Ardupilot2/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.

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).

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			No
5	vertical Box	length	height	radius		No
6	Banked Circle	radius	bank angle	height		No
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	roll rate			Yes

The "Turnaround" column indicates if the manoeuvre results in a course reversal, which impacts how it is used in AUTO missions.

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 = 200000
• 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.