Base-fixed multi-link motion system and its control method and control device

Abstract

This invention relates to a base-fixed multi-link motion system, its control method, and control device, belonging to the field of biomimetic simulation technology of mechanical environments, particularly concerning the structural design and control technology of six-degree-of-freedom parallel motion systems. It solves the limitations imposed on system bandwidth by lateral vibration of hydraulic cylinders and nonlinear factors in existing conventional hydraulically driven six-degree-of-freedom parallel mechanisms, increasing the system bandwidth to 100Hz. The system includes a mechanical structure subsystem, an acceleration detection subsystem, and a servo control subsystem. The hydraulic actuators are used to perform telescopic movements based on motion commands, driving the linkages to swing, thereby causing the platform to move and exhibit different postures. The base-fixed multi-link motion system and its control method and control device are applicable to the structural design and control of six-degree-of-freedom parallel motion systems.

Description

Technical Field

[0001] This invention relates to the field of biomimetic simulation technology of mechanical environment, and in particular to the structural design and control technology of six-degree-of-freedom parallel motion system. Background Technology

[0002] In the field of (mimicry) simulation testing technology for mechanical environments, multi-degree-of-freedom motion testing can realistically simulate actual dynamic environments to test the performance of large and complex structures under multi-degree-of-freedom motion excitation or expose defects and hidden dangers that are not easily detected. In fields such as high-speed rail, automobiles, and civil engineering, multi-degree-of-freedom motion testing can be used to test instruments or components that require environmental vibration or mechanical response characteristics, ensuring that these devices can function normally in high-altitude or extreme environments. In multi-degree-of-freedom motion testing, excitation is achieved through actuator vibration.

[0003] Actuators used for vibration excitation are mainly divided into electrically driven (such as voice coil driven) actuators and hydraulically driven actuators. Generally, actuators in conventional small-load applications mainly use electrically driven devices, while hydraulically driven actuators are required for tests with larger loads.

[0004] A commonly used device for multi-degree-of-freedom motion testing is a six-degree-of-freedom parallel mechanism, such as... Figure 15 As shown. For example, in the Chinese invention patent document with publication number "CN102004822A" and titled "Frequency Analysis Method for Spatial Six-DOF Parallel Motion System Based on Modality", a "spatial six-DOF parallel motion system" is described: the spatial (docking mechanism) six-DOF parallel motion system adopts the typical Stewart platform form of hydraulic drive, has ultra-large motion space capability, ultra-long outrigger working stroke and high system bandwidth, and its system working bandwidth can reach 10Hz.

[0005] It should be noted that in multi-degree-of-freedom motion tests, to fully reproduce the signal and achieve wideband performance testing of the specimen, the testing equipment must be able to reproduce high-bandwidth signals. The prerequisite for the equipment to reproduce wide-bandwidth signals is that the equipment's natural mechanical frequency must be high enough. Currently, conventional hydraulically driven six-degree-of-freedom parallel mechanisms can only reproduce signals of around 10Hz at most, which cannot meet the signal reproduction requirements of high-bandwidth instruments or components (requiring the reproduction of signals of at least 100Hz).

[0006] In conventional hydraulically driven six-DOF parallel mechanisms, the main reasons limiting the improvement of system bandwidth include: lateral vibration of the hydraulic cylinder and nonlinear factors of the system, specifically:

[0007] (1) Regarding "lateral vibration of hydraulic cylinders":

[0008] For general equipment, theoretically, the natural frequency of mechanical equipment is:

[0009]

[0010] Where f is the natural frequency, < is the mass matrix of the system, K is the stiffness matrix of the system, and λ is the eigenvalue of the matrix. It is evident that increasing the natural frequency of the equipment requires either increasing the system stiffness K or decreasing the system mass M.

[0011] However, for conventional hydraulically driven six-degree-of-freedom parallel mechanisms, the hydraulic actuators oscillate along with the platform during their extension and retraction. The large mass of the actuator body causes the inertial tensor during oscillation to affect the system's natural frequency. This is primarily because the lateral vibration natural frequency of the hydraulic cylinder is too low, limiting the natural frequency of the entire mechanism. According to mechanics, slender rods will bend laterally under pressure, and the greater the axial pressure, the greater the bending. In six-degree-of-freedom parallel mechanisms, the hydraulic cylinders used are often slender, and their working condition is frequently under axial heavy pressure. Therefore, for such hydraulic cylinders, the lateral vibration caused by lateral bending cannot be ignored; the lateral component is large during high-frequency motion, thus limiting the improvement of the system bandwidth.

[0012] (2) Regarding "nonlinear factors of the system":

[0013] For conventional hydraulically driven six-degree-of-freedom parallel mechanisms, the relevant control algorithms are mainly classical methods such as PID control. For hydraulically driven actuators, the drive signal passes through servo valves, hydraulic cylinders, connecting ball joints, platforms, and fixtures before finally reaching the test piece. This transmission process involves many nonlinear factors, which limit the improvement of system bandwidth. Traditional control algorithms cannot suppress these nonlinear factors, thus making it difficult to increase the system bandwidth.

[0014] In summary, there is an urgent need to make technological breakthroughs in the mechanical structure and control algorithms of six-degree-of-freedom parallel mechanisms in order to complete multi-degree-of-freedom motion tests of high-frequency wideband instruments or components and achieve the reproduction of high-frequency wideband signals of around 100Hz. Summary of the Invention

[0015] This invention proposes a base-fixed multi-link motion system and its control method and device, which solves the problem of the limitation on the improvement of system bandwidth caused by the lateral vibration of the hydraulic cylinder and the nonlinear factors of the system in the existing conventional hydraulically driven six-degree-of-freedom parallel mechanism, thereby increasing the system bandwidth to 100Hz.

[0016] The base-fixed multi-link motion system of the present invention includes: a mechanical structure subsystem, an acceleration detection subsystem, and a servo control subsystem;

[0017] The mechanical structure subsystem includes three embedded parts, a base, a support, six sets of linkage actuator legs, and a platform.

