A non-road agricultural tractor series hybrid special control method

Abstract

The application relates to a non-road agricultural tractor series hybrid special control method, belonging to the technical field of non-road hybrid power control, which is based on a tractor series hybrid special power architecture, constructs a layered field operation multi-working-condition multi-target cooperative control system, takes the engine field operation steady-state high-efficiency operation, mild charging and discharging of a power battery, dynamic load power rapid prediction response and optimal energy consumption of the whole field operation working condition as core control targets, introduces a nonlinear gradient regulation, a fuzzy PID control and a field operation load prediction mechanism, realizes optimal distribution of power energy of plowing, rotary tillage, deep loosening and transportation whole operation working conditions, and considers tractor operation energy-saving performance, power performance, smoothness and component reliability.

Description

Technical Field

[0001] This invention belongs to the field of non-road hybrid power control technology, specifically relating to a dedicated control method for series hybrid non-road agricultural tractors. Background Technology

[0002] With the advancement of agricultural mechanization, intelligentization, and green low-carbon development in my country, emission regulations for non-road mobile machinery are becoming increasingly stringent. Series hybrid powertrains, with their advantages of high efficiency in low-speed, heavy-load field operations, smooth driving, and simple maintenance, have become the mainstream solution for upgrading the power of agricultural tractors. However, most existing series hybrid control schemes are general-purpose for road vehicles, directly transplanted to agricultural machinery applications without in-depth optimization for the specific operating characteristics of agricultural tractors, such as sudden changes in soil resistance and different loads in field operations and road transport. In actual field applications, this results in numerous technical defects, including battery overcharging or over-discharging, lag in motor output torque response, and large fluctuations in motor speed with load, severely restricting the operating efficiency and reliability of series hybrid tractors.

[0003] The main shortcomings of existing conventional control technologies are as follows: The engine's operating conditions are poorly adapted to field operations, resulting in high fuel consumption. Existing hybrid control strategies mostly employ fixed SOC (State of Charge) threshold switching control, comparing the actual SOC value with set upper and lower thresholds: when the actual SOC value is lower than the lower threshold, the engine starts generating electricity; when the actual SOC value is higher than the upper threshold, the engine shuts off. This control relies solely on the battery charge level, failing to precisely adjust power generation for heavy-duty field operations such as plowing, deep tillage, and rotary tillage. During steady-state operations in large plots, the engine's operating point frequently deviates from the efficient operating range. Under dynamic conditions such as sudden changes in soil resistance and field turning, the engine response lags, power fluctuates rapidly, fuel combustion efficiency is low, and overall fuel consumption is high, failing to leverage the core advantage of controllable operating conditions of the series hybrid engine.

[0004] Power batteries operate in harsh environments and degrade rapidly. Existing hybrid control strategies have fixed charge and discharge thresholds for power batteries, failing to consider the impact of sudden high-current surges caused by outdoor high and low temperature operations, prolonged continuous high-power operation, and abrupt changes in soil load during field work. Tractor operations frequently encounter problems such as high-current charging and discharging, alternating shallow charging and discharging, forced discharge in low winter temperatures, and deep depletion during continuous operation. These issues exacerbate the increase in internal resistance and capacity degradation of power batteries, shorten their lifespan, and significantly increase the later maintenance costs of agricultural machinery.

[0005] The existing control strategies lack adaptability to various field operation conditions and exhibit poor operational power stability. They are poorly suited to complex field conditions such as clay soil, sandy soil, hilly slopes, and large, heavily loaded plots. In low-speed, heavy-load field operations, the power battery frequently discharges at high power, and the engine starts and stops frequently. In deep tillage and uphill heavy-load operations, the engine's power generation lags behind, relying on high-power battery replenishment, which easily leads to power attenuation and battery overheating protection, resulting in unstable working depth, missed tillage, and decreased operational efficiency.

[0006] The jerkiness during mode switching is obvious, resulting in poor operational smoothness. Existing control strategies mostly use hard switching logic for mode switching, lacking a dedicated transition compensation mechanism for agricultural machinery operations. This leads to lag in response to scenarios such as engine start-stop, sudden power changes, and rapid changes in battery current, which can easily cause the tractor to vibrate, affecting the flatness of the tilled land, and causing fatigue damage to engine and transmission components.

[0007] Existing hybrid agricultural machinery solutions focus on energy consumption optimization or power battery protection, failing to achieve multi-objective coordinated optimization of power performance, energy efficiency, smoothness, reliability, and operational continuity. They also exhibit weak load prediction capabilities and poor adaptability, making them unsuitable for all types of field operations and significantly limiting their practical application.

