What is High Speed Pick & Place?

The motion control challenge involved with high speed pick and place boils down to four essential elements; minimizing vibrational energy injected into the load, choosing and optimally controlling motors capable of high acceleration rates, maximizing use of feedforward to reduce settling time, and high position and current servo loop rates.

The most impactful way to minimize injected vibrational energy is through the use of s-curve profiling. A typical pick and place mechanism makes a point-to-point move from and to a commanded position. A key consideration is injecting as little vibrational energy as possible into the mechanism during the move. Seven-segment s-curve profiles, which do not have acceleration discontinuities (unlike a trapezoidal profile, which instantaneously changes acceleration) achieve this and thereby result in reduced settling time.

Another important motion technique used with high speed pick and place is selecting motors and mechanisms capable of high rates of acceleration. For rotary motors this means selecting motors with high torque output relative to their rotational inertia. Typically Brushless DC motors serve this purpose but new motor/control combinations such as step motors driven using a closed loop stepper technique can equal or even exceed some BLDC motor acceleration specs.

For low to medium accuracy applications linear belt drive mechanisms are favored because they add very little mass to the moving part of the arm. Alternatively for higher resolution applications linear Brushless DC direct drive motors are used. Although more expensive, they provide accuracy limited only by the encoder that is used and very high acceleration rates.