An electric drive type tractor CVT power assembly and control method of a mechanical through-pin PTO structure

Abstract

The present application relates to the technical field of new energy power tractor, in particular to a kind of mechanical wear heart PTO structure's electric drive type tractor CVT power assembly and control method, control system also includes total controller, ECU chassis controller, MCU main drive motor controller, also includes wheel speed sensor, steering angle sensor and driving cabin entity button.The control system and method of the present application realize full-time / minute-time four-wheel drive mode switching, left and right differential control, anti-skid control method, the method takes safety as core priority, through sensor information acquisition, multiple condition determination, accurate electric control execution, realizes the real-time dynamic regulation and control of tractor driving process, gives consideration to driving safety, power and energy economy.

Description

Technical Field

[0001] This invention relates to the field of new energy power tractor technology, specifically to a CVT powertrain and control method for an electric drive tractor with a mechanical through-hole PTO structure. Background Technology

[0002] As a core piece of agricultural machinery, the performance of a tractor's transmission system directly determines its operational efficiency, ease of operation, and operating costs. Existing tractor transmission systems are mainly divided into three categories: manual shift transmissions, power-uninterrupted automatic shift transmissions, and hydraulic-mechanical continuously variable transmissions (HMCVT). Each type has significant technical shortcomings, making it difficult to meet the high-efficiency, energy-saving, and easy-to-maintain requirements of modern agricultural operations, as detailed below:

[0003] 1. Manual shift transmission system: When the tractor is working in the field, the load of the whole machine fluctuates greatly due to the change in soil resistance. It is necessary to stop frequently to shift gears to match the traction force and working speed requirements of the implements. This not only greatly increases the workload of the operator, but also causes low work efficiency and poor work quality stability. At the same time, the engine speed is directly coupled with the vehicle speed. The change in vehicle speed will cause the engine speed to fluctuate greatly, making it impossible to operate stably in the economic speed range. This will lead to problems such as high fuel consumption, failure to meet emission standards, and accelerated vibration and wear of the whole machine and parts.

[0004] 2. Uninterrupted Power Automatic Shift Transmission: This transmission system can perform gear shifting while the vehicle is moving and the power is uninterrupted. It uses a wet multi-plate clutch as the shifting actuator, controlling oil pressure changes to achieve sequential disengagement and engagement of the two clutches, enabling non-stop gear shifting under load. This effectively solves the drawbacks of manual transmissions requiring stopping for gear shifting, reducing operator workload and improving handling comfort and work efficiency. However, this transmission system still has several technical shortcomings: engine speed and vehicle speed are still directly coupled, and changes in vehicle speed easily cause significant fluctuations in engine speed, making it difficult to stabilize within the economical speed range, resulting in high fuel consumption, poor emissions, and severe component vibration and wear; the complex operating conditions of tractors and the large number of gears required necessitate a large number of clutches and hydraulic proportional valves in the transmission system. For example, a 160-horsepower 16-speed automatic transmission requires 8 clutches and 8 hydraulic proportional valves; due to the inconsistency of parts, shifting performance needs to be calibrated on a dedicated factory test bench, and clutch wear will change with increased usage time. The timing of gear shifting reduces smoothness and causes noticeable shift shock. The core technology of this transmission system is currently controlled by foreign companies, and the products are mainly imported. It is not only complex in structure and high in manufacturing cost, but also has little room for price reduction and high maintenance costs. Due to price constraints, this type of transmission system is mainly used in tractor products with speeds of 80-200 hp in advanced countries. Traditional power shift gearboxes are single-power stepped transmissions. To achieve ultra-low speed super crawling gears, complex reduction gear systems need to be added, and continuously variable transmission cannot be achieved in core operating conditions such as rotary tillage. Theoretically, it cannot match the optimal driving speed of rotary tillers.

[0005] 3. Hydraulic-Mechanical Continuously Variable Transmission (HMCVT): This transmission system consists of core components such as a high-pressure variable displacement piston pump / motor, a multi-row planetary gear mechanism, a wet clutch, and brakes. Its core principle is to split the engine power into two power routes through the planetary gear set: one is a mechanical power route, which is directly transmitted to the gearbox input shaft; the other is a hydraulic power route, which, after a machine-hydraulic-machine power conversion, merges with the gearbox input shaft to achieve full power convergence. With the synergistic effect of power splitting and convergence, the torque and speed of the transmission system can be automatically and continuously adjusted according to the vehicle speed and traction requirements, meeting the traction and speed requirements during vehicle gear shifting.

