matrix_operations.cc

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/******************************************************************************
 * Copyright 2017 The Apollo Authors. All Rights Reserved.
 *
 * 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.
 *****************************************************************************/
 
#include <cmath>
#include <utility>
 
#include "Eigen/Dense"
#include "Eigen/SVD"
 
#include "modules/common/math/matrix_operations.h"
 
namespace apollo {
namespace common {
namespace math {
 
bool ContinuousToDiscrete(const Eigen::MatrixXd &m_a,
                          const Eigen::MatrixXd &m_b,
                          const Eigen::MatrixXd &m_c,
                          const Eigen::MatrixXd &m_d, const double ts,
                          Eigen::MatrixXd *ptr_a_d, Eigen::MatrixXd *ptr_b_d,
                          Eigen::MatrixXd *ptr_c_d, Eigen::MatrixXd *ptr_d_d) {
  if (ts <= 0.0) {
    AERROR << "ContinuousToDiscrete : ts is less than or equal to zero";
    return false;
  }
 
  // Only matrix_a is mandatory to be non-zeros in matrix
  // conversion.
  if (m_a.rows() == 0) {
    AERROR << "ContinuousToDiscrete: matrix_a size 0 ";
    return false;
  }
 
  if (m_a.cols() != m_b.rows() || m_b.cols() != m_d.cols() ||
      m_c.rows() != m_d.rows() || m_a.cols() != m_c.cols()) {
    AERROR << "ContinuousToDiscrete: matrix dimensions mismatch";
    return false;
  }
 
  Eigen::MatrixXd m_identity =
      Eigen::MatrixXd::Identity(m_a.cols(), m_a.rows());
 
  *ptr_a_d =
      (m_identity - ts * 0.5 * m_a).inverse() * (m_identity + ts * 0.5 * m_a);
 
  *ptr_b_d = std::sqrt(ts) * (m_identity - ts * 0.5 * m_a).inverse() * m_b;
 
  *ptr_c_d = std::sqrt(ts) * m_c * (m_identity - ts * 0.5 * m_a).inverse();
 
  *ptr_d_d = 0.5 * m_c * (m_identity - ts * 0.5 * m_a).inverse() * m_b + m_d;
 
  return true;
}
 
}  // namespace math
}  // namespace common
}  // namespace apollo