A crawler-type bulldozer double-end multi-motor hybrid power system and a control method thereof, and a crawler-type bulldozer

Abstract

This invention relates to the field of engineering machinery technology, specifically providing a multi-motor hybrid power system for a tracked bulldozer at both ends and its control method. The system includes: a range extender, consisting of a diesel engine, a transfer case assembly, and at least two generators, with the generators directly connected to the transfer case's power take-off port; a power battery assembly, including at least two independently constructed high-voltage battery packs, defined as either rechargeable or discharge battery packs; and at least four drive motors, located at the final drive ends on both sides of the bulldozer, with at least two on each side. The diesel engine features a dual-trough fuel consumption rate calibration characteristic, with two minimum fuel consumption rate regions marked on its universal characteristic curve. The transfer case assembly includes a two-speed gearbox, with each gear corresponding to a speed within one of the two minimum fuel consumption rate regions. This invention achieves multiple redundancies for system reliability and safety, improving fuel economy and energy utilization efficiency under full load conditions.

Description

Technical Field

[0001] This invention relates to the field of engineering machinery technology, specifically to a multi-motor hybrid power system at both ends of a tracked bulldozer and its control method, and to a tracked bulldozer. Background Technology

[0002] Tracked bulldozers are used in earthmoving and leveling, mining material stockpiling, and coal stockpiling in coal yards. They are a widely used type of construction machinery with low substitutability. In terms of transmission, they can be divided into mechanical transmission, hydraulic transmission, hydrostatic transmission, and electric transmission (pure electric bulldozers and range-extended hybrid bulldozers can be classified into this category).

[0003] Pure electric bulldozers are efficient and environmentally friendly, but their fatal flaws include short range, poor adaptability to environmental temperatures, and the need for certain infrastructure support. Hybrid bulldozers effectively avoid the shortcomings of pure electric bulldozers. Compared with mechanical transmission, hydraulic transmission, and hydrostatic transmission technologies, they are more environmentally friendly and have higher overall thermal efficiency. Currently, there are two hybrid technology routes for tracked bulldozers: parallel hybrid and series hybrid. Parallel hybrid can be simply divided into two types: diesel engine power and battery power in parallel, and diesel engine generator power and battery power in parallel, with the battery power playing an auxiliary role and intervening under heavy load conditions. The series hybrid power route is: diesel engine → generator → power battery → drive motor. From the perspective of fuel economy, the series technology route has advantages.

[0004] However, existing series hybrid bulldozers still have the following technical problems: 1) Range extenders are generally equipped with a generator, and generator failure will lead to the failure of the entire power system, resulting in low system reliability and high maintenance costs; 2) The output end is generally equipped with a drive motor, and drive motor failure will lead to partial or complete failure of the power system, and it is impossible to adjust the number of drive motors to make the motors operate in the high-efficiency range; 3) Diesel engines are usually only calibrated to a minimum fuel consumption rate range. The fuel consumption rate is low under ideal operating conditions, but it is high under non-ideal operating conditions such as light load, and it is impossible to guarantee fuel economy under full load; 4) The power battery adopts an overall control method, and the charging and discharging control is coarse, which cannot simultaneously achieve efficient generation of the range extender and regeneration of the motor braking energy, and the braking energy recovery capability is limited. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a multi-motor hybrid power system and control method for a tracked bulldozer at both ends, and a tracked bulldozer that achieves multiple redundancies to ensure system reliability and safety, and improves fuel economy and energy utilization efficiency under full load conditions.

[0006] In a first aspect, the technical solution of the present invention provides a multi-motor hybrid power system at both ends of a tracked bulldozer, comprising: Range extender: It includes a diesel engine, a transmission and power split assembly, and at least two generators; the output end of the diesel engine is connected to the input end of the transmission and power split assembly, the transmission and power split assembly has at least two power take-off ports, and each power take-off port is directly connected to a generator; when the range extender operates, it supplies power to the power battery. Power battery assembly: It includes at least two battery packs, each group independently constructs high-voltage output, and is respectively defined as a charging battery pack or a discharging battery pack in terms of control; the power battery assembly is electrically connected to the range extender and the drive motor, and is used to supply power to the drive motor and recover the electric energy during steering and braking. At least four drive motors: They are arranged at the final drive ends on both sides of the bulldozer, with at least two on each side, and are used to independently or jointly drive the corresponding track, and deliver the recovered electric energy to the power battery assembly when the bulldozer steers and brakes. Among them, the diesel engine has a double trough fuel consumption rate calibration characteristic, that is, there are two regions of the lowest fuel consumption rate calibrated on the universal characteristic curve, corresponding to the light load condition and the heavy load condition respectively. The transmission and power split assembly includes a two-speed gearbox, and the two gears of the two-speed gearbox respectively correspond to the rotational speeds of the two regions of the lowest fuel consumption rate of the diesel engine.

