default_robot_hw_sim.cpp

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/* Author: Dave Coleman, Jonathan Bohren
   Desc:   Hardware Interface for any simulated robot in Gazebo
*/


#include <gazebo_ros_control/default_robot_hw_sim.h>
#include <urdf/model.h>


namespace
{

double clamp(const double val, const double min_val, const double max_val)
{
  return std::min(std::max(val, min_val), max_val);
}

}

namespace gazebo_ros_control
{


bool DefaultRobotHWSim::initSim(
  const std::string& robot_namespace,
  ros::NodeHandle model_nh,
  gazebo::physics::ModelPtr parent_model,
  const urdf::Model *const urdf_model,
  std::vector<transmission_interface::TransmissionInfo> transmissions)
{
  // getJointLimits() searches joint_limit_nh for joint limit parameters. The format of each
  // parameter's name is "joint_limits/<joint name>". An example is "joint_limits/axle_joint".
  const ros::NodeHandle joint_limit_nh(model_nh);

  // Resize vectors to our DOF
  n_dof_ = transmissions.size();
  joint_names_.resize(n_dof_);
  joint_types_.resize(n_dof_);
  joint_lower_limits_.resize(n_dof_);
  joint_upper_limits_.resize(n_dof_);
  joint_effort_limits_.resize(n_dof_);
  joint_control_methods_.resize(n_dof_);
  pid_controllers_.resize(n_dof_);
  joint_position_.resize(n_dof_);
  joint_velocity_.resize(n_dof_);
  joint_effort_.resize(n_dof_);
  joint_effort_command_.resize(n_dof_);
  joint_position_command_.resize(n_dof_);
  joint_velocity_command_.resize(n_dof_);

  // Initialize values
  for(unsigned int j=0; j < n_dof_; j++)
  {
    // Check that this transmission has one joint
    if(transmissions[j].joints_.size() == 0)
    {
      ROS_WARN_STREAM_NAMED("default_robot_hw_sim","Transmission " << transmissions[j].name_
        << " has no associated joints.");
      continue;
    }
    else if(transmissions[j].joints_.size() > 1)
    {
      ROS_WARN_STREAM_NAMED("default_robot_hw_sim","Transmission " << transmissions[j].name_
        << " has more than one joint. Currently the default robot hardware simulation "
        << " interface only supports one.");
      continue;
    }

    std::vector<std::string> joint_interfaces = transmissions[j].joints_[0].hardware_interfaces_;
    if (joint_interfaces.empty() &&
        !(transmissions[j].actuators_.empty()) &&
        !(transmissions[j].actuators_[0].hardware_interfaces_.empty()))
    {
      // TODO: Deprecate HW interface specification in actuators in ROS J
      joint_interfaces = transmissions[j].actuators_[0].hardware_interfaces_;
      ROS_WARN_STREAM_NAMED("default_robot_hw_sim", "The <hardware_interface> element of tranmission " <<
        transmissions[j].name_ << " should be nested inside the <joint> element, not <actuator>. " <<
        "The transmission will be properly loaded, but please update " <<
        "your robot model to remain compatible with future versions of the plugin.");
    }
    if (joint_interfaces.empty())
    {
      ROS_WARN_STREAM_NAMED("default_robot_hw_sim", "Joint " << transmissions[j].joints_[0].name_ <<
        " of transmission " << transmissions[j].name_ << " does not specify any hardware interface. " <<
        "Not adding it to the robot hardware simulation.");
      continue;
    }
    else if (joint_interfaces.size() > 1)
    {
      ROS_WARN_STREAM_NAMED("default_robot_hw_sim", "Joint " << transmissions[j].joints_[0].name_ <<
        " of transmission " << transmissions[j].name_ << " specifies multiple hardware interfaces. " <<
        "Currently the default robot hardware simulation interface only supports one. Using the first entry");
      //continue;
    }

    // Add data from transmission
    joint_names_[j] = transmissions[j].joints_[0].name_;
    joint_position_[j] = 1.0;
    joint_velocity_[j] = 0.0;
    joint_effort_[j] = 1.0;  // N/m for continuous joints
    joint_effort_command_[j] = 0.0;
    joint_position_command_[j] = 0.0;
    joint_velocity_command_[j] = 0.0;

    const std::string& hardware_interface = joint_interfaces.front();

    // Debug
    ROS_DEBUG_STREAM_NAMED("default_robot_hw_sim","Loading joint '" << joint_names_[j]
      << "' of type '" << hardware_interface << "'");

