cartesian_wrench.cpp

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/*
 * Derived a bit from pr2_controllers/cartesian_wrench_controller.cpp
 * Author: Michael Ferguson, Wim Meeussen
 */

#include <pluginlib/class_list_macros.h>
#include <robot_controllers/cartesian_wrench.h>

#include <urdf/model.h>
#include <kdl_parser/kdl_parser.hpp>

PLUGINLIB_EXPORT_CLASS(robot_controllers::CartesianWrenchController, robot_controllers::Controller)

namespace robot_controllers
{

CartesianWrenchController::CartesianWrenchController() :
    initialized_(false)
{
}

int CartesianWrenchController::init(ros::NodeHandle& nh, ControllerManager* manager)
{
  // We absolutely need access to the controller manager
  if (!manager)
  {
    initialized_ = false;
    return -1;
  }

  Controller::init(nh, manager);
  manager_ = manager;

  // Initialize KDL structures
  std::string tip_link;
  nh.param<std::string>("root_name", root_link_, "torso_lift_link");
  nh.param<std::string>("tip_name", tip_link, "gripper_link");

  // Load URDF
  urdf::Model model;
  if (!model.initParam("robot_description"))
  {
    ROS_ERROR("Failed to parse URDF");
    return -1;
  }

  // Load the tree
  KDL::Tree kdl_tree;
  if (!kdl_parser::treeFromUrdfModel(model, kdl_tree))
  {
    ROS_ERROR("Could not construct tree from URDF");
    return -1;
  }

  // Populate the chain
  if(!kdl_tree.getChain(root_link_, tip_link, kdl_chain_))
  {
    ROS_ERROR("Could not construct chain from URDF");
    return -1;
  }

  jac_solver_.reset(new KDL::ChainJntToJacSolver(kdl_chain_));
  jnt_pos_.resize(kdl_chain_.getNrOfJoints());
  jnt_eff_.resize(kdl_chain_.getNrOfJoints());
  jacobian_.resize(kdl_chain_.getNrOfJoints());

  // Init joint handles
  joints_.clear();
  for (size_t i = 0; i < kdl_chain_.getNrOfSegments(); ++i)
    if (kdl_chain_.getSegment(i).getJoint().getType() != KDL::Joint::None)
      joints_.push_back(manager_->getJointHandle(kdl_chain_.getSegment(i).getJoint().getName()));

  // Subscribe to command
  command_sub_ = nh.subscribe<geometry_msgs::Wrench>("command", 1,
                    boost::bind(&CartesianWrenchController::command, this, _1));
  last_command_ = ros::Time(0);

  initialized_ = true;
  return 0;
}

bool CartesianWrenchController::start()
{
  if (!initialized_)
  {
    ROS_ERROR_NAMED("CartesianWrenchController",
                    "Unable to start, not initialized.");
    return false;
  }

  if (ros::Time::now() - last_command_ > ros::Duration(3.0))
  {
    ROS_ERROR_NAMED("CartesianWrenchController",
                    "Unable to start, no goal.");
    return false;
  }

  return true;
}

bool CartesianWrenchController::stop(bool force)
{
  return true;
}

bool CartesianWrenchController::reset()
{
  // Simply stop
  return (manager_->requestStop(getName()) == 0);
}

void CartesianWrenchController::update(const ros::Time& now, const ros::Duration& dt)
{
  // Need to initialize KDL structs
  if (!initialized_)
    return;

  if (ros::Time::now() - last_command_ > ros::Duration(0.1))
  {
    // Command has timed out, shutdown
    manager_->requestStop(getName());
    return;
  } 

  // This updates jnt_pos_
  updateJoints();

  // Get jacobian
  jac_solver_->JntToJac(jnt_pos_, jacobian_);

  // Convert wrench to joint efforts
  for (size_t i = 0; i < kdl_chain_.getNrOfJoints(); ++i)
  {
    jnt_eff_(i) = 0;
    for (unsigned int j = 0; j < 6; ++j)
      jnt_eff_(i) += (jacobian_(j,i) * desired_wrench_(j));
  }

  // Actually update joints
  for (size_t j = 0; j < joints_.size(); ++j)
    joints_[j]->setEffort(jnt_eff_(j));
}

void CartesianWrenchController::updateJoints()
{
  for (size_t i = 0; i < joints_.size(); ++i)
    jnt_pos_(i) = joints_[i]->getPosition();
}

void CartesianWrenchController::command(const geometry_msgs::Wrench::ConstPtr& goal)
{
  // Update command
  desired_wrench_.force(0) = goal->force.x;
  desired_wrench_.force(1) = goal->force.y;
  desired_wrench_.force(2) = goal->force.z;
  desired_wrench_.torque(0) = goal->torque.x;
  desired_wrench_.torque(1) = goal->torque.y;
  desired_wrench_.torque(2) = goal->torque.z;

  // Update last command time before trying to start controller
  last_command_ = ros::Time::now();

  // Try to start up
  if (manager_->requestStart(getName()) != 0)
  {
    ROS_ERROR("CartesianWrenchController: Cannot start, blocked by another controller.");
    return;
  }
}

std::vector<std::string> CartesianWrenchController::getCommandedNames()
{
  std::vector<std::string> names;
  if (initialized_)
  {
    for (size_t i = 0; i < kdl_chain_.getNrOfSegments(); ++i)
      if (kdl_chain_.getSegment(i).getJoint().getType() != KDL::Joint::None)
        names.push_back(kdl_chain_.getSegment(i).getJoint().getName());
  }
  return names;
}

std::vector<std::string> CartesianWrenchController::getClaimedNames()
{
  return getCommandedNames();
}

}  // namespace robot_controllers