[0006] This transmission system achieves stepless automatic adjustment of vehicle transmission, which greatly reduces the operator's workload, improves the comfort of operation, and effectively improves work efficiency and quality. Moreover, the engine speed and torque are completely decoupled from the vehicle speed and traction, allowing the engine to operate stably in a low fuel consumption range, resulting in low vibration and excellent emission performance. However, the technical defects of this transmission system are also prominent: core components such as high-pressure variable displacement piston pumps / motors and proportional valves are all precision hydraulic pairs, which have strict requirements for assembly cleanliness, usage cleanliness, and maintenance cleanliness, and require the use of special hydraulic oil, resulting in high usage and maintenance costs; the gearbox achieves 4 to 6 gear range shifts through a multi-row planetary mechanism and wet clutches / brakes, with a large number of parts and a complex overall structure. The core technology is controlled by foreign companies, the product is highly dependent on imports, and the manufacturing cost is high and it is difficult to reduce the price; the transmission efficiency is low, with a maximum transmission efficiency of only about 80%, which is significantly inferior to other types of transmission systems, and the fuel economy is poor; due to the dual limitations of price and usage and maintenance costs, the application rate of this transmission system in the Chinese market is extremely low, and in advanced countries of the world, it is mainly used in high-horsepower tractors of 200-400Hp.

[0007] In view of the above-mentioned technical defects of various transmission systems of existing tractors, there is an urgent need for a powertrain and control method to realize continuously variable transmission, efficient transmission, flexible four-wheel drive and safe anti-skid of tractors, and adapt to various field operation conditions.

[0008] The information disclosed in the above background section is only intended to enhance the understanding of the overall background of the present invention, and should not be construed as an admission or implication in any way that such information constitutes prior art known to those skilled in the art. Summary of the Invention

[0009] This invention provides a CVT powertrain and control method for an electric tractor with a mechanical through-hole PTO structure, which realizes stepless speed change, high-efficiency transmission, flexible four-wheel drive and safe anti-skid, and is suitable for various field operation conditions.

[0010] A CVT powertrain control system for an electric tractor with a mechanical through-hole PTO structure includes an engine, a generator, a main drive motor, a transmission, a transfer case, a PTO transmission case, an energy storage unit, a charging interface, and a power supply interface. The engine and the generator are electrically connected. The generator is electrically connected to the energy storage unit and the main drive motor. The energy storage unit and the main drive motor are electrically connected. The power output end of the main drive motor is connected to the transmission. One power output from the transmission is transmitted to the mechanically driven front axle via the transfer case, and the other power output is transmitted to the rear axle. The main shafts of the main drive motor and the transmission are both hollow shaft structures. The PTO shaft of the PTO transmission box passes through the main shaft of the transmission and the main shaft of the main drive motor in sequence and is then connected to the engine. The charging interface and the power supply interface are both electrically connected to the energy storage unit.

[0011] The engine of this invention is connected to the generator to drive the generator to generate electricity; the power output end of the main drive motor is connected to the transmission to form a rear-wheel drive structure of main drive motor + transmission; the output end of the transmission transmits power in two ways, one way is transmitted to the front axle differential through the transfer case and drive shaft to realize the mechanical drive of the front wheels, and the other way is transmitted directly to the rear axle to realize the power drive of the rear wheels; the main shafts of the main drive motor and the transmission are both hollow shaft structures, and the PTO shaft of the PTO transmission box passes through the main shaft of the transmission and the main shaft of the main drive motor 3 in sequence before being connected to the engine power, realizing the structural design of PTO output by the engine power through the core.

[0012] This invention employs a flywheel-integrated generator design. The front wheels are mechanically driven, while the rear wheels are driven via a combination of a main drive motor and a transmission. It enables full-time / part-time four-wheel drive switching, differential speed control for the left and right wheels, and anti-slip functionality. The PTO transmission is directly connected to the engine and outputs power through a through-type structure. The entire unit is equipped with an energy storage unit, supporting external charging / discharging and enabling pure electric driving. The overall structure is compact and highly integrated.

