Servo Ramping Options In ARC

Yes - ARC does have servo ramping, but the best approach depends on what kind of servo you mean and how you’re controlling it.

Short answer

For a standard hobby PWM servo on an EZ-B v4, the most practical built-in options are:

• Auto Position use Steps, Delay, and optionally SW Ramping
• Servo Speed skill useful for experimenting with speed behavior
• JavaScript/Python best if you want custom acceleration/deceleration logic

For a basic hobby servo, the EZ-B/ARC is usually not doing a true hardware "acceleration profile" like a smart servo would. Instead, ARC typically moves the servo in small increments over time, which creates the ramp effect.

Best option for hobby servos

1) Auto Position

If you’re already using Auto Position, this is usually the best place to do it.

In Auto Position:

• Steps controls how many increments are used between poses
• Delay controls how fast those increments are sent
• SW Ramping adds a soft start and soft stop behavior

You’ll find those settings inside the Action configuration for each transition.

How to access it

1. Open the Auto Position skill
2. Click Configuration
3. Open Actions
4. Select the transition step you want to edit
5. Adjust:
   • Steps
   • Delay
   • SW Ramping

Practical starting point

Try something like:

• Steps: 10
• Delay: 20 ms
• SW Ramping: 1000 or similar non-zero value

That gives you a smoother start and stop without making the motion too sluggish.

2) Servo Speed skill

There is also a Servo Speed skill in ARC:

• Project Add robot skill servo servo Speed

This skill is handy if you want to set and experiment with a servo speed value for a specific port.

It’s not really a full "ramping profile editor," but it can help you tune how fast a servo moves.

Docs:

• https://synthiam.com/Support/Skills/Servo/Servo-Speed?id=16044

3) Scripted ramping

If you want full control over acceleration and deceleration, scripting is the most flexible approach.

You can ramp a servo by moving it in small degree steps with a short sleep() between each move.

Example JavaScript ramp

function rampServo(port, startPos, endPos, stepSize, delayMs) {
    let direction = startPos < endPos ? 1 : -1;
    let pos = startPos;

    Servo.setPosition(port, pos);

    while (pos !== endPos) {
        pos += stepSize * direction;

        if (direction > 0 && pos > endPos) pos = endPos;
        if (direction < 0 && pos < endPos) pos = endPos;

        Servo.setPosition(port, pos);
        sleep(delayMs);
    }
}

// Example usage:
rampServo(d0, 90, 150, 2, 20);
sleep(200);
rampServo(d0, 150, 90, 2, 20);

That gives you a controlled move up and a controlled move down.

What about "true" hardware ramping?

That usually applies to smart servos or servo controllers that support:

• velocity
• acceleration
• profile moves

ARC supports those features when the hardware/driver exposes them.

For example, some smart servo systems may support:

• setVelocity()
• setAcceleration()

But for a standard hobby servo, those hardware ramp parameters generally don’t exist on the servo itself.

If you connect the hobby servo directly to the PC

If you mean directly to the PC without an EZ-B, then the answer depends on which hardware/adapter is actually driving the servo.

ARC itself doesn’t drive a hobby servo directly from the PC’s USB port unless you have an intermediate controller or supported hardware interface. In that case, the ramping behavior would still be determined by:

• the robot skill / driver
• or your script
• or the external controller’s firmware

So for a plain hobby servo, the EZ-B plus ARC scripting or Auto Position is the normal route.

Recommendation

For your case, I’d recommend:

• Auto Position if the servo is part of a pose/action sequence
• JavaScript ramping if you want custom easing behavior
• Servo Speed only if you want a quick tuning tool

Useful references

• Auto Position skill: https://synthiam.com/Support/Skills/Servo/Auto-Position-Gait?id=20314
• Servo Controls overview: https://synthiam.com/Support/ARC-Overview/Servo-Controls
• Servo Speed skill: https://synthiam.com/Support/Skills/Servo/Servo-Speed?id=16044
• Create your own robot skill: https://synthiam.com/Support/Create-Robot-Skill/Overview

If you want, I can also give you:

1. a JavaScript easing/ramp function that accelerates then decelerates smoothly, or
2. the exact Auto Position settings I’d use for a walking/arm motion on hobby servos.

I'm very sure the SW Ramping feature in the Auto Position skill is what I am remembering. This sounds like the perfect solution I'm looking for.

Presently I have a few scripts that operate some servos. I've tried scripting ramp effects on these servos but have struggled to get a good "ramp down" effect and the timing needs to be almost exact.

Moving their control to the Frames and Actions in the AP skill should give me softer start and stop of these hobby servos.

Thanks.

You can also use the PWM servo Ramping skill to add ramping (known as acceleration in software) to a PWM servo on any EZB.

PWM Servo Ramping by Synthiam Inc.

Smoothly ramps PWM servos on EZB D0-D23 via Vx-to-Dx mapping for natural, gradual motion without snapping.

Requires ARC v1

Servo

Thanks @Synthiam Support. I'll be giving this skill a try to add ramping to my servos. After reading through this skill's directions in the article you pointed to it all sounds a bit compacted by not really too bad. I'm looking forward to setting it all up and doing the needed adjusting to the settings to get the ramp effect I'm looking for. I'm going to have to change a few of my current scripts but that's doable.