A series hybrid tractor walking and PTO direct connection engine power coordination control method

Abstract

The application relates to a series hybrid tractor walking and PTO direct connection type engine power coordination control method, which comprises the following steps: collecting real-time working condition parameters and rated parameters of the tractor; judging the power output gap of the engine; comparing the total power required by the current engine and the rated power of the engine by the vehicle controller, and simultaneously, according to the residual power SOC of the power battery, the engine power is constrained into three modes; the vehicle controller performs hierarchical control on the engine power modes, takes the PTO rated speed as the PTO target speed, preferentially maintains the current PTO speed by weight, dynamically distributes the engine power and the driving motor output power, and dynamically regulates the SOC of the power battery. Under the condition that the engine power is limited, the PTO power and the driving motor output power can be dynamically coordinated, the PTO speed is preferentially ensured to be stable, and the operation quality is improved.

Description

Technical Field

[0001] This invention relates to a method for coordinated control of the travel and PTO direct-drive engine power of a series hybrid tractor, belonging to the technical field of series hybrid tractors. Background Technology

[0002] With the acceleration of global agricultural modernization, high-horsepower tractors, as core equipment in agricultural production, are facing the dual pressures of improving operational efficiency and reducing energy consumption and emissions. Traditional high-horsepower tractors generally adopt a purely mechanical transmission architecture. When facing high-load field operations such as rotary tillage and drive harrowing, the engine operates in an inefficient range for extended periods, resulting in poor fuel economy and high emissions. Hybrid technology, with its flexible power distribution capabilities and efficient energy management advantages, has become an important direction for upgrading the power systems of high-horsepower tractors.

[0003] In the series hybrid tractor configuration, see Figure 3 As shown, the engine and generator are coaxially connected, and the output power is supplied to the drive motor and accessory loads via the DC bus. The PTO (Power Take-Off) shaft provides power to each implement. The PTO maintains direct mechanical coupling with the engine. Because the engine output shaft directly drives the PTO to provide power to each implement, it can obtain power directly from the engine without going through the electrical system, thus achieving high torque output. However, the series hybrid tractor architecture gives the walking system an electrical control capability independent of the engine. Tractors need to achieve multiple operating modes under different working conditions. For sandy loam, loam, clay, compacted hard clay, and extra-hard clay and sloping terrain, under full-load operating conditions, the PTO consumes most of the engine's mechanical power, usually accounting for 60% to 75% of the engine's total power. At the same time, the generator still needs to provide power to the drive motor and accessory system. The following problems often occur during field operations: 1. When the total demand of the engine exceeds the engine's rated power, the engine's full power is insufficient. 2. When the generator output power decreases, the battery SOC continues to decrease, resulting in a battery power gap and reduced system stability. 3. Because PTO cannot be controlled independently of the engine, it can only be indirectly affected by adjusting the engine speed / torque or the drive motor, resulting in low control freedom. 4. The existing control strategy only controls the PTO speed through feedback, causing PTO speed fluctuations to frequently exceed 5%. Therefore, the large fluctuation in PTO speed severely affects the quality of operation.

[0004] A systematic study has been conducted on the power matching problem of series hybrid tractors, proposing energy management strategies based on fuzzy logic. For example, CN121608727A discloses an intelligent power allocation method for series hybrid tractors based on multi-domain joint control. This method collects data from the power domain, chassis domain, and work domain of the series hybrid tractor to construct a multi-domain perception map reflecting the current working conditions. Based on the multi-domain perception map and power data, it integrates work energy-saving priorities and traction load to construct a multi-source power supply-demand mapping model. According to the supply-demand mapping model, the optimal drive mode is selected, and the drive switching logic and power allocation commands are output based on the efficiency, energy, and thermal load of each power source, achieving intelligent power scheduling. This enables intelligent drive mode switching and efficient power allocation for series hybrid tractors under different working conditions, improving work efficiency and system responsiveness. Therefore, current research in the field of hybrid tractor power management mainly focuses on energy management strategies and engine operating point optimization. However, the contradiction between PTO speed stability and travel power demand under engine power constraints remains unresolved. Summary of the Invention

[0005] The purpose of this invention is to provide a method for coordinating the power of the PTO (Power Transfer Engine) and the PTO (Power Drive Motor) in a series hybrid tractor under limited engine power conditions, prioritizing the stability of the PTO speed to improve work quality.

