A dual-wheel robot with dual-wheel driving and dual-steering control and a control method

Abstract

This invention provides a two-wheeled robot with dual-wheel drive and dual-steering control, and a control method thereof. The front end of the vehicle frame of the vehicle module is equipped with a guide rail slider mechanism arranged in the extension direction. The front torso connecting plate is fixedly connected to the slider and has linear motion degrees of freedom. The rear torso connecting plate is fixedly located at the rear end of the frame. The front motion module is connected to the front torso connecting plate, and the rear motion module is connected to the rear torso connecting plate. They have identical structures and respectively include thighs, lower legs, and wheels. The two-wheeled robot is configured to switch between three different configurations: bicycle, self-balancing vehicle, and slant vehicle. The slant vehicle is used to bridge the configuration change between bicycle and self-balancing vehicle. The provided two-wheeled robot and control method can achieve smooth switching between the bicycle and self-balancing vehicle configurations, and solves the over-constraint problem caused by redundant actuators by introducing the structural deformation degrees of freedom of the two-wheeled vehicle and active control of these degrees of freedom.

Description

Technical Field

[0001] This invention relates to the field of two-wheeled robot technology, and in particular provides a two-wheeled robot and control method with dual-wheel drive and dual-steering control. Background Technology

[0002] Two-wheeled vehicles have a simple structure and flexible maneuverability, making them suitable for crowded and complex environments. Bicycles and self-balancing scooters are the two main configurations of two-wheeled vehicles, and their combination allows for good stability at both high and low speeds. However, due to the inconsistency in the configuration spaces of the two types of vehicles, switching between the configurations of bicycles and self-balancing scooters in the two-dimensional workspace requires the introduction of redundant actuators, which can lead to over-constraint and wheel slippage.

[0003] The main types of two-wheeled vehicles include bicycles and self-balancing bicycles. A bicycle's two wheels are positioned along the longitudinal axis of the frame, making it essentially a statically unstable system, with its forward direction differing from its tilting direction. When moving at higher speeds, it generates lateral centrifugal force to counteract the gravitational torque of tipping. Based on this characteristic, a bicycle can achieve a stable balance at high speeds through active control of the handlebar angle, and can even achieve self-stability without active control. However, the balance stability of a bicycle is poor at low speeds.

[0004] Unlike bicycles, self-balancing scooters are driven by two coaxial drive wheels, with their forward direction being the same as their tilting direction. At low speeds and near standstill, self-balancing scooters can maintain balance using inertial forces by changing the angular acceleration of the drive wheels. However, because the vehicle's acceleration is used for balance, the speed controllability of self-balancing scooters is limited, making it difficult to achieve high acceleration and deceleration performance. Furthermore, since the direction of instability is parallel to the direction of travel, self-balancing scooters are generally not used at high speeds due to safety concerns after instability. If a two-wheeled vehicle could switch between bicycle and self-balancing scooter modes, it could combine the advantages of both, offering better maneuverability, flexibility, and balance across a wide speed range.

[0005] Switching between bicycle and self-balancing vehicle modes requires the two-wheeled vehicle to possess omnidirectional motion with three degrees of freedom in a planar plane. Self-balancing vehicles lack steering wheels, but their two wheels are independently driven, enabling two degrees of freedom of forward movement and rotation. Currently, neither of these configurations can achieve omnidirectional motion in a planar plane. Intuitively, when the two wheels rotate to the configuration of a self-balancing vehicle, the passive wheel cannot be driven by the active wheel, creating a singularity in drive control. From a configuration space perspective, this is due to the fundamental difference between the configurations of self-balancing vehicles and dual-steering-wheel bicycles.

[0006] Therefore, to enable the two-wheeled vehicle to switch between bicycle and self-balancing modes and achieve planar three-degree-of-freedom motion, both wheels need to be able to steer and drive. However, this design contains four control inputs, exceeding the number of planar motion degrees of freedom, resulting in over-constraint. The presence of over-constraint causes wheel slippage, rendering the vehicle kinematics and dynamics model based on no-slip conditions invalid, causing frame vibration, and making dexterous handling difficult. Summary of the Invention

[0007] Based on this, the present invention provides a two-wheeled robot with dual-wheel drive and dual-steering control and a control method to achieve smooth switching between bicycle and self-balancing vehicle configurations, and solves the over-constraint problem caused by redundant actuators by introducing the structural deformation degree of freedom of the two-wheeled vehicle and the active control of the degree of freedom.

