Transmission control method and device of three-motor transmission system

Abstract

The application relates to the field of electrical transmission and control of engineering machinery, in particular to a transmission control method and device of a three-motor transmission system, which comprises a front axle, a rear axle and a hydraulic switched reluctance motor in parallel to the driving architecture of the same direct current bus; the system combines the motor phase current change rate difference and a preset flux linkage equation to calculate the equivalent load difference, so as to identify the wheel slip deviation and extract the voltage ripple; the core is that when the slip deviation is out of limit and the phase current reaches the magnetization saturation critical point, the main driving current is kept unchanged, the high-frequency harmonic current is injected into the stator winding of the motor with load mutation, and the motor duty ratio and the chopping opening and closing angle are adjusted in parallel; the high-frequency harmonic current is used to reduce the phase current peak and torque pulsation under the impact working condition.

Description

Technical Field

[0001] This invention relates to the field of electrical transmission and control of engineering machinery, specifically to a transmission control method and device for a three-motor transmission system. Background Technology

[0002] In the current operating environment of construction machinery and pure electric vehicles, the underlying transmission system often adopts a rigid direct-drive transmission chain structure without mechanical gearboxes and differentials. Under such operating conditions, due to the constant changes in wheel-ground adhesion and high-frequency external impacts, the phase current and electromagnetic parameters of the switched reluctance motor in the transmission architecture, influenced by the doubly salient pole structure, exhibit complex nonlinear fluctuations with sudden load changes. Furthermore, frequent load rebounds and impacts periodically generate a large amount of regenerative energy. To ensure traction transmission under complex conditions, existing solutions generally employ a purely mechanical structure to distribute power and rely on conventional braking... The dynamic resistor consumes regenerative energy in one direction. Although this solution has basic transmission and buffering capabilities under stable operation scenarios, due to the high rigidity of the direct drive transmission chain, external sudden loads will act directly on the motor with a very short time delay. This causes the switched reluctance motor to easily cross the magnetization critical point and enter the deep magnetic saturation region, resulting in a disordered surge in local magnetic flux and a significant increase in torque pulsation. At the same time, relying solely on resistor energy consumption lacks a potential energy storage path, which can easily cause the DC bus voltage to pump up due to a large amount of transient regenerative energy being fed back in the opposite direction. Furthermore, the fixed mechanical transmission chain is difficult to support the real-time redistribution and dynamic response of traction torque among multiple axles.

[0003] Therefore, how to effectively suppress deep magnetic saturation of the motor caused by sudden loads and dynamically absorb regenerated energy to prevent DC bus voltage surge under a rigid direct drive architecture without a mechanical differential, thereby improving the timeliness and accuracy of the vehicle's traction torque distribution, has become an urgent technical problem to be solved. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides a transmission control method and device for a three-motor transmission system. Specifically, the technical solution of the present invention is as follows:

[0005] A transmission control method for a three-motor drive system includes:

[0006] S1. The front, rear and middle sections of the chassis base are respectively equipped with a front axle drive unit, a rear axle drive unit and a hydraulic buffer unit; the above three units respectively include a front axle switched reluctance motor, a rear axle switched reluctance motor and a hydraulic switched reluctance motor.

[0007] S2. Connect the front axle switched reluctance motor, the rear axle switched reluctance motor, and the hydraulic switched reluctance motor in parallel to the same DC bus.

[0008] S3. Real-time acquisition of the phase current of the front axle switched reluctance motor and the rear axle switched reluctance motor, and differentiation to obtain the current change rate, and extraction of the voltage ripple of the DC bus.

[0009] S4. Based on the difference in current change rate between the front axle switched reluctance motor and the rear axle switched reluctance motor, and combined with the preset flux linkage equation, calculate the equivalent load difference and identify the wheel slip deviation.

[0010] S5. When the slip deviation exceeds the preset safety threshold and the phase current reaches the magnetization saturation critical point, keep the main drive current of the front axle switched reluctance motor and the rear axle switched reluctance motor that generate the fundamental electromagnetic torque unchanged, and inject high-frequency harmonic current into the stator winding of the front axle switched reluctance motor or the rear axle switched reluctance motor that has experienced a sudden load change.

[0011] S6. Increase the duty cycle of the hydraulic switched reluctance motor according to the voltage ripple rise slope, and adjust the chopper turn-on angle and turn-off angle of the front axle switched reluctance motor and the rear axle switched reluctance motor based on the equivalent load difference.

[0012] In one possible implementation, in step S1: the front axle drive unit further includes a front axle drive shaft, the main shaft of the front axle switched reluctance motor is connected to the input end of the front axle drive shaft through a first plum blossom-shaped flexible coupling, and the output end of the front axle drive shaft is connected to the hub of the front wheel.

[0013] The rear axle drive unit also includes a rear axle drive shaft. The main shaft of the rear axle switched reluctance motor is connected to the input end of the rear axle drive shaft through a second plum blossom-shaped flexible coupling. The output end of the rear axle drive shaft is connected to the hub of the rear wheel.

[0014] In one possible implementation, in step S1: the hydraulic buffer unit further includes a hydraulic triple pump and a pneumatic high-pressure accumulator; the main shaft of the hydraulic switched reluctance motor is connected to the power input shaft of the hydraulic triple pump via a third plum blossom-shaped flexible coupling; and the oil outlet of the hydraulic triple pump is connected to the liquid inlet of the pneumatic high-pressure accumulator.

[0015] In one possible implementation, step S4 includes: calculating the equivalent load difference between the front axle drive shaft and the rear axle drive shaft by comparing the angular acceleration difference between the front and rear axles, based on the inverse relationship between the current change rate and the rotor's angular acceleration; and comparing the equivalent load difference with the vehicle's current speed to identify the wheel slip deviation.

[0016] In one possible implementation, in step S5: the high-frequency harmonic current is used to generate a high-frequency alternating magnetic field.

[0017] In one possible implementation, increasing the duty cycle of the hydraulic switched reluctance motor in step S6 includes: the output torque of the hydraulic switched reluctance motor driving the hydraulic triple pump to pressurize hydraulic oil into the airbag-type high-pressure accumulator; the gas inside the airbag-type high-pressure accumulator is compressed to generate hydraulic back pressure; the hydraulic back pressure acts in reverse on the main shaft of the hydraulic switched reluctance motor through the hydraulic triple pump, forming equivalent electrical damping.

[0018] In one possible implementation, step S6, adjusting the chopper turn-on angle and the turn-off angle of the front axle switched reluctance motor and the rear axle switched reluctance motor, includes: redistributing the fundamental electromagnetic torque by changing the chopper turn-on angle and the turn-off angle, transferring the fundamental electromagnetic torque to the axle side where slippage has not occurred.

[0019] A transmission device for a three-motor drive system, applied to the transmission control method of the three-motor drive system according to any one of claims 1 to 7, characterized in that it comprises:

[0020] Chassis base;

[0021] A front axle drive unit is disposed at the front end of the chassis base, wherein the front axle drive unit includes a front axle switched reluctance motor;

[0022] A rear axle drive unit is disposed at the rear end of the chassis base, wherein the rear axle drive unit includes a rear axle switched reluctance motor;

[0023] A hydraulic buffer unit is disposed in the middle of the chassis base, wherein the hydraulic buffer unit includes a hydraulic switched reluctance motor;

[0024] The DC bus is connected in parallel with the electrical power supply terminals of the front axle switched reluctance motor, the rear axle switched reluctance motor, and the hydraulic switched reluctance motor.

[0025] In one possible implementation, the hydraulic buffer unit further includes a hydraulic triple pump and a pneumatic high-pressure accumulator. The main shaft of the hydraulic switched reluctance motor is connected to the power input shaft of the hydraulic triple pump via a third plum blossom-shaped flexible coupling. The oil outlet of the hydraulic triple pump is connected to the inlet of the pneumatic high-pressure accumulator via a high-pressure resistant steel pipe. The pneumatic high-pressure accumulator is filled with nitrogen gas at a preset pressure.

[0026] In one possible implementation, the front axle drive unit further includes a front axle drive shaft, the main shaft of the front axle switched reluctance motor is connected to the input end of the front axle drive shaft via a first quincunx flexible coupling, and the output end of the front axle drive shaft is connected to the hub of the front wheel via an involute spline.

[0027] The rear axle drive unit also includes a rear axle drive shaft. The main shaft of the rear axle switched reluctance motor is connected to the input end of the rear axle drive shaft through a second plum blossom-shaped flexible coupling. The output end of the rear axle drive shaft is connected to the hub of the rear wheel through an involute spline.

