Legged robot body posture control method

Abstract

The application discloses a kind of foot type robot body posture control method, the application is assumed that foot type robot body is rigid under the premise, the deformation energy of foot type robot branch leg and the calculation formula of deformation amount of branch leg end are given, then considering the constraint of foot type robot deformation coordination equation and balance equation, the overall stiffness matrix of foot type robot calculated offline is obtained, then in real-time control process, the body center posture requirement of task planning is combined, the pose parameters of branch leg are calculated, so as to complete the posture control of foot type robot body.The method provided by the application adopts analytical method, establishes the functional relationship between body posture and branch leg posture, in the process of controlling the posture of foot type robot body, the real-time calculation amount is small, the operation speed is fast, and the motion accuracy and dynamic performance of the quadruped robot can be effectively improved.

Description

Technical Field

[0001] This invention relates to the field of robotics, and in particular to a method for controlling the posture of a legged robot. Background Technology

[0002] Legged robots are used for welding large equipment such as ship and bridge prefabricated components. A legged robot consists of a welding arm, legs for movement, and a body connecting the legs and the welding arm. The welding arm is attached to the body and can move within a certain range around the connection point. The legs consist of several sequentially connected rods and actuators attached to the rods. The rods are connected by hinge points, and the angle between adjacent rods can change under the drive of the actuators. The end of the leg away from the body is the ground end, and the end connecting the leg to the body is the support end. The posture of the robot is controlled by adjusting the position of the ground end of each leg and the distance between the ground end and the support end, i.e., adjusting the posture of the legs. The change in the distance between the ground end and the support end of the leg can be achieved by adjusting the angle between adjacent rods of the leg.

[0003] In existing technologies, the body attitude control method is achieved through the finite element method. Specifically, it is necessary to first obtain the material and dimensions of the branch legs and the body, establish the geometric model of the branch legs and the body, and divide the mesh to establish the finite element model. Then, the body attitude requirements are treated as displacement boundary conditions and applied to the finite element model and solved. Finally, the attitude of each branch leg is obtained, including the ground end position and the angle between adjacent members of the branch leg, thus completing the body attitude control.

[0004] Because the constraints in the finite element model solution process are insufficient, other constraints need to be introduced to complete the solution. These other constraints are often empirical, lacking a real physical context, making it difficult to determine the optimal solution. Furthermore, the finite element solution involves numerous inversion operations, resulting in a large computational load and placing high demands on the legged robot's processor. Summary of the Invention

[0005] Based on this, it is necessary to propose a method for controlling the body posture of a legged robot to address the above problems. An analytical method is used to establish a functional relationship between the body posture and the branch leg posture, which has low computational load and fast operation speed.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for controlling the posture of a legged robot, the legged robot comprising a body, multiple branch legs connected to the body, and a welded arm connected to the body, each branch leg comprising sequentially connected rods, the end of the branch leg facing away from the body being the ground end, and the end of the branch leg connecting to the body being the support end; the method includes:

[0008] S1: The offline calculation process includes the following steps:

[0009] S11: Obtain the structural information of the legged robot, the structural information including body structural information, branch leg structural information and welding arm structural information;

[0010] S12: Establish the branch leg stiffness matrix of the branch leg based on the branch leg construction information;

[0011] S13: Establish the deformation coordination equation of the body and the branch leg based on the body structure information and the branch leg structure information;

[0012] S14: Establish the overall stiffness matrix based on the branch leg stiffness matrix and the body-branch leg deformation coordination equation;

[0013] S2: The machine control process during welding operations includes the following steps:

[0014] S21: Obtain the current posture of the main body and the current posture of each branch leg;

[0015] S22: Obtain the subsequent welding posture requirements of the legged robot according to the welding task; calculate the subsequent posture of the robot body based on the subsequent welding posture requirements and the welding arm structure information;

[0016] S23: Calculate the subsequent posture of each branch leg based on the subsequent posture of the body and the overall stiffness matrix. The subsequent posture of the branch leg includes the position of the ground end of the branch leg and the distance between the ground end and the support end.

[0017] S24: Based on the current posture and subsequent posture of each branch leg, control the rotation of the linkage on the branch leg to adjust the posture of the branch leg to the subsequent posture, thus completing the current posture control of the legged robot body.

[0018] S25: Repeat steps S21 to S24 according to the welding task until the welding task is completed.

[0019] Preferably, the branch leg construction information includes the dimensions and material information of the rods in the branch leg, as well as the kinematic pair relationships between the rods.

[0020] Preferably, the branch leg includes a first rod, a second rod, and a third rod connected in sequence. The third rod is connected to the ground end via a ball joint. The second rod is connected to the third rod via a third planar rotational hinge. The first rod is connected to the second rod via a second planar rotational hinge. The first rod is connected to the body via a first planar rotational hinge.

[0021] Preferably, the ball joint provides a first revolute joint, a second revolute joint, and a third revolute joint, wherein the first revolute joint is about x. i The rotation of the axis, the second revolute joint is about y i The rotation, wherein the third revolute joint is about z i Rotation of the axis, where x i y i z i These are the coordinate axes for each branch leg, where i represents the sequence number of the branch leg;

[0022] The third planar rotational hinge provides a fourth rotational joint, the rotation direction of which is perpendicular to the plane formed by the second member and the third member;

[0023] The second planar rotational hinge provides a fifth rotational joint, the rotation direction of which is perpendicular to the plane formed by the second member and the first member;

[0024] The first planar rotary hinge provides a sixth rotary joint, the rotation direction of which is perpendicular to the surface formed by the support ends of each of the branch legs.

