset threshold, the system is deemed to have a smaller impact from heat generation during slippage. In this case, the control unit decreases the thermal deduction intensity during subsequent slippage states or increases the thermal compensation intensity during lockup states to enhance the system's tolerance to slippage.

[0041] When the thermal load is not higher than the second threshold, the control unit increases the lock-up duty cycle according to the aforementioned control logic and performs periodic lock-up and unlocking to limit the duration of continuous slip. Whenever the above control action is triggered due to insufficient thermal load, the control unit increments the thermal shock memory value. The thermal shock memory value reflects the frequency with which the thermal load repeatedly reaches the low threshold within a certain operating phase, and is used to characterize the torque converter operating under high thermal stress.

[0042] When the thermal shock memory value reaches a preset value, the system is determined to have a risk of continuous or repetitive thermal shock. At this point, the control unit temporarily lowers the upper limit of the thermal allowance, reducing the maximum recoverable value of the thermal allowance, and simultaneously lowers the first and second thresholds, shifting the overall thermal management control range towards a more conservative approach. By lowering the upper limit and thresholds, the subsequent increase in the lock-up duty cycle is triggered earlier, further compressing the slippage space and mitigating the heating trend.

[0043] After entering the enhanced suppression phase, the control unit continuously monitors the cumulative duration of the lock-up state and the torque converter oil temperature. When the cumulative lock-up duration reaches the preset recovery time and the oil temperature meets the cooling criterion, the system is determined to have entered the stable cooling phase. The control unit clears the thermal shock memory value to zero and restores the thermal limit, first threshold, and second threshold to their original settings, returning the control strategy to the normal thermal management range.

[0044] When the number of switching operations counted by the control unit within a preset time window reaches a preset entry threshold, it is determined that the current system has an oscillation trend, and then it enters the vibration suppression control state. After entering the vibration suppression control state, the control unit suspends the dynamic adjustment of the lock-up duty cycle based on the thermal rating, so that the current lock-up duty cycle remains unchanged, in order to avoid further fluctuations caused by frequent adjustments with changes in the thermal rating.

[0045] Meanwhile, during vibration suppression control, the control unit applies holding constraints to the state switching, ensuring that the holding time of the sliding state is not less than a preset sliding holding time threshold, and the holding time of the locked state is not less than a preset locking holding time threshold.

[0046] Furthermore, upon entering vibration suppression control, the control unit temporarily increases the interval between the first and second thresholds, thus expanding the thermal limit control range and reducing the impact of slight thermal limit fluctuations on the lock-up strategy. This increased interval operation only takes effect during vibration suppression control and is used to stabilize the system state.

[0047] When the number of switching operations counted by the control unit within a preset time window drops to a preset exit threshold, the oscillation trend is determined to be eliminated, and the vibration suppression control is exited. After exiting, the control unit resumes the lock-up duty cycle adjustment strategy based on thermal allowance and restores the original interval setting between the first and second thresholds, allowing the system to resume power output control according to thermal management logic.

[0048] When the control unit determines that the conditions for entering vibration suppression control are met, it retraces the preset retracing period before entry and counts the peak number of switching between the slip state and the lock state during this retracing period. The peak number of switching is used to characterize the oscillation intensity. Based on the range of this peak, the control unit selects the corresponding preset level and determines the threshold interval increment accordingly. Subsequently, it updates the interval between the first threshold and the second threshold, increasing it by the increment corresponding to the selected level, thereby improving the ability to suppress oscillation.

[0049] During vibration suppression control, the control unit continuously monitors the number of switching times within a preset time window. When the conditions for entering vibration suppression control are met again, it indicates that the oscillation trend still exists or has intensified. At this time, the control unit switches the threshold interval increment to the next preset level and updates the interval between the first and second thresholds again to further expand the thermal control range, reduce the sensitivity near the threshold, and thus enhance stability.

[0050] To avoid affecting system responsiveness due to prolonged high-intensity vibration suppression, the control unit is configured with preset rollback conditions. These rollback conditions can be defined as the number of switching operations within a certain number of consecutive time windows falling below a preset recovery criterion. When the rollback conditions are met, the control unit allows the threshold interval to be rolled back to the previous preset level by a large increment, and correspondingly reduces the interval between the first and second thresholds, gradually restoring the control strategy to the normal range.