[0008] To achieve the above objectives, in a first aspect, the present invention provides a two-wheeled robot with dual-wheel drive and dual-steering control, comprising a vehicle module, a front motion module, and a rear motion module. The vehicle module includes a frame, a front trunk connecting plate, and a rear trunk connecting plate. The front end of the frame is provided with a guide rail slider mechanism arranged in the extension direction. The front trunk connecting plate is fixedly connected to the slider and has linear motion freedom. The rear trunk connecting plate is fixedly disposed at the rear end of the frame. The front motion module and the rear motion module are connected to the front trunk connecting plate and the rear motion module is connected to the rear trunk connecting plate, and have the same structure, each including a thigh, a lower leg, and a wheel. The two-wheeled robot is configured to switch between three different motion modes: bicycle, self-balancing vehicle, and slant vehicle. The slant vehicle is used to connect the mode switching between bicycle and self-balancing vehicle.

[0009] Furthermore, the front and rear motion modules are equipped with a hip rotation motor, a hip flexion motor, a knee joint motor, and a wheel hub motor. The hip rotation motor is located at the top of the motion module and is configured to change the orientation of the motion module relative to the frame. The hip flexion motor is located below the hip rotation motor and its rotation axis is perpendicular to that of the hip rotation motor. The hip flexion motor is connected to the knee joint motor via a thigh connector, and the knee joint motor is connected to the wheel hub motor via the lower leg. The wheel hub motor is connected to the wheel drive.

[0010] Furthermore, the front motion module / rear motion module is configured to extend and retract under the drive of the hip flexion motor and the knee joint motor; the hip rotation motor and the knee joint motor have the same fixed angle during movement to maintain the height of the wheel from the frame and make the center of the wheel pass through the axis of the hip rotation motor.

[0011] Furthermore, the vehicle frame is equipped with a linear position sensor and an inertial measurement unit. The two ends of the linear position sensor are respectively mounted on the front frame and the rear frame to measure the relative displacement between the two. The inertial measurement unit is configured to measure the vehicle body attitude.

[0012] Secondly, this invention provides a two-wheeled robot and its control method with dual-wheel drive and dual-steering control. A two-wheeled vehicle coordinate system is established, including: the contact points between the front and rear wheels and the ground are P and Q, respectively; and the vectors from the centers A and B of the front and rear wheels to the contact points P and Q are respectively... Assuming neither wheel slips, there are two velocity constraint equations at their contact points P and Q with the road surface; the position equations for points P and Q are:

[0013] r OP =r OC +r CF +r FA +r AP

[0014] r OQ =r OC +r CR +r RB +r BQ .

[0015] Furthermore, the forward kinematic equations of the two-wheeled vehicle:

[0016]

[0017] Furthermore, in bicycle motion mode, the robot maintains a 0-degree rear fork rotation angle, and its forward kinematic equation is as follows:

[0018]

[0019] Furthermore, the control input equations for the bicycle motion mode are:

[0020]

[0021] Furthermore, in the self-balancing vehicle motion mode, the two wheels are perpendicular to the frame, and there is no velocity component along the frame direction for the two wheels. Its forward kinematic equation is:

[0022]

[0023] Furthermore, when the robot moves in a zigzag pattern, the two forks can rotate to any equal angle, and its forward kinematic equations are as follows:

[0024]

[0025] Compared with existing technologies, the technical advantages of the two-wheeled robot and control method with dual-wheel drive and dual-steering control provided by this invention are at least reflected in the following aspects:

[0026] 1. A two-wheeled robot with a vehicle model module, a front motion module, and a rear motion module was constructed. A slider joint was set between the frame and the front motion module, which transformed the robot's workspace into three-degree-of-freedom planar motion and single-degree-of-freedom structural deformation. Two steering inputs and one wheel drive input were used to control the planar motion, while the other wheel drive input was used to control the structural deformation. Thus, the over-constraint problem was avoided through mechanism design, and the robot was able to switch between bicycle, balance bike, and scooter configurations.

[0027] 2. By introducing the deformation degree of freedom of the two-wheeled vehicle structure and the active control of this degree of freedom, the over-constraint problem caused by redundant actuators is solved, so as to realize the planar omnidirectional motion of the two-wheeled robot, and be able to smoothly switch between bicycle and self-balancing vehicle configurations during the motion. It can switch between different motion modes as needed, and has smooth motion performance and configuration switching capability.

[0028] 3. Based on the mechanism design, kinematic modeling was performed on the two-wheeled robot with this configuration, incorporating the motion modes of bicycles, self-balancing vehicles, and inclined vehicles into the model. Combined with the provided kinematic control method for switching between bicycle and self-balancing vehicle configurations, the over-constraint removal and switching modes were realized. Attached Figure Description

[0029] 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 these drawings without creative effort.