[0028] The present invention has the following beneficial effects:

[0029] 1. This invention obtains the difference in the phase current change rate between the front and rear axle switched reluctance motors by real-time acquisition and differentiation, calculates the equivalent load difference by combining the preset flux linkage equation, and identifies the wheel slip deviation. When the slip deviation exceeds the limit and the phase current reaches the saturation critical point, a high-frequency alternating magnetic field is generated by injecting high-frequency harmonic current into the stator winding with sudden load changes. This effectively solves the problem of increased motor torque pulsation under high load impact and improves the stability of system operation.

[0030] 2. This invention utilizes the voltage ripple rise slope to increase the duty cycle of the hydraulic switched reluctance motor, driving a hydraulic triple pump to pressurize hydraulic oil into a pneumatic high-pressure accumulator. The hydraulic back pressure generated by compressed gas forms an equivalent electrical damping on the motor spindle, actively absorbing regenerated energy and preventing bus voltage surge. Simultaneously, based on the equivalent load difference, the chopper turn-on and turn-off angles of the front and rear axle motors are adjusted, realizing the real-time transfer and redistribution of the fundamental electromagnetic torque to the axle on the side where slippage has not occurred. This solution does not rely on a mechanical differential, significantly improving the accuracy of traction torque distribution and adhesion utilization under complex working conditions. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the overall structure of the device;

[0032] Figure 2 This is a schematic diagram of the hydraulic buffer unit structure of the device;

[0033] Figure 3 This is a schematic diagram of a pneumatic high-voltage accumulator device.

[0034] Figure 4 This is a flowchart of the method of the present invention.

[0035] In the diagram: 1. Chassis base; 2. Front axle drive unit; 3. Front axle switched reluctance motor; 4. Rear axle drive unit; 5. Rear axle switched reluctance motor; 6. Hydraulic buffer unit; 7. Hydraulic switched reluctance motor; 8. DC bus; 9. Front axle drive shaft; 10. First plum blossom-shaped flexible coupling; 11. Front wheel hub; 12. Rear axle drive shaft; 13. Second plum blossom-shaped flexible coupling; 14. Rear wheel hub; 15. Hydraulic triple pump; 16. Airbag-type high-pressure accumulator; 17. Third plum blossom-shaped flexible coupling; 18. High-pressure resistant steel pipe; 19. Involute spline. Detailed Implementation

[0036] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0037] Example 1:

[0038] A transmission control method for a three-motor drive system, combined with Figure 1 and Figure 4 As shown, it includes:

[0039] S1. The front, rear and middle parts of the chassis base 1 are respectively provided with a front axle drive unit 2, a rear axle drive unit 4 and a hydraulic buffer unit 6; the above three units respectively include a front axle switched reluctance motor 3, a rear axle switched reluctance motor 5 and a hydraulic switched reluctance motor 7.

[0040] S2. Connect the front axle switched reluctance motor 3, the rear axle switched reluctance motor 5, and the hydraulic switched reluctance motor 7 in parallel to the same DC bus 8.

[0041] S3. Real-time acquisition of the phase current of the front axle switched reluctance motor 3 and the rear axle switched reluctance motor 5, and differentiation to obtain the current change rate, and extraction of the voltage ripple of the DC bus 8.

[0042] S4. Based on the difference in the rate of change of current between the front axle switched reluctance motor 3 and the rear axle switched reluctance motor 5, and combined with the preset flux linkage equation, calculate the equivalent load difference and identify the wheel slip deviation.

[0043] S5. When the slip deviation exceeds the preset safety threshold and the phase current reaches the magnetization saturation critical point, keep the main drive current of the fundamental electromagnetic torque generated by the front axle switched reluctance motor 3 and the rear axle switched reluctance motor 5 unchanged, and inject high-frequency harmonic current into the stator winding of the front axle switched reluctance motor 3 or the rear axle switched reluctance motor 5 that has experienced a sudden load change.

[0044] S6. Increase the duty cycle of the hydraulic switched reluctance motor 7 according to the voltage ripple rise slope, and adjust the chopper turn-on angle and turn-off angle of the front axle switched reluctance motor 3 and the rear axle switched reluctance motor 5 based on the equivalent load difference.

[0045] This embodiment is used to solve the problems of high rigidity of direct drive transmission chain in engineering machinery, easy deep magnetic saturation of switched reluctance motor under sudden load, and easy voltage rise of DC bus 8 due to regenerative energy pumping; the chassis base 1 adopts box-type welded structure, and the length can be set to 2.5m to 4.5m. The front axle drive unit 2 is installed at the front end, the rear axle drive unit 4 is installed at the rear end, and the hydraulic buffer unit 6 is installed in the middle.

[0046] The front axle switched reluctance motor 3, the rear axle switched reluctance motor 5, and the hydraulic switched reluctance motor 7 can all be 8-phase or 6-phase switched reluctance motors. The rated DC bus 8 voltage can be set from 540V to 750V, and the rated power can be set from 30kW to 180kW depending on the tonnage of the whole machine. The electrical power supply terminals of the three motors are connected in parallel to the same DC bus 8 through copper busbars. The DC bus 8 is equipped with a bus voltage sensor and a bus current sensor to obtain information on voltage fluctuations caused by regenerative energy.

[0047] In step S3, the phase current is collected by Hall current sensors or shunts installed at the output terminals of each phase inverter bridge arm, and the sampling frequency can be set from 10kHz to 50kHz; the controller performs discrete differentiation on the collected phase current sequence to obtain the current change rate.

[0048] To reduce the impact of switching noise on the derivative results, the controller can perform first-order low-pass filtering or moving average filtering on the original phase current data; the bus voltage ripple can be obtained by real-time acquisition of DC bus 8 voltage and calculation of the difference between the instantaneous voltage value and the average value within a set time window, the time window length of which can be set from 1ms to 20ms.

[0049] In step S4, the controller reads the difference in the rate of change of current between the front axle switched reluctance motor 3 and the rear axle switched reluctance motor 5, and calculates the load by combining the preset flux linkage equation. The flux linkage equation can be obtained in advance through bench calibration and is expressed as a nonlinear correspondence between flux linkage and phase current and rotor position.

[0050] Based on the phase voltage equation of the switched reluctance motor, the controller can comprehensively process the current change rate, bus voltage, phase winding resistance and rotor position to obtain the corresponding equivalent back EMF change, which is then converted into the load-related angular acceleration change, and further obtained the equivalent load difference between the front axle and the rear axle.

[0051] The controller compares the equivalent load difference with the current vehicle speed and the preset wheel speed model to identify the wheel slip deviation. The slip deviation can be defined as the difference between the current estimated slip ratio and the set target slip ratio. The target slip ratio can be calibrated to 0.08 to 0.20 based on the adhesion utilization rate of the engineering machinery.

[0052] In step S5, when the slip deviation exceeds the safety threshold and the phase current reaches the magnetization saturation critical point, the controller does not reduce the main drive current used to generate the fundamental electromagnetic torque in order to maintain the required traction force, and at the same time injects high-frequency harmonic current into the stator winding of the motor on the side where the load change occurs; the magnetization saturation critical point can be obtained through offline calibration, and can be specifically defined as the phase current value when the flux linkage increment corresponding to the unit current increment drops to 40% to 70% of the linear region;

[0053] The frequency of the high-frequency harmonic current is higher than that of the fundamental current, preferably 5 to 30 times the fundamental frequency, and the amplitude can be set to 3% to 20% of the amplitude of the main drive current; this high-frequency harmonic current is used to reduce torque pulsation under impact conditions.

[0054] In step S6, the controller calculates the rise slope of the bus voltage ripple in real time. When the rise slope is greater than the threshold, the pulse width modulation duty cycle of the hydraulic switched reluctance motor 7 inverter is increased. The duty cycle increment can be set to 5% to 35%. The output torque of the hydraulic switched reluctance motor 7 drives the hydraulic buffer unit 6 to absorb the energy of the bus.

[0055] At the same time, the controller adjusts the chopper turn-on angle and turn-off angle of the front axle switched reluctance motor 3 and the rear axle switched reluctance motor 5 according to the sign and amplitude of the equivalent load difference. The adjustment range can be set to advance angle from 0° to 12° electrical angle and lag angle from 0° to 15° electrical angle, respectively, to change the fundamental electromagnetic torque distribution ratio of the two bridges.

[0056] This method allows for the transfer of torque to the axle with higher traction while maintaining overall traction requirements, thus reducing the idling of the slip wheel. Bench and whole-machine tests have shown that, under the same impact input, this method can reduce the peak bus voltage by 10% to 28% and the electromagnetic torque fluctuation amplitude during impact by 15% to 35%.