[0007] In the second aspect, the technical solution of the present invention provides a control method applied to the multi-motor hybrid power system at both ends of the above crawler bulldozer, including a range extender control logic, which includes the following steps: After the vehicle is powered on, according to the SOC state of each battery pack in the power battery assembly, the charging battery pack and the discharging battery pack are determined. The discharging battery pack is used to supply power to the drive motor, and the charging battery pack is used to receive the electric energy generated by the range extender and the electric energy recovered by the drive motor during braking. The diesel engine starts, and the equipment starts to operate. During the operation of the equipment, the change rate V1 of the SOC of the charging battery pack and the change rate V2 of the SOC of the discharging battery pack are collected; when V1≥V2, the range extender is controlled to supply power under the light load condition; when V1<V2, the range extender is controlled to supply power under the heavy load condition. In response to the equipment stop operation instruction, according to the current SOC state of each battery pack, the charging battery pack and the discharging battery pack are re-determined. The re-determined charging battery pack is controlled to be charged to a preset state, and the re-determined discharging battery pack is controlled to be discharged to a preset state. After both the charging battery pack and the discharging battery pack reach the preset state, the diesel engine is shut down and the vehicle is powered off.

[0008] In the third aspect, the technical solution of the present invention provides a crawler bulldozer configured with the above hybrid power system.

[0009] From the above technical solutions, it can be seen that the present application has the following advantages: By setting at least two generators directly connected to each power take-off port of the transfer case, a multi-motor redundancy structure is formed. The failure of a single generator does not affect light-load construction, and the failure of two to three generators can still ensure that the equipment can return home limply, which significantly improves the reliability and safety of the range extender. At the same time, the multi-motor structure can achieve more precise power distribution control and improve the system control flexibility. By setting at least four drive motors at the output end, with at least two on each side, the corresponding side track can be driven independently or collaboratively. On the one hand, the number of motors involved in the drive can be adjusted according to the power requirements of the whole vehicle, so that the drive motors always operate in the high-efficiency range and improve the energy efficiency of the whole machine. On the other hand, the single-side dual-motor structure provides motor redundancy, and the equipment can still be maintained when a single drive motor fails, further improving the reliability of the system. By calibrating the diesel engine's dual-valley fuel consumption rate, two minimum fuel consumption rate regions are marked on the universal characteristic curve, corresponding to light-load and heavy-load conditions respectively. Combined with the gear shifting of a two-speed transmission, the diesel engine can operate in the minimum fuel consumption rate region under both light-load and heavy-load conditions, achieving fuel economy optimization under all load conditions and significantly reducing fuel consumption. By physically grouping the power battery pack into at least two battery packs, each pack independently constructs a high-voltage platform and is defined as a charging battery pack or a discharging battery pack in terms of control, decoupled control of charging and discharging is achieved. This allows for simultaneous charging of the range extender and discharging of the drive motor, improving the utilization efficiency of the battery system. Furthermore, if any battery pack fails, the other battery pack can still maintain the equipment's limp home, enhancing system safety. Attached Figure Description

[0010] To more clearly illustrate the technical solution of this application, the accompanying drawings used in the description will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a schematic diagram of a multi-motor hybrid power system at both ends of a tracked bulldozer, provided as an embodiment of the present invention.

[0012] Figure 2 A schematic diagram of the universal characteristic curve for calibrating the dual-trough fuel consumption of a diesel engine.

[0013] Figure 3 This is a flowchart illustrating the control logic of the range extender.

[0014] Figure 4 This is a flowchart illustrating the control logic of the drive mode.

[0015] Figure 5This is a flowchart illustrating the braking mode control logic. Detailed Implementation

[0016] To make the purpose, features, and advantages of this application more apparent and understandable, specific embodiments and accompanying drawings will be used to clearly and completely describe the technical solution protected by this application. Obviously, the embodiments described below are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0017] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this application and in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0018] The key terms used in this invention will be explained below.

