A robot arm adaptive fault-tolerant control method

Abstract

The application discloses a kind of mechanical arm adaptive fault-tolerant control methods, comprising S1, the angle information obtained by each joint encoder is established;S2, considering actuator failure, the dynamics model of mechanical arm system is reconstructed;S3, high-order sliding mode observer is established, and actuator failure compensation is carried out;S4, non-singular fast terminal sliding surface is established;S5, according to the non-singular fast terminal sliding surface obtained in S4 and the high-order sliding mode observer estimation failure in S3, the control torque of each joint actuator of mechanical arm is determined, and trajectory tracking control is continued.The application first compensates the influence of high-order sliding mode fault observer on failure rapidly, and the mechanical arm actuator fault-tolerant control method is designed by means of adaptive method and super-helix algorithm characteristics, the fault-tolerant performance of system is enhanced, so that the mechanical arm can track the desired target in finite time under the condition of actuator failure, and the control performance of control system is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of manipulator actuator fault-tolerant control and relates to a manipulator adaptive fault-tolerant control method. BACKGROUND

[0002] The wide application of manipulators liberates human beings from repetitive, dangerous and physical labor, greatly promoting the development of social production and economy. However, due to long-term operation of the body, environmental corrosion, unreasonable controller design and other reasons, various unpredictable faults of the manipulator may occur. Mechanical faults not only reduce production efficiency and affect economic development, but also seriously endanger the lives of workers. Therefore, the research on the fault detection method and fault-tolerant control technology of the manipulator has practical significance for maintaining economic and social stability and protecting people's life safety.

[0003] The sliding mode control algorithm is often mentioned in the design of manipulator fault-tolerant control due to its excellent tracking performance and strong robustness to external disturbances. However, when dealing with uncertain factors, the conventional sliding mode control algorithm often violently uses a large upper bound to offset the influence, which may cause serious chattering phenomenon of the control input and affect the control performance. Therefore, in view of the above defects existing in the prior art, it is necessary to conduct research to provide a solution to solve the defects existing in the prior art. SUMMARY

[0004] In view of the problem of multiplicative fault and additive fault of the manipulator actuator during task execution in the prior art, the influence of fault is rapidly compensated by a high-order sliding mode fault observer, and a manipulator actuator fault-tolerant control method is designed by means of adaptive method and super-spiral algorithm characteristics, which enhances the fault-tolerant performance of the system, enables the manipulator to track the desired target within a limited time in the case of actuator fault, and improves the control performance of the control system.

[0005] The technical scheme of the application is a manipulator fault-tolerant control method based on high-order sliding mode observer and self-adaption, comprising initialization of a tracking trajectory, and further comprising the following steps:

[0006] S1, establishing each joint encoder to obtain angle information;

[0007] S2, considering actuator fault, reconstructing the dynamics model of the manipulator system;

[0008] S3, establishing a high-order sliding mode observer to compensate for actuator fault;

[0009] S4, establishing a non-singular fast terminal sliding mode surface;

[0010] S5, according to the non-singular fast terminal sliding mode surface obtained in S4 and the high-order sliding mode observer in S3, estimating the fault, determining the control torque of each joint actuator of the manipulator, and continuing the trajectory tracking control.

[0011] Preferably, S1 includes establishing a dynamic model of the n-degree-of-freedom joint manipulator system:

[0012]

[0013] wherein, respectively represent the angle, angular velocity and acceleration vectors of each joint of the manipulator; is a positive definite inertia matrix when the manipulator is running, is a centrifugal force term; is a friction term; is a gravity term; is a control torque vector of each joint, and is an external disturbance torque vector.

[0014] Preferably, S2 includes considering the actuator fault problem, and the actual output torque of the actuator can be expressed as wherein, is a desired torque, is an actuator fault signal; let the fault signal be wherein is an actuator effective factor, is an additional disturbance torque; then considering the actuator fault problem, the dynamic model of the manipulator system is reconstructed as:

[0015]

[0016] wherein, let convert the dynamics into a state space form:

[0017]

[0018] wherein, , .

