Method and system for motion control of a tendon-driven spatial robot under variable load

Abstract

The application discloses a kind of tendon-driven space manipulator motion control method and system under variable load, the method includes: the geometric analysis is carried out to tendon-driven space manipulator, constructs the relationship between the length of rope and joint rotation angle formula;Tendon-driven space manipulator is modeled;Considering tracking error, motion controller is constructed based on the dynamic equation;According to task requirement, trajectory planning is carried out;According to the joint motion trajectory, tendon-driven space manipulator is driven, and real-time feedback information is obtained and trajectory tracking control is carried out in combination with the motion controller.The system includes: mapping relationship module, dynamic modeling module, controller construction module, initial trajectory construction module and tracking control module.Through using the application, variable load situation can be coped with, the stability and precision of tendon-driven space manipulator when high speed high-precision motion are ensured.The application can be widely applied in the field of manipulator control.

Description

Technical Field

[0001] This invention relates to the field of robotic arm control, and more particularly to a motion control method and system for a tendon-driven spatial robotic arm under variable load. Background Technology

[0002] With the continuous advancement of aerospace technology and space technology, the number of various space facilities is constantly increasing, and the complexity of missions is rising daily. On the one hand, the extreme conditions of the space environment, such as microgravity, extreme temperature differences, and strong radiation, constrain astronauts' survival and operational capabilities outside the spacecraft. On the other hand, astronauts are ill-equipped for complex and demanding tasks involving large spacecraft with high quality, high inertia, and long spans, such as the construction and maintenance of large space facilities in orbit, docking and parking of spacecraft, capture and acquisition of non-cooperative targets, and the release and recovery of satellites. Therefore, applying space robotics technology to replace astronauts in performing in-orbit operational tasks has become an inevitable trend in the field of space exploration.

[0003] The technology of assembling large modular structures in orbit using space robotic arms to build space structure platforms has advantages such as strong feasibility, high safety and stability, large construction scope, and low cost, making it one of the best technical paths for the in-orbit construction of ultra-large spacecraft. However, ultra-large spacecraft are not only enormous in overall size, but their assembly modules are also often tens of meters in size and weigh hundreds of kilograms or even several tons. This requires space robotic arms providing in-orbit services to have greater carrying capacity, long-span operation capabilities, safe and stable operation performance, and efficient and low-power motion characteristics. However, traditional rotary joint space robotic arms are difficult to meet the above-mentioned requirements for in-orbit operation tasks due to defects such as flexible vibration, high joint rotational inertia, high system power consumption, and poor compliance.

[0004] A tendon-driven space robotic arm has emerged, which, through a unique rope-driven structure, can achieve a long operating arm span while maintaining lightweight, high extension-to-retraction ratio, and high rigidity. It represents one of the important development directions for large space robotic arms.

[0005] However, previous studies have focused on relatively small robotic arms, typically within a few meters. The methods and conclusions drawn from these studies are often inapplicable or invalid for large tendon-driven robotic arms with arm spans of tens of meters. Existing research cannot solve the technical challenges of assembling large spatial structures in orbit with tendon-driven space robotic arms, and there has been no in-depth research on the high-speed, high-precision motion control issues under variable loads involved in the assembly operations of large structures by tendon-driven robotic arms in space. Summary of the Invention

[0006] In view of this, in order to solve the problem of high-speed and high-precision motion control under variable load in the on-orbit assembly of large space structures by tendon-driven space robotic arms, this invention proposes a motion control method for tendon-driven space robotic arms under variable load, the method comprising the following steps:

[0007] Geometric analysis was performed on the tendon-driven spatial robotic arm to construct the relationship between rope length and joint rotation angle;

[0008] Based on the relationship between the rope length and the joint rotation angle, the tendon-driven spatial manipulator is modeled to obtain the dynamic equations;

[0009] Considering tracking error, a motion controller is constructed based on the aforementioned dynamic equations;

[0010] Based on task requirements, trajectory planning is performed to obtain joint motion trajectories;

[0011] The tendon-driven spatial robotic arm is driven according to the joint motion trajectory, real-time feedback information is obtained, and trajectory tracking control is performed in conjunction with the motion controller.

