arm_kinematics.cpp

Go to the documentation of this file.

// bsd license blah blah

#include <string>
#include <exception>
#include <math.h>

#include <ros/ros.h>
#include <tf/transform_listener.h>
#include <tf_conversions/tf_kdl.h>
#include <tf/transform_datatypes.h>
#include <kdl_parser/kdl_parser.hpp>
#include <kdl/jntarray.hpp>
#include <kdl/chainiksolverpos_nr_jl.hpp>
#include <kdl/chainiksolvervel_wdls.hpp>
#include <kdl/chainfksolverpos_recursive.hpp>
#include <kinematics_msgs/GetPositionFK.h>
#include <kinematics_msgs/GetPositionIK.h>
#include <kinematics_msgs/GetKinematicSolverInfo.h>
#include <kinematics_msgs/KinematicSolverInfo.h>
#include <kdl_arm_kinematics/GetWeightedIK.h>

using std::string;

class Kinematics
{
public:
  class InitFailed : public std::runtime_error
  {
  public:
    InitFailed(const string &what)
      : std::runtime_error(what) {}
  };
  
  Kinematics();

private:
  ros::NodeHandle nh, nh_private;
  std::string root_name, tip_name;
  KDL::JntArray joint_min, joint_max;
  KDL::Chain chain;
  unsigned int num_joints;
  int max_iterations;
  double epsilon;
  Eigen::MatrixXd default_weight_ts;
  Eigen::MatrixXd default_weight_js;
  double default_lambda;

  ros::ServiceServer ik_service,ik_solver_info_service;
  ros::ServiceServer fk_service,fk_solver_info_service;
  ros::ServiceServer weighted_ik_service;

  tf::TransformListener tf_listener;

  kinematics_msgs::KinematicSolverInfo info;

  void parseWeightParams(ros::NodeHandle &nh);
  bool loadModel(const std::string xml);
  bool readJoints(urdf::Model &robot_model);
  int getJointIndex(const std::string &name);
  int getKDLSegmentIndex(const std::string &name);
  bool solveCartToJnt(const KDL::JntArray &q_init, const KDL::Frame &q_in, KDL::JntArray &q_out,
    const KDL::Frame &tool_frame = KDL::Frame::Identity());
  bool solveCartToJnt(const KDL::JntArray &q_init, const KDL::Frame &q_in, KDL::JntArray &q_out,
    const KDL::Frame &tool_frame, const Eigen::MatrixXd &weight_ts,
    const Eigen::MatrixXd &weight_js, const double lambda);
  double calculateEps(const KDL::Frame &f, const KDL::Frame &ref,
    const Eigen::MatrixXd &weight=Eigen::MatrixXd::Identity(6,6));
  void initializeWeights(const kdl_arm_kinematics::KDLWeights &msg,
    Eigen::MatrixXd &weight_ts, Eigen::MatrixXd &weight_js, double &lambda);

  bool getPositionIK(kinematics_msgs::GetPositionIK::Request &request,
    kinematics_msgs::GetPositionIK::Response &response);

  bool getIKSolverInfo(kinematics_msgs::GetKinematicSolverInfo::Request &request,
    kinematics_msgs::GetKinematicSolverInfo::Response &response);

  bool getFKSolverInfo(kinematics_msgs::GetKinematicSolverInfo::Request &request,
    kinematics_msgs::GetKinematicSolverInfo::Response &response);

  bool getPositionFK(kinematics_msgs::GetPositionFK::Request &request,
    kinematics_msgs::GetPositionFK::Response &response);

  bool getWeightedIK(kdl_arm_kinematics::GetWeightedIK::Request &request,
    kdl_arm_kinematics::GetWeightedIK::Response &response);
};



