Describing the features of its software SystemModeler, Wolfram writes that a user can “attach visualization geometries from CAD software to components, and automatically create live 3D animations for models with 3D mechanical components.” Using system model variables-usually sensor data from tests-as input to CAD to initiate real-time visualization of the simulated operations of a cyber-mechanical system is not out of the question. For example, constraints that define how the parts move with respect to one another are not always defined because the CAD engineer may only be interested in designing the shape of the parts, not in how they move,” says Steve Miller, technical marketing manager for Simscape, MathWorks. Often, not all data that is necessary for a Simscape model is present. “Any relevant data in the CAD system can be extracted for use in a Simscape model. The purpose is to design and simulate the performance of a speed controller attempting to maintain car speed at a desired value as the incline angle is dynamically varied. VisSim is used here to model the speed response of a car, with a function of the throttle position and incline angle. Then you can refine that model to adequately represent the control system by adding other mass concentration points,” says Kolk. At the simplest level, we can transform a CAD model into a single mass-spring-damper model in VisSim. “Mass-spring-damper models are the most basic building blocks for system models. But, according to the system-modeling experts, the CAD model could be the starting point. The general impression is that the detailed 3D CAD model that defines the geometry of a product is not readable in system modeling software therefore, the mechanical behaviors, geometric values and component shapes already described in CAD have to be redrawn from scratch for the system model in another software program. Efforts to bridge the two disciplines will likely continue as multidisciplinary, collaborative product development becomes standard practice and not just a theory. “The computational fluid dynamics (CFD) model-or a simplified version of it, at any rate-could drive a system model in VisSim ,” says Richard Kolk, chief technical specialist for VisSim at Altair. In ours, some parts of this are automated so you can get a skeleton structure to start your system model,” says Johan Rhodin, kernel developer at Wolfram. Most tools are moving in the direction to allow data import from CAD models. That hasn’t been well communicated to the CAD community. “The tools in the system modeling and simulation industry-not just ours but others as well-have made a big leap in the last five years or so. So the work completed in one side won’t be of benefit to the other-or so it seems. The two groups use different software tools. System modelers, on the other hand, conduct simulation by computing the effects of varying inputs on the overall structure of the design. In CAD, simulation means studying how stress, pressure and forces would affect the integrity of the design. System modelers work with fan speed, valve modulation, temperature and power as inputs. A CAD modeler includes inputs such as wall thickness, extrusion lengths, trim angles and other values that define the geometry of the design. The other side uses the same word to describe a schematic (mostly 2D) representing the data flow, input-output relationship and component hierarchy that depict the inner workings of a vehicle, plane, robot, plant or another complex system. When CAD modelers talk about “the model,” they’re usually referring to a detailed 3D assembly model, complete with electric components, standard mechanical parts, wire harnesses and manufacturing information. The two disciplines rely on the same vocabulary-model, model-based design, components, input parameters and simulation-to describe different objects and practices from their respective fields. The same might be said of CAD modeling and system modeling. It has been said that England and the United States are two nations separated by a common language. In the image above, the parts of the piston are clearly visible in the Simscape model and the 3D animation. Models you create in Simscape have the same structure as the system you are modeling.
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