阅读说明：本技术 一种可滑行轮足机器人及其控制方法 (Slidable wheel-foot robot and control method thereof ) 是由 冯嘉鹏 贺培 李钟� 于 2020-12-24 设计创作，主要内容包括：本发明提供一种可滑行轮足机器人及其控制方法,机器人包括机器人本体和设置在机器人本体上的六条腿；每条腿包括第一关节、第二关节、第三关节、被动轮和轮子固定架,被动轮无需动力装置,该机器人具有足式运动和滑行运动两种模式,从而进一步增加了机器人的适用范围,通过在不同场景切换不同的运用模式；本发明通过调节第三关节电机和第二关节电机的旋转角度,使被动轮的宽度中心线垂直于地面,同时被动轮的外表面与地面充分接触；六足机器人的单腿的运动学和力学分析可以知道如果在给定机器人的姿态ξ的情况下,每条腿部按照一定的规律周期性的摆动即可实现机器人的运动。(The invention provides a slidable wheel-foot robot and a control method thereof, wherein the robot comprises a robot body and six legs arranged on the robot body; each leg comprises a first joint, a second joint, a third joint, a driven wheel and a wheel fixing frame, the driven wheel does not need a power device, the robot has two modes of foot type motion and sliding motion, the application range of the robot is further enlarged, and different application modes are switched in different scenes; the width center line of the driven wheel is perpendicular to the ground by adjusting the rotating angles of the third joint motor and the second joint motor, and meanwhile, the outer surface of the driven wheel is fully contacted with the ground; the kinematics and mechanics analysis of a single leg of the hexapod robot can know that if the posture xi of the robot is given, the motion of the robot can be realized by periodically swinging each leg according to a certain rule.)

1. A slidable wheeled-foot robot comprises a robot body and six legs arranged on the robot body;

each leg comprises a first joint, a second joint, a third joint, a driven wheel and a wheel fixing frame, wherein the first joint is rotatably connected with the robot body, and the second joint is rotatably connected with the first joint and the third joint respectively; the wheel fixing device is characterized in that a wheel fixing frame is arranged at the lower end of the third joint, a supporting foot is arranged at the lower end of the wheel fixing frame, a buffer rubber pad is sleeved on the supporting foot, a driven wheel is further arranged on one side of the wheel fixing frame, and the driven wheel is connected with the wheel fixing frame through a bearing and can rotate around the center of the wheel.

2. A scooter-capable robot as claimed in claim 1, wherein: the first joint comprises a first structural member and a first joint motor, the first joint motor is arranged in the first structural member and is connected with the robot body through a rotating shaft, and the other end of the first structural member is rotatably connected with the second joint.

3. A scooter-capable robot as claimed in claim 1, wherein: the second joint comprises a second joint motor, a second structural member and a third structural member, the second joint motor is arranged in the second structural member and is connected with the first structural member through a rotating shaft, the second structural member and the third structural member are fixed through screws, and the third structural member is rotatably connected with the third joint.

4. A scooter-capable robot as claimed in claim 1, wherein: the third joint include third joint motor, fourth structure and fifth structure, the third joint motor set up in the fourth structure, and the third joint motor rotate with the third structure through a rotating shaft and be connected, fourth structure and fifth structure pass through screw fixed connection, and the fifth structure on still be provided with the wheel mount.

5. A foot type motion control method of a wheeled foot robot is characterized by comprising the following steps:

s1), establishing a kinematic model of a single leg of the legged robot according to a general robot D-H representation method;

s2), by performing geometric analysis on the legs of the hexapod robot, an inverse kinematics equation of a single leg can be obtained:

in the formula, theta₀Is the initial angle of the first joint, θ₁、θ₂And theta₃Is the target rotation angle of the first joint, the second joint and the third joint, l₁Is the length between the center of the rotation shaft of the first joint motor and the rotation shaft of the second joint motor, l₂Is the length between the rotating shaft of the second joint motor and the rotating shaft of the third joint motor, l₃The length between a rotating shaft of a third joint motor and a supporting foot is h, and the height of the origin of the coordinate system of the first joint under the coordinate system of the hexapod robot body is h;

s3), obtaining coordinate values (x, y, z) of the end of one leg of the hexapod robot, thereby obtaining the target rotation angle theta of the first joint, the second joint and the third joint of the leg of the hexapod robot₁、θ₂、θ₃；