[0013] The powertrain of this invention fully utilizes the inherent characteristics of electric motors—high torque at low speeds and a wide speed adjustment range—eliminating the need for gear shifting in traditional transmissions. It directly achieves stepless speed change throughout the tractor's operation by adjusting the speed of the motor, significantly simplifying the transmission structure and improving the smoothness and adaptability of the shifting. At the same time, the PTO through-hole structure design achieves compact power transmission and high space utilization. Combined with the combination of electric drive and mechanical drive, it balances power performance and transmission stability.

[0014] The present invention also includes a main controller, and an ECU chassis controller and an MCU main drive motor controller that are communicatively connected to the main controller. The MCU main drive motor controller is connected to the main drive motor, and the main controller is communicatively connected to the transfer case. It also includes wheel speed sensors, steering angle sensors, and physical buttons in the driver's cabin. The wheel speed sensors are installed on the front and rear wheels of the vehicle, the steering angle sensors are installed on the front wheels of the vehicle, and the physical buttons in the driver's cabin are located inside the driver's cabin. The wheel speed sensors and steering angle sensors are both communicatively connected to the ECU chassis controller, and the physical buttons in the driver's cabin are communicatively connected to the main controller.

[0015] Through the aforementioned control system components, this invention includes a full-time / part-time four-wheel drive mode switching system, left and right differential control, and an anti-slip control method. This method prioritizes safety, achieving real-time dynamic control of the tractor's driving process through sensor information acquisition, multi-condition judgment, and precise electronic control execution, thus balancing driving safety, power performance, and energy economy. Preferably, the main controller controls the engagement or disengagement of the transfer case clutch and distributes the loading torque to the front and rear axles according to the load ratio. The main controller commands the transfer case clutch to engage (hard-wired) to enter full-time four-wheel drive mode, and commands the transfer case clutch to disengage (hard-wired), with all torque output from the main drive motor being loaded onto the rear axle to enter two-wheel drive mode. This invention achieves linear gradual change by controlling the engagement pressure of the transfer case clutch through PID closed-loop control; and ensures smooth switching through a torque gradual change algorithm. Physical buttons in the driver's cab are used to dynamically switch the drive mode according to the actual driving conditions of the tractor.

[0016] Preferably, the present invention further includes a high-voltage distribution box, which is electrically connected to the main drive motor, generator, energy storage unit, charging interface, and discharging interface respectively, for realizing the distribution and management of high-voltage electrical energy. It is used to realize the distribution and regulation of electrical energy for each electrical component. The front axle is equipped with a front axle differential and front axle half-shafts connected in sequence to realize differential drive of the front wheels.

[0017] Preferably, the present invention further includes an Electronic Stability Control (ESC) system and an Electronically Controlled Limited-Slip Differential (eLSD) system, which are communicatively connected to the main controller. The ESC system is used to suppress wheel slippage; that is, the main controller sends a command to the ESC system to apply braking force to the slipping wheel, thereby suppressing wheel slippage. The eLSD system limits the differential speed range between the left and right wheels; that is, the main controller sends a command to the eLSD system on the drive axle where the slipping wheel is located to increase the clamping force, limit the differential speed range between the left and right wheels, and quickly eliminate slippage.

[0018] This invention also provides a control method for an electric tractor CVT powertrain with a mechanical through-hole PTO structure, applied to the aforementioned control system, comprising the following steps: S1: The system powers on, the main controller completes initialization self-test, and collects and processes sensor information; in the specific steps of S1... S2: Slippage Detection and Anti-Slip Control: The wheel speed is detected by the wheel speed sensor. If the speed difference between the wheels is detected to be >15% and lasts for 50ms, anti-slip control is executed; otherwise, proceed to the next step. S3: Steering Detection and Differential Control: The steering angle sensor detects the front wheel steering angle. If the front wheel steering angle is greater than 5°, left and right differential control is executed: The main controller sends a command to the electronically controlled limited-slip differential (eLSD) to reduce pressure, release the natural differential between the left and right wheels, match the Ackermann steering geometry, and reduce the turning radius; otherwise, proceed to the next step. S4: Four-wheel drive mode switching control: If a full-time four-wheel drive command is received, the main controller controls the vehicle to maintain four-wheel drive mode; otherwise, part-time four-wheel drive control is executed: if the current vehicle speed is greater than 20 kph, or the estimated road adhesion coefficient is greater than 0.6, or the throttle opening is less than 30%, then switch to two-wheel drive mode; otherwise switch to four-wheel drive mode. During the switching process, a torque gradient algorithm is used to keep the total torque constant. S5: The MCU main drive motor controller collects the main drive motor sensor signal, calculates the actual speed and torque of the main drive motor and feeds it back to the main controller, then jumps to step S2 for repeated execution.

