Virtual Prototyping Technology and Mechatronics

This article shows how modern computer-aided design (CAD) systems with embedded analysis tools can enable mechatronics design.

Users always ask us to improve the performance of the designed machinery while reducing the capital cost. In order to achieve these two conflicting goals, we focus on mechatronics, which has great potential in mechanical design.

This article examines how today's computer-aided design (CAD) tools combined with mechatronics can help you build better machines. So you need to design a new machine, and you're convinced that mechatronic design methods and virtual prototyping are the right way to go, but where do you start? Let's start with a simpler pick-and-place machine.

In mechatronics design, three design teams (mechanical, motor and control) work in parallel. However, before the mechanical team completes the design, the motor and control team needs to get information about the machinery in advance. Virtual prototyping technology can provide mechanical information in advance. By connecting the 3D CAD system with a motion and structural analysis tool and a virtual controller, SolidWorks and NI have created a real mechatronics design environment. Using these tools does not mean that the heavy work in the mechanical design process is reduced, but the workload is shared by the design team throughout the design cycle.

The great value of virtual prototyping is that it allows you to make and correct design errors without the expense and time delay of building a physical prototype.

Virtual Prototyping Technology Design Process

Failing often and failing early is the way to go for virtual prototyping, and the way to fail is during the design process - not afterwards. So how do you 'fail' and still succeed? The trick is to fail at the right things, determine what are the key performance indicators (KPI's) for your machine, and use these as parameters and targets for subsequent testing. So, let's look at a pick and place machine and see how virtual prototyping can guide us in the design process.

Pick and place machine

Motion profiles are the building blocks of all machines. The simplest case is to move object A from B to C. But in some cases, the best way to get from B to C is not so obvious. One-step motion or two-step? Cam or servo? CAD allows you to quickly arrange the moving parts of a machine and check for collisions and range of motion. Since most machines do not start with a sketch, the initial CAD assembly is likely to be a mixture of a 3D model and a layout sketch or block diagram. [page]

Pick and place assembly layout

Even with such simple geometries, SolidWorks can calculate approximate forces and torques based on sketches or user-defined parts. We can now communicate these requirements to the electrical engineers, who will make recommendations for motors and drives. Furthermore, it is possible to take advantage of the software to download CAD models of motors and drives directly from the 3D Information Center (with more than a million models) or from the manufacturer's website.

Pick and place layout for assembling motors and drives

Initial design iterations provide force sizing to determine “first guess” motor and drive sizes. Using the motor and drive CAD models included in the assembly drawings, motion simulation can be quickly iterated to refine the motor and drive requirements. As the mechanical design matures and the CAD assembly becomes more complete, motion analysis software can be periodically iterated to ensure that there are no surprises when the physical prototype is built.

Once the motor size is determined, we can turn our attention to the performance of the machine and its structure. The typical machine KPI is its positional tolerance, which, at the mechanical level, is determined by the stiffness of the mechanism and the compliance of the drive. For our pick-and-place machine, we need a light, but very stiff moving structure combined with a very rigid support structure, drive and connection system that can fully meet the needs of the machine. We say fully because the compliance of the motor and drive is closely linked to the cost.

Using the SolidWorks integrated simulation suite, we can take the forces and torques from motion analysis and put them into structural simulation to evaluate machine strength, durability, and flexibility. Now, mechanical engineers can answer fundamental questions about machine performance. Does the machine resonate at any operating speed? Does the machine exceed the design specifications? Can we reduce the weight of the machine and the resulting cost? What is the service life of the machine components? This is not a simulation that is done only once, but it is constantly run to evolve and improve as the machine is developed, constantly providing the mechatronics team with the latest and most accurate information to make design decisions based on the specific situation. We are now fully involved in the design iteration cycle, and for a good design, the "what if situation" can be improved to a "no problem" design.

So far, we have only considered mechanical and electrical engineers, and the mechatronics design model is about three engineering teams working in parallel. So how can virtual prototyping help control engineers? We have seen how virtual machines can be driven from a CAD system, but what control engineers want is a virtual controller that can talk directly to CAD geometry and drive motion analysis, as is possible with LabVIEW NI SoftMotion for SolidWorks.

By determining the size of the motor and other components, the virtual controller can communicate directly with the CAD drawing and drive the motion analysis.

Now, control engineers can drive the virtual machine, fine-tune the control code and observe the machine behavior in real time. Control engineers can ensure that the motion profile is correct, investigate the effect of compliance on machine performance, and take care to design in safety features such as sensors or limit switches. For mechanical and electrical engineers, because the virtual machine is driven by "real" code, the added benefit is that mechanical engineers can determine "real" forces and torques, while electrical engineers can estimate "real" motor and drive requirements.