Vector force loading calibration method

Abstract

The invention discloses a vector force loading calibration method, and relates to the technical field of calibration, and the method comprises the steps: constructing a kinetic model of a vector force loading calibration mechanism; the vector force loading calibration mechanism comprises a loading rod and a 6UPS parallel mechanism, the 6UPS parallel mechanism is composed of a movable platform, a static platform and branch chains of UPS structures, each UPS structure is arranged between the movable platform and the static platform, and one end of the loading rod is rigidly connected with the movable platform; based on the dynamic model, force feedback control is carried out on the vector force loaded at the tail end of the vector force loading calibration mechanism body, pose feedback control is carried out on a movable platform in the vector force loading calibration mechanism body, and the calibrated vector force is output; wherein the input of the pose feedback control is determined by carrying out admittance control calculation on a vector force tracking value and a vector force feedback value output by the force feedback control and the target pose of the movable platform. According to the invention, the loading precision of vector force loading calibration can be improved.

Description

Technical Field

[0001] The present application relates to the field of calibration technology, and in particular to a vector force loading calibration method. Background Art

[0002] At present, the calibration method of aircraft engine force measurement system is usually based on in-situ loading. This method realizes in-situ force loading of the sensor through different configurations of weights to complete the calibration of the sensor. This calibration method is cumbersome to configure, has low accuracy and poor stability, which is not conducive to the development of testing work. When common mechanical loading mechanisms are performing vector force loading, there is a serious output force coupling phenomenon between the force loading channels of each degree of freedom, resulting in the parallel vector force loading system having disadvantages such as low frequency response and poor robust stability, which will seriously restrict the overall control performance of the parallel mechanism vector force loading system. Summary of the invention

[0003] The purpose of this application is to provide a vector force loading calibration method, which can improve the loading accuracy of vector force loading calibration.

[0004] To achieve the above objectives, this application provides the following solutions:

[0005] The present application provides a vector force loading calibration method, the vector force loading calibration method comprising:

[0006] A dynamic model of a vector force loading calibration mechanism is constructed; the vector force loading calibration mechanism includes a loading rod and a 6UPS parallel mechanism, the 6UPS parallel mechanism is composed of a dynamic platform, a static platform and a branch chain of a UPS structure, each UPS structure is arranged between the dynamic platform and the static platform, and one end of the loading rod is rigidly connected to the dynamic platform;

[0007] Based on the dynamic model, force feedback control is performed on the vector force loaded by the loading rod, and posture feedback control is performed on the moving platform to output a calibrated vector force; wherein the input of the posture feedback control is determined by performing admittance control calculation on the vector force tracking value output by the force feedback control, the vector force feedback value and the target posture of the moving platform.

[0008] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0009] The present application provides a vector force loading calibration method, which, based on the dynamic model, performs force feedback control on the vector force loaded by the loading rod, performs posture feedback control on the moving platform, and outputs the calibrated vector force; wherein the input of the posture feedback control is determined by performing admittance control calculation on the vector force tracking value output by the force feedback control, the vector force feedback value, and the target posture of the moving platform, thereby achieving the unification of position control and force control, avoiding the impact and instability caused by the control mode conversion during the control process, and at the same time reducing the influence of environmental errors on the control accuracy through vector force feedback, thereby improving the loading accuracy of the vector force loading calibration. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0011] Figure 1 A schematic diagram of a flow chart of a vector force loading calibration method provided in one embodiment of the present application;

[0012] Figure 2 A schematic diagram of the structure of a vector force loading calibration system provided in one embodiment of the present application;

[0013] Figure 3 A schematic diagram of the main structure of a vector force loading calibration mechanism provided in an embodiment of the present application;

[0014] Figure 4 A schematic diagram of the connection relationship between a loading rod and a loaded object provided in one embodiment of the present application;

[0015] Figure 5 A schematic diagram of the main structure of a vector force loading calibration mechanism provided in an embodiment of the present application;

[0016] Figure 6 A block diagram of a force-based loading control strategy provided in one embodiment of the present application.

