servoAfma6AprilTagPBVS.cpp

Example of eye-in-hand image-based control law. We control here the Afma6 robot at Inria. The velocity is computed in the camera frame. Visual features correspond to the 3D pose of the target (an AprilTag) in the camera frame.

The device used to acquire images is a Realsense D435 device.

Camera intrinsic parameters are retrieved from the Realsense SDK.

The target is an AprilTag that is by default 12cm large. To print your own tag, see https://visp-doc.inria.fr/doxygen/visp-daily/tutorial-detection-apriltag.html You can specify the size of your tag using –tag_size command line option.

/*
 * ViSP, open source Visual Servoing Platform software.
 * Copyright (C) 2005 - 2024 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 https://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:
 * Data acquisition with RealSense RGB-D sensor and Franka robot.
 */
 
#include <iostream>
 
#include <visp3/core/vpConfig.h>
 
#if defined(VISP_HAVE_REALSENSE2) && defined(VISP_HAVE_DISPLAY) && defined(VISP_HAVE_AFMA6)
 
#include <visp3/core/vpCameraParameters.h>
#include <visp3/detection/vpDetectorAprilTag.h>
#include <visp3/gui/vpDisplayFactory.h>
#include <visp3/gui/vpPlot.h>
#include <visp3/io/vpImageIo.h>
#include <visp3/robot/vpRobotAfma6.h>
#include <visp3/sensor/vpRealSense2.h>
#include <visp3/visual_features/vpFeatureThetaU.h>
#include <visp3/visual_features/vpFeatureTranslation.h>
#include <visp3/vs/vpServo.h>
#include <visp3/vs/vpServoDisplay.h>
 
#ifdef ENABLE_VISP_NAMESPACE
using namespace VISP_NAMESPACE_NAME;
#endif
 
void display_point_trajectory(const vpImage<unsigned char> &I,
                              const std::vector<vpImagePoint> &vip,
                              std::vector<vpImagePoint> *traj_vip)
{
  for (size_t i = 0; i < vip.size(); ++i) {
    if (traj_vip[i].size()) {
      // Add the point only if distance with the previous > 1 pixel
      if (vpImagePoint::distance(vip[i], traj_vip[i].back()) > 1.) {
        traj_vip[i].push_back(vip[i]);
      }
    }
    else {
      traj_vip[i].push_back(vip[i]);
    }
  }
  for (size_t i = 0; i < vip.size(); ++i) {
    for (size_t j = 1; j < traj_vip[i].size(); ++j) {
      vpDisplay::displayLine(I, traj_vip[i][j - 1], traj_vip[i][j], vpColor::green, 2);
    }
  }
}
 
int main(int argc, char **argv)
{
  double opt_tagSize = 0.120;
  int opt_quad_decimate = 2;
  bool opt_verbose = false;
  bool opt_plot = false;
  bool opt_adaptive_gain = false;
  bool opt_task_sequencing = false;
  double opt_convergence_threshold_t = 0.0005; // Value in [m]
  double opt_convergence_threshold_tu = 0.5;   // Value in [deg]
 
  bool display_tag = true;
 
  for (int i = 1; i < argc; ++i) {
    if ((std::string(argv[i]) == "--tag-size") && (i + 1 < argc)) {
      opt_tagSize = std::stod(argv[i + 1]);
      ++i;
    }
    else if (std::string(argv[i]) == "--verbose") {
      opt_verbose = true;
    }
    else if (std::string(argv[i]) == "--plot") {
      opt_plot = true;
    }
    else if (std::string(argv[i]) == "--adaptive-gain") {
      opt_adaptive_gain = true;
    }
    else if (std::string(argv[i]) == "--task-sequencing") {
      opt_task_sequencing = true;
    }
    else if ((std::string(argv[i]) == "--quad-decimate") && (i + 1 < argc)) {
      opt_quad_decimate = std::stoi(argv[i + 1]);
      ++i;
    }
    else if (std::string(argv[i]) == "--no-convergence-threshold") {
      opt_convergence_threshold_t = 0.;
      opt_convergence_threshold_tu = 0.;
    }
    else if ((std::string(argv[i]) == "--help") || (std::string(argv[i]) == "-h")) {
      std::cout
        << argv[0]
        << " [--tag-size <marker size in meter; default " << opt_tagSize << ">]"
        << " [--quad-decimate <decimation; default " << opt_quad_decimate << ">]"
        << " [--adaptive-gain]"
        << " [--plot]"
        << " [--task-sequencing]"
        << " [--no-convergence-threshold]"
        << " [--verbose]"
        << " [--help] [-h]"
        << std::endl;;
      return EXIT_SUCCESS;
    }
  }
 
  vpRobotAfma6 robot;
  vpCameraParameters::vpCameraParametersProjType projModel = vpCameraParameters::perspectiveProjWithDistortion;
 
