sc_landing_control.h

//
//  sc_landing_control.h
//  SCControl
//
//  Created by Michael Paluszek on 08/14/2017
//
//  Implements landing control
// Landing controller.
//
//   Determines the thrust vector and throttle for landing on a planet.
//   Uses a bang-bang for vertical control during terminal ascent.
//   Horizontal control is velocity damping.
//
//   This function generates throttle and thrust vector
//   orientation. Thrust vector orientation is achieved by reorienting
//   the vehicle or the engine nozzle. The reorientation controller needs
//   to be fast enough so that the engine is pointing along the desired
//   vector. You can set the throttle to zero until you reach the desired
//   orientation.
//
//   The control has four modes:
//
//   Mode 1 - Drive the vertical velocity to zero and hover
//   Mode 2 - Drive all velocities to zero
//   Mode 3 - Bang-Bang vertical control
//   Mode 4 - Engine balances gravity
//
//   vMaxFrac is the fraction of the maximum velocity allowed during Mode 3.
//   The maximum velocity is for free-fall.
//
//   This is used as the terminal control for an optimal landing
//   guidance algorithm.
//
//   When you reach mode 4 it is up to you to set the throttle to zero.
//
//   The terminal errors will depend on the time step of your controller.
//
//
 
#ifndef __SC_LANDING_CONTROL__
#define __SC_LANDING_CONTROL__
 
#include <stdio.h>
#ifdef AS_OS_WINDOWS
#include "matrixlib.h"
#else
#include <MatrixLib/MatrixLib.h>
#endif
 
 
class landing_control {
    
    private:
        bool initialized;
        double accel;           // Maximum acceleration (km/s^2)
        double gain_velocity;   // Velocity gain
        double g;               // Gravitational acceleration at the surface in (km/s^2)
        int mode;               // Mode setting 1-4
        double v_threshold;     // Rate to switch modes
        double h_touchdown;     // Landing gear height
        double v_max_frac;      // Maximum velocity during mode 3
    
        ml_matrix u_thrust;     // Thrust unit vector
        double throttle;        // Throttle setting
    
        double h_3;
        double a_mag;
    
        ml_matrix accel_demand;
    
    public:
        landing_control(void);
        ~landing_control();
        void initialize( const double accel, const double gain_rate, const double g, const double v_threshold, const double h_landing, const double v_max_frac );
        void update( const ml_matrix& v, const double h, const ml_matrix& u_v );
        bool is_initialized( void ) { return initialized;};
        double get_throttle( void ) { return throttle;};
        int get_mode( void ) { return mode;};
        ml_matrix get_thrust_unit_vector( void ){ return u_thrust; };
        void set_defaults( void );
        void set_acceleration( double a ){accel = a;};
        ml_matrix get_acceleration( void ){return accel_demand;};
 
};
 
 
#endif