[0017] Reference numerals:

[0018] 1-horizontal frame, 2-loaded object, 3-loading rod, 4-vector force loading calibration mechanism body, 41-static platform, 42-compound ball joint, 43-servo motor, 44-servo electric cylinder, 45-first tension pressure sensor, 46-Hook's hinge, 47-moving platform, 31-slide rail group, 32-tension pressure sensor group, 33-ball joint. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0020] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0021] This application provides a vector force loading calibration method, such as Figure 1 As shown, the vector force loading calibration method includes:

[0022] Step 101: Construct a dynamic model of a vector force loading calibration mechanism; the vector force loading calibration mechanism includes a loading rod and a 6UPS parallel mechanism, the 6UPS parallel mechanism consists of a moving platform, a static platform and a branch chain of a UPS structure, each UPS structure is arranged between the moving platform and the static platform, and one end of the loading rod is rigidly connected to the moving platform.

[0023] Step 102: Based on the dynamic model, force feedback control is performed on the vector force loaded by the loading rod, posture feedback control is performed on the moving platform, and a calibrated vector force is output; wherein the input of the posture feedback control is determined by performing admittance control calculation on the vector force tracking value output by the force feedback control, the vector force feedback value and the target posture of the moving platform.

[0024] The vector force loading calibration mechanism of the present application comprises two parts: a vector force loading mechanism body and a control system; the vector force loading calibration mechanism is in the form of a 6UPS parallel mechanism with a loading rod.

[0025] This application realizes the unification of position control and force control, avoids the impact and instability caused by the control mode conversion during the control process, and reduces the influence of environmental errors on the control accuracy through vector force feedback, thereby improving the loading accuracy of vector force loading calibration. Position control in this application refers to position attitude (position and posture) control.

[0026] The calibrated vector force output by the present application is used to calibrate the sensor to be tested.

[0027] like Figure 2As shown, the vector force loading calibration system includes a frame 1, a loaded object 2, a loading rod 3 and a vector force loading calibration mechanism body 4. The horizontal frame 1 connects the vector force loading calibration mechanism body 4 and the loaded object 2 through flanges and bolts, the loading rod 3 and the vector force loading calibration mechanism body 4 are connected by rigid means such as welding, and are connected to the loaded object 2 through a ball joint 33 and a flange. The frame 1 is specifically a horizontal frame 1. The vector force loading calibration mechanism body 4 is a 6UPS parallel mechanism, which is composed of a dynamic platform, a static platform and 6 UPS structure branches.

[0028] The vector force loading calibration mechanism body 4 applies vector force to the loaded object 2 through the loading rod 3, and the frame 1 unifies the loaded object 2 and the vector force loading calibration mechanism body 4 on a horizontal plane, simulating the thrust of an actual turbojet engine.

[0029] like Figure 3 As shown, each branch chain in the 6UPS parallel mechanism is provided with a composite ball joint 42, a Hooke's joint 46, a servo motor 43, a servo electric cylinder 44 and a first tension and pressure sensor 45; one end of the first tension and pressure sensor 45 is fixed to one end of the branch chain, and the other end of the first tension and pressure sensor 45 is connected to the moving platform 47 through the Hooke's joint 46, and is connected to the static platform 41 through the composite ball joint 42. The servo motor 43 is used to adjust the length of the branch chain through the servo electric cylinder 44.

[0030] The vector force loading calibration mechanism body 4 is connected to the loaded object 2 through the loading rod 3. The connection between the loading rod 3 and the loaded object 2 is as follows: Figure 4 As shown, the loading rod 3 and the loaded object 2 also include a tension and pressure sensor group 2 and a slide rail group 31, one end of the loading rod 3 is rigidly connected to the moving platform 47, and the other end of the loading rod 3 is connected to the tension and pressure sensor group 2 through a ball joint 33, the tension and pressure sensor group 2 is fixed to the slide rail group 31, and the slide rail group 31 is fixed to the loaded object 2. The loading rod 3 and the tension and pressure sensor group 2 can move up, down, left, and right on the bearing surface of the loaded object 2 through the slide rail group 31, and the bearing surface of the loaded object 2 is the surface where the slide rail group 31 is fixed.

