Double-closed-loop cooperative control method and power system for direct-driven electric chassis

Abstract

The invention discloses a double-closed-loop cooperative control method of a direct-drive electric chassis and a power system, relates to the technical field of power control of electric special vehicles, and provides a rotating speed and torque double-closed-loop cooperative control architecture, and realizes double-core real-time cooperative operation and dynamic optimization of motor output characteristics through a 32-bit processor. A direct-drive transmission structure is combined, a traditional speed reduction device is omitted, a flat wire motor directly drives a rear axle through a transmission shaft, and a four-in-one controller is matched, so that the system loss is reduced by 33%, and the power density is improved by 15%; on the basis of real-time temperature / electric quantity data of a lithium iron phosphate battery management system, control parameters are adaptively adjusted, and the bottleneck of performance attenuation in a low-temperature environment of-35 DEG C is broken through; and a high-voltage interlocking and insulation monitoring module is integrated, and an emergency hydraulic system is automatically switched when an electrical fault occurs, so that multi-stage safety guarantee is formed. According to the technology, the energy recovery efficiency is remarkably improved by 20%, and the wind resistance stability and the extreme environment reliability are effectively enhanced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electric special vehicle power control, in particular to a double closed-loop cooperative control method of a direct-drive electric chassis and a power system. BACKGROUND

[0002] As the core power system of new energy special vehicles, direct-drive electric chassis has been widely used in airport ground equipment in recent years. The existing technology generally adopts the structure of motor driving the axle through a reducer, which can improve torque output, but has problems such as large mechanical loss (transmission efficiency < 85%) and slow response (control period > 100 ms). At the same time, the traditional single closed-loop control strategy cannot balance the extreme temperature adaptability, and the available capacity of the battery decreases by more than 40% in a low-temperature environment below-20℃, resulting in a sharp decrease in vehicle range.

[0003] The Chinese patent CN119116710B discloses a "full-vector power chassis automobile drive and braking redundancy cooperative control method", which solves the problems that the existing full-vector power chassis automobile drive and braking control strategy is not comprehensive enough and cannot well reduce the requirement for computing power. The upper layer calculates the vehicle demand longitudinal force moment and yaw moment, and the lower layer uses a combination of rules and lookup tables to distribute the longitudinal force moment and yaw moment issued by the upper controller. The intelligent evolution method is used to train the upper and lower layer actuator neural networks, to realize the reinforcement learning control based on the vehicle state to the instruction output, to simplify the control system "signal acquisition-computing processing-output execution" and other links, especially the hysteresis effect of the computing processing link, to improve the control efficiency and precision, and to ensure the economy, safety and stability of the vehicle during the whole life cycle.

[0004] In view of the existing technical bottlenecks, three core problems need to be solved in this field: 1) the control instability problem caused by the deterioration of battery characteristics in low-temperature working conditions of direct-drive systems; 2) the safety risk of regenerative braking impact caused by the inability of traditional control strategies to coordinate energy recovery and dynamic response; 3) the low switching efficiency of existing hydraulic emergency devices and the lack of redundancy interlocking mechanism with electronic control systems. Especially for special equipment such as airport passenger boarding bridges, the existing technical solutions cannot meet the requirements of the civil aviation AHM910 safety standard in terms of-35℃ environmental wind stability, millimeter-level precise control of aircraft docking, and rapid evacuation within 90 seconds after failure. SUMMARY

[0005] In view of the above existing problems, the present application is proposed.

[0006] Therefore, the present application provides a double closed-loop cooperative control method of a direct-drive electric chassis to solve the problems of control instability, safety risk of regenerative braking impact, and lack of redundancy interlocking mechanism with electronic control systems.

[0007] To solve the above technical problems, the present application provides the following technical solutions:

[0008] In a first aspect, the present application provides a double 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 collected by a 17-bit absolute value encoder, and the phase current signal of the motor is collected by a current sensor;

[0011] The real-time temperature and remaining capacity SOC data of the lithium iron phosphate battery are collected by the battery management unit BMS;

[0012] Step 2: Double closed-loop cooperative calculation

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

[0014] The 32-bit dual-core processor is used to superimpose the double error signals according to a 7:3 weight, and the incremental PID algorithm is used to output the PWM control instruction;

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

[0016] Step 3: Instruction execution and feedback

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

[0018] At the same time, the energy recovery state is monitored, and the reverse torque control is activated when the brake pedal opening is greater than 30%;

[0019] Step 4: Safety redundancy response

[0020] The high-voltage loop-to-ground insulation resistance is detected in real time, and if the resistance value is less than 500Ω / m, the high-voltage interlock is triggered;

[0021] The motor power is cut off within 0.5 seconds and switched to the hydraulic emergency module;

[0022] The outrigger oil cylinder is driven by the hand pump to retract the outrigger at a speed of 5mm / s.

[0023] As a preferred scheme of the double closed-loop cooperative control method for the direct-drive electric chassis, in the step 2, the specific operation of the speed loop control comprises:

[0024] Firstly, the motor speed signal and the motor rotor position are collected in real time by the Hall sensor installed on the motor rotor shaft end at a sampling frequency of every 10 milliseconds, the speed signal is converted into a real-time speed value by a 17-bit absolute value encoder, and the real-time speed value is input into the speed loop; the speed loop compares the real-time speed value with the preset speed command, and generates a first error signal input into the proportional integral controller, wherein the proportional coefficient is fixedly set to 0.8, and the integral coefficient is set to 0.05, and the output signal amplitude after proportional integral operation is limited in the range of ±15% of the rated torque of the motor;

[0025] Meanwhile, the torque loop receives a dynamic current limit value instruction from the battery management system, which is adaptively adjusted according to the real-time temperature of the lithium iron phosphate battery: when the battery temperature is in the interval of-35℃ to-20℃, the current limit value is reduced to 60% of the normal temperature rated value, and when the temperature is higher than 0℃, it returns to 100%; the torque loop compares the actual phase current sensor detection value with the dynamic current limit value, and the second error signal is processed by the fuzzy PID controller, and the proportional band is set to ±5 amperes, and the integral time constant is 200 milliseconds.

[0026] Subsequently, the speed loop output signal and the torque loop output signal are superimposed according to the weight of 7:3, and the superimposed composite signal is corrected by the incremental PID algorithm, wherein the proportional gain Kp is 1.2, the integral time Ti is 50 milliseconds, and the differential time Td is 10 milliseconds; the corrected signal is further filtered by the Kalman filter to eliminate high-frequency interference, and finally generates a PWM control instruction with a duty cycle accuracy of 0.1%, and the whole calculation process is completed in a 32-bit dual-core processor and strictly controlled within 50 milliseconds.

[0027] As a preferred scheme of the double closed loop cooperative control method of the direct drive electric chassis, wherein: the specific operation of the torque loop control in step 2 comprises:

[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 value according to the battery temperature: when the temperature is in the interval of-35℃ to-20℃, the current limit value is dynamically adjusted to 60% of the normal temperature rated value, when the temperature rises to the interval of-20℃ to 0℃, the current limit value is adjusted to 80%, and when the temperature is higher than 0℃, the current limit value returns to 100% of the rated value; the dynamic limit value is sent to the torque loop controller through the CAN bus every 50 milliseconds;

[0029] After receiving the current limit instruction, the torque ring collects the actual phase current values of the motor three-phase winding through the Hall current sensor, and takes the maximum value of the three-phase current absolute value as the feedback signal; the difference between the feedback current and the dynamic current limit is input into the fuzzy PID controller, and the controller divides the control rule according to the temperature difference: if the battery temperature is lower than-20℃, the proportional gain Kp is increased by 20%, and the integral time is shortened to 150 milliseconds; if the temperature difference exceeds 5℃, the anti-windup integral algorithm is enabled to prevent overshoot;

[0030] The torque correction signal output by the fuzzy PID is superimposed with the speed ring output signal with a weight of 7:3, and the superimposed composite signal enters the Kalman filter; the filter adopts a five-state variable model, including current noise, sampling delay, temperature drift, and its process noise covariance matrix Q is set to a diagonal matrix [0.01, 0.01, 0.005, 0.005, 0.001], and the measurement noise covariance R=0.1, and the smooth instruction signal with a high-frequency interference attenuation rate≥40dB is output after filtering;

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

[0032] As a preferred scheme of the double closed loop cooperative control method of the direct drive electric chassis, in the step 3, the specific operation of energy recovery includes:

[0033] When the brake pedal opening sensor detects that the opening value exceeds 30%, the vehicle controller immediately sends a mode switching instruction to the four-in-one controller, and switches the flat wire motor from the motor mode to the generator mode within 10 milliseconds; at this time, the regenerative alternating current generated by the motor three-phase winding is rectified through the freewheeling diode connected in parallel on the IGBT module, and the pulsed direct current enters the input end of the bidirectional DC / DC converter;

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

[0035] In the energy recovery process, the battery management system continuously monitors the DC bus power. When the instantaneous recovery power exceeds 30 kW, which is 25% of the motor rated power 120 kW, the power limiting algorithm is automatically triggered: reduce the PWM duty cycle by 5% per millisecond until the power falls below the safety threshold; if the high-power recovery state lasts more than 30 seconds, the power device is forced to exit the power generation mode and activate the air cooling system to prevent overheating and damage;

[0036] When the recovered energy is finally input into the battery pack, the liquid cooling temperature control system synchronously monitors the single cell temperature difference. If the temperature difference between the highest and lowest single cell temperature reaches 5℃, 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 stability of the vehicle braking posture.