[0051] When the current state is a sliding state and the conditions for switching from the sliding state to the locked state are met, the control unit does not immediately execute the switch. Instead, it determines whether the cumulative duration of the sliding state is not less than a preset sliding duration threshold, and simultaneously determines whether the number of switches counted within the current preset time window is not greater than a preset fallback threshold. Only when both conditions are met simultaneously will the control unit allow the switch from the sliding state to the locked state and output the corresponding locking control command. If either condition is not met, the sliding state will continue to be maintained.

[0052] When the current state is locked and the conditions for switching from locked to sliding are met, the control unit determines whether the cumulative duration of the locked state is not less than a preset lock duration threshold, and simultaneously determines whether the number of switching attempts within a preset time window is not greater than a preset fallback threshold. The control unit only allows the switch from locked to sliding if both conditions are met simultaneously. If not, the locked state remains unchanged.

[0053] When the control unit determines that vibration suppression control needs to be activated, it traces back a preset traceback period before activation and counts the peak number of transitions between the slip and lock states during that period. Then, the peak number of transitions is compared with several pre-set intervals to determine the interval to which it belongs. Different intervals correspond to different oscillation intensity levels.

[0054] After determining the range to which the peak value belongs, the control unit selects the preset level corresponding to that range and reads the threshold interval increment corresponding to that level. Then, the original interval between the first and second thresholds is updated by increasing the increment. This update causes the thermal limit control range to expand in stages according to oscillation intensity, thereby reducing sensitivity near the threshold and suppressing frequent switching.

[0055] After confirming that the entry conditions are met again, the control unit switches the current threshold interval increment to the next preset level. The next preset level corresponds to a larger threshold interval increment, which is used to further expand the interval between the first threshold and the second threshold, so as to reduce the system's sensitivity to thermal fluctuations and thus enhance vibration suppression.

[0056] To avoid frequent increases and subsequent retractions in the threshold interval that could lead to repeated changes in the control strategy, the control unit sets a preset hold time after completing the gear shift. Within this hold time, even if the retraction conditions are met, it is prohibited to significantly retract the threshold interval to the previous preset gear. The hold time ensures that the adjusted vibration suppression intensity has a stable duration, allowing the system to operate at a higher vibration suppression level for a sufficient period to observe whether the oscillations are alleviated.

[0057] Once the torque converter switches from the slip state to the lock-up state and completes the lock-up control command output, the control unit starts timing and prohibits the switching from the lock-up state to the slip state during the selected unidirectional holding time. Even if the thermal rating changes or other switching conditions are met during this period, the lock-up state remains unchanged until the unidirectional holding time ends.

[0058] Once the torque converter switches from lock-up to slip and completes the corresponding control command output, the control unit prohibits triggering a switch from slip to lock-up for a selected unidirectional holding period. During this holding period, even if the lock-up condition is met, the slip state is maintained to avoid a short-term reverse switch.

[0059] If the number of switching counts within the first time window still exceeds the preset adjustment threshold, it is determined that the current unidirectional hold strength is insufficient to suppress oscillations. At this time, the control unit switches the unidirectional hold duration to the next preset hold duration. The next preset hold duration corresponds to a longer hold time, which is used to enhance the restriction on reverse switching, thereby further reducing the probability of back-and-forth switching in a short period of time.

[0060] When the number of switching counts within the first time window is not greater than the preset adjustment threshold, it is determined that the current one-way holding strategy has produced a suppressive effect. At this time, the control unit switches the one-way holding duration to the preset holding duration of the previous gear, or keeps it unchanged in the current gear, in order to gradually restore the system's response sensitivity and avoid maintaining excessively strong restrictions for a long time, which would affect the power output characteristics.

