Nonlinear Control Design for a Gravity Compensation Mechanism for Human Lower Limb Rehabilitation

2020 ◽  
Author(s):  
Zeki Okan Ilhan ◽  
Meng-Sang Chew
Keyword(s):  
Feedback Control ◽  
Nonlinear Control ◽  
Numerical Simulations ◽  
Dynamic Model ◽  
Lower Limb ◽  
Sliding Mode ◽  
Control Design ◽  
Nonlinear Controller ◽  
Modeling Uncertainties ◽  
Limb Injuries

Abstract Dynamics of a two degree-of-freedom suspension mechanism is incorporated into nonlinear control design to facilitate its potential use as a rehabilitation device to aid people with lower-limb injuries. The proposed mechanism is a variation of the standard four-bar linkage with an extra link and two springs. The system dynamic model is first extracted based on the Lagrange’s equations in conservative form. The performance deviations due to the link inertia is demonstrated in open-loop numerical simulations under an impulsive force scenario. Finally, the dynamic model of the suspension mechanism is incorporated into feedback control design based on nonlinear, sliding mode control strategy that can add robustness against modeling uncertainties and external disturbances. The tracking performance of the proposed nonlinear controller is validated in closed-loop numerical simulations to demonstrate possible performance improvements under feedback control.

Operator-Based Robust Nonlinear Control Design of a Robot Arm with Micro-Hand

2016 ◽  
Vol 28 (4) ◽  
pp. 568-578 ◽  
Author(s):  
Zhengxiang Ma ◽  
◽  
Aihui Wang ◽  
Tiejun Chen ◽  
Keyword(s):  
Control System ◽  
Feedback Control ◽  
Nonlinear Control ◽  
Angular Position ◽  
Control Design ◽  
Robot Arm ◽  
Robust Nonlinear Control ◽  
Precise Position ◽  
Control Scheme ◽  
Loop Feedback

[abstFig src='/00280004/14.jpg' width='300' text='Robot arm with micro-hand system' ] This work focuses on a robust nonlinear control design of a robot arm with micro-hand (RAMH) by using operator-based robust right coprime factorization (RRCF) approach. In the proposed control system, we can control the endpoint position of robot arm and obtain the desired force of micro-hand to perform a task, and a miniature pneumatic curling soft (MPCS) actuator which can generate bidirectional curling motions in different positive and negative pressures is used to develop the fingers of micro-hand. In detail, to control successively the precise position of robot arm and the desired force of three fingers according to the external environment or task involved, this paper proposes a double-loop feedback control architecture using operator-based RRCF approach. First, the inner-loop feedback control scheme is designed to control the angular position of the robot arm, the operator controllers and the tracking controller are designed, and the robust stability and tracking conditions are derived. Second, the complex stable inner-loop and micro-hand with three fingers are viewed as two right factorizations separately, a robust control scheme using operator-based RRCF approach is presented to control the fingers forces, and the robust tracking conditions are also discussed. Finally, the effectiveness of the proposed control system is verified by experimental and simulation results.

scholarly journals Modeling and Finite-Time Sliding Model Control of a Lower Limb Exoskeleton for Use in Rehabilitation

2021 ◽  
Author(s):  
Uddesh Kishor Tople ◽  
Amrapali Anandkumar Khandare ◽  
Atharv Dipak Itankar ◽  
Satya Kartheek Dogga
Keyword(s):  
Dynamic Model ◽  
Lower Limb ◽  
Finite Time ◽  
Sliding Mode ◽  
Dynamic Modelling ◽  
Work Load ◽  
Modeling And Control ◽  
Lower Limb Exoskeleton ◽  
Exoskeleton Robot ◽  
Model Control

Abstract Exoskeleton systems in recent years has become a prime choice technology due to the various possibilities it can deliver. These possibilities comprise the assisting and rehabilitative techniques designed for disabled and elderly people, so that they can regain control of their limbs and in addition to this also to augment and boost the abilities of able-bodied persons during heavy work-load conditions. Many works are reported on the modeling and control of a exoskeleton robot, but very few paper discuss the complete derivation of the model of the system. Here, first the dynamic model of a physical system used as lower limb exoskeleton robot is obtained. Secondly the analysis of the system done that is derived through dynamic modelling of a 3-link robotic manipulator using Euler-Lagrange approach and validation of the corresponding model in simulation. Further, design of a finite-time SMC for desired trajectory tracking of the system is implemented. The dynamic model of the 3-link system and its control using finite-time sliding mode control are validated in MATLAB simulation environment.

