Double-rudder wheelchair with active posture adjustment function and control system and method thereof

Abstract

The application discloses a double-rudder wheel stair climbing wheelchair with active posture adjustment function and a control system and method thereof, and belongs to the field of medical rehabilitation robots. The wheelchair comprises a chassis assembly, the left and right sides of the chassis are provided with rudder wheels, the front and rear ends are provided with universal wheels, the bottom is suspended with a liftable crawler climbing assembly, and the top is connected with a posture adjustment assembly. The front and rear ends of the climbing assembly are provided with small swing arms which can be retracted and extended, so that the contact length of the crawler is increased when climbing stairs. The posture adjustment assembly adjusts the seat inclination and the barycenter position through double-hydraulic push rod hinged adjustment. The control system fuses IMU and 3D laser radar data, identifies the terrain in real time, automatically switches the flat ground / climbing mode, and actively adjusts the seat posture during the climbing process to keep the barycenter stable and ensure safety. The application takes into account the flat ground omnidirectional movement and the stair climbing ability, and improves the mobility, safety and adaptability of the wheelchair.

Description

Technical Field

[0001] This invention belongs to the field of medical rehabilitation robots and intelligent assistive devices, and specifically relates to a dual-steering wheelchair with active posture adjustment function, as well as its control system and method. Background Technology

[0002] With the increasing global trend of population aging and the rising demands for quality of life among people with disabilities, the market demand for intelligent wheelchairs, as an important assistive mobility tool, is growing. However, existing wheelchair technology still has many limitations in dealing with complex environments, especially stair obstacles.

[0003] Firstly, regarding performance on flat ground, traditional stair-climbing wheelchairs often employ fixed tracked chassis or complex star-wheel structures to ensure the stability of their stair-climbing structure, resulting in a heavy chassis and a large turning radius. These wheelchairs have poor maneuverability on flat ground, making it difficult to maneuver flexibly, move laterally (crawl), or rotate in place in narrow indoor spaces (such as home corridors or bathrooms), causing significant inconvenience to users.

[0004] Secondly, regarding safety and stability when climbing stairs, existing tracked stair-climbing wheelchairs mostly employ a passive center-of-gravity balance design. During stair climbing, the user's center of gravity shifts significantly as the wheelchair's tilt angle changes. Current devices typically have a fixed seat angle or can only be manually adjusted, unable to dynamically adjust the seat, backrest, and footrest positions based on real-time posture. In the event of an emergency or a change in stair incline, the wheelchair is prone to tipping backward or sliding forward, posing a significant safety hazard.

[0005] Secondly, regarding track adaptability, the track length and contact area of ​​traditional stair-climbing devices are usually fixed. During contact with the edge of a staircase, the fixed track structure often has a small contact area, easily leading to insufficient traction, slippage, or jamming. Furthermore, when not climbing stairs, the exposed track structure increases the chassis width, affecting maneuverability.

[0006] Finally, regarding the control system architecture, existing intelligent wheelchair control systems are mostly based on low-computing-power microcontrollers (MCUs), which are unable to support complex kinematic calculations, multi-sensor fusion (such as IMU attitude calculation), and multi-bus collaborative control. At the same time, most devices lack integrated communication modules (such as 4G remote monitoring), and drive control and safety control (such as attitude adjustment) often share the same bus, lacking real-time performance and safety isolation, making it difficult to meet the high safety requirements of stair-climbing scenarios.

[0007] In conclusion, developing an intelligent wheelchair that combines high mobility on flat ground, high stability when climbing stairs, the ability to actively adjust its center of gravity to adapt to changes in posture, and a high-performance integrated control system has become an urgent technical problem to be solved in the field of medical rehabilitation robots. Summary of the Invention

[0008] This invention addresses the aforementioned problems by proposing a dual-steering wheelchair with active posture adjustment function, along with its control system and method. The concept lies in combining ground-moving steering wheels with a track mechanism folded into the bottom of the wheelchair chassis to enhance the flexibility of posture adjustment. Simultaneously, a posture adjustment component that adjusts the center of gravity and an integrated control system adaptively adjust the wheelchair's posture while climbing stairs, improving safety and expanding the applicable scenarios for stair-climbing wheelchairs.

[0009] In the first aspect, the present invention proposes a dual-steering wheel stair-climbing wheelchair with active posture adjustment function, comprising a chassis assembly 1, with steering wheels 5 respectively provided on the left and right sides of the bottom of the chassis assembly 1, and universal wheels 6 that contact the ground connected to the front and rear ends of the left and right sides of the chassis assembly 1. A stair-climbing actuator 4 is suspended at the bottom of the chassis component 1, and an attitude adjustment component 7 is connected to the top of the chassis component 1. The stair-climbing execution component 4 includes a track mechanism 42, with drive motors 43 connected to the front and rear ends of the track mechanism 42, and the drive shafts of the drive motors 43 are all in the left-right direction; small swing arms 44 are connected to the left and right ends of the drive shafts; the small swing arms 44 can rotate around the drive shaft to be parallel to the track mechanism 42, or rotate to be retracted to the bottom of the chassis component 1. The top of the track mechanism 42 is connected to the transverse connecting rod 14 located at the bottom of the chassis assembly 1 via a connecting rod 45 and a hydraulic push rod 41; an IMU is installed on the transverse connecting rod 14; the axis of the hydraulic push rod 41 is inclined forward. The posture adjustment component 7 includes a seat 71, a footrest 73 is provided on the front side of the seat 71, and a backrest 72 is connected to the rear side of the seat 71 via a backrest motor; armrests 75 are connected to the left and right sides of the seat 71; and 3D LiDAR sensors 8 are provided on the armrests 75. One end of a connector 76 is hinged to the left and right sides of the bottom of the seat 71; the other end of the connector 76 is hinged to the front of the chassis assembly 1; a connecting plate 761 connects the left and right connectors 76. One end of the second hydraulic push rod 742 is hinged to the rear of the seat 71, and the other end of the second hydraulic push rod 742 is hinged to the connecting plate 761; one end of the first hydraulic push rod 741 is hinged to the connecting plate 761, and the other end is hinged to the rear of the chassis assembly 1. An installation compartment is located behind the backrest 72, which contains the wheelchair battery and the main control computing module. The main control computing module is connected to the control terminals of the steering wheel 5, drive motor 43, attitude adjustment component 7, and 3D laser radar sensor 8.

