phase_durations.cc

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#include <towr/variables/phase_durations.h>

#include <numeric> // std::accumulate

#include <towr/variables/variable_names.h>
#include <towr/variables/spline.h> // for Spline::GetSegmentID()


namespace towr {


PhaseDurations::PhaseDurations (EndeffectorID ee,
                                const VecDurations& timings,
                                bool is_first_phase_in_contact,
                                double min_duration,
                                double max_duration)
    // -1 since last phase-duration is not optimized over, but comes from total time
    :VariableSet(timings.size()-1, id::EESchedule(ee))
{
  durations_ = timings;
  t_total_ = std::accumulate(timings.begin(), timings.end(), 0.0);
  phase_duration_bounds_ = ifopt::Bounds(min_duration, max_duration);
  initial_contact_state_ = is_first_phase_in_contact;
}

void
PhaseDurations::AddObserver (PhaseDurationsObserver* const o)
{
  observers_.push_back(o);
}

void
PhaseDurations::UpdateObservers () const
{
  for (auto& spline : observers_)
    spline->UpdatePolynomialDurations();
}

Eigen::VectorXd
PhaseDurations::GetValues () const
{
  VectorXd x(GetRows());

  for (int i=0; i<x.rows(); ++i)
    x(i) = durations_.at(i);

  return x;
}

void
PhaseDurations::SetVariables (const VectorXd& x)
{
  // the sum of all phase durations should never be larger than the total time of
  // the trajectory. This would e.g. query constraints after duration of the trajectory and
  // causes undefined behavior. However, when IPOPT optimizes the phase durations,
  // it's not possible to enforce that in every iteration this condition is fulfilled. Sure,
  // we can set this as a constraint, but during the solution process constraints might still
  // be violated.
  // Fortunately, violation of this doesn't seem to mess up IPOPT too much and a solution is
  // often found. So if you get this error you can ignore it by compiling in Release mode,
  // but I'm leaving this in here to show that this is undefined behavior and a clean
  // implementation is still required. PR desired ;)
  assert(t_total_>x.sum());

  for (int i=0; i<GetRows(); ++i)
    durations_.at(i) = x(i);

  // last phase duration not optimized, used to fill up to total time.
  durations_.back() =  t_total_ - x.sum();
  UpdateObservers();
}

PhaseDurations::VecBound
PhaseDurations::GetBounds () const
{
  VecBound bounds;

  for (int i=0; i<GetRows(); ++i)
    bounds.push_back(phase_duration_bounds_);

  return bounds;
}

PhaseDurations::VecDurations
PhaseDurations::GetPhaseDurations() const
{
  return durations_;
}

bool
PhaseDurations::IsContactPhase (double t) const
{
  int phase_id = Spline::GetSegmentID(t, durations_);
  return phase_id%2 == 0? initial_contact_state_ : !initial_contact_state_;
}

PhaseDurations::Jacobian
PhaseDurations::GetJacobianOfPos (int current_phase,
                                  const VectorXd& dx_dT,
                                  const VectorXd& xd) const
{
  int n_dim = xd.rows();
  Eigen::MatrixXd jac = Eigen::MatrixXd::Zero(n_dim, GetRows());

  bool in_last_phase = (current_phase == durations_.size()-1);

  // duration of current phase expands and compressed spline
  if (!in_last_phase)
    jac.col(current_phase) = dx_dT;

  for (int phase=0; phase<current_phase; ++phase) {
    // each previous durations shifts spline along time axis
    jac.col(phase) = -1*xd;

    // in last phase previous duration cause expansion/compression of spline
    // as final time is fixed.
    if (in_last_phase)
      jac.col(phase) -= dx_dT;
  }

  // convert to sparse, but also regard 0.0 as non-zero element, because
  // could turn nonzero during the course of the program
  // as durations change and t_global falls into different spline
  return jac.sparseView(1.0, -1.0);
}

} /* namespace towr */