In our previous post in this series, we noted that it’s key to think through how the device or human-machine interface (HMI) will be used and for what purpose. From there, designers must consider how the marriage of mechanical engineering and design engineering can support that goal.

In service of that idea, we also noted that it’s critical to think about the machine’s human dimension and particularly about harmonizing the HMI. Today, we’re going to take a deeper look at that question and how it intersects with human psychology. Specifically:

  • How does the device trigger or facilitate desired behaviors in its human users?
  • How does it minimize or eliminate undesirable behaviors or outcomes?
  • What kind of user experience does it create?

If the physical components of an HMI (whether a membrane switch, capacitive switch or touchscreen) make it hard to operate the machine correctly and as desired, the design will cause problems and frustrate users. These issues can range from trivial (e.g., constantly pushing the wrong button to increase or decrease volume) to tragic (causing users to miss catastrophic safety alerts). It will also affect whether the user likes using the product – a critical element of design (and market) success.

Facilitating desired behaviors:

Users must be able to operate the device or machine effectively and safely, and the operator must be able use telemetry from the interface effectively to make good operational decisions. For example, think about driving a vehicle. The steering wheel, braking system, and all of the telemetry provided by the dashboard serve as the HMI. Drivers might apply the brakes in response to information from the speedometer, alerts generated by the dashboard, or other data. Or proximity sensors and related alerts might push the driver to swerve if another car is nearing. In both cases, the interface has helped them to drive more skillfully and responsively.

Minimizing or eliminating undesired behaviors or outcomes:

The product design must also recognize the realities of working with humans. For example, inadequate alerting – too slow, too quiet, too subtle – will delay emergency response times. Humans need bright colors and loud noises to catch their attention! Intermittent or inadequate responsiveness in the interface will also compromise performance. Imagine if a car only slowed sometimes when pressing the brakes, or if the driver always had to slam the brakes even just to slow incrementally, leading to sometimes over-braking and sometimes under-braking. That wouldn’t result in just an unpleasant driving experience, it could cause potentially catastrophic harm.

User experience:

It’s important to understand that both of the above questions impact how the user experiences the device. A mechanical engineer might only care about what the machine does, but the user also cares about how it feels. If information and operational controls are clear, easy to find, and easy to use, the experience will be more satisfying and less frustrating. Users will be more likely to use the device as intended and to produce desirable outcomes more reliably. They’ll also like using the product more, which can impact market success. As Amy Bucher, a psychologist and Associate Director of Behavioral Science for Wellness & Prevention, Inc., a Johnson & Johnson Company, says, “Sleek technology and elegant functionality increase product appeal. But to really hook users with your product, help fulfill their psychological needs.”

In our next post in this series, we’ll look at how these questions translate into aesthetic and stylistic design considerations. In the meantime, if you’d like an additional in-depth guide into the precise components and specifications that should be considered when designing and developing your next input device, please download our “Design Guide To Your Perfect User-Interface.”

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