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[vision] Added more documentation about optical flow

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This commit is contained in:
Freek van Tienen
2015-03-31 11:35:44 +02:00
parent 5f49f54faa
commit abc2859fbe
2 changed files with 45 additions and 13 deletions
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25
conf/modules/cv_opticflow.xml
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@@ -3,15 +3,14 @@
<module name="cv_opticflow" dir="computer_vision">
<doc>
<description>
Compute Optic Flow from Ardrone2 Bottom Camera
Computes Pitch- and rollrate corrected optic flow from downward looking
ARDrone2 camera looking at a textured floor.
Hovers the drone based on optical flow made for Linux video Devices.
Computes Pitch- and roll attide from downward looking camera looking at a textured floor.
- Sonar is required.
- Controller can hold position
</description>
<!-- Satbilization parameters and gains -->
<section name="VISION" prefix="VISION_">
<define name="PHI_PGAIN" value="400" description="Optic flow proportional gain on the roll velocity error"/>
<define name="PHI_IGAIN" value="20" description="Optic flow integrated gain on the summed roll velocity error"/>
@@ -21,14 +20,30 @@
<define name="DESIRED_VY" value="0" description="The desired velocity in the body frame y direction"/>
</section>
<!-- Optical flow calculation parameters -->
<section name="OPTICFLOW" prefix="OPTICFLOW_">
<define name="AGL_ID" value="ABI_SENDER_ID" description="ABI sender id for AGL message (sonar measurement) (default: ABI_BROADCAST)"/>
<!-- Video device parameters -->
<define name="DEVICE" value="/dev/video2" description="The V4L2 camera device that is used for the calculations"/>
<define name="DEVICE_SIZE" value="320,240" description="The V4L2 camera device width and height"/>
<define name="DEVICE_BUFFERS" value="15" description="Amount of V4L2 video buffers"/>
<define name="SUBDEV" description="The V4L2 subdevice to initialize before the main device"/>
<!-- Camera parameters -->
<define name="FOV_W" value="0.89360857702" description="The field of view width of the bottom camera (Defaults are from an ARDrone 2)"/>
<define name="FOV_H" value="0.67020643276" description="The field of view height of the bottom camera (Defaults are from an ARDrone 2)"/>
<define name="FX" value="343.1211" description="Field in the x direction of the camera (Defaults are from an ARDrone 2)"/>
<define name="FY" value="348.5053" description="Field in the y direction of the camera (Defaults are from an ARDrone 2)"/>
<!-- Lucas Kanade optical flow calculation parameters -->
<define name="MAX_TRACK_CORNERS" value="25" description="The maximum amount of corners the Lucas Kanade algorithm is tracking between two frames"/>
<define name="WINDOW_SIZE" value="10" description="Window size used in Lucas Kanade algorithm"/>
<define name="SUBPIXEL_FACTOR" value="10" description="Amount of subpixels per pixel, used for more precise (subpixel) calculations of the flow"/>
<define name="MAX_ITERATIONS" value="10" description="Maximum number of iterations the Lucas Kanade algorithm should take"/>
<define name="THRESHOLD_VEC" value="2" description="TThreshold in subpixels when the iterations of Lucas Kanade should stop"/>
<!-- FAST9 corner detection parameters -->
<define name="FAST9_ADAPTIVE" value="TRUE" description="Whether we should use and adapative FAST9 crner detection threshold"/>