  // Load the end-effector to camera frame transformation obtained
  // using a camera intrinsic model with distortion
  robot.init(vpAfma6::TOOL_INTEL_D435_CAMERA, projModel);
 
  try {
    std::cout << "WARNING: This example will move the robot! "
      << "Please make sure to have the user stop button at hand!" << std::endl
      << "Press Enter to continue..." << std::endl;
    std::cin.ignore();
 
    vpRealSense2 rs;
    rs2::config config;
    unsigned int width = 640, height = 480, fps = 60;
    config.enable_stream(RS2_STREAM_COLOR, width, height, RS2_FORMAT_RGBA8, fps);
    config.enable_stream(RS2_STREAM_DEPTH, width, height, RS2_FORMAT_Z16, fps);
    config.enable_stream(RS2_STREAM_INFRARED, width, height, RS2_FORMAT_Y8, fps);
    rs.open(config);
 
    // Warm up camera
    vpImage<unsigned char> I;
    for (size_t i = 0; i < 10; ++i) {
      rs.acquire(I);
    }
 
    // Get camera intrinsics
    vpCameraParameters cam;
    robot.getCameraParameters(cam, I);
    std::cout << "cam:\n" << cam << std::endl;
 
    std::shared_ptr<vpDisplay> d = vpDisplayFactory::createDisplay(I, 10, 10, "Current image");
 
    vpDetectorAprilTag::vpAprilTagFamily tagFamily = vpDetectorAprilTag::TAG_36h11;
    vpDetectorAprilTag::vpPoseEstimationMethod poseEstimationMethod = vpDetectorAprilTag::HOMOGRAPHY_VIRTUAL_VS;
    // vpDetectorAprilTag::vpPoseEstimationMethod poseEstimationMethod = vpDetectorAprilTag::BEST_RESIDUAL_VIRTUAL_VS;
    vpDetectorAprilTag detector(tagFamily);
    detector.setAprilTagPoseEstimationMethod(poseEstimationMethod);
    detector.setDisplayTag(display_tag);
    detector.setAprilTagQuadDecimate(opt_quad_decimate);
    detector.setZAlignedWithCameraAxis(true);
 
    // Tag frame for pose estimation is the following
    // - When using
    //   detector.setZAlignedWithCameraAxis(false);
    //   detector.detect();
    //   we consider the tag frame (o) such as z_o axis is not aligned with camera frame
    //   (meaning z_o axis is facing the camera)
    //
    //   3    y    2
    //        |
    //        o--x
    //
    //   0         1
    //
    //   In that configuration, it is more difficult to set a desired camera pose c_M_o.
    //   To ease this step we can introduce an extra transformation matrix o'_M_o to align the axis
    //   with the camera frame:
    //
    //         o'--x
    //         |
    //         y
    //
    //   where
    //            | 1  0  0  0 |
    //   o'_M_o = | 0 -1  0  0 |
    //            | 0  0 -1  0 |
    //            | 0  0  0  1 |
    //
    //   Defining the desired camera pose in frame o' becomes than easier.
    //
    // - When using rather
    //   detector.setZAlignedWithCameraAxis(true);
    //   detector.detect();
    //   we consider the tag frame (o) such as z_o axis is aligned with camera frame
    //
    //   3         2
    //
    //        o--x
    //        |
    //   0    y    1
    //
    //   In that configuration, it is easier to define a desired camera pose c_M_o since all the axis
    //   (camera frame and tag frame are aligned)
 
    // Servo
    vpHomogeneousMatrix cd_M_c, c_M_o, o_M_o;
 
    // Desired pose to reach
    vpHomogeneousMatrix cd_M_o(vpTranslationVector(0, 0, opt_tagSize * 3.5), // 3.5 times tag with along camera z axis
                               vpThetaUVector(vpMath::rad(10), vpMath::rad(3), vpMath::rad(5)));
    if (!detector.isZAlignedWithCameraAxis()) {
      vpHomogeneousMatrix oprim_M_o = { 1,  0,  0, 0,
                                        0, -1,  0, 0,
                                        0,  0, -1, 0,
                                        0,  0,  0, 1 };
      cd_M_o *= oprim_M_o;
    }
 
    cd_M_c = cd_M_o * c_M_o.inverse();
 
