Linear Positioners Catalog_en-US_revA - Kollmorgen

Linear Motion Terminology: Linear Positioner PrecisionParameter Definition Dominating FactorsAbsolute AccuracyRepeatabilityResolutionThe maximum error between expected andactual position.The ability of a positioning system to return toa location during operation when approachingfrom the same direction, at the same speed anddeceleration rate.The smallest positioning increment achievable. Indigital control systems, resolution is the smallestspecifiable position increment.• Accuracy of the motor/drive system• Screw pitch error (lead accuracy)• System backlash (drive train, screw and nutassembly)• Angular repeatability of the motor/drive system• System friction• Changes in load, speed, and deceleration• Angular resolution of the motor/drive system• Drive train reduction• Screw pitch• Lead screw assembly wearL I N E A R P O S I T I O N E R SBacklashThe amount of play (lost motion) between a set ofmoveable parts.• Drive train wear• Spaces between moving partsAccuracy and RepeatabilityAssume three linear positioningsystems each attempt five moves froman absolute zero position to absoluteposition “A”. The individual endpositions of each move are charted on alinear scale below to demonstrate theiraccuracy and repeatability by displayingtheir proximities to the expected position.Ideal SystemStartPositionMotionExpected PositionANoErrorSystem 1Move 1Move 2Move 3Move 4Move 5System 2Move 1Move 2Move 3Move 4Move 5System 3Move 1Move 2Move 3Move 4Move 5Start PositionExpected PositionDegree ofAccuracyDegree ofRepeatabilityCommentHigh High System 1 is both accurate and repeatable, theend positions are tightly grouped together andare close to the expected position.Low High System 2 is inaccurate but repeatable,the end positions are tightly grouped around apoint but are not close to the expected position.Low Low System 3 is neither accurate nor repeatable, theend positions are not tightly grouped and arenot close to the expected position.www.kollmorgen.com91