Visual Servoing Platform  version 3.6.1 under development (2024-06-21)

Example of eye-in-hand control law. We control here a real robot, the Afma6 robot (cartesian robot, with 6 degrees of freedom). The velocity is computed in the camera frame. Visual features are the image coordinates of 4 vpDot2 points. The interaction matrix is computed using the current visual features.

* ViSP, open source Visual Servoing Platform software.
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* Description:
* tests the control law
* eye-in-hand control
* velocity computed in the camera frame
#include <stdlib.h>
#include <visp3/core/vpConfig.h>
#include <visp3/core/vpDebug.h> // Debug trace
#if (defined(VISP_HAVE_AFMA6) && defined(VISP_HAVE_DC1394))
#include <visp3/core/vpDisplay.h>
#include <visp3/core/vpImage.h>
#include <visp3/core/vpImagePoint.h>
#include <visp3/gui/vpDisplayGTK.h>
#include <visp3/gui/vpDisplayOpenCV.h>
#include <visp3/gui/vpDisplayX.h>
#include <visp3/sensor/vpRealSense2.h>
#include <visp3/blob/vpDot.h>
#include <visp3/core/vpHomogeneousMatrix.h>
#include <visp3/core/vpIoTools.h>
#include <visp3/core/vpMath.h>
#include <visp3/core/vpPoint.h>
#include <visp3/core/vpRotationMatrix.h>
#include <visp3/core/vpRxyzVector.h>
#include <visp3/core/vpTranslationVector.h>
#include <visp3/robot/vpRobotAfma6.h>
#include <visp3/vision/vpPose.h>
#include <visp3/visual_features/vpFeatureBuilder.h>
#include <visp3/visual_features/vpFeaturePoint.h>
#include <visp3/vs/vpServo.h>
#include <visp3/vs/vpServoDisplay.h>
// Exception
#include <visp3/core/vpException.h>
#define L 0.06 // to deal with a 12cm by 12cm square
using namespace VISP_NAMESPACE_NAME;
void compute_pose(vpPoint point[], vpDot2 dot[], int ndot, vpCameraParameters cam, vpHomogeneousMatrix &cMo, bool init)
vpPose pose;
for (int i = 0; i < ndot; i++) {
double x = 0, y = 0;
cog = dot[i].getCog();
y); // pixel to meter conversion
// std::cout << "point cam: " << i << x << " " << y << std::endl;
point[i].set_x(x); // projection perspective p
// std::cout << "point " << i << std::endl;
// point[i].print();
if (init == true) {
else { // init = false; use of the previous pose to initialise VIRTUAL_VS
int main()
// 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 mesured joint velocities (m/s, rad/s)
// - the 6 mesured joint positions (m, rad)
// - the 8 values of s - s*
// - the 6 values of the pose cMo (tx,ty,tz, rx,ry,rz) with translation
// in meters and rotations in radians
std::string username;
// Get the user login name
// Create a log filename to save velocities...
