A multi-degree-of-freedom self-adaptive leveling carrying trolley suitable for aerospace final assembly

Abstract

The application discloses a multi-degree-of-freedom self-adaptive leveling carrying trolley suitable for aerospace final assembly, which comprises a heavy load chassis assembly, an omni-directional rudder wheel walking module, a four-point independent servo leveling lifting module, a swing mechanism, a turnover mechanism, a bearing tool, a multi-source sensing acquisition unit and a control system. The chassis adopts a thick-walled rectangular tube welded frame, four groups of independent suspension rudder wheel mounting seats are arranged at the bottom, and lifting mechanism mounting flanges are arranged at the four corners; the walking module comprises four sets of servo rudder wheel units; the leveling lifting module comprises four sets of turbine worm servo lifting mechanisms; the swing mechanism is arranged above the chassis, the turnover mechanism is arranged above the swing mechanism, and the bearing tool is arranged on the turnover mechanism table; the sensing unit comprises double-axis inclination sensors and weighing pressure sensors at the four corners of the table; and the control system independently controls the stroke of the four sets of lifting mechanisms according to feedback signals, so as to realize high-precision automatic leveling, dynamic compensation and integrated transfer and posture adjustment.

Description

Technical Field

[0001] This invention relates to the field of transport vehicle technology, and more particularly to a multi-degree-of-freedom adaptive leveling transport vehicle suitable for aerospace assembly. Background Technology

[0002] A typical heavy-duty AGV transport chassis consists of a rectangular welded chassis, four sets of independent steering wheel walking mechanisms, a fixed support platform, and simple manual jacks. The walking unit uses servo steering wheels in conjunction with suspension springs, enabling only forward and backward movement, lateral movement, and turning on the spot. Leveling relies on four independent manual screw jacks at the corners, lacking a closed-loop electronic leveling system. The support platform is rigidly connected to the chassis, and there is no electrical linkage between the walking mechanism and the leveling mechanism. Furthermore, no real-time sensors for acquiring tilt angles, height, or other parameters are installed.

[0003] The working process is as follows: Before the transfer, the jacks are raised and lowered point by point using a wrench. The level of the platform is observed by the naked eye or a simple level. After the single-point leveling is completed, the nuts are tightened. When encountering uneven ground, slight slopes or ground joints during the transfer, the chassis tilts with the road surface and the supporting platform tilts synchronously. When the aircraft is assembled and docked, if there are deviations in the height or level of the interface, the transfer needs to be stopped repeatedly and the jacks need to be raised and lowered manually for fine adjustment. The whole process relies on manual intervention.

[0004] A typical aerospace-grade transfer platform with simple lifting mechanisms consists of a chassis, multiple sets of hydraulic lifting cylinders, fixed load-bearing fixtures, and independent wheels. The lifting cylinders can only lift the entire structure synchronously, lacking independent fine-tuning and leveling capabilities at individual points; they are equipped only with a single-point level sensor, without real-time multi-axis tilt feedback; movement and lifting are controlled by two separate controllers, and their data is not interconnected. The lifting cylinders use a unified hydraulic circuit for synchronous control, without independent servo drive branches; the movement drive, lifting hydraulics, and level detection hardware are isolated from each other, and there is no closed-loop adaptive leveling control circuit.

[0005] Its working process is as follows: the entire vehicle can only be raised or lowered as a whole, and the height of the four corners of the platform cannot be adjusted individually to compensate for the difference in ground level; once the platform tilts to the left or right or forward or backward, there is no automatic correction logic, and the machine must be stopped and manual shims must be used to assist in leveling; it can only complete simple transfer and cannot meet the requirements of high-precision docking and multi-station continuous assembly of aircraft; if attitude adjustment such as flipping or rotating is required, an additional two-dimensional turntable is required to hoist and transfer the workpiece, and the transfer and attitude adjustment equipment are separated from each other.

[0006] The purely manual tooling support cart has no autonomous walking ability and relies on forklifts and overhead cranes for transportation; leveling relies entirely on pads and manual top blocks, without electric adjustment or real-time data display, and is only suitable for static storage, unable to meet the needs of dynamic transportation and assembly.