[0025] Preferably, the number of branch legs is four, the four branch legs are symmetrically distributed, and the four branch legs are coplanar with the four support ends of the body;

[0026] The body is rigid, while the branch legs are elastic.

[0027] Preferably, establishing the branch leg stiffness matrix based on the branch leg construction information includes the following steps:

[0028] S121: Establish the pose parameters θ for each of the branch legs. ij The relationship between different poses of the legged robot, where i represents the sequence number of the branch leg and j represents the sequence number of the planar rotation hinge;

[0029] S122: According to the pose parameter θ ij and the center coordinates of the landing end Calculate the coordinates of the support end

[0030] S123: Calculate the strain energy of each branch leg, and calculate the total strain energy of the branch leg based on the strain energy of each branch leg;

[0031] S124: Calculate the stiffness matrix of the branch leg based on the total strain energy of the branch leg.

[0032] Preferably, the step of establishing the pose parameter θ for each of the branch legs... ijThe relationships between different poses of a legged robot include:

[0033] In the body coordinate system, A i The coordinates of the point are (x Ai y Ai 0), A i This represents the support end of the branch leg with serial number i;

[0034] In the initial pose, the direction of the linear vector of the axis of the branch leg plane rotation hinge is:

[0035] ω i1 =[0 0 1] T

[0036] ω i2 =ω i3 =[1 0 0] T

[0037] In this context, subscripts 1, 2, and 3 represent the first planar rotational hinge, the second planar rotational hinge, and the third planar rotational hinge, respectively.

[0038] In the initial pose, the vector of a point on the rotation axis of the first, second, and third planar rotational hinges is:

[0039] r i1 =[x Ai y Ai 0] T

[0040] r i2 =[x Ai +L1 y Ai 0] T

[0041] r i3 =[x Ai +L1+L2 y Ai 0] T

[0042] The rotational spins of the first, second, and third planar rotational hinges are:

[0043]

[0044]

[0045]

[0046] Therefore, the matrix exponent of the transformation matrix

[0047]

[0048] In the formula

[0049]

[0050]

[0051]

[0052]

[0053]

[0054]

[0055] Where θ i1 θ i2 θ i3 The pose parameters, sθ, are for the first, second, and third planar rotational hinges of the branch leg numbered i, in sequence. ij It is sinθ ij abbreviation, cθ ij It is cosθ ij The abbreviation for i = 1 to 4, j = 1 to 3, where 1, 2, and 3 represent the first plane rotational hinge, the second plane rotational hinge, and the third plane rotational hinge, respectively.

[0056] When the quadruped welding robot is in its initial pose, θ i1 =θ i2 =θ i3 =0, where the subscripts 1, 2, and 3 represent the first plane rotational hinge, the second plane rotational hinge, and the third plane rotational hinge, respectively;

[0057] Branch leg coordinate system {A i The transformation matrix relative to the body coordinate system o-xyz is:

[0058]

[0059] Then, in any pose, the branch leg coordinate system {A} i The transformation matrix relative to the body coordinate system o-xyz is:

[0060]

[0061] Preferably, the step of determining the pose parameter θ ij and the center coordinates of the landing end Calculate the coordinates of the support end include:

[0062] Define the following parameters:

[0063]

[0064]

[0065]

[0066]

[0067] In the above formula, L′ AiDi H represents the horizontal distance between the ground end and the ball joint. i L represents the vertical distance between the ball joint and the second-plane rotational joint, and L1 represents the length of the first member. BiDi Represents the straight-line distance between the ball joint and the second-plane rotational hinge;

[0068]

[0069]

[0070]

[0071] β i =θ i3 -α i

[0072]

[0073]

[0074] In the above formula, α i and β i These are calculation process quantities. L2 represents the length of the second member, and L3 represents the length of the third member.

[0075] Preferably, the step of calculating the strain energy of each branch leg and calculating the total strain energy of the branch legs based on the strain energy of each branch leg includes:

[0076] In A i Point of application of force spiral for

[0077]

[0078] in Represents the branch leg coordinate system {A i}Down A i The force acting on the point, Represents the coordinate system {A} i}Down A i The torque acting on a point; and In the text, the superscript at the top left indicates the coordinate system {A}. iThe superscript in the upper right corner indicates the point of application, the blank subscript in the lower left corner is meaningless, and the subscript in the lower right corner indicates the branch number. A i D i A represents i and D i Distance vector between points;

[0079] In the i-th branch leg, A i B i strain energy of the rod for:

[0080]

[0081] A represents i Point along {A i Coordinate system The force acting on the shaft;

[0082] A represents i Point around {A i Coordinate system The torque acting on the shaft;

[0083] Indicates rod A i B i The elastic modulus and shear modulus;

[0084] Indicates rod A i B i The area of ​​the cross-section;

[0085] Indicates rod A i B i Cross section along Effective shear area of ​​the shaft;

[0086] Indicates rod A i B i Polar moment of inertia of the cross section;

[0087] Indicates rod A i B i Cross section about Moment of inertia of the axis;

[0088] In the i-th branch leg, B i C i strain energy of the rod It can be represented as:

[0089]

[0090] In the formula, In the i-th branch leg, B represents... i C i The strain energy of the rod;

[0091] B i Point along {A i Coordinate system The force acting on the shaft;

