A double closed loop cooperative control method and power system of a direct drive electric chassis

Abstract

This invention discloses a dual-closed-loop collaborative control method and power system for a direct-drive electric chassis, relating to the field of electric special vehicle power control technology. It proposes a dual-closed-loop collaborative control architecture for speed and torque, using a 32-bit processor to achieve real-time collaborative computation between the two cores, dynamically optimizing motor output characteristics. Combined with a direct-drive transmission structure, the traditional reduction gear is eliminated, with a flat-wire motor directly driving the rear axle via a drive shaft. This, along with a four-in-one controller, reduces system losses by 33% and increases power density by 15%. Based on real-time temperature / charge data from the lithium iron phosphate battery management system, control parameters are adaptively adjusted, overcoming the performance degradation bottleneck at -35℃. An integrated high-voltage interlock and insulation monitoring module automatically switches to the emergency hydraulic system in case of electrical faults, forming a multi-level safety guarantee. This technology achieves a significant 20% improvement in energy recovery efficiency, effectively enhancing wind resistance and reliability in extreme environments.

Description

Technical Field

[0001] This invention relates to the field of electric special vehicle power control technology, and in particular to a dual closed-loop cooperative control method and power system for a direct-drive electric chassis. Background Technology

[0002] Direct-drive electric chassis, as the core power system of new energy special vehicles, has been widely used in the field of airport ground equipment in recent years. Existing technologies generally adopt a structure in which the motor drives the axle through a reducer. Although this can improve torque output, it has problems such as high mechanical losses (transmission efficiency <85%) and slow response (control cycle >100ms). At the same time, the traditional single closed-loop control strategy is difficult to take into account the adaptability to extreme temperatures. In low-temperature environments below -20℃, the usable battery capacity decreases by more than 40%, resulting in a sharp reduction in the vehicle's driving range.

[0003] The typical solution of the "Redundant Cooperative Control Method for Drive and Braking of a Full Vector Power Chassis Vehicle" disclosed in Chinese Patent CN119116710B addresses the problem that existing drive and braking control strategies for full vector power chassis vehicles are not comprehensive enough and cannot effectively reduce computational requirements. This invention calculates the required longitudinal and yaw moments of the vehicle at the upper layer, and distributes the longitudinal and yaw moments issued by the upper-layer controller using a combination of rules and lookup tables at the lower layer. It employs an intelligent evolutionary method to train the neural networks of the upper and lower layer actuators, realizing reinforcement learning control based on vehicle state to command output. This simplifies the control system's "signal acquisition-computation processing-output execution" process to the greatest extent, especially reducing the hysteresis effect in the computation processing stage, thus improving control efficiency and accuracy; thereby ensuring the economy, safety, and stability of the vehicle throughout its entire lifecycle.

[0004] Based on existing technological bottlenecks, three core issues urgently need to be addressed in this field: 1) Control instability of direct-drive systems due to battery degradation at low temperatures; 2) The inability of traditional control strategies to coordinate energy recovery and dynamic response, leading to safety risks from regenerative braking impacts; 3) Low switching efficiency of existing hydraulic emergency devices and a lack of redundant interlocking mechanisms with electronic control systems. Especially for special equipment such as airport passenger boarding stairs, under stringent requirements such as wind resistance stability in -35℃ environments, millimeter-level precision control during aircraft docking, and rapid evacuation within 90 seconds after a malfunction, existing technical solutions cannot meet the civil aviation AHM910 safety standards. Summary of the Invention

[0005] In view of the aforementioned existing problems, the present invention is proposed.

[0006] Therefore, this invention provides a dual closed-loop cooperative control method for a direct-drive electric chassis to solve the problems of control instability, safety risks of regenerative braking shock, and lack of redundant interlocking mechanism with the electronic control system.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0008] In a first aspect, the present invention provides a dual-closed-loop cooperative control method for a direct-drive electric chassis, comprising the following steps:

[0009] Step 1: Real-time data acquisition

[0010] The motor speed signal is acquired by a 17-bit absolute encoder, and the motor phase current signal is acquired by a current sensor.

[0011] The battery management unit (BMS) collects real-time temperature and remaining state of charge (SOC) data of the lithium iron phosphate battery.

[0012] Step 2: Dual-loop collaborative computing

[0013] The speed signal and the preset speed value are input into the speed loop to generate the first error signal, and the phase current signal and the dynamic current limit provided by the BMS are input into the torque loop to generate the second error signal.

[0014] A 32-bit dual-core processor is used to superimpose the two error signals with a 7:3 weight, and then outputs PWM control commands through an incremental PID algorithm.

[0015] The calculation cycle is strictly controlled within 50ms;

[0016] Step 3: Command Execution and Feedback

[0017] The PWM command is sent to the four-in-one controller to adjust the phase current of the flat wire motor;

[0018] Simultaneously monitor the energy recovery status, and activate reverse torque control when the brake pedal opening is greater than 30%.

[0019] Step 4: Safety Redundancy Response

[0020] Real-time monitoring of the insulation resistance to ground of the high-voltage circuit; if the resistance is <500Ω / m, high-voltage interlock is triggered.

[0021] Within 0.5 seconds, the motor power is cut off and the system switches to the hydraulic emergency module;

[0022] The outriggers are retracted at a speed of 5 mm / s by driving the outrigger cylinders with a hand-cranked pump.

[0023] As a preferred embodiment of the dual closed-loop cooperative control method for a direct-drive electric chassis described in this invention, the specific operation of the speed loop control in step 2 includes:

[0024] First, a Hall sensor installed at the end of the motor rotor shaft collects the motor speed signal and rotor position in real time at a sampling frequency of 10 milliseconds. The speed signal is converted into a real-time speed value by a 17-bit absolute encoder and input to the speed loop. The speed loop compares the real-time speed value with a preset speed command, and the resulting first error signal is input to the proportional-integral controller, where the proportional coefficient is fixed at 0.8 and the integral coefficient is set at 0.05. The amplitude of the output signal after proportional-integral calculation is limited to ±15% of the rated torque of the motor.

[0025] Meanwhile, the torque loop receives dynamic current limit instructions from the battery management system. This limit is adaptively adjusted according to the real-time temperature of the lithium iron phosphate battery: when the battery temperature is in the range of -35℃ to -20℃, the current limit drops to 60% of the rated value at room temperature, and returns to 100% when the temperature is above 0℃. The torque loop compares the actual phase current sensor detection value with the dynamic current limit, and the resulting second error signal is processed by a fuzzy PID controller with a proportional band set to ±5 amperes and an integral time constant of 200 milliseconds.

[0026] Subsequently, the output signals of the speed loop and torque loop are superimposed with a weight of 7:3. The superimposed composite signal is then corrected by an incremental PID algorithm, where the proportional gain Kp = 1.2, the integral time Ti = 50 milliseconds, and the derivative time Td = 10 milliseconds. The corrected signal is then filtered by a Kalman filter to eliminate high-frequency interference, and finally a PWM control command with a duty cycle accuracy of 0.1% is generated. The entire calculation process is completed in a 32-bit dual-core processor and strictly controlled within a 50-millisecond cycle.

[0027] As a preferred embodiment of the dual closed-loop cooperative control method for a direct-drive electric chassis described in this invention, the specific operation of the torque loop control in step 2 includes:

[0028] The battery management system first monitors the temperature sensor data of the lithium iron phosphate battery in real time, and dynamically adjusts the current limit according to the battery temperature. When the temperature is in the range of -35℃ to -20℃, the current limit is dynamically adjusted to 60% of the rated value at room temperature. When the temperature rises to the range of -20℃ to 0℃, it is adjusted to 80%. When the temperature is above 0℃, it returns to 100% of the rated value. This dynamic limit is sent to the torque ring controller every 50 milliseconds via the CAN bus.

[0029] After receiving the current limit command, the torque loop collects the actual phase current values ​​of the three-phase windings of the motor through the Hall current sensor, and takes the maximum absolute value of the three-phase current as the feedback signal. The difference between the feedback current and the dynamic current limit is input to the fuzzy PID controller, which divides the control rules according to the temperature difference: if the battery temperature is below -20℃, the proportional gain Kp increases by 20% and the integral time is shortened to 150 milliseconds; if the temperature difference exceeds 5℃, the anti-saturation integral algorithm is activated to prevent overshoot.

[0030] The torque correction signal output by the fuzzy PID controller is superimposed with the speed loop output signal using a 7:3 weighting. The resulting composite signal enters a Kalman filter. The filter adopts a five-state variable model, which includes current noise, sampling delay, and temperature drift. Its process noise covariance matrix Q is set as a diagonal matrix [0.01, 0.01, 0.005, 0.005, 0.001]. The measurement noise covariance R = 0.1. After filtering, a smooth command signal with a high-frequency interference attenuation rate ≥ 40dB is output.

[0031] The final output signal is directly written to the PWM register through the DMA channel of the 32-bit processor, with a duty cycle resolution accurate to 0.1%, ensuring that the system efficiency fluctuation does not exceed ±3% under low battery conditions.

[0032] As a preferred embodiment of the dual closed-loop cooperative control method for a direct-drive electric chassis described in this invention, the specific operation of energy recovery in step 3 includes:

[0033] When the brake pedal opening sensor detects that the opening value exceeds 30%, the vehicle controller immediately sends a mode switching command to the four-in-one controller, switching the flat wire motor from motor mode to generator mode within 10 milliseconds; at this time, the regenerative AC power generated by the motor's three-phase windings is rectified by the freewheeling diode connected in parallel on the IGBT module, and the output pulsating DC power enters the input terminal of the bidirectional DC / DC converter.

