Question

Discuss the idea of parametric models from a system level perspective and proceed to develop a 2-port
model for the small-signal diode experiment using h-parameters. Explain what gets abstracted with this
model. Are there any restrictions using this particular model?

Answer 1

Parametric is a term used to describe a dimension’s ability to change the shape of model geometry as soon as the dimension value is modified.

Feature-based is a term used to describe the various components of a model. For example, a part can consists of various types of features such as holes, grooves, fillets, and chamfers. A ‘feature’ is the basic unit of a parametric solid model.

Parametric modelling uses the computer to design objects or systems that model component attributes with real world behaviour. Parametric models use feature-based, solid and surface modelling design tools to manipulate the system attributes. One of the most important features of parametric modelling is that attributes that are interlinked automatically change their features. In other words, parametric modelling allows the designer to define entire classes of shapes, not just specific instances. Before the advent of parametrics, editing the shape was not an easy task for designers. For example, to modify a 3D solid, the designer had to change the length, the breadth and the height. However, with parametric modelling, the designer need only alter one parameter; the other two parameters get adjusted automatically. So, parametric models focus on the steps in creating a shape and parameterize them. This benefits product design engineering services providers a lot.

The Parametric Modelling Process

Parametric models are built from a set of mathematical equations. For parametric models to have any legitimacy, they must be based on real project information. It is the modernity of the information examination techniques and the breadth of the hidden undertaking information which decides the viability of a modelling solution.

There are two popular parametric representation models:

Constructive Solid Geometry (CSG)

CSG defines a model in terms of combining basic (primitive) and generated (using extrusion and sweeping operation) solid shapes. It uses Boolean operations to construct a model. CSG is a combination of 3D solid primitves (for example a cylinder, cone, prism, rectangle or sphere) that are then manipulated using simple Boolean operations.

Boundary Representation (BR)

In BR, a solid model is formed by defining the surfaces that form its spatial boundaries (points, edges, etc.) The object is then made by joining these spatial points. Many Finite Element Method (FEM) programs use this method, as it allows the interior meshing of the volume to be more easily controlled.