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EZ Pilot Autopilot
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sbuc(at)hiwaay.net
Guest

Posted: Sat Jan 14, 2006 8:45 am Post subject: EZ Pilot Autopilot

Charlie Kuss wrote:

 	  Quote: 	
		   

 

 Sam,

   You you explain to me what a "stepper" motor is and how it differs?


	




Charlie, you are asking the wrong person for insight on the design of 

stepping motors! This is beyond my scope of expertise.  



Here is a link that might help:



http://www.cs.uiowa.edu/~jones/step



As I understand it, the stepping motor can be controlled via digital 

signals in order to command very precise and repeatable rotation and 

parking positions of the motor shaft. The analog motor that most of us 

are familiar with doesn't have discrete "stops" in its rotation and 

needs some sort of feedback sensor in order for the control head to 

determine the position of the motor shaft.



There, I have made an idiot of myself by diving into an area in which I 

have no real knowledge. But hopefully some of the actual motor experts 

on the list will jump in and straighten out my mess.  



In the real world, I can't tell any difference in the performance of the 

analog system in the Navaid servo and the digital stepper in the AlTrak 

servo. Both servos work extremely well at driving the control surfaces 

in very small, precise increments.



The first time you move the stick on the ground in a plane with the 

DigiTrak servo you will notice the servo motor dragging through the 

steps since it doesn't have a clutch that disconnects the servo drive 

when it isn't engaged. But the drag isn't noticeable in flight. The 

Navaid servo has a solenoid that disengages the gear train when power is 

not supplied to the servo.



Hope I haven't muddied the water too much.  



Sam Buchanan

SSampson.SLN21(at)london.
Guest

Posted: Sat Jan 14, 2006 10:15 am Post subject: EZ Pilot Autopilot

Sam - thanks for the input. Any idea when Tru track bring out their new 

servo. I havnt bought them yet and hate to buy just before things become the 

'old' model. Thanks, Steve.



---

shempdowling2(at)earthlin
Guest

Posted: Sat Jan 14, 2006 11:12 am Post subject: EZ Pilot Autopilot

You could purchase the tru track alt hold regardless of your a/p setup.  I 

have the Navaid and tru traks alt hold and love it.  I would put the alt 

hold in before the wing leveler.  Its really nice when you're by yourself.



GO BEARS



Shemp/Jeff Dowling

RV-6A, N915JD

235 hours

Chicago/Louisville



---

sportav8r(at)aol.com
Guest

Posted: Sat Jan 14, 2006 11:21 am Post subject: EZ Pilot Autopilot

Both functions are VERY nice to have (I can say that from experience, now that I have both).  For x/c, the alt hold is the most desirable of the two, but for an inadvertent IMC encounter (not that I've ever had one , the wing-leveler is more helpful, IMO. 

 

-Stormy

 

GO, TRIO  

 

do not archive

 

--

lwalters2(at)cfl.rr.com
Guest

Posted: Sat Jan 14, 2006 11:32 am Post subject: EZ Pilot Autopilot

Charlie, a stepper motor doesn't 'run' like a linear motor.  Apply power 

to a linear motor and it runs, and after power removal the motor will 

coast to a stop .... depending on the load, of course.  A stepper motor 

is 'pulsed' (best way I can describe it) and moves a few degrees, or 

portions of a degree, depending on it's design, for each pulse.  If you 

have one of each (stepper and linear) you can tell the difference by 

twisting the rotor.  A stepper will have a definite 'hump' and stop at 

the 'step'.  Kinda like pulling a prop over compression.  The linear 

will just rotate freely.  A DC linear motor will have two wires, and the 

stepper will have 4 or more depending on how many field coils it has.  

Steppers need a 'controller' that generates the pulses in the proper 

phase for rotation and direction.  The linear motor only needs a switch.

The advantage of the stepper is the ability to move in fine, incremental 

steps while the linear motor just comes close to a position.

Hope this helps.

Linn

do not archive

Charlie Kuss wrote:

 	  Quote: 	

Sam,

  You you explain to me what a "stepper" motor is and how it differs?

Charlie Kuss

snipped

>The TruTrak servo is indeed a nice looking and hefty unit. It uses a

>stepping motor instead of a linear motor and clutch. However, I have

>heard that a new version of this servo is in the works that has a clutch.

>

>The Navaid servo is much lighter than the TruTrak and based on analog

>technology that has been around for many years. In spite of its dated

>appearance and light weight, the servo has an excellent field history in

>service with both Navaid control heads and more recently with the

>EZ-Pilot heads. This servo incorporates a clutch that releases the gear

>train when power is removed from the servo.

>    

>

snipped

sbuc(at)hiwaay.net
Guest

Posted: Sat Jan 14, 2006 12:03 pm Post subject: EZ Pilot Autopilot

Steve Sampson wrote:

 	  Quote: 	
		   

 

 Sam - thanks for the input. Any idea when Tru track bring out their new 

 servo. I havnt bought them yet and hate to buy just before things become the 

 'old' model. Thanks, Steve.


	




Steve, sorry I don't know, but I bet a call to TruTrak would provide you 

with that and any other info you need.  



Sam Buchanan

SSampson.SLN21(at)london.
Guest

Posted: Sat Jan 14, 2006 12:32 pm Post subject: EZ Pilot Autopilot

Thanks!! Steve.