[0037] As a preferred scheme of the double closed loop cooperative control method of the direct drive electric chassis, the specific operation of the low temperature adaptation of the safety redundancy response in step 4 comprises:

[0038] When the battery temperature sensor detects that the lithium iron phosphate battery temperature is lower than-20℃, the battery management system immediately starts the pulse heating mode: control the main positive contactor and the main negative contactor to alternately turn on and off at a frequency of 10Hz, each on-off period is 50 milliseconds on and 50 milliseconds off, generate Joule heat through the battery internal resistance, and make the single cell temperature rise at a rate of 1.5℃ per minute; During this process, the single cell temperature difference is monitored in real time. If the temperature difference between the highest and lowest single cell temperature exceeds 5℃, the pulse heating is automatically suspended and the liquid cooling circulating pump is started to run at a flow rate of 2L / min for 30 seconds for temperature equalization.

[0039] At the same time, the vehicle controller sends a DC preheating instruction to the four-in-one controller to switch the three-phase winding of the flat wire motor to a DC power mode: the U-phase and V-phase windings are connected in parallel and connected to positive DC power, and the W-phase winding is connected to negative DC power. The current value is strictly controlled at 30A, which is 15% of the motor rated current 200A, and the power-on time is 180 seconds; During preheating, the winding temperature rise is monitored through the motor temperature sensor, and the preheating is automatically stopped when the temperature reaches-5℃ or reaches 180 seconds.

[0040] During the cooperative operation of pulse heating and motor preheating, the battery management system collects the battery internal resistance value every 10 seconds. When the internal resistance is detected to be within 120% of the normal temperature reference value, the current limit is immediately removed and the drive capability is restored. If the battery temperature is still lower than-10℃ after continuous heating for 300 seconds, the secondary protection mechanism is triggered: the high-voltage output is cut off and the "low temperature protection activated" is prompted through the red warning light on the instrument panel. It needs to be confirmed manually before restarting.

[0041] As a preferred scheme of the double closed loop cooperative control method of the direct drive electric chassis, in the step 4, the specific operation of the emergency switching of the safety redundant response comprises:

[0042] When the insulation monitoring module detects that the high-voltage loop resistance to ground is lower than 500Ω / m, the vehicle controller sends an interlocking signal to the hydraulic bypass valve control circuit within 0.5 seconds; the bypass valve adopts an electromagnetic pilot valve structure, and in a normal state, the electromagnetic coil is powered to generate a magnetic force to attract the pilot valve core, push the main valve core to block the manual pump oil circuit, and maintain the motor pump oil supply state of the hydraulic system;

[0043] After the interlocking signal is triggered, the electromagnetic coil is immediately powered off, the pilot valve core is returned to the original position at a speed of 50 milliseconds under the action of the reset spring, and the main valve core switches the oil circuit direction under the pressure difference driving of the hydraulic balance hole: the manual pump outlet oil circuit is connected with the rodless chamber of the outrigger oil cylinder, and the motor pump output oil circuit is closed; at this time, the operator pulls the hand pump lever, the lever fulcrum is designed with a stroke ratio of 1:8, and 147N of force applied by the operator can generate 1176N of output force at the end of the lever to drive the plunger pump piston to complete the oil suction and oil compression cycle;

[0044] Every time the lever is shaken, 12ml of hydraulic oil is discharged from the plunger pump, the cylinder diameter is 32mm / 15mm, and the hydraulic oil enters the rodless chamber of the outrigger oil cylinder through the one-way valve to drive the piston rod to recover; the built-in displacement sensor in the oil cylinder feedbacks the recovery progress in real time, and when the piston rod displacement rate is detected to be lower than 5mm / s, the boost mode is automatically started: the accumulator auxiliary oil supply is activated at the plunger pump outlet, so that the oil pressure is increased from the conventional 20MPa to the upper limit of 25MPa, and it is ensured that the single operation cycle time does not exceed 90 seconds to complete all the outrigger recovery;

[0045] If the manual pump pressure exceeds 25MPa during the emergency process, the overflow valve integrated on the valve block is immediately opened to release pressure, and the relief flow is set to 5L / min; at the same time, the mechanical lock tooth mechanism is automatically engaged at the position where the guide column is retracted by 50mm, and the hardening steel tooth groove is locked to prevent accidental falling, and the locking action is decoupled from the hydraulic system, so that physical protection can be provided even if the oil circuit leaks.

[0046] In a second aspect, the application provides a double closed loop power system of a direct drive electric chassis, comprising,

[0047] The direct drive transmission unit directly connects the transmission shaft through the H7 / g6 tolerance flange of the output shaft of the flat wire motor, and connects the rear axle through the cross universal joint at a speed ratio of 1:1;

[0048] The control hardware unit comprises a dual-core controller, and the dual-core controller is internally provided with a 32-bit processor and a CAN bus interface;

[0049] The energy management unit comprises a lithium iron phosphate battery, and is provided with a liquid cooling temperature control system;

[0050] Safety redundancy unit, including insulation monitoring module, hydraulic hand pump, mechanical outrigger locking mechanism.

[0051] As a preferred scheme of the double closed loop power system of the direct drive electric chassis, the specific structure of the direct drive transmission unit is realized by:

[0052] The motor stator core is made of 0.2mm thick 50WW350 silicon steel sheets stacked, and the hairpin type flat copper wire winding is embedded in the stator slot, the winding is treated by three times of immersion process, the slot fill rate is strictly controlled within 78%±1%, the interphase insulation adopts 0.25mm thick corona-resistant polyimide film, and the winding temperature rise is ensured to be less than or equal to 85K; the rotor assembly is composed of 16-pole Halbach array neodymium-iron-boron permanent magnet, each permanent magnet is coated with 0.5mm thick 316L stainless steel laser welding sheath, the gap between the sheath and the magnet is filled with epoxy heat conducting glue, and the thermal conductivity is 1.2W / m·K, so that the rotor eddy current loss is reduced to 0.8% of the rated power;

[0053] The transmission shaft is forged and shaped by 42CrMo alloy steel, the front end is rigidly connected with the motor output shaft through the flange plate with H7 / g6 tolerance fit, the flange plate mounting surface flatness error is less than or equal to 0.02mm, and the bolt pretightening torque is set to 120N·m±5%; the rear end of the transmission shaft is connected with the rear axle input shaft through the cross universal joint, the universal joint fork head is treated by carburizing and quenching of 20CrMnTi, the surface hardness reaches HRC58-62, the shaft pipe wall thickness is 6mm and is strengthened by internal high pressure forming process, and the overall dynamic balance level meets the G2.5 level standard, and the unbalance amount is not more than 15g·cm under the working condition of 3000rpm speed;

[0054] In order to suppress torque fluctuation, a torsional damper is arranged in the middle of the transmission shaft: the rubber bushing Shore hardness is set to 70HA, the inside is vulcanized and bonded with annular steel plate, the stiffness coefficient is 200N / mm in radial direction and 500N / mm in axial direction; the interference fit amount of the damper and the shaft pipe is 0.05-0.08mm, and the overall torsional angular displacement after assembly is less than or equal to 0.15°; the finally assembled transmission unit has an actual measured value of transmission efficiency greater than or equal to 97.5% under the condition of full load 7350kg, and the idle noise is less than or equal to 65dB.

[0055] As a preferred scheme of the double closed loop power system of the direct drive electric chassis, the circuit design of the control hardware unit comprises:

[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, the coverage rate is greater than or equal to 85%, the outer layer is an aluminum plastic composite film wrapping shielding layer, the two shielding layers are grounded through a 1kΩ resistor single point, the cable insulation medium adopts cross-linked polyethylene material, the voltage resistance level is AC2500V, the core wire cross-sectional area is strictly matched with the motor peak current 400A, and the 50mm 2 The multi-stranded twisted copper conductor is controlled to be within 3 meters in total length to reduce the distributed inductance to less than or equal to 2 mu H; the signal control line adopts a double-twisted shielding line, the twist pitch is 20 mm, the shielding layer is grounded through a ferrite magnetic ring at both ends, and the electromagnetic compatibility meets the GB / T18655-2018 Class 3 level.