[0034] The bidirectional DC / DC converter adopts a peak current control strategy, which collects the inductor current in real time through a high-frequency Hall sensor. When the instantaneous current value exceeds 25A, the duty cycle of the upper bridge arm MOSFET is immediately adjusted to linearly reduce it from 65% to 40%. At the same time, through closed-loop feedback of the output voltage, the output voltage of the converter is precisely stabilized within the range of 600V±5%, which is strictly matched with the nominal voltage of the lithium iron phosphate battery pack.

[0035] During energy recovery, the battery management system continuously monitors the DC bus power. When the instantaneous recovered power exceeds 25% of the motor's rated power of 120kW, i.e., 30kW, the power limiting algorithm is automatically triggered: the PWM duty cycle is reduced by 5% per millisecond until the power drops back to the safe threshold. If the high power recovery state lasts for more than 30 seconds, the power generation mode is forcibly exited and the air-cooled heat dissipation system is activated to prevent the power devices from overheating and being damaged.

[0036] When the recovered energy is finally input into the battery pack, the liquid cooling temperature control system monitors the temperature difference between individual cells simultaneously. If the temperature difference between the highest and lowest individual cells reaches 5°C, the liquid cooling pump is started to circulate the coolant at a flow rate of 3L / min. At the same time, the vehicle controller compares the actual motor speed with the preset value. When the speed deviation is greater than 50rpm for 50 milliseconds, the recovery process is immediately interrupted and the drive torque output is restored to ensure the vehicle's braking posture is stable.

[0037] As a preferred embodiment of the dual closed-loop cooperative control method for a direct-drive electric chassis described in this invention, the specific operation of low-temperature adaptation for safety redundancy response in step 4 includes:

[0038] When the battery temperature sensor detects that the temperature of the lithium iron phosphate battery is below -20℃, the battery management system immediately activates the pulse heating mode: controlling the main positive contactor and the main negative contactor to alternately turn on and off at a frequency of 10Hz, with each on-off cycle being 50 milliseconds of conduction and 50 milliseconds of deactivation. Joule heat is generated through the battery's internal resistance, causing the individual cells to heat up at a rate of 1.5℃ per minute. During this process, the temperature difference between individual cells is monitored in real time. If the temperature difference between the highest and lowest individual cells exceeds 5℃, the pulse heating is automatically paused and the liquid cooling circulation pump is started to run at a flow rate of 2L / min for 30 seconds to achieve temperature equalization.

[0039] Simultaneously, the vehicle controller sends a DC preheating command to the four-in-one controller, switching the three-phase windings of the flat wire motor to DC energization mode: the U-phase and V-phase windings are connected in parallel and then supplied with forward DC power, while the W-phase winding is connected with reverse DC power. The current value is strictly controlled at 15% of the motor's rated current of 200A, i.e., 30A, and the energization time is 180 seconds. During the preheating period, the winding temperature rise is monitored by the motor temperature sensor, and the motor automatically stops when the temperature reaches -5℃ or the 180-second time limit is reached.

[0040] During the coordinated operation of pulse heating and motor preheating, the battery management system collects the battery internal resistance value every 10 seconds. When the internal resistance drops to within 120% of the normal temperature reference value, the current limit is immediately released and the driving capability is restored. If the battery temperature is still below -10℃ after 300 seconds of continuous heating, the secondary protection mechanism is triggered: the high voltage output is cut off and the red alarm light on the instrument panel indicates "low temperature protection activated". Manual confirmation is required before restarting.

[0041] As a preferred embodiment of the dual closed-loop cooperative control method for a direct-drive electric chassis described in this invention, the specific operation of the emergency switching of the safety redundancy response in step 4 includes:

[0042] When the insulation monitoring module detects that the resistance to ground of the high-voltage circuit is less than 500Ω / m, the vehicle controller sends an interlock signal to the hydraulic bypass valve control circuit within 0.5 seconds. The bypass valve adopts an electromagnetic pilot-operated spool valve structure. Under normal conditions, the electromagnetic coil is energized to generate magnetic force to attract the pilot valve core, which pushes the main valve core to block the manual pump oil circuit, so that the hydraulic system maintains the oil supply state of the motor pump.

[0043] After the interlock signal is triggered, the electromagnetic coil is immediately de-energized. The pilot valve core returns to its original position in 50 milliseconds under the action of the return spring. The main valve core switches the oil circuit direction under the pressure difference of the hydraulic balance hole: connecting the manual pump outlet oil circuit with the rodless chamber of the outrigger cylinder, while closing the motor pump output oil circuit. At this time, the operator moves the hand pump lever. The lever fulcrum adopts a 1:8 stroke ratio design. When the operator applies a force of 147N, it can generate an output force of 1176N at the end of the lever, driving the plunger pump piston to complete the oil suction-oil pressure cycle.

[0044] With each rotation of the lever, the plunger pump discharges 12ml of hydraulic oil. The cylinder diameter is 32mm and the stroke is 15mm. The hydraulic oil enters the rodless chamber of the outrigger cylinder through the check valve, pushing the piston rod to retract. The cylinder's built-in displacement sensor provides real-time feedback on the retraction progress. When the piston rod displacement rate is detected to be lower than 5mm / s, the booster mode is automatically activated: the accumulator is activated at the plunger pump outlet to assist in oil supply, increasing the oil pressure from the normal 20MPa to the upper limit of 25MPa, ensuring that the single operation cycle time does not exceed 90 seconds to complete the retraction of all outriggers.

[0045] In an emergency, if the manual pump pressure exceeds 25MPa, the relief valve integrated on the valve block will immediately open to release pressure, with the pressure release flow rate set at 5L / min. At the same time, the mechanical locking mechanism will automatically engage when the guide post retracts 50mm, and lock it with hardened steel teeth to prevent accidental fall. This locking action is decoupled from the hydraulic system, and can provide physical protection even if there is an oil leak.

[0046] Secondly, the present invention provides a dual closed-loop power system for a direct-drive electric chassis, comprising,

[0047] The direct drive unit has a flat wire motor output shaft that is directly connected to the drive shaft via an H7 / g6 tolerance flange. The drive shaft is connected to the rear axle via a universal joint at a 1:1 speed ratio.

[0048] The control hardware unit features a dual-core controller, a built-in 32-bit processor, and a CAN bus interface.

[0049] Energy management unit, lithium iron phosphate battery, equipped with liquid cooling temperature control system;

[0050] The safety redundancy unit includes an insulation monitoring module, a hydraulic hand pump, and a mechanical outrigger locking mechanism.

[0051] As a preferred embodiment of the dual closed-loop power system for a direct-drive electric chassis according to the present invention, the specific structural implementation of the direct-drive transmission unit is as follows:

[0052] The motor stator core is made of 0.2mm thick 50WW350 silicon steel sheets laminated together. Hairpin-type flat copper wire windings are embedded in the stator slots. These windings undergo a three-stage impregnation process, and the slot fill factor is strictly controlled within 78% ± 1%. The phase-to-phase insulation uses a 0.25mm thick corona-resistant polyimide film to ensure that the winding temperature rise is ≤85K. The rotor assembly is composed of 16-pole Halbach array neodymium iron boron permanent magnets. Each permanent magnet is covered with a 0.5mm thick 316L stainless steel laser-welded sheath. The gap between the sheath and the magnet is filled with epoxy thermally conductive adhesive with a thermal conductivity of 1.2W / m·K, which reduces the rotor eddy current loss to 0.8% of the rated power.

[0053] The drive shaft is forged from 42CrMo alloy steel. The front end is rigidly connected to the motor output shaft via a flange with H7 / g6 tolerance fit. The flatness error of the flange mounting surface is ≤0.02mm, and the bolt preload torque is set to 120N·m±5%. The rear end of the drive shaft is connected to the rear axle input shaft via a universal joint. The universal joint fork head is made of 20CrMnTi carburized and quenched, with a surface hardness of HRC58-62. The shaft tube wall thickness is 6mm and is reinforced by internal high-pressure forming process. The overall dynamic balance level meets the G2.5 standard, and the imbalance does not exceed 15g·cm under the working condition of 3000rpm.

[0054] To suppress torque fluctuations, a torsional damper is installed in the middle of the drive shaft: the rubber bushing has a Shore hardness of 70HA, and the internal vulcanized bonded annular steel plate has a stiffness coefficient of 200N / mm radially and 500N / mm axially; the damper has an interference fit with the shaft tube of 0.05-0.08mm, and the overall torsional angular displacement after assembly is ≤0.15°; the final assembled transmission unit has a measured transmission efficiency of ≥97.5% and an unloaded noise of ≤65dB under a full load of 7350kg.

[0055] As a preferred embodiment of the dual closed-loop power system for a direct-drive electric chassis according to the present invention, the circuit design of the control hardware unit includes:

[0056] The power cable between the four-in-one controller and the flat-wire motor adopts a double-layer shielding structure. The inner layer is a tinned copper wire braided shielding layer with a coverage of ≥85%, and the outer layer is an aluminum-plastic composite film wrapped shielding layer. The two shielding layers are grounded at a single point through a 1kΩ resistor. The cable insulation medium is cross-linked polyethylene material with a withstand voltage rating of AC2500V. The core wire cross-sectional area is strictly matched to the peak current of the motor (400A), using 50mm² wires. 2 The cable uses multi-stranded copper conductors, with the total length controlled within 3 meters to reduce distributed inductance to ≤2μH; the signal control line uses twisted-pair shielded cable with a twist pitch of 20mm, and the two ends of the shielding layer are grounded through ferrite magnetic rings to ensure electromagnetic compatibility meets GB / T18655-2018 Class 3 level.