[0008] To address the shortcomings of the existing technologies, there is an urgent need to design a dedicated series hybrid control strategy for agricultural tractors, featuring multi-condition adaptive operation in the field, nonlinear smooth compensation, and multi-objective collaborative optimization, in order to solve the technical pain points of poor adaptability to agricultural machinery operation conditions and unsatisfactory operation smoothness. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention provides a dedicated control method for series hybrid non-road agricultural tractors. Based on the dedicated power architecture of series hybrid tractors, it constructs a hierarchical multi-condition and multi-objective collaborative control system for field operations. It introduces nonlinear gradient power regulation, fuzzy PID control, and field operation load prediction mechanism to achieve optimal power energy allocation for all operating conditions, including plowing, rotary tillage, deep loosening, and transportation, while taking into account the energy efficiency, power, smoothness, and component reliability of tractor operations.

[0010] To achieve the above objectives, the technical solution adopted by this invention is: a dedicated control method for series hybrid non-road agricultural tractors, comprising the following steps: S1. Real-time high-frequency acquisition of the overall status of the tractor; S2. Preset control thresholds and field operation condition classification: Preset basic thresholds, including upper and lower SOC thresholds of the power battery, high-efficiency operating speed range of the engine in field operations, normal operating temperature range of the battery, low-speed field operation condition thresholds, and field road transport condition thresholds; Combined with real-time operating conditions including battery temperature, cycle number, and operating load, the threshold boundaries are dynamically corrected; Based on the changes in basic thresholds, dynamic correction thresholds, and operating load rate, the current field operation condition of the tractor is determined and divided into four major working modes; S3. Based on the results of the working condition assessment, implement differentiated control for different working modes; S3-1, Pure Electric Operation Mode: When the battery SOC is greater than the upper threshold, the vehicle speed is ≤5km / h and the tractor is in a light-load idling condition, the engine is controlled to stop and the motor is driven solely by the power battery. S3-2, High-efficiency power generation steady-state mode: The battery SOC is between the upper and lower thresholds, and the steady-state operation conditions of plowing, rotary tillage, and deep loosening are maintained; the engine is controlled at the optimal economic speed to generate power at constant power and efficiency. S3-3, Dynamic Power Follow-up Mode: When the tractor turns at the end of the field, the soil hardness changes suddenly, the hilly slope is climbed, the rotary tillage resistance fluctuates, and the dynamic operation conditions of heavy load and variable load, the demand is predicted by the load trend and the engine power generation is adjusted by nonlinear gradient to quickly respond to transient power demand. S3-4 Forced charging mode: When the battery SOC is less than the lower threshold, the battery temperature is <5℃, or the tractor is engaged in long-term deep tillage, heavy load, and high-power continuous operation, the engine-generator set is forcibly started to lock the high-efficiency power generation range, continuously generate power and charge the battery, and quickly replenish the power battery. S4. Nonlinear smooth switching compensation for operating modes: During the transition phase between the four operating modes, nonlinear gradient adjustment of power generation, fuzzy PID fine-tuning of charging and discharging current, and superimposed dynamic torque compensation are used to suppress the mechanical shock caused by load fluctuations of the whole machine during the mode switching process. S5. Closed-loop correction and iteration: Combining the characteristics of power battery life degradation with real-time field operation conditions, the control parameters are dynamically corrected, and the control strategy is iterated in a closed loop to continuously optimize the control strategy and adapt to different soil, different environment and different operation duration scenarios.

[0011] Furthermore, in step S1, the core operating parameters of the tractor are collected through the tractor's vehicle controller, including the load rate of the implements, the equivalent signal of soil resistance, the vehicle speed, the throttle opening, the SOC value of the power battery, the temperature of the power battery, the engine speed, the generator power, and the drive motor power. The instantaneous interference signals in the field are removed by sliding mean filtering, and a field operation status database is constructed to provide accurate data support for the determination of working conditions.

[0012] Furthermore, in step S2, the preset basic thresholds are: upper threshold of power battery SOC = 78%, lower threshold of SOC = 28%; high-efficiency working speed range of engine in field operation: 1600r / min~1900r / min; normal operating temperature range of battery: 5℃~50℃; threshold of low-speed operation in field ≤18km / h, threshold of road transport in field ≥18km / h.