[0012] In some embodiments, the relationship between the rope length and the joint angle is as follows:

[0013]

[0014] dl i =J qi dθ i

[0015] Among them, l i1 Indicates the length of the first rope, l i2 Indicates the length of the second rope, l i3 Indicates the length of the third rope, l i4 Let S represent the length of the fourth rope, and let S represent the distance between the connection point and the vertex of the vertical rod. The angle between the line connecting the vertex of the vertical rod and the connection point and the connecting rod is represented by r, which represents the winch radius, and θ. i L represents the angles of each joint of the robotic arm. i J represents the length of the i-th robotic arm. qi This represents the mapping matrix.

[0016] In some embodiments, the kinetic equations are as follows:

[0017]

[0018] Where M(θ) represents the system inertia matrix, and θ represents the joint rotation angle of the robotic arm. Represents the Coriolis force and centripetal force matrix, τ sThe torque represents the elastic loss torque of the rope, and d represents the external time-varying disturbance. Represents joint angular acceleration. τ represents the joint angular velocity. s τ represents the elastic torque of the rope, and τ represents the system control input torque.

[0019] In some embodiments, the motion controller is as follows:

[0020]

[0021]

[0022] Where u0 represents the linear constant coefficient part of the control input, u a This indicates an external control signal input. This represents the desired joint angular velocity. Indicates angular velocity tracking error. This indicates the angular acceleration tracking error, with B, h, and Δh representing different intermediate symbols.

[0023] In some embodiments, a non-singular terminal sliding mode is introduced as an external control signal, wherein:

[0024] The non-singular terminal sliding surface is selected as follows:

[0025]

[0026] The expression for the external control signal is as follows:

[0027]

[0028] Where w represents an intermediate variable. α, β, q, p, φ, γ represent different sliding mode adjustment parameters, and e represents the tracking error.

[0029] In some embodiments, the feedback information is provided by an angle encoder and a tension sensor.

[0030] This invention also proposes a motion control system for a tendon-driven spatial robotic arm under variable load, the system comprising:

[0031] The mapping module is used for geometric analysis of tendon-driven spatial robotic arms and to construct the relationship between rope length and joint rotation angle.

[0032] The dynamic modeling module models the tendon-driven spatial manipulator based on the relationship between the rope length and the joint rotation angle, and obtains the dynamic equations.

[0033] A controller construction module is used to consider tracking errors and construct a motion controller based on the dynamic equations.

[0034] The initial trajectory construction module is used to plan the trajectory according to the task requirements and obtain the joint motion trajectory;

[0035] The tracking control module is used to drive the tendon-driven spatial robotic arm according to the joint motion trajectory, obtain real-time feedback information, and perform trajectory tracking control in conjunction with the motion controller.

[0036] This invention also proposes a motion control device for a tendon-driven spatial robotic arm under variable load, comprising:

[0037] At least one processor;

[0038] At least one memory for storing at least one program;

[0039] When the at least one program is executed by the at least one processor, the at least one processor implements the motion control method for a tendon-driven space robot under variable load as described above.

[0040] Based on the above scheme, the present invention provides a motion control method and system for a tendon-driven spatial manipulator under variable load. Considering multiple factors such as rope deformation and external interference, the nonlinear and non-uniform multi-coupled kinematics of the tendon-driven spatial manipulator are established, and the dynamic model of the tendon-driven spatial manipulator is derived according to the second type of Lagrange method.

[0041] In addition, based on the all-drive system approach, a terminal sliding mode composite controller was designed to solve the problem of high-speed and high-precision motion control of tendon-driven spatial robotic arms under variable load conditions. Attached Figure Description

[0042] Figure 1 This is a flowchart of the motion control method for a tendon-driven spatial robotic arm under variable load according to the present invention.

[0043] Figure 2 This is a schematic diagram of the tendon-driven spatial robotic arm joint module of the present invention;

[0044] Figure 3 This is a simulation diagram of the actual operation of the tendon-driven spatial robotic arm of the present invention;

[0045] Figure 4 This is a schematic diagram of the actual operation of the tendon-driven spatial robotic arm of the present invention.

