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in your documentation you have:
v = Kse*R.'n + [0;0;1];
u = KbtR.'*m;

whereas it shoule be:
v = Kse^-1*R.'n + [0;0;1];
u = Kbt^-1R.'*m;

Hi John,
I have read your paper "Real-time dynamics of soft and continuum robots based on Cosserat rod models", it's a very nice job. I am very happy to learn your code.

There is a Build error when I buid the project “01_Statics\06_Tendon_Robot_Variants\Cpp_3\Tendon_Displacement_Control”:
:-1: error: dependent '..\..\..\Library\eigen\Eigen\src\Core\products\GeneralBlockPanelKernel.h' does not exist.

The project "01_Statics\05_Tendon_Robot" dosen't have this problem, I think it's strange.

The project "02_Dynamics\03_Tendon_Robot" also have a problem that the Final sum of squares is so big and solution failed. I'm confused. I don't know what's wrong.

Could you help me?

Thanks,
Lisong

The fsolve() function in TendonRobotStatics.m can easily diverge when you give a little larger tendon forces. After tunning, this can be fixed by a more accurate initial guess, for example:

n0_guess = [0;0;-sum(tau)];
v0_guess = inv(Kse)*inv(R0)*n0_guess + [0;0;1];
m0_guess = zeros(3,1);
for i = 1:length(tau)
    m0_guess = m0_guess + cross( r{i}, tau(i)*[0;0;-1] );
end
u0_guess = inv(Kbt)*inv(R0)*m0_guess + [0;0;0];

init_guess = [n0_guess; u0_guess];
global Y; % Forward declaration for future scoping rule changes
fsolve(@shootingFunction, init_guess, options);

Hi John,

I'm working on a project involving a tendon driven continuum robot. I would like to implement your frictional model from you paper "Real-time dynamics of soft and continuum robots based on Cosserat rod models", section 5.2.1 and was hoping you could help.

Do you simply sum solutions for each of the tendons for f_f,i and l_f,i, and and then subtract them from f_c and l_c respectively? I'm also not sure about how to calculate v_i. An example would be useful if you have one, preferably in MATLAB. Thanks in advance.

Kind regards,
Solomon

Hi John,

All your simulated cases are with force at the tip.
I want o know how you deal with the force that is not at the tip. For example, there is a force Fe = [0 1,2] at s = L/2, which is at the middle of the robot.

I guess, if there is only one force, probably just need to change the boundary condition. If there are multiple forces at different location of the robot, it will be more complicated.

Thank you!

Hello John,

Thank you for your work and I learned so much from your work.

I have run the 05_Tendon_Robot.m. I found when the tension of tendon /tau is larger, the solver stopped prematurely. If it because I didn't pick the init_guess right?

Thanks again,
Xue

Although the final moment equation at the bottom of page 42 in the dissertation is correct, the initial statement of the equation located just above is missing terms.

• Create an erratum
• Potentially create a modified version of the document with a fix and/or a footnote recognizing the error

in line 109 of 'TendonRobotStatics.m', you have v0 = Kse\n0 + [0;0;1];
did you neglect R0? I know it does not affect the numerical solution since R0 = eye(3).

the pdf on page.2 says "array 'r' which contains the translation from the end effector to the rod attachment points in
the end effector frame" and you used 'r' in the EM summation. Isn't for the EM summation we need p_i(L_i) x n_i instead of R. r_i x n_i in reference frame?

Hello John,

I saw that you have graduated and Congratulations! Not sure if you have memory on the stuff or not. But I have a problem to initialize a complicated geometry curve as a reference configuration.

I am trying to see if the code can be applied to a rod with more complicated reference shapes rather than a planar straight rod or regularly curved rod. After some trials, it seems to work well for some complicated shape as long as I can reparameterize the shape using arc length s.

However, for a curve that cannot be parameterized using s, it will be a pain. For example, a rod that has Archimedean spiral shape as a reference configuration using cylindrical system $r =a*\theta$ or using position vector $p = [\thetacos(\theta), \thetasin(\theta), 0]'$.
To set up such a reference shape, u_0(s) and v_0(s) are required and they are functions of s. Ideally, we need to find $\theta = f(s)$, which is represent \theta using s. But this is not possible, which can be seen from the following picture: we can not find an explicit function. Do you have any good ideas about this?

Thanks,
Jiefeng

The animation scripts result in errors in newer releases of Blender. I believe the break occurs for 2.7.9 => 2.8.0

Great job. By the way, do you have a Matlab code for Tendon Static Case?