[0057] Each arm of the IGBT switch in the PWM drive module is connected in parallel with an RC snubber circuit. The resistors are non-inductive metal film resistors with a resistance of 10Ω±1%, and the capacitors are polypropylene film capacitors with a capacitance of 0.1μF±5%. The circuit layout follows the shortest path principle—the pin spacing between resistors and capacitors is ≤5mm, and the total trace length of the snubber circuit is ≤30mm, effectively suppressing the switching spike voltage to within 15% of the DC bus voltage. The output stage of the drive optocoupler adds a totem pole buffer circuit, using 2SC1623 and 2SA1015 transistors, compressing the rise / fall time to within 100 nanoseconds.

[0058] The processor cooling system consists of a 3mm thick copper substrate and 6mm diameter sintered heat pipes. The evaporation section of the heat pipes is bonded to the processor chip surface with 0.1mm thick indium foil solder, and the condensation section extends to the aluminum heat sink fins with a fin spacing of 2mm. The surface of the heat sink fins is coated with a thermally conductive ceramic coating with a thickness of 50μm and a thermal conductivity of 3.5W / m·K. Forced air cooling uses a 24V axial fan with an airflow of 12CFM. Under full load conditions at an ambient temperature of 65℃, the measured temperature difference between the processor junction temperature and the copper substrate is ≤15℃, and the temperature difference between the copper substrate and the heat sink fins is ≤10℃. The overall temperature rise is strictly controlled within the range of 40℃.

[0059] As a preferred embodiment of the dual closed-loop power system for a direct-drive electric chassis according to the present invention, the mechanical structure of the safety redundancy unit includes:

[0060] The piston rod of the outrigger cylinder integrates a mechanical locking mechanism, which consists of a hardened 42CrMo alloy steel rack and a spring-loaded pawl. When the guide post rises to 50mm from the fully retracted position, the trigger cam fixed to the inner wall of the cylinder pushes the pawl shaft, causing the pawl to engage with the 5th tooth groove of the rack in a 0.5-second response time. The tooth groove spacing is 10mm, the tooth profile angle is 60°, and the contact stress on the tooth surface after locking is ≤800MPa, which can withstand an impact load of 1.5 times the vehicle weight of 7350kg. The pawl shaft is equipped with redundant return springs, with two springs arranged in parallel and each with a preload of 15N, ensuring stable engagement even under vibration.

[0061] The hand-cranked pump is equipped with a two-way hydraulic lock in the inlet and outlet oil circuits. The valve adopts a cone valve sealing structure with a 90° cone angle and hard chrome plating. The sealing pair matching accuracy reaches IT6 level. Under the rated pressure of 25MPa, the pressure holding leakage is <5ml / min by controlling the gap between the valve core and the valve seat to ≤3μm. The hydraulic lock control oil circuit is equipped with a piston with a pilot ratio of 1:4. When the hand-cranked pump stops operating, the system pressure drives the piston to close the cone valve within 50ms. At the same time, the accumulator maintains a replenishment oil pressure ≥2MPa to compensate for micro-leakage.

[0062] The emergency button adopts a dual-contact redundancy design: the main contact is made of silver tin oxide material with a contact pressure of 8N, and is connected in series with the main contactor coil circuit; the auxiliary contact is made of gold-nickel alloy with a contact pressure of 5N, and directly controls the high-voltage relay to disconnect the circuit; the physical isolation distance between the two contacts is ≥5mm, and they are linked by an independent transmission rod. When the operator applies a 30N pressing force, the time difference between the synchronous action of the two contacts is ≤10ms; the button reset mechanism adopts a double torsion spring design with a torque coefficient of 0.8N·mm / °, and the contact opening gap during the reset stroke is >3mm, which meets the GB14048.5 electrical isolation standard.

[0063] Thirdly, the present invention provides a computer device including a memory and a processor, wherein the memory stores a computer program, wherein when the computer program is executed by the processor, it implements any step of the dual closed-loop cooperative control method for a direct-drive electric chassis as described in the first aspect of the present invention.

[0064] Fourthly, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein: when the computer program is executed by a processor, it implements any step of the dual closed-loop cooperative control method for a direct-drive electric chassis as described in the first aspect of the present invention.

[0065] The beneficial effects of this invention are:

[0066] This invention achieves a breakthrough in the field of electric special vehicles for airports through the deep integration of a direct-drive powertrain and a dual-closed-loop collaborative control system. The most significant benefit lies in the substantial improvement in adaptability to extreme environments: the torque loop control mechanism, based on the dynamic adjustment of current limits for lithium iron phosphate battery temperature, combined with a collaborative strategy of pulse heating and DC preheating of the motor, reduces the cold start time of the entire system at -35℃ to 180 seconds, and lowers preheating energy consumption to 1.5% of the total power (compared to 8% for traditional PTC heating); simultaneously, the dual-closed-loop controller integrates speed and torque error signals with a 7:3 weighting, achieving a PWM command accuracy of 0.1% after Kalman filtering, and controlling torque output fluctuation within ±3% at -20℃, completely solving the industry-wide problem of ±10% in traditional single-closed-loop systems, ensuring stable docking of passenger boarding stairs on icy roads and in strong winds.

[0067] In terms of energy efficiency optimization, the innovatively designed energy recovery safety chain brings multiple benefits: the 1:1 transmission structure of the flat wire motor direct drive rear axle eliminates reducer losses, increasing transmission efficiency to 97.5%; the bidirectional DC / DC converter achieves a stable output of 600V±5% with peak current control, and with the gradient load reduction strategy of 25% power limit, the regenerative braking energy recovery efficiency can be stably reached 20%, thereby increasing the single vehicle's driving range to 226km; more importantly, the recovery process is protected by real-time speed deviation monitoring (50rpm / 50ms threshold) and liquid cooling temperature control system (5℃ temperature difference trigger), eliminating the risk of attitude instability caused by regenerative braking. The measured displacement deviation of the docking platform is ≤2mm, meeting the stringent requirements of the Civil Aviation AHM920 standard for aircraft safety distance.

[0068] The third core benefit is the innovation of the safety redundancy mechanism: within 0.5 seconds of high-voltage interlock triggering, a triple electromechanical-hydraulic protection response is completed—when the insulation monitoring module detects a leakage resistance of 500Ω / m, three operations are executed simultaneously: 1) The dual-contact emergency button cuts off the main circuit, with a contact action time difference of ≤10ms; 2) The hydraulic bypass valve is de-energized and switches the oil circuit, and the mechanical locking mechanism automatically engages when the guide column retracts 50mm, withstanding an impact load of 11 tons; 3) The hand-cranked pump achieves an output force of 1176N through a 1:8 leverage ratio, driving the outrigger to retract at a speed of 5mm / s, with the entire process taking less than 90 seconds. This is 4 times more efficient than the manual valve operation described in the comparison document, and through the 3μm-level sealing of the bidirectional hydraulic lock (leakage <5ml / min) and the accumulator pressure replenishment mechanism, the risk of outrigger falling due to hydraulic failure is completely eliminated. Attached Figure Description

[0069] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0070] Figure 1 This is a flowchart of a dual-closed-loop collaborative control method for a direct-drive electric chassis in Example 1.

[0071] Figure 2 This is a block diagram of the dual closed-loop power system of the direct-drive electric chassis in Example 1. Detailed Implementation

[0072] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0073] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0074] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0075] Example 1, referring to Figure 1 This is the first embodiment of the present invention, which provides a dual closed-loop cooperative control method for a direct-drive electric chassis, comprising the following steps:

[0076] Step 1: Real-time data acquisition

[0077] The motor speed signal is acquired by a 17-bit absolute encoder, and the motor phase current signal is acquired by a current sensor.

[0078] The battery management unit (BMS) collects real-time temperature and remaining state of charge (SOC) data of the lithium iron phosphate battery.

[0079] Step 2: Dual-loop collaborative computing

[0080] The speed signal and the preset speed value are input into the speed loop to generate the first error signal, and the phase current signal and the dynamic current limit provided by the BMS are input into the torque loop to generate the second error signal.

[0081] A 32-bit dual-core processor is used to superimpose the two error signals with a 7:3 weight, and then outputs PWM control commands through an incremental PID algorithm.

[0082] The calculation cycle is strictly controlled within 50ms;

[0083] The specific operations of speed loop control in step 2 include:

[0084] First, a Hall sensor installed at the end of the motor rotor shaft collects the motor speed signal and rotor position in real time at a sampling frequency of 10 milliseconds. The speed signal is converted into a real-time speed value by a 17-bit absolute encoder and input to the speed loop. The speed loop compares the real-time speed value with a preset speed command, and the resulting first error signal is input to the proportional-integral controller, where the proportional coefficient is fixed at 0.8 and the integral coefficient is set at 0.05. The amplitude of the output signal after proportional-integral calculation is limited to ±15% of the rated torque of the motor.

[0085] Meanwhile, the torque loop receives dynamic current limit instructions from the battery management system. This limit is adaptively adjusted according to the real-time temperature of the lithium iron phosphate battery: when the battery temperature is in the range of -35℃ to -20℃, the current limit drops to 60% of the rated value at room temperature, and returns to 100% when the temperature is above 0℃. The torque loop compares the actual phase current sensor detection value with the dynamic current limit, and the resulting second error signal is processed by a fuzzy PID controller with a proportional band set to ±5 amperes and an integral time constant of 200 milliseconds.

