Affect different weight to different axis in the task space

It is possible to affect different weights to different axis in the task-space (e.g. ignore the vertical position of the CoM).

Most tasks can take in an additional parameter dimWeight of type Eigen::VectorXd that allows you to weigh differently different directions:

• The dimWeight does not replace the total weight. It is multiplicative with it. For example, a comTask with weight 1000 and a dimWeight of [1., 1., 1e-3] will behave like a task of total weight [1000., 1000., 1.]
• The dimWeight is a dynamic size vector. It is up to you to make sure it has the right size. Note that you can obtain the (lower-level) task size by calling dim() on it.
• You can pass this parameter at construction and/or change it later.

Example

To ignore the vertical error on a comTask:

Eigen::VectorXd dimWeight(3);
dimWeight.setOnes();
dimWeight[2] = 0.;

comTask = std::make_shared<mc_tasks::CoMTask>(robots, robots().robotIndex(), 5.0, 100.);
comTask->dimWeight(dimWeight);

EndEffectorTask is composed of two tasks in order to control the orientation and the position of the end-effector. As such, its dimWeight method excepts a 6d vector, the first three dimensions control the orientation dimension weight while the last three control the position dimension weight. To ignore the x and y translations on an EndEffectorTask:

Eigen::VectorXd dimWeight(6);
dimWeight << 1., 1., 1., 0., 0., 1.;

efTask = std::make_shared<mc_tasks::EndEffectorTask>("RARM_LINK6", robots(), 5.0, 100);
efTask->dimWeight(dimWeight);

Alternatively, you could address the position part of the task directly:

Eigen::VectorXd dimWeight(3);
dimWeight.setZero();
dimWeight(2) = 1.;

efTask = std::make_shared<mc_tasks::EndEffectorTask>("RARM_LINK6", robots(), 5.0, 100);
efTask->positionTask->dimWeight(dimWeight);

Note: this is not a constraint, it simply means that the task has no effect in those directions. If you want to constrain motion in a certain direction, you should use either a DoF Contact or a Bounded Speed Constraint.