Applications of Variation Analysis Methods to Automotive Mechanisms

• Main Author: Leishman, Robert C.
• Format: Others
• Published: BYU ScholarsArchive 2009
• Subjects: direct linearization method; kinematic variation; tolerance analysis; rack and pinion; mechansim synthesis; mechansims; Mechanical Engineering
• Online Access: https://scholarsarchive.byu.edu/etd/2192; https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=3191&context=etd

Variation analysis, or tolerance analysis as it is sometimes called, is typically used to predict variation in critical dimensions in assemblies by calculating the stack-up of the contributing component variations. It is routinely used in manufacturing and assembly environments with great success. Design engineers are able to account for the small changes in dimensions that naturally occur in manufacturing processes, in equipment, and due to operators and still ensure that the assemblies will meet the design specifications and required assembly performance parameters. Furthermore, geometric variation not only affects critical fits and clearances in static assemblies, it can also cause variation in the motion of mechanisms, and their dynamic performance. The fact that variation and motion analysis are both dependent upon the geometry of the assembly makes this area of study much more challenging. This research began while investigating a particular application of dynamic assemblies - automobiles. Suspension and steering systems are prime examples dynamic assemblies. They are also critical systems, for which small changes in dimension can cause dramatic changes in the vehicle performance and capabilities. The goals of this research were to develop the tools necessary to apply the principles of static variation analysis to the kinematic motions of mechanisms. Through these tools, suspension and steering systems could be analyzed over a range of positions to determine how small changes in dimensions could affect the performance of those systems. There are two distinct applications for this research, steering systems and suspension systems. They are treated separately, as they have distinct requirements. Steering systems are mechanisms, for which position information is most critical to performance. In suspension systems, however, the higher order kinematic terms of velocity and acceleration often are more important than position parameters.