[0010] More specifically, a Hall encoder is installed inside the hydraulic push rod 41.

[0011] The number of connecting rods 45 provided between the track mechanism 42 and the transverse link 14 is two.

[0012] More specifically, the end of the small swing arm 44 connected to the drive motor 43 is provided with a swing arm drive wheel 441 that passes through the drive shaft of the drive motor 43; the other end of the small swing arm 44 is provided with a swing arm driven wheel 442, and the swing arm drive wheel 441 and the swing arm driven wheel 442 are connected by track drive.

[0013] More specifically, the steering wheel 5 includes a steering motor 52 connected to the chassis assembly 1, and a drive hub motor 51 is connected to the bottom of the steering motor 52.

[0014] Secondly, the present invention proposes a dual-steering wheelchair control system with active posture adjustment function, which is applied to the above-mentioned wheelchair and includes a main control computing module, a drive control module and a sensor module. The sensor module includes an IMU and a 3D lidar sensor 8 mounted on the transverse link 14; The main control computing module includes a core processing unit and an expansion baseboard; the expansion baseboard integrates a communicator, power supply, and signal transmission bus interface; the main control computing module functions as the control motherboard for the wheelchair. The core processing unit receives the pose data from the IMU and the point cloud data from the 3D LiDAR sensor 8, fuses them, runs the positioning and navigation algorithm program, and generates real-time navigation status and target control parameters. The core processing unit receives task instructions from an external host computer via an expansion baseboard. These task instructions include motor speed gear instructions and mode switching gear signals. The core processing unit logically integrates navigation status parameters with task instructions from the host computer to generate underlying execution instructions. These underlying execution instructions include hub motor speed instructions, steering angle instructions, track lifting hydraulic valve instructions, swing arm angle instructions, and seat posture adjustment instructions. After protocol adaptation, the underlying execution instructions are sent to the drive control module via the expansion base plate. The drive control module includes a hub motor drive unit, a track motor drive unit, a hydraulic control unit, and an attitude motor drive unit; The hub motor drive unit receives the motor commands and controls the drive hub motor 51 and steering motor 52. The track motor drive unit receives the swing arm angle command and controls the small swing arm 44; The hydraulic control unit receives hydraulic valve commands to control the hydraulic push rod 41 to lift and lower the stair-climbing actuator 4; The posture motor drive unit receives motor commands to control the footrest and backrest motors.

[0015] More specifically, the communicator is a 4G communicator, and the signal transmission interface is an RS485 bus communication interface and a CAN bus communication interface; More specifically, the hub motor drive unit communicates with the drive hub motor 51 and the steering motor 52 via an RS485 bus; the hydraulic control unit communicates with the hydraulic push rod 41 via a CAN bus; and the posture motor drive unit communicates with the footrest and backrest motors via a CAN bus.

[0016] Thirdly, the present invention proposes the above-mentioned wheelchair control method, the steps of which include: S1. The wheelchair is powered on, the main control computing module loads the operating system, and the drive control module completes the underlying hardware self-test; the system calibrates the IMU zero bias installed on the transverse link 14 and establishes the initial attitude reference system; the lidar sensor 8 installed on the armrest 75 is initialized and the local environment coordinate system is established. S2. The main control computing module receives user instructions and combines the ground slope information detected by the IMU and the point cloud data scanned by the lidar sensor 8 to determine the current terrain features; if it is determined to be flat ground, it enters flat ground mode; if it is determined to be stairs or a stair climbing instruction is received, it enters stair climbing preparation mode. When entering flat ground mode, the hydraulic push rod 41 retracts, driving the stair-climbing actuator 4 to rise and be stored between the two drive hub motors 51 via the connecting rod 45. The small swing arm 44 retracts to the bottom of the chassis assembly 1. The main control calculation module calculates the kinematic parameters according to the user's instructions and sends control commands to adjust the speed of the drive hub motors 51 and the steering angle of the steering mechanism 52, realizing differential steering, crab-like translation, or stationary rotation of the wheelchair. During this process, the IMU monitors the chassis posture in real time. If abnormal vibration or tilt is detected, the speed of the drive hub motors 51 is adjusted. When entering the stair-climbing preparation mode, the wheelchair stops moving on flat ground; the main control calculation module controls the hydraulic push rod 41 to extend, which drives the stair-climbing execution component 4 to descend until the track contacts the ground through the connecting rod 45; the small swing arm 44 motor is controlled to rotate, so that the small swing arm 44 unfolds to the same plane as the track mechanism 42 and the universal wheel 6; the system detects the load current of the track mechanism 42, and when the hydraulic push rod 41 extends to the preset grounding length, after confirming that the track has been reliably grounded, the state of the steering wheel is locked or the steering wheel is put into the follow-up unloading state.

