pitch yaw control

package net.sf.openrocket.simulation.listeners.example;

import net.sf.openrocket.aerodynamics.FlightConditions;
import net.sf.openrocket.rocketcomponent.FinSet;
import net.sf.openrocket.rocketcomponent.RocketComponent;
import net.sf.openrocket.simulation.FlightDataType;
import net.sf.openrocket.simulation.SimulationStatus;
import net.sf.openrocket.simulation.exception.SimulationException;
import net.sf.openrocket.simulation.listeners.AbstractSimulationListener;
import net.sf.openrocket.unit.UnitGroup;
import net.sf.openrocket.util.MathUtil;

/**
 * An example listener that applies a PI-controller to adjust the cant of fins
 * named "CONTROLPY" to control the rocket's pitch (for now) and yaw (l8r).
 *
 * @author Sampo Niskanen <sampo.niskanen@iki.fi>
 * modified by me
 */
public class PitchYawControlListener extends AbstractSimulationListener {

    // Name of control fin set
    private static final String CONTROL_FIN_NAME1 = "CONTROLPYLEFT";
    private static final String CONTROL_FIN_NAME2 = "CONTROLPYRIGHT";

    // Define custom flight data type
    private static final FlightDataType FIN_CANT_TYPE = FlightDataType.getType("Control fin cant", "\u03B1fc", UnitGroup.UNITS_ANGLE);

    // Simulation time at which PID controller is activated
    private static final double START_TIME = 0.5;

    // Desired pitch rate (rad/sec)
    private static final double SETPOINT = 0.0;

    // Maximum control fin turn rate (rad/sec)
    private static final double TURNRATE = 10 * Math.PI / 180;

    // Maximum control fin angle (rad)
    private static final double MAX_ANGLE = 15 * Math.PI / 180;


    /*
     * PID parameters
     *
     * At M=0.3 KP oscillation threshold between 0.35 and 0.4.    Good KI=3
     * At M=0.6 KP oscillation threshold between 0.07 and 0.08    Good KI=2
     * At M=0.9 KP oscillation threshold between 0.013 and 0.014  Good KI=0.5
     */
    private static final double KP = 0.007;
    private static final double KI = 0.2;




    private double pitchrate;
    private double prevTime = 0;
    private double intState = 0;
    private double finPosition = 0;



    @Override
    public FlightConditions postFlightConditions(SimulationStatus status, FlightConditions flightConditions) {
        // Store the current pitch rate for later use
        pitchrate = flightConditions.getPitchRate();
        return null;
    }


    @Override
    public void postStep(SimulationStatus status) throws SimulationException {

        // Activate PID controller only after a specific time
        if (status.getSimulationTime() < START_TIME) {
            prevTime = status.getSimulationTime();
            return;
        }

        // Find the fin set named CONTROLPYLEFT
        FinSet finset1 = null;
        for (RocketComponent c : status.getConfiguration()) {
            if ((c instanceof FinSet) && (c.getName().equals(CONTROL_FIN_NAME1))) {
                finset1 = (FinSet) c;
                break;
            }
        }
        if (finset1 == null) {
            throw new SimulationException("A fin set with name '" + CONTROL_FIN_NAME1 + "' was not found");
        }

        // Find the fin set named CONTROLPYRIGHT
        FinSet finset2 = null;
        for (RocketComponent c : status.getConfiguration()) {
            if ((c instanceof FinSet) && (c.getName().equals(CONTROL_FIN_NAME2))) {
                finset2 = (FinSet) c;
                break;
            }
        }
        if (finset2 == null) {
            throw new SimulationException("A fin set with name '" + CONTROL_FIN_NAME2 + "' was not found");
        }


        // Determine time step
        double deltaT = status.getSimulationTime() - prevTime;
        prevTime = status.getSimulationTime();


        // PID controller
        double error = SETPOINT - pitchrate;

        double p = KP * error;
        intState += error * deltaT;
        double i = KI * intState;

        double value = p + i;


        // Clamp the fin angle between -MAX_ANGLE and MAX_ANGLE
        if (Math.abs(value) > MAX_ANGLE) {
            System.err.printf("Attempting to set angle %.1f at t=%.3f, clamping.\n",
                    value * 180 / Math.PI, status.getSimulationTime());
            value = MathUtil.clamp(value, -MAX_ANGLE, MAX_ANGLE);
        }


        // Limit the fin turn rate
        if (finPosition < value) {
            finPosition = Math.min(finPosition + TURNRATE * deltaT, value);
        } else {
            finPosition = Math.max(finPosition - TURNRATE * deltaT, value);
        }

        // Set the control fin cant and store the data
        finset1.setCantAngle(finPosition);
        finset2.setCantAngle(finPosition*-1);
        status.getFlightData().setValue(FIN_CANT_TYPE, finPosition);

    }
}