[0057] Furthermore, the preset safety threshold is preferably defined as a first-level trigger value for the slip deviation, which is used to characterize the upper limit of the allowable deviation between the current wheel slip state and the target adhesion utilization state; this threshold can be determined according to the vehicle type, tire or track parameters, and ground adhesion coefficient calibration data, and is preferably set to 0.03 to 0.10;

[0058] The controller does not make a judgment based on a single sampling point, but compares the slip deviation over multiple consecutive control cycles. Only when the slip deviation exceeds the threshold for 2 to 10 consecutive control cycles will it be determined to enter the abnormal traction state that requires the execution of S5, in order to avoid malfunctions caused by transient noise.

[0059] The side where the load change occurs refers to the side where, within the same comparison time window, the direction of change of the equivalent load difference corresponding to the switched reluctance motor on one side is consistent with the direction of deterioration of the slip deviation on that side, and the current change rate on that side exhibits a jump exceeding the allowable difference relative to the other side.

[0060] The allowable difference can be obtained through calibration under three working conditions: no load, standard attached road surface, and impact test bench. Preferably, it can correspond to 10% to 35% of the average steady-state current change rate. The controller's identification process can be as follows: first, read the current change rate sequence on both sides; then calculate the difference between the two sides and its direction of change.

[0061] The equivalent load difference is obtained by combining the rotor position, bus voltage and flux linkage table lookup results; the sign of the equivalent load difference is matched with the side with the increase in slip deviation. The side with successful matching is determined to be the side with load change, and the determination result is output to the high frequency harmonic injection module.

[0062] The rising slope of the voltage ripple is a criterion used to characterize the rate of regenerative energy accumulation on the DC bus 8. Its input source is a continuously acquired bus voltage ripple sequence. The controller can first obtain the current peak value or average absolute value of the ripple within a set time window, and then compare it with the corresponding value of the previous time window to obtain the rising slope. When the rising slope exceeds the threshold, it indicates that the transient excess energy on the bus side has reached a level that requires the hydraulic buffer unit 6 to participate in the absorption.

[0063] The threshold can be calibrated based on the bus rated voltage, bus capacitance value and allowable voltage surge, preferably set to 10V / ms to 120V / ms; the result of the rise slope judgment is output to the duty cycle adjustment module of the hydraulic switched reluctance motor 7, while the result of the equivalent load difference judgment is output to the front and rear axle chopper angle adjustment module. The two can be executed in parallel, thereby completing the bus energy absorption and traction torque redistribution respectively.

[0064] In this embodiment, the preset flux linkage equation serves as an intermediate mapping model for converting electrical measurements into mechanical state judgments. Without directly installing bridge load sensors, the inherent flux linkage-current-rotor position correspondence of the switched reluctance motor is used to identify the changes in equivalent back EMF and angular acceleration caused by wheel-ground interaction, thus supporting the calculation of equivalent load difference and slip deviation.

[0065] The preset flux linkage equations can be logically divided into a calibration data layer, a real-time matching layer, and a status output layer; the calibration data layer is used to store the flux linkage correspondence under different rotor position ranges and different phase current levels;

[0066] The real-time matching layer receives phase current, current change rate, bus voltage, winding resistance correction value and rotor position, and maps the current sampling point to the corresponding calibration interval; the status output layer provides the equivalent back EMF change direction, angular acceleration change trend and intermediate quantities that can be used for load calculation under the current operating condition based on the matching results.

[0067] Its data flow is as follows: first, the phase current, bus voltage and rotor position are obtained by the sensor, then the controller performs filtering, differential and temperature correction, and enters the flux lookup table or segmented fitting unit, and outputs the equivalent load difference for comparing the front and rear axle states; through such structured processing, the controller does not make slip judgment directly from a single current value, but first completes the step-by-step inference from electrical quantities to magnetic state quantities, then to mechanical state quantities, and finally to the vehicle adhesion state quantities.

[0068] The specific example of this data flow process is as follows: Assume that the bus voltage acquisition value is 600V, the sensor obtains a phase current of 150A, and the rotor position is in the inductance rising region; the controller uses these three data as input pointers to address the corresponding equivalent back EMF coefficient in the calibration data layer; combined with the calculated current change rate, the estimated value of angular acceleration is obtained by using four arithmetic operations.

[0069] The specific execution logic of the four arithmetic operations is as follows: The controller uses the arithmetic logic unit to subtract the product of the phase current and the winding resistance from the bus voltage, and then subtract the product of the current change rate and the phase inductance, thereby obtaining the instantaneous value of the equivalent back EMF. According to Faraday's law of electromagnetic induction, the equivalent back EMF is proportional to the angular velocity. Dividing this instantaneous value of the equivalent back EMF by the equivalent back EMF coefficient obtained through addressing yields an estimated value of the angular velocity. The corresponding angular velocity estimation formula is:

[0070]

[0071] In the formula, This is an estimated value for angular velocity, in rad / s. This is the instantaneous value of the DC bus voltage, in V. Phase current, unit: A; Phase winding resistance, unit: ; Phase inductance corresponding to rotor position and current, unit: H; The rate of change of phase current, in A / s; The equivalent back electromotive force coefficient, in units of V·s / rad, is determined by the rotor position. and current Determine by referring to the table; Rotor position;

[0072] During this process, sensor data flows to the filtering module. The filtered data and the lookup table results are input into the arithmetic logic unit, and finally the change in angular acceleration is output to the state output layer. There is no need to solve complex differential equations throughout the process, which ensures the real-time programmable implementation of automotive-grade controllers in microsecond cycles.

[0073] The physical relationship represented by the flux linkage equation is as follows: the magnetic circuit conduction capability, phase inductance variation trend, and back EMF level of the switched reluctance motor change together with the excitation current and mechanical motion state under different rotor positions; when the wheel end load changes abruptly, the rotor angular velocity and angular acceleration of the motor change, and this change will be fed back to the slope of the phase current rise or fall and the energy exchange state of the bus.

[0074] Therefore, the flux linkage equation essentially characterizes the coupling relationship from stator winding excitation, air gap magnetic field establishment, rotor force movement to changes in electrical feedback. It is precisely because of this physical coupling that the controller can use the difference in current change rate as an entry point, combined with bus voltage and rotor position information, to infer the degree of imbalance between the front and rear axle wheel-to-ground action.

[0075] The controller's control logic is as follows: Due to changes in wheel-ground adhesion or external impacts, the mechanical state of a motor on a certain bridge side changes, so the phase current change rate and equivalent back EMF change on that bridge side first deviate; Since the states of the front and rear bridges deviate, the controller obtains the equivalent load difference and identifies the slip deviation degree accordingly.

[0076] Because the slip deviation is too large and the corresponding phase current has entered the saturation edge, high-frequency harmonic injection is initiated; and because load impact is often accompanied by regenerative energy reinjection into the bus, the controller simultaneously increases the duty cycle of the hydraulic switched reluctance motor 7 according to the voltage ripple rise slope to transfer excess electrical energy to the hydraulic side; thus, the controller performs slip control, saturation suppression and bus energy absorption in parallel.

[0077] In step S1:

[0078] The front axle drive unit 2 also includes a front axle drive shaft 9. The main shaft of the front axle switched reluctance motor 3 is connected to the input end of the front axle drive shaft 9 through a first plum blossom-shaped flexible coupling 10. The output end of the front axle drive shaft 9 is connected to the wheel hub 11 of the front wheel.

[0079] The rear axle drive unit 4 also includes a rear axle drive shaft 12. The main shaft of the rear axle switched reluctance motor 5 is connected to the input end of the rear axle drive shaft 12 through a second plum blossom-shaped flexible coupling 13. The output end of the rear axle drive shaft 12 is connected to the wheel hub 14 of the rear wheel.

[0080] This embodiment limits the mechanical transmission chain of the front axle drive unit 2 and the rear axle drive unit 4. The purpose is to shorten the power transmission path so that changes in road load can be reflected in the electromagnetic parameters of the switched reluctance motor with a shorter time delay. Both the front axle drive shaft 9 and the rear axle drive shaft 12 can be made of alloy steel integral forging structure, and the shaft diameter can be set from 50mm to 120mm according to the vehicle weight.

[0081] The main shaft of the front axle switched reluctance motor 3 is connected to the input end of the front axle drive shaft 9 via a first plum blossom-shaped flexible coupling 10, and the main shaft of the rear axle switched reluctance motor 5 is connected to the input end of the rear axle drive shaft 12 via a second plum blossom-shaped flexible coupling 13. The elastic body of the plum blossom-shaped flexible coupling can be made of polyurethane material, and the hardness can be set to 80 Shore A to 98 Shore A. Its function is to compensate for the slight eccentricity and angular deviation when the motor shaft and the drive shaft are installed, and to suppress the direct action of high-frequency mechanical impact on the bearing.

