Double-wheel robot with double-wheel driving and double-steering control functions and control method

Abstract

The invention provides a double-wheel robot with double-wheel driving and double-steering control and a control method. A guide rail sliding block mechanism arranged in the length direction is arranged at the front end of a frame of a vehicle body module, and a front trunk connecting plate is fixedly connected with a sliding block and has the linear motion freedom degree; the rear trunk connecting plate is fixedly arranged at the rear end of the frame front and back; the front movement module is connected to the front trunk connecting plate, the rear movement module is connected to the rear trunk connecting plate, and the front movement module and the rear movement module are consistent in structure and respectively comprise thighs, shanks and wheels; the two-wheeled robot is configured to be switched among three different configurations of a bicycle, a self-balancing vehicle and a slant vehicle, and the slant vehicle is used for connecting configuration changes between the bicycle and the self-balancing vehicle. According to the double-wheel robot and the control method, smooth switching of the bicycle and the self-balancing vehicle can be achieved, and the over-constraint problem caused by a redundant driver is solved by introducing active control of the deformation freedom degree and the modified freedom degree of the double-wheel vehicle structure.

Description

Technical Field

[0001] The invention relates to the technical field of two-wheel robots, and in particular to a two-wheel robot with two-wheel drive and two-steering control and a control method thereof. Background Art

[0002] Two-wheeled vehicles have a simple structure and flexible mobility, and are suitable for crowded and complex environments. Bicycles and self-balancing vehicles are the two main configurations of two-wheeled vehicles, and their combination can make two-wheeled vehicles have good motion stability at both high and low travel speeds. Since the configuration spaces of the two types of vehicles are inconsistent, the configuration switching of bicycles and self-balancing vehicles in the two-dimensional plane workspace requires the introduction of redundant drives to achieve, which will produce over-constraints and wheel slippage.

[0003] The main types of two-wheeled vehicles include bicycles and self-balancing vehicles. The two wheels of a bicycle are placed along the longitudinal axis of the frame. It is essentially a statically unstable system, and its forward direction is different from the tipping direction. When it moves at a higher speed, it can generate lateral centrifugal force to balance the tipping gravity moment. Based on this feature, the bicycle can achieve a stable equilibrium state at high speed through active control of the handlebar angle, and can even achieve self-stabilization without active control. However, the stability of the equilibrium state of a bicycle at low speed is poor.

[0004] Unlike bicycles, self-balancing vehicles are driven by two coaxial active wheels, and their forward direction is the same as the dumping direction. At low speeds and near rest, self-balancing vehicles can use inertial force to maintain balance by changing the angular acceleration of the active wheels. However, since the acceleration of the vehicle body is used to maintain balance, the speed controllability of the self-balancing vehicle is limited, and it is difficult to achieve high acceleration and deceleration performance. At the same time, since the instability direction is parallel to the driving direction, considering the safety after instability, self-balancing vehicles generally do not travel at high speeds. If a two-wheeled vehicle can switch between the two forms of a bicycle and a self-balancing vehicle, it can take into account the advantages of both forms, with better maneuverability, flexibility and balance in a wide speed range.

[0005] The switch between bicycle and self-balancing vehicle requires the two-wheeled vehicle to have three-degree-of-freedom omnidirectional motion in the plane. The self-balancing vehicle does not have steering wheels, but the two wheels are independently driven, which can achieve two-degree-of-freedom motion of forward and rotation. At present, neither of these two configurations can achieve planar omnidirectional motion. Intuitively, when the two wheels rotate to the configuration of the self-balancing vehicle, the passive wheel cannot be driven by the active wheel, resulting in a singularity of drive control. From the perspective of configuration space, this is because the configuration of the self-balancing vehicle is essentially different from that of the dual-steering wheel bicycle.

