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MMAN3210 Engineering Experimentation Laser Scanner Laboratory Laboratory Exercise 3: Semester 2 2010 Mohsen Alizadehfard Z3308893 Part 1: focusing on estimating the accuracy of the sensor, particularly the random errors in the measurement 1.1 Approach 1.1.1 Test conditions Nine conditions are selected which are tabulated in table below: Test No. #1 #2 #3 #4 #5 #6 #7 #8 #9 Inclination angle1 00 00 100 100 100 200 200 30o 30o Distance2 1m 3m 1m 2m 3m 1m 3m 1m 3m 1.1.2 Data extraction from multiple scans against time Data is extracted from the laser scanner. It takes 15 scans every 0.1 seconds and then the data are saved in the Matlab file name NameOfMyFile.dat. SaveLaserScans3210(‘NameofMyFile’,15,0.1) There are 361 columns and 15 rows corresponding to 361 half-degree increment and 15 scans. 1.1.3 Standard deviation Standard deviation is obtained using the following Matlab command. This will calculate standard deviation of values in columns 180 which corresponds to angle of 90 degree. std(X.Scans(:,180)) 1.1.4 Expectation of Error It is expected for error independence against test to be related to scanner noise. There are expecting to be some random errors in each of the cases. The error could be due to internal factors in the sensor. 1 2 Inclination angle respected to the perpendicular surface (90 degree) Distance from beam to laser Laser Scanner Laboratory Page 1 of 4 Mohsen Alizadehfard 1.2 Results 1.2.1 Plot of multiple scans The plots of four conditions are shown below using the following commands: load test001.mat disp(X); % display information about data % plot of 361 points, scan #2 figure(1); plot(X.Scans(2,:),'.'); title('Scan number 2'); std1=std(X.Scans(:,180)) % plot of 15 scans of single angle (ie 90 degrees) figure(2); plot(X.Scans(:,180),'.'); title('15 scans of angle 90 degrees ( 30 degree & 1 meter)'); xlabel(strcat('standard deviation = ',num2str(std1))) Laser Scanner Laboratory Page 2 of 4 Mohsen Alizadehfard 1.2.2 Annotation of the flat surface 1.2.3 Histograms From the following commands, four histograms are plotted. R = X.Scans(:,180); hist(R); title('Histogram of 15 scans of one angle ( 0 degree & 1 meter)'); Laser Scanner Laboratory Page 3 of 4 Mohsen Alizadehfard 1.3 Investigation The values of standard deviations are shown in section of plot of multiple scans. The values are very small which show that the error is small. Part 2: the application of the sensor for estimating the shape of objects through the measurements and the application of regression techniques 2.1 Approach 2.1.1 Plot the scan 2.1.2 Extraction of lines The lines are determined by converting the polar to certesian: a R x y = = = = ([1:361]-1)*0.5* pi/180 ; X.Scans(4,:) ; R.*cos(a) ; R.*sin(a) ; % % % % 361 of 0.5 degrees rotation Range of scans x co-ordinate y co-ordinate 2.2 Results From the plot the radius of the object is approximately 0.2m and estimated centre is 1.4 away from the laser scanner. Laser Scanner Laboratory Page 4 of 4 Mohsen Alizadehfard