[0057] The IGBT switch tube of the PWM driving module is connected in parallel with an RC absorbing circuit, the resistance element is selected from a non-inductive metal film resistance, the resistance value is 10Ω±1%, the capacitor element is selected from a polypropylene film capacitor, the capacitance value is 0.1 mu F±5%, the circuit layout adopts the shortest path principle, the pin spacing of the resistance and the capacitor is less than or equal to 5 mm, the total wire length of the absorbing circuit is less than or equal to 30 mm, and the switching peak voltage is effectively suppressed within 15% of the DC bus voltage; the output stage of the driving optocoupler is provided with a totem pole buffer circuit, 2SC1623 and 2SA1015 transistors are used for pair connection, and the rise / fall time is compressed to less than or equal to 100 nanoseconds.

[0058] The processor heat dissipation system is composed of a 3mm-thick copper substrate and a 6mm-diameter sintered heat pipe, the evaporation section of the heat pipe is attached to the surface of the processor chip through a 0.1mm-thick indium foil solder, the condensation section extends to an aluminum heat dissipation fin, the fin spacing is 2mm; the surface of the heat dissipation fin is sprayed with a heat-conducting ceramic coating with a thickness of 50 mu m and a thermal conductivity of 3.5W / m·K, forced air cooling is achieved by using a 24V axial flow fan with a wind volume of 12 CFM, under the full load working condition at an ambient temperature of 65℃, the actual measured temperature difference from the processor junction to the copper substrate is less than or equal to 15℃, the temperature difference from the copper substrate to the heat dissipation fin is less than or equal to 10℃, and the overall temperature rise is strictly controlled within the range of 40℃.

[0059] As a preferred scheme of the double closed loop power system of the direct drive electric chassis, the mechanical structure of the safety redundancy unit comprises:

[0060] The mechanical lock tooth mechanism is integrated inside the outrigger oil cylinder piston rod, the mechanism is composed of hardened 42CrMo alloy steel rack and spring-loaded pawl, when the guide column rises to 50mm from the fully retracted position, the trigger cam fixed on the inner wall of the cylinder pushes the pawl shaft, the pawl is clamped into the No.5 tooth slot of the rack with a response time of 0.5 seconds, the tooth slot spacing is 10mm, the tooth shape angle is 60°, the contact stress of the locked tooth surface is ≤800MPa, and 1.5 times impact load of 7350kg vehicle quality can be borne; the pawl shaft is provided with a redundant reset spring, the two springs are arranged in parallel and the pre-tightening force of each spring is 15N, so that stable meshing can be ensured in a vibrating environment;

[0061] The hand pump import and export oil way is provided with a bidirectional hydraulic lock, the valve adopts a cone valve sealing structure, the valve core cone angle is 90° and is plated with hard chromium, and the sealing pair matching precision reaches IT6 level; under the rated pressure of 25MPa, the pressure leakage amount is less than 5ml / min by controlling the gap between the valve core and the valve seat to be less than 3μm; the hydraulic lock control oil way is provided 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, and the accumulator maintains the oil supplement pressure to be greater than or equal to 2MPa to compensate for the micro leakage;

[0062] The emergency button adopts a double-contact point redundant design: the main contact point is made of silver tin oxide material, the contact pressure is 8N, and the main contactor coil loop is connected in series; the auxiliary contact point is made of gold nickel alloy, the contact pressure is 5N, and the high-voltage relay breaking circuit is directly controlled; the physical isolation distance of the two contact points is greater than or equal to 5mm, and the two contact points are linked through independent transmission rods, when an operator applies a pressing force of 30N, the synchronous action time difference of the two contact points is less than or equal to 10ms; the button reset mechanism adopts a double torsional spring design, the torque coefficient is 0.8N·mm / °, the contact point opening gap in the reset stroke is greater than 3mm, and the GB14048.5 electrical isolation standard is met.

[0063] In a third aspect, the present application provides a computer device, comprising a memory and a processor, and the memory stores a computer program, wherein the computer program is executed by the processor to implement any step of the double closed-loop cooperative control method of the direct drive electric chassis according to the first aspect of the present application.

[0064] In a fourth aspect, the present application provides a computer readable storage medium, which stores a computer program, wherein the computer program is executed by the processor to implement any step of the double closed-loop cooperative control method of the direct drive electric chassis according to the first aspect of the present application.

[0065] The present application has the following beneficial effects:

[0066] The application realizes a breakthrough in the field of electric special vehicles in airports through the deep integration of direct drive power assembly and double closed-loop cooperative control. The most significant beneficial effect is reflected in the substantial improvement in extreme environment adaptability: the torque ring control mechanism based on the dynamic adjustment of current limit value of lithium iron phosphate battery temperature, combined with the cooperative strategy of pulse heating and motor direct current preheating, shortens the cold start time of the whole system to 180 seconds at-35℃ low temperature, and reduces the preheating energy consumption to 1.5% of the total power (8% for traditional PTC heating); at the same time, the double closed-loop controller fuses the speed and torque error signals with a weight of 7:3, and the PWM instruction accuracy after Kalman filtering reaches 0.1%, the torque output fluctuation in-20℃ environment is controlled within ±3%, which completely solves the industry's stubborn problem of ±10% of traditional single closed-loop system, and ensures that the passenger elevator car can still stably dock the cabin door on the ice and snow road and in strong wind conditions.

[0067] In terms of energy efficiency optimization, the creatively designed energy recovery safety chain brings multiple gains: the 1:1 transmission structure of the flat wire motor direct drive rear axle eliminates the reducer loss, and the transmission efficiency is improved to 97.5%; the bidirectional DC / DC converter realizes 600V±5% stable voltage output with peak current control, and cooperates with the gradient load shedding strategy with a power upper limit of 25%, so that the regenerative braking energy recovery efficiency is stably reached 20%, and the single vehicle driving range is increased to 226km; more importantly, the recovery process is double protected by real-time monitoring of speed deviation (50rpm / 50ms threshold) and liquid cooling temperature control system (5℃ temperature difference trigger), which eliminates the risk of attitude instability caused by regenerative braking, and the actual docking platform displacement deviation is ≤2mm, which meets the stringent requirements of civil aviation AHM920 standard for aircraft safety distance.

[0068] The innovation of safety redundancy mechanism is the third core benefit: within 0.5 seconds after the high-voltage interlock trigger, the electromechanical and hydraulic triple protection response is completed: when the insulation monitoring module detects a leakage resistance value of 500Ω / m, three operations are performed simultaneously: 1) the double-contact emergency button cuts off the main circuit, and the contact action time difference is ≤10ms; 2) the hydraulic bypass valve switches the oil circuit when the mechanical lock tooth mechanism is automatically engaged when the guide column is retracted by 50mm, and can withstand an impact load of 11 tons; 3) the hand pump realizes an output force of 1176N through a lever ratio of 1:8, drives the outrigger to retract at a speed of 5mm / s, and the whole process takes less than 90 seconds. This is 4 times more efficient than the manual valve operation in the comparative document, and through the 3μm level sealing of the bidirectional hydraulic lock (leakage <5ml / min) and the accumulator pressure compensation mechanism, the risk of outrigger falling caused by hydraulic failure is completely eliminated. BRIEF DESCRIPTION OF DRAWINGS

[0069] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort.

[0070] Figure 1 Flow chart of a double closed loop collaborative control method of a direct drive electric chassis in embodiment 1.

[0071] Figure 2 Module diagram of a double closed loop power system of a direct drive electric chassis in embodiment 1. DETAILED DESCRIPTION

[0072] In order to make the above-mentioned objects, features and advantages of the present application more apparent and comprehensible, the specific embodiments of the present application will be described in detail below with reference to the drawings.

[0073] In the following description, a large number of specific details are set forth in order to facilitate a thorough understanding of the present application, but the present application can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the connotation of the present application, therefore the present application is not limited by the specific embodiments disclosed below.

[0074] Secondly, the "one embodiment" or "embodiment" referred to herein means that the specific features, structures or characteristics can be included in at least one implementation of the present application. "In one embodiment" appearing in different places in the specification does not mean the same embodiment, nor is it an independent or alternative embodiment that excludes other embodiments.

