Driving control method of wheel-foot robot and wheel-foot robot

Abstract

The invention discloses a running control method of a wheel-foot robot and the wheel-foot robot, belongs to the technical field of wheel-foot robots, and is used for solving one of the problems that the wheel-foot robot bears large impact force in the high-speed running or turning process, the stability is poor, and steering is difficult to control. The running control method of the wheel-foot robot comprises the steps that a state sensing unit sends environment information and robot motion state information which are obtained in real time to a central control unit; the central control unit generates a motion instruction according to information fed back by the state sensing unit; and the wheel leg execution mechanism executes the motion instruction of the central control unit. The stability of the wheel-foot robot during high-speed running or turning can be effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of wheeled robot technology, and relates to a driving control method for a wheeled robot and a wheeled robot. Background Technology

[0002] The wheels of wheel-legged hybrid robots can reduce motion vibration by directly contacting the ground, and can achieve driving motion by controlling only a few active degrees of freedom. However, they still have many problems such as poor stability, difficulty in steering control, low energy efficiency, and complex control system when traveling at high speed and turning.

[0003] Four-wheeled robots combine the efficient mobility of wheeled structures with the obstacle-crossing capabilities of legged structures. However, when traveling at high speeds on flat surfaces, compared to traditional cars, four-wheeled robots typically have a higher center of gravity, relatively smaller wheelbase and track width, and lack the robust suspension system and mature wheel alignment parameter design of automobiles. This makes them prone to rollover, skidding, or inflexible steering control at high speeds. Furthermore, they are susceptible to instability due to greater impact forces from uneven surfaces. Current industry solutions, such as adding mechanical mechanisms to the robot's underside, can improve high-speed driving and cornering stability to some extent, but this significantly increases the robot's weight and overall size, indirectly affecting its overall range and increasing the cost and difficulty of transportation and storage. Summary of the Invention

[0004] Based on the above analysis, the present invention aims to provide a driving control method for a wheeled robot and a wheeled robot, in order to solve one of the problems of wheeled robots experiencing large impact forces, poor stability, and difficulty in steering control during high-speed driving or cornering.

[0005] The objective of this invention is mainly achieved through the following technical solutions.

[0006] The first aspect of the present invention provides a method for controlling the movement of a wheeled robot, comprising the following steps:

[0007] The S100 state perception unit acquires environmental information and robot motion state information in real time and sends them to the central control unit.

[0008] The S200 central control unit generates motion commands based on information fed back from the status sensing unit.

[0009] The S300 wheel-leg actuator executes the motion commands from the central control unit.

[0010] Furthermore, the S200 also includes a central control unit that activates corresponding control strategies based on the task.

[0011] Furthermore, the S200 also includes: when the task is high-speed driving, a high-speed driving stability control strategy is activated.

[0012] Furthermore, the S200 also includes the following: when the task involves driving at low to medium speeds or traversing complex terrain, the high-speed driving stability control strategy is not activated.

[0013] Furthermore, S200 also includes: a central control unit that determines the desired position and desired speed of each joint of the robot based on the control strategy.

[0014] Furthermore, the S200 also includes: a central control unit sending motion commands to the wheel-leg actuators.

[0015] Furthermore, the environmental information acquired in S100 includes: road surface slippage, road surface flatness, and obstacle information.

[0016] Furthermore, the motion state information of the ring robot acquired in S100 includes: body posture, body angular velocity, body linear velocity, and the position of each joint of the robot.

[0017] Furthermore, in S100, the robot motion state information also includes the values ​​of the toe angle δ and the camber angle γ of the robot's foot wheel; the toe angle δ is the angle between the longitudinal centerline of the foot wheel and the centerline of the robot body when viewed from below the robot; the camber angle γ is the angle between the longitudinal centerline of the foot wheel and the centerline of the robot body when viewed from the horizontal direction of the wheeled robot.

[0018] Furthermore, the high-speed driving stability control strategy in the S200 also includes: the central control unit dynamically calculates the optimal heading angle required for each foot wheel based on the robot's real-time motion state and speed control commands; the heading angle includes the toe angle δ and the camber angle γ.