[0031] Among them, the compound ball joint 42 is composed of a horizontal Hooke's joint and a revolute pair; each leg forms a UPS structure and is connected to the static platform 41 and the dynamic platform 47 through the compound ball joint 42 and the Hooke's joint 46 respectively. The mobile pair is composed of a servo motor 43 and a servo electric cylinder 44 to realize the change of the leg length, and the posture adjustment of the dynamic platform 47 is realized through the different length configurations of the six legs, and the loading of vector force is realized in combination with the designed control algorithm.

[0032] The tension and pressure sensor group 2 includes four second tension and pressure sensors, which are evenly distributed between the ball joint 33 and the slide rail group 31. The four second tension and pressure sensor groups 2 realize the decoupled measurement of vector force, and the two slide rail groups 31 realize the movement on the plane, transmit the force perpendicular to the plane, and prevent the sensor from receiving lateral force.

[0033] In order to perform vector force loading in this application, it is necessary to first obtain the mapping relationship (Jacobian matrix) between the joint space and the Cartesian space through the kinematic model. The independent variable in the following analysis is L i , the output variable is and P.

[0034] The definition of inverse kinematics is to solve the vector after given the terminal position posture (the position of the moving platform 47 relative to the static platform 41 and the posture of the coordinate system Px′y′z′ relative to the coordinate system O-xyz) like Figure 5 As shown, θ1 is the angle between A5 and A6 and the center P of the moving platform, and θ2 is the angle between B1 and B5 and the center O of the static platform. Define vector a i and b i A i and B i The position vectors in the moving coordinate system and the stationary platform 41 coordinate system, and the position vector of the moving platform 47 relative to the stationary platform 41 And the rotation matrix of the moving coordinate system relative to the stationary platform 41 coordinate system definition in for:

[0035]

[0036] Where c1 is cosα and c2 is s1 is sinα, s2 is α and are all Euler angles, such as Figure 5 shown.

[0037] According to the geometric relationship, we can get:

[0038]

[0039] Where P is the position vector

[0040] Taking the modulus on both sides of the equation gives the length of the branch (leg):

[0041]

[0042] Among them, L irepresents the length of branch i.

[0043] Then the unit direction vector s of branch i is i for:

[0044] s i = l i / L i (4)

[0045] Taking the time derivative of both ends of equation (1) we can get the velocity A of the moving platform 47: i for:

[0046]

[0047] in, For dynamic platform 47A i The speed, v p Represents the position vector The velocity of the The angular velocity of rotation.

[0048] Decompose the velocity of the branch chain in the static platform 41 coordinate system into the branch chain direction and obtain the moving velocity v of the branch chain joint L , where the vector set s = [s1,…,s6]

[0049]

[0050] Therefore, the velocity Jacobian matrix can be defined as:

[0051] J=[s T (r a ×s) T ] -1 (7)

[0052] According to the principle of virtual work, the force Jacobian matrix J can be derived f =J T

[0053] The kinematic and static mapping relationship between the moving platform 47 and the branch chain joints has been determined through the above derivation. In order to reduce the error caused by factors such as inertia during the loading process, a dynamic model of the loading calibration mechanism is established.

[0054] The dynamic model includes the Newton-Euler equations of the outriggers and the Newton-Euler equations of the moving platform 47 .

