IQ Fortiq BLS42

Compact, high-performance servo motors for industrial and robotics applications

Jun 03, 2021

Project update 2 of 11

The IQ Minimum Jerk Trajectory Generator

by Jon B

In IQ’s first update since launch, we’d like to discuss one of the Fortiq’s unique features. IQ has a built-in "minimum jerk trajectory generator" in the Fortiq BLS42. This lets users instruct the motor to make smooth, lifelike motions with two simple commands.

A minimum jerk trajectory generator guarantees the trajectory of the motor experiences as little change in acceleration as possible. It can be compared to the smooth and controlled movement of human limbs. IQ uses minimum jerk trajectories in place of a trapezoidal or s-curve trajectory generator since they run more quietly and result in smoother curves for applications like 3D prints. With trapezoidal trajectories, maximum acceleration and maximum velocity limits are respected. In order to get straight lines across different machine axes, the full trajectory must be computed on every axis and checked for limits, then the limiting motor must be found and then all other motors’ timing must be adjusted accordingly. S-curve trajectories are between trapezoidal and minimum jerk generators, they are smoother but slower than trapezoidal and require a minimum of six values to specify the trajectory. Meanwhile, minimum jerk trajectories are the smoothest and respect no limits. The straight lines across the machine happen naturally, as opposed to trapezoidal and s-curve generators.

As a robotics company, IQ inclined to use minimum jerk trajectories and is now able to specify final position, final time and average speed. With this, the Fortiq BLS42 motors can be kept in sync by using the same duration values. They will have a queue for trajectories, so users can string together multiple minimum jerk trajectories to make more complex motion profiles.

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