[0092] B i Point around {A i Coordinate system The torque acting on the shaft;

[0093] Indicates bar B i C i The elastic modulus and shear modulus;

[0094] Indicates bar B i C i The area of ​​the cross-section;

[0095] Indicates bar B i C i Cross section along Effective shear area of ​​the shaft;

[0096] Indicates bar B i C i Polar moment of inertia of the cross section;

[0097] Indicates bar B i C i Cross section about Moment of inertia of the axis;

[0098] C in the i-th branch leg i D i strain energy of the rod It can be represented as:

[0099]

[0100] In the formula, In the i-th branch leg, C represents... i D i The strain energy of the rod;

[0101] Indicate C i Point along {A i Coordinate system The force acting on the shaft;

[0102] Indicate C i Point around {A i Coordinate system The torque acting on the shaft;

[0103] Indicates member C i D i The elastic modulus and shear modulus;

[0104] Indicates member C i D i The area of ​​the cross-section;

[0105] Indicates member C i D i Cross section along Effective shear area of ​​the shaft;

[0106] Indicates member C i D i Polar moment of inertia of the cross section;

[0107] Indicates member C i D i Cross section about Moment of inertia of the axis;

[0108] The strain energy of the i-th branch leg is equal to the sum of the strain energies of all the members:

[0109]

[0110] Preferably, the step of establishing the overall stiffness matrix K based on the branch leg stiffness matrix and the body-branch leg deformation coordination equation is as follows:

[0111]

[0112] The stiffness matrix of the branch leg Where the flexibility matrix of the i-th branch leg is C i for

[0113]

[0114] The C i The component is determined by the following formula:

[0115]

[0116]

[0117]

[0118] In the formula for calculating the overall stiffness matrix K of the quadruped welding robot, , in

[0119]

[0120]

[0121]

[0122] In the formula, Center D of the joint ball joint i In coordinate system {A i Coordinates are represented under}.

[0123] Implementing the embodiments of the present invention will have the following beneficial effects:

[0124] This invention, assuming the legged robot body is rigid, employs offline calculation to obtain the overall stiffness matrix of the legged robot. Then, during real-time control, it plans the subsequent welding posture requirements based on the welding task. According to these requirements and the welding arm's structural information, the subsequent posture of the robot body is planned. Based on the subsequent posture of the robot body and the overall stiffness matrix, the subsequent posture of each branch leg is calculated. Based on the current and subsequent postures of the branch legs, the linkages are rotated to adjust the branch leg posture to the subsequent posture, thus completing the legged robot's posture control. This invention has low real-time computational load and high processing speed, effectively improving the motion accuracy and dynamic performance of quadruped robots. Attached Figure Description

[0125] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0126] in:

[0127] Figure 1 This is a simplified structural diagram of a quadruped welding robot in a specific embodiment of the present invention.

[0128] Figure 2 This is a simplified structural diagram of a branch leg in a specific embodiment of the present invention.

[0129] Figure 3 This is a simplified kinematic analysis diagram of each kinematic pair in a quadruped welding robot according to a specific embodiment of the present invention.

[0130] Figure 4 This is a simplified kinematic analysis diagram of a branch leg in a specific embodiment of the present invention.

[0131] Figure 5 This is a schematic diagram of the motion analysis of a branch leg in a specific embodiment of the present invention.

[0132] Figure 6 This is a simplified kinematic analysis diagram of another branch leg in a specific embodiment of the present invention.

[0133] Figure 7 A is a branch leg in a specific embodiment of the present invention. i and D i Simplified diagram of force analysis between points.

[0134] Figures 8-9 This is a simplified force analysis diagram of a branch leg member in a specific embodiment of the present invention. Detailed Implementation

[0135] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0136] refer to Figure 1 First, a physical model of the legged robot is constructed. The legged robot includes a body, multiple branch legs connected to the body, and a welded arm connected to the body. Each branch leg includes two or more sequentially connected links. The end of the branch leg away from the body is the ground end, and the end of the branch leg connected to the body is the support end. The ground end is connected to the links of the branch leg through ball joints. Adjacent links are connected to each other and to the body through planar rotational hinges. In one embodiment, the ground end is a magnetic adsorption device.

[0137] Continue to refer to Figure 1 In one specific embodiment, the legged robot is quadrupedal, that is, it includes four branch legs. The four branch legs are symmetrically distributed about the center of the body. The four connection points (i.e. support ends) between the four branch legs and the body are coplanar, and the form and size of each branch leg are consistent.

[0138] First, a body coordinate system is introduced. The body coordinate system o-xyz is a right-handed coordinate system with its origin at the center of the body. The z-axis of the body coordinate system is perpendicular to the plane shared by the connection points of the four branch legs and the body, and the x-axis is parallel to the line shared by the connection points of two adjacent branch legs and the body. Next, a global coordinate system O-XYZ is introduced. In the initial pose, the axes of the global coordinate system are parallel to the axes of the body coordinate system, and its origin is located at any fixed point outside the robot. Finally, a branch leg coordinate system {A} is established. i}=o i x i y i z i i = 1 to 4 are the branch leg numbers. In the initial pose, the x-axis of the branch leg coordinate system is... i y i z i Parallel to the coordinate axes of the body coordinate system, with the origin located at the center point of the ball joint at the ground end.