[0046] Figure 5 This is a schematic diagram illustrating the tracking of joint angle 1 in a specific embodiment of the present invention;

[0047] Figure 6This is a schematic diagram illustrating the tracking of joint angle 2 in a specific embodiment of the present invention;

[0048] Figure 7 This is a schematic diagram of the tension of each rope in joint module 1 according to a specific embodiment of the present invention;

[0049] Figure 8 This is a schematic diagram of the tension of each rope in the joint module 2 of a specific embodiment of the present invention. Detailed Implementation

[0050] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0051] It should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings. Unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0052] It should be understood that the terms "system," "apparatus," "unit," and / or "module" used in this application are a method of distinguishing different components, elements, parts, sections, or assemblies at different levels. However, if other terms can achieve the same purpose, they may be replaced by other expressions.

[0053] Unless the context explicitly indicates an exception, words such as "a," "an," "a kind," and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list; a method or apparatus may also include other steps or elements. An element defined by the phrase "comprising a..." does not exclude the presence of other identical elements in the process, method, product, or apparatus that includes the element.

[0054] In the description of the embodiments of this application, "a plurality of" refers to two or more. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0055] Furthermore, flowcharts are used in this application to illustrate the operations performed by the system according to embodiments of this application. It should be understood that the preceding or following operations are not necessarily performed precisely in sequence. Instead, the steps can be processed in reverse order or simultaneously. Additionally, other operations can be added to these processes, or one or more steps can be removed from them.

[0056] Reference Figure 1 The diagram below is a schematic flowchart of an optional example of the motion control method for a tendon-driven spatial robotic arm under variable load proposed in this invention. This method can be applied to computer equipment, and the motion control method proposed in this embodiment may include, but is not limited to, the following steps:

[0057] Step S1: Perform geometric analysis on the tendon-driven spatial robotic arm and construct the relationship between rope length and joint rotation angle;

[0058] Step S2: Based on the relationship between the rope length and the joint rotation angle, model the tendon-driven spatial manipulator to obtain the dynamic equation;

[0059] Step S3: Considering the tracking error, construct a motion controller based on the aforementioned dynamic equations;

[0060] Step S4: Perform trajectory planning according to task requirements to obtain joint motion trajectories;

[0061] Step S5: Drive the tendon-driven spatial robotic arm according to the joint motion trajectory, obtain real-time feedback information, and perform trajectory tracking control in conjunction with the motion controller.

[0062] In some feasible embodiments, in step S1:

[0063] Reference Figure 2 Geometric analysis was performed on a tendon-driven spatial robotic arm.

[0064] From geometric relationships, we know that:

[0065]

[0066]

[0067] The relationship between rope length and joint angle is as follows:

[0068]

[0069] dl i =J qi dθ i (5)

[0070] The mapping matrix is ​​represented as follows:

[0071]

[0072] As can be seen from equation (6), the change in rope length is only related to the joint angle.

[0073] In some feasible embodiments, in step S2:

[0074] The elastic loss torque of the rope, derived from the principle of virtual work, is:

[0075]

[0076] Among them, δW s δW represents the elastic loss torque of the rope. θ Joint torque, where T represents the transpose and f represents the rope tension matrix on a joint module.

[0077] Combining equations (5) and (7), the mapping relationship between the change in rope length and the elastic loss torque of the rope is obtained as follows:

[0078]

[0079] Among them, R n×4n It represents the set of real numbers.

[0080] If the ropes have the same cross-sectional area and elastic modulus, then the work done by the elastic loss is:

[0081]

[0082] Where E is the elastic modulus of the rope, and S represents the cross-sectional area of ​​the rope.

[0083] Taking the partial derivative of both sides of equation (9), we obtain the elastic loss torque as follows:

[0084]

[0085] Among them, f s J represents the system rope tension matrix. θ This represents the Jacobian matrix of the mapping.

[0086] Based on the Lagrange method, the dynamic equations of the tendon-driven spatial manipulator are obtained:

[0087]

[0088] Furthermore, dynamic modeling is not limited to the Lagrange method; it can also use the Newton-Euler method, the Kane method, and so on.