[0017] In stair-climbing mode, the lidar sensor 8 scans the edges and height information of the stair steps in real time, and combines the real-time tilt angle of the wheelchair detected by the IMU to perform multi-sensor fusion positioning; the main control computing module controls the differential drive of the two side track mechanisms 42 to drive the wheelchair to climb the stairs in the forward direction based on the fused pose information. The main control computing module compares the pitch angle fed back by the IMU with the safety threshold in real time; if the backward tilt angle of the wheelchair increases, the hydraulic control unit drives the first hydraulic push rod 741 and the second hydraulic push rod 742 to adjust the seat height and tilt angle, and controls the backrest motor to tilt the backrest 72 forward, while adjusting the angle of the footrest 73 to move the center of gravity of the person forward to counteract the backward tilting torque. If the wheelchair tilts forward too much, adjust the seat height, tilt angle, and backrest angle to shift the person's center of gravity backward. If the IMU detects that the wheelchair tilt angle exceeds the limit safety threshold, or if the lidar sensor 8 detects that the staircase structure ahead has collapsed, an obstacle is too close, or the hydraulic system pressure is abnormal, the main control computing module triggers an emergency stop command, cuts off the power to the track assembly and hub motor, controls the first hydraulic push rod 741 and the second hydraulic push rod 742 to lock the current posture, and sends an alarm message to the host computer; after user confirmation, the power to the track assembly and hub motor is restored, and the hydraulic system is unlocked. When the main control computing module performs ground segmentation and plane fitting on the forward point cloud data collected in real time by the 3D LiDAR sensor 8, determines that the wheelchair has completely reached the stair platform, and the chassis pitch angle fed back by the IMU is within the horizontal threshold range, the stair climbing is determined to be over.

[0018] More specifically, the process by which the main control computing module determines that the wheelchair has fully reached the stair landing is as follows: The criteria for determining the arrival of the stair platform are as follows: Laser point cloud data for a preset number of consecutive frames (preferably 5-8 frames) shows that, within a preset safe distance (preferably 0.8m-1.2m) directly in front of the wheelchair, the point cloud height variance is lower than the flatness threshold (preferably ≤15mm), and no step edge feature points with abrupt changes in vertical height are detected; simultaneously, the spatial angle between the fitted forward ground plane and the wheelchair travel reference plane is less than the horizontal tolerance angle (preferably ≤2°). When the above conditions are met, and the absolute value of the chassis pitch angle fed back by the IMU in real time is less than or equal to the horizontal threshold (preferably 1.5°), the main control computing module outputs the platform arrival status flag after cross-verification by multiple sensors, triggering the storage and mode switching process; controls the hydraulic push rod 41 to retract, and lifts and stores the stair climbing execution component 4 through the connecting rod 45, controls the small swing arm 44 to retract; releases the lock of the steering wheel 5, and the system automatically switches back to the flat ground mode, waiting for the next instruction.

[0019] The innovation of this invention lies in: (1) A composite chassis structure consisting of two side steering wheel drive units and four corner universal support wheels was designed. Each steering wheel drive unit integrates a hub motor and a steering motor to achieve decoupled control of drive and steering; together with the four corner universal wheels, a stable four-point support system is formed. This structure breaks through the limitations of the traditional wheelchair's degree of freedom of movement at the mechanical level, and realizes the physical basis of three movement modes: differential steering, lateral crabbing, and stationary rotation without the need for additional auxiliary wheels.

[0020] (2) A suspended stair-climbing actuator layout is proposed. The stair-climbing mechanism is suspended from the transverse connecting rod in the middle of the chassis via a connecting rod, and is located between the two steering wheel drive units. The connecting rod is mechanically linked with the hydraulic push rod, and the linear thrust of the hydraulic system is converted into the vertical lifting motion of the stair-climbing mechanism through the connecting rod. This suspension structure not only optimizes the spatial envelope of the chassis and avoids motion interference between the stair-climbing mechanism and the drive wheels, but also uses the transverse connecting rod as a rigid support to ensure the synchronization and stability of the stair-climbing mechanism during the lifting process.

[0021] (3) Four rotatable and retractable small swing arms are designed at the front and rear ends of the track device. Driven by the built-in motor, the swing arms can retract into the inner envelope of the chassis in flat mode and unfold to the same plane as the track in stair climbing mode. This track structure with variable geometry mechanically increases the effective contact length between the track and the stair steps in stair climbing mode, solving the structural defects of traditional fixed track with small contact area and easy slippage.

[0022] The beneficial effects of this invention include: (1) Thanks to the composite chassis structure composed of dual steering wheel drive unit and four corner universal support wheels, the wheelchair breaks through the traditional wheelchair's freedom of movement when driving on flat ground. It can achieve lateral crabging and rotation in place in narrow spaces without additional auxiliary wheels. At the same time, the universal wheels distributed at the four corners form a stable four-point support system, which effectively prevents the risk of tipping over when turning at high speed and significantly improves the physical stability and passability when driving on flat ground.

[0023] (2) Through the four-arm track structure with variable contact area, the wheelchair can mechanically increase the effective contact length between the track and the stair steps when climbing stairs, which significantly improves friction and grip, effectively reduces slipping and jamming during the climbing process, enhances the mechanical adaptability of the wheelchair to non-standard stair terrain, and makes the climbing process more stable and smooth.

[0024] (3) The hydraulic linkage stair climbing mechanism based on the transverse linkage suspension realizes the embedded integration of the drive and stair climbing module. The stair climbing execution component is completely hidden between the two drive wheels in the storage state, without increasing the extra width and length of the wheelchair. This avoids the risk of collision with ground obstacles when the stair climbing mechanism travels on flat ground, protects the track device from damage, optimizes the spatial envelope of the chassis, and ensures the synchronicity and rigidity of the stair climbing mechanism during the lifting process.

[0025] (4) The optimized mechanical layout frees up key space for the multi-degree-of-freedom hydraulic adjustment mechanism under the seat. The stable chassis suspension structure provides a solid mechanical basis for the dynamic posture adjustment of the seat during the stair climbing process, so that the active center of gravity adjustment mechanism can be executed safely and effectively, thereby ensuring the overall safety of the stair climbing process at the mechanical structure level and preventing overturning accidents caused by center of gravity shift.