[0006] Therefore, in order to switch between the two modes of bicycle and self-balancing vehicle and realize the three-degree-of-freedom motion in the plane, both wheels need to be able to steer and drive. However, this design contains four control inputs, which exceeds the number of degrees of freedom of the plane motion and produces over-constraints. The existence of over-constraints will cause the wheels to slip, making the vehicle kinematic and dynamic models based on the no-slip condition invalid, causing the frame to vibrate, and making it difficult to perform agile maneuvers. 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 the two configurations of a bicycle and a self-balancing vehicle, and solves the over-constraint problem caused by redundant drives by introducing the two-wheeled vehicle's structural deformation freedom and active control of the changed freedom.

[0008] In order to achieve the above-mentioned objectives, in a first aspect, the present invention provides a two-wheeled robot with dual-wheel drive and dual steering control, including a vehicle body module, a front motion module and a rear motion module, the vehicle body module including 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 an extension direction, the front trunk connecting plate is fixedly connected to the slider and has a linear motion degree of freedom, and the rear trunk connecting plate is fixedly arranged at the rear end of the frame in a front and rear position; the front motion module and the rear motion module, the front motion module is connected to the front trunk connecting plate, the rear motion module is connected to the rear trunk connecting plate, the structures are consistent and respectively include thighs, calves and wheels; the two-wheeled robot is configured to switch between three different motion modes of bicycle, self-balancing car and oblique car, wherein the oblique car is used to connect the mode conversion between bicycle and self-balancing car.

[0009] Furthermore, the front motion module and the rear motion module are provided with a hip rotation motor, a hip-leg flexion motor, a knee joint motor and a hub motor. The hip rotation motor is located at the uppermost end of the motion module and is configured to change the orientation of the motion module relative to the frame; the hip-leg flexion motor is located below the hip rotation motor and its rotating shaft is perpendicular to the rotating shaft of the hip rotation motor; the hip-leg flexion motor is connected to the knee joint motor through a thigh connector, and the knee joint motor is connected to the hub motor through a calf; and the hub motor is drive-connected to the wheel.

[0010] Furthermore, the front motion module / rear motion module is configured to perform extension and retraction movements driven by 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 to the frame and make the center of the wheel pass through the axis of the hip rotation motor.

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

[0012] In the second aspect, the present invention provides a two-wheeled robot with two-wheel drive and two-steering control and a control method, and establishes a two-wheeled vehicle coordinate system, including: the contact points of the front and rear wheels with the ground are P and Q respectively, and the vectors from the center of the front and rear wheels A and B to the contact points P and Q are respectively Assuming that both wheels do not slip, there are two velocity constraint equations at their contact points P and Q with the road surface; the position equations of 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 kinematics equation of a two-wheeled vehicle is:

[0016]

[0017] Furthermore, when the robot is in bicycle motion mode, the rear fork angle remains at 0 degrees, and its positive kinematic equation is:

[0018]

[0019] Furthermore, the control input equation of the bicycle motion mode is:

[0020]

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

[0022]

[0023] Furthermore, when the robot moves in the oblique vehicle mode, the two forks can rotate to any equal angle, and its forward kinematic equation is:

[0024]

[0025] Compared with the prior art, the technical advantages of the two-wheeled robot with two-wheel drive and two-steering control and the control method provided by the present invention are at least reflected in:

[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, so that the robot's workspace was converted into three-degree-of-freedom planar motion and single-degree-of-freedom structural deformation. The two steering 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 the mechanism design, and the switching of bicycle, balance car and oblique car configurations could be realized;

[0027] 2. The over-constraint problem caused by redundant drivers is solved by introducing the two-wheeled vehicle's structural deformation freedom and active control of the modified freedom, so as to realize the two-wheeled robot's planar omnidirectional motion, and be able to smoothly switch between bicycle and self-balancing vehicle configurations during the motion process, and be able to convert different motion modes as needed, with smooth motion performance and configuration switching capabilities;

[0028] 3. Based on the mechanism design, the kinematic modeling of the two-wheeled robot with this configuration was carried out, and the motion modes of bicycles, self-balancing vehicles and oblique vehicles were included in the model. Combined with the kinematic control method of switching between bicycle and self-balancing vehicle configurations provided, the over-constraint removal and switching method were realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0030] Figure 1 is a first perspective stereogram of an embodiment of a provided two-wheeled robot with two-wheel drive and two-steering controls;

