Research On Approach To Fixture Plane Location Errors Probability Analysis Based On ADAMS Mechanical Simulation

Approach to automated analysis of fixture location errors based on mechanism calculation model of workpiece-fixture system is studied in this paper. After this mechanism model of the process system is represented, the overall location errors analysis of workpiece-fixture system is transformed into calculating relative movement position range of mechanism’s objective component. This mechanism model is a complex linkage mechanism system with multi-DOF and multi-driving links, and the law of driving links’motion is equal to probability distribution law of corresponding error elements existing in process system, so when the position of driving links are generated through sampling, the relative position of objective component can be obtained according to mechanism position analysis. If there are enough positions of driving links, a sample of relative positions of objective components can also be obtained. Then the position variation probability analysis result of objective component is determined through probability statistics, which is the probability result of fixture location errors.Modeling programs of equivalent sub-mechanism are written in ADAMS command language which are used to establish equivalent mechanism model interactively; user-written subroutine defining driving links’motion which follow a certain probability distribution law is programmed in C language; a sample of objective component’s relative positions is obtained through ADMAS’s mechanism simulation module; the sample’s statistics analysis result is fixture locating errors. The prototype system is mainly made of:1. Interactive establishment of equivalent mechanism model. After inputting nominal dimensions, location and orientation of related characteristics lie in process drawing through human-computer interaction interface which is made of customize menus and dialogs, the corresponding equivalent mechanism model of a workpiece-fixture system is established.2. Defining of driving links’s random motion. The random position sequence of driving links which follow a certain probability distribution are generated by Monte Carlo Simulation method.3. Data extraction. Extract objective component’s relative positions datum during simulation automatically to database through clicking the corresponding button on customize dialog.4. Data analysis. Secondary development of ADAMS/Postprocessor module is made to export extracted datum file, display curve and output statistics result of extracted sample. The location variation of objective component is determined by statistics result, the probability result of fixture location errors is obtained.The calculation results show the method is correct after some examples are verified at the end of this paper.