CN-122008153-A - Time independent control method of lower limb exoskeleton robot based on vector field generator

CN122008153ACN 122008153 ACN122008153 ACN 122008153ACN-122008153-A

Abstract

The invention discloses a lower limb exoskeleton robot time independent control method based on a vector field generator, which relates to the technical field of lower limb exoskeleton robot control, in particular to a lower limb exoskeleton robot time independent control method based on a vector field generator, comprising the steps of mapping a target periodic motion into a limit ring in a phase space; the method comprises the steps of constructing a vector field generator, driving a system state error to be converged to zero by a stabilizing term and a period adjusting term, designing a control law based on an exoskeleton dynamics model, wherein the control law comprises estimated values of an inertia matrix, a Coriolis force matrix, a gravity term and a friction force term, and applying the control law to enable the exoskeleton joint state to be converged and stabilized to a target limit cycle in a time independent mode. The method can adapt to gait rhythm change and active intention of a user, ensure global asymptotic stability through a vector field and effectively process self-intersecting tracks in joint space.

Inventors

ZHANG SHU
ZHANG JIAJUN
CAO TIANCHENG
ZHAO ZITENG
XU JIAN

Assignees

同济大学

Dates

Publication Date: 20260512
Application Date: 20260409

Claims (10)

1. The time independent control method of the lower limb exoskeleton robot based on the vector field generator is characterized by comprising the following steps of: Step one, constructing a target limit cycle, namely mapping the target periodic motion into a closed track in a phase space, namely a limit cycle, and describing the closed track as a phase parameter theta And defining the nearest point of the system state (q, v) to the limit cycle as the target state ; Step two, vector field construction, designing a vector field generator The vector field is composed of stable terms And period adjustment item The constitution, i.e For driving the system state error to converge to zero; Step three, designing a control law based on a dynamic model of the exoskeleton Wherein (q, v) is a state vector of the exoskeleton system, , , , Respectively estimating values of an inertia matrix, a Coriolis force matrix, a gravity term and a friction term in the dynamic model; and fourthly, applying the control law to the lower limb exoskeleton robot to enable the joint state of the lower limb exoskeleton robot to be converged and stabilized in the target limit cycle in a time-independent mode.
2. The method for time-independent control of a lower extremity exoskeleton robot based on a vector field generator as set forth in claim 1, wherein in said step one, the target state is By calculating phase parameters The process is carried out in a manner that, The following relationship is satisfied: ; thereby obtaining the target state And construct time independent errors 。
3. The method for time-independent control of a lower extremity exoskeleton robot based on a vector field generator as set forth in claim 1, wherein said vector field generator constructed in step two Which acts to make the time independent systematic state errors Asymptotically converges to zero.
4. The method of time independent control of a lower extremity exoskeleton robot based on a vector field generator as set forth in claim 1, wherein said control law in step three is a model-based control law which designs a dynamic equation based on the exoskeleton system.
5. The method for controlling the time independence of the lower extremity exoskeleton robot based on the vector field generator as set forth in claim 1, wherein the stability of the method is demonstrated by LaSalle invariant set theorem, and the system state is ensured to be converged to the target limit cycle in a global asymptotic manner from any initial point.
6. The method for time-independent control of a lower extremity exoskeleton robot based on a vector field generator as claimed in claim 1, wherein said target periodic motion is gait motion, said method being capable of adapting to changes in gait rhythm and to the user's intention to apply actively.
7. The method for time-independent control of a lower extremity exoskeleton robot based on a vector field generator as claimed in claim 1, wherein said vector field is constructed in a complete phase space, capable of clearly defining and stably tracking periodic trajectories that appear to self-intersect in joint space or two-dimensional phase plane projection.
8. The method of time independent control of a lower extremity exoskeleton robot based on a vector field generator of claim 1, wherein said control law is capable of driving the system states to re-synchronize autonomously and converge back to the target limit cycle when the system states deviate from the target limit cycle due to external disturbances or user activity.
9. A lower extremity exoskeleton robot system, characterized in that the system is configured with a controller programmed to perform the time independent control method according to any one of claims 1 to 8.
10. A computer-readable storage medium, on which a computer program is stored, characterized in that the program, when being executed by a processor, implements the steps of the method according to any one of claims 1 to 8.