[0018] Each linkage actuator leg includes a hydraulic actuator, a cross hinge, and a linkage; the cross hinge includes a middle cross hinge and an upper cross hinge;

[0019] The lower cylinder of the hydraulic actuator is fixed to the base by a support; the base is fixedly connected to three embedded parts embedded in the foundation;

[0020] The end of the hydraulic actuator is connected to the lower end of the connecting rod via a central cross hinge; the upper end of the connecting rod is connected to the platform via an upper cross hinge.

[0021] The acceleration detection subsystem includes nine unidirectional acceleration sensors, divided into three groups of three; these three sensor groups are arranged on the platform.

[0022] The three sensor groups are arranged at 120 degrees and tangent to each other on the same circle, which is set as the reference circle;

[0023] The three sensor groups and the hinge point on the platform are on the same plane;

[0024] In each sensor group, the positive direction of the sensitive axis of one unidirectional accelerometer is vertically upward, the positive direction of the sensitive axis of another unidirectional accelerometer is the direction from the center of the reference circle toward the tangent point of the sensor group on the reference circle, and the positive direction of the sensitive axis of the last unidirectional accelerometer is the direction of the right tangent line drawn from the tangent point of the sensor group on the reference circle.

[0025] The acceleration detection subsystem is used to measure the acceleration of the platform's motion and send the acceleration measurement value to the servo control device;

[0026] The servo control device is used to obtain motion commands based on acceleration measurements and eight structural parameters of the mechanical structure subsystem.

[0027] The hydraulic actuator is used to perform telescopic movements according to motion commands, driving the connecting rod to swing, thereby making the platform move and present different postures;

[0028] The eight structural parameters of the mechanical structure subsystem are:

[0029] Each pair of upper cross hinges forms a cluster, for a total of three clusters. These three clusters are located on a reference circle with radius r. a The distance between the two hinge points within each cluster of the upper cross hinge is d. a Each pair of intermediate cross hinges forms a cluster, for a total of three clusters, all located on the same circle with radius r. b The distance between the two hinge points within each cluster of the central cross hinge is d.b The elevation angle of each hydraulic actuator to the horizontal plane is φ; the deflection angle of each hydraulic actuator is γ; the center length of each hydraulic actuator is l. o The length of each link is l c .

[0030] Furthermore, in a preferred embodiment, the lower cylinder of the hydraulic actuator is connected to a support by bolts.

[0031] Furthermore, in a preferred embodiment, a three-stage electro-hydraulic servo valve is installed on the lower cylinder of the hydraulic actuator to receive motion commands and control the movement of the hydraulic actuator.

[0032] Furthermore, in a preferred embodiment, the hydraulic actuator is provided with a flange at its end; the flange is connected to the lower end of the connecting rod via an intermediate cross hinge.

[0033] Furthermore, a preferred embodiment is provided in which each cross hinge includes two outer frames and two rotation axes, forming two rotational degrees of freedom.

[0034] This invention also proposes a control method for a base-fixed multi-link motion system, the method comprising the following steps:

[0035] Inertial frame representation steps: Obtain the acceleration measurement value collected by the acceleration detection subsystem of the base-fixed multi-link motion system described above; convert the acceleration measurement value into the acceleration of the corresponding sensor group's mounting point on the platform in the inertial frame;

[0036] Steps for estimating degree-of-freedom feedback signals: Based on the eight structural parameters of the mechanical subsystem and the acceleration of the corresponding sensor group at its mounting point on the platform in the inertial frame, obtain the degree-of-freedom feedback signals; the degree-of-freedom feedback signals include translational acceleration and platform rotational angular acceleration;

[0037] Vibration control outer loop steps: Based on the degree of freedom feedback signal, the error between the acceleration command signal and the response signal is corrected by calculating the inverse function to obtain the driving signal;

[0038] Servo control loop steps: Based on the eight structural parameters of the mechanical structure subsystem, the drive signal is used to perform servo control through inverse kinematics solution to obtain the elongation of each hydraulic actuator as the motion command, and control the hydraulic actuator to perform telescopic motion.

[0039] The present invention also proposes a control device for a base-fixed multi-link motion system, the device comprising the following modules:

[0040] Inertial frame representation module: acquires the acceleration measurement value collected by the acceleration detection subsystem of the base-fixed multi-link motion system described above; converts the acceleration measurement value into the acceleration of the corresponding sensor group's mounting point on the platform in the inertial frame;

[0041] The degree-of-freedom feedback signal estimation module obtains the degree-of-freedom feedback signals based on the eight structural parameters of the mechanical structure subsystem and the acceleration of the corresponding sensor group at its mounting point on the platform in the inertial frame. The degree-of-freedom feedback signals include translational acceleration and platform rotational angular acceleration.

[0042] Vibration control outer loop module: Based on the degree of freedom feedback signal, the error between the acceleration command signal and the response signal is corrected by calculating the inverse function to obtain the drive signal;

[0043] Servo control loop module: Based on the eight structural parameters of the mechanical structure subsystem, the drive signal is used to perform servo control through inverse kinematics solution to obtain the elongation of each hydraulic actuator as the motion command, and control the hydraulic actuator to perform telescopic motion.

[0044] The present invention also proposes a computer device comprising: a processor and a memory, the memory being used to store executable instructions of the processor, the processor being configured to execute the control method of the base-fixed multi-link motion system described above by executing the executable instructions.

[0045] The present invention also proposes a computer storage medium storing a computer program, wherein when the computer program is executed, the control method of the base-fixed multi-link motion system described above is performed.

[0046] The present invention also proposes a computer program product, including a computer program / instruction, which, when executed by a processor, implements the steps of the control method for the base-fixed multi-link motion system described above.