[0061] Example 1:

[0062] Taking a 36-ton tracked hydraulic excavator as an example, this machine operates continuously at a loading station in an open-pit mine. The ambient temperature is 34℃, the road longitudinal slope is 8%, and the material is high-hardness weathered rock. The equipment operates in a cycle of digging, boom raising, slewing, unloading, and reverse slewing, with each cycle lasting approximately 22 seconds. During the full-bucket start-up and uphill slewing phases, the engine output torque fluctuates significantly, and the torque converter operates under high slip conditions for an extended period. On-site, the oil temperature rose from 86℃ to 103℃ within 110 seconds. After continuous slippage exceeding 9 seconds, the operational response became sluggish, and significant impact occurred during forced lock-up recovery. To facilitate the illustration of the evolution of key variables within a typical time period, Figure 2The combined trends of oil temperature, thermal capacity, and lock-up duty cycle within a time window of 60s to 172s are presented to visually demonstrate the timing relationship between threshold triggering and protection actions.

[0063] The control unit is installed within the powertrain controller, with a control cycle of 20ms. Each control cycle, the control unit acquires the torque converter oil temperature T (in °C) and inputs the engine speed. The unit is Output speed The unit is And the lock-up state quantity S. The speed difference is defined as... The speed difference threshold is 120. Define the lockout duty cycle. The initial value is 58%. Define the hot quota. The unit is credit points, with an upper limit of 100 and a lower limit of 0. Define the first threshold. The value is 72, the second threshold. It is 38, and Define thermal shock memory. The initial value is 0, and the upper limit trigger value is 6. Define the continuous locking stability duration. The pulse unlock duration is 12 seconds. The cumulative lock duration in the recovery criterion is 0.6s. The cooling criterion is 18 seconds. ℃ or .in, Figure 2 The corresponding sample data shows that the heat value at 124 seconds... The value decreased to 36.9, which is below the second threshold of 38, thus triggering an increase in the locking duty cycle and entering periodic locking and unlocking control. The locking duty cycle increased from 58% to 66%, consistent with step S5 described later. Furthermore, the thermal shock memory value at 172s... When the threshold reaches 6, the secondary protection logic of temporarily lowering the threshold is triggered, that is, the upper limit of the hot limit is lowered from 100 to 88, and the first threshold is lowered from 72 to 64, and the second threshold is lowered from 38 to 31, so that the system enters the protection zone earlier to reduce repeated hot shocks.

[0064] The control unit executes the following procedure. Step S1: Read the current cycle... , , and ,calculate Step S2, when If the current locking state is not fully locked, it is determined to be a sliding state, and the sliding duration is set. Increment by 20ms, and simultaneously adjust the lockout duration. Reset to zero. When And when the locking state is locked, it is determined to be in the locked state, and then... Increment by 20ms, and simultaneously Zero. Step S3: Calculate the oil temperature change rate of adjacent control cycles, and take... The unit is ℃ Step S4: If in a sliding state, deduct the heat allowance based on the sliding duration and the rate of oil temperature rise. If in a locked state, replenish the heat allowance based on the locked duration and the rate of oil temperature drop. Step S5: When At that time, increase the locking duty cycle and perform periodic locking and unlocking control, specifically taking... The current value is increased to 66%, using a pulse rhythm of 1.2s lockout followed by 0.4s unlock to limit the duration of continuous slippage. When At this time, reduce the locking duty cycle to suppress locking impact, specifically take... Reduced to 52%. At that time, keep the current Unchanged. Step S6: Output a lock-up control command to the lock-up solenoid valve and simultaneously update the status timer, thermal limit, and thermal shock memory value.

[0065] Heat credit is updated discretely. Under slip conditions, a deduction intensity coefficient is defined. The initial value is 0.45. Under locked conditions, the recovery strength coefficient is defined. The initial value is 0.30. Let... , The formula for updating the hot quota is:

[0066]

[0067] in, This indicates amplitude limiting. Taking five consecutive sampling points during the slip phase as an example, [the value is...]. , The times are 0.02s, 0.04s, 0.06s, 0.08s, and 0.10s respectively, and the oil temperatures are 92.00℃, 92.03℃, 92.07℃, 92.12℃, 92.18℃, and 92.25℃ respectively. The temperatures are 1.50, 2.00, 2.50, 3.00, and 3.50℃ respectively. Substituting, we get:

[0068]

[0069]

[0070]

[0071]

[0072]

[0073] It is evident that as the rate of oil temperature increase, the slope of heat deduction also increases, thus providing early intervention against continuous slippage.

