A trajectory tracking control method, device and medium of a flexible upper limb exoskeleton

Abstract

The application discloses a trajectory tracking control method and device of a flexible upper limb exoskeleton and a medium, and belongs to the field of exoskeleton robots. The method comprises the following steps: firstly, a dynamic model of the flexible upper limb exoskeleton is established; then, an improved super-helix second-order sliding mode controller is designed according to the dynamic model of the exoskeleton; and finally, trajectory tracking control is performed on the exoskeleton robot according to the improved sliding mode controller. The application overcomes the problem of poor anti-chatter effect in the prior art, provides a flexible exoskeleton trajectory tracking control method based on an improved super-helix sliding mode, and improves the anti-chatter effect and anti-interference ability of the flexible exoskeleton by replacing the switching function under the integral term with a non-smooth term through the improved super-helix second-order sliding mode controller.

Description

Technical Field

[0001] This invention belongs to the field of exoskeleton robots, and more specifically, relates to a trajectory tracking control method, device and medium for a flexible upper limb exoskeleton. Background Technology

[0002] Current rehabilitation training is conducted with the accompaniment of medical staff, which consumes a significant amount of manpower and time. Exoskeleton robots, however, have made tremendous progress and development in military, medical, and rehabilitation fields over the past few decades. Robots used in rehabilitation can reduce the costs of traditional rehabilitation training. In rehabilitation training, exoskeleton robots employ two modes: active training and passive training. In passive training, the exoskeleton drives the upper limbs to repeat training along a pre-designed trajectory. In active training, after passive training has reached a certain level and the upper limbs can perform limited movements, the exoskeleton assists in motor training. Flexible upper limb exoskeletons are rigid-flexible coupled nonlinear systems and are easily affected by external disturbances and structural parameters during rehabilitation training. Therefore, designing a suitable controller for trajectory tracking is a key research focus.

[0003] To address the aforementioned issues, existing technologies have proposed several solutions. For example, an invention titled "A Control Method for Upper Limb Exoskeleton Based on Sliding Mode Impedance" (application number: 202010739539.4) constructs a dynamic model by collecting motion signals from the upper limb exoskeleton. A sine curve is input into the sliding mode impedance control module, and combined with the Adams dynamic model of the upper limb exoskeleton, the tracking curves of the shoulder and elbow joint angles and angular velocities are output. The output curves are then compared with the input curves to optimize the input curves and control the motion of the upper limb exoskeleton. This solution achieves compliant tracking of the human upper limb by the upper limb exoskeleton. However, a drawback of this solution is its relatively low tracking accuracy.

[0004] In addition, there is an invention entitled "A Motion Control Method for an Upper Limb Exoskeleton Robot Based on RBF Networks," application number CN202210557091.3. This scheme obtains the desired angles and angular velocity changes of each joint based on the mechanical structure of the upper limb exoskeleton robot. This scheme applies multiple RBP neural networks to the controller design, solving the problem of approximating the uncertainties in the dynamics of the exoskeleton robot under model uncertainty, reducing steady-state errors, and optimizing the control performance of the upper limb exoskeleton robot. The drawback of this scheme is that it only uses neural network control without feedback, resulting in poor anti-interference ability and a lack of robustness. Summary of the Invention

[0005] 1. Technical problems to be solved

[0006] To address the problem of poor anti-flutter performance in existing technologies, this invention provides a trajectory tracking control method, device, and medium for a flexible upper limb exoskeleton. By using an improved super-spiral second-order sliding mode controller, the switching function under the integral term is replaced with a non-smooth term, which improves the anti-flutter effect and anti-interference capability of the flexible exoskeleton and enhances its robustness.

[0007] 2. Technical Solution

[0008] The objective of this invention is achieved through the following technical solutions.

[0009] The present invention discloses a trajectory tracking control method for a flexible upper limb exoskeleton. First, a dynamic model of the flexible upper limb exoskeleton is established. Then, an improved super-spiral second-order sliding mode controller is designed based on the dynamic model of the exoskeleton. Finally, the trajectory tracking control of the exoskeleton is performed based on the improved sliding mode controller.

[0010] As a further improvement to the present invention, a dynamic model of the flexible upper limb exoskeleton is established based on the following formula:

[0011]

[0012] Where q = [q1, q2] T It represents the rotation angle at the joint, θ = [θ1, θ2] T It refers to the rotation angle on the motor side. J, B, K n These represent the rotor inertia, damping, and torsion spring coefficient on the motor side, respectively. M(q) is the inertia matrix of the exoskeleton. Let G(q) be the Coriolis force and centripetal force matrix, G(q) be the gravity matrix of the exoskeleton robot, and τ be the control torque vector.

[0013] As a further improvement to the present invention, the specific process of designing the improved superspiral second-order sliding mode controller is as follows:

[0014] The dynamic equations are transformed into the following state equations:

[0015]

[0016]

[0017]

[0018]

[0019]

[0020] W1 and W2 represent the external disturbances experienced by the motor and joint sides, respectively, while d1 and d2 represent the non-matching and matched disturbances experienced by the system. This includes the uncertainties in the unmodeled dynamic model parameters of the system and external load disturbances.