[0019] Furthermore, the high-speed driving stability control strategy in S200 also includes: when the robot is in a high-speed straight-line cruise state, assigning each foot wheel toe angle δ to zero or a small positive toe angle δ1; when the robot is making a high-speed turn, assigning differentiated toe angles δ to the inner and outer wheels; when the robot body yaws excessively, independently adjusting the toe angle δ of the foot wheel on the yaw direction side; and when the robot needs to brake urgently, assigning a small positive toe angle δ1 to all foot wheels.

[0020] Furthermore, the high-speed driving stability control strategy in S200 also includes: when the road surface is uneven or the robot tilts, applying a negative camber angle γ2 to the foot wheel on the lower side and a positive camber angle γ1 to the foot wheel on the higher side.

[0021] Furthermore, the S300 also includes: a foot joint rotary motor that executes motion commands to adjust the toe angle δ of the foot wheel; and a side swing joint motor that executes motion commands to adjust the camber angle γ of the foot wheel.

[0022] The second aspect of the present invention provides a wheeled robot that uses the driving control method of the wheeled robot of the first aspect of the present invention for driving control. The wheeled robot includes a central control unit, a state sensing unit, wheel and leg actuators and a body.

[0023] Furthermore, the wheel-leg actuator has five degrees of freedom.

[0024] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0025] 1. The driving control method of the wheeled robot of the present invention can effectively improve the stability when driving at high speed or turning by dynamically adjusting the motion state of the wheeled actuator in S100 to S300.

[0026] 2. The driving control method of the wheeled robot of the present invention, by synchronously acquiring the values ​​of the toe angle δ and the camber angle γ of the robot's foot wheel in S100, can provide more comprehensive motion state feedback to the central control unit, thereby enhancing the driving stability of the robot in complex road conditions.

[0027] 3. The driving control method for the wheeled robot of the present invention, by activating a high-speed driving stability control strategy in S200, can dynamically calculate the required toe angle δ of each foot wheel, which can effectively prevent phenomena such as separation and swaying of the wheeled robot during travel, thereby ensuring the stability and safety of the robot. At the same time, dynamically calculating the required camber angle γ of each foot wheel can optimize the contact area between the foot wheel and the ground, enhance grip, and effectively reduce the risk of sideslip, especially when traveling on slopes or uneven roads.

[0028] 4. The driving control method of the wheeled robot of the present invention can enhance road holding ability, lateral stability and safety simultaneously by actively adjusting the toe angle δ and camber angle γ of the foot wheel in S300, thereby improving the motion performance of the wheeled robot when driving at high speed.

[0029] 5. The driving control method of the wheeled robot of the present invention, by setting toe angle and camber angle adjustment strategies under various conditions in the high-speed driving stability control strategy in S200, can effectively cope with complex working conditions such as steering, sideslip and uneven road surface during high-speed driving, and achieve precise intervention in vehicle posture.

[0030] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained through the embodiments described and the accompanying drawings. Attached Figure Description

[0031] Figure 1 This is a schematic diagram illustrating the steps of a driving control method for a wheeled robot according to an embodiment of the present invention;

[0032] Figure 2 This is a schematic diagram of the positive toe angle δ1 of the foot wheel according to an embodiment of the present invention;

[0033] Figure 3 This is a schematic diagram of the negative toe angle δ2 of the foot wheel according to an embodiment of the present invention;

[0034] Figure 4 This is a schematic diagram of the positive outward tilt angle γ1 of the foot wheel according to an embodiment of the present invention;

[0035] Figure 5 This is a schematic diagram of the positive outward tilt angle γ2 of the foot wheel according to an embodiment of the present invention;

[0036] Figure 6 This is a schematic diagram of step S220 in Embodiment 2 of the present invention;

[0037] Figure 7 This is a schematic diagram of the wheel-leg actuator of Embodiment 3 of the present invention.