[0031] Figure 2 is a second perspective stereogram of an embodiment of a provided two-wheeled robot with two-wheel drive and two-steering control;

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

[0033] Figure 4 is a front view of a plan view of an embodiment of a provided two-wheeled robot with two-wheel drive and two-steering controls;

[0034] Figure 5 is a top view of a plan view of an embodiment of a provided two-wheeled robot with two-wheel drive and two-steering controls;

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

[0036] Description of the accompanying drawings:

[0037] 1-frame, 11-guide rail slider mechanism, 2-front trunk connecting plate, 3-rear trunk connecting plate;

[0038] 41 - front motion module, 42 - rear motion module, 401 - hip rotation motor, 402 - hip leg flexion motor, 403 - thigh, 404 - knee joint motor, 405 - calf, 406 - wheel hub motor, 407 - wheel.

[0039] It should be understood that the size of each part shown in the accompanying drawings is not drawn according to the actual proportional relationship. In addition, the same or similar reference numerals represent the same or similar components. DETAILED DESCRIPTION

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0041] like Figures 1 to 6 As shown, a two-wheel robot with two-wheel drive and two-steering control, the body module is composed of a frame 1, a guide rail slider mechanism 11, a front trunk connecting plate 2, and a rear trunk connecting plate 3; the frame 1 composed of aluminum profiles is the main body of the body, and the guide rail slider mechanism 11 is installed at the front end of the frame 1; the front trunk connecting plate 2 is fixedly connected to the slider, and can slide relative to the frame 1 along the guide rail, and has a linear motion degree of freedom; the rear trunk connecting plate 3 is installed at the tail end of the rear frame 1; the front and rear hip rotation motors 401 are respectively installed on the front and rear trunk connecting plates 3, which are used to connect the front and rear motion modules 42. At the same time, the body module provides an installation platform for equipment such as batteries, control panels, linear sensors, and inertial measurement units.

[0042] The front and rear motion modules 42 have the same structure, and are both composed of a thigh 403, a shank 405 and a wheel 407, which are used to realize the motion function of the robot; each motion module is composed of a hip rotation motor 401, a hip flexion leg motor 402, a knee joint motor 404, a hub motor 406 and a connecting piece; the hip rotation 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 flexion leg 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 leg motor 402 is connected to the knee joint motor 404 through the thigh 403 connecting piece, and the latter is connected to the hub motor 406 through the shank 405 connecting piece; the 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 driven by the hip flexion leg and knee joint motor 404, which will be used to achieve functions such as walking or jumping in the future; the two motors have the same fixed angle during movement 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.

[0043] Based on the above scheme, a two-wheeled robot with a vehicle model module, a front motion module 41 and a rear motion module 42 is constructed, and a slider joint is set between the frame 1 and the front motion module 41, so that the robot's working space is converted into three-degree-of-freedom planar motion and single-degree-of-freedom structural deformation. The two steering and one wheel drive input of the two-wheeled robot are used to control the planar motion, while the other wheel drive input is used to control the structural deformation, thereby avoiding the over-constraint problem through mechanism design, and realizing smooth switching of bicycle, balance car and oblique car configurations.

[0044] The electrical hardware consists of the eight different motors mentioned above, linear position sensors, inertial measurement units, microcomputers with communication expansion boards, and lithium batteries. The two ends of the linear position sensor are mounted on the front frame 1 and the rear frame 1 respectively to measure the relative displacement between the two. The inertial measurement unit is used to measure the body posture. The microcomputer, motors, and linear position sensors receive and send signals to and from the microcomputer via the communication bus. The data from the inertial measurement unit is sent to the microcomputer via serial communication. All electrical hardware is powered by lithium batteries.

[0045] Based on the above-mentioned robot mechanism design, the present invention performs kinematic modeling of the two-wheeled robot of this configuration, covering the motion modes of bicycles, self-balancing vehicles and inclined vehicles in the model, and combines the provided kinematic control method for switching the bicycle and self-balancing vehicle configurations to achieve the release of over-constraints and the switching method.