    // Create joint state interface for all joints
    js_interface_.registerHandle(hardware_interface::JointStateHandle(
        joint_names_[j], &joint_position_[j], &joint_velocity_[j], &joint_effort_[j]));

    // Decide what kind of command interface this actuator/joint has
    hardware_interface::JointHandle joint_handle;
    if(hardware_interface == "EffortJointInterface" || hardware_interface == "hardware_interface/EffortJointInterface")
    {
      // Create effort joint interface
      joint_control_methods_[j] = EFFORT;
      joint_handle = hardware_interface::JointHandle(js_interface_.getHandle(joint_names_[j]),
                                                     &joint_effort_command_[j]);
      ej_interface_.registerHandle(joint_handle);
    }
    else if(hardware_interface == "PositionJointInterface" || hardware_interface == "hardware_interface/PositionJointInterface")
    {
      // Create position joint interface
      joint_control_methods_[j] = POSITION;
      joint_handle = hardware_interface::JointHandle(js_interface_.getHandle(joint_names_[j]),
                                                     &joint_position_command_[j]);
      pj_interface_.registerHandle(joint_handle);
    }
    else if(hardware_interface == "VelocityJointInterface" || hardware_interface == "hardware_interface/VelocityJointInterface")
    {
      // Create velocity joint interface
      joint_control_methods_[j] = VELOCITY;
      joint_handle = hardware_interface::JointHandle(js_interface_.getHandle(joint_names_[j]),
                                                     &joint_velocity_command_[j]);
      vj_interface_.registerHandle(joint_handle);
    }
    else
    {
      ROS_FATAL_STREAM_NAMED("default_robot_hw_sim","No matching hardware interface found for '"
        << hardware_interface << "' while loading interfaces for " << joint_names_[j] );
      return false;
    }

    if(hardware_interface == "EffortJointInterface" || hardware_interface == "PositionJointInterface" || hardware_interface == "VelocityJointInterface") {
      ROS_WARN_STREAM("Deprecated syntax, please prepend 'hardware_interface/' to '" << hardware_interface << "' within the <hardwareInterface> tag in joint '" << joint_names_[j] << "'.");
    }

    // Get the gazebo joint that corresponds to the robot joint.
    //ROS_DEBUG_STREAM_NAMED("default_robot_hw_sim", "Getting pointer to gazebo joint: "
    //  << joint_names_[j]);
    gazebo::physics::JointPtr joint = parent_model->GetJoint(joint_names_[j]);
    if (!joint)
    {
      ROS_ERROR_STREAM_NAMED("default_robot_hw", "This robot has a joint named \"" << joint_names_[j]
        << "\" which is not in the gazebo model.");
      return false;
    }
    sim_joints_.push_back(joint);

    // get physics engine type
#if GAZEBO_MAJOR_VERSION >= 8
    gazebo::physics::PhysicsEnginePtr physics = gazebo::physics::get_world()->Physics();
#else
    gazebo::physics::PhysicsEnginePtr physics = gazebo::physics::get_world()->GetPhysicsEngine();
#endif
    physics_type_ = physics->GetType();
    if (physics_type_.empty())
    {
      ROS_WARN_STREAM_NAMED("default_robot_hw_sim", "No physics type found.");
    }

    registerJointLimits(joint_names_[j], joint_handle, joint_control_methods_[j],
                        joint_limit_nh, urdf_model,
                        &joint_types_[j], &joint_lower_limits_[j], &joint_upper_limits_[j],
                        &joint_effort_limits_[j]);
    if (joint_control_methods_[j] != EFFORT)
    {
      // Initialize the PID controller. If no PID gain values are found, use joint->SetAngle() or
      // joint->SetParam("vel") to control the joint.
      const ros::NodeHandle nh(robot_namespace + "/gazebo_ros_control/pid_gains/" +
                               joint_names_[j]);
      if (pid_controllers_[j].init(nh, true))
      {
        switch (joint_control_methods_[j])
        {
          case POSITION:
            joint_control_methods_[j] = POSITION_PID;
            break;
          case VELOCITY:
            joint_control_methods_[j] = VELOCITY_PID;
            break;
        }
      }
      else
      {
        // joint->SetParam("fmax") must be called if joint->SetAngle() or joint->SetParam("vel") are
        // going to be called. joint->SetParam("fmax") must *not* be called if joint->SetForce() is
        // going to be called.
#if GAZEBO_MAJOR_VERSION > 2
        joint->SetParam("fmax", 0, joint_effort_limits_[j]);
#else
        joint->SetMaxForce(0, joint_effort_limits_[j]);
#endif
      }
    }
  }

