How To Measure The Performance Characteristics Of A Linear Motion Device

By Rob Steves, Zaber Technologies Inc.

Once you've determined the requirements of your linear motion application, how can you qualify a linear motion product to ensure it meets your application's needs? Manufacturer's specs are often vague and/or incomplete. The only sure way is to test the product yourself. However, simply testing a product in the final application is usually not possible at such an early stage in the design process. This article will describe a series of tests that can be performed by the average user with little experience and without sophisticated measuring instruments to quickly determine the most important performance characteristics of linear motion systems.

Any object in space has 6 degrees of freedom: linear motion along X, Y, and Z axes, and rotation about each of those axes. Consider a typical linear motion system, in this case a Zaber T-LSR75D linear slide. With reference to Photo 1, let's define a coordinate system as follows:

X - Horizontal axis parallel to axis of travel
Y - Horizontal axis perpendicular to axis of travel
Z - Vertical axis perpendicular to X and Y axes
Roll - Rotation about X axis
Pitch - Rotation about Y axis
Yaw - Rotation about Z axis

The goal of a single axis motion control device is to constrain 5 degrees of freedom while precisely controlling motion in the 6th. In the case of the pictured linear slide, all 3 rotational degrees of freedom are constrained, as well as 2 linear degrees of freedom. Motion in the X dimension is controlled.