[0082] The output end of the front axle driveshaft 9 can be connected to the hub of the front wheel using a spline connection, and the output end of the rear axle driveshaft 12 can be connected to the hub of the rear wheel using a spline connection or a flange connection. Since this connection path does not have a mechanical gearbox and differential, the changes in ground adhesion experienced by the front and rear axles will be directly reflected in the difference in motor speed perturbation and current change rate.

[0083] The connection in this invention is not limited to a single structure. As long as it can achieve rigid power transmission between the front axle switched reluctance motor 3 and the front wheel hub, and between the rear axle switched reluctance motor 5 and the rear wheel hub, it can be used for implementation.

[0084] The technical advantage of this implementation is that the rotational inertia and transmission clearance of the mechanical link are significantly reduced, and the rate of change of current collected by the controller is more sensitive to the changes in wheel-to-ground interaction, thereby improving the real-time performance and reliability of the equivalent load difference calculation.

[0085] In step S1:

[0086] The hydraulic buffer unit 6 also includes a hydraulic triple pump 15 and a pneumatic high-pressure accumulator 16. The main shaft of the hydraulic switched reluctance motor 7 is connected to the power input shaft of the hydraulic triple pump 15 through a third plum blossom-shaped flexible coupling 17. The oil outlet of the hydraulic triple pump 15 is connected to the liquid inlet of the pneumatic high-pressure accumulator 16.

[0087] This embodiment defines the mechanical and hydraulic configuration of the hydraulic buffer unit 6, with the aim of converting the sudden increase in electrical energy on the DC bus 8 into storable fluid potential energy; the hydraulic switched reluctance motor 7 is connected to the power input shaft of the hydraulic triple pump 15 through the third plum blossom-shaped flexible coupling 17. The third plum blossom-shaped flexible coupling 17 can adopt the same elastic structure as the aforementioned coupling, and its rated transmission torque is configured from 300 N·m to 2000 N·m according to the hydraulic pump displacement.

[0088] The hydraulic triple pump 15 can be composed of three parallel pump cores, and the total displacement can be set from 30mL / r to 180mL / r, with the aim of forming sufficient energy absorption capacity within a limited speed fluctuation time; the nominal volume of the airbag high-pressure accumulator 16 can be set from 5L to 50L, and the pre-charge pressure can be set from 0.5 times to 0.8 times the rated hydraulic working pressure of the system. Nitrogen is preferred for the internal gas to obtain more stable compressible characteristics.

[0089] The oil outlet of the hydraulic triple pump 15 is connected to the inlet of the pneumatic high-pressure accumulator 16 via a high-pressure steel pipe. The pressure resistance rating of the high-pressure steel pipe can be set from 25MPa to 45MPa. The hydraulic triple pump 15 outputs flow under the drive of the hydraulic switched reluctance motor 7. After the hydraulic oil is pressed into the pneumatic high-pressure accumulator 16, the gas inside the accumulator is compressed, forming a hydraulic back pressure related to the pump displacement and speed. This hydraulic back pressure is transmitted back to the main shaft of the hydraulic switched reluctance motor 7 along the hydraulic triple pump 15, so that the hydraulic switched reluctance motor 7 exhibits adjustable power absorption characteristics on the electrical side.

[0090] Compared with simply using a braking resistor, this structure retains a potential energy storage path while absorbing the energy of the busbar, making it suitable for engineering machinery under frequent impacts and load rebound conditions. In this embodiment, a check valve, a relief valve and a pressure sensor can also be installed at the outlet of the hydraulic triple pump 15 so that the controller can monitor the working status of the hydraulic buffer unit 6.

[0091] Step S4 includes: calculating the equivalent load difference between the front axle drive shaft 9 and the rear axle drive shaft 12 by comparing the difference in angular acceleration between the front and rear axles, based on the inverse relationship between the rate of change of current and the angular acceleration of the rotor; and comparing the equivalent load difference with the current vehicle speed to identify the wheel slip deviation.

[0092] This embodiment elaborates on the calculation logic of equivalent load difference and slip deviation; the current change rate is inversely proportional to the rotor angular acceleration, which means that under the same bus voltage and similar rotor positions, the greater the rotor angular acceleration, the more obvious the change in equivalent back EMF and the lower the phase current rise slope.

[0093] When the rotor angular acceleration is smaller or deceleration occurs, the phase current change rate will increase accordingly. Therefore, the controller can use the difference in the current change rate between the front axle switched reluctance motor 3 and the rear axle switched reluctance motor 5 at the same moment, combined with the rotor position sensor signal, to calculate the load difference on both sides.

[0094] In practice, the controller saves the front axle phase current sequence and the rear axle phase current sequence, and performs differential calculations with a fixed sampling period to obtain the front axle current change rate and the rear axle current change rate. The controller then looks up the flux linkage data obtained from the calibration table to obtain the phase inductance change rate and flux linkage increment at the corresponding rotor position, and estimates the front axle rotor angular acceleration and the rear axle rotor angular acceleration.

[0095] The controller compares the front axle angular acceleration and the rear axle angular acceleration to obtain the difference in angular acceleration. This difference is then multiplied by the equivalent moment of inertia to obtain the equivalent load difference between the front axle driveshaft 9 and the rear axle driveshaft 12. The equivalent moment of inertia can be obtained through no-load acceleration tests and known resistance tests. The specific mathematical model for calculating the equivalent load difference based on the front and rear axle angular accelerations is as follows:

[0096]

[0097]

[0098] In the formula, This is an estimated value for angular acceleration, in rad / s². and These are the angular velocities at the current and previous sampling times, respectively. The sampling time sequence number; Sampling period, unit: seconds; The equivalent load difference between the front and rear axles, in N·m; The system's preset moment of inertia, in kg·m². and These are the calculated angular accelerations of the front and rear axles, respectively.

[0099] When identifying slip deviation, the controller reads the current vehicle speed; the vehicle speed can be provided by the vehicle inertial navigation module, non-drive wheel speed sensors, or a fusion estimation module; the controller calculates the theoretical wheel circumference speed based on the vehicle speed and compares it with the actual wheel circumference speed converted from the motor speed, thereby obtaining the front axle slip ratio and the rear axle slip ratio; the specific calculation logic for the actual wheel circumference speed converted from the motor speed is as follows:

[0100]

[0101] In the formula, This refers to the actual wheel circumference speed, in m / s. Pi; The rolling diameter of the wheel, in meters (m). Motor speed collected by the sensor, unit: r / min; The fixed mechanical transmission ratio from the motor spindle to the hub is defined by a constant 60, used to convert the speed unit from r / min to r / s to unify the dimensions of the formula. Since the preferred embodiment of this application employs a rigid direct-drive transmission structure without a mechanical differential, the following settings are used under normal operating conditions: The retention of this parameter item facilitates compatibility with variant architectures that incorporate fixed-ratio reducers.

[0102] If the front axle slip deviation is greater than the threshold and the equivalent load difference points to a sudden increase in front axle load, the controller determines that the front axle is in an abnormal state of impact or adhesion; if the rear axle meets the same conditions, the controller determines that the rear axle is in an abnormal state of impact or adhesion; through this implementation method, slip recognition does not rely on mechanical differential feedback and can be directly calculated based on electrical quantities and vehicle speed, which is suitable for rigid direct drive structures without gearboxes; the processing flow of S4 can be executed in the following order;

[0103] Step 1: Collect input quantities. The input quantities should include at least the front axle phase current, rear axle phase current, front axle rotor position, rear axle rotor position, bus voltage, phase resistance correction value corresponding to winding temperature, and current vehicle speed.

[0104] Step 2: Filter and differentiate the front axle phase current and the rear axle phase current respectively to obtain the current change rate at their respective current rotor positions;

[0105] Step 3: The controller enters the preset flux linkage lookup interval according to the current rotor position, reads the flux linkage increment and phase inductance change trend near the position, and combines the bus voltage and winding resistance voltage drop to obtain the equivalent back EMF change direction corresponding to the current operating condition.

[0106] Step 4: Based on the direction of change of the equivalent back electromotive force and the magnitude of the rate of change of the current, estimate the angular velocities of the front and rear axles respectively, and further differentiate to obtain the changes in angular acceleration of the front and rear axles.

[0107] Step 5: Calculate the difference between the changes in angular acceleration of the front and rear axles to obtain the angular acceleration difference value;

[0108] Step 6: Map this difference to the equivalent load difference between the front and rear axles;

[0109] Step 7: Then input the comparison results of the equivalent load difference and the theoretical wheel circumference speed derived from the vehicle speed into the slip recognition module, and output the front axle slip deviation and the rear axle slip deviation.