Kinematics::Kinematics()
  : nh(),
    nh_private ("~"),
    default_weight_ts(Eigen::MatrixXd::Identity(6,6)),
    default_lambda(0.1)
{
  // Get URDF XML
  std::string urdf_xml, full_urdf_xml;
  nh_private.param("robot_description_name",urdf_xml,std::string("robot_description"));
  nh.searchParam(urdf_xml,full_urdf_xml);
  ROS_DEBUG("Reading xml file from parameter server");
  std::string result;
  if (!nh.getParam(full_urdf_xml, result))
    throw Kinematics::InitFailed("Could not load the xml from parameter server: " + urdf_xml);

  // Get Root and Tip From Parameter Service
  if (!nh_private.getParam("root_name", root_name))
    throw Kinematics::InitFailed("GenericIK: No root name found on parameter server");

  if (!nh_private.getParam("tip_name", tip_name))
    throw Kinematics::InitFailed("GenericIK: No tip name found on parameter server");

  // Load and Read Models
  if (!loadModel(result))
    throw Kinematics::InitFailed("Could not load models!");

  default_weight_js = Eigen::MatrixXd::Identity(chain.getNrOfJoints(), chain.getNrOfJoints());
  parseWeightParams(nh_private);

  nh_private.param("maxIterations", max_iterations, 100);
  nh_private.param("epsilon", epsilon, 1e-2);

  ROS_INFO("Advertising services");
  fk_service = nh_private.advertiseService("get_fk", &Kinematics::getPositionFK,this);
  ik_service = nh_private.advertiseService("get_ik", &Kinematics::getPositionIK,this);
  ik_solver_info_service = nh_private.advertiseService("get_ik_solver_info", &Kinematics::getIKSolverInfo,this);
  fk_solver_info_service = nh_private.advertiseService("get_fk_solver_info", &Kinematics::getFKSolverInfo,this);
  weighted_ik_service = nh_private.advertiseService("get_weighted_ik", &Kinematics::getWeightedIK, this);
}

void Kinematics::parseWeightParams(ros::NodeHandle &nh)
{
  ros::NodeHandle weights_nh(nh, "weights");
  
  if(weights_nh.hasParam("lambda"))
  {
    weights_nh.getParam("lambda", default_lambda);
    ROS_INFO("Setting lambda to %lf", default_lambda);
  }

  if(weights_nh.hasParam("weight_ts"))
  {
    ros::NodeHandle weight_ts_nh(weights_nh, "weight_ts");
    double value;
    
    if(weight_ts_nh.getParam("x", value))
    {
      ROS_INFO("Reading weight_ts/x: %lf", value);
      default_weight_ts(0,0) = value;
    }

    if(weight_ts_nh.getParam("y", value))
    {
      ROS_INFO("Reading weight_ts/y: %lf", value);    
      default_weight_ts(1,1) = value;
    }

    if(weight_ts_nh.getParam("z", value))
    {
      ROS_INFO("Reading weight_ts/z: %lf", value);    
      default_weight_ts(2,2) = value;
    }

    if(weight_ts_nh.getParam("roll", value))
    {
      ROS_INFO("Reading weight_ts/roll: %lf", value);
      default_weight_ts(3,3) = value;
    }

    if(weight_ts_nh.getParam("pitch", value))
    {
      ROS_INFO("Reading weight_ts/pitch: %lf", value);    
      default_weight_ts(4,4) = value;
    }

    if(weight_ts_nh.getParam("yaw", value))
    {
      ROS_INFO("Reading weight_ts/yaw: %lf", value);
      default_weight_ts(5,5) = value;
    }
  }

  if(weights_nh.hasParam("weight_js"))
  {
    ros::NodeHandle weight_js_nh(weights_nh, "weight_js");
    double value;

    for (unsigned int i=0; i < info.joint_names.size(); i++)
    {
      if(weight_js_nh.getParam(info.joint_names[i], value))
      {
        ROS_INFO("Setting weight for joint '%s' to %lf", info.joint_names[i].c_str(), value);
        default_weight_js(i, i) = value;
      }
    }
  }
}

bool Kinematics::loadModel(const std::string xml) {
  urdf::Model robot_model;
  KDL::Tree tree;