[0026] (5) The overall structure adopts a layout with the battery and main control computing module at the rear and the lidar integrated into the armrest. This not only lowers the center of gravity of the whole vehicle and improves driving stability, but also makes the wheelchair look more like an ordinary electric wheelchair, reducing the psychological burden on users and making it easier to enter various public places. At the same time, it protects the core control components and sensors from external collision damage and extends the service life of the equipment. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall structure of the dual-steering wheelchair with active posture adjustment function for climbing stairs in the flat ground mode of the present invention.

[0028] Figure 2 This is a side view of the overall structure of the stair-climbing mode of the dual-steering wheelchair with active posture adjustment function of the present invention.

[0029] Figure 3a This is a top view of the chassis assembly of the present invention.

[0030] Figure 3b This is a top view of the chassis assembly of the present invention from another angle.

[0031] Figure 4a This is a schematic diagram of the structure of the stair-climbing execution component of the present invention.

[0032] Figure 4b This is a schematic diagram of the structure of the stair-climbing execution component of the present invention.

[0033] Figure 5 This is a schematic diagram of the attitude adjustment component structure of the present invention.

[0034] Figure 6 This is a block diagram of the hardware architecture of the control system of the present invention.

[0035] Figure 7This is the kinematic topology diagram of the planar linkage mechanism of the present invention.

[0036] Figure 8 This is a flowchart of the control method of the present invention.

[0037] Figure 9 This is an exploded view of the small swing arm of the present invention. Detailed Implementation

[0038] according to Figure 1 and Figure 2 A dual-steering wheelchair with active posture adjustment function includes a chassis assembly 1. Steering wheels 5 are respectively provided on the left and right sides of the bottom of the chassis assembly 1, and omnidirectional wheels 6 that contact the ground are respectively connected to the front and rear ends of the left and right sides of the chassis assembly 1. A stair-climbing actuator 4 is suspended at the bottom of the chassis component 1, and an attitude adjustment component 7 is connected to the top of the chassis component 1. according to Figures 3a-4b The stair-climbing execution component 4 includes a track mechanism 42, with drive motors 43 connected to the front and rear ends of the track mechanism 42 respectively. The drive shafts of the drive motors 43 are all in the left-right direction. Small swing arms 44 are connected to the left and right ends of the drive shaft respectively. The small swing arms 44 can rotate around the drive shaft to be parallel to the track mechanism 42, or rotate to retract to the bottom of the chassis component 1. The top of the track mechanism 42 is connected to the transverse connecting rod 14 located at the bottom of the chassis assembly 1 via a connecting rod 45 and a hydraulic push rod 41; an IMU is installed on the transverse connecting rod 14; the axis of the hydraulic push rod 41 is inclined forward. The posture adjustment component 7 includes a seat 71, a footrest 73 is provided on the front side of the seat 71, and a backrest 72 is connected to the rear side of the seat 71 via a backrest motor; armrests 75 are connected to the left and right sides of the seat 71; and 3D LiDAR sensors 8 are provided on the armrests 75. One end of a connector 76 is hinged to the left and right sides of the bottom of the seat 71; the other end of the connector 76 is hinged to the front of the chassis assembly 1; a connecting plate 761 connects the left and right connectors 76. One end of the second hydraulic push rod 742 is hinged to the rear of the seat 71, and the other end of the second hydraulic push rod 742 is hinged to the connecting plate 761; one end of the first hydraulic push rod 741 is hinged to the connecting plate 761, and the other end is hinged to the rear of the chassis assembly 1. An installation compartment is located behind the backrest 72, which contains the wheelchair battery and the main control computing module. The main control computing module is connected to the control terminals of the steering wheel 5, drive motor 43, attitude adjustment component 7, and 3D laser radar sensor 8.

[0039] A Hall encoder is installed inside the hydraulic push rod 41.

[0040] The number of connecting rods 45 provided between the track mechanism 42 and the transverse link 14 is two.

[0041] The end of the small swing arm 44 connected to the drive motor 43 is provided with a swing arm drive wheel 441 that passes through the drive shaft of the drive motor 43; the other end of the small swing arm 44 is provided with a swing arm driven wheel 442, and the swing arm drive wheel 441 and the swing arm driven wheel 442 are connected by track drive.

[0042] The steering wheel 5 includes a steering motor 52 connected to the chassis assembly 1, and a drive hub motor 51 is connected to the bottom of the steering motor 52.

[0043] according to Figure 6 The aforementioned wheelchair control system includes a main control computing module, a drive control module, and a sensor module. The sensor module includes an IMU and a 3D lidar sensor 8 mounted on the transverse link 14; The main control computing module includes a core processing unit and an expansion baseboard; the expansion baseboard integrates a communicator, power supply, and signal transmission bus interface; the main control computing module functions as the control motherboard for the wheelchair. The core processing unit receives the pose data from the IMU and the point cloud data from the 3D LiDAR sensor 8, fuses them, runs the positioning and navigation algorithm program, and generates real-time navigation status and target control parameters. The core processing unit receives task instructions from an external host computer via an expansion baseboard. These task instructions include motor speed gear instructions and mode switching gear signals. The core processing unit logically integrates navigation status parameters with task instructions from the host computer to generate underlying execution instructions. These underlying execution instructions include hub motor speed instructions, steering angle instructions, track lifting hydraulic valve instructions, swing arm angle instructions, and seat posture adjustment instructions. After protocol adaptation, the underlying execution instructions are sent to the drive control module via the expansion base plate. The drive control module includes a hub motor drive unit, a track motor drive unit, a hydraulic control unit, and an attitude motor drive unit; The hub motor drive unit receives the motor commands and controls the drive hub motor 51 and steering motor 52. The track motor drive unit receives the swing arm angle command and controls the small swing arm 44; The hydraulic control unit receives hydraulic valve commands to control the hydraulic push rod 41 to lift and lower the stair-climbing actuator 4; The posture motor drive unit receives motor commands to control the footrest and backrest motors.

