CN-116788383-B - Wheel leg type robot and control method thereof

CN116788383BCN 116788383 BCN116788383 BCN 116788383BCN-116788383-B

Abstract

The invention discloses a wheel leg type robot and a control method thereof, and belongs to the technical field of robots. The robot adopts a wheel-leg combined structure and comprises a wheel part, a leg part and a hardware circuit module. The wheel type part adopts the existing mature bicycle frame and comprises a frame, a front wheel, a rear wheel and a steering structure part. The leg parts are fixed on two sides of the frame, which is favorable for physical interaction with the ground environment and improves the adaptability to the complex environment. The invention combines the advantages of the wheeled robot and the leg robot, designs different controllers aiming at different terrains, enables the mobile robot to rapidly and stably run on a flat ground and dynamically overcome the obstacle, and improves the mobility of the mobile robot.

Inventors

LIU TAO
HUANG XINYAN
HE LONG
YI JINGANG

Assignees

浙江大学

Dates

Publication Date: 20260505
Application Date: 20230516

Claims (7)

1. A control method using a wheel-legged robot, characterized in that the wheel-legged robot includes a wheel portion, a leg portion, and a hardware circuit module; The wheel type part comprises a front wheel (11), a rear wheel (10) and a steering component, wherein the front wheel (11) is arranged on a frame (1), and is used as a power wheel of a robot and driven by a hub motor (9), the steering component is positioned above the front wheel (11) and comprises a steering handle (5), a synchronous pulley (4) and a steering motor (3), and the steering motor (3) transmits torque to the steering handle (5) through the synchronous pulley (4) so as to steer the robot; The leg part comprises a left leg and a right leg, and each leg is provided with a motor module consisting of a hip side swing joint motor (13), a hip positive swing joint motor (14) and a knee joint motor (15); The hardware circuit module comprises a main control board, a motor control board, an information acquisition module and a power supply module, wherein the power supply module is used for providing working voltage for the whole circuit system and a motor, the hub motor (9) and the steering motor (3) are both connected with the motor control board, the motor control board is connected with the main control board and is communicated by using a USART, and the information acquisition module is communicated with the main control board by adopting the USART; the control method specifically comprises the following steps: S1, aiming at flat terrain, in order to enable the robot to rapidly run with high mobility, an internal and external dynamic coordination balance control strategy is adopted, and the method specifically comprises the following steps: Ground contact point of rear wheel (10) Is the coordinates of (a) Then there is ; In the formula, Indicating the ground contact speed of the rear wheel (10), Representing the speed of the robot in the x-axis direction in World coordinate system, The method comprises the steps of representing the speed of a robot along the y-axis direction under a World coordinate system, wherein the World coordinate system is fixed on the ground, the Z-axis is vertically upwards, and the X-axis advances in the direction; represents the linear velocity of the outer edge of the rear wheel (10), A cosine function representing the yaw of the robot, A sinusoidal function representing the yaw angle of the robot; Continue to pair Solving the two guides, and assuming that the robot runs forwards at a constant speed, finally obtaining ; In the formula, The intermediate control quantity is indicated as such, Representing a yaw angle of the robot; Given a desired trajectory Tracking this trajectory for an externally dynamic design linear controller ; In the formula, Representing the desired x-coordinate of the robot, Representing a desired y-coordinate of the robot, a desired robot position Positional deviation of , A feedback gain variable representing the controller; Will be Substituting the above data to obtain external dynamic control input ; In the formula, Represents the linear velocity of the outer edge of the rear wheel (10); To allow the robot to balance, the tilt acceleration of 0 is required to be satisfied, i.e. the system is not directly used as a control input ; In the formula, Representation and yaw angle A related amount; Will be Substituting into the above formula and solving by Newton's method And then to The total derivative can be sequentially calculated 、 For the obtained Representing the expected tilt angle, tilt angle speed and tilt angle acceleration that can ensure system trajectory tracking; In order to enable the system to track the track with the expected inclination angle and achieve the purposes that the robot can ensure balance and track tracking, the whole system needs to be partially fed back and linearized at first and then the linear controller can be used for tracking And derivatives thereof; Thus designing an internal dynamic feedback control law ; Substitution into kinetic formula Can be obtained ; The tilt acceleration from this system can be arbitrarily configured; In the formula, , , Wherein, the method comprises the steps of, Indicating a desired tilt angle acceleration of the robot, Indicating the acceleration of the robot's