segway_rmp400_odom_alg_node.cpp

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#include "segway_rmp400_odom_alg_node.h"

SegwayRmp400OdomAlgNode::SegwayRmp400OdomAlgNode(void) :
  algorithm_base::IriBaseAlgorithm<SegwayRmp400OdomAlgorithm>()
{
  //init class attributes if necessary
  loop_rate_ = 100;//in [Hz]

  public_node_handle_.param<std::string>("tf_prefix",    tf_prefix_,    "");
  public_node_handle_.param<std::string>("odom_id",      odom_id_,      "odom" );
  public_node_handle_.param<std::string>("base_link_id", base_link_id_, "base_footprint" );
  public_node_handle_.param<bool>       ("publish_tf",   publish_tf_,   true  );
  
  // push down frame ids if necessary
  if( tf_prefix_.size()!=0 )
  {
    odom_id_      = tf_prefix_ + "/" + odom_id_;
    base_link_id_ = tf_prefix_ + "/" + base_link_id_;
  }

  // [init publishers]
  odom_publisher_ = public_node_handle_.advertise<nav_msgs::Odometry>("odom", 100);
  
  // [init subscribers]
  segway_status_subscriber_ = public_node_handle_.subscribe("segway_status", 100, &SegwayRmp400OdomAlgNode::segway_status_callback, this);
  
  // [init services]
  
  // [init clients]
  
  // [init action servers]
  
  // [init action clients]
}

SegwayRmp400OdomAlgNode::~SegwayRmp400OdomAlgNode(void)
{
  // [free dynamic memory]
}

void SegwayRmp400OdomAlgNode::mainNodeThread(void)
{
  ros::Time current_time = ros::Time::now();
  geometry_msgs::TransformStamped odom_trans_msg;
  static ros::Time last_time = ros::Time::now();
  static double accum_th=0;

  //compute differencial
  double dt = (current_time - last_time).toSec();

  //get current translational velocity and component velocities
  segway_status_mutex_.enter(); 
  double vT  = (left_wheels_velocity_ + right_wheels_velocity_) / 2;
  double vth = - yaw_rate_;
  segway_status_mutex_.exit(); 
  
  accum_th  += vth * dt/2;
  double vx  = vT*cos(accum_th);
  double vy  = vT*sin(accum_th);

  // Integrate velocities with time to get current position
  double xx  = vx * dt;
  double yy  = vy * dt;

  //update second half theta
  accum_th += vth * dt/2;

  // [fill msg structures]
  //since all odometry is 6DOF we'll need a quaternion created from yaw
  geometry_msgs::Quaternion odom_quat = tf::createQuaternionMsgFromYaw(accum_th);

  //update transform message
  transform_.translation.x += xx;
  transform_.translation.y += yy;
  transform_.translation.z += 0.0;
  transform_.rotation       = odom_quat;

  //update pose
  pose_.pose.position.x += xx;
  pose_.pose.position.y += yy;
  pose_.pose.position.z += 0.0;
  pose_.pose.orientation = odom_quat;

  pose_.covariance[0]  =
  pose_.covariance[7]  =
  pose_.covariance[14] =
  pose_.covariance[21] =
  pose_.covariance[28] =
  pose_.covariance[35] = 0.5;

  //update twist
  twist_.twist.linear.x  = vT;
  twist_.twist.linear.y  = 0.0;
  twist_.twist.linear.z  = 0.0;
  twist_.twist.angular.x = 0.0;
  twist_.twist.angular.y = 0.0;
  twist_.twist.angular.z = vth;

  // Add the covariances to use with EKF
  // for x and y velocity, Error ~= +-10%
  twist_.covariance[0]  = pow(0.1*vx,2);
  twist_.covariance[7]  = pow(0.1*vy,2);
  twist_.covariance[14] =
  twist_.covariance[21] =
  twist_.covariance[28] = 1;
  // for theta velocity, Error ~= +-50%
  twist_.covariance[35] = pow(0.5*vth,2);
  
  //update last time
  last_time = current_time;

  //send the transform
  if(publish_tf_)
  {
    //first, we'll publish the transform over tf
    odom_trans_msg.header.stamp    = current_time;
    odom_trans_msg.header.frame_id = odom_id_;
    odom_trans_msg.child_frame_id  = base_link_id_;
    odom_trans_msg.transform       = transform_;

    odom_broadcaster_.sendTransform(odom_trans_msg);
  }

  //next, we'll publish the odometry message over ROS
  Odometry_msg_.header.stamp    = current_time;
  Odometry_msg_.header.frame_id = odom_id_;
  Odometry_msg_.child_frame_id  = base_link_id_;
  Odometry_msg_.pose            = pose_;
  Odometry_msg_.twist           = twist_;

  // [fill msg structures]
  //Odometry_msg_.data = my_var;
  
  // [fill srv structure and make request to the server]
  
  // [fill action structure and make request to the action server]

  // [publish messages]
  odom_publisher_.publish(Odometry_msg_);
}

/*  [subscriber callbacks] */
void SegwayRmp400OdomAlgNode::segway_status_callback(const iri_segway_rmp_msgs::SegwayRMP400Status::ConstPtr& msg) 
{ 
  ROS_DEBUG("SegwayRmp400OdomAlgNode::segway_status_callback: New Message Received"); 

  //use appropiate mutex to shared variables if necessary 
  //alg_.lock(); 
  segway_status_mutex_.enter(); 

  //std::cout << msg->data << std::endl;
  left_wheels_velocity_  = (msg->rmp200[0].left_wheel_velocity + msg->rmp200[1].left_wheel_velocity)/2;
  right_wheels_velocity_ = (msg->rmp200[0].right_wheel_velocity + msg->rmp200[1].right_wheel_velocity)/2;
  yaw_rate_              = msg->rmp200[0].yaw_rate; //(msg->rmp200[0].yaw_rate + msg->rmp200[1].yaw_rate)/2;

  //unlock previously blocked shared variables 
  //alg_.unlock(); 
  segway_status_mutex_.exit(); 
}

/*  [service callbacks] */

/*  [action callbacks] */

/*  [action requests] */

void SegwayRmp400OdomAlgNode::node_config_update(Config &config, uint32_t level)
{
  alg_.lock();

  alg_.unlock();
}

void SegwayRmp400OdomAlgNode::addNodeDiagnostics(void)
{
}

/* main function */
int main(int argc,char *argv[])
{
  return algorithm_base::main<SegwayRmp400OdomAlgNode>(argc, argv, "segway_rmp400_odom_alg_node");
}