[0019] The control method of this invention is based on the aforementioned control system. Through a cyclical logic of self-test initialization, slippage and anti-slip control, steering differential control, dynamic switching of four-wheel drive modes, and closed-loop control, it achieves adaptive vehicle operation condition regulation. Relying on the low-speed, high-torque, and wide-range speed characteristics of the electric motor, it completely eliminates mechanical gear shifting, achieving continuously variable transmission throughout the entire operation. Simultaneously, it achieves complete decoupling between the engine and vehicle speed, and, in conjunction with an energy recovery strategy, reduces energy consumption. Equipped with a precise left and right differential control strategy and matched with Ackermann steering geometry, it effectively reduces the tractor's turning radius and improves steering flexibility in field operations.

[0020] Preferably, the anti-slip control in step 2 includes: the main controller issuing a command to enter the full-time four-wheel drive mode; the main controller issuing a command to the MCU main drive motor controller to reduce torque; the main controller sending a command to the vehicle electronic stability control system (ESC) to suppress wheel slippage; and the main controller sending a command to the electronically controlled anti-slip differential (eLSD) of the drive axle where the slipping wheel is located to limit the differential range between the left and right wheels.

[0021] Preferably, in step S4, the physical buttons in the driver's cab include a full-time four-wheel drive mode button and a work mode button. If either button is pressed, the controller enters the full-time four-wheel drive control mode.

[0022] Preferably, in step S4, the road surface adhesion coefficient is calculated by back-calculating the wheel speed difference and slip ratio.

[0023] By optimizing both structural design and control strategies, this invention offers the following advantages compared to existing technologies: 1. By utilizing the characteristics of low speed, high torque, and wide speed adjustment range of motors, the traditional gear shifting of gearboxes is eliminated, and stepless speed regulation is achieved directly through motor speed control throughout the entire operation process. The transmission structure is simple and the control is precise.

[0024] 2. It achieves complete decoupling between engine speed and vehicle speed, allowing the engine to operate stably within the economic speed range, significantly improving operating efficiency and reducing fuel consumption and emissions.

[0025] 3. Equipped with a precise left and right differential control strategy, matched with Ackermann steering geometry, effectively reducing the tractor's turning radius and improving steering flexibility in field operations.

[0026] 4. By utilizing the forward and reverse rotation characteristics of the motor, the tractor can be easily reversed, simplifying the operation process and improving the comfort of operation.

[0027] 5. The transmission form that combines electric drive and mechanical drive has a significantly improved transmission efficiency and better fuel economy compared to the hydraulic mechanical continuously variable transmission (HMCVT).

[0028] 6. The energy storage unit enables battery-assisted power supply, which, combined with the short-term overload capability of the motor, significantly improves the tractor's ability to pass through complex working conditions such as climbing slopes, crossing bumps, and overcoming obstacles.

[0029] 7. The high torque of the motor can assist in starting the engine, improving its starting performance and operational stability.

[0030] 8. The motor has a fast power response, enabling the vehicle to start quickly and accelerate well, adapting to the power requirements of various working conditions.

[0031] 9. The motor can achieve stable low-speed operation without the need for a complex reduction gear system, thus enabling the tractor to crawl at ultra-low speeds and adapt to precision field operations.

[0032] 10. Decoupling engine speed from vehicle speed, combined with the vehicle's energy recovery system, enables energy recovery during driving, turning, and other low-load operating conditions, further saving fuel and reducing consumption, and improving the overall energy efficiency of the machine.

[0033] 11. The PTO adopts a through-hole structure design, which directly outputs power from the engine. The structure is simple and compact, with high space utilization and excellent power transmission efficiency.

[0034] 12. The machine supports external charging / discharging, enabling pure electric driving mode, adapting to low-noise and zero-emission operation requirements, and also meeting the emergency power supply needs for outdoor operations.

[0035] 13. The supporting four-wheel drive, differential, and anti-slip control strategies have clear priorities, accurate judgments, and efficient execution, achieving a balance between driving safety, power, and energy economy, and are suitable for various field operations and driving conditions. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the overall structure of a CVT powertrain control system for an electric tractor with a mechanical through-hole PTO structure as described in this invention.