[0047] The present invention has the following beneficial effects:

[0048] 1. The base-fixed multi-link motion system of the present invention proposes a novel mechanical structure subsystem. By fixing the base of the hydraulic actuator cylinder and the linkage structure, the natural frequency of the system is improved, which makes up for the shortcomings of conventional pendulum actuators in achieving high-frequency motion.

[0049] 2. The control method of the base-fixed multi-link motion system described in this invention, by combining the inverse function drive control algorithm with the structural parameters of the mechanical structure subsystem, further expands the system bandwidth (up to 100Hz) while ensuring control accuracy, and finally realizes a six-degree-of-freedom high-frequency, high-precision motion function.

[0050] The base-fixed multi-link motion system, its control method, and control device described in this invention are applicable to the structural design and control of six-degree-of-freedom parallel motion systems. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the embodiments 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 from these drawings without creative effort.

[0052] Figure 1 This is a schematic diagram of the mechanical mechanism subsystem of a base-fixed multi-link motion system according to one embodiment of the present invention.

[0053] Figure 2 A schematic diagram of the hydraulic actuator layout is shown in one embodiment of the present invention;

[0054] Figure 3 This is a schematic diagram of the support structure in one embodiment of the present invention;

[0055] Figure 4 As one embodiment of the present invention, a stress analysis diagram of the support structure is shown.

[0056] Figure 5 This is a schematic diagram of the connecting rod in one embodiment of the present invention;

[0057] Figure 6 As one embodiment of the present invention, a stress analysis diagram of the connecting rod structure is shown.

[0058] Figure 7 This is a schematic diagram of the external structure of a cross hinge in one embodiment of the present invention;

[0059] Figure 8 This is a schematic diagram of the structure of the two rotating shafts inside the cross hinge in one embodiment of the present invention;

[0060] Figure 9 This is a schematic diagram of the cross hinge installation and range of motion in one embodiment of the present invention;

[0061] Figure 10 This is a schematic diagram of the structure of the embedded part in one embodiment of the present invention;

[0062] Figure 11 This is a schematic diagram of the platform structure in one embodiment of the present invention;

[0063] Figure 12 As one embodiment of the present invention, a stress analysis diagram of the platform structure is shown.

[0064] Figure 13 This is a schematic diagram showing the position arrangement and installation direction of a unidirectional acceleration sensor in one embodiment of the present invention;

[0065] Figure 14 A flowchart of a control method for a base-fixed multi-link motion system is provided in one embodiment of the present invention.

[0066] Figure 15 This is a schematic diagram of the structure of a conventional six-degree-of-freedom parallel mechanism in one embodiment of the present invention;

[0067] Figure label:

[0068] 1. Embedded part; 2. Base; 3. Linkage actuator support leg; 4. Platform; 5. Support; 5-1, 5-2. Rib plate; 5-3. Floor; 6. Hydraulic actuator; 7. Three-stage electro-hydraulic servo valve; 8-1, 8-2. Outer frame; 9-1, 9-2. Rotary shaft; 10. Linkage rod; 11. Flange. Detailed Implementation

[0069] To make the technical solutions and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail and completely below with reference to the accompanying drawings. The various embodiments described below are only some preferred embodiments of the present invention, and not all of them; the various embodiments described below are intended to explain the present invention and should not be construed as limiting the present invention; reasonable combinations of the technical features defined in the various embodiments of the present invention, as well as all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort, are all within the scope of protection of the present invention.

[0070] In one embodiment, a base-fixed multi-link motion system is provided, the system comprising: a mechanical structure subsystem, an acceleration detection subsystem, and a servo control subsystem;

[0071] The mechanical structure subsystem includes three embedded parts 1, a base 2, a support 5, six sets of linkage actuator legs 3, and a platform 4, all embedded in the foundation.

[0072] Each linkage actuator leg 3 includes a hydraulic actuator 6, a cross hinge, and a linkage 10; the cross hinge includes a middle cross hinge and an upper cross hinge.

[0073] The lower cylinder of the hydraulic actuator 6 is fixed to the base 2 by the support 5; the base 2 is fixedly connected to the three embedded parts 1 embedded in the foundation.

[0074] The end of the hydraulic actuator 6 is connected to the lower end of the connecting rod 10 via a central cross hinge; the upper end of the connecting rod 10 is connected to the platform 4 via an upper cross hinge.

[0075] The acceleration detection subsystem includes nine unidirectional acceleration sensors, divided into three groups of three; these three sensor groups are arranged on platform 4.

[0076] The three sensor groups are arranged at 120 degrees and tangent to each other on the same circle, which is set as the reference circle;

[0077] The hinge points of the three sensor groups and platform 4 are on the same plane;

[0078] In each sensor group, the positive direction of the sensitive axis of one unidirectional accelerometer is vertically upward, the positive direction of the sensitive axis of another unidirectional accelerometer is the direction from the center of the reference circle toward the tangent point of the sensor group on the reference circle, and the positive direction of the sensitive axis of the last unidirectional accelerometer is the direction of the right tangent line drawn from the tangent point of the sensor group on the reference circle.

[0079] The acceleration detection subsystem is used to measure the acceleration of the platform 4 and send the acceleration measurement value to the servo control device;

[0080] The servo control device is used to obtain motion commands based on acceleration measurements and eight structural parameters of the mechanical structure subsystem.

[0081] The hydraulic actuator 6 is used to perform telescopic movements according to motion commands, driving the connecting rod 10 to swing, thereby causing the platform 4 to move and present different postures.

[0082] The eight structural parameters of the mechanical structure subsystem are:

[0083] Each pair of upper cross hinges forms a cluster, for a total of three clusters. These three clusters are located on a reference circle with radius r. a The distance between the two hinge points within each cluster of the upper cross hinge is d. a Each pair of intermediate cross hinges forms a cluster, for a total of three clusters, all located on the same circle with radius r. b The distance between the two hinge points within each cluster of the central cross hinge is d. b The elevation angle of each hydraulic actuator 6 to the horizontal plane is φ; the deflection angle of each hydraulic actuator 6 is γ; the center length of each hydraulic actuator 6 is l. o The length of each link 10 is l. c .

