191 lines
6.8 KiB
Text
191 lines
6.8 KiB
Text
# This is a small script that adjusts autopilot target values to track
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# (fly in formation with) an AI or Multiplayer aircraft.
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# Quick start instructions:
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#
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#
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# 1. Copy this file into $FGROOT/data/Nasal (along with the other
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# system nasal scripts.)
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#
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# 2. Start up FlightGear selecting an airplane with a reasonably configured
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# autopilot that responds to and works with the standard autopilot
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# dialog box (F11). The MiG 15 is one that works, the 777-200 works,
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# the Citation Bravo does not work, the default c172 probably does not
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# work, etc.
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#
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# 3. Take off and establish stable flight.
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#
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# 4. Open the property browser (File->Browse Internal Properties) and navigate
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# to /ai/models/ Choose one of the available aircraft[] or multiplayer[]
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# entries. You can look at all those subtrees to find the call sign you
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# want. Also note that the subtree for each entity has a radar area that
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# will show range and offset from your current heading.
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#
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# 5. Open a second property browser window (upper left click box in the first
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# property browser window.) Navigate to /autopilot/target-tracking/
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#
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# 6. Set "/autopilot/target-tracking/target-root" to point to the entity
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# path you discovered in step #4. For instance, this should be set to
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# something like /ai/models/multiplayer[2] or /ai/models/aircraft[0]
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#
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# 7. Set "/autopilot/target-tracking/goal-range-nm" to the follow distance
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# you want.
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#
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# 8. Set "/autopilot/target-tracking/enable" = 1, this will turn on the radar
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# computation for each ai/multiplayer entity and will tell the tracking
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# script to start updating the autopilot settings.
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#
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# 9. Open up the autopilot configuration window (F11) and activate any of the
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# heading, pitch, and speed axes. The script will begin updating the heading
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# bug angle, the "speed with throttle" value, and the "altitude hold" value.
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#
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# 10. You can choose to mix and match any of the autopilot modes you want, i.e.
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# you could turn off the heading control and turn manually while the system
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# holds speed and altitude for you.
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#
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# 11. It always helps to have a sensible target arcraft to chase. You are
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# flying within the turn radius and climb rate limits of your autopilot.
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#
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# Don't forget you are pilot in command and at all times responsible for
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# maintaining safe airspeed and altitude.
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#
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# Enjoy the ride!
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# print("Target Tracking script loading ...");
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# script defaults (configurable if you like)
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default_update_period = 0.05;
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default_goal_range_nm = 0.05;
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default_target_root = "/ai/models/aircraft[0]";
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default_min_speed_kt = 120;
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# master enable switch
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target_tracking_enable = 0;
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# update period
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update_period = default_update_period;
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# goal range to acheive when following target
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goal_range_nm = 0;
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# minimum speed so we don't drop out of the sky
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min_speed_kt = 0;
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# Target property tree root
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target_root = "";
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# Initialize target tracking
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TrackInit = func {
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target_tracking_enable = getprop("/autopilot/target-tracking/enable");
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if ( target_tracking_enable == nil ) {
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target_tracking_enable = 0;
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setprop("/autopilot/target-tracking/enable", target_tracking_enable);
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}
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update_period = getprop("/autopilot/target-tracking/update-period");
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if ( update_period == nil ) {
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update_period = default_update_period;
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setprop("/autopilot/target-tracking/update-period", update_period);
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}
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goal_range_nm = getprop("/autopilot/target-tracking/goal-range-nm");
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if ( goal_range_nm == nil ) {
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goal_range_nm = default_goal_range_nm;
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setprop("/autopilot/target-tracking/goal-range-nm", goal_range_nm);
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}
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min_speed_kt = getprop("/autopilot/target-tracking/min-speed-kt");
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if ( min_speed_kt == nil ) {
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min_speed_kt = default_min_speed_kt;
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setprop("/autopilot/target-tracking/min-speed-kt", min_speed_kt);
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}
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target_root = getprop("/autopilot/target-tracking/target-root");
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if ( target_root == nil ) {
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target_root = default_target_root;
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setprop("/autopilot/target-tracking/target-root", target_root);
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}
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}
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settimer(TrackInit, 0);
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# If enabled, update our AP target values based on the target range,
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# bearing, and speed
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TrackUpdate = func {
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target_tracking_enable = getprop("/autopilot/target-tracking/enable");
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update_period = getprop("/autopilot/target-tracking/update-period");
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if ( target_tracking_enable == 1 ) {
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# refresh user configurable values
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goal_range_nm = getprop("/autopilot/target-tracking/goal-range-nm");
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target_root = getprop("/autopilot/target-tracking/target-root");
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# force radar debug-mode on (forced radar calculations even if
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# no radar instrument and ai aircraft are out of range
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setprop("/instrumentation/radar/debug-mode", 1);
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my_hdg_prop = sprintf("/orientation/heading-magnetic-deg" );
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my_hdg = getprop(my_hdg_prop);
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my_hdg_true_prop = sprintf("/orientation/heading-deg" );
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my_hdg_true = getprop(my_hdg_true_prop);
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alt_prop = sprintf("%s/position/altitude-ft", target_root );
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alt = getprop(alt_prop);
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if ( alt == nil ) {
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print("bad property path: ", alt_prop);
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return;
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}
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speed_prop = sprintf("%s/velocities/true-airspeed-kt", target_root );
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speed = getprop(speed_prop);
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if ( speed == nil ) {
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print("bad property path: ", speed_prop);
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return;
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}
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range_prop = sprintf("%s/radar/range-nm", target_root );
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range = getprop(range_prop);
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if ( range == nil ) {
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print("bad property path: ", range_prop);
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return;
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}
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h_offset_prop = sprintf("%s/radar/h-offset", target_root );
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h_offset = getprop(h_offset_prop);
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if ( h_offset == nil ) {
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print("bad property path: ", h_offset_prop);
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return;
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}
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if ( h_offset > -90 and h_offset < 90 ) {
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# in front of us
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range_error = range - goal_range_nm;
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} else {
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# behind us
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range_error = goal_range_nm - range;
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}
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target_speed = speed + range_error * 100.0;
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if ( target_speed < min_speed_kt ) {
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target_speed = min_speed_kt;
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}
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setprop( "/autopilot/settings/target-altitude-ft", alt );
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setprop( "/autopilot/settings/heading-bug-deg", my_hdg + h_offset );
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setprop( "/autopilot/settings/true-heading-deg",
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my_hdg_true + h_offset );
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setprop( "/autopilot/settings/target-speed-kt", target_speed );
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}
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# last thing to do before we return from this function
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registerTimer();
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}
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# timer handling to cause our update function to be called periodially
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registerTimer = func {
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settimer(TrackUpdate, update_period );
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}
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registerTimer();
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