[0044] The communicator is a 4G communicator, and the signal transmission interface is an RS485 bus communication interface and a CAN bus communication interface. The hub motor drive unit communicates with the drive hub motor 51 and the steering motor 52 via an RS485 bus; the hydraulic control unit communicates with the hydraulic push rod 41 via a CAN bus; and the posture motor drive unit communicates with the footrest and backrest motors via a CAN bus.

[0045] according to Figure 8 The above-mentioned wheelchair control method includes the following steps: S1. The wheelchair is powered on, the main control computing module loads the operating system, and the drive control module completes the underlying hardware self-test; the system calibrates the IMU zero bias mounted on the transverse link 14 and establishes the initial attitude reference frame. S11. Establish a body coordinate system with the geometric center of chassis component 1 as the origin. ,in The axis points directly in front of the wheelchair. The axis points to the left. The desired velocity vector of the wheelchair body is defined as... ,in This represents the longitudinal speed (forward / backward). This refers to the lateral speed (crab walk). The angular velocity is the rotational velocity in place. These three variables constitute the three degrees of freedom for the wheelchair's motion in a plane.

[0046] S12. Let the coordinates of the center of the left steering wheel drive unit 5 in the body coordinate system be... The center coordinates of the right steering wheel drive unit 5 are Because of the symmetrical structure of wheelchairs, they are usually... , , ,in This refers to the wheel track.

[0047] S13. Based on the principles of rigid body planar kinematics, calculate the theoretical linear velocity vector of each steering wheel center in the body coordinate system. For the left-hand steering wheel ( ) and right steering wheel ( ):

[0048] in, The center of the left steering wheel in the body coordinate system Theoretical linear velocity components in the axial direction, The center of the left steering wheel in the body coordinate system Theoretical linear velocity components in the axial direction; The center of the right steering wheel in the body coordinate system Theoretical linear velocity components in the axial direction, The center of the right steering wheel in the body coordinate system Theoretical linear velocity components in the axial direction; These are the x and y coordinates of the center of the left steering wheel in the aircraft coordinate system. These are the x and y coordinates of the center of the right steering wheel in the body coordinate system. This step distributes the three degrees of freedom components of the body to the contact points of each wheel.

[0049] S2. The main control computing module receives user instructions and combines the ground slope information detected by the IMU and the point cloud data scanned by the lidar sensor 8 to determine the current terrain features; if it is determined to be flat ground, it enters flat ground mode; if it is determined to be stairs or a stair climbing instruction is received, it enters stair climbing preparation mode. When entering the flat ground mode, control the hydraulic push rod 41 to retract, and drive the stair climbing execution component 4 to rise through the connecting rod 45 and be stored between the two drive hub motors 51, and control the small swing arm 44 to retract to the bottom of the chassis component 1; At this point, the steering motor 52 of each steering wheel needs to adjust the orientation of the steering wheel 5 to align it with the theoretical velocity vector direction. Target steering angle (relative to) The axis is calculated by the main control calculation module using the arctangent function:

[0050] in, The target steering angle for the left wheel steering motor. The target steering angle for the right wheel steering motor.

[0051] Drive speed of each drive hub motor 51 The magnitude of the theoretical velocity vector:

[0052] The main control computing module will solve the and As the target position command, the calculated and As the target speed command, it is sent to the controllers of the left and right wheel hub motors via the 485 bus.

[0053] When the theoretical velocity vector magnitude approaches zero or the rate of change of the steering angle is too large, the main control calculation module algorithm introduces damped smoothing filtering to prevent high-frequency oscillations of the steering wheel. Based on the above general kinematic model, this embodiment achieves three typical motion modes by setting different combinations of input variables: (a) Differential mode: Setting , (Or maintain the current course), through Enables steering. This mode is suitable for high-speed driving in open spaces.

[0054] (b) Crab-shaped (translation) mode: Settings ,and (Pure horizontal) or (Obliquely), at this time The two wheels rotate in parallel, allowing the wheelchair to move horizontally as a whole. This mode is suitable for lateral movement in narrow corridors.

[0055] (c) In-place rotation mode: Setting , ,at this time (The two wheels are perpendicular to the transverse link 14), and The wheelchair rotates around the center point. This mode is suitable for turning around inside elevators or doorways.

[0056] This embodiment successfully distributes the three degrees of freedom motion requirements of the wheelchair body to the four execution degrees of freedom of the dual steering wheels through the above kinematic model, realizing omnidirectional mobility.

[0057] When entering the stair-climbing preparation mode, the wheelchair stops moving on flat ground; the main control calculation module controls the hydraulic push rod 41 to extend, which drives the stair-climbing execution component 4 to descend through the connecting rod 45 until the track mechanism 42 contacts the ground; the small swing arm 44 motor is controlled to rotate, so that the small swing arm 44 unfolds to the same plane as the track mechanism 42 and the universal wheel 6; the system detects the load current of the track mechanism 42, and when the hydraulic push rod 41 extends to the preset grounding length, after confirming that the track has been reliably grounded, the state of the steering wheel is locked or the steering wheel is put into the follow-up unloading state.

[0058] At this point, the main control calculation module completely severs its reliance on the wheel hub motor's wheel odometer to eliminate invalid data interference caused by slippage at the edge of a step or suspension. The main control calculation module defines a global absolute geodetic coordinate system. Based on the system's kinematic topology, the multi-degree-of-freedom state vector is defined as:

[0059] in, The absolute pitch angle for the stair-climbing execution component. The angular velocity of the absolute pitch angle of the stair-climbing component. The angle between the connector and chassis assembly 1. The angle between the connector and seat 71, The absolute angle of inclination of the plane containing seat 71 relative to the horizontal plane.