<define name="FAST9_THRESHOLD" value="20" description="FAST9 default threshold"/>
<define name="FAST9_MIN_DISTANCE" value="10" description="The amount of pixels between corners that should be detected"/>
@@ -37,6 +52,7 @@
<settings>
<dl_settings NAME="Vision stabilization">
<!-- Satabilization loop parameters and gains -->
<dl_settings name="vision_stab">
<dl_setting var="opticflow_stab.phi_pgain" module="computer_vision/opticflow_module" min="0" step="1" max="10000" shortname="kp_v_phi" param="VISION_PHI_PGAIN"/>
<dl_setting var="opticflow_stab.phi_igain" module="computer_vision/opticflow_module" min="0" step="1" max="1000" shortname="ki_v_phi" param="VISION_PHI_IGAIN"/>
@@ -46,6 +62,7 @@
<dl_setting var="opticflow_stab.desired_vy" module="computer_vision/opticflow_module" min="-5" step="0.01" max="5" shortname="desired_vy" param="VISION_DESIRED_VY"/>
</dl_settings>
<!-- Optical flow calculations parameters for Lucas Kanade and FAST9 -->
<dl_settings name="vision_calc">
<dl_setting var="opticflow.max_track_corners" module="computer_vision/opticflow_module" min="0" step="1" max="500" shortname="max_trck_corners" param="OPTICFLOW_MAX_TRACK_CORNERS"/>
<dl_setting var="opticflow.window_size" module="computer_vision/opticflow_module" min="0" step="1" max="500" shortname="window_size" param="OPTICFLOW_WINDOW_SIZE"/>

33
sw/airborne/modules/computer_vision/opticflow/opticflow_calculator.c
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@@ -40,11 +40,26 @@
#include "lib/vision/lucas_kanade.h"
#include "lib/vision/fast_rosten.h"
// ARDrone Vertical Camera Parameters
#define FOV_H 0.67020643276
#define FOV_W 0.89360857702
#define Fx_ARdrone 343.1211
#define Fy_ARdrone 348.5053
// Camera parameters (defaults are from an ARDrone 2)
#ifndef OPTICFLOW_FOV_W
#define OPTICFLOW_FOV_W 0.89360857702
#endif
PRINT_CONFIG_VAR(OPTICFLOW_FOV_W);
#ifndef OPTICFLOW_FOV_H
#define OPTICFLOW_FOV_H 0.67020643276
#endif
PRINT_CONFIG_VAR(OPTICFLOW_FOV_H);
#ifndef OPTICFLOW_FX
#define OPTICFLOW_FX 343.1211
#endif
PRINT_CONFIG_VAR(OPTICFLOW_FX);
#ifndef OPTICFLOW_FY
#define OPTICFLOW_FY 348.5053
#endif
PRINT_CONFIG_VAR(OPTICFLOW_FY);
/* Set the default values */
#ifndef OPTICFLOW_MAX_TRACK_CORNERS
@@ -208,16 +223,16 @@ void opticflow_calc_frame(struct opticflow_t *opticflow, struct opticflow_state_
}
// Flow Derotation
float diff_flow_x = (state->phi - opticflow->prev_phi) * img->w / FOV_W;
float diff_flow_y = (state->theta - opticflow->prev_theta) * img->h / FOV_H;
float diff_flow_x = (state->phi - opticflow->prev_phi) * img->w / OPTICFLOW_FOV_W;
float diff_flow_y = (state->theta - opticflow->prev_theta) * img->h / OPTICFLOW_FOV_H;
result->flow_der_x = result->flow_x - diff_flow_x * opticflow->subpixel_factor;
result->flow_der_y = result->flow_y - diff_flow_y * opticflow->subpixel_factor;
opticflow->prev_phi = state->phi;
opticflow->prev_theta = state->theta;
// Velocity calculation
result->vel_x = -result->flow_der_x * result->fps / opticflow->subpixel_factor * img->w / Fx_ARdrone;
result->vel_y = result->flow_der_y * result->fps / opticflow->subpixel_factor * img->h / Fy_ARdrone;
result->vel_x = -result->flow_der_x * result->fps / opticflow->subpixel_factor * img->w / OPTICFLOW_FX;
result->vel_y = result->flow_der_y * result->fps / opticflow->subpixel_factor * img->h / OPTICFLOW_FY;
// *************************************************************************************
// Next Loop Preparation