velocity_smoother.cpp

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/*
 * Copyright 2017 Fraunhofer Institute for Manufacturing Engineering and Automation (IPA)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0

 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*****************************************************************************
 ** Includes
 *****************************************************************************/

#include <ros/ros.h>

#include <dynamic_reconfigure/server.h>
#include <cob_base_velocity_smoother/velocity_smoother.h>

#include <boost/thread.hpp>

/*****************************************************************************
 ** Preprocessing
 *****************************************************************************/

#define PERIOD_RECORD_SIZE    5
#define ZERO_VEL_COMMAND      geometry_msgs::Twist();
#define IS_ZERO_VEOCITY(a)   ((a.linear.x == 0.0) && (a.linear.y == 0.0) && (a.angular.z == 0.0))

/*****************************************************************************
** Namespaces
*****************************************************************************/

namespace cob_base_velocity_smoother {

/*********************
** Implementation
**********************/

VelocitySmoother::VelocitySmoother(const std::string &name)
: name(name)
, shutdown_req(false)
, input_active(false)
, pr_next(0)
, dynamic_reconfigure_server(NULL)
{
}

void VelocitySmoother::reconfigCB(cob_base_velocity_smoother::paramsConfig &config, uint32_t level)
{
  ROS_INFO("Reconfigure request : %f %f %f %f %f %f %f %f",
           config.speed_lim_vx, config.speed_lim_vy, config.speed_lim_w, config.accel_lim_vx, config.accel_lim_vy, config.accel_lim_w, config.decel_factor, config.decel_factor_safe);

  speed_lim_vx  = config.speed_lim_vx;
  speed_lim_vy  = config.speed_lim_vy;
  speed_lim_w  = config.speed_lim_w;
  accel_lim_vx  = config.accel_lim_vx;
  accel_lim_vy  = config.accel_lim_vy;
  accel_lim_w  = config.accel_lim_w;
  decel_factor = config.decel_factor;
  decel_factor_safe = config.decel_factor_safe;
  decel_lim_vx  = decel_factor*accel_lim_vx;
  decel_lim_vy  = decel_factor*accel_lim_vy;
  decel_lim_w  = decel_factor*accel_lim_w;
  decel_lim_vx_safe = decel_factor_safe*accel_lim_vx;
  decel_lim_vy_safe = decel_factor_safe*accel_lim_vy;
  decel_lim_w_safe = decel_factor_safe*accel_lim_w;
}

void VelocitySmoother::velocityCB(const geometry_msgs::Twist::ConstPtr& msg)
{
  // Estimate commands frequency; we do continuously as it can be very different depending on the
  // publisher type, and we don't want to impose extra constraints to keep this package flexible
  if (period_record.size() < PERIOD_RECORD_SIZE)
  {
    period_record.push_back((ros::Time::now() - last_cb_time).toSec());
  }
  else
  {
    period_record[pr_next] = (ros::Time::now() - last_cb_time).toSec();
  }

  pr_next++;
  pr_next %= period_record.size();
  last_cb_time = ros::Time::now();

  if (period_record.size() <= PERIOD_RECORD_SIZE/2)
  {
    // wait until we have some values; make a reasonable assumption (10 Hz) meanwhile
    cb_avg_time = 0.1;
  }
  else
  {
    // enough; recalculate with the latest input
    cb_avg_time = median(period_record);
  }

  input_active = true;

  // Bound speed with the maximum values
  target_vel.linear.x  =
      msg->linear.x  > 0.0 ? std::min(msg->linear.x,  speed_lim_vx) : std::max(msg->linear.x,  -speed_lim_vx);
  target_vel.linear.y  =
      msg->linear.y  > 0.0 ? std::min(msg->linear.y,  speed_lim_vy) : std::max(msg->linear.y,  -speed_lim_vy);
  target_vel.angular.z =
      msg->angular.z > 0.0 ? std::min(msg->angular.z, speed_lim_w) : std::max(msg->angular.z, -speed_lim_w);
}

void VelocitySmoother::odometryCB(const nav_msgs::Odometry::ConstPtr& msg)
{
  if (robot_feedback == ODOMETRY)
    current_vel = msg->twist.twist;

  // ignore otherwise
}

void VelocitySmoother::robotVelCB(const geometry_msgs::Twist::ConstPtr& msg)
{
  if (robot_feedback == COMMANDS)
    current_vel = *msg;