[0084] In this embodiment, 120deg represents an angle of 120 degrees.

[0085] In this embodiment, the hinge point on platform 4 is the position where platform 4 is hinged to the cross hinge (upper cross hinge).

[0086] In this embodiment, nine unidirectional acceleration sensors, such as... Figure 13 As shown:

[0087] The three sensor groups are arranged at 120 degrees and tangent to each other on the same circle, which is designated as the reference circle; the center of the reference circle is O. b The radius of the reference circle is r. a ;

[0088] exist Figure 13 In the diagram, the red line represents the sensitive axis, and the blue line indicates the positive direction:

[0089] Suppose there are 9 unidirectional acceleration sensors a1, a2, a3, a4, a5, a6, a7, a8 and a9, where a1, a6 and a7 form one group, a2, a3 and a8 form another group, and a4, a5 and a9 form yet another group.

[0090] For each sensor group, the positive directions of the sensing axes of the three unidirectional accelerometers form a right-hand screw:

[0091] The sensitive axes of a7, a8, and a9 are perpendicular to the horizontal plane, and their positive direction is vertically upward. Figure 13 (Not marked in the text);

[0092] The positive directions of the sensitive axes a1, a3, and a5 are the directions from the center of the reference circle toward the point of tangency of the sensor group on the reference circle, such as y. aac1 y aac2 and y aac3 As shown;

[0093] The positive directions of the sensitive axes a2, a4, and a6 are the directions of the right-hand tangent line drawn from the point of tangency of the sensor group on the reference circle, such as x. aac1 x aac2 and x aac3 As shown.

[0094] In this embodiment, the six sets of linkage actuator legs 3 are used to provide the driving force for the movement of the platform 4.

[0095] In this embodiment, the base 2 is an equilateral triangle; two supports 5 are fixedly installed at the three corners of the base 2, and each support 5 is connected to the lower cylinder of a hydraulic actuator 6; for a hydraulic actuator 6 installed at any corner of the base 2, the angle between the direction of the perpendicular line drawn from the end of the hydraulic actuator 6 to the base 2 and the direction of the center line of the base 2 is the deflection angle.

[0096] In this embodiment, the three corners of the base 2 are respectively fixedly connected to a pre-embedded part 1 embedded in the foundation.

[0097] In this embodiment, the lower end of the linkage actuator leg 3 is directly fixed to the base 2 via a rigid support 5, forming an "integral rigid connection". This design improves rigidity in the following ways:

[0098] "Eliminating intermediate force transmission links": There are no flexible hinges or complex base structures between the outriggers and the base. They are directly fixed by high-strength bolts or welding, reducing the risk of deformation at the connection points.

[0099] "Stress distribution optimization": The centralized rigid fixation of the support can evenly distribute the load transmitted by the outriggers, avoiding platform deformation caused by local stress concentration.

[0100] "Enhanced vibration resistance": As an overall load-bearing frame, the base can effectively suppress structural resonance under high-frequency vibration.

[0101] In addition, the base 2 is an "integral rigid structure," typically made of high-rigidity materials (such as cast iron or welded steel structures), and its bending and torsional resistance is enhanced through reinforcing rib design (embedded parts). The leg fixing point (support 5) is integrated with the base, ensuring that the mounting reference surface of the leg is rigidly coupled with the base, reducing stiffness loss due to assembly errors.

[0102] Meanwhile, the rigid connection between the outrigger 3 and the base 2 forms a "fully constrained boundary condition". The outrigger only bears the axial load, and the lateral force is directly absorbed by the base, avoiding the bending moment introduced by the multi-degree-of-freedom hinge of the support.

[0103] Meanwhile, the high-rigidity design is suitable for "high-load, high-precision positioning scenarios" and can withstand greater inertial forces while maintaining dynamic stability.

[0104] In summary, the "rigid integrated design of the legs and base" significantly improves the system's rigidity, making it suitable for high-load and high-dynamic-response scenarios.

[0105] In this embodiment, the eight structural parameters determine the kinematic and dynamic characteristics of the mechanical structure subsystem.

[0106] In this embodiment, the lower end of the linkage actuator leg 3 (i.e., the cylinder of the lower part of the hydraulic actuator 6) is fixed to the base 2 by the support 5, which eliminates lateral sway and improves the rigidity of the mechanical structure subsystem.

[0107] In this embodiment, the upper surface of platform 4 is used to connect the load, and the load completes various posture movements under the drive of the platform.

[0108] It should be noted that actuators can be driven by various methods, including hydraulic drives and electric motor (such as voice coil motors) drives. Actuators using different drive methods have different performance characteristics and application scenarios. For example, the table below compares the differences between voice coil motor and hydraulic actuators:

[0109]

[0110] In another embodiment, the three embedded parts 1 are pre-cast in the foundation pit (or foundation).

[0111] In another embodiment, each embedded part 1 includes two base plates and a plurality of long bolts that fix the two base plates together; one base plate is fixedly connected to the base 2, and the other base plate is fixed to the bottom of the foundation.

[0112] In another embodiment, platform 4 adopts a grid structure and is made of steel plates welded into a whole.

[0113] It should be noted that, in order to accurately transmit the force and motion laws of the servo control subsystem to the load, platform 4 should minimize its weight while ensuring sufficient stiffness and a high natural frequency. In this embodiment, a grid structure is adopted, which is welded from steel plates into a whole, effectively reducing weight while ensuring sufficient stiffness and a high natural frequency.

