ardupilot/libraries/AP_Scripting/examples/Aerobatics/Trajectory

Scripted Aerobatics

The lua script "plane_aerobatics.lua" implements scripted aerobatics, allowing fixed wing aircraft to execute a number of aerobatic manoeuvres either in AUTO mission or by triggering using pilot commands using RC switches.

As always, but particularly with scriped aerobatics, test in SITL until you understand the function and behaviour of each manouver. You will need an appropriate aircraft, and be ready to take manual control if necessary!

Available Manoeuvres

The following table gives the available manoeuvres. Each manoeuvre has an ID number which is used in the AUTO mission or in the TRIKn_ID parameters (described below). The "Turnaround" column indicates if the manoeuvre results in a course reversal, which impacts how it is used in AUTO missions.

ID	Name	Arg1	Arg2	Arg3	Arg4	Turnaround
1	Figure Eight	radius	bank angle			No
2	Loop	radius	bank angle	num loops		No
3	Horizontal Rectangle	length	width	radius	bank angle	No
4	Climbing Circle	radius	height	bank angle		No
5	vertical Box	length	height	radius		No
6	Immelmann (FastRoll)	radius				Yes
7	Straight Roll	length	num rolls			No
8	Rolling Circle	radius	num rolls			No
9	Half Cuban Eight	radius				Yes
10	Half Reverse Cuban Eight	radius				Yes
11	Cuban Eight	radius				No
12	Humpty Bump	radius	height			Yes
13	Straight Flight	length	bank angle			No
14	Scale Figure Eight	radius	bank angle			No
15	Immelmann Turn	radius				Yes
16	Split-S	radius				Yes
17	Upline-45	radius	height gain			No
18	Downline-45	radius	height loss			No
19	Stall Turn	radius	height	direction		Yes
20	Procedure Turn	radius	bank angle	step-out		Yes
21	Derry Turn	radius	bank angle			No
22	Two Point Roll	length				No
23	Half Climbing Circle	radius	height	bank angle		Yes
24	Crossbox Humpty	radius	height			Yes
25	Laydown Humpty	radius	height			Yes

Note: In the script you will find other (specialised) manouvers which do not appear in the 'command table'. These tend to be specialised manouvers which may expect an inverted entry or finish inverted as well - so will not end well if started upright at a low altitude! These manouvers are used in some of the schedules defined below.

Available Schedules (pre-defined sequences of manouvers)

The following table gives the available pre-defined schedules. Each schedule has an ID number which is used in the AUTO mission or in the TRIKn_ID parameters (described below).

ID	Name
200	Test Suite (dont fly!)
201	NZ Clubman Schedule
202	FAI F3A P-23 (left to right)
203	FAI F3C Scale Example (left to right)
204	AirShow

Note: ID's 202-203 are best flown with a mission start point 150m out from the pilot, with the prior and subsequent mission waypoints in a straight line with the model starting teh script flying down wind. ID 201 is best started in teh same manner, but the model positioned 100m out from the pilot.

Loading the script

Put the plane_aerobatics.lua script on your microSD card in the APM/SCRIPTS directory. You can use MAVFtp to do this.

Then set

• SCR_ENABLE = 1
• SCR_HEAP_SIZE = 250000
• SCR_VM_I_COUNT = 200000

You will need to refresh parameters after setting SCR_ENABLE. Then reboot to start scripting.

Aircraft Setup

The aircraft needs to be setup to perform well in ACRO mode. You need to enable the yaw rate controller by setting:

• YAW_RATE_ENABLE = 1
• ACRO_YAW_RATE = 90

The ACRO_YAW_RATE depends on the capabilities of the aircraft, but around 90 degrees/second is reasonable.

You need to tune the yaw rate controller by flying in AUTOTUNE mode and moving the rudder stick from side to side until the yaw rate tuning is reported as being finished.

Use In AUTO Missions

To use in an AUTO mission you can create waypoint missions containing NAV_SCRIPT_TIME elements (shown as SCRIPT_TIME in MissionPlanner). These mission items take the following arguments:

• the command ID from the table above
• the timeout in seconds
• up to four arguments as shown in the above table

The aerobatics system will use the location of the previous and next waypoints to line up the manoeuvre. You need to plane a normal waypoint just before the location where you want to start the manoeuvre, then the NAV_SCRIPT_TIME and then a normal waypoint after the manoeuvre.

Use with "tricks on a switch"

You can trigger the manoeuvres using RC switches, allowing you to have up to 11 tricks pre-programmed on your transmitter ready for use in fixed wing flight. You can trigger the tricks in the following flight modes:

• CIRCLE
• STABILIZE
• ACRO
• FBWA
• FBWB
• CRUISE
• LOITER

To setup tricks you need to first set the parameter TRIK_ENABLE to 1.

After setting TRIK_ENABLE, either restart scripting or reboot. Then set TRIK_COUNT to the number of tricks you want to make available, with a maximum of 11.

After setting TRIK_COUNT, reboot and refresh parameters. You will find you will now have 5 parameters per trick.

• TRIKn_ID
• TRIKn_ARG1
• TRIKn_ARG2
• TRIKn_ARG3
• TRIKn_ARG4

The ID parameter is the manoeuvre from the above table, and the arguments are the arguments to each manoeuvre.

Now you need to setup your two control channels. You should have one 3 position switch for activating tricks, and one knob or switch to select tricks. It is best to use a knob for the trick selector so you can have up to 11 tricks.

Work out which RC input channel you want to use for activation (a 3 position switch) and set

• RCn_OPTION = 300

Then work out what RC input channel you want to use for selection and set

• RCn_OPTION = 301

Flying with tricks

When the activation channel (the one marked with option 300) is in the middle position then when you move the knob it will display the currently selected trick.

To activate a trick you move the activation channel to the top position, and the trick will run.

Moving the activation switch to the bottom position cancels any running trick and stops the trick system.

Changing flight modes will also cancel any active trick.