Visual Servoing Platform  version 3.2.0 under development (2018-08-18)
servoSimu3D_cMcd_CamVelocityWithoutVpServo.cpp

Simulation of a 3D visual servoing where the current visual feature is given by $s=({^{c}}{\bf t}_{c^*}, \; \theta u_{{^{c}}{\bf R}_{c^*}})$ and the desired one $s^*=(0, \; 0)$.

The control law is set as:

Considering the visual feature, the interaction matrix to consider is

\[{\bf L}_s = \left[ \begin{array}{cc} -I_3 & [{^{c}}{\bf t}_{c^*}]_\times\\ 0 & {\bf Lw} \end{array} \right]\]

with

\[ {\bf Lw} = -I_3 + \frac{\theta}{2} \; [u]_\times - \left(1 - \frac{sinc \theta}{sinc^2 \frac{\theta}{2}}\right) [u]^2_\times \]

The camera velocity skew is given by:

\[ \left( \begin{array}{c} {\bf v} \\ {\bf w} \end{array} \right) = -\lambda \; {\bf L}_s^{-1} \; ({\bf s} - {\bf s}^*)\]

which becomes:

\[ \left( \begin{array}{c} {\bf v} \\ {\bf w} \end{array} \right) = -\lambda \; \left( \begin{array}{c} -{^c}{\bf t}_{c^*} - [{^{c}}{\bf t}_{c^*}]_\times \; \theta u_{{^c}{\bf R}_{c^*}} \\ -\theta U_{{^c}{\bf R}_{c^*}} \end{array} \right) \]

This relation is also equal to:

\[ \left( \begin{array}{c} {\bf v} \\ {\bf w} \end{array} \right) = \lambda \; \left( \begin{array}{c} (I - [\theta u_{{^c}{\bf R}_{c^*}}]_\times) \; {^c}{\bf t}_{c^*} \\ \theta U_{{^c}{\bf R}_{c^*}} \end{array} \right) \]

This example is to make into relation with servoSimu3D_cMcd_CamVelocity.cpp where vpServo and vpFeature classes are used.