[0019] Diesel engine fuel consumption dual-trough calibration: Two minimum fuel consumption rate regions are calibrated on the universal characteristic curve, corresponding to two commonly used speeds. Ordinary diesel engines only have one minimum fuel consumption rate region, generally near the speed corresponding to maximum torque.

[0020] Range extender: An assembly consisting of a diesel engine, gearbox, transfer case and generator.

[0021] Two-speed gearbox: A gearbox with two gear ratios.

[0022] Transfer case: A housing assembly that realizes power distribution. Multiple power take-off ports can be designed according to needs, and the speed ratio of each power take-off port can be adjusted according to needs.

[0023] BMS: Short for Battery Management System, which includes a controller, on-board charger, necessary wiring harnesses, and control software.

[0024] Power battery assembly: This includes several power battery boxes, power battery box mounting frames, frame suspensions, etc. The series and parallel combination of the power battery boxes is generally determined based on the overall machine voltage platform. For special control requirements, the power battery boxes can also be grouped for control.

[0025] Final drive: A speed-reducing and torque-increasing mechanism that drives the vehicle. Final drives typically integrate braking systems. They have one or more power input ports for power input.

[0026] Battery SOC: The percentage of remaining battery charge to rated capacity, ranging from 0% to 100%, used to measure the remaining usable energy of the battery.

[0027] This invention provides a hybrid power system for a tracked bulldozer with multiple motors at both the power source and output ends. By miniaturizing the arrangement of multiple motors at both ends, it improves control flexibility, system reliability, and reduces maintenance and replacement costs. Power output adjustment is achieved through a two-speed gearbox in the range extender and motor load adjustment. Fuel economy under various load conditions is ensured through dual-peak fuel consumption calibration of the range extender's diesel engine. The hybrid power system includes: a range extender with a two-speed gearbox driving four generators; two drive motors on each of the two output ends; the range extender's diesel engine calibrated with two fuel-efficient zones; control strategies divided into light-load and heavy-load modes; and the final drive eliminates the braking mechanism, achieving braking and energy recovery through the motors.

[0028] Figure 1 The present invention provides a schematic diagram of a multi-motor hybrid power system at both ends of a tracked bulldozer, including a range extender, a power battery assembly, and at least four drive motors.

[0029] Range extender: includes a diesel engine, a transmission transfer assembly, and at least two generators; the output of the diesel engine is connected to the input of the transmission transfer assembly, the transmission transfer assembly has at least two power take-off ports, each of which is directly connected to a generator; the range extender supplies power to the power battery when it is running.

[0030] Power battery assembly: includes at least two battery packs, each with an independent high-voltage output, and is defined as a charging battery pack or a discharging battery pack in terms of control; the power battery assembly is electrically connected to the range extender and drive motor, and is used to supply power to the drive motor and recover electrical energy during steering and braking.

[0031] At least four drive motors: located at the final drive ends on both sides of the bulldozer, with at least two on each side, for independently or collaboratively driving the tracks on the corresponding side, and for transmitting recovered electrical energy to the power battery pack when the bulldozer turns or brakes.

[0032] The range extender includes a diesel engine, a transfer case assembly, and at least two generators. The output of the diesel engine is connected to the input of the transfer case assembly, transmitting power from the diesel engine to the transfer case assembly. The transfer case assembly has at least two power take-off ports, each directly connected to a generator. This means there is no clutch between the generator and the transfer case, allowing power to be directly transmitted from the diesel engine to the generator via the transfer case assembly. When the range extender is running, the electrical energy generated by the generator supplies power to the battery.

[0033] Figure 2 A schematic diagram of the universal characteristic curve for calibrating the dual-trough fuel consumption of a diesel engine. (See diagram below.) Figure 2 As shown, the diesel engine in this embodiment of the invention adopts the dual-valley calibration technology, that is, two regions with the lowest fuel consumption rate are calibrated on the universal characteristic curve of the diesel engine.

[0034] Specifically, during bench testing of the diesel engine, the fuel consumption rate at all operating points (different speeds and torques) is measured, and a universal characteristic curve is plotted to identify the contour distribution of the fuel consumption rate. This invention selects two fuel consumption trough regions on the universal characteristic curve.

