Multidisciplinary machine building

A view of mechatronics, a system-level approach to the process of designing intelligent, embedded systems.

In today's world it is rare to find electromechanical devices without some kind of embedded intelligence. From production systems, remote control vehicles and automotive subsystems, like ABS, to everyday equipment like digital cameras, CD players and washing machines, most electromechanical devices rely on embedded controllers.

Embedded systems offer enhanced performance, reduced energy consumption, better reliability and safer operation, and help differentiate a product from the competition.

However, the benefits of an embedded system can come at a price. As devices take advantage of more powerful microprocessors to provide the intelligence for embedded systems, the interaction between hardware and software becomes more complex. Managing this complexity can prove challenging when hardware and software development processes are not integrated. The problem is that when you have separate hardware and software engineering teams, they will state requirements, describe problems, and test and implement solutions in very different ways.

Mechatronics is a system-level approach to the process of designing intelligent, embedded systems - devices that are not just electrical or mechanical, and are more than just control systems. It is a complete integration of electrical, mechanical and control system design processes.

Most engineers are surprised to learn that the term mechatronics is nearly 40 years old. It was first used in 1969 by Tetsuro Mori, an engineer at the Yaskawa Company.

The evolution of mecha-tronics can best be compared to the evolution of the car. In the 1960s, the radio was the only significant electronic device in a car, all other parts were either mechanical or electrical. Since the introduction of the electronic ignition system in the late 1970s, there are now 30-70 microcontrollers in a typical car, with luxury vehicles often hosting over 100.

Mechatronics has become a necessity for product differentiation in automobiles. We have now come to expect quality and reliability from all car models. It is the intelligent features of a car, born from mechatronic system design, that enable manufacturers to stand out from the competition.

Complex design

If you take a look at all of the different aspects that go into a modern-day mechatronic machine, you can see that they are quite complex to design and manufacture.

In addition to the mechanical design that has always been a key aspect of machine development, today's machine builders must also be proficient in a wide variety of additional skills. From motion control design and the correct selection of motors and drives, to the development of HMIs for human interaction, requiring networking and GUI development, modern machine design requires myriad different design tools and skills.

In most traditional design approaches, engineers test software on hardware prototypes, addressing software validation very late in the development process. Errors found in hardware or software at this stage could create costly delays and are time consuming to trace back to their root cause. Errors related to incomplete, incorrect or conflicting requirements could even necessitate a fundamental redesign.

Solving this multidisciplinary engineering challenge requires improvements in three key areas: development techniques, design tools and embedded control technology. The good news is that industry trends are beginning to address these increases in design complexity and associated risk, allowing machine builders to reduce their development time from initial design to final deployment.

The first trend that we will look at is the movement from a sequential design process to the mechatronics approach of concurrent design. The concurrent design process is tightly coupled with the second industry trend, which is the movement from executing the first prototype of a machine on a physical system, to executing it on a virtual system.

Perhaps the most important aspect of both of these is the integration of different design tools, often from different vendors, allowing them to work together and share data.

Sequential to concurrent design

In the traditional approach to machine design, the first task is to complete is the system specification.

Once the system has been defined, the machine design begins with a mechanical engineer designing the mechanics, typically with a CAD tool. After this is completed, the CAD drawing is then given to electrical engineers to begin work on the electrical design.

The electrical design, which includes tasks such as the selection of motors and drives, layout of the electrical system, and identification of specific sensors and actuators, is performed and given to embedded engineer for the embedded hardware and software design. The embedded hardware and software design includes selecting a control platform. If it is an off-the-shelf system, the engineer can begin work on the embedded software development.

If the control platform is a custom design, this process can take significantly longer, and requires board bring-up before the software development can begin. It may even involve two engineers, a hardware engineer and a software engineer. One of the most important aspects of machine design is the control theory, which is the last design aspect to be finalised in the sequential approach.

The further down the design process, the more and more each engineer has their hands tied because more of the machine has already been designed. Only after all of these steps are finished is the first prototype of the machine built. Any problems at this stage can lead to long delays and increased expense and can mean the difference between profit and loss for the machine builder. Getting input from electrical, embedded and controls engineers early on 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.

With the mechatronics approach (also referred to as the concurrent approach), all aspects of the machine design process take place in parallel. Once the system is specified, the mechanical, electrical, embedded and control portions of the design are worked on in parallel. This approach offers less constraints and it allows the design engineers to provide feedback to each other about how their part of the design is affected by the others. As the control and electrical design are key factors in development, this greatly reduces the risk of the project and provides the additional benefit of shortened development.

Prototyping on a virtual system

The second industry trend influencing mechatronics system design is the move from executing the first prototype of a machine on a physical system, to executing it on a virtual system.

A virtual machine prototype is a 3D CAD model that interacts with a simulation of a machine controller to visualise 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.

Virtual machine prototyping can help in solving many challenges machine builders face today.

In the mechanical design phase, machine designers have traditionally faced the challenge of completely understanding the customer requirements. Integrating a control design tool with the 3D CAD model of the machine can help in improving communication with the customer, building confidence that you completely understand the system requirements.

In addition it can also help in improving communication internally within the design team. It can assist the mechanical, electrical and control engineers in communicating earlier in the design phase to iron out the design concerns. This process can improve the architectural design of the machine.

The key to virtual machine prototyping is design tool integration - linking mechanical, electrical and control design tools.

Design tool integration

Design tool integration requires that the tools used for the different phases of machine design should tie in together and be able to exchange relevant information with each other. 

For example, a 3D CAD tool should be able to take in the output of a control system and show the simulation on a machine model. The tighter the integration between the tools the more efficient the design process will be.

The most common level of integration is to manually transfer information between design tools. This process can be very tedious and for most cases is not practical. Basic integration between design tools can be achieved using files; writing to a CSV (comma separated value) file from the control design tool and passing that information to the mechanical tool. While this gets the job done, it is a slow process. The holy grail of design tool integration of course is a common tool that can solve all aspects of machine design allowing the user to automatically pass information from one tool to another.

National Instruments (NI) and SolidWorks have collaborated to provide easy-to-use tools for virtual machine prototyping NI LabVIEW graphical programming language connects with 3D CAD mechanical models designed in SolidWorks and can implement motion on them.

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

After testing control logic and motion profiles, machine builders can easily deploy the application to a variety of control platforms using NI LabVIEW ranging from embedded PCs to NI CompactRIO embedded programmable automation controllers (PACs).

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