[0046] The angles of the thigh 403 and the calf 405 of the front motion module 41 relative to the axis of the hip rotation motor 401 are respectively denoted as θ ft ,θ fs, the rear motion module 42 is θ rt ,θ rs During the movement, these four angles are kept at fixed angles θ ft =θ fs =θ rt =θ rs =θ0, so that the extension lines of the front and rear hip rotation motor 401 axes pass through the centers of the front and rear hub motors 406 respectively, and the extension distance is maintained at h. Therefore, the thigh 403 and the calf 405 can form a rigid body that rotates around the hip rotation motor 401. Here, the guide rail center F0 is set as the reference position of the front motion module 41, and its distance from the axis of the rear trunk hip rotation motor 401 is L, the distance from the hip flexion leg motor 402 axis to the plane of the frame 1 is a, the length of the thigh 403 and the calf 405 are both b, and the wheel radius is r w From the geometric relationship, we can know that h = 2bcosθ0.

[0047] The coordinate system for the two-wheeled vehicle is defined according to 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 downward, such as Figure 2 As shown. In the embodiment, the frame 1 is fixedly connected to 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 plane of the vertical frame 1 points downward. The fixed connections of the front and rear trunks are The origin F, R is on the plane of frame 1, and its position is Where d is the displacement of the slider of the front trunk relative to the center of the slide rail, and the vector Along the axis direction of each hip flexion leg motor 402, vector The fixed connections of the front and rear wheels 407 are respectively Where A and B are fixedly connected to the center of mass of the hub motor 406, which coincides with the center of shape of the hub motor 406 and is located at vector Along the rotation axis direction of the front and rear wheels 407 respectively. The front and rear wheels contact the ground at points P and Q respectively. This work studies the planar motion of a two-wheeled robot. Therefore, it is assumed that the two-wheeled vehicle maintains balance during the motion process, that is, the tilt angle is zero. Then the direction vector k, In the vertical direction and and In this work, this condition will be achieved by auxiliary wheels, and in subsequent studies, it will be achieved by balance control. Since the axis of the hip rotation motor 401 passes through the shaft of the hub motor 406, the vectors from the center of the front and rear wheels A and B to the contact points P and Q are respectively

[0048] The heading angle of the frame 1 relative to the ground system is ψ, and the rotation angle of the front and rear trunks relative to the longitudinal axis of the frame 1 is δ f ,δ r , the turning angle of the front and rear wheels relative to the initial position 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 In general, the coordinate system The transformation relationship between them is T XY with X,Y∈{I,C,F,R,A,B}, which represents the coordinate system arrive The homogeneous transformation matrix of . Transformation matrix T IC ,T CF ,T CR ,T FA ,T RB The translation vectors are [0,0,-ah] T ,[0,0,-ah] T , and the rotation matrices are For the coordinate system of The rotation matrix that rotates the axis by angle α.

[0049] Assuming that both wheels 407 do not slip, 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 time derivative of the contact point position can be used to obtain the velocity For wheels in pure rolling motion, the speed at the contact points P and Q should be 0. Therefore, combined with the previous coordinate system change relationship, the non-holonomic constraint equation of the two-wheeled vehicle can be obtained:

[0053]

[0054] because The orthogonality of the above constraint equations is equivalent to four algebraic equations, and the forward kinematics form is: The orthogonality of the above constraint equations is equivalent to four algebraic equations. By solving the algebraic equations, the forward kinematic expression of the two-wheeled vehicle can be obtained:

[0055]

[0056] By solving the above equations, we can get the forward kinematic expression of the two-wheeled vehicle:

[0057]

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

[0059] During the movement, the front trunk origin F remains at the initial position F0, that is, d = 0. Substituting into the forward kinematics equation, we obtain:

[0060]

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

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

[0063]

[0064] This set of equations gives the control input quantities of the four configurational spatial degrees of freedom when the robot is to realize the three-degree-of-freedom planar motion and satisfy the structural servo constraints of the frame 1.

