Mechatronics Resolves Design Challenges

Intense global competition is putting pressure on machine builders to deliver machines with higher throughput, reduced operating cost, increased safety and more features that improve productivity and differentiate their machines from the competition. For this reason, today’s machine builders have switched from designing rigid, single-purpose machines that rely purely on mechanical gears a...

By Nipun Mathur, National Instruments June 1, 2007

Intense global competition is putting pressure on machine builders to deliver machines with higher throughput, reduced operating cost, increased safety and more features that improve productivity and differentiate their machines from the competition. For this reason, today’s machine builders have switched from designing rigid, single-purpose machines that rely purely on mechanical gears and cams to creating flexible multipurpose machines by adopting modern control systems and servomotors.

Along with designing the machine mechanicals, machine builders now incorporate control logic, human machine interfaces (HMIs), networking, machine condition monitoring and Web reporting systems into their designs. Although these additions have made machines more adaptable, they have also introduced a significant amount of complexity to the machine design process. The added complexity has created inefficiencies that increase design time, cost, and risk.

Solving this multidisciplinary engineering challenge requires improvements in three key areas: development techniques, design tools and embedded control technology. The term “mechatronics” is gaining in popularity as a way to describe this evolution. Mechatronics represents an industry-wide effort to improve the machine design process by integrating the best available development practices and technologies to streamline machine design, prototyping and deployment.

An increasing number of machine builders are receiving significant business benefits by adopting the mechatronics approach. Design & Assembly Concepts, a custom machine design house takes advantage of the latest mechatronics design techniques to increase efficiency and productivity. “As a custom design house, our machines have to be right the first time we build them,” said Mark Ganninger, president. “Any design changes late in the design process can mean a transition from profit to loss. The mechatronics design approach significantly reduces this risk for us by streamlining the design process.”

A mechatronics-based approach lowers the risks associated with machine design, speeds the design process, improves understanding of customer requirements, and streamlines debugging.

Serial and slow machine design

A typical machine design today starts with mechanical engineers using CAD tools to design the machine mechanicals. Once they complete the CAD model and develop 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 machine model. Any problems 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.

Mechatronics is a system-level approach to designing electro mechanical systems that merges mechanical, electrical, control system and embedded software design.

Getting input from controls and electrical engineers early in the design process can significantly lower this risk. The mechatronics 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 that interacts with a simulation of a 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. For example, collaboration between control-system hardware and software vendor National Instruments and CAD-software vendor SolidWorks to integrate their tools for virtual machine prototyping connects NI LabView graphical programming language with 3D CAD mechanical models designed in SolidWorks.

Using this integration, machine builders can develop the control logic and motion profiles and create a 3D CAD model of their machines to test the operation of the machines in software before developing any machine mechanicals.

Communication with customers

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 customers by providing a virtual model of machine mechanicals.

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

Machine builders have traditionally used a sequential approach to machine design, resulting in a lengthened design process. Mechatronics streamline machine design, prototyping, and deployment and reduces the risk and cost of machine design.

“Virtual prototyping gives us a competitive advantage during the bidding process, allowing us to clearly demonstrate the conceptual design to our customer and provide accurate estimates for specification such as throughput,” Ganninger adds.

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 with a 3D CAD model of the machine, machine builders can detect potential collisions on virtual machine prototypes, safely verify and fine-tune their motion profiles and avoid any collisions on the physical machine.

10x throughput increase

Using a mechatronics-based approach and open graphical system design tools helped engineering-services company Boston Engineering reduce development time and cost for a digital photo kiosk. As a result, image printing was more predictable, more reliable and higher in quality at an imaging output speed 10 times faster than similar devices on the market.

The kiosk uses an innovative printing process that allows customers to instantly print images from digital camera files. The key to success is to deliver high print quality in images. This requires precise tension control of media spools. The tension controller needs to adjust to vibrations from the cutter head, the varying number of photos printed at a time and variances in speeds of the motors driving the device.

Control system development demanded ongoing, cross-domain consultation among mechanical engineers, hardware designers, software developers and those knowledgeable about the details of the application. Modeling and prototyping were important for a successful design. Boston Engineering used higher-level tools for electromechanical design, including modeling the controller and prototyping the system.

Boston Engineering mechanical engineers created a CAD model of the mechanical system using SolidWorks. This mechanical modeling required several iterations as the customer better defined the subsystem mounting and volume allocation. The mechanical model was further refined based on control system specifications such as motor size, maximum inertia of moving parts and sensor selection.

Through modeling and feedback, it became evident that a simple PID controller would not provide the closed-loop bandwidth with the required stability margins. Therefore, the engineers resorted to a more sophisticated sixth-order phase-lead controller to meet the system’s closed-loop bandwidth of 20 Hz. Once the simulation showed that the system could meet the design specifications, engineers created a physical prototype.

Boston Engineering used the LabView graphical programming environment and the CompactRIO (reconfigurable I/O) FPGA-based (field programmable gate array) hardware platform, both from National Instruments. CompactRIO is a programmable automation controller (PAC) that combines an open embedded architecture with small size, extreme ruggedness, and hot-swappable industrial I/O modules. LabView was used to program the supervisory program on the module’s embedded microcontroller and to implement the motor control algorithm on an FPGA. This provided similarity in programming between the prototype and the deployed system. The PAC delivered pulse-width modulator (PWM) outputs to control two motors; encoders to provide velocity feedback for the motors; analog input channels for a Hall effect sensor position detector; digital lines for signaling; and channels for thermal and air readings.

The mechatronics approach helped provide more accurate, timely predictions of the system’s reaction, facilitated greater team-wide input, and helped in meeting higher-level customer goals for the new kiosk. By streamlining the design process, the mechatronics approach improves communication with the customer and within the design team, verifies motion profiles, lowers the cost of machine design, and gives machine builders a clear competitive edge.

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Author Information
Nipun Mathur is product manager for motion control and mechatronics at National Instruments. Reach Nipun at .