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Modeling and Evaluation of Adaptive Super Twisting Sliding Mode Control in Lower Extremity Exoskeleton
International Journal of Precision Engineering and Manufacturing-Green Technology ( IF 4.2 ) Pub Date : 2021-04-13 , DOI: 10.1007/s40684-021-00335-6
D. Ezhilarasi , Anjali S. Nair

In this paper, an integrated human-in-the-loop simulation paradigm for the design and performance analysis of a 6 DOF lower extremity exoskeleton is presented. An adaptive Super Twisting Sliding Mode Controller (ASTSMC) is designed for the trajectory tracking control of the exoskeleton by considering the human motion as reference trajectory. The dynamic model, that include linear and rotational displacement of hip, knee and ankle joints of both the legs is developed using Lagrange energy formulation. The position and angular velocity error of the wearer and the exoskeleton are being considered to establish the control law. Super twisting SMC is a robust control scheme that works effectively in the presence of external disturbances and parameter variations. However, the STSMC introduces chattering in the closed loop because of its high gain, to overcome this drawback, an adaptive STSMC is proposed for the control of exoskeleton against unknown disturbances without chattering. An adaptation scheme using Lyapunov criterion is derived that ensures the stability of the system in closed loop. The performance of the proposed control strategy is verified by implementing on the integrated CAD model of the exoskeleton along with the wearer. The effectiveness of the controller is tested under wind disturbance of varying velocity and direction. The results demonstrate improved tracking performance of the proposed control scheme with least error and less control effort compared to constant gain STSMC in normal and uneven terrain.



中文翻译:

下肢外骨骼自适应超扭曲滑模控制的建模与评估

在本文中,提出了一种用于六自由度下肢外骨骼设计和性能分析的集成的在环仿真范例。自适应超扭曲滑模控制器(ASTSMC)被设计为通过将人体运动作为参考轨迹来控制外骨骼的轨迹。使用拉格朗日能量公式开发了动态模型,其中包括两条腿的髋部,膝盖和踝关节的线性和旋转位移。正在考虑穿戴者和外骨骼的位置和角速度误差,以建立控制律。超扭曲SMC是一种鲁棒的控制方案,可在存在外部干扰和参数变化的情况下有效工作。但是,由于其高增益,STSMC在闭环中引入了颤动,为了克服这个缺点,提出了一种自适应STSMC,用于控制外骨骼不受未知干扰的干扰。推导了使用Lyapunov准则的自适应方案,该方案可确保闭环系统的稳定性。通过与穿戴者一起在外骨骼的集成CAD模型上实施,验证了所提出控制策略的性能。在风速和风向变化的情况下,对控制器的有效性进行了测试。结果证明,与正常和不平坦地形上的恒定增益STSMC相比,所提出的控制方案的跟踪性能具有最小的误差和更少的控制工作量。推导了使用Lyapunov准则的自适应方案,该方案可确保闭环系统的稳定性。通过与穿戴者一起在外骨骼的集成CAD模型上实施,验证了所提出控制策略的性能。在风速和风向变化的情况下,对控制器的有效性进行了测试。结果证明,与正常和不平坦地形上的恒定增益STSMC相比,所提出的控制方案的跟踪性能具有最小的误差和更少的控制工作量。推导了使用Lyapunov准则的自适应方案,该方案可确保闭环系统的稳定性。通过与穿戴者一起在外骨骼的集成CAD模型上实施,验证了所提出控制策略的性能。在风速和风向变化的情况下,对控制器的有效性进行了测试。结果证明,与正常和不平坦地形上的恒定增益STSMC相比,所提出的控制方案的跟踪性能具有最小的误差和更少的控制工作量。在风速和风向变化的情况下,对控制器的有效性进行了测试。结果表明,与正常和不平坦地形上的恒定增益STSMC相比,所提出的控制方案的跟踪性能具有最小的误差和更少的控制工作量。在风速和风向变化的情况下,对控制器的有效性进行了测试。结果证明,与正常和不平坦地形上的恒定增益STSMC相比,所提出的控制方案的跟踪性能具有最小的误差和更少的控制工作量。

更新日期:2021-04-13
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