[0055] Outrigger Newton-Euler equations:

[0056] -m i2 a ci2 +m i2 g+f bi +f ci=0 (8)

[0057] M ai s i +l i s i ′f bi =C i (9)

[0058] make

[0059] Further simplification yields: si -f bi =K i (11)

[0060] Where: f si =s i ·f bi ,

[0061] Among them, m i1 、m i2 Indicates the mass of the upper and lower legs, c i1 、c i2 It represents the distance from the center of mass of the upper and lower legs to the hinge point. represents the moment of inertia of the upper and lower legs around the center of mass, a ci1 、a ci2 represents the acceleration of the center of mass of the upper and lower legs, M ai It is expressed as the restraint moment at the outrigger Hooke's hinge 46 along the outrigger direction, f bi is the force of the moving platform 47 on the upper leg, f ci is the force exerted by the lower leg on the upper leg, w i is the outrigger angular velocity, C i , K i and f si They are all intermediate parameters, the upper leg is the leg connected to the moving platform 47, and the lower leg is the leg connected to the static platform 41.

[0062] Newton-Euler equations for the moving platform 47:

[0063]

[0064] F p =-m p a+m p g (14)

[0065]

[0066] Among them, F p is an intermediate parameter. Substituting Formula 12 into Formula 13 and Formula 15, we can get:

[0067]

[0068] Among them, m p ,c,I p and ω are respectively the mass, center of mass, moment of inertia and angular velocity of the moving platform 47, and q i is the actual position of branch chain i in the Cartesian coordinate system, and the above formulas can be combined to obtain:

[0069]

[0070] To simplify the subsequent content, the dynamic model can be written as follows:

[0071]

[0072] Wherein, M(q) is the inertia matrix of the vector force loading calibration mechanism body 4, is the damping matrix of the vector force loading calibration mechanism body 4, G(q) is the gravity matrix of the vector force loading calibration mechanism body 4, q represents the actual position of the center of mass of the moving platform 47 in the Cartesian coordinate system, and through each q i We can determine q, is the first-order derivative of q, is the second-order derivative of q, J is the velocity Jacobian matrix of the leg joint in the 6UPS parallel mechanism, τ represents the control quantity, which is the torque of the motor or the thrust of the push rod, and F ext Represents the vector force feedback value, N p is the intermediate parameter.

[0073] The above analysis establishes a control model (dynamic model) of the vector force loading calibration mechanism. In order to achieve accurate tracking of the vector force, it is also necessary to design a safe, sensitive, high-precision and high-robust force loading control strategy.

[0074] like Figure 6 As shown, the present application adopts composite admittance control and synovial film control rate to perform feedback control on vector force loading.

[0075] In order to achieve the control of posture and vector force, a force / position hybrid control strategy is required. This application selects admittance control as the basic control strategy, and designs a force tracking controller and a position controller based on a dynamic model to meet the tracking accuracy of the vector force due to the vector force error caused by environmental error and position control error.

[0076] Wherein, step 102 specifically includes:

[0077] Through the force tracking controller, according to the target vector force F d , vector force feedback value F extand the actual position q of the moving platform 47 outputs the vector force tracking value F r ; The vector force feedback value is determined according to the collected value of the tension and pressure sensor group 2;

[0078] Through the admittance controller, according to the target position q of the moving platform 47 d , the vector force tracking value F r and the vector force feedback value F ext Perform admittance control and output the desired position q of the moving platform 47 c ;

[0079] Through the position controller, according to the desired posture q c And the actual posture q outputs the control torque τ;

[0080] The control torque is input into the control system of the vector force loading calibration mechanism body 4 to control the posture of the moving platform 47; the control system is used to output the actual posture of the moving platform 47.

[0081] The control law of the admittance controller is expressed as:

[0082]

[0083] Among them, M d , B d , K d are impedance parameters of the admittance controller, q represents the actual position (current actual position) of the center of mass of the moving platform 47 in the Cartesian coordinate system, and q c represents the desired position (current desired position) of the center of mass of the moving platform 47 in the Cartesian coordinate system, q d represents the target position of the center of mass of the moving platform 47 in the Cartesian coordinate system, for q c The first derivative of for q c The second-order derivative of q0 represents the equilibrium position of the center of mass of the moving platform 47 in the Cartesian coordinate system, F r represents the vector force tracking value, represents the environmental stiffness of the loaded object 2, Δk e and Δq e represent the environmental stiffness error and the environmental equilibrium position error respectively, F ext Represents the vector force feedback value.

