Eliminating the “gap”: How force-sensitive sensors drive novel HMI designs
Latest update time：2023-11-03 16:35
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The controls we use to interact with systems or machines have changed dramatically; from rotary dials and switches on telephones, or physical keys for driving your car, what were once crude devices have transformed into sleeker, more intuitive devices. The user interface allows us to connect seamlessly with the machine.
This article explores how human-machine interfaces (HMIs) are revolutionizing the way we interact with technology.
By Shaune Reynolds, Product Marketing Manager
The more information we have, the better decisions we can make. Today, we use a large number of sensors to obtain data, and then use application software to convert this data into valuable information. We have become the most information-rich group of people in history.
The sensors built into our phones alone can tell us a wealth of information
: Global Positioning System (GPS) receivers can determine our location with one-meter accuracy—and some new phones with
ultra-wideband (UWB)
can locate our locations with centimeter-level accuracy. ; Accelerometers measure how fast we're traveling; magnetometers determine the direction we're moving; and smartwatches have added heart rate detection capabilities and can even identify atrial fibrillation and measure blood pressure.
In addition, there are some sensors that allow us to control the device.
Human Machine Interface (HMI) sensors have been around for a long time and are mainly used to detect changes in activity or measure certain quantities. If you remember the dial telephone; it used a simple switch to detect the number of digits in the phone number. When the rotating dial returns to its original position, the switch will make a "click" sound from one to ten times. After seven repetitions - ten-digit dialing came later - your favorite aunt will answer the call.
As personal devices (such as simple watches) become more complex, the emergence of multiple HMI buttons allows us to use more functions. Today, everyone is familiar with HMI sensors, especially the touch-sensing devices built into tablets, cell phones, watches, automotive systems, machinery, and even refrigerators. The development of sensors has changed people's lives and made it easier for us to interact with more innovative technologies.
touch interface
Capacitive touch sensing technology is currently the most important sensor technology.
It's usually built into the display; a finger creates an increment of capacitance on the glass to identify the finger's position on the glass surface. The HMI software does the rest; it associates the location information with a function—whether that's activating a button, drawing a line, changing a parameter by moving a finger, or setting a function when a finger is held down in that location. Some HMIs also add strain gauges, image sensors (such as for fingerprint recognition), or simple buttons in unique ways; modern mobile phones incorporate many similar functions into complex mechanical designs.
Capacitive touch sensing allows us to use our fingers or a stylus designed for touch screens. The interaction is excellent,
but becomes less responsive when gloves are worn (for protection), when fingers get wet, or when exposed to other environmental conditions.
Of course, special conductive gloves can be used with capacitive touch technology; some thin gloves can also be used. The performance and reliability of sensors based on strain gauge and resistance technology will change with changes in environmental conditions, which may result in false alarms or no-sensing buttons, reducing the reliability of the HMI.
When capacitive touch needs to be combined with other technologies, the design at the mechanical level becomes more complex; for example, for physical and mechanical buttons, seals must be added to meet dust and moisture-proof requirements. In addition, special testing is required to ensure that resistance and reliability requirements are met. And when complexity increases, so do costs.
Force-sensitive MEMS devices for richer HMI
Modern force sensor technology allows for "gapless" designs by integrating highly force-sensitive devices under any surface—sometimes more than two inches thick. Force-sensitive devices eliminate the need for mechanical buttons and simplify design and requirements while providing touch responsiveness—regardless of how pressure is applied (gloved ungloved hand; stylus, pencil, or other object) or Or what the environmental conditions are (humid, dry, dusty, etc.).
The gapless design eliminates many challenges for designers and users, as well as the need for testing of seals and effectiveness of seals.
Instead of using flexible materials and the gaps that physical buttons often have, where dust and bacteria can hide, buttons have a smooth surface. Cleaning and care become easier; this is especially important in cleanroom and medical applications.
Human Machine Interface (HMI) Sensing Solutions
Whether the touch surface is made of materials such as plastic, leather, glass, or carbon fiber,
Qorvo's force sensors deliver high performance in any industrial design.
Our solutions recognize touches from any input in any environment, enabling a truly gapless and waterproof design.
"Solid surface" is a relative concept. Even the slightest amount of pressure causes most surfaces to deflect, allowing force-sensitive sensors to detect the change. HMIs designed for the harshest environments may require very rugged, thick surfaces and "bulletproof" displays. Some highly sensitive force sensors can detect the slightest pressure exerted on plastic surfaces more than two inches thick—whether flat or curved.
Force-sensing devices can also detect varying degrees of pressure. The app can be programmed to respond to different pressures, giving the buttons multiple functions: a light press activates a function; a heavier press selects a parameter; and the heaviest pressure changes that parameter. Innovative HMI designs can be realized with a single sensor.
Of course, not all force sensors are created equal.
Qorvo force sensing devices, as MEMS silicon chips, can sense micrometer or even nanometer-scale deflections covering the surface, allowing very thick surfaces to achieve high-sensitivity functions.
These very small silicon devices can be easily integrated into almost any design and consume very low power, making them ideal for mobile and portable devices such as cell phones and wearables.
Force sensors can be installed individually under surfaces to perform a variety of functions, or they can be combined with other technologies such as capacitive touch to build responsive, reliable and innovative interfaces.
For example, blending force sensing with capacitive touch can create a seamless functional interface that combines intent with location to reduce or even eliminate false positives.
Force-sensing devices offer engineers a new realm of creative freedom. Functions can now be implemented on any surface, in any material, and in any shape, without complex components such as seals and the problems that come with them. With these sensors, you can easily achieve a gapless design on your mobile phone without using physical buttons.
Application of Qorvo's innovative human-machine interface (HMI) technology in two-wheelers/μ-Mobility
: Qorvo's HMI sensors transform power buttons, touch displays, bicycle computers, and handlebar switches into stylish, intelligent control interfaces; Open to a variety of input methods and immune to most environmental factors, it also works with any material.
Achieve Design Success with Force Sensitive Sensors
MEMS force-sensing silicon devices are ideal for next-generation gapless designs.
Careful integration depends on several factors: location, sensitivity, covering material, software, and other technologies that may be used; these are important for the successful integration of the sensor into the design. Therefore, when considering a force-sensitive sensor, the manufacturer needs to be consulted to ensure a successful design. Manufacturers can provide design-specific insights to help engineers select and integrate equipment to optimize designs.
Qorvo builds the industry's most sensitive MEMS force sensors, offering extremely small, predictable, and low-power product options for low-cost, high-reliability applications.
Qorvo also provides end-to-end design expertise and assistance, simulation capabilities, and software integration to help engineers achieve product innovation in multiple market sectors; including Qorvo's major design achievements.
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