User`s manual

AscTec Hummingbird with AutoPilot User’s Manual
transmit all structures that were requested and wait
for the next poll. Due to the limited bandwidth of al-
most all kinds of radio modems it is recommended
that you only request (poll) the packets you need, e.g.
if you are only interested in the computed pitch and
roll angles you should only poll IMU
CalcData and
none of the other packets.
4.2.2 Command input
Operation
The serial command interface must be enabled by
the switch on channel 5 of your 35 MHz or 72 MHz
R/C. Please use the AscTec AutoPilot PC-Software
to see which position of the switch enables the serial
interface.
During operation through the serial command inter-
face the R/C has to stay on all the time to enable a
safety pilot to take over if the autonomous control is
not working as desired. Please make sure that there
is always a safety pilot ready to immediately disable
the serial interface and to take manual control of the
vehicle.
Data protocol
The current control dataset must be available in the
following format:
struct CTRL_INPUT { //serial commands
→
(= Scientific Interface)
short pitch; //Pitch input:

→
-2047..+2047 (0=neutral)
short roll; //Roll input:

→
-2047..+2047 (0=neutral)
short yaw; //(=R/C Stick input)

→
-2047..+2047 (0=neutral)
short thrust; //Collective: 0..4095

→
= 0..100%
short ctrl; /
*
control byte:
bit 0: pitch control enabled
bit 1: roll control enabled
bit 2: yaw control enabled
bit 3: thrust control enabled
These bits can be used to only

→
enable one axis at a time and
→
thus to control the other 
→
axes manually. This usually 
→
helps a lot to set up and 
→
finetune controllers for each
→
axis seperately.
*
/
short chksum;
};
struct CTRL_INPUT CTRL_Input;
The chksum is calculated as follows right before the
structure is sent:
CTRL_Input.chksum = CTRL_Input.pitch 
→
+ CTRL_Input.roll + CTRL_Input.yaw 
→
+ CTRL_Input.thrust + CTRL_Input.
→
ctrl + 0xAAAA;
The data should be sent to the vehicle with a mini-
mum rate of 10 Hz over the XBee link as follows:
1. startstring: >*>di
2. directly followed by the above data structure,
e.g.
UART_send( &CTRL_Input, sizeof(
→
CTRL_Input));
If data is sent with significantly less than 10 Hz or
if the transmission stops completely the system will
switch back to manual control over the R/C.
4.3 System calibration
The AscTec Hummingbird with AutoPilot comes
fully calibrated. Calibration usually lasts for the
whole lifetime of the vehicle. If you feel something
is wrong with the calibration of your system please
contact Ascending Technologies for assistance.
Ascending Technologies GmbH - 17 - www.asctec.de