[0084] Since the accuracy of vector force control is positively correlated with the measurement accuracy of environmental stiffness, in actual engineering, there will be steady-state errors in the vector force due to processing errors, measurement errors, etc. To address this problem, a force tracking controller needs to be introduced.

[0085] The control law of the force tracking controller is expressed as:

[0086]

[0087] Among them, F d is the target vector force, k d , k i and k p are control parameters, k d , k i and k p is a known quantity, F d The first derivative of F d The second-order derivative of F ext The first derivative of , t is time.

[0088] The control law of the admittance controller and the control law of the force tracking controller solve the steady-state error caused by the environmental error and improve the control accuracy. On the other hand, due to the nonlinear characteristics of the vector force loading calibration mechanism, the performance of the traditional model-free position control strategy is poor. Therefore, it is necessary to introduce a model-based sliding film control strategy to improve the accuracy and robustness of the control system.

[0089] The control hardware of the control system includes: industrial computer, analog input module, transmitter amplifier, servo motor 43 driver, tension and pressure sensor, and IO coupling module.

[0090] The control method is a nonlinear model force loading control strategy based on composite admittance control. This control strategy obtains the leg length through the encoder of the servo motor 43 and solves the position posture in the Cartesian coordinate system, then outputs the vector force feedback through the pull-pressure sensor strategy, and finally calculates the control quantity through composite admittance control, and indirectly realizes force loading by position tracking through model-based synovial membrane control.

[0091] Based on the dynamic model, force feedback control is performed on the vector force loaded at the end of the vector force loading calibration mechanism body 4, and posture feedback control is performed on the moving platform 47 in the vector force loading calibration mechanism body 4, and the calibrated vector force is output, which specifically also includes: introducing a synovial control strategy based on the dynamic model in the position controller.

[0092] The non-singular terminal sliding surface in the sliding film control strategy based on the dynamic model is expressed as:

[0093]

[0094] Where s′ is the terminal sliding mode function, s′=(s1,s2,...,s6) T , is the trajectory tracking error of the moving platform 47, q d To represent the target position of the center of mass of the moving platform in the Cartesian coordinate system, β = diag(β1, β2, ..., β6) and β i >0, γ=diag(γ1,γ2,...,γ6) and 1<γ i <2,1≤i≤6,β and γ are both synovial control parameters,β i and γ i are all intermediate parameters; n is the number of degrees of freedom, specifically n=6, sig(x) represents the saturation function, which is used to adjust the direction of change of the control rate, x is the input of sig(x), and sign() is the sign function.

[0095] The synovial approach rate is:

[0096]

[0097] in, is the synovial approach rate, k1 and k2 are both intermediate parameters, k1 = diag(k 11 ,k 12 ,...,k 16 ), k2=diag(k 21 ,k 22 ,...,k 26 ), k 1i ,k 2i >0, 1≤i≤6; ρ=(ρ1,ρ2,...,ρ6) T ,0<ρ1=...=ρ6<1,ρ i Parameter representing the convergence rate.

[0098] The synovial controller is expressed as:

[0099]

[0100] Wherein, τ is the control torque of the leg in the 6UPS parallel mechanism, τ1, τ2 and τ3 are all intermediate parameters, J is the velocity Jacobian matrix of the leg joint in the 6UPS parallel mechanism, is the adaptive disturbance estimation term, k3=diag(k 31 ,k 32 ,...,k 36 ), k 3i >0, is the inertia matrix without error, is the damping matrix without error, is the gravity matrix without error.

[0101] The negative feedback system of the vector force loading calibration mechanism is the posture feedback in the Cartesian coordinate system and the end vector force feedback. First, the length of each leg is obtained through the encoder of the servo motor and the dynamic platform position and posture of the mechanism are obtained in combination with the kinematic model, and negative feedback is given to the ideal position to achieve the position control accuracy based on the model. On this basis, the vector force in the Cartesian coordinate system is measured by the tension and pressure sensor group on the loading rod and negative feedback is given in the composite admittance control to achieve vector force control.