[0007] Analysis of the problems and causes of existing technologies: (1) Leveling is fully manual, low precision and low efficiency: The existing device needs to be manually adjusted by jack one by one before transfer and docking, and the leveling precision is usually only ±0.5° by relying on the eye judgment of a level. The slight concave-convex of the ground or the transfer vibration will cause the table to tilt again, and the assembly and docking need to be repeatedly stopped and re-adjusted. The leveling of a single aircraft can take 1 to 3 hours. The reason is that: there is a lack of distributed servo independent lifting leveling mechanism, there is no multi-sensor closed-loop real-time collection system for inclination, height, etc., there is a lack of automatic compensation control algorithm, and there is no linkage between walking and leveling systems.

[0008] (2) There is no dynamic self-adaptive leveling during the transfer process, and there is a safety risk for the aircraft: When the trolley drives through the workshop joint, a slope of 3° or a concave-convex ground, the chassis is tilted, and the bearing table is tilted synchronously, causing the center of gravity of the aircraft to shift. The precise aerospace shell and onboard instruments may bear additional shear force, which is prone to deformation, insulation failure or damage to precision sensors; when fully loaded with 1.5t aerospace workpieces, there is even a risk of side slipping and dumping. The reason is that the table and the chassis are rigidly connected, the four-corner lifting mechanism has no independent real-time compensation function, and the driving attitude real-time correction logic is not established.

[0009] (3) Transfer and attitude adjustment equipment are separated, and the process is complicated: The existing trolley usually only has the function of walking and transferring, and the horizontal rotation and left-right inclination need to be adjusted by an additional two-dimensional turntable to hoist and transfer the workpiece, which increases the risk of collision and occupies the hoisting equipment resources of the plant. The reason is that the existing transfer trolley only retains the functions of walking and simple lifting, and does not integrate a rotary and inclination attitude adjustment integrated module. The transfer and assembly attitude adjustment belong to two independent devices.

[0010] (5) Poor load bearing adaptability and no compensation ability for eccentric load: The aircraft has large size and eccentric center of mass, the traditional four-point synchronous lifting is uneven in stress, the local stress of the frame is out of standard, and the rigidity is insufficient. The reason is that the lifting mechanism uses synchronous control, there is no single-point independent load adaptive adjustment logic, and no dynamic balancing algorithm for eccentric load is designed.

[0011] In summary, the existing aerospace assembly carrying device has deficiencies in leveling precision, dynamic adaptive ability, attitude adjustment integration, electrical safety and clean adaptability, data centralized control, and eccentric load bearing, etc., and it is difficult to meet the requirements of modern aerospace assembly for high precision, high efficiency, high safety and intelligence. Therefore, a multi-degree-of-freedom self-adaptive leveling transfer trolley suitable for aerospace assembly is urgently needed. SUMMARY

[0012] The technical solution of this invention to solve the above-mentioned technical problems is to provide a multi-degree-of-freedom adaptive leveling transport vehicle suitable for aerospace assembly, comprising: The heavy-duty chassis assembly adopts a thick-walled rectangular tube integral welded frame, with four sets of independent suspension steering wheel mounting seats installed at the bottom and lifting mechanism mounting flanges arranged at the four corners. The omnidirectional steering wheel travel module includes four sets of servo steering wheel units, which are respectively installed on four sets of independent suspension steering wheel mounting seats at the bottom of the heavy-duty chassis assembly. Each set of servo steering wheel units integrates a travel drive motor, a reducer, a suspension device and a travel wheel, supporting omnidirectional movement. The four-point independent servo leveling and lifting module includes four sets of worm gear servo lifting mechanisms, which are respectively installed on the lifting mechanism mounting flanges at the four corners of the heavy-duty chassis assembly. Each lifting mechanism is equipped with an independent servo motor and an absolute encoder, and the four lifting mechanisms are driven independently. A rocking mechanism is disposed above the heavy-duty chassis assembly; A flipping mechanism is disposed above the swinging mechanism; A support fixture is provided on the support platform of the flipping mechanism; The multi-source sensing acquisition unit includes a dual-axis tilt sensor and a weighing pressure sensor installed at the four corners of the support platform of the flipping mechanism; The system is installed within the heavy-duty chassis assembly and is electrically connected to four sets of servo steering wheel units, four sets of worm gear servo lifting mechanisms, the swing mechanism, the tilting mechanism, the dual-axis tilt sensor, and the weighing pressure sensor. It is used to independently control the lifting stroke of the four sets of worm gear servo lifting mechanisms based on the feedback signals from the dual-axis tilt sensor and the weighing pressure sensor.