[0060] like Figure 5 and Figure 7 Define the local coordinate system of the chassis Its origin is located at the hinge point between connector 76 and chassis assembly 1. (Located at the midpoint between the front swivel wheel and the drive wheel). Based on the mechanical physical configuration, extract the key points and length parameters: 1. First hydraulic push rod 741 chassis end Located at the rear caster wheel position, set arrive The chassis baseline length is .

[0061] 2. Connector seat end A rigid main body for the connector is located at the halfway point of the base. arrive The length is Its angle relative to the chassis is .

[0062] 3. Connection of the first hydraulic push rod 741 Midpoint of the connecting plate 761 The length of the first hydraulic push rod is .

[0063] 4. Connection of the second hydraulic push rod 742 Rear hinge point of the base (Near the backrest rotation axis), the length of the second hydraulic push rod 742 is Assume the total length of the base is... ,by The angle between the connector at the vertex and the base is... .

[0064] The system establishes a direct mapping relationship between the hydraulic rod's extension and contraction and the angle through closed-loop vector equations:

[0065] First hydraulic rod 741 closed-loop constraint:

[0066] in, The midpoint of the 761 consecutive boards Coordinate vector in the local coordinate system of the chassis The first hydraulic push rod 741 is at the chassis end hinge point. Coordinate vector in the local coordinate system of the chassis For point In the local coordinate system of the chassis The coordinate values ​​along the axis. For point In the local coordinate system of the chassis The coordinate values ​​along the axis.

[0067] Second hydraulic rod 742 closed-loop constraint:

[0068] in, The rearmost hinge point of the base Coordinate vector in the local coordinate system of the chassis This refers to the real-time length of the first hydraulic push rod 741. This is the real-time length of the second hydraulic push rod 742.

[0069] To ensure absolute stability for occupants during stair climbing, the system incorporates "absolute horizontal kinematic constraints on the base." This constraint applies when the seat is completely parallel to the ground. The target attitude function satisfies:

[0070] Let the total mass of the human-machine system be... ,set up Let be the origin of the seat's local coordinate system, and let the local centroid offset of the origin of the seat's local coordinate system be... Global center of gravity In the horizontal direction of the geodetic coordinate system ( The projected coordinates of the axis are analyzed as follows:

[0071] in, The absolute coordinates of the instantaneous rotation center (ICR) of the track mechanism 42 when it engages with the edge of the step at a specific moment are given. Its position jumps periodically as it crosses the step and is calibrated in real time by the lidar point cloud. This represents the offset of the equivalent centroid along the seat plane in the local coordinate system of the seat. This represents the offset of the equivalent centroid in the local coordinate system of the seat, perpendicular to the seat plane.

[0072] In stair-climbing mode, the LiDAR sensor 8 scans the edges and height of the stair steps in real time, and combines this with the real-time tilt angle of the wheelchair detected by the IMU for multi-sensor fusion positioning; the deployed front and rear small swing arms 44 greatly extend the effective contact surface of the tracks. The system establishes inequality hard constraints on the track-supported polygon:

[0073] in, and These are the real-time projected coordinates of the stair climbing execution component 4 and the edges of the stairs below and above; This is to provide a safety margin for preventing overturning.

[0074] The main control computing module uses the chassis pitch angle fed back in real time by the IMU. Calculate stability risk. The control system transforms center of gravity adjustment and attitude maintenance into a quadratic programming problem with inequality physical boundary constraints:

[0075] The objective function of the quadratic programming problem It includes a center of gravity stability term and a posture comfort term, each composed of dynamic weighting coefficients. and Weighted averages are used to achieve layered optimization that balances safety and comfort. Among these, The center of gravity stability weighting coefficient is used to measure the global center of gravity of the system. With Security Center The degree of punishment for deviation; This is a posture comfort weighting coefficient used to measure the seat tilt angle constraint error. The degree of punishment; and To adapt to dynamic weights, in normal stable cruise mode Prioritize keeping the base level, in extreme anti-tipping maneuver mode. Prioritize ensuring the stability of the center of gravity.

[0076] Its hierarchical control execution logic is as follows: 1. When the overall center of gravity When far from the stability boundary, the optimizer assigns extremely high weights to attitude level tracking. The algorithm forces the solution to satisfy... The inverse kinematics of the linkage. The main control calculation module calculates the corresponding [function / method] based on the inverse kinematics target. and The hydraulic cylinder's target stroke drives the hydraulic valve circuit, ensuring that the base remains parallel to the ground throughout the entire climbing process.

[0077] 2. If suddenly encountering a steep slope or obstacle... Surge, calculate center of gravity Imminent Breakthrough of Physical Hard Boundaries At that time, the system immediately flips the weights ( The optimizer actively discards level constraints (breaking the equation). Prioritize solving the safety center The optimal approximate solution is obtained by instructing the first and second hydraulic rods to perform large-stroke nonlinear compensation, forcibly shifting the center of gravity of the human and machine forward or backward to counteract the overturning moment, thus ensuring the safety of personnel at the algorithm level.

[0078] If the IMU detects that the wheelchair tilt angle exceeds the limit safety threshold, or if the lidar sensor 8 detects that the staircase structure ahead has collapsed, an obstacle is too close, or the hydraulic system pressure is abnormal, the main control computing module triggers an emergency stop command, cuts off the power to the track assembly and hub motor, controls the first hydraulic push rod 741 and the second hydraulic push rod 742 to lock the current posture, and sends an alarm message to the host computer; after user confirmation, the power to the track assembly and hub motor is restored, and the hydraulic system is unlocked.

[0079] When the main control computing module performs ground segmentation and plane fitting on the forward point cloud data collected in real time by the 3D LiDAR sensor 8, determines that the wheelchair has completely reached the stair platform, and the chassis pitch angle fed back by the IMU is within the horizontal threshold range, the stair climbing is determined to be over.