[0013] Furthermore, in step S2, the dynamic threshold correction includes dynamically correcting the maximum charge / discharge current based on the battery temperature and the number of battery cycles. When the battery temperature is below 5℃, the SOC threshold is dynamically increased to 34%, limiting the battery discharge power to 45%. When the battery charge-discharge cycle count exceeds 900, the internal resistance increases by 20%, and the maximum charge-discharge current is reduced by 22%. When the battery has been used for electrical cycles less than 900 times and the internal resistance increases by less than 5%, the maximum charge and discharge current will not be reduced. When the battery has been used for less than 900 electrical cycles and its internal resistance increases by more than 5% but less than 15%, the maximum charge and discharge current is reduced by 10% of the current value to achieve dynamic adjustment.

[0014] Furthermore, the dynamic correction threshold also includes: when the tractor is engaged in deep tillage or heavy plowing operations, dynamically widening the range of efficient power generation of the engine and improving the load prediction power response rate.

[0015] Furthermore, in step S3-3, the control logic of the dynamic power following mode is as follows: the vehicle controller predicts the subsequent power demand based on the soil resistance and load change trend in the first 300ms, adjusts the engine fuel injection quantity and speed in real time, and dynamically adjusts the generator power output; the engine power adjustment rate adopts nonlinear gradient control, and determines the appropriate fuel injection quantity in the calibrated fuel quantity map based on the real-time speed and load. The fuel injection quantity is controlled by the closed loop of the demand load on the engine generator side. When the load increases, the fuel injection quantity is increased synchronously to achieve a smooth change in engine power. When there is a sudden high power demand, the engine power output is superimposed with the instantaneous battery power replenishment to quickly respond to the dynamic load of field operations; when there is a small power fluctuation, the engine power is finely adjusted as the main method and the battery is slightly compensated as a supplement, taking into account both power response and energy consumption stability.

[0016] Furthermore, in the forced charging mode of steps S3-4, the power generation prioritizes meeting the tractor's drive power requirements, and the remaining power is used to replenish the power battery, quickly raising the battery's SOC, improving the battery's low-temperature operating condition, while limiting the maximum output torque of the drive motor, reducing the instantaneous power of the entire machine, avoiding continuous battery depletion, and protecting the core performance of the power battery.

[0017] Furthermore, in step S4, when switching working modes, a nonlinear smoothing compensation algorithm is used to plan the trajectory of the engine-generator power generation change over time. The engine power generation adopts a quadratic nonlinear gradient increase / decrease method to achieve a smooth transition of power generation and meet the needs of the drive motor.

[0018] Furthermore, in S4, when switching working modes, a dynamic torque compensation coefficient is superimposed based on the power difference before and after the mode switch, and the compensation torque does not exceed 35% of the motor's rated power to prevent motor overload.

[0019] Furthermore, the closed-loop iterative mechanism is divided into two parallel optimization links: battery-side adaptive correction: real-time acquisition of battery cycle count, internal resistance, and capacity decay data, and dynamic adjustment of charge and discharge thresholds and maximum current limits through nonlinear decay coefficients, so that the control strategy always adapts to the performance changes of the battery throughout its entire life cycle. Operating condition self-learning optimization: By collecting and statistically analyzing energy consumption data from various typical field scenarios such as clay soil, sandy soil, and hilly slopes, a unique comprehensive road spectrum MAP is generated. This MAP is then cross-compared with the engine universal MAP and motor efficiency MAP to automatically select high-efficiency operating conditions with lower fuel consumption and higher efficiency. The load prediction response parameters are then optimized through fuzzy PID closed-loop iteration.

[0020] By adopting the technical solution described above, the present invention can achieve the following beneficial effects: This invention, from a practical application perspective, precisely matches operating conditions, optimizes engine operating range, and reduces fuel consumption in agricultural machinery operations. Specifically designed for plowing, deep tillage, and rotary tillage operations, this invention sets dedicated high-efficiency operating points for field operations, employs non-linear power flexible tracking, widens the engine's high-efficiency operating range, and avoids engine operation in low-efficiency ranges, thus helping to reduce overall fuel consumption of tractors in field operations.

[0021] Adaptive to field operating environments, effectively protecting the power battery. This invention sets dynamic adaptive charge and discharge thresholds based on soil load, operating time, and ambient temperature, combined with nonlinear correction for battery life degradation. It avoids harsh operating conditions such as deep battery depletion, high current in low winter temperatures, and frequent charge and discharge due to sudden changes in field operating load, significantly reducing the battery degradation rate, extending battery cycle life, and reducing the later maintenance costs of agricultural machinery.

