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Concept Vehicle Prototyping: Driving Costs Down

The design of any road vehicle is innately complex and time-consuming, but this is even more prominent when designing concept cars, as the futuristic cars are more innovative in design and unbounded by production constraints. The Mercedes-Benz F300 Life Jet, presented at the Frankfurt Motor Show (IAA 1997), is a prime example of such a complex vehicle.  The inspiration behind the F300 was to combine the benefits of a motorcycle with those of a car.  Its key component is its “Active Tilt Control” Technology, which incorporates a closed-loop computer control system with tilt actuators and a complex 28-joint, 3 degrees-of-freedom front suspension, allowing the car to lean into corners sharply as a motorcycle does.

Designing such a vehicle, from concept to modeling to prototyping, is very time-intensive and the Benz F300 Life Jet was no exception. The design and coding of the mathematical dynamics model of the suspension took a team of engineers thousands of hours to complete. However, using the latest tools from Maplesoft, Maple 11™ together with DynaFlexPro™, this work can be reduced by four orders of magnitude.

Building Models, over 10,000 Times Faster
 
In February 2007, Omer Yagel, Engineering Director of DigiSec, Maplesoft Partner in Israel, decided to find a smarter method for modeling and simulation that would significantly reduce the time and cost involved. That’s when he turned to the modern technology tools offered by DynaFlexPro.  Working from publicly available sketches, he chose the F300 to be his test case model and completely modeled its suspension dynamics from scratch, including non-linear geometric constraints, single side constraints and tire response, in only 45 minutes.

DynaFlexPro, an add-on tool to Maple, is ideal for modeling and simulating the dynamics of mechanical multi-body systems. It combines graph theory algorithms with robust mechanical engineering formulations to automatically generate a symbolic set of equations from the system model. Once exported into the Maple environment, this set of equations enables further insight and analysis, which is a great improvement over the basic time domain simulation that is the sole offering of all other tools.

DynaFlexPro ModelBuilder™, the graphical user interface of DynaFlexPro, facilitates the rapid creation of system models using block diagrams, drop-down menus and property boxes. Each block represents a body and is symbolically assigned properties such as inertia tensor, physical dimensions, rigidity and viscosity. ModelBuilder also enables adding reference points on the bodies as well as links and joints with their properties, such as locations, order of rotation and degrees of freedom. Linking the bodies is simply done by drawing a line between two joints. Constructing models in the DFP environment is incredibly easy, with only a small learning curve.

The DynaFlexPro algorithms, together with Maple’s powerful computer algebra technologies, are used to generate a minimal set of ordinary differential equations (ODEs). The model is more efficient and manageable, and therefore easier and faster to work with than manually generated models. In addition, since the solution’s derived equations are symbolic they provide a deep physical insight, helping the user to obtain all needed information and ease both viewing and sharing.

The Maple software itself can be used to manipulate these complex equations and provide analysis almost instantly, in whatever form the user desires, including automatic generation of code for real-time simulation.

“Using Maple 11 together with DynaFlexPro was absolutely stunning,” said Mr. Yagel. “In the past, manually constructing such a complex dynamics model, analyzing the system and coding the model for simulation would have taken a team of senior engineers and experts over 10,000 hours; with DynaFlexPro it took me merely 45 minutes! It is shockingly impressive.”

Apart from the productivity benefits, working with DynaFlexPro offers other advantages.  First, exporting to real-time simulation is much faster because Maple allows the automatic creation of Simulink® blocks or programmatic code in a variety of languages.  The equations comprising the model can thus be easily embedded into different real-time simulation platforms, potentially saving years of work; a time saving that otherwise would be impossible to achieve. Introducing changes and altering the model, a requirement in the research phase, is made effortless using DynaFlexPro.

Mr. Yagel believes that these advantages are only a glimpse of what is to come. “It is absolutely inevitable that dynamics and control design will be impacted positively by Maple and DynaFlexPro,” he said. “Using Maple and DynaFlexPro returns its cost the first day you put it into real use. No manufacturer, designer or engineer can afford to ignore a 1,000,000% increase in productivity… that is when 10,000 hours of work shrink into merely 45 minutes! Furthermore, in merely a couple of hours I got to exploit DynaFlexPro fully! In over 20 years of academic and industrial career I have never seen such a revolutionary tool.”

_{Simulink is a registered trademark of The MathWorks, Inc.}