[0139] In this embodiment of the invention, the method for controlling the posture of a legged robot includes the following steps:

[0140] S1: The offline calculation process includes the following steps:

[0141] S11: Obtain the structural information of the legged robot, including the body structure information, branch leg structure information, and welding arm structure information.

[0142] In one specific embodiment, it is assumed that the body is rigid and all kinematic pairs are rigid and frictionless.

[0143] The structural information of the fuselage includes the position and connection relationship of each branch leg support end on the fuselage, as well as the size, mass and material of the fuselage.

[0144] The branch leg construction information includes the branch leg's structure, the relationships between various kinematic pairs, and the dimensions and materials of the links. (Refer to...) Figure 1 and Figure 2 In one embodiment, each branch leg includes a first member, a second member, and a third member connected in sequence. The third member is connected to the ground end of the branch leg via a ball joint, which provides three revolute joints: a first revolute joint, a second revolute joint, and a third revolute joint. The first revolute joint is about x... i The rotation of the axis, the second revolute joint is about y i The rotation, the third revolute joint is about z iRotation of the shaft. The second link is connected to the third link via a third-plane rotary hinge, which provides a fourth rotary joint. The rotation direction of the fourth rotary joint is perpendicular to the plane formed by the second and third links. The first link is connected to the second link via a second-plane rotary hinge, which provides a fifth rotary joint. The rotation direction of the fifth rotary joint is perpendicular to the plane formed by the second and first links. The first link is connected to the machine body via a first-plane rotary hinge, which provides a sixth rotary joint. The rotation direction of the sixth rotary joint is perpendicular to the surface formed by the support ends of the four branch legs.

[0145] like Figure 3 The quadruped welding robot shown is denoted as A for the first link. i B i The length is L1, and the second member is B. i C i The length is L2, and the third member is C. i D i The length is L3, and i = 1 to 4 are the branch leg numbers. For example... Figure 4 As shown, the landing end is denoted as E. i And record D i E i The length is h.

[0146] The welding arm construction information includes the installation position of the welding arm on the machine body, the composition of the welding arm, the relationship and dimensions of each kinematic pair, and material information.

[0147] S12: Establish the branch leg stiffness matrix based on the branch leg construction information.

[0148] In one embodiment, the branch leg stiffness matrix can be calculated using the following method:

[0149] First, kinematic analysis is performed, and pose parameters are used to express the state of the quadruped welding robot in different poses.

[0150] The second step is to perform inverse kinematics analysis on the quadruped welding robot, that is, assuming that the pose parameters θ of the quadruped welding robot are known. ij With the center coordinates of the ground end Calculate the coordinates of the support end

[0151] Next, the strain energy of each branch leg is calculated.

[0152] Finally, using Carnot's theorem, the stiffness matrix of the branch leg is calculated from the strain energy.

[0153] In another embodiment, the branch leg stiffness matrix can also be calculated using a direct analysis method.

[0154] In this embodiment, kinematic analysis is first performed using the pose parameter θ. ij The states of the quadruped welding robot in different poses are expressed, where i represents the sequence number of the branch leg and j represents the sequence number of the planar rotation hinge.

[0155] Consider as Figure 3 The initial pose of the quadruped welding robot shown is given in the body coordinate system, A. i The coordinates of the point (i.e., the supporting end of each branch leg) are denoted as (x Ai y Ai 0), i = 1 to 4 are the branch leg numbers. In the initial pose, the direction of the linear vector of the axis of the branch leg planar rotation hinge is:

[0156] ω i1 =[0 0 1] T

[0157] ω i2 =ω i3 =[1 0 0] T

[0158] The subscripts 1, 2, and 3 represent the first plane rotation hinge, the second plane rotation hinge, and the third plane rotation hinge, respectively.

[0159] In the initial pose, the vector of a point on the rotation axis of the first, second, and third planar rotational hinges is:

[0160] r i1 =[x Ai y Ai 0] T

[0161] r i2 =[x Ai +L1 y Ai 0] T

[0162] r i3 =[x Ai +L1+L2 y Ai 0] T

[0163] The rotational spins of the first, second, and third planar rotational hinges are:

[0164]

[0165]

[0166]

[0167] therefore

[0168]

[0169] In the formula

[0170]

[0171]

[0172]

[0173]

[0174]

[0175]

[0176] Where θ i1 θ i2 θ i3 The pose parameters, sθ, are for the first, second, and third planar rotational hinges of the branch leg numbered i, in sequence. ij It is sinθ ij abbreviation, cθ ij It is cosθ ij The abbreviation, i = 1 to 4, j = 1 to 3 (where 1, 2, and 3 represent the first plane rotational hinge, the second plane rotational hinge, and the third plane rotational hinge, respectively).

[0177] When the quadruped welding robot is in its initial pose, θ i1 =θ i2 =θ i3 =0 (where the subscripts 1, 2, and 3 represent the first plane rotational hinge, the second plane rotational hinge, and the third plane rotational hinge, respectively).

[0178] Branch leg coordinate system {A i The transformation matrix relative to the body coordinate system o-xyz is:

[0179]

[0180] Then, in any pose, the branch leg coordinate system {A} i The transformation matrix relative to the body coordinate system o-xyz is:

[0181]

[0182] Next, we will perform an inverse kinematics analysis of the quadruped welding robot, that is, assuming that the pose parameters θ of each leg of the quadruped welding robot are known. ij (i represents the number of the branch leg, j represents the number of the planar rotation hinge) and the center coordinates of the grounding end. Calculate the coordinates of the support end Among them, E i A represents the grounding end of the branch leg with serial number i. i This represents the support end of the branch leg with serial number i.