std::string logdirname;
logdirname = "/tmp/" + username;
// 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;
std::string logfilename;
logfilename = logdirname + "/log.dat";
// Open the log file name
std::ofstream flog(logfilename.c_str());
try {
vpServo task;
int i;
rs2::config config;
config.enable_stream(RS2_STREAM_COLOR, 640, 480, RS2_FORMAT_RGBA8, 30);
config.enable_stream(RS2_STREAM_DEPTH, 640, 480, RS2_FORMAT_Z16, 30);
config.enable_stream(RS2_STREAM_INFRARED, 640, 480, RS2_FORMAT_Y8, 30);;
// Warm up camera
for (size_t i = 0; i < 10; ++i) {
#ifdef VISP_HAVE_X11
vpDisplayX display(I, 100, 100, "Current image");
#elif defined(HAVE_OPENCV_HIGHGUI)
vpDisplayOpenCV display(I, 100, 100, "Current image");
#elif defined(VISP_HAVE_GTK)
vpDisplayGTK display(I, 100, 100, "Current image");
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 << " Use of the Afma6 robot " << std::endl;
std::cout << " Interaction matrix computed with the current features " << std::endl;
std::cout << " task : servo 4 points on a square with dimension " << L << " meters" << std::endl;
std::cout << "-------------------------------------------------------" << std::endl;
std::cout << std::endl;
vpDot2 dot[4];
std::cout << "Click on the 4 dots clockwise starting from upper/left dot..." << std::endl;
for (i = 0; i < 4; i++) {
cog = dot[i].getCog();
vpRobotAfma6 robot;
// Load the end-effector to camera frame transformation obtained
// using a camera intrinsic model with distortion
// Update camera parameters
robot.getCameraParameters(cam, I);
// Sets the current position of the visual feature
for (i = 0; i < 4; i++)
vpFeatureBuilder::create(p[i], cam, dot[i]); // retrieve x,y of the vpFeaturePoint structure
// Set the position of the square target in a frame which origin is
// centered in the middle of the square
vpPoint point[4];
point[0].setWorldCoordinates(-L, -L, 0);
point[1].setWorldCoordinates(L, -L, 0);
point[2].setWorldCoordinates(L, L, 0);
point[3].setWorldCoordinates(-L, L, 0);
// Initialise a desired pose to compute s*, the desired 2D point features
vpTranslationVector cto(0, 0, 0.5); // tz = 0.7 meter
vpMath::rad(0)); // No rotations
vpRotationMatrix cRo(cro); // Build the rotation matrix, cRo); // Build the homogeneous matrix
// Sets the desired position of the 2D visual feature
// Compute the desired position of the features from the desired pose
for (int i = 0; i < 4; i++) {
vpColVector cP, p;
point[i].changeFrame(cMo, cP);
point[i].projection(cP, p);
// Define the task
// - we want an eye-in-hand control law
// - robot is controlled in the camera frame
// - Interaction matrix is computed with the current visual features
// We want to see a point on a point
std::cout << std::endl;
for (i = 0; i < 4; i++)
task.addFeature(p[i], pd[i]);
// Set the proportional gain
// Display task information
// Initialise the velocity control of the robot
std::cout << "\nHit CTRL-C to stop the loop...\n" << std::flush;
bool init_pose_from_linear_method = true;
bool quit = false;
while (!quit) {
// Acquire a new image from the camera
// Display this image
// For each point...
for (i = 0; i < 4; i++) {
// Achieve the tracking of the dot in the image
// Get the dot cog
cog = dot[i].getCog();
// Display a green cross at the center of gravity position in the
// image
// At first iteration, we initialise non linear pose estimation with a linear approach.
// For the other iterations, non linear pose estimation is initialized with the pose estimated at previous iteration of the loop
compute_pose(point, dot, 4, cam, cMo, init_pose_from_linear_method);
if (init_pose_from_linear_method) {
init_pose_from_linear_method = false;
for (i = 0; i < 4; i++) {
// Update the point feature from the dot location
vpFeatureBuilder::create(p[i], cam, dot[i]);
// Set the feature Z coordinate from the pose
point[i].changeFrame(cMo, cP);
// Printing on stdout concerning task information
// task.print() ;
// Compute the visual servoing skew vector
v = task.computeControlLaw();
// Display the current and desired feature points in the image display
vpServoDisplay::display(task, cam, I);
// Apply the computed camera velocities to the robot
// Save velocities applied to the robot in the log file