[0086] Subsequently, the output signals of the speed loop and torque loop are superimposed with a weight of 7:3. The superimposed composite signal is then corrected by an incremental PID algorithm, where the proportional gain Kp = 1.2, the integral time Ti = 50 milliseconds, and the derivative time Td = 10 milliseconds. The corrected signal is then filtered by a Kalman filter to eliminate high-frequency interference, and finally a PWM control command with a duty cycle accuracy of 0.1% is generated. The entire calculation process is completed in a 32-bit dual-core processor and strictly controlled within a 50-millisecond cycle.

[0087] The specific operations of torque loop control in step 2 include:

[0088] The battery management system first monitors the temperature sensor data of the lithium iron phosphate battery in real time, and dynamically adjusts the current limit according to the battery temperature. When the temperature is in the range of -35℃ to -20℃, the current limit is dynamically adjusted to 60% of the rated value at room temperature. When the temperature rises to the range of -20℃ to 0℃, it is adjusted to 80%. When the temperature is above 0℃, it returns to 100% of the rated value. This dynamic limit is sent to the torque ring controller every 50 milliseconds via the CAN bus.

[0089] After receiving the current limit command, the torque loop collects the actual phase current values ​​of the three-phase windings of the motor through the Hall current sensor, and takes the maximum absolute value of the three-phase current as the feedback signal. The difference between the feedback current and the dynamic current limit is input to the fuzzy PID controller, which divides the control rules according to the temperature difference: if the battery temperature is below -20℃, the proportional gain Kp increases by 20% and the integral time is shortened to 150 milliseconds; if the temperature difference exceeds 5℃, the anti-saturation integral algorithm is activated to prevent overshoot.

[0090] The torque correction signal output by the fuzzy PID controller is superimposed with the speed loop output signal using a 7:3 weighting. The resulting composite signal enters a Kalman filter. The filter adopts a five-state variable model, which includes current noise, sampling delay, and temperature drift. Its process noise covariance matrix Q is set as a diagonal matrix [0.01, 0.01, 0.005, 0.005, 0.001]. The measurement noise covariance R = 0.1. After filtering, a smooth command signal with a high-frequency interference attenuation rate ≥ 40dB is output.

[0091] The final output signal is directly written to the PWM register through the DMA channel of the 32-bit processor, with a duty cycle resolution accurate to 0.1%, ensuring that the system efficiency fluctuation does not exceed ±3% under low battery conditions.

[0092] Step 3: Command Execution and Feedback

[0093] The PWM command is sent to the four-in-one controller to adjust the phase current of the flat wire motor;

[0094] Simultaneously monitor the energy recovery status, and activate reverse torque control when the brake pedal opening is greater than 30%.

[0095] The specific operations for energy recovery in step 3 include:

[0096] When the brake pedal opening sensor detects that the opening value exceeds 30%, the vehicle controller immediately sends a mode switching command to the four-in-one controller, switching the flat wire motor from motor mode to generator mode within 10 milliseconds; at this time, the regenerative AC power generated by the motor's three-phase windings is rectified by the freewheeling diode connected in parallel on the IGBT module, and the output pulsating DC power enters the input terminal of the bidirectional DC / DC converter.

[0097] The bidirectional DC / DC converter adopts a peak current control strategy, which collects the inductor current in real time through a high-frequency Hall sensor. When the instantaneous current value exceeds 25A, the duty cycle of the upper bridge arm MOSFET is immediately adjusted to linearly reduce it from 65% to 40%. At the same time, through closed-loop feedback of the output voltage, the output voltage of the converter is precisely stabilized within the range of 600V±5%, which is strictly matched with the nominal voltage of the lithium iron phosphate battery pack.

[0098] During energy recovery, the battery management system continuously monitors the DC bus power. When the instantaneous recovered power exceeds 25% of the motor's rated power of 120kW, i.e., 30kW, the power limiting algorithm is automatically triggered: the PWM duty cycle is reduced by 5% per millisecond until the power drops back to the safe threshold. If the high power recovery state lasts for more than 30 seconds, the power generation mode is forcibly exited and the air-cooled heat dissipation system is activated to prevent the power devices from overheating and being damaged.

[0099] When the recovered energy is finally input into the battery pack, the liquid cooling temperature control system monitors the temperature difference between individual cells simultaneously. If the temperature difference between the highest and lowest individual cells reaches 5°C, the liquid cooling pump is started to circulate the coolant at a flow rate of 3L / min. At the same time, the vehicle controller compares the actual motor speed with the preset value. When the speed deviation is greater than 50rpm for 50 milliseconds, the recovery process is immediately interrupted and the drive torque output is restored to ensure the vehicle's braking posture is stable.

[0100] Step 4: Safety Redundancy Response

[0101] Real-time monitoring of the insulation resistance to ground of the high-voltage circuit; if the resistance is <500Ω / m, high-voltage interlock is triggered.

[0102] Within 0.5 seconds, the motor power is cut off and the system switches to the hydraulic emergency module;

[0103] The outriggers are retracted at a speed of 5 mm / s by driving the outrigger cylinders with a hand-cranked pump.

[0104] The specific operations for low-temperature adaptation of the safety redundancy response in step 4 include:

[0105] When the battery temperature sensor detects that the temperature of the lithium iron phosphate battery is below -20℃, the battery management system immediately activates the pulse heating mode: controlling the main positive contactor and the main negative contactor to alternately turn on and off at a frequency of 10Hz, with each on-off cycle being 50 milliseconds of conduction and 50 milliseconds of deactivation. Joule heat is generated through the battery's internal resistance, causing the individual cells to heat up at a rate of 1.5℃ per minute. During this process, the temperature difference between individual cells is monitored in real time. If the temperature difference between the highest and lowest individual cells exceeds 5℃, the pulse heating is automatically paused and the liquid cooling circulation pump is started to run at a flow rate of 2L / min for 30 seconds to achieve temperature equalization.

[0106] Simultaneously, the vehicle controller sends a DC preheating command to the four-in-one controller, switching the three-phase windings of the flat wire motor to DC energization mode: the U-phase and V-phase windings are connected in parallel and then supplied with forward DC power, while the W-phase winding is connected with reverse DC power. The current value is strictly controlled at 15% of the motor's rated current of 200A, i.e., 30A, and the energization time is 180 seconds. During the preheating period, the winding temperature rise is monitored by the motor temperature sensor, and the motor automatically stops when the temperature reaches -5℃ or the 180-second time limit is reached.

[0107] During the coordinated operation of pulse heating and motor preheating, the battery management system collects the battery internal resistance value every 10 seconds. When the internal resistance drops to within 120% of the normal temperature reference value, the current limit is immediately released and the driving capability is restored. If the battery temperature is still below -10℃ after 300 seconds of continuous heating, the secondary protection mechanism is triggered: the high voltage output is cut off and the red alarm light on the instrument panel indicates "low temperature protection activated". Manual confirmation is required before restarting.

[0108] The specific procedures for emergency switching of the safety redundancy response in step 4 include:

[0109] When the insulation monitoring module detects that the resistance to ground of the high-voltage circuit is less than 500Ω / m, the vehicle controller sends an interlock signal to the hydraulic bypass valve control circuit within 0.5 seconds. The bypass valve adopts an electromagnetic pilot-operated spool valve structure. Under normal conditions, the electromagnetic coil is energized to generate magnetic force to attract the pilot valve core, which pushes the main valve core to block the manual pump oil circuit, so that the hydraulic system maintains the oil supply state of the motor pump.

[0110] After the interlock signal is triggered, the electromagnetic coil is immediately de-energized. The pilot valve core returns to its original position in 50 milliseconds under the action of the return spring. The main valve core switches the oil circuit direction under the pressure difference of the hydraulic balance hole: connecting the manual pump outlet oil circuit with the rodless chamber of the outrigger cylinder, while closing the motor pump output oil circuit. At this time, the operator moves the hand pump lever. The lever fulcrum adopts a 1:8 stroke ratio design. When the operator applies a force of 147N, it can generate an output force of 1176N at the end of the lever, driving the plunger pump piston to complete the oil suction-oil pressure cycle.

[0111] With each rotation of the lever, the plunger pump discharges 12ml of hydraulic oil. The cylinder diameter is 32mm and the stroke is 15mm. The hydraulic oil enters the rodless chamber of the outrigger cylinder through the check valve, pushing the piston rod to retract. The cylinder's built-in displacement sensor provides real-time feedback on the retraction progress. When the piston rod displacement rate is detected to be lower than 5mm / s, the booster mode is automatically activated: the accumulator is activated at the plunger pump outlet to assist in oil supply, increasing the oil pressure from the normal 20MPa to the upper limit of 25MPa, ensuring that the single operation cycle time does not exceed 90 seconds to complete the retraction of all outriggers.

[0112] In an emergency, if the manual pump pressure exceeds 25MPa, the relief valve integrated on the valve block will immediately open to release pressure, with the pressure release flow rate set at 5L / min. At the same time, the mechanical locking mechanism will automatically engage when the guide post retracts 50mm, and lock it with hardened steel teeth to prevent accidental fall. This locking action is decoupled from the hydraulic system, and can provide physical protection even if there is an oil leak.

[0113] Example 2, refer to Figure 2 This is a second embodiment of the present invention, which provides a dual closed-loop power system for a direct-drive electric chassis, comprising:

[0114] The direct drive unit has a flat wire motor output shaft that is directly connected to the drive shaft via an H7 / g6 tolerance flange. The drive shaft is connected to the rear axle via a universal joint at a 1:1 speed ratio.