[0075] Embodiment 1, refer to Figure 1 , as the first embodiment of the present application, the embodiment provides a double closed loop collaborative control method of a direct drive electric chassis, comprising the following steps:

[0076] Step 1: Real-time data acquisition

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

[0078] The real-time temperature and remaining capacity SOC data of the lithium iron phosphate battery are collected by the battery management unit BMS;

[0079] Step 2: Double closed loop collaborative calculation

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

[0081] The 32-bit dual-core processor is used to superimpose the double error signals according to a 7:3 weight, and the incremental PID algorithm is used to output a PWM control instruction;

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

[0083] The specific operation of the speed loop control in step 2 includes:

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

[0085] At the same time, the torque loop receives a dynamic current limit instruction from the battery management system. The limit value is adaptively adjusted according to the real-time temperature of the lithium iron phosphate battery. When the battery temperature is in the interval of -35℃ to -20℃, the current limit value is reduced to 60% of the normal temperature rated value, and when the temperature is higher than 0℃, it returns to 100%. The torque loop compares the actual phase current sensor detection value with the dynamic current limit value, generates a second error signal, and processes it through the fuzzy PID controller. The proportional band is set to ±5 amperes, and the integral time constant is 200 milliseconds.

[0086] Subsequently, the speed loop output signal and the torque loop output signal are superimposed according to a 7:3 weight, and the superimposed composite signal is corrected through the incremental PID algorithm, with a proportional gain Kp = 1.2, an integral time Ti = 50 milliseconds, and a 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 instruction with a duty cycle accuracy of 0.1% is generated. The entire calculation process is completed in a 32-bit dual-core processor and is strictly controlled within a 50 ms period.

[0087] The specific operation of the torque loop control in step 2 includes:

[0088] The battery management system first monitors the temperature sensor data of the lithium iron phosphate battery in real time, dynamically adjusts the current limit value according to the battery temperature, and when the temperature is in the interval of -35℃ to -20℃, the current limit value is dynamically adjusted to 60% of the normal temperature rated value, when the temperature rises to the interval of -20℃ to 0℃, it is adjusted to 80%, and when the temperature is higher than 0℃, it returns to 100% of the rated value. The dynamic limit value is sent to the torque loop controller through the CAN bus every 50 milliseconds;

[0089] After receiving the current limit instruction, the torque ring collects the actual phase current value of the motor three-phase winding through the Hall current sensor, and takes the maximum value of the absolute value of the three-phase current as the feedback signal; the difference between the feedback current and the dynamic current limit is input into the fuzzy PID controller, which divides the control rules according to the temperature difference: if the battery temperature is lower than-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-windup integral algorithm is enabled to prevent overshoot;

[0090] The torque correction signal output by the fuzzy PID is superimposed with the speed ring output signal with a weight of 7:3, and the superimposed composite signal enters the Kalman filter; the filter uses a five-state variable model, including current noise, sampling delay, temperature drift, and its process noise covariance matrix Q is set to a diagonal matrix [0.01, 0.01, 0.005, 0.005, 0.001], and the measurement noise covariance R = 0.1, after filtering, the smooth instruction signal with a high-frequency interference attenuation rate ≥40dB is output;

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

[0092] Step 3: instruction execution and feedback

[0093] Send PWM instructions to the four-in-one controller to adjust the phase current of the flat wire motor;

[0094] At the same time, monitor the energy recovery state, and activate the reverse torque control when the brake pedal opening is >30%;

[0095] The specific operation of energy recovery in step 3 includes:

[0096] When the brake pedal opening sensor detects that the opening value exceeds 30%, the vehicle control unit immediately sends a mode switching instruction to the four-in-one controller, which switches the flat wire motor from motor mode to generator mode within 10 milliseconds; At this time, the regenerative alternating current generated by the motor three-phase winding is rectified by the freewheeling diode connected in parallel on the IGBT module, and the pulsed direct current enters the input end 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, and immediately adjusts the duty cycle of the upper bridge arm MOSFET from 65% to 40% when the detected current instantaneous value exceeds 25A; At the same time, through the output voltage closed-loop feedback, the converter output end voltage is accurately stabilized within the range of 600V±5%, which is strictly matched with the nominal voltage of the lithium iron phosphate battery pack.

[0098] During the energy recovery process, the battery management system continuously monitors the DC bus power. When the instantaneous recovery power exceeds 30 kW, which is 25% of the motor rated power 120 kW, the power limiting algorithm is automatically triggered: reduce the PWM duty cycle by 5% per millisecond until the power falls below the safety threshold; if the high-power recovery state lasts more than 30 seconds, the power device is forced to exit the generation mode and activate the air cooling system to prevent overheating and damage;

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

[0100] Step 4: Safety Redundancy Response

[0101] Real-time detection of high-voltage loop-to-ground insulation resistance, if the resistance is less than 500Ω / m, trigger high-voltage interlock;

[0102] Turn off the motor power within 0.5 seconds and switch to the hydraulic emergency module;

[0103] Retract the outrigger with a hand pump at a speed of 5 mm / s.

[0104] The specific operation of the low-temperature adaptation of the safety redundancy response in step 4 includes:

[0105] When the battery temperature sensor detects that the lithium iron phosphate battery temperature is lower than -20°C, the battery management system immediately starts the pulse heating mode: control the main positive and negative contactors to alternately turn on and off at a frequency of 10 Hz, each on-off period is 50 milliseconds on and 50 milliseconds off, generate Joule heat through the battery internal resistance, and raise the single cell temperature at a rate of 1.5°C per minute; During this process, the single cell temperature difference is monitored in real time. If the difference between the highest and lowest single cell temperature exceeds 5°C, the pulse heating is automatically suspended and the liquid cooling circulating pump is started to run at a flow rate of 2 L / min for 30 seconds for temperature equalization;

[0106] At the same time, the vehicle controller sends a DC preheating command to the four-in-one controller to switch the flat wire motor three-phase winding to DC power mode: the U and V phase windings are connected in parallel and connected to positive DC power, and the W phase winding is connected to negative DC power. The current value is strictly controlled at 30A, which is 15% of the motor rated current 200A, and the power time is 180 seconds; During preheating, the winding temperature rise is monitored through the motor temperature sensor. When the temperature reaches -5°C or the time limit of 180 seconds is reached, the preheating is automatically stopped;

[0107] During the pulse heating and motor preheating coordination, the battery management system collects the battery internal resistance value every 10 seconds, and when the internal resistance is detected to be 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 lower than -10℃ after continuous heating for 300 seconds, a secondary protection mechanism is triggered: the high-voltage output is cut off and the "low-temperature protection activated" is prompted through the red warning light of the instrument desk, and the restart needs to be confirmed manually.

[0108] The specific operation of the emergency switching of the security redundancy response in step 4 includes:

[0109] When the insulation monitoring module detects that the high-voltage loop resistance to ground is lower than 500Ω / m, the vehicle controller sends an interlocking signal to the hydraulic bypass valve control circuit within 0.5 seconds; the bypass valve adopts an electromagnetic pilot valve structure, and under normal circumstances, the electromagnetic coil is powered to generate a 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 motor pump oil supply state;

[0110] After the interlocking signal is triggered, the electromagnetic coil is immediately powered off, the pilot valve core is returned to the original position at a speed of 50 milliseconds under the action of the reset spring, and the main valve core switches the oil circuit direction under the driving of the pressure difference of the hydraulic balance hole: the manual pump outlet oil circuit is connected with the no-rod chamber of the outrigger cylinder, and the motor pump output oil circuit is closed; at this time, the operator pulls the hand pump lever, and the lever fulcrum is designed with a stroke ratio of 1:8, so that the operator can exert an output force of 1176N at the end of the lever by exerting an action force of 147N, to drive the plunger pump piston to complete the oil suction and oil compression cycle.

[0111] Every time the lever is shaken, 12ml of hydraulic oil is discharged from the plunger pump, with a cylinder diameter of 32mm and a stroke of 15mm, and the hydraulic oil enters the no-rod chamber of the outrigger cylinder through the check valve to push the piston rod back; the built-in displacement sensor in the cylinder real-time feedbacks the recovery progress, and when the piston rod displacement rate is detected to be lower than 5mm / s, the boost mode is automatically started: the accumulator auxiliary oil supply is activated at the plunger pump outlet, so that the oil pressure is increased from the conventional 20MPa to the upper limit of 25MPa, to ensure that the single operation cycle time does not exceed 90 seconds to complete all outrigger recovery.

[0112] If the manual pump pressure exceeds 25MPa during the emergency process, the overflow valve integrated on the valve block is immediately opened to release pressure, and the relief flow is set to 5L / min; at the same time, the mechanical lock tooth mechanism is automatically engaged at the 50mm retraction position of the guide column, which locks the steel tooth groove to prevent accidental falling, and the locking action is decoupled from the hydraulic system, so that physical protection can be provided even if the oil circuit leaks.