  if (!robot_model.initString(xml)) {
    ROS_FATAL("Could not initialize robot model");
    return -1;
  }
  if (!kdl_parser::treeFromString(xml, tree)) {
    ROS_ERROR("Could not initialize tree object");
    return false;
  }
  if (!tree.getChain(root_name, tip_name, chain)) {
    ROS_ERROR("Could not initialize chain object");
    return false;
  }

  if (!readJoints(robot_model)) {
    ROS_FATAL("Could not read information about the joints");
    return false;
  }

  return true;
}

bool Kinematics::readJoints(urdf::Model &robot_model) {
  num_joints = 0;
  // get joint maxs and mins
  boost::shared_ptr<const urdf::Link> link = robot_model.getLink(tip_name);
  boost::shared_ptr<const urdf::Joint> joint;

  while (link && link->name != root_name) {
    joint = robot_model.getJoint(link->parent_joint->name);
    if (!joint) {
      ROS_ERROR("Could not find joint: %s",link->parent_joint->name.c_str());
      return false;
    }
    if (joint->type != urdf::Joint::UNKNOWN && joint->type != urdf::Joint::FIXED) {
      ROS_INFO( "adding joint: [%s]", joint->name.c_str() );
      num_joints++;
    }
    link = robot_model.getLink(link->getParent()->name);
  }

  joint_min.resize(num_joints);
  joint_max.resize(num_joints);
  info.joint_names.resize(num_joints);
  info.link_names.clear();
  info.limits.resize(num_joints);

  link = robot_model.getLink(tip_name);
  unsigned int i = 0;
  while (link && i < num_joints) {
    joint = robot_model.getJoint(link->parent_joint->name);
    info.link_names.push_back(link->name);
    if (joint->type != urdf::Joint::UNKNOWN && joint->type != urdf::Joint::FIXED) {
      ROS_INFO( "getting bounds for joint: [%s]", joint->name.c_str() );

      float lower, upper;
      int hasLimits;
      if ( joint->type != urdf::Joint::CONTINUOUS ) {
        lower = joint->limits->lower;
        upper = joint->limits->upper;
        hasLimits = 1;
      } else {
        lower = -M_PI;
        upper = M_PI;
        hasLimits = 0;
      }
      int index = num_joints - i -1;

      joint_min.data[index] = lower;
      joint_max.data[index] = upper;
      info.joint_names[index] = joint->name;
      info.limits[index].joint_name = joint->name;
      info.limits[index].has_position_limits = hasLimits;
      info.limits[index].min_position = lower;
      info.limits[index].max_position = upper;
      i++;
    }
    link = robot_model.getLink(link->getParent()->name);
  }
  return true;
}


int Kinematics::getJointIndex(const std::string &name) {
  for (unsigned int i=0; i < info.joint_names.size(); i++) {
    if (info.joint_names[i] == name)
      return i;
  }
  return -1;
}

int Kinematics::getKDLSegmentIndex(const std::string &name) {
  int i=0; 
  while (i < (int)chain.getNrOfSegments()) {
    if (chain.getSegment(i).getName() == name) {
      return i+1;
    }
    i++;
  }
  return -1;
}

bool Kinematics::solveCartToJnt(const KDL::JntArray &q_init, const KDL::Frame &q_in, KDL::JntArray &q_out,
  const KDL::Frame &tool_frame)
{
  return solveCartToJnt(q_init, q_in, q_out, tool_frame,
    default_weight_ts, default_weight_js, default_lambda);
}

bool Kinematics::solveCartToJnt(const KDL::JntArray &q_init, const KDL::Frame &p_in, KDL::JntArray &q_out,
  const KDL::Frame &tool_frame, const Eigen::MatrixXd &weight_ts, const Eigen::MatrixXd &weight_js,
  const double lambda)
{
  KDL::Frame f;
  KDL::JntArray delta_q;
  KDL::Twist delta_twist;  
  int i;
  double err;

  KDL::Chain chain_with_tool(chain);
  chain_with_tool.addSegment(KDL::Segment(KDL::Joint(KDL::Joint::None), tool_frame));
  
