Control method for controlling over-constrained robot by calculating branch force based on six-dimensional force feedback and shaft hole assembly system

Abstract

The invention belongs to the technical field of robot control, and discloses a control method for controlling an over-constrained robot by calculating branch force based on six-dimensional force feedback and a shaft hole assembly system.The control method comprises the steps that an assembly system is built, and the mapping relation between generalized external force of an over-constrained six-dimensional force sensor and the branch force of the over-constrained six-dimensional force sensor is built; a branch force signal of the over-constrained six-dimensional force sensor is collected in real time, generalized external force borne by a shaft part at the tail end of the over-constrained six-dimensional force sensor is calculated, the calculated generalized external force of the shaft part is transmitted to a hole part, and then the hole part transmits the generalized external force to the tail end of the over-constrained robot. And the mapping relation between the over-constrained robot tail end stress and the branch driving force of the over-constrained robot is established, the generalized external force borne by the over-constrained robot serves as an input parameter, the branch driving force of the over-constrained robot is calculated, and the over-constrained robot is controlled to complete shaft hole assembling according to the calculated branch driving force. The shaft hole assembling system comprises an over-constrained six-dimensional force sensor used for fixing the shaft part and an over-constrained robot used for fixing the hole part. According to the method, the statically indeterminate branch internal force can be accurately solved, universal and efficient feedback control is achieved, and the method can be widely applied to high-precision force control scenes such as spacecraft docking devices and precision assembly robots.

Description

Technical Field

[0001] The present invention belongs to the technical field of robot control methods, and relates to a control method for controlling an over-constrained robot, specifically a control method for controlling an over-constrained robot based on six-dimensional force feedback solution branch force. Background Art

[0002] Over-constrained structures occupy an important position in high-end equipment manufacturing fields such as aerospace and precision testing due to their high stiffness, high load-bearing capacity and superior motion accuracy. For example, to ensure the stability of force transmission during space docking, the end effector of a space robot often adopts an over-constrained configuration. In the mechanical property testing of spacecraft components, over-constrained six-dimensional force sensors are also widely used due to their high reliability. The number of branches is usually more than six to improve measurement redundancy. However, the statically indeterminate problem caused by the introduction of redundant constraints has become a key bottleneck that hinders the full performance of such structures. The core difficulty lies in how to accurately solve and control the internal forces of each branch.

[0003] In the existing technologies, control methods for over-constrained structures are mostly based on the assumption of statically determinate structures. When dealing with an over-determined system with more than six branches, it is impossible to directly solve the branch forces by relying solely on the static equilibrium equation. Moreover, such methods often ignore the decisive influence of the stiffness heterogeneity between branches on the internal force distribution, which directly leads to a decrease in the accuracy of the branch force information input by the control system and makes it difficult to achieve effective dynamic regulation. Especially under high-speed motion or variable load conditions, it is very easy for the system to have a serious uneven distribution of internal forces, which in turn induces vibration and local stress concentration, and even threatens the safety of the structure. In addition, the versatility of the existing technologies is seriously insufficient. For over-constrained structures with different branch layouts or configurations, it is often necessary to spend a lot of effort to re-derive complex mechanical models and design specific control strategies. This not only greatly increases the development cost and time cycle of engineering applications, but also cannot guarantee the reliability and consistency between different solutions. Summary of the Invention

[0004] The purpose of the present invention is to provide a control method and an axis-hole assembly system for an over-constrained robot based on six-dimensional force feedback solution to control branch forces, so as to achieve the purpose of realizing branch force control through force feedback solution and ensuring assembly accuracy and stability.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A control method for an over-constrained robot based on six-dimensional force feedback solution branch force control includes the following steps:

[0007] S1. Build an assembly system including an over-constrained six-dimensional force sensor, shaft parts, an over-constrained robot, and hole parts. In this assembly system, the shaft parts are assembled at the end of the over-constrained six-dimensional force sensor, and the hole parts are assembled at the end of the over-constrained robot.