[0110] The final output of the process includes the equivalent load difference, front axle slip deviation, rear axle slip deviation, and load abrupt change side identifier, which are respectively used by the subsequent harmonic injection and torque distribution modules. A quantitative derivation example of the calculation process of the above algorithm modules is as follows:

[0111] Assuming that the front bridge phase current changes from 100A to 102A and the rear bridge phase current changes from 100A to 105A under a sampling period of Ts=100μs, the controller calculates the change rate of the front bridge current to be 20000A / s and the rear bridge current to be 50000A / s through the differential module.

[0112] The equivalent back EMF coefficient is obtained by looking up the table based on the current rotor position, and then algebraically transformed according to the phase voltage balance equation. That is, the angular velocity is equal to the bus voltage minus the voltage drop of the resistor and the voltage drop of the inductor, and then divided by the equivalent back EMF coefficient.

[0113] The controller first calculates the angular velocity sequence of the front and rear axles, then performs differential calculations using a set sampling period, and finally calculates the angular acceleration of the front axle. rad / s², rear axle angular acceleration is The difference between the two is -15 rad / s², which, when multiplied by the preset equivalent moment of inertia of 10 kg·m², yields an equivalent load difference of -150 N·m.

[0114] Since the front axle acceleration is lower than the rear axle and the equivalent load difference reflects a lighter load on the rear axle, the slip detection module determines that the rear axle has slipped; the current change rate can be obtained using a discrete difference method, i.e.:

[0115] in, is the rate of change of phase current; k is the sampling time number; The phase current at the current sampling time. The phase current at the previous sampling time. The sampling period is used because the controller operates directly on the sampling sequence, and a slope that can be used for comparison can be obtained without introducing a complex continuous model. Preferably, the phase current can be processed by a 3-point to 15-point moving average before differential processing to reduce the influence of switching ripple on the results. After obtaining the equivalent load difference, it is necessary to further identify the wheel slip state. The slip ratio is obtained by comparing the vehicle speed and the wheel circumference speed. If a certain axle is taken as the object, its slip ratio can be expressed as:

[0116]

[0117] In the formula, This represents the slip ratio of the axle; The wheel circumference speed converted from the motor speed; The theoretical speed converted from the current vehicle speed; This indicates the operation of finding the maximum value. This is a preset minimum speed limit, in m / s, used to avoid numerical calculation overflow caused by the denominator being zero under low-speed or stationary conditions.

[0118] To obtain the slip ratio of the axle Then, the controller further calculates the slip deviation of the axle. The corresponding calculation formula is:

[0119]

[0120] In the formula, This refers to the degree of slip deviation. This represents the currently calculated axle slip ratio; The target slip ratio is preset for the system, and this target slip ratio is set according to the adhesion utilization rate of the engineering machinery;

[0121] In the control logic, the equivalent load difference represents the degree of imbalance between the front and rear axle wheel-to-ground action. It is not a directly measured mechanical load, but an equivalent judgment quantity obtained by inverting electrical quantities. The decision-making role of this quantity is as follows: its sign is used to determine whether the fundamental electromagnetic torque should be transferred to the front or rear axle, and its amplitude is used to determine the adjustment level of the chopper turn-on angle and turn-off angle. When this quantity increases synchronously with the slip deviation on one side, it can also be used as a basis for identifying load abrupt changes and triggering high-frequency harmonic injection in S5.

[0122] The current change rate is inversely proportional to the rotor's angular acceleration, and this relationship is valid within the comparable operating range after calibration. The controller compares the trend of angular acceleration change using the current change rate when the same phase conduction range, the bus voltage fluctuation is within the allowable range, and the positions of the rotors on both sides fall within similar lookup table ranges.

[0123] Since the phase current slope of a switched reluctance motor is affected by the voltage drop across the winding resistance, the change in phase inductance, the back EMF, and the switching state, the controller needs to map the rate of change of current to the mechanical state under the above constraints.

[0124] The controller processes data in the order of measured quantity—intermediate state quantity—mechanical judgment quantity; it obtains the current change rate from the phase current sequence; and, in combination with the current rotor position, bus voltage, and winding resistance correction value, determines whether the change rate corresponds to enhanced excitation, increased back EMF, or increased load drag.

[0125] The determination is then mapped to the direction of angular acceleration change and compared with the difference on the other side of the bridge. Since the front and rear axles share the road excitation background and control cycle on the same vehicle, the difference is compared with the absolute value, which can weaken the combined effects of the overall bus fluctuation and environmental changes, thereby improving the stability of the equivalent load difference identification.

[0126] The causal relationship between the quantities in S4 can be described as follows: because of the change in the wheel end adhesion coefficient or the impact from the external force, the mechanical resistance torque and rotor angular acceleration of the corresponding axle change first; because the change in angular acceleration causes a change in the equivalent back electromotive force, under similar energizing conditions, the phase current change rate deviates from the original trend; because the degree of this deviation is different between the front and rear axles, the controller can obtain the equivalent load difference by comparing the current change rates on both sides and combining the magnetic flux lookup table results.

[0127] Since slippage is essentially a deviation between wheel circumference speed and vehicle speed, the degree of slippage deviation can be identified by using the equivalent load difference together with the theoretical wheel circumference speed derived from the vehicle speed.

[0128] In step S5:

[0129] High-frequency harmonic currents are used to generate high-frequency alternating magnetic fields.

[0130] This embodiment explains the working mechanism and injection method of high-frequency harmonic current; in this invention, high-frequency harmonic current is not used to provide the main driving force, but to adjust the magnetization state of the local magnetic circuit of the switched reluctance motor; since the switched reluctance motor has a double salient pole structure, under high load impact, part of the magnetic circuit is prone to enter the deep magnetic saturation region where the magnetic flux grows slowly and the current continues to rise.

[0131] In this state, the increase in unit current cannot be effectively converted into an increase in torque, and it will also increase the interphase torque pulsation; this implementation method superimposes high-frequency harmonic current onto the stator winding of the motor on the side where the load change occurs.

[0132] In practice, the controller acquires the rotor position sensor signal in real time based on the saturation identification result, and takes the phase winding that is currently in the inductance rising region and whose conducting phase current has reached the magnetization saturation critical point as the target injection phase, while not implementing high-frequency harmonic injection for the phase winding that is in the inductance falling region or dead region position, so as to avoid generating braking torque.

[0133] The high-frequency harmonic current can be a sine wave, square wave, or a pulse sequence with amplitude limiting. The frequency can be set from 500Hz to 5000Hz, the injection duration can be set from 5ms to 200ms, and the injection amplitude can be adaptively set according to the phase current saturation level. To avoid excessive additional copper loss, the controller can limit the high-frequency harmonic current amplitude according to the output of the motor temperature sensor.

[0134] Experiments have shown that, under the same impact load, injecting high-frequency harmonic current can reduce phase current spikes by 5% to 15% and torque ripple root mean square value by 10% to 30%. This implementation method allows the main drive current to maintain traction capability while reducing additional vibrations caused by deep magnetic saturation.

[0135] First, the fundamental main drive current is kept basically unchanged to ensure that the traction force required by the vehicle is not significantly weakened.

[0136] Its control execution process is as follows: The controller first determines whether to enter the injection condition based on the slip deviation, phase current amplitude and saturation critical point. Then, it selects the injection phase group and injection duration according to the load change side identifier. The power converter superimposes high-frequency harmonic current, and finally uses the reduction of phase current peak and torque pulsation as the effect feedback. Thus, the harmonic injection module and the main drive module form a cooperative control mechanism of fundamental frequency maintenance and harmonic correction, rather than a mutual substitution relationship.

[0137] The physical relationship characterized by high-frequency alternating magnetic fields is that when the iron core enters deep saturation locally, the effective flux increment brought about by further increasing DC or low-frequency excitation is limited.

[0138] The reduction of additional ineffective current components under the same main drive current is manifested in the suppression of phase current spikes and torque pulsation; this causal chain shows that the effect of high-frequency harmonic current is not to directly increase the average driving force, but to improve the conversion efficiency of the main drive current to stable electromagnetic torque by improving the local magnetization state.

[0139] When implementing this high-frequency harmonic injection, the controller can use a combination of entry and exit conditions. The entry condition can be: the slip deviation exceeds the threshold within several consecutive control cycles, the phase current reaches the saturation critical point, and the load change side has been determined. The exit condition can be: the slip deviation falls back to below the exit threshold, the phase current leaves the saturation edge region, or the motor temperature reaches the limit value.

[0140] To avoid increasing copper losses and reducing system efficiency by injecting high-frequency harmonic current for a long time when there is no local deep saturation trend, the controller is equipped with a high-frequency harmonic injection state machine, which includes monitoring state, injection state and decay exit state.

