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AC_PosControl: compensate for velocity FF when initializing controller #32758

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AC_PosControl: compensate for velocity FF when initializing controller #32758

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14 changes: 9 additions & 5 deletions libraries/AC_AttitudeControl/AC_PosControl.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -557,7 +557,10 @@ void AC_PosControl::NE_init_controller()
_pos_target_ned_m.xy() = _pos_estimate_ned_m.xy();
_pos_desired_ned_m.xy() = _pos_target_ned_m.xy() - _pos_offset_ned_m.xy();

_vel_target_ned_ms.xy() = _vel_estimate_ned_ms.xy();
// Set velocity target so that P and FF sum to zero on the first cycle:
// 0 = (target - measurement) * kP + target * kFF
// target = measurement * kP / (kP + kFF)
_vel_target_ned_ms.xy() = _vel_estimate_ned_ms.xy() * (_pid_vel_ne_m.kP() / (_pid_vel_ne_m.kP() + MAX(_pid_vel_ne_m.ff(), 0)));
Comment on lines +560 to +563

@rmackay9 rmackay9 Apr 20, 2026 •
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We should probably ensure we don't get a divide-by-zero if (_pid_vel_ne_m.kP() + MAX(_pid_vel_ne_m.ff())) is zero

_vel_desired_ned_ms.xy() = _vel_target_ned_ms.xy() - _vel_offset_ned_ms.xy();

// Set desired acceleration to zero because raw acceleration is prone to noise
Expand All @@ -574,9 +577,7 @@ void AC_PosControl::NE_init_controller()

// initialise I terms from lean angles
_pid_vel_ne_m.reset_filter();
// initialise the I term to (_accel_target_ned_mss - _accel_desired_ned_mss)
// _accel_desired_ned_mss is zero and can be removed from the equation
_pid_vel_ne_m.set_integrator((_accel_target_ned_mss.xy() - _vel_target_ned_ms.xy() * _pid_vel_ne_m.ff()));
_pid_vel_ne_m.set_integrator(_accel_target_ned_mss.xy());

// initialise ekf xy reset handler
NE_init_ekf_reset();
Expand Down Expand Up @@ -896,7 +897,10 @@ void AC_PosControl::D_init_controller()
_pos_target_ned_m.z = _pos_estimate_ned_m.z;
_pos_desired_ned_m.z = _pos_target_ned_m.z - _pos_offset_ned_m.z;

_vel_target_ned_ms.z = _vel_estimate_ned_ms.z;
// Set velocity target so that P and FF sum to zero on the first cycle:
// 0 = (target - measurement) * kP + target * kFF
// target = measurement * kP / (kP + kFF)
_vel_target_ned_ms.z = _vel_estimate_ned_ms.z * (_pid_vel_d_m.kP() / (_pid_vel_d_m.kP() + MAX(_pid_vel_d_m.ff(), 0)));
_vel_desired_ned_ms.z = _vel_target_ned_ms.z - _vel_offset_ned_ms.z;

// Reset I term of velocity PID
Expand Down
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