[0030] Figure 1 This is a first-view perspective perspective view of an embodiment of a two-wheeled robot with dual-wheel drive and dual-steering control.

[0031] Figure 2 This is a second-view perspective perspective view of an embodiment of a two-wheeled robot with dual-wheel drive and dual-steering control.

[0032] Figure 3 A third-view perspective view of an embodiment of a two-wheeled robot with dual-wheel drive and dual-steering control;

[0033] Figure 4 This is a front view of a plan view of an embodiment of a two-wheeled robot with dual-wheel drive and dual-steering control.

[0034] Figure 5 This is a top view of a plan view of an embodiment of a two-wheeled robot with dual-wheel drive and dual-steering control.

[0035] Figure 6 This is a front view of a plan view of an embodiment of a two-wheeled robot with dual-wheel drive and dual-steering control.

[0036] Explanation of reference numerals in the attached diagram:

[0037] 1-Frame, 11-Guide rail slider mechanism, 2-Front body connecting plate, 3-Rear body connecting plate;

[0038] 41-Front motion module, 42-Rear motion module, 401-Hip rotation motor, 402-Hip flexion motor, 403-Thigh, 404-Knee joint motor, 405-Lower leg, 406-Wheel hub motor, 407-Wheel.

[0039] It should be understood that the dimensions of the various parts shown in the accompanying drawings are not drawn to actual scale. Furthermore, the same or similar reference numerals denote the same or similar components. Detailed Implementation

[0040] 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 these drawings without creative effort.

[0041] like Figures 1 to 6 As shown, a two-wheeled robot with dual-wheel drive and dual-steering control is described. The vehicle module consists of a frame 1, a guide rail slider mechanism 11, a front torso connecting plate 2, and a rear torso connecting plate 3. The frame 1, made of aluminum profiles, is the main body of the vehicle, while the guide rail slider mechanism 11 is installed at the front end of the frame 1. The front torso connecting plate 2 is fixed to the slider and can slide relative to the frame 1 along the guide rail, possessing one degree of linear motion freedom. The rear torso connecting plate 3 is installed at the rear end of the rear frame 1. Front and rear hip rotary motors 401 are respectively installed on the front and rear torso connecting plates 3 for connecting the front and rear motion modules 42. The vehicle module also provides a mounting platform for devices such as batteries, control boards, linear sensors, and inertial measurement units.

[0042] The front and rear motion modules 42 have identical structures, each consisting of a thigh 403, a lower leg 405, and a wheel 407, used to realize the robot's motion function. Each motion module consists of a hip rotary motor 401, a hip flexor motor 402, a knee joint motor 404, a wheel hub motor 406, and connecting parts. The hip rotary motor 401 is located at the top of the motion module and is used to change the orientation of the motion module relative to the frame 1. The hip flexor motor 402 is located below the hip rotary motor 401, and its rotation axis is perpendicular to the rotation axis of the hip rotary motor 401. The hip flexor motor 402 is connected to the knee joint motor 404 through the thigh 403 connecting part, and the latter is connected to the wheel hub motor 406 through the lower leg 405 connecting part. The wheel hub motor 406 is used to drive the wheel 407, thereby controlling the forward speed of the two-wheeled vehicle. The motion module can extend and retract under the drive of the hip flexion and knee joint motors 404, which will be used in the future to realize functions such as walking or jumping; the two motors have the same fixed angle during the movement to keep the wheel at the same height as the frame 1 and make the center of the wheel 407 pass through the axis of the hip rotation motor 401.

[0043] Based on the above scheme, a two-wheeled robot with a vehicle module, a front motion module 41, and a rear motion module 42 was constructed. A slider joint was set between the frame 1 and the front motion module 41, so that the robot's workspace was transformed into three-degree-of-freedom planar motion and single-degree-of-freedom structural deformation. Two steering inputs and one wheel drive input of the two-wheeled robot were used to control the planar motion, while the other wheel drive input was used to control the structural deformation. Thus, the over-constraint problem was avoided through mechanism design, and smooth switching between bicycle, balance bike, and inclined vehicle configurations could be achieved.

[0044] The electrical hardware comprises the eight different motors mentioned earlier, linear position sensors, an inertial measurement unit (IMU), a microcomputer with a communication expansion board, and lithium batteries. The linear position sensors are mounted on the front and rear frames 1 respectively, and are used to measure the relative displacement between them. The IMU measures the vehicle's attitude. The microcomputer, motors, and linear position sensors receive and transmit signals to the microcomputer via a communication bus. Data from the IMU is transmitted to the microcomputer via serial communication. All electrical hardware is powered by lithium batteries.