[0008] S2. Establishing the mapping relationship between the generalized external force of the over-constrained six-dimensional force sensor and its branch forces;

[0009] S3, collecting branch force signals of the over-constrained six-dimensional force sensor in real time, and solving the generalized external force on the end shaft part of the over-constrained six-dimensional force sensor;

[0010] S4, transferring the calculated generalized external force of the shaft part to the hole part through action and reaction, and then transferring it from the hole part to the end of the over-constrained robot;

[0011] S5. Establish a mapping relationship between the end force of the over-constrained robot and its branch driving force;

[0012] S6. Using the generalized external force on the over-constrained robot as input parameters, solve the driving force of each branch;

[0013] S7. Control the over-constrained robot to complete the shaft-hole assembly according to the calculated branch driving force of the over-constrained robot.

[0014] As a limitation of the present invention, in S2, the mapping relationship is established based on the displacement coordination equation and the static equilibrium equation, and satisfies the following mathematical model: ; in, For the S-type tension and pressure sensor in the over-constrained six-dimensional force sensor in the generalized external force The internal force of the unbroken hyperstatic group branch, δ is the hyperstatic group branch flexibility coefficient matrix, The deformation of the S-type tension and compression sensor in the over-constrained six-dimensional force sensor in the direction of force when the over-constrained branch is disconnected and only subjected to external force is generated; The mapping relationship is: ,in, is the generalized external force acting on the over-constrained six-dimensional force sensor, To over-constrain the branch force on each branch of the six-dimensional force sensor, It is the influence matrix between the generalized external force and its branch forces acting on the over-constrained six-dimensional force sensor.

[0015] As another limitation of the present invention, in S5, the mapping relationship between the end force of the over-constrained robot and its branch driving force is: ,in, is the branch driving force of each branch of the over-constrained robot, is the generalized external force on the over-constrained robot, It is the influence matrix between the generalized external force acting on the over-constrained robot and its branch driving force.

[0016] A shaft-hole assembly system based on six-dimensional force feedback to solve branch forces includes an over-constrained six-dimensional force sensor for fixing shaft parts and an over-constrained robot for fixing hole parts. The over-constrained six-dimensional force sensor drives the shaft parts to move and transmits the force to the hole parts through action and reaction forces. The over-constrained robot drives the hole parts to move according to the force feedback of the hole parts using the above-mentioned control method for controlling the over-constrained robot based on six-dimensional force feedback to solve branch forces.

[0017] As a limitation of the present invention, an axis-hole assembly system based on six-dimensional force feedback solution of branch forces, the over-constrained robot includes an upper platform, a middle platform and a lower platform, the hole parts are assembled on the upper platform, and a variable stiffness drive structure is installed between the upper platform and the middle platform, as well as between the middle platform and the lower platform. The variable stiffness drive structure includes at least three UPS branches and one variable stiffness branch. The variable stiffness branch is arranged in the middle, and the UPS branches are evenly arranged in the circumferential direction of the variable stiffness branch. The UPS branch is used to receive the generalized external force transmitted by the hole parts, and each branch driving force is obtained after solution, and is re-acted on the hole parts through the UPS branch. The variable stiffness branch is used to make the UPS branch move smoothly.

[0018] As a further limitation of the present invention, an axis-hole assembly system for solving branch forces based on six-dimensional force feedback, the variable stiffness branch chain includes a connecting piece, a telescopic rod, a spring, a connecting tube and a variable stiffness joint. The telescopic rod is fixedly connected to the connecting piece, the connecting tube is fixedly connected to the variable stiffness joint, the spring is arranged in the connecting tube, the telescopic rod is inserted in the connecting rod, and the rod end of the telescopic rod is against one end of the spring.

[0019] As a further limitation of the shaft-hole assembly system of the present invention based on six-dimensional force feedback to solve branch forces, the variable stiffness joint includes a load-bearing module, a Hooke's hinge, a variable stiffness shaft and three active-passive variable stiffness modules. The Hooke's hinge is rotatably arranged on the load-bearing module through a first connecting shaft, wherein two active-passive variable stiffness modules are connected to the Hooke's hinge through a second connecting shaft, the first connecting shaft and the second connecting shaft are arranged perpendicularly, the variable stiffness shaft is fixed on the Hooke's hinge, and the third active-passive variable stiffness module is connected to the variable stiffness shaft.