[0006] The technical solution of this invention to achieve the above-mentioned objective is: a method for coordinated control of the travel and PTO direct-drive engine power of a series hybrid tractor, characterized by comprising the following steps: (1) Receive and collect real-time operating parameters and rated parameters of the tractor through the data acquisition module; (2) Determine the power output gap of the engine; The power balance module receives real-time operating parameters and rated parameters from the data acquisition module to determine if there is a power shortage in the engine, and transmits the received parameters and judgment data to the vehicle controller. To check for insufficient engine power, follow these steps: Ⅰ. Calculate the real-time total power required by the tractor's electrical and accessory loads, Pelec_demand, as follows: Pelec_demand = Pwalk+Paux+ +Pcharg, When SOC > 50% and SOC < 30%, Pcharg = 0; Where: Pelec_demand is the real-time total power required by electrical components and accessories (kW); Pwalk is the real-time drive motor power (kW); Paux is the real-time total power of accessory loads (kW); Pcharg is the real-time charging and discharging power of the power battery (kW); and SOC is the remaining power battery charge (%). II. Calculate the current total engine power demand (Peng) using the following formula. Peng=Pelec_demand / ηgen+Ppto, Where: Peng is the current total power demand of the engine (kW), ηgen is the rated efficiency of the generator (%), ηgen is between 0.88 and 0.94 (%), and Ppto is the real-time power output shaft power (kW). III. Determine if there is a shortfall in the total power required by the engine; The current total engine power demand Peng is compared with the engine rated power Peng_rated, and the remaining power battery charge SOC is observed. If the current total engine power demand Peng > the engine rated power Peng_rated and the remaining power battery charge SOC < 50%, then the total engine power demand is determined to be in a state of shortfall. If it is not met, then the total engine power demand is determined to be in a balanced state. (3) The vehicle controller receives data from the power balancing module at least every 50ms per cycle, including at least 10ms of receiving data on the remaining battery charge. It then compares the current total engine power demand (Peng) with the engine's rated power (Peng_rated), and based on the remaining battery charge (SOC), constrains the engine power to enter one of the following three modes: When Peng < Peng_rated and 30% ≤ SOC ≤ 70%, it is in normal mode; When Peng > Peng_rated and 30% ≤ SOC ≤ 70%, it is in coordination mode; Emergency mode is activated when Peng > Peng_rated and 30% < SOC. (4) The vehicle controller performs hierarchical control for each mode of engine power, using the PTO rated speed as the PTO target speed, prioritizing the maintenance of the current PTO speed, and sending PTO target speed commands, feedforward torque compensation signals, power limit value commands, and charge / discharge commands to dynamically allocate engine power and drive motor output power, and dynamically regulate the SOC of the power battery. In normal mode, there is no power shortage in the engine. The engine adjusts the current output speed of the engine according to the PTO target speed so that the current PTO speed reaches the PTO target speed. The fluctuation of the current PTO speed in normal mode does not exceed ±1%. There is no limitation on the output power of the drive motor. When 50%≤SOC, the engine charges the power battery. In coordination mode, the vehicle controller coordinates based on the engine power shortfall, prioritizing PTO power output, limiting and reducing drive motor output power, discharging the power battery for recharge, and adjusting the current engine output speed to bring the current PTO speed to the target PTO speed. If the current PTO speed still fails to reach the target PTO speed after the above coordination, the drive motor output power and the current PTO power are further reduced, and the current engine output speed is adjusted and reduced again, thus adjusting and reducing the current PTO speed. The fluctuation of the current PTO speed in coordination mode does not exceed ±2%. In emergency mode, the vehicle controller triggers an emergency full reduction and alarm, the drive motor stops outputting power, the engine switches to pure PTO operation mode while idling, and the generator quickly charges the power battery. When SOC ≥ 65%, the drive motor output power is limited and reduced according to the engine power gap, the feedforward torque compensation signal and the power limit value command, and the current PTO power is reduced. The current PTO speed is adjusted and reduced by adjusting the current output speed of the engine. The fluctuation of the current PTO speed in emergency mode does not exceed ±2.8%.