Description

Time independent control method of lower limb exoskeleton robot based on vector field generator Technical Field The invention relates to the technical field of control of lower limb exoskeleton robots, in particular to a time independent control method of a lower limb exoskeleton robot based on a vector field generator. Background The lower limb exoskeleton robot is used as important man-machine cooperative auxiliary equipment, and has wide application prospects in the fields of rehabilitation, exercise assistance, load carrying and the like. The performance of its control system directly affects the user experience and device performance. At present, the control method of the lower limb exoskeleton robot mainly adopts traditional technical schemes such as time index track control (e.g. PID control), speed field control or limit cycle control and the like. The time-dependent control method realizes motion control by presetting a time-parameterized reference track, however, the method has obvious limitations. When the gait rhythm of a user changes or active intervention occurs, a time parameterized control strategy cannot flexibly adapt to the change, so that antagonistic moment is generated between people and machines, and the naturalness and safety of interaction are seriously affected. In addition, external disturbances can disrupt the time synchronicity of the system, making the recovery process less smooth and natural. The velocity field control method, while somewhat reducing the dependence on time, has inherent drawbacks in handling complex trajectories. When the motion of the lower limb is in the condition of the self-intersecting of the track in the phase space projection, the speed field method can face the problem of direction blurring, and the motion direction cannot be definitely defined, so that the control performance is reduced. This limitation severely constrains its application in complex gait patterns. The limit cycle control method can describe periodic motion, but the prior art lacks a systematic design method, and is difficult to accurately match a natural gait pattern. Conventional limit cycle control generally relies on empirical adjustment, and lacks strict theoretical guarantees, so that convergence and stability cannot be effectively guaranteed in practical applications. The robustness of the system performs poorly, especially in the presence of model uncertainty and external disturbances. In summary, the existing lower limb exoskeleton control method has defects in terms of time dependence, complex track processing capability and theoretical guarantee, and a novel control method which can adapt to gait change, process complex motion tracks and has strict stability guarantee is needed. Disclosure of Invention The invention aims to provide a time-independent control method of a lower limb exoskeleton robot based on a vector field generator, which is characterized in that a model-based control law is designed by constructing a target limit cycle and the vector field generator, so that the system state is globally asymptotically converged to a target periodic motion from any initial point, gait rhythm change and active intention of a user can be adapted, and meanwhile, the autonomous resynchronization to a target track under external disturbance is ensured. The invention aims at realizing the aim by adopting the following technical scheme that the time-independent control method of the lower limb exoskeleton robot based on the vector field generator comprises the following steps: Step one, constructing a target limit cycle, wherein the step maps the periodic movement (such as gait movement) of the target into a closed track in a phase space, namely a limit cycle. The phase parameter θ for the limit cycle is described as WhereinAndRepresenting the function of joint position and velocity as a function of phase, respectively. By defining the system state (q, v) to the nearest point of the limit cycle as the target stateAnd introducing a functionTo correlate the state with the limit cycles, thereby establishing a time independent frame of reference. Step two, vector field construction, which is to design a vector field generator to generate a vector field. The vector field consists of a stable term and a period adjustment termThe constitution, i.e. The stability term ensures asymptotic stability of the system state error, while the period adjustment term is used to accommodate dynamic changes in periodic motion, which together drive the system state error to converge to zero. Step three, control law design, namely designing a control law based on a dynamics model of the lower limb exoskeleton robot. Wherein, (q, v) is a state vector of the exoskeleton system, representing joint position and velocity, respectively;,,, The estimated values of an inertia matrix, a Coriolis force matrix, a gravity term and a friction term in the dynamic model are obtained through model parameter identificatio