void IDIM::computeY(const MultiBody& mb, const MultiBodyConfig& mbc)
{
const std::vector<Body>& bodies = mb.bodies();
const std::vector<Joint>& joints = mb.joints();
const std::vector<int>& pred = mb.predecessors();
Eigen::Matrix<double, 6, 10> bodyFPhi;
for(int i = static_cast<int>(bodies.size()) - 1; i >= 0; --i)
{
const sva::MotionVecd& vb_i = mbc.bodyVelB[i];
Eigen::Matrix<double, 6, 10> vb_i_Phi(IMPhi(vb_i));
bodyFPhi.noalias() = IMPhi(mbc.bodyAccB[i]);
// bodyFPhi += vb_i x* IMPhi(vb_i)
// is faster to convert each col in a ForceVecd
// than using sva::vector6ToCrossDualMatrix
for(int c = 0; c < 10; ++c)
{
bodyFPhi.col(c).noalias() +=
(vb_i.crossDual(sva::ForceVecd(vb_i_Phi.col(c)))).vector();
}
int iDofPos = mb.jointPosInDof(i);
Y_.block(iDofPos, i*10, joints[i].dof(), 10).noalias() =
mbc.motionSubspace[i].transpose()*bodyFPhi;
int j = i;
while(pred[j] != -1)
{
const sva::PTransformd& X_p_j = mbc.parentToSon[j];
// bodyFPhi = X_p_j^T bodyFPhi
// is faster to convert each col in a ForceVecd
// than using X_p_j.inv().dualMatrix()
for(int c = 0; c < 10; ++c)
{
bodyFPhi.col(c) =
X_p_j.transMul(sva::ForceVecd(bodyFPhi.col(c))).vector();
}
j = pred[j];
int jDofPos = mb.jointPosInDof(j);
if(joints[j].dof() != 0)
{
Y_.block(jDofPos, i*10, joints[j].dof(), 10).noalias() =
mbc.motionSubspace[j].transpose()*bodyFPhi;
}
}
}
}
void forwardKinematics(const MultiBody& mb, MultiBodyConfig& mbc)
{
const std::vector<Joint>& joints = mb.joints();
const std::vector<int>& pred = mb.predecessors();
const std::vector<int>& succ = mb.successors();
const std::vector<sva::PTransformd>& Xt = mb.transforms();
for(std::size_t i = 0; i < joints.size(); ++i)
{
mbc.jointConfig[i] = joints[i].pose(mbc.q[i]);
mbc.parentToSon[i] = mbc.jointConfig[i]*Xt[i];
if(pred[i] != -1)
mbc.bodyPosW[succ[i]] = mbc.parentToSon[i]*mbc.bodyPosW[pred[i]];
else
mbc.bodyPosW[succ[i]] = mbc.parentToSon[i];
}
}
void forwardAcceleration(const MultiBody& mb, MultiBodyConfig& mbc,
const sva::MotionVecd& A_0)
{
const std::vector<Joint>& joints = mb.joints();
const std::vector<int>& pred = mb.predecessors();
const std::vector<int>& succ = mb.successors();
for(std::size_t i = 0; i < joints.size(); ++i)
{
const sva::PTransformd& X_p_i = mbc.parentToSon[i];
const sva::MotionVecd& vj_i = mbc.jointVelocity[i];
sva::MotionVecd ai_tan = joints[i].tanAccel(mbc.alphaD[i]);
const sva::MotionVecd& vb_i = mbc.bodyVelB[i];
if(pred[i] != -1)
mbc.bodyAccB[succ[i]] = X_p_i*mbc.bodyAccB[pred[i]] + ai_tan + vb_i.cross(vj_i);
else
mbc.bodyAccB[succ[i]] = X_p_i*A_0 + ai_tan + vb_i.cross(vj_i);
}
}
void forwardVelocity(const MultiBody& mb, MultiBodyConfig& mbc)
{
const std::vector<Joint>& joints = mb.joints();
const std::vector<int>& pred = mb.predecessors();
const std::vector<int>& succ = mb.successors();
for(std::size_t i = 0; i < joints.size(); ++i)
{
const sva::PTransformd& X_p_i = mbc.parentToSon[i];
mbc.jointVelocity[i] = joints[i].motion(mbc.alpha[i]);
mbc.motionSubspace[i] = joints[i].motionSubspace();
if(pred[i] != -1)
mbc.bodyVelB[succ[i]] = X_p_i*mbc.bodyVelB[pred[i]] + mbc.jointVelocity[i];
else
mbc.bodyVelB[succ[i]] = mbc.jointVelocity[i];
sva::PTransformd E_0_i(mbc.bodyPosW[succ[i]].rotation());
mbc.bodyVelW[succ[i]] = E_0_i.invMul(mbc.bodyVelB[succ[i]]);
}
}