Two things are always in short supply during machine development: time and money. Traditionally, design of motion-based machines has been a serial process. The mechanical engineers would design the frame and the motion elements. They would pass the mechanical design along to the electrical engineers, who would specify the motors, drives, controllers, and feedback devices necessary to meet spec. Finally, the system would be handed over to the controls engineers who were responsible for making the finished machine operate to spec.
This silo method wasted both time and money. Frequently, prototypes revealed errors that were not caught earlier in the process, leading to expensive reworks and missed deadlines. At Motion Solutions, we think there is a better way: an integrated design approach known as mechatronics.
Mechatronics emphasizes an interdisciplinary approach to machine development. Instead of each engineering group performing their tasks separately, all teams participate from the very beginning. They exchange feedback at every step in the process. This is really the only way to build sophisticated electromechanical systems.
For an example, consider a patient bed in a medical diagnostic system. The unit needed to offer high-speed, precise positioning while being strong enough to hold even very heavy patients without introducing error or increasing settling time. In addition, space constraints required that all electronics be located under the bed.
It is impossible to effectively design this type of system without a multidisciplinary approach. We had to know the size of the motors, the gearboxes, and the other sensors during the mechanical design to ensure that everything would fit and there were no surprises. Because this was a medical device, it had to satisfy redundancy requirements by including dual position sensors.
In addition, these devices need to be included in the CAD model upfront to guarantee that there was enough space and that the system performed to specifications. If we had not planned ahead for the sensors during mechanical design, there would not have been room.
The integrated approach also helps with cabling design. It’s easy to focus on the mechanical design and electronics, but cabling design is one of the trickiest aspects of space-constrained electromechanical systems. Factors to take into account range from bending radius to cable diameter to threat of crosstalk. As a result, cabling has to be taken into consideration from the very beginning.
A Model-Based Approach
The shift to mechatronic design has been enabled in part by the development of sophisticated software tools. Today’s mechanical engineers apply finite element analysis and perform extensive simulations and modeling to understand exactly what the design will look like—and how it will perform—before they build anything. Sizing software makes it possible to select the optimal motors, gearboxes, and drives to do the job within the budget.
Using model-based definition models helps engineers and builders predict stress points, possible failures, and areas of improvement prior to manufacturing.
Particularly for complex problems, mechatronics provides a more efficient path to an optimal solution. For experienced design teams, simple XYZ systems are straightforward to build. The number of issues that can arise are limited and have typically been faced and solved over time. For very complex systems unlike anything that has been built before, however, an integrated design approach is absolutely essential.
Of course, systems have to operate in the real world. A team can develop multiple models and run the calculations, but when the prototype is built, it may display unexpected results. The more analysis performed upfront, the lower the chance of major design changes.
The mechatronic approach can be effective whether applied to a clean-sheet design or just a part. Customers sometimes reach out to us asking for troubleshooting assistant with a specific component like a ballscrew or a motor. Frequently, though, that component is not the root problem. If we go back to the beginning and get all the details on the system, we find out that it’s not an issue with the motor or the ballscrew. It might be the bearing, it might be the mount, or it might be a combination of other factors. You need to have the details of the entire system and how it works before you can effectively diagnose a problem.
Complex designs require partners that understand mechatronics because that is the most effective route to the best design. By applying mechatronics techniques, engineers can optimize around all aspects of the problem, whether mechanical or electrical or controls. It’s essential to bring the complete team together on a project from the beginning. Development should always be an integrated process.
Wally Logan is vice president of engineering at Motion Solutions. Check out Motion Solutions for more information.