This study focuses on a mobile robot guidance control system in which a mobile robot tracks the reference trajectory parallel to a guide wall. A laboratory mobile robot which has two driving wheels and two distance measurement sensors on each side to measure distances from the guide wall is considered. Because measured distances are influenced by noise such as guide wall undulations and mobile robot vibrations, a nonlinear observer based on the extended linearization method is adopted to estimate state variables in mobile robot motion dynamics. A mobile robot heading angle and lateral deviation estimation algorithm based on this nonlinear observer are proposed, and the observer stability condition is derived. The estimation algorithm combined with state feedback controller comprises the mobile robot guidance control system. Estimation and control performance of the system are evaluated with a simulation model and the laboratory mobile robot.

A time diversity automatic repeat-request (ARQ) scheme with a finite number of transmissions is investigated for a digital FM mobile radio with frequency demodulation (FD). It processes all the retransmissions of a single data block using postdetection diversity combining. The analysis of the signal energy per bit required for a given bit error rate (BER) and the spectral efficiency in a cellular mobile radio system are presented. The results obtained from the numerical calculations show that this ARQ scheme offers a performance superior to both the basic ARQ scheme and the time-diversity scheme.>