[0038] Figure label:

[0039] 100-Wheel-Leg Actuator;

[0040] 11-Side swing joint; 111-Side swing joint motor;

[0041] 12-Front swing joint; 121-Front swing joint motor;

[0042] 13- Knee joint; 131- Telescopic joint motor

[0043] 14-Ankle joint;

[0044] 15-Foot joint rotation; 151-Foot joint rotation motor;

[0045] 16-Wheel rotary joint; 161-Wheel-side motor;

[0046] 2-Thigh; 21-Thigh linkage; 3-Lower leg; 31-Lower leg linkage; 4-Foot; 41-Foot wheel;

[0047] δ - Anterior head angle; δ1 - Positive anterior head angle; δ2 - Negative anterior head angle;

[0048] γ - outward inclination; γ1 - positive outward inclination; γ2 - negative outward inclination. Detailed Implementation

[0049] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0050] Example 1

[0051] This embodiment provides a method for controlling the movement of a wheeled robot, such as... Figure 1 As shown, it includes the following steps:

[0052] The S100 state perception unit acquires environmental information and robot motion state information in real time and sends them to the central control unit.

[0053] The S200 central control unit generates motion commands based on information fed back from the status sensing unit.

[0054] The S300 wheel-leg actuator executes the motion commands from the central control unit.

[0055] The driving control method of the wheeled robot in this embodiment can effectively improve stability when driving at high speed or turning by dynamically adjusting the motion state of the wheel and leg actuators.

[0056] Specifically, in S100, the state perception unit includes an IMU (Inertial Measurement Unit), joint encoders, a vision camera, and a LiDAR sensor; environmental information includes road surface conditions such as slipperiness, flatness, and obstacles, with the vision camera and LiDAR sensor used to identify these conditions; robot motion state information includes body posture, angular velocity, linear velocity, and joint positions, with the robot's real-time linear velocity measured by a velocity sensor, its angular velocity and posture monitored by a three-axis gyroscope, and its joint encoders providing feedback on the position parameters of each joint.

[0057] Considering that during high-speed travel, the motion control of the wheels directly affects the motion state of the wheeled robot due to the influence of air resistance and friction, in S100 of this embodiment, the motion state information of the robot includes the values ​​of the toe angle δ and the camber angle γ of the robot's foot wheel.

[0058] The toe angle δ of a robot's foot wheel is defined as: the angle between the longitudinal centerline of the foot wheel and the centerline of the robot body when viewed from below the wheeled robot. For example... Figure 2As shown, if the distance between the front point of the foot wheel and the centerline of the robot body is shorter than the distance between the rear point, then it is a positive toe angle δ1; conversely, if... Figure 3 As shown, if the distance between the front point of the foot wheel and the center line of the robot body is longer than the distance between the rear point, then it is a negative toe angle δ2.

[0059] The camber angle γ of a robot's foot wheel is defined as: the angle between the longitudinal centerline of the foot wheel and the centerline of the robot body when viewed horizontally from the robot's perspective. For example... Figure 4 As shown, if the distance between the point on the foot wheel and the centerline of the robot body is longer than the distance between the point on the foot wheel and the bottom wheel, then it is a positive outward tilt angle γ1; otherwise, it is a positive outward tilt angle γ1. Figure 5 As shown, if the distance between the upper point of the foot wheel and the center line of the robot body is shorter than the distance between the lower point, then it is a negative outward tilt angle γ2.

[0060] In this embodiment, in S100, the values ​​of the toe angle δ and camber angle γ of the robot's foot wheels are acquired synchronously, which can provide more comprehensive motion status feedback to the central control unit, thereby enhancing the robot's driving stability in complex road conditions.

[0061] Furthermore, S200 includes the following steps:

[0062] The S210 central control unit plans the optimal route based on environmental information;

[0063] The S220 central control unit determines the desired position and speed of each joint based on the control strategy;

[0064] The S230 central control unit sends motion commands to the wheel-leg actuators.