[0037] Figure 2 This is a schematic diagram of the power connection structure of the PTO transmission box described in this invention.

[0038] Figure 3 This is a schematic diagram of the control process of the control method described in this invention.

[0039] Figure 4 This is a diagram showing the transmission relationship of anti-slip control signals in the control method described in this invention.

[0040] Figure 5 This is a diagram showing the transmission relationship of the left and right speed difference control signals in the control method described in this invention.

[0041] Figure 6 This is a diagram showing the signal transmission relationship of the full-time / part-time four-wheel drive control method described in this invention.

[0042] Attached reference numerals: 1-Engine, 2-Generator, 3-Main drive motor, 4-Transmission, 5-Transfer case, 6-PTO transmission case, 7-Energy storage unit, 8-Charging interface, 9-Power supply interface, 10-High voltage distribution box, 11-Drive shaft, 12-PTO shaft, 13-Main controller, 14-ECU chassis controller, 15-MCU main drive motor controller, 16-Driving cockpit physical buttons. Detailed Implementation

[0043] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0044] To illustrate the technical content, objectives, and effects of this invention in detail, the following description is provided in conjunction with embodiments and accompanying drawings. It should be understood that in the description of this embodiment, terms indicating orientation or positional relationships are based on the orientation or positional relationships shown in the accompanying drawings and are used only for the convenience of describing this embodiment and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on this invention. Example 1:

[0045] like Figures 1-2As shown, a CVT powertrain control system for an electric tractor with a mechanical through-hole PTO structure includes an engine 1, a generator 2, a main drive motor 3, a transmission 4, a transfer case 5, a PTO transmission case 6, an energy storage unit 7, a charging interface 8, and a power supply interface 9.

[0046] The engine 1 and the generator 2 are electrically connected. The generator 2 is electrically connected to the energy storage unit 7 and the main drive motor 3. The energy storage unit 7 and the main drive motor 3 are electrically connected. The power output end of the main drive motor 3 is connected to the transmission 4. One power output from the transmission 4 is transmitted to the mechanically driven front axle via the transfer case 5 and the drive shaft 11, and the other power is transmitted to the rear axle. The main shafts of the main drive motor 3 and the transmission 4 are both hollow shaft structures. The PTO shaft 12 of the PTO transmission case 6 passes through the main shaft of the transmission 4 and the main shaft of the main drive motor in sequence and is then connected to the engine. The charging interface 8 and the power supply interface 9 are both electrically connected to the energy storage unit 7.

[0047] In this embodiment, the engine 1 is powered by the generator 2, driving the generator 2 to generate electricity; the power output end of the main drive motor 3 is connected to the transmission 4, forming a rear-wheel drive structure of main drive motor + transmission; the output end of the transmission 4 transmits power in two ways, one way is transmitted to the front axle differential via the transfer case 5 and the drive shaft 11 to realize the mechanical drive of the front wheels, and the other way is transmitted directly to the rear axle to realize the power drive of the rear wheels; the main shafts of the main drive motor 3 and the transmission 4 are both hollow shaft structures, and the PTO shaft of the PTO transmission case 6 passes through the main shaft of the transmission and the main shaft of the main drive motor 3 in sequence before being powered by the engine 1, realizing the structural design of PTO output through the engine 1.

[0048] This embodiment employs a flywheel-integrated generator design. The front wheels are mechanically driven, while the rear wheels are driven via a combination of a main drive motor and a transmission. This enables full-time / part-time four-wheel drive switching, differential speed control for the left and right wheels, and anti-slip functionality. The PTO transmission box 6 is directly connected to the engine and outputs power through a through-type structure. The entire unit is equipped with an energy storage unit, supporting external charging / discharging.

[0049] This embodiment adopts a mechanical through-hole PTO structure, in which the main drive motor and the main shaft of the transmission are hollow shafts. The PTO shaft passes through the transmission and the main drive motor shaft in sequence and then connects to the engine power, achieving compact power output.

[0050] This embodiment also includes a main controller 13, an ECU chassis controller 14 and an MCU main drive motor controller 15 that are communicatively connected to the main controller 13. The MCU main drive motor controller 15 is connected to the main drive motor, and the main controller 13 is communicatively connected to the transfer case 5.

