Visual Servoing Platform  version 3.6.1 under development (2024-05-26)

Example of eye-in-hand control law. We control here a real robot, the Viper S650 robot (arm with 6 degrees of freedom). The velocity is computed in the camera frame. The inverse jacobian that converts cartesian velocities in joint velocities is implemented in the robot low level controller. Visual features are the image coordinates of 4 points. The target is made of 4 dots arranged as a 10cm by 10cm square.The device used to acquire images is a firewire camera (PointGrey Flea2)

Camera extrinsic (eMc) and intrinsic parameters are retrieved from the robot low level driver that is not public.

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* Description:
* tests the control law
* eye-in-hand control
* velocity computed in the camera frame
#include <fstream>
#include <iostream>
#include <sstream>
#include <stdio.h>
#include <stdlib.h>
#include <visp3/core/vpConfig.h>
#if defined(VISP_HAVE_VIPER650) && defined(VISP_HAVE_DC1394) && defined(VISP_HAVE_X11)
#include <visp3/blob/vpDot2.h>
#include <visp3/core/vpHomogeneousMatrix.h>
#include <visp3/core/vpIoTools.h>
#include <visp3/core/vpPoint.h>
#include <visp3/gui/vpDisplayX.h>
#include <visp3/robot/vpRobotViper650.h>
#include <visp3/sensor/vp1394TwoGrabber.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>
#define L 0.05 // to deal with a 10cm by 10cm square
void compute_pose(std::vector<vpPoint> &point, std::vector<vpDot2> &dot, vpCameraParameters cam,
vpPose pose;
for (size_t i = 0; i < point.size(); i++) {
double x = 0, y = 0;
vpImagePoint cog = dot[i].getCog();
y); // pixel to meter conversion
point[i].set_x(x); // projection perspective p
if (init == true) {
} else {
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*
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 {
// Load the end-effector to camera frame transformation obtained
// using a camera intrinsic model with distortion
std::cout << "Camera extrinsic parameters (eMc): \n" << eMc << std::endl;
vpServo task;
bool reset = false;
vp1394TwoGrabber g(reset);;
vpDisplayX display(I, 100, 100, "Current image");
std::vector<vpDot2> dot(4);
std::cout << "Click on the 4 dots clockwise starting from upper/left dot..." << std::endl;
for (size_t i = 0; i < dot.size(); i++) {
vpImagePoint cog = dot[i].getCog();
// Update camera parameters
robot.getCameraParameters(cam, I);
std::cout << "Camera intrinsic parameters: \n" << cam << std::endl;
// Sets the current position of the visual feature
for (size_t i = 0; i < dot.size(); 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
std::vector<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);
// Compute target initial pose
compute_pose(point, dot, cam, cMo, true);
std::cout << "Initial camera pose (cMo): \n" << cMo << std::endl;
// Initialise a desired pose to compute s*, the desired 2D point features
vpHomogeneousMatrix cMo_d(vpTranslationVector(0, 0, 0.5), // tz = 0.5 meter
vpRotationMatrix()); // no rotation
// 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_d, cP);
point[i].projection(cP, p);
// We want to see a point on a point
for (size_t i = 0; i < dot.size(); i++)
task.addFeature(p[i], pd[i]);
// Set the proportional gain
// Define the task
// - we want an eye-in-hand control law
// - camera velocities are computed
// Initialise the velocity control of the robot
std::cout << "\nHit CTRL-C or click in the image to stop the loop...\n" << std::flush;
for (;;) {
// Acquire a new image from the camera
// Display this image
try {
// For each point...
for (size_t i = 0; i < dot.size(); i++) {
// Achieve the tracking of the dot in the image
// Display a green cross at the center of gravity position in the
// image
vpImagePoint cog = dot[i].getCog();
} catch (...) {
std::cout << "Error detected while tracking visual features.." << std::endl;
// During the servo, we compute the pose using a non linear method. For
// the initial pose used in the non linear minimization we use the pose
// computed at the previous iteration.