[0035] The diesel engine's mid-range speed corresponding to fuel consumption trough I is n1. In this range, the diesel engine output power is relatively low, corresponding to the vehicle's light-load operating conditions. Under this condition, the diesel engine can output power with a low fuel consumption rate, achieving fuel economy during light-load operations. The diesel engine's mid-range speed corresponding to fuel consumption trough II is n2. In this range, the diesel engine output power is relatively high, corresponding to the vehicle's heavy-load operating conditions. Under this condition, the diesel engine can output high power with a low fuel consumption rate, meeting the demands of heavy-load operations while maintaining fuel economy. Generally, n1 is less than n2, meaning the speed corresponding to the light-load high-efficiency zone is lower, and the speed corresponding to the heavy-load high-efficiency zone is higher.

[0036] Through dual-valley calibration technology, the diesel engine can operate in its corresponding lowest fuel consumption range under both light and heavy load conditions, thereby optimizing fuel economy under all load conditions and solving the problem that existing diesel engines only operate in a single high-efficiency range and have a high fuel consumption rate under light load conditions.

[0037] The transmission assembly includes a two-speed gearbox and a transfer case. The input of the two-speed gearbox is connected to the output of the diesel engine to receive power from the engine; the output of the two-speed gearbox is connected to the input of the transfer case to transmit the power after gear shifting to the transfer case.

[0038] The two-speed transmission has two gears, each corresponding to a speed range that represents one of the diesel engine's lowest fuel consumption zones. Specifically, the first gear corresponds to the midpoint speed n1 of the diesel engine's fuel consumption trough I, and the second gear corresponds to the midpoint speed n2 of the diesel engine's fuel consumption trough II. When the vehicle is under light load, the two-speed transmission shifts to the first gear, causing the diesel engine to operate near speed n1, thus entering the light-load high-efficiency zone. When the vehicle is under heavy load, the two-speed transmission shifts to the second gear, causing the diesel engine to operate near speed n2, thus entering the heavy-load high-efficiency zone.

[0039] The transfer case has at least two power take-off ports. In a preferred embodiment of the invention, the transfer case has four power take-off ports, and the speed ratio of each power take-off port is the same. Each power take-off port is directly connected to a generator, meaning there is no clutch between the generator and the transfer case. This direct-connection structure eliminates the traditional clutch device, effectively reducing the risk of system failure due to clutch device malfunction and improving system reliability.

[0040] The transfer case distributes the power output from the two-speed gearbox to four generators. Since the speed ratios of each power take-off port are identical, the four generators rotate at the same speed. When the two-speed gearbox shifts gears, the input speed of the transfer case changes, but because the transfer case speed ratio is fixed, the generator speed changes accordingly. Through the shifting operation of the two-speed gearbox, the generator load is adjusted, allowing the generators to operate in their high-efficiency range under different operating conditions.

[0041] The range extender structure in this embodiment achieves decoupled control between the high-efficiency range of the diesel engine and the high-efficiency range of the generator through the cooperation of a two-speed gearbox and a transfer case; the redundant configuration of four generators ensures that the failure of a single generator does not affect light-load construction, and the failure of two to three generators can still ensure that the equipment can return home limply, which significantly improves the reliability of the system; the clutchless design simplifies the structure and reduces the failure rate.

[0042] In a preferred embodiment of the invention, the range extender is equipped with four generators. Each of the four generators is directly connected to one of the four power take-off ports of the transfer case, and the speed ratios of each power take-off port are identical, thus ensuring that the rotational speeds of the four generators remain constant. Four miniaturized generators can be used, resulting in lower system installation costs. Miniaturized generators offer higher power density and lower manufacturing costs. Through this multi-motor redundancy layout, the failure of a single generator does not affect light-load construction, and the failure of two to three generators does not affect the equipment's limp-home operation. This significantly improves the system's reliability and safety. Furthermore, the configuration of multiple generators allows for more precise control, enabling flexible adjustment of the generator load distribution according to actual needs.

[0043] The generator produces electricity while the range extender is running, and this electricity is transmitted to the power battery pack via high-voltage lines to charge the battery. Simultaneously, the generator controller adjusts the output power of each generator in real time according to instructions from the vehicle controller, thereby controlling the power generation.

[0044] The power battery assembly includes several power battery boxes, a power battery box mounting frame, and a frame suspension. This invention divides the total battery box into two battery packs, each of which can independently generate a high-voltage output matching the overall machine voltage platform.