[0022] This invention features adaptive adjustment for various field conditions, ensuring strong operational power stability. It divides the work into four operating modes, precisely adapting to diverse scenarios such as clay soil, sandy soil, hilly slopes, field turning, and road transport. A load prediction mechanism is introduced, enabling rapid and accurate power response under dynamic conditions, eliminating issues such as power lag and fluctuations in machine operating depth. It balances smooth operation under low-speed heavy loads with continuous operational power.

[0023] The non-linear smooth switching ensures smooth machine operation. This invention incorporates a non-linear power gradual transition, fuzzy PID control, and dynamic torque compensation mechanism, completely resolving the issue of jerky switching during tractor operation mode transitions and significantly improving work quality.

[0024] It boasts strong versatility and engineering practicality. This invention requires no modification to the tractor hardware architecture; performance upgrades can be achieved solely through control algorithm optimization. It is compatible with various wheeled and tracked agricultural tractors, and possesses closed-loop correction and iteration capabilities, adapting to different soil conditions and environmental working conditions, making it highly valuable for industrial applications. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating a dedicated control method for series hybrid non-road agricultural tractors according to the present invention. Detailed Implementation

[0026] This invention proposes a dedicated control method for series hybrid non-road agricultural tractors. It relies on the tractor vehicle controller (VCU) as the core control unit, and works with the engine controller (ECU), generator controller (MCU), drive motor controller (GCU), and power battery management system (BMS) to achieve multi-component collaborative control. Its core includes five major steps: real-time acquisition of the tractor's overall operating status, hierarchical determination of operating condition intervals, multi-mode collaborative and precise control, nonlinear smooth switching compensation of operating modes, and closed-loop correction iteration.

[0027] First, the vehicle controller collects key parameters in real time at high frequency, such as the load rate of the work implements, the equivalent signal of soil resistance, the vehicle speed, the throttle opening, the SOC value of the power battery, the power battery temperature, the engine speed, the generator power, and the drive motor power. By filtering out instantaneous interference signals in the field through sliding mean, a field operation status database is constructed to provide accurate data support for the determination of working conditions.

[0028] Secondly, by combining the characteristics of steady-state and dynamic load conditions in field operations, four exclusive operation modes are defined, and precise zoning of operating conditions is achieved by combining basic thresholds and dynamic correction thresholds.

[0029] Next, specific nonlinear power distribution logic is developed for different operating modes to differentiate the control of engine start / stop, power generation, power battery charging / discharging status, and drive motor output torque.

[0030] Furthermore, during mode switching, nonlinear gradual compensation and fuzzy PID control are used to achieve seamless switching between multiple modes, suppressing the mechanical shock caused by load fluctuations in the entire machine.

[0031] Finally, by combining the power battery life degradation with the characteristics of soil conditions in the field, the control parameters are dynamically adjusted to achieve continuous optimization of the strategy and adapt to various operating conditions.

[0032] This invention abandons the linear switching control logic of existing hybrid control schemes and is fully adapted to the characteristics of agricultural tractors where the engine does not participate in driving, the entire process generates electricity, and the working load fluctuates greatly. With "steady-state and efficient operation of the engine in the field, gentle charging and discharging of the power battery, rapid prediction and response of dynamic load power, and optimal energy consumption in all field working conditions" as the core control objectives, it adopts innovative algorithms of nonlinear adjustment, load prediction, and fuzzy compensation to achieve multi-dimensional performance synergy improvement. It effectively overcomes the problems of poor adaptability to field working conditions, insufficient energy consumption optimization, serious power battery loss, mode switching jerkiness, and dynamic response lag in existing series hybrid control technologies.

[0033] The present invention will now be described in further detail and in complete form with reference to specific embodiments.

[0034] like Figure 1 As shown, this embodiment is based on a 220-horsepower wheeled agricultural tractor series hybrid architecture, equipped with a high-efficiency diesel generator for field operations, a permanent magnet synchronous generator, a permanent magnet synchronous motor for walking drive, and a ternary lithium power battery pack. The tractor's overall power control is achieved through the dedicated control strategy proposed in this invention. The specific implementation steps are as follows.

[0035] S1: Real-time high-frequency acquisition of the overall status of the tractor.

[0036] The tractor vehicle control unit (VCU) synchronously collects core operating parameters of the entire machine with an 8ms cycle, including: throttle control opening, braking signal, real-time drive motor power, implement load rate, soil resistance equivalent signal, vehicle speed, real-time SOC value of the power battery, individual battery cell temperature, battery charging and discharging current, real-time engine speed, generator power and output voltage, and output torque and speed of the travel motor and implement motor. It also receives field ambient temperature and overall machine operating load signals, and uses sliding mean filtering to perform parameter noise reduction processing, eliminating data interference from instantaneous soil impacts to ensure accurate determination of field operating conditions.