  // Register interfaces
  registerInterface(&js_interface_);
  registerInterface(&ej_interface_);
  registerInterface(&pj_interface_);
  registerInterface(&vj_interface_);

  // Initialize the emergency stop code.
  e_stop_active_ = false;
  last_e_stop_active_ = false;

  return true;
}

void DefaultRobotHWSim::readSim(ros::Time time, ros::Duration period)
{
  for(unsigned int j=0; j < n_dof_; j++)
  {
    // Gazebo has an interesting API...
#if GAZEBO_MAJOR_VERSION >= 8
    double position = sim_joints_[j]->Position(0);
#else
    double position = sim_joints_[j]->GetAngle(0).Radian();
#endif
    if (joint_types_[j] == urdf::Joint::PRISMATIC)
    {
      joint_position_[j] = position;
    }
    else
    {
      joint_position_[j] += angles::shortest_angular_distance(joint_position_[j],
                            position);
    }
    joint_velocity_[j] = sim_joints_[j]->GetVelocity(0);
    joint_effort_[j] = sim_joints_[j]->GetForce((unsigned int)(0));
  }
}

void DefaultRobotHWSim::writeSim(ros::Time time, ros::Duration period)
{
  // If the E-stop is active, joints controlled by position commands will maintain their positions.
  if (e_stop_active_)
  {
    if (!last_e_stop_active_)
    {
      last_joint_position_command_ = joint_position_;
      last_e_stop_active_ = true;
    }
    joint_position_command_ = last_joint_position_command_;
  }
  else
  {
    last_e_stop_active_ = false;
  }

  ej_sat_interface_.enforceLimits(period);
  ej_limits_interface_.enforceLimits(period);
  pj_sat_interface_.enforceLimits(period);
  pj_limits_interface_.enforceLimits(period);
  vj_sat_interface_.enforceLimits(period);
  vj_limits_interface_.enforceLimits(period);

  for(unsigned int j=0; j < n_dof_; j++)
  {
    switch (joint_control_methods_[j])
    {
      case EFFORT:
        {
          const double effort = e_stop_active_ ? 0 : joint_effort_command_[j];
          sim_joints_[j]->SetForce(0, effort);
        }
        break;

      case POSITION:
#if GAZEBO_MAJOR_VERSION >= 9
        sim_joints_[j]->SetPosition(0, joint_position_command_[j], true);
#else
        ROS_WARN_ONCE("The default_robot_hw_sim plugin is using the Joint::SetPosition method without preserving the link velocity.");
        ROS_WARN_ONCE("As a result, gravity will not be simulated correctly for your model.");
        ROS_WARN_ONCE("Please set gazebo_pid parameters, switch to the VelocityJointInterface or EffortJointInterface, or upgrade to Gazebo 9.");
        ROS_WARN_ONCE("For details, see https://github.com/ros-simulation/gazebo_ros_pkgs/issues/612");
        sim_joints_[j]->SetPosition(0, joint_position_command_[j]);
#endif
        break;

      case POSITION_PID:
        {
          double error;
          switch (joint_types_[j])
          {
            case urdf::Joint::REVOLUTE:
              angles::shortest_angular_distance_with_limits(joint_position_[j],
                                                            joint_position_command_[j],
                                                            joint_lower_limits_[j],
                                                            joint_upper_limits_[j],
                                                            error);
              break;
            case urdf::Joint::CONTINUOUS:
              error = angles::shortest_angular_distance(joint_position_[j],
                                                        joint_position_command_[j]);
              break;
            default:
              error = joint_position_command_[j] - joint_position_[j];
          }

          const double effort_limit = joint_effort_limits_[j];
          const double effort = clamp(pid_controllers_[j].computeCommand(error, period),
                                      -effort_limit, effort_limit);
          sim_joints_[j]->SetForce(0, effort);
        }
        break;

      case VELOCITY:
#if GAZEBO_MAJOR_VERSION > 2
        if (physics_type_.compare("ode") == 0)
        {
          sim_joints_[j]->SetParam("vel", 0, e_stop_active_ ? 0 : joint_velocity_command_[j]);
        }
        else 
        {
          sim_joints_[j]->SetVelocity(0, e_stop_active_ ? 0 : joint_velocity_command_[j]);
        }
#else
        sim_joints_[j]->SetVelocity(0, e_stop_active_ ? 0 : joint_velocity_command_[j]);
#endif
        break;

      case VELOCITY_PID:
        double error;
        if (e_stop_active_)
          error = -joint_velocity_[j];
        else
          error = joint_velocity_command_[j] - joint_velocity_[j];
        const double effort_limit = joint_effort_limits_[j];
        const double effort = clamp(pid_controllers_[j].computeCommand(error, period),
                                    -effort_limit, effort_limit);
        sim_joints_[j]->SetForce(0, effort);
        break;
    }
  }
}

void DefaultRobotHWSim::eStopActive(const bool active)
{
  e_stop_active_ = active;
}