[0080] The main control computing module determines that the wheelchair has fully reached the stair landing as follows: The platform arrival determination condition is defined as a multi-sensor feature joint logic. Let the number of consecutive valid frames be... A preset safe distance scanning range is set directly in front of the wheelchair, with a point cloud flatness threshold of [value missing]. Define the wheelchair travel reference plane. The global horizontal reference plane is calculated from the IMU gravity vector, and the forward ground plane fitted by the 3D LiDAR sensor 8 is... The spatial angle between the two normal vectors is denoted as . The horizontal tolerance angle is denoted as The IMU level threshold is denoted as .

[0081] "Platform Arrived" status indicator The following combined conditions must be met simultaneously for the trigger to be effective:

[0082] in, For the first The variance of point cloud height within the scan range of the frame point cloud. This refers to the chassis pitch angle, which is fed back in real-time by the IMU. When the main control computing module continuously... When the frame detects that the above joint conditions are met, and no step edge feature points with abrupt changes in vertical height are detected in the point cloud data, it is determined that the wheelchair has fully reached the stair platform.

[0083] The main control computing module outputs a "platform arrived" status flag after cross-verification by multiple sensors, triggering the storage and mode switching process; it controls the hydraulic push rod 41 to retract, and lifts and stores the stair climbing execution component 4 through the connecting rod 45, and controls the small swing arm 44 to retract to the bottom of the chassis component 1; it releases the lock of the steering wheel 5, and the system automatically switches back to the flat ground mode, waiting for the next instruction.

Claims

1. A dual-stair-climbing wheelchair with active posture adjustment function, characterized in that: It includes a chassis assembly (1), with steering wheels (5) on the left and right sides of the bottom of the chassis assembly (1), and omnidirectional wheels (6) that contact the ground connected to the front and rear ends of the left and right sides of the chassis assembly (1). A stair-climbing actuator (4) is suspended at the bottom of the chassis assembly 1, and an attitude adjustment assembly (7) is connected to the top of the chassis assembly (1). The stair-climbing execution component (4) includes a track mechanism (42), with drive motors (43) connected to the front and rear ends of the track mechanism (42), and the drive shafts of the drive motors (43) are all in the left and right direction; small swing arms (44) are connected to the left and right ends of the drive shafts; the small swing arms (44) can rotate around the drive shaft to be parallel to the track mechanism (42), or rotate to be retracted to the bottom of the chassis component (1); The top of the track mechanism (42) is connected to the transverse link (14) at the bottom of the chassis assembly (1) via a connecting rod (45) and a hydraulic push rod (41); an IMU is provided on the transverse link (14); the axis of the hydraulic push rod (41) is inclined forward; The posture adjustment component (7) includes a seat (71), a footrest (73) is provided on the front side of the seat (71), and a backrest (72) is connected to the back side of the seat (71) via a backrest motor; armrests (75) are connected to the left and right sides of the seat (71); and a 3D laser radar sensor (8) is provided on the armrest (75). The bottom of the seat (71) is hinged to one end of the connector (76) on the left and right sides respectively; the other end of the connector (76) is hinged to the front of the chassis assembly (1); a connecting plate (761) is connected between the connectors (76) on the left and right sides. One end of the second hydraulic push rod (742) is hinged to the rear of the seat (71), and the other end of the second hydraulic push rod (742) is hinged to the connecting plate (761); one end of the first hydraulic push rod (741) is hinged to the connecting plate (761), and the other end is hinged to the rear of the chassis assembly (1); An installation compartment is provided behind the backrest (72), which contains a wheelchair battery and a main control computing module. The main control computing module is connected to the control terminals of the steering wheel (5), drive motor (43), posture adjustment component (7), and 3D laser radar sensor (8).

2. The dual-stair-climbing wheelchair with active posture adjustment function according to claim 1, characterized in that: A Hall encoder is installed inside the hydraulic push rod (41).

3. The dual-stair-climbing wheelchair with active posture adjustment function according to claim 1, characterized in that: The number of connecting rods (45) between the track mechanism (42) and the transverse link (14) is two.

4. The dual-stair-climbing wheelchair with active posture adjustment function according to claim 1, characterized in that: The end of the small swing arm (44) connected to the drive motor (43) is provided with a swing arm drive wheel (441) that passes through the drive shaft of the drive motor (43); the other end of the small swing arm (44) is provided with a swing arm driven wheel (442), and the swing arm drive wheel (441) and the swing arm driven wheel (442) are connected by track drive.

5. The dual-stair-climbing wheelchair with active posture adjustment function according to claim 1, characterized in that: The steering wheel (5) includes a steering motor (52) connected to the chassis assembly (1), and a drive hub motor (51) is connected to the bottom of the steering motor (52).

6. A dual-steering wheelchair control system with active posture adjustment function, applied to the dual-steering wheelchair with active posture adjustment function as described in claim 5, characterized in that: It includes a main control computing module, a drive control module, and a sensor module; The sensor module includes an IMU mounted on the transverse link (14) and a 3D lidar sensor (8); The main control computing module includes a core processing unit and an expansion baseboard; the expansion baseboard integrates a communicator, power supply, and signal transmission bus interface. The core processing unit receives the pose data from the IMU and the point cloud data from the 3D lidar sensor (8), fuses them, runs the positioning and navigation algorithm program, and generates real-time navigation status and target control parameters. The core processing unit receives task instructions from an external host computer via an expansion baseboard. These task instructions include motor speed gear instructions and mode switching gear signals. The core processing unit logically integrates navigation status parameters with task instructions from the host computer to generate underlying execution instructions. These underlying execution instructions include hub motor speed instructions, steering angle instructions, track lifting hydraulic valve instructions, swing arm angle instructions, and seat posture adjustment instructions. After protocol adaptation, the underlying execution instructions are sent to the drive control module via the expansion base plate. The drive control module includes a hub motor drive unit, a track motor drive unit, a hydraulic control unit, and an attitude motor drive unit; The hub motor drive unit receives the motor commands and controls the drive hub motor (51) and steering motor (52); The track motor drive unit receives the swing arm angle command and controls the small swing arm (44); The hydraulic control unit receives hydraulic valve commands to control the hydraulic push rod (41) to lift and climb the stairs actuator (4); The posture motor drive unit receives motor commands to control the footrest and backrest motors.