[0065] Specifically, the central control unit first plans the optimal path in S210 to reduce the impact of sudden turns or braking on stability during movement. In S220, the central control unit combines the current motion state and environmental information to calculate the torque and motion parameters required by each joint in real time, and performs feedforward compensation based on the dynamic model to improve motion control accuracy. In S230, the central controller sends the generated joint torque commands and trajectory parameters to each drive unit through the communication bus, driving the wheel and leg actuators to complete the corresponding actions, ensuring that the robot runs stably and at high speed along the planned path.

[0066] To enable the wheeled robot to adapt to complex terrain, the S220 also includes a high-speed driving stability control strategy when the task is high-speed driving.

[0067] Specifically, the high-speed driving stability control strategy in S220 includes: the central control unit dynamically calculates the optimal heading angle required for each foot wheel based on the robot's real-time motion state and speed control commands; the heading angle includes the toe angle δ and the camber angle γ.

[0068] The driving control method of the wheeled robot in this embodiment, by activating the high-speed driving stability control strategy in S220, can dynamically calculate the required toe angle δ for each foot wheel, effectively preventing phenomena such as separation and swaying during the robot's movement, thereby ensuring the robot's stability and safety. Simultaneously, dynamically calculating the required camber angle γ for each foot wheel optimizes the contact area between the foot wheel and the ground, enhancing grip, especially effectively reducing the risk of sideslip when driving on slopes or uneven surfaces. Through the fusion control of the toe angle δ and the camber angle γ, the wheeled robot can improve its anti-slip, anti-yaw, and pitch stability during high-speed movement, high-speed cornering, and handling uneven road surfaces, thereby comprehensively improving its high-speed dynamic performance.

[0069] It is understandable that introducing the toe angle δ and camber angle γ of the foot-end wheels into a wheel-legged robot will affect its dynamic characteristics during high-speed travel. When establishing the motion model, the influence of these angles on tire forces, kinematics, and dynamics needs to be considered. The wheel-legged robot adopts a hybrid wheel-leg motion, with wheel motion as the main mode of movement during high-speed travel, while the legs maintain a fixed posture.

[0070] For example, the kinematic model of the wheeled robot after introducing the toe angle δ and camber angle γ of the foot-end wheels is as follows:

[0071] 1. Foot wheel speed relationship

[0072] For each foot-end wheel, its rolling direction changes due to the toe angle δ and camber angle γ. Definition:

[0073] The rolling direction of the foot wheel is in the local coordinate system.

[0074] The toe angle δ and camber angle γ are used to transform the wheel speed from the local coordinate system to the global coordinate system through the rotation matrix R(δ,γ).

[0075] Foot wheel linear velocity v w,i The components in the global coordinate system are:

[0076]

[0077] Where R z and R x These are the rotation matrices around the z-axis (yaw) and x-axis (roll), respectively.

[0078] 2. Overall kinematic model of the robot

[0079] The robot's speed v = [v x ,v y ,ω] T The speed is determined by the combined speeds of all the foot-end wheels, where v x v y ω and ω represent the robot's linear velocity along the x-axis, linear velocity along the y-axis, and angular velocity (yaw rate) about the z-axis, respectively. Mapped using the Jacobian matrix J:

[0080]

[0081] The construction of the Jacobian matrix needs to take into account the correction of the wheel velocity direction by the toe angle and camber angle.

[0082] Dynamic model:

[0083] (1) Tire force model

[0084] Toe angle and camber angle affect the tire's lateral characteristics and vertical force distribution. A simplified linear tire model is used:

[0085] Lateral force:

[0086] F y,i =-C α α i

[0087] Where α i It is the sideslip angle, which is affected by the toe angle and lateral tilt angle.

[0088]

[0089] k γ It is the outward stiffness coefficient.

[0090] Vertical force:

[0091] An outward tilt angle can cause uneven distribution of vertical force, which can be calculated using static equilibrium.

[0092]

[0093] (2) Dynamic equations

[0094] The robot's equation of motion is:

[0095]

[0096] Where F i It is the resultant force (including longitudinal and lateral forces) of the i-th tire, r i It is the tire position vector.

