Jeom-Keun Kim

H ∞ control of discrete-time linear systems with norm-bounded uncertainties and time delay in state

This paper deals with H∞ control problem for discrete-time linear systems with norm-bounded uncertainties and time delay in state. In terms of a modified Riccati inequality for discrete-time linear systems, a sufficient condition is presented and a state feedback control law is also given. The proposed control law is a memoryless state feedback control law.

Robust adaptive control of uncertain nonlinear systems via disturbance observer techniques

This paper deals with robust control problems for nonlinear systems with matched uncertainties. In order to handle the uncertainties, the uncertainties are considered as disturbances. First, a disturbance observer is designed and the uncertainties can be rejected by subtracting these estimated values of disturbances from the plant input. Since the disturbance observer is a kind of low-pass filter, it has inevitably estimation errors. To get rid of the effects of these errors, the additional control should be applied. This additional control input is designed using adaptive control scheme. The unknown disturbance error bounds are estimated by adaptive parameter estimation methods and then the control input is calculated using these estimate values. But the control input needs to be switched on the sliding surface and provokes a chattering phenomenon. The control method suggested in this paper can, however, reduce the chattering phenomenon as small as possible by using large disturbance observer gain because the magnitude of the switching control input is dependent on the disturbance estimation errors which are decided by the accuracy of the designed disturbance observer.

Case Study: Long-term Experiments on a Daily Activity Monitoring System for an Elderly Living Alone

Abstract: This paper describes analysis of long-term experiments on a monitoring system to assess the daily activities of the elderly who live alone. The developed system is composed of an in-house sensing system and a server system. The in-house sensing system installed in their own houses is a typical wireless sensor network system including three kinds of wireless sensors. The server system has a database server and an assessment server. We have installed the system into an elderly house, collected data during over two years continuously, then analyze the data. From the analysis, we could measure the energy consumption profile of three kinds of sensor nodes. The experiment shows all kinds of nodes can operate over one year with two AA-size alkaline batteries. Using a measure of reliability of the monitoring system called ‘deadzone’, the system has showed the failure operation for 842 hours (4.66 %) during over 18,000 hours total operation period.Keywords: case study, elderly, monitoring system, reliability analysis, long-term experiments

Simultaneous Switching Noise Minimization Technique Using Dual Layer Power Line Mutual Inductors

A novel technique for minimization of simultaneous switching noise is presented. Dual Layer Power Line (DLPL) structure is newly proposed for a possible silicon realization of a mutual inductor, with which an instant large current in the power line is halfdivided flowing through two different, but closely coupled, layers in opposite directions. This mutual inductance between two power layers enables us to significantly minimize the switching noise. SPICE simulations show that with a mutual coupling coefficient higher than 0.8, the switching noise reduces by 63% compared to the previously reported solutions. This DLPL technique can also be applied to PCB artworks.

Design of a STT missile autopilot using functional inversion and LMI approach

We present a systematic approach for the autopilot design of skid-to-turn (STT) missiles. First, the nonlinear model of a STT missile is partially linearized via functional inversion techniques and then, the additional set-point tracking controller can be designed by the well-known LMI approach. The stabilization conditions are given in terms of LMIs.