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//  Engine.h - an engine for the drivetrain.
//  Copyright (C) 2001--2003 Sam Varner
//  This file is part of Vamos Automotive Simulator.
//  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 2 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
//  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, write to the Free Software
//  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

#ifndef _ENGINE_H_
#define _ENGINE_H_

#include <vamos/geometry/Conversions.h>
#include <vamos/geometry/Spline.h>
#include <vamos/geometry/Two_Point.h>
#include <vamos/body/Particle.h>

namespace Vamos_Body
  //* An engine for the drivetrain.  Although it produces a torque,
  // Engine is not derived from Component because the Engine's torque
  // is a scalar, not a vector.
  class Engine : public Particle
      // Used to calculate torque in torque_map ().
      double m_max_power;

      // Used to calculate torque in torque_map ().
      double m_peak_engine_speed;

      // The highest allowed engine speed (rev limit).
      double m_engine_speed_limit;

      // The rotational inertia of the engine.
      double m_inertia;

      // The fraction of throttle used when idling.
      double m_idle_throttle;

      // The rotational speed that the engine is set to when starting.
      double m_start_speed;

      // The engine shuts off if the rotational speed goes below this
      // value. 
      double m_stall_speed;

      // The rate of fuel consumption.
      double m_fuel_consumption;

      // The rotational speed of the engine.
      double m_rotational_speed;

      double m_last_rotational_speed;

      // The throttle position.
      double m_gas;

      // The load on the engine from the clutch.
      double m_drag;

      double m_transmission_speed;

      // true if the gas tank is empty, false otherwise.
      bool m_out_of_gas;

      // The minimum throttle position.
      double m_idle;

      // The current torque produced by the engine.
      double m_drive_torque;

      // The impulse calculated in the last call to torque ().
      double m_drive_impulse;

      // true if the clutch is fully engaged, false otherwise.
      bool m_engaged;
      // Return the torque for a given throttle setting, GAS, and engine
      // speed ROTATIONAL_SPEED.
      double torque_map (double gas, double rotational_speed);

    Vamos_Geometry::Spline m_torque_curve;

    double m_friction;

      //** Constructor
      // MAX_POWER is in the correct derived units (Watts in SI), 
      // PEAK_ENGINE_RPM is in rotations per minute.
      Engine (double mass, const Vamos_Geometry::Three_Vector& position, 
                  double max_power,
                  double peak_engine_rpm,
                  double rpm_limit,
                  double inertia,
                  double idle_throttle,
                  double start_rpm,
                  double stall_rpm,
                  double fuel_consumption);

      void set_torque_curve (const std::vector <Vamos_Geometry::Two_Point>& 

    void set_friction (double friction) { m_friction = friction; }

      // Handle the input parameters.  GAS is the throttle position.
      // TRANSMISSION_SPEED is the rotational speed of the transmission
      // side of the clutch.  DRAG is the torque due to friction when
      // the clutch is not fully engaged.  ENGAGED is true when the
      // clutch is fully engaged, false otherwise.
      void input (double gas, double drag, double transmission_speed, 
                        bool engaged);

      void find_forces ();

      // Advance the engine in time by TIME.
      void propagate (double time);
      void rewind ();

      // Return the current rotational speed in radians per second.
      double rotational_speed () const { return m_rotational_speed; }

      // Return the engine speed where the rev limiter kicks in.
      double max_rotational_speed () const { return m_engine_speed_limit; }

      double peak_engine_speed () const { return m_peak_engine_speed; }
      // Return the current torque.
      double drive_torque () const { return m_drive_torque; }

      double drive_impulse () const { return m_drive_impulse; }

      double throttle () const { return m_gas; }

      // Return the current rate of fuel consumption. 
      double fuel_rate () const 
      { return m_fuel_consumption * m_rotational_speed * m_gas; }

      // Tell the engine if we're out of gas.
      void out_of_gas (bool out) { m_out_of_gas = out; }

      // Start the engine.
      void start () { speed (m_start_speed); }
      // Set the engine speed to SPEED_IN and calculate the resulting
      // impulse.
      void speed (double speed_in);
      void set_rotational_speed(double newrs) {m_rotational_speed = newrs; m_last_rotational_speed = newrs;}
      double drag() {return m_drag;}
      void set_drag(double newdrag) {m_drag = newdrag;}
      double max_power() {return m_max_power;}
      double stall_speed() {return m_stall_speed;}

#endif // !_ENGINE_H_

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