generic_hw_control_loop.cpp

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/* Author: Dave Coleman
   Desc:   Example control loop for reading, updating, and writing commands to a hardware interface
   using MONOTOIC system time
*/

#include <ros_control_boilerplate/generic_hw_control_loop.h>

// ROS parameter loading
#include <rosparam_shortcuts/rosparam_shortcuts.h>

namespace ros_control_boilerplate
{
GenericHWControlLoop::GenericHWControlLoop(
    ros::NodeHandle& nh, boost::shared_ptr<hardware_interface::RobotHW> hardware_interface)
  : nh_(nh), hardware_interface_(hardware_interface)
{
  // Create the controller manager
  controller_manager_.reset(new controller_manager::ControllerManager(hardware_interface_.get(), nh_));

  // Load rosparams
  ros::NodeHandle rpsnh(nh, name_);
  std::size_t error = 0;
  error += !rosparam_shortcuts::get(name_, rpsnh, "loop_hz", loop_hz_);
  error += !rosparam_shortcuts::get(name_, rpsnh, "cycle_time_error_threshold", cycle_time_error_threshold_);
  rosparam_shortcuts::shutdownIfError(name_, error);

  // Get current time for use with first update
  clock_gettime(CLOCK_MONOTONIC, &last_time_);

  desired_update_period_ = ros::Duration(1 / loop_hz_);
}

void GenericHWControlLoop::run()
{
  ros::Rate rate(loop_hz_);
  while(ros::ok()) {
    update();
    rate.sleep();
  }
}

void GenericHWControlLoop::update()
{
  // Get change in time
  clock_gettime(CLOCK_MONOTONIC, &current_time_);
  elapsed_time_ =
      ros::Duration(current_time_.tv_sec - last_time_.tv_sec + (current_time_.tv_nsec - last_time_.tv_nsec) / BILLION);
  last_time_ = current_time_;
  ros::Time now = ros::Time::now();
  // ROS_DEBUG_STREAM_THROTTLE_NAMED(1, "generic_hw_main","Sampled update loop with elapsed
  // time " << elapsed_time_.toSec());

  // Error check cycle time
  const double cycle_time_error = (elapsed_time_ - desired_update_period_).toSec();
  if (cycle_time_error > cycle_time_error_threshold_)
  {
    ROS_WARN_STREAM_NAMED(name_, "Cycle time exceeded error threshold by: "
                                     << cycle_time_error << ", cycle time: " << elapsed_time_
                                     << ", threshold: " << cycle_time_error_threshold_);
  }

  // Input
  hardware_interface_->read(now, elapsed_time_);

  // Control
  controller_manager_->update(now, elapsed_time_);

  // Output
  hardware_interface_->write(now, elapsed_time_);
}

}  // namespace