[0037] S2: Preset control threshold and field operation condition classification.

[0038] Preset basic control thresholds: upper threshold of power battery SOC (SOC_H) = 78%, lower threshold of SOC (SOC_L) = 28%; high-efficiency working speed range of engine in field operations: 1600r / min~1900r / min; normal operating temperature range of battery: 5℃~50℃; threshold of low-speed operation in the field ≤18km / h, threshold of road transport in the field ≥18km / h.

[0039] Simultaneously, the threshold boundaries are dynamically adjusted based on real-time operating conditions such as battery temperature, cycle count, and workload. Based on the base threshold and the dynamically adjusted threshold, the current field operating condition of the tractor is determined, accurately classifying it into four working modes.

[0040] The dynamic threshold correction rules for field operations dynamically adjust the SOC threshold to 34% when the battery temperature is below 5℃, limiting the battery discharge power to 45%; when the battery cycle count exceeds 900 times, the maximum charge and discharge current is reduced to 22% based on the nonlinear decay coefficient; when the tractor is engaged in heavy-load operations such as deep tillage and plowing, the efficient power generation range of the engine is dynamically expanded to improve the load prediction power response rate.

[0041] Among them, the nonlinear decay coefficient and dynamic adjustment refer to the coefficient that nonlinearly corrects the control parameters based on the degree of battery aging. Its threshold is that when the battery has been used for charging cycles more than 900 times and the internal resistance increases by 20%, the maximum charge and discharge current is reduced by 22% based on this coefficient. When the battery has been used for charging cycles less than 900 times and the internal resistance increases by less than 5%, the maximum charge and discharge current is not reduced. When the battery has been used for charging cycles less than 900 times and the internal resistance increases by more than 5% but less than 15%, the maximum charge and discharge current is reduced by 10% based on this coefficient, thus achieving dynamic adjustment.

[0042] Dynamically expanding the engine's high-efficiency power generation range refers to relying on a field operation load prediction-power dynamic following algorithm: When the tractor is engaged in heavy-load operations such as deep tillage or plowing, the engine's high-efficiency power generation range is dynamically expanded. The engine operating speed is broadened from a single constant speed to a speed range, such as expanding the engine speed from 1900 r / min to 1600 r / min to 1900 r / min. Based on the soil resistance and load change trend in the previous 300ms, the subsequent power demand is predicted through changes in the overall machine lift force adjustment mechanism. The engine's fuel injection quantity and speed are adjusted in real time. When it is necessary to increase power generation, the engine fuel injection quantity is increased, increasing the engine power and thus increasing the generator power generation. When it is necessary to reduce power generation, the engine fuel injection quantity is reduced, decreasing the engine power and thus reducing the generator power generation. When the engine is running at a certain speed, if the engine fuel injection quantity has reached the external characteristic fuel quantity at that speed and the subsequent load is predicted to increase, the engine speed can be reduced within a preset speed range to increase the output torque and improve the load prediction power response rate.

[0043] S3: Precise and coordinated control of different operating modes.

[0044] S3-1: Pure electric operation mode, applicable working conditions: battery SOC>78%, vehicle speed≤5km / h, tractor light-load shallow tillage, short-distance transportation, and idling standby conditions at the field.

[0045] Control logic: The vehicle controller sends a shutdown command to completely stop the engine-generator set and cut off the power generation circuit; the power battery supplies power to the drive motor separately, and outputs drive torque linearly according to the throttle opening to ensure smooth low-speed operation in the field; at the same time, the battery management system limits the maximum discharge current of the battery to avoid damage to the cells caused by the instantaneous resistance impact of the soil, and prioritizes the use of the battery's stored energy to achieve zero fuel consumption and light-load operation.

[0046] S3-2: High-efficiency power generation steady-state mode, applicable to the following working conditions: battery SOC between 28% and 78%, vehicle speed stability range of 5km / h to 18km / h, and steady-state operation conditions such as plowing, rotary tillage, and deep loosening.

[0047] Control Logic: The engine is locked at the optimal economic speed of 1900 r / min for field operations, maintaining constant torque and high-efficiency power generation. This operating point is suitable for continuous tractor operation in the field, with the lowest fuel consumption and highest power generation efficiency. The generator output prioritizes real-time power supply to the drive motors of the walking and working implements to meet the steady-state power requirements of the entire machine. Any remaining excess power is automatically stored in the power battery, slowly replenishing the battery charge and maintaining the SOC value stable within the high-efficiency range. Throughout the entire process, the engine operates without fluctuations or frequent start-stop cycles, minimizing steady-state fuel consumption.