[0007] This invention presents a method for coordinated power control of the drive and PTO (Power Transfer Engine) direct-drive (PTO) systems in a series hybrid tractor. It proposes a multi-objective power coordination control strategy prioritizing PTO speed stability. When the total engine power demand is limited, a coordination mode is entered to prioritize meeting the PTO mechanical power requirements, ensuring PTO speed stability. Under full-load conditions, the fluctuation of the current PTO speed is controlled within ±2%, a reduction of over 60% compared to traditional strategies, achieving dynamic PTO power priority assurance. Under the premise of ensuring PTO power, this invention dynamically adjusts the generator output power and the power battery charging and discharging power based on the battery's SOC (State of Charge) and drive power requirements, thereby dynamically adjusting the drive motor power. Within the feasible speed-torque range that satisfies the PTO power demand, this invention selects the engine operating point with optimal fuel economy and optimizes the engine operating point. This invention addresses extreme operating conditions where the engine's total power demand exceeds its limit. It enters an emergency mode for pure PTO (Power Toll-off) operation while the engine is idling. After rapid charging to a set threshold, temporary coordinated control of power priority ranking and adaptive redistribution ensures that the current PTO speed fluctuation is controlled within ±2.8%. This prevents engine overload leading to engine stalling or battery SOC depletion, guaranteeing stable system operation. Therefore, regardless of whether the battery SOC drops to the lower threshold or there are sudden changes in accessory load, adaptive power redistribution can be achieved, ensuring stable PTO speed operation. Under engine power constraints, this invention prioritizes stable PTO speed as the highest-priority control constraint. Based on this, it optimizes fuel economy and mobility, better meeting the practical needs of agricultural operations where "operational quality is paramount." This invention's engine power coordination control method utilizes online identification results of operating conditions as feedforward information, combined with PTO speed feedback errors, to construct a feedforward-feedback composite control architecture. The feedforward channel adjusts the power distribution benchmark in advance based on the identified operating condition type, while the feedback channel corrects deviations in real time. This significantly improves the response speed and anti-interference capability to sudden changes in operating conditions. Simultaneously, through automatic operating condition identification and intelligent matching of drive modes, drivers do not need extensive experience in mode selection; they only need to operate the tractor normally for field operations, and the system automatically adapts to the optimal power mode. This significantly reduces the demands on driver expertise and improves the driving experience. This invention can achieve reasonable power distribution and stable PTO speed control in different operating scenarios, combining the comprehensive technical effects of ensuring work quality, optimizing fuel economy, and improving driving comfort. Attached Figure Description

[0008] The embodiments of the present invention will now be described in further detail with reference to the accompanying drawings.

[0009] Figure 1 This is a flowchart of the engine power coordination control method of the present invention.

[0010] Figure 2This is a comparison curve of the current PTO speed in various embodiments of the present invention with the existing controlled PTO speed.

[0011] Figure 3 This is a schematic diagram of the structure of the series hybrid tractor travel and PTO direct-drive engine of the present invention. Detailed Implementation

[0012] See Figure 2 As shown, the present invention provides a method for coordinated control of the travel and PTO direct-drive engine power of a series hybrid tractor, comprising the following steps: (1) The data acquisition module receives and collects various real-time operating parameters and rated parameters of the tractor. The real-time operating parameters of the tractor of this invention include generator power, power output shaft power, total power of accessory loads, drive motor power, and remaining power battery charge and DC bus voltage. The real-time operating parameters can be obtained through existing sensor modules, battery management system, and motor controller. For example, the generator power and power output shaft power can be obtained through torque sensors and speed sensors, while the drive motor power and generator power can be obtained through the motor controller. The DC bus voltage and current can be obtained through voltage / current sensors, and the real-time charging and discharging power of the power battery and the remaining power battery charge can be obtained through the battery management system. Tractor accessories include hydraulic, mechanical, and electrical components. Hydraulic components include hydraulic pumps and piston pumps; mechanical components include radiators, condensers, and compressors; and electrical components include low-voltage generators and starter motors. Therefore, the total power of the accessory load is the sum of the power of the hydraulic, mechanical, and electrical components. The corresponding power of the hydraulic, mechanical, and electrical components can be obtained using pressure sensors, flow sensors, torque sensors, speed sensors, and voltage / current sensors. The total accessory load power can also be estimated based on the power of each accessory mounted on the tractor. The rated parameters of this invention include the engine's rated power, generator's rated efficiency, power output shaft's rated power, power output shaft's rated speed, and the drive motor's maximum peak value. These rated parameters can be obtained from the engine, the accessories, the drive motor controller, and the battery management system. Therefore, the data acquisition module collects the tractor's real-time operating parameters and rated parameters.

[0013] (2) Determine the power output gap of the engine; The power balance module receives real-time operating parameters and rated parameters from the data acquisition module, determines whether there is a power shortage in the engine, and transmits the received parameters and judgment data to the vehicle controller. The data acquisition module and power balance module of this invention use existing microprocessors to communicate with the vehicle controller. The power balance module judges the power output shortage of the engine and realizes intelligent matching of the corresponding drive mode in each operating state in subsequent steps to prioritize the quality of operation.

[0014] The determination of whether there is a power gap in the engine of the present invention is carried out by the following steps: Ⅰ. Calculate the real-time total power required by the tractor's electrical and accessory loads, Pelec_demand, as follows: Pelec_demand = Pwalk+Paux+ +Pcharg, When SOC > 50% and SOC < 30%, Pcharg = 0; Where: Pelec_demand is the real-time total power required by electrical components and accessories (kW); Pwalk is the real-time drive motor power (kW); Paux is the real-time total power of accessory loads (kW); Pcharg is the real-time charging and discharging power of the power battery (kW); and SOC is the remaining power battery charge (%).

[0015] II. Calculate the current total engine power demand (Peng) using the following formula. Peng=Pelec_demand / ηgen+Ppto, Where: Peng is the current total power demand of the engine (kW), ηgen is the rated efficiency of the generator (%), ηgen is between 0.88 and 0.94 (%), and Ppto is the real-time power output shaft power (kW).