[0097] Furthermore, the S300 also includes: a foot joint rotary motor that executes motion commands to adjust the toe angle δ of the foot wheel. Specifically, the foot joint rotary motor adjusts the toe angle δ of the foot wheel by controlling its horizontal rotation.

[0098] The S300 also includes a lateral swing joint motor that executes motion commands to adjust the camber angle γ of the foot wheel. Specifically, the lateral swing joint motor adjusts the camber angle γ of the foot wheel by controlling the leg abduction movement.

[0099] The driving control method of the wheeled robot in this embodiment can enhance road holding ability, lateral stability and safety simultaneously by actively adjusting the toe angle δ and camber angle γ of the foot wheels, thereby improving the motion performance of the wheeled robot when driving at high speed.

[0100] Example 2

[0101] This embodiment provides a driving control method for a wheeled robot, the steps of which are basically the same as those of the driving control method for a wheeled robot provided in Embodiment 1, the difference being:

[0102] like Figure 6 As shown, S220 further includes the following steps:

[0103] S221: When the task is to travel at low to medium speed or to pass through complex terrain, the heading angle of the foot wheels is not calculated, and the robot moves with normal body height and gait.

[0104] S222: When the task involves high-speed movement, activate the high-speed movement stability control strategy. This strategy also includes reducing the robot's height. This allows the four-wheeled robot to adjust its direction in real time and improve stability during high-speed movement.

[0105] Furthermore, the high-speed driving stability control strategy in S222 also includes:

[0106] When the robot is in a high-speed straight-line cruising state, the toe angle δ of each foot wheel is assigned to zero or a small positive toe angle δ1. For example, 0 ≤ toe angle δ ≤ 10°.

[0107] By assigning zero or a small positive toe angle δ1 to each foot wheel, the directional stability of the robot in straight-line travel can be enhanced, and the suppression effect on lateral drift can be improved.

[0108] Furthermore, the high-speed driving stability control strategy in S222 also includes:

[0109] When the robot makes a high-speed turn, a different toe angle δ is assigned to the inner and outer wheels. Specifically, the inner wheel is assigned a negative toe angle δ2, and the outer wheel is assigned a positive toe angle δ1. For example, the toe angle of the inner wheel is 2° to 4° larger than that of the outer wheel.

[0110] By assigning different toe angles to the inner and outer wheels, a virtual "Ackermann geometry" enhancement effect can be created, generating a yaw moment in the same direction as the turning direction, assisting in turning and suppressing understeer.

[0111] Furthermore, the high-speed driving stability control strategy in S222 also includes:

[0112] When the fuselage yaws excessively, the toe angle δ of the foot wheel on the yaw direction is adjusted independently. Here, a negative toe angle δ2 is applied relative to the rear wheel in the yaw direction, and a positive toe angle δ1 is applied relative to the front wheel in the yaw direction.

[0113] By independently adjusting the toe angle δ of the foot wheel on the yaw direction, a corrective yaw moment can be generated. The yaw moment can effectively suppress fuselage sideslip and improve handling stability when cornering at high speed.

[0114] Furthermore, the high-speed driving stability control strategy in S222 also includes:

[0115] When the road surface is uneven or the robot tilts to one side, apply a negative camber angle γ2 to the foot wheel on the lower side and a positive camber angle γ1 to the foot wheel on the higher side.

[0116] By adjusting the camber angle γ of the two foot wheels respectively, the tire surface can make better contact with the road surface, generating greater lateral force, resisting the tendency to roll, and improving cornering support.

[0117] Furthermore, the high-speed driving stability control strategy in S222 also includes:

[0118] When the robot needs to brake suddenly, a small positive toe angle δ1 is given to all foot wheels.

[0119] By giving all foot wheels a small positive toe angle δ, directional stability during braking can be improved, preventing deviation.

[0120] The driving control method of the wheeled robot in this embodiment, by setting toe angle and camber angle adjustment strategies under various conditions in the high-speed driving stability control strategy of S222, can effectively cope with complex working conditions such as steering, sideslip and uneven road surface during high-speed driving, and achieve precise intervention in vehicle posture.

