Mastering Haptic Feedback Selection: How to Choose the Right Actuator for Next-Gen User Experiences

1.Introduction
2.Step 1
3.Step 2
4.Step 3
5.Step 4
6.Step 5
7.Conclusion

Introduction: Why Selection Is the Secret of Success
Early devices were based on a simple motor buzzing. Today, in a duly engineered haptic feedback system, you can have an artificial feeling of the click of a mechanical button, the texture of the surface or the resistance of the pull of a drawstring, all without the user's eye perceiving the moving parts.
What makes selection to be so important is that range. A low cost ERM motor will be fine for a basic notification wrist band. But put that same motor in a medical training simulator or in a high-end car touchscreen, and your product will be cheap and unconvincing.
The most common mistake is seeking out raw power. More voltage and higher levels of vibration is not better feedback. What is responded to by users is precision, the right sensation, at the right time, with the right timing. 
In fact, market data supports this change. Search interest in terms such as HD Haptics and Linear Resonant Actuator (LRA) has really increased over the past three years while basic "vibration motor" queries have leveled out. Buzzers are no longer enough for designers and engineers. They want nuance.
This blog proceeds through how to choose the right Haptic Feedback device. In the case of the product, beginning with what your product needs to do and then backward through the components and architecture that fulfill those needs.

Step 1: Define your Application & Interaction Goals
Usually, you have to answer one question: what job is this haptic feedback doing? The answer dictates just about anything that follows.
Most uses cases for haptic feedback fall into three categories.
Simple to wear or track activity or notifications cover wearables, fitness trackers and notification bands. The goal is awareness, no texture. It is not necessary to make brief pulses long-term, repeatable. Users are only required to know that something happened.
Interaction confirmation is covered for such applications as in-car touchscreens, smart appliances and virtual buttons. Users need to know an action done without having to look at the screen. The feedback has to feel immediate and deliberate, not an afterthought.
Immersive experience includes game controllers, VR haptic feedback gloves and surgical simulators. Here the haptic feedback has to be convincing. Texture, resistance and directionality are all important. Users are creating a model of a physical environment in their minds using touch alone.
Beyond the types of things that are in the category, consider quality of feedback. Do you need sharp, instantaneous "click" , what engineers call a transient response? Or do you need sustained layer upon layer of sensation, texture simulation? Transients call for fast rise and fast fall control. Texture simulation needs the specific frequency and amplitude modulation with respect to time. These are different problems, they are directing you to different possibilities of actuators.

Step 2: Basic of the Technical Parameters
1. Actuator Type
The three technologies dominate the market. Each of them makes different trade-offs.
ERM (Eccentric Rotating Mass) motors are simple, cheap and proven. This is done by spinning an off-center weight to create vibration. The problem there is physics, the motor takes some time to spin up and slow down and so the feedback is always blurred a little bit. Response time sits around 100-200ms. ERMs are good for simple notifications but not for anything that requires precision of time or texture.
LRA (Linear Resonant Actuator) motors can be defined as motors operating in a straight line as opposed to rotating. That makes them far more under control. They are able to start and stop almost instantaneously, normally in 10-40ms and respond quite well to custom waveforms. This is why LRA is what it is today the standard choice for mid to high-end consumer devices or the most actively searched actuator type on the market.
Piezoelectric actuators make use of crystals materials, which are deformed by the application of voltage. They have virtually zero moving parts, have a response in less than 5 milliseconds, and can fit in a small space that an LRA just won't. They are the preferred choice where thinness is paramount, TWS earbuds, smart rings and flexible wearables and will become an increasingly popular choice in the medical and industrial world where long-term reliability is more important than unit cost.
2. Key Performance Indicators
The time from trigger signal till the user-perceptible sensation is referred to as latency. Below 20ms feels instant. Above 80ms feels laggy. This one number determines the responsiveness of confirmation feedback or its sluggishness.
Frequency is measured in Hz. Lower frequencies (50-100Hz) amount to a thump. Higher frequencies (200-300Hz) give a sharp tap or buzz. Matching frequency to intention of what you intend to feel while omitting to consider the rest, which is fundamental not optional.
Amplitude is the control of intensity. This should be scaled based on the emotional weightiness of the event. Destruction of an action should be more prominent than confirmation of a routine. More amplitude is not always a good thing.
Size and power are extremely limited for mobile and wearable applications. Check the footprint of the actuator with your layout on the printed circuit board as early as possible on your project. 

Step 3: Integration Driver Architecture And Software
1. Driver IC Selection
A haptic driver is an IC that translates information from your processor (digital commands) into the basic voltage waveforms the Stepper Driver needs in order to give commands to the actuator. Not all driver ICs have the ability to support all types of actuators. Some are optimized for LRA with closed loop resonance tracking that negates the effects of temperature and aging to maintain consistency of the feedback during the product's lifetime. Others are less complicated open-loop designs that are cheaper, but degrade over time.
2. Waveform Libraries vs. The Custom Design
Most haptic driver ICs have some level of waveform library, a set of pre-built vibrations patterns for common events, e.g., clicks, warnings and confirmations. These are adequate for most applications and greatly shorten the development time.
3. Optimization of System Latency
Total latency is not only the actuation response time. It is the sum of it all: Unexcept the processing of interrupts in the processor and communications to the driver's IC within the system controller. Driver wake up time and the rise time of the actuator itself. In a poorly integrated system these add up fast.

Step 4: Trends in the Industry and Market Insights
TWS earphones and smart rings have opened up a whole new class of problem of haptic challenge, meaningful touch feedback in components smaller than a coin. They don't fit in traditional LRA motors. This has led to an accelerated adoption of miniaturized piezoelectric actuators that can be made into thin films or as piezoelectric ceramic as small as 5mm in diameter.
Industrial and Automotive: Staying Strong as Strong as Possible
In the case of automotive and industrial applications, "does it feel good?" to "if it will still be working after five years and 200 000 cycles in a hot cabin?" These types of environments require actuators that have a proven MTBF rating, as well as good temperature capability and the ability to withstand the shock of the surrounding environment.
It is here where piezoelectric actuators are structurally acclaimed. Fewer moving parts, the fewer the failure modes. This is one reason that they are becoming a more common specification on automotive touchscreens and industrial control panels.
Bestarsensor: Ease of Selection Through Engineering Partnership
Choose the haptic feedback components that is far easier to do if the supplier knows your product context. Bestarsensor offer piezoelectric actuators developed through years