[0114] In this embodiment, a natural frequency analysis (stress analysis) was performed on platform 4. The boundary conditions for the stress analysis were: full constraint on the surfaces of the six hinge mounting plates of the platform; and the inertial force generated under load acceleration conditions was applied as the load to a certain area on the upper surface of the platform. The natural frequency analysis results are as follows: Figure 12 As shown. Some simulation parameters in the natural frequency analysis are as follows:

[0115] Model Name: Upper Platform - Frequency-Force - V3-181229;

[0116] Example name: Example 1;

[0117] Graphic type: Frequency shift 7;

[0118] Pattern shape: 7 values ​​= 186.28 Hz;

[0119] Deformation ratio: 2.75588.

[0120] Analysis of the inherent frequency shows that the inherent frequency of platform 4 is basically twice that of the expected reproducible signal (100Hz). In the later stage, the signal can be increased to the required bandwidth through control algorithms.

[0121] In another embodiment, the lower cylinder of the hydraulic actuator 6 is connected to the support 5 by bolts.

[0122] In this embodiment, the lower cylinder of the hydraulic actuator 6 is connected to the support 5 by bolts to ensure that the cylinder remains stationary when the piston of the hydraulic actuator 6 performs telescopic movements.

[0123] In another embodiment, the support 5 includes two ribs 5-1 and 5-2 and a floor 5-3; in order to ensure the fixing effect of the cylinder, the two ribs 5-1 and 5-2 fix the hydraulic actuator 6 in an elevation angle of φ with respect to the horizontal plane; the two ribs 5-1 and 5-2 are vertically fixed on the floor 5-3; the floor 5-3 is fixedly connected to the base 2 by bolts.

[0124] In this embodiment, if the strength of the entire support 5 is insufficient, it will have a significant impact on the vibration effect of the entire hydraulic actuator 6. Therefore, the support 5 is made of high-strength material.

[0125] In this embodiment, the inherent characteristics (stress analysis) of support 5 were analyzed, such as... Figure 4 As shown. Some simulation parameters in the inherent characteristic analysis are as follows:

[0126] Model Name: Mounting Base (Modified) - Frequency - 190107;

[0127] Example name: Example 1;

[0128] Graphic type: Frequency shift 7;

[0129] Pattern shape: 7 values ​​= 432.17 Hz;

[0130] Deformation ratio: 0.481301.

[0131] Analysis of inherent characteristics shows that the support mechanism obtained under the premise of satisfying dynamic force and strength has a natural frequency that is much greater than twice the frequency of the 100Hz signal to be reproduced, thus meeting the requirements.

[0132] In another embodiment, a three-stage electro-hydraulic servo valve 7 is installed on the lower cylinder of the hydraulic actuator 6 to receive motion commands and control the movement of the hydraulic actuator 6.

[0133] In another embodiment, the hydraulic actuator 6 is provided with a flange 11 at its end; the flange 11 is connected to the lower end of the connecting rod 10 via a central cross hinge.

[0134] In another embodiment, the connecting rod 10 is a lightweight rod.

[0135] In this embodiment, a lightweight rod is used as the connecting rod 10, which can indirectly increase the natural frequency of the entire system.

[0136] On the one hand, the introduction of lightweight connecting rods reduces the piston stroke of the hydraulic actuator. According to hydraulic transmission theory, a reduced piston stroke can increase the natural frequency of the hydraulic system, thereby indirectly increasing the natural frequency of the entire system.

[0137] On the other hand, the introduction of lightweight connecting rods reduces the driving mass at the hydraulic actuator end and also increases the natural frequency of the entire system.

[0138] In this embodiment, in order to reduce the influence of the link inertia tensor on the control characteristics, the link 10 is required to be a high-strength, lightweight link.

[0139] In another embodiment, while ensuring sufficient strength, a high-strength, lightweight rod can be obtained through material selection or structural design. For example, steel can be selected as the material, and the structure can be designed as a hollow, thin-walled cylindrical structure.

[0140] In another embodiment, the connecting rod 10 is made of Q235, Q345, or Q460 steel to ensure it is a high-strength material.

[0141] In this embodiment, stress analysis was performed on the connecting rod 10, such as... Figure 6 As shown. Some simulation parameters in the stress analysis are as follows:

[0142] Model Name: Linkage - Frequency-Force - V2-181228;

[0143] Example name: Example 1;

[0144] Graphic type: Frequency shift 7;

[0145] Pattern shape: 7 values ​​= 787.73 Hz;

[0146] Deformation ratio: 0.183746.

[0147] The stress analysis shows that the natural frequency of the linkage structure obtained under the premise of satisfying the dynamic force and strength requirements is much greater than twice the frequency of the 100Hz signal to be reproduced, thus meeting the requirements.

[0148] In another embodiment, each cross hinge includes two outer frames 8-1, 8-2 and two rotation axes 9-1, 9-2, forming two rotational degrees of freedom.

[0149] In another embodiment, the installation and range of motion of the cross hinge are as follows: Figure 9 As shown:

[0150] (1) Installation of the cross hinge:

[0151] Let k1 and m1 represent the axes of rotation of the two axes of rotation of the upper cross hinge, and k2 and m2 represent the axes of rotation of the two axes of rotation of the middle cross hinge. The mounting plane of the upper cross hinge on platform 4 is the first plane, and the plane perpendicular to the horizontal plane and passing through the axis of the hydraulic actuator 6 is the second plane. The axis vector of the hydraulic actuator 6 is l. n The axis vector of link 10 is lcn ;

[0152] When platform 4 is installed in the middle position, for each linkage actuator leg 3:

[0153] The axis vector l of link 10 cn Perpendicular to the first plane (i.e., the mounting plane);

[0154] The axis k1 of rotation of the upper cross hinge is parallel to the second plane;

[0155] For the upper cross hinge and the middle cross hinge located at the two ends of the same link 10, the rotation axis m1 of the upper cross hinge is perpendicular to the rotation axis m2 of the middle cross hinge.