[0013] Furthermore, each servo steering wheel unit of the omnidirectional steering wheel travel module integrates a 48V absolute servo motor, reducer, spring suspension, and polyurethane anti-slip and shock-absorbing tires. It supports forward and backward movement, lateral movement, 45° diagonal movement, and stationary rotation, with both manual and electric control modes. The maximum travel speed is 15m / min; the climbing ability is ≤3°, and the obstacle crossing ability is ≤10mm; the travel controller communicates with the main PLC via a PROFINET bus, with start / stop acceleration limited to ≤0.5g to avoid inertial impact; the travel motor has a built-in brake that automatically locks the wheels in case of emergency stop or power failure.

[0014] Furthermore, each worm gear servo lifting mechanism of the four-point independent servo leveling and lifting module is an SWL35 worm gear servo lifting mechanism, with a rated load of 15t per set and a lifting stroke of 0-100mm. Each set is equipped with a 20-bit absolute encoder. The four lifting mechanisms are driven completely independently and are not forced to synchronize with each other. The four-point independent servo leveling and lifting module has two switchable working modes: static assembly leveling mode and dynamic transfer leveling mode. In dynamic transfer leveling mode, road surface feedback is collected in real time during driving for dynamic leveling. The lifting screw of the four-point independent servo leveling and lifting module has an anti-reverse self-locking structure. After power failure, the worm gear is mechanically locked to prevent the platform from falling.

[0015] Furthermore, the swing mechanism employs a backlash-free dual-gear drive to achieve stepless speed regulation rotation from 0 to 360°, with three speed settings: 5° / min, 15° / min, and 30° / min, and a rotation positioning accuracy of ±0.1°. The tilting mechanism uses an RV reducer servo drive, with a tilting angle of 0 to 15° left and right, and three speed settings: 3° / min, 5° / min, and 10° / min. The integrated rotary tilting bearing platform automatically interlocks with the rotary drive unit to prevent rotation when tilted at 15°. Both the motors of the tilting drive unit and the rotary drive unit are equipped with brakes, and hardware limit switches are provided at the extreme positions to cut off power.

[0016] Furthermore, the bearing platform of the swing mechanism has 98 M16 standard threaded interfaces reserved for matching the spacecraft mounting flange, and the flatness of the platform is ≤0.2mm.

[0017] Furthermore, the supporting fixture includes an insulating pad with an insulation resistance of ≥100MΩ; the entire trolley is independently grounded with a grounding resistance of <1Ω; all electrical components are insulated from the main structure to eliminate the risk of electrostatic breakdown of aerospace precision equipment and meet aerospace electrical safety standards.

[0018] Furthermore, the multi-source sensing acquisition unit also includes a rotary multi-turn encoder, a flip multi-turn encoder, a battery SOC detection sensor, a walking speed sensor, and limit switches; all sensing signals are uploaded to the PLC in real time to achieve millisecond-level response leveling compensation.

[0019] The control system adopts a Siemens S7-150F safety PLC, equipped with a 12-inch fixed HMI and a 7-inch mobile handheld operating box; the PLC uniformly manages all motion axes including walking, four-point leveling, lifting, rotation, and tilting; the HMI displays the real-time height of the four corners of the platform, X / Y horizontal tilt angle, single-point load, battery level, speed of each axis, and fault codes; it has a built-in multi-level threshold early warning function, automatically popping up audible and visual alarms when tilt angle exceeds tolerance, load is overloaded, or voltage is too low; it has three levels of operation permissions: operator permission, maintenance permission, and administrator permission; the emergency stop button has a hardware dual-channel safety circuit; it is equipped with a 48V 200Ah battery pack and a smart charger, supporting 380V external charging.

