simple_car.h

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/*********************************************************************
 *
 *  Software License Agreement
 *
 *  Copyright (c) 2020, Christoph Rösmann, All rights reserved.
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
 *
 *  Authors: Christoph Rösmann
 *********************************************************************/

#ifndef SYSTEMS_SIMPLE_CAR_H_
#define SYSTEMS_SIMPLE_CAR_H_

#include <mpc_local_planner/systems/base_robot_se2.h>

#include <cmath>

namespace mpc_local_planner {

class SimpleCarModel : public BaseRobotSE2
{
 public:
    SimpleCarModel() = default;

    SimpleCarModel(double wheelbase) : _wheelbase(wheelbase) {}

    // implements interface method
    SystemDynamicsInterface::Ptr getInstance() const override { return std::make_shared<SimpleCarModel>(); }

    // implements interface method
    int getInputDimension() const override { return 2; }

    // implements interface method
    void dynamics(const Eigen::Ref<const StateVector>& x, const Eigen::Ref<const ControlVector>& u, Eigen::Ref<StateVector> f) const override
    {
        assert(x.size() == getStateDimension());
        assert(u.size() == getInputDimension());
        assert(x.size() == f.size() && "SimpleCarModel::dynamics(): x and f are not of the same size, do not forget to pre-allocate f.");

        f[0] = u[0] * std::cos(x[2]);
        f[1] = u[0] * std::sin(x[2]);
        f[2] = u[0] * std::tan(u[1]) / _wheelbase;
    }

    // implements interface method
    bool getTwistFromControl(const Eigen::Ref<const Eigen::VectorXd>& u, geometry_msgs::Twist& twist) const override
    {
        assert(u.size() == getInputDimension());
        twist.linear.x = u[0];
        twist.linear.y = twist.linear.z = 0;

        twist.angular.z = u[1];  // warning, this is the angle and not the angular vel
        twist.angular.x = twist.angular.y = 0;

        return true;
    }

    void setWheelbase(double wheelbase) { _wheelbase = wheelbase; }
    double getWheelbase() const { return _wheelbase; }

 protected:
    double _wheelbase = 1.0;
};

class SimpleCarFrontWheelDrivingModel : public SimpleCarModel
{
 public:
    SimpleCarFrontWheelDrivingModel() = default;

    SimpleCarFrontWheelDrivingModel(double wheelbase) : SimpleCarModel(wheelbase) {}

    // implements interface method
    SystemDynamicsInterface::Ptr getInstance() const override { return std::make_shared<SimpleCarFrontWheelDrivingModel>(); }

    // implements interface method
    void dynamics(const Eigen::Ref<const StateVector>& x, const Eigen::Ref<const ControlVector>& u, Eigen::Ref<StateVector> f) const override
    {
        assert(x.size() == getStateDimension());
        assert(u.size() == getInputDimension());
        assert(x.size() == f.size() &&
               "SimpleCarFrontWheelDrivingModel::dynamics(): x and f are not of the same size, do not forget to pre-allocate f.");

        f[0] = u[0] * std::cos(x[2]);
        f[1] = u[0] * std::sin(x[2]);
        f[2] = u[0] * std::sin(u[1]) / _wheelbase;
    }
};

}  // namespace mpc_local_planner

#endif  // SYSTEMS_SIMPLE_CAR_H_