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Appendix J. CL Controller App - Input UDP Data Format

The CL Controller is a new app which combines the loading test functions available in the Driver Test App with a new operating mode which accepts loading command data from 3rd party apps via UDP.

This allows 3rd party apps to control the CL drive cards via the CL Controller. Applies to CL_SPU_USB and BLDRV3 cards only.

NOTE the CL Controller can not drive the same CL_SPU_USB card at the same time as the main CL Software. So if the CL Software AND the CL Controller are to be used at the same time then two CL_SPU_USB cards with their own BLDRV3 drives are required.

Installation:

The CL Controller is included in the main CL software download zip in the Driver Test App folder.

Operation:

NOTE: if the CL Controller is being used to provide specialised axes at the same time as the main BFF CL Software is driving the main control axes then the CL Software CL_SPU_USB card should be jumper set as "Pilot", and the CL Controller should connect to the jumper set Co_Pilot CL_SPU_USB card. Parameter CP_Ignore should be set =1 in the Background.ini file to instruct the main CL Software to then ignore any Co-Pilot CL_SPU card.

The CL Controller should be running and the UDP Input radio button selected to make the UDP data mode active.

When running in UDP input mode, the CL Controller will listen for UDP data on the Port and IP Address specified in the CL_Controller ini file (also shown on the GUI). You must write your own application to send valid loading data. The data format is shown below.

WARNING - Improperly formatted or controlled user loading input data can produce erratic or uncontrolled force and movement outputs at the driven flight control motors - you must thoroughly test your UDP data "feeder" application before making the card output live to connected flight controls.

Use the progress bar displays on the CL Controller to monitor the output force demands that result from your Feeder application before driving live flight controls. A UDP data view window is also provided to allow visual inspection of received data packets.

UDP Data Formats:

When in UDP Input mode the CL Controller looks for loading control data in 180 byte packets received by UDP on the Port and IP Address specified in the CL_Controller.ini config file (parameters Port and IPAddress in the [Comms] section).

The CL Controller will return a 50 byte response packet on each input packet receive. This UDP return will be via port Port+1 to the IP Address and Port specified by the feeder app within the 180 byte input packet.

The 180 byte input packet format is:

UChar = 8 bit (1 byte) unsigned integer (value 0-255)

UShort = 16 bit (2 byte) unsigned integer

Short = 16 bit (2 byte) signed integer

UInt = 32 bit (4 byte) unsigned integer

Int = 32 bit (4 byte) signed integer

Float = 32 bit (4 byte) floating point number

The frequency of data packets should typically be about 50Hz to match the command rate of the CL Controller to the drive cards

You should experiment to obtain processing rates to suit your application. If the data packets arrive faster than the CL Controller can process them it will simply drop unused packets.

The UDP_Display button on the GUI can be use to display the incoming UDP data.

UDP Return Packet Format:

The CL Controller will return a 50 byte response packet on each input packet receive. This UDP return will be via port Port+1 to the IP Address and Port specified by the Feeder app in the 180 byte input packet.

The 50 byte return packet format is:

Test Feeder Application:

The download zip package contains a test "Feeder" application which can be used to confirm UDP comms with the CL Controller. The Feeder application can pull position data from the x, y & z axes of the joystick specified in the Sender.cfg file and use this to set load or stiffness components to send to the CL Controller. It will send the data to the CL Controller using correctly formatted UDP packets. If UDP comms are active the data will appear at the CL Controller....

The test Feeder app will also display returned response packets from the CL Controller if the UDP comms are correctly configured.

The port and IP address settings for the Feeder should be made in the Sender.cfg file.

This is intended for checking UDP comms only - DO NOT use this facility to control live flight controls.

Demonstration Steering Tiller Feeder Application:

A demonstration feeder app is also provided in the download zip which provides simple loading for a heavy jet steering tiller axis.

Further information here....

Comments:

The data components used in the data packets are designed to suit control loader type applications. In particular the spring rate parameter (spring force coefficient) should be used when loading proportional to control displacement is present. The fixed force parameter should be used for slower changing forces only. In order to maintain stability in the drive it is important to minimise lag between axis position changes and the responding torque demand applied to the motors when there is a possibility that the position can change rapidly. The most critical type of loading in this regard is force that changes directly with stick displacement such as aerofoil lift forces. By using a spring rate term the critical calculations for this type of loading can be carried out onboard the BLDRV3 cards and so minimise the lag between position feedback and torque response. These onboard calculations are carried out once every 2ms (ie at 500Hz) and ensure that the torque demand output "keeps up" even with fast changing stick position and so ensures stability of the drive by preventing unstable oscillations from developing.

The principal applies to other applications in which there is a significant force component which changes directly in response to axis position change.

Updates:

V0.91 adds a new window which displays monitoring data for the APUC movements of the controls. This requires recent BLDRV3 card firmware to operate.

If you find any bugs or strange behaviours in the beta version then please let me know.

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