  KDL::ChainFkSolverPos_recursive fk_solver(chain_with_tool);
  KDL::ChainIkSolverVel_wdls ik_solver(chain_with_tool);

  ik_solver.setWeightTS(weight_ts);
  ik_solver.setWeightJS(weight_js);
  ik_solver.setLambda(lambda);
  
  q_out = q_init;

  for(i=0;i<max_iterations;i++)
  {
    fk_solver.JntToCart(q_out, f);

    err = calculateEps(f, p_in, weight_ts);

    if(isnan(err))
    {
      ROS_WARN("NaN in IK");
      return false;
    }

    if( err < epsilon )
      break;

    delta_twist = diff(f, p_in);
    ik_solver.CartToJnt(q_out, delta_twist, delta_q);
    KDL::Add(q_out, delta_q, q_out);

    for(unsigned int j=0; j<joint_min.rows(); j++)
    {
      if(q_out(j) < joint_min(j))
        q_out(j) = joint_min(j);
    }

    for(unsigned int j=0; j<joint_max.rows(); j++)
    {
      if(q_out(j) > joint_max(j))
        q_out(j) = joint_max(j);
    }
  }

  ROS_INFO("IK terminating after %d iterations and error %lf", i, err);
  
  if(i < max_iterations)
    return true;
  return false;
}

double Kinematics::calculateEps(const KDL::Frame &f, const KDL::Frame &ref, const Eigen::MatrixXd &weight)
{
  double f_roll, f_pitch, f_yaw;
  double ref_roll, ref_pitch, ref_yaw;
  f.M.GetRPY(f_roll, f_pitch, f_yaw);
  ref.M.GetRPY(ref_roll, ref_pitch, ref_yaw);

  double x_diff = f.p.x() - ref.p.x();
  double y_diff = f.p.y() - ref.p.y();
  double z_diff = f.p.z() - ref.p.z();
  double roll_diff = f_roll - ref_roll;
  double pitch_diff = f_pitch - ref_pitch;
  double yaw_diff = f_yaw - ref_yaw;

  return (x_diff * x_diff * weight(0, 0)) +
    (y_diff * y_diff * weight(1, 1)) +
    (z_diff * z_diff * weight(2, 2)) +
    (roll_diff * roll_diff * weight(3, 3)) +
    (pitch_diff * pitch_diff * weight(4, 4)) +
    (yaw_diff * yaw_diff * weight(5, 5));
}

void Kinematics::initializeWeights(const kdl_arm_kinematics::KDLWeights &msg,
    Eigen::MatrixXd &weight_ts, Eigen::MatrixXd &weight_js, double &lambda)
{
  if(msg.mode == kdl_arm_kinematics::KDLWeights::INVALID_MODE)
  {
    return;
  }
  if(msg.mode & kdl_arm_kinematics::KDLWeights::SET_TS)
  {
    for(int i=0, a=0; i<6; i++)
    {
      for(int j=0; j<6; j++, a++)
        weight_ts(i, j) = msg.weight_ts[a];
    }
  }
  if(msg.mode & kdl_arm_kinematics::KDLWeights::SET_JS)
  {
    int dim = sqrt(msg.weight_js.size());
    weight_js = Eigen::MatrixXd(dim, dim);
    for(int i=0, a=0; i<dim; i++)
    {
      for(int j=0; j<dim; j++, a++)
        weight_js(i, j) = msg.weight_js[a];
    }
  }
  if(msg.mode & kdl_arm_kinematics::KDLWeights::SET_LAMBDA)
    lambda = msg.lambda;
}

bool Kinematics::getPositionIK(kinematics_msgs::GetPositionIK::Request &request,
                               kinematics_msgs::GetPositionIK::Response &response) {

  geometry_msgs::PoseStamped pose_msg_in = request.ik_request.pose_stamped;
  tf::Stamped<tf::Pose> transform;
  tf::Stamped<tf::Pose> transform_root;
  tf::poseStampedMsgToTF( pose_msg_in, transform );