[0115] The control hardware unit features a dual-core controller, a built-in 32-bit processor, and a CAN bus interface.

[0116] Energy management unit, lithium iron phosphate battery, equipped with liquid cooling temperature control system;

[0117] The safety redundancy unit includes an insulation monitoring module, a hydraulic hand pump, and a mechanical outrigger locking mechanism.

[0118] The specific structural implementation of the direct drive transmission unit is as follows:

[0119] The motor stator core is made of 0.2mm thick 50WW350 silicon steel sheets laminated together. Hairpin-type flat copper wire windings are embedded in the stator slots. These windings undergo a three-stage impregnation process, and the slot fill factor is strictly controlled within 78% ± 1%. The phase-to-phase insulation uses a 0.25mm thick corona-resistant polyimide film to ensure that the winding temperature rise is ≤85K. The rotor assembly is composed of 16-pole Halbach array neodymium iron boron permanent magnets. Each permanent magnet is covered with a 0.5mm thick 316L stainless steel laser-welded sheath. The gap between the sheath and the magnet is filled with epoxy thermally conductive adhesive with a thermal conductivity of 1.2W / m·K, which reduces the rotor eddy current loss to 0.8% of the rated power.

[0120] The drive shaft is forged from 42CrMo alloy steel. The front end is rigidly connected to the motor output shaft via a flange with H7 / g6 tolerance fit. The flatness error of the flange mounting surface is ≤0.02mm, and the bolt preload torque is set to 120N·m±5%. The rear end of the drive shaft is connected to the rear axle input shaft via a universal joint. The universal joint fork head is made of 20CrMnTi carburized and quenched, with a surface hardness of HRC58-62. The shaft tube wall thickness is 6mm and is reinforced by internal high-pressure forming process. The overall dynamic balance level meets the G2.5 standard, and the imbalance does not exceed 15g·cm under the working condition of 3000rpm.

[0121] To suppress torque fluctuations, a torsional damper is installed in the middle of the drive shaft: the rubber bushing has a Shore hardness of 70HA, and the internal vulcanized bonded annular steel plate has a stiffness coefficient of 200N / mm radially and 500N / mm axially; the damper has an interference fit with the shaft tube of 0.05-0.08mm, and the overall torsional angular displacement after assembly is ≤0.15°; the final assembled transmission unit has a measured transmission efficiency of ≥97.5% and an unloaded noise of ≤65dB under a full load of 7350kg.

[0122] The circuit design of the control hardware unit includes:

[0123] The power cable between the four-in-one controller and the flat-wire motor adopts a double-layer shielding structure. The inner layer is a tinned copper wire braided shielding layer with a coverage of ≥85%, and the outer layer is an aluminum-plastic composite film wrapped shielding layer. The two shielding layers are grounded at a single point through a 1kΩ resistor. The cable insulation medium is cross-linked polyethylene material with a withstand voltage rating of AC2500V. The core wire cross-sectional area is strictly matched to the peak current of the motor (400A), using 50mm² wires. 2 The cable uses multi-stranded copper conductors, with the total length controlled within 3 meters to reduce distributed inductance to ≤2μH; the signal control line uses twisted-pair shielded cable with a twist pitch of 20mm, and the two ends of the shielding layer are grounded through ferrite magnetic rings to ensure electromagnetic compatibility meets GB / T18655-2018 Class 3 level.

[0124] Each arm of the IGBT switch in the PWM drive module is connected in parallel with an RC snubber circuit. The resistors are non-inductive metal film resistors with a resistance of 10Ω±1%, and the capacitors are polypropylene film capacitors with a capacitance of 0.1μF±5%. The circuit layout follows the shortest path principle—the pin spacing between resistors and capacitors is ≤5mm, and the total trace length of the snubber circuit is ≤30mm, effectively suppressing the switching spike voltage to within 15% of the DC bus voltage. The output stage of the drive optocoupler adds a totem pole buffer circuit, using 2SC1623 and 2SA1015 transistors, compressing the rise / fall time to within 100 nanoseconds.

[0125] The processor cooling system consists of a 3mm thick copper substrate and 6mm diameter sintered heat pipes. The evaporation section of the heat pipes is bonded to the processor chip surface with 0.1mm thick indium foil solder, and the condensation section extends to the aluminum heat sink fins with a fin spacing of 2mm. The surface of the heat sink fins is coated with a thermally conductive ceramic coating with a thickness of 50μm and a thermal conductivity of 3.5W / m·K. Forced air cooling uses a 24V axial fan with an airflow of 12CFM. Under full load conditions at an ambient temperature of 65℃, the measured temperature difference between the processor junction temperature and the copper substrate is ≤15℃, and the temperature difference between the copper substrate and the heat sink fins is ≤10℃. The overall temperature rise is strictly controlled within the range of 40℃.

[0126] The mechanical structure of the safety redundancy unit includes:

[0127] The piston rod of the outrigger cylinder integrates a mechanical locking mechanism, which consists of a hardened 42CrMo alloy steel rack and a spring-loaded pawl. When the guide post rises to 50mm from the fully retracted position, the trigger cam fixed to the inner wall of the cylinder pushes the pawl shaft, causing the pawl to engage with the 5th tooth groove of the rack in a 0.5-second response time. The tooth groove spacing is 10mm, the tooth profile angle is 60°, and the contact stress on the tooth surface after locking is ≤800MPa, which can withstand an impact load of 1.5 times the vehicle weight of 7350kg. The pawl shaft is equipped with redundant return springs, with two springs arranged in parallel and each with a preload of 15N, ensuring stable engagement even under vibration.

[0128] The hand-cranked pump is equipped with a two-way hydraulic lock in the inlet and outlet oil circuits. The valve adopts a cone valve sealing structure with a 90° cone angle and hard chrome plating. The sealing pair matching accuracy reaches IT6 level. Under the rated pressure of 25MPa, the pressure holding leakage is <5ml / min by controlling the gap between the valve core and the valve seat to ≤3μm. The hydraulic lock control oil circuit is equipped with a piston with a pilot ratio of 1:4. When the hand-cranked pump stops operating, the system pressure drives the piston to close the cone valve within 50ms. At the same time, the accumulator maintains a replenishment oil pressure ≥2MPa to compensate for micro-leakage.

[0129] The emergency button adopts a dual-contact redundancy design: the main contact is made of silver tin oxide material with a contact pressure of 8N, and is connected in series with the main contactor coil circuit; the auxiliary contact is made of gold-nickel alloy with a contact pressure of 5N, and directly controls the high-voltage relay to disconnect the circuit; the physical isolation distance between the two contacts is ≥5mm, and they are linked by an independent transmission rod. When the operator applies a 30N pressing force, the time difference between the synchronous action of the two contacts is ≤10ms; the button reset mechanism adopts a double torsion spring design with a torque coefficient of 0.8N·mm / °, and the contact opening gap during the reset stroke is >3mm, which meets the GB14048.5 electrical isolation standard.

[0130] The workflow of the AI ​​model training parameter dynamic optimization system in this embodiment begins with the real-time data acquisition stage: the speed signal is captured by a 17-bit absolute encoder installed at the end of the motor rotor shaft at a sampling period of 10 milliseconds, while the Hall current sensor synchronously acquires the phase current value of the three-phase winding. The signal is filtered by a second-order Butterworth filter (cutoff frequency 1kHz) to eliminate high-frequency noise. The battery management unit (BMS) acquires the real-time temperature of the lithium iron phosphate battery (PT1000 sensor accuracy ±0.5℃) and the remaining power (coulomb measurement error <3%) in parallel. The three data are uploaded to the dual-core processor via the CAN bus at a period of 50 milliseconds. After entering the dual-loop collaborative calculation stage, the speed loop compares the filtered actual speed with the preset speed command (from the vehicle control unit VCU), and the generated first error signal is input to the proportional-integral controller (Kp=0.8, Ki=0.05), with the output amplitude limited to ±15% of the rated torque. The torque loop receives the current limit dynamically adjusted by the BMS (limited to 60% of the normal temperature value at -35℃), and generates a second error signal by combining it with the phase current feedback. This signal is then processed by a fuzzy PID controller (proportional band ±5A, integral time 200ms). The two error signals are superimposed with a 7:3 weight, corrected by an incremental PID algorithm (Kp=1.2, Ti=50ms, Td=10ms), and then filtered by a Kalman filter (Q matrix diag[0.01,0.01,0.005], R=0.1) to eliminate interference. Finally, a PWM command with a duty cycle accuracy of 0.1% is output, and the entire calculation cycle is strictly compressed within 50 milliseconds. During the instruction execution phase, the four-in-one controller parses the PWM instruction into an IGBT drive signal (switching frequency 10kHz, dead time 2μs) to drive the flat wire motor. If the brake pedal opening sensor detects an opening greater than 30%, the reverse torque control mode is immediately activated. The regenerated current is rectified by a full-bridge rectifier and stabilized to 600V±5% by a bidirectional DC / DC converter, and the upper limit of the regenerated power is locked at 30kW (25% of the rated power). During the safety redundancy response phase, the insulation resistance of the high-voltage circuit is monitored in real time. When the detected value is less than 500Ω / m, a three-level linkage is triggered within 0.5 seconds: 1) The double-contact emergency button cuts off the main contactor; 2) The hydraulic bypass valve is de-energized and switches the oil circuit; 3) The hand-cranked pump drives the outrigger to retract at a speed of 5mm / s via a 1:8 lever mechanism (outputting 12ml of hydraulic oil per revolution), while the mechanical locking mechanism automatically engages and locks when the guide post retracts 50mm. Detailed Implementation

[0132] Hardware System Setup: A data acquisition sensor assembly is installed on the direct-drive electric chassis. A Heidenhain ECN413 17-bit absolute encoder is configured at the motor shaft end to acquire speed signals in real time and output square wave pulses. Each phase of the three-phase winding is equipped with a LEM HAH3DR-SB closed-loop Hall current sensor with a range covering ±500A and a measurement error controlled within ±0.5%. A four-wire PT1000 platinum resistance temperature sensor is embedded inside the battery pack, with eight monitoring points evenly distributed along the battery cells. Temperature data is acquired through an ISO60751 Class A precision circuit. All sensor signals are pre-processed by a second-order Butterworth filter (cutoff frequency 1kHz) and then connected to a dual-core controller via shielded twisted-pair cables. This controller is equipped with a 200MHz main frequency processor and a dual-channel CAN bus interface, with a fixed data transmission cycle of 50 milliseconds.