    // Create current visual features
    vpFeatureTranslation s_t(vpFeatureTranslation::cdMc);
    vpFeatureThetaU s_tu(vpFeatureThetaU::cdRc);
    s_t.buildFrom(cd_M_c);
    s_tu.buildFrom(cd_M_c);
 
    // Create desired visual features
    vpFeatureTranslation s_t_d(vpFeatureTranslation::cdMc);
    vpFeatureThetaU s_tu_d(vpFeatureThetaU::cdRc);
 
    vpServo task;
    task.addFeature(s_t, s_t_d);
    task.addFeature(s_tu, s_tu_d);
    task.setServo(vpServo::EYEINHAND_CAMERA);
    task.setInteractionMatrixType(vpServo::CURRENT);
 
    // Set the gain
    if (opt_adaptive_gain) {
      vpAdaptiveGain lambda(1.5, 0.4, 30); // lambda(0)=4, lambda(oo)=0.4 and lambda'(0)=30
      task.setLambda(lambda);
    }
    else {
      task.setLambda(0.5);
    }
 
    vpPlot *plotter = nullptr;
    int iter_plot = 0;
 
    if (opt_plot) {
      plotter = new vpPlot(2, static_cast<int>(250 * 2), 500, static_cast<int>(I.getWidth()) + 80, 10,
                           "Real time curves plotter");
      plotter->setTitle(0, "Visual features error");
      plotter->setTitle(1, "Camera velocities");
      plotter->initGraph(0, 6);
      plotter->initGraph(1, 6);
      plotter->setLegend(0, 0, "error_feat_tx");
      plotter->setLegend(0, 1, "error_feat_ty");
      plotter->setLegend(0, 2, "error_feat_tz");
      plotter->setLegend(0, 3, "error_feat_theta_ux");
      plotter->setLegend(0, 4, "error_feat_theta_uy");
      plotter->setLegend(0, 5, "error_feat_theta_uz");
      plotter->setLegend(1, 0, "vc_x");
      plotter->setLegend(1, 1, "vc_y");
      plotter->setLegend(1, 2, "vc_z");
      plotter->setLegend(1, 3, "wc_x");
      plotter->setLegend(1, 4, "wc_y");
      plotter->setLegend(1, 5, "wc_z");
    }
 
    bool final_quit = false;
    bool has_converged = false;
    bool send_velocities = false;
    bool servo_started = false;
    std::vector<vpImagePoint> *traj_vip = nullptr; // To memorize point trajectory
 
    static double t_init_servo = vpTime::measureTimeMs();
 
    robot.setRobotState(vpRobot::STATE_VELOCITY_CONTROL);
 
    while (!has_converged && !final_quit) {
      double t_start = vpTime::measureTimeMs();
 
      rs.acquire(I);
 
      vpDisplay::display(I);
 
      std::vector<vpHomogeneousMatrix> c_M_o_vec;
      detector.detect(I, opt_tagSize, cam, c_M_o_vec);
 
      std::stringstream ss;
      ss << "Left click to " << (send_velocities ? "stop the robot" : "servo the robot") << ", right click to quit.";
      vpDisplay::displayText(I, 20, 20, ss.str(), vpColor::red);
 
      vpColVector v_c(6);
 
      // Only one tag is detected
      if (c_M_o_vec.size() == 1) {
        c_M_o = c_M_o_vec[0];
 
        static bool first_time = true;
        if (first_time) {
          // Introduce security wrt tag positioning in order to avoid PI rotation
          std::vector<vpHomogeneousMatrix> v_o_M_o(2), v_cd_M_c(2);
          v_o_M_o[1].buildFrom(0, 0, 0, 0, 0, M_PI);
          for (size_t i = 0; i < 2; ++i) {
            v_cd_M_c[i] = cd_M_o * v_o_M_o[i] * c_M_o.inverse();
          }
          if (std::fabs(v_cd_M_c[0].getThetaUVector().getTheta()) < std::fabs(v_cd_M_c[1].getThetaUVector().getTheta())) {
            o_M_o = v_o_M_o[0];
          }
          else {
            std::cout << "Desired frame modified to avoid PI rotation of the camera" << std::endl;
            o_M_o = v_o_M_o[1]; // Introduce PI rotation
          }
        }
 
        // Update current visual features
        cd_M_c = cd_M_o * o_M_o * c_M_o.inverse();
        s_t.buildFrom(cd_M_c);
        s_tu.buildFrom(cd_M_c);
 
        if (opt_task_sequencing) {
          if (!servo_started) {
            if (send_velocities) {
              servo_started = true;
            }
            t_init_servo = vpTime::measureTimeMs();
          }
          v_c = task.computeControlLaw((vpTime::measureTimeMs() - t_init_servo) / 1000.);
        }
        else {
          v_c = task.computeControlLaw();
        }
 