[0102] The present application automatically adjusts the posture and applies the required vector force through the vector force loading calibration mechanism, which reduces the labor cost of the traditional method and improves the stability and anti-interference ability of the calibration system.

[0103] The structure of the vector force loading calibration mechanism realizes the loading of vector force by adjusting the position and posture of the loading mechanism. Compared with the traditional rigid connection, this structure can effectively improve the bearing capacity of the mechanism. This advantage comes from the loading of the structural part and the connection method of the loaded object. The connection method of the present application enables the loading calibration mechanism to adjust its posture. Since the force mapping relationship and posture of the parallel mechanism are strongly correlated, there must be an optimal posture in the workspace for vector forces in different directions. The structure of the present application can make the loading calibration mechanism always be in the optimal posture to apply vector force, which can effectively improve the stiffness and bearing capacity of the mechanism.

[0104] The connecting flange structure between the loading rod and the loaded object effectively realizes the decoupled measurement of vector force and avoids the introduction of six-dimensional force sensor, which provides necessary feedback information for the control algorithm and improves the control accuracy of the mechanism.

[0105] Composite impedance control unifies position control and force control on one level, which avoids the impact and instability caused by control mode conversion during the control process. At the same time, the addition of a force tracker reduces the impact of environmental errors on control accuracy, achieving high-precision vector force loading. At the same time, the introduction of a model-based synovial position control strategy enhances the robustness and response speed of the control system, further improving the loading accuracy of the vector force loading calibration system.

[0106] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, 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.

[0107] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A vector force loading calibration method, It is characterized in that The vector force loading calibration method comprises: A dynamic model of a vector force loading calibration mechanism is constructed; the vector force loading calibration mechanism includes a loading rod and a 6UPS parallel mechanism, the 6UPS parallel mechanism is composed of a dynamic platform, a static platform and a branch chain of a UPS structure, each UPS structure is arranged between the dynamic platform and the static platform, and one end of the loading rod is rigidly connected to the dynamic platform; Based on the dynamic model, force feedback control is performed on the vector force loaded by the loading rod, and posture feedback control is performed on the moving platform to output a calibrated vector force; wherein the input of the posture feedback control is determined by performing admittance control calculation on the vector force tracking value output by the force feedback control, the vector force feedback value and the target posture of the moving platform.

2. The vector force loading calibration method according to claim 1, It is characterized in that A tension and pressure sensor group and a slide rail group are included between the loading rod and the loaded object. The other end of the loading rod is connected to the tension and pressure sensor group through a ball joint. The tension and pressure sensor group is fixed to the slide rail group, and the slide rail group is fixed to the loaded object.

3. The vector force loading calibration method according to claim 2, It is characterized in that Based on the dynamic model, force feedback control is performed on the vector force loaded by the loading rod, posture feedback control is performed on the moving platform, and the calibrated vector force is output, which specifically includes: Outputting a vector force tracking value according to the target vector force, the vector force feedback value and the actual position and posture of the moving platform through a force tracking controller; the vector force feedback value is determined according to the collected value of the tension and pressure sensor group; By means of an admittance controller, admittance control is performed according to the target posture of the moving platform, the vector force tracking value and the vector force feedback value, and a desired posture of the moving platform is output; Outputting a control torque according to the desired posture and the actual posture through a position controller; The control torque is input into the control system of the vector force loading calibration mechanism to control the position and posture of the moving platform; the control system is used to output the actual position and posture of the moving platform.

4. The vector force loading calibration method according to claim 1, It is characterized in that The kinetic model is expressed as: Wherein, M(q) is the inertia matrix of the vector force loading calibration mechanism, is the damping matrix of the vector force loading calibration mechanism, G(q) is the gravity matrix of the vector force loading calibration mechanism, q represents the actual position of the center of mass of the moving platform in the Cartesian coordinate system, is the first-order derivative of q, is the second-order derivative of q, J is the velocity Jacobian matrix of the leg joint in the 6UPS parallel mechanism, τ represents the control quantity, and F ext Represents the vector force feedback value.

