About property value optimization

[Chonghui Zhang]

Hi all,

I would like to ask two questions about body mass optimization in Moco.

1. I wish to get the maximum weight of a barbell that a human model can lift. Is the following code correct?

Code: Select all

param = MocoParameter('barbell_mass', '/bodyset/barbell', 'mass', MocoBounds(1,500));
problem.addParameter(param)	

2. If maximizing the mass is a cost function, how to set its weighting coefficient when it is combined with other cost functions (e.g. MocoControlGoal)?

Thanks,
Chonghui

[Nicholas Bianco]

Hi Chonghui,

Your code looks correct.

Unfortunately, there's no way to directly maximize the value of a parameter in the model. If the Moco problem you're running solves quickly, it might be easiest to optimize the mass using a two-level optimization approach.

-Nick

[Chonghui Zhang]

Hi Nick,

Thanks for your reply. But I'm not sure how to conduct a two-level optimization. Could you please give me some tips?

Thanks,
Chonghui

[Nicholas Bianco]

Hi Chonghui,

The simplest way is to use one of Matlab's optimizers (i.e., fmincon) and when writing the objective function, run your Moco problem and return some value that indicates failure or success.

Here's a paper on using bi-level optimization for lifting: https://www.frontiersin.org/articles/10 ... 83633/full.

-Nick