[0045] Based on the above-mentioned robot mechanism design, this invention performs kinematic modeling on this configuration of a two-wheeled robot, encompassing the motion modes of bicycles, self-balancing vehicles, and scooters in the model. Combined with the provided kinematic control method for switching between bicycle and self-balancing vehicle configurations, it realizes the release of over-constraints and the switching mode.

[0046] Let θ denote the angles of the thigh 403 and calf 405 of the front motion module 41 relative to the axis of the hip rotary motor 401. ft ,θ fsThe subsequent motion module 42 is θ rt ,θ rs During the motion, these four angles are maintained at a fixed angle θ. ft =θ fs =θ rt =θ rs =θ0, such that the extended axes of the front and rear hip rotation motors 401 pass through the centers of the front and rear hub motors 406 respectively, and the extended distance is kept to be h. Therefore, the thigh 403 and the lower leg 405 can be combined into a rigid body that rotates around the hip rotation motor 401. Here, the center F0 of the guide rail is set as the reference position of the front motion module 41, the distance from its distance to the axis of the rear torso hip rotation motor 401 is L, the distance from the axis of the hip flexion motor 402 to the plane of the frame 1 is a, the length of the thigh 403 and the lower leg 405 is b, and the wheel radius is r. w From geometric relations, we know that h = 2bcosθ0.

[0047] A coordinate system is established for the two-wheeled vehicle, and its definition follows the right-hand rule. The inertial coordinate system fixed to the ground is... Where O is the origin, i and j are general orthogonal vectors in the horizontal plane, and k is vertically downwards, as shown below. Figure 2 As shown. In In the middle, the frame 1 is fixedly connected as Where C is the center of mass of frame 1, and its position is r. OC =x c i+y c j+(a+h+r w k, vector Along the longitudinal axis of frame 1, vector The vertical frame plane 1 points downwards. The front and rear trunk rigid connections are respectively... The origin F and R lie on plane 1 of the frame, and their positions are as follows: Where d is the offset of the slider of the forequarters relative to the center of the slide rail, vector Vector along the axis of each hip flexor motor 402 Pointing downwards along their respective steering axes. Let the fixed connections of the front and rear wheels 407 be respectively... A and B are fixed to the center of mass of hub motor 406, and their positions coincide with the centroid of hub motor 406. vector Along the 407 axis of rotation of the front and rear wheels respectively. The contact points between the front and rear wheels and the ground are P and Q respectively. This work studies the planar motion of a two-wheeled robot, therefore it is assumed that the two-wheeled vehicle remains in balance during the motion, i.e., the tilt angle is zero, then the direction vector k, Along the vertical direction and and They are parallel. This work will achieve this condition using auxiliary wheels, while subsequent research will use balance control. Since the axis of the hip rotary motor 401 passes through the hub motor 406 shaft, the vectors from the centers A and B of the front and rear wheels to the contact points P and Q are respectively...

[0048] Let ψ be the heading angle of the frame 1 relative to the ground frame, and δ be the rotation angle of the front and rear torsos relative to the longitudinal axis of the frame 1. f ,δ r The angle of rotation of the front and rear wheels relative to their initial positions is In the initial state, ψ = 0, d = 0, δ f =δ r =0, At this time there is j are parallel to each other. and They are parallel respectively. Generally, the coordinate system... The transformation relationship between them is T XY with X,Y∈{I,C,F,R,A,B}, it represents from the coordinate system arrive The homogeneous transformation matrix. Transformation matrix T IC ,T CF ,T CR ,T FA ,T RB The translation vectors are respectively [0,0,-ah] T ,[0,0,-ah] T And the rotation matrices are respectively For about the coordinate system of A rotation matrix for rotating the axis by an angle α.