[0051] This embodiment also includes wheel speed sensors, steering angle sensors, and physical buttons 16 in the driver's cabin. The wheel speed sensors are installed on the front and rear wheels of the vehicle, the steering angle sensors are installed on the front wheels of the vehicle, and the physical buttons 16 in the driver's cabin are located inside the driver's cabin. The wheel speed sensors and steering angle sensors are both communicatively connected to the ECU chassis controller 14, and the physical buttons 16 in the driver's cabin are communicatively connected to the main controller 13.

[0052] In this embodiment, through the aforementioned control system components, the present invention is equipped with a full-time / part-time four-wheel drive mode switching, left and right differential control, and anti-slip control method. This method prioritizes safety and achieves real-time dynamic control of the tractor's driving process through sensor information acquisition, multi-condition judgment, and precise electronic control execution, taking into account driving safety, power performance, and energy economy.

[0053] In this embodiment, the main controller 13 controls the engagement or disengagement of the clutch of the transfer case 5, and distributes the loading torque of the front and rear axles according to the load ratio of the front and rear axles. The main controller 13 instructs the clutch of the transfer case 5 to engage (hard wire) to enter the full-time four-wheel drive mode, and instructs the clutch of the transfer case 5 to disengage (hard wire), so that all the torque output by the main drive motor is loaded to the rear axle to enter the two-wheel drive mode. The physical button 16 in the driver's cab is used to dynamically switch the drive mode according to the actual driving conditions of the tractor.

[0054] This embodiment also includes a high-voltage distribution box, which is electrically connected to the main drive motor, generator, energy storage unit, charging interface, and discharging interface, respectively, for the distribution and management of high-voltage power. It is used to achieve power distribution and regulation of various electrical components. The front axle is equipped with a front axle differential and front axle half-shafts connected in sequence to achieve differential drive of the front wheels.

[0055] In this embodiment, the system also includes an Electronic Stability Control (ESC) system and an Electronically Controlled Limited-Slip Differential (eLSD) system, which are communicatively connected to the main controller 13. The ESC system is used to suppress wheel slippage; that is, the main controller 13 sends a command to the ESC system to apply braking force to the slipping wheel, thus suppressing wheel slippage. The eLSD system limits the differential range between the left and right wheels; that is, the main controller 13 sends a command to the eLSD system on the drive axle where the slipping wheel is located to increase the clamping force, limiting the differential range between the left and right wheels and quickly eliminating slippage. Example 2:

[0056] like Figure 3 As shown, this embodiment is a control method for an electric tractor CVT powertrain with a mechanical through-hole PTO structure, applied to the control system described in Embodiment 1 above, and includes the following steps: S1: The system is powered on, and the main controller 13 completes the initialization self-test and collects and processes sensor information. In the specific steps of S1, after the system is powered on, the controller first completes the initialization self-test, confirms that the chassis ECU and the main drive motor are working normally, and then begins to collect and process the information fed back by each component in real time to provide data support for the execution of subsequent control strategies.

[0057] like Figure 4 As shown, S2: Based on the principle of prioritizing operational safety, slippage judgment and anti-slip control: The wheel speed is detected by the wheel speed sensor. If the speed difference between the wheels is detected to be >15% and lasts for 50ms, anti-slip control is executed; if the above slippage conditions are not detected, it is determined that the current vehicle is not slipping and proceeds to the next step.

[0058] like Figure 5 As shown, S3: Steering determination and differential control: The steering angle of the front wheels is detected by the steering angle sensor. If the front wheel steering angle is detected to be >5°, the left and right differential control is executed: The main controller 13 sends a command to the electronically controlled limited-slip differential (eLSD) to reduce the pressure, release the natural differential of the left and right wheels, match the Ackermann steering geometry, and reduce the turning radius; if the above steering conditions are not detected, it is determined that the current vehicle is in a straight-line driving state and there is no need for steering, and the next step of the control process is entered. S4: Four-wheel drive mode switching control: If a full-time four-wheel drive command is received, the main controller controls the vehicle to maintain four-wheel drive mode; otherwise, part-time four-wheel drive control is executed: if the current vehicle speed is greater than 20 kph, or the estimated road adhesion coefficient is greater than 0.6, or the throttle opening is less than 30%, then switch to two-wheel drive mode; otherwise switch to four-wheel drive mode. During the switching process, a torque gradient algorithm is used to keep the total torque constant. like Figure 6 As shown, specific step S4 involves executing the switching control between full-time and part-time four-wheel drive. The drive mode is dynamically switched according to the actual driving conditions of the tractor, ensuring both overall vehicle power and energy economy, and achieving a smooth switching process through precise control. The specific switching logic is as follows: The tractor cab is equipped with a full-time four-wheel drive mode button and an operation mode button. If the driver presses either button, the controller enters the full-time four-wheel drive control mode, instructs the transfer case 5 clutch to engage (hard wire), and distributes the loading torque of the front and rear axles according to the load ratio of the front and rear axles to adapt to complex operation or driving conditions.