7. The control system according to claim 6, characterized in that: The communicator is a 4G communicator, and the signal transmission interface is an RS485 bus communication interface and a CAN bus communication interface.

8. The control system according to claim 7, characterized in that: The hub motor drive unit communicates with the drive hub motor (51) and the steering motor (52) via an RS485 bus; the hydraulic control unit communicates with the hydraulic push rod (41) via a CAN bus. The posture motor drive unit communicates with the footrest and backrest motors via a CAN bus.

9. The control method for a dual-steering wheelchair with active posture adjustment function according to claim 1, comprising the following steps: S1. The wheelchair is powered on, the main control computing module loads the operating system, and the drive control module completes the underlying hardware self-test; The system calibrates the IMU zero bias mounted on the transverse link (14) and establishes the initial attitude reference system; the lidar sensor (8) mounted on the handrail (75) is initialized and a local environment coordinate system is established; S2. The main control computing module receives user instructions, combines the ground slope information detected by the IMU and the point cloud data scanned by the lidar sensor (8), and judges the current terrain features; when it is judged to be flat, it enters flat mode; when it is judged to be stairs or when a stair climbing instruction is received, it enters stair climbing preparation mode. When entering the flat ground mode, the hydraulic push rod (41) is retracted, and the stair climbing execution component (4) is raised and stored between the two drive hub motors (51) via the connecting rod (45). The small swing arm (44) is retracted to the bottom of the chassis component (1). The main control calculation module calculates the kinematic parameters according to the user's instructions and sends control instructions to adjust the speed of the drive hub motor 51 and the steering angle of the steering mechanism (52) to realize differential steering, crab-like translation or stationary rotation of the wheelchair. During this process, the IMU monitors the chassis posture in real time. If abnormal vibration or tilt is detected, the speed of the drive hub motor (51) is adjusted. When entering the stair-climbing preparation mode, the wheelchair stops moving on flat ground; the main control calculation module controls the hydraulic push rod (41) to extend, and drives the stair-climbing execution component (4) to descend through the connecting rod (45) until the track mechanism (42) contacts the ground; controls the small swing arm (44) motor to rotate, so that the small swing arm (44) unfolds to the same plane as the track mechanism (42) and the universal wheel (6); the system detects the load current of the track mechanism (42), and when the hydraulic push rod (41) extends to the preset grounding length, after confirming that the track has been reliably grounded, it locks the state of the steering wheel or puts the steering wheel in the follow-up unloading state; In the stair climbing mode, the lidar sensor (8) scans the edge and height information of the stair steps in real time, and combines the real-time tilt angle of the wheelchair detected by the IMU to perform multi-sensor fusion positioning; the main control calculation module controls the two side track mechanisms (42) to differentially drive the wheelchair to climb the stairs in the forward direction according to the fused pose information; The control calculation unit compares the pitch angle fed back by the IMU with the safety threshold in real time; if the backward tilt angle of the wheelchair increases, the control unit first drive seat hydraulic push rod (741) and second drive seat hydraulic push rod (742) adjust the seat height and tilt angle, and control the backrest motor to tilt the backrest (72) forward, while adjusting the footrest (73) angle to move the center of gravity of the person forward to counteract the backward tilting torque; If the wheelchair tilts forward too much, adjust the seat height, tilt angle, and backrest angle to shift the person's center of gravity backward. If the IMU detects that the wheelchair tilt angle exceeds the limit safety threshold, or the lidar sensor (8) detects that the staircase structure in front has collapsed, the obstacle is too close, or the hydraulic system pressure is abnormal, the main control computing module triggers an emergency stop command, cuts off the power to the track assembly and the hub motor, controls the first hydraulic push rod (741) and the second hydraulic push rod (742) to lock the current posture, and sends an alarm message to the host computer; after user confirmation, the power to the track assembly and the hub motor is restored, and the hydraulic system is unlocked; When the main control computing module performs ground segmentation and plane fitting on the forward point cloud data collected in real time by the 3D LiDAR sensor (8), and determines that the wheelchair has completely reached the stair platform and the chassis pitch angle fed back by the IMU is within the horizontal threshold range, it determines that the stair climbing has ended.

10. The method according to claim 9, characterized in that, The main control computing module determines that the wheelchair has fully reached the stair landing as follows: The criteria for determining the arrival of the stair platform are as follows: Laser point cloud data of a preset number of consecutive frames show that, within the preset safe distance scanning range directly in front of the wheelchair, the point cloud height variance is lower than the flatness threshold, and no step edge feature points with abrupt changes in vertical height are detected; at the same time, the spatial angle between the fitted forward ground plane and the wheelchair travel reference plane is less than the horizontal tolerance angle. When the above conditions are met, and the absolute value of the chassis pitch angle fed back by the IMU in real time is less than or equal to the horizontal threshold, the main control calculation module outputs the platform arrival status flag after cross-verification by multiple sensors, triggering the storage and mode switching process; controls the hydraulic push rod (41) to retract, and lifts and stores the stair climbing execution component (4) through the connecting rod (45), controls the small swing arm (44) to retract; releases the lock of the steering wheel (5), and the system automatically switches back to the flat ground mode, waiting for the next instruction.

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