5. The vector force loading calibration method according to claim 3, It is characterized in that The control law of the admittance controller is expressed as: Among them, M d , B d , K d are the impedance parameters of the admittance controller, q represents the actual position of the center of mass of the moving platform in the Cartesian coordinate system, and q c represents the expected position of the center of mass of the moving platform in the Cartesian coordinate system, q d To express the target position of the center of mass of the moving platform in the Cartesian coordinate system, for q c The first derivative of is the second-order derivative of qc, q 0 represents the equilibrium position of the center of mass of the moving platform in the Cartesian coordinate system, F r represents the vector force tracking value, Indicates the environmental stiffness of the loaded object, Δk e and Δq e represent the environmental stiffness error and the environmental equilibrium position error respectively, F ext Represents the vector force feedback value.

6. The vector force loading calibration method according to claim 5, It is characterized in that The control law of the force tracking controller is expressed as: Among them, F d is the target vector force, k d , k i and k p are control parameters, F d The first derivative of F d The second-order derivative of F ext The first derivative of , t is time.

7. The vector force loading calibration method according to claim 6, It is characterized in that Based on the dynamic model, force feedback control is performed on the vector force loaded by the loading rod, posture feedback control is performed on the moving platform, and a calibrated vector force is output. Specifically, the method also includes: introducing a synovial control strategy based on the dynamic model into the position controller.

8. The vector force loading calibration method according to claim 7, It is characterized in that The non-singular terminal sliding surface in the sliding film control strategy based on the dynamic model is expressed as: Where s′ is the terminal sliding mode function, is the trajectory tracking error of the moving platform, q d To represent the target position of the center of mass of the moving platform in the Cartesian coordinate system, γ = diag (γ 1 ,γ 2 ,...,γ 6 ) and 1<γ i <2, 1≤i≤6, β and γ are both synovial control parameters; n is the number of degrees of freedom, sig(x) represents the saturation function, x is the input of sig(x), and sign() is the sign function; The synovial approach rate is: in, is the synovial approach rate, k 1 and k 2 are all intermediate parameters, k 1 =diag(k 11 ,k 12 ,...,k 16 ), k 2 =diag(k 21 ,k 22 ,...,k 26 ), k 1i ,k 2i >0,1≤i≤6;ρ=(ρ 1 ,ρ 2 ,...,ρ 6 ) T , 0<ρ 1 =... =ρ 6 <1,ρ i Parameter representing the convergence rate; The synovial controller is expressed as: τ=(J T (q)) -1 (t 1 +t 2 +t 3 ) Wherein, τ is the control torque of the legs in the 6UPS parallel mechanism, τ 1 , τ 2 and τ 3 are all intermediate parameters, J is the velocity Jacobian matrix of the leg joints in the 6UPS parallel mechanism, is the adaptive disturbance estimation term, k 3 =diag(k 31 ,k 32 ,...,k 36 ), k 3i >0, is the inertia matrix without error, is the damping matrix without error, is the gravity matrix without error.

9. The vector force loading calibration method according to claim 2, It is characterized in that Each branch chain in the 6UPS parallel mechanism is provided with a composite ball joint, a Hooke's joint, a servo motor, a servo electric cylinder and a first tension and pressure sensor; one end of the first tension and pressure sensor is fixed to one end of the branch chain, the other end of the first tension and pressure sensor is connected to the moving platform through the Hooke's joint, the other end of the branch chain is connected to the static platform through the composite ball joint, and the servo motor is used to adjust the length of the branch chain through the servo electric cylinder.

10. The vector force loading calibration method according to claim 2, It is characterized in that The tension and pressure sensor group includes four second tension and pressure sensors, and the four second tension and pressure sensors are evenly distributed between the ball joint and the slide rail group.

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