// Register the limits of the joint specified by joint_name and joint_handle. The limits are
// retrieved from joint_limit_nh. If urdf_model is not NULL, limits are retrieved from it also.
// Return the joint's type, lower position limit, upper position limit, and effort limit.
void DefaultRobotHWSim::registerJointLimits(const std::string& joint_name,
                         const hardware_interface::JointHandle& joint_handle,
                         const ControlMethod ctrl_method,
                         const ros::NodeHandle& joint_limit_nh,
                         const urdf::Model *const urdf_model,
                         int *const joint_type, double *const lower_limit,
                         double *const upper_limit, double *const effort_limit)
{
  *joint_type = urdf::Joint::UNKNOWN;
  *lower_limit = -std::numeric_limits<double>::max();
  *upper_limit = std::numeric_limits<double>::max();
  *effort_limit = std::numeric_limits<double>::max();

  joint_limits_interface::JointLimits limits;
  bool has_limits = false;
  joint_limits_interface::SoftJointLimits soft_limits;
  bool has_soft_limits = false;

  if (urdf_model != NULL)
  {
    const urdf::JointConstSharedPtr urdf_joint = urdf_model->getJoint(joint_name);
    if (urdf_joint != NULL)
    {
      *joint_type = urdf_joint->type;
      // Get limits from the URDF file.
      if (joint_limits_interface::getJointLimits(urdf_joint, limits))
        has_limits = true;
      if (joint_limits_interface::getSoftJointLimits(urdf_joint, soft_limits))
        has_soft_limits = true;
    }
  }
  // Get limits from the parameter server.
  if (joint_limits_interface::getJointLimits(joint_name, joint_limit_nh, limits))
    has_limits = true;

  if (!has_limits)
    return;

  if (*joint_type == urdf::Joint::UNKNOWN)
  {
    // Infer the joint type.

    if (limits.has_position_limits)
    {
      *joint_type = urdf::Joint::REVOLUTE;
    }
    else
    {
      if (limits.angle_wraparound)
        *joint_type = urdf::Joint::CONTINUOUS;
      else
        *joint_type = urdf::Joint::PRISMATIC;
    }
  }

  if (limits.has_position_limits)
  {
    *lower_limit = limits.min_position;
    *upper_limit = limits.max_position;
  }
  if (limits.has_effort_limits)
    *effort_limit = limits.max_effort;

  if (has_soft_limits)
  {
    switch (ctrl_method)
    {
      case EFFORT:
        {
          const joint_limits_interface::EffortJointSoftLimitsHandle
            limits_handle(joint_handle, limits, soft_limits);
          ej_limits_interface_.registerHandle(limits_handle);
        }
        break;
      case POSITION:
        {
          const joint_limits_interface::PositionJointSoftLimitsHandle
            limits_handle(joint_handle, limits, soft_limits);
          pj_limits_interface_.registerHandle(limits_handle);
        }
        break;
      case VELOCITY:
        {
          const joint_limits_interface::VelocityJointSoftLimitsHandle
            limits_handle(joint_handle, limits, soft_limits);
          vj_limits_interface_.registerHandle(limits_handle);
        }
        break;
    }
  }
  else
  {
    switch (ctrl_method)
    {
      case EFFORT:
        {
          const joint_limits_interface::EffortJointSaturationHandle
            sat_handle(joint_handle, limits);
          ej_sat_interface_.registerHandle(sat_handle);
        }
        break;
      case POSITION:
        {
          const joint_limits_interface::PositionJointSaturationHandle
            sat_handle(joint_handle, limits);
          pj_sat_interface_.registerHandle(sat_handle);
        }
        break;
      case VELOCITY:
        {
          const joint_limits_interface::VelocityJointSaturationHandle
            sat_handle(joint_handle, limits);
          vj_sat_interface_.registerHandle(sat_handle);
        }
        break;
    }
  }
}

}

PLUGINLIB_EXPORT_CLASS(gazebo_ros_control::DefaultRobotHWSim, gazebo_ros_control::RobotHWSim)