[0074] Oil temperature changes are described using a first-order thermal model. Ambient temperature is taken as... ℃, slip heat power is If the unit is kW, then:

[0075]

[0076] in, , During a certain full-bucket rotation phase, the measured average sliding heat power was 28kW, and the oil temperature was 96℃. Therefore:

[0077]

[0078] The theoretical temperature rise within 10 seconds is approximately 5.64℃. Under the same operating conditions, the measured oil temperature rose from 95.8℃ to 101.2℃, a rise of 5.4℃, consistent with the model trend. This indicates that using the oil temperature change rate as the input for heat deduction is verifiable. If the lock-up phase is entered and... If the value is approximately 0 and the oil temperature is 98℃, then:

[0079]

[0080] This indicates that the locked state has a significant heat dissipation trend and can be used for heat credit replenishment.

[0081] To further characterize the heat input, the slip energy is estimated by summation. An equivalent coefficient is used. Input torque The equivalent torque on the engine side is approximated, and the unit is... m, then the sliding heat power within the window is approximately:

[0082]

[0083] The slip energy is:

[0084]

[0085] Taking a 4-second window as an example, there are a total of 200 control cycles, and the average value is taken. ,average m, then:

[0086]

[0087]

[0088] This heat input, together with the aforementioned first-order thermal model, explains the rapid rise in oil temperature during the high-load rotation phase, and also provides a basis for setting... This provides evidence that when the short-term slip energy approaches 180kJ, the heat value will rapidly approach the second threshold and trigger a limiting strategy.

[0089] when And continuous locking reaches At this time, pulse unlock self-calibration is performed. The control unit first maintains the current state. No change, then force unlock Then, the original lock-up duty cycle is restored. Assuming the average oil temperature before the pulse is 94.6℃ and after the pulse is 94.9℃, then... ℃. A combination of proportional correction and exponential smoothing is used to correct the subsequent slip reduction strength coefficient. Let the target pulse temperature rise be... At ℃, with a smoothing coefficient of 0.7, then:

[0090]

[0091] Substitution have to:

[0092]

[0093] Since the measured pulse temperature rise is lower than the target value, it indicates that the current system's thermal sensitivity is lower than expected. Therefore, the subsequent slip reduction intensity should be appropriately reduced to avoid an excessively rapid decrease in thermal load. If the pulse temperature rise is higher than the target value, the equation will be increased. Similarly, the locking compensation strength can be modified according to the same structure. Prioritize correction .

[0094] when And when the duty cycle is increased and the periodic locking and unlocking are triggered, the thermal shock memory amount Accumulates periodically. The memory amount is incremented once for each completed 1.6-second control rhythm. If six consecutive rhythms remain in this restricted mode, then... Reaching 6 and triggering a temporary reduction in the threshold, specifically... The number was reduced from 100 to 88. The value was reduced from 72 to 64. The value was reduced from 38 to 31. This adjustment allows the system to enter the protection zone earlier, reducing the probability of another high thermal shock. When the subsequent cumulative lockout duration reaches 18 seconds and meets the requirements... ℃ or ℃ At that time, the control unit will Clear to zero, and , , Restored to 100, 72, 38. Figure 2 At 172s Reaching level 6 corresponds to the threshold reduction action, serving as empirical evidence for the thermal shock memory triggering secondary protection. Field verification showed that during the no-load slewing phase after a continuous heavy-load loading operation, when the oil temperature dropped to 89.4℃ and the system remained locked for 19.2 seconds, the system recovered according to the aforementioned logic.

[0095] Table 1 shows the evolution of key variables from 60 s to 172 s. States in the table are represented by glide or lockout.

[0096]

[0097] Table 2 presents the statistical results of continuous 30-minute operations at the same workstation before and after the system was put into use. Figure 3 The changes in each indicator are presented intuitively. The peak oil temperature decreased from 108.7℃ to 101.9℃, a decrease of 6.8℃, or about 6.3%. The longest continuous coasting time decreased from 9.4s to 4.8s, a reduction of 4.6s, or about 48.9%. The number of times the thermal index bottomed out decreased from 7 to 1, a reduction of about 85.7%. The average lock-up duty cycle increased by 3.9 percentage points. The driver impact score decreased by about 37.2%. These results support the overall effectiveness of this embodiment in terms of thermal protection and smoothness.

