第 34卷 第 1期 控 制 与 决 策 Vol.34 No.1
2019年 1月 Control and Decision Jan. 2019
文章编号: 1001-0920(2019)01-0162-05 DOI: 10.13195/j.kzyjc.2017.0976
快速二阶终端滑模控制及其在下肢外骨骼的应用
宋胜利, 陈文浩
†
, 张兴龙, 曹宇轩
(陆军工程大学 野战工程学院,南京 210007)
摘 要: 为了提高传统二阶终端滑模控制的全局收敛性, 提出一种快速二阶终端滑模控制算法. 设计一种二阶趋
近律, 将绝对值函数隐藏在积分项里, 并增加线性项以提高全局收敛性. 当系统状态未到达滑模面时, 采用二阶趋
近律, 并通过调整参数避免奇异问题; 当系统状态到达滑模面时, 采用不含不连续符号项的指数趋近律, 以保证控
制误差有限时间收敛. 采用Lyapunov直接法证明快速二阶终端滑模控制算法的稳定性, 及其比 super twisting算法
具有更优良的收敛特性. 以下肢外骨骼为研究对象, 建立动力学模型. 在考虑建模误差和外部干扰的情况下, 将该
算法应用于下肢外骨骼的姿态控制. 仿真结果表明,所提出的控制算法能够有效抑制抖振,并且比super twisting算
法具有更良好的跟踪性能,验证了该算法的有效性.
关键词: 二阶终端滑模控制;抖振;收敛速度;下肢外骨骼;super twisting算法;Lyapunov直接法
中图分类号: TP351 文献标志码: A
Fast second-order terminal sliding mode control and its application in
exoskeleton of lower extremities
SONG Sheng-li, CHEN Wen-hao
†
, ZHANG Xing-long, CAO Yu-xuan
(College of Field Engineering,PLA Army Engineering University,Nanjing 210007,China)
Abstract: In order to improve the global convergence rate of traditional second-order terminal sliding mode control, a fast
second-order terminal sliding mode control algorithm is proposed in this paper. Compared to the traditional second-order
terminal sliding mode control, a new second-order approximation law is designed with absolute value functions hidden in
the integral term, also a linear term is included to improve the global convergence rate. A second-order approaching rule is
initially used with the possibility to avoid singularity via parameter tuning until the state has reached the sliding manifold,
then a continuous exponential approaching rule is adopted instead to guarantee finite time convergence. Lyapunov
direct method is used to prove the stability of fast second-order terminal sliding mode control algorithm and has better
convergence properties than that of the super twisting algorithm. A lower extremity exoskeleton is taken as the research
object, and its dynamics model is established. The algorithm is applied to the attitude control of the lower extremity
exoskeleton with modeling errors and additive disturbance. Simulation results show that the proposed control algorithm
can effectively alleviate the chattering effect, and outperforms than that of the super twisting algorithm, which verifies the
effectiveness of the proposed algorithm.
Keywords: second-order terminal sliding mode control;chattering;convergence rate;lower extremity exoskeleton;
super twisting algorithm;Lyapunov direct method
0 引
滑模变结构控制是一类特殊的非线性控制, 可以
根据系统的当前状态动态地变化系统结构, 迫使系统
按照预定的状态轨迹滑动. 由于滑动模态可以被设
计且与对象参数及扰动无关,使得变结构系统具有对
参数及扰动不敏感、快速响应、鲁棒性强和物理实现
简单等优点
[1-2]
. 因此,滑模控制被广泛应用于高速和
高精度控制系统
[3-7]
.
近年来, 终端滑模 (Terminal sliding mode, TSM)
因在滑模面中引入非线性项, 提高了系统的收敛速
度而成为研究热点
[8]
. 但是, TSM 存在奇异性问题
[9]
,
对此, 文 献 [10] 提出了 一种非 奇异终 端滑模 (Non-
singular terminal sliding mode, NTSM)方法,克服了奇
异问题. NTSM 越远离平衡状态, 其收敛速度越快, 而
收稿日期: 2017-07-20;修回日期: 2017-11-23.
责任编委: 吴立刚.
作者简介: 宋胜利 (1966−), 男, 教授, 博士, 从事机器人智能控制技术等研究;陈文浩 (1993−), 男, 硕士生, 从事控
制理论、外骨骼的研究.
†
通讯作者. E-mail: cwh74320@foxmail.com.