[0141] In the monitoring state, the controller cyclically compares the slip deviation with the safety threshold at 100μs intervals. Once the entry condition is met for 5 consecutive cycles, the state machine immediately jumps to the injection state. In the injection state, the algorithm module reads the current main drive current amplitude and calculates the high-frequency harmonic reference amplitude using the following linear mapping model:

[0142]

[0143] In the formula, This is the reference amplitude for high-frequency harmonics. To read the current main drive current amplitude, This is a preset proportional coefficient; the coefficient here... The value should be adaptively selected from 3% to 20% based on the phase current saturation level to ensure that torque pulsation is reduced without significantly increasing copper loss;

[0144] It also calls the internal numerically controlled oscillator to generate an alternating reference signal with a frequency of 2000Hz; this signal is superimposed on the fundamental reference current in the adder register, transmitted to the current loop proportional-integral regulator, and finally converted into a pulse width modulation duty cycle command output to the power converter;

[0145] When the exit condition is met, the state machine transitions to the decay exit state, and smoothly reduces the harmonic amplitude to zero within 50ms using step-decreasing instructions, before returning to the monitoring state; this state machine model defines the state switching nodes and interaction conditions.

[0146] In step S6, increasing the duty cycle of the hydraulic switched reluctance motor 7 includes:

[0147] The hydraulic switched reluctance motor 7 outputs torque to drive the hydraulic triple pump 15 to pressurize hydraulic oil into the pneumatic high-pressure accumulator 16.

[0148] The gas inside the airbag-type high-voltage accumulator 16 is compressed to generate hydraulic back pressure.

[0149] The hydraulic back pressure acts in the opposite direction on the main shaft of the hydraulic switched reluctance motor 7 through the hydraulic triple pump 15, forming an equivalent electrical damping.

[0150] This embodiment describes in detail the energy absorption process of the hydraulic switched reluctance motor 7 after the duty cycle is increased; the controller continuously monitors the rising slope of the DC bus voltage ripple; when the rising slope of the bus voltage within the set time window exceeds the threshold, for example, exceeding 20V / ms to 150V / ms, the controller outputs a control signal to the power converter of the hydraulic switched reluctance motor 7 to increase the duty cycle, so that the hydraulic switched reluctance motor 7 switches from a low load state to a high energy absorption state; after the duty cycle is increased, the hydraulic switched reluctance motor 7 obtains more electrical energy from the DC bus 8 and converts it into mechanical torque, driving the hydraulic triple pump 15 to increase the output flow and output pressure;

[0151] The hydraulic triple pump 15 pressurizes hydraulic oil into the airbag-type high-pressure accumulator 16. The nitrogen gas in the accumulator is compressed as the liquid enters, and the gas pressure rises to form hydraulic back pressure. The hydraulic back pressure acts in the opposite direction on the main shaft of the hydraulic switched reluctance motor 7 through the mechanical transmission chain of the hydraulic triple pump 15, so that the hydraulic switched reluctance motor 7 generates a load torque related to the speed and pressure.

[0152] The load torque is manifested as a higher power absorption requirement on the electrical side, and the controller realizes the active absorption of excess energy of DC bus 8 accordingly; the equivalent electrical damping refers to the suppression effect of load torque change caused by hydraulic back pressure on bus voltage fluctuation. Its performance is similar to resistive energy consumption, but the energy is not completely converted into heat loss, but stored in the airbag high-voltage accumulator 16 in the form of fluid potential energy.

[0153] In this embodiment, the controller can also limit the upper limit of the duty cycle of the hydraulic switched reluctance motor 7 based on the accumulator pressure value; for example, when the accumulator pressure reaches 90% to 100% of the set upper limit, the controller reduces the duty cycle increment to prevent overpressure in the hydraulic system.

[0154] This implementation method can guide regenerative impact energy from the electrical side to the hydraulic side, thereby slowing down the rate of increase in the peak bus voltage. In actual measurements, after adopting this implementation method, the peak value of the voltage ripple can be reduced by 12% to 30%, and the hydraulic buffer unit 6 can release the stored potential energy through the subsequent hydraulic circuit after the impact disappears.

[0155] The voltage ripple rise slope threshold can be determined by combining the allowable overvoltage of the bus and the current energy absorption capacity of the hydraulic side. Specifically, the controller first reads the rated voltage of the bus, the current bus voltage, the accumulator pressure, and the current speed of the hydraulic switch reluctance motor 7; then it determines whether the hydraulic side has a margin to continue absorbing energy.

[0156] When the bus voltage is close to the allowable upper limit, or when the hydraulic side still has a large pressure margin, the rise slope threshold can be set lower to trigger hydraulic energy absorption earlier. When the accumulator pressure is close to the upper limit, the rise slope threshold can be appropriately increased, and the duty cycle adjustment range can be limited simultaneously to avoid hydraulic side overload. Thus, the rise slope threshold in the control logic represents whether the trigger boundary of the hydraulic buffer unit 6 needs to be enabled, rather than an isolated fixed value. The process of increasing the duty cycle can be executed sequentially.

[0157] Step 1: Read the characteristic values ​​of the bus voltage ripple in the current time window and the previous time window;

[0158] Step 2: Calculate the difference between the two and divide by the time window interval to obtain the ripple rise slope; the discrete calculation formula for the ripple rise slope is:

[0159]

[0160] In the formula, The ripple rise slope, This represents the characteristic value of the bus voltage ripple within the currently set time window. The characteristic value of the bus voltage ripple within the previously set time window. The set time window interval length, To set the sequence number of the time window;

[0161] Step 3: Read the accumulator pressure, hydraulic oil temperature, and hydraulic switch reluctance motor 7 speed to determine whether the hydraulic buffer unit 6 is in an energy absorption state.

[0162] Step 4: If the energy absorption state is allowed and the ripple rise slope exceeds the threshold, then increase the duty cycle according to the graded rules;

[0163] Step 5: After the duty cycle is increased, continue to monitor the bus voltage change. If the ripple rise slope falls back to below the exit threshold, maintain the current duty cycle or retreat according to the preset gradient. This is to avoid frequent and large fluctuations in the duty cycle and to maintain a causal relationship between the hydraulic energy absorption action and the bus energy change.

[0164] To ensure that the grading rules have defined executable boundaries, a three-level regulation is used as an example for quantitative explanation: Assume that the set ripple rise slope threshold is 20V / ms; when the ripple rise slope is in the first interval of 20V / ms to 50V / ms, the controller determines that there is slight energy accumulation and outputs the first-level duty cycle increment, preferably 5%;

[0165] When the rising slope is in the second range of 50V / ms to 100V / ms, it is determined to be moderate energy accumulation, and the second-stage duty cycle increment is output, preferably 15%; when the rising slope is greater than the third range of 100V / ms, and the accumulator pressure is lower than 80% of the rated upper limit, it is determined to be heavy energy accumulation, and the third-stage duty cycle increment is output, preferably 30%; after obtaining the duty cycle increment, the controller iteratively calculates the target duty cycle of the hydraulic switched reluctance motor 7 according to the following formula:

[0166]

[0167] In the formula, The target duty cycle for output to the power converter. This is the base duty cycle for the current control cycle. The duty cycle increment is output in stages based on the voltage ripple rise slope; and the constraints must be met. , The preset maximum duty cycle limit value is set to 90% to 95% to prevent hydraulic system overload;

[0168] The output of this graded adjustment is the target duty cycle of the hydraulic switched reluctance motor 7, which is transmitted to the power converter execution module. By gradually increasing the duty cycle according to the slope range, the process of the hydraulic triple pump 15 building up pressure can be made more stable, reducing the current and mechanical shocks caused by a one-time large increase in the duty cycle.

[0169] In step S6, adjusting the chopper turn-on and turn-off angles of the front axle switched reluctance motor 3 and the rear axle switched reluctance motor 5 includes:

[0170] By changing the chopper's turn-on and turn-off angles, the fundamental electromagnetic torque is redistributed, transferring the fundamental electromagnetic torque to the axle side that has not slipped.

[0171] This embodiment describes the electromagnetic torque distribution method of the front axle switched reluctance motor 3 and the rear axle switched reluctance motor 5; the average electromagnetic torque of the switched reluctance motor is related to the phase conduction interval, turn-on angle, turn-off angle and the phase current rise process; the controller determines which side of the axle is in a slipping state and which side of the axle has a higher adhesion ability based on the equivalent load difference and slip deviation.

[0172] For the axle on the side that slips, the controller can appropriately delay the turn-on angle, advance the turn-off angle, or reduce the upper limit of the chopper current to reduce its fundamental electromagnetic torque; for the axle on the side that does not slip, the controller can appropriately advance the turn-on angle and delay the turn-off angle to increase the average torque within its effective conduction range.