[0020] Compared with existing technologies, this invention integrates a heavy-duty chassis assembly, an omnidirectional steering wheel travel module, a four-point independent servo leveling and lifting module, a swing mechanism, a tilting mechanism, a load-bearing fixture, a multi-source sensor acquisition unit, and a control system. This achieves automated, high-precision leveling, dynamic adaptive compensation, and integrated transport and attitude adjustment for aerospace assembly transport vehicles. The four-point independent servo lifting, combined with closed-loop control using dual-axis tilt sensors and weighing pressure sensors, enables static leveling accuracy of ±0.1° and real-time dynamic leveling during operation. This eliminates the need for repeated manual adjustments of jacks or shims, reducing the leveling time for a single aircraft by 90%. When traversing ramps, seams, or uneven surfaces, the platform remains level, preventing the aircraft from experiencing additional shear forces and the risk of overturning. It also strictly limits start-stop acceleration, improving the safety of transporting precision aerospace products. The system integrates 0-36... The 0° rotation and 0-15° left-right tilting functions allow for direct assembly posture adjustment after transport to the correct position, eliminating the need for secondary hoisting on a two-dimensional turntable, reducing the risk of collisions and saving factory crane resources. Four-point independent bearing and adaptive eccentric load adjustment ensure uniform local stress in the frame. Combined with a Q345B thick-walled rectangular tube integral welded chassis, a rated load of 1.5t, bending resistance of 12000Nm, and a safety factor of 3, it meets the requirements for heavy loads, high rigidity, and long service life. Meanwhile, the insulation resistance of the insulating pads is ≥100MΩ, the overall grounding resistance is <1Ω, and the electrical insulation isolation and dustproof / rustproof design meet aerospace electrical safety and Class 100,000 cleanroom requirements. The S7-150F safety PLC, HMI, multi-source sensor monitoring, multi-level early warning, three-level access control, dual-channel emergency stop, and dual mechanical and electrical self-locking further enhance the equipment's intelligence, safety, and ease of maintenance. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the structure of the multi-degree-of-freedom adaptive leveling transport vehicle applicable to aerospace assembly as described in this invention.

[0023] Explanation of icon numbers: 10. Heavy-duty chassis assembly; 20. Omnidirectional steering wheel travel module; 30. Independent servo leveling and lifting module; 40. Swing mechanism; 50. Tilting mechanism; 60. Load-bearing fixture. Detailed Implementation

[0024] This invention proposes a multi-degree-of-freedom adaptive leveling transport vehicle suitable for aerospace assembly, aiming to design a multi-degree-of-freedom adaptive leveling transport vehicle suitable for aerospace assembly.

[0025] The anti-aging solid beverage composition proposed in this invention will be described below in specific embodiments: A multi-degree-of-freedom adaptive leveling transport vehicle suitable for aerospace assembly includes: The heavy-duty chassis assembly 10 adopts a thick-walled rectangular tube integral welded frame, with four sets of independent suspension steering wheel mounting seats installed at the bottom and lifting mechanism mounting flanges arranged at the four corners. The omnidirectional steering wheel travel module 20 includes four sets of servo steering wheel units, which are respectively installed on four independent suspension steering wheel mounting seats at the bottom of the heavy-duty chassis assembly 10. Each set of servo steering wheel units integrates a travel drive motor, a reducer, a suspension device and a travel wheel, supporting omnidirectional movement. The four-point independent servo leveling and lifting module 30 includes four sets of worm gear servo lifting mechanisms, which are respectively installed on the lifting mechanism mounting flanges at the four corners of the heavy-duty chassis assembly 10. Each lifting mechanism is equipped with an independent servo motor and an absolute encoder, and the four lifting mechanisms are driven independently. A swaying mechanism 40 is positioned above the heavy-duty chassis assembly 10; A flipping mechanism 50 is positioned above the swing mechanism 40; The bearing fixture 60 is mounted on the bearing platform of the flipping mechanism 50; The multi-source sensing acquisition unit includes a dual-axis tilt sensor and a weighing pressure sensor installed at the four corners of the support platform of the flipping mechanism 50. The system is installed in the heavy-duty chassis assembly 10 and is electrically connected to four servo steering wheel units, four worm gear servo lifting mechanisms, a swing mechanism 40, a tilting mechanism 50, a dual-axis tilt sensor, and a weighing pressure sensor. It is used to independently control the lifting stroke of the four worm gear servo lifting mechanisms based on the feedback signals from the dual-axis tilt sensor and the weighing pressure sensor.