[0016] III. Determine if there is a shortfall in the total power required by the engine; The current total engine power demand (Peng) is compared with the engine rated power (Peng_rated), and the remaining battery charge (SOC) is observed. If the current total engine power demand (Peng) is greater than the engine rated power (Peng_rated) and the remaining battery charge (SOC) is less than 50%, then the total engine power demand is determined to be in a state of shortfall. If neither of the above conditions is met, then the total engine power demand is determined to be in a balanced state.

[0017] (3) The vehicle controller receives data from the power balancing module at least every 50ms per cycle, including at least 10ms of receiving data on the remaining battery charge. It then compares the total power demand (Peng) of the front engine with the engine's rated power (Peng_rated), and based on the remaining battery charge (SOC), constrains the engine power to enter one of the following three modes: When Peng < Peng_rated and 30 ≤ SOC ≤ 70, it is in normal mode; When Peng > Peng_rated and 30 ≤ SOC ≤ 70, it is in coordination mode; Emergency mode is activated when Peng > Peng_rated and 30 < SOC. This invention receives data at the millisecond level and simultaneously constrains the engine power gap, quickly identifies the working conditions online, and uses the identification results as feedforward information. Then, it performs hierarchical control through feedback to stabilize the current PTO speed in real time, thereby achieving the goal of prioritizing work quality.

[0018] (4) The vehicle controller performs hierarchical control according to the engine power modes, using the PTO rated speed as the PTO target speed, prioritizing the maintenance of the current PTO speed. The vehicle controller sends PTO target speed commands, feedforward torque compensation signals, power limit value commands, and charge / discharge commands to dynamically allocate engine power and drive motor output power, and dynamically regulate the SOC of the power battery. Under the premise of ensuring PTO power, the controller dynamically adjusts the generator output power and the real-time charge / discharge power of the power battery according to the battery SOC status and driving power requirements.

[0019] In normal mode, the engine power is unaffected. The engine adjusts its current output speed according to the PTO target speed to achieve it. During this mode, the drive motor output power is not limited, and when the SOC is 50% ≤ SOC, the generator charges the power battery through the battery management system. In normal engine power mode, neither the current PTO power nor the drive motor output power is limited. Under full-load operating conditions, normal mode ensures stable current PTO speed, with fluctuations not exceeding 1%, resulting in high operational quality and meeting the power requirements for travel before proceeding to the next cycle of online identification and control of operating conditions.

[0020] In the coordinated mode, the vehicle controller coordinates based on the engine power shortage, prioritizing PTO power output, limiting and reducing the drive motor output power, and discharging the power battery for recharge. This can be achieved through the battery management system controlling the power battery to charge the drive motor, or by the battery recharging accessories. The power distribution between the engine and drive motor outputs maintains the current PTO speed, adjusts the engine's current output speed to reach the target PTO speed, and then proceeds to the next cycle of online identification and control of the operating conditions. Therefore, under full-load operating conditions, when there is a shortage in the total engine power demand, the engine prioritizes outputting the power required for PTO, while appropriately reducing the generator power and automatically decreasing the drive motor output power. This reduces the vehicle's travel speed while maintaining a stable current PTO speed, ensuring improved work quality and meeting the travel power requirements.

[0021] Even after the aforementioned coordination, if the current PTO speed still cannot reach the target PTO speed, the present invention further reduces the output power of the drive motor and the current PTO power during the coordination mode. This redistributes the engine power and drive motor output power, thereby readjusting and reducing the current engine output speed, and consequently reducing the current PTO speed. The fluctuation of the current PTO speed in the coordination mode does not exceed ±2%. Therefore, as the engine power deficit increases, even after the power battery discharges and recharges, the vehicle speed decreases and still cannot meet the power deficit. The current PTO power can then be further reduced to decrease the current PTO speed, minimizing the impact on the current PTO speed. In the coordination mode, the reduction in drive motor output power is less than 60% of the drive motor's maximum peak value, while the reduction in current PTO power does not exceed 10% of the real-time power output shaft power. Therefore, during the coordination process of this invention, the power distribution can be adjusted in advance according to the identified working condition type, so that the fluctuation of the current PTO speed does not exceed ±2%. Therefore, when the tractor is operating under full load conditions, the PTO speed fluctuation is ≥ ±5% compared with the original full load conditions where only the PTO speed feedback strategy is used, which can greatly improve the work quality and maximize the satisfaction of the travel power requirements.