[0173] In practice, if the front axle slips while the rear axle is more attached, the controller will delay the front axle's opening angle by 2° to 10° electrical angle and advance the closing angle by 2° to 12° electrical angle, while simultaneously advancing the rear axle's opening angle by 1° to 8° electrical angle and delaying the closing angle by 1° to 10° electrical angle; if the rear axle slips, the opposite adjustment method will be used.

[0174] The controller can also add a current reference value correction to limit excessive torque on the slipping axle. The specific execution logic for adding the current reference value correction is as follows: the controller dynamically adjusts the main drive current reference value of the motor on the slipping side of the axle by introducing a damping coefficient based on the slip deviation of the slipping side of the axle. The calculation formula is as follows:

[0175]

[0176] In the formula, The target reference current after adding the correction amount. The reference value of the primary fundamental main drive current is given based on driving requirements. The preset slip suppression ratio coefficient, This represents the currently calculated slip deviation of the sliding bridge; thus ensuring that the more severe the slip, the greater the reduction in the drive current on that side.

[0177] By changing the chopper's on and off angles, the basic electromagnetic torque is redistributed between the front and rear axles without introducing a mechanical differential. The technical effect of this implementation is that the axle with higher adhesion obtains more available driving force, the slippage of the axle on the slipping side is reduced, and the overall traction utilization rate is improved. Test results show that on road surfaces with significant differences in adhesion coefficients, this implementation can increase the effective traction of the vehicle by 8% to 22%.

[0178] Example 2:

[0179] A transmission device for a three-motor drive system includes:

[0180] Chassis base 1;

[0181] The front axle drive unit 2 is located at the front end of the chassis base 1, wherein the front axle drive unit 2 includes a front axle switched reluctance motor 3;

[0182] The rear axle drive unit 4 is located at the rear end of the chassis base 1, and the rear axle drive unit 4 includes a rear axle switched reluctance motor 5.

[0183] The hydraulic buffer unit 6 is located in the middle of the chassis base 1, and the hydraulic buffer unit 6 includes a hydraulic switched reluctance motor 7.

[0184] DC bus 8 is connected in parallel with the electrical power supply terminals of the front axle switched reluctance motor 3, the rear axle switched reluctance motor 5, and the hydraulic switched reluctance motor 7.

[0185] This embodiment provides a three-motor drive system device for implementing the aforementioned control method; the chassis base 1 is the main load-bearing body of the entire device, and can be made of high-strength steel plate welded parts or profile assembly parts; the front axle drive unit 2 is installed at the front end of the chassis base 1, the rear axle drive unit 4 is installed at the rear end of the chassis base 1, and the hydraulic buffer unit 6 is installed in the middle of the chassis base 1, so that the front and rear counterweights and the length of the hydraulic pipeline are within a reasonable range.

[0186] The front axle drive unit 2 includes a front axle switched reluctance motor 3, the rear axle drive unit 4 includes a rear axle switched reluctance motor 5, and the hydraulic buffer unit 6 includes a hydraulic switched reluctance motor 7. The electrical power supply terminals of the three motors are connected in parallel through a DC bus 8 to form a common bus energy exchange structure. The DC bus 8 may include a bus capacitor, a bus copper bus, a fuse, a contactor, and a voltage detection module.

[0187] The device is also equipped with a controller, power converter, phase current sensor, bus voltage sensor and rotor position sensor; the controller can be an automotive-grade microcontroller or an industrial controller with a control cycle of not less than 100μs, used to perform phase current sampling, current change rate calculation, flux linkage equation lookup, slip deviation identification, high frequency harmonic current injection, duty cycle adjustment of hydraulic switched reluctance motor 7 and front and rear axle chopper angle adjustment.

[0188] The structural layout of this device allows the front and rear axle drives and the hydraulic buffer unit 6 to work together within the same electrical platform. On the mechanical side, it forms a combined structure of the front axle, rear axle, and hydraulic energy absorption unit; on the electrical side, it forms a common bus energy distribution path; and on the control side, it forms an adjustment basis based on the rate of change of current and bus voltage ripple. Therefore, this embodiment can provide a clear hardware implementation basis for the aforementioned method.

[0189] The hydraulic buffer unit 6 also includes a hydraulic triple pump 15 and a pneumatic high-pressure accumulator 16. The main shaft of the hydraulic switched reluctance motor 7 is connected to the power input shaft of the hydraulic triple pump 15 via a third flexible coupling 17. (Refer to...) Figure 2 The oil outlet of the hydraulic triple pump 15 is connected to the inlet of the pneumatic high-pressure accumulator 16 via a high-pressure resistant steel pipe 18. Figure 3 As shown, the airbag-type high-voltage accumulator 16 is filled with nitrogen at a preset pressure.

[0190] This embodiment further defines the hydraulic buffer unit 6; the hydraulic triple pump 15 is installed on one side of the output shaft of the hydraulic switched reluctance motor 7, and the two are connected by a third plum blossom-shaped flexible coupling 17; the hydraulic triple pump 15 can adopt a combination structure of a three-section gear pump, a three-section piston pump or a three-section vane pump, wherein the purpose of selecting a three-section pump is to improve the instantaneous flow rate and pressure resistance while keeping the structural length controllable.

[0191] The oil outlet of the hydraulic triple pump 15 is connected to the inlet of the pneumatic high-pressure accumulator 16 through a high-pressure resistant steel pipe 18. The outer diameter of the steel pipe can be set to 12mm to 25mm, and the pressure resistance level is not less than 1.25 times the maximum working pressure of the system. The pneumatic high-pressure accumulator 16 is fixed in the middle of the chassis base 1 and is filled with nitrogen gas at a preset pressure. The preset pressure can be set in the range of 8MPa to 22MPa according to the hydraulic system design pressure.

[0192] The working mechanism of this structure is as follows: the hydraulic switched reluctance motor 7 rotates under the power supply of the DC bus 8, and the third plum blossom-shaped flexible coupling 17 transmits the torque to the hydraulic triple pump 15; the hydraulic oil output by the hydraulic triple pump 15 enters the airbag-type high-pressure accumulator 16 through the high-pressure resistant steel pipe 18, which compresses the nitrogen gas in the accumulator; after the nitrogen gas is compressed, a thrust is generated, which is transmitted back to the shaft of the hydraulic switched reluctance motor 7 through the hydraulic oil and the hydraulic triple pump 15, forming a mechanical resistance corresponding to the rotational speed;

[0193] Compared to a structure that only has an accumulator without a hydraulic triple pump 15, this embodiment establishes a direct mechanical-hydraulic energy conversion path between the electrical and hydraulic sides, enabling it to absorb more transient energy when the bus voltage ripple increases. This embodiment can also install pressure and temperature sensors on the high-pressure steel pipe for the controller to identify the hydraulic energy absorption capacity boundary.

[0194] The front axle drive unit 2 also includes a front axle drive shaft 9. The main shaft of the front axle switched reluctance motor 3 is connected to the input end of the front axle drive shaft 9 through a first plum blossom-shaped flexible coupling 10. The output end of the front axle drive shaft 9 is connected to the hub 11 of the front wheel through an involute spline 19.

[0195] The rear axle drive unit 4 also includes a rear axle drive shaft 12. The main shaft of the rear axle switched reluctance motor 5 is connected to the input end of the rear axle drive shaft 12 through a second plum blossom-shaped flexible coupling 13. The output end of the rear axle drive shaft 12 is connected to the hub 14 of the rear wheel through an involute spline 19.

[0196] This embodiment further defines the front axle drive unit 2 and the rear axle drive unit 4; the front axle drive unit 2 includes a front axle switched reluctance motor 3 and a front axle drive shaft 9. The main shaft of the front axle switched reluctance motor 3 is connected to the input end of the front axle drive shaft 9 through a first plum blossom-shaped elastic coupling 10, and the output end of the front axle drive shaft 9 is connected to the front wheel hub through an involute spline 19.

[0197] The rear axle drive unit 4 includes a rear axle switched reluctance motor 5 and a rear axle drive shaft 12. The main shaft of the rear axle switched reluctance motor 5 is connected to the input end of the rear axle drive shaft 12 through a second plum blossom-shaped flexible coupling 13. The output end of the rear axle drive shaft 12 is connected to the rear wheel hub through an involute spline 19. The involute spline 19 can adopt an external spline and internal spline combination structure, and the number of teeth can be set from 16 to 36 teeth to balance torque transmission capability and ease of disassembly and assembly.

[0198] The device structure eliminates the traditional mechanical gearbox and differential, allowing the wheel-to-ground interaction changes of the front and rear axles to be directly fed back to the corresponding motor rotors through the front axle drive shaft 9 and the rear axle drive shaft 12; the first plum blossom-shaped flexible coupling 10 and the second plum blossom-shaped flexible coupling 13 are used to absorb assembly deviations and some high-frequency mechanical shocks, but do not change the basic characteristics of direct drive transmission.

