lspb_trajectory.cpp

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#include <spline_smoother/lspb_trajectory.h>

namespace spline_smoother
{
  LSPBTrajectory::LSPBTrajectory()
  {
    apply_limits_ = true;
  }

  double LSPBTrajectory::calculateMinimumTime(const trajectory_msgs::JointTrajectoryPoint &start, 
                                              const trajectory_msgs::JointTrajectoryPoint &end, 
                                              const std::vector<arm_navigation_msgs::JointLimits> &limits)
  {
    double minJointTime(MAX_ALLOWABLE_TIME);
    double segmentTime(0);
    int num_joints = (int) start.positions.size();

    for(int i = 0; i < num_joints; i++)
    {
      minJointTime = minSegmentTime(start.positions[i],end.positions[i],start.velocities[i],end.velocities[i],limits[i]);
      if(segmentTime < minJointTime)
        segmentTime = minJointTime;
    }
    return segmentTime;
  }

/*  double LSPBTrajectory::minSegmentTime(double q0, double q1, double v0, double v1, manipulation_msgs::Limits limit)
  {
    double vmax = limit.max_velocity;
    double amax = limit.max_acceleration;
    double diff = jointDiff(q0,q1,limit);

    double tb = std::max(fabs(vmax/amax),sqrt(fabs(diff)/amax));

    double acc(0);
    if(diff>0)
      acc = amax;
    else
      acc = -amax;
    double dist_tb = acc*tb*tb;
    double ts = (diff - dist_tb)/(acc*tb);
    if(ts < 0)
      ts = 0;

    return (2*tb+ts);
  }
*/

  double LSPBTrajectory::minSegmentTime(const double &q0, 
                                        const double &q1, 
                                        const double &v0, 
                                        const double &v1, 
                                        const arm_navigation_msgs::JointLimits &limit)
  {
    double vmax = limit.max_velocity;
    double amax = limit.max_acceleration;
    double diff = jointDiff(q0,q1,limit);

    double tb = fabs(vmax/amax);

    double acc(0);
    if(diff>0)
      acc = amax;
    else
      acc = -amax;
    double dist_tb = acc*tb*tb;
    double ts = (diff - dist_tb)/(acc*tb);
    if(ts < 0)
    {
      ts = 0.0;
    }
    return (2*tb+ts);
  }


  double LSPBTrajectory::blendTime(const double &aa,
                                   const double &bb,
                                   const double &cc)
  {
    double disc = (pow(bb,2) - 4*aa*cc);
    if(disc < 0)
    {   
      ROS_DEBUG("Blend time quadratic coeff: %f %f %f",aa,bb,cc);
      return 0.0;
    }
    double tb1 = (-bb + sqrt(disc))/(2*aa);
    double tb2 = (-bb - sqrt(disc))/(2*aa);
    if(std::isnan(tb1))
      tb1 = 0.0;
    if(std::isnan(tb2))
      tb2 = 0.0;
    return std::min(tb1,tb2);
  }

/*  double LSPBTrajectory::blendTime(double diff,double a,double tf)
  {
    return fabs(diff/(a*tf));
  }
*/
  bool LSPBTrajectory::parameterize(const trajectory_msgs::JointTrajectory& trajectory_in,
                                    const std::vector<arm_navigation_msgs::JointLimits>& limits,
                                    spline_smoother::LSPBTrajectoryMsg& spline)
  {
    int num_traj = trajectory_in.points.size();
    int num_joints = trajectory_in.joint_names.size();
    spline.names = trajectory_in.joint_names;
    spline.segments.resize(num_traj-1);

    for(int i=0; i<num_joints; i++)
    {
      if(!limits[i].has_velocity_limits)
      {
        ROS_ERROR("Trying to apply velocity limits without supplying them. Set velocity_limits in the message and set has_velocity_limits flag to true.");
        return false;
      }
      if(!limits[i].has_acceleration_limits)
      {
        ROS_ERROR("Trying to apply acceleration limits without supplying them. Set acceleration_limits in the message and set has_acceleration_limits flag to true.");
        return false;
      }
    }
    for (int i=1; i< num_traj; ++i)
    {
      spline.segments[i-1].joints.resize(num_joints);
      for(unsigned int j=0; j < spline.segments[i-1].joints.size(); j++)
        spline.segments[i-1].joints[j].coefficients.resize(3);

      double dT = (trajectory_in.points[i].time_from_start - trajectory_in.points[i-1].time_from_start).toSec();
      if(apply_limits_)
      {
        double dTMin = calculateMinimumTime(trajectory_in.points[i-1],trajectory_in.points[i],limits);
        if(dTMin > dT) // if minimum time required to satisfy limits is greater than time available, stretch this segment
          dT = dTMin;      
      }
      spline.segments[i-1].duration = ros::Duration(dT);
      for(int j=0; j<num_joints; j++)
      {
        double diff = jointDiff(trajectory_in.points[i-1].positions[j],trajectory_in.points[i].positions[j],limits[j]);
        double acc = 0.0;
        if(diff > 0)
          acc = limits[j].max_acceleration;
        else
          acc = - limits[j].max_acceleration;
        double tb = blendTime(acc,-acc*dT,diff);
//        double tb = blendTime(diff,acc,dT);

        spline.segments[i-1].joints[j].coefficients[0] = trajectory_in.points[i-1].positions[j];
        spline.segments[i-1].joints[j].coefficients[1] = 0.0;
        spline.segments[i-1].joints[j].coefficients[2] = 0.5*acc;
        spline.segments[i-1].joints[j].quadratic_segment_duration = tb;
        spline.segments[i-1].joints[j].linear_segment_duration = std::max(dT-2*tb,0.0);
      }
    }
    return true;
  }
}