[0098]

[0099] As the data above shows, without changing the main drive hardware, the peak oil temperature decreased by 6.8℃, the longest continuous slip time was shortened by 48.9%, and the number of times the thermal limit was reached was significantly reduced. This is because the reduction based on the rate of oil temperature rise during slip makes the system more sensitive to the high-heat phase, the compensation during the lock-up phase avoids excessive conservatism, and the pulse unlock self-calibration... Adjustable according to operating conditions, thermal shock memory value This creates a secondary constraint on the operating conditions that repeatedly enter the high-temperature protection mode, thereby reducing repeated thermal shocks. Figure 2 This is used to illustrate the correspondence between threshold triggering and protection actions on the timeline. Figure 3 Used to illustrate the improvement in statistical indicators before and after implementation. Figure 4 This is used to explain the coupling mechanism between thermal power input, oil temperature response and thermal rating evolution, as well as the effect of pulse self-calibration on coefficient correction.

[0100] Example 2:

[0101] Taking a 49-ton tracked hydraulic excavator as an example, this machine operates continuously under combined loading and heavy-load slewing conditions on a slope, with an ambient temperature of 31℃, a slope of 12%, and a soil layer containing approximately 40% gravel. When slewing uphill with a full bucket and coordinating with secondary slope trimming, the engine speed and torque converter output speed fluctuate periodically, resulting in high-frequency alternation between locking and unlocking. The field log shows that without vibration suppression control, the number of state transitions within three consecutive 10-second time windows were 28, 31, and 34, respectively. The driver recorded slight vibrations in the control handle, increased abnormal noise from the transmission, and continuous shaking in the seat, with the highest number of transitions reaching 34 within a single 10-second window. To illustrate the distribution pattern of transition events within the statistical window and the role of the release threshold, [further details are needed]. Figure 5 A schematic diagram of the sliding window switching count and the release threshold is provided to intuitively correspond the state switching count and the threshold release logic.

[0102] Preset time window Count the number of times the slider state and the locked state switch within each window. Set entry threshold Exit threshold and satisfy Set the preset backtracking period. This is used to search for the peak number of switching times within the most recent three windows before entering vibration damping control. At the same time, set the fallback criterion threshold. State transition release threshold ,Should By the same time window Statistics are used to determine whether the next state transition is allowed during the vibration suppression period. Figure 5 The corresponding calculation results show that, At that time, 13 switching events were counted within the last 10 seconds of the window, that is... ,because Therefore, the next handover can be allowed if the minimum duration is met; if the number of times ...

[0103] Statistics within each time window .when When the vibration damping control is activated, the duty cycle is locked. Keeping the value at the moment of entry unchanged, take the value at the moment of entry. During vibration suppression, the lock-up duty cycle adjustment based on the thermal rating is suspended. That is, even if the thermal rating exceeds the original thermal threshold, the control unit will no longer increase or decrease the thermal rating accordingly. Only allow maintaining the current state. It also suppresses frequent switching by using duration constraints and threshold interval expansion. After entering vibration suppression mode, the forced slip duration is maintained for no less than [amount missing]. The forced locking duration shall not be less than And temporarily increase the interval between the first threshold and the second threshold. When the subsequent window statistics drop to When the vibration suppression control is exited, the lock-up duty cycle adjustment logic based on the thermal allowance is immediately restored, so that... Reheating threshold control. Figure 7 A window evolution diagram of vibration damping level and unidirectional holding time is given to illustrate the complete state transition process of entering vibration damping, upgrading, holding, reverting and exiting vibration damping.