[0049] Assuming neither wheel 407 slips, there are two velocity constraint equations at their contact points P and Q with the road surface. The positions of points P and Q are:

[0050] r OP =r OC +r CF +r FA +r AP

[0051] r OQ =r OC +r CR +r RB +r BQ

[0052] The velocity can be obtained by taking the time derivative at the contact point location. For a wheel undergoing pure rolling motion, the velocities at its contact points P and Q should be zero. Therefore, combining the coordinate system transformation relationships mentioned earlier, we can obtain the nonholonomic constraint equations for the two-wheeled vehicle:

[0053]

[0054] because Due to the orthogonality of the above constraint equations, they are equivalent to four algebraic equations, which can be written in forward kinematics as follows: Given the orthogonality of the equations, the above constraint equations are equivalent to four algebraic equations. By solving this system of algebraic equations, we can obtain the forward kinematic expression of the two-wheeled vehicle:

[0055]

[0056] By solving the above system of equations, we can obtain the forward kinematics expression for the two-wheeled vehicle:

[0057]

[0058] It presents the kinematic relationship between the workspace and configuration space of the two-wheeled robot, where the workspace includes three planar degrees of freedom. and a structural deformation degree of freedom The configuration space includes the front and rear wheels at 407 rpm. and front and rear handlebar angles δ f ,δ r These four independent variables.

[0059] During the movement, the origin F of the forequarters remains at the initial position F0, i.e., d = 0. This and its derivative form... Substituting into the forward kinematics equations, we get:

[0060]

[0061] The first equation represents the kinematic relationship between the planar motion workspace and the configuration space, while the last equation is a servo constraint condition that needs to be added artificially to maintain d=0. Its physical meaning is that the velocity components of the front wheel and the rear wheel along the longitudinal axis of the frame 1 are the same.

[0062] By inversely solving the control input from the forward kinematics equations, the inverse kinematics equations are obtained as follows:

[0063]

[0064] This set of equations gives the control input quantities for the four configuration spatial degrees of freedom when the robot’s three-degree-of-freedom planar motion is to be achieved while simultaneously satisfying the servo constraints of the frame 1 structure.

[0065] Two-wheeled robots can exhibit three different motion modes: bicycle, self-balancing vehicle, and inclined vehicle. The inclined vehicle mode serves as a bridge between the configuration changes of a bicycle and a self-balancing vehicle. These three motion modes are formed by adding different additional constraints to a general two-wheeled robot. The forward and inverse kinematic equations for these three motion modes are given below. Specifically:

[0066] (I) Bicycle Mode

[0067] When the robot moves in bicycle mode, the rear fork angle remains constant at 0 degrees, meaning the additional constraint equation is δ. r =0. The forward kinematics at this point are:

[0068]

[0069] The equation shows the robot's heading angular velocity. With lateral translational velocity Satisfy the equation The two are not independent. Therefore, the robot can only perform two-degree-of-freedom planar motion while maintaining a structural servo constraint. Let's take... and If we consider two independent motion control objectives in inverse kinematics, then the control inputs for the bicycle configuration are:

[0070]

[0071] (II) Self-balancing vehicle mode

[0072] When the robot moves in self-balancing vehicle mode, the two wheels 407 remain perpendicular to the frame 1, i.e., the additional constraint equation is: Since at this time cos(δ) f )=cos(δ r Since ) = 0, the two wheels 407 have no velocity component along the direction of frame 1, therefore the structural servo constraints are naturally satisfied, and the forward kinematic equation is:

[0073]

[0074] At this point, the robot can only perform... Translational motion in direction and rotation achieved by the differential speed of the two wheels. Take the lateral movement speed. and rotational speed As the control target quantity, the inverse kinematic equation of the self-balancing vehicle can be written as:

[0075]

[0076] (III) Inclined Vehicle Mode

[0077] When the robot moves in a diagonal driving pattern, the two forks can rotate to any equal angle, with an additional constraint δ. f =δ r Take δ r and As the control input, the forward kinematics is:

[0078]

[0079] The structural servo constraint becomes:

[0080]

[0081] At this point, the robot can perform planar translational movements with two degrees of freedom while maintaining a structural servo constraint, but the heading angle of frame 1 remains unchanged. Let's consider... As two independent control objectives in inverse kinematics, the inverse kinematic equations of the self-balancing vehicle are:

[0082]

[0083] There are multiple ways to convert between bicycle and self-balancing bike configurations. During these conversions, the distance between the front and rear torso must remain constant, meaning the constraint d=0 must be satisfied at all times. The angled bike configuration automatically satisfies this constraint, and the drive space of the angled bike mode coincides with the drive spaces of both the bicycle and self-balancing bike modes at a single point. When δ f =δ r =0, At that time, the robot was simultaneously in bicycle mode and angled vehicle mode. At the same time, the robot is simultaneously in self-balancing mode and angled mode. Therefore, using the angled mode as a transitional state between bicycle and self-balancing modes has a simple kinematic form.