        // Display desired and current pose features
        vpDisplay::displayFrame(I, cd_M_o * o_M_o, cam, opt_tagSize / 1.5, vpColor::yellow, 2);
        vpDisplay::displayFrame(I, c_M_o, cam, opt_tagSize / 2, vpColor::none, 3);
        // Get tag corners
        std::vector<vpImagePoint> vip = detector.getPolygon(0);
        // Get the tag cog corresponding to the projection of the tag frame in the image
        vip.push_back(detector.getCog(0));
        // Display the trajectory of the points
        if (first_time) {
          traj_vip = new std::vector<vpImagePoint>[vip.size()];
        }
        display_point_trajectory(I, vip, traj_vip);
 
        if (opt_plot) {
          plotter->plot(0, iter_plot, task.getError());
          plotter->plot(1, iter_plot, v_c);
          iter_plot++;
        }
 
        if (opt_verbose) {
          std::cout << "v_c: " << v_c.t() << std::endl;
        }
 
        vpTranslationVector cd_t_c = cd_M_c.getTranslationVector();
        vpThetaUVector cd_tu_c = cd_M_c.getThetaUVector();
        double error_tr = sqrt(cd_t_c.sumSquare());
        double error_tu = vpMath::deg(sqrt(cd_tu_c.sumSquare()));
 
        ss.str("");
        ss << "error_t: " << error_tr;
        vpDisplay::displayText(I, 20, static_cast<int>(I.getWidth()) - 150, ss.str(), vpColor::red);
        ss.str("");
        ss << "error_tu: " << error_tu;
        vpDisplay::displayText(I, 40, static_cast<int>(I.getWidth()) - 150, ss.str(), vpColor::red);
 
        if (opt_verbose)
          std::cout << "error translation: " << error_tr << " ; error rotation: " << error_tu << std::endl;
 
        if ((error_tr < opt_convergence_threshold_t) && (error_tu < opt_convergence_threshold_tu)) {
          has_converged = true;
          std::cout << "Servo task has converged" << std::endl;
          ;
          vpDisplay::displayText(I, 100, 20, "Servo task has converged", vpColor::red);
        }
 
        if (first_time) {
          first_time = false;
        }
      } // end if (c_M_o_vec.size() == 1)
      else {
        v_c = 0;
      }
 
      if (!send_velocities) {
        v_c = 0;
      }
 
      // Send to the robot
      robot.setVelocity(vpRobot::CAMERA_FRAME, v_c);
 
      ss.str("");
      ss << "Loop time: " << vpTime::measureTimeMs() - t_start << " ms";
      vpDisplay::displayText(I, 40, 20, ss.str(), vpColor::red);
      vpDisplay::flush(I);
 
      vpMouseButton::vpMouseButtonType button;
      if (vpDisplay::getClick(I, button, false)) {
        switch (button) {
        case vpMouseButton::button1:
          send_velocities = !send_velocities;
          break;
 
        case vpMouseButton::button3:
          final_quit = true;
          break;
 
        default:
          break;
        }
      }
    }
    std::cout << "Stop the robot " << std::endl;
    robot.setRobotState(vpRobot::STATE_STOP);
 
    if (opt_plot && plotter != nullptr) {
      delete plotter;
      plotter = nullptr;
    }
 
    if (!final_quit) {
      while (!final_quit) {
        rs.acquire(I);
        vpDisplay::display(I);
 
        vpDisplay::displayText(I, 20, 20, "Click to quit the program.", vpColor::red);
        vpDisplay::displayText(I, 40, 20, "Visual servo converged.", vpColor::red);
 
        if (vpDisplay::getClick(I, false)) {
          final_quit = true;
        }
 
        vpDisplay::flush(I);
      }
    }
 
    if (traj_vip) {
      delete[] traj_vip;
    }
  }
  catch (const vpException &e) {
    std::cout << "ViSP exception: " << e.what() << std::endl;
    std::cout << "Stop the robot " << std::endl;
    robot.setRobotState(vpRobot::STATE_STOP);
    return EXIT_FAILURE;
  }
 
  return EXIT_SUCCESS;
}
#else
int main()
{
#if !defined(VISP_HAVE_REALSENSE2)
  std::cout << "Install librealsense-2.x" << std::endl;
#endif
#if !defined(VISP_HAVE_AFMA6)
  std::cout << "ViSP is not build with Afma-6 robot support..." << std::endl;
#endif
  return EXIT_SUCCESS;
}
#endif