• IEMEK Journal of Embedded Systems and Applications
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• v.16 no.4
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• pp.119-127
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• 2021

The aim of this paper is to propose a less conservative stabilization condition for leader-following sampled-data control of wheeled mobile robot (WMR) systems by using a clock-dependent Lyapunov function (CDLF) with looped functionals. In the leader-following WMR system, the state and input of the leader robot are measured by digital devices mounted on the following robot, and they are utilized to construct the sampled-data controller of the following robot. To design the sampled-data controller, a stabilization condition is derived by using the CDLF with looped functionals, and formulated in terms of sum of squares (SOS). The considered Lyapunov function is a polynomial form with respect to the clock related to the transmitted sampling instants. As the degree of the Lyapunov function increases, the stabilization condition becomes less conservative. This ensures that the designed controller is able to stabilize the system with a larger maximum sampling interval. The simulation results are provided to demonstrate the effectiveness of the proposed method.

• IEMEK Journal of Embedded Systems and Applications
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• v.14 no.5
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• pp.269-275
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• 2019

This paper addresses the control problem of cyber-physical systems under controller attack. A novel discontinuous Lyapunov functionals are employed to fully utilize sampled-data pattern which characteristic is commonly appeared in cyber-physical systems. By considering the limited resource of networks, cyber-attacks on the controller are considered randomly occurring and are described as an attack function which is nonlinear but assumed to be satisfying Lipschitz condition. Novel criteria for designing controller with robustness for cyber-attacks are developed in terms of linear matrix inequality (LMI). Finally, a numerical example is given to prove the usefulness of the proposed method.

• Journal of the Korean Arthroscopy Society
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• v.9 no.2
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• pp.123-131
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• 2005

The central third of the patellar tendon and hamstring tendons(semitendinosus and gracilis) are the most frequently used tissues for intra-articular replacement of the anterior cruciate ligament(ACL). At present, many surgeons consider the central third patellar ten don graft to be the gold standard for replacement of the ACL. Recent prospective studies by Marder et at and Aglietti et al, however, have failed to show any statistically significant differences in knee stability and functional outcome between central third patellar tendon grafts and hamstring tendon grafts. The review of this article is to (1) review the historical use of hamstring tendon grafts for ACL reconstruction; (2) discuss indications for use of hamstring tendon grafts for ACL reconstruction; (3) describe our present operative technique using a combined double-looped semitendinosus and gracilis graft with $RIGIDFIX^{circledR}$ and $INTRAFIX^{circledR}$ and (4) review the results of hamstring ACL reconstructions.