[0022] In emergency mode, the vehicle controller triggers an emergency full descent and alarm, which can be displayed as a red alarm via a buzzer or / and the instrument panel. The drive motor stops outputting power, and the engine switches to pure PTO (Power To-Drive) mode while idling. The generator rapidly charges the power battery, controlled by the battery management system. For example, using a 10C power battery, the charge / discharge rate can be 7C-8C. When SOC ≥ 65%, based on the engine power deficit and the feedforward torque compensation signal and power limiting command from the vehicle controller, the drive motor power is limited and reduced, decreasing its output. Simultaneously, based on the remaining engine power deficit, the current PTO power is reduced, allocating power between the engine and drive motor. The PTO speed closed-loop controller, based on the PTO speed feedback error, sends feedback to the engine controller to adjust and reduce the current engine output speed, thus reducing the current PTO speed. The fluctuation of the current PTO speed in emergency mode does not exceed ±2.8%. After coordinated control by the emergency module, the next cycle of online identification and control of the operating conditions begins. This invention also prioritizes PTO operation in emergency mode, improving operational quality. This invention triggers an emergency mode when the output power reduction of the drive motor is greater than 60% of the maximum peak value of the drive motor, and the current PTO power reduction in the emergency mode does not exceed 25% of the real-time power output shaft power.

[0023] When the tractor of this invention is operating at full load in the field, it promptly enters different working modes according to the current total power demand of the engine. It prioritizes maintaining the current PTO speed and implements hierarchical control, identifies the working conditions online, dynamically allocates the engine power and drive motor output power, and combines the PTO speed feedback error to adjust the current PTO speed in real time through the engine. In extreme conditions, it switches the engine from idling to pure PTO working mode, which also avoids engine overload that could cause engine stalling or battery depletion, thus ensuring stable operation.

[0024] The bus voltage Udc of the power battery of this invention is 585±20V, which can maintain the DC bus voltage stability and provide the required power to the drive motor and various accessories through high voltage DC power.

[0025] This invention further refines the coordination mode and enables rapid online identification of different coordination modes. The coordination modes for engine power include mild coordination mode, moderate coordination mode and severe coordination mode. Therefore, the constraints on the coordination mode can be further refined, and rapid coordination control can be automatically performed according to different operating conditions.

[0026] In this invention, when Peng > Peng_rated and SOC > 50%, it is a mild coordination mode. When Peng > Peng_rated and 40% < SOC ≤ 50%, it is a moderate coordination mode; When Peng > Peng_ratedd and 30% ≤ SOC ≤ 40%, it is a heavily coordinated mode; In the mild coordination mode, the power battery slowly discharges to replenish energy according to the power gap. For example, if a 10C power battery is used in this application, the battery management system provides power to the drive motor or accessories at a charge / discharge rate of 1C-2C to maintain the current PTO power. The PTO speed closed-loop controller sends the engine speed adjustment amount to the engine controller to adjust the current output speed of the engine. Therefore, the PTO speed closed-loop controller sends the adjustment amount to the engine controller based on the PTO speed feedback error as feedback information to adjust the current output speed of the engine so that the current PTO speed reaches the PTO target speed and maintains the output power of the drive motor unchanged.

[0027] In the medium-coordination mode, this invention replenishes energy by discharging the power battery at a medium speed according to the power gap. For example, if this application uses a 10C power battery, the battery management system controls the battery to discharge at a rate of 3C-5C to maintain the current PTO power. Based on the feedforward torque compensation signal and power limiting command, the output power of the drive motor is limited and reduced. This can be achieved through a drive motor torque closed-loop controller and a power limiter, thereby reducing the drive motor's output power. The PTO speed closed-loop controller sends an engine speed adjustment to the engine controller, adjusting the current engine output speed to reach the PTO target speed. By limiting the drive motor's output power, the current PTO speed is maintained. When the engine power enters the medium-coordination mode, the reduction in drive motor output power is no less than 80% of the drive motor's maximum peak value.

[0028] In the heavily coordinated mode, this invention rapidly discharges the power battery to replenish energy based on the power gap. The battery management system controls the battery to discharge at a 6C-7C rate. Based on the feedforward torque compensation signal and power limiting command, the drive motor output power is further reduced. Simultaneously, by reducing the current PTO power, the PTO speed closed-loop controller sends an engine speed adjustment to the engine controller, adjusting and reducing the current engine output speed, thus lowering the current PTO speed. When the engine power enters the heavily coordinated mode, the reduction in drive motor output power is between greater than 60% and less than 80% of the drive motor's maximum peak value.

[0029] The hybrid tractor uses an engine with a rated power of 206kW and a PTO rated speed of 540rpm for field operations. The power coordination control method of this invention is used to identify different operating scenarios online, prioritize maintaining the current PTO speed, dynamically allocate the engine power and drive motor output power, and control the current PTO speed. See the following embodiments for details. Example 1

[0030] This invention uses a lightweight rotary tiller for shallow rotary tillage.

[0031] The work site is a sandy loam plot, with shallow rotary tillage at a depth of 12cm. The land is flat and has no hard soil layer.