[0020] Due to the adoption of the above technical solution, the present invention has the following technical advancements compared with the prior art:

[0021] The present invention is based on the displacement coordination equation and the static equilibrium equation, constructs a mathematical mapping model of the branch force of the over-constrained six-dimensional force sensor and the generalized external force it is subjected to, collects the branch force signal of the over-constrained six-dimensional force sensor and uses the mapping model to solve the generalized external force suffered by the shaft parts, and according to the law of action and reaction, transmits the external force to the end of the over-constrained robot to obtain the generalized external force suffered by the over-constrained robot; then, according to the structural characteristics of the over-constrained robot, establishes a mapping relationship between the end force and the branch driving force, and uses the generalized external force suffered by the over-constrained robot as input to solve each branch force, and finally controls the over-constrained robot to drive the end hole parts and the shaft parts to complete the precise shaft hole assembly according to the solved branch force. This method does not require the installation of sensors on the branches of the over-constrained robot, realizes branch force control through force feedback solution, ensures assembly accuracy and stability, uses the law of action and reaction to enhance the rigidity and flexibility between branches, and evenly distributes the internal force, can achieve effective dynamic adjustment, can adapt to over-constrained structures with different branch layouts or configurations, and has strong versatility.

[0022] In summary, the present invention can accurately solve the hyperstatic branch internal forces and realize universal and efficient feedback control, and can be widely used in high-precision force control scenarios such as spacecraft docking devices and precision assembly robots. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a flow chart of Example 1 of the present invention;

[0024] Figure 2 This is a simplified structural diagram of the over-constrained six-dimensional force sensor in Example 1 of the present invention before the constraints are removed;

[0025] Figure 3 This is a schematic diagram of an over-constrained six-dimensional force sensor after redundant constraints are removed according to Example 1 of the present invention;

[0026] Figure 4 This is a simplified force diagram of the basic system of the over-constrained six-dimensional force sensor in Example 1 of the present invention after the broken constraints are replaced by unit forces;

[0027] Figure 5 This is a schematic structural diagram of Example 2 of the present invention;

[0028] Figure 6 This is a schematic structural diagram of an over-constrained robot according to embodiment 2 of the present invention;

[0029] Figure 7 This is a structural diagram of a UPS branch chain according to embodiment 2 of the present invention;

[0030] Figure 8 This is a schematic structural diagram of a variable stiffness branch chain according to embodiment 2 of the present invention;

[0031] Figure 9This is a schematic cross-sectional view of the installation of the telescopic rod and the connecting pipe according to Example 2 of the present invention;

[0032] Figure 10 This is a schematic structural diagram of a variable stiffness joint according to embodiment 2 of the present invention;

[0033] Figure 11 This is a structural diagram of the connection between the variable stiffness shaft and the active-passive variable stiffness module in Example 2 of the present invention.

[0034] In the figure: 1. Over-constrained robot; 2. Hole parts; 3. Shaft parts; 4. Over-constrained six-dimensional force sensor; 41. S-type tension and pressure sensor; 5. Upper platform; 6. Middle platform; 7. Lower platform; 8. UPS branch chain; 81. Ball pair; 82. Electric push rod; 9. Variable stiffness branch chain; 91. Connector; 92. Telescopic rod; 93. Spring; 94. Connecting pipe; 95. Variable stiffness joint; 951. Load-bearing module; 952. Variable stiffness shaft; 953. First connecting shaft; 954. Second connecting shaft; 955. Active-passive variable stiffness module; 10. Hooke's joint. DETAILED DESCRIPTION

[0035] The present invention will be further described in detail below by way of specific examples. It should be understood that the described examples are only used to illustrate the present invention and are not intended to limit the present invention.

[0036] Example 1 A control method for an over-constrained robot based on six-dimensional force feedback solution and branch force control

[0037] This embodiment follows Figure 1 The process shown explains each step in detail.

