joint_impedance_example_controller.cpp

Go to the documentation of this file.

// Copyright (c) 2017 Franka Emika GmbH
// Use of this source code is governed by the Apache-2.0 license, see LICENSE
#include <franka_example_controllers/joint_impedance_example_controller.h>
 
#include <cmath>
#include <memory>
 
#include <controller_interface/controller_base.h>
#include <pluginlib/class_list_macros.h>
#include <ros/ros.h>
 
#include <franka/robot_state.h>
 
namespace franka_example_controllers {
 
bool JointImpedanceExampleController::init(hardware_interface::RobotHW* robot_hw,
                                           ros::NodeHandle& node_handle) {
  std::string arm_id;
  if (!node_handle.getParam("arm_id", arm_id)) {
    ROS_ERROR("JointImpedanceExampleController: Could not read parameter arm_id");
    return false;
  }
  if (!node_handle.getParam("radius", radius_)) {
    ROS_INFO_STREAM(
        "JointImpedanceExampleController: No parameter radius, defaulting to: " << radius_);
  }
  if (std::fabs(radius_) < 0.005) {
    ROS_INFO_STREAM("JointImpedanceExampleController: Set radius to small, defaulting to: " << 0.1);
    radius_ = 0.1;
  }
 
  if (!node_handle.getParam("vel_max", vel_max_)) {
    ROS_INFO_STREAM(
        "JointImpedanceExampleController: No parameter vel_max, defaulting to: " << vel_max_);
  }
  if (!node_handle.getParam("acceleration_time", acceleration_time_)) {
    ROS_INFO_STREAM(
        "JointImpedanceExampleController: No parameter acceleration_time, defaulting to: "
        << acceleration_time_);
  }
 
  std::vector<std::string> joint_names;
  if (!node_handle.getParam("joint_names", joint_names) || joint_names.size() != 7) {
    ROS_ERROR(
        "JointImpedanceExampleController: Invalid or no joint_names parameters provided, aborting "
        "controller init!");
    return false;
  }
 
  if (!node_handle.getParam("k_gains", k_gains_) || k_gains_.size() != 7) {
    ROS_ERROR(
        "JointImpedanceExampleController:  Invalid or no k_gain parameters provided, aborting "
        "controller init!");
    return false;
  }
 
  if (!node_handle.getParam("d_gains", d_gains_) || d_gains_.size() != 7) {
    ROS_ERROR(
        "JointImpedanceExampleController:  Invalid or no d_gain parameters provided, aborting "
        "controller init!");
    return false;
  }
 
  double publish_rate(30.0);
  if (!node_handle.getParam("publish_rate", publish_rate)) {
    ROS_INFO_STREAM("JointImpedanceExampleController: publish_rate not found. Defaulting to "
                    << publish_rate);
  }
  rate_trigger_ = franka_hw::TriggerRate(publish_rate);
 
  if (!node_handle.getParam("coriolis_factor", coriolis_factor_)) {
    ROS_INFO_STREAM("JointImpedanceExampleController: coriolis_factor not found. Defaulting to "
                    << coriolis_factor_);
  }
 
  auto* model_interface = robot_hw->get<franka_hw::FrankaModelInterface>();
  if (model_interface == nullptr) {
    ROS_ERROR_STREAM(
        "JointImpedanceExampleController: Error getting model interface from hardware");
    return false;
  }
  try {
    model_handle_ = std::make_unique<franka_hw::FrankaModelHandle>(
        model_interface->getHandle(arm_id + "_model"));
  } catch (hardware_interface::HardwareInterfaceException& ex) {
    ROS_ERROR_STREAM(
        "JointImpedanceExampleController: Exception getting model handle from interface: "
        << ex.what());
    return false;
  }
 
  auto* cartesian_pose_interface = robot_hw->get<franka_hw::FrankaPoseCartesianInterface>();
  if (cartesian_pose_interface == nullptr) {
    ROS_ERROR_STREAM(
        "JointImpedanceExampleController: Error getting cartesian pose interface from hardware");
    return false;
  }
  try {
    cartesian_pose_handle_ = std::make_unique<franka_hw::FrankaCartesianPoseHandle>(
        cartesian_pose_interface->getHandle(arm_id + "_robot"));
  } catch (hardware_interface::HardwareInterfaceException& ex) {
    ROS_ERROR_STREAM(
        "JointImpedanceExampleController: Exception getting cartesian pose handle from interface: "
        << ex.what());
    return false;
  }
 
