Browsing by Author "Jung, J. H."
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Item Discretisation method and stability criteria for non-linear systems under discrete-time time delay control(2011-07-21) Jung, J. H.; Chang, P. H.; Stefanov, D.; Medical TechnologiesTime delay control (TDC) for non-linear systems has rapidly drawn attention as a result of its unusually robust performance and yet its extraordinarily compact form. In many real applications, TDC has been implemented digitally and the time delay, λ, was set to the sampling period of the control system, which is a constant during the control process. The existing stability analysis, however, has been made based on the assumption of the continuous-time TDC and infinitesimal time delay (λ→0). The assumption not only fails to reflect the reality that the closed-loop system (CLS) is a sampled-data system, but also leads to a stability criterion in which important parameters, such as λ, are absent. In this paper, therefore, sufficient stability criteria for a non-linear system based on the premise of discrete-time TDC and λ that is equal to the sampling period are presented. To this end, we have first proposed a discretization method to derive the approximate discrete-time model of CLS. Then by using the model and the concepts of consistency and Lyapunov stability, we have derived stability criteria for the exact discrete-time model of CLS. The suggested criteria consist of the sampling period and other parameters of TDC. These criteria have been verified by simulation results.Item Kinematic and dynamic modeling of a multifunctional rehabilitation robot UHP(Springer Netherlands, 2018) Mancisidor, A.; Zubizarreta, A.; Cabanes, I.; Bengoa, P.; Jung, J. H.; Hofbaur, Michael; Husty, Manfred; Medical TechnologiesThe design of a suitable controller that handles robot-human interaction is one of the critical tasks in rehabilitation robotics. For this purpose, an accurate model of the robot is required. The Universal Haptic Pantograph (UHP) is a novel upper limb rehabilitation robot that can be configured to perform arm or wrist exercises. This work is focused on the latter, solving the kinematic model by the use of the closure loop equations, while Lagrangian formulation is used to estimate the interaction force. In order to prove the effectiveness of the model, several experimental tests are carried out. Results demonstrate that the mean motion error is less than 1 mm, and the estimated force error less than 10%.Item A new robotic platform for gait rehabilitation of bedridden stroke patients(2009) Monaco, V.; Galardi, G.; Jung, J. H.; Bagnato, S.; Boccagni, C.; Micera, S.; Medical TechnologiesRobotic aided therapy has been developed in the last decades in order to improve the effects of gait rehabilitation on stroke patients. Although several platforms have nowadays used in clinical practice, contrasting results have been achieved with reduced significant improvements in stroke patients when they experience robotic based therapy. In particular, an improvement of the clinical outcome may be achieved by starting the rehabilitation process almost immediately after the stroke. To address this issue a new robotic system, called "NEUROBike", has been developed. This approach is based on the hypothesis that a better recovery of the neuro-motor control of the leg could result from an early, intensive and task-oriented rehabilitation therapy. Therefore, the leg manipulation during the acute phase, following joint trajectories comparable with the ones obtained during natural walking, could improve the outcome of the rehabilitation. In this regard, desired trajectories of the end-effector of NEUROBike have been estimated in accordance with data collected from young and elderly people when walking on treadmill in a range of speeds from 0.5 to 1.3 m/s. Moreover, tracking performance of a traditional position control algorithm has been investigated. This paper is aimed at showing the first results obtained during the test of the platform. In the next months NEUROBike will be applied for the first clinical pilot studies.