What is High-Definition (HD) Haptic Feedback?

Person-using-smartwatch

Have you heard about HD Haptics? Mobile devices OEMs over the world start to pay more attention to haptic technologies and their clear advantages for improving user experience. Now that big companies are starting to spend more time and resources to develop better haptic feedback, we are starting to hear and see the term HD Haptics being used.

But what is HD haptic feedback exactly?

Is it real or is it just another marketing buzzword?

Here’s our take on the question!

Standard vs High-Definition Haptics

Hand touching tree

High-definition haptics exist, but it’s also used as a buzzword. There isn’t any way to measure with accuracy the quality of haptic feedback, so there’s no way to define a level of performance to separate HD from standard haptic effects. Video resolution allows to separate the different level of image quality. You know that by watching a Full HD video you’ll get a 1920 x 1080 pixels image. Haptics are defined by the fidelity of the feeling they can replicate. Unfortunately, the term HD haptics is currently being used for basic solutions, but there is a way to see clearer!

Standard haptics can be defined as normal vibrations. One example would be when you receive a call on your smartphone. Your device vibrates to tell you that you need to answer. This is currently the main application of haptics in the electronic devices that surround us.

High-definition Haptics bring the technology on another level. You can replicate with a high level of accuracy normal touch feelings like clicking buttons and textures. In fact, HD haptics technologies are so convincing that the user is not able to notice that he’s using haptics! The best haptic technologies can trick our brains into believing that we’re touching real textures or real mechanical buttons. It can have a significant impact on user experience. They can even improve typing accuracy!

We have a prototype phone named SmartClik that is using piezoelectric actuators to replace mechanical buttons under an aluminum frame. We bring it in tradeshows to showcase HD haptics. People (even haptic engineers) have a hard time to believe they’re not using a mechanical button when they try the SmartClik phone. We have to cut the device’s power so people can feel the frame stiffness without the haptic feedback and believe us!

Mechanical Requirements for HD Haptics

Haptic technologies use waveform patterns to create effects. High-definition haptic feedback often need to use dynamic waveforms (that change intensity through the effect length). You’ll see that few haptic technologies can produce high-definition feedback due to their mechanical restrictions.

We’ll compare Eccentric Rotating Mass (ERM), Linear and Resonant Actuators (LRA) and piezoelectric actuators. You can read How Piezoelectric Haptics Can Help You Improve Your Device if you want to learn more on the difference between these technologies.

Comparison of Haptic Technologies

Eccentric rotating mass actuator
Linear Resonant Actuator
piezo actuator
Description ERM LRA Piezo
Performance Good Better Best
Acceleration ~ 1g to 2g ~ 1g to 2g ~ 3g to 7g (and more)
Audible Noise Moderate to very noisy Moderate to very noisy Silent
Response Time ~ 30 to 50 ms and up ~ 30 to 50 ms and up Below ms
Energy Consumption High Low Lowest
High-definition Haptics No No Yes

Faster Response Time

Haptic feedback fidelity relies on time. The time an actuator takes to accelerate and reach its vibration peak, the times it takes to decelerate and the time it takes to start-up can have a major impact on the quality of the feedback the user will feel.

ERM and LRA technologies are based on moving mass. Just like a car can’t accelerate and reach 100 km/h instantaneously, they need some time to accelerate their mass to reach their vibration peak. This limits the quality of feedback they can produce. The acceleration and deceleration period produce unwanted feedback if you want to create high fidelity effects. They can take more than 50 ms to reach their peak. While it may not look that big, 50 ms can make the difference between muddy and crisp feedback.

The acceleration and deceleration time of ERM and LRA also eliminates the possibilities of using dynamic waveforms. ERM and LRA simply can’t change their frequency fast enough to create high fidelity feedback.

Piezoelectric, on the other hand, don’t rely on mass vibration to create feedback. Once the actuator piezo material is under tension, it moves almost instantaneously. You can reach the vibration peak under 1 ms and create crisp feedback.

Higher Bandwidth

High-definition feedback requires different waveforms patterns to create multiple touch effects. Your actuator needs to be able to operate at different frequency levels and therefore needs higher bandwidth to have a bigger repertoire of haptic effects.

ERM and LRA are once again limited by their design. To offer the best effect possible, ERM and LRA need to be operated in a very narrow range of frequencies. If you go out of the ideal range, you get undefined feedback.

Piezo actuators can create haptic effect with infinite frequency levels. You can create richer and more defined touch feedback. You can customize different effects depending on the application with one single piezo actuator.

Lower Audible Noise

The user shouldn’t be able to tell when he’s using haptics in order to trick the user’s brain. This is why your haptic solution needs to be silent. The user will notice he’s using haptics if the device keeps buzzing every time it generates an effect.

ERM and LRA motors can produce small discernible noise. If you can hear it, your brain knows that the haptic technology is working.

Piezoelectric haptics don’t use any motor. They are silent. Therefore, you can trick the user’s brain with haptics since there isn’t any trigger to tell when the haptic solution is working.

Stronger Vibration

High-definition haptics sometimes need strong vibration to create a more immersive experience. The strength of the effect the user can feel is measured with acceleration. Higher acceleration results in a stronger haptic feedback.

ERM and LRA can produce strong vibration and feedback, but in order to achieve this they need to use bigger mass, therefore be big and waste precious space in your device.

Piezoelectric actuators can create stronger vibration then ERM and LRA, for the same actuator size. This gives you the choice of using the same space for your haptic solution and have the opportunity to create stronger feedback or to reduce the size of your haptic solution and create the same feedback strength as a bigger ERM or LRA based solution.

Definition of HD Haptic Feedback

After all of this, what is really high-definition haptic feedback?

HD Haptic is crisp and high-fidelity touch feedback generated by a piezoelectric based haptic solution thanks to its faster start-up time, its higher bandwidth, its silent operation and its stronger vibrations. It can replace mechanical buttons, create different touch feedback for different applications and even recreate textures. The most important part of it, it improves greatly the user experience.

The next step in haptics is coming. OEM around the world are paying more attention to haptics than ever before. Is your business ready for this new step? It should be!

Start experimenting HD Piezo haptics with our BOS1901 development kit here. It’s an affordable way to see the potential of better haptic effects in your application. The BOS1901 integrated circuit is the most power efficient haptic piezo driver on the market. We also have sales representatives around the world available to meet you and give a demo of our SmartClik buttonless phone proof-of concept.


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