---

ptrotter

Joined: 10 Jan 2006
Posts: 28
Location: Westchester County, NY

Posted: Sat Jan 14, 2006 12:37 pm Post subject: EZ Pilot Autopilot

Both stepper motors and servo motors have their own advantages and 

disadvantages.  As Lynn stated, steppers have a definitive, known, rotation 

per pulse.  This makes them easier and cheaper to control, but has the 

disadvantage of jerky motion (probably not an issue for an A/P) and the 

fineness of control is limited by the number of steps per revolution (again 

probably not an issue for an A/P).  Servos have continuous motion and need a 

feedback circuit to determine their location.  This is more expensive but 

give much smoother control and can be positioned in virtually unlimited 

fineness as opposed to steps.  In the case of an A/P, I think either will 

work just fine and the differentiating factor between A/Ps being the 

features of the electronics rather than the motor type.  Steppers and servos 

are use extensively in the CNC industry, with lower end equipment using 

steppers and higher end equipment using servos.  My little CNC mill has 

stepper motors and you can really see the limitations due to the steps.  Of 

course we are talking thousands of an inch here, which is just not necessary 

for an A/P.



I think both Tru-Trak and Trio are great products.  Right now I'm planning 

on using Trio in my 8, but I could very well change my mind by the time I 

get to that point.  I like the clutch idea on the Trio servo, but it doesn't 

take much effort to override the Tru-Trak stepper.  I believe Trio is now 

shipping the same servo for both the EZ-Pilot and the EZ-1 altitude hold 

units.



Paul Trotter

RV-8 82080 Fuselage Kit



---

_________________
Paul Trotter
RV-8 82080 Fuselage Kit
N801PT (reserved)

Dan.Beadle(at)hq.InclineS
Guest

Posted: Sat Jan 14, 2006 12:41 pm Post subject: EZ Pilot Autopilot

A stepper motor is computer controlled.  They basically have windings

that are offset.  When you energize one set, the motor moves a fraction

of a turn in one direction. If you then engage the other set, it

continues to move the same direction for another step.  Alternate them,

and the motor turns round and round.  If you change the order - the

phase - of powering up the windings, it moves the other direction.



Step motors are the basis for a lot of CNC machines.  By counting steps,

you know where the head is.  And steps can be very small.  



On nice thing about most stepper motors is that if you don't engage

either set of windings, the motor will free wheel.  (It takes energy to

hold it on the current step - no energy = free wheel). This is a nice

feature that 



 eliminates the need for a separate clutch.  If

the autopilot is not engaged, just let the motor freewheel.



--

lwalters2(at)cfl.rr.com
Guest

Posted: Sat Jan 14, 2006 12:47 pm Post subject: EZ Pilot Autopilot

In my response to Charlie, I pointed out a benefit of steppers.  The 

linear motors also have a benefit, especially in an autopilot.  The 

stepper has inherent drag, because of the stepping nature of the beast 

where the linear motor doesn't.  Given the same gearing, the stepper 

will have more drag than the linear motor.  However, both systems will 

have drag due to gearing, and the addition of a clutch in the system 

will remove the drag from both.



Sorry if I've confused anyone!!!

Linn

do not archive



--

Doug Gray

Joined: 10 Jan 2006
Posts: 112
Location: Sydney, Australia

Posted: Sat Jan 14, 2006 1:14 pm Post subject: EZ Pilot Autopilot

 	  Quote: 	
		   I looked inside one of these servos at OSH and the engineering and 

 materials look first class; should be a worthy component for their 

 excellent autopilots.

 

 Sam Buchanan

 

 

It the new 'Servo' for EZ-Pilot a stepper or a true (analogue) servo?
	




I had discounted the EZ-Pilot previously because it had a stepper. I could not get my mind around 

how they delt with overtorquing the stepper, I suspect they have needed to resort to another 

micro-controller within their new 'servo' to keep track of the actual position.



Doug Gray

sbuc(at)hiwaay.net
Guest

Posted: Sat Jan 14, 2006 2:43 pm Post subject: EZ Pilot Autopilot

Doug Gray wrote:

 	  Quote: 	
		   

 

 

> I looked inside one of these servos at OSH and the engineering and

>  materials look first class; should be a worthy component for their

>  excellent autopilots.

> 

> Sam Buchanan

> 

> 


	


 	  Quote: 	
		   Is the new 'Servo' for EZ-Pilot a stepper or a true (analogue) servo?


	


I don't know, Doug.



 	  Quote: 	
		   I had discounted the EZ-Pilot previously because it had a stepper.


	


Nope, Trio's EZ-Pilot has been using the Navaid servo which is *not* a 

stepper setup. TruTrak uses a stepper design with their systems.

 	  Quote: 	
		   I could not get my mind around how they delt with overtorquing the

 stepper, I suspect they have needed to resort to another 

 micro-controller within their new 'servo' to keep track of the actual

 position.


	


There is *no* way I am going to speculate on the specifics of Trio's new 

servo design! 



Here is what Trio has on their web site about the new servo:



http://www.trioavionics.com/servo.htm



It appears to be a well thought-out design which is what I have come to 

expect from the Trio guys.



Sam Buchanan

mannanj(at)alltel.net
Guest

Posted: Sat Jan 14, 2006 4:16 pm Post subject: EZ Pilot Autopilot

Steve:



Check with Tru Track to be certain, but I think I remember that they will 

let you upgrade to a newer or better version for just the difference in 

price between the two.



Mannan Thomason

RV-8 Tru Track installed, hoping to fly this spring.

---

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