Faster, better, cheaper

Machine builders can now expect their engineering software tools to provide an integrated solution to mechanical and electrical simulation. Nipun Mathur, the National Instruments motion control and mechatronics product manager explains how.

Intense competition is putting pressure on machine builders to deliver machines with higher throughput, reduced operating cost, and increased safety. For this reason, today’s machine builders have switched from rigid, single-purpose machines – relying purely on mechanical gears and cams – to flexible multipurpose machines by adopting modern control systems and servomotors.

Although these improvements have made machines more adaptable, they also have introduced a significant amount of complexity to the machines and subsequently to the machine design process.

Along with designing the mechanicals, machine builders now incorporate control logic, human machine interfaces (HMIs), networking, and machine condition monitoring systems into their designs. The added complexity has created inefficiencies in the machine design process that lengthen design time and increase design cost.

Solving this multidisciplinary engineering problem requires improvements in three key areas – development techniques, design tools, and embedded control technology. The term mechatronics is gaining popularity as a way to describe this evolution. It represents an industry-wide effort to improve the design process by integrating the best available development practices and technologies to streamline machine design, prototyping, and deployment. A mechatronics-based approach can lower the risks associated with machine design and meet the following five key challenges that machine designers face today.

A typical machine design starts with mechanical engineers designing the machine mechanicals using CAD tools. Once they complete the CAD model and create a physical machine, electrical and controls engineers lay out the electrical system and program the machine controller. The design team performs the first test run of the integrated machine on the physical model. Any problems at this stage that require reworking machine parts can lead to long delays and increased expenses and can mean the difference between profit and loss for the machine builder. Getting input from controls and electrical engineers early in the design process can significantly lower this risk. The mechatronics design approach addresses this challenge by connecting machine design tools and creating a virtual machine prototype before engineers design the physical machine.

A virtual machine prototype is a 3D CAD model of a machine that interacts with a simulation of the machine controller to visualize and test machine movements and logical operations. By creating a virtual machine prototype, design teams can test and improve their machine designs in software before creating any physical components. The key to virtual machine prototyping is design tool integration – linking mechanical, electrical, and control design tools.

Machine builders can use graphical system design tools from National Instruments and 3D CAD tools from vendors including SolidWorks to create a virtual machine prototype. They can test the operation of their machines before creating any physical models by developing their control logic and motion profiles with National Instruments LabVIEW and by creating a 3D CAD model of their machine and simulating it with SolidWorks.

After testing control logic and motion profiles, machine builders can deploy the code to a National Instruments CompactRIO embedded system. The NI LabVIEW FPGA Module and the NI 9505 motion power drive module for NI CompactRIO offer a flexible platform to create precise motion control for machines.

Understanding customer requirements and developing an appropriate design plan for the machine’s mechanical and control systems can be a long and involved process. Miscommunication with the customer in this process can lead to unsuitable machine design and increased cost. By using 3D CAD, machine builders have improved communication with their customers by providing a virtual model of machine mechanicals.

By using virtual machine prototyping and adding logic simulation to the 3D CAD model, machine builders now can show their customers how a machine will function before investing in the development of the physical mechanical structures. In addition to demonstrating the machine operation for the customer, virtual machine prototyping also can increase interaction among design team members early in the machine design process, resulting in a better final machine.

Debugging motion profiles on a live machine can be risky. A crash can result in weeks of downtime and added cost for replacement parts. By integrating motion profiles generated in LabVIEW with a 3D CAD model of the machine in SolidWorks, machine builders can detect potential collisions on virtual prototypes, safely verify and fine-tune their motion profiles, and avoid any collisions on the physical machine.

Because of the complexity of motor drive systems, choosing a motor with the optimal size, cost, weight, and performance for an application can be challenging. If a motor is too small, it can result in overheating, poor control performance, and difficult tuning. If a motor is too large, it can add unnecessary weight and cost to the machine. Machine builders can use virtual machine prototyping to improve the motor sizing process.

With LabVIEW and SolidWorks, machine builders can easily determine the torque required to drive the machine with the desired motion profile. They then can use LabVIEW for motor simulation and determine the best-fit motor for their application to meet the machine’s torque and speed requirements.

Determining the initial PID tuning parameters of a complex machine is difficult, and incorrect settings can produce unexpected machine movements. Using virtual machine prototyping, machine builders can tune PID control algorithms on a 3D CAD model of a machine and gain insight into the PID tuning parameters for the physical machine. These PID tuning settings can then be used on the real machine as a safe starting point.

By integrating machine design tools, the mechatronics approach to machine design streamlines the design process, improves communication both with the customer and within the design team, verifies motion profiles, improves motor sizing and PID tuning, and can give machine builders a clear competitive edge.

This article first appeared in the Q2 2007 issue of the National Instruments Instrumentation Newsletter.