[0104] The threshold interval is increased using a tiered mapping method. When entering vibration suppression mode, the control unit first reads the retrospective time period. Peak within Then determine the gear position according to the interval mapping. Four levels are set, and the mapping relationship is as follows: When Take the first gear. ;when Take the second gear. ;when Take the 3rd gear. ;when Take the 4th gear. Before entering the vibration suppression phase, the peak frequency was 34 times in the last 30 seconds, therefore it is mapped to the 3rd level. . Figure 7 The corresponding calculation results are consistent with this, namely, within the last 30 seconds before the first vibration suppression. ,satisfy Therefore, it is mapped to level 3, corresponding to If the entry condition is met again during the vibration suppression period, i.e., continuous... A time window satisfies Then the gear will be upgraded to the next gear and the duration will be set. During this holding period, it is prohibited to revert to the previous gear. Expired and continuous A time window satisfies Then the gear can be changed from Back to .

[0105] State switching conditions are set during vibration suppression. When switching from the sliding state to the locked state, the following conditions must be met simultaneously: and When switching from the locked state to the sliding state, the following conditions must be met simultaneously. and . and This one-to-one correspondence means that if the number of switching times is still higher than 14 within the last 10 seconds, then even if the single hold duration is reached, a new state switch will not be allowed. This avoids the re-triggering of dense switching due to short-term fluctuations during vibration suppression, thus ensuring that vibration suppression control relies on both threshold expansion and switching release thresholds for dual constraints.

[0106] To further suppress back-and-forth bounce during direction switching, the control unit is set with a one-way hold duration. This is one of the preset gear sets, which are 0.3s, 0.5s, 0.8s, 1.2s, and 1.8s. After the slide to lock transition is complete, in... The lock-to-slide transition is prohibited from being triggered; after the lock-to-slide transition is completed, Sliding to the lockout trigger is prohibited. Initial selection. .when After the expiration date, in the first time window Internal recount of switch counts .like And take ,but Move to the next level; if And if the current gear is higher than the lowest gear, then Downgrade to the next higher gear; if If the current gear position remains unchanged, then the duration of the unidirectional hold will be dynamically adjusted according to the degree of oscillation, rather than remaining fixed.

[0107] The number of switches is counted using a sliding window. Its mathematical expression is:

[0108]

[0109] in For the first The timestamp of the next state transition. Let it be an indicator function. At a certain moment... For example, the timestamps of the switching events within the last 10 seconds are 30.4s, 31.1s, 31.9s, 32.8s, 33.5s, 34.6s, 35.2s, 36.0s, 36.8s, 37.5s, 38.1s, 38.9s, and 39.3s, a total of 13 times. Therefore:

[0110]

[0111] at this time This indicates that the next state transition can be allowed if the required holding time has been met. If 16 transitions are counted at the same time, the transition will be suppressed because 16 > 14, even though the time condition is met, thus satisfying the release condition.

[0112] The vibration suppression effect is quantified using switching frequency and a cost function. The window switching frequency is defined as:

[0113]

[0114] And set the target frequency Construct the discrete cost function:

[0115]

[0116] Taking the number of times the first five windows were switched (28, 31, 34, 27, 25) as an example, the frequencies are 2.8, 3.1, 3.4, 2.7, and 2.5. Therefore:

[0117]

[0118]

[0119] After enabling, the number of window switching times for the five windows are 18, 15, 12, 11, and 9, respectively, with frequencies of 1.8, 1.5, 1.2, 1.1, and 0.9. Therefore:

[0120]

[0121] Therefore, the percentage decrease in the cost function is:

[0122]

[0123] This indicates that vibration suppression control significantly reduced the degree to which the switching frequency deviated from the target value.

[0124] The gearing strategy can be explained using finite set comparisons. Let there be three candidate combinations, namely, taking option A... , , The actual number of window switching times was 16, and the impact score was 6.2 points; Option B was selected. , , The actual number of window switching times was 11, and the impact score was 4.3 points; Option C was selected. , , The actual number of window switches was 9, but the job cycle time increased significantly, resulting in an impact score of 4.1. Define the overall objective:

[0125]

[0126] in To boost the score, This represents the increment in cycle time relative to the baseline, in seconds. Measurements were taken for the three schemes. If the values ​​are 0.1, 0.3, and 1.1 respectively, then:

[0127]

[0128]

[0129]

[0130] If only the minimum If option C is chosen, then option C is optimal; however, this embodiment has an additional constraint that the increase in job cycle time must not exceed 0.8 seconds, i.e. Since scheme C does not satisfy the constraint, scheme B is selected from the feasible set as the default control combination. This demonstrates that higher gear ratios and holding times are not necessarily better; rather, a constrained optimization is needed between vibration suppression effectiveness and operational efficiency. Figure 7 The corresponding calculation instructions also provide the comprehensive objectives for the three candidate schemes as follows: , , Although scheme C has the smallest numerical value, scheme B was ultimately chosen because the cycle time increment exceeded the constraint.

