ArduPlane: initialize the accz integrator at takeoff

[magate]

Currently the integrator gets set to the lowest value at takeoff since throttle demand is near zero and hover throttle could be saved in the Q_M_THST_HOVER parameter. This allows the user to specify a desired initialization percentage/100.

For small vehicles this is unlikely to be needed. For larger (heavier) quadplanes this should prevent prolonged time on the ground at a low power setting where the vehicle could be light on the landing gear and skip across the ground.

Testing

Baseline

baseline.BIN.txt

Figure:

1. Integrator initializes at large negative value.
2. Vehicle lifts off ~1.5 seconds later

Feature Disabled

disabled.BIN.txt

Figure: Similar results to baseline.

1. Integrator initializes at large negative value.
2. Vehicle lifts off ~1.5 seconds later

Feature Enabled at zero

enabled.BIN.txt

Figure:

1. Integrator initializes at zero.
2. Vehicle lifts off ~1 second later

[IamPete1]

My preference would be to copy copter rather than re-inventing the wheel. It has better takeoff handling that we do on plane.

I think this is the key bit we need:

ardupilot/ArduCopter/takeoff.cpp

Lines 159 to 181 in 00a6563

	// aircraft stays in landed state until vertical movement is detected or 90% throttle is reached
	if (copter.ap.land_complete) {
	// send throttle to attitude controller with angle boost
	float throttle = constrain_float(copter.attitude_control->get_throttle_in() + copter.G_Dt / copter.g2.takeoff_throttle_slew_time, 0.0, 1.0);
	copter.attitude_control->set_throttle_out(throttle, true, 0.0);
	// tell position controller to reset alt target and reset I terms
	copter.pos_control->init_z_controller();
	pos_control->relax_velocity_controller_xy();
	pos_control->update_xy_controller();
	attitude_control->reset_rate_controller_I_terms();
	attitude_control->input_thrust_vector_rate_heading(pos_control->get_thrust_vector(), 0.0);
	if (throttle >= MIN(copter.g2.takeoff_throttle_max, 0.9) ||
	(copter.pos_control->get_z_accel_cmss() >= 0.5 * copter.pos_control->get_max_accel_z_cmss()) ||
	(copter.pos_control->get_vel_desired_cms().z >= 0.1 * copter.pos_control->get_max_speed_up_cms()) ||
	( no_nav_active && (inertial_nav.get_position_z_up_cm() >= no_nav_alt_cm))) {
	// throttle > 90%
	// acceleration > 50% maximum acceleration
	// velocity > 10% maximum velocity
	// altitude change greater than half auto_takeoff_no_nav_alt_cm
	copter.set_land_complete(false);
	}
	return;
	}

[magate]

My preference would be to copy copter rather than re-inventing the wheel. It has better takeoff handling that we do on plane.

I think this is the key bit we need:

ardupilot/ArduCopter/takeoff.cpp

Lines 159 to 181 in 00a6563

	// aircraft stays in landed state until vertical movement is detected or 90% throttle is reached
	if (copter.ap.land_complete) {
	// send throttle to attitude controller with angle boost
	float throttle = constrain_float(copter.attitude_control->get_throttle_in() + copter.G_Dt / copter.g2.takeoff_throttle_slew_time, 0.0, 1.0);
	copter.attitude_control->set_throttle_out(throttle, true, 0.0);
	// tell position controller to reset alt target and reset I terms
	copter.pos_control->init_z_controller();
	pos_control->relax_velocity_controller_xy();
	pos_control->update_xy_controller();
	attitude_control->reset_rate_controller_I_terms();
	attitude_control->input_thrust_vector_rate_heading(pos_control->get_thrust_vector(), 0.0);
	if (throttle >= MIN(copter.g2.takeoff_throttle_max, 0.9) ||
	(copter.pos_control->get_z_accel_cmss() >= 0.5 * copter.pos_control->get_max_accel_z_cmss()) ||
	(copter.pos_control->get_vel_desired_cms().z >= 0.1 * copter.pos_control->get_max_speed_up_cms()) ||
	( no_nav_active && (inertial_nav.get_position_z_up_cm() >= no_nav_alt_cm))) {
	// throttle > 90%
	// acceleration > 50% maximum acceleration
	// velocity > 10% maximum velocity
	// altitude change greater than half auto_takeoff_no_nav_alt_cm
	copter.set_land_complete(false);
	}
	return;
	}

Perfect, thanks. Will close this and open a new PR.