  // ignore otherwise
}

void VelocitySmoother::spin()
{
  double period = 1.0/frequency;
  ros::Rate spin_rate(frequency);

  double decel_vx;
  double decel_vy;
  double decel_w;

  while (! shutdown_req && ros::ok())
  {
    if ((input_active == true) && (cb_avg_time > 0.0) &&
        ((ros::Time::now() - last_cb_time).toSec() > std::min(3.0*cb_avg_time, 0.5)))
    {
      // Velocity input no active anymore; normally last command is a zero-velocity one, but reassure
      // this, just in case something went wrong with our input, or he just forgot good manners...
      // Issue #2, extra check in case cb_avg_time is very big, for example with several atomic commands
      // The cb_avg_time > 0 check is required to deal with low-rate simulated time, that can make that
      // several messages arrive with the same time and so lead to a zero median
      input_active = false;
      if (IS_ZERO_VEOCITY(target_vel) == false)
      {
        ROS_WARN_STREAM("Velocity Smoother : input got inactive leaving us a non-zero target velocity ("
              << target_vel.linear.x << ", " << target_vel.linear.y << ", " << target_vel.angular.z << "), zeroing...[" << name << "]");
        target_vel = ZERO_VEL_COMMAND;
      }
    }

    if(input_active)
    {
      decel_vx = decel_lim_vx;
      decel_vy = decel_lim_vy;
      decel_w = decel_lim_w;
    }
    else
    {
      //increase decel factor because this is a safty case, no more commands means we should stop as fast as it is safe
      decel_vx = decel_lim_vx_safe;
      decel_vy = decel_lim_vy_safe;
      decel_w = decel_lim_w_safe;
    }

    if ((robot_feedback != NONE) && (input_active == true) && (cb_avg_time > 0.0) &&
        (((ros::Time::now() - last_cb_time).toSec() > 5.0*cb_avg_time)     || // 5 missing msgs
          (std::abs(current_vel.linear.x  - last_cmd_vel.linear.x)  > 0.2) ||
          (std::abs(current_vel.linear.y  - last_cmd_vel.linear.y)  > 0.2) ||
          (std::abs(current_vel.angular.z - last_cmd_vel.angular.z) > 2.0)))
    {
      // If the publisher has been inactive for a while, or if our current commanding differs a lot
      // from robot velocity feedback, we cannot trust the former; relay on robot's feedback instead
      // This can happen mainly due to preemption of current controller on velocity multiplexer.
      // TODO: current command/feedback difference thresholds are 진짜 arbitrary; they should somehow
      // be proportional to max v and w...
      // The one for angular velocity is very big because is it's less necessary (for example the
      // reactive controller will never make the robot spin) and because the gyro has a 15 ms delay
      ROS_WARN("Using robot velocity feedback (%s) instead of last command: %f, %f, %f, %f",
                robot_feedback == ODOMETRY ? "odometry" : "end commands",
               (ros::Time::now()      - last_cb_time).toSec(),
                current_vel.linear.x  - last_cmd_vel.linear.x,
                current_vel.linear.y  - last_cmd_vel.linear.y,
                current_vel.angular.z - last_cmd_vel.angular.z);
      last_cmd_vel = current_vel;
    }

    geometry_msgs::TwistPtr cmd_vel;

    if ((target_vel.linear.x  != last_cmd_vel.linear.x) ||
        (target_vel.linear.y  != last_cmd_vel.linear.y) ||
        (target_vel.angular.z != last_cmd_vel.angular.z))
    {
      // Try to reach target velocity ensuring that we don't exceed the acceleration limits
      cmd_vel.reset(new geometry_msgs::Twist(target_vel));

      double vx_inc, vy_inc, w_inc, max_vx_inc, max_vy_inc, max_w_inc;

      vx_inc = target_vel.linear.x - last_cmd_vel.linear.x;
      if ((robot_feedback == ODOMETRY) && (current_vel.linear.x*target_vel.linear.x < 0.0))
      {
        // countermarch (on robots with significant inertia; requires odometry feedback to be detected)
        max_vx_inc = decel_vx*period;
      }
      else
      {
        max_vx_inc = ((vx_inc*target_vel.linear.x > 0.0)?accel_lim_vx:decel_vx)*period;
      }

      vy_inc = target_vel.linear.y - last_cmd_vel.linear.y;
      if ((robot_feedback == ODOMETRY) && (current_vel.linear.y*target_vel.linear.y < 0.0))
      {
        // countermarch (on robots with significant inertia; requires odometry feedback to be detected)
        max_vy_inc = decel_vy*period;
      }
      else
      {
        max_vy_inc = ((vy_inc*target_vel.linear.y > 0.0)?accel_lim_vy:decel_vy)*period;
      }

      w_inc = target_vel.angular.z - last_cmd_vel.angular.z;
      if ((robot_feedback == ODOMETRY) && (current_vel.angular.z*target_vel.angular.z < 0.0))
      {
        // countermarch (on robots with significant inertia; requires odometry feedback to be detected)
        max_w_inc = decel_w*period;
      }
      else
      {
        max_w_inc = ((w_inc*target_vel.angular.z > 0.0)?accel_lim_w:decel_w)*period;
      }

