Radio Control Baby
Bully Servo Amplifier
• LOW COST CLOSED
• 7- 26 VDC
• UP TO 15A SERVO
• 5 SECOND 30A
Order at (800) 882-6832
Low cost, yet powerful servo
amplifier for DC PM motors to
fabricate your own position servos.
You supply the motor and 5K feedback
pot. Plugs into your R/C like any other
servo, 1-2 ms, optically isolated.
Limit switch inputs included.
34 SERVO 12.2013
speed best when the environmental conditions are relatively
constant. Like the purely proportional controller, the
predictions made by a PI controller are predisposed to
instability with some variable combinations. To counteract this
instability, a derivative term (D) — the equivalent of a
smoothing capacitor in a power supply — can be used to
suppress the instability. Tuning a PID controller consists of
optimizing the values of the three constants: proportion
constant, integral constant, and the derivative constant.
If you’ve worked with a PID controller, you’ve no doubt
discovered that there’s no guarantee that it can predict the
future speed or velocity of your robot platform. Not only do
you have to be smart about adjusting the constants, but the
conditions must be repeatable. If you tune a PID controller for
the hardwood floor in your living room, don’t expect your
robot to operate smoothly on your lawn.
Of course, the PID controller isn’t the final word in
predicting, say, velocity. There are numerous variations and
enhancements to the basic PID algorithms, as well as more
sophisticated algorithms such as various flavors of the Kalman
filter. The Kalman filter has a number of potential advantages
over a PID controller, including relative resistance to noise. The
downside is that the computational overhead favors a Parallax
Prop or Raspberry Pi over a simple Arduino or PIC.
Given the availability of low cost, high performance
microcontrollers, I predict that we’ll be seeing robots with
more sophisticated prediction algorithms — whether for
tracking movement with a servo-based camera, the speed of a
drive motor, or the relative RPM of quadcopter rotors. SV
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