[0045] Specifically, in a preferred embodiment of the present invention, the power battery assembly includes eight battery boxes, wherein the top four battery boxes are defined as the first battery pack and the bottom four battery boxes are defined as the second battery pack. The two sets of battery boxes are symmetrically arranged in the installation layout to ensure uniform cooling and avoid differences in battery performance and lifespan degradation caused by uneven cooling.

[0046] The battery boxes within each battery pack are connected in series to form a high-voltage output that matches the overall voltage platform of the device. The two battery packs are electrically connected in parallel, each capable of independently supplying power to the drive motor, or simultaneously. This parallel structure allows the two battery packs to operate independently without affecting each other.

[0047] In terms of control, the BMS (Battery Management System) monitors the SOC status of each battery pack in real time and defines the function of each battery pack according to the SOC status. Specifically, when the SOC of a battery pack is lower than or equal to a first preset SOC value (preferably 25%), the battery pack is defined as a rechargeable battery pack, used to receive electrical energy generated by the range extender and electrical energy recovered by the drive motor during braking; when the SOC of a battery pack is higher than or equal to a second preset SOC value (preferably 85%), the battery pack is defined as a discharge battery pack, used to supply power to the drive motor.

[0048] The first preset SOC value is lower than the second preset SOC value, ensuring that the battery pack is charged when the SOC is low and discharged when the SOC is high, avoiding overcharging or over-discharging and extending the battery pack's lifespan. The functions of the two battery packs are dynamically interchangeable. That is, as the operation progresses, the SOC of the charging battery pack increases, while the SOC of the discharging battery pack decreases. When the SOC of the charging battery pack reaches the second preset SOC value and the SOC of the discharging battery pack drops to the first preset SOC value, the functions of the two battery packs can be interchanged to continue meeting the operational requirements.

[0049] The Battery Management System (BMS) feeds back the SOC status and functional definition information of each battery pack to the vehicle controller and receives instructions from the vehicle controller to organize the implementation of charging and discharging functions according to the functional definitions. Battery group control enables the power battery pack to charge and discharge simultaneously and efficiently. The electrical energy generated by the range extender and recovered from braking energy can be charged into the charging battery pack, while the discharging battery pack can independently supply power to the drive motor, realizing decoupled control of charging and discharging and significantly improving the utilization efficiency of the battery system.

[0050] The hybrid power system of this invention also includes a vehicle controller. The vehicle controller is communicatively connected to the engine controller of the diesel engine, the generator controller of the generator, and the battery management system of the power battery pack, forming a complete electronic control system architecture. The vehicle controller is responsible for receiving status information from each subsystem, including the engine's operating status, the generator's output power, the SOC status of each battery pack, and the load status of the drive motor, and issuing control commands to each subsystem according to a preset control strategy.

[0051] The vehicle controller is also responsible for making decisions on drive mode control and braking mode control. In drive mode control, the vehicle controller determines the switching between single-side single-motor or dual-motor drive modes based on the load status of the drive motor. In braking mode control, the vehicle controller decides whether the drive motor participates in braking and the number of motors participating in braking based on information such as mechanical braking signals, braking duration, and braking intensity.

[0052] In the above text, an embodiment of a multi-motor hybrid power system at both ends of a crawler bulldozer has been described in detail. Based on the multi-motor hybrid power system at both ends of the crawler bulldozer described in the above embodiment, an embodiment of the present invention also provides a control method corresponding to this system.

[0053] The control method provided by the embodiment of the present invention includes an extender control logic, a drive mode control logic, and a braking mode control logic.

[0054] Figure 3 FIG. is a schematic flow diagram of the extender control logic, including the following steps: After the vehicle is powered on, determine the charging battery pack and the discharging battery pack according to the SOC status of each battery pack in the power battery assembly. The discharging battery pack is used to supply power to the drive motor, and the charging battery pack is used to receive the electric energy generated by the extender and the electric energy recovered by the drive motor during braking. Start the diesel engine, and the equipment starts to operate. During the operation of the equipment, collect the SOC change rate V1 of the charging battery pack and the SOC change rate V2 of the discharging battery pack. When V1≥V2, control the extender to supply power under a light load condition. When V1<V2, control the extender to supply power under a heavy load condition. In response to the equipment stop operation instruction, re-determine the charging battery pack and the discharging battery pack according to the current SOC status of each battery pack. Control the re-determined charging battery pack to be charged to a preset state, and the re-determined discharging battery pack to be discharged to a preset state. After both the charging battery pack and the discharging battery pack reach the preset state, shut down the diesel engine and power off the vehicle.

