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Fix one-timestep logging skew and document GetTorque() sign convention #5

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Merged
salhus merged 2 commits into from
Jul 8, 2026
Merged

Fix one-timestep logging skew and document GetTorque() sign convention #5

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Copilot Jul 8, 2026
3eb1d1b
Fix per-step logging skew and add GetTorque() sign convention comment
Copilot Jul 8, 2026
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40 changes: 30 additions & 10 deletions src/demo_vgoswec.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -250,17 +250,27 @@ int main(int argc, char* argv[]) {
while (system.GetChTime() <= sim_duration) {
if (!ui.IsRunning(dt)) break;
if (ui.simulationStarted) {
const double pitch_rad = rsda->GetAngle();
const double pitch_vel = rsda->GetVelocity();

system.DoStepDynamics(dt);

const auto& per_comp = hydro_system.GetLastComponentForces();
if (!per_comp.empty()) {
exc_provider->Update(per_comp, system.GetChTime());
}
const double exc_tau = exc_provider->GetLatestExcitationTorque();
const double pto_tau = rsda->GetTorque();

// Read all logged quantities AFTER the step so every CSV column is consistent
// at this record's timestamp (system.GetChTime()). Reading angle/velocity
// before the step previously introduced a one-timestep skew vs. torque/time.
const double pitch_rad = rsda->GetAngle();
const double pitch_vel = rsda->GetVelocity();
const double exc_tau = exc_provider->GetLatestExcitationTorque();
// GetTorque() is expected to return the applied PTO actuator torque about the
// hinge Y-axis, matching the sign of RsdaPtoFunctor/IPTOModel::ComputeForce
// and the docs/CONTROLLERS.md convention (positive torque opposes positive theta;
// P_abs = -tau*omega). Quick validation: in a `passive` run, pto_torque_nm
// should have the OPPOSITE sign to flap_pitch_vel_rads, yielding net-positive
// power_w. If it does not, negate pto_tau here (logging-only) to restore the
// documented convention.
const double pto_tau = rsda->GetTorque();

records.push_back(
{system.GetChTime(), pitch_rad, pitch_vel, pto_tau, exc_tau, -pto_tau * pitch_vel});
Expand All @@ -275,17 +285,27 @@ int main(int argc, char* argv[]) {

// Headless loop
while (system.GetChTime() <= sim_duration) {
const double pitch_rad = rsda->GetAngle();
const double pitch_vel = rsda->GetVelocity();

system.DoStepDynamics(dt);

const auto& per_comp = hydro_system.GetLastComponentForces();
if (!per_comp.empty()) {
exc_provider->Update(per_comp, system.GetChTime());
}
const double exc_tau = exc_provider->GetLatestExcitationTorque();
const double pto_tau = rsda->GetTorque();

// Read all logged quantities AFTER the step so every CSV column is consistent
// at this record's timestamp (system.GetChTime()). Reading angle/velocity
// before the step previously introduced a one-timestep skew vs. torque/time.
const double pitch_rad = rsda->GetAngle();
const double pitch_vel = rsda->GetVelocity();
const double exc_tau = exc_provider->GetLatestExcitationTorque();
// GetTorque() is expected to return the applied PTO actuator torque about the
// hinge Y-axis, matching the sign of RsdaPtoFunctor/IPTOModel::ComputeForce
// and the docs/CONTROLLERS.md convention (positive torque opposes positive theta;
// P_abs = -tau*omega). Quick validation: in a `passive` run, pto_torque_nm
// should have the OPPOSITE sign to flap_pitch_vel_rads, yielding net-positive
// power_w. If it does not, negate pto_tau here (logging-only) to restore the
// documented convention.
const double pto_tau = rsda->GetTorque();

records.push_back(
{system.GetChTime(), pitch_rad, pitch_vel, pto_tau, exc_tau, -pto_tau * pitch_vel});
Expand Down