[0131] Table 3 shows the control data for 10 consecutive windows before and after entering the vibration suppression mode. Figure 7 This is a chart based on the data in Table 1, used to display the number of window switching times and the window level. Duration of one-way contact Synchronous evolution.

[0132]

[0133] Table 4 provides a statistical comparison before and after the activation of vibration suppression control. Figure 6 The changes in each indicator are presented in a bar chart format to visually illustrate the improvement effect of vibration suppression control on peak switching frequency, average switching frequency, impact score, and oil temperature fluctuation. Figure 6 The corresponding calculation results show that the peak number of 10-second window switching times decreased from 34 to 18, a decrease of 16 times, or about 47.1%; the average switching frequency decreased from 2.9 Hz to 1.3 Hz, a decrease of 1.6 Hz, or about 55.2%; the driver's subjective impact score decreased from 7.1 to 4.2, a decrease of about 40.8%; the oil temperature fluctuation range decreased from 8.4℃ to 4.9℃, a decrease of about 41.7%; the average time per cycle increased by only 0.3 seconds, and the amount of earthwork per hour decreased by 5 m³, a decrease of about 1.6%.

[0134]

[0135] As can be seen from Tables 3 and 4, after entering vibration suppression control, the control unit first maps back the peak value 34 times to level 3, and then upgrades to level 4 after reaching the entry threshold again in three consecutive windows. At the same time, a 20-second hold time is set to prevent rollback. Figure 7 Windows 1 to 3 are visible in the middle. The values ​​are 28, 31, and 27 respectively, and all three windows satisfy the condition. Therefore, in window 4, the system upgrades to level 4 and enters the hold duration range. As the number of switching operations drops below 12, the level reverts to level 3 after the hold duration expires and two consecutive windows are below the backoff threshold. It then exits vibration suppression in window 10 after meeting the exit conditions. Throughout the process, the lockout duty cycle... During vibration suppression, the duty cycle remains constant at 61% from the moment of entry until exiting vibration suppression, at which point it resumes the duty cycle adjustment based on thermal allowance. Therefore, the control boundary is clear, satisfying vibration suppression constraints while avoiding interference with thermal protection logic. Although the single-cycle time increased from 23.6s to 23.9s, the increase was only 0.3s, resulting in a 47.1% reduction in switching peak value, a 40.8% reduction in impact score, and a 41.7% reduction in oil temperature fluctuation amplitude, making it more suitable for continuous heavy-load operations. Figure 5 This is used to illustrate the process of determining the sliding window count and the release threshold. Figure 6 Used to illustrate the improvement in statistical indicators before and after implementation. Figure 7 This is used to illustrate the evolution of the window for adjusting gear levels, holding, reverting, and dynamically adjusting the duration of one-way holding.

Claims

1. A control method for torque converter power output of an excavator, applicable to a power transmission system with a torque converter and a lock-up unit, executed by a control unit, characterized in that: The control unit collects torque converter oil temperature, input speed, output speed and lock-up status according to the control cycle; compares the difference between input speed and output speed with the speed difference threshold, and determines whether the torque converter is in slip state or lock-up state in combination with the lock-up status, and accumulates the duration of the corresponding state. The control unit sets a thermal limit, which has an upper and lower limit. In the sliding state, the thermal limit is deducted based on the duration and the rate of oil temperature rise. In the locked state, the thermal limit is replenished based on the duration and the rate of oil temperature fall. The rate of oil temperature rise and the rate of oil temperature fall are determined by the amount of oil temperature change in adjacent control cycles. The control unit sets a first threshold greater than a second threshold. When the thermal load is not higher than the second threshold, it increases the locking duty cycle and periodically locks / unlocks to limit the duration of continuous sliding. When the thermal load is not lower than the first threshold, it decreases the locking duty cycle. When the thermal load is between the two thresholds, it maintains the current locking duty cycle. The control unit outputs a locking control command.