[0156] (2) The range of motion of the cross hinge is the rotation angle around the two axes of rotation of the cross hinge:

[0157] The range of motion of the two rotating axes k1 and m1 of the upper cross hinge:

[0158] The range of motion of the axis k1 of the rotation shaft: the range of the angle between m1 and the first plane;

[0159] The range of motion of the rotation axis m1: k1 and m1 with l cn The range of the included angles of the planes formed;

[0160] The range of motion of the two rotation axes k2 and m2 of the central cross hinge:

[0161] The range of motion of the rotation axis k2: m2 and l n The range of the included angle;

[0162] The range of motion of the rotation axis m2: k2 and m2 with l cn The range of the included angles of the planes formed.

[0163] In another embodiment, a control method for a base-fixed multi-link motion system is provided, the method comprising the following steps:

[0164] Inertial frame representation steps: Obtain the acceleration measurement value collected by the acceleration detection subsystem of the base-fixed multi-link motion system described in any of the above embodiments; convert the acceleration measurement value into the acceleration of the corresponding sensor group at the mounting point on platform 4 in the inertial frame;

[0165] Steps for estimating degree-of-freedom feedback signals: Based on the eight structural parameters of the mechanical structure subsystem and the acceleration of the corresponding sensor group at its mounting point on platform 4 in the inertial frame, obtain the degree-of-freedom feedback signals; the degree-of-freedom feedback signals include translational acceleration and platform rotational angular acceleration;

[0166] Vibration control outer loop steps: Based on the degree of freedom feedback signal, the error between the acceleration command signal and the response signal is corrected by calculating the inverse function to obtain the driving signal;

[0167] Servo control loop steps: Based on the eight structural parameters of the mechanical structure subsystem, the drive signal is used to perform servo control through inverse kinematics solution to obtain the elongation of each hydraulic actuator 6 as a motion command, and control the hydraulic actuator 6 to perform telescopic motion.

[0168] In another embodiment, the acceleration of the mounting point of the i-th sensor group on platform 4 in the inertial frame is:

[0169] A i =T i A measure,i ;

[0170] Among them, A i It is a 3×1 matrix; i = 1, 2, 3, representing 3 sensor groups respectively; T i A is the transformation matrix; measure,i It is a matrix composed of the acceleration measurement values ​​output by each sensitive axis of the i-th sensor group, and is a 3×1 matrix.

[0171] In this embodiment, the control method is built into the servo control subsystem of the base-fixed multi-link motion system and executed.

[0172] In another embodiment, the translational acceleration is:

[0173]

[0174] The rotational angular acceleration of the platform is:

[0175]

[0176] Among them, A i,j Let ε represent the acceleration of the i-th sensor group installation point in the direction corresponding to value j in the inertial frame, where j=1 is the x-direction in the inertial frame; j=2 is the y-direction in the inertial frame; j=3 is the z-direction in the inertial frame; ε x Let ε be the angular acceleration in the x-direction. y Let ε be the angular acceleration in the y-direction. z Let be the angular acceleration in the z-direction.

[0177] In another embodiment, the vibration control outer ring step includes the following steps:

[0178] The steps to obtain the time-domain error of the acceleration given signal and the response signal are as follows:

[0179] e(t) = A in (t)-A out(t);

[0180] Among them, A in (t) is the acceleration given signal; A out (t) is the degree-of-freedom feedback signal A. c ε x ε y and ε z The vector representation of is the response signal;

[0181] The steps to obtain the frequency domain error of the acceleration given signal and the response signal are as follows:

[0182] E(f) = FFT(e(t));

[0183] Steps to obtain drive signals:

[0184] ΔDrv(f)=Z(f)E(f);

[0185] Where Z(f) is the inverse function, Z(f) = G xy (f) / G xx (f), G inout (f) is the cross-spectral density estimation matrix of the acceleration given signal response signal, G inin (f) is the self-spectral density estimation matrix of the given acceleration signal.

[0186] In another embodiment, the inverse kinematic solution is:

[0187]

[0188] Where, Δd i The elongation of each hydraulic actuator 6; g ki The center coordinates of support 5; b ki It is the center coordinate of flange 11 at the end of hydraulic actuator 6; g ki and b ki The values ​​are calculated based on the coordinates of the degrees of freedom represented by the eight structural parameters of the mechanical structure subsystem.

[0189] In this embodiment, since the measurement result (acceleration measurement value) of the unidirectional acceleration sensor is a value of the sensitive axis, it is necessary to convert this value to an inertial frame of reference.

[0190] In this embodiment, compared with conventional servo control, a vibration control outer loop is added to the servo control loop. Combined with the structural parameters of the mechanical structure subsystem, the limitation of nonlinear factors on the improvement of system bandwidth is overcome.

[0191] In this embodiment, the vibration control outer loop step is based on an iterative control method (or inverse function driven control algorithm) using the inverse function of acceleration, which corrects the acceleration control error by obtaining the inverse function of the system.

[0192] It should be noted that for hydraulically driven actuators, if traditional servo control methods such as PID are used, many nonlinear factors will be generated during signal transmission. These nonlinear factors will limit the improvement of system bandwidth. Specifically:

[0193] The reasons why nonlinear factors limit the improvement of system bandwidth can be summarized at the following levels:

[0194] (1) Phase distortion caused by nonlinearity of mechanical structure:

[0195] Nonlinear factors such as ball joint clearance, connecting rod elastic deformation, and cross joint friction in a hydraulic drive chain introduce a time-varying hysteresis effect. During high-frequency motion:

[0196] "Accumulated phase lag": The phase lag caused by the superposition of the servo valve response delay (about 1-2ms) and mechanical nonlinearity causes the phase margin of the system's open-loop transfer function to drop sharply in the high-frequency range (>50Hz), which can easily lead to resonance.

[0197] "Energy dissipation": For example, friction of the cross joint can cause the high-frequency vibration energy to be absorbed, making the system unable to accurately reproduce the high-frequency acceleration signal (such as the waveform clipping of a 100Hz sine wave).

[0198] (2) The inherent nonlinearity of hydraulic systems contradicts bandwidth:

[0199] Hydraulic actuators inherently possess nonlinearities such as "flow-pressure coupling, hydraulic compressibility, and valve spool dead zone."

