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csu-hmc / opty

A library for using direct collocation in the optimization of dynamic systems.
http://opty.readthedocs.io
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Question #132

Closed Peter230655 closed 2 months ago

Peter230655 commented 3 months ago

I simulate a 2D n closed link pendulum and want opty to get the first pendulum to a specified end position, say upright. The control force is a torque acting on the first pendulum. I ran it with n = 5, and after 100 min of running I got this error: message from optimizer: b"Restoration phase failed, algorithm doesn't know how to proceed." (There IS a possible solution: I integrate the pendulum, apply a constant torque, where the control torque is, and stop solve_ivp if/when the endposition is reached. In the case I tried, the end position can be reached. Also, the pendulums slide past each other, there is no possible impact)

What does this message mean?

Thanks!!

moorepants commented 2 months ago

The message comes from IPOPT, you can read about the error message there for specific answers. But, in general, it means IPOPT couldn't find a solution to your problem.

Peter230655 commented 2 months ago

thanks! I will try to find the IPOPT messages.