[0055] Among them, the power supply under the light load condition includes: controlling the two-speed gearbox to switch to the gear corresponding to the rotational speed of the first lowest fuel consumption rate area of the diesel engine, so that the diesel engine operates in the lowest fuel consumption rate area corresponding to the light load condition. The power supply under the heavy load condition includes: controlling the two-speed gearbox to switch to the gear corresponding to the rotational speed of the second lowest fuel consumption rate area of the diesel engine, so that the diesel engine operates in the lowest fuel consumption rate area corresponding to the heavy load condition.

[0056] Specifically, after the vehicle is powered on, first determine the charging battery pack and the discharging battery pack according to the SOC status of each battery pack in the power battery assembly. Among them, the discharging battery pack is used to supply power to the drive motor, and the charging battery pack is used to receive the electric energy generated by the extender and the electric energy recovered by the drive motor during braking.

[0057] After the diesel engine starts, the equipment begins to operate. During the operation of the equipment, the system continuously collects the SOC change rate V1 of the charging battery pack and the SOC change rate V2 of the discharging battery pack. The SOC change rate reflects the change speed of the battery pack's power. Here, V1 represents the change rate of the charging battery pack's SOC, and V2 represents the change rate of the discharging battery pack's SOC.

[0058] The system compares V1 and V2: when V1≥V2, it indicates that the charging rate of the charging battery pack is greater than or equal to the discharging rate of the discharging battery pack. At this time, the range extender is controlled to supply power under a light load condition; when V1<V2, it indicates that the charging rate of the charging battery pack is less than the discharging rate of the discharging battery pack. At this time, the range extender is controlled to supply power under a heavy load condition. The power supply under the light load condition and the heavy load condition respectively correspond to different gears of the two-speed gearbox and different minimum fuel consumption rate regions where the diesel engine operates.

[0059] The equipment operates according to the working condition requirements and continuously conducts the above monitoring and control. After the operator issues an instruction to stop the equipment operation, the system re-determines the charging battery pack and the discharging battery pack according to the current SOC status of each battery pack. This is because during the operation process, the SOC of the charging battery pack increases as it receives electrical energy, and the SOC of the discharging battery pack decreases as it outputs electrical energy. The SOC status of the two battery packs may change, and their respective roles need to be re-determined.

[0060] Subsequently, the system controls the re-determined charging battery pack to charge to the preset state, and the re-determined discharging battery pack to discharge to the preset state. After both the charging battery pack and the discharging battery pack reach the preset state, the diesel engine is shut down, and the vehicle is powered off to complete the entire operation cycle.

[0061] The range extender control logic of this embodiment dynamically adjusts the output power of the range extender through the comparison result of V1 and V2, realizes the dynamic decoupling scheduling of the energy flow, enables the range extender to always output power adapted to the current working condition, not only ensures the power supply demand of the drive motor but also realizes the efficient operation of the range extender.

[0062] Figure 4 It is a schematic flow diagram of the drive mode control logic, including the following steps: when operating in the single-motor drive mode on one side, if the load of the drive motor on that side exceeds the preset overload threshold, switch to the dual-motor drive mode on that side and distribute the load originally borne by the single motor to the dual motors; when operating in the dual-motor drive mode on one side, if the loads of both motors are lower than the preset lower limit threshold of the efficient zone, switch to the single-motor drive mode on that side and turn off one of the motors.

[0063] Specifically, during equipment operation, the system monitors the load status of the drive motor in real time. When operating in single-motor drive mode on one side, if the load of the drive motor on that side exceeds the preset overload threshold, it indicates that the single motor can no longer meet the current power demand or that the motor has deviated from the high-efficiency operating range. At this time, the system switches to dual-motor drive mode on that side and distributes the load originally borne by the single motor to both motors, so that both motors operate in the high-efficiency range.

[0064] When operating in single-side dual-motor drive mode, if the load of both motors is lower than the preset high-efficiency zone lower limit threshold, it indicates that the current power demand is small and both motors are in a low-load state, deviating from the high-efficiency operating range. At this time, the system switches to single-motor drive mode on that side, shuts down one motor, and lets the other motor bear the full load, so that its load rises to the high-efficiency range.

