When creating splines using bsplinepolytraj() the last values for the x and y component of velocity and acceleration are always zero. Here’s an example from the documentation:
% Interpolate with B-Spline
% Create waypoints to interpolate with a B-Spline.
wpts1 = [0 1 2.1 8 4 3];
wpts2 = [0 1 1.3 .8 .3 .3];
wpts = [wpts1; wpts2];
L = length(wpts) – 1;
% Form matrices used to compute interior points of control polygon
r = zeros(L+1, size(wpts,1));
A = eye(L+1);
for i= 1:(L-1)
A(i+1,(i):(i+2)) = [1 4 1];
r(i+1,:) = 6*wpts(:,i+1)’;
end
% Override end points and choose r0 and rL.
A(2,1:3) = [3/2 7/2 1];
A(L,(L-1):(L+1)) = [1 7/2 3/2];

r(1,:) = (wpts(:,1) + (wpts(:,2) – wpts(:,1))/2)’;
r(end,:) = (wpts(:,end-1) + (wpts(:,end) – wpts(:,end-1))/2)’;

dInterior = (Ar)’;
% Construct a complete control polygon and use bsplinepolytraj to compute a polynomial with the new control points
cpts = [wpts(:,1) dInterior wpts(:,end)];
t = 0:0.01:1;
[q, dq, ddq, ~] = bsplinepolytraj(cpts, [0 1], t);
The values for
disp(dq(:,end))
and
disp(ddq(:, end))
I feel like this is wrong. Why are these values zero and how can I get a non-zero answer?When creating splines using bsplinepolytraj() the last values for the x and y component of velocity and acceleration are always zero. Here’s an example from the documentation:
% Interpolate with B-Spline
% Create waypoints to interpolate with a B-Spline.
wpts1 = [0 1 2.1 8 4 3];
wpts2 = [0 1 1.3 .8 .3 .3];
wpts = [wpts1; wpts2];
L = length(wpts) – 1;
% Form matrices used to compute interior points of control polygon
r = zeros(L+1, size(wpts,1));
A = eye(L+1);
for i= 1:(L-1)
A(i+1,(i):(i+2)) = [1 4 1];
r(i+1,:) = 6*wpts(:,i+1)’;
end
% Override end points and choose r0 and rL.
A(2,1:3) = [3/2 7/2 1];
A(L,(L-1):(L+1)) = [1 7/2 3/2];

r(1,:) = (wpts(:,1) + (wpts(:,2) – wpts(:,1))/2)’;
r(end,:) = (wpts(:,end-1) + (wpts(:,end) – wpts(:,end-1))/2)’;

dInterior = (Ar)’;
% Construct a complete control polygon and use bsplinepolytraj to compute a polynomial with the new control points
cpts = [wpts(:,1) dInterior wpts(:,end)];
t = 0:0.01:1;
[q, dq, ddq, ~] = bsplinepolytraj(cpts, [0 1], t);
The values for
disp(dq(:,end))
and
disp(ddq(:, end))
I feel like this is wrong. Why are these values zero and how can I get a non-zero answer? When creating splines using bsplinepolytraj() the last values for the x and y component of velocity and acceleration are always zero. Here’s an example from the documentation:
% Interpolate with B-Spline
% Create waypoints to interpolate with a B-Spline.
wpts1 = [0 1 2.1 8 4 3];
wpts2 = [0 1 1.3 .8 .3 .3];
wpts = [wpts1; wpts2];
L = length(wpts) – 1;
% Form matrices used to compute interior points of control polygon
r = zeros(L+1, size(wpts,1));
A = eye(L+1);
for i= 1:(L-1)
A(i+1,(i):(i+2)) = [1 4 1];
r(i+1,:) = 6*wpts(:,i+1)’;
end
% Override end points and choose r0 and rL.
A(2,1:3) = [3/2 7/2 1];
A(L,(L-1):(L+1)) = [1 7/2 3/2];

r(1,:) = (wpts(:,1) + (wpts(:,2) – wpts(:,1))/2)’;
r(end,:) = (wpts(:,end-1) + (wpts(:,end) – wpts(:,end-1))/2)’;

dInterior = (Ar)’;
% Construct a complete control polygon and use bsplinepolytraj to compute a polynomial with the new control points
cpts = [wpts(:,1) dInterior wpts(:,end)];
t = 0:0.01:1;
[q, dq, ddq, ~] = bsplinepolytraj(cpts, [0 1], t);
The values for
disp(dq(:,end))
and
disp(ddq(:, end))
I feel like this is wrong. Why are these values zero and how can I get a non-zero answer? bsplinepolytraj, spline, curve fitting, robotics, trajectory MATLAB Answers — New Questions

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