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Interface Design Involves Highest Levels of Complexity

Today's electronic products may often combine clever use of different technologies, but the design of the human-machine interface (HMI) for those products can often be as instrumental to the success of those products as the design of the product's main functionality. Effective HMIs have contributed to the success of a wide range of products, from popular consumer electronic products to the most advanced military and aerospace equipment.

Aerospace applications range from cockpit controls and displays and cabin environment controls to in-flight entertainment systems. HMIs are used throughout defense electronic systems, whether for shipboard, airborne, or ground mobile applications, such as hand-held computers, high-resolution monitors, and secure voice/data communications devices. Because of their exposure to harsh environments and rough treatment, these products often require ruggedized HMIs.

Having the Correct Interface
"You've got to have the right interface for the right application," says Hemant Mistry, president of Jayco MMI (man-machine interface) of Corona, CA. "HMIs for defense and aerospace applications must be designed to improve cognition and comprehension to enable rapid decision-making. Thus, it is essential that not only is information clearly presented, but that inputs to a system are easy and intuitive to make in order to eliminate errors in stressful situations."

While an HMI might be considered an integral part of a product (which it ultimately becomes), the design and manufacture of the interface is often a separate, specialized process that involves the highest levels of complexity, both human and technological. At the same time, build-to-print HMI designs created without the collaboration of an interface specialist are almost always fraught with problems.

Developing a successful man-machine interface involves design subtleties, such as ergonomics, psychology, and other "user-centric" considerations. It may also involve a choice of materials and interface technologies, the need to perform in harsh environments, and the need to fit within limited space on smaller products. Whether an interface is displaying information, collecting data, or controlling operations, it may require special design consideration such as ruggedized features or the integration of multiple elements. These are among the many design challenges faced by developers of HMIs.

Avoiding Design Pitfalls
Improper design of an HMI can render a product ineffective. As an example, video cassette recorders (VCRs) were consumer products designed to revolutionize television viewing habits, but they offered interfaces that discouraged users from even setting the time. Other newly developed consumer, scientific, and industrial products have also been compromised by user-unfriendly interfaces. One example is requiring the use of touch screen typing, which is considerably more difficult than keyboard typing, particularly in turbulent or bumping conditions. When developing professional equipment for critical applications, the design of the most appropriate HMI has become even more challenging.

Given so many available interface solutions available, it is difficult for most product designers to determine which switch and display technologies are appropriate, which control modalities should be used, which functions require direct user access, which materials and construction techniques are optimum, and how different engineering constraints may influence both design and costs.

Complete Documentation Needed
Experienced engineers with knowledge of HMI solutions often provide complete documentation for their designs. While these approaches may be excellent, they may also represent lost opportunities for cost reductions and other benefits when not consulting with HMI experts. According to Keith Henzig, Vice-President of Engineering at Secure Communication Systems in Santa Ana, CA ( "There are serious challenges involved when customers build-to-print their own interface designs. Those include possible errors requiring redesign and additional time and money. Also, depending on the application, reliability is always a key constraint."

Heinzig notes that his firm's engineers are not open to compromises that may impact reliability. The company provides custom rugged computers and custom contract manufacturing solutions for defense, aerospace, and industrial applications that involve extreme environmental conditions. He explains: "Our systems can be found in the hands of troops and on vehicles all around the world. "Our commitment to providing high levels of service and quality has made us a long-term partner to many manufacturers in the defense industry." The company specializes in commercial-off-the-shelf (COTS) equipment that is cost-effective and reliable.

Jayco's Mistry offers that from an interface developer /manufacturer's perspective, the built-to-print approach carries with it certain avoidable risks: "In most cases, a build-to-print HMI requires re-design, re-thinking that can be unnecessarily expensive and delay product releases." His firm specializes in extreme applications for defense, aerospace, and other sectors, and is capable of handling extremely complex design work, utilizing virtually any available interface technology from mechanical switches to touch panels.

Mistry, whose company designs and builds equipment to meet or exceed military standard (MIL STD) requirements, views HMIs as key systems within a design, not just a component. Through early involvement during a system's design phase and integrating an HMI's components into a complete subassembly, including enclosures, displays, switches, and electronics, a high-performance HMI can be developed that will be easier for an end-user to manage and integrate into their system. He points out that the most efficient and effective approach to HMI design usually involves a team approach that includes the product engineering staff as well as the interface supplier. Such a consultative approach can reduce product development time and costs while solving complex problems with superior solutions and packaging.

Mistry says: "By working together the team can ensure that all of the relevant ideas are thoroughly explored, and that various manufacturing issues are taken into account." He adds: "I think the best HMIs are actually simple and intuitive," he adds. "But to make them simple and intuitive is not easy. What is required is a thorough understanding of the application, an understanding of the environment that the product is going to be used in, and the technologies that are available to achieve the end."

A major concern in military and aerospace applications is ensuring that interface devices are ruggedized for extreme environments. This includes protection from corrosion, providing for military-grade shielding, protection against shock and vibration, contaminate sealing, sunlight readability, night vision lighting, and extended-life grade products. As Heinzig explains: "We have worked successfully with Jayco for a number of years, and their preliminary design consultation has been very helpful in keeping us on the right track as far as planning and implementing the HMIs for our products. Some of our more recent projects include very small controls, such as wrist displays for the military."

Jayco often provides a digital or virtual prototype for a customer to see a proposed solution. Heinzig explains: "The trend today is that products have to be smaller, lighter, and use lower power. Yet, you somehow have to find room to squeeze some HMI controls onto the equipment, and that gets more difficult as product sizes continue to be reduced." He summarizes that finding room for HMI controls often requires creativity and advanced planning.


Contact: Jayco MMI, Inc., 1351 Pico St., Corona, CA 92881-3373 877-529-2648 or

951-738-2000 fax: 951-738-2010 E-mail: Web:

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