S4), in order to coordinate the 6 legs of the hexapod robot, the 6 legs of the hexapod robot are divided into two groups, wherein when one group is lifted, the other group is used as a support; the 6 legs of the hexapod robot are assumed to be A group and B group; and a state in which the leg tip is swung in the air is defined as a swing phase, and a state in which the leg tip is supported on the ground is defined as a support phase;

s5), in a gait cycle, 6 legs of the hexapod robot are all in an original state, and six walking legs land at the same time;

s6), lifting the 3 legs of the group A first, swinging the legs forwards for 1 step distance, and meanwhile, supporting the ground by the 3 legs of the group B and driving the robot body to move forwards for 1/2 step distances;

s7), after the group A walking legs fall to the ground, the group B3 legs are switched to a swing state and swing forwards for 1 step distance, and meanwhile, the group A walking legs support the ground and drive the robot body to move forwards for 1/2 step distances;

s8), the B group walking legs land on the ground, and the step length is repeated when the walking legs walk forwards by a step length.

6. The method for controlling the foot-type motion of a wheeled-foot robot according to claim 5, wherein:

step S4), the right front leg, the right rear leg, and the left middle leg of the robot are defined as a group a, and the right middle leg, the left front leg, and the left rear leg are defined as a group B.

7. A sliding control method of a wheeled-foot robot is characterized by comprising the following steps:

1) the rotation angles of the third joint motor and the second joint motor are adjusted to enable the width center line of the driven wheel to be perpendicular to the ground, and meanwhile, the outer surface of the driven wheel is in full contact with the ground;

2) then, the rotation angle of a second joint motor is adjusted to enable a third joint to swing, so that the distance between the driven wheel and the longitudinal symmetry line of the robot body is adjusted, and the driven wheel generates corresponding sliding friction force relative to the ground;

3) and at a certain moment, the rotating angles of the third joint motor and the second joint motor are fixed to a certain value, the vertical directions of the second joint and the third joint keep fixed postures, and then the first joint motor horizontally swings to adjust the direction angle of the driven wheel, so that the direction of the sliding friction force is adjusted, and the linear sliding or turning of the robot is realized.

8. The sliding control method of a wheeled-foot robot as claimed in claim 7, wherein in step 1), the rotation angle of the third joint motor is adjusted to ensure that the third joint of the leg of each leg is perpendicular to the ground and the swing amplitude of the inner and outer parts is small during the whole movement of the robot, so that the robot can be considered to perform plane movement approximately, the width center of the driven wheel is always perpendicular to the ground, all the driven wheels on the robot perform pure rolling on the running surface, and when the normal friction coefficient is large enough, all the rollers can be considered to have no sliding in the normal direction, i.e. the normal speed of the contact point between the roller and the ground is zero.

9. A coasting control method for a wheeled-foot robot as claimed in claim 7, wherein said method comprises the steps of:

step 1), setting an inertial coordinate system (O) of the robot_uX_uY_uRobot coordinate system { O }_bX_bY_b}, roller coordinate system { O_cX_cY_c}，(x_i,y_i) The position of the ith roller in the robot coordinate system is shown, and theta is the direction angle of the roller (i.e. the normal direction of the roller and the axis X of the robot coordinate system)_bAngle of (x), the pose of the robot is ξ ═ (x)_b,y_b,φ)^TIs represented by (x)_b,y_b) Represents the position coordinate of the robot mass center, namely the robot coordinate system origin under the inertial coordinate system, phi is the axis X of the robot coordinate system_bAnd axis X of the inertial frame_uThe included angle of (A);

step 2), by the assumption of step 1), if the six rollers of the robot all satisfy the conditions of pure rolling and no sliding constraint, each roller is at x of the roller_cAll of the velocities above are 0 at y_cThe speed in the direction is the rolling linear speed of the roller wheel, namely, the following conditions are met:

whereinLinear velocity r of the robot's center of mass in an inertial frame_iRadius of the i-th roller, beta_iIs the rotational angular velocity of the ith roller,swinging of rollers under robot coordinate system brought about by leg swingingAn angular velocity;

the rotation angular velocity beta of the roller can be obtained by the formulas (1) and (2)_iAnd the direction angle θ of the roller is as follows:

step 3) because the driving force of the robot is the friction force F_nAnd F_tThe following assumptions are made:

(1) six legs of the robot are used for evenly supporting the weight of the robot;

(2) normal friction force F to which the roller is subjected_nIs the coulomb friction whose magnitude and sliding friction coefficient f_nIs in direct proportion;

(3) tangential friction force F to which the roller is subjected_tNot only in relation to positive pressure of the roller, but also in relation to the speed of rotation of the roller(ii) related;

thus, the friction force F that the rollers receive when the robot slides_nAnd F_tCan be written as:

in the formula: f. of_t、f_n、f_tc、And T₁Rolling friction coefficient and sliding friction coefficient between the roller and the ground, damping torque coefficient including a bearing, speed of the robot during linear sliding and driving torque of a robot supporting leg motor are respectively set;

and sign (T)₁) Is defined as follows:

therefore, the relationship between the speed of the robot when the robot slides and turns linearly and the motion parameters of the robot can be obtained through the above.

