[Technology Report]
Multicore Matters With Mechatronic Models
Complex mechatronic simulation is key to application development, because a device in hand isn't always an option.
Whether it's single microcontrollers handling motor control or an automobile assembly line containing multiple robots, you can be sure mechatronics is in the mix. Simulating such complex systems allows developers to build without having the hardware in hand. This is critical when some or all of the hardware doesn’t exist, but becomes even more valuable when considering “what if ” scenarios.
However, two major issues continue to crop up: speed and complexity. Larger systems, more detailed simulation, and a host of other factors push the need for high-performance host development systems. Tradeoffs between simulation speed and the level of accuracy must often be made because of available resources. Faster processors always help, but the trend toward multicore systems actually works in favor of simulation because the systems being simulated are distributed as well.
The environment is more complex than typical programming environments because of physical concerns. For example, Figure 1 shows a control system for a Stewart platform commonly used in production lines and many other industrial applications. The graphical programming environment is the MathWorks’ Simulink.
The SimMechanics add-on to Simulink highlights the kind of simulation environment needed for today’s mechatronics development requirements. SimMechanics complements the MathWorks’ other simulation tools, including SimElectronics, SimDriveline, SimHydraulics, and SimPowerSystems.
In this case, there are effectively two models: the simulated physical world model and the application model. The latter occurs because Simulink and Matlab are model-based development tools, so the application is a model. The physical model accounts for the physics-based simulated environment. The application model interacts with this environment to simulate the application running in the real world.
The mechanical aspects of the physical world represent just the start in many designs, due to the growing importance of other considerations. For instance, temperature, hydraulics power, and radio transmission often come into play with applications that range from robotics to cell-phone design. Often, this is where the CAD realm merges with the programming realm.
Several CAD vendors, such as Autodesk and Solidworks, have advanced packages designed to handle simulations, though they’re typically oriented toward physical construction versus process-control development. SolidWorks Simulation Premium contains advanced finite-element-analysis (FEA) support. The package can target stress under dynamic load. It also addresses nonlinear analysis like deflection and impact with flexible materials such as foam, rubber, and plastic.
CAD designers are familiar with modular construction. Remmele Engineering uses models of Nook Industries’ actuators and components to create assembly-line designs using SolidWorks (Fig. 2). Also, Remmele Engineering develops products for a range of applications from novel drug-delivery systems to energy-storage systems that require physical as well as control components.
Nook Industries offers a line of linear actuators that typically wind up in computer-controlled systems. The company’s Web site is set up to deliver 2D/3D models of its products so a designer can drop in an array of linear actuators and develop a virtual device or production line. This approach is common for companies that deliver physical devices, but less so when it comes to support for control applications.
Simulation and analysis of physical entities is useful in a design that doesn’t include a computer-based controller. However, if there is one, it can be even more valuable due to this type of system’s greater complexity. Most CAD packages work with software-development tools, too.
Take Solidworks and National Instruments, who have worked together to integrate Solidworks’ COSMOSMotion with National Instruments’ LabVIEW (see “Cooperation Leads To Complex, Real- World Simulations” at www.electronicdesign. com, ED Online 17273). This type of integration allows CAD designers to prepare object models of physical entities like gears, arms, and boxes while programmers concentrate on the feedback and control algorithms that will handle the motors and actuators within the system.
Tying objects together enables the models to cooperate, and rendering systems permit visualization of the models in action. Either modeling environment alone can demand significant amounts of computing power, and rendering can tax the best graphics subsystems. Putting it all together can burden even the most powerful systems when creating large models. At this stage, multicore hosts can make a significant difference.
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