Static Optimization Muscle Forces
Posted: Thu Aug 24, 2017 1:43 pm
Hi everyone,
I'm working on a full body back-lifting model and have run into some trouble during Static Optimization. It's my understanding that coordinate actuators placed at the joints should not be used until the muscles cannot stabilize the model. However, there are many muscles in my model that remain inactive while coordinate actuators see a force. I have checked the muscle lengths, and during the motion they go from being larger than the optimal fiber length to smaller than the optimal fiber length - yet no activation occurs.
I have also messed around with the coordinate actuator optimal force values to be anywhere from 5N to 10,000N. At CA optimal force of 5N, almost all back muscles are inactive and the coordinate actuators have values of around 200-300N. At a CA optimal limit of 10,000N, many muscles are recruited (although a good amount are still inactive even while being stretched) and the coordinate actuators see a force of about 1000-1400N. To me this result doesn't make much sense, as the coordinate actuators are meant to be reserved for when needed, but are activated regardless of how much the muscles are involved in my model. The stretched muscles remaining inactive is also confusing to me. Any help on either of these issues would be much appreciated.
I'm working on a full body back-lifting model and have run into some trouble during Static Optimization. It's my understanding that coordinate actuators placed at the joints should not be used until the muscles cannot stabilize the model. However, there are many muscles in my model that remain inactive while coordinate actuators see a force. I have checked the muscle lengths, and during the motion they go from being larger than the optimal fiber length to smaller than the optimal fiber length - yet no activation occurs.
I have also messed around with the coordinate actuator optimal force values to be anywhere from 5N to 10,000N. At CA optimal force of 5N, almost all back muscles are inactive and the coordinate actuators have values of around 200-300N. At a CA optimal limit of 10,000N, many muscles are recruited (although a good amount are still inactive even while being stretched) and the coordinate actuators see a force of about 1000-1400N. To me this result doesn't make much sense, as the coordinate actuators are meant to be reserved for when needed, but are activated regardless of how much the muscles are involved in my model. The stretched muscles remaining inactive is also confusing to me. Any help on either of these issues would be much appreciated.