[0026] Optionally, the heavy-duty chassis assembly 10 adopts a Q345B thick-walled rectangular tube integral welded frame with a safety factor of 3, and is equipped with reserved lifting points, transportation fixing interfaces, and grounding terminals; four sets of independent suspension steering wheel mounting seats are installed at the bottom, and lifting mechanism mounting flanges are arranged at the four corners. Cable channels are laid inside the frame, and the exterior is coated with white anti-rust paint to meet the requirements of a 100,000-level cleanroom; the vehicle's self-weight is matched with a bending moment of 12,000 Nm, and the width meets the limits for railway and highway transportation.

[0027] Furthermore, each servo steering wheel unit of the omnidirectional steering wheel travel module 20 integrates a 48V absolute servo motor, reducer, spring suspension, and polyurethane anti-slip shock-absorbing tires. It supports forward and backward movement, lateral movement, 45° diagonal movement, and stationary rotation, and has both manual operation and electric control modes. The maximum travel speed is 15m / min; the climbing ability is ≤3°, and the obstacle crossing ability is ≤10mm; the travel controller communicates with the main PLC via PROFINET bus, and the start-stop acceleration limit is ≤0.5g; the travel motor has a built-in brake that automatically locks the wheels in case of emergency stop or power failure.

[0028] Furthermore, each set of worm gear servo lifting mechanism in the four-point independent servo leveling and lifting module 30 is an SWL35 worm gear servo lifting mechanism, with a rated load of 15t per set and a lifting stroke of 0-100mm. Each set is equipped with a 20-bit absolute encoder. The four lifting mechanisms are driven completely independently and are not forced to synchronize with each other. The four-point independent servo leveling and lifting module 30 has two switchable working modes: static assembly leveling mode and dynamic transfer leveling mode. In dynamic transfer leveling mode, road feedback is collected in real time during driving for dynamic leveling. The lifting screw of the four-point independent servo leveling and lifting module 30 has an anti-reverse self-locking structure. After power failure, the worm gear is mechanically locked to prevent the platform from falling.

[0029] Furthermore, the swing mechanism 40 adopts a backlash-free double gear drive to achieve stepless speed regulation rotation from 0 to 360°, with three speed settings: 5° / min, 15° / min, and 30° / min, and a rotation positioning accuracy of ±0.1°. The tilting mechanism 50 adopts an RV reducer servo drive, with a tilting angle of 0 to 15° left and right, and three speed settings: 3° / min, 5° / min, and 10° / min. The integrated slewing and tilting bearing platform automatically interlocks to prevent rotation when tilted at 15°. Both the motors of the tilting and slewing drive units are equipped with brakes, and hardware limit switches are provided at the extreme positions to cut off power.

[0030] Furthermore, the bearing platform of the swing mechanism 40 has 98 M16 standard threaded interfaces reserved for matching the spacecraft mounting flange, and the flatness of the platform is ≤0.2mm.

[0031] Furthermore, the bearing fixture 60 includes an insulating pad with an insulation resistance of ≥100MΩ; the entire trolley is independently grounded with a grounding resistance of <1Ω; and all electrical components are insulated from the main structure.

[0032] Furthermore, the multi-source sensing acquisition unit also includes a rotary multi-turn encoder, a flip multi-turn encoder, a battery SOC detection sensor, a walking speed sensor, and limit switches; all sensing signals are uploaded to the PLC in real time to achieve millisecond-level response leveling compensation.

