Cooperation Leads To Complex, Real-World Simulations

If you build it, they will control it. These days, the building is going on virtually since soft systems are faster and easier to build. Some systems may never be turned into physical entities, but knowing what will work ahead of time can save time and money.

Yet the quality of simulations can vary significantly, especially when open-loop or closed-loop control is part of the equation. Likewise, the cost of creating more accurate simulations can be very high. It's typically cost-effective for large projects such as Boeing's new 787 Dreamliner or the latest line of cars showing up at the Detroit Auto Show.

The changes these days are the dropping costs in creating simulations and rising quality of those simulations. In many cases, the overhead to run a simulation after creating the hardware and software design is getting lower. Likewise, simulation is becoming part of the development and diagnostic process.

Simulation's advantage lies in the ability to significantly reduce the overall design and implementation of a machine or assembly-line design. This is especially true when the simulation can help detect unforeseen errors, such as improper interaction between components.

Mechanical CAD systems like SolidWorks Office are already used to create very accurate 3D designs. COSMOSMotion, a SolidWorks add-on, can provide standalone motion simulation based on these designs by incorporating physics-based dynamics, including forces, energy, and friction. It's often used to test the mechanical aspects of a design.

But these days, microprocessors control more of these designs. 3D visualization of the mechanics alone has proven invaluable. Combining these with programmatic control is even more valuable.

Integrating the virtual process control
National Instruments' LabVIEW is a graphical programming environment whose SoftMotion module has been widely used in advanced process control applications. It recently has been integrated with SolidWorks in a bidirectional linkage that allows LabVIEW applications to control virtual physical entities created in Solid- Works (Fig. 1).

The LabVIEW SolidWorks Mechatronics Toolkit is still in its infancy. However, it highlights a growing trend of cooperation that's necessary as designs become more complex. The combination of systems simulates movement and interaction, accounting for the physics model of the virtual environment.

Integration like this has been possible in the past. Both tools had application programming interfaces (API), but the amount of work required to glue these two packages together was extensive. Now, National Instruments and SolidWorks have delivered this linkage, significantly simplifying a designer's simulation chores (Fig. 2).

Combining the two systems is no easy matter because of the two-way interaction between the two programs. Both need to maintain synchronization during the simulation as well as support debugging and diagnostic hooks. Likewise, there are the user-interface aspects for handling the interaction between programs. All of this is required just to allow a simulation to be set up and run.

Exposing this support and its interface would be great for bringing other systems together. But this particular instance is likely to remain specific to this pair of platforms primarily because the combination is still in its infancy. It will probably be a few years until a standard interface could be presented given the number of planned enhancements.

Product advancement typically takes precedence over standards and publishing application programming interfaces (APIs). Still, the SolidWorks/LabVIEW combination will not be unique given the possibilities for this level of co-simulation. One of the key aspects of the integration is how it enables users to concentrate on one side or the other while retaining access to both sides.

For example, a programmer can concentrate on the LabVIEW process control program, also called a virtual instrument (VI), while seeing the results of its operation via the SolidWorks simulation using a Solid- Works model provided by the CAD designer. The reverse is true as well. This works especially well because of the kind of user interface that's essentially inherent with a VI.

Integration issues
Simulation doesn't come for free. The simulation's fidelity and presentation affect the amount of computation involved.

For instance, a simulation may display a 3D line drawing without hidden line removal accounting for gravity but not friction. At the other end of the spectrum may be a 3D view with lighting effects and a physical simulation environment that tracks not only movement and momentum but also stress and heat distribution.

Fortunately, multicore systems are providing increasingly powerful compute platforms. This allows some of the Lab- VIEW/SolidWorks simulations to run in real time with solid 3D rendering.

A migration to multicore PCs is only part of the issue. Larger screens and multiple screens make a difference since the amount of information presented is increasing. Minimally, a pair of displays is handy with the LabVIEW/SolidWorks integration so the user can see both interfaces at the same time. They both tend to require large amounts of screen real estate.

Debugging integration is one area open to significant improvement. This is true when integrating diverse components like LabVIEW and SolidWorks that were designed to work alone and where designers tend to work primarily within one environment or the other. Eventually, the linkages between systems would allow things such as breakpoints on both sides to be used with equal ease.

The two platforms can exchange a great deal of information, but the amount of information can make it difficult to determine what piece of information will be required. For example, a breakpoint might be triggered if the application is in a certain state and the pressure in a particular spot in the simulation has exceeded a selected amount.

Debugging techniques such as tracing can be invaluable. But features like backtrace execution supported by products like Green Hills Software's TimeMachine will take longer to implement because of the level of integration required to implement these features. These debug tools are important because designers want to refine proportional-integral-derivative (PID) controllers or look for collisions when various parts of objects are being moved.

These tools open up opportunities for designers who work at the integration level, but these opportunities will require a new level of modularization and integration. For instance, the Lab- VIEW SolidWorks Mechatronics Toolkit provides a single simulation environment.

At the next level, designers would want to select which subsets of the simulation and control system would be tested. This level of control will be necessary as the breadth of simulation increases from a single workstation on a production line to the production line to an entire building. Such changes need to allow for different levels of fidelity.

Robot simulations
Robotics also incorporate mechatronics. It has always had varying levels of simulation, but the level and sophistication have been growing as well. The CAD and robotic simulation environments have been distinct, but this will likely change as combinations like National Instruments' and SolidWorks' offering becomes more common. Given National Instruments' support of Lego Mindstorm, this support is quite likely.

The Microsoft Robotics Studio (MSRS) platform has brought robotic simulation to the forefront. Its simulation environment is specific to testing robots and, more specifically, those robotic applications programmed using the Microsoft Robotic Studio .NET-based programming languages. One interesting aspect of MSRS simulation is its support for physics engine hardware acceleration like that available from Ageia, which can significantly increase simulation fidelity (see "Virtually Real" at www.electronicdesign.com, ED Online 12541). And, Ageia is not alone in using massive parallel processing to accelerate simulations.

Platforms like AMD's R580 stream-processing platform provide a similar approach (see "Turn Stream Processing Into A Raging River," ED Online 14554). Combining this range of raw computational power into a system that can deliver real-time simulation results will require a significant amount of integration, but the result will be the ability to handle larger and more complex simulations that cross many support applications.

Integration like that between National Instruments' Lab- VIEW and SolidWorks COSMOSMotion aren't unique, though this particular implementation is quite impressive. Both this integration and general integration among CAD and control software vendors will improve over time.

National Instruments www.ni.com

Microsoft www.microsoft.com

SolidWorks www.solidworks.com