compute_pose(point, dot, cam, cMo, false);
for (size_t i = 0; i < dot.size(); 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);
// Compute the visual servoing skew vector
// Display the current and desired feature points in the image display
vpServoDisplay::display(task, cam, I);
// Apply the computed joint 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() << std::endl;
vpDisplay::displayText(I, 10, 10, "Click to quit...", vpColor::red);
if (vpDisplay::getClick(I, false))
// Flush the display
// std::cout << "\t\t || s - s* || = " << ( task.getError()
// ).sumSquare() << std::endl;
std::cout << "Display task information: " << std::endl;
flog.close(); // Close the log file
} catch (const vpException &e) {
flog.close(); // Close the log file
std::cout << "Catched an exception: " << e.getMessage() << std::endl;
int main()
std::cout << "You do not have an Viper 650 robot connected to your computer..." << std::endl;
Class for firewire ieee1394 video devices using libdc1394-2.x api.
Generic class defining intrinsic camera parameters.
@ perspectiveProjWithDistortion
Perspective projection with distortion model.
Implementation of column vector and the associated operations.
Definition: vpColVector.h:163
static const vpColor red
Definition: vpColor.h:211
static const vpColor blue
Definition: vpColor.h:217
static const vpColor green
Definition: vpColor.h:214
Use the X11 console to display images on unix-like OS. Thus to enable this class X11 should be instal...
Definition: vpDisplayX.h:128
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)
error that can be emitted by ViSP classes.
Definition: vpException.h:59
const char * getMessage() const
Definition: vpException.cpp:64
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.
Class that defines a 2D point in an image. This class is useful for image processing and stores only ...
Definition: vpImagePoint.h:82
void init(unsigned int h, unsigned int w, Type value)
Definition: vpImage.h:629
static bool checkDirectory(const std::string &dirname)
Definition: vpIoTools.cpp:834
static std::string getUserName()
Definition: vpIoTools.cpp:727
static void makeDirectory(const std::string &dirname)
Definition: vpIoTools.cpp:983
static void convertPoint(const vpCameraParameters &cam, const double &u, const double &v, double &x, double &y)
Class used for pose computation from N points (pose from point only). Some of the algorithms implemen...
Definition: vpPose.h:78
void addPoint(const vpPoint &P)
Definition: vpPose.cpp:93
Definition: vpPose.h:99
Definition: vpPose.h:93
bool computePose(vpPoseMethodType method, vpHomogeneousMatrix &cMo, bool(*func)(const vpHomogeneousMatrix &)=nullptr)
Definition: vpPose.cpp:341
void getVelocity(const vpRobot::vpControlFrameType frame, vpColVector &velocity)
void setVelocity(const vpRobot::vpControlFrameType frame, const vpColVector &vel) vp_override
Control of Irisa's Viper S650 robot named Viper650.
Definition: vpRobot.h:78
Definition: vpRobot.h:82
Initialize the velocity controller.
Definition: vpRobot.h:65
virtual vpRobotStateType setRobotState(const vpRobot::vpRobotStateType newState)
Definition: vpRobot.cpp:198
Implementation of a rotation matrix and operations on such kind of matrices.
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:378
Definition: vpServo.h:155
void addFeature(vpBasicFeature &s_cur, vpBasicFeature &s_star, unsigned int select=vpBasicFeature::FEATURE_ALL)
Definition: vpServo.cpp:329
void print(const vpServo::vpServoPrintType display_level=ALL, std::ostream &os=std::cout)
Definition: vpServo.cpp:169
void setLambda(double c)
Definition: vpServo.h:976
void setServo(const vpServoType &servo_type)
Definition: vpServo.cpp:132
vpColVector getError() const
Definition: vpServo.h:504
Definition: vpServo.h:229
vpColVector computeControlLaw()
Definition: vpServo.cpp:703
Definition: vpServo.h:196
Class that consider the case of a translation vector.
Definition: vpViper650.h:120
void display(vpImage< unsigned char > &I, const std::string &title)
Display a gray-scale image.