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Username Post: The Need for Servo DeadBand        (Topic#76849)
Jim Mahoney 
Senior Member
Posts: 2328
Jim Mahoney
Loc: California
Reg: 06-17-03

06-06-10 04:31 PM - Post#87965    

Hello All,

If you as most folks if the best servos have zero Dead Band at center - Effective thought of as "You can't move the stick without the servo moving most will say yes.

In the last few days I was looking at a thread over on Curtis Youngblood's AllMyRC Forum/Website and there was a very good discussion on this subject. It all started with a question about the compatibility between Hyperion Servos and certain brands of gyros.

Without getting into the long details of the thread the result was to program the Hyperion Servo to have about 4 to 6us (micro seconds) of dead band. This eliminated the Hunting or what I call the nervous Servo Syndrome - Servos sitting buzzing all the time.

The person doing this adjusted the dead band to eliminate the Hunting while still having the control response that he wanted.

Dead band is not a bad thing - ask any Control Systems Engineer, Dead Band is an important parameter in control system design.

Now another example from the past, back in the days when I flew Control Line Combat and Stunt - The top pilots of the day committed on how their Stunt Ships were not In the Grove
until a little Slop developed in the Bellcrank/Pushrod hole. Until then the plane would Hunt Continuously, never achieving Silky Smooth Flight between maneuvers.

Now what was said in the article was extending this same dead band technique to the other servos, will they will be the same, some dead band will be needed.

This is a strong case for having programmable servos! And Hyperion Servos are great, not just because they are low cost compared to JR, Futaba, etc.

Seeing is believing, for those of you who have programmable servos, Hitec, Multiplex or Hyperion try some careful experiments.

Deadband will occur due to servo backlash or control linkage slop or pushrod bending, this is not where we want the effective dead band - we want it electronically, where we can fully control the parameter.

Happy Flying,
Cherokee Jim Mahoney

Airtronics Radios, Helos - Anderson Servos, Novarossi Engines, Blitz AVRO 90 - Phoenix Simulator - SFour Helicopters - Helos Aviation Technologies

Edited by Jim Mahoney on 06-06-10 04:34 PM. Reason for edit: No reason given.

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