2. The control method for torque converter power output of an excavator according to claim 1, characterized in that... When the thermal load is not lower than the first threshold and the torque converter is continuously locked for a preset stable duration, the control unit releases the lock and resumes locking after a preset pulse duration; and adjusts the thermal load deduction intensity in the subsequent slip state or the thermal load recovery intensity in the locked state according to the oil temperature change before and after the pulse.

3. The control method for torque converter power output of an excavator according to claim 1, characterized in that... The control unit counts the number of times the sliding state and the locked state are switched within a preset time window. When the number of switching reaches a preset entry threshold, vibration suppression control is entered to keep the locked duty cycle unchanged, and to keep the sliding state holding time no less than a preset sliding holding time threshold and the locked state holding time no less than a preset locked holding time threshold. At the same time, the interval between the first threshold and the second threshold is temporarily increased. When the number of switching drops to a preset exit threshold, vibration suppression control is exited. During vibration suppression control, the locking duty cycle adjustment based on the thermal load is paused, and it is resumed after exiting.

4. The control method for torque converter power output of an excavator according to claim 1, characterized in that... The control unit sets a thermal shock memory value; when the thermal rating is not higher than the second threshold and triggers an increase in the lock-up duty cycle and periodic lock / unlock, the thermal shock memory value is accumulated; when the thermal shock memory value reaches a preset value, the upper limit of the thermal rating is temporarily lowered and the first threshold and the second threshold are lowered simultaneously; when the cumulative lock-up duration reaches the preset recovery time and the oil temperature meets the cooling criterion, the thermal shock memory value is cleared and the upper limit of the thermal rating and the threshold are restored.

5. The control method for torque converter power output of an excavator according to claim 3, characterized in that... When entering the vibration suppression control, the threshold interval increase is selected as one of the preset levels based on the peak number of switching times during the preset backtracking period before entering; if the entry condition is met again during the vibration suppression control period, the threshold interval increase is switched to the next preset level and the interval between the first threshold and the second threshold is updated; when the preset backtracking condition is met, backtracking to the previous preset level is allowed.

6. The control method for torque converter power output of an excavator according to claim 3, characterized in that... During vibration suppression control, the control unit sets release conditions for state switching: switching from sliding state to locked state requires that the sliding holding time is not less than a preset sliding holding time threshold and the number of switching is not greater than a preset fall-off threshold; switching from locked state to sliding state requires that the locking holding time is not less than a preset locking holding time threshold and the number of switching is not greater than the preset fall-off threshold.

7. The control method for torque converter power output of an excavator according to claim 5, characterized in that... The preset gears are mapped according to the interval to which the peak number of switching times belongs, and each preset gear corresponds to a threshold interval increment. When entering vibration suppression control, the interval to which the peak belongs is first determined, then the corresponding preset gear is selected and the interval between the first threshold and the second threshold is updated.

8. The control method for torque converter power output of an excavator according to claim 5, characterized in that... The conditions for re-entering the vibration suppression control include continuously meeting the entry threshold a preset number of times within a preset time window; when the condition is met, the threshold interval is increased and the system switches to the next preset level, and a preset holding time is set, during which it is prohibited to revert to the previous preset level.

9. The control method for torque converter power output of an excavator according to claim 6, characterized in that... The control unit sets a one-way holding time during vibration suppression control, which is one of a plurality of preset holding time levels; after the switch from sliding state to locked state is completed, the switch from locked state to sliding state is prohibited from being triggered within the one-way holding time; after the switch from locked state to sliding state is completed, the switch from sliding state to locked state is prohibited from being triggered within the one-way holding time.

10. The control method for torque converter power output of an excavator according to claim 9, characterized in that... The one-way holding duration is dynamically adjusted based on the number of times the sliding state and the locked state switch within the first time window after the one-way holding duration expires. When the number of switching is still greater than the preset adjustment threshold, the one-way holding duration is switched to the next preset holding duration. When the number of switching is not greater than the preset adjustment threshold, the one-way holding duration is switched to the previous preset holding duration or remains unchanged.

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