// v[0], v[1], v[2] correspond to camera translation velocities in m/s
// v[3], v[4], v[5] correspond to camera rotation velocities in rad/s
flog << v[0] << " " << v[1] << " " << v[2] << " " << v[3] << " " << v[4] << " " << v[5] << " ";
// Get the measured joint velocities of the robot
// Save measured joint velocities of the robot in the log file:
// - qvel[0], qvel[1], qvel[2] correspond to measured joint translation
// velocities in m/s
// - qvel[3], qvel[4], qvel[5] correspond to measured joint rotation
// velocities in rad/s
flog << qvel[0] << " " << qvel[1] << " " << qvel[2] << " " << qvel[3] << " " << qvel[4] << " " << qvel[5] << " ";
// Get the measured joint positions of the robot
robot.getPosition(vpRobot::ARTICULAR_FRAME, q);
// Save measured joint positions of the robot in the log file
// - q[0], q[1], q[2] correspond to measured joint translation
// positions in m
// - q[3], q[4], q[5] correspond to measured joint rotation
// positions in rad
flog << q[0] << " " << q[1] << " " << q[2] << " " << q[3] << " " << q[4] << " " << q[5] << " ";
// Save feature error (s-s*) for the 4 feature points. For each feature
// point, we have 2 errors (along x and y axis). This error is
// expressed in meters in the camera frame
flog << (task.getError()).t() << " "; // s-s* for points
// Save the current cMo pose: translations in meters, rotations (rx, ry,
// rz) in radians
flog << cto[0] << " " << cto[1] << " " << cto[2] << " " // translation
<< cro[0] << " " << cro[1] << " " << cro[2] << std::endl; // rot
vpDisplay::displayText(I, 20, 20, "Click to quit...", vpColor::red);
if (vpDisplay::getClick(I, false)) {
quit = true;
// Flush the display
flog.close(); // Close the log file
// Display task information
catch (const vpException &e) {
flog.close(); // Close the log file
std::cout << "Test failed with exception: " << e << std::endl;
int main()
std::cout << "You do not have an afma6 robot connected to your computer..." << std::endl;
Definition: vpAfma6.h:131
Generic class defining intrinsic camera parameters.
@ perspectiveProjWithDistortion
Perspective projection with distortion model.
Implementation of column vector and the associated operations.
Definition: vpColVector.h:171
static const vpColor red
Definition: vpColor.h:213
static const vpColor blue
Definition: vpColor.h:219
static const vpColor green
Definition: vpColor.h:216
The vpDisplayGTK allows to display image using the GTK 3rd party library. Thus to enable this class G...
Definition: vpDisplayGTK.h:129
The vpDisplayOpenCV allows to display image using the OpenCV library. Thus to enable this class OpenC...
Use the X11 console to display images on unix-like OS. Thus to enable this class X11 should be instal...
Definition: vpDisplayX.h:131
static bool getClick(const vpImage< unsigned char > &I, bool blocking=true)
static void display(const vpImage< unsigned char > &I)
static void displayCross(const vpImage< unsigned char > &I, const vpImagePoint &ip, unsigned int size, const vpColor &color, unsigned int thickness=1)
static void flush(const vpImage< unsigned char > &I)
static void displayText(const vpImage< unsigned char > &I, const vpImagePoint &ip, const std::string &s, const vpColor &color)
This tracker is meant to track a blob (connex pixels with same gray level) on a vpImage.
Definition: vpDot2.h:125
void track(const vpImage< unsigned char > &I, bool canMakeTheWindowGrow=true)
Definition: vpDot2.cpp:452
vpImagePoint getCog() const
Definition: vpDot2.h:181
void initTracking(const vpImage< unsigned char > &I, unsigned int size=0)
Definition: vpDot2.cpp:269
error that can be emitted by ViSP classes.
Definition: vpException.h:60
static void create(vpFeaturePoint &s, const vpCameraParameters &cam, const vpDot &d)
Class that defines a 2D point visual feature which is composed by two parameters that are the cartes...
void set_y(double y)
void set_x(double x)
void set_Z(double Z)
Implementation of an homogeneous matrix and operations on such kind of matrices.
vpHomogeneousMatrix & build(const vpTranslationVector &t, const vpRotationMatrix &R)
Class that defines a 2D point in an image. This class is useful for image processing and stores only ...