[0019] Preferably, the actuator fault in S3 has a great impact on the system performance as part of the control output, and the robustness of the system can be further enhanced by compensation estimation. But in the actual system, the fault value cannot be directly measured, and an observer needs to be designed to obtain disturbance information. Therefore, a high-order sliding mode observer is designed in this paper to estimate fault information. As an extended observer, the working principle of the high-order sliding mode observer is to expand the to-be-estimated quantity into a new system state, and through the feedback of the error to configure a nonlinear function, the purpose of the dynamic of the observer being much higher than that of the system is achieved, so as to complete the state tracking. Including the establishment of a high-order sliding mode observer:

[0020]

[0021] wherein the observer gain is a normal number, is a high-order sliding mode observer internal state variable, wherein , ;

[0022]

[0023] Preferably, a non-singular fast terminal sliding mode surface is established in S4:

[0024]

[0025] wherein , is a desired trajectory; and are normal numbers; is a positive odd number and satisfies , ; The definition of the sign function acting on a vector is that, if there exists an n-dimensional constant vector , , .

[0026] Preferably, the control torque of each joint actuator of the mechanical arm is determined in S5:

[0027]

[0028] The adaptive gain that can dynamically adjust the control gain is:

[0029]

[0030] wherein and is a normal number.

[0031] The present application has at least the following beneficial effects: the present application is composed of a non-singular fast terminal sliding mode surface, an adaptive hyper-spiral sliding mode controller based on a manipulator dynamics actuator fault reconstruction model and a high-order sliding mode observer part. The non-singular fast terminal sliding mode surface eliminates the non-singular problem while ensuring fast convergence, ensuring the global robustness of the system; the high-order sliding mode observer estimates the actuator faults of each joint and the disturbances of the system based on the measured information of each joint angle, and designs the sliding mode surface and the control law with the observation value; the adaptive hyper-spiral sliding mode controller includes the design of the adaptive rate and the design of the sliding mode control law, which does not need to know the upper bound of the system uncertainty and external disturbance in advance, and can effectively suppress the system chattering. Simulation experiments show that the control scheme of the present application can quickly and accurately track the reference trajectory when the manipulator actuator fails according to the measured joint angle information, and has global robustness to actuator fault problems and unknown disturbances. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is a step flow chart of the manipulator adaptive fault-tolerant control method of the embodiment of the present application;

[0033] Figure 2 is a model structure diagram of a two-link joint rigid manipulator in the manipulator adaptive fault-tolerant control method of the embodiment of the present application;

[0034] Figure 3 is a working principle diagram of manipulator actuator fault fault-tolerant control based on a high-order observer and an adaptive sliding mode in the manipulator adaptive fault-tolerant control method of the embodiment of the present application;

[0035] Figure 4 is an estimation diagram of a high-order sliding mode observer for manipulator actuator faults and external disturbances in the simulation of the manipulator adaptive fault-tolerant control method of the embodiment of the present application;

[0036] Figure 5 is a trajectory tracking effect diagram considering actuator fault fault-tolerant control in the simulation of the manipulator adaptive fault-tolerant control method of the embodiment of the present application;

[0037] Figure 6 is a trajectory tracking error diagram considering actuator fault fault-tolerant control in the simulation of the manipulator adaptive fault-tolerant control method of the embodiment of the present application;

[0038] Figure 7 is a trajectory tracking control torque diagram considering actuator fault fault-tolerant control in the simulation of the manipulator adaptive fault-tolerant control method of the embodiment of the present application. DETAILED DESCRIPTION

[0039] In order to make the objects, technical solutions and advantages of the present application clearer, further detailed description will be given below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application.

[0040] On the contrary, the present application covers any substitution, modification, equivalent method and solution defined by the claims within the essence and scope of the present application. Further, in order to make the public have a better understanding of the present application, some specific details are described in the following detailed description of the present application. The present application can also be completely understood without the description of these details by those skilled in the art.

[0041] Reference is made to Figure 1 , the step flow chart of the adaptive fault-tolerant control method of the mechanical arm of the embodiment of the present application.

[0042] S1, establish joint encoders to obtain angle information;

[0043] S2, consider actuator faults, and reconstruct the dynamics model of the mechanical arm system;

[0044] S3, establish a high-order sliding mode observer to compensate for actuator faults;

[0045] S4, establish a non-singular fast terminal sliding mode surface;

[0046] S5, according to the non-singular fast terminal sliding mode surface obtained in S4 and the high-order sliding mode observer in S3, estimate the fault, determine the control torque of the actuator of each joint of the mechanical arm, and continue to perform trajectory tracking control.