[0183] In one specific embodiment, when the quadruped welding robot adheres to the work surface, the end touching the ground will necessarily be perpendicular to the work surface due to the magnetic attraction, such as... Figure 4 and Figure 5 As shown. Therefore, the ball joint D i coordinates It is easy to calculate, so I will not go into details here.

[0184] according to Figure 4 As shown, the following parameters are defined:

[0185]

[0186]

[0187]

[0188]

[0189] In the above formula, L′ AiDi H represents the horizontal distance between the ground end and the support end (or ball joint). i L represents the vertical distance between the ball joint and the second-plane rotational hinge. BiDi This represents the straight-line distance between the ball joint and the second-plane rotary joint.

[0190] according to Figure 4 H shown i Based on the relationship with L3, the expressions for the other quantities in the graph can be obtained as follows:

[0191]

[0192]

[0193]

[0194] β i =θ i3 -α i

[0195]

[0196]

[0197] In the above formula, α represents the computational process quantity, and β represents the computational process quantity. Please refer to [the relevant documentation]. Figure 5 .

[0198] The coordinates of the support end can be calculated using the above formula. Alright.

[0199] Next, the strain energy of each branch leg is calculated.

[0200] In this embodiment, the following assumptions are introduced: the weight of the quadruped welding robot body is considered in the form of external forces, and the weight of other mechanical components other than the body body is negligible. The body is rigid, and all kinematic pairs are rigid and frictionless. The branch legs exhibit complex elastic deformation, including tensile, shear, bending, and torsional deformation.

[0201] It should be noted that in some embodiments, the body may also be considered as an elastomer; and in other embodiments, the kinematic pairs may also be considered as frictional.

[0202] In this embodiment, the ball joint of the branch leg can withstand the support reaction force but not the support reaction moment. Therefore, in the branch leg coordinate system {A} i Below, the branch leg bears the load through D. i The three support reactions f at the point i =[f i1 f i2 f i3 ] T Where i = 1 to 4 are the branch leg numbers, and the subscripts 1, 2, and 3 represent the branch leg coordinate system {A}, respectively. i The x, y, and z axes are shown below.

[0203] According to the principle of force translation in theoretical mechanics, a force acting on a rigid body can be equivalently translated to any point on the rigid body, but a couple determined by the force and the point of translation must be added. Therefore, in order to... i point f i Equivalent, in A i Point of application of force spiral for

[0204]

[0205] in Represents the branch leg coordinate system {A i}Down A i The force acting on the point, Represents the coordinate system {A} i}Down A i The torque acting on the point. Note that... and In the text, the superscript at the top left indicates the coordinate system {A}. i The superscript in the upper right corner indicates the point of application, the blank subscript in the lower left corner is meaningless, and the subscript in the lower right corner indicates the branch number. A i Di A represents i and D i Distance vector between points.

[0206] Please refer to Figures 7-9 Especially Figure 7 In order to act on D i point f i Equivalent, needs to be in A i Point application of force and torque That is, the composition acts on A i Point force spiral Among them, torque Therefore, coordinate system {A i Under}, it can be represented as:

[0207]

[0208] Obviously, reference Figure 8 and Figure 9 In B i and C i Apply the corresponding force to the spiral point and There are similar calculation methods, which will not be elaborated here.

[0209] Based on the knowledge of strain energy in mechanics of materials, A in the i-th branch leg i B i strain energy of the rod It can be represented as:

[0210]

[0211] In the formula, In the i-th branch leg, A represents... i B i The strain energy of the rod;

[0212] A represents i Point along {A i Coordinate system The force acting on the shaft;

[0213] A represents i Point around {A i Coordinate system The torque acting on the shaft;

[0214] Indicates rod A i B i The elastic modulus and shear modulus;

[0215] Indicates rod A i B i The area of ​​the cross-section;

[0216] Indicates rod A i B i Cross section along Effective shear area of ​​the shaft;

[0217] Indicates rod A i B i Polar moment of inertia of the cross section;

[0218] Indicates rod A i B i Cross section about Moment of inertia of the axis.

[0219] Similarly, the analysis can yield B in the branch leg. i C i Rod and C i D i strain energy of the rod as follows:

[0220] In the i-th branch leg, B i C i strain energy of the rod It can be represented as:

[0221]

[0222] In the formula, In the i-th branch leg, B represents... i C i The strain energy of the rod;

[0223] B i Point along {A i Coordinate system The force acting on the shaft;

[0224] B i Point around {A i Coordinate system The torque acting on the shaft;

[0225] Indicates bar B i C i The elastic modulus and shear modulus;

[0226] Indicates bar B i Ci The area of ​​the cross-section;

[0227] Indicates bar B i C i Cross section along Effective shear area of ​​the shaft;

[0228] Indicates bar B i C i Polar moment of inertia of the cross section;

[0229] Indicates bar B i C i Cross section about Moment of inertia of the axis.

[0230] C in the i-th branch leg i D i strain energy of the rod It can be represented as:

[0231]

[0232] In the formula, In the i-th branch leg, C represents... i D i The strain energy of the rod;

[0233] Indicate C i Point along {A i Coordinate system The force acting on the shaft;

[0234] Indicate C i Point around {A i Coordinate system The torque acting on the shaft;

[0235] Indicates member C i D i The elastic modulus and shear modulus;

[0236] Indicates member C i D i The area of ​​the cross-section;

[0237] Indicates member C i D i Cross section along Effective shear area of ​​the shaft;

[0238] Indicates member Ci D i Polar moment of inertia of the cross section;

[0239] Indicates member C i D i Cross section about Moment of inertia of the axis.