Definition: vpImagePoint.h:82
static bool checkDirectory(const std::string &dirname)
Definition: vpIoTools.cpp:851
static std::string getUserName()
Definition: vpIoTools.cpp:744
static void makeDirectory(const std::string &dirname)
Definition: vpIoTools.cpp:1003
static double rad(double deg)
Definition: vpMath.h:129
static void convertPoint(const vpCameraParameters &cam, const double &u, const double &v, double &x, double &y)
Class that defines a 3D point in the object frame and allows forward projection of a 3D point in the ...
Definition: vpPoint.h:79
void set_x(double x)
Set the point x coordinate in the image plane.
Definition: vpPoint.cpp:464
void projection(const vpColVector &_cP, vpColVector &_p) const vp_override
Definition: vpPoint.cpp:247
void changeFrame(const vpHomogeneousMatrix &cMo, vpColVector &cP) const vp_override
Definition: vpPoint.cpp:267
void setWorldCoordinates(double oX, double oY, double oZ)
Definition: vpPoint.cpp:111
void set_y(double y)
Set the point y coordinate in the image plane.
Definition: vpPoint.cpp:466
Class used for pose computation from N points (pose from point only). Some of the algorithms implemen...
Definition: vpPose.h:77
void addPoint(const vpPoint &P)
Definition: vpPose.cpp:94
Definition: vpPose.h:98
Definition: vpPose.h:92
bool computePose(vpPoseMethodType method, vpHomogeneousMatrix &cMo, funcCheckValidityPose func=nullptr)
Definition: vpPose.cpp:382
void acquire(vpImage< unsigned char > &grey, double *ts=nullptr)
bool open(const rs2::config &cfg=rs2::config())
Control of Irisa's gantry robot named Afma6.
Definition: vpRobotAfma6.h:210
void getVelocity(const vpRobot::vpControlFrameType frame, vpColVector &velocity)
void setVelocity(const vpRobot::vpControlFrameType frame, const vpColVector &vel) vp_override
Definition: vpRobot.h:80
Definition: vpRobot.h:84
Initialize the velocity controller.
Definition: vpRobot.h:67
virtual vpRobotStateType setRobotState(const vpRobot::vpRobotStateType newState)
Definition: vpRobot.cpp:198
Implementation of a rotation matrix and operations on such kind of matrices.
Implementation of a rotation vector as Euler angle minimal representation.
Definition: vpRxyzVector.h:179
static void display(const vpServo &s, const vpCameraParameters &cam, const vpImage< unsigned char > &I, vpColor currentColor=vpColor::green, vpColor desiredColor=vpColor::red, unsigned int thickness=1)
void setInteractionMatrixType(const vpServoIteractionMatrixType &interactionMatrixType, const vpServoInversionType &interactionMatrixInversion=PSEUDO_INVERSE)
Definition: vpServo.cpp:380
Definition: vpServo.h:157
void addFeature(vpBasicFeature &s_cur, vpBasicFeature &s_star, unsigned int select=vpBasicFeature::FEATURE_ALL)
Definition: vpServo.cpp:331
void print(const vpServo::vpServoPrintType display_level=ALL, std::ostream &os=std::cout)
Definition: vpServo.cpp:171
void setLambda(double c)
Definition: vpServo.h:978
void setServo(const vpServoType &servo_type)
Definition: vpServo.cpp:134
vpColVector getError() const
Definition: vpServo.h:506
Definition: vpServo.h:231
vpColVector computeControlLaw()
Definition: vpServo.cpp:705
Definition: vpServo.h:198
Class that consider the case of a translation vector.
void display(VISP_NAMESPACE_ADDRESSING vpImage< unsigned char > &I, const std::string &title)
Display a gray-scale image.
void init(VISP_NAMESPACE_ADDRESSING vpImage< unsigned char > &Iinput, VISP_NAMESPACE_ADDRESSING vpImage< unsigned char > &IcannyVisp, VISP_NAMESPACE_ADDRESSING vpImage< unsigned char > *p_dIx, VISP_NAMESPACE_ADDRESSING vpImage< unsigned char > *p_dIy, VISP_NAMESPACE_ADDRESSING vpImage< unsigned char > *p_IcannyimgFilter)
Initialize the different displays.