Nonlinear Control Techniques for a SMA Active Ankle Foot Orthosis

Volume 10: Mechanics of Solids and Structures, Parts A and B ◽

10.1115/imece2007-43788 ◽

2007 ◽

Cited By ~ 1

Author(s):

Ehsan Tarkesh ◽

Mohammad Elahinia

Keyword(s):

Nonlinear Control ◽

Sliding Mode ◽

Nonlinear Behavior ◽

Good Alternative ◽

Switching Control ◽

Experimental Result ◽

Ankle Foot Orthosis ◽

Control Techniques ◽

Slow Walking ◽

Foot Orthosis

This paper is aimed toward the development and evaluation of a novel active ankle foot orthosis (AAFO) based on shape memory alloy (SMA) actuators. This device intends to fill the gap in the existing research aimed at helping patients with drop foot muscle deficiencies as well as rehabilitation activities. To check the feasibility of this idea, a brief study is done on the dynamic behavior of ankle joint and then an SMA manipulator with a similar biological concept is used for experiment. Nonlinear behavior of SMA wires requires nonlinear control techniques such as Sliding Mode Controller (SMC) for tracking the desired ankle angle. Simulation results of three different techniques are compared (PID, SMC and SMC-PID) and finally the experimental result of a SMC-PID switching control is provided. This results shows that a switching control between simple PID and Sliding Mode Control can be a good alternative to follow the desired trajectory in slow walking cycles.

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Experimental and Numerical Comparison Between Two Nonlinear Control Logics

International Journal of Applied Mechanics ◽

10.1142/s1758825116500617 ◽

2016 ◽

Vol 08 (05) ◽

pp. 1650061 ◽

Cited By ~ 9

Author(s):

Francesco Ripamonti ◽

Egidio Leo ◽

Ferruccio Resta

Keyword(s):

Nonlinear Control ◽

Sliding Mode ◽

Nonlinear Behavior ◽

Operating Conditions ◽

System Stability ◽

Flexible Manipulator ◽

Engineering Practice ◽

Numerical Comparison ◽

System A ◽

Nonlinear Form

Nonlinear behavior is present in the operating conditions of many mechanical systems, especially if nonsmall oscillations are considered. In these cases, in order to improve vibration control performance, a common engineering practice is to design the control system on a set of linearized models, for given operating conditions. The well-known gain-scheduling technique allows the parameters of the control law to be changed according to the current working condition, also increasing system stability. However, more recently new control logics directly applicable to the systems in nonlinear form have been developed. The aim of this paper is to study, both numerically and experimentally, the dynamic of a mechanical system (a 3-link flexible manipulator) comparing the performance of a fully nonlinear control (the sliding-mode control) and a standard linearized approach.

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Assessment of the Adaptive Sliding Mode Control of an Active Ankle Foot Orthosis with an Impedance Reference

2019 7th International Conference on Robotics and Mechatronics (ICRoM) ◽

10.1109/icrom48714.2019.9071905 ◽

2019 ◽

Author(s):

Ahmad Bagheri ◽

Davood Dorostkar ◽

Mohammad Reza Zakerzadeh ◽

Mohammad Jafar Sadigh ◽

Mohamad Mahjoob

Keyword(s):

Sliding Mode Control ◽

Sliding Mode ◽

Adaptive Sliding Mode Control ◽

Ankle Foot Orthosis ◽

Adaptive Sliding Mode ◽

Mode Control ◽

Foot Orthosis

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Adaptive Proxy-Based Controller of an Active Ankle Foot Orthosis to Assist Lower Limb Movements of Paretic Patients

Robotica ◽

10.1017/s0263574719000250 ◽

2019 ◽

Vol 37 (12) ◽

pp. 2147-2164 ◽

Cited By ~ 5

Author(s):

Weiguang Huo ◽

Victor Arnez-Paniagua ◽

Guangzheng Ding ◽

Yacine Amirat ◽

Samer Mohammed

Keyword(s):

Sliding Mode ◽

State Of The Art ◽

Tracking Error ◽

Reference Trajectory ◽

Tracking Accuracy ◽

Parameter Uncertainties ◽

External Disturbances ◽

Ankle Foot Orthosis ◽

Gait Phase ◽

Foot Orthosis

SummaryThis paper deals with the control of an active ankle foot orthosis (AAFO) for paretic patients. State of the art methods using an AAFO try to track a predefined trajectory of the ankle joint while guaranteeing the wearer’s safety in the presence of a large tracking error. Combining the wearer’s safety and tracking accuracy is generally difficult to achieve at the same time, hence a trade-off should be found. Proxy-based sliding mode control (PSMC) offers great performances in both position tracking and safety guarantee. However, its tracking performance is subject to the influences of parameter uncertainties and external disturbances that generally occur during walking. This paper introduces an adaptation interaction method to the basic PSMC with an online adaptation of the proportional, integral and derivative parameters. At the same time, a gait phase-based ankle reference generation algorithm was proposed to adjust the joint reference trajectory in real time. The experiments using the AAFO show better tracking results with respect to basic PSMC while guaranteeing the safety.