[0048] S3-3: Dynamic power following mode, applicable to working conditions such as tractor turning at the end of the field, sudden changes in soil hardness, climbing hilly slopes, fluctuations in rotary tillage resistance, and heavy load changes, where the instantaneous power demand of the whole machine fluctuates greatly.

[0049] Control Logic: The system exits the engine's constant power steady-state power generation mode and activates the field operation load prediction-power dynamic following algorithm. The vehicle controller predicts subsequent power demand based on soil resistance and load change trends over the previous 300ms, adjusting engine fuel injection quantity and speed in real time to dynamically adjust generator power output. The engine power regulation rate employs nonlinear gradient control, determining the appropriate fuel injection quantity based on real-time speed and load within a pre-calibrated fuel quantity map. The fuel injection quantity is controlled in a closed loop by the engine's demand load (used for power generation); as the load increases, the fuel injection quantity increases, achieving smooth engine power changes and avoiding sudden power fluctuations. During periods of high instantaneous power demand, the engine's power generation is superimposed with instantaneous battery replenishment power for rapid response to dynamic field operation loads. During periods of low power fluctuation, the system primarily uses fine-tuning of engine power, supplemented by minor battery compensation, balancing power response and energy consumption stability.

[0050] S3-4: Forced charging mode, applicable to working conditions: battery SOC < 28%, battery temperature < 5℃, or tractor long-term deep tillage heavy load high-power continuous operation.

[0051] Control Logic: Regardless of the real-time power demand of the entire machine, the engine-generator set is forcibly started, locking in the high-efficiency, high-power generation range for continuous power generation. The generated power prioritizes meeting the tractor's drive power requirements, with any remaining energy used to recharge the power battery, quickly raising the battery's SOC and improving its low-temperature operating condition. Simultaneously, the maximum output torque of the drive motor is limited, reducing the machine's instantaneous power, preventing continuous battery depletion, protecting the core performance of the power battery, and ensuring continuous all-weather operation of the entire machine.

[0052] S4: Nonlinear smooth compensation control for switching between work modes. Applicable working conditions: During the transition between the four work modes.

[0053] Control logic: A nonlinear smooth compensation algorithm is adopted, with a 320ms gradual transition interval. The engine power generation adopts a quadratic nonlinear gradient increase / decrease method; the charging and discharging current of the power battery is precisely fine-tuned through a fuzzy PID algorithm to suppress current fluctuations caused by load impacts during field operations; at the same time, based on the power difference before and after mode switching, a dynamic torque compensation coefficient is superimposed to offset power gaps and power redundancy, completely eliminating the problems of machine vibration and implement jerking during tractor operation, and ensuring stable power output throughout the entire process.

[0054] Specifically, when switching operating modes, a nonlinear smoothing compensation algorithm is activated. The algorithm's logic involves planning the trajectory of the engine-generator power output changes over time, without directly jumping to the new mode's target power. The engine's power output uses a quadratic nonlinear gradient increase / decrease method to achieve a smooth transition, meeting the drive motor's requirements. A 320ms transition interval is set, and the new and old power outputs satisfy the following relationship: ; In the formula, --Generator power output during the switching process, unit: kW; --Generator output power in old mode before switching, unit: kW; --Generator power output in the new mode after switching, in kW; --Time after transition, in milliseconds, 0≤t≤T; -- Gradual transition interval, unit: ms.

[0055] During this process, fuzzy PID closed-loop fine-tuning is used to suppress current surges during battery charging and discharging, achieving stable charging and discharging of the battery. Simultaneously, a dynamic torque (power) compensation coefficient (ranging from 0% to 35% of the motor's rated power) is superimposed on the drive motor power, ensuring that the compensated torque (power) does not exceed 35% of the motor's rated power to prevent motor overload. This maintains a constant overall output torque. After the transition, the compensation coefficient returns to zero, completing the mode switch.

[0056] S5: Closed-loop correction and iteration of control strategy for field operation conditions.