[0240] The strain energy of the i-th branch leg is equal to the sum of the strain energies of all the members. That is:

[0241]

[0242] Finally, using Cassavetes' second theorem, the stiffness matrix of the branch leg is calculated from the strain energy.

[0243] According to Castiglione's second theorem, the strain energy U i For any load F i The partial derivative is equal to the value along F. i Infinitely small deformation δ in the direction i Thus, the elastic deformation of the i-th branch leg's ground-touching end along the constraint helical axis can be obtained as follows:

[0244]

[0245]

[0246]

[0247] The writing matrix format is as follows

[0248] δ i =C i f i

[0249]

[0250] In the formula, δ i =[δ i1 δ i2 δ i3 ] T It is a 3×1 vector; f i =[f i1 f i2 f i3 ] T It is a 3×1 vector; C i It is the compliance matrix of the i-th branch leg constraint screw in a 3×3 matrix, where i = 1 to 4 are the branch leg indices, and the subscripts 1, 2, and 3 represent the branch leg coordinate system {A}, respectively. i The x, y, and z axes are shown below.

[0251] The compliance matrix of the i-th branch leg of the quadruped welding robot is C. i Then the stiffness matrix of the branch leg can be obtained as follows:

[0252]

[0253] S13: Establish the deformation coordination equation of the body and branch leg based on the body structure information and the branch leg structure information.

[0254] In this embodiment, each leg of the quadruped robot applies constraint forces along the x, y, and z axes to the body. After the four legs of the quadruped welding robot determine their poses based on the pose parameters, they form an over-constrained parallel structure with the body, which is a statically indeterminate structure. As many supplementary equilibrium equations as there are over-constraints, it is necessary to introduce them to complete the elastostatic analysis of the statically indeterminate structure.

[0255] Taking the body as the object of study, the equilibrium equation of the robot body can be expressed as:

[0256] W = [J1 J2 J3 J4]f = G f f

[0257] In the formula, G f =[J1 J2 J3 J4] is a 6×12 matrix; f = [f1 f2 f3 f4] T It is a 12×1 matrix; W=[FM] is the external helical system acting on the quadruped robot body.

[0258] In the above formula, It is a 6×3 matrix; It is the j-th unit constraint screw applied by the i-th branch leg to the quadruped robot body, and its expression is:

[0259]

[0260]

[0261]

[0262] In the formula, Center D of the joint ball joint i In coordinate system {A i Coordinates are represented under}.

[0263] According to the principle of virtual work, the virtual work W done by the external force W on the virtual displacement D is... T D equals the virtual work done by the internal force on the corresponding virtual deformation. We can obtain:

[0264]

[0265] Right now In the formula, D is a 6×1 matrix, representing the infinitesimal twist of the geometric center point of the quadruped robot.

[0266] The equation representing the body-branch leg deformation coordination equation is given between the elastic deformation of the i-th branch leg's ground-touching end along the constraint helical axis and the infinitesimal twist of the robot's geometric center point.

[0267] S14: Establish the overall stiffness matrix based on the branch leg stiffness matrix and the body-branch leg deformation coordination equation.

[0268] Substituting the branch leg stiffness matrix and the body-branch leg deformation coordination equation into the robot's body equilibrium equation, we obtain:

[0269]

[0270] The overall stiffness matrix K of the quadruped welding robot is:

[0271]

[0272] At this point, the offline calculation process is complete, and the overall stiffness matrix of the quadruped welding robot is calculated based on the structural information of the legged robot.

[0273] S2: The machine control process during welding operations includes the following steps:

[0274] S21: Obtain the current posture of the main body and the current posture of each branch leg.

[0275] The robot's current posture can be obtained from sensors mounted on the robot or from visual analysis; these are both relatively mature technologies and will not be elaborated upon here. The robot's current posture includes three translational displacements and three rotational displacements in the global coordinate system.

[0276] The current posture of the branch leg can be obtained by the posture sensors installed on each link, or by the current stroke of each motion pair actuator.

[0277] In one embodiment, the actuators of the fourth, fifth, and sixth rotary joints of the branch leg, which are driven by an integrated motor and / or EHA-driven rotary joints, can all obtain the rotation amount by the actuators themselves, that is, obtain the current posture of the branch leg.

[0278] S22: Obtain the subsequent welding posture requirements of the legged robot based on the welding task; calculate the subsequent posture of the robot body based on the subsequent welding posture requirements and welding arm structure information.

[0279] The subsequent welding posture requirements of the legged robot are determined by the welding task. Welding task planning is not within the scope of this invention, but it is a mature and well-known technology, and will not be elaborated here.

[0280] The subsequent welding posture requirements for legged robots include the position coordinates of the welding head in the global coordinate system and the angle between the welding head and the working surface.

[0281] Based on the welding arm construction information, the subsequent attitude of the aircraft can be calculated, including the three translational displacements of the aircraft's center point in the global coordinate system and the three rotational displacements of the aircraft.

[0282] In one embodiment, the welding arm is considered a rigid body, which may or may not include motion joints, but there is a ball joint between the welding arm and the body.