[0033] The control system uses a Siemens S7-150F safety PLC, equipped with a 12-inch fixed HMI and a 7-inch mobile handheld control box; the PLC uniformly manages all motion axes including walking, four-point leveling, lifting, rotation, and tilting; the HMI displays the real-time height of the four corners of the table, X / Y horizontal tilt angle, single-point load, battery level, speed of each axis, and fault codes; it has a built-in multi-level threshold warning function, automatically popping up audible and visual alarms when tilt angle exceeds tolerance, load is overloaded, or voltage is too low; it has three levels of operation permissions: operator permission, maintenance permission, and administrator permission; the emergency stop button has a hardware dual-channel safety circuit; it is equipped with a 48V 200Ah battery pack and a smart charger, supporting 380V external charging.

[0034] The control system includes a main circuit breaker, CPU, switching power supply, filter, servo controller, AC contactor, remote I / O module, and circuit breaker. Briefly: The main circuit breaker is responsible for the overall power supply protection of the system; the CPU is the main control unit of the entire equipment, using load sensor signals from the dual-axis tilt sensor and weighing pressure sensor to run the adaptive leveling control algorithm; the switching power supply supplies power to the low-voltage components; the filter suppresses electromagnetic interference generated by servo operation; multiple servo controllers drive the walking, lifting, swinging, and rotating servo axes respectively; the remote I / O module collects external sensor signals; the AC contactor and circuit breaker provide branch circuit disconnection and overload protection. The CPU, servo controller, and remote I / O module communicate in a network to form a closed-loop adaptive leveling control system, which is the hardware core for achieving high-precision dynamic leveling in this invention.

[0035] Safety features: Mechanical double self-locking: travel, lifting, rotation, and tilting motor brakes + mechanical self-locking structure; Hardware interlocking: automatic locking of the rotation shaft when the tilting shaft tilts by 15°, and power cut-off when exceeding the limit; Insulated and anti-static structure; Anti-collision buffer strips, lifting markings, grounding markings, and movement limit markings for the whole machine; Complete fault diagnosis program to distinguish hardware faults / parameter alarms and store historical fault logs; Manual leveling backup hand crank mechanism for emergency fine-tuning in case of power failure.

[0036] The technical solution of this invention has the following technical effects: automated leveling, high precision, and high efficiency; a four-point independent servo leveling and lifting module with 30 closed-loop adaptive leveling; static leveling accuracy of ±0.1°; continuous dynamic compensation during travel; no need for repeated manual operation; and a 90% reduction in leveling time for a single aircraft; relying on the collaboration of tilt angle and weighing multi-sensor systems, it automatically compensates for ground unevenness and eccentric loads, eliminating the need for manual shims.

[0037] Significantly improves the safety of aerospace products. When traveling over ramps, seams, and uneven surfaces, the platform is dynamically leveled in real time, ensuring that the platform remains level at all times. The spacecraft is free from additional shear and overturning stress, eliminating deformation and damage to precision instruments and composite material shells. Start-stop acceleration is strictly controlled to ≤0.5g, eliminating the risk of inertial impact.

[0038] The integrated transfer and posture adjustment eliminates multiple lifting processes. The trolley integrates 360° rotation and 0~15° tilting functions. After the workpiece is transferred to the position, the final assembly posture adjustment can be completed directly on the table. There is no need for secondary lifting and transfer on a two-dimensional turntable, which reduces the risk of collisions during lifting, saves factory crane resources, and shortens the final assembly cycle.

[0039] Meets stringent aerospace electrical and cleanroom standards. The layered insulation structure meets an insulation index of ≥100MΩ, and the independent grounding meets aerospace anti-static requirements. The whole machine is designed to be dustproof and rustproof, and is suitable for Class 100,000 cleanrooms. The entire motion mechanism has mechanical and electrical double self-locking in the event of power failure, eliminating the risk of workpiece displacement or falling.

[0040] The control system features intelligent early warning and maintenance. A single HMI integrates all data on walking, leveling, turning, tilting, power consumption, and load, providing a visual and intuitive operation. It offers automatic audible and visual warnings for tilt angle, overload, and low voltage, along with built-in fault diagnosis logs to reduce maintenance difficulty. Three-level access control prevents accidental operation.