10. A coasting control method for a wheeled-foot robot as claimed in claim 9, wherein in step 11), the pure rolling constraint conditions of the six rollers of the robot and the no-slip constraint conditions of the six rollers are respectively as follows:

the pure rolling constraint conditions of the six rollers are as follows:

the pure rolling constraint conditions of the six rollers are as follows:

the conditions of no sliding constraint of the six rollers are as follows:

wherein the content of the first and second substances,is the derivative of the pose vector of the robot,is the roller angular velocity vector, J_t(phi, theta) is the normal motion characteristic vector of the robot, J_rIs a roller radius matrix of the robot, J_n(φ, θ) is the tangential motion feature matrix of the robot, namely:

therefore, the position of the moving roller of the roller is determined by the robot pose ξ, the rotation angular speed β and the direction angle θ of the roller, and a generalized coordinate q composed of these three parameter vectors is defined:

q＝(ξ β θ)^T (12)；

in the formula:

θ＝(θ₁ θ₂ θ₃ θ₄ θ₅ θ₆)^T (13)；

the robot kinematics constraint equation according to equations (5) and (6) is written in the form:

wherein j (q) is a motion constraint matrix:

where T is transposed.

Technical Field

The invention relates to the technical field of wheel-foot robots, in particular to a slidable wheel-foot robot and a control method thereof.

Background

The robot is a comprehensive technology integrating multiple subjects such as machinery, electronics, computers, sensors, control technologies and the like. The mobile robots can be roughly classified into leg type, wheel type, crawler type, rail type, and peristaltic type according to the movement method, but the use of these robots is limited to some extent.

In order to make the mobile robot have larger applicable capability, a combined motion mode must be used, and a wheel-foot hybrid mode is one of the motion modes.

The main body of a common wheel-foot robot consists of a horizontal connecting rod, a vertical connecting rod and a roller wheel which can rotate around a rotating shaft, and the roller wheel is generally driven by a power driving wheel and is matched with an independent driving device, a reversing device and a braking device.

These mechanisms and devices increase the weight of the system, reduce stability and limit flexibility to some extent while enhancing the maneuverability of the mobile robot.

For example, the master academic paper of Nanjing university of technology for six-wheel-leg autonomous mobile robot structural design and fuzzy control research proposes a six-wheel robot, which has the advantage of high speed, but the structure is a pure wheel type, and although the angle of the wheels can be controlled by a pull rod, the six-wheel-type robot still cannot pass through a rugged road surface. The leg type also includes single foot, double feet, multiple feet, etc.

For example, the master academic paper of the university of aerospace, Nanjing, "development of four-footed bionic crawling robot", proposes a four-footed bionic crawling robot, which is of a leg structure, can span large obstacles, but has no better rapidity, and has insufficient walking speed on a relatively flat road surface. The crawler-type robot and the ground have larger acting force, and can adapt to a plurality of complicated and various pavements. Like the study on the system design and motion control technology of the tracked mobile robot in the university of transportation, the study proposes a tracked mobile robot, which has many similar places to the wheeled robot mentioned above, but has no strong adaptability on a rugged road surface like the previous one, namely, the crawler is added on the wheels.

The wheel-leg robot has more complicated structure and more functions, for example, the invention patent with the application number of 201210101127.3 provides a six-wheel-foot serial-parallel hybrid robot, which has six legs, and the bottom of each leg is provided with a small rotatable wheel. The wheel can be used as a foot of a leg structure and is a main motion source of the wheel. The wheels and the legs of the robot are separated, namely the wheels and the legs exist at the same time, the wheels are rotated to form the legs through deformation, and the wheels and the legs cannot be smoothly transited.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a slidable wheel-foot robot and a control method thereof, and the invention removes a power device on a roller in order to reduce the weight of a system and enhance the maneuvering performance of the robot and uses a passive wheel without power to replace the passive wheel. Through the coordinated action of the horizontal connecting rod, the vertical connecting rod and the roller, the characteristic that the normal force borne by the roller is far greater than the tangential force is utilized, so that the resultant force of the friction force borne by the system points to the front, and the propelling force is generated to push the robot to move, namely the driven wheel type sliding robot generates the movement by utilizing the friction force between the roller and the ground surface. Furthermore, the robot can rotate in situ by coordinating the coordination action among different legs.