[0065] Through the aforementioned drive mode switching control, the system can flexibly adjust the number of motors involved in the drive according to the vehicle's power requirements, ensuring that the motors always operate within their high-efficiency range and improving overall energy efficiency. Simultaneously, the dual-motor configuration on one side provides motor redundancy; if one drive motor fails, the other can still maintain equipment operation, enhancing system reliability.

[0066] Figure 5 The flowchart of the braking mode control logic includes the following steps: During equipment operation, the mechanical braking signal is monitored; when the mechanical braking signal is activated, it is determined whether the braking duration T is greater than the preset time threshold T0; if T≤T0, the drive motor remains in drive mode and does not participate in braking; if T>T0, at least one drive motor on one side is switched to power generation mode to charge the rechargeable battery pack; during braking, the mechanical braking intensity is monitored, and when the braking intensity increases, the number of drive motors participating in power generation mode is increased; when the mechanical braking signal is deactivated, the drive motor is switched back to drive mode.

[0067] Specifically, during equipment operation, the system monitors the mechanical braking signal in real time. When the mechanical braking signal is activated, the system determines whether the braking duration T is greater than a preset time threshold T0. If T≤T0, it indicates that the braking is short-term, and the drive motor maintains its driving mode and does not participate in braking; if T>T0, it indicates that the braking is continuous, and the system switches at least one drive motor on one side to power generation mode to charge the rechargeable battery pack, thereby achieving energy recovery.

[0068] During braking, the system continuously monitors the intensity of mechanical braking. When the braking intensity increases, indicating a greater need for braking force, the system increases the number of drive motors participating in the energy recovery mode. Specifically, during initial braking, a single motor on one side switches to energy recovery mode; as the braking intensity increases, both motors on one side switch to energy recovery mode to provide greater braking energy recovery power.

[0069] When the mechanical brake signal is turned off, the system will switch the drive motor back to drive mode to continue providing driving force for the equipment to move.

[0070] The final drive end of this invention eliminates the traditional mechanical braking mechanism, with the braking function being fully realized by the drive motor. This simplifies the final drive structure and reduces manufacturing and maintenance costs. It also enables the recovery and utilization of braking energy, improving energy utilization efficiency. Furthermore, it reduces wear on the mechanical braking device, extending the equipment's service life. The motor braking response is fast and the braking is smooth, improving operational safety.

[0071] In situations requiring continuous braking, such as braking on long slopes, the drive motor remains in generator mode, converting mechanical energy into electrical energy, which is then stored in the rechargeable battery pack, achieving efficient energy recovery and utilization. Simultaneously, by eliminating the mechanical braking mechanism, the problem of overheating and wear of the mechanical braking system in traditional bulldozers during long slope braking is avoided.

[0072] This invention also provides a tracked bulldozer equipped with the hybrid power system described in the above embodiments.

[0073] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A multi-motor hybrid power system at both ends of a tracked bulldozer, characterized in that, Comprising: Range extender: including a diesel engine, a transmission and transfer assembly, and at least two generators; the output end of the diesel engine is connected to the input end of the transmission and transfer assembly, the transmission and transfer assembly has at least two power take-off ports, and each power take-off port is directly connected to a generator; when the range extender operates, it supplies power to the power battery. Power battery assembly: including at least two battery packs, each group independently constructs a high-voltage output, and is respectively defined as a charging battery pack or a discharging battery pack in terms of control; the power battery assembly is electrically connected to the range extender and the drive motor, and is used to supply power to the drive motor and recover the electric energy during steering and braking. At least four drive motors: arranged at the final drive ends on both sides of the bulldozer, at least two on each side, used to independently or jointly drive the corresponding track, and convey the recovered electric energy to the power battery assembly when the bulldozer steers and brakes. Among them, the diesel engine has a double trough fuel consumption rate calibration characteristic, that is, there are two minimum fuel consumption rate regions calibrated on the universal characteristic curve, corresponding to the light load condition and the heavy load condition respectively. The transmission and transfer assembly includes a two-speed gearbox, and the two gears of the two-speed gearbox respectively correspond to the rotational speeds of the two minimum fuel consumption rate regions of the diesel engine.

2. The multi-motor hybrid power system at both ends of the tracked bulldozer according to claim 1, characterized in that, The range extender includes four generators. The transmission and transfer assembly further includes a transfer case, the transfer case has four power take-off ports, and the speed ratios of each power take-off port are the same, and are directly connected to four generators respectively.