[0113] Embodiment 2, with reference to Figure 2 The second embodiment of the present application provides a double-closed-loop power system of a direct-drive electric chassis, which comprises:

[0114] Direct drive transmission unit, flat wire motor output shaft through H7 / g6 flange direct connection transmission shaft, transmission shaft through the cross universal joint to 1:1 speed ratio connection rear axle;

[0115] Control hardware unit, dual-core controller, built-in 32-bit processor and CAN bus interface;

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

[0117] Safety redundancy unit, including insulation monitoring module, hydraulic hand pump, mechanical outrigger locking mechanism.

[0118] The specific structure of the direct drive transmission unit is:

[0119] The motor stator core is made of 0.2mm thick 50WW350 silicon steel sheet, and the hairpin type flat copper wire winding is embedded in the stator slot. The winding is treated by three times of immersion process, and the slot fill rate is strictly controlled within 78%±1%. The interphase insulation adopts 0.25mm thick corona-resistant polyimide film to ensure that the winding temperature rise is less than or equal to 85K. The rotor assembly is composed of 16-pole Halbach array neodymium-iron-boron permanent magnet, and each permanent magnet is coated with 0.5mm thick 316L stainless steel laser welding sheath. The gap between the sheath and the magnet is filled with epoxy heat conducting glue 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 transmission shaft is made of 42CrMo alloy steel and is forged into shape. The front end is rigidly connected with the motor output shaft through the H7 / g6 tolerance flange. The flange mounting surface flatness error is less than or equal to 0.02mm, and the bolt pre-tightening torque is set to 120N·m±5%. The rear end of the transmission shaft is connected with the rear axle input shaft through the cross universal joint. The universal joint fork head is made of 20CrMnTi carburizing and quenching treated, with a surface hardness of HRC58-62. The shaft tube wall thickness is 6mm and is strengthened by internal high pressure forming process. The overall dynamic balance level meets the G2.5 level standard, and the unbalance amount is not more than 15g·cm under the working condition of 3000rpm speed.

[0121] To suppress torque fluctuation, a torsional damper is provided in the middle of the transmission shaft. The rubber bushing has a Shore hardness of 70HA, and an annular steel plate is vulcanized and bonded inside. The stiffness coefficient is 200N / mm in the radial direction and 500N / mm in the axial direction. The interference fit amount between the damper and the shaft tube is 0.05-0.08mm, and the overall torsional angular displacement after assembly is less than or equal to 0.15°. The final assembled transmission unit has a measured transmission efficiency value of greater than or equal to 97.5% under the condition of full load 7350kg, and an idle noise of less than or equal to 65dB.

[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 rate of ≥85%, and the outer layer is an aluminum plastic composite film wrapping shielding layer. The two shielding layers are grounded through a 1kΩ resistor at a single point. The cable insulation medium is cross-linked polyethylene material with an AC 2500V voltage resistance level. The core wire cross-sectional area is strictly matched with the motor peak current of 400A, and a 50mm 2 The multi-stranded twisted copper conductor is controlled within a total cable length of 3 meters to reduce the distributed inductance to ≤2μH. The signal control line uses a twisted pair shielding line with a twist pitch of 20mm. The shielding layer is grounded at both ends through a ferrite magnetic ring to ensure that the electromagnetic compatibility meets the GB / T18655-2018 Class 3 level.

[0124] The IGBT switch tube of the PWM drive module has an RC absorption circuit connected in parallel to each bridge arm. The resistance element is a non-inductive metal film resistor with a resistance of 10Ω±1%. The capacitor element is a polypropylene film capacitor with a capacitance of 0.1μF±5%. The circuit layout follows the shortest path principle, with the pin spacing of the resistance and the capacitor ≤5mm, and the total wire length of the absorption circuit ≤30mm, effectively suppressing the switching peak voltage within 15% of the DC bus voltage. The output stage of the drive optocoupler is increased with a totem pole buffer circuit using 2SC1623 and 2SA1015 transistors in a pair. The rise / fall time is compressed to within 100 nanoseconds.

[0125] The processor heat dissipation system is composed of a 3mm thick copper substrate and a 6mm diameter sintered heat pipe. The heat pipe evaporation section is attached to the surface of the processor chip through a 0.1mm thick indium foil solder. The condensation section extends to the aluminum heat dissipation fins with a fin spacing of 2mm. The surface of the heat dissipation fins is sprayed with a heat-conducting ceramic coating with a thickness of 50μm and a thermal conductivity of 3.5W / m·K. Forced air cooling uses a 24V axial flow fan with a wind volume of 12CFM. Under full load conditions at an ambient temperature of 65℃, the measured temperature difference from the processor junction to the copper substrate is ≤15℃, and the temperature difference from the copper substrate to the heat dissipation 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 outrigger oil cylinder piston rod is internally integrated with a mechanical lock tooth mechanism composed of a hardened 42CrMo alloy steel rack and a spring-loaded pawl. When the guide column 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 the 5th tooth slot of the rack with a response time of 0.5 seconds. The tooth slot spacing is 10mm, and the tooth angle is 60°. After locking, the tooth surface contact stress is ≤800MPa, which can withstand 1.5 times the impact load of a 7350kg vehicle. The pawl shaft is equipped with a redundant return spring, with both springs arranged in parallel and each with a pre-tightening force of 15N, ensuring stable engagement even in a vibrating environment.

[0128] The hand pump import and export oil circuit is installed with a two-way hydraulic lock, the valve adopts a conical valve sealing structure, the valve core angle is 90° and is plated with hard chromium, the sealing pair matching precision reaches IT6 level; under a 25 MPa rated pressure, by controlling the gap between the valve core and the valve seat to be ≤3 μm, a pressure maintaining leakage of <5 ml / min is realized; the hydraulic lock control oil circuit is provided 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 conical valve within 50 ms, and the accumulator maintains a makeup oil pressure ≥2 MPa to compensate for the micro leakage;

[0129] The emergency button adopts a double-contact redundant design: the main contact is made of silver tin oxide material, the contact pressure is 8N, and is connected in series in the main contactor coil loop; the auxiliary contact is made of gold nickel alloy, the contact pressure is 5N, and directly controls the high-voltage relay breaking circuit; the physical isolation distance of the two contacts is ≥5mm, and through independent transmission rods, when an operator applies a 30N pressing force, the double-contact synchronous action time difference is ≤10ms; the button reset mechanism adopts a double torsion spring design, the torque coefficient is 0.8N·mm / °, the contact opening gap in the reset stroke is >3mm, and the GB14048.5 electrical isolation standard is met.

[0130] The AI model training parameter dynamic optimization system workflow of this embodiment begins with the real-time data acquisition phase: a 17-bit absolute value encoder installed on the motor rotor shaft captures the speed signal at a 10-millisecond sampling period, while a Hall current sensor synchronously acquires three-phase winding phase current values, and the signals are filtered by a second-order Butterworth filter (cutoff frequency 1 kHz) to eliminate high-frequency noise; a battery management unit (BMS) acquires real-time temperature (PT1000 sensor accuracy ±0.5°C) and remaining capacity (coulomb counting method error <3%) of the lithium iron phosphate battery in parallel, and the three-way data is uploaded to a dual-core processor through a CAN bus at a 50-millisecond period. After entering the dual-closed-loop collaborative calculation phase, the speed loop compares the filtered actual speed with the preset speed command (from the vehicle control unit VCU) to generate a first error signal input to the proportional-integral controller (Kp=0.8, Ki=0.05), and the output amplitude is limited to the rated torque ±15%; the torque loop receives the current limit value dynamically adjusted by the BMS (-35°C limit to 60% of the normal temperature value), combines the phase current feedback to generate a second error signal, and processes it through the fuzzy PID controller (proportional band ±5A, integral time 200ms). The two error signals are superimposed with a 7:3 weight, corrected by the incremental PID algorithm (Kp=1.2, Ti=50ms, Td=10ms), and then passed through the Kalman filter (Q matrix diag[0.01, 0.01, 0.005], R=0.1) to eliminate interference, and finally output the PWM command with a duty cycle accuracy of 0.1%, and the entire calculation process is strictly compressed within 50 milliseconds. In the command execution phase, the four-in-one controller parses the PWM command into IGBT drive signals (switching frequency 10kHz, dead time 2μs) to drive the flat wire motor to run; if the brake pedal opening sensor detects an opening >30%, the reverse torque control mode is immediately activated, and the regenerative current is stabilized to 600V±5% through full-bridge rectification and bidirectional DC / DC converter, with a maximum recovery power of 30kW (25% rated power). In the safety redundancy response phase, the high-voltage loop insulation resistance is monitored in real time, and when the detected value <500Ω / m, the three-level joint control is triggered within 0.5 seconds: 1) the double-contact emergency button cuts off the main contactor; 2) the hydraulic bypass valve is powered off to switch the oil circuit; 3) the hand pump drives the outrigger to retract at a speed of 5mm / s through a 1:8 lever mechanism (output 12ml of hydraulic oil per revolution), while the mechanical lock tooth mechanism automatically engages and locks when the guide column retracts 50mm. DETAILED DESCRIPTION

[0131] Hardware system setup: The data acquisition sensor components are installed on the direct drive electric chassis. The motor shaft end is configured with a Heidenhain ECN413 type 17-bit absolute value encoder to collect real-time speed signals and output square wave pulses. The LEM HAH3DR-SB closed-loop Hall current sensor is set for each phase of the three-phase winding, with a measurement range of ±500A and a measurement error controlled within ±0.5%. The four-wire PT1000 platinum resistance temperature sensor is embedded in the battery pack, with 8 monitoring points evenly distributed along the battery monomer. The temperature data is collected through the ISO60751 Class A precision circuit. After pre-processing by a second-order Butterworth filter (cutoff frequency 1kHz), all sensor signals are connected to the dual-core controller through shielded twisted pair lines. The controller is equipped with a 200MHz processor and a dual-channel CAN bus interface, with a fixed data transmission period of 50 milliseconds.