  auto* effort_joint_interface = robot_hw->get<hardware_interface::EffortJointInterface>();
  if (effort_joint_interface == nullptr) {
    ROS_ERROR_STREAM(
        "JointImpedanceExampleController: Error getting effort joint interface from hardware");
    return false;
  }
  for (size_t i = 0; i < 7; ++i) {
    try {
      joint_handles_.push_back(effort_joint_interface->getHandle(joint_names[i]));
    } catch (const hardware_interface::HardwareInterfaceException& ex) {
      ROS_ERROR_STREAM(
          "JointImpedanceExampleController: Exception getting joint handles: " << ex.what());
      return false;
    }
  }
  torques_publisher_.init(node_handle, "torque_comparison", 1);
 
  std::fill(dq_filtered_.begin(), dq_filtered_.end(), 0);
 
  return true;
}
 
void JointImpedanceExampleController::starting(const ros::Time& /*time*/) {
  initial_pose_ = cartesian_pose_handle_->getRobotState().O_T_EE_d;
}
 
void JointImpedanceExampleController::update(const ros::Time& /*time*/,
                                             const ros::Duration& period) {
  if (vel_current_ < vel_max_) {
    vel_current_ += period.toSec() * std::fabs(vel_max_ / acceleration_time_);
  }
  vel_current_ = std::fmin(vel_current_, vel_max_);
 
  angle_ += period.toSec() * vel_current_ / std::fabs(radius_);
  if (angle_ > 2 * M_PI) {
    angle_ -= 2 * M_PI;
  }
 
  double delta_y = radius_ * (1 - std::cos(angle_));
  double delta_z = radius_ * std::sin(angle_);
 
  std::array<double, 16> pose_desired = initial_pose_;
  pose_desired[13] += delta_y;
  pose_desired[14] += delta_z;
  cartesian_pose_handle_->setCommand(pose_desired);
 
  franka::RobotState robot_state = cartesian_pose_handle_->getRobotState();
  std::array<double, 7> coriolis = model_handle_->getCoriolis();
  std::array<double, 7> gravity = model_handle_->getGravity();
 
  double alpha = 0.99;
  for (size_t i = 0; i < 7; i++) {
    dq_filtered_[i] = (1 - alpha) * dq_filtered_[i] + alpha * robot_state.dq[i];
  }
 
  std::array<double, 7> tau_d_calculated;
  for (size_t i = 0; i < 7; ++i) {
    tau_d_calculated[i] = coriolis_factor_ * coriolis[i] +
                          k_gains_[i] * (robot_state.q_d[i] - robot_state.q[i]) +
                          d_gains_[i] * (robot_state.dq_d[i] - dq_filtered_[i]);
  }
 
  // Maximum torque difference with a sampling rate of 1 kHz. The maximum torque rate is
  // 1000 * (1 / sampling_time).
  std::array<double, 7> tau_d_saturated = saturateTorqueRate(tau_d_calculated, robot_state.tau_J_d);
 
  for (size_t i = 0; i < 7; ++i) {
    joint_handles_[i].setCommand(tau_d_saturated[i]);
  }
 
  if (rate_trigger_() && torques_publisher_.trylock()) {
    std::array<double, 7> tau_j = robot_state.tau_J;
    std::array<double, 7> tau_error;
    double error_rms(0.0);
    for (size_t i = 0; i < 7; ++i) {
      tau_error[i] = last_tau_d_[i] - tau_j[i];
      error_rms += std::sqrt(std::pow(tau_error[i], 2.0)) / 7.0;
    }
    torques_publisher_.msg_.root_mean_square_error = error_rms;
    for (size_t i = 0; i < 7; ++i) {
      torques_publisher_.msg_.tau_commanded[i] = last_tau_d_[i];
      torques_publisher_.msg_.tau_error[i] = tau_error[i];
      torques_publisher_.msg_.tau_measured[i] = tau_j[i];
    }
    torques_publisher_.unlockAndPublish();
  }
 
  for (size_t i = 0; i < 7; ++i) {
    last_tau_d_[i] = tau_d_saturated[i] + gravity[i];
  }
}
 
std::array<double, 7> JointImpedanceExampleController::saturateTorqueRate(
    const std::array<double, 7>& tau_d_calculated,
    const std::array<double, 7>& tau_J_d) {  // NOLINT (readability-identifier-naming)
  std::array<double, 7> tau_d_saturated{};
  for (size_t i = 0; i < 7; i++) {
    double difference = tau_d_calculated[i] - tau_J_d[i];
    tau_d_saturated[i] = tau_J_d[i] + std::max(std::min(difference, kDeltaTauMax), -kDeltaTauMax);
  }
  return tau_d_saturated;
}
 
}  // namespace franka_example_controllers
 
PLUGINLIB_EXPORT_CLASS(franka_example_controllers::JointImpedanceExampleController,
                       controller_interface::ControllerBase)