[0032] The data acquisition module receives and collects real-time operating parameters and rated parameters of the tractor. The engine load rate is approximately 77%, with ample margin. At this time, the SOC of the power battery is 65%, so Pcharg is 0 kW, Ppto is 75 kW, PTO target speed is 540 rpm, Pwalk is 60 kW, and Paux is 30 kW.

[0033] The power balance module receives real-time operating parameters and rated parameters from the data acquisition module, determines whether there is a power shortage in the engine, and transmits the received parameters and judgment data to the vehicle controller. It calculates the real-time total power required by electrical components and accessories, Pelec_demand = 60 + 30 = 90 (kW), and the current total power demand of the engine, Peng = 90 / 0.92 + 75 = 172.8 (kW). Since the power demand is less than the rated power of the engine, Peng_rated, there is no power shortage in the total power demand of the engine, and the total power demand of the engine is determined to be in a balanced state.

[0034] The vehicle controller receives data from the power balance module every 50ms per cycle, including at least 10ms of data on the remaining battery charge. If the current total engine power demand (Peng) exceeds the engine's rated power (Peng_rated), and the battery SOC is at 65%, the system automatically recognizes the engine power and enters normal mode, without limiting the current PTO power or drive motor output power. The current PTO speed is 540±5 rpm, with a fluctuation of ±0.93%. When the SOC is 50% ≤ SOC, the generator charges the battery through the battery management system. Example 2

[0035] This invention uses a medium-sized driven harrow for land preparation.

[0036] The work site is a sandy loam soil plot, driven by a harrow to till the land to a depth of 18cm, containing a small amount of gravel, with a medium load.

[0037] The data acquisition module receives and collects real-time operating parameters and rated parameters of the tractor. The engine is near full load, at which point the SOC of the power battery is 52%, Pcharg is 0kW, Ppto is 80kW, Pwalk is 95kW, and Paux is 32kW.

[0038] The power balance module receives real-time operating parameters and rated parameters from the data acquisition module, calculates the real-time total power required by electrical components and accessories (Pelec_demand = 95 + 32 = 127 kW), and the current total power required by the engine (Peng = 127 / 0.92 + 80 = 218 kW), and determines that there is a shortfall in the total power required by the engine.

[0039] The vehicle controller receives data from the power balance module every 50ms per cycle. Among these data, at least 10ms are spent receiving data on the remaining power of the power battery. The current total power demand of the engine (Peng) is greater than the engine's rated power (Peng_rated), and the power shortfall is 218-206=12 (kW). The power battery's SOC is 52%, and the system is automatically identified as a mild coordination mode. Priority is given to using the power battery to discharge and replenish 12kW of power, while maintaining the bus voltage. The current PTO power and drive motor output power are not limited. The current PTO speed is 540±6rpm, and the fluctuation of the current PTO speed is ±1.11%. Example 3

[0040] This invention uses a heavy-duty rotary tiller for heavy-duty rotary tillage operations.

[0041] The operation was conducted on clay soil, involving heavy-duty rotary tillage to a depth of 22cm. The soil was highly sticky and had high resistance.

[0042] The data acquisition module receives and collects real-time operating parameters and rated parameters of the tractor. The engine is near full load, and the SOC of the power battery is 48%. The battery management system requests charging power: Pcharg 10kW, Ppto 90kW, Pwalk 100kW, and Paux 35kW.

[0043] The power balance module receives real-time operating parameters and rated parameters from the data acquisition module, calculates the real-time total power required by electrical components and accessories (Pelec_demand = 100 + 35 + 10 = 145 kW), and the current total power required by the engine (Peng = 145 / 0.94 + 90 = 244.3 kW), and determines that there is a shortfall in the total power required by the engine.

[0044] The vehicle controller receives data from the power balance module every 50ms per cycle. The current total power demand of the engine (Peng) is greater than the engine's rated power (Peng_rated), and the power gap is 244.3-206=38.3 (kW). The SOC of the power battery is 48%, and it is automatically identified as a moderate coordination mode, limiting the output power of the drive motor from 100kW to 84kW. The current PTO power remains unchanged, and the power battery discharges and replenishes energy at 22.3kW while maintaining the bus voltage. The current PTO speed is 540±8rpm, and the current PTO speed fluctuation is ±1.48%. Example 4

[0045] This invention uses a heavy-duty driven rake for soil breaking and land preparation operations.

[0046] Working scenario: Hardened, clayey soil, using a drive harrow to break up and level the soil to a depth of 25cm, containing a large number of stones, resulting in an extremely heavy workload.

[0047] The data acquisition module receives and collects real-time operating parameters and rated parameters of the tractor. The engine is near full load, and the SOC of the power battery is 38%. The battery management system requests charging power: Pcharg 13kW, Ppto 90kW, Pwalk 100kW, and Paux 35kW.