[0132] Control algorithm execution:

[0133] Double closed-loop collaborative computing process:

[0134] After the controller receives 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. At the same time, the torque loop receives the dynamic current limit value sent by the battery management system (-35℃ set to 60% of the normal temperature value), and compares it with the maximum phase current detected by the Hall sensor. The error signal is processed by the fuzzy PID controller, with a proportional band set to ±5 amperes and an integral time constant of 200 milliseconds. The output signals of the two control loops are superimposed with a weight of 7:3, and the superimposed result is corrected by an incremental PID algorithm (proportional gain 1.2, integral time 50 milliseconds, and derivative time 10 milliseconds). Finally, the Kalman filter is used to eliminate high-frequency interference, and the duty cycle accuracy is 0.1%. The PWM command is generated.

[0135] Energy recovery trigger mechanism:

[0136] The brake pedal opening sensor monitors the pedal position in real time. When the opening exceeds the 30% threshold, the controller immediately switches the motor to generator mode. The regenerative current is rectified to pulsed DC by the freewheeling diode of the IGBT module, and the peak current control strategy is used by the bidirectional DC / DC converter: when the inductor current instantaneous value exceeds 25 amperes, the MOSFET duty cycle is automatically adjusted from 65% linearly to 40%, and the output voltage is stabilized within 600V±5%. The upper limit of the recovered power is locked at 30kW (25% of the rated power of the motor), and if the continuous over-power operation exceeds 30 seconds, the system automatically exits the power generation mode and activates the cooling fan.

[0137] Safety redundancy response implementation:

[0138] High-voltage loop insulation monitoring module uses bridge method to measure resistance to ground. When the detection value is lower than 500Ω / m, the third level interlock response is activated within 0.5 seconds:

[0139] 1. Electrical breaking: dual-contact emergency button synchronous action, main contact cuts off the main contactor coil circuit, auxiliary contact directly breaks the high-voltage relay, contact action time difference ≤10 milliseconds;

[0140] 2. Hydraulic switching: Bosch RE 16308 type electromagnetic pilot spool is powered off, the spool switches the oil path direction under the action of the return spring, connecting the hand pump outlet to the leg cylinder rodless chamber;

[0141] 3. Mechanical execution: the operator pulls the hand pump lever (lever ratio 1:8, displacement 12ml per circle), drives the hydraulic oil into the oil cylinder at a pressure of 20MPa, and the piston rod is retracted at a speed of 5mm / s. When the guide column is retracted to a position 50mm away from the end point, the ratchet pawl with built-in mechanical lock tooth mechanism automatically engages the 5th tooth slot of the 42CrMo alloy steel rack (tooth pitch 10mm), achieving physical locking through tooth surface engagement.

[0142] Performance verification scheme:

[0143] Start the test in a -35℃ environment chamber, and immediately perform pulse heating after the battery management system detects the low temperature: the main contactor is turned on and off at a frequency of 10Hz (on for 50ms / off for 50ms), while 30A DC current is applied to the motor winding for preheating. After 182 seconds, the battery temperature rises to -5℃, and the system restores the driving capability. Under the full load condition of 7350kg, the torque output fluctuation is ±2.8%, and the energy recovery efficiency reaches 20.7%. In the safety test, an artificial 500Ω / m insulation fault is set, and the system completes the leg oil path switching within 0.48 seconds, and the mechanical lock tooth mechanism accurately engages at a position of 49.7mm. The whole process takes 86.5 seconds. After being certified by China Special Equipment Inspection Research Institute, the system meets all the requirements of IATA AHM913 standard.

[0144] Key implementation details

[0145] 1. Temperature adaptive control

[0146] The battery management system dynamically adjusts the current limit value according to the temperature interval: 60% of the rated value for -35℃~-20℃, 80% for -20℃~0℃, and 100% for >0℃;

[0147] The motor preheating uses a specific wiring mode: U / V phase windings are connected in parallel to the positive pole, and W phase is connected to the negative pole, forming a closed magnetic circuit to reduce eddy current loss.

[0148] 2. Hydraulic-mechanical linkage

[0149] The hand pump outputs 12 milliliters of hydraulic oil per rotation, and according to the volume of the outrigger cylinder, 37.5 rotations are needed to complete the full stroke (450 millimeters).

[0150] The mechanical lock tooth trigger cam adopts Archimedes spiral design to ensure accurate meshing at 50±0.5 millimeters.

[0151] 3. Fault protection level

[0152] Primary protection: insulation monitoring module scans high-voltage loop every 100 milliseconds;

[0153] Secondary protection: physical isolation distance of double-contact button ≥5 millimeters, electrical gap withstand voltage >10 kilovolts;

[0154] Ultimate protection: tensile strength of rack material ≥1080 megapascals, can withstand 11 tons of impact load.

[0155] This embodiment has completed engineering verification at Wuxi Ximeite Special Automobile Co., Ltd., and is installed on the WXQ5050DKTZ type electric boarding ladder for batch production, with a cumulative operation of 120,000 hours without safety failure record, proving the industrial feasibility of the technical scheme.

[0156] The embodiment also provides a computer device suitable for the case of the double-closed-loop cooperative control method of the direct-drive electric chassis, which comprises 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 realize the double-closed-loop cooperative control method of the direct-drive electric chassis as described in the above embodiment.

[0157] The computer device can be a terminal, and the computer device comprises a processor, a memory, a communication interface, a display screen and an input device connected through a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device comprises a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operating system and the computer program in the non-volatile storage medium. The communication interface of the computer device is used to communicate with external terminals in a wired or wireless manner. The wireless manner can be achieved through WIFI, an operator network, NFC (near field communication) or other technologies. The display screen of the computer device can be a liquid crystal display screen or an electronic ink display screen. The input device of the computer device can be a touch layer overlaid on the display screen, or a key, trackball or touchpad arranged on the shell of the computer device, or an external keyboard, touchpad or mouse, etc.

[0158] The embodiment also provides a storage medium having a computer program stored thereon, the program being executed by a processor to implement the double closed-loop cooperative control method of the direct-drive electric chassis as proposed in the above embodiment; 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 read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, magnetic disk or optical disk.

[0159] To sum up, the application realizes a breakthrough in the field of electric special vehicles in airports through deep integration of the direct-drive power assembly and the double closed-loop cooperative control. The most significant beneficial effect is reflected in a substantial improvement in adaptability to extreme environments: the torque loop control mechanism based on dynamic adjustment of current limits of lithium iron phosphate batteries in combination with the cooperative strategy of pulse heating and direct current preheating of the motor shortens the cold start time of the whole system to 180 seconds at a low temperature of-35℃, and reduces the preheating energy consumption to 1.5% of the total power (8% for the traditional PTC heating); meanwhile, the double closed-loop controller fuses the speed and torque error signals with a weight of 7:3, and the precision of the Kalman filtered PWM instruction reaches 0.1%, and the torque output fluctuation is controlled within ±3% at an environment of-20℃, which completely solves the industry problem of ±10% of the traditional single closed-loop system, and guarantees that the passenger loading vehicle can still stably dock the cabin door on the ice and snow road and in strong wind conditions.