[0200] "Flow saturation": When the piston speed approaches the hydraulic pump's oil supply limit during high-frequency motion, the proportion of the nonlinear term "leakage coefficient × load pressure" in the flow equation increases, which undermines the effectiveness of the linearization model.

[0201] "Pressure pulsation resonance": When the three-stage servo valve switches at high frequency, the compressibility of the oil (bulk elastic modulus β≈1.4GPa) and the pipeline cavity form a resonant system. If the resonant frequency is close to the target bandwidth (such as 100Hz), it will cause instability.

[0202] (3) Limitations of traditional control algorithms:

[0203] The shortcomings of traditional linear control methods such as PID control when dealing with nonlinearity:

[0204] "Gain scheduling failure": The "Stribeck curve characteristic" of the hydraulic cylinder friction force changes with speed, causing the system damping coefficient to vary over time, and fixed PID parameters cannot cover the entire frequency band.

[0205] "Harmonic distortion amplification": For example, high-frequency components (>50Hz) in the platform acceleration signal generate "superharmonic resonance" (such as the 3rd harmonic at 150Hz) after passing through a nonlinear element, which cannot be suppressed by traditional frequency domain correction.

[0206] "Lack of inverse dynamics": The lack of a feedforward compensation mechanism makes it impossible to compensate for nonlinear transmission characteristics.

[0207] It should be noted that nonlinear factors result in a difference between the actual response signal and the given signal. In this embodiment, the control method uses an inverse function approach to modify the driving signal to compensate for the error caused by the system's nonlinear factors. This is equivalent to correcting the given signal (driving signal) before inputting it into the system. After several iterations of control, the actual output signal of the system gradually matches the initial reproduced signal, thereby increasing the system bandwidth to 100Hz.

[0208] In this embodiment, after adopting inverse function iterative control, the system's -3dB bandwidth is increased from "52Hz" of the traditional PID to "98Hz", and the 100Hz sine wave tracking phase lag is reduced from 28° to 6°.

[0209] In another embodiment, a control device for a base-fixed multi-link motion system is provided, the device comprising the following modules:

[0210] Inertial frame representation module: acquires the acceleration measurement value collected by the acceleration detection subsystem of the base-fixed multi-link motion system described in any of the above embodiments; converts the acceleration measurement value into the acceleration of the corresponding sensor group at the mounting point on platform 4 in the inertial frame;

[0211] The degree-of-freedom feedback signal estimation module obtains the degree-of-freedom feedback signals based on the eight structural parameters of the mechanical structure subsystem and the acceleration of the corresponding sensor group at its mounting point on platform 4 in the inertial frame. The degree-of-freedom feedback signals include translational acceleration and platform rotational angular acceleration.

[0212] Vibration control outer loop module: Based on the degree of freedom feedback signal, the error between the acceleration command signal and the response signal is corrected by calculating the inverse function to obtain the drive signal;

[0213] Servo control loop module: Based on the eight structural parameters of the mechanical structure subsystem, the drive signal is used to perform servo control through inverse kinematics solution to obtain the extension amount of each hydraulic actuator 6 as a motion command, and control the hydraulic actuator 6 to perform telescopic motion.

[0214] The above description of several specific embodiments further details the technical solution provided by the present invention in order to highlight the advantages and benefits of the technical solution provided by the present invention. However, the above-described specific embodiments are not intended to limit the present invention. Any reasonable modifications and improvements to the present invention, reasonable combinations of embodiments, and equivalent substitutions based on the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A control method for a base-fixed multi-link motion system, characterized in that, The method includes the following steps: Inertial frame representation steps: Obtain acceleration measurement values ​​collected by the acceleration detection subsystem of the base-fixed multi-link motion system; convert the acceleration measurement values ​​into the acceleration of the corresponding sensor group's mounting point on the platform in the inertial frame; Steps for estimating degree-of-freedom feedback signals: Based on the eight structural parameters of the mechanical subsystem and the acceleration of the corresponding sensor group at its mounting point on the platform in the inertial frame, obtain the degree-of-freedom feedback signals; the degree-of-freedom feedback signals include translational acceleration and platform rotational angular acceleration; Vibration control outer loop steps: Based on the degree of freedom feedback signal, the error between the acceleration command signal and the response signal is corrected by calculating the inverse function to obtain the driving signal; Servo control loop steps: Based on the eight structural parameters of the mechanical structure subsystem, the drive signal is used to perform servo control through inverse kinematics solution to obtain the elongation of each hydraulic actuator as a motion command to control the hydraulic actuator to perform telescopic motion; The base-fixed multi-link motion system includes: a mechanical structure subsystem, an acceleration detection subsystem, and a servo control subsystem; The mechanical structure subsystem includes three embedded parts, a base, a support, six sets of linkage actuator legs, and a platform. Each linkage actuator leg includes a hydraulic actuator, a cross hinge, and a linkage; the cross hinge includes a middle cross hinge and an upper cross hinge; The lower cylinder of the hydraulic actuator is fixed to the base by a support; the base is fixedly connected to three embedded parts embedded in the foundation; The end of the hydraulic actuator is connected to the lower end of the connecting rod via a central cross hinge; the upper end of the connecting rod is connected to the platform via an upper cross hinge. The acceleration detection subsystem includes nine unidirectional acceleration sensors, divided into three groups of three; these three sensor groups are arranged on the platform. The three sensor groups are arranged at 120 degrees and tangent to each other on the same circle, which is set as the reference circle; The three sensor groups and the hinge point on the platform are on the same plane; In each sensor group, the positive direction of the sensitive axis of one unidirectional accelerometer is vertically upward, the positive direction of the sensitive axis of another unidirectional accelerometer is the direction from the center of the reference circle toward the tangent point of the sensor group on the reference circle, and the positive direction of the sensitive axis of the last unidirectional accelerometer is the direction of the right tangent line drawn from the tangent point of the sensor group on the reference circle. The acceleration detection subsystem is used to measure the acceleration of the platform's motion and send the acceleration measurement value to the servo control device; The servo control device is used to obtain motion commands based on acceleration measurements and eight structural parameters of the mechanical structure subsystem. The hydraulic actuator is used to perform telescopic movements according to motion commands, driving the connecting rod to swing, thereby making the platform move and present different postures; The eight structural parameters of the mechanical structure subsystem are: Each pair of upper cross hinges forms a cluster, for a total of three clusters. These three clusters are located on a reference circle with a radius of [radius value missing]. r a The distance between the two hinge points within each cluster of the upper cross hinge is... d a Each pair of intermediate cross hinges forms a cluster, for a total of three clusters. All three clusters lie on the same circle with a radius of [radius value missing]. r b The distance between the two hinge points within each cluster of the central cross hinge is... d b The elevation angle of each hydraulic actuator to the horizontal plane is... φ The deflection angle of each hydraulic actuator is γ; the median length of each hydraulic actuator is... l o The length of each link is l c .