/*
      // Calculate and normalise vectors A (desired velocity increment) and B (maximum velocity increment),
      // where v acts as coordinate x and w as coordinate y; the sign of the angle from A to B determines
      // which velocity (v or w) must be overconstrained to keep the direction provided as command
      double MA = sqrt(    vx_inc *     vx_inc +     w_inc *     w_inc);
      double MB = sqrt(max_vx_inc * max_vx_inc + max_w_inc * max_w_inc);

      double Av = std::abs(vx_inc) / MA;
      double Aw = std::abs(w_inc) / MA;
      double Bv = max_vx_inc / MB;
      double Bw = max_w_inc / MB;
      double theta = atan2(Bw, Bv) - atan2(Aw, Av);

      if (theta < 0)
      {
        // overconstrain linear velocity
        max_vx_inc = (max_w_inc*std::abs(vx_inc))/std::abs(w_inc);
      }
      else
      {
        // overconstrain angular velocity
        max_w_inc = (max_vx_inc*std::abs(w_inc))/std::abs(vx_inc);
      }
*/
      if (std::abs(vx_inc) > max_vx_inc)
      {
        // we must limit linear velocity
        cmd_vel->linear.x  = last_cmd_vel.linear.x  + sign(vx_inc)*max_vx_inc;
      }

      if (std::abs(vy_inc) > max_vy_inc)
      {
        // we must limit linear velocity
        cmd_vel->linear.y  = last_cmd_vel.linear.y  + sign(vy_inc)*max_vy_inc;
      }

      if (std::abs(w_inc) > max_w_inc)
      {
        // we must limit angular velocity
        cmd_vel->angular.z = last_cmd_vel.angular.z + sign(w_inc)*max_w_inc;
      }

      smooth_vel_pub.publish(cmd_vel);
      last_cmd_vel = *cmd_vel;
    }
    else if (input_active == true)
    {
      // We already reached target velocity; just keep resending last command while input is active
      cmd_vel.reset(new geometry_msgs::Twist(last_cmd_vel));
      smooth_vel_pub.publish(cmd_vel);
    }

    spin_rate.sleep();
  }
}

bool VelocitySmoother::init(ros::NodeHandle& nh)
{
  // Dynamic Reconfigure
  dynamic_reconfigure_callback = boost::bind(&VelocitySmoother::reconfigCB, this, _1, _2);

  dynamic_reconfigure_server = new dynamic_reconfigure::Server<cob_base_velocity_smoother::paramsConfig>(nh);
  dynamic_reconfigure_server->setCallback(dynamic_reconfigure_callback);

  // Optional parameters
  int feedback;
  nh.param("frequency",      frequency,     20.0);
  nh.param("decel_factor",   decel_factor,   1.0);
  nh.param("decel_factor_safe",   decel_factor_safe,   1.0);
  nh.param("robot_feedback", feedback, (int)NONE);

  if ((int(feedback) < NONE) || (int(feedback) > COMMANDS))
  {
    ROS_WARN("Invalid robot feedback type (%d). Valid options are 0 (NONE, default), 1 (ODOMETRY) and 2 (COMMANDS)",
             feedback);
    feedback = NONE;
  }

  robot_feedback = static_cast<RobotFeedbackType>(feedback);

  // Mandatory parameters
  if ((nh.getParam("speed_lim_vx", speed_lim_vx) == false) ||
      (nh.getParam("speed_lim_vy", speed_lim_vy) == false) ||
      (nh.getParam("speed_lim_w", speed_lim_w) == false))
  {
    ROS_ERROR("Missing velocity limit parameter(s)");
    return false;
  }

  if ((nh.getParam("accel_lim_vx", accel_lim_vx) == false) ||
      (nh.getParam("accel_lim_vy", accel_lim_vy) == false) ||
      (nh.getParam("accel_lim_w", accel_lim_w) == false))
  {
    ROS_ERROR("Missing acceleration limit parameter(s)");
    return false;
  }

  // Deceleration can be more aggressive, if necessary
  decel_lim_vx = decel_factor*accel_lim_vx;
  decel_lim_vy = decel_factor*accel_lim_vy;
  decel_lim_w = decel_factor*accel_lim_w;
  // In safety cases (no topic command anymore), deceleration should be very aggressive
  decel_lim_vx_safe = decel_factor_safe*accel_lim_vx;
  decel_lim_vy_safe = decel_factor_safe*accel_lim_vy;
  decel_lim_w_safe = decel_factor_safe*accel_lim_w;

  // Publishers and subscribers
  odometry_sub    = nh.subscribe("odometry",      1, &VelocitySmoother::odometryCB, this);
  current_vel_sub = nh.subscribe("robot_cmd_vel", 1, &VelocitySmoother::robotVelCB, this);
  raw_in_vel_sub  = nh.subscribe("raw_cmd_vel",   1, &VelocitySmoother::velocityCB, this);
  smooth_vel_pub  = nh.advertise <geometry_msgs::Twist> ("smooth_cmd_vel", 1);

  return true;
}
}