Modular robot truss crawling gait planning method

Abstract

The invention provides a truss crawling gait planning method for a modular robot, and aims to solve the problem of efficient and stable movement of the modular robot in a complex truss structure environment. Analytical design is carried out according to the structure of a modular unit, and modeling is carried out on the modular robot; researching a truss structure, and designing a method to process a truss map; semicircular motion and linear motion trails are researched, and the motion trail of the tail end of the modular robot is designed; solving an angle value of each joint of the modular robot by using an analytical method; and designing four gaits of an opposite side crossing gait, an adjacent side transverse climbing gait, a gait of rotating around a rod piece and a gait of inchworm along the rod piece, and selecting strategies for planning the stable crawling gait of the truss structure of the modular robot. The method adapts to a non-fixed structure and different truss structures of the modular robot, the accurate joint angle value can be rapidly obtained, the stability of truss crawling of the modular robot is improved, and the method is suitable for aerospace, building maintenance and other scenes.

Description

Technical Field

[0001] The invention relates to a modular robot truss crawling gait planning method and belongs to the field of robots. Background Art

[0002] In recent years, truss structures have been widely used in the fields of architecture, aerospace, bridges and towers. However, due to the particularity of truss structures, robots can only grab rods to move, and the direction of movement is limited. Traditional robots usually have fixed structures, lack flexibility and adaptability in moving on trusses, and have difficult-to-reach areas, which requires robots to have higher flexibility and stability to adapt to the truss environment.

[0003] Modular robots have flexible structures and strong adaptability, and it is more advantageous to use modular robots to complete truss crawling tasks. However, the current gait design is mostly for robots with traditional fixed structures, which is difficult to adapt to the non-fixed structure of modular robots. In addition, the crawling gait design in the truss structure must also ensure the motion stability of the robot in the truss movement. Therefore, the research on the truss crawling gait planning method of modular robots has important theoretical research value. Summary of the invention

[0004] In view of this, the present invention provides a modular robot truss crawling gait planning method, designs four gait modes, so that the robot can adapt to a variety of truss structure scenarios and improve movement efficiency and stability.

[0005] The present invention provides a modular robot truss crawling gait planning method, comprising:

[0006] 1. A modular robot truss crawling gait planning method, characterized in that the method comprises:

[0007] Designing a structure of a modular robot, including: the modular robot is connected by N modular units, each modular unit includes two shells, three motor-reducer assemblies, two male interfaces and two female interfaces, the three motor-reducer assemblies are distributed on the body center and two shells of the modular unit body, each modular unit has three joints inside, and each joint of the modular unit can rotate around the central axis of the male interface and the central axis of the modular unit;

[0008] Based on the truss structure and the motion pattern of the modular robot on the truss, a truss map is constructed;

[0009] According to the motion requirements of the modular robot, the motion is decomposed into motion in the same plane and three-dimensional plane conversion motion. The motion in the same plane includes motion along the direction of the rod, crossing the opposite side of the truss and climbing the adjacent side of the truss. The three-dimensional plane conversion motion includes rotational motion around the rod.

[0010] Construct mathematical expressions of motion trajectories according to gait requirements and design the motion trajectories of the modular robot terminal;

[0011] Establish the kinematic model of the modular robot and use the inverse kinematics analytical method to solve the joint angle values ​​of the modular robot;

[0012] According to the decomposed modular robot motion types, four gaits are designed, including opposite-side crossing gait, adjacent-side climbing gait, rotation gait around the rod, and inchworm gait along the rod, and a gait selection strategy is established.

[0013] 2. The method according to claim 1, characterized in that the step of constructing a truss map based on the truss structure and the motion pattern of the modular robot on the truss comprises:

[0014] Assuming 2 as the length of a member, q i =[x i ,y i ,z i ] T represents the node coordinates of the i-th node on the truss structure, where x i ,y i 、z i are all even numbers, construct the node coordinate set Q = {q1,q2,......,q m}, m means there are m nodes on the truss; identify and select node q i , calculate its relationship with the existing adjacent nodes q i_1 =[x i +2,y i ,z i ] T ,q i_2 =[x i ,y i +2,z i ] T ,q i_3 =[x i ,y i ,z i +2] T The geometric midpoint of the middle point, record the coordinates of the middle point and number it s j 、s j+1 、s j+2 , forming the reachable point set S in the truss map = {s1,s2,......,s n}.

