737NG Moving throttle handles using Stepper motors

[olealm]

Started planning 737NG Autothrottle.

Have a few questions, hoping a kind gentleman with experience could give me answers..

- Stepper motors.. As I understand it there is no feedback from the motor itself, like there are from servos. Movement is based on pulses given from a controller moving the motor a certain amount of steps clockwise or counter-clockwise. "Calibration" is based on the controller "counting" number of pulses given (+/-) thus calculating the position. So far so good, but what happens when A/T is off and the handles are moved manually. Invoking any speedmode or TOGA thereafter - wouldnt the controller then have lost its knowledge of the current position??

- Anyone successfully used Steppermotors and FSBUS to implement moving throttles? Program example for FSBUS Router?

- Is there ONE FSUIPC Offset (for MCP or CDU auto-throttle setting) that can be used as input for controlling the throttle levers? Or are there many offsets depending on which mode is active?

[AndreasH22]

Hello!

Im also building my autothrottle.

For calculating the position of the lever you have to use a potentiometer. With fsbus you should be able to write a programm in ccc which moves the lever with the stepper according to the fsuipc offset for the lever position e.g. 088C for engine 1(see throught the sdk)


If autothrottle is armed the lever is moved by the stepper according to the offset. If you mave it manually the potentiometer reads the position and sends it to fsuipc.


I haven`t tryed it jet becouse I use IOCards. but the way it should work is very similar.


regards,

andreas

[olealm]

Hi, Andreas!

Makes sence to me, but I cant seem to understand how the FSBUS stepper controller can cope with the throttle levers having been manually moved between two A/T events.

When in no A/T the steppers will have to be "shut down" and the stepper controller will have no idea of the position of the levers. The steppers will move with the manual positioning but the stepper controller will not "sence" the movment. Then suddenly it gets a new setpiont upon A/T enabled, remembering the last position when A/T was disarmed.

Say the current position was 50% when A/T was disarmed. You control the throttle manually and leave it at 20% when enabling a speed mode. The MCP commands 50% throttle, but the Stepper controller thinks all is OK since it was at 50% "last time". What is should do was stepping up the levers 30%.

Or do you mean introducing a "controller" in CCC calculating setpoints to the stepper controller based on AI input and the FSUIPC offset?

What maybe could ease up things was if the stepper controller was always controlling the steppers based on the offset (both in armed and disarmed A/T) and using an eletrical operated clutch to connect the stepper motor axis to the lever when in TOGA or any other A/T mode ?

Really appreciating this discussion! I obviously have lots to learn in this field.

[AndreasH22]

Hi,

The way to use a clutch is in fact a way to solve this problem but not really cheap!

Im going to try to programm a kind of automatic control loop.

Every time the AT is armed the program reads the position of the lever from the potentiometer. Then it reads the fsuipc offset to know where the lever "sould be"

The programm compares these two values to know in wich direction and angle the stepper has to move the trottle to get the differece between the two values near to zero.

I haven`t tried it yet becouse I have just one stepper at the time.


regards,
andreas

[AndreasH22]

Hi,

The way to use a clutch is in fact a way to solve this problem but not really cheap!

Im going to try to programm a kind of automatic control loop.

Every time the AT is armed the program reads the position of the lever from the potentiometer. Then it reads the fsuipc offset to know where the lever "sould be"

The programm compares these two values to know in wich direction and angle the stepper has to move the trottle to get the differece between the two values near to zero.

I haven`t tried it yet becouse I have just one stepper at the time.


regards,
andreas

[olealm]

Sounds interesting, Andreas.

Building control loops isn't the easiest task, but hopefully achievable in CCC.

Anyway, I have sent Dirk a mail asking for his input on this.

Lets get back to this if anything new!

[AndreasH22]

ok then I will try it with IOCards inthe next weeks an let you know my results!


good luck,

andreas