This module implements optical flow landings in which the divergence is kept constant. More...

#include "std.h"

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Data Structures
struct	OpticalFlowLanding

Macros
#define	COV_WINDOW_SIZE 60

#define	GUIDANCE_H_MODE_MODULE_SETTING GUIDANCE_H_MODE_HOVER

#define	GUIDANCE_V_MODE_MODULE_SETTING GUIDANCE_V_MODE_MODULE

Functions
float	get_cov (float a, float b, int n_elements)
	Get the covariance of two arrays. More...

float	get_mean_array (float *a, int n_elements)
	Get the mean value of an array. More...

void	reset_all_vars (void)
	Reset all variables: More...

void	guidance_v_module_init (void)

void	guidance_v_module_enter (void)
	Entering the module (user switched to module) More...

void	guidance_v_module_run (bool in_flight)

Variables
struct OpticalFlowLanding	of_landing_ctrl

float	thrust_history [COV_WINDOW_SIZE]

float	divergence_history [COV_WINDOW_SIZE]

float	past_divergence_history [COV_WINDOW_SIZE]

unsigned long	ind_hist

Detailed Description

This module implements optical flow landings in which the divergence is kept constant.

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 & biomimetics, 11(1), 016004. http://iopscience.iop.org/article/10.1088/1748-3190/11/1/016004

Definition in file optical_flow_landing.h.

Data Structure Documentation

struct OpticalFlowLanding

Definition at line 44 of file optical_flow_landing.h.

Data Fields
float	agl	agl = height from sonar (only used when using "fake" divergence)
float	agl_lp	low-pass version of agl
int	CONTROL_METHOD	type of divergence control: 0 = fixed gain, 1 = adaptive gain
float	cov_limit	for fixed gain control, what is the cov limit triggering the landing
int	COV_METHOD	method to calculate the covariance: between thrust and div (0) or div and div past (1)
float	cov_set_point	for adaptive gain control, setpoint of the covariance (oscillations)
int	delay_steps	number of delay steps for div past
float	dgain	D-gain for constant divergence control.
float	dgain_adaptive	D-gain for adaptive gain control.
float	divergence_setpoint	setpoint for constant divergence approach
float	igain	I-gain for constant divergence control.
float	igain_adaptive	I-gain for adaptive gain control.
float	lp_factor	low-pass factor in [0,1], with 0 purely using the current measurement
float	nominal_thrust	nominal thrust around which the PID-control operates
float	pgain	P-gain for constant divergence control (from divergence error to thrust)
float	pgain_adaptive	P-gain for adaptive gain control.
float	sum_err	integration of the error for I-gain
float	vel	vertical velocity as determined with sonar (only used when using "fake" divergence)
int	VISION_METHOD	whether to use vision (1) or Optitrack / sonar (0)