Nonlinear Control of a Transient Inductrack System Using State Feedback

2021 ◽  
Author(s):  
Ruiyang Wang ◽  
Bingen Yang
Keyword(s):  
Feedback Control ◽  
Nonlinear Control ◽  
Dynamic Modeling ◽  
State Feedback ◽  
Permanent Magnets ◽  
Control Method ◽  
Linear Part ◽  
Control Design ◽  
Nonlinear Part ◽  
Highly Nonlinear

Abstract The concept of Inductrack refers to the magnetic levitation technology achieved by Halbach arrays of permanent magnets. In an Inductrack system, the dynamic behaviors involved with transient responses are difficult to capture due to the highly nonlinear, time-varying, electromagnetic-mechanical couplings. In the literature, dynamic modeling of Inductrack systems that aims to analyze the transient behaviors has been widely addressed. However, one common issue with the previous investigations is that most of the dynamic models either partly or completely adopted certain steady-state and ideal case assumptions. These assumptions are extremely difficult to maintain in a transient scenario, if not impossible. Therefore, while providing good understanding of Inductrack systems, the previous results in dynamic modeling have a limited utility in providing guidance for feedback control of Inductrack systems. Recently, a benchmark transient Inductrack model was created for characterizing the transient time response of the system with fidelity, which enables model-based feedback control design. In this work, based on the transient model, a new control method for the Inductrack dynamic system is developed. The proposed control method consists of a linear part and a nonlinear part. The linear part is devised based on a state feedback configuration; the nonlinear part is accomplished by fitting a nonlinear “force-current” mapping function. With this nonlinear feedback controller, the levitation gap of the Inductrack vehicle can be effectively stabilized at both constant and time-dependent traveling speed. The proposed control law is demonstrated in numerical examples. The nonlinear control design is potentially extensible to more complicated Inductrack systems with higher degrees of freedom.

A novel nonlinear controller for enhancement of the transient dynamics performance of a three-wheeled vehicle during different conditions

2021 ◽  
pp. 146441932110499
Author(s):  
Mohammad Amin Saeedi
Keyword(s):  
Control System ◽  
Feedback Control ◽  
Dynamic Model ◽  
Control Method ◽  
Full Range ◽  
Nonlinear Controller ◽  
Lateral Dynamics ◽  
Braking System ◽  
Wheeled Vehicle ◽  
Feedback Control Method

In this study, a new controller to prevent the yaw instability and rollover of a three-wheeled vehicle has been proposed. This controller offers the most obvious opportunity for affecting the vehicle's lateral dynamics performance on the full range of nonlinearities during various operating boundaries. The active combined controller has been designed based on sliding mode control method using an active roll system and an active braking system to dominate the uncertainties of the nonlinear dynamic model. Firstly, to avoid rollover of the three-wheeled vehicle, the roll angle was considered as the control objective, and the anti-roll bar was employed as an actuator to produce the roll moment. Secondly, to increase the maneuverability and lateral dynamics enhancement, an active braking system was designed. In the control system, the yaw rate and the lateral velocity were regarded as the control variables to track their references. Moreover, to verify the performance of the mentioned combined controller, another control system has been designed using the linearization feedback control method. Then, computer simulation has been carried out with a 12 degrees of freedom dynamic model of the three-wheeled vehicle called the delta. Furthermore, a nonlinear tire model has been utilized to compute the longitudinal and the lateral forces. Next, the comparative simulation results confirmed the effectiveness of the robust control system to raise the vehicle's maneuverability and its rollover stability in comparison with the linearization feedback control method, especially when the three-wheeled vehicle is subjected to critical conditions.

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