[NSRCA-discussion] Futaba and pattern ( A plus for Futaba)

Tue Dec 25 11:56:03 AKST 2007

Rusty,

Thanks for the explanation.  This makes more sense but I wish that they don't called hysteresis.  Probably it is better to use the term "programmable condition".

I believe that Jim and Earl were talking about hysteresis around neutral with the hysteresis values been programmable in the 14Z.

--
Vicente "Vince" Bortone

-------------- Original message -------------- 
From: "Boyd E. "Rusty" Dose" <rdose at wi.rr.com> 

One application for using hysterisis or my definition "variability of rate/conditon vs. neutral":  Snap roll "condition" activated by a stick

A very experienced world class F3A pilot shared one way to execute snaps using the elevator stick to activate a different "condition" which has a different aileron, rudder rates and exponential values.

Why would one want this?  The pilot may have established a preferred snap (speed, how deep...) for a model and desire to have those values be throwing rudder and elevator sticks to the "stops" on the transmitter.  

Challenges:

1.  When do you have this special condition begin?
2. When do you want the condition to end (hysterisis application) and return to normal flying?

My preferences, based on the advice of the aerobatic sage and personal comfortability:

1.  I use the elevator stick to activate the condition at 90% of travel.  I have one condition for positive snaps and another for negative snaps.  The condition alters the rudder and aileron travel with unique values for left, right, positve and negative snap rates/exponential.

2.  By using the hysterisis function allows my condition to "end" once the elevator stick reaches 20% transmitter movement, returning the model to the original condition or flying set-up.  The variability of when the condition ends or relative value to neutral is my understanding of hysterisis.

The Futaba 14MZ makes the aforementioned process reasonably simple and speedy to program.  Although I have a 12MZ, I am not positive if the hysterisis is available, but it seems to me it does.

Other applications for this "variablility of rate/condition vs.neutral" for different set-up preferences:

Rudder-  You may prefer to have one rate of travel to initiate a manuever such as a stall turn and desire to select a different rate for which that rate ends and a new rate/exponential begins. 

Rusty Dose
Team Futaba
----- Original Message ----- 
From: vicenterc at comcast.net 
To: NSRCA Mailing List ; NSRCA Mailing List 
Sent: Tuesday, December 25, 2007 8:13 AM
Subject: Re: [NSRCA-discussion] Futaba and pattern ( A plus for Futaba)

Earl,

I think we are confusing two different concepts (hysteresis and dead band).  I can explain hysteresis better in materials.  For example and spring made with a material that loads and unloads in a different way causing an hysteresis loop.  That is very bad for us and I think we want to minimize hysteresis in our systems.  I will guess that if te 14Z has an adjustment for the hysteresis you want to adjusted to reduce it as much as possible.  It is possible that in some cases we want hysteresis but I am sure we want to minimize it in pattern.  I am not sure why the hely guys will want some hysteresis around neutral.  This means that the servo will respond in one way when going in one direction and the respond will be different when the stick is coming back.  Actually hysteresis not necessarily needs to happen around neutral.  It is possible that there are situations where we want that in RC.  However, I ! am sure that we don't want any in pattern.

Thanks and Merry Christmas,

--
Vicente "Vince" Bortone

-------------- Original message -------------- 
From: "Earl Haury" <ejhaury at comcast.net> 

Jim

Hmmm - I wonder if it's a definition thing. Some consider "hysteresis" to be the same as "dead band" and I assumed that was the case with the 14MZ as a translation thing (my bad). If this were the case, then adding a little would provide some slight bit of stick movement at neutral without servo response at the trim neutral, the latter being most important. Of course, as you've measured, hysteresis provides some freedom of movement with neutral being at one side or the other of the "gap". Definitely not good! I'll post a query on the Futaba Flyers Forum to see what Baxter has to say about these settings.

When you fly your 14MZ you will find the control to be exceptionally "tight". My guess is that Futaba provided the stick adjustments to "numb" it a bit for folks moving from loose systems. Obviously true hysteresis isn't what we want. (For those wondering - hysteresis might be explained as the gap in a furnace control thermostat which turns the heating unit on at some low temp and off at a higher - useful to prevent rapid cycling. However, there are then two set-points, ergo two neutrals with a gap in the middle for our purposes.) 

While you were measuring the effect of the hysteresis settings - did you happen to also take a look at the effect of the "Response" settings? Specifically, does the high or low number provide the best response and in what terms? 

Earl
----- Original Message ----- 
From: James Oddino 
To: NSRCA Mailing List 
Sent: Monday, December 24, 2007 6:30 PM
Subject: Re: [NSRCA-discussion] Futaba and pattern ( A plus for Futaba)

Earl, 

I set the maximum Hysteresis (32) and it looks like the it is about 8 microseconds so you'd have two neutrals about 8 microseconds apart.  In fact the pulse width tends to jump in 8 microsecond steps as you move the sticks slowly.  Not desirable.  
Some of my original lack of a consistent neutral was probably due to the default hysteresis set to 1.  So the sticks are better than I thought.  
I also noted that when switching rates I was getting a shift in neutral until I put the "stick deadband" (with zero hysteresis) in all rates.  
I think I'm going to love this radio.