[0015] 3. The method according to claim 1, characterized in that the step of constructing a mathematical expression of the motion trajectory according to the gait requirements and designing the motion trajectory of the terminal of the modular robot comprises:

[0016] The semicircular motion trajectory formula is established as follows:

[0017]

[0018] Among them, x s is the initial horizontal position of the modular robot, x f is the end horizontal position of the modular robot, z s is the starting height position of the modular robot, T s is the step period of the semicircular motion of the modular robot, is the radius of the semicircular motion of the modular robot, x t is the horizontal position function with respect to time t, z t is the height function about time t, σ is the radian function about time t;

[0019] In linear motion, only the height changes, and the trajectory formula is established as follows:

[0020]

[0021] Among them, z s is the starting height position of the modular robot, z f is the final height position of the modular robot, T s is the step period of the linear motion of the modular robot, is the linear motion speed of the modular robot, z t is a function of height with respect to time t.

[0022] 4. The method according to claim 1 is characterized in that the kinematic model of the modular robot is established and the joint angle values ​​of the modular robot are solved by the inverse kinematics analytical method, including: modeling a single-chain robot, decoupling a multi-branch robot into multiple single-chain robots, modeling using the DH method, and solving the joint i transformation matrix The formula is as follows:

[0023]

[0024] Among them, θ i is the joint angle, d i is the connecting rod offset, a i is the connecting rod length, α i is the connecting rod torsion angle;

[0025] The inverse kinematics analysis is used to solve the angles of the three rotation joints of each module unit of the modular robot. The final position and posture of the end effector of the modular robot are assumed to be k is the total number of joints, is the total transformation matrix, and both sides of the equation are gradually multiplied by the transformation matrix The formula is as follows:

[0026]

[0027] Establish a new equation based on the elements of the matrices on the left and right sides of the equation to solve the angle value θ of the joint i .

[0028] 5. The method according to claim 1 is characterized in that the four gaits designed include: opposite side crossing gait, adjacent side lateral climbing gait, rod rotation gait, and rod inchworm gait, including:

[0029] ①Define the basic parameters of the modular robot gait;

[0030] ② In the opposite side crossing gait, the modular robot crosses to the opposite rod, and the two branches switch between the fixed branch and the moving branch. In one movement cycle, the moving distance of the robot is one rod length;

[0031] ③ In the adjacent side climbing gait, the modular robot climbs horizontally to the adjacent rod, and the two branches switch between the fixed branch and the moving branch. In one movement cycle, the body moves a distance of Length of rod;

[0032] ④ The modular robot performs a three-dimensional plane transformation in the rod-rotating gait, and the two branches transform between the fixed branch and the moving branch. In one movement cycle, the position of the body on the rod does not move;

[0033] ⑤ The modular robot moves toward the rod in the inchworm gait along the rod, and the two branches switch between the fixed branch and the moving branch. In one movement cycle, the moving distance of the body is one rod length.

[0034] 6. The method according to claim 1, characterized in that the gait selection strategy comprises:

[0035] ① Since the modular robot crawls on the truss surface, each reachable point in the reachable point set S must have a coordinate representing the truss plane. When the coordinate value of the next moving point representing the truss plane changes by comparing the previous moving point with the current moving point, the movement needs to perform a truss plane transformation and use a gait of rotating around the rod;

[0036] ② When one of the coordinate values ​​of the current moving point and the next moving point changes, the movement is that the truss plane moves along the direction of the rod, using the inchworm gait along the rod;

[0037] ③ When two coordinate values ​​of the current movement point and the next movement point change, and the odd coordinates change, the movement is a rapid oblique movement of the truss plane, using the adjacent side horizontal climbing gait;

[0038] ④ When two coordinate values ​​of the current moving point and the next moving point change, and the odd coordinates do not change, the movement is a rapid crossing between the plane members of the truss, using the opposite side crossing gait. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creativity and labor.

[0040] Figure 1 It is a flowchart of the steps of a modular robot truss crawling gait planning method provided by an embodiment of the present invention.

[0041] Figure 2 It is a physical structure diagram of a modular robot provided by an embodiment of the present invention.

[0042] Figure 3 It is a schematic diagram of a side-crossing gait of a modular robot provided by an embodiment of the present invention.

[0043] Figure 4 It is a schematic diagram of an edge-climbing gait of a modular robot provided by an embodiment of the present invention.

