What controller does smoothest movement?

Lynxmotion Electronics & Software
1

Hello, thanks for reading my post.

This grasshopper would like your expert opinion on which servo controller produces the smoothest (non-jerky, non-staccato) servo movement while moving at less than max speed.

My understanding is that Hobby servos use a pulse width modulated
(PWM) signal where the width of a pulse determines the angular position and adjusting the voltage of the PWM will have no affect on servo rotation speed (It will simply cause unstable operation and reduce torque)

So when it comes to hobby servos, one can’t control speed by adjusting the voltage (Please scream NO if I’m wrong…)

However one can “ramp” the width of that PWM pulse kinda like bellows of accordion. And each “newly rampped” PWM signal will represent a new distinct angular position.

Mini SSC II for example, is capable of 255 distinct angular positions (and no more).

LynxMotion SSC32 however, is capable of 2000 distinct angular positions.

This means, SSC32 is capable of more “fine” ramping (SSC32 has more resolution)

However ramping is not contiguos (if it is contiguous, the resolution will be infinite and the servo movement will be absolutely smooth in any speed)

Now one should realize that, when it comes to hobby servo, there is no such thing as “speed control” as we normally think of speed control. Surprisingly, at any given “moving” moment, the servo is rotating at full speed under any “speed”

However the upper mentioned “ramping” capability can be utilized into creating an “equivalent” of speed control: The controller commands the servo to frequently alternate start and stop to achieve an end result of speed control.

However, this method will have an innate flaw, that is, the servo movement cannot avoid being jerky (unless the number of “ramping” is infinite)

And naturally, the “finer” PWM rampings a controller is capable of producing, the smoother the servo movements will get.

Am I right till now? (Please scream NO if I’m wrong…)

If I’m right, SSC32 should be producing far smoother movements than Mini SSC II. However I found a few other controllers that claim 5000 distinct rampings(angular positions) such as Pololu’s.

Now there can be many other factors that I am not aware of, that will affect the smoothness so I’d like to hear from some of you who has extensive experience :bulb: with various controllers (and would like to hear too which controller you think is the champ when it comes to smooth movements)

Thank you for reading my post again and have a great day.

2

I say go with the SSC-32,i don’t quite have it yet,but what I’ve heard from everyone else,i think its the best Servo Controller ever made :smiley:

3

You might want to read thru the below discussion. Controllers cand send out control positions much more discrete than the actual servo can resolve. I found a cheap standard hobby servo only could resolve ~426 discrete positions in its ~190 deg of rotation. The 2000 and 5000 figures are more sales fluff than what you can realistically expect with a typical servo.

lynxmotion.net/phpbb/viewtop … 32&start=0

4

The SSC-32 takes care of sending the pulses to move the servo from point A to point B. The move can be at a certain rate by using the S (speed) modifier, or the move can be controlled by time with the T (time) modifier. The SSC-32 has more resolution than an analog servo can utilize. The SSC-32 has the apropriate resolution to handle digital servos. I do not believe more than 2000 points will result in more accurate resolution though.

The servo’s destination position is updated every 20mS. Depending on how fast the servo is moving will determine how many updated destination positions will be received by the servo. The servo’s own electronics handles ramping the motion at the start and end of the move. It’s built in to the servos PID control.

The number of points from 500uS to 2500uS will effect the resolution, but not so much the smoothness. This is mostly effected by the quality of the servo itself.