[0065] The two-wheeled robot can exhibit three different motion modes: bicycle, self-balancing car and inclined car. The inclined car is used to connect the configuration changes of bicycle and self-balancing car. These three motion modes are formed by adding different additional constraints on the general two-wheeled robot. The forward and inverse kinematic equations of these three motion modes are given below. They are as follows:

[0066] (I) Bicycle mode

[0067] When the robot moves in the bicycle mode, the rear fork angle remains at 0 degrees, that is, the additional constraint equation is δ r = 0. At this time, the positive kinematics is:

[0068]

[0069] The equation shows the robot's angular velocity The lateral translation speed Satisfy the equation The two are not independent. Therefore, the robot can only perform two-degree-of-freedom motion in the plane while maintaining a structural servo constraint. and are two independent motion control objectives of inverse kinematics, then the control input of the bicycle configuration is

[0070]

[0071] (II) Self-balancing vehicle mode

[0072] When the robot moves in the self-balancing mode, the two wheels 407 are perpendicular to the frame 1, that is, the additional constraint equation is: Since cos(δ f )=cos(δ r )=0, the two wheels 407 have no velocity component along the direction of the frame 1, so the structural servo constraint is naturally satisfied, and the positive kinematic equation is:

[0073]

[0074] At this time, the robot can only Directional movement and rotation achieved by the differential speed of the two wheels. and rotation speed As the control target, the inverse kinematics equation of the self-balancing vehicle can be written as:

[0075]

[0076] (III) Oblique vehicle mode

[0077] When the robot moves in the oblique car mode, the two forks can rotate to any equal angle, and the additional constraint is δ f =δ r . Take δ r and As control input, the forward kinematics is:

[0078]

[0079] The structural servo constraint becomes:

[0080]

[0081] At this time, the robot can perform two-degree-of-freedom translation in the plane while maintaining a structural servo constraint, but the heading angle of frame 1 will never change. As two independent control objectives of inverse kinematics, the inverse kinematics equation of the balancing car is:

[0082]

[0083] There are many ways to convert between the bicycle configuration and the self-balancing vehicle configuration. During the conversion, the distance between the front and rear trunks needs to remain constant, that is, the constraint of d = 0 is always satisfied. The oblique vehicle configuration automatically satisfies this constraint, and the driving space of the oblique vehicle mode overlaps with the driving space of the bicycle mode and the self-balancing vehicle mode. When δ f =δ r =0, When , the robot is in both bicycle mode and inclined car mode. When the robot is in the self-balancing vehicle mode and the inclined vehicle mode at the same time, the inclined vehicle configuration as the transition state between the bicycle and the self-balancing vehicle configuration has a simple kinematic form.

[0084] The following is the transformation process from bicycle to self-balancing vehicle with the inclined vehicle as the transition state, and the process from self-balancing vehicle to bicycle is the opposite. Without loss of generality, the control input in bicycle mode at the beginning of the transformation is δ f =δ0,δ r =0, After the deformation is completed, the control input in the self-balancing car mode is The deformation process is as follows: Step 1, the rear trunk rotation angle δ r = 0 and rear wheel speed Keep the front trunk angle δ f From δ0 back to 0, at the same time the front wheel speed according to The change is to maintain the constraint of d = 0, thereby deforming the turning bicycle to a critical state where it coincides with the diagonal vehicle; the second step is to rotate the front and rear wheels at 407 speeds. Maintaining the same, the front and rear trunk rotation angle δ f =δ r From 0 to Thus, the robot is deformed to another critical state that coincides with the self-balancing vehicle state under the oblique vehicle configuration; the third step is to rotate the front and rear trunk angles Maintained unchanged, front and rear wheels 407 rpm Gradually from becomes Thereby, the robot changes from a critical state to a target state in the self-balancing vehicle state.

[0085] In order to further illustrate the technical solution of the present invention in detail, the two-wheeled robot with two-wheel drive and two-steering control is introduced below in combination with a specific experimental process.

