Choosing a sail servo – 6 Deadband / Chatter

[Tony Bell 2Participant @tonybell2]

Servo Hunting and Chattering

The Tx sends out a control signal to the servo’s microprocessor. The servo’s Pot (potentiometer/variable resistor) sends out a reference signal. When the two match, the servo does nothing.
In a sailing boat, the servo arm/drum/pot constantly moves backwards and forewards due to the varying wind pressure and wave motion. The microprocessor senses this and making the servo motor osscillate trying to correct itself. This is called Hunting and the noise of the motor and gears is called Chattering

Servo Deadband

The deadband is the small difference between the control and servo reference signals when the servo motor is stationary. They can never be exactly equal.

Analogue servos are made with a deadband of about 5usec.

 

If the difference between the two signals is smaller than the servo’s deadband, the servo does not move. If it is larger, the motor moves until the sigal difference is lower than the deadband.
For sail boats, the larger the deadband, the less sensitive it becomes to sail pressure fluctuations.

Hitec HB815BB has a 8usec deadband. Digital servos have no deadband! read Futaba’s article

 

Digital FET servos

 

Based on  Robot Builder’s Bonanza

[Tony Bell 2Participant @tonybell2]

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