[0041] Heavy-duty and high-rigidity, it is compatible with the Q345 integral welded chassis with four independent balanced lifting for eccentric aerospace components. It has a rated load of 1.5t, bending resistance of 12000Nm, and a safety factor of 3. It automatically distributes the load to the four support points to address the eccentric center of gravity of the aircraft. The frame has uniform local stress and no permanent deformation. The equipment design life meets the requirements of 15 years for the main structure and 10 years for electrical components.

[0042] The target leveling tilt angle accuracy of this application is ±0.1°, which is ensured by the SWL35 worm gear screw jack, a 20-bit multi-turn absolute encoder, and a dual-axis tilt sensor. 1) SWL35 screw parameters: screw lead (P=10mm); 2) Servo-compatible 20-bit absolute encoder, single-turn resolution: R res =360 / 2 20 ≈0.000343 degrees, screw jack reduction ratio (i=32), theoretical displacement of the screw per LSB count by the encoder: △LSB=P / i2 20 =2.98*10 -7 For a 400mm span of mm / LSB support, the diagonal height difference is calculated as follows: a 0.1-degree tilt of the tabletop corresponds to a diagonal height difference of 0.698mm. To correct a tilt angle of ±0.1°, the diagonal lifting mechanism needs to have an adjustment stroke of at least 4.19mm; while the encoder's theoretical minimum displacement is much smaller than that value, and the hardware resolution margin is sufficient.

[0043] The system input includes dual-axis tilt sensors (X and Y tilt angles) and four-point pressure load cells (single-point support load). The PLC switches the sensor weights and control targets according to the working mode. A. Static leveling mode (assembly docking station): Control priority: Tilt angle closed loop is the first priority, and load balancing is the second priority.

[0044] Signal processing logic: The original signal from the tilt sensor is subjected to mean filtering (sampling window 500ms); the four-point load cells collect the actual load at each support point.

[0045] Control logic: The primary objective is to bring the X / Y tilt angle of the platform close to 0°. Under the constraint of a tilt angle accuracy of ±0.1°, the height of the four-point lead screw is then finely adjusted to minimize the load difference between the four support points and achieve load balance. If the load on a support point exceeds the rated 1.5t hardware protection threshold during the leveling process, the leveling is immediately interrupted and an alarm is triggered to prioritize structural safety.

[0046] B. Dynamic transfer and leveling mode (cart driving status): Control priority: Tilt angle closed-loop control takes precedence, while load balancing is relegated to an auxiliary constraint. During operation, road surface excitation changes rapidly, so ensuring the platform remains level is prioritized; load balancing only performs slow-cycle corrections to avoid high-frequency, violent reciprocating motion of the lead screw.

[0047] Signal processing logic: The tilt angle signal uses a second-order Butterworth low-pass filter to filter out high-frequency vibration noise caused by the bumps of the walking wheels; the load cell increases the filter window (2s moving average) to suppress impact load spikes; the load signal is only used for overload protection and does not participate in high-frequency leveling calculations.

[0048] Technical specifications: Under a 15° rotation condition, the maximum allowable bending moment Mmax at the center point of the interface surface is 12000 N·m. Simplified mechanical model: The maximum mass of the workpiece is M = 1500 kg, the eccentric distance e is taken as the load eccentric arm, and the gravitational acceleration g = 9.8 m / s².

[0049] When fully loaded with a 1.5t workpiece and the eccentricity is no more than 0.816m, the bending moment generated will not exceed 12000Nm, which is the design boundary condition of this trolley.

[0050] The chassis and tilting frame are made of Q345B with a yield strength of 345MPa, a safety factor of 3, and an allowable stress of 115MPa.

