Need a smple airspeed control loop

[johnorama]

I am posting here because you guys seem to be the smartest on these subjects!

I would like the wings of an F-14 to automatically re-configure based on indicated airspeed. for example, slow speeds = more forward/open and higher speeds = swept back.

I do not want to simply adjust the wings based on throttle position. Although this would be easy, it is not how it should work. If I am doing a high angle of attack maneuver to enter a near-hover the throttle will be medium to high but the airspeed will be low and the wings should be extended forward for max lift. Or I could be at low throttle in a dive and the wings should sweep back. It would be good to have a manual mode also, switchable in flight.

Any ideas?

[FAKHREALAM]

I am posting here because you guys seem to be the smartest on these subjects!

I would like the wings of an F-14 to automatically re-configure based on indicated airspeed. for example, slow speeds = more forward/open and higher speeds = swept back.

I do not want to simply adjust the wings based on throttle position. Although this would be easy, it is not how it should work. If I am doing a high angle of attack maneuver to enter a near-hover the throttle will be medium to high but the airspeed will be low and the wings should be extended forward for max lift. Or I could be at low throttle in a dive and the wings should sweep back. It would be good to have a manual mode also, switchable in flight.

Any ideas?

You 1st need to measure the air flow on which your plane will float, u can do it by using this SPI based AIR FLOW MEASUREMENT BOARD. You can get it from

http://thesiliconhorizon.com/store/alam-tech-airspeed-sensor-mpxv7002dp-p-87.html?osCsid=cd2d5c7837b8e6fc1ce3f4fadd74bb04

ADJUST YOUR THROTLE AS PER AIR FLOW NEEDED AND MAKE YOUR SERVO ADJUSTMENT AS PER ANGLE NEEDED FOR WING.

Fakhre Alam

[johnorama]

You 1st need to measure the air flow on which your plane will float, u can do it by using this SPI based AIR FLOW MEASUREMENT BOARD. You can get it from

http://thesiliconhorizon.com/store/alam-tech-airspeed-sensor-mpxv7002dp-p-87.html?osCsid=cd2d5c7837b8e6fc1ce3f4fadd74bb04

ADJUST YOUR THROTLE AS PER AIR FLOW NEEDED AND MAKE YOUR SERVO ADJUSTMENT AS PER ANGLE NEEDED FOR WING.

Fakhre Alam

Thanks for the info. It looks like I would still need to add a microprocessor between this sensor and the servo. I still need more info to make this work. I am not a programmer, just a military UAV pilot and avionics technician.

[jglenn]

Use a PICAXE, from the UK, you need the 18X chip. It is simple BASIC, I am using it for some simple stuff like that. Has everything you need, 8 or 10bit
A/D for measuring a diff pressure sensor (I can give you a part # if you want),
will need an OPAMP for that, will go to 125MPH. Has servo commands for positioning servos. You will have to use a spare channel, the flaps knob or
something, to select auto/manual. Parts cost for this would be about $40.

The nice thing about the 'AXE is there is an onscreen debug command that
will display registers, or sensor values. I find this very useful when kludging
new designs together, testing and optimizing them. You should see my earth
mag field detector platform.. :cool:

[FAKHREALAM]

Thanks for the info. It looks like I would still need to add a microprocessor between this sensor and the servo. I still need more info to make this work. I am not a programmer, just a military UAV pilot and avionics technician.

Its up to you, for making any auto pilot u need to know some language you can do programming in or you can buy one alreday build for you. Its all up to you which way u want to go. There is lot of development boards are available to program in c,c++ and Basic for under $200.

Thanks.
Fakhre Alam

[yyz]

Thanks for the info. It looks like I would still need to add a microprocessor between this sensor and the servo. I still need more info to make this work. I am not a programmer, just a military UAV pilot and avionics technician.

PM sent

[johnorama]

it looks like the PICAXE is a good way to go. I can build the kits they sell and I can figure out BASIC programming (I used to know some basic in high school). Now I need to figure out a good airspeed sensor that will work with this. The one listed above makes no sense. I read all the documentation and you need a 6 year degree to make any sense of it, unlike the PICAXE materials and web site.

[dmgoedde]

Is there interest in a small and simple complete airspeed sensor? I am referring to somethign with sensor and logic, and it interfaces with a host controller via SPI or I2C, or an analog output that is already scaled into airspeed? I am NOT talking about a breakout... I mean something that is a complete low cost sensor with onboard logic to calc airspeed. This could be failry inexpensive. Recycled code from my standpoint.

[FAKHREALAM]

Is there interest in a small and simple complete airspeed sensor? I am referring to somethign with sensor and logic, and it interfaces with a host controller via SPI or I2C, or an analog output that is already scaled into airspeed? I am NOT talking about a breakout... I mean something that is a complete low cost sensor with onboard logic to calc airspeed. This could be failry inexpensive. Recycled code from my standpoint.

The board I mentiond have the sensor and serial interface for 12 bit SAR ADC (1 MS), its very high speed (adc and sensor is the part of the sensor board).

Board info can be found in this pdf.
http://www.thesiliconhorizon.com/images/airspeed.pdf

Just need serial clk and cs, only need to read the data from dout pin. May be 10 to 15 line of code. Here simple flow

SELECT_CS
READ_DATA: GIVE_CLK
READ_DATA_OUT_PIN
IF (CLK_COUNT < 12)
{
MOVE BIT ONE RIGHT
GOTO_READ_DATA
}
ELSE
DISABLE_CS
SAVE_DATA
DONE

Fakhre Alam

[jglenn]

john: there are many ways to do this, C, assembly, even the Propeller chip, heck, they are down to $8, but probably not easy for a beginner to use.

The PICAXE is simple, better than the Basic Stamp due to being only about $6, and comes with a/d inputs. The folks on the forum are very helpful, they will often write your program for you. But don't ask for the whole thing, post your first solution, and they love to pick it apart and improve it!

Here is the sensor I use for measuring airspeed up to 125MPH, with a pitot tube and static port:

http://www.mouser.com/Search/Refine.aspx?Keyword=841-MPXV7002DPT1

I buffer the output with a diffamp made from an opamp. Send me a pm and I can provide a schematic for that, just hook it to an 'AXE and you're good to go.

You can sense rcvr servo outputs with PULSIN, and also control a servo, if that is what is controlling the wing sweep.

[FAKHREALAM]

john: I have the PCB made for that sensor too, just put the prerssure sensor (MPXV7002DPT1) give +5v or +3v( sensor is a available) and connect analog output to your NXP/PIC/AD/TI/BASIC STAMP controller. Just pm me if you need pcb or email me at fakhre@rocketmail.com if you need any help. The link to pdf in my last posting have the circuit diagram, its very easy. We all can help you but most of the part coding you have to do on your own, we all can guide you in right direction, with coding and hardware error.

Fakhre Alam

[jglenn]

I like buffering the sensor with an opamp. I use an RC filter, the sensors have a bit of noise, especially for altitude (different sensor). The diffamp allows me to "magnify" the area of interest, for a desired range, and get a full 0-5V output.

Lastly, the opamp provides a nice low impedance for the a/d input.

I was a little slow in starting with the PICAXE, having done mostly assembly on PICs. It helps to do some simple things first, like reading a pot and displaying the value on the screen. Many look down on Basic, but they are coming out with the 20X2 chips soon. A program that takes 2 minutes to run on a 4mHz chip will execute in 8 seconds on an X2. Smokin! I leave C for the experts.