  //Do the IK
  KDL::JntArray jnt_pos_in;
  KDL::JntArray jnt_pos_out;
  jnt_pos_in.resize(num_joints);

  if(request.ik_request.ik_seed_state.joint_state.name.size() < num_joints ||
     request.ik_request.ik_seed_state.joint_state.position.size() < num_joints)
  {
    ROS_ERROR("Invalid seed state. It must contain states for all joints used by the IK solver.");
    return false;
  }
  for (unsigned int i=0; i < num_joints; i++) {
    int tmp_index = getJointIndex(request.ik_request.ik_seed_state.joint_state.name[i]);
    if (tmp_index >=0) {
      jnt_pos_in(tmp_index) = request.ik_request.ik_seed_state.joint_state.position[i];
    } else {
      ROS_ERROR("i: %d, No joint index for %s",i,request.ik_request.ik_seed_state.joint_state.name[i].c_str());
      return false;
    }
  }

  //Convert F to our root_frame
  try {
    tf_listener.transformPose(root_name, transform, transform_root);
  } catch (...) {
    ROS_ERROR("Could not transform IK pose to frame: %s", root_name.c_str());
    response.error_code.val = response.error_code.FRAME_TRANSFORM_FAILURE;
    return false;
  }

  KDL::Frame F_dest;
  tf::TransformTFToKDL(transform_root, F_dest);

  if (solveCartToJnt(jnt_pos_in, F_dest, jnt_pos_out))
  {
    response.solution.joint_state.name = info.joint_names;
    response.solution.joint_state.position.resize(num_joints);
    for (unsigned int i=0; i < num_joints; i++)
    {
      response.solution.joint_state.position[i] = jnt_pos_out(i);
      ROS_INFO("IK Solution: %s %d: %f",response.solution.joint_state.name[i].c_str(),i,jnt_pos_out(i));
    }
    response.error_code.val = response.error_code.SUCCESS;
    return true;
  } else {
    ROS_INFO("An IK solution could not be found");
    response.error_code.val = response.error_code.NO_IK_SOLUTION;
    return true;
  }
}

bool Kinematics::getIKSolverInfo(kinematics_msgs::GetKinematicSolverInfo::Request &request,
                                 kinematics_msgs::GetKinematicSolverInfo::Response &response) {
  response.kinematic_solver_info = info;
  return true;
}

bool Kinematics::getFKSolverInfo(kinematics_msgs::GetKinematicSolverInfo::Request &request,
                                 kinematics_msgs::GetKinematicSolverInfo::Response &response) {
  response.kinematic_solver_info = info;
  return true;
}

bool Kinematics::getPositionFK(kinematics_msgs::GetPositionFK::Request &request,
                               kinematics_msgs::GetPositionFK::Response &response) {
  KDL::Frame p_out;
  KDL::JntArray jnt_pos_in;
  geometry_msgs::PoseStamped pose;
  tf::Stamped<tf::Pose> tf_pose;

  KDL::ChainFkSolverPos_recursive fk_solver(chain);

  jnt_pos_in.resize(num_joints);
  for (unsigned int i=0; i < num_joints; i++) {
    int tmp_index = getJointIndex(request.robot_state.joint_state.name[i]);
    if (tmp_index >=0)
      jnt_pos_in(tmp_index) = request.robot_state.joint_state.position[i];
  }

  response.pose_stamped.resize(request.fk_link_names.size());
  response.fk_link_names.resize(request.fk_link_names.size());