tilt angle, The mass of the robot is indicated and, Representing the slave robot center of gravity To the ground contact point of the rear wheel (10) The vertical distance of the front wheel (11) and the rear wheel (10) of the robot are respectively marked as And , Indicating robot winding Is a rotational inertia of (a); a cosine function representing the tilt angle of the robot, A sinusoidal function representing the tilt angle of the robot, Representing the slave robot center of gravity To the ground contact point of the rear wheel (10) Is arranged in the horizontal direction of the frame, Indicating the trail of the front wheel (11), The projection angle of the turning handle on the ground is shown, A cosine function representing the angle of inclination of the front fork of the robot, Representation of And Is a distance of (2); To track And its derivative, let ; In the formula, Representing a trajectory tracking parameter; So long as it The tracking error can be guaranteed to converge to zero; Finally, the internal and external dynamic coordination motion controller during flat ground running is that ; S2, aiming at the rugged road surface, adopting a wheel leg cooperative control strategy of combining model prediction and internal and external dynamic coordination, wherein the method comprises the following steps of: The wheel-leg cooperative control strategy integrates leg control and internal and external dynamic cooperative control, and generates wheel-leg cooperative control signals through a desired state track given by a user and sensing information fed back by a robot, and the wheel-leg cooperative control signals respectively drive a hip lateral swing joint motor (13), a hip positive swing joint motor (14), a knee joint motor (15), a steering motor (3) and a hub motor (9); The auxiliary leg control consists of a supporting phase and a swinging phase, wherein the two states are scheduled by a gait generator, the supporting phase adopts an MPC algorithm to generate the needed joint motor moment as moment feedforward, and simultaneously, the feedback control is added to carry out force-position mixed control; The MPC is used for calculating the system input capable of minimizing the state track error according to the expected state track and the current sensing information, and simultaneously minimizing the system input for saving energy, and the MPC is in the form of the following formula: ; ; ; Wherein the method comprises the steps of Is that Is used for the control sequence of (a), Is the period of the model predictive control, Representing the prediction time domain, wherein Error of state vector , A state variable representing the state of the system, Representing the desired state variables of the system, And Is a diagonal weight matrix; Coefficients representing state variables in the state space equations, Representing coefficients of the system input in the state space equations, The term of the constant is represented by a term, Representing the displacement of the projection of the center of gravity of the robot to the tail end of the ith leg; the control input is represented as such, Represents the ground reaction force of the i-th leg end, wherein i=0 is the left leg and i=1 is the right leg; respectively representing upper and lower limits of friction force and motor moment, subscript Representing the first of the vectors An element; Matrix array Is that ; Wherein the method comprises the steps of Representing the coefficient of static friction between the leg and the ground, then solving the above optimization problem by discretization and using qpOASES solver; When the i-th leg is in contact with the ground, The joint moment of (2) can be calculated by the following formula ; Wherein, the Representing a rotation matrix from a Body coordinate system to a World coordinate system; representing the transpose of the jacobian matrix, thereby obtaining the feedforward moment of the leg joint; the supporting leg should track a track to ensure that the leg can always contact the ground at the same point, and the desired joint angle, joint angular velocity and joint angular acceleration at a certain time are respectively Feedback control amount Is that ; In the formula, The differential gain is represented by a value of, The proportional gain is indicated as such, The angular velocity of the joint is indicated, Representing the joint angle; Thus the final joint motor moment ; The key point of the swing phase is to determine the position of the falling foot point, and the position of the tail end of the expected leg can be calculated by adopting a heuristic formula, so that the effect of speed adjustment is achieved: ; In the formula, Indicating the desired position of the leg ends in the x-y plane, Is the gait cycle of the person, Is the position of the hip lateral swing joint motor (13) on the x-y plane, Is the desired speed of the center of gravity of the robot in the x-y plane, Is the corresponding center of gravity velocity of the vehicle, Is the gain; in the running process of the robot, the balance and track tracking of the robot are realized through internal and external dynamic coordination control, the physical interaction between the robot and the ground is enhanced through the periodic leg-taking of the auxiliary legs, and the stability of the robot is greatly improved under the condition of limited turning moment; s3, aiming at obstacle