[0044] Figure 5 It is a schematic diagram of a modular robot rotating around a rod provided by an embodiment of the present invention.

[0045] Figure 6 It is a schematic diagram of a modular robot gaiting along a rod provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0046] In order to better understand the technical solution of the present invention, the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0047] It should be clear that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] The embodiment of the present invention provides a modular robot truss crawling gait planning method.

[0049] Please refer to Figure 1 , which is a flowchart of a modular robot truss crawling gait planning method provided by an embodiment of the present invention, the method comprising the following steps:

[0050] Step 101, design the structure of the modular robot.

[0051] For the modular robot structure diagram, please refer to Figure 2 As shown, the modular robot is connected by N module units, each module unit includes 2 shells, 3 motor-reducer assemblies, two male interfaces and two female interfaces, and the 3 motor-reducer assemblies are distributed on the body center and two shells of the module unit body. Each module unit has 3 joints inside, and each joint of the module unit can rotate around the central axis of the male interface and the central axis of the module unit.

[0052] According to the motion requirements of the modular robot, the motion is decomposed into motion in the same plane and three-dimensional plane conversion motion. The motion in the same plane includes motion along the direction of the rod, spanning the opposite sides of the truss and climbing the adjacent sides of the truss. The three-dimensional plane conversion motion includes rotational motion around the rod.

[0053] Step 102: construct a truss map based on the truss structure and the motion pattern of the modular robot on the truss.

[0054] Specifically, 2 is the length of a rod, q i =[x i ,y i ,z i ] T represents the node coordinates of the i-th node on the truss structure, where x i ,y i 、z i are all even numbers, construct the node coordinate set Q = {q1,q2,......,q m}, m means there are m nodes on the truss; identify and select node q i , calculate its relationship with the existing adjacent nodes q i_1 =[x i +2,y i ,z i ] T ,q i_2 =[x i ,y i +2,z i ] T ,q i_3 =[x i ,y i ,z i +2] T The geometric midpoint of the middle point, record the coordinates of the middle point and number it s j 、s j+1 、s j+2 , forming the reachable point set S in the truss map = {s1,s2,......,s nEach reachable point in the reachable point set S has a coordinate value that is an odd number. The reachable points are used to modularize the robot gait planning process and establish subsequent gait selection strategies to ensure that the robot achieves stable and efficient path planning and motion control in the truss structure.

[0055] Step 103, constructing a mathematical expression of the motion trajectory according to the gait requirements, and designing the motion trajectory of the modular robot terminal.

[0056] Specifically, the research determined that the motion trajectory is a cycloid, and the motion trajectory of the modular robot end is designed to be a semicircle with a straight line connecting the front and back:

[0057] The semicircular motion trajectory formula is established as follows:

[0058]

[0059] Among them, x s is the initial horizontal position of the modular robot, x f is the end horizontal position of the modular robot, z s is the starting height position of the modular robot, T s is the step period of the semicircular motion of the modular robot, is the radius of the semicircular motion of the modular robot, x t is the horizontal position function with respect to time t, z t is the height function about time t, σ is the radian function about time t;

[0060] In linear motion, only the height changes, and the trajectory formula is established as follows:

[0061]

[0062] Among them, z s is the starting height position of the modular robot, z f is the final height position of the modular robot, T s is the step period of the linear motion of the modular robot, is the linear motion speed of the modular robot, z t is a function of height with respect to time t.

[0063] Step 104 , establishing a kinematic model of the modular robot, and using an inverse kinematics analytical method to solve the joint angle values ​​of the modular robot.

[0064] Specifically, a single-chain robot is modeled. For a multi-branch robot, it is decoupled into multiple single-chain robots for processing. The DH method is used for modeling and the joint i transformation matrix is ​​solved. The formula is as follows:

[0065]

[0066] Among them, θ i is the joint angle, d i is the connecting rod offset, a i is the connecting rod length, α i is the connecting rod torsion angle;

[0067] The inverse kinematics analysis is used to solve the angles of the three rotation joints of each module unit of the modular robot. The final position and posture of the end effector of the modular robot are assumed to be k is the total number of joints, is the total transformation matrix, and both sides of the equation are gradually multiplied by the transformation matrix The formula is as follows:

[0068]

[0069] Establish a new equation based on the elements of the matrices on the left and right sides of the equation to solve the angle value θ of the joint i .

