Hi IHNF - Show me a system that controls jerk directly. I have not changed the meaning of any words you seem to be the only one that's debating the terminology. I'm interested in how systems are creating smooth motion. If its just like acceleration and velocity with a capped figure input this is a poor strategy as capping eng jerk will cap accels and velocities rather then smooth them. If Shineworld is an algoritm developer he maybe able to explain better as the Rosetta software does a good job of smoothing eng jerk from his recent post. Peter