[0038] S1. Build an assembly system that includes an over-constrained six-dimensional force sensor, shaft parts, an over-constrained robot, and hole parts. In this assembly system, the shaft parts are assembled at the end of the over-constrained six-dimensional force sensor, and the hole parts are assembled at the end of the over-constrained robot to form a shaft-hole assembly system.

[0039] S2. Establishing the mapping relationship between the generalized external force of the over-constrained six-dimensional force sensor and its branch forces;

[0040] Based on the displacement coordination equation and the static equilibrium equation, a mathematical mapping model is constructed between the branch forces of the over-constrained six-dimensional force sensor and the generalized external forces it is subjected to. This mathematical mapping model is uniquely determined by the structural parameters of the S-type tension and pressure sensor in the over-constrained six-dimensional force sensor. The branch force vector can be directly converted into the generalized external force at the center of the shaft part, and the quantitative mapping relationship between the two can be obtained. The following is a detailed solution process for the mapping relationship between the branch forces and external forces of the over-constrained six-dimensional force sensor.

[0041] Static equilibrium equation part: For the over-constrained six-dimensional force sensor, assume that it has n (n>6) branches, and the force of each branch is According to the force equilibrium condition, in the Cartesian coordinate system, the resultant force in each direction is zero and the resultant moment in each direction is zero.

[0042] Figure 2 is the displacement coordination equation part. In this embodiment, n is 10. The over-constrained six-dimensional force sensor has ten branches. The four redundant branch constraints in the over-constrained six-dimensional force sensor structure are removed and replaced with unknown forces to obtain the following: Figure 3 The basic system shown in Figure 3 In the basic system, after disconnecting the four redundant constraint branches, six undisconnected branches are left. The undisconnected branches are defined as statically determinate branches, and the remaining four branches are statically indeterminate branches. The following mathematical model can be listed to satisfy the displacement coordination equation and the static equilibrium equation (the left side is the displacement coordination equation, and the right side is the matrix expansion of the displacement coordination equation): ;

[0043] in, =[ ], for the S-type tension and pressure sensor in the over-constrained six-dimensional force sensor in the generalized external force Internal forces of the lower unbroken statically indeterminate group branches; is the flexibility coefficient matrix of the statically indeterminate group branches, which represents the displacement deformation in the force direction of each branch when the force with a value of 1 after replacing the residual constraint in the statically indeterminate group branches acts on the basic system alone; The deformation of the S-type tension and pressure sensor in the over-constrained six-dimensional force sensor in the direction of force when the over-constrained branch is disconnected and only subjected to external force is generated; the physical meaning of this equation represents the deformation of the basic system under external force. With unknown forces Under the combined action, the relative displacement of the ports on both sides of the disconnected branch No. i is zero ( is a matrix, is an element in the matrix, that is , i is the number of each branch).

[0044] like Figure 4 As shown, the basic system of the over-constrained six-dimensional force sensor is in a force state after the redundant constraints are replaced by unit forces when subjected to external force, that is, the force state of the basic system after the four redundant branch constraints in the over-constrained six-dimensional force sensor are disconnected in this embodiment. It represents the generalized external force on the S-type tension and pressure sensor in the over-constrained six-dimensional force sensor. exist Figure 4where represents the unit force of the statically indeterminate branch after the disconnection of the i-th redundant constraint. Figure 4 The stress state is the stress state of the basic system of the S-type tension and pressure sensor in the over-constrained six-dimensional force sensor when it is subjected to external force and the redundant constraints are replaced by unit forces.

[0045] .

[0046] The matrix elements are obtained according to Mohr integral:

[0047] Indicates that the basic system is subjected to a unit force that replaces the broken branch j When the basic system is subjected to the force of the j branch, the deformation of the basic system along the axial direction of the i branch is, that is, the deformation of the i rod when the basic system is subjected to the force of the j branch. It represents the deformation of the basic system along the axial direction of branch i when the basic system is subjected to the original generalized external force.