[0021] As a further improvement to the present invention,

[0022] The sliding surface is obtained as follows:

[0023] s(t)=c1e1+c2e2+c3e3+e4

[0024] in q r From the perspective of the target; and This is the actual angle of rotation;

[0025] Differentiating the sliding surface, we get:

[0026]

[0027] As a further improvement to this invention, based on the improved superspiral second-order sliding mode control law, the specific control law of the system is obtained as follows:

[0028]

[0029] Where k1 and k2 are controller gains greater than 0, λ is an adjustable parameter between -0.5 and 0, and u m It is the improved superspiral reaching law, where τ is the control torque. and z m In the approach law, sign(s) is an intermediate variable, and |s| is the sign function. 1 / 2 It is the square root of the absolute value, J is the torque of the motor, |s| 1+λ and |s| 1+2λ It is an exponential function.

[0030] A virtual device, the virtual device comprising an application and an operating system, wherein the application executes the process execution control method described in any one of the preceding claims.

[0031] A data processing device includes: a memory, a processor, and a data processing program stored in the memory and executable on the processor, wherein the data processing program, when executed by the processor, implements any of the control methods described above.

[0032] Preferably, a data processing device, including but not limited to smartphones, tablets, or portable computers.

[0033] A storage medium comprising a stored application program, wherein the application program executes the process execution control method described in any one of the preceding claims.

[0034] 3. Beneficial effects

[0035] Compared with the prior art, the advantages of this invention are:

[0036] This invention discloses a trajectory tracking control method for a flexible upper limb exoskeleton. By employing an improved superspiral second-order sliding mode controller, the switching function under the integral term is replaced with a non-smooth term, thereby improving the anti-flutter effect and anti-interference capability of the flexible exoskeleton. This invention proposes an improved superspiral second-order sliding mode controller, replacing the switching function with a non-smooth term, which reduces the flutter problem of the system compared to the traditional superspiral algorithm. Furthermore, this invention selects appropriate parameters to improve the system's anti-disturbance capability. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0038] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0039] Example 1

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention; moreover, the various embodiments are not relatively independent and can be combined with each other as needed to achieve better results. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0041] To further understand the content of this invention, a detailed description of the invention will be provided in conjunction with the accompanying drawings and embodiments.

[0042] like Figure 1 As shown, the trajectory tracking control method for a flexible upper limb exoskeleton of the present invention improves the anti-flutter effect and anti-interference capability of the flexible exoskeleton by replacing the switching function in the integral term with a non-smooth term through an improved super-spiral second-order sliding mode controller. The specific steps of the trajectory tracking control method for a flexible upper limb exoskeleton of the present invention are as follows:

[0043] (1) Establish the motion equations of the flexible upper limb exoskeleton. Specifically, the motion equations of the flexible upper limb exoskeleton are established using the Lagrange dynamics equations. The established motion equations of the flexible upper limb exoskeleton are as follows:

[0044]

[0045] Where q = [q1, q2] T It represents the rotation angle at the joint, θ = [θ1, θ2] T It refers to the rotation angle on the motor side, J, B, K. n Let represent the rotor inertia, damping, and torsion spring coefficient on the motor side, respectively, and M(q) be the inertia matrix of the exoskeleton. Let G(q) be the Coriolis force and centripetal force matrix, G(q) be the gravity matrix of the exoskeleton robot, and τ be the control torque vector. It should be noted that the joint rotation angle q in this invention is obtained through an angle encoder, and the motor-side rotation angle θ is also obtained through an angle encoder. The one or two points above the corresponding letters represent the corresponding first or second derivative, such as... The first derivative represents the rotation angle on the motor side. It is the second derivative. Let be the first derivative of q. Let q be the second derivative of q. This expression is the common way to express q in this field, and the same applies below.

[0046] (2) Furthermore, to facilitate controller design, let The kinematic equation of the upper limb exoskeleton in equation (1) above can be transformed into the following state-space equation:

[0047]

[0048]

[0049]

[0050]

[0051] W1 and W2 represent the external disturbances experienced by the motor and joint sides, respectively, while d1 and d2 represent the non-matching and matched disturbances experienced by the system. This includes the uncertainties in the unmodeled dynamic model parameters of the system and external load disturbances.

[0052] (3) Further, the specific steps for constructing the improved super-spiral second-order sliding mode controller based on the motion equation of the flexible upper limb exoskeleton are as follows:

[0053] Obtaining the sliding surface:

[0054] s = c1e1 + c2e2 + c3e3 + e4

[0055] in For the target angle of rotation, and This is the actual angle of rotation;

[0056] Differentiating the sliding surface yields the sliding mode convergence rate:

[0057]

[0058] The improved superhelical algorithm is then combined as follows:

[0059]

[0060] Combining the above three equations, the improved superspiral second-order sliding mode controller is obtained as follows:

[0061]

[0062] Where k1 and k2 are controller gains greater than 0, λ is an adjustable parameter between -0.5 and 0, and u m It is the improved superspiral reaching law, where τ is the control torque. and z m In the approach law, sign(s) is an intermediate variable, and |s| is the sign function. 1 / 2 It is the square root of the absolute value, J is the torque of the motor, |s| 1+λ and |s| 1+2λ It is an exponential function, and in actual control, the effect of mismatch disturbances is ignored.

