Diverging results

2011 5 25
1 个回答
148 次查看（30 天）

0 个投票

Hi,
I am currently developing a control system for a 3 link manipulator as part of my project. I got some torque control values that is needed to be applied at each joint of the manipulator to produce desired trajectory. I've developed a matlab simulink model to simulate this as well(I dont want to use Sim mechanics model as of now), but the values produced by my model are diverging/blowing.
For instance even if I am providing holding torque (to counter-act gravity term, in this case angles of manipulator should not change), initial angle values do not change, but over a time period these values starts changing and eventually goes on to infinity.
Sorry for the long question.
Prompt response would be deeply appreciated.

2 个评论
显示 无 隐藏 无

Jan
Jan 2011-5-25
"The initial values do not change, but... go to infinity"? I cannot follow. What exactly happens?
Shobhit Gupta
Shobhit Gupta 2011-5-29
Hey,
I've shared the .mdl file, please go through it.

请先登录，再进行评论。

请先登录，再回答此问题。

回答（1 个）

Jan
Jan 2011-5-25

1 个投票

I guess, that you apply the counter-act gravity term with a limited accuracy. Then the small resulting torque will accumulate over the time.
There is no way to solve this drift in an open-loop control system, which acts on the torques only. To control the position of a robot, you have to control te position ;-)

4 个评论
显示 2更早的评论 隐藏 2更早的评论

Shobhit Gupta
Shobhit Gupta 2011-5-26
Hey Jan, yes the counter-act gravity term is indeed little inaccurate (differs by e-13).
Are you sure this drift can't be removed? Basic robotic equations do have thetadot and thetadotdot (coriolis and acceleration terms in it as well).
The problem persists when I apply 0 torque to check if the system is okay(Ideally it should oscillate in a gravity field, with constant energy). My system is blowing up for any open loop torque I am providing to it. In that case, how can I check correctness of my system.
Thank You
Arnaud Miege
Arnaud Miege 2011-5-26
Can you upload your model to a filesharing site? There may be some modelling errors in the model of the robot.
Shobhit Gupta
Shobhit Gupta 2011-5-29
Hey,
please find the files at this URL.
Simulink model file :
http://www.4shared.com/file/mzPgomP6/holdingtorque.html?
.mat file to give data into the modeled system.
http://www.4shared.com/file/YKF3Xzvt/torXv.html?
Shobhit Gupta
Shobhit Gupta 2011-5-29
Hi,
It basically simulates torque = D(q)qdotdot+C(q,qdot)qdot+G.
If you'll run the model for holding torques(equivalent to gravity torque, it works by changing solvers) but it does not work for torXv which should produce a linear motion in the links. Please help!

请先登录，再进行评论。

类别

在 帮助中心 和 File Exchange 中查找有关 Robotics 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by