3 R link system simulink model

Hi guys,

I am a final year student at IIT Bombay. Currently I am developing a forward dynamics model (input : torque and output : theta) of a 3 Revolute robotic arm. I've developed a simulink model for that, but there has been some error. I've double checked the equations of D, C, G matrix (standard robotic dynamics matrix).

I've checked probably 10s of configuration of the 3 link system. One of them is the slight disturbance torque that I give to the 3 link system. Ideally it should give me some small angle variation as output. But it doesn't. Value of theta just keeps on increasing. This is not it, I also tried it for 0 torque case, it should behave as a 3- link pendulum and oscillate, rather value of angles and their derivatives (angular rates, accelerations) keep on increasing.

I believe there is some problem with integrators, discrete values, small values?

I need to apply already planned controller on this model as soon as possible, but as my model is not behaving as expected, controller implementation is not giving any result.(singularity problem)

Hereby I attach my files (please download them, may take few minutes).

Disturbance torque data file http://www.4shared.com/file/sOvl0nfu/tordis_grav_scaled.html

Simulink model file http://www.4shared.com/file/2s8QwhTS/test_tordis_scaled.html?

Please help if possible.

BTW, does anyone have a 3 link system simulink file? I dont want to use sim-mechanics to make this model.

Thanks in advance,

Shobhit Gupta

[Arnaud Miege]

Why do you not want to use SimMechanics? It would be a lot easier.

[Shobhit Gupta]

Arnaud, since I want to use link parameters in controls (and my project forbids me using simmechanics :)).

Did you go to the model link?

[Arnaud Miege]

Yes, but the model runs, so if it's not giving you the expected results, there's obviously a mistake somewhere, but I can't go and debug your model for you, especially since I don't know the "standard robotic dynamics theory". It's strange that you're not allowed to use SimMechanics, it would make it so much easier..