[0133] Control algorithm execution:

[0134] Dual closed-loop collaborative computing process:

[0135] After receiving the speed command, the speed loop compares the encoder feedback value with the target value, and the resulting error signal is input to the proportional-integral controller for calculation. The proportional coefficient is fixed at 0.8, the integral coefficient is 0.05, and the output signal amplitude is limited to ±15% of the rated torque. Simultaneously, the torque loop receives the dynamic current limit (set to 60% of the normal temperature value at -35℃) from the battery management system and compares it with the maximum phase current detected by the Hall sensor. The error signal is processed by a fuzzy PID controller with a proportional band set to ±5 amps and an integral time constant of 200 milliseconds. The output signals of the two control loops are superimposed with a 7:3 weighting. The superposition result is corrected by an incremental PID algorithm (proportional gain 1.2, integral time 50 milliseconds, derivative time 10 milliseconds), and then passed through a Kalman filter to eliminate high-frequency interference, finally generating a PWM command with a duty cycle accuracy of 0.1%.

[0136] Energy recovery triggering mechanism:

[0137] A brake pedal opening sensor monitors the pedal position in real time. When the opening exceeds a 30% threshold, the controller immediately switches the motor to generator mode. The regenerative current is rectified into pulsating DC by the freewheeling diode of the IGBT module. A peak current control strategy is then applied via a bidirectional DC / DC converter: when the instantaneous inductor current exceeds 25 amps, the MOSFET duty cycle is automatically adjusted to linearly decrease from 65% to 40%, stabilizing the output voltage within 600V ± 5%. The maximum regenerative power is locked at 30 kW (25% of the motor's rated power). If the system continues to operate at overpower for more than 30 seconds, it automatically exits generator mode and activates the cooling fan.

[0138] Implementation of security redundancy response:

[0139] The high-voltage circuit insulation monitoring module uses the bridge method to measure the resistance to ground. When the detected value is below 500Ω / m, a three-level interlocking response is activated within 0.5 seconds.

[0140] 1. Electrical disconnection: The dual-contact emergency button operates synchronously, with the main contact cutting off the main contactor coil circuit and the auxiliary contact directly disconnecting the high-voltage relay. The contact action time difference is ≤10 milliseconds.

[0141] 2. Hydraulic switching: When the Bosch RE 16308 electromagnetic pilot valve is de-energized, the valve core switches the oil circuit direction under the action of the return spring, connecting the outlet of the hand pump with the rodless chamber of the outrigger cylinder;

[0142] 3. Mechanical Actuation: The operator cranks the hand pump lever (lever ratio 1:8, displacement 12 ml per revolution), driving hydraulic oil into the cylinder at a pressure of 20 MPa, and the piston rod retracts at a speed of 5 mm / s. When the guide post retracts to a position 50 mm from the end point, the pawl of the built-in mechanical locking mechanism automatically engages with the 5th tooth slot (10 mm pitch) of the 42CrMo alloy steel rack, achieving physical locking through tooth surface meshing.

[0143] Performance verification solution:

[0144] The system was started up in a -35°C environmental chamber. Upon detecting the low temperature, the battery management system immediately initiated pulse heating: the main contactor switched on and off at a frequency of 10 Hz (50 ms on / 50 ms off), while simultaneously applying 30 amps of DC current to the motor windings for preheating. After 182 seconds, the battery temperature rose to -5°C, and the system regained its driving capability. Under a full load of 7350 kg, the measured torque output fluctuation was ±2.8%, and the energy recovery efficiency reached 20.7%. In a safety test, with a manually set 500Ω / m insulation fault, the system completed the outrigger oil circuit switching within 0.48 seconds, the mechanical locking mechanism accurately engaged at a position of 49.7 mm, and the entire retraction process took 86.5 seconds. Certified by the China Special Equipment Inspection and Research Institute, the system meets all requirements of the IATA AHM913 standard.

[0145] Key implementation details

[0146] 1. Temperature adaptive control

[0147] The battery management system dynamically adjusts the current limit according to the temperature range: 60% of the rated current for -35℃ to -20℃, 80% for -20℃ to 0℃, and 100% for >0℃.

[0148] The motor preheating adopts a specific wiring mode: the U / V phase windings are connected in parallel to the positive pole, and the W phase is connected to the negative pole, forming a closed magnetic circuit to reduce eddy current losses.

[0149] 2. Hydraulic-mechanical linkage

[0150] Each rotation of the hand pump outputs 12 ml of hydraulic oil. Based on the outrigger cylinder volume, it takes 37.5 rotations to complete the full retraction (450 mm stroke).

[0151] The mechanical locking tooth trigger cam adopts an Archimedean spiral design to ensure precise engagement at a position of 50±0.5 mm.

[0152] 3. Fault protection levels

[0153] Primary protection: The insulation monitoring module scans the high-voltage circuit every 100 milliseconds;

[0154] Secondary protection: Physical isolation distance of double-contact buttons ≥ 5 mm, electrical clearance withstand voltage > 10 kV;

[0155] Ultimate protection: The rack material has a tensile strength of ≥1080 MPa and can withstand an impact load of 11 tons.

[0156] This implementation method has been successfully verified by Wuxi Ximei Special Vehicle Co., Ltd., and has been installed in the mass production of the WXQ5050DKTZ electric boarding ladder. It has accumulated 120,000 hours of operation without any safety failures, proving the industrial feasibility of the technical solution.

[0157] This embodiment also provides a computer device applicable to a dual-closed-loop cooperative control method for a direct-drive electric chassis, comprising: a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to implement the dual-closed-loop cooperative control method for a direct-drive electric chassis as proposed in the above embodiment.

[0158] The computer device can be a terminal, comprising a processor, memory, communication interface, display screen, and input devices connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, carrier networks, NFC (Near Field Communication), or other technologies. The display screen can be an LCD screen or an e-ink screen. The input devices can be a touch layer covering the display screen, buttons, a trackball, or a touchpad on the computer device's casing, or an external keyboard, touchpad, or mouse.

[0159] This embodiment also provides a storage medium storing a computer program, which, when executed by a processor, implements the dual-closed-loop cooperative control method for a direct-drive electric chassis as proposed in the above embodiments. The storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as Static Random Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read Only Memory (EPROM), Programmable Red-Only Memory (PROM), Read-Only Memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk.

[0160] In summary, this invention achieves a breakthrough in the field of electric special vehicles for airports through the deep integration of a direct-drive powertrain and dual closed-loop collaborative control. The most significant benefit lies in the substantial improvement in adaptability to extreme environments: the torque loop control mechanism based on the dynamic adjustment of current limits for lithium iron phosphate battery temperature, combined with a collaborative strategy of pulse heating and DC preheating of the motor, reduces the cold start time of the entire system at -35℃ to 180 seconds, and reduces preheating energy consumption to 1.5% of the total power (compared to 8% for traditional PTC heating); at the same time, the dual closed-loop controller integrates speed and torque error signals with a 7:3 weighting, and the PWM command accuracy after Kalman filtering reaches 0.1%, controlling torque output fluctuation within ±3% in an environment of -20℃, completely solving the industry problem of ±10% in traditional single closed-loop systems, and ensuring that passenger boarding stairs can still stably dock with the cabin doors on icy and snowy roads and in strong winds.

[0161] In terms of energy efficiency optimization, the innovatively designed energy recovery safety chain brings multiple benefits: the 1:1 transmission structure of the flat wire motor direct drive rear axle eliminates reducer losses, increasing transmission efficiency to 97.5%; the bidirectional DC / DC converter achieves a stable output of 600V±5% with peak current control, and with the gradient load reduction strategy of 25% power limit, the regenerative braking energy recovery efficiency can be stably reached 20%, thereby increasing the single vehicle's driving range to 226km; more importantly, the recovery process is protected by real-time speed deviation monitoring (50rpm / 50ms threshold) and liquid cooling temperature control system (5℃ temperature difference trigger), eliminating the risk of attitude instability caused by regenerative braking. The measured displacement deviation of the docking platform is ≤2mm, meeting the stringent requirements of the Civil Aviation AHM920 standard for aircraft safety distance.