[0086] In the experiment, the outer frame size of the aluminum frame 1 is 800mm×260mm. The distance between the two hip rotation motors 401 with a maximum torque of 5.8Nm is L=500mm in the initial state. The hip leg 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 power is turned on. Limited by the length of the guide rail and the edge of the frame 1, the relative displacement d of the front frame 1 ranges from d∈[-30mm,30mm]. The linear position sensor has a range of 150mm and an accuracy of ±0.01mm, which can cover the slider stroke. A 24V lithium battery and a 36V lithium battery are installed in the center above the frame 1, where the latter is used to power the hub motor 406 and the former is used to power other components. The linear position sensor is installed directly below the geometric center of the frame 1. In the motion module, the distance a from the hip flexion motor 402 axis to the plane of the frame 1 is 136 mm, the length of the thigh 403 and the calf 405 is b=250 mm, and the radius r of the wheel 407 is w = 100mm, the wheel 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 keep the robot balanced, an auxiliary bracket is installed around the body. The main body of the bracket consists of four vertical aluminum profiles and omnidirectional wheels at the end. In the experiment, the height of the auxiliary bracket will be adjusted to the same height as the motion module to provide support. Since the omnidirectional wheel does not generate speed constraints when in contact with the ground, the robot's motion mode is still determined only by the motion module and is not affected by the auxiliary bracket.

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

[0089] Bicycle mode: rear wheel speed in bicycle mode and the front wheel steering angle δ f They are used to control the forward speed and driving direction of the vehicle. The target degree of freedom of deformation 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 hand side is the reference control quantity obtained by the inverse kinematics equation xx, and the second term is the feedback control term, where is the nominal proportional coefficient, and d is the measured displacement of the slider. f From 0 to ± Rotation, the longitudinal component of the front wheel speed decreases, causing The ability to control the deformation freedom is weakened. Therefore, cos(δ f ) is used to perform nonlinear correction on the nominal proportionality factor, while the angle limit is added to prevent the denominator singularity. In the bicycle morphology experiment, the robot moves straight, turns right, turns left, and returns to the center in sequence. In the state space quantity and workspace quantity in the experiment, |d|≤3mm, which means that the control rate xx can keep the deformation freedom degree stable during the movement.

[0092] Self-balancing vehicle form: In the self-balancing vehicle form, the front and rear wheel speeds It is used to control the forward speed and driving direction of the vehicle. Both wheels 407 have no amount along the longitudinal axis of the frame 1, so ideally the structural freedom d always remains constant. However, experiments show that when the two-wheeled vehicle rotates, d will increase rapidly until it reaches the upper limit, which is caused by centrifugal force. Therefore, a control rate is designed here to use the offset of the front wheel steering angle to balance the effect of the centrifugal force and keep d constant:

[0093]

[0094] in is the kinematic feedforward of the front wheel angle, is the proportional coefficient of the feedback term, sgn is the sign function, and d is the measured value of the slider displacement. When d≠0, the front wheel steering angle deviates The wheel 407 speed generates a component along the length direction of the frame 1 to adjust d. At the same time, wheel speed control is introduced to keep the speed component of the front wheel perpendicular to the longitudinal direction of the vehicle body at a preset value.

[0095]

[0096] Due to δf exist Nearby, the above formula will not produce singularity. In the self-balancing car experiment, the robot rotates 360° on the spot, moves forward, and turns around while moving forward. When moving forward and turning with a large radius, the structural degree of freedom d≤3mm, but when the body rotates on the spot, there is a steady-state error of about 8mm. This is because the centrifugal force on the front legs during rotation is large, which exceeds the adjustment capacity of linear feedback control. In the future, the steady-state error will be eliminated through nonlinear feedback control.

[0097] Oblique vehicle state: In the oblique vehicle state, the steering angle δ of the two wheels 407 f =δ r Used to control the direction and speed of the two wheels 407 Used to control the vehicle moving speed, is the reference control quantity obtained by the inverse kinematics equation xx. The front wheel speed is also used to control the structural freedom d. The control equation is equation (xx, the same as that of the bicycle). In the experiment, the oblique vehicle performs straight and turning movements. In the steady state, the structural freedom d≤2mm.