[0070] Step 105, according to the decomposed modular robot motion types, four gaits are designed, namely, opposite-side crossing gait, adjacent-side lateral climbing gait, rod-rotating gait, and rod-loop gait, and a gait selection strategy is established. Among them, the opposite-side crossing gait, adjacent-side lateral climbing gait, rod-rotating gait, and rod-loop gait include:

[0071] ①Define the basic parameters of the modular robot gait;

[0072] ②Please refer to Figure 3 ,In the opposite side crossing gait, the modular robot crosses to the opposite rod, and the two branches switch between the fixed branch and the moving branch. In one movement cycle, the moving distance of the robot is one rod length;

[0073] ③Please refer to Figure 4 In the adjacent side climbing gait, the modular robot climbs horizontally to the adjacent rod, and the two branches switch between the fixed branch and the moving branch. In one movement cycle, the body moves a distance of Length of rod;

[0074] ④Please refer to Figure 5 ,The modular robot performs a transformation of the three-dimensional plane in the gait of rotating around the rod, and the two branches transform between the fixed branch and the moving branch. In one movement cycle, the position of the body on the rod does not move;

[0075] ⑤Please refer to Figure 6, the modular robot moves toward the rod in the rod-like inchworm gait, and the two branches switch between the fixed branch and the moving branch. In one movement cycle, the moving distance of the body is one rod length.

[0076] The gait selection strategy includes:

[0077] ① Since the modular robot crawls on the truss surface, each reachable point in the reachable point set S must have a coordinate representing the truss plane. When the coordinate value of the next moving point representing the truss plane changes by comparing the previous moving point with the current moving point, the movement needs to perform a truss plane transformation and use a gait of rotating around the rod;

[0078] ② When one of the coordinate values ​​of the current moving point and the next moving point changes, the movement is that the truss plane moves along the direction of the rod, using the inchworm gait along the rod;

[0079] ③ When two coordinate values ​​of the current movement point and the next movement point change, and the odd coordinates change, the movement is a rapid oblique movement of the truss plane, using the adjacent side horizontal climbing gait;

[0080] ④ When two coordinate values ​​of the current moving point and the next moving point change, and the odd coordinates do not change, the movement is a rapid crossing between the truss plane rods, using the opposite side crossing gait. The technical solution of the embodiment of the present invention has the following beneficial effects:

[0081] In the technical solution of the embodiment of the present invention, a modular robot truss crawling gait planning method is designed, and the modular robot is modeled according to the analysis and design of the structure of a modular unit; the truss structure is studied, and a method is designed to process the truss map; the trajectory of semicircular motion is studied, and the motion trajectory of the end of the modular robot is designed; the angle value of each joint of the modular robot is solved by an analytical method; four gaits, namely, the opposite side crossing gait, the adjacent side horizontal climbing gait, the rod rotation gait, and the rod inchworm gait, are designed, and the selection strategy is used for the modular robot truss structure stable crawling gait planning. The present invention is adaptable to the non-fixed structure and different truss structures of the modular robot, can quickly obtain accurate joint angle values, improves the stability of the modular robot truss crawling, and is suitable for scenes such as aerospace and building maintenance.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0083] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A modular robot truss crawling gait planning method, characterized in that: The method comprises: Designing a structure of a modular robot, including: the modular robot is connected by N modular units, each modular unit includes two shells, three motor-reducer assemblies, two male interfaces and two female interfaces, the three motor-reducer assemblies are distributed on the body center and two shells of the modular unit body, each modular unit has three joints inside, and each joint of the modular unit can rotate around the central axis of the male interface and the central axis of the modular unit; Based on the truss structure and the motion pattern of the modular robot on the truss, a truss map is constructed; According to the motion requirements of the modular robot, the motion is decomposed into motion in the same plane and three-dimensional plane conversion motion. The motion in the same plane includes motion along the direction of the rod, crossing the opposite side of the truss and climbing the adjacent side of the truss. The three-dimensional plane conversion motion includes rotational motion around the rod. Construct mathematical expressions of motion trajectories according to gait requirements and design the motion trajectories of the modular robot terminal; Establish the kinematic model of the modular robot and use the inverse kinematics analytical method to solve the joint angle values ​​of the modular robot; According to the decomposed modular robot motion types, four gaits are designed, including opposite-side crossing gait, adjacent-side climbing gait, rotation gait around the rod, and inchworm gait along the rod, and a gait selection strategy is established.