[0162] The third core benefit is the innovation of the safety redundancy mechanism: within 0.5 seconds of high-voltage interlock triggering, a triple electromechanical-hydraulic protection response is completed—when the insulation monitoring module detects a leakage resistance of 500Ω / m, three operations are executed simultaneously: 1) The dual-contact emergency button cuts off the main circuit, with a contact action time difference of ≤10ms; 2) The hydraulic bypass valve is de-energized and switches the oil circuit, and the mechanical locking mechanism automatically engages when the guide column retracts 50mm, withstanding an impact load of 11 tons; 3) The hand-cranked pump achieves an output force of 1176N through a 1:8 leverage ratio, driving the outrigger to retract at a speed of 5mm / s, with the entire process taking less than 90 seconds. This is 4 times more efficient than the manual valve operation described in the comparison document, and through the 3μm-level sealing of the bidirectional hydraulic lock (leakage <5ml / min) and the accumulator pressure replenishment mechanism, the risk of outrigger falling due to hydraulic failure is completely eliminated.

[0163] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A dual-closed-loop cooperative control method for a direct-drive electric chassis, characterized in that, Includes the following steps: Step 1: Real-time data acquisition The motor speed signal is acquired by a 17-bit absolute encoder, and the motor phase current signal is acquired by a current sensor. The battery management unit (BMS) collects real-time temperature and remaining state of charge (SOC) data of the lithium iron phosphate battery. Step 2: Dual-loop collaborative computing The speed signal and the preset speed value are input into the speed loop to generate the first error signal, and the phase current signal and the dynamic current limit provided by the BMS are input into the torque loop to generate the second error signal. A 32-bit dual-core processor is used to superimpose the two error signals with a 7:3 weight, and then outputs PWM control commands through an incremental PID algorithm. The calculation cycle is strictly controlled within 50ms; Step 3: Command Execution and Feedback The PWM command is sent to the four-in-one controller to adjust the phase current of the flat wire motor; Simultaneously monitor the energy recovery status, and activate reverse torque control when the brake pedal opening is greater than 30%. Step 4: Safety Redundancy Response Real-time monitoring of the insulation resistance to ground of the high-voltage circuit; if the resistance is <500Ω / m, high-voltage interlock is triggered. Within 0.5 seconds, the motor power is cut off and the system switches to the hydraulic emergency module; The outrigger retracts at a speed of 5 mm / s by driving the outrigger cylinder with a hand-cranked pump. The specific operations of the speed loop control in step 2 include: First, a Hall sensor installed at the end of the motor rotor shaft collects the motor speed signal and the motor rotor position in real time at a sampling frequency of 10 milliseconds. The speed signal is converted into a real-time speed value by a 17-bit absolute encoder and input to the speed loop. The speed loop compares the real-time speed value with a preset speed command, and the resulting first error signal is input to the proportional-integral controller, where the proportional coefficient is fixed at 0.8 and the integral coefficient is set at 0.

05. The amplitude of the output signal after proportional-integral calculation is limited to ±15% of the rated torque of the motor. Simultaneously, the torque loop receives dynamic current limit commands from the battery management system. These commands are adaptively adjusted based on the real-time temperature of the lithium iron phosphate battery: when the battery temperature is between -35℃ and -20℃, the dynamic current limit drops to 60% of the rated value at room temperature, and returns to 100% when the temperature is above 0℃. The torque loop compares the actual phase current sensor readings with the dynamic current limit, and the resulting second error signal is processed by a fuzzy PID controller with a proportional band set to ±5 amperes and an integral time constant of 200 milliseconds. Subsequently, the output signals of the speed loop and torque loop are superimposed with a weight of 7:

3. The superimposed composite signal is then corrected by an incremental PID algorithm, where the proportional gain Kp = 1.2, the integral time Ti = 50 milliseconds, and the derivative time Td = 10 milliseconds. The corrected signal is then filtered by a Kalman filter to eliminate high-frequency interference, and finally a PWM control command with a duty cycle accuracy of 0.1% is generated. The entire calculation process is completed in a 32-bit dual-core processor and strictly controlled within a 50-millisecond cycle. The specific operations of torque loop control in step 2 also include: The battery management system first monitors the temperature sensor data of the lithium iron phosphate battery in real time. Based on the battery temperature, the dynamic current limit is dynamically adjusted to 60% of the rated value at room temperature when the temperature is in the range of -35℃ to -20℃, to 80% when the temperature rises to the range of -20℃ to 0℃, and to 100% of the rated value when the temperature is above 0℃. This dynamic current limit is sent to the torque ring controller every 50 milliseconds via the CAN bus. After receiving the dynamic current limit command, the torque loop collects the actual phase current values ​​of the three-phase windings of the motor through the Hall current sensor, and takes the maximum absolute value of the three-phase current as the feedback signal. The difference between the feedback current and the dynamic current limit is input to the fuzzy PID controller, which divides the control rules according to the temperature difference: if the battery temperature is below -20℃, the proportional gain Kp increases by 20% and the integral time is shortened to 150 milliseconds; if the temperature difference exceeds 5℃, the anti-saturation integral algorithm is activated to prevent overshoot. The torque correction signal output by the fuzzy PID controller is superimposed with the speed loop output signal using a 7:3 weighting. The resulting composite signal enters a Kalman filter. The filter adopts a five-state variable model, which includes current noise, sampling delay, and temperature drift. Its process noise covariance matrix Q is set as a diagonal matrix [0.01, 0.01, 0.005, 0.005, 0.001]. The measurement noise covariance R=0.

1. After filtering, a smooth command signal with a high-frequency interference attenuation rate ≥40dB is output. The final output signal is written directly to the PWM register through the DMA channel of the 32-bit processor, with a duty cycle resolution accurate to 0.1%, ensuring that the system efficiency fluctuation does not exceed ±3% under low battery conditions.

2. The dual closed-loop cooperative control method for a direct-drive electric chassis as described in claim 1, characterized in that: The specific operations for energy recovery in step 3 include: When the brake pedal opening sensor detects that the opening value exceeds 30%, the vehicle controller immediately sends a mode switching command to the four-in-one controller, switching the flat wire motor from motor mode to generator mode within 10 milliseconds; at this time, the regenerative AC power generated by the motor's three-phase windings is rectified by the freewheeling diode connected in parallel on the IGBT module, and the output pulsating DC power enters the input terminal of the bidirectional DC / DC converter. The bidirectional DC / DC converter employs a peak current control strategy, using a high-frequency Hall sensor to collect inductor current in real time. When the detected instantaneous current value exceeds 25A, the duty cycle of the upper bridge arm MOSFET is immediately adjusted to linearly decrease from 65% to 40%. Simultaneously, through closed-loop feedback of the output voltage, the converter's output voltage is precisely stabilized within a range of 600V±5%, which strictly matches the nominal voltage of the lithium iron phosphate battery pack. During energy recovery, the battery management system continuously monitors the DC bus power. When the instantaneous recovered power exceeds 25% of the motor's rated power of 120kW, i.e., 30kW, the power limiting algorithm is automatically triggered: the PWM duty cycle is reduced by 5% every millisecond until the power drops back to the safe threshold. If the high power recovery state lasts for more than 30 seconds, the power generation mode is forcibly exited and the air-cooled heat dissipation system is activated to prevent the power devices from overheating and being damaged. When the recovered energy is finally input into the battery pack, the liquid cooling temperature control system monitors the temperature difference between individual cells simultaneously. If the temperature difference between the highest and lowest individual cells reaches 5°C, the liquid cooling pump is started to circulate the coolant at a flow rate of 3L / min. At the same time, the vehicle controller compares the actual motor speed with the preset value. When the speed deviation is greater than 50rpm for 50 milliseconds, the recovery process is immediately interrupted and the drive torque output is restored to ensure the vehicle's braking posture is stable.

3. The dual closed-loop cooperative control method for a direct-drive electric chassis as described in claim 2, characterized in that: The specific operations for low-temperature adaptation of the safety redundancy response in step 4 include: When the battery temperature sensor detects that the temperature of the lithium iron phosphate battery is below -20℃, the battery management system immediately activates the pulse heating mode: controlling the main positive contactor and the main negative contactor to alternately turn on and off at a frequency of 10Hz, with each on-off cycle being 50 milliseconds of conduction and 50 milliseconds of deactivation. Joule heat is generated through the battery's internal resistance, causing the individual cells to heat up at a rate of 1.5℃ per minute. During this process, the temperature difference between individual cells is monitored in real time. If the temperature difference between the highest and lowest individual cells exceeds 5℃, the pulse heating is automatically paused and the liquid cooling circulation pump is started to run at a flow rate of 2L / min for 30 seconds to achieve temperature equalization. Simultaneously, the vehicle controller sends a DC preheating command to the four-in-one controller, switching the three-phase windings of the flat wire motor to DC energization mode: the U-phase and V-phase windings are connected in parallel and then supplied with forward DC power, while the W-phase winding is connected with reverse DC power. The current value is strictly controlled at 15% of the motor's rated current of 200A, i.e., 30A, and the energization time is 180 seconds. During the preheating period, the winding temperature rise is monitored by the motor temperature sensor, and the motor automatically stops when the temperature reaches -5℃ or the 180-second time limit is reached. During the coordinated operation of pulse heating and motor preheating, the battery management system collects the battery internal resistance value every 10 seconds. When the internal resistance drops to within 120% of the normal temperature reference value, the current limit is immediately released and the driving capability is restored. If the battery temperature is still below -10℃ after 300 seconds of continuous heating, the secondary protection mechanism is triggered: the high voltage output is cut off and the red alarm light on the instrument panel indicates "low temperature protection activated". Manual confirmation is required before restarting.

