【作者】 李强；

【导师】 薛开；

【作者基本信息】 哈尔滨工程大学 ， 机械制造及其自动化， 2013， 博士

【摘要】 为了在行星（如月球和火星）表面探测及在地球表面的危险环境（如沙漠、沼泽、火灾现场、核辐射区域等）中作业，要求自主移动机器人能自主地识别环境，完成使命，避免处于危险境地。地面识别或地面分类是环境识别中重要的一部分。机器人安全有效地穿越不同的地面需要与之相适应的控制策略。当地面发生变化时，自主移动机器人应能适应所穿越的地面。研究地面分类可以解决自主移动机器人在复杂地面的通过性问题，对于提高移动机器人的自主移动性能十分重要。本文在深入分析综合国内外同类研究的基础上，从地面分类特征提取以及分类器设计这两个基本层次展开对自主轮式机器人地面分类相关理论与技术问题的研究。本文设计了数据采集的实验，以四轮移动机器人为实验平台，在机器人左前轮轮臂上安装x、 y、 z向加速度计和z向传声器。机器人在沙、碎石、草、土和沥青五种地面上分别以六种速度行驶，提取车轮与地面相互作用的加速度和声压信号作为地面分类的原始数据。对原始数据进行时域幅值分析，提取地面特征，对于每个传感器数据选用若干个幅值域参数作为地面特征。对于传统的k-近邻（kNN）方法来说，有k值选择问题；用kNN方法解决多类分类问题采用投票法决策，当出现票数相同的情况时，目前尚没有更好的决策策略，尽管随机挑选法是一个实用的策略，但分类精度会降低。针对以上两个问题，本文给出改进的kNN方法，即给出k值的选择方法；对于多种地面分类出现两种以上（包含两种）得票数相同的情况，给出kNN循环寻优的方法。对于传统的概率神经网络（PNN）方法来说，有平滑因子σ的估计问题，估计得好有利于提高分类精度。以前的学者认为对于所有的样本应选用同一个σ或对于相同维数的样本选用相同的σ，但这种选法不能保证对于所有的测试样本σ都是最优的或较优的，甚至得不到测试结果。针对这一问题，本文给出改进的PNN方法，即给出平滑因子σ的迭代寻优方法。应用现有的一对一支持向量机（SVM）方法解决多类分类问题采用投票法决策，当出现票数相同的情况时，目前尚没有更好的决策策略。针对这个问题，本文提出改进的一对一SVM方法，即利用LIBSVM中的一对一SVM二值分类程序，对于多种地面分类出现两种以上（包含两种）得票数相同的情况，提出新的算法。从分类准确率和数据处理时间两个方面对改进的kNN、改进的PNN及改进的一对一SVM方法进行比较。基于时间序列重构的吸引子轨迹矩阵奇异值分解（SVD）的方法原用于故障诊断领域，用于降低原信号中的噪声。本文给出基于奇异值分解（SVD）的特征提取方法，即利用振动信号时间序列重构的吸引子轨迹矩阵奇异值分解的前若干个奇异值作为特征值，取得了好的分类效果。研究基于快速傅里叶变换（FFT）的特征提取方法和基于功率谱密度（PSD）的特征提取方法，阐述二者特征选择的方法。从分类准确率和数据处理时间两个方面对以上三种特征提取方法进行比较。基于实测数据和相应的分类实验验证了所提方法的效力。更多还原

【Abstract】 In order to explore in the planets’(such as the moon and Mars) surface and work in thedangerous environment (such as desert, marsh, the scene of the fire, nuclear radiation area, etc)of the earth’s surface, autonomous mobile robots should be able to independently identifyenvironment, complete the mission without a dangerous situation. Terrain identification orterrain classification is an important part of environmental identification. Correspondingcontrol strategy is necessary for robot to travel on different terrain safely and effectively,when the terrain changes, autonomous mobile robot must be able to adapt to the terrain whereit is traversing. Terrain classification can solve the issue of trafficability of autonomousmobile robot in complex terrain. It is very important to improve robot autonomous mobileperformance.Based on in-depth analysis and synthesis of similar studies home and abroay, the theoryand techniques are researched from the two aspects, i.e. terrain classification featureextraction and classification method.In this dissertation，experiments for data acquisition are designed. The experimentalplatform is a four-wheeled mobile robot on which arm accelerometers in x, y, zdirections and a microphone in z direction are installed in left front wheel. When the robotis traversing respectively on sand, gravel, grass, soil and asphalt terrain with six differentvelocities, the acceleration and sound pressure signals of wheel-terrain interaction arecollected as the original data.By time domain amplitude analysis of original data, several parameters of amplitudedomain are selected as the terrain features for each sensor data. To the conventionalk-nearest neighbors (kNN) algorithm, it is necessary to deal with the choice of k, and nowthere is no best decision strategy for the situation when number of votes is the same in theprocess of multi-classification based on voting decisions, though a practical strategy selectedis random method, which is reduces classification accuracy. To the two problems, animproved kNN method was proposed, i.e. the choice method of k was proposed and kNNcycle optimization method was also investigated to deal with the problem that more than twokinds (including two) of terrains have the same number of votes.To the conventional probabilistic neural network (PNN) method, there is a problem aboutthe estimation of smoothing factor σ which is important to improve the classification accuracy. Previous scholars considered that the same σ was chosen for all samples orsamples of the same dimensions, but it could not make sure that the σ was the best orsub-optimal for all test samples, even there was no result. For the problem, an improved PNNmethod was proposed to deal with the choice of smoothing factor σ by iterativeoptimization method.The traditional one-against-one support vector machine (SVM) method, now there is nobest decision strategy for the situation when number of votes is the same in the process ofmulti-classification based on voting decisions, an improved one-against-one SVM methodwas rendered to deal with the problem that more than two kinds (including two) of terrainshave the same number of votes based on two-classification program of LIBSVM. Yetimproved kNN，improved PNN and improved one-against-one SVM methods were comparedin terms of classification accuracy and data processing time.In the field of fault diagnosis, a method based on singular value decomposition of trackmatrix of attractor reconstructed by time series is always used to reduce the noise in originalsignal. Based on singular value decomposition (SVD), a feature extraction method wasproposed using the fore several singular values of track matrix of attractor reconstructed byvibration signals time series as eigenvalues, and better classification effect was achieved.Feature extraction methods based on the fast Fourier transform (FFT) and the power spectraldensity (PSD) were studied, and both feature selections methods were described. Yet the threefeature extraction methods were compared in terms of classification accuracy and dataprocessing time.Based on measured data, the proposed methods have been validated by correspondingclassification experiments.更多还原