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Old Aug 24, 2007, 02:43 PM
Alam
RENO
Joined Aug 2007
521 Posts
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Low Cost Auto Pilot Using Fma Autopilot And Gps

Hi

I Am Trying To Develop Small Auto Pilot Using Fma Auto Pilot And Gps Receiver Along With Rabbit Rcm3720 For Gps Packet Filtering. Any One Have Any Good Idea How This Will Work Out.

1) Fam Auto Pilot Will Control Pitch And Roll.
2) Rabbit Rcm3720 Will Control Only Rudder servo (PWM), Input
Hedaing Info COMING From Gps Receiver.
3) User Can Turn Off/on Auto Pilot By Using Ch6 On His Transmitter.
4) Speed Contol Will Done By Rcm3270 Using Pwm (to Motor Throtle Servo) By Comparing Against Speed Getting From Gps.
5) Altitude Hold Will Add Later On.
6) Plane Will Hold The Current Heading.

Is Any One Have Any Ideas, For Low Cost Development ?
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Old Aug 24, 2007, 03:26 PM
The reviewer
XJet's Avatar
Tokoroa
Joined Mar 2004
3,827 Posts
The use of an FMA Co-pilot combined with a GPS receiver and some form of simple onboard computer is a fairly common way to create a low-cost autopilot.

One problem you may encounter is getting a good match between the amount of "stability" the co-pilot provides and the amount of rudder authority your flight computer provides.

Too much rudder and you'll zig-zag between waypoints (possibly even going into a tight circle occasionally), too little and you'll find it hard to get around waypoints without using a *huge* "hit-radius".

Have a go though -- I've done it before and it's fun.
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Old Aug 24, 2007, 04:59 PM
Alam
RENO
Joined Aug 2007
521 Posts
Quote:
Originally Posted by XJet
The use of an FMA Co-pilot combined with a GPS receiver and some form of simple onboard computer is a fairly common way to create a low-cost autopilot.

One problem you may encounter is getting a good match between the amount of "stability" the co-pilot provides and the amount of rudder authority your flight computer provides.

Too much rudder and you'll zig-zag between waypoints (possibly even going into a tight circle occasionally), too little and you'll find it hard to get around waypoints without using a *huge* "hit-radius".

Have a go though -- I've done it before and it's fun.
Is you tried to mix PWM output to FMA input by adding/decreaing the analog voltage output of FMA co-pilt sensor that goes to main FMA auto pilot unit.
When turn is needed just increase or decrease the roll sensor output voltage (using D/A converter 8 bit). I did not try this approach, I will test it.
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Old Aug 27, 2007, 11:36 PM
Alam
RENO
Joined Aug 2007
521 Posts
Is any one know what is the reationship between surface control gain and air speed. For differnt air speed different surface control gain needed but how much, is any formula available. How often rudder servo need to move to control the heading.
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Old Aug 30, 2007, 05:33 PM
Alam
RENO
Joined Aug 2007
521 Posts
Quote:
Originally Posted by FAKHREALAM
Is any one know what is the reationship between surface control gain and air speed. For differnt air speed different surface control gain needed but how much, is any formula available. How often rudder servo need to move to control the heading.
Today I added rudder gain control, depending on the speed auto pilot is getting from GPS it will select a gain and rudder pwm time will control. The benefit is that

1) If plane is flying at high speed then increase/decrease of rudder surface (rudder servo) will be less.
2) Also add the max angle rudder servo can turn when auto pilot on +/- 45 degrees only.
3) All the servo pwm time is getting showed on 4x20 LCD display.
4) 4X20 line LCD CHAR display show
- CURRENT HEADING
- AUTO PILOT REF HEADING
- CURRENT SPEED
- AUTO PILOT REF SPEED
- CURRENT ALTITUDE
- AUTO PILOT REF ALTITUDE
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Old Sep 04, 2007, 03:20 PM
Alam
RENO
Joined Aug 2007
521 Posts
AUTO PILOT software in c for RCM3720.

Here is the simple AUTO PILOT code which is written in c, can run on Rabbit semiconductor RCM3720 board. I will post the updated one as I will move forward.
Its for controlling heading (by moving the rudder servo) and speed control by changing the pulse on time (PWM) of the speed controller (throttle servo can be attached).
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Old Sep 04, 2007, 04:43 PM
HyperFlight Support
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United Kingdom, England, Stratford-upon-Avon
Joined Feb 2001
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Quote:
Originally Posted by FAKHREALAM
4) Speed Contol Will Done By Rcm3270 Using Pwm (to Motor Throtle Servo) By Comparing Against Speed Getting From Gps.
I think throttle should be set by the difference between desired ROC/descent and actual ROC/descent, as measured by an altimeter.

Neil.
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Old Sep 07, 2007, 12:15 AM
Alam
RENO
Joined Aug 2007
521 Posts
Two Axis Tit Sensor

I Just Made Two Axis Tilt Sensor MESURING BOARD, That Can Be Use To Measure Static Tilt Angle, I Will Try This With My Auto Pilot To Measure Roll And Pitch Along With Fma Sensor.
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Old Sep 07, 2007, 03:27 AM
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South Africa, JNB
Joined Mar 2007
41 Posts
thanks for the photos, but i can't see much because the photos are blured.
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Old Sep 07, 2007, 10:04 AM
Alam
RENO
Joined Aug 2007
521 Posts
Clone Of Fma Thermopile Sensor

Here is the IC SENS THERMOPILE W/THERM TO-39 (MLX90247-ESF-DSA) board (4 sensors). I designed it using the different parts. I am working on rf modem for talking to plane and base station, its XECOM 927 MHZ, 500 mw power output, go up to 20 miles range. The cost is only US$ 75.00 per piece which is much less then available in market, please visit www.xecom.com if you interested.

CLONE TO FMA AUTO PILOT SENSOR CIRCUIT.
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Old Sep 09, 2007, 04:02 PM
Alam
RENO
Joined Aug 2007
521 Posts
Aerial Snaps , Reno/Stead, May 2001

Here Is The Aerial Snaps Taken Using Manual Still Camera, Receiver Landing Channel Was Used To Activate Standard Servo. Servo Was Used To Press The Camera Click Button. Works good, just need to adjust the servo lever correctly.
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Old Sep 11, 2007, 11:09 AM
JettPilot's Avatar
Miami
Joined Apr 2005
10,107 Posts
Neat project, it would be very useful ! I currently fly something close to this, but yours is better.

One comment I have is that Altitude control would be better to have than speed control. Most RC planes of the UAV type have one most efficient flight speed, changing it only makes things worse, and is not needed. In all my planes, I can set a good throttle position, and it will fly all day. Stalls are not an issue, as the autopilot will not give enough up elevator to stall.

I think altitude hold would be much more useful.

JettPilot
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Old Sep 11, 2007, 12:23 PM
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United Kingdom, England, Stratford-upon-Avon
Joined Feb 2001
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That is what I tried to say in post 8 but he ignored me.

Neil.
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Old Sep 11, 2007, 02:04 PM
Alam
RENO
Joined Aug 2007
521 Posts
Quote:
Originally Posted by Neil Stainton
That is what I tried to say in post 8 but he ignored me.

Neil.
I did not ignore you Neil, you are right but what I was thinking is:

For altitude control, elevator as well as heading speed is also important because if tail wind speed is more then plane speed or so, plane will lose the altitude. What my observation is that, I need to controls both (throtle and elevator to maintain the altitude, head wind and tail wind). In the case of head wind, may be only elevator control is enough for altitude maintaining but for tail wind I think both controls are needed. If I am not correct please correct me, I learn it by flying my 60 size Tower trainer.
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