2. The method according to claim 1, characterized in that: The method of constructing a truss map based on the truss structure and the motion mode of the modular robot on the truss includes: Assuming 2 as the length of a rod, q i =[x i ,y i ,z i ] T represents the node coordinates of the i-th node on the truss structure, where x i ,y i 、z i are all even numbers, construct the node coordinate set Q = {q1,q2,......,q m }, m means there are m nodes on the truss; identify and select node q i , calculate its relationship with the existing adjacent nodes q i_1 =[x i +2,y i ,z i ] T ,q i_2 =[x i ,y i +2,z i ] T ,q i_3 =[x i ,y i ,z i +2] T The geometric midpoint of the middle point, record the coordinates of the middle point and number it s j 、s j+1 、s j+2 , forming the reachable point set S in the truss map = {s1,s2,......,s n }.

3. The method according to claim 1, characterized in that The method of constructing a mathematical expression of the motion trajectory according to the gait requirements and designing the motion trajectory of the modular robot terminal includes: The semicircular motion trajectory formula is established as follows: Among them, x s is the initial horizontal position of the modular robot, x f is the end horizontal position of the modular robot, z s is the starting height position of the modular robot, T s is the step period of the semicircular motion of the modular robot, is the radius of the semicircular motion of the modular robot, x t is the horizontal position function with respect to time t, z t is the height function about time t, σ is the radian function about time t; In linear motion, only the height changes, and the trajectory formula is established as follows: Among them, z s is the starting height position of the modular robot, z f is the final height position of the modular robot, T s is the step period of the linear motion of the modular robot, is the linear motion speed of the modular robot, z t is a function of height with respect to time t.

4. The method according to claim 1, characterized in that The kinematic model of the modular robot is established, and the joint angle values ​​of the modular robot are solved by the inverse kinematics analytical method, including: Model the single-chain robot. For the multi-branch robot, decouple it into multiple single-chain robots for processing. Use the DH method to model and solve the joint i transformation matrix. The formula is as follows: Among them, θ i is the joint angle, d i is the connecting rod offset, a i is the connecting rod length, α i is the connecting rod torsion angle; The inverse kinematics analysis is used to solve the angles of the three rotation joints of each module unit of the modular robot. The final position and posture of the end effector of the modular robot are assumed to be k is the total number of joints, is the total transformation matrix, and both sides of the equation are gradually multiplied by the transformation matrix The formula is as follows: Establish a new equation based on the elements of the matrices on the left and right sides of the equation to solve the angle value θ of the joint i .

5. The method according to claim 1, characterized in that The four gaits designed are opposite side crossing gait, adjacent side horizontal climbing gait, rod rotation gait, and rod inchworm gait, including: ①Define the basic parameters of the modular robot gait; ② In the opposite side crossing gait, the modular robot crosses to the opposite rod, and the two branches switch between the fixed branch and the moving branch. In one movement cycle, the moving distance of the robot is one rod length; ③ In the adjacent side climbing gait, the modular robot climbs horizontally to the adjacent rod, and the two branches switch between the fixed branch and the moving branch. In one movement cycle, the body moves a distance of Length of rod; ④ The modular robot performs a three-dimensional plane transformation in the rod-rotating gait, and the two branches transform between the fixed branch and the moving branch. In one movement cycle, the position of the body on the rod does not move; ⑤ The modular robot moves toward the rod in the inchworm gait along the rod, and the two branches switch between the fixed branch and the moving branch. In one movement cycle, the moving distance of the body is one rod length.

6. The method according to claim 1, characterized in that The gait selection strategy includes: ① Since the modular robot crawls on the truss surface, each reachable point in the reachable point set S must have a coordinate representing the truss plane. When the coordinate value of the next moving point representing the truss plane changes by comparing the previous moving point with the current moving point, the movement needs to perform a truss plane transformation and use a gait of rotating around the rod; ② When one of the coordinate values ​​of the current moving point and the next moving point changes, the movement is that the truss plane moves along the direction of the rod, using the inchworm gait along the rod; ③ When two coordinate values ​​of the current movement point and the next movement point change, and the odd coordinates change, the movement is a rapid oblique movement of the truss plane, using the adjacent side horizontal climbing gait; ④ When two coordinate values ​​of the current moving point and the next moving point change, and the odd coordinates do not change, the movement is a rapid crossing between the plane members of the truss, using the opposite side crossing gait.

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