[0047] In a specific embodiment, the mechanical arm is a two-joint rigid mechanical arm, and a model schematic diagram is shown in Figure 1 , and a schematic diagram of the entire control system is shown in Figure 3 . The non-singular fast terminal sliding mode surface designed for the mechanical arm system of the present application, the adaptive hyper-spiral sliding mode controller based on the dynamics model and the steps of the high-order sliding mode fault observer are as follows:

[0048] S1, considering the influence of actuator faults and other uncertainties, the dynamics reconstruction model of the two-joint rigid mechanical arm system can be established as:

[0049] (2)

[0050] wherein, .

[0051] Let , convert the dynamics into a state space form, see equation (16).

[0052] (3)

[0053] in, , .

[0054]

[0055] in

[0056]

[0057] The physical parameters of the two-joint robotic arm system are shown in Table 1.

[0058] Table 1

[0059]

[0060]

[0061] S2, using sensors to obtain the angles of each joint of the robotic arm. The measurement information, and based on the set desired joint angle Calculate the tracking error of the robotic arm trajectory. The initial joint angles and angular velocities are respectively... The tracking reference trajectory is set as follows:

[0062]

[0063] S3, The specific steps for establishing a high-order sliding mode observer are as follows:

[0064] (4)

[0065] Among them, the observer gain For positive integers, , ;

[0066] (5)

[0067] S4, Establish a non-singular fast terminal sliding surface The specific steps are as follows:

[0068] (6)

[0069] in, , For the desired trajectory; and It is a positive number; It is a positive odd number and satisfies , ; definition , .

[0070] S5, mechanical arm actuator control torque The specific design is as follows:

[0071] (7)

[0072] The adaptive gain that can dynamically adjust the control gain is:

[0073] (8)

[0074] Wherein, And Is a normal number.

[0075] Also includes the stability of the entire control system is analyzed. , The Lyapunov function is selected as follows:

[0076]

[0077] Wherein, , , . Is Upper limit value, that is . Derivation, finally can obtain:

[0078]

[0079] Can obtain Convergence will be realized within a finite time , that is, the sliding mode variable finite time stability is proved.

[0080] The above only for the preferred embodiment of the present application, and not to limit the present application, any modification, equivalent replacement and improvement, etc. within the spirit and principles of the present application, should be included in the protection scope of the present application.

Claims

1.A method for adaptive fault-tolerant control of a robot manipulator, comprising initializing a tracking trajectory, characterized in that, Further comprising the following steps: S1, establishing joint encoders to obtain angle information; S2, considering actuator failure, reconstructing the dynamics model of the robot arm system; S3, establishing a high-order sliding mode observer to compensate for actuator failure; S4, establishing a non-singular fast terminal sliding mode surface; S5, determining the control torque of each joint actuator of the robot arm according to the non-singular fast terminal sliding mode surface obtained in S4 and the high-order sliding mode observer in S3, and continuing to perform trajectory tracking control; S1 includes establishing a dynamics model of an n-degree-of-freedom joint robot arm system: ； wherein respectively represent the angle, angular velocity and acceleration vectors of the joints of the robot arm; is a positive definite inertia matrix for the robot arm in operation, is a Coriolis and centrifugal force term; is a friction term; is a gravity term; is a control torque vector for the joints and is an external disturbance torque vector; The S2 includes considering the actuator failure problem, and the actual output torque of the actuator can be expressed as Wherein, is the desired torque, is the actuator failure signal; suppose the failure signal is Wherein is the actuator effective factor, is the external disturbance torque; then considering the actuator failure problem, the dynamics model of the manipulator system is reconstructed as: ； where, ; set Convert the dynamics to state-space form: ； wherein ; S3 includes establishing a high-order sliding mode observer: ； wherein the observer gain is a positive constant, wherein , ; ； S4 establishes a non-singular fast terminal sliding mode surface: ； wherein , is a desired trajectory; and are positive constants; is a positive odd integer and satisfies , ; The definition of the sign function acting on a vector is that, if there exists an n-dimensional constant vector then ; S5 determines the control torque of each joint actuator of the robot arm: ； The adaptive gain that can dynamically adjust the control gain is: ； wherein and are positive numbers.

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