crossing scenes, adopting a pulse control strategy based on leg force to enhance obstacle crossing and anti-interference capabilities of the robot, wherein the method comprises the following steps of: the robot triggers a collision detection program in the process of passing through an obstacle, and when the system is unstable, the robot starts triggering leg force pulses, so that the system returns to the previous equilibrium position by applying force pulses to the system, and the method is concretely as follows: Representing leg-ground interaction forces The moment applied to the robot is Setting the moment vector of the joint of the single leg as Then Wherein Is a rotation matrix transformed from a Body coordinate system to a World coordinate system, so that the applied moment can be obtained as ; In which the pulsed balancing moment that can be applied to the robot is a component along the x-axis, i.e For balance purposes, attention is paid mainly to While the torque components in the y-axis and z-axis directions And It is desirable to be as small as possible; Assuming a pulse moment At the position of The moment passes for a very short time Up to Under the action of moment pulse, the inclination angle speed of robot will jump discontinuously while the inclination angle is unchanged Obtaining ; Note that due to the angle of inclination The period remains unchanged, thus Obtainable according to the above ; Wherein the method comprises the steps of The amount of change in the tilt angle speed is indicated, And Respectively representing the inclination angles before and after the moment pulse acts; can be converted into an optimization problem, i.e. finding a suitable desired tilt angle speed The balance and track tracking error of the system and the control input of the system can be minimized, so the optimization problem can be described as ; ; ; Wherein the method comprises the steps of Is an error vector, matrix And Are all symmetric positive definite matrixes, and the positive definite matrixes are formed, Is a predicted time period, and the objective function is expressed in The optimization problem is used for searching the optimal initial inclination angle speed, so that the robot can carry out balancing and track tracking tasks again; The value should be as small as possible to ensure that the leg and ground contact duration is short enough, provided that during this time Is kept unchanged, and can be solved by SQP algorithm Then further get ; To generate It is necessary to design leg-ground interaction forces When the leg is in contact with the ground, the contact point is located Then Wherein , At the same time, in order to eliminate And The influence produced increases Restraint, in practice, collisions of the wheels with obstacles will generally prevent the robot from rotating in the y-axis and z-axis directions, thus And Has little influence on the system and can be ignored, thereby obtaining : ; Wherein, the Is the maximum vertical ground reaction force, and the leg-ground contact point position Dynamically adjusting in an experiment; finally, the required joint moment can be obtained ; Wherein the method comprises the steps of , , , 。
2. The control method according to claim 1, wherein the left leg and the right leg each comprise a thigh and a shank, the upper ends of the thighs are rotatably connected to a leg base (12), the leg base (12) is fixedly connected with the frame (1) through a bracket (8), and the upper ends of the shanks are rotatably connected with the thighs.
3. A control method according to claim 2, characterized in that the hip side swing joint motor (13) and the hip side swing joint motor (14) are used for controlling the rotation mode of the joint between the thigh and the leg base (12), and the knee joint motor (15) is used for controlling the rotation mode of the joint between the thigh and the shank.
4. The control method according to claim 1, wherein the power supply module comprises a voltage stabilizing module and a plurality of model airplane lithium batteries, the model airplane lithium batteries can directly output 42V and 12V voltages or output 5V and 19V voltages through the voltage stabilizing module, wherein the 42V voltages are used for supplying power to the hub motor (9) and the steering motor (3), the 12V voltages are used for supplying power to the motor module, the 5V voltages are used for supplying power to the motor control board, and the 19V voltages are used for supplying power to the main control board.
5. The control method according to claim 1, wherein the information acquisition module comprises an inertial measurement unit (2), a meter wheel (6) and a motor encoder, the inertial measurement unit (2) is used for collecting gesture and speed information of the robot and is fixed in the middle of the frame (1), the meter wheel (6) is used for acquiring the position of the robot and is arranged at the rear of the frame (1), and the motor encoder is integrated in a motor module and is used for acquiring the rotation angle and the angular speed of each motor.
6. The control method according to claim 1, wherein the main control board is Jetson TX F429 development board, and the motor control board is STM32F429 development board.
7. The control method according to claim 1, characterized in that the power module, the main control board and the motor control board are all placed on a rear seat (7) of the frame (1).