4. The dual closed-loop cooperative control method for a direct-drive electric chassis as described in claim 3, characterized in that: The specific operations for emergency switching of the security redundancy response in step 4 include: When the insulation monitoring module detects that the resistance to ground of the high-voltage circuit is less than 500Ω / m, the vehicle controller sends an interlock signal to the hydraulic bypass valve control circuit within 0.5 seconds. The bypass valve adopts an electromagnetic pilot-operated spool valve structure. Under normal conditions, the electromagnetic coil is energized to generate magnetic force to attract the pilot valve core, which pushes the main valve core to block the manual pump oil circuit, so that the hydraulic system maintains the oil supply state of the motor pump. After the interlock signal is triggered, the electromagnetic coil is immediately de-energized. The pilot valve core returns to its original position in 50 milliseconds under the action of the return spring. The main valve core switches the oil circuit direction under the pressure difference of the hydraulic balance hole: connecting the manual pump outlet oil circuit with the rodless chamber of the outrigger cylinder, while closing the motor pump output oil circuit. At this time, the operator moves the hand pump lever. The lever fulcrum adopts a 1:8 stroke ratio design. When the operator applies a force of 147N, it can generate an output force of 1176N at the end of the lever, driving the plunger pump piston to complete the oil suction-oil pressure cycle. With each rotation of the lever, the plunger pump discharges 12ml of hydraulic oil. The cylinder diameter is 32mm and the stroke is 15mm. The hydraulic oil enters the rodless chamber of the outrigger cylinder through the check valve, pushing the piston rod to retract. The cylinder's built-in displacement sensor provides real-time feedback on the retraction progress. When the piston rod displacement rate is detected to be lower than 5mm / s, the booster mode is automatically activated: the accumulator is activated at the plunger pump outlet to assist in oil supply, increasing the oil pressure from the normal 20MPa to the upper limit of 25MPa, ensuring that the single operation cycle time does not exceed 90 seconds to complete the retraction of all outriggers. In an emergency, if the manual pump pressure exceeds 25MPa, the overflow valve integrated on the valve block will immediately open to release pressure, with the pressure release flow rate set at 5L / min. At the same time, the mechanical locking mechanism will automatically engage when the guide post retracts 50mm, and the hardened steel tooth groove will lock to prevent accidental fall. The locking action of the mechanical locking mechanism is decoupled from the hydraulic system, so it can provide physical protection even if there is an oil leak.

5. A dual-closed-loop power system for a direct-drive electric chassis, based on the dual-closed-loop cooperative control method for a direct-drive electric chassis according to any one of claims 1 to 4, characterized in that: include, The direct drive unit has a flat wire motor output shaft that is directly connected to the drive shaft via an H7 / g6 tolerance flange. The drive shaft is connected to the rear axle via a universal joint at a 1:1 speed ratio. The control hardware unit features a dual-core controller, a built-in 32-bit processor, and a CAN bus interface. Energy management unit, lithium iron phosphate battery, equipped with liquid cooling temperature control system; The safety redundancy unit includes an insulation monitoring module, a hydraulic hand pump, and a mechanical outrigger locking mechanism.

6. The dual closed-loop power system for a direct-drive electric chassis as described in claim 5, characterized in that: The specific structural implementation of the direct drive transmission unit is as follows: The motor stator core is made of 0.2mm thick 50WW350 silicon steel sheets laminated together. Hairpin-type flat copper wire windings are embedded in the stator slots. These windings undergo a three-stage impregnation process, and the slot fill factor is strictly controlled within 78%±1%. The phase-to-phase insulation uses a 0.25mm thick corona-resistant polyimide film to ensure that the winding temperature rise is ≤85K. The rotor assembly consists of 16-pole Halbach array neodymium iron boron permanent magnets. Each permanent magnet is covered with a 0.5mm thick 316L stainless steel laser-welded sheath. The gap between the sheath and the magnet is filled with epoxy thermally conductive adhesive with a thermal conductivity of 1.2W / m·K, reducing the rotor eddy current loss to 0.8% of the rated power. The drive shaft is forged from 42CrMo alloy steel. The front end is rigidly connected to the motor output shaft via a flange with H7 / g6 tolerance fit. The flatness error of the flange mounting surface is ≤0.02mm, and the bolt preload torque is set to 120N·m±5%. The rear end of the drive shaft is connected to the rear axle input shaft via a universal joint. The universal joint fork head is made of 20CrMnTi carburized and quenched, with a surface hardness of HRC58-62. The shaft tube wall thickness is 6mm and is reinforced by internal high-pressure forming process. The overall dynamic balance level meets the G2.5 standard, and the imbalance does not exceed 15g·cm under the working condition of 3000rpm. To suppress torque fluctuations, a torsional damper is installed in the middle of the drive shaft: the rubber bushing has a Shore hardness of 70HA, and the internal vulcanized bonded annular steel plate has a stiffness coefficient of 200N / mm radially and 500N / mm axially; the damper has an interference fit with the shaft tube of 0.05-0.08mm, and the overall torsional angular displacement after assembly is ≤0.15°; the final assembled transmission unit has a measured transmission efficiency of ≥97.5% and an unloaded noise of ≤65dB under a full load of 7350kg.

7. The dual closed-loop power system for a direct-drive electric chassis as described in claim 6, characterized in that: The circuit design of the control hardware unit includes: The power cable between the four-in-one controller and the flat-wire motor adopts a double-layer shielding structure. The inner layer is a tinned copper wire braided shielding layer with a coverage of ≥85%, and the outer layer is an aluminum-plastic composite film wrapped shielding layer. The two shielding layers are grounded at a single point through a 1kΩ resistor. The cable insulation medium is cross-linked polyethylene material with a withstand voltage rating of AC2500V. The core wire cross-sectional area is strictly matched to the peak current of the motor (400A) using 50mm² multi-strand stranded copper conductors. The total cable length is controlled within 3 meters to reduce the distributed inductance to ≤2μH. The signal control line uses twisted-pair shielded cable with a twist pitch of 20mm. The two ends of the shielding layer are grounded through ferrite magnetic rings to ensure electromagnetic compatibility meets GB / T18655-2018 Class 3 level. Each arm of the IGBT switch in the PWM drive module is connected in parallel with an RC snubber circuit. The resistors are non-inductive metal film resistors with a resistance of 10Ω±1%, and the capacitors are polypropylene film capacitors with a capacitance of 0.1μF±5%. The circuit layout follows the shortest path principle—the pin spacing between resistors and capacitors is ≤5mm, and the total trace length of the snubber circuit is ≤30mm, effectively suppressing the switching spike voltage to within 15% of the DC bus voltage. The output stage of the drive optocoupler adds a totem-pole buffer circuit, using 2SC1623 and 2SA1015 transistors, compressing the rise / fall time to within 100 nanoseconds. The processor cooling system consists of a 3mm thick copper substrate and 6mm diameter sintered heat pipes. The evaporation section of the heat pipes is bonded to the processor chip surface with 0.1mm thick indium foil solder, and the condensation section extends to the aluminum heat sink fins with a fin spacing of 2mm. The surface of the heat sink fins is coated with a thermally conductive ceramic coating with a thickness of 50μm and a thermal conductivity of 3.5W / m·K. Forced air cooling uses a 24V axial fan with an airflow of 12CFM. Under full load conditions at an ambient temperature of 65℃, the measured temperature difference between the processor junction temperature and the copper substrate is ≤15℃, and the temperature difference between the copper substrate and the heat sink fins is ≤10℃. The overall temperature rise is strictly controlled within the range of 40℃.

8. The dual closed-loop power system for a direct-drive electric chassis as described in claim 7, characterized in that: The mechanical structure of the safety redundancy unit includes: The piston rod of the outrigger cylinder integrates a mechanical locking mechanism, which consists of a hardened 42CrMo alloy steel rack and a spring-loaded pawl. When the guide post rises to 50mm from the fully retracted position, the trigger cam fixed to the inner wall of the cylinder pushes the pawl shaft, causing the pawl to engage with the 5th tooth groove of the rack in a 0.5-second response time. The tooth groove spacing is 10mm, the tooth profile angle is 60°, and the contact stress on the tooth surface after locking is ≤800MPa, which can withstand an impact load of 1.5 times the vehicle weight of 7350kg. The pawl shaft is equipped with redundant return springs, with two springs arranged in parallel and each with a preload of 15N, ensuring stable engagement even under vibration. The hand pump is equipped with a two-way hydraulic lock in the inlet and outlet oil circuits. The two-way hydraulic lock valve adopts a cone valve sealing structure with a valve core cone angle of 90° and hard chrome plating. The matching accuracy of the sealing pair reaches IT6 level. Under the rated pressure of 25MPa, the pressure holding leakage is <5ml / min by controlling the gap between the valve core and the valve seat to ≤3μm. The hydraulic lock control oil circuit is equipped with a piston with a pilot ratio of 1:

4. When the hand pump stops operating, the system pressure drives the piston to close the cone valve within 50ms. At the same time, the accumulator maintains the replenishment oil pressure ≥2MPa to compensate for micro-leakage. The emergency button adopts a dual-contact redundancy design: the main contact is made of silver tin oxide material with a contact pressure of 8N, and is connected in series with the main contactor coil circuit; the auxiliary contact is made of gold-nickel alloy with a contact pressure of 5N, and directly controls the high-voltage relay to disconnect the circuit; the physical isolation distance between the two contacts is ≥5mm, and they are linked by an independent transmission rod. When the operator applies a 30N pressing force, the time difference between the synchronous action of the two contacts is ≤10ms; the button reset mechanism adopts a double torsion spring design with a torque coefficient of 0.8N·mm / °, and the contact opening gap during the reset stroke is >3mm, which meets the GB14048.5 electrical isolation standard.

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