[0051] Dynamic leveling is used during the vehicle's driving and transportation process to suppress chassis attitude disturbances caused by road joints, minor slopes, and uneven ground. Sampling frequency: The original sampling frequency of the tilt sensor is 100Hz; Filtering algorithm: The original tilt angle signal is passed through a second-order Butterworth low-pass filter with a cutoff frequency of fc=2,mathrmHz, which filters out high-frequency bumps and vibrations above 5Hz caused by the walking wheels and spring suspension, avoids misjudging the walking vibration as the platform tilt, and prevents high-frequency vibration of the lead screw. System control cycle: The PLC closed-loop control cycle is set to 50ms (20Hz) to balance response speed and actuator life; The complete dynamic leveling process is as follows: 1. The system detects that the walking enable signal is valid and automatically switches to dynamic leveling mode; 2. The system collects raw X and Y axis tilt angle data at 100Hz; 3. Second-order low-pass filtering removes high-frequency vibration interference from walking; 4. The PLC reads the filtered tilt angle and calculates the target height that the four lifting screws need to compensate for; 5. The output position command drives the four servo screws to perform differential lifting compensation; 6. The encoder position and the filtered tilt angle are read every 50ms control cycle to form a closed loop; 7. The load cell uses a 2-second moving average filter, which is only used for overload protection and does not participate in the rapid leveling calculation; 8. Once the walking enable is revoked, the system automatically switches back to static leveling mode and re-executes the tilt angle priority + load balancing complete leveling logic.

Claims

1. A multi-degree-of-freedom adaptive leveling transport vehicle suitable for aerospace assembly, characterized in that, include: The heavy-duty chassis assembly adopts a thick-walled rectangular tube integral welded frame, with four sets of independent suspension steering wheel mounting seats installed at the bottom and lifting mechanism mounting flanges arranged at the four corners. The omnidirectional steering wheel travel module includes four sets of servo steering wheel units, which are respectively installed on four sets of independent suspension steering wheel mounting seats at the bottom of the heavy-duty chassis assembly; The four-point independent servo leveling and lifting module includes four sets of worm gear servo lifting mechanisms, which are respectively installed on the lifting mechanism mounting flanges at the four corners of the heavy-duty chassis assembly. A rocking mechanism is disposed above the heavy-duty chassis assembly; A flipping mechanism is disposed above the swinging mechanism; A support fixture is provided on the support platform of the flipping mechanism; The multi-source sensing acquisition unit includes a dual-axis tilt sensor and a weighing pressure sensor installed at the four corners of the support platform of the flipping mechanism; The system is installed within the heavy-duty chassis assembly and is electrically connected to four sets of servo steering wheel units, four sets of worm gear servo lifting mechanisms, the swing mechanism, the tilting mechanism, the dual-axis tilt sensor, and the weighing pressure sensor. It is used to independently control the lifting stroke of the four sets of worm gear servo lifting mechanisms based on the feedback signals from the dual-axis tilt sensor and the weighing pressure sensor.

2. The multi-degree-of-freedom adaptive leveling transport trolley according to claim 1, characterized in that, Each servo steering wheel unit of the omnidirectional steering wheel travel module integrates a 48V absolute servo motor, a reducer, spring suspension, and polyurethane anti-slip and shock-absorbing tires.

3. The multi-degree-of-freedom adaptive leveling transport trolley according to claim 1, characterized in that, Each set of the four-point independent servo leveling and lifting module is a SWL35 worm gear servo lifting mechanism, with a rated load of 15t per set and a lifting stroke of 0-100mm. Each set is equipped with a 20-bit absolute encoder.

4. The multi-degree-of-freedom adaptive leveling transport trolley according to claim 1, characterized in that, The swing mechanism is driven by a backlash-free double gear, achieving stepless speed regulation rotation from 0 to 360°, with three speed settings: 5° / min, 15° / min, and 30° / min, and a rotation positioning accuracy of ±0.1°. The flipping mechanism is driven by an RV reducer servo, with a flipping angle of 0 to 15° to the left and right, and three speed settings: 3° / min, 5° / min, and 10° / min.

5. The multi-degree-of-freedom adaptive leveling transport trolley according to claim 1, characterized in that, The bearing platform of the swing mechanism has 98 M16 standard threaded interfaces reserved for matching the spacecraft mounting flange, and the flatness of the platform is ≤0.2mm.

6. The multi-degree-of-freedom adaptive leveling transport trolley according to claim 1, characterized in that, The supporting fixture includes an insulating pad with an insulation resistance of ≥100MΩ.

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