[0089] In some feasible embodiments, in step S3:

[0090] Define the following symbolic expressions:

[0091] A 0～n-1 =[A0 A1 LA] n-1 ]

[0092]

[0093] Make the joint angle θ of the robotic arm track the desired trajectory The tracking error is defined as:

[0094] e = θ - θ d (12)

[0095] but:

[0096]

[0097] Substituting equation (13) into the dynamic equation (11), we get:

[0098]

[0099] make:

[0100]

[0101] Equation (14) can be expressed as:

[0102]

[0103] Where u0 represents the linear constant coefficient part of the control input, u a This indicates an external control signal input.

[0104] Based on the all-drive control system approach, the linear constant-coefficient closed-loop control input can be designed as follows:

[0105]

[0106] Furthermore, writing it as a linear closed-loop system with constant coefficients gives:

[0107]

[0108] Right now:

[0109]

[0110] As can be seen from equation (19), the key to making a linear constant-coefficient closed-loop system stable lies in appropriately selecting the coefficient matrix Φ(A). 0～1 ) makes it a Herwitz matrix.

[0111] In some feasible embodiments, in step S3, in order to improve the speed and stability of the control system, a non-singular terminal sliding mode is introduced as an external control signal, and the non-singular terminal sliding mode surface is selected as follows:

[0112]

[0113] Then the external signal u a Designed in the following form:

[0114]

[0115] in,

[0116] The present invention also provides a simulation example:

[0117] Tendon-driven space robotic arms are typically mounted on the base of ultra-large spacecraft, such as... Figure 3 As shown, compared to the spacecraft base, the mass of the tendon-driven space robotic arm is negligible, and it can be considered as the robotic arm mounted on a fixed base. Its schematic diagram is as follows. Figure 4 As shown.

[0118] Numerical simulation experiments were conducted on a tendon-driven spatial manipulator using the Matlab simulation platform to verify the superior performance of the designed control system. The simulation parameters of the tendon-driven spatial manipulator are shown in Table 1.

[0119] Table 1. Structural parameters of tendon-driven spatial robotic arm

[0120]

[0121] The initial joint angles of the dual-joint module tendon-driven spatial robotic arm are: θ = [0.2 0.1] T The joint angular velocity is: The desired joint angle is: The external time-varying disturbance is: To demonstrate the superior performance of the proposed method, comparative simulation experiments were conducted with linear sliding mode and novel non-singular terminal sliding mode. The linear sliding mode controller is designed as shown in equation (22), and the non-singular terminal sliding mode controller is designed as shown in equation (23).

[0122]

[0123]

[0124] Finally, to highlight the robustness of the proposed controller, the robotic arm grasped a 5kg weight during a simulation lasting 20 seconds. Simulation results. Figures 5 to 8 As shown.

[0125] Figures 5-6 This demonstrates the joint angle trajectory tracking capabilities of a tendon-driven spatial robotic arm. Figures 7-8 The simulation results depict the changes in rope tension on each joint module. As can be seen from the above simulation results, the control method proposed in this invention has significant advantages over the control simulation experiment in terms of both error convergence speed and stability, enabling high-speed and high-precision motion control of a tendon-driven spatial robotic arm under variable load.

[0126] A motion control system for a tendon-driven spatial robotic arm under variable load includes:

[0127] Geometric analysis was performed on the tendon-driven spatial robotic arm to construct the relationship between rope length and joint rotation angle;

[0128] Based on the relationship between the rope length and the joint rotation angle, the tendon-driven spatial manipulator is modeled to obtain the dynamic equations;

[0129] Considering tracking error, a motion controller is constructed based on the aforementioned dynamic equations;

[0130] Based on task requirements, trajectory planning is performed to obtain joint motion trajectories;

[0131] The tendon-driven spatial robotic arm is driven according to the joint motion trajectory, real-time feedback information is obtained, and trajectory tracking control is performed in conjunction with the motion controller.

[0132] The content of the above method embodiments is applicable to this system embodiment. The specific functions implemented in this system embodiment are the same as those in the above method embodiments, and the beneficial effects achieved are also the same as those achieved in the above method embodiments.

[0133] A motion control device for a tendon-driven spatial robotic arm under variable load:

[0134] At least one processor;

[0135] At least one memory for storing at least one program;

[0136] When the at least one program is executed by the at least one processor, the at least one processor implements the motion control method for a tendon-driven space robot under variable load as described above.