The technical scheme of the invention is as follows: a slidable wheeled-foot robot comprises a robot body and six legs arranged on the robot body;

every the leg include first joint, second joint, third joint, follower and wheel mount, first joint rotate with the robot body and be connected, the second joint with rotate with first joint and third joint respectively and be connected, and third joint lower extreme be provided with the wheel mount, wheel mount one side be provided with the follower, wheel mount lower extreme still have a support foot.

Furthermore, the first joint comprises a first structural member and a first joint motor, the first joint motor is arranged in the first structural member and is connected with the robot body through a rotating shaft, and the other end of the first structural member is rotatably connected with the second joint.

Further, the second joint comprises a second joint motor, a second structural member and a third structural member, the second joint motor is arranged in the second structural member and is connected with the first structural member through a rotating shaft, the second structural member and the third structural member are fixed through screws, and the third structural member is rotatably connected with the third joint.

Furthermore, the third joint comprises a third joint motor, a fourth structural member and a fifth structural member, the third joint motor is arranged in the fourth structural member and is rotatably connected with the third structural member through a rotating shaft, the fourth structural member and the fifth structural member are fixedly connected through screws, and the fifth structural member is further provided with a wheel fixing frame.

Furthermore, a cushion rubber pad is sleeved on the supporting foot.

Further, the driven wheel is connected with the wheel fixing frame through a bearing and can rotate around the center of the wheel.

The invention further provides a control method of the slidable wheel-foot robot, and the robot control method comprises a foot type control method and a wheel type sliding control method.

Further, the robot foot type control method comprises the following steps:

s1), establishing a kinematic model of a single leg of the legged robot according to a general robot D-H representation method;

s2), by performing geometric analysis on the legs of the hexapod robot, an inverse kinematics equation of a single leg can be obtained:

in the formula, theta₀Is the initial angle of the first joint, θ₁、θ₂And theta₃Is the target rotation angle of the first joint, the second joint and the third joint, l₁Is the length between the center of the rotation shaft of the first joint motor and the rotation shaft of the second joint motor, l₂Is the length between the rotating shaft of the second joint motor and the rotating shaft of the third joint motor, l₃The length between a rotating shaft of a third joint motor and a supporting foot is h, and the height of the origin of the coordinate system of the first joint under the coordinate system of the hexapod robot body is h;

s3), obtaining coordinate values (x, y, z) of the end of one leg of the hexapod robot, thereby obtaining the target rotation angle theta of the first joint, the second joint and the third joint of the leg of the hexapod robot₁、θ₂、θ₃；

S4), in order to coordinate the 6 legs of the hexapod robot, the 6 legs of the hexapod robot are divided into two groups, wherein when one group is lifted, the other group is used as a support; the 6 legs of the hexapod robot are assumed to be A group and B group;

and a state in which the leg tip is swung in the air is defined as a swing phase, and a state in which the leg tip is supported on the ground is defined as a support phase;

s5), in a gait cycle, 6 legs of the hexapod robot are all in an original state, and six walking legs land at the same time;

s6), lifting the 3 legs of the group A first, swinging the legs forwards for 1 step distance, and meanwhile, supporting the ground by the 3 legs of the group B and driving the robot body to move forwards for 1/2 step distances;

s7), after the group A walking legs fall to the ground, the group B3 legs are switched to a swing state and swing forwards for 1 step distance, and meanwhile, the group A walking legs support the ground and drive the robot body to move forwards for 1/2 step distances;

s8), the B group walking legs land on the ground, and the step length is repeated when the walking legs walk forwards by a step length.

Further, in step S4), the right front leg, the right rear leg, and the left middle leg of the robot are defined as a group a, and the right middle leg, the left front leg, and the left rear leg are defined as a group B.

Further, the wheel type sliding control method comprises the following steps:

1) the rotation angles of the third joint motor and the second joint motor are adjusted to enable the width center line of the driven wheel to be perpendicular to the ground, and meanwhile, the outer surface of the driven wheel is in full contact with the ground;

2) then, the rotation angle of a second joint motor is adjusted to enable a third joint to swing, so that the distance between the driven wheel and the longitudinal symmetry line of the robot body is adjusted, and the driven wheel generates corresponding sliding friction force relative to the ground;

3) and at a certain moment, the rotating angles of the third joint motor and the second joint motor are fixed to a certain value, the vertical directions of the second joint and the third joint keep fixed postures, and then the first joint motor horizontally swings to adjust the direction angle of the driven wheel, so that the direction of the sliding friction force is adjusted, and the linear sliding or turning of the robot is realized.