[0048] When the basic system is subjected to different unit forces that replace redundant constraints, the internal forces of other branch rods are uniformly expressed as , is a matrix of n rows and n-6 ​​columns composed of branch forces (n is the total number of branch forces, n-6 is the total number of redundant constraints in the spatial structure), where the elements in the matrix are The internal force of the kth branch when the i-th unit redundant force acts, and the superscript i indicates that the basic system is subject to the unit force that replaces the redundant constraint of the i-th branch. (i=1,2,…,n-6), the subscript k represents the internal force of the kth branch (k=1,2,…,n).

[0049] .

[0050] When the basic system is subjected to the original generalized external force, the internal forces of the other branch rods are uniformly expressed as , It is a matrix with n rows and 1 columns composed of the forces of each branch rod. For the elements in the matrix The superscript n-5 indicates the original generalized external force on the basic system at this time. , the subscript k represents the internal force of the kth branch.

[0051] .

[0052] The internal force of each branch and Merge into a matrix of n rows and n-5 columns, and use Indicates that, and They are all internal forces of different branches in the six-dimensional force sensor structure under different force conditions when the basic system is analyzed using the force method.

[0053] .

[0054] For each branch force in the matrix in the above formula, according to the different stress states and different branch groups (hyperstatic group branches and statically determinate group branches) of its basic system, its branch forces can be expressed as follows: .

[0055] When k=i and is 1 to n-6, It is expressed as the unit force of the k-branch received by the basic system, so it is equal to 1. When the force on the basic system is the unit force of a certain branch, the branches of the S-type tension and pressure sensor in the over-constrained six-dimensional force sensor can be divided into the statically indeterminate group branch force and the statically determinate group branch force. For the other statically indeterminate group branches except the k-branch, since they are already in a disconnected state, they are 0, while the other six statically determinate groups are , The matrix of the influence coefficients of the remaining statically determinate groups after removing the influence coefficients corresponding to the hyperstatic group branches from the original first-order static influence coefficient matrix G of the S-type tension and pressure sensor in the over-constrained six-dimensional force sensor is obtained. It is the influence coefficient corresponding to the k branch subjected to unit force. Since k=i at this time, the subscript is represented by i. When the basic system is subjected to the original generalized external force, the branches of the over-constrained six-dimensional force sensor are also divided into the statically indeterminate group and the statically determinate group. For the statically indeterminate group, since it is already in a disconnected state, it is 0, while the six branches of the statically determinate group are , The matrix of the influence coefficients of the remaining statically determinate groups after removing the influence coefficients corresponding to the hyperstatic group branches from the original first-order static influence coefficient matrix G of the S-type tension and pressure sensor in the over-constrained six-dimensional force sensor is obtained. It is the original generalized external force acting on the S-type tension and pressure sensor in the over-constrained six-dimensional force sensor.

[0056] f k The specific expression is as follows: .

[0057] According to the superposition principle, the expression of the statically determinate group branch can be obtained: .

[0058] Rearranging the above formula gives: .

[0059] The statically indeterminate branch forces and statically determinate branch forces are: ;

[0060] The combination of the two is expressed as : ;

[0061] Rearranging the formula again: ;

[0062] Combining the above displacement coordination equations, we can get: ;

[0063] ;

[0064] .

[0065] Among them, from the expression of axial stiffness, we can know that the axial stiffness expression of a branch is For the convenience of representation, the axial stiffness of each branch of the hyperstatic group and the axial stiffness of each branch of the statically determinate group are respectively composed into stiffness matrices and , both are diagonal matrices composed of the axial stiffness of each branch. The corresponding matrices of the statically indeterminate group branches and the statically determinate group branches are specifically expressed as follows, and the two are merged.

[0066] .

[0067] as well as It can be expressed as: ;

[0068] ;

[0069] Substituting the above formula into the equation, we get: .

[0070] When its generalized inverse matrix exists, the measurement model expression under the condition of anisotropic stiffness of each branch of the over-constrained parallel six-dimensional force sensor is:

[0071] ; .