[0160] In terms of energy efficiency optimization, the energy recovery safety chain designed creatively brings multiple gains: the 1:1 transmission structure of the flat wire motor directly driving the rear axle eliminates the loss of the reducer, and the transmission efficiency is improved to 97.5%; the bidirectional DC / DC converter realizes 600V±5% stable voltage output with peak current control, and cooperates with the gradient load reduction strategy with a power upper limit of 25%, so that the regenerative braking energy recovery efficiency is stabilized to reach 20%, and the single vehicle driving range is increased to 226km; more importantly, the recovery process is double-protected by real-time monitoring of the speed deviation (50rpm / 50ms threshold) and the liquid cooling temperature control system (5℃ temperature difference trigger), which eliminates the risk of attitude instability caused by regenerative braking, and the actual docking platform displacement deviation is ≤2mm, which meets the stringent requirements of the civil aviation AHM920 standard for the safety distance of the aircraft.

[0161] The innovation of the safety redundancy mechanism is the third core benefit: the completion of the mechatronic triple protection response within 0.5 seconds after the high-voltage interlock trigger - when the insulation monitoring module detects a leakage resistance of 500Ω / m, three operations are performed simultaneously: 1) the double-contact emergency button cuts off the main circuit, and the contact action time difference is ≤10ms; 2) the hydraulic bypass valve switches the oil circuit by power-off, and the mechanical lock tooth mechanism automatically engages when the guide column retracts 50mm, bearing an impact load of 11 tons; 3) the hand pump realizes an output force of 1176N through a 1:8 lever ratio, driving the outrigger to retract at a speed of 5mm / s, and the whole process takes less than 90 seconds. This is 4 times more efficient than the manual valve operation in the comparative document, and through the 3μm level sealing (leakage <5ml / min) of the bidirectional hydraulic lock and the accumulator pressure compensation mechanism, the risk of outrigger falling caused by hydraulic failure is completely eliminated.

[0162] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application rather than limit the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. A dual closed-loop coordinated control method for a direct-drive electric chassis, characterized in that: The following steps are involved: Step 1: Real-time data collection The motor speed signal is collected through a 17-bit absolute encoder, and the motor phase current signal is collected through a current sensor; The real-time temperature and remaining capacity SOC data of the lithium iron phosphate battery are collected through the battery management unit BMS; Step 2: Double-loop collaborative computing The speed signal and the preset speed value are input into the speed loop to generate a first error signal, and the phase current signal and the dynamic current limit value provided by the BMS are input into the torque loop to generate a second error signal; A 32-bit dual-core processor is used to superimpose the dual error signals according to a 7:3 weight ratio, and output PWM control instructions through an incremental PID algorithm; The calculation cycle is strictly controlled within 50ms; Step 3: Instruction execution and feedback Send PWM instructions to the four-in-one controller to adjust the phase current of the flat wire motor; At the same time, the energy recovery status is monitored and reverse torque control is activated when the brake pedal opening is greater than 30%; Step 4: Safe and redundant response Real-time detection of the insulation resistance of the high-voltage circuit to ground. If the resistance is less than 500Ω / m, the high-voltage interlock is triggered. Cut off the motor power supply and switch to the hydraulic emergency module within 0.5 seconds; The outrigger cylinder is driven by a hand pump to retract the outrigger at a speed of 5mm / s.

2. The dual closed-loop coordinated control method for a direct-drive electric chassis according to claim 1, characterized in that: The specific operations of the speed loop control in step 2 include: First, a Hall sensor mounted on the motor rotor shaft acquires the motor speed signal and rotor position in real time at a sampling frequency of every 10 milliseconds. This speed signal is converted into a real-time speed value via a 17-bit absolute encoder and input into a speed loop. The speed loop compares the real-time speed value with a preset speed command, and the resulting first error signal is input into a 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 the proportional-integral operation is limited to within ±15% of the motor's rated torque. At the same time, the torque loop receives a dynamic current limit command 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°C to -20°C, the current limit is reduced to 60% of the rated value at normal temperature, and when the temperature is above 0°C, it returns to 100%; 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 amps and an integral time constant of 200 milliseconds. Subsequently, the speed loop output signal and the torque loop output signal are superimposed with a weight ratio of 7:

3. The superimposed composite signal is corrected using an incremental PID algorithm, with a proportional gain Kp = 1.2, an integral time Ti = 50 milliseconds, and a differential time Td = 10 milliseconds. The corrected signal is then filtered through a Kalman filter to eliminate high-frequency interference, ultimately generating a PWM control instruction with a duty cycle accuracy of 0.1%. The entire calculation process is completed on a 32-bit dual-core processor and is strictly controlled within a 50-millisecond period.

3. The dual closed-loop coordinated control method for a direct-drive electric chassis according to claim 2, characterized in that: The specific operations of the torque loop control in step 2 include: 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 based on the battery temperature. When the temperature is between -35°C and -20°C, the current limit is dynamically adjusted to 60% of the rated value at room temperature. When the temperature rises to the range of -20°C to 0°C, it is adjusted to 80%. When the temperature rises above 0°C, it returns to 100% of the rated value. This dynamic limit is sent to the torque loop controller via the CAN bus every 50 milliseconds. After receiving the current limit command, the torque loop uses a Hall current sensor to collect the actual phase current values ​​of the motor's three-phase windings, and the maximum absolute value of the three-phase current is used as the feedback signal. The difference between the feedback current and the dynamic current limit is input into the fuzzy PID controller, which divides the control rules according to the temperature difference: if the battery temperature is below -20°C, the proportional gain Kp is increased by 20%, and the integration time is shortened to 150 milliseconds. If the temperature difference exceeds 5°C, the anti-saturation integral algorithm is activated to prevent overshoot. The torque correction signal output by the fuzzy PID is superimposed with the speed loop output signal in a 7:3 weighted ratio. The superimposed composite signal enters the Kalman filter. The filter uses a five-state variable model that includes current noise, sampling delay, and temperature drift. Its process noise covariance matrix Q is set to a diagonal matrix of [0.01, 0.01, 0.005, 0.005, 0.001], and the measurement noise covariance R = 0.

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

4. The dual closed-loop coordinated control method for a direct-drive electric chassis according to claim 3, characterized in that: The specific operation of energy recovery in step 3 includes: When the brake pedal opening sensor detects an opening value exceeding 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 full-bridge rectified by the freewheeling diodes connected in parallel to the IGBT module, and the output pulsating DC power enters the input terminal of the bidirectional DC / DC converter. The bidirectional DC / DC converter adopts a peak current control strategy, using a high-frequency Hall sensor to collect the inductor current in real time. When the instantaneous current value exceeds 25A, it immediately adjusts the duty cycle of the upper bridge arm MOSFET to linearly reduce it from 65% to 40%. At the same time, through output voltage closed-loop feedback, the converter output voltage is precisely stabilized within the range of 600V±5%, which strictly matches the nominal voltage of the lithium iron phosphate battery pack. During the energy recovery process, 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, or 30kW, the power limiting algorithm is automatically triggered: the PWM duty cycle is reduced by 5% per millisecond until the power drops back to a safe threshold; if the high power recovery state lasts for more than 30 seconds, the power generation mode is forced to exit and the air cooling system is activated to prevent overheating and damage to the power devices; when the recovered energy is finally input into the battery pack, the liquid cooling temperature control system synchronously monitors the temperature difference of the single cells. If the difference between the highest and lowest single cell temperatures 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 consecutive milliseconds, the recovery process is immediately interrupted and the drive torque output is restored to ensure the stability of the vehicle's braking posture.

5. The dual closed-loop coordinated control method for a direct-drive electric chassis according to claim 4, characterized in that: The specific operations of the low temperature adaptation of the safety redundancy response in step 4 include: When the battery temperature sensor detects that the lithium iron phosphate battery temperature is below -20°C, the battery management system immediately activates pulse heating mode: the main positive contactor and the main negative contactor are controlled to alternately switch on and off at a frequency of 10Hz, with each on-off cycle of 50 milliseconds on and 50 milliseconds off. This generates Joule heat through the battery's internal resistance, causing the single cell temperature to rise at a rate of 1.5°C per minute. During this process, the temperature difference between the single cells is monitored in real time. If the difference between the highest and lowest cell temperatures exceeds 5°C, the pulse heating mode is automatically suspended and the liquid cooling circulation pump is activated at a flow rate of 2L / min for 30 seconds to achieve temperature equalization. At the same time, the vehicle controller sends a DC preheating command to the four-in-one controller, switching the three-phase winding of the flat wire motor to DC power-on mode: the U-phase and V-phase windings are connected in parallel and then fed with forward DC power, while the W-phase winding is fed with reverse DC power. The current value is strictly controlled at 15% of the motor's rated current of 200A, or 30A, and the power-on time is continuous for 180 seconds. During the preheating period, the winding temperature rise is monitored by the motor temperature sensor, and the system automatically stops when the temperature reaches -5°C or the 180-second limit is reached. During the coordinated pulse heating and motor preheating, the battery management system collects the battery's internal resistance value every 10 seconds. When it detects that the internal resistance has dropped to within 120% of the normal temperature reference value, it immediately releases the current limit and restores the driving capability. If the battery temperature is still below -10°C after 300 seconds of continuous heating, the secondary protection mechanism is triggered: the high-voltage output is cut off and a red alarm light on the instrument panel indicates "low temperature protection activated", which requires manual confirmation before restarting.