[0048] The power balance module receives real-time operating parameters and rated parameters from the data acquisition module, calculates the real-time total power required by electrical components and accessories (Pelec_demand = 100 + 35 + 13 = 148 kW), and the current total power required by the engine (Peng = 148 / 0.92 + 90 = 250.9 kW), and determines that there is a shortfall in the total power required by the engine.

[0049] The vehicle controller receives data from the power balance module every 50ms per cycle. Among these, at least 10ms is spent receiving data on the remaining power of the power battery. Since the current total power demand of the engine (Peng) is greater than the engine's rated power (Peng_rated), the power shortfall is 250.9-206=44.9kW. The power battery's SOC is 38%, and the system is automatically identified as being in a heavy coordination mode. The drive motor output power is limited from 100kW to 80kW, the PTO power is reduced from 110kW to 100kW, and the power battery provides auxiliary discharge and replenishment at 14.9kW while maintaining the bus voltage. The current PTO speed is 538±10rpm, and the current PTO speed fluctuation is ±1.86%. Example 5

[0050] This invention uses a heavy-duty rotary tiller for extreme deep rotary tillage operations.

[0051] The work site consisted of extremely hard clay and sloping terrain, with extreme deep rotary tillage, reaching a depth of 30cm, and occasional encounters with large rocks.

[0052] The data acquisition module receives and collects various real-time operating parameters and rated parameters of the tractor. Under extreme engine load, the SOC continuously drops to 28%, Pcharg 0kW, Ppto 120kW, Pwalk 110kW (climbing condition), and Paux 40kW.

[0053] The power balance module receives real-time operating parameters and rated parameters from the data acquisition module, calculates the real-time total power required by electrical components and accessories (Pelec_demand = 110 + 40 = 150 kW), and the current total power required by the engine (Peng = 150 / 0.92 + 120 = 283 kW), and determines that there is a shortfall in the total power required by the engine.

[0054] The vehicle controller receives data from the power balance module every 50ms per cycle, including at least 10ms of data on the remaining battery charge. Since the current total engine power demand (Peng) exceeds the engine's rated power (Peng_rated), and the battery's state of charge (SOC) is 28%, it automatically enters emergency mode. The vehicle controller triggers an emergency power reduction and alarm, which can be displayed as a red alarm via a buzzer or / and the instrument panel. The drive motor stops outputting power, and the engine switches to pure PTO operation mode while idling. The generator rapidly charges the battery. When the SOC is ≥ 65%, the power deficit is 283 - 206 = 77 (kW), limiting the drive motor output power from 110kW to 65kW, reducing the PTO power from 120kW to 95kW, and providing 7kW of auxiliary battery discharge. The current PTO speed is 535±14rpm, with a fluctuation of ±2.6%.

[0055] See Figure 2 The figure shows a comparison curve of the current PTO speed in the above embodiments and the current PTO speed controlled by the traditional strategy. It can be seen from the figure that the fluctuation of the current PTO speed of the present invention is significantly smaller than that of the traditional current PTO speed, thus having better operation quality.

