基于信息势能的鲁棒估计器及其在同时定位与地图构建问题中的应用

提出了一种基于信息势能鲁棒估计器来解决机器人室内的同时定位与地图构建（SLAM）问题．结构化的室内环境可以用线段近似表示．然而动态环境中,测距传感器测得的数据通常湮没在大量的噪声信号中．本文采用“分割与合并”（split—and．merge）方法进行线段的分类,根据信息势能的性能指标衡量每个采样数据对该线段的信息贡献量．按照信息优化理论设计估计器,选择信息量贡献大的样本点作为信息内点提取线段参数,构建局部地图．采用粒子滤波器进行地图及机器人路径的更新．采用递推的方法估计信息势能,降低了对样本点的信息量贡献做估计时的复杂度．仿真和实验结果证明,本文所提出的方法具有较强的鲁棒性,提高了SLAM策略的准确性和实时性．     

A new approach to auto-tuning of PID controllers

Delayed state variable filters are implemented for the estimation of parameters of monotone open-loop processes that can be approximated by a first-order lag coupled with a time delay. Based on the delayed filtered step output response, and the first and second-order derivatives, a new estimation procedure has been derived for on-line estimation of the corresponding static process gain, the apparent dead time and the apparent time constant. A new PID tuning formula is formed that is based on the placement of the open-loop zeros related to the apparent time constant and time delay, to give a controlled system with a damping of 0-5 or a maximum overshoot of approximately 16-3%. Extensive simulation studies have also been carried out to relate the controlled output step response to the open-loop system parameters, which could then be re-applied in closed loop retuning of PID controllers. Efforts have also been made to apply the tuning technique to the control of multivariable systems. Simulations are included to illustrate the concepts.     

Adaptive PID control of systems with unknown time delay

A new algorithm for the adaptive control of systems with unknown time delay is presented in which the underlying control law has the familiar PID structure. The design is based on a continuous-time approach. This algorithm can be applied to a class of high-order systems which can be modelled by either a second-order system with time delay or a first-order system with time delay. The parameters of the system including time delay are estimated recursively by a derivative-free least-squares algorithm. The controller settings are selected according to a set of analytical formulae derived from mean-square error criteria. The algorithm is tested on simulated examples as well as a laboratory-scale coupled-tank apparatus.     

Analysis of the DNA Sequence of a 34 038 bp Region on the Left Arm of Yeast Chromosome XV

We report the DNA sequence of a 34 038 bp segment of Saccharomyces cerevisiae chromosome XV. Subsequent analysis revealed 20 open reading frames (ORFs) longer than 300 bp and two tRNA genes. Five ORFs correspond to genes previously identified in S. cerevisiae, including RPLA2, PRE6, MSE1, IFM1 and SCM2 (TAT2, TAP2, LTG3). Two putative proteins share considerable homology with other proteins in the current data libraries. ORF O2145 shows 41·2% identity with the glycophospholipid-anchored surface glycoprotein Gas1p of S. cerevisiae and ORF O2197 has 53·2% identity to chromosome segregation protein Dis3p of Schizosaccharomyces pombe. Accession Numbers for these sequences are provided in Table 1.©1997 John Wiley & Sons, Ltd.