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A Comparative Study of Nonlinear Control Schemes for Induction Motor Operation Improvement

International Journal of Robotics and Control Systems ◽

10.31763/ijrcs.v2i1.521 ◽

2021 ◽

Vol 2 (1) ◽

pp. 1-17

Author(s):

Yassine Zahraoui ◽

Mohamed Akherraz ◽

Alfian Ma’arif

Keyword(s):

Nonlinear Control ◽

Induction Motor ◽

Sliding Mode ◽

External Disturbances ◽

Control Techniques ◽

Integral Action ◽

Control Schemes ◽

The Stability ◽

Motor Operation ◽

The Cost

In the objective of improving the performance of induction motor operation and ensuring a robust control against different uncertainties and external disturbances, especially at low-speed regions, this research highlights the main features of two nonlinear control techniques. First, the control design is based on the backstepping approach (BSA) with integral action, and then the sliding mode control (SMC) theory. The BSA principle is to define successive causal relations in order to construct the control law in a recursive and systematic way. This allows overcoming the obstacle of the higher-order system's dimension. SMC is designed to drive and then constrain the system state to lie within a neighborhood of the switching surface, this provides very strong and inherent robustness to the resulting controllers. The main reason behind developing the nonlinear control techniques is to ensure a decoupled control of the machine. Besides, it guarantees the stability of the overall system by tracking the speed reference with the fewest static error. Moreover, as the sensorless control increases the reliability and decreases the cost of the control system, an extended Kalman filter is implemented to improve speed and flux observation. The simulations of all the discussed results have been obtained by MATLAB/Simulink.

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Effectiveness of an ankle–foot orthosis on walking in patients with stroke: a systematic review and meta-analysis

Scientific Reports ◽

10.1038/s41598-021-95449-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Yoo Jin Choo ◽

Min Cheol Chang

Keyword(s):

Stride Length ◽

Walking Speed ◽

Sagittal Plane ◽

Meta Analysis ◽

Step Length ◽

Stride Time ◽

Plane Angle ◽

Ankle Foot Orthosis ◽

Biomechanical Parameters ◽

Foot Orthosis

AbstractWe conducted a meta-analysis to investigate the effectiveness of ankle–foot orthosis (AFO) use in improving gait biomechanical parameters such as walking speed, mobility, and kinematics in patients with stroke with gait disturbance. We searched the MEDLINE (Medical Literature Analysis and Retrieval System Online), CINAHL (Cumulative Index to Nursing and Allied Health Literature), Cochrane, Embase, and Scopus databases and retrieved studies published until June 2021. Experimental and prospective studies were included that evaluated biomechanics or kinematic parameters with or without AFO in patients with stroke. We analyzed gait biomechanical parameters, including walking speed, mobility, balance, and kinematic variables, in studies involving patients with and without AFO use. The criteria of the Cochrane Handbook for Systematic Reviews of Interventions were used to evaluate the methodological quality of the studies, and the level of evidence was evaluated using the Research Pyramid model. Funnel plot analysis and Egger’s test were performed to confirm publication bias. A total of 19 studies including 434 participants that reported on the immediate or short-term effectiveness of AFO use were included in the analysis. Significant improvements in walking speed (standardized mean difference [SMD], 0.50; 95% CI 0.34–0.66; P < 0.00001; I2, 0%), cadence (SMD, 0.42; 95% CI 0.22–0.62; P < 0.0001; I2, 0%), step length (SMD, 0.41; 95% CI 0.18–0.63; P = 0.0003; I2, 2%), stride length (SMD, 0.43; 95% CI 0.15–0.71; P = 0.003; I2, 7%), Timed up-and-go test (SMD, − 0.30; 95% CI − 0.54 to − 0.07; P = 0.01; I2, 0%), functional ambulation category (FAC) score (SMD, 1.61; 95% CI 1.19–2.02; P < 0.00001; I2, 0%), ankle sagittal plane angle at initial contact (SMD, 0.66; 95% CI 0.34–0.98; P < 0.0001; I2, 0%), and knee sagittal plane angle at toe-off (SMD, 0.39; 95% CI 0.04–0.73; P = 0.03; I2, 46%) were observed when the patients wore AFOs. Stride time, body sway, and hip sagittal plane angle at toe-off were not significantly improved (p = 0.74, p = 0.07, p = 0.07, respectively). Among these results, the FAC score showed the most significant improvement, and stride time showed the lowest improvement. AFO improves walking speed, cadence, step length, and stride length, particularly in patients with stroke. AFO is considered beneficial in enhancing gait stability and ambulatory ability.

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