[0137] The content of the above method embodiments is applicable to the device embodiments. The specific functions implemented by the device embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0138] A storage medium storing processor-executable instructions, which, when executed by a processor, are used to implement the motion control method for a tendon-driven space robot under variable load as described above.

[0139] The content of the above method embodiments is applicable to this storage medium embodiment. The specific functions implemented in this storage medium embodiment are the same as those in the above method embodiments, and the beneficial effects achieved are also the same as those achieved in the above method embodiments.

[0140] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A motion control method for a tendon-driven spatial robotic arm under variable load, characterized in that... Includes the following steps: Geometric analysis was performed on the tendon-driven spatial robotic arm to construct the relationship between rope length and joint rotation angle; Based on the relationship between the rope length and the joint rotation angle, the tendon-driven spatial manipulator is modeled to obtain the dynamic equations; Considering tracking error, a motion controller is constructed based on the aforementioned dynamic equations; Based on task requirements, trajectory planning is performed to obtain joint motion trajectories; Drive the tendon-driven spatial robotic arm according to the joint motion trajectory, obtain real-time feedback information, and combine it with the motion controller for trajectory tracking control; The motion controller is shown below: in, This represents the linear constant coefficient control input. This indicates an external control signal input. This represents the desired joint angular velocity. Indicates angular velocity tracking error. This indicates the angular acceleration tracking error, with B, h, and Δh representing different intermediate symbols. A non-singular terminal sliding mode is introduced as an external control signal, wherein: The non-singular terminal sliding surface is selected as follows: The expression for the external control signal is as follows: Where w represents an intermediate variable. ; , ,q,p, , These represent different sliding mode adjustment parameters, and e represents the tracking error.

2. The motion control method for a tendon-driven spatial robotic arm under variable load according to claim 1, characterized in that, The relationship between the rope length and the joint angle is shown in the following formula: in, Indicates the length of the first rope. Indicates the length of the second rope. Indicates the length of the third rope. Let S represent the length of the fourth rope, and let S represent the distance between the connection point and the vertex of the vertical rod. The angle between the line connecting the vertex of the longitudinal rod and the connection point and the connecting rod is represented by r, where r represents the winch radius. This indicates the angles of each joint of the robotic arm. This represents the length of the i-th robotic arm. This represents the mapping matrix.

3. The motion control method for a tendon-driven spatial robotic arm under variable load according to claim 2, characterized in that, The dynamic equations are as follows: in, Represents the system inertia matrix. This indicates the joint rotation angle of the robotic arm. Represents the Coriolis force and centripetal force matrices. The torque represents the elastic loss torque of the rope, and d represents the external time-varying disturbance. Represents joint angular acceleration. Indicates joint angular velocity, This represents the elastic torque of the rope. This indicates the system control input torque.

4. The motion control method for a tendon-driven spatial robotic arm under variable load according to claim 1, characterized in that, The feedback information is provided by the angle encoder and the tension sensor.

5. A motion control system for a tendon-driven spatial robotic arm under variable load, characterized in that, For performing motion control of a tendon-driven spatial robotic arm under variable load as described in claim 1, comprising: The mapping module is used for geometric analysis of tendon-driven spatial robotic arms and to construct the relationship between rope length and joint rotation angle. The dynamic modeling module models the tendon-driven spatial manipulator based on the relationship between the rope length and the joint rotation angle, and obtains the dynamic equations. A controller construction module is used to consider tracking errors and construct a motion controller based on the dynamic equations. The initial trajectory construction module is used to plan the trajectory according to the task requirements and obtain the joint motion trajectory; The tracking control module is used to drive the tendon-driven spatial robotic arm according to the joint motion trajectory, obtain real-time feedback information, and perform trajectory tracking control in conjunction with the motion controller.

6. A motion control device for a tendon-driven spatial robotic arm under variable load, characterized in that, include: At least one processor; At least one memory for storing at least one program; When the at least one program is executed by the at least one processor, the at least one processor implements the motion control method for a tendon-driven space robot under variable load as described in any one of claims 1-4.

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