Automatic throttles?

[Guest rahulsh]

Hi all,I have been dreaming about an automatic throttle a lot these days (Daydreaming is the best part of this hobby...). The idea is to use a stepper motor to drive the throttle levers and the pots. I will read the current pot level from FSBUS and the target MSFS throttle level and compare the difference in both values. Depending on the difference being positive or negative, I will step the motor in the required direction until the difference is acceptably minimum. However, a few things come to mind:1. If there are a lot of variations on the MSFS throttle settings or if the pots are not sensitive enough, the throttles may not reach a static position, especially when trying to maintain airspeed in varying wind speeds.2. Are Stepper motors strong enough to drive a home built throttle unit? Can I use the motors from an old dot matrix printer to get the results I need?3. Anyone tried to build something like this before and has any experiences to share?Rahul SharmaNew Delhi, India.vt737ng@yahoo.com

[LawnDart 19]

Hello~Having built my 777 throttle quadrant to accept motor drives for the Autopilot Commands, here is a list of my engineering hurdles1. The Throttle levers must be able to move manually without also bumping into any physical limits, such as stepper motor stops or limit switches.2. The friction coupling that allows the levers to move must be loose enough to provide just friction when the levers are moved manually, but strong enough to not slip when actuated by motors.Here's a diagram as to how I assembled my throttle levershttp://192.168.2.200/sim/throttle.gifI hope that gives you some ideas in your assembly.

[LawnDart 19]

Oops!That would be://67.170.8.23/sim/throttle2.gif

[Guest jpcxcf]

Nice and simple.Too bad my crj doesn't has AT.regards,Pedro

[Guest Alkit]

I am more concern of the the MSFS input to your propose throttle. It may damage your unit within a few minutes.Alkit

[Guest rahulsh]

>I am more concern of the the MSFS input to your propose>throttle. It may damage your unit within a few minutes.>>AlkitYes, that is what I would have wrried about as well.Ray, how do you control the autothrottle? Does it have a problem of excessive movements?Rahul SharmaNew Delhi, India.vt737ng@yahoo.com

[Guest Alkit]

I think:To allow the A/T movement work, first thing to do is the software/program side. Not the hardware. Even someone can build a perfect A/T with movement for MSFS, it will behave more like a vibrator doing funny act.may be a program which can convert and smoothen the A/T movement data inside MSFS, then export to a sense making movement output to the throttle.In fact, how does the engine work catch up with airspeed so precisely in real life?Alkit

[Guest High Octane]

A/T motor with EPIC hardware like Ray metioned does not sent data input to MSFS. It recieves data (to EPIC output card) from MSFS which will set the motor at the correct position. In otherword... If you set MCP IAS at 250 Knots the motor will align at correct position. With EPL language you can tell motor how much movement it can makes from min (idle) to max (full thrust) depending on the type of quaduant you have or one you created. I have tried that myself and it works well with EPIC. But I dont know about other interfacesGo visit Junji Hiriyama's webpage about Autothrottle mechanism, his ideas on creating AT is almost similar to mine.http://www.wakayamanet.or.jp/jun/fs/autothrottle-e.html

[Guest LGA]

I'm no expert, but surely the autothrottle works from software that is able to take the current speed and pitch of the aircraft and apply a power setting that will either raise or lower the airspeed to the target speed. As an example, when I used to fly the Piper Warriors, I remember 1950rpm's holding 60kts with a nose up pitch. Taking that idea into account, if you lowered the pitch by 2 or three degrees, it would take slightly less power to hold the airspeed, let's say 1875rpm for arguments sake. To further the point let's make a table...60kts at 15 degree pitch=1950rpm 60kts at 5 degree pitch=1850rpm 60kts at 0 degree pitch=1750rpm and 60kts at -5 pitch=1400rpm. Eventually there is a negative pitch attidude where 60kts can be maitained with idle power. If these figures are programmed for every possible combination of speed and pitch plus further programming that can take into account the weight/altitude/configuratiion/speed at which the pitch is changing of the aircraft among other variables, then there is enough lead to the autothrottles where the rest of the throttle movement is in smaller increments to catch up with the desired speed and scenario. By configuration, suppose that the programmed rpm/thrust would be increased if the gear was down or the flaps were lowered.

[Guest Mark McG]

If you read the N1 values from FS, then you can achieve this. It would also be better/more accurate than reading the throttle lever positions which could be quite jittery.

[Guest LGA]

Just a small not to mention that my previous comment speculates how AT's might work in a real aircraft, not how it can be done for a flightdeck.

[Guest mbessler]

>Just a small not to mention that my previous comment>speculates how AT's might work in a real aircraft, not how it>can be done for a flightdeck.Real Autopilots use PID Controllers/Algorithms AFAIK, so I assume the the A/T does the same. (PID stands for Proportional, Intregral, Derivative.ask google for more info if you are interested. One link that showed up was this one:http://www.expertune.com/tutor.html )In fact, using a PID for your Autothrottle at home might be a good idea.I know I could do that with flightgear since PIDs are implemented and are tuneable)Manuel

[Guest High Octane]

>I'm no expert, but surely the autothrottle works from software>that is able to take the current speed and pitch of the>aircraft and apply a power setting that will either raise or>lower the airspeed to the target speed. As an example, when I>used to fly the Piper Warriors, I remember 1950rpm's holding>60kts with a nose up pitch.Did it work acturate with FS?? let say if the FS show autotrottle is set at 60 knots...Assume at 15 degree from the idle. would that set the same way as the one you build compared to what FS shown?I have heard so many methods of using software getting that autothrottle mechansim to work but from my experience they can not be so acturate based on the quadrant you have or the one you created. Let say if you create quadrant that doesnt have same diameter from idle to full thrust, you would be hearing ticking sound which gears is slipping between handler and motor. And I found the cause is because the software doesn't interact with FS or not yet have created Via linking with FS. However, I found a solution, using FSUIPC to get the potentiometer value from Idle to full. and write the language to interface program to tell where the motor cans tart and where it will stop. Also to metion that, you would have to have something that can work forward and backward. for instance if correcting the airspeed it would just go foward bad backwaord repeatly or if climbing or descending, it will the degree of handle will stand at different degree. It took me about 4 months to get that work, but not sucessfully. Still have a liitle g;itch.

[LawnDart 19]

"It may damage your unit within a few minutes."Not necessarily. I use the absolute position of the sim throttles when they are under A/P control in the sim. There's a direct correlation between A/P Throttle position, and the potentiometer position in my throttle assembly. Translated correctly, the throttles track nicely. The throttles just move to where the A/P has moved them.Any noise or jitter is eliminated by setting up and tuning a dead-zone when the throttle levers reach agreement with the A/P. This is the extent of any filtering I use. Once a lever reaches the deadzone, it just stops until the A/P moves the sim throttles far enough that the deadzone values are exceeded.Any possible damage is eliminated by the use of the friction clutch. If the throttles somehow are commanded to travel past the physical limits, (as they will during setting up and troubleshooting) the passive friction clutch allows the motor/pulley assembly to freewheel while the levers rest against the stops. The friction clutch is nothing more than 2 large round peices of felt pressed againt the actuator arm, allowing that arm to move until it reaches a physical limit. I'll snap a photo in the next few days to show my work.

[Guest Mark McG]

Ray,what variables are you reading from FS for the Autothrottle. I am assuming it's throttle lever position.