Further, in step 1), the rotation angle of the third joint motor is adjusted to ensure that the third joint of the leg of each leg is perpendicular to the ground and the inner and outer swing amplitudes are small in the whole moving process of the robot, at this time, the robot can be considered to perform plane motion approximately, the width center of the driven wheel is always perpendicular to the ground, all the driven wheels on the robot perform pure rolling on the running surface, and under the condition that the normal friction coefficient is large enough, all the rollers can be considered to have no sliding in the normal direction, that is, the normal speed of the contact point between the rollers and the ground is zero.

Further, the method specifically comprises the following steps:

11) and setting an inertial coordinate system of the robot as { O }_uX_uY_uRobot coordinate system { O }_bX_bY_b}, roller coordinate system { O_cX_cY_c}，(x_i,y_i) The position of the ith roller in the robot coordinate system is shown, and theta is the direction angle of the roller (i.e. the normal direction of the roller and the axis X of the robot coordinate system)_bAngle of (x), the pose of the robot is ξ ═ (x)_b,y_b,φ)^TIs represented by (x)_b,y_b) Represents the position coordinate of the robot mass center, namely the robot coordinate system origin under the inertial coordinate system, phi is the axis X of the robot coordinate system_bAnd axis X of the inertial frame_uThe included angle of (A);

12) by the assumption of step 11), if the six wheels of the robot all satisfy the conditions of pure rolling and no sliding constraint, then each wheel is at its x_cAll of the velocities above are 0 at y_cThe speed in the direction is the rolling linear speed of the roller wheel, namely, the following conditions are met:

whereinLinear velocity r of the robot's center of mass in an inertial frame_iRadius of the i-th roller, beta_iIs the rotational angular velocity of the ith roller,the swing angular velocity of the roller under the robot coordinate system brought by the swing of the leg;

the rotation angular velocity beta of the roller can be obtained by the formulas (1) and (2)_iAnd the direction angle θ of the roller is as follows:

13)、since the driving force of the robot is the friction force F_nAnd F_tThe following assumptions are made:

(1) six legs of the robot are used for evenly supporting the weight of the robot; (2) normal friction force F to which the roller is subjected_nIs the coulomb friction whose magnitude and sliding friction coefficient f_nIs in direct proportion; (3) tangential friction force F to which the roller is subjected_tNot only in relation to positive pressure of the roller, but also in relation to the speed of rotation of the roller(ii) related;

thus, the friction force F that the rollers receive when the robot slides_nAnd F_tCan be written as:

in the formula: f. of_t、f_n、f_tc、And T₁Rolling friction coefficient and sliding friction coefficient between the roller and the ground, damping torque coefficient including a bearing, speed of the robot during linear sliding and driving torque of a robot supporting leg motor are respectively set;

and sign (T)₁) Is defined as follows:

therefore, the relationship between the speed of the robot when the robot slides and turns linearly and the motion parameters of the robot can be obtained through the above.

Further, in step 11), the pure rolling constraint conditions of the six rollers of the robot and the non-sliding constraint conditions of the six rollers are respectively as follows:

the pure rolling constraint conditions of the six rollers are as follows:

the conditions of no sliding constraint of the six rollers are as follows:

wherein the content of the first and second substances,is the derivative of the pose vector of the robot,is the roller angular velocity vector, J_t(phi, theta) is the normal motion characteristic vector of the robot, J_rIs a roller radius matrix of the robot, J_n(φ, θ) is the tangential motion feature matrix of the robot, namely:

as can be seen from the above formula, the position of the moving roller is determined by the pose ξ of the robot, the rotation angular velocity β and the direction angle θ of the roller, and a generalized coordinate q composed of these three parameter vectors is defined:

q＝(ξ β θ)^T (12)；

in the formula:

θ＝(θ₁ θ₂ θ₃ θ₄ θ₅ θ₆)^T (13)

the robot kinematics constraint equation according to equations (5) and (6) is written in the form:

wherein j (q) is a motion constraint matrix:

where T denotes transposition.

