Omnidirectional Rehabilitative Training Walker Research Articles

Tracking Control for a Rehabilitative Training Walker Considering Human-Robot Interaction

A new extended state observer combined with a Backstepping tracking control method were proposed in this paper for the omnidirectional rehabilitative training walker. The aim of this study is to obtain a stable tracking controller, and it considered the interaction forces of the user and walker to ensure that the omnidirectional walker can track accurately specified trajectory. The extended state observer was designed to estimate the unknown interaction forces of user and the walker using output position and speed states. Further, a Backstepping controller based on the observed value was constructed to resist the adverse effects of interaction forces. The asymptotic stability of the trajectory tracking error, the velocity tracking error and the state observation error were guaranteed. Through programming, simulation results show the effectiveness of the proposed design method.

Nonfragile predictive control for an omnidirectional rehabilitative training walker with constraints on the tracking errors of position and velocity

SummaryHere, we propose a novel nonfragile predictive control method for an omnidirectional rehabilitative training walker. The aim of the study was to design a tracking controller that includes simultaneous constraints on the tracking errors in the position and velocity in order to guarantee safe system states for the omnidirectional walker. The nonfragile controller uses incremental control to solve the optimal quadratic program problem. The exponential stability of the system is guaranteed by constructing constraints on the trajectory‐tracking error and the velocity‐tracking error. Simulation and experimental testing were conducted to confirm the effectiveness of the proposed method and verify that it can provide safe positions and velocities when applied to control the motion of an omnidirectional walker.

Interaction Forces Identification Modeling and Tracking Control for Rehabilitative Training Walker

In this study, we propose a model and an adaptive backstepping tracking control method for omnidirectional rehabilitative training walker. The aim of the study is to design a stable tracking controller that can guarantee accurate tracking motion of the omnidirectional walker considering the interaction forces of the user and walker. A novel fuzzy model identification method was proposed to describe the interaction forces by using the reduced values of tracking performance. Further, an adaptive backstepping controller was developed to compensate the interaction forces on the basis of the identified model and adapt the change of user’s mass. The asymptotic stability of the trajectory tracking error and the velocity tracking error were guaranteed. As an application, simulation and experiment results were provided to illustrate the effectiveness of the proposed design procedures.

Stochastic adaptive tracking for a rehabilitative training walker with control constraints considering the omniwheel touchdown characteristic

ABSTRACTThis article investigates the improvement of trajectory tracking on an omnidirectional rehabilitative training walker (ORTW) with random shifts in the centre of gravity, control constraints, and touchdown characteristics of omniwheels. Analysis of the touchdown characteristic improved the accuracy of the dynamic ORTW model. The control constraints guarantee the safety of the omniwheels and the ORTW training process. After describing the random centre-of-gravity shifts using Wiener process, an improved stochastic dynamic model was constructed. Under trajectory tracking control with adaptive technology, the ORTW followed the trajectory designed by the rehabilitation therapist. The exponentially practical stability in mean absolute of the tracking-error system was derived from stochastic theory and Markov's inequality. The effectiveness of the proposed methods was confirmed in simulations.

Output tracking control for an omnidirectional rehabilitative training walker with incomplete measurements and random parameters

ABSTRACTIn this study, we propose a model and an output feedback tracking control for an omnidirectional rehabilitative training walker (ODW) with unmeasurable speed, incomplete measurements of position output, and random structural parameters. A stochastic model and an incomplete measurement model were proposed to describe the motion of an ODW subject to random structural parameters and to account for any incomplete data transmission phenomenon caused by possible sensor ageing or failures. A speed observer and a state observer were designed to estimate the unmeasurable speed and the incomplete measurements of position output. Moreover, a dynamic output feedback controller was constructed to ensure the exponential stability in mean square of the tracking error system. Furthermore, the results verify that the choice of appropriate design parameters can result in the mean square of the tracking error becoming arbitrarily small. A simulation example was provided to illustrate the effectiveness of the proposed design procedures.