2. The control method for the base-fixed multi-link motion system according to claim 1, characterized in that, The lower cylinder of the hydraulic actuator is connected to the support by bolts.

3. The control method for the base-fixed multi-link motion system according to claim 1, characterized in that, A three-stage electro-hydraulic servo valve is installed on the lower cylinder of the hydraulic actuator to receive motion commands and control the movement of the hydraulic actuator.

4. The control method for the base-fixed multi-link motion system according to claim 1, characterized in that, The hydraulic actuator is provided with a flange at its end; the flange is connected to the lower end of the connecting rod via a central cross hinge.

5. The control method for the base-fixed multi-link motion system according to claim 1, characterized in that, Each cross hinge consists of two outer frames and two rotation axes, forming two rotational degrees of freedom.

6. A control device for a base-fixed multi-link motion system, characterized in that, The device includes the following modules: Inertial frame representation module: acquires acceleration measurement values ​​collected by the acceleration detection subsystem of the base-fixed multi-link motion system; converts the acceleration measurement values ​​into the acceleration of the corresponding sensor group's mounting point on the platform in the inertial frame; The degree-of-freedom feedback signal estimation module obtains the degree-of-freedom feedback signals based on the eight structural parameters of the mechanical structure subsystem and the acceleration of the corresponding sensor group at its mounting point on the platform in the inertial frame. The degree-of-freedom feedback signals include translational acceleration and platform rotational angular acceleration. Vibration control outer loop module: Based on the degree of freedom feedback signal, the error between the acceleration command signal and the response signal is corrected by calculating the inverse function to obtain the drive signal; Servo control loop module: Based on the eight structural parameters of the mechanical structure subsystem, the drive signal is used to perform servo control through inverse kinematics solution to obtain the elongation of each hydraulic actuator as a motion command to control the hydraulic actuator to perform telescopic motion; The base-fixed multi-link motion system includes: a mechanical structure subsystem, an acceleration detection subsystem, and a servo control subsystem; The mechanical structure subsystem includes three embedded parts, a base, a support, six sets of linkage actuator legs, and a platform. Each linkage actuator leg includes a hydraulic actuator, a cross hinge, and a linkage; the cross hinge includes a middle cross hinge and an upper cross hinge; The lower cylinder of the hydraulic actuator is fixed to the base by a support; the base is fixedly connected to three embedded parts embedded in the foundation; The end of the hydraulic actuator is connected to the lower end of the connecting rod via a central cross hinge; the upper end of the connecting rod is connected to the platform via an upper cross hinge. The acceleration detection subsystem includes nine unidirectional acceleration sensors, divided into three groups of three; these three sensor groups are arranged on the platform. The three sensor groups are arranged at 120 degrees and tangent to each other on the same circle, which is set as the reference circle; The three sensor groups and the hinge point on the platform are on the same plane; In each sensor group, the positive direction of the sensitive axis of one unidirectional accelerometer is vertically upward, the positive direction of the sensitive axis of another unidirectional accelerometer is the direction from the center of the reference circle toward the tangent point of the sensor group on the reference circle, and the positive direction of the sensitive axis of the last unidirectional accelerometer is the direction of the right tangent line drawn from the tangent point of the sensor group on the reference circle. The acceleration detection subsystem is used to measure the acceleration of the platform's motion and send the acceleration measurement value to the servo control device; The servo control device is used to obtain motion commands based on acceleration measurements and eight structural parameters of the mechanical structure subsystem. The hydraulic actuator is used to perform telescopic movements according to motion commands, driving the connecting rod to swing, thereby making the platform move and present different postures; The eight structural parameters of the mechanical structure subsystem are: Each pair of upper cross hinges forms a cluster, for a total of three clusters. These three clusters are located on a reference circle with a radius of [radius value missing]. r a The distance between the two hinge points within each cluster of the upper cross hinge is... d a Each pair of intermediate cross hinges forms a cluster, for a total of three clusters. All three clusters lie on the same circle with a radius of [radius value missing]. r b The distance between the two hinge points within each cluster of the central cross hinge is... d b The elevation angle of each hydraulic actuator to the horizontal plane is... φ The deflection angle of each hydraulic actuator is γ; the median length of each hydraulic actuator is... l o The length of each link is l c .

7. A computer device, comprising: A processor and a memory, characterized in that the memory is used to store executable instructions of the processor, the processor being configured to perform the control method of the base-fixed multi-link motion system of claim 1 by executing the executable instructions.

8. A computer storage medium, characterized in that, The storage medium stores a computer program, and when the computer program is run, it executes the control method of the base-fixed multi-link motion system as described in claim 1.

9. A computer program product comprising a computer program / instructions, characterized in that, When the computer program / instruction is executed by the processor, it implements the steps of the control method for the base-fixed multi-link motion system as described in claim 1.

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