[ozrien]

You can call it anytime. You can call it once or periodically, it will have the same result either way. You really can't go wrong. Are you having trouble with your robot?

Section 6.4 talks about the slowest ramp possible (~10% per sec). Maybe start with 50% throttle per second (which is 6V per second depending on what language you are using). That's a slow enough ramp to visibly see it work.