[0063] It is worth noting that the improved superspiral second-order sliding mode control of the present invention replaces the switching function under the integral term with a non-smooth term, which reduces the system chattering problem caused by the switching function in the integral term of the traditional superspiral control, and ensures that the system converges in finite time. At the same time, selecting appropriate parameters improves the system's anti-disturbance capability.

[0064] This invention discloses a trajectory tracking control method for flexible exoskeleton based on an improved superspiral sliding mode controller. By using an improved superspiral second-order sliding mode controller, the switching function under the integral term is replaced with a non-smooth term. This method is used for the control of flexible exoskeleton robots, improving the anti-flutter effect and anti-interference capability of the flexible exoskeleton.

[0065] Those skilled in the art will understand that embodiments of this application can be provided as methods, virtual systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0066] The corresponding virtual device may include an application and an operating system, wherein the application performs the methods described above. It should be understood that each block of the flowchart and / or block diagram, and combinations of blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing device to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing device, generate instructions for implementing the methods described above. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0067] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The functions specified in one or more boxes. These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable apparatus for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0068] It can also be a type of storage medium, which is an example of a computer-readable medium. Computer-readable media includes both permanent and non-permanent, removable and non-removable media that can store information by any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0069] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Terms such as "first," "second," etc., are used to denote names and do not indicate any particular order. The invention and its embodiments have been described above illustratively, and this description is not restrictive. The invention can be implemented in other specific forms without departing from its spirit or essential characteristics. The accompanying drawings are only one embodiment of the invention, and the actual structure is not limited thereto. No reference numerals in the claims should limit the scope of the claims. Therefore, if a person skilled in the art, inspired by this description, designs a similar structure and embodiment without departing from the spirit of the invention, such design should fall within the scope of protection of this patent.

Claims

1. A trajectory tracking control method for a flexible upper limb exoskeleton, characterized in that, First, a dynamic model of a flexible upper limb exoskeleton is established. Then, an improved super-helical second-order sliding mode controller is designed based on the dynamic model of the exoskeleton. Finally, the trajectory tracking control of the exoskeleton is performed based on the improved super-helical second-order sliding mode controller. A dynamic model of the flexible upper limb exoskeleton is established based on the following formula: in, It refers to the angle of rotation at the joint. It is the rotation angle of the motor side. These represent the rotor moment of inertia, damping, and torsion spring coefficient on the motor side, respectively. Here is the rotational inertia matrix of the exoskeleton. The matrix represents the Coriolis force and the centripetal force. For the gravity matrix of the exoskeleton robot, To control the torque vector, Indicates the rotation angle of the motor side The first derivative, It is the second derivative. Let be the first derivative of q. is the second derivative of q; The specific process of designing the improved superspiral second-order sliding mode controller is as follows: The dynamic equations are transformed into the following state equations: External disturbances experienced by the motor side and the joint side. The system is subjected to both mismatched and matched disturbances, including the uncertainty of the unmodeled dynamic model parameters of the system and external load disturbances; The specific process of designing the improved superspiral second-order sliding mode controller is as follows: The sliding surface is obtained as follows: in ; qr is the target angle of rotation; , and This is the actual angle of rotation; Differentiating the sliding surface, we get: The improved superhelical algorithm is then combined as follows: Combining the above three equations, the improved superspiral second-order sliding mode controller is obtained as follows: in, For controller gain greater than 0, It is an adjustable parameter between -0.5 and 0. It is an improved superhelical reaching law. It is the control torque. and It is an intermediate variable in the law of convergence. It is a symbolic function. It is taking the square root of the absolute value. It is the torque of the motor. and It is an exponential function.

2. The trajectory tracking control method for a flexible upper limb exoskeleton according to any one of claims 1, characterized in that, A dynamic model of a flexible upper limb exoskeleton was established using the Lagrange dynamics equations.

3. A virtual device, characterized in that, The virtual device includes an application and an operating system, wherein the application executes the trajectory tracking control method of the flexible upper limb exoskeleton as described in claim 1 or 2.

4. A data processing device, characterized in that, The data processing device includes: a memory, a processor, and a data processing program stored in the memory and executable on the processor. When the data processing program is executed by the processor, it implements the trajectory tracking control method of the flexible upper limb exoskeleton as described in claim 1 or 2.

5. A data processing device according to claim 4, characterized in that, Data processing devices include, but are not limited to, smartphones, tablets, or laptops.

6. A storage medium, characterized in that, The storage medium includes a stored application program, wherein the application program executes the trajectory tracking control method for the flexible upper limb exoskeleton as described in claim 1 or 2.

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