[0084] The following describes the transformation process from a bicycle to a self-balancing vehicle, using a slanted vehicle as the transition state; the process from a self-balancing vehicle to a bicycle is the reverse. Without loss of generality, the control input in bicycle mode at the initial stage of the transformation is δ. f =δ0,δ r =0, The control input for the self-balancing vehicle mode after deformation is completed is The deformation process is as follows: First step, the rear torso rotates at an angle δ. r =0 and rear wheel speed Keeping it unchanged, rotate the forequarters at angle δ. f From δ0 back to 0, the front wheel speed... according to The first step involves changing the constraint to maintain d=0, thereby deforming the turning bicycle to a critical state where it coincides with the angled bicycle; the second step involves rotating the front and rear wheels at 407 revolutions per minute. Keeping constant, the front and rear torso rotation angle δ f =δ r Gradually changing from 0 to This allows the robot to deform in its oblique vehicle configuration to another critical state that coincides with the state of a self-balancing vehicle; the third step is the front and rear torso rotation. Keeping the speed unchanged, front and rear wheels at 407 RPM Gradually from Become This allows the robot to transition from a critical state to a target state while in self-balancing vehicle mode.

[0085] To further explain the technical solution of the present invention in detail, the following describes the two-wheeled robot with dual-wheel drive and dual-steering control in conjunction with a specific experimental process.

[0086] In the experiment, the outer frame of the aluminum chassis 1 has dimensions of 800mm × 260mm. The two hip rotary motors 401, each with a maximum torque of 5.8Nm, are initially spaced L = 500mm apart. The hip flexion motor 402 is the same model as the knee joint motor 404, with a maximum output torque of 34Nm, and can be locked at a fixed angle after being powered on. Due to limitations imposed by the guide rail length and the edge of the chassis 1, the relative displacement d of the front chassis 1 ranges from d ∈ [-30mm, 30mm]. A linear position sensor, with a range of 150mm and an accuracy of ±0.01mm, can cover the slider stroke. A 24V lithium battery and a 36V lithium battery are mounted at the top center of the chassis 1; the latter powers the hub motor 406, and the former powers other components. The linear position sensor is mounted directly below the geometric center of the chassis 1. In the motion module, the distance a = 136 mm from the hip flexion motor 402 shaft to the plane of frame 1, the length b = 250 mm for thigh 403 and lower leg 405, and the radius r of wheel 407. w =100mm, the hub motor 406 has a rated torque of 4Nm and a maximum speed of 500rpm. All motors have servo control functions for angle and angular velocity.

[0087] To maintain the robot's balance, an auxiliary support frame was installed around the vehicle. The frame consisted of four vertical aluminum profiles and omnidirectional wheels at the ends. During the experiment, the height of the auxiliary support frame was adjusted to match the height of the motion module to provide support. Since the omnidirectional wheels do not create speed constraints when in contact with the ground, the robot's motion pattern was still determined solely by the motion module and was not affected by the auxiliary support frame.

[0088] The bending angle of the hip extension motor and knee joint motor 404 is θ0 = 45°, the height of the frame 1 from the ground is a + h = 490 mm, and the turning angle range of the front and rear wheels is...

[0089] Bicycle mode: Rear wheel speed in bicycle mode and front wheel steering angle δ f These are used to control the vehicle's forward speed and direction of travel, respectively. The target of the deformation degree of freedom, d=0, is determined by the front wheel speed. Control: When d < 0, the front wheel speed increases; when d > 0, the front wheel speed decreases. The control rate is:

[0090]

[0091] The first item on the right end Let be the reference control quantity obtained through the inverse kinematic equation xx, and let the second term be the feedback control term, where is the nominal proportionality coefficient, and d is the measured value of the slider displacement. As the front wheel steering angle δ... f From 0 to ± As the wheels rotate, the longitudinal component of the front wheel speed decreases, causing... The ability to control the degrees of freedom of deformation is weakened. Therefore, cos(δ) f ) was used for nonlinear correction of the nominal scaling factor, while the angle limiting was used. An addition was made to prevent singularity in the denominator. In the bicycle-shaped experiment, the robot sequentially moved straight, turned right, turned left, and returned to center. In the state space and workspace quantities of the experiment, |d|≤3mm, indicating that the control law xx can maintain the stability of the deformation degrees of freedom during the motion.