[0059] If the driver does not press the above button, the part-time four-wheel drive control will be automatically activated, as follows: If the current vehicle speed is greater than 15 kph, it means that the vehicle is in a high-speed driving state, and two-wheel drive can meet the power requirements at this time.

[0060] If the estimated value of the road adhesion coefficient obtained by back-calculation through wheel speed difference and slip ratio is greater than 0.6, it indicates that the road surface condition is good and there is no need for four-wheel drive to provide additional traction.

[0061] If the current operating condition determines that high power output is not required, in this embodiment, the condition for determining that high power output is not required is that the throttle opening is <30%. When any of the above conditions are met, the main controller 13 controls the vehicle to switch to two-wheel drive mode, instructs the transfer case 5 to disengage the clutch (hard wire), and all the torque output by the main drive motor is loaded onto the rear axle to reduce energy consumption. Otherwise, it switches to four-wheel drive mode, with all four motors working simultaneously to ensure sufficient power to meet the needs of heavy-duty field operations.

[0062] During the switching between full-time and part-time four-wheel drive modes, a torque gradient algorithm is used for the main drive motor to achieve smooth adjustment of the motor torque, ensuring the smoothness of mode switching and avoiding shocks. S5: The MCU main drive motor controller 15 collects the main drive motor sensor signals, calculates the actual speed and torque of the main drive motor, and feeds them back to the main controller 13, then jumps to step S2 for cyclic execution. Specifically, in this embodiment, step S5 involves the main controller 13 collecting the actual speed and torque data of the main drive motor in real time, using it as a feedback signal to participate in the dynamic adjustment of the control strategy, and then jumping back to step 2 to enter the next round of cyclic control, thus realizing real-time dynamic control of the entire process.

[0063] The control method in this embodiment is based on the aforementioned control system. Through a cyclical logic of self-test initialization, slippage and anti-slip control, steering differential control, dynamic switching of four-wheel drive modes, and closed-loop control, it achieves adaptive vehicle operation condition regulation. Relying on the low-speed, high-torque, and wide-range speed characteristics of the electric motor, it completely eliminates mechanical gear shifting, achieving continuously variable transmission throughout the entire operation. Simultaneously, it achieves complete decoupling between the engine and vehicle speed, and reduces energy consumption in conjunction with an energy recovery strategy. Equipped with a precise left and right differential control strategy and matched with Ackermann steering geometry, it effectively reduces the tractor's turning radius and improves steering flexibility in field operations.

[0064] In this embodiment, the anti-slip control in step 2 includes: the main controller 13 issuing a command to enter the full-time four-wheel drive mode; the main controller 13 issuing a command to the MCU main drive motor controller 15 to reduce torque; the main controller 13 sending a command to the vehicle electronic stability control system ESC to suppress wheel slippage; and the main controller 13 sending a command to the electronically controlled anti-slip differential eLSD of the drive axle where the slipping wheel is located to limit the differential range of the left and right wheels.