Guaranteed cost non-fragile tracking control for omnidirectional rehabilitative training walker with velocity constraints

In this study, a new nonlinear tracking control method with velocity constraints performance is proposed for omnidirectional rehabilitative training walker. The aim of the study is to design an asymptotically stable nonfragile controller that can guarantee the safety of the rehabilitee and ensure tracking on a training trajectory planned by a physical therapist. According to Lyapunov theory, the guaranteed cost non-fragile controller can be designed to maintain stability in terms of solutions of linear matrix inequalities. The concept of safety velocity is given and the sufficient conditions for the existence of such a controller with safety velocity constraints performance are derived. As an application, simulation results confirm the effectiveness of the proposed method and verify that the walker can provide safe training velocity.

Redundant Input Safety Tracking for Omnidirectional Rehabilitative Training Walker with Control Constraints

AbstractThis study proposes a nonlinear safety tracking method based on redundant degrees of freedom with control constraints to protect against actuator faults that may occur in robotic rehabilitative walkers. A redundant input model with uniform actuator faults is constructed by separating the corresponding columns of the control matrix, and an adaptive robust control method is presented to deal with the separated term that is considered in relation to the extrinsic bounded interference that occurs on robotic walker systems. Based on the backstepping technique, an adjustable control law can be designed to maintain stability in terms of solving linear matrix inequality. The trajectory tracking error performance and the velocity tracking error performance are derived simultaneously. As an application, simulation results confirm the effectiveness of the proposed method and verify that the walker can provide safe sequential motions even when one wheel actuator fails.

Redundant input guaranteed cost non-fragile tracking control for omnidirectional rehabilitative training walker

In this study, the problem of guaranteed cost non-fragile tracking control on the omnidirectional rehabilitative training walker is examined. The nonlinear redundant input method is proposed when one wheel actuator fault occurs. The aim of the study is to design an asymptotically stable controller that can guarantee the safety of the user and ensure tracking on a training path planned by a physical therapist. The guaranteed cost control and the asymptotically zero state detectable concept of the walker are presented, and the model of redundant degree is constructed. The cost performance index is defined to restrain initial oversize input forces. On the grounds of LMI, a controller with gain variations that can satisfy asymptotic stability is obtained using a common Lyapunov function for admissible uncertainties resulting from an actuator fault. Simulation results confirm the effectiveness of the proposed method and verify that the walker can provide safe sequential motion when one wheel actuator is at fault.

Tracking Control for the Center-of-Gravity Constant Shift of Omnidirectional Rehabilitative Training Walker

This paper discusses the problem of tracking control on the center-of-gravity constant shift of omnidirectional rehabilitative training walker. The solution is proposed by pre-multiplication transposition matrix on the kinetics model of the system and the property is obtained when the center-of-gravity shift is invariable. The controller of independent rehabilitee mass property was designed. The problem of rehabilitee mass constant change is solved on the basis of center-of-gravity constant shift. The asymptotic stability of the closed system was proved using Lyapunov stable theory and LaSalle principle. The simulation results confirm the feasibility and effectiveness of the designed scheme.

Robust Redundant Input Reliable Tracking Control for Omnidirectional Rehabilitative Training Walker

The problem of robust reliable tracking control on the omnidirectional rehabilitative training walker is examined. The new nonlinear redundant input method is proposed when one wheel actuator fault occurs. The aim of the study is to design an asymptotically stable controller that can guarantee the safety of the user and ensure tracking on a training path planned by a physical therapist. The redundant degrees of freedom safety control and the asymptotically zero state detectable concept of the walker are presented, the model of redundant degree is constructed, and the property of center of gravity constant shift is obtained. A controller that can satisfy asymptotic stability is obtained using a common Lyapunov function for admissible uncertainties resulting from an actuator fault. Simulation results confirm the effectiveness of the proposed method and verify that the walker can provide safe sequential motion when one wheel actuator is at fault.