sensor.h

/**
 * This file contains the declaration for a class that holds
 * the necessary functions and data to process raw data taken
 * by the ATS's onboard sensors.
 *
 * A sensor object contains a single variable, offset, which
 * corresponds to the launch vehicle's initial elevation above
 * sea-level. It also includes several functions which can be used
 * to process raw sensor data into useable data for the prediction
 * and control algorithm.
 */

#ifndef SENSOR_H
#define SENSOR_H

#ifndef ATS_INT_H
#define ATS_INT_H
#include "ATS_int.h"
#endif


class sensor
{

    private:
    /* altitude above ground level (AGL) = altitude above sea level (ASL) - offset */
    double offset;

    public:

    sensor();

    /**
     * This function is to be called once the launch vehicle is on the 
     * pad, but before launch. The result is to set the offset variable
     * to the launch pad's elevation above sea level. Subsequent
     * measurements of the altitude will subtract this offset to return
     * an altitude AGL.
     *
     * Inputs: a1, a2, a3, a4 : raw value of each of the 4 ATS altimeters
     *
     * Outputs: None
     */
    void zero_altimeters(double a1, double a2, double a3, double a4);
  
    /**
     * Given a current state along with the raw value from each of the 
     * 4 altimeters, this function returns the calculated vertical velocity.
     * It does this by performing a calculation of finite differences on the
     * altitude calculation, with appropriate corrections for accuracy.
     *
     * Inputs: 
     * X_tm1 : previous state
     * a1, a2, a3, a4 : raw value of each of the 4 altimeters
     *
     * Outputs: calculated vertical speed
     */
    double get_vertical_speed(state_t X_tm1, double a1, double a2, 
                              double a3, double a4);

    /**
     * Given a previous state along with the current raw value from each of the
     * 4 altimeters, this function returns the calculated altitude AGL.
     *
     * Inputs:
     * X_tm : current state
     * a1, a2, a3, a4 : raw value of each of the 4 altimeters
     *
     * Outputs: calculated altitude AGL
     */
    double get_altitude(state_t X_tm1, double a1, double a2, double a3, double a4);

    /**
     * This function returns the calculated polar angle.
     * The polar angle is the angle between the longitudinal axis of the
     * launch vehicle and the vertical direction.
     *
     * Inputs: 
     * th_y : y Euler angle in radians
     * th_z : z Euler angle in radians
     *
     * Outputs: 
     * calculated polar angle in radians
     */
    double get_polar_angle(double th_y, double th_z);

    /**
     * This trivial polar angle calculation function is used to provide a uniform
     * API in the case that polar angle is directly measurable.
     */
    double get_polar_angle(double th);

};

#endif