[0121] Preferably, the heading angle of the foot wheel is controlled by a separate PD controller. Once the optimal desired speed is obtained, the desired speed is input to the joint controller. The underlying joint controller uses the PD controller to execute the action generated by the strategy. The PD controller is used to reduce the deviation between the joint position and the target position, and the PD controller reduces the jitter caused by speed changes to ensure smoothness.

[0122] Example 3

[0123] This embodiment provides a wheeled robot, which uses the driving control methods of wheeled robots in Embodiments 1 and 2 for driving control. The wheeled robot includes a central control unit, a state perception unit, wheel and leg actuators 100, and a body.

[0124] To achieve adjustment of the toe angle δ and camber angle γ of the foot wheel, such as Figure 7 As shown, the wheel-leg actuator includes a joint, thigh 2, lower leg 3, and foot 4. The thigh 2 and lower leg 3 each include a thigh link 21 and a lower leg link 31, respectively, and the bottom of the foot 4 is connected to a foot wheel 41.

[0125] like Figure 7 As shown, there are six joints that can achieve five degrees of freedom. The joints include a lateral swing joint 11, a forward swing joint 12, a knee joint 13, an ankle joint 14, a foot rotation joint 15, and a wheel rotation joint 16.

[0126] like Figure 7 As shown, the lateral swing joint motor 111 controls the abduction of the leg, thereby adjusting the camber angle γ of the foot wheel; the forward swing joint motor 121 controls the forward or backward swing of the leg; the telescopic joint motor 131 controls the combined movement of the knee joint 13 and the ankle joint 14 by driving the thigh linkage 21; the foot wheel rotation motor 151 controls the horizontal rotation of the foot wheel, thereby adjusting the positive and negative toe angle δ of the foot wheel; and the wheel-side motor 161 controls the rotation of the foot wheel 41.

[0127] The wheeled robot in this embodiment, by setting up a wheel-leg actuator with six joints and five degrees of freedom, can flexibly adjust the toe angle δ and camber angle γ of the foot wheels, achieving precise control over its walking posture. The coordinated movement of each joint enables the wheel-leg to have both efficient mobility and stable support capabilities in complex terrain.

[0128] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for controlling the movement of a wheeled robot, characterized in that, Includes the following steps: The S100 state perception unit acquires environmental information and robot motion state information in real time and sends them to the central control unit. The S200 central control unit generates motion commands based on information fed back from the status sensing unit. The S300 wheel-leg actuator executes the motion commands from the central control unit.

2. The method for controlling the movement of a wheeled robot according to claim 1, characterized in that, The S200 also includes a central control unit that activates corresponding control strategies based on the task.

3. The method for controlling the movement of a wheeled robot according to claim 2, characterized in that, The S200 also includes: when the task is high-speed driving, a high-speed driving stability control strategy is activated.

4. The method for controlling the movement of a wheeled robot according to claim 2, characterized in that, The S200 also includes: when the task involves driving at low to medium speeds or traversing complex terrain, the high-speed driving stability control strategy is not activated.

5. The method for controlling the movement of a wheeled robot according to claim 2, characterized in that, The S200 also includes a central control unit that determines the desired position and speed of each joint of the robot based on the control strategy.

6. The method for controlling the movement of a wheeled robot according to claim 1, characterized in that, The S200 also includes: a central control unit that sends motion commands to the wheel-leg actuators.

7. The method for controlling the movement of a wheeled robot according to claim 1, characterized in that, The environmental information acquired in S100 includes: road surface slipperiness, road surface flatness, and obstacle information.

8. The method for controlling the movement of a wheeled robot according to claim 1, characterized in that, The motion state information of the ring robot obtained in S100 includes: body posture, body angular velocity, body linear velocity, and the position of each joint of the robot.

9. A wheeled robot, characterized in that, The driving control is performed using the driving control method of the wheeled robot according to any one of claims 1 to 8. The wheeled robot includes a central control unit, a state perception unit, wheel and leg actuators (100), and a body.

10. The wheeled robot according to claim 9, characterized in that, The wheel-leg actuator (100) has five degrees of freedom.

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