[0092] Self-balancing vehicle mode: In self-balancing vehicle mode, the speeds of the front and rear wheels It is used to control the vehicle's forward speed and direction of travel. Neither wheel 407 has any amount along the longitudinal axis of the frame 1, so ideally, the structural degree of freedom d remains constant. However, experiments show that d increases rapidly to its upper limit when the two-wheeled vehicle rotates, due to centrifugal force. Therefore, a control law is designed here to utilize the offset of the front wheel steering angle to balance the effect of centrifugal force and keep d constant:

[0093]

[0094] in The kinematic feedforward of the front wheel steering angle. Let be the proportional coefficient of the feedback term, sgn be the sign function, and d be the measured value of the slider displacement. When d ≠ 0, the front wheel steering angle deviates from... This causes the speed of wheel 407 to have a component along the length of the frame 1, thereby adjusting d. Simultaneously, wheel speed control is introduced to maintain the speed component of the front wheels perpendicular to the longitudinal direction of the vehicle body at a preset value.

[0095]

[0096] Due to δf exist In the vicinity, the above equation does not produce singularities. In the self-balancing vehicle experiment, the robot sequentially performed a 360° rotation in place, forward movement, and a movement that involved turning around while moving forward. During forward movement and large-radius turns, the structural degrees of freedom d ≤ 3 mm, but when the vehicle rotates in place, there is a steady-state error of approximately 8 mm in d. This is because the centrifugal force experienced by the front legs during rotation is relatively large, exceeding the adjustment capability of linear feedback control. In the future, nonlinear feedback control will be used to eliminate the steady-state error.

[0097] Inclined vehicle configuration: In the inclined vehicle configuration, the steering angle δ of the two wheels is 407. f =δ r Used for steering, the speed of the two wheels is 407. Used to control the speed of vehicle movement, among which The reference control quantity obtained through the inverse kinematic equation xx is used, and the front wheel speed is also used to control the structural degree of freedom d. The control equation is equation (xx, the same as that for bicycles). In the experiment, the inclined vehicle performs straight-line and turning motions, and the structural degree of freedom d ≤ 2 mm in steady state.

[0098] Configuration transformation: The robot transforms from a standard bicycle configuration to a standard self-balancing vehicle configuration, and then back to a standard bicycle configuration. Experimental results show that the robot can smoothly switch between bicycle and self-balancing vehicle configurations, and the structural degrees of freedom always satisfy d≤2mm during the process.

[0099] Based on the above experiments and analysis, the over-constraint problem caused by redundant actuators is solved by introducing the deformation degree of freedom of the two-wheeled vehicle structure and the active control of the modified degree of freedom. This enables the two-wheeled robot to achieve omnidirectional planar motion and smoothly switch between bicycle and self-balancing vehicle configurations during motion. It can also switch between different motion modes as needed, and has smooth motion performance and configuration switching capability.