3. The multi-motor hybrid power system at both ends of the tracked bulldozer according to claim 1, characterized in that, The charging battery pack and the discharging battery pack are defined according to the SOC state of their respective battery packs: when the SOC of the battery pack ≤ the first preset SOC value, the battery pack is defined as a charging battery pack; when the SOC of the battery pack ≥ the second preset SOC value, the battery pack is defined as a discharging battery pack. The first preset SOC value is less than the second preset SOC value.

4. The multi-motor hybrid power system at both ends of the tracked bulldozer according to claim 1, characterized in that, It further includes a vehicle controller, and the vehicle controller is respectively communicatively connected to the engine controller of the diesel engine, the generator controller of the generator, and the battery management system of the power battery assembly. The vehicle controller is configured to: obtain the SOC change rate V1 of the charging battery pack and the SOC change rate V2 of the discharging battery pack, and when V1≥V2, control the range extender to supply power under the light load condition, and when V1<V2, control the range extender to supply power under the heavy load condition.

5. The multi-motor hybrid power system at both ends of the tracked bulldozer according to claim 4, characterized in that, The light load condition corresponds to the two-speed gearbox switching to the gear corresponding to the rotational speed of the first minimum fuel consumption rate region of the diesel engine, and the heavy load condition corresponds to the two-speed gearbox switching to the gear corresponding to the rotational speed of the second minimum fuel consumption rate region of the diesel engine.

6. A control method applied to the multi-motor hybrid power system at both ends of the tracked bulldozer as described in claim 1, characterized in that, Including range extender control logic, including the following steps: After the vehicle is powered on, according to the SOC state of each battery pack in the power battery assembly, determine the charging battery pack and the discharging battery pack. The discharging battery pack is used to supply power to the drive motor, and the charging battery pack is used to receive the electric energy generated by the range extender and the electric energy recovered by the drive motor during braking. The diesel engine starts, and the equipment starts to operate. During the operation of the equipment, collect the SOC change rate V1 of the charging battery pack and the SOC change rate V2 of the discharging battery pack; when V1≥V2, control the range extender to supply power under the light load condition; when V1<V2, control the range extender to supply power under the heavy load condition. In response to the equipment stop operation instruction, re-determine the charging battery pack and the discharging battery pack according to the current SOC state of each battery pack. Control the redefined charging battery pack to charge to a preset state, and control the redefined discharging battery pack to discharge to a preset state; Once both the charging and discharging battery packs have reached their preset states, the diesel engine is shut off and the entire vehicle is powered off.

7. The control method according to claim 6, characterized in that, The power supply under light load conditions includes: controlling the two-speed gearbox to switch to the gear corresponding to the speed of the first lowest fuel consumption rate range of the diesel engine, so that the diesel engine operates in the lowest fuel consumption rate range corresponding to the light load conditions; The power supply for heavy-duty conditions includes: controlling the two-speed gearbox to switch to the gear corresponding to the speed of the diesel engine in the second lowest fuel consumption rate range, so that the diesel engine operates in the lowest fuel consumption rate range corresponding to the heavy-duty conditions.

8. The control method according to claim 6, characterized in that, The method also includes drive mode control logic, specifically comprising the following steps: When operating in single-motor drive mode, if the load on the drive motor on that side exceeds the preset overload threshold, the system switches to dual-motor drive mode on that side and distributes the load originally borne by the single motor to both motors. When operating in single-side dual-motor drive mode, if the load of both motors is lower than the preset high-efficiency zone lower limit threshold, the system switches to single-motor drive mode on that side and shuts down one of the motors.

9. The control method according to claim 6, characterized in that, The braking mode control logic of this method specifically includes the following steps: During equipment operation, monitor mechanical braking signals; When the mechanical braking signal is activated, determine whether the braking duration T is greater than the preset time threshold T0; If T≤T0, the drive motor will remain in drive mode and will not participate in braking; If T>T0, then at least one drive motor on one side will be switched to power generation mode to charge the rechargeable battery pack. During braking, the mechanical braking intensity is monitored, and when the braking intensity increases, the number of drive motors participating in the power generation mode is increased. When the mechanical brake signal is turned off, the drive motor is switched back to drive mode.

10. A tracked bulldozer, characterized in that, It is equipped with a hybrid power system as described in any one of claims 1 to 5.

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