Description

Wheel leg type robot and control method thereof Technical Field The invention belongs to the technical field of robots, and particularly relates to a novel wheel leg type robot and a control method thereof. Background Ground mobile robots are one of the fastest growing fields in scientific research. Since the ground mobile robot can autonomously move, it does not require the assistance of an external human operator, and replaces human work in many fields. Including field detection, planetary detection, urban patrol, emergency rescue operations, field reconnaissance, industrial automation, construction, entertainment, museum guides, personal services, transportation, and medical applications. Ground mobile robots can be divided into two main areas, foot-based robots based on legs and wheel-based wheeled robots. Although some indoor walking foot robots perform well in overcoming obstacles such as stairs or complex uneven terrain, they generally require a great deal of time to perform these complex actions. Wheeled robots, in contrast, are well suited for level ground because they can move smoothly, efficiently and quickly. However, they are generally not capable of handling rough terrain, particularly when encountering obstacles that are larger than the radius of their wheels. Therefore, due to the above-mentioned drawbacks, i.e., the limitations of both the pure wheeled robot and the legged robot, there is an urgent need to develop a legged robot that can combine the advantages of the legged robot and the legged robot, so that the robot can rapidly move on a flat road surface, and simultaneously can stably travel and surmount obstacles in a complex environment. In addition, the structure and the control method of the robot with the combined wheel legs are researched, so that a new thought and a new method can be provided for researching other unstable and nonlinear complex systems, and a new solution is provided for unmanned distribution, urban security and other application scenes. Disclosure of Invention The invention aims to overcome the defects in the prior art and provides a wheel leg robot and a control method thereof. According to the invention, the advantages of the wheeled robot and the leg robot are fused on one robot through structural design and control algorithm design, so that the robot plays different roles in different scenes. The specific technical scheme adopted by the invention is as follows: In a first aspect, the present invention provides a wheeled legged robot comprising a wheeled portion, a leg portion, and a hardware circuit module; the wheel type part comprises a front wheel, a rear wheel and a steering part, wherein the front wheel is arranged on a frame and is used as a power wheel of the robot and driven by a hub motor; The leg part comprises a left leg and a right leg, and each leg is provided with a motor module consisting of a hip lateral swing joint motor, a hip positive swing joint motor and a knee joint motor; The hardware circuit module comprises a main control board, a motor control board, an information acquisition module and a power supply module, wherein the power supply module is used for providing working voltage for the whole circuit system and the motor, the wheel hub motor and the steering motor are connected with the motor control board, the motor control board is connected with the main control board and is communicated by using a USART, and the information acquisition module is communicated with the main control board by adopting the USART. Preferably, the left leg and the right leg comprise thighs and shanks, the upper ends of the thighs are rotatably connected to a leg base, the leg base is fixedly connected with the frame through a bracket, and the upper ends of the shanks are rotatably connected with the thighs. Further, the hip side swing joint motor and the hip positive swing joint motor are used for controlling the rotation mode of the joint of the thigh and the leg base, and the knee joint motor is used for controlling the rotation mode of the joint of the thigh and the shank. The power supply module comprises a voltage stabilizing module and a plurality of model airplane lithium batteries, wherein the model airplane lithium batteries can directly output 42V and 12V voltages or output 5V and 19V voltages through the voltage stabilizing module, the 42V voltages are used for supplying power to a hub motor and a steering motor, the 12V voltages are used for supplying power to a motor module, the 5V voltages are used for supplying power to a motor control board, and the 19V voltages are used for supplying power to a main control board. Preferably, the information acquisition module comprises an inertia measurement unit, a meter wheel and a motor encoder, wherein the inertia measurement unit is used for collecting the gesture and speed information of the robot and is fixed at the middle part of the frame, the meter wheel is used for acquiring the position of