6. The dual closed-loop coordinated control method for a direct-drive electric chassis according to claim 5, characterized in that: The specific operations of the emergency switching of the safety redundancy response in step 4 include: When the insulation monitoring module detects that the high-voltage circuit's resistance to ground 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 uses a solenoid-operated pilot spool valve structure. Under normal conditions, the solenoid 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, allowing the hydraulic system to maintain the motor pump oil supply state. After the interlock signal is triggered, the solenoid coil is immediately de-energized, and the pilot valve core returns to its original position at a speed of 50 milliseconds under the action of the return spring. Driven by the pressure differential of the hydraulic balance hole, the main valve core switches the oil circuit direction: the manual pump outlet oil circuit is connected to the rodless chamber of the outrigger oil cylinder, and the motor pump output oil circuit is closed at the same time. At this time, the operator pulls the hand pump lever. The lever fulcrum adopts a 1:8 stroke ratio design. The operator applies a force of 147N to generate an output force of 1176N at the end of the lever, driving the plunger pump piston to complete the oil suction and oil pressure cycle. Each time the lever is cranked, the plunger pump discharges 12ml of hydraulic oil. The cylinder has a diameter of 32mm and a stroke of 15mm. The hydraulic oil enters the rodless chamber of the outrigger cylinder through a one-way valve, pushing the piston rod back. The cylinder's built-in displacement sensor provides real-time feedback on the retraction progress. When it detects that the piston rod displacement rate is less than 5mm / s, the boost mode is automatically activated: the accumulator at the plunger pump outlet is activated to assist in oil supply, raising the oil pressure from the normal 20MPa to the upper limit of 25MPa, ensuring that a single operation cycle does not exceed 90 seconds to complete the retraction of all outriggers. During an emergency, if the manual pump pressure exceeds 25MPa, the relief valve integrated in the valve block will immediately open to relieve pressure, and the pressure relief flow rate is set to 5L / min; at the same time, the mechanical locking gear mechanism automatically engages when the guide column retracts 50mm, and the hardened steel tooth groove is locked to prevent accidental falling. This locking action is decoupled from the hydraulic system and can provide physical protection even if the oil line leaks.

7. A dual closed-loop power system for a direct-drive electric chassis, based on the dual closed-loop coordinated control method for a direct-drive electric chassis according to any one of claims 1 to 6, characterized in that: include, Direct drive transmission unit, the flat wire motor output shaft is directly connected to the drive shaft through the H7 / g6 tolerance flange, and the drive shaft is connected to the rear axle through a cross universal joint with a 1:1 speed ratio; Control hardware unit, dual-core controller, built-in 32-bit processor and CAN bus interface; Energy management unit, lithium iron phosphate battery, equipped with liquid cooling temperature control system; Safety redundancy unit, including insulation monitoring module, hydraulic hand pump, and mechanical outrigger locking mechanism.

8. The dual closed-loop power system of a direct-drive electric chassis according to claim 7, characterized in that: The specific structural implementation of the direct drive transmission unit is as follows: The motor's stator core is constructed from laminated 0.2mm-thick 50WW350 silicon steel sheets. Hairpin-style flat copper wire windings are embedded in the stator slots. These windings undergo a triple-impregnation process, ensuring a strictly controlled slot fill rate of 78% ± 1%. Phase-to-phase insulation utilizes 0.25mm-thick corona-resistant polyimide film to ensure a winding temperature rise of ≤85K. The rotor assembly consists of a 16-pole Halbach array of neodymium-iron-boron permanent magnets. Each magnet is sheathed in a 0.5mm-thick laser-welded 316L stainless steel jacket. The gap between the jacket and the magnet is filled with epoxy thermal adhesive with a thermal conductivity of 1.2W / m·K, reducing rotor eddy current losses to 0.8% of rated power. The drive shaft is forged from 42CrMo alloy steel, and the front end is rigidly connected to the motor output shaft via a flange with H7 / g6 tolerance. The flatness error of the flange mounting surface is ≤0.02mm, and the bolt pre-tightening torque is set at 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 is carburized and quenched with 20CrMnTi, achieving a surface hardness of HRC58-62. The shaft tube is 6mm thick and reinforced by an internal high-pressure forming process. The overall dynamic balance grade meets the G2.5 standard, with an imbalance of no more than 15g·cm at a speed of 3000rpm. To suppress torque fluctuations, a torsional vibration damper is installed in the middle of the drive shaft: the Shore hardness of the rubber bushing is set to 70HA, and the internal vulcanized and bonded annular steel plate has a radial stiffness coefficient of 200N / mm and an axial stiffness coefficient of 500N / mm; the interference fit between the vibration damper and the shaft tube is 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% under a full load of 7350kg, and the no-load noise is ≤65dB.

9. The dual closed-loop power system of a direct-drive electric chassis according to claim 7, 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 rate of ≥85%. 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 made of cross-linked polyethylene material with a withstand voltage rating of AC2500V. The core wire cross-sectional area strictly matches the motor peak current of 400A and is selected as 50mm 2 The cable is constructed of multi-stranded copper conductors with a total length of less than 3 meters to reduce the distributed inductance to ≤2μH. The signal control line uses a twisted-pair shielded cable with a lay length of 20mm. Both ends of the shield are grounded through ferrite rings to ensure that the electromagnetic compatibility meets GB / T18655-2018 Class 3. Each bridge arm of the PWM drive module's IGBT switching tube has an RC snubber circuit connected in parallel. The resistors use non-inductive metal film resistors with a resistance value of 10Ω±1%, and the capacitors use polypropylene film capacitors with a capacitance value of 0.1μF±5%. The circuit layout follows the shortest path principle—the pin spacing between the resistor and capacitor is ≤5mm, and the total snubber loop trace length is ≤30mm. This effectively suppresses the switching spike voltage to within 15% of the DC bus voltage. A totem pole snubber circuit is added to the output stage of the driver optocoupler, using a 2SC1623 and 2SA1015 transistor pair to compress rise / fall times to less than 100 nanoseconds. The processor cooling system consists of a 3mm-thick copper baseplate and a 6mm-diameter sintered heat pipe. The evaporation section of the heat pipe is bonded to the processor chip surface with 0.1mm-thick indium foil solder, and the condensation section extends to aluminum heat sink fins with a 2mm fin spacing. The surface of the heat sink fins is sprayed with a thermally conductive ceramic coating with a thickness of 50μm and a thermal conductivity coefficient of 3.5W / m·K. Forced air cooling uses a 24V axial fan with an air volume of 12CFM. Under full load conditions at an ambient temperature of 65°C, the measured temperature difference from the processor junction temperature to the copper baseplate is ≤15°C, and the temperature difference from the copper baseplate to the heat sink fins is ≤10°C. The overall temperature rise is strictly controlled within 40°C.

10. The dual closed-loop power system of a direct-drive electric chassis according to claim 7, characterized in that: The mechanical structure of the safety redundant unit includes: A mechanical locking mechanism is integrated into the outrigger cylinder piston rod. This mechanism 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, a trigger cam fixed to the inner wall of the cylinder pushes the pawl shaft, causing the pawl to engage the rack's fifth tooth groove with a response time of 0.5 seconds. The tooth groove spacing is 10mm, and the tooth profile angle is 60°. After locking, the tooth surface contact stress is ≤800MPa, and it can withstand an impact load of 1.5 times the vehicle mass of 7350kg. The pawl shaft is equipped with redundant return springs. The two springs are arranged in parallel and have a preload of 15N each, ensuring stable engagement even in vibrating environments. A bidirectional hydraulic lock is installed on the inlet and outlet oil circuits of the hand pump. This valve adopts a cone valve sealing structure, with a 90° cone angle of the valve core and hard chrome plating. The sealing pair matching precision reaches IT6 level. At a rated pressure of 25MPa, the pressure-maintaining leakage is less than 5ml / min by controlling the clearance 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 oil charge pressure ≥2MPa to compensate for minor leaks. The emergency button adopts a dual-contact redundant 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 two contacts are physically isolated by a distance of ≥5mm and are linked by an independent transmission rod. When the operator applies a pressing force of 30N, the time difference between the two contacts in synchronous action is ≤10ms; the button reset mechanism adopts a dual torsion spring design with a torque coefficient of 0.8N·mm / °. The contact disconnection gap during the reset stroke is greater than 3mm, meeting the GB14048.5 electrical isolation standard.

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