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Introduction to Servos

INTRODUCTION

1.   Servos (aka actuators) are essential to the operation of most UAVs* because they provide the ability to move control surfaces.

* some multirotor UAVs use only speed control of individual motors to achieve aerodynamic control.

2.   A typical servo consists of an electric motor that moves a rotary actuator via a reduction gearset, normally providing increased torque and perhaps a clutch mechanism.

3.   Servo Parameters.   Each servo output in a UAV Navigation autopilot can generate a standard (i.e. Futaba, JR or Spektrum) PWM signal: the peak of the signal lasts for a period of between one and two milliseconds (μs), with a resolution control of 1 μs. The width (i.e. duration) of the signal is used by the servo control electronics to command a proportional servo deflection. The following diagram represents these parameters graphically:

4.   Supported Servo Brands.   Although most servos use PWM signals, there are some special servos that report back information about the servo's state (position, current consumption, internal temperature etc.). This type of servo generally uses serial port communication. Contact UAV Navigation for an updated list of compatible devices.

5.   Servo Calibration and Configuration.