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. However, these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A control method for a two-wheeled robot with dual-wheel drive and dual-steering control, the two-wheeled robot comprising: The vehicle body module includes a frame (1), a front trunk connecting plate (2) and a rear trunk connecting plate (3). The front end of the frame (1) is provided with a guide rail slider mechanism (11) arranged along the length direction. The front trunk connecting plate (2) is fixedly connected to the slider and has linear motion freedom. The rear trunk connecting plate (3) is fixedly arranged at the rear end of the frame (1). The vehicle body module includes a front motion module (41) and a rear motion module (42). The front motion module (41) is connected to the front trunk connecting plate (2), and the rear motion module (42) is connected to the rear trunk connecting plate (3). The modules have the same structure and include a thigh (403), a lower leg (405) and a wheel (407) respectively. The two-wheeled robot is configured to switch between three different movement modes: bicycle, self-balancing vehicle, and scooter. The scooter is used to connect the mode switching between bicycle and self-balancing vehicle. Its features are: Establishing a coordinate system for the two-wheeled vehicle includes: denoting the angles of the thigh (403) and lower leg (405) of the front motion module (41) relative to the axis of the hip rotary motor (401) as follows: The rear motion module (42) is During the movement, the four angles are maintained at a fixed angle. This ensures that the extended axes of the front and rear hip rotary motors (401) pass through the centers of the front and rear hub motors (406), respectively, and the extended distance remains constant. The thigh (403) and calf (405) form a rigid body that rotates around a hip rotary motor (401); here the center of the guide rail is... The reference position of the anterior motion module (41) is set at a distance from the axis of the posterior trunk hip rotary motor (401) as follows: The distance from the hip flexor motor (402) shaft to the frame (1) plane is The lengths of the thigh (403) and calf (405) are both The wheel radius is From geometric relationships, we know ; Establish a coordinate system for the two-wheeled vehicle, with the inertial coordinate system fixed to the ground as follows: ,in With the origin as the point, For general orthogonal vectors in the horizontal plane, Vertically downwards; in In the middle, the frame (1) is fixedly connected as ,in The center of mass of the frame (1) is located at... ,vector Along the longitudinal axis of the frame (1), vector The vertical frame (1) plane points downwards; the fixed connections of the front and rear torsos are respectively The origin On the plane of the frame (1), its position is ,in The vector is the offset of the slider of the forequarters relative to the center of the slide rail. Vector along the axis of each hip flexor motor (402) Pointing downwards along their respective steering axes; the fixed connections of the front and rear wheels (407) are respectively... ,in It is fixed to the center of mass of the hub motor (406), and its position coincides with the centroid of the hub motor (406). ,vector Along the direction of the front and rear wheel (407) axles respectively; the contact points between the front and rear wheels and the ground are respectively The two-wheeled robot maintains balance during its planar motion, meaning the tilt angle is zero; therefore, the direction vector... Along the vertical direction and and Parallel to each other; center of front and rear wheels To the contact point The vectors are respectively , ; Let the heading angle of the vehicle frame (1) relative to the ground system be... The rotation angle of the front and rear torsos relative to the longitudinal axis of the frame (1) is The angle of rotation of the front and rear wheels relative to their initial positions is In the initial state, ; Parallel to each other, and Parallel; coordinate system The transformation relationship between them is with Its representation is from the coordinate system arrive The homogeneous transformation matrix; transformation matrix The translation vectors are respectively And the rotation matrices are respectively , For about the coordinate system of Axis rotation Angle rotation matrix; If neither wheel (407) slips, then their contact points with the road surface are... There are two velocity constraint equations at each point; The location is: ； ； The velocity is obtained by taking the time derivative at the contact point location. , For a wheel undergoing pure rolling motion, its contact point and The speed at that point should be Combining the coordinate system transformation relationships mentioned above, we can obtain the nonholonomic constraint equations for the two-wheeled vehicle: ； ； because The orthogonality of the constraint equations means that the equations are equivalent to four algebraic equations, and the forward kinematic form is as follows: Due to The orthogonality of the system means that the constraint equations are equivalent to four algebraic equations. By solving this system of algebraic equations, we can obtain the forward kinematic expression of the two-wheeled vehicle: ； By solving the above system of equations, the forward kinematics expression of the two-wheeled vehicle is obtained: ； The kinematic relationship between the workspace and configuration space of a two-wheeled robot is given, wherein the workspace includes three planar degrees of freedom. and a structural deformation degree of freedom The configuration space includes the front and rear wheel (407) rotation speeds. and front and rear handlebar corners These four independent variables; During the movement, the origin of the forequarters Stay in the initial position ,Right now ; and its derivative form Substituting into the forward kinematics equations, we get: ； ； The first equation represents the kinematic relationship between the planar motion workspace and the configuration space, while the last equation is to maintain... The servo constraint conditions that need to be added manually have the physical meaning that the velocity components of the front wheel and the rear wheel along the longitudinal axis of the frame (1) are the same.

2. The two-wheeled robot control method with dual-wheel drive and dual-steering control according to claim 1, characterized in that, The front motion module (41) and the rear motion module (42) are equipped with a hip rotation motor (401), a hip flexion motor (402), a knee joint motor (404), and a wheel hub motor (406). The hip rotation motor (401) is located at the top of the motion module and is configured to change the orientation of the motion module relative to the frame (1). The hip flexion motor (402) is located below the hip rotation motor (401) and its rotation axis is perpendicular to the rotation axis of the hip rotation motor (401). The hip flexion motor (402) is connected to the knee joint motor (404) through a thigh (403) connector. The knee joint motor (404) is connected to the wheel hub motor (406) through a lower leg (405). The wheel hub motor (406) is driven by the wheel (407).

3. The two-wheeled robot control method with dual-wheel drive and dual-steering control according to claim 2, characterized in that, The front motion module (41) / rear motion module (42) is configured to extend and retract under the drive of the hip flexion motor (402) and the knee joint motor (404); the hip rotation motor (401) and the knee joint motor (404) have the same fixed angle in motion to maintain the height of the wheel to the frame (1) and make the center of the wheel (407) pass through the axis of the hip rotation motor (401).

4. The two-wheeled robot control method with dual-wheel drive and dual-steering control according to claim 1, characterized in that, The frame (1) is equipped with a linear position sensor and an inertial measurement unit. The two ends of the linear position sensor are respectively set on the front frame (1) and the rear frame (1) to measure the relative displacement between them. The inertial measurement unit is configured to measure the vehicle body attitude.

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