common.h

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/*
 * Copyright 2015 Fadri Furrer, ASL, ETH Zurich, Switzerland
 * Copyright 2015 Michael Burri, ASL, ETH Zurich, Switzerland
 * Copyright 2015 Mina Kamel, ASL, ETH Zurich, Switzerland
 * Copyright 2015 Janosch Nikolic, ASL, ETH Zurich, Switzerland
 * Copyright 2015 Markus Achtelik, ASL, ETH Zurich, Switzerland
 * Copyright 2016 Geoffrey Hunter <gbmhunter@gmail.com>
 *
 * 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.
 */

#ifndef ROTORS_GAZEBO_PLUGINS_COMMON_H_
#define ROTORS_GAZEBO_PLUGINS_COMMON_H_

#include <Eigen/Dense>
#include <gazebo/gazebo.hh>

namespace gazebo {

//===============================================================================================//
//========================================= DEBUGGING ===========================================//
//===============================================================================================//


// The following boolean constants enable/disable debug printing when certain plugin methods are called.
// Suitable for debugging purposes. Left on permanently can swamp std::out and can crash Gazebo.

static const bool kPrintOnPluginLoad    = false;
static const bool kPrintOnUpdates       = false;
static const bool kPrintOnMsgCallback   = false;


// Default values
static const std::string kDefaultNamespace = "";
static constexpr double kDefaultRotorVelocitySlowdownSim = 10.0;

//===============================================================================================//
//================================== TOPICS FOR ROS INTERFACE ===================================//
//===============================================================================================//

// These should perhaps be defined in an .sdf/.xacro file instead?
static const std::string kConnectGazeboToRosSubtopic = "connect_gazebo_to_ros_subtopic";
static const std::string kConnectRosToGazeboSubtopic = "connect_ros_to_gazebo_subtopic";

static const std::string kBroadcastTransformSubtopic = "broadcast_transform";


template<class T>
bool getSdfParam(sdf::ElementPtr sdf, const std::string& name, T& param, const T& default_value, const bool& verbose =
                     false) {
  if (sdf->HasElement(name)) {
    param = sdf->GetElement(name)->Get<T>();
    return true;
  }
  else {
    param = default_value;
    if (verbose)
      gzerr << "[rotors_gazebo_plugins] Please specify a value for parameter \"" << name << "\".\n";
  }
  return false;
}

}

template <typename T>
class FirstOrderFilter {

 public:
  FirstOrderFilter(double timeConstantUp, double timeConstantDown, T initialState):
      timeConstantUp_(timeConstantUp),
      timeConstantDown_(timeConstantDown),
      previousState_(initialState) {}

  T updateFilter(T inputState, double samplingTime) {

    T outputState;
    if (inputState > previousState_) {
      // Calcuate the outputState if accelerating.
      double alphaUp = exp(-samplingTime / timeConstantUp_);
      // x(k+1) = Ad*x(k) + Bd*u(k)
      outputState = alphaUp * previousState_ + (1 - alphaUp) * inputState;

    }
    else {
      // Calculate the outputState if decelerating.
      double alphaDown = exp(-samplingTime / timeConstantDown_);
      outputState = alphaDown * previousState_ + (1 - alphaDown) * inputState;
    }
    previousState_ = outputState;
    return outputState;

  }

  ~FirstOrderFilter() {}

 protected:
  double timeConstantUp_;
  double timeConstantDown_;
  T previousState_;
};

template<class Derived>
Eigen::Quaternion<typename Derived::Scalar> QuaternionFromSmallAngle(const Eigen::MatrixBase<Derived> & theta) {
  typedef typename Derived::Scalar Scalar;
  EIGEN_STATIC_ASSERT_FIXED_SIZE(Derived);
  EIGEN_STATIC_ASSERT_VECTOR_SPECIFIC_SIZE(Derived, 3);
  const Scalar q_squared = theta.squaredNorm() / 4.0;

  if (q_squared < 1) {
    return Eigen::Quaternion<Scalar>(sqrt(1 - q_squared), theta[0] * 0.5, theta[1] * 0.5, theta[2] * 0.5);
  }
  else {
    const Scalar w = 1.0 / sqrt(1 + q_squared);
    const Scalar f = w * 0.5;
    return Eigen::Quaternion<Scalar>(w, theta[0] * f, theta[1] * f, theta[2] * f);
  }
}

template<class In, class Out>
void copyPosition(const In& in, Out* out) {
  out->x = in.x;
  out->y = in.y;
  out->z = in.z;
}

#endif /* ROTORS_GAZEBO_PLUGINS_COMMON_H_ */