[0065] Although the present invention has been described in detail above with specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A CVT powertrain control system for an electric tractor with a mechanical through-hole PTO structure, characterized in that... Includes engine, generator, main drive motor, transmission, transfer case, PTO gearbox, energy storage unit, charging interface and power supply interface; The engine and the generator are electrically connected. The generator is electrically connected to the energy storage unit and the main drive motor. The energy storage unit and the main drive motor are electrically connected. The power output end of the main drive motor is connected to the transmission. One power output from the transmission is transmitted to the mechanically driven front axle via the transfer case, and the other power output is transmitted to the rear axle. The main shafts of the main drive motor and the transmission are both hollow shaft structures. The PTO shaft of the PTO transmission box passes through the main shaft of the transmission and the main shaft of the main drive motor in sequence and is then connected to the engine. The charging interface and the power supply interface are both electrically connected to the energy storage unit. It also includes a main controller, an ECU chassis controller and an MCU main drive motor controller that are communicatively connected to the main controller, the MCU main drive motor controller being connected to the main drive motor, and the main controller being communicatively connected to the transfer case; It also includes wheel speed sensors, steering angle sensors, and physical buttons in the driver's cabin. The wheel speed sensors are installed on the front and rear wheels of the vehicle, the steering angle sensors are installed on the front wheels of the vehicle, and the physical buttons in the driver's cabin are located inside the driver's cabin. The wheel speed sensors and steering angle sensors are both communicatively connected to the ECU chassis controller, and the physical buttons in the driver's cabin are communicatively connected to the main controller.

2. The CVT powertrain control system for an electric tractor with a mechanical through-hole PTO structure according to claim 1, characterized in that: The main controller controls the engagement or disengagement of the transfer case clutch and distributes the load torque to the front and rear axles according to the front and rear axle load ratio; the physical buttons in the driver's cab are used to dynamically switch the drive mode according to the actual driving conditions of the tractor.

3. The CVT powertrain control system for an electric tractor with a mechanical through-hole PTO structure according to claim 1, characterized in that, It also includes a high-voltage distribution box, which is electrically connected to the main drive motor, generator, energy storage unit, charging interface and discharging interface respectively, for realizing the distribution and management of high-voltage power.

4. The CVT powertrain control system for an electric tractor with a mechanical through-hole PTO structure according to claim 1, characterized in that... It also includes an electronic stability control system (ESC) and an electronically controlled limited-slip differential (eLSD) that are connected to the main controller. The electronic stability control system (ESC) is used to suppress wheel slippage, and the electronically controlled limited-slip differential (eLSD) is used to limit the differential range between the left and right wheels.

5. A control method for an electric tractor CVT powertrain with a mechanical through-hole PTO structure, characterized in that, The control system applied to any one of claims 1-4 includes the following steps: S1: The system powers on, the main controller completes initialization self-test, and collects and processes sensor information; S2: Slippage Detection and Anti-Slip Control: The wheel speed is detected by the wheel speed sensor. If the speed difference between the wheels is detected to be >15% and lasts for 50ms, anti-slip control is executed; otherwise, proceed to the next step. S3: Steering Detection and Differential Control: The steering angle sensor detects the front wheel steering angle. If the front wheel steering angle is greater than 5°, left and right differential control is executed: The main controller sends a command to the electronically controlled limited-slip differential (eLSD) to reduce pressure, release the natural differential between the left and right wheels, match the Ackermann steering geometry, and reduce the turning radius; otherwise, proceed to the next step. S4: Four-wheel drive mode switching control: If a full-time four-wheel drive command is received, the main controller controls the vehicle to maintain four-wheel drive mode; otherwise, part-time four-wheel drive control is executed: if the current vehicle speed is greater than 20 kph, or the estimated road adhesion coefficient is greater than 0.6, or the throttle opening is less than 30%, then switch to two-wheel drive mode; otherwise switch to four-wheel drive mode. During the switching process, a torque gradient algorithm is used to keep the total torque constant. S5: The MCU main drive motor controller collects the main drive motor sensor signal, calculates the actual speed and torque of the main drive motor and feeds it back to the main controller, then jumps to step S2 for repeated execution.

6. The control method according to claim 5, characterized in that: Step 2 describes the execution of anti-slip control, which includes: the main controller issuing a command to enter the full-time four-wheel drive mode; the main controller issuing a command to the MCU main drive motor controller to reduce torque; the main controller sending a command to the vehicle electronic stability control system (ESC) to suppress wheel slippage; and the main controller sending a command to the electronically controlled anti-slip differential (eLSD) of the drive axle where the slipping wheel is located to limit the differential range between the left and right wheels.

7. The control method according to claim 5, characterized in that: In step S4, the physical buttons in the driver's cab include a full-time four-wheel drive mode button and a work mode button. If either button is pressed, the controller enters the full-time four-wheel drive control mode.

8. The control method according to claim 5, characterized in that: In step S4, the road surface adhesion coefficient is calculated by back-calculating the wheel speed difference and slip ratio.

Images