Page Comparison

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• Transition to landing from any state

• Automated with pilot override

• Initiate constant speed gaussian profile for descent

  If accurate GPS or Ground height sensor:

  Gaussian profile/deceleration on approach to ground

  velocity

• Landing Detection

• Emergency state (Can be automatically transitioned to on coms loss)

• Uneven landing surface

  • Eg, Only half drone experiencing ground effect, try not to crash

• Spin-down after landing is detected

The Plan:

Add a single landing state to MVP first:

• At signal (Not when powered on) can descend using a state in path manager that

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• passes targets to attitude manager

• At another signal transitions out of landing state

• When altitude has been constant for a few seconds and below threshold then transition out of landing.

Later steps:

• Ensure drone is in a hover before descending

• After descent, transitions to a standby or disarmed state

• Update the target ground height with a sensor (Would be nice to stop assuming earth is flat)

• Use Passby control to “spin down” motors to 20% throttle after landing (in standby state), increases motor longevity and can prevent motor cogging.

• Use optical Flow sensor to keep waypoint targets perfectly vertical

• Add a better landing detection system (possibly with optical flow sensor)

Path Manager Component:

Call the LandingTakeoffManager to calculate the waypoints to follow to get to the ground. Feed that data into the waypoint manager.

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the Attitude Manager.

Landing Detection:

This may require a sensor (optical flow) or something as simple as a limit switch attached to an antenna pointed at the ground. When landing is detected, the drone will either directly transition to the next mode or move to spin down/cool off the motors

Velocity-based Landing Takeoff Manager:

Use Gaussian Profile equation to generate a velocity:

https://www.desmos.com/calculator/tjtx8ogtno

Waypoint-based Landing Takeoff Manager (Not for 2023 Competition):

Not in use as velocity target provide smoother flight.

Use waypoints as targets that the drone attempts to meet at a set frequency. As drone approaches target, shorten the distance to the next waypoint to slow down drone ascent.

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Note that for low altitude landings the done will not use the higher descent velocity part of the profile right at the start and instead will be given the slower descent speed so the drone does not accelerate into the ground.

Landing Detection:

This may require a sensor or something as simple as a limit switch attached to an antenna pointed at the ground. When landing is detected, the drone will either directly transition to the next mode or move to spin down/cool off the motors

Code Prototype:

For calculating waypoint targets after the ground height sensor has been checked to see if the drone has landed.

_PathData LandingTakeoffManager::createLandingWaypoint(const SFOutput_t & input)
{
    // Use current Lat/long if origin not known
    if (landingLat == -1 and landingLong == -1) {
        landingLat = input.latitude;
        landingLong = input.longitude;
    }
    _PathData desiredWaypoint;

    desiredWaypoint.latitude = landingLat;
    desiredWaypoint.longitude = landingLong;
    desiredWaypoint.waypointType = LANDING_WAYPOINT;

    int curAltitude = input.altitude;

    desiredWaypoint.altitude = getLandingAltitudeTarget(curAltitude, groundHeight);

    return desiredWaypoint;
}

double LandingTakeoffManager::getLandingAltitudeTarget(double curAltitude, double targetAltitude)
{
    double waypointTarget;
    double droneHeight = (curAltitude - targetAltitude);
    if (droneHeight < 1.0) {
        // Touchdown speed of 0.1 m/s, set as waypoint targets at PM Freq
        waypointTarget = curAltitude - (0.1 / PM_FREQ);
    } else {
        // Scale descent velocity based on 0.2 * height (Eg. 0.4 m/s at 2m)
        // Use altitude waypoint targets geing calculated at PM Freq
        waypointTarget = droneHeight * (0.2 / PM_FREQ);
    }
    return waypointTarget;
}

Future Landing Takeoff Manager (Not for 2022 Competition):

Use Gaussian Profile equation to generate a velocity:

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