/****************************************************************************
*
* This file is part of the ViSP software.
* Copyright (C) 2005 - 2017 by Inria. All rights reserved.
*
* This software is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
* See the file LICENSE.txt at the root directory of this source
* distribution for additional information about the GNU GPL.
*
* For using ViSP with software that can not be combined with the GNU
* GPL, please contact Inria about acquiring a ViSP Professional
* Edition License.
*
* See http://visp.inria.fr for more information.
*
* This software was developed at:
* Inria Rennes - Bretagne Atlantique
* Campus Universitaire de Beaulieu
* 35042 Rennes Cedex
* France
*
* If you have questions regarding the use of this file, please contact
* Inria at visp@inria.fr
*
* This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
* WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*
* Description:
* Simulation of a 3D visual servoing.
*
* Authors:
* Eric Marchand
* Fabien Spindler
*
*****************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <visp3/core/vpHomogeneousMatrix.h>
#include <visp3/core/vpIoTools.h>
#include <visp3/core/vpMath.h>
#include <visp3/io/vpParseArgv.h>
#include <visp3/robot/vpSimulatorCamera.h>
#include <visp3/visual_features/vpFeatureThetaU.h>
#include <visp3/visual_features/vpFeatureTranslation.h>
#include <visp3/vs/vpServo.h>
// List of allowed command line options
#define GETOPTARGS "h"
void usage(const char *name, const char *badparam);
bool getOptions(int argc, const char **argv);
void usage(const char *name, const char *badparam)
{
fprintf(stdout, "\n\
Simulation of a 3D visual servoing:\n\
- eye-in-hand control law,\n\
- velocity computed in the camera frame,\n\
- without display.\n\
\n\
SYNOPSIS\n\
%s [-h]\n", name);
fprintf(stdout, "\n\
OPTIONS: Default\n\
\n\
-h\n\
Print the help.\n");
if (badparam)
fprintf(stdout, "\nERROR: Bad parameter [%s]\n", badparam);
}
bool getOptions(int argc, const char **argv)
{
const char *optarg_;
int c;
while ((c = vpParseArgv::parse(argc, argv, GETOPTARGS, &optarg_)) > 1) {
switch (c) {
case 'h':
usage(argv[0], NULL);
return false;
break;
default:
usage(argv[0], optarg_);
return false;
break;
}
}
if ((c == 1) || (c == -1)) {
// standalone param or error
usage(argv[0], NULL);
std::cerr << "ERROR: " << std::endl;
std::cerr << " Bad argument " << optarg_ << std::endl << std::endl;
return false;
}
return true;
}
int main(int argc, const char **argv)
{
try {
// Read the command line options
if (getOptions(argc, argv) == false) {
exit(-1);
}
// Log file creation in /tmp/$USERNAME/log.dat
// This file contains by line:
// - the 6 computed camera velocities (m/s, rad/s) to achieve the task
// - the 6 values of s - s*
std::string username;
// Get the user login name
// Create a log filename to save velocities...
std::string logdirname;
#if defined(_WIN32)
logdirname = "C:/temp/" + username;
#else
logdirname = "/tmp/" + username;
#endif
// Test if the output path exist. If no try to create it
if (vpIoTools::checkDirectory(logdirname) == false) {
try {
// Create the dirname
} catch (...) {
std::cerr << std::endl << "ERROR:" << std::endl;
std::cerr << " Cannot create " << logdirname << std::endl;
exit(-1);
}
}
std::string logfilename;
logfilename = logdirname + "/log.dat";
// Open the log file name
std::ofstream flog(logfilename.c_str());
std::cout << std::endl;
std::cout << "-------------------------------------------------------" << std::endl;
std::cout << " Test program for vpServo " << std::endl;
std::cout << " Eye-in-hand task control, velocity computed in the camera frame" << std::endl;
std::cout << " Simulation " << std::endl;
std::cout << " task : 3D visual servoing " << std::endl;
std::cout << "-------------------------------------------------------" << std::endl;
std::cout << std::endl;
// Sets the initial camera location
vpPoseVector c_r_o( // Translation tx,ty,tz
0.1, 0.2, 2,
// ThetaU rotation
// From the camera pose build the corresponding homogeneous matrix
vpHomogeneousMatrix cMo(c_r_o);
// Set the robot initial position
robot.getPosition(wMc);
wMo = wMc * cMo; // Compute the position of the object in the world frame
// Sets the desired camera location
vpPoseVector cd_r_o( // Translation tx,ty,tz
0, 0, 1,
// ThetaU rotation
// From the camera desired pose build the corresponding homogeneous matrix
vpHomogeneousMatrix cdMo(cd_r_o);
vpHomogeneousMatrix cMcd; // Transformation between current and desired camera frame
vpRotationMatrix cRcd; // Rotation between current and desired camera frame
// Set the constant gain of the servo
double lambda = 1;
unsigned int iter = 0;
// Start the visual servoing loop. We stop the servo after 200 iterations
while (iter++ < 200) {
std::cout << "------------------------------------" << iter << std::endl;
// get the robot position
robot.getPosition(wMc);
// Compute the position of the camera wrt the object frame
cMo = wMc.inverse() * wMo;
// new displacement to achieve
cMcd = cMo * cdMo.inverse();
// Extract the translation vector ctc* which is the current
// translational visual feature.
cMcd.extract(ctcd);
// Compute the current theta U visual feature
vpThetaUVector tu_cRcd(cMcd);
// Create the identity matrix
vpMatrix I(3, 3);
I.eye();
// Compute the camera translational velocity
v = lambda * (I - vpColVector::skew(tu_cRcd)) * ctcd;
// Compute the camera rotational velocity
w = lambda * tu_cRcd;
// Update the complete camera velocity vector
vpColVector velocity(6);
for (unsigned int i = 0; i < 3; i++) {
velocity[i] = v[i]; // Translational velocity
velocity[i + 3] = w[i]; // Rotational velocity
}
// Send the camera velocity to the controller
robot.setVelocity(vpRobot::CAMERA_FRAME, velocity);
// Retrieve the error (s-s*)
std::cout << "|| s - s* || = " << ctcd.t() << " " << tu_cRcd.t() << std::endl;
// Save log
flog << velocity.t() << " " << ctcd.t() << " " << tu_cRcd.t() << std::endl;
}
// Close the log file
flog.close();
return EXIT_SUCCESS;
} catch (const vpException &e) {
std::cout << "Catch a ViSP exception: " << e << std::endl;
return EXIT_FAILURE;
}
}