Error: Static optimization of closed loop mechanism

Vinay Kumar · Post by **Vinay Kumar** » Thu Oct 10, 2019 3:08 am

Hi,

I'm trying to determine the torques required to actuate a fourbar mechanism for a given trajectory. I have provided only one actuator to the mechanism since it's effective DOF is one. The error that I am getting while using static optimization is that the mechanism is over-constrained.

Can you please tell me the workaround for using static optimization with closed-loop mechanisms?

Kind regards
Vinay

Karthick Ganesan · Post by **Karthick Ganesan** » Thu Oct 10, 2019 5:50 am

Static optimization is used for resolving actuator redundancy. There is no actuator redundancy in four bar mechanism. I think Inverse dynamics is suitable for this .

Vinay Kumar · Post by **Vinay Kumar** » Thu Oct 10, 2019 5:24 pm

Inverse dynamics is giving me four generalized torques (1) rather than one actuator. What OpenSim does for closed-loop is it bifurcates the last link and then uses a weld constraint to solve for generalized torques (2). My question is how we interpret these four generalized torques into the actuator's torque.

I think we have to use static optimization of CMC to convert generalized torques to let's say an off-axis pneumatic cylinder's actuation force.

Static optimization works fine for fully actuated serial link mechanism, I have tried double pendulum and the likes (using torque actuator).

1) https://simtk-confluence.stanford.edu/d ... e+Dynamics
2) Pg 11, https://usermanual.wiki/Document/Simbod ... .622093507

Error: Static optimization of closed loop mechanism

Error: Static optimization of closed loop mechanism

Re: static optimization of closed loop mechanism

Re: static optimization of closed loop mechanism