  for (unsigned int i=0; i < request.fk_link_names.size(); i++) {
    int segmentIndex = getKDLSegmentIndex(request.fk_link_names[i]);
    ROS_DEBUG("End effector index: %d",segmentIndex);
    ROS_DEBUG("Chain indices: %d",chain.getNrOfSegments());
    if (fk_solver.JntToCart(jnt_pos_in,p_out,segmentIndex) >=0) {
      tf_pose.frame_id_ = root_name;
      tf_pose.stamp_ = ros::Time();
      tf::PoseKDLToTF(p_out,tf_pose);
      try {
        tf_listener.transformPose(request.header.frame_id,tf_pose,tf_pose);
      } catch (...) {
        ROS_ERROR("Could not transform FK pose to frame: %s",request.header.frame_id.c_str());
        response.error_code.val = arm_navigation_msgs::ArmNavigationErrorCodes::FRAME_TRANSFORM_FAILURE;
        return false;
      }
      tf::poseStampedTFToMsg(tf_pose,pose);
      response.pose_stamped[i] = pose;
      response.fk_link_names[i] = request.fk_link_names[i];
      response.error_code.val = response.error_code.SUCCESS;
    } else {
      ROS_ERROR("Could not compute FK for %s",request.fk_link_names[i].c_str());
      response.error_code.val = arm_navigation_msgs::ArmNavigationErrorCodes::NO_FK_SOLUTION;
    }
  }
  return true;
}

bool Kinematics::getWeightedIK(kdl_arm_kinematics::GetWeightedIK::Request &request,
  kdl_arm_kinematics::GetWeightedIK::Response &response)
{
  geometry_msgs::PoseStamped pose_msg_in = request.pose;
  tf::Stamped<tf::Pose> transform;
  tf::Stamped<tf::Pose> transform_root;
  tf::poseStampedMsgToTF( pose_msg_in, transform );

  //Do the IK
  KDL::JntArray jnt_pos_in;
  KDL::JntArray jnt_pos_out;
  jnt_pos_in.resize(num_joints);

  if(request.ik_seed.name.size() < num_joints ||
     request.ik_seed.position.size() < num_joints)
  {
    ROS_ERROR("Invalid seed state. It must contain states for all joints used by the IK solver.");
    return false;
  }
  for (unsigned int i=0; i < num_joints; i++)
  {
    int tmp_index = getJointIndex(request.ik_seed.name[i]);
    if (tmp_index >=0)
      jnt_pos_in(tmp_index) = request.ik_seed.position[i];
    else
    {
      ROS_ERROR("i: %d, No joint index for %s",i,request.ik_seed.name[i].c_str());
      return false;
    }
  }

  //Convert F to our root_frame
  try
  {
    tf_listener.transformPose(root_name, transform, transform_root);
  }
  catch (...)
  {
    ROS_ERROR("Could not transform IK pose to frame: %s", root_name.c_str());
    response.error_code.val = response.error_code.FRAME_TRANSFORM_FAILURE;
    return false;
  }

  KDL::Frame F_dest;
  tf::TransformTFToKDL(transform_root, F_dest);

  KDL::Frame tool;
  tf::PoseMsgToKDL(request.tool_frame, tool);

  Eigen::MatrixXd weight_ts(default_weight_ts);
  Eigen::MatrixXd weight_js(default_weight_js);
  double lambda = default_lambda;

  initializeWeights(request.weights, weight_ts, weight_js, lambda);
  
  if (solveCartToJnt(jnt_pos_in, F_dest, jnt_pos_out, tool, weight_ts, weight_js, lambda))
  {
    response.solution.name = info.joint_names;
    response.solution.position.resize(num_joints);
    for (unsigned int i=0; i < num_joints; i++)
    {
      response.solution.position[i] = jnt_pos_out(i);
      ROS_INFO("IK Solution: %s %d: %f",response.solution.name[i].c_str(),i,jnt_pos_out(i));
    }
    response.error_code.val = response.error_code.SUCCESS;
    return true;
  } else {
    ROS_INFO("An IK solution could not be found");
    response.error_code.val = response.error_code.NO_IK_SOLUTION;
    return true;
  }
}

int main(int argc, char **argv) {
  ros::init(argc, argv, "arm_kinematics");
  try
  {
    Kinematics k;
    ros::spin();
  }
  catch(Kinematics::InitFailed &e)
  {
    ROS_ERROR("Could not initialize kinematics node: %s", e.what());
    return -1;
  }

  return 0;
}