[0072] This is the mapping relationship between the branch force and the generalized external force under the condition of the anisotropic stiffness of each branch of the general over-constrained parallel six-dimensional force sensor, where: is the generalized external force acting on the over-constrained six-dimensional force sensor, To over-constrain the branch force on each branch of the six-dimensional force sensor, is the calculated influence matrix.

[0073] S3, real-time collection of the branch force signals of the constrained six-dimensional force sensor, and the calculation of the generalized external force on the end shaft part of the constrained six-dimensional force sensor through the mapping model of S3.

[0074] S4. The calculated generalized external force of the shaft part is transferred to the hole part through the action force and reaction force, and then transferred to the end of the over-constrained robot by the hole part.

[0075] S5. Establish a mapping relationship between the end force of the over-constrained robot and its branch driving force. This mapping relationship is the same as the mapping relationship between the six-dimensional force sensor and its branch forces. ,in, is the branch driving force of each branch of the over-constrained robot, is the generalized external force on the over-constrained robot, The influence matrix is ​​calculated, and the detailed solution process of its mapping relationship is not repeated here.

[0076] S6. Taking the generalized external force on the over-constrained robot as the input parameter, the driving force of each branch is solved through the mapping model of S5.

[0077] S7. Control the over-constrained robot to complete the shaft-hole assembly based on the calculated branch driving force of the over-constrained robot. By adjusting each branch force in real time, the force balance and position accuracy during the assembly process are guaranteed to achieve precise assembly.

[0078] Example 2 Axle-hole assembly system based on six-dimensional force feedback to solve branch forces

[0079] like Figure 5 As shown, this embodiment includes an over-constrained six-dimensional force sensor 4 for fixing shaft parts 3 and an over-constrained robot 1 for fixing hole parts 2. The over-constrained six-dimensional force sensor 4 drives the shaft parts 3 to move, and transmits the force to the hole parts 2 through action and reaction forces. The over-constrained robot 1 drives the hole parts 2 to move based on the force feedback of the hole parts 2 using the control method of embodiment 1.

[0080] The overconstrained six-axis force sensor 4 utilizes existing technology, a mature technology in the field of artificial intelligence robotics, and will not be elaborated on in detail. This embodiment utilizes a ten-branch overconstrained six-axis force sensor 4. The shaft component 3 is assembled on the overconstrained six-axis force sensor 4. Each branch of the overconstrained six-axis force sensor 4 is equipped with an S-shaped tension and pressure sensor 41 to detect the magnitude of the force in each branch of the overconstrained six-axis force sensor 4.

[0081] like Figure 6 As shown, the over-constrained robot 1 includes an upper platform 5, a middle platform 6 and a lower platform 7. The hole-type part 2 is assembled on the upper platform 5. A variable stiffness drive structure is assembled between the upper platform 5 and the middle platform 6, as well as between the middle platform 6 and the lower platform 7. The variable stiffness drive structure is used to receive the force transmitted by the over-constrained six-dimensional force sensor 4, and after solution, it acts on the hole-type part 2 again. The variable stiffness drive structure includes four UPS branches 8 and one variable stiffness branch 9. The variable stiffness branch 9 is arranged in the middle of the platform. The UPS branch 8 is evenly arranged in the circumferential direction of the variable stiffness branch 9. The UPS branch 8 is used to receive the generalized external force transmitted by the hole-type part 2, and obtain the driving force of each branch after solution, and re-act on the hole-type part 2 through the UPS branch 8. The variable stiffness branch 9 is used to make the UPS branch 8 move smoothly and ensure the flexibility of the overall movement. As shown Figure 7 As shown, the UPS branch chain 8 adopts the existing technology, including a ball joint 81, an electric push rod 82 and a Hooke's hinge 10.

