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minimumCurvaturePathGeneration.m
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minimumCurvaturePathGeneration.m
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function [trajMCP, trackData] = minimumCurvaturePathGeneration(track,name)
%% Processing track data
% track data - first point repeated
data = track;
% x,y and track width data
x = data(:,1);
y = data(:,2);
twr = data(:,3);
twl = data(:,4);
% interpolate data to get finer curve with equal distances between each segment
% higher no. of segments causes trajectory to follow the reference line
nseg = 1500;
pathXY = [x y];
stepLengths = sqrt(sum(diff(pathXY,[],1).^2,2));
stepLengths = [0; stepLengths]; % add the starting point
cumulativeLen = cumsum(stepLengths);
finalStepLocs = linspace(0,cumulativeLen(end), nseg);
finalPathXY = interp1(cumulativeLen, pathXY, finalStepLocs);
xt = finalPathXY(:,1);
yt = finalPathXY(:,2);
twrt = interp1(cumulativeLen, twr, finalStepLocs,'spline')';
twlt = interp1(cumulativeLen, twl, finalStepLocs,'spline')';
% normal direction for each vertex
dx = gradient(xt);
dy = gradient(yt);
dL = hypot(dx,dy);
% offset curve - anonymous function
xoff = @(a) -a*dy./dL + xt;
yoff = @(a) a*dx./dL + yt;
% plot reference line
plot(xt,yt,'g')
hold on
% offset data
offset = [-twrt twlt];
for i = 1:numel(xt)
xin = xoff(offset(i,1)); % get inner offset curve
yin = yoff(offset(i,1));
xout = xoff(offset(i,2)); % get outer offset curve
yout = yoff(offset(i,2));
end
% plot inner track
plot(xin,yin,'color','b','linew',2)
% plot outer track
plot(xout,yout,'color','r','linew',2)
hold off
axis equal
xlabel('x(m)','fontweight','bold','fontsize',14)
ylabel('y(m)','fontweight','bold','fontsize',14)
title(sprintf(name),'fontsize',16)
% % plot segments
% figure
% hold on
% for i=1:numel(xout)
% plot([xin(i) xout(i)], [yin(i) yout(i)])
% end
% form delta matrices
delx = xout - xin;
dely = yout - yin;
trackData = [xt yt xin yin xout yout];
%% Matrix Definition
% number of segments
n = numel(delx);
% preallocation
H = zeros(n);
B = zeros(size(delx)).';
% formation of H matrix (nxn)
for i=2:n-1
% first row
H(i-1,i-1) = H(i-1,i-1) + delx(i-1)^2 + dely(i-1)^2;
H(i-1,i) = H(i-1,i) - 2*delx(i-1)*delx(i) - 2*dely(i-1)*dely(i);
H(i-1,i+1) = H(i-1,i+1) + delx(i-1)*delx(i+1) + dely(i-1)*dely(i+1);
%second row
H(i,i-1) = H(i,i-1) - 2*delx(i-1)*delx(i) - 2*dely(i-1)*dely(i);
H(i,i) = H(i,i ) + 4*delx(i)^2 + 4*dely(i)^2;
H(i,i+1) = H(i,i+1) - 2*delx(i)*delx(i+1) - 2*dely(i)*dely(i+1);
% third row
H(i+1,i-1) = H(i+1,i-1) + delx(i-1)*delx(i+1) + dely(i-1)*dely(i+1);
H(i+1,i) = H(i+1,i) - 2*delx(i)*delx(i+1) - 2*dely(i)*dely(i+1);
H(i+1,i+1) = H(i+1,i+1) + delx(i+1)^2 + dely(i+1)^2;
end
% formation of B matrix (1xn)
for i=2:n-1
B(1,i-1) = B(1,i-1) + 2*(xin(i+1)+xin(i-1)-2*xin(i))*delx(i-1) + 2*(yin(i+1)+yin(i-1)-2*yin(i))*dely(i-1);
B(1,i) = B(1,i) - 4*(xin(i+1)+xin(i-1)-2*xin(i))*delx(i) - 4*(yin(i+1)+yin(i-1)-2*yin(i))*dely(i);
B(1,i+1) = B(1,i+1) + 2*(xin(i+1)+xin(i-1)-2*xin(i))*delx(i+1) + 2*(yin(i+1)+yin(i-1)-2*yin(i))*dely(i+1);
end
% define constraints
lb = zeros(n,1);
ub = ones(size(lb));
% if start and end points are the same
Aeq = zeros(1,n);
Aeq(1) = 1;
Aeq(end) = -1;
beq = 0;
%% Solver
options = optimoptions('quadprog','Display','iter');
[resMCP,fval,exitflag,output] = quadprog(2*H,B',[],[],Aeq,beq,lb,ub,[],options);
%% Plotting results
% co-ordinates for the resultant curve
xresMCP = zeros(size(xt));
yresMCP = zeros(size(xt));
for i = 1:numel(xt)
xresMCP(i) = xin(i)+resMCP(i)*delx(i);
yresMCP(i) = yin(i)+resMCP(i)*dely(i);
end
% plot minimum curvature trajectory
figure
plot(xresMCP,yresMCP,'color','r','linew',2)
hold on
% plot starting line
plot([xin(1) xout(1)], [yin(1) yout(1)],'color','b','linew',2)
% plot([xin(2) xout(2)], [yin(2) yout(2)],'color','k','linew',2)
% plot reference line
plot(xt,yt,'--')
hold on
% plot inner track
plot(xin,yin,'color','k')
%plot outer track
plot(xout,yout,'color','k')
hold off
axis equal
xlabel('x(m)','fontweight','bold','fontsize',14)
ylabel('y(m)','fontweight','bold','fontsize',14)
title(sprintf(name,'%s - Minimum Curvature Trajectory'),'fontsize',16)
trajMCP = [xresMCP yresMCP];