[0057] The tractor vehicle control unit (VCU) stores real-time data on fuel consumption, battery status, frequency of field operation mode switching, and power response, constructing a big data iterative model for field operation conditions. On one hand, based on the number of battery cycles, changes in internal resistance, and capacity decay, a nonlinear decay coefficient is used to dynamically correct the charge / discharge threshold and maximum current limit, adapting to the performance changes throughout the battery's life cycle. On the other hand, by collecting road spectrum data, energy consumption data for typical field operation conditions such as clay soil, sandy soil, hilly slopes, large plains, and low winter temperatures are statistically analyzed. This data includes parameters such as engine speed, fuel quantity, power generation, and power consumption, resulting in an initial comprehensive road spectrum MAP for various operating conditions. This MAP is compared with the universal MAP for the engine and the universal MAP for motor efficiency. Under the premise of meeting the requirements for engine speed and torque output, the operating point with lower fuel consumption and higher efficiency is extracted. Fuzzy PID control closed-loop iterative optimization optimizes the engine's high-efficiency operating point in field operation and the response parameters of the predicted load power, enabling the control strategy to continuously adapt to different soil, environment, and operation duration scenarios, achieving long-term optimal control performance.

[0058] This embodiment verifies the superior performance of the control strategy of the present invention through simulation of typical field operation conditions and field testing of the whole machine: 1) Energy consumption performance: The overall fuel consumption of tractor plowing is significantly reduced, and it shows good energy-saving effect in both deep tillage heavy load conditions and road transport conditions.

[0059] 2) Battery protection performance: The frequency of high-current charging and discharging of the battery in farmland operations is greatly reduced, the duration of extreme and harsh operating conditions is shortened, and battery degradation is effectively slowed down.

[0060] 3) Smooth operation: The tractor switches between operating modes without shaking or implement impact, the dynamic response speed is improved, the power output is stable under sudden changes in soil load, and the operating depth is uniform.

[0061] 4) Working condition adaptability: It can stably adapt to ambient temperatures of -15℃ to 45℃, no-load to heavy-load farmland operation, and various complex soil operation conditions. The whole machine operates stably and reliably.

[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A dedicated control method for series hybrid non-road agricultural tractors, characterized in that, Includes the following steps: S1. Real-time high-frequency acquisition of the overall status of the tractor; S2. Preset control thresholds and field operation condition classification: Preset basic thresholds, including upper and lower SOC thresholds of the power battery, high-efficiency operating speed range of the engine in field operations, normal operating temperature range of the battery, low-speed field operation condition thresholds, and field road transport condition thresholds; Combined with real-time operating conditions including battery temperature, cycle number, and operating load, the threshold boundaries are dynamically corrected; Based on the changes in basic thresholds, dynamic correction thresholds, and operating load rate, the current field operation condition of the tractor is determined and divided into four major working modes; S3. Based on the results of the working condition assessment, implement differentiated control for different working modes; S3-1, Pure Electric Operation Mode: When the battery SOC is greater than the upper threshold, the vehicle speed is ≤5km / h and the tractor is in a light-load idling condition, the engine is controlled to stop and the motor is driven solely by the power battery. S3-2, High-efficiency power generation steady-state mode: The battery SOC is between the upper and lower thresholds, and the steady-state operation conditions of plowing, rotary tillage, and deep loosening are maintained; the engine is controlled at the optimal economic speed to generate power at constant power and efficiency. S3-3, Dynamic Power Follow-up Mode: When the tractor turns at the end of the field, the soil hardness changes suddenly, the hilly slope is climbed, the rotary tillage resistance fluctuates, and the dynamic operation conditions of heavy load and variable load, the demand is predicted by the load trend and the engine power generation is adjusted by nonlinear gradient to quickly respond to transient power demand. S3-4 Forced charging mode: When the battery SOC is less than the lower threshold, the battery temperature is <5℃, or the tractor is engaged in long-term deep tillage, heavy load, and high-power continuous operation, the engine-generator set is forcibly started to lock the high-efficiency power generation range, continuously generate power and charge the battery, and quickly replenish the power battery. S4. Nonlinear smooth switching compensation for operating modes: During the transition phase between the four operating modes, nonlinear gradient adjustment of power generation, fuzzy PID fine-tuning of charging and discharging current, and superimposed dynamic torque compensation are used to suppress the mechanical shock caused by load fluctuations of the whole machine during the mode switching process. S5. Closed-loop correction and iteration: Combining the characteristics of power battery life degradation with real-time field operation conditions, the control parameters are dynamically corrected, and the control strategy is iterated in a closed loop to continuously optimize the control strategy and adapt to different soil, different environment and different operation duration scenarios.

2. The dedicated control method for series hybrid non-road agricultural tractors according to claim 1, characterized in that, In step S1, the core operating parameters of the tractor are collected through the tractor's vehicle controller, including the load rate of the implements, the equivalent signal of soil resistance, the vehicle speed, the throttle opening, the SOC value of the power battery, the temperature of the power battery, the engine speed, the generator power, and the drive motor power. The instantaneous interference signals in the field are removed by sliding mean filtering, and a field operation status database is constructed to provide accurate data support for the determination of working conditions.

