Modelling of Mechatronic Systems by an Object-Oriented Data Model

An object oriented data model is defmed to describe multibody systems. Extensions for modelIing mechatronic elements like sensors and actuators within the multibody system as weil as interfaces to ather dynamic systems have been developed. An implementation in a neutral modelIing kernel and a format to store the description cf a multibody system on a data exchange file are directly derivcd from this data model. Data convcrters transfer these data to several multibody formalism •. 1 lntroduclion In this paper an object-oriented data model for multibody systems with extensions to mechatranic elements is described. A multibody system defmed by this data model consists of rigid bodies connccted by ideal joints and force elements. Measurement elements called sensors deIiver internal, time dependent quantities like distances, accelerations as weil as forces. Position actuators are defined to model drives within the multibody system. The data model is independent of a spccific multibody program and can therefore be used as a neutral format for the exchange of multibody system descriptions. The datamodel is given as a block with inpUt/output interfaces for the connection to control units or other elements. 2 Object-Oriented D.ta Model Engineering applications, such as multibody systems may be described by an objcct oriented data model in a natural and efficient way. following the discussion of a data model by Otter, Hocke, Daberkow, Leister [1]. The data model for the description of multibody systems is based on the simple, neutral, object-oriented data model duc to Ullman [2]. In an object-oricnted data model, the structure of thc objects and their behaviour are described by classes. A dass description consists of two parts: the scheme description of the object type and the specification of the available methods. Both aspects of a class arc discussed in more detail in the following sections. Object types: The first part of a dass description consists of the definition of the object type. At a basic level the data model supports a set of elcmeotary data types, like integer values, real values or character soiogs. Funhermorc, multi-dimensional arrays of the elcmentaJy data types are supponcd. New object types are defmed by building composed or complex objcct types out of already defincd obiect type. ( ... cordol) or by building coUections of a number of obieclS of the same class (Selof) and by deriving dass descriptions by inheritance from superclasses, according to UUman (2]. Applying these mIes, arbitrary complex obiect types can be defined bascd on a small set of elementary data types. Methods: The second part of a dass description consists of the specification of the available methods.