[0082] like Figure 8 As shown, the variable stiffness branch chain 9 includes a connecting member 91, a telescopic rod 92, a spring 93, a connecting tube 94 and a variable stiffness joint 95. The telescopic rod 92 is fixedly connected to the connecting member 91. The connecting member 91 of this embodiment includes a rectangular plate and four rods. The telescopic rod 92 is fixed to the rectangular plate. The four rods are fixedly connected to the upper platform 5 and the middle platform 6. The connecting tube 94 is fixedly connected to the variable stiffness joint 95. Figure 9 As shown, the spring 93 is arranged in the connecting tube 94 , the telescopic rod 92 is inserted into the connecting rod, and the rod end of the telescopic rod 92 is against one end of the spring 93 .

[0083] like Figure 10 As shown, the variable stiffness joint 95 includes a load-bearing module 951, a Hooke's hinge 10, a variable stiffness shaft 952, and three active-passive variable stiffness modules 955. The load-bearing module 951 is an inverted U-shaped structure, which is used to be fixed on the lower platform 7 and the middle platform 6 to play a supporting role. The Hooke's hinge 10 is rotatably set on the load-bearing module 951 through the first connecting shaft 953. The two active-passive variable stiffness modules 955 are connected to the Hooke's hinge 10 through the second connecting shaft 954 and are respectively located on both sides of the second connecting shaft 954. The first connecting shaft 953 is perpendicular to the second connecting shaft 954. Figure 11As shown, the variable stiffness shaft 952 is fixed on the Hooke's hinge 10, and the third active-passive variable stiffness module 955 is slidably connected to the variable stiffness shaft 952. The active-passive variable stiffness module 955 adopts the existing technology, that is, the structure of the active-passive variable stiffness module in the Chinese invention patent with publication number CN118876110B, entitled "Bidirectional active-passive variable stiffness joint 95 and robot based on changing the preload of spring 93". Its operating principle has been disclosed in the document and will not be elaborated on again. In this application, the assembly direction of the active-passive variable stiffness modules 955 on both sides of the second connecting shaft 954 is opposite to the assembly direction of the active-passive variable stiffness modules in the "Bidirectional active-passive variable stiffness joint and robot based on changing the preload of spring". The active-passive variable stiffness modules 955 of this application are assembled upward.

[0084] The control method of Example 1 is used to assemble a shaft-hole structure, integrating mechanical mapping and force-position hybrid control. Beginning in the initial position control phase, the overconstrained robot 1 guides the hole component 2 toward the shaft component 3 in pure position mode. When the overconstrained six-dimensional force sensor 4 detects that the contact force exceeds a threshold through the real-time branch force mapping relationship, it immediately switches to a force-position hybrid control mode. In this embodiment, the branch forces are acquired via S-shaped tension and pressure sensors 41 on the branches of the overconstrained six-dimensional force sensor 4, and then resolved into the shaft-hole assembly process to detect the contact force. The resolution process is the same as that described in Example 1. During the hybrid control phase, the system decouples the task space into a position control loop and a force control loop. Simultaneously, Newton's third law is used to transfer the generalized external force resolved by the overconstrained six-dimensional force sensor 4 to the external force at the end of the overconstrained robot 1. This external force is resolved in real time into the driving forces of each branch via the mapping model of the overconstrained robot 1. These driving force parameters are input into the joint controller to achieve precise actuator output and participate in the force control loop calculation and dynamic compensation.

[0085] The above descriptions are merely optional embodiments of the present invention and are 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.

Claims

1. A control method for an over-constrained robot based on six-dimensional force feedback solution branch force control, characterized in that: The following steps are involved: S1. Build an assembly system including an over-constrained six-dimensional force sensor, shaft parts, an over-constrained robot, and hole parts. In this assembly system, the shaft parts are assembled at the end of the over-constrained six-dimensional force sensor, and the hole parts are assembled at the end of the over-constrained robot. S2. Establishing the mapping relationship between the generalized external force of the over-constrained six-dimensional force sensor and its branch forces; S3, collecting branch force signals of the over-constrained six-dimensional force sensor in real time, and solving the generalized external force on the end shaft part of the over-constrained six-dimensional force sensor; S4, transferring the calculated generalized external force of the shaft part to the hole part through action and reaction, and then transferring it from the hole part to the end of the over-constrained robot; S5. Establish a mapping relationship between the end force of the over-constrained robot and its branch driving force; S6. Using the generalized external force on the over-constrained robot as input parameters, solve the driving force of each branch; S7. Control the over-constrained robot to complete the shaft-hole assembly according to the calculated branch driving force of the over-constrained robot.