[0199] Because the hub and drive shaft are connected by an involute spline 19, the backlash can be kept small while transmitting large torque, so that the phase current change rate of the switched reluctance motor has a high responsiveness to the change of wheel end load.

[0200] This structure provides the physical basis for calculating the equivalent load difference based on the rate of change of current, identifying the slip deviation, and performing torque redistribution between the front and rear axles in the aforementioned methods. In actual tests, under the same wheel-end impact input conditions, the system using this device structure can obtain more direct load feedback than the structure with a multi-stage gear transmission chain, and the response time of electrical measurements to sudden load changes can be shortened to the millisecond level.

[0201] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A transmission control method for a three-motor drive system, characterized in that, include: S1. The front, rear and middle parts of the chassis base (1) are respectively provided with a front axle drive unit (2), a rear axle drive unit (4) and a hydraulic buffer unit (6); the above three units respectively include a front axle switched reluctance motor (3), a rear axle switched reluctance motor (5) and a hydraulic switched reluctance motor (7). S2. Connect the front axle switched reluctance motor (3), the rear axle switched reluctance motor (5) and the hydraulic switched reluctance motor (7) in parallel to the same DC bus (8). S3. Real-time acquisition of the phase current of the front axle switched reluctance motor (3) and the rear axle switched reluctance motor (5) and differentiation to obtain the current change rate, and extraction of the voltage ripple of the DC bus (8). S4. Based on the difference in the rate of change of current between the front axle switched reluctance motor (3) and the rear axle switched reluctance motor (5), the equivalent load difference is calculated by combining the preset flux linkage equation, and the wheel slip deviation is identified. S5. When the slip deviation exceeds the preset safety threshold and the phase current reaches the magnetization saturation critical point, the main drive current of the front axle switched reluctance motor (3) and the rear axle switched reluctance motor (5) that generate the fundamental electromagnetic torque remains unchanged, and a high-frequency harmonic current is injected into the stator winding of the front axle switched reluctance motor (3) or the rear axle switched reluctance motor (5) that has experienced a sudden load change. The high-frequency harmonic current is used to generate a high-frequency alternating magnetic field to reduce the phase current spike and torque pulsation under impact conditions. Among them, the phase winding that is currently in the inductance rising region and the conducting phase current reaches the magnetization saturation critical point is taken as the target injection phase, and the phase winding that is in the inductance falling region or dead region is not injected with high-frequency harmonics. The frequency of the high-frequency harmonic current is 500Hz to 5000Hz, the amplitude is 3% to 20% of the amplitude of the main drive current, the injection duration is 5ms to 200ms, and the amplitude of the high-frequency harmonic current is limited according to the output of the motor temperature sensor. S6. Increase the duty cycle of the hydraulic switched reluctance motor (7) according to the voltage ripple rise slope, and adjust the chopper turn-on angle and turn-off angle of the front axle switched reluctance motor (3) and the rear axle switched reluctance motor (5) based on the equivalent load difference.

2. The transmission control method for the three-motor transmission system according to claim 1, characterized in that, In step S5: the magnetization saturation critical point is the phase current value when the flux linkage increment corresponding to a unit current increment drops to 40% to 70% of the linear region.

3. The transmission control method for the three-motor transmission system according to claim 1, characterized in that, In step S5, a high-frequency harmonic injection state machine is used to inject the high-frequency harmonic current. The high-frequency harmonic injection state machine includes a monitoring state, an injection state, and a decay exit state. In the monitoring state, when the entry conditions are met for several consecutive control cycles, the system jumps to the injection state. The entry conditions include: the slip deviation exceeds a preset safety threshold, the phase current reaches the magnetization saturation critical point, and the side where the load change occurs has been determined. When the exit conditions are met, the system enters the attenuation exit state, smoothly reduces the amplitude of the high-frequency harmonic current to zero, and then returns to the monitoring state. The exit conditions include: the slip deviation falls back below the exit threshold, the phase current leaves the saturation edge region, or the motor temperature reaches the limit value.

4. The transmission control method for the three-motor transmission system according to claim 1, characterized in that, In step S1: The front axle drive unit (2) also includes a front axle drive shaft (9). The main shaft of the front axle switched reluctance motor (3) is connected to the input end of the front axle drive shaft (9) through a first plum blossom-shaped flexible coupling (10). The output end of the front axle drive shaft (9) is connected to the wheel hub (11) of the front wheel. The rear axle drive unit (4) also includes a rear axle drive shaft (12). The main shaft of the rear axle switched reluctance motor (5) is connected to the input end of the rear axle drive shaft (12) through a second plum blossom-shaped flexible coupling (13). The output end of the rear axle drive shaft (12) is connected to the wheel hub (14) of the rear wheel.

5. The transmission control method for the three-motor transmission system according to claim 1, characterized in that, In step S1: the hydraulic buffer unit (6) further includes: The hydraulic triple pump (15) and the airbag high-pressure accumulator (16) are connected by the main shaft of the hydraulic switched reluctance motor (7) to the power input shaft of the hydraulic triple pump (15) through a third plum blossom-shaped flexible coupling (17). The oil outlet of the hydraulic triple pump (15) is connected to the liquid inlet of the airbag high-pressure accumulator (16).

6. The transmission control method for the three-motor transmission system according to claim 4, characterized in that, The steps in S4 include: By comparing the difference in angular acceleration between the front and rear axles, the equivalent load difference between the front axle drive shaft (9) and the rear axle drive shaft (12) can be calculated, based on the inverse relationship between the current change rate and the rotor angular acceleration. The equivalent load difference is compared with the vehicle's current speed to identify the wheel slip deviation.

7. The transmission control method for a three-motor drive system according to claim 5, characterized in that, In step S6, increasing the duty cycle of the hydraulic switched reluctance motor (7) includes: The hydraulic switched reluctance motor (7) outputs torque to drive the hydraulic triple pump (15) to pressurize hydraulic oil into the airbag high-pressure accumulator (16). The gas inside the airbag-type high-voltage accumulator (16) is compressed to generate hydraulic back pressure; The hydraulic back pressure acts in the reverse direction on the main shaft of the hydraulic switched reluctance motor (7) through the hydraulic triple pump (15), forming an equivalent electrical damping.

8. The transmission control method for a three-motor drive system according to any one of claims 1 to 5, characterized in that, In step S6, adjusting the chopper turn-on angle and turn-off angle of the front axle switched reluctance motor (3) and the rear axle switched reluctance motor (5) includes: By changing the chopper turn-on angle and the turn-off angle, the fundamental electromagnetic torque is redistributed, transferring the fundamental electromagnetic torque to the axle side that has not slipped.

9. A transmission device for a three-motor transmission system, applied to the transmission control method of the three-motor transmission system according to any one of claims 1 to 8, characterized in that, include: Chassis base (1); A front axle drive unit (2) is disposed at the front end of the chassis base (1), wherein the front axle drive unit (2) includes a front axle switched reluctance motor (3). The rear axle drive unit (4) is located at the rear end of the chassis base (1), wherein the rear axle drive unit (4) includes a rear axle switched reluctance motor (5). A hydraulic buffer unit (6) is disposed in the middle of the chassis base (1), wherein the hydraulic buffer unit (6) includes a hydraulic switched reluctance motor (7). The DC bus (8) is connected in parallel with the electrical power supply terminals of the front axle switched reluctance motor (3), the rear axle switched reluctance motor (5), and the hydraulic switched reluctance motor (7).

10. The apparatus according to claim 9, characterized in that, The hydraulic buffer unit (6) also includes a hydraulic triple pump (15) and a pneumatic high-pressure accumulator (16). The main shaft of the hydraulic switched reluctance motor (7) is connected to the power input shaft of the hydraulic triple pump (15) through a third plum blossom-shaped flexible coupling (17). The oil outlet of the hydraulic triple pump (15) is connected to the liquid inlet of the pneumatic high-pressure accumulator (16) through a high-pressure resistant steel pipe (18). The pneumatic high-pressure accumulator (16) is filled with nitrogen gas at a preset pressure. The front axle drive unit (2) also includes a front axle drive shaft (9). The main shaft of the front axle switched reluctance motor (3) is connected to the input end of the front axle drive shaft (9) through a first plum blossom-shaped flexible coupling (10). The output end of the front axle drive shaft (9) is connected to the hub (11) of the front wheel through an involute spline (19). The rear axle drive unit (4) also includes a rear axle drive shaft (12). The main shaft of the rear axle switched reluctance motor (5) is connected to the input end of the rear axle drive shaft (12) through a second plum blossom-shaped flexible coupling (13). The output end of the rear axle drive shaft (12) is connected to the wheel hub (14) of the rear wheel through an involute spline (19).

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