Do You Know How Haptics Work?
Haptics make our devices more interactive, but how?
“All devices [will] need to interact. If a thing does not interact, it will be considered broken.” — The Inevitable, by Kevin Kelly
In my previous article, Why Touch is the Next Important Step for VR, I explored the importance of perception and interactivity to creating immersive experiences. But beyond just VR, interactivity is increasingly critical to all our devices, which is why I so liked the above quote from Kevin Kelly.
One of the ways in which our devices can interact is through haptic feedback. “Haptic feedback” (or just “haptics”) is the application of forces, vibrations, and motions to help recreate the sense of touch for the user when interacting with a given piece of technology. Haptic technology is often associated with the buzzes and clicks of our smartphone alerts, notifications, and the subtle way they give us feedback as we interact with the device.
Haptics aren’t a new technology. Manufacturers have been using them in electronics since the late 1990’s, from video game systems like Nintendo 64 rumble pack (ah, my first game system), to early mobile phones. Haptics are also used widely in medical and automotive applications.
There are four different types of hardware most frequently used to provide haptic feedback:
1. Eccentric Rotating Mass (ERM)
The majority of electronics from the 1990s offer haptic feedback in the form of vibrations, with the most popular type being an eccentric rotating mass (ERM) actuator. This component is a rotating electric motor with an off-center mass. As the ERM rotates, the force of the offset mass becomes asymmetric. This results in a net centrifugal force, which causes the motor to become displaced. As it rapidly spins, the motor is constantly displaced, which creates the vibration feeling.
ERMs are most commonly used in gaming systems like Sony’s DualShock controllers. The effects that you get out of ERMs are low end rumbles.
Despite being a cost effective component, many manufacturers have moved away from this technology due to its large form factor and it being power hungry.
2. Linear Resonant Actuator (LRA)
The next leap in haptic innovation is the linear resonant actuator (LRA). It consists of a magnet attached to a spring, surrounded by a coil, and encased in a housing. It’s driven by an electromagnetic coil that is energized. The mass moves back and forth within the coil, which causes the vibration.
LRAs became popular with a lot of handset companies and are still found in the GS8 smartphone, Nintendo Switch, and Steam controller.
LRAs have a leg up on ERMs because they consume less power and have a faster response time, making them a great way to provide simulated clicks for texting or typing applications on handsets.
However, this improved haptic performance over ERMs comes with a slight component cost increase. At the same time, efficiency and performance do drop off considerably as the LRA’s drive frequency moves outside of its resonant band. The spring design is susceptible to wear and tear, as well as temperature fluctuations.
Apple Taptic Engine
Apple’s Taptic Engine is a proprietary haptic system that is based on LRA technology. It’s tuned to a specific resonant frequency and is optimized to simulate a “click” effect. Like the LRA, the Apple Tactic Engine provides localized haptic experience, which is important for isolating the “click” so it feels natural and in sync with what the users is touching on the keyboard.
Used in Apple devices, like the iPhone, Apple watch, and MacBook, this component technology is very expensive compared to other LRAs. It is also one of the more complex haptics to manufacture.
It’s rumored that Steve Jobs spent an incredible amount of time fine tuning the haptics for the iPhone home button. As someone highly focused on user interaction, it was an important part of making sure the button was a pleasure to use and provided a much more immersive experience for the user.
3. Piezoelectric Actuators
Piezoelectric actuators are made of type of ceramic material that expands or contracts when an electrical charge is applied, generating motion and force. When differential voltage is applied across both ends of a piezo actuator, it bends or deforms, generating a vibration.
Piezoelectric actuators are more precise than both ERM motors and LRA’s because of their ability to vibrate at a wide range of frequencies and amplitudes that can be independently controlled using the driving AC voltage. Since the vibration doesn’t rely on the resonant frequency of a spring, the frequency may be modified freely without a significant loss of efficiency.
An example of a device that contains Piezoelectric actuators is the Kindle Voyage. The three factors that have impeded wider adoption of piezoelectric actuators is the cost of components, fragile nature of the materials, and power consumption, as it requires higher voltages than ERM and LRA.
4. Forced Impact (Accelerated Ram)
The latest in haptic actuator technology is the TacHammer, which is based on a forced impact (also known as accelerated ram). It contains a magnetic hammer that is suspended in the air by a magnetic array.
It’s capable of producing the same effects of the other haptic actuators, along with two other modes; hard tap and soft tap. The soft tap is created when the hammer is driven into the magnetic array, which results in a pulse like feeling. This can be used to simulate feelings like a beating heart. The hard tap is created by driving the hammer in the opposite direction of the magnetic array, resulting in the acceleration ram striking a solid surface, resulting in realistic gun shot, kick effect.
The TacHammer uses significantly less power consumption than the LRA and ERM, and the voltage and the frequency can be varied, which gives developers the widest spectrum of effects to use, with no real power downside.
With the continued proliferation of gaming, smartphones, and new hardware devices, haptics will continue to be an integral part of bridging the human-device experience.
In particular, VR has taken the gaming experience from something that is 2D to something that is visually immersive. As I’ve argued, more senses (particularly touch) will need to enter the fray to create total immersion, which is why new technologies like TacHammer are so fascinating to track.