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

[0099] Based on the above experiments and analysis, the over-constraint problem caused by redundant drives is solved by introducing the structural deformation degrees of freedom of the two-wheeled vehicle and the active control of the changed degrees of freedom, so as to realize the planar omnidirectional motion of the two-wheeled robot, and be able to smoothly switch between the bicycle and self-balancing vehicle configurations during the movement. It can convert different motion modes as needed and has smooth motion performance and configuration switching capabilities.

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein, but these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A two-wheeled robot with dual-wheel drive and dual steering control, characterized in that: include: A vehicle body module comprises a vehicle frame (1), a front trunk connecting plate (2) and a rear trunk connecting plate, wherein a guide rail slider mechanism (11) arranged along the length direction is provided at the front end of the vehicle frame (1), the front trunk connecting plate (2) is fixedly connected to the slider and has a linear motion freedom, and the rear trunk connecting plate (3) is fixedly arranged at the rear end of the vehicle frame (1) in a front-to-rear position; and A front movement module (41) and a rear movement module (42), wherein the front movement module (41) is connected to the front trunk connection plate (2), and the rear movement module (42) is connected to the rear trunk connection plate (3), and the structures are consistent and respectively include a thigh (403), a calf (405) and a wheel (407); The two-wheeled robot is configured to switch between three different motion modes: a bicycle, a self-balancing vehicle and an inclined vehicle, wherein the inclined vehicle is used to connect the mode switching between the bicycle and the self-balancing vehicle.

2. The two-wheeled robot 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 provided with a hip rotation motor (401), a hip-leg flexion motor (402), a knee joint motor (404) and a wheel hub motor (406); the hip rotation motor (401) is located at the uppermost end of the motion module and is configured to change the orientation of the motion module relative to the frame (1); the hip-leg flexion motor (402) is located below the hip rotation motor (401) and its rotating shaft is perpendicular to the rotating shaft of the hip rotation motor (401); the hip-leg flexion motor (402) is connected to the knee joint motor (404) through a thigh (403) connector, and the knee joint motor (404) is connected to the wheel hub motor (406) through a calf (405); and the wheel hub motor (406) is drivingly connected to a wheel (407).

3. The two-wheeled robot with two-wheel drive and two-steering control according to claim 1, characterized in that: The front motion module (41) / rear motion module (42) is configured to perform extension and retraction movements driven by 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 during movement to maintain the height of the wheel to the frame (1) and to allow the center of the wheel (407) to pass through the axis of the hip rotation motor (401).

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

5. A two-wheeled robot with two-wheel drive and two-steering control and a control method, characterized in that: Establish a two-wheeled vehicle coordinate system, including: the front and rear wheels contact the ground at points P and Q respectively, and the vectors from the center of the front and rear wheels A and B to the contact points P and Q are respectively Assuming that both wheels (407) do not slip, there are two velocity constraint equations at their contact points P and Q with the road surface; the position equations of points P and Q are: r OP ＝r OC +r CF +r FA +r AP r OQ ＝r OC +r CR +r RB +r BQ 。 6. The two-wheeled robot with two-wheel drive and two-steering control and the control method according to claim 5, characterized in that: The forward kinematics equation of a two-wheeled vehicle:

7. The two-wheeled robot with two-wheel drive and two-steering control and the control method according to claim 6, characterized in that: When the robot is in bicycle motion mode, the rear fork angle remains at 0 degrees and its positive kinematic equation is:

8. The two-wheeled robot with two-wheel drive and two-steering control and the control method according to claim 7, characterized in that: The control input equation for the bicycle motion mode is:

9. The two-wheeled robot with two-wheel drive and two-steering control and the control method according to claim 6, characterized in that: When the robot is in the self-balancing vehicle motion mode, the directions of the two wheels (407) remain perpendicular to the frame (1), and the two wheels (407) have no velocity component along the direction of the frame (1). Its positive kinematic equation is:

10. The two-wheeled robot with two-wheel drive and two-steering control and the control method according to claim 6, characterized in that: When the robot moves in the oblique car mode, the two forks can rotate to any equal angle, and its forward kinematic equation is:

Images