2. A control method for an over-constrained robot based on six-dimensional force feedback solution branch force control according to claim 1, characterized in that: In S2, the mapping relationship is established based on the displacement coordination equation and the static equilibrium equation, and satisfies the following mathematical model: ； in, is the internal force of the hyperstatic group branch of the S-type tension and pressure sensor in the overconstrained six-dimensional force sensor that is not disconnected under the generalized external force F, δ is the hyperstatic group branch flexibility coefficient matrix, Δ The deformation of the S-type tension and compression sensor in the over-constrained six-dimensional force sensor in the direction of force when the over-constrained branch is disconnected and only subjected to external force is generated; The mapping relationship is: ,in, is the generalized external force acting on the over-constrained six-dimensional force sensor, is the branch force on each branch of the over-constrained six-dimensional force sensor, and G is the influence matrix between the generalized external force acting on the over-constrained six-dimensional force sensor and its branch forces.

3. A control method for an over-constrained robot based on six-dimensional force feedback solution branch force control according to claim 1 or 2, characterized in that: In S5, the mapping relationship between the end force of the over-constrained robot and its branch driving force is: ,in, is the branch driving force of each branch of the over-constrained robot, is the generalized external force on the over-constrained robot, It is the influence matrix between the generalized external force acting on the over-constrained robot and its branch driving force.

4. A shaft-hole assembly system based on six-dimensional force feedback to solve branch forces, characterized in that: It includes an over-constrained six-dimensional force sensor for fixing shaft parts and an over-constrained robot for fixing hole parts. The over-constrained six-dimensional force sensor drives the shaft parts to move and transmits the force to the hole parts through action and reaction forces. The over-constrained robot drives the hole parts to move according to the force feedback of the hole parts and a control method for controlling the over-constrained robot based on six-dimensional force feedback solution branch force as described in any one of claims 1-3.

5. The shaft-hole assembly system based on six-dimensional force feedback for branch force calculation according to claim 4 is characterized in that: The over-constrained robot includes an upper platform, a middle platform and a lower platform. The hole-type parts are assembled on the upper platform. Variable stiffness drive structures are installed between the upper platform and the middle platform, as well as between the middle platform and the lower platform. The variable stiffness drive structure includes at least three UPS branches and one variable stiffness branch. The variable stiffness branch is arranged in the middle, and the UPS branches are evenly arranged in the circumferential direction of the variable stiffness branch. The UPS branch is used to receive the generalized external force transmitted by the hole-type parts. After solution, the driving force of each branch is obtained and re-acted on the hole-type parts through the UPS branch. The variable stiffness branch is used to make the UPS branch move smoothly.

6. The shaft-hole assembly system based on six-dimensional force feedback for branch force calculation according to claim 5, characterized in that: The variable stiffness branch chain includes a connecting piece, a telescopic rod, a spring, a connecting tube and a variable stiffness joint. The telescopic rod is fixedly connected to the connecting piece, the connecting tube is fixedly connected to the variable stiffness joint, the spring is arranged in the connecting tube, the telescopic rod is inserted in the connecting rod, and the rod end of the telescopic rod is against one end of the spring.

7. The shaft-hole assembly system based on six-dimensional force feedback for branch force calculation according to claim 6, characterized in that: The variable stiffness joint includes a load-bearing module, a Hooke's hinge, a variable stiffness shaft and three active-passive variable stiffness modules. The Hooke's hinge is rotatably arranged on the load-bearing module through a first connecting shaft. Two active-passive variable stiffness modules are connected to the Hooke's hinge through a second connecting shaft. The first connecting shaft and the second connecting shaft are arranged perpendicularly. The variable stiffness shaft is fixed on the Hooke's hinge. The third active-passive variable stiffness module is connected to the variable stiffness shaft.

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