[0283] In another embodiment, the welding arm can be regarded as an elastic rigid frame structure, and the angle of each beam in the rigid frame is determined by the construction information of the welding arm.

[0284] S23: Calculate the subsequent attitude of each branch leg based on the subsequent attitude of the body and the overall stiffness matrix. The subsequent attitude of the branch leg includes the position of the landing end of the branch leg and the distance between the landing end of the branch leg and the supporting end of the branch leg.

[0285] Based on the subsequent attitude of the aircraft, namely the three translational displacements of the aircraft's center point and the three rotational displacements of the aircraft in the global coordinate system, the coordinates of the support ends of each branch leg can be calculated. This assumes that the organism is rigid.

[0286] Then, based on the coordinates of each branch leg support end... And from the overall stiffness matrix of the welding robot, the subsequent pose parameters θ can be calculated. ij With the center coordinates of the ground end

[0287] S24: Based on the current posture and subsequent posture of each branch leg, control the rotation of the rods on the branch leg to adjust the posture of the branch leg to the subsequent posture of the branch leg, thus completing the current body control process.

[0288] Based on the current posture of each branch leg obtained in S21 and the subsequent posture of each branch leg calculated in S23, the linkages on the branch legs are controlled to rotate, so that the posture of the branch leg is adjusted to the subsequent posture of the branch leg, thus completing the current body control process.

[0289] After completing the current control process, the branch legs, the main body, and the welding arm all meet the requirements of the current welding task.

[0290] S25: Repeat steps S21 to S24 according to the welding task until the welding task is completed.

[0291] In this embodiment of the invention, the finite element method is not used to calculate the body attitude. Instead, the overall stiffness matrix is ​​pre-calculated offline, avoiding a large amount of computation during operation and reducing the requirements on the processor.

[0292] A numerical example is provided here to verify the consistency between the finite element method and the method of the present invention, thereby verifying the effectiveness of the present invention.

[0293] Example 1: Using a quadruped welding robot as an example, consider the positioning posture parameter θ. ij Computer body posture.

[0294] Note that this example is used to verify the consistency between the finite element method and the method of this invention, and the positioning pose parameter θ is given. ij The scheme for calculating the body posture. This is similar to step S23 of the invention, where the pose parameter θ is calculated based on the body posture. ij The solution is an inverse operation, which does not hinder the need to verify the consistency of the method.

[0295] First, the robot's physical and geometric parameters are given.

[0296]

[0297]

[0298] Consider two different states: the first is that the grounding ends of all four branch legs are on the ground simultaneously, and the second is that the grounding ends of three branch legs are on the ground simultaneously, while the grounding end of the fourth branch leg is raised. Since the four branch legs are identical, there is no need to distinguish between them.

[0299] The table below shows the calculation results and relative errors of the finite element method and the method of this invention. It can be seen that the maximum relative error does not exceed 1%, which meets the requirements of practical use.

[0300]

[0301]

[0302] The above examples demonstrate the consistency between the finite element method and the method of this invention.

[0303] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0304] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for controlling the posture of a legged robot, characterized in that, The legged robot includes a body, multiple branch legs connected to the body, and a welded arm connected to the body. Each branch leg includes sequentially connected rods. The end of the branch leg away from the body is the ground end, and the end of the branch leg connected to the body is the support end. The branch leg includes a first rod, a second rod, and a third rod connected in sequence. The third rod is connected to the ground end via a ball joint. The second rod is connected to the third rod via a third plane rotation hinge. The first rod is connected to the second rod via a second plane rotation hinge. The first rod is connected to the body via a first plane rotation hinge. The ball joint provides a first revolute joint, a second revolute joint, and a third revolute joint, wherein the first revolute joint is a... The rotation of the shaft, the second revolute joint is about The rotation, wherein the third revolute joint is about The rotation of the shaft, where, , , These are the coordinate axes for each of the branch legs. The number representing the branch leg; The third planar rotational hinge provides a fourth rotational joint, the rotation direction of which is perpendicular to the plane formed by the second member and the third member; The second planar rotational hinge provides a fifth rotational joint, the rotation direction of which is perpendicular to the plane formed by the second member and the first member; The first planar rotary hinge provides a sixth rotary joint, the rotation direction of which is perpendicular to the surface formed by the support ends of each of the branch legs; The method includes: S1: The offline calculation process includes the following steps: S11: Obtain the structural information of the legged robot, the structural information including body structural information, branch leg structural information and welding arm structural information; S12: Establish the branch leg stiffness matrix of the branch leg based on the branch leg construction information; S13: Establish the deformation coordination equation of the body and the branch leg based on the body structure information and the branch leg structure information; S14: Establish the overall stiffness matrix based on the branch leg stiffness matrix and the body-branch leg deformation coordination equation; S2: The machine control process during welding operations includes the following steps: S21: Obtain the current posture of the main body and the current posture of each branch leg; S22: Obtain the subsequent welding posture requirements of the legged robot according to the welding task; calculate the subsequent posture of the robot body based on the subsequent welding posture requirements and the welding arm structure information; S23: Calculate the subsequent posture of each branch leg based on the subsequent posture of the body and the overall stiffness matrix. The subsequent posture of the branch leg includes the position of the ground end of the branch leg and the distance between the ground end and the support end. S24: Based on the current posture and subsequent posture of each branch leg, control the rotation of the linkage on the branch leg to adjust the posture of the branch leg to the subsequent posture, thus completing the current posture control of the legged robot body. S25: Repeat steps S21 to S24 according to the welding task until the welding task is completed.