Jim O

On Dec 23, 2007, at 12:24 PM, Earl Haury wrote:

Jim O

On the 14MZ, go to system, H/W, Stick Settings and you are able to globally set the Response & Hysteresis for each stick. You might find this easier than using the spline for setting a deadband. (Be interested in the actual pw / bits difference with each setting if you measure it.)

Earl

----- Original Message -----
From: James Oddino
To: NSRCA Mailing List
Sent: Sunday, December 23, 2007 12:08 PM
Subject: Re: [NSRCA-discussion] Futaba and pattern ( A plus for Futaba)

Bob, 

I would think that 256 resolution would mask poor stick centering.  Think about 3 step resolution. Right, neutral left.  When you select neutral it is always the same unless you move the stick to the extreme where you get right or left.  The problem is you can't trim neutral unless you do it with another channel like folks did back in the reed days.  Move the servo with another servo. 

You had many factors affecting trim in your 8 bit system starting with drift in the servos and an AM link that introduced large changes in pulse width to the servos as signal strength changed.  You could adjust linkages everyday and not keep up with everything that was fighting you.

So if low resolution masks poor stick centering then more resolution must emphasize it.  This has always bothered me.  I learned long ago that the servos can resolve pulse widths that would appear to be in the servo deadband.  In the early dual rate schemes we had to adjust the neutral if we changed the dual rate setting.  I tried using a servo to do this.  Adjust the pot until the servo didn't move as I switched the dual rate    switch back and forth. Go fly.  Every time I threw the rate switch the trim would change.  Went home looked at it on a scope and sure enough the pulse width was changing.  Adjusted it so it didn't and the trim didn't change with the position of the rate switch when I flew.

This week I got a Futaba 14MZ.  I checked the stick centering with a scope.  Not perfect.  Plus or minus a few bits.  Now a bit in a 2048 is only about a half of a microsecond change in pulse width to the servo so most folks don't care.  However I found that with the line or spline curve programming of the control sicks I can put in a plus and minus .5% deadband in the stick.  Now the centering is perfect no matter how I return the stick to neutral and I can trim it in .5 microsecond increments.  

I love this high tech stuff.

Jim O

On Dec 23, 2007, at 5:37 AM, Bob Richards wrote:

Jim,

You may be correct, the stick centering depends on the quality of the stick. But, throw in 256 instead of 1024 resolution, the step size is now 4 times as much and it would be much more noticeable.

Ok, if we were flying the 4 channel Conquest transmitter (cheap plastic gimbals) with 148 servos (non-ball bearing) in a slow moving trainer, we probably could not tell the difference between 256 and 2048 resolution. So, would I be better to fly a Conquest radio in pattern? That seems to be the type logic I would get from people that say 256 is "better than most servos".

Oops, I forgot the Conquest is an analog radio. No steps whatsoever. ;-)

Bob R.

J N Hiller <jnhiller at earthlink.net> wrote:
Guys I don’t believe the mechanical stick centering is absolute enough especially on a somewhat used radio at least on less than top of the line transmitters. The detent design and pivot bearings are less than shall we say industrial quality. Bob, I had the roll-centering problem you described with my super 7 and felt it was due to stick centering not being equal from either left or right. I think my 9-C is better but not absolute. I wish I had one of those little devices that displayed the signal count to verify my suspicion.
Jim Hiller
-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of Bob Richards
Sent: Saturday, December 22, 2007 3:37 PM
To: NSRCA Mailing List
Subject: Re: [NSRCA-discussion] Futaba and pattern
Ron,
All I can say is, I flew the Micropro with every intention of competing at the '93 NATS with it. I had trimming issues with my plane that I could not tune out. Some flights would be good, some I could not trim the plane for level flight (slight roll left or right). And, yes, I had taken out all the throw I could mechanically so I had 100% throws programmed into the radio. Frustrated, I decided to put my 7UAP in the plane, and it immediately felt good. That is when I decided to do a little digging and discovered the resolution issue.
Whenever I mention that 256 is not good enough, I hear all sorts of reasons why 256 should be sufficient. Yes, once the stick is moved away from center, 256 probably is good enough. But when the stick is at center, the darn servo better go back to the same position every time. And you need fine resolution at center so the neutral position can be varied in small enough amouts to arrive at precisely the desired position. 
With a slightly worn stick or pot, the neutral position might be bouncing between two adjacent steps. With 256 resolution, this can be VERY noticeable. With 1024 or higher resolution, not nearly as noticeable, if at all.
Given the outcome of the '93 season with my old 7UAP, I'm glad I switched out the radios.
Bob R.

Ron Van Putte <vanputte at cox.net> wrote:
Hmmmm, I never thought of blaming my radio's resolution for my bad flying.  Let's see now..........
Ron Van Putte

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