Claims

1. A method for coordinated control of the travel and PTO direct-drive engine power of a series hybrid tractor, characterized in that: Includes the following steps: (1) Receive and collect real-time operating parameters and rated parameters of the tractor through the data acquisition module; (2) Determine the power output gap of the engine; The power balance module receives real-time operating parameters and rated parameters from the data acquisition module to determine if there is a power shortage in the engine, and transmits the received parameters and judgment data to the vehicle controller. To check for insufficient engine power, follow these steps: Ⅰ. Calculate the real-time total power required by the tractor's electrical and accessory loads, Pelec_demand, as follows: Pelec_demand = Pwalk+Paux+ +Pcharg, When SOC > 50% and SOC < 30%, Pcharg = 0; Where: Pelec_demand is the real-time total power required by electrical components and accessories (kW); Pwalk is the real-time drive motor power (kW); Paux is the real-time total power of accessory loads (kW); Pcharg is the real-time charging and discharging power of the power battery (kW); and SOC is the remaining power battery charge (%). II. Calculate the current total engine power demand (Peng) using the following formula. Peng=Pelec_demand / ηgen+Ppto, Where: Peng is the current total power demand of the engine (kW), ηgen is the rated efficiency of the generator (%), ηgen is between 0.88 and 0.94 (%), and Ppto is the real-time power output shaft power (kW). III. Determine if there is a shortfall in the total power required by the engine; The current total engine power demand Peng is compared with the engine rated power Peng_rated, and the remaining power battery charge SOC is observed. If the current total engine power demand Peng > the engine rated power Peng_rated and the remaining power battery charge SOC < 50%, then the total engine power demand is determined to be in a state of shortfall. If it is not met, then the total engine power demand is determined to be in a balanced state. (3) The vehicle controller receives data from the power balancing module at least every 50ms per cycle, including at least 10ms of receiving data on the remaining battery charge. It then compares the current total engine power demand (Peng) with the engine's rated power (Peng_rated), and based on the remaining battery charge (SOC), constrains the engine power to enter one of the following three modes: When Peng < Peng_rated and 30% ≤ SOC ≤ 70%, it is in normal mode; When Peng > Peng_rated and 30% ≤ SOC ≤ 70%, it is in coordination mode; Emergency mode is activated when Peng > Peng_rated and 30% < SOC. (4) The vehicle controller performs hierarchical control for each mode of engine power, using the PTO rated speed as the PTO target speed, prioritizing the maintenance of the current PTO speed, and sending PTO target speed commands, feedforward torque compensation signals, power limit value commands, and charge / discharge commands to dynamically allocate engine power and drive motor output power, and dynamically regulate the SOC of the power battery. In normal mode, there is no power shortage in the engine. The engine adjusts the current output speed of the engine according to the PTO target speed so that the current PTO speed reaches the PTO target speed. The fluctuation of the current PTO speed in normal mode does not exceed ±1%. There is no limitation on the output power of the drive motor. When 50%≤SOC, the engine charges the power battery. In coordination mode, the vehicle controller coordinates based on the engine power shortfall, prioritizing PTO power output, limiting and reducing drive motor output power, discharging the power battery for recharge, and adjusting the current engine output speed to bring the current PTO speed to the target PTO speed. If the current PTO speed still fails to reach the target PTO speed after the above coordination, the drive motor output power and the current PTO power are further reduced, and the current engine output speed is adjusted and reduced again, thus adjusting and reducing the current PTO speed. The fluctuation of the current PTO speed in coordination mode does not exceed ±2%. In emergency mode, the vehicle controller triggers an emergency full reduction and alarm, the drive motor stops outputting power, the engine switches to pure PTO operation mode while idling, and the generator quickly charges the power battery. When SOC ≥ 65%, the drive motor output power is limited and reduced according to the engine power gap, the feedforward torque compensation signal and the power limit value command, and the current PTO power is reduced. The current PTO speed is adjusted and reduced by adjusting the current output speed of the engine. The fluctuation of the current PTO speed in emergency mode does not exceed ±2.8%.

2. The method for coordinated control of the travel and PTO direct-drive engine power of a series hybrid tractor according to claim 1, characterized in that: The engine power coordination modes include mild coordination mode, moderate coordination mode, and severe coordination mode; When Peng > Peng_rated and SOC > 50%, it is a mild coordination mode. When Peng > Peng_rated and 40% < SOC ≤ 50%, it is a moderate coordination mode; When Peng > Peng_rated and 30% ≤ SOC ≤ 40%, it is a heavily coordinated mode; In mild coordination mode, the power battery slowly discharges to replenish energy according to the power gap, maintaining the current PTO power. The PTO speed closed-loop controller sends the engine speed adjustment amount to the engine controller to adjust the current output speed of the engine, so that the current PTO speed reaches the PTO target speed, and the output power of the drive motor remains unchanged. In the medium coordination mode, the power battery discharges at a medium speed to replenish energy according to the power gap, maintaining the current PTO power. The output power of the drive motor is limited and reduced according to the feedforward torque compensation signal and the power limit value command. The PTO speed closed-loop controller sends the engine speed adjustment amount to the engine controller to adjust the current output speed of the engine so that the current PTO speed reaches the PTO target speed. In the heavy coordination mode, the power battery is rapidly discharged to replenish energy according to the power gap. The output power of the drive motor is further reduced according to the feedforward torque compensation signal and the power limit value command. At the same time, the current PTO power is reduced. The PTO speed closed-loop controller sends the engine speed adjustment amount to the engine controller to adjust and reduce the current output speed of the engine, thereby reducing the current PTO speed.

3. The method for coordinated control of the travel and PTO direct-drive engine power of a series hybrid tractor according to claim 1, characterized in that: In the coordinated mode, the reduction in drive motor output power is less than 60% of the maximum peak value of the drive motor, while the reduction in current PTO power does not exceed 10% of the real-time power output shaft power. When the drop in drive motor output power is greater than 60% of the maximum peak value of the drive motor, an emergency mode is triggered, and the drop in current PTO power in the emergency mode does not exceed 25% of the real-time power output shaft power.

4. The method for coordinated control of the travel and PTO direct-drive engine power of a series hybrid tractor according to claim 2, characterized in that: When the engine power enters the medium coordination mode, the reduction in the output power of the drive motor is not less than 80% of the maximum peak value of the drive motor. When the engine power enters the heavy coordination mode, the reduction in the output power of the drive motor is between greater than 60% and less than 80% of the maximum peak value of the drive motor.

5. The method for coordinated control of the travel and PTO direct-drive engine power of a series hybrid tractor according to claim 1, characterized in that: The bus voltage Udc of the power battery is 585±20V.

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