3. The dedicated control method for series hybrid non-road agricultural tractors according to claim 1, characterized in that, In step S2, the preset basic thresholds are: upper threshold of power battery SOC = 78%, lower threshold of SOC = 28%; high-efficiency working speed range of engine in field operation: 1600r / min~1900r / min; normal operating temperature range of battery: 5℃~50℃; threshold of low-speed operation in field ≤18km / h, threshold of road transport in field ≥18km / h.

4. The dedicated control method for series hybrid non-road agricultural tractors according to claim 1, characterized in that, In step S2, the dynamic threshold correction includes dynamically adjusting the maximum charge / discharge current based on battery temperature and battery cycle count. When the battery temperature is below 5℃, the SOC threshold is dynamically increased to 34%, limiting the battery discharge power to 45%. When the battery charge-discharge cycle count exceeds 900, the internal resistance increases by 20%, and the maximum charge-discharge current is reduced by 22%. When the battery has been used for electrical cycles less than 900 times and the internal resistance increases by less than 5%, the maximum charge and discharge current will not be reduced. When the battery has been used for less than 900 electrical cycles and its internal resistance increases by more than 5% but less than 15%, the maximum charge and discharge current is reduced by 10% of the current value to achieve dynamic adjustment.

5. A dedicated control method for series hybrid non-road agricultural tractors according to claim 4, characterized in that, The dynamic correction threshold also includes: when the tractor is engaged in deep tillage or heavy plowing operations, dynamically widening the range of high-efficiency power generation of the engine and improving the load prediction power response rate.

6. The dedicated control method for series hybrid non-road agricultural tractors according to claim 1, characterized in that, In step S3-3, the control logic of the dynamic power following mode is as follows: The vehicle controller predicts the subsequent power demand based on the soil resistance and load change trend in the first 300ms, adjusts the engine fuel injection quantity and speed in real time, and dynamically adjusts the generator power output; the engine power adjustment rate adopts nonlinear gradient control, and determines the appropriate fuel injection quantity in the calibrated fuel quantity map based on the real-time speed and load. The fuel injection quantity is controlled by the closed loop of the demand load on the engine generator side. When the load increases, the fuel injection quantity is increased synchronously to achieve a smooth change in engine power. When there is a sudden large power demand, the engine power output is superimposed with the instantaneous battery power replenishment to quickly respond to the dynamic load of field operations; when there is a small power fluctuation, the engine power is finely adjusted as the main method and the battery is slightly compensated as a supplement, taking into account both power response and energy consumption stability.

7. The dedicated control method for series hybrid non-road agricultural tractors according to claim 1, characterized in that, In step S3-4, during forced charging mode, the power generation prioritizes meeting the tractor's drive power requirements, and the remaining power is used to replenish the power battery, quickly raising the battery's SOC and improving its low-temperature operating condition. At the same time, it limits the maximum output torque of the drive motor, reduces the instantaneous power of the entire machine, avoids continuous battery depletion, and protects the core performance of the power battery.

8. The dedicated control method for series hybrid non-road agricultural tractors according to claim 1, characterized in that, In step S4, when switching working modes, a nonlinear smooth compensation algorithm is used to plan the trajectory of the engine-generator power generation change over time. The engine power generation adopts a quadratic nonlinear gradient increase / decrease method to achieve a smooth transition of power generation and meet the needs of the drive motor.

9. A dedicated control method for series hybrid non-road agricultural tractors according to claim 1, characterized in that, In S4, when switching working modes, a dynamic torque compensation coefficient is added based on the power difference before and after the mode switch. The compensation torque does not exceed 35% of the motor's rated power to prevent motor overload.

10. A dedicated control method for series hybrid non-road agricultural tractors according to claim 1, characterized in that, The closed-loop iterative mechanism consists of two parallel optimization links: battery-side adaptive correction, which collects battery cycle count, internal resistance, and capacity decay data in real time, and dynamically adjusts the charge and discharge thresholds and maximum current limits through nonlinear decay coefficients, so that the control strategy always adapts to the performance changes of the battery throughout its entire life cycle. Operating condition self-learning optimization: By collecting and statistically analyzing energy consumption data from various typical field scenarios such as clay soil, sandy soil, and hilly slopes, a unique comprehensive road spectrum MAP is generated. This MAP is then cross-compared with the engine universal MAP and motor efficiency MAP to automatically select high-efficiency operating conditions with lower fuel consumption and higher efficiency. The load prediction response parameters are then optimized through fuzzy PID closed-loop iteration.

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