2. The method according to claim 1, characterized in that, The branch leg construction information includes the dimensions and material information of the members in the branch leg, as well as the kinematic pair relationships between the members.

3. The method according to claim 2, characterized in that, The number of branch legs is 4, the 4 branch legs are symmetrically distributed, and the four branch legs are coplanar with the four support ends of the body; The body is rigid, while the branch legs are elastic.

4. The method according to claim 3, characterized in that, The step of establishing the branch leg stiffness matrix based on the branch leg construction information includes the following steps: S121: Establish the pose parameters of each of the aforementioned branch legs. The relationship between different poses of a legged robot, among which, The number representing the branch leg. The serial number representing the planar rotational hinge; S122: According to the pose parameters and the center coordinates of the landing end Calculate the coordinates of the support end. ; S123: Calculate the strain energy of each branch leg, and calculate the total strain energy of the branch leg based on the strain energy of each branch leg; S124: Calculate the stiffness matrix of the branch leg based on the total strain energy of the branch leg.

5. The method according to claim 4, characterized in that, The pose parameters for each of the branch legs are established. The relationships between different poses of a legged robot include: In the body coordinate system Coordinates are , The representative serial number is The supporting end of the branch leg; In the initial pose, the direction of the linear vector of the axis of the branch leg plane rotation hinge is: In this context, the subscripts 1, 2, and 3 represent the first planar rotational hinge, the second planar rotational hinge, and the third planar rotational hinge, respectively. In the initial pose, the vector of a point on the rotation axis of the first, second, and third planar rotational hinges is: The rotational spins of the first, second, and third planar rotational hinges are: Therefore, the matrix exponent of the transformation matrix is, In the formula in The sequence numbers are as follows: The pose parameters of the first, second, and third plane rotation hinges of the branch leg. yes abbreviations yes abbreviation, , where 1, 2, and 3 represent the first plane rotational hinge, the second plane rotational hinge, and the third plane rotational hinge, respectively; When the quadruped welding robot is in its initial pose , where the subscripts 1, 2, and 3 represent the first plane rotational hinge, the second plane rotational hinge, and the third plane rotational hinge, respectively; Branch leg coordinate system The transformation matrix relative to the body coordinate system o-xyz is: Then, in any pose, the branch leg coordinate system The transformation matrix relative to the body coordinate system o-xyz is: 。 6. The method according to claim 5, characterized in that, According to the pose parameters and the center coordinates of the landing end Calculate the coordinates of the support end. ,include: Define the following parameters: In the above formula, This represents the horizontal distance between the ground end and the ball joint. This represents the vertical distance between the ball joint and the second-plane rotational hinge. Represents the length of the first member. Represents the straight-line distance between the ball joint and the second-plane rotational hinge; In the above formula, It is a quantity calculated during the process. Represents the length of the second member. This represents the length of the third member.

7. The method according to claim 6, characterized in that, The calculation of the strain energy of each branch leg, and the calculation of the total strain energy of the branch legs based on the strain energy of each branch leg, includes: exist Point of application of force spiral for in Represents the branch leg coordinate system Down The force acting on the point, Representing the coordinate system Down The torque acting on a point; and In the text, the superscript in the upper left corner indicates the coordinate system. The superscript in the upper right corner indicates the point of application, the blank subscript in the lower left corner is meaningless, and the subscript in the lower right corner indicates the branch number. express Distance vector between points; No. In each branch leg strain energy of the rod for: , , express Point edge coordinate system , , The force acting on the shaft; , , express dot wrap coordinate system , , The torque acting on the shaft; , Indicating rods The elastic modulus and shear modulus; Indicating rods The area of ​​the cross-section; , Indicating rods Cross section along , Effective shear area of ​​the shaft; Indicating rods Polar moment of inertia of the cross section; , Indicating rods Cross section about , Moment of inertia of the axis; No. In each branch leg strain energy of the rod It can be represented as: In the formula, Indicates the first In each branch leg The strain energy of the rod; , , express Point edge coordinate system , , The force acting on the shaft; , , express dot wrap coordinate system , , The torque acting on the shaft; , Indicating rods The elastic modulus and shear modulus; Indicating rods The area of ​​the cross-section; , Indicating rods Cross section along , Effective shear area of ​​the shaft; Indicating rods Polar moment of inertia of the cross section; , Indicating rods Cross section about , Moment of inertia of the axis; No. In each branch leg strain energy of the rod It can be represented as: In the formula, Indicates the first In each branch leg The strain energy of the rod; , , express Point edge coordinate system , , The force acting on the shaft; , , express dot wrap coordinate system , , The torque acting on the shaft; , Indicating rods The elastic modulus and shear modulus; Indicating rods The area of ​​the cross-section; , Indicating rods Cross section along , Effective shear area of ​​the shaft; Indicating rods Polar moment of inertia of the cross section; , Indicating rods Cross section about , Moment of inertia of the axis; No. The strain energy of each branch leg is equal to the sum of the strain energies of all the individual members: 。 8. The method according to claim 7, characterized in that, The overall stiffness matrix is ​​established based on the branch leg stiffness matrix and the body-branch leg deformation coordination equation. for The stiffness matrix of the branch leg , of which Branch leg flexibility matrix for The The component is determined by the following formula: The overall stiffness matrix of the quadruped welding robot In the calculation formula, ,in In the formula, Center of the joint ball joint In coordinate system The coordinates below.

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