The invention has the beneficial effects that:

1. the power device on the roller is removed by the robot, and a driven wheel without power is used for replacing the power device, so that the mass of the robot is further reduced;

2. the invention uses the characteristic that the normal force received by the roller is far larger than the tangential force through the coordinated actions of the horizontal connecting rod, the vertical connecting rod and the roller, so that the resultant force of the friction force received by the system points to the front, and the propelling force is generated to push the robot to move, namely, the driven wheel type sliding robot uses the friction force between the roller and the ground surface to generate the movement, and further, the robot can rotate in situ by coordinating the coordinated actions among different legs;

3. the robot can move in a foot type motion mode, the buffer pads are sleeved at the foot ends, so that the stable operation of the robot is ensured, and meanwhile, the robot can move in a sliding mode, so that the application range of the robot is further enlarged, and different application modes are switched in different scenes;

4, the width center line of the driven wheel is perpendicular to the ground by adjusting the rotating angles of the third joint motor and the second joint motor, and meanwhile, the outer surface of the driven wheel is fully contacted with the ground; the kinematics and mechanics analysis of a single leg of the hexapod robot can know that if the posture xi of the robot is given, the motion of the robot can be realized by controlling different swings of the legs of the robot as long as each leg of the robot swings periodically according to a certain rule.

Drawings

FIG. 1 is a schematic structural diagram of a robot according to embodiment 1 of the present invention;

FIG. 2 is a schematic structural diagram of a robot according to embodiment 1 of the present invention, in which the foot end of a single leg contacts the ground;

FIG. 3 is a schematic diagram of a structure of a robot according to embodiment 1 of the present invention in which a driven wheel of a single leg contacts the ground;

fig. 4 is a schematic view of a coordinate system of a robot according to embodiment 2 of the present invention;

FIG. 5 is a schematic diagram of the robot with 6 legs marked according to the embodiment 2 of the present invention;

FIG. 6 is a schematic diagram of a triangular gait cycle of the robot according to embodiment 2 of the present invention;

FIG. 7 is a schematic view of a robot walking with triangular gait according to embodiment 2 of the invention;

fig. 8 is a schematic diagram of the coordinates of the driven wheels of the robot according to the embodiment 3 of the present invention;

in the figure, 1-a robot body, 2-legs, 3-a first joint, 4-a second joint, 5-a third joint, 6-driven wheels, 7-wheel fixing frames, 8-supporting feet, 9-buffer rubber pads and 10-rotating shafts.

31-a first structural member, 32-a first articulation motor;

41-a second joint motor, 42-a second structural member, 43-a third structural member;

51-third joint motor, 52-fourth structural member, 53-fifth structural member.

Detailed Description

The following further describes embodiments of the present invention with reference to the accompanying drawings:

example 1

As shown in fig. 1, the present embodiment provides a scooter-type wheeled robot, which comprises a robot body 1 and six legs 2 provided on both sides of the robot body 1; in this embodiment, the 6 legs 2 have the same structure.

Wherein, in this embodiment, every leg 2 include first joint 3, second joint 4, third joint 5, driven wheel 6 and wheel mount 7, first joint 3 rotate with robot body 1 and be connected, second joint 4 with respectively with first joint 3 and third joint 5 rotate and be connected, and third joint 5 lower extreme be provided with wheel mount 7, wheel mount 7 lower extreme have a support foot 8, and wheel mount 7 one side be provided with driven wheel 6, support foot 8 on still the cover be equipped with buffering rubber pad 9, and driven wheel 6 pass through the bearing and link to each other and can be rotatory around the wheel center with wheel mount 7.

Further, as shown in fig. 2 and 3, the first joint 3 includes a first structural member 31 and a first joint motor 32, the first joint motor 32 is disposed in the first structural member 31, in this embodiment, the first joint motor 32 is fixed in the first structural member 31 by a screw, the first joint motor 32 and the first structural member 31 are connected to the robot body 1 by a rotating shaft 10, and the other end of the first structural member 32 is rotatably connected to the second joint 4.

Further, the second joint 4 includes a second joint motor 41, a second structural member 42 and a third structural member 43, in this embodiment, the second joint motor 41 is disposed in the second structural member 42 by a screw, the second joint motor 41 is connected to the first structural member 31 by a rotating shaft 10, the second structural member 42 and the third structural member 43 are fixed by a screw, and the third structural member 43 is rotatably connected to the third joint 4.

Further, the third joint 5 includes a third joint motor 51, a fourth structural member 52 and a fifth structural member 53, the third joint motor 51 is disposed in the fourth structural member 52, the third joint motor 51 is rotatably connected to the third structural member 43 through a rotating shaft 10, the fourth structural member 52 and the fifth structural member 53 are fixedly connected by screws, and the fifth structural member 53 is further provided with a wheel fixing frame 7.

Example 2

The embodiment provides a foot type control method of a walking wheel foot robot, which comprises the following steps:

s1), establishing a kinematic model of a single leg of the legged robot according to a general robot D-H representation, wherein the coordinate system of the embodiment is as shown in fig. 4.

S2), by performing geometric analysis on the legs of the hexapod robot, an inverse kinematics equation of a single leg can be obtained:

in the formula, theta₀Is the initial angle of the first joint 3, theta₁、θ₂And theta₃Is a target rotation angle of the first joint 3, the second joint 4 and the third joint 5, l₁Is a length between the center of the rotary shaft 10 of the first joint motor 32 and the rotary shaft 10 of the second joint motor 41,/₂The rotation shaft 10 of the second joint motor 41 is connected with the third jointLength between rotary shafts 10 of the joint motor 51,/₃H is the length between the rotating shaft 10 of the third joint motor 51 and the support foot 8, and h is the height of the origin of the coordinate system of the first joint 3 under the coordinate system of the hexapod robot body 1;

s3), obtaining coordinate values (x, y, z) of the distal end of one leg of the hexapod robot, thereby obtaining the target rotation angle θ of the first joint 3, the second joint 4, and the third joint 5 of the leg of the hexapod robot₁、θ₂、θ₃；

S4), in order to coordinate the 6 legs of the hexapod robot, the 6 legs of the hexapod robot are divided into two groups, wherein when one group is lifted, the other group is used as a support; the 6 legs of the hexapod robot are assumed to be A group and B group; wherein, by regarding the right front leg, the right rear leg, and the left middle leg of the robot as a group and regarding the right middle leg, the left front leg, and the left rear leg as a group B, see fig. 5, in the present embodiment, 6 legs of the hexapod robot are labeled as 1, 2, 3, 4, 5, 6, and 1, 3, 5 as a group a, and 2, 4, 6 as a group B.

And it is specified that a state when the leg tip is swung in the air is called a swing phase and a state when the leg tip is supported on the ground is called a support phase, as shown in fig. 6.

S5), when the hexapod robot walks with triangle gait, as shown in fig. 7, in one gait cycle, 6 legs of the hexapod robot are all in original state, and the six walking legs land at the same time;

s6), lifting the 3 legs of the group A first, swinging the legs forwards for 1 step distance, and meanwhile, supporting the ground by the 3 legs of the group B and driving the robot body to move forwards for 1/2 step distances;

s7), after the group A walking legs fall to the ground, the group B3 legs are switched to a swing state and swing forwards for 1 step distance, and meanwhile, the group A walking legs support the ground and drive the robot body to move forwards for 1/2 step distances;

s8), the B group walking legs land on the ground, and the step length is repeated when the walking legs walk forwards by a step length.

Example 3

Further, the present embodiment provides a method for controlling sliding of a robot with wheel and foot, the method comprising the steps of:

in addition, the roller wheel in the embodiment is a driven wheel 6.

1) The rotation angles of the third joint motor 51 and the second joint motor 41 are adjusted to enable the width center line of the driven wheel to be vertical to the ground, and meanwhile, the outer surface of the driven wheel 6 is in full contact with the ground;

2) then, the rotation angle of the second joint motor 41 is adjusted to enable the third joint 5 to swing, so that the distance between the driven wheel 6 and the longitudinal symmetry line of the robot body 1 is adjusted, and the driven wheel 6 generates corresponding sliding friction force relative to the ground;

3) and at a certain moment, the rotation angles of the third joint motor 51 and the second joint motor 41 are fixed to a certain value, the vertical directions of the second joint 4 and the third joint 5 are kept in fixed postures, and then the first joint motor 3 horizontally swings to adjust the direction angle of the driven wheel 6, so that the direction of the sliding friction force is adjusted, and the linear sliding or turning of the robot is realized.

Further, in step 1), the rotation angle of the third joint motor 51 is adjusted to ensure that the third joint 5 of the leg of each leg is perpendicular to the ground and the swing amplitudes of the inside and the outside are small in the whole moving process of the robot, at this time, the robot can be considered to perform plane motion approximately, the width center of the driven wheel is always perpendicular to the ground, all the driven wheels on the robot perform pure rolling on the running surface, and under the condition that the normal friction coefficient is large enough, all the rollers can be considered to have no sliding in the normal direction, that is, the normal speed of the contact point between the rollers and the ground is zero.

Further, the above method specifically includes, as shown in fig. 8, a step in which a rectangular shape represents the robot body 1, and six black dots on the surface of the rectangular parallelepiped are the rotation shafts 10 of the first joint motors 32 of each leg. In the figure, the round corner rectangle shaded by oblique lines is a roller of one leg of the robot, and the dotted line indicates that the roller is connected with the robot body 1 through a third joint 5, a second joint 4 and a first joint 3. A series of reference coordinate systems and parameters are set in the figure, the specific meaning of which is explained below.

11) And setting an inertial coordinate system of the robot as { O }_uX_uY_uRobot coordinate system { O }_bX_bY_b}, roller coordinate system { O_cX_cY_c}，(x_i,y_i) The position of the ith roller in the robot coordinate system is shown, and theta is the direction angle of the roller (i.e. the normal direction of the roller and the axis X of the robot coordinate system)_bAngle of (x), the pose of the robot is ξ ═ (x)_b,y_b,φ)^TIs represented by (x)_b,y_b) Represents the position coordinate of the robot mass center, namely the robot coordinate system origin under the inertial coordinate system, phi is the axis X of the robot coordinate system_bAnd axis X of the inertial frame_uThe included angle of (A);

12) by the assumption of step 11), if the six wheels of the robot all satisfy the conditions of pure rolling and no sliding constraint, then each wheel is at its x_cAll of the velocities above are 0 at y_cThe speed in the direction is the rolling linear speed of the roller wheel, namely, the following conditions are met:

whereinLinear velocity r of the robot's center of mass in an inertial frame_iRadius of the i-th roller, beta_iIs the rotational angular velocity of the ith roller,the swing angular velocity of the roller under the robot coordinate system brought by the swing of the leg;

the rotation angular velocity beta of the roller can be obtained by the formulas (1) and (2)_iAnd the direction angle θ of the roller is as follows:

the inertial frame is generated to simplify the conversion of the world frame to the inertial frame. The origin of the inertial frame coincides with the origin of the object frame, the axes of the inertial frame being parallel to the axes of the world frame. After the inertial coordinate system is introduced, the object coordinate system is only required to rotate when converted into the inertial coordinate system, and only translation is required when the inertial coordinate system is converted into the world coordinate system.

Further, in step 11), the pure rolling constraint conditions of the six rollers of the robot and the non-sliding constraint conditions of the six rollers are respectively as follows:

the pure rolling constraint conditions of the six rollers are as follows:

the conditions of no sliding constraint of the six rollers are as follows:

wherein the content of the first and second substances,is the derivative of the pose vector of the robot,is the roller angular velocity vector, J_t(phi, theta) is the normal motion characteristic vector of the robot, J_rIs a roller radius matrix of the robot, J_n(φ, θ) is the tangential motion feature matrix of the robot, namely:

in the formula, beta₁、β₂、β₃、β₄、β₅、β₆The angular velocity vector of the wheel rollers of the wheels of the six legs of the robot respectively, phi is the axis X of the robot coordinate system_bAnd axis X of the inertial frame_uAngle of (a) of₁、θ₂、θ₃、θ₄、θ₅、θ₆The direction angles of the rollers of the six legs are respectively;

as can be seen from the above, the position of the moving roller is determined by the pose ξ of the robot, the rotation angular velocity β, and the direction angle θ of the roller, and a generalized coordinate q composed of these three parameter vectors is defined:

q＝(ξ β θ)^T (12)

in the formula:

θ＝(θ₁ θ₂ θ₃ θ₄ θ₅ θ₆)^T (13)

the robot kinematics constraint equation according to equations (5) and (6) is written in the form:

wherein j (q) is a motion constraint matrix:

where T denotes transposition.

Since the driving force of the robot is the friction force F_nAnd F_tThe following assumptions are made:

(1) six legs of the robot are used for evenly supporting the weight of the robot; (2) normal friction force F to which the roller is subjected_nIs the coulomb friction whose magnitude and sliding friction coefficient f_nIs in direct proportion; (3) tangential friction force F to which the roller is subjected_tNot only in relation to positive pressure of the roller, but also in relation to the speed of rotation of the roller(ii) related;

thus, the friction force F that the rollers receive when the robot slides_nAnd F_tCan be written as:

in the formula: f. of_t、f_n、f_tc、And T₁Rolling friction coefficient and sliding friction coefficient between the roller and the ground, damping torque coefficient including a bearing, speed of the robot during linear sliding and driving torque of a robot supporting leg motor are respectively set;

and sign (T)₁) Is defined as follows:

therefore, the relationship between the speed of the robot when the robot slides and turns linearly and the motion parameters of the robot can be obtained through the above.

The foregoing embodiments and description have been presented only to illustrate the principles and preferred embodiments of the invention, and various changes and modifications may be made therein without departing from the spirit and scope of the invention as hereinafter claimed.