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use chain::*;
use joint::*;
use na::{DMatrix, RealField, Vector3};
pub fn jacobian<T>(arm: &SerialChain<T>) -> DMatrix<T>
where
T: RealField,
{
let dof = arm.dof();
let t_n = arm.end_transform();
arm.update_transforms();
let p_n = t_n.translation;
let jacobi_vec = arm
.iter_joints()
.map(|joint| {
let t_i = joint.world_transform().unwrap();
match joint.joint_type {
JointType::Linear { axis } => {
let p_i = t_i.rotation * axis;
[p_i[0], p_i[1], p_i[2], na::zero(), na::zero(), na::zero()]
}
JointType::Rotational { axis } => {
let p_i = t_i.translation;
let a_i = t_i.rotation * axis;
let dp_i = a_i.cross(&(p_n.vector - p_i.vector));
[dp_i[0], dp_i[1], dp_i[2], a_i[0], a_i[1], a_i[2]]
}
JointType::Fixed => panic!("impossible, bug of jacobian"),
}
})
.collect::<Vec<_>>();
DMatrix::from_fn(6, dof, |r, c| jacobi_vec[c][r])
}
pub fn center_of_mass<T>(chain: &Chain<T>) -> Vector3<T>
where
T: RealField,
{
let mut total_mass = T::zero();
let mut com = Vector3::zeros();
chain.update_transforms();
chain.iter().for_each(|node| {
if let Some(trans) = node.joint().world_transform() {
if let Some(ref link) = *node.link() {
let inertia_trans = trans * link.inertial.origin().translation;
com += inertia_trans.translation.vector * link.inertial.mass;
total_mass += link.inertial.mass;
}
}
});
com / total_mass
}
#[test]
fn test_update_center_of_mass() {
use super::joint::*;
use super::link::*;
use super::node::*;
use na::*;
let j0 = JointBuilder::new()
.translation(Translation3::new(0.0, 1.0, 0.0))
.into_node();
let j1 = JointBuilder::new()
.translation(Translation3::new(0.0, 0.0, 1.0))
.joint_type(JointType::Rotational {
axis: Vector3::y_axis(),
})
.into_node();
j0.set_link(Some(
LinkBuilder::new()
.name("l0")
.inertial(Inertial::new(Isometry3::identity(), 1.0, Matrix3::zeros()))
.finalize(),
));
let mut i1 = Inertial::new(Isometry3::identity(), 4.0, Matrix3::zeros());
i1.set_origin(Isometry3::from_parts(
Translation3::new(0.0, 0.0, 1.0),
UnitQuaternion::identity(),
));
j1.set_link(Some(LinkBuilder::new().name("l1").inertial(i1).finalize()));
j1.set_parent(&j0);
let tree = Chain::from_root(j0);
let com1 = center_of_mass(&tree);
assert_eq!(com1.x, 0.0);
assert_eq!(com1.y, 1.0);
assert_eq!(com1.z, 1.6);
j1.set_joint_position(0.5).unwrap();
let com2 = center_of_mass(&tree);
assert!((com2.x - 0.383540).abs() < 0.0001);
assert_eq!(com2.y, 1.0);
assert!((com2.z - 1.502066).abs() < 0.0001);
}