This module implements optical flow landings in which the divergence is kept constant (for rotorcraft). When using a fixed gain for control, the covariance between thrust and divergence is tracked, so that the drone knows when it has arrived close to the landing surface. Then, a final landing procedure is triggered. It can also be set to adaptive gain control, where the goal is to continuously gauge the distance to the landing surface. In this mode, the drone will oscillate all the way down to the surface.
de Croon, G.C.H.E. (2016). Monocular distance estimation with optical flow maneuvers and efference copies: a stability-based strategy. Bioinspiration and Biomimetics, 11(1), 016004.
Add to your firmware section: This example contains all possible configuration options, not all of them are mandatory!
<!DOCTYPE module SYSTEM "module.dtd">
<module name="optical_flow_landing" dir="ctrl">
<doc>
<description>
Optical flow landing.
This module implements optical flow landings in which the divergence is kept constant (for rotorcraft). When using a fixed gain for control, the covariance between thrust and divergence is tracked, so that the drone knows when it has arrived close to the landing surface. Then, a final landing procedure is triggered. It can also be set to adaptive gain control, where the goal is to continuously gauge the distance to the landing surface. In this mode, the drone will oscillate all the way down to the surface.
de Croon, G.C.H.E. (2016). Monocular distance estimation with optical flow maneuvers and efference copies: a stability-based strategy. Bioinspiration and Biomimetics, 11(1), 016004.
</description>
<define name="OFL_AGL_ID" value="ABI_BROADCAST" description="Sender id of the AGL (sonar) ABI message"/>
<section name="OFL" prefix="OFL_">
<define name="PGAIN" value="0.50" description="P gain on divergence error"/>
<define name="IGAIN" value="0.10" description="I gain on summed divergence error"/>
<define name="DGAIN" value="0.0" description="D gain on differential of divergence error"/>
<define name="VISION_METHOD" value="1" description="0 = fake vision, 1 = real vision"/>
<define name="CONTROL_METHOD" value="0" description="0 = fixed gain control, 1 = adaptive gain control, 2 = exponential control, 3 = learning-based control."/>
<define name="COV_METHOD" value="0" description="0 = cov(uz, div), 1 = cov(div_past, div)"/>
<define name="COV_WINDOW_SIZE" value="30" description="Number of time steps for window size for getting the covariance over time."/>
<define name="COV_LANDING_LIMIT" value="2.2" description="Covariance where the vehicle engages final landing procedure."/>
<define name="COV_SETPOINT" value="-0.10" description="Target Covariance for adaptive gain increment."/>
<define name="LP_CONST" value="0.05" description="Low pass filter constant for divergence input."/>
<define name="ELC_OSCILLATE" value="true" description="Oscillate to find optimum gain before initiating landing."/>
<define name="CLOSE_TO_EDGE" value="0.025" description="When the cov_div value gets this close to the setpoint, we consider the drone to oscillate"/>
<define name="PGAIN_ADAPTIVE" value="0.50" description="P gain on cov error"/>
<define name="IGAIN_ADAPTIVE" value="0.10" description="I gain on summed cov error"/>
<define name="DGAIN_ADAPTIVE" value="0.0" description="D gain on differential cov error"/>
<define name="P_LAND_THRESHOLD" value="0.15" description="P-value at which the drone will initiate a final landing procedure, for adaptive control"/>
<define name="PGAIN_HORIZONTAL_FACTOR" value="0.0625" description="Factor multiplied with P gain for horizontal control"/>
<define name="IGAIN_HORIZONTAL_FACTOR" value="0.0001" description="Factor multiplied with I gain for horizontal control"/>
<define name="ROLL_TRIM" value="0.0" description="Roll trim in degrees"/>
<define name="PITCH_TRIM" value="0.0" description="Pitch trim in degrees"/>
<define name="FRONT_DIV_THRESHOLD" value="0.3" description="Threshold on front divergence for stopping."/>
</section>
</doc>
<settings>
<dl_settings>
<dl_settings NAME="OpticalFlowLanding">
<dl_setting var="of_landing_ctrl.nominal_thrust" min="0" step="0.001" max="1" module="ctrl/optical_flow_landing" shortname="nominal_thrust"/>
<dl_setting var="of_landing_ctrl.lp_const" min="0.005" step="0.005" max="1" module="ctrl/optical_flow_landing" shortname="lp_factor" param="OFL_LP_CONST"/>
<dl_setting var="of_landing_ctrl.divergence_setpoint" min="-1" step="0.01" max="1" module="ctrl/optical_flow_landing" shortname="div sp"/>
<dl_setting var="of_landing_ctrl.cov_set_point" min="-6" step="0.0001" max="6" module="ctrl/optical_flow_landing" shortname="cov_set_point" param="OFL_COV_SETPOINT"/>
<dl_setting var="of_landing_ctrl.cov_limit" min="0" step="0.0001" max="6" module="ctrl/optical_flow_landing" shortname="cov_limit" param="OFL_COV_LANDING_LIMIT"/>
<dl_setting var="of_landing_ctrl.pgain" min="0" step="0.001" max="6" module="ctrl/optical_flow_landing" shortname="pgain" param="OFL_PGAIN"/>
<dl_setting var="of_landing_ctrl.igain" min="0" step="0.001" max="1" module="ctrl/optical_flow_landing" shortname="igain" param="OFL_IGAIN"/>
<dl_setting var="of_landing_ctrl.dgain" min="0" step="0.1" max="6" module="ctrl/optical_flow_landing" shortname="dgain" param="OFL_DGAIN"/>
<dl_setting var="of_landing_ctrl.VISION_METHOD" min="0" step="1" max="1" values="Ground truth|Online" module="ctrl/optical_flow_landing" shortname="VISION_METHOD" param="OFL_VISION_METHOD"/>
<dl_setting var="of_landing_ctrl.CONTROL_METHOD" min="0" step="1" max="5" values="Simple|Adaptive|Exp|Pred|Mixed|HoverPred" module="ctrl/optical_flow_landing" shortname="CONTROL_METHOD" param="OFL_CONTROL_METHOD"/>
<dl_setting var="of_landing_ctrl.COV_METHOD" min="0" step="1" max="1" values="Div-Thrust|Div-Shift div" module="ctrl/optical_flow_landing" shortname="COV_METHOD" param="OFL_COV_METHOD"/>
<dl_setting var="of_landing_ctrl.delay_steps" min="0" step="1" max="60" module="ctrl/optical_flow_landing" shortname="delay_steps"/>
<dl_setting var="of_landing_ctrl.window_size" min="5" step="5" max="100" module="ctrl/optical_flow_landing" shortname="window_size"/>
<dl_setting var="of_landing_ctrl.pgain_adaptive" min="0" step="0.1" max="20.0" module="ctrl/optical_flow_landing" shortname="pgain_adaptive"/>
<dl_setting var="of_landing_ctrl.igain_adaptive" min="0" step="0.01" max="1.0" module="ctrl/optical_flow_landing" shortname="igain_adaptive"/>
<dl_setting var="of_landing_ctrl.dgain_adaptive" min="0" step="0.01" max="5.0" module="ctrl/optical_flow_landing" shortname="dgain_adaptive"/>
<dl_setting var="of_landing_ctrl.reduction_factor_elc" min="0.1" step="0.01" max="3.0" module="ctrl/optical_flow_landing" shortname="reduction_factor_elc"/>
<dl_setting var="of_landing_ctrl.elc_oscillate" min="0" step="1" max="1" values="FALSE|TRUE" module="ctrl/optical_flow_landing" shortname="oscillate" param="OFL_ELC_OSCILLATE"/>
<dl_setting var="of_landing_ctrl.learn_gains" min="0" step="1" max="1" shortname="learn_gains" module="ctrl/optical_flow_landing">
<strip_button name="Learn gains from file" icon="learn.png" value="1"/>
</dl_setting>
<dl_setting var="of_landing_ctrl.close_to_edge" min="0" step="0.001" max="1.0" module="ctrl/optical_flow_landing" shortname="close_to_edge"/>
<dl_setting var="of_landing_ctrl.use_bias" min="0" step="1" max="1" shortname="use_bias" module="ctrl/optical_flow_landing"/>
<dl_setting var="of_landing_ctrl.snapshot" min="0" step="1" max="1" shortname="snapshot" module="ctrl/optical_flow_landing"/>
<dl_setting var="of_landing_ctrl.lp_factor_prediction" min="0" step="0.001" max="1" module="ctrl/optical_flow_landing" shortname="lp_factor_prediction"/>
<dl_setting var="of_landing_ctrl.p_land_threshold" min="0" step="0.01" max="2.0" module="ctrl/optical_flow_landing" shortname="p_land_threshold"/>
<dl_setting var="of_landing_ctrl.ramp_duration" min="0" step="0.01" max="2.0" module="ctrl/optical_flow_landing" shortname="ramp_duration"/>
<dl_setting var="of_landing_ctrl.pgain_horizontal_factor" min="0" step="0.001" max="1" module="ctrl/optical_flow_landing" shortname="pgain_hfact" param="OFL_PGAIN_HORIZONTAL_FACTOR"/>
<dl_setting var="of_landing_ctrl.igain_horizontal_factor" min="0" step="0.0001" max="1" module="ctrl/optical_flow_landing" shortname="igain_hfact" param="OFL_IGAIN_HORIZONTAL_FACTOR"/>
<dl_setting var="of_landing_ctrl.roll_trim" min="-60.0" step="0.1" max="60.0" module="ctrl/optical_flow_landing" shortname="roll_trim" param="OFL_ROLL_TRIM"/>
<dl_setting var="of_landing_ctrl.pitch_trim" min="-60.0" step="0.1" max="60.0" module="ctrl/optical_flow_landing" shortname="pitch_trim" param="OFL_PITCH_TRIM"/>
<dl_setting var="of_landing_ctrl.omega_LR" min="-60.0" step="1.0" max="60.0" module="ctrl/optical_flow_landing" shortname="omega_LR" param="OFL_OMEGA_LR"/>
<dl_setting var="of_landing_ctrl.omega_FB" min="-60.0" step="1.0" max="60.0" module="ctrl/optical_flow_landing" shortname="omega_FB" param="OFL_OMEGA_FB"/>
<dl_setting var="of_landing_ctrl.active_motion" min="0" step="1" max="2" values="none|flow|angle" module="ctrl/optical_flow_landing" shortname="active_motion" param="OFL_ACTIVE_MOTION"/>
<dl_setting var="of_landing_ctrl.front_div_threshold" min="0.0" step="0.01" max="5.0" module="ctrl/optical_flow_landing" shortname="front_div_threshold" param="OFL_FRONT_DIV_THRESHOLD"/>
</dl_settings>
</dl_settings>
</settings>
<dep>
<depends>cv_textons</depends>
</dep>
<header>
<file name="optical_flow_landing.h"/>
</header>
<makefile target="ap|nps">
<file name="optical_flow_landing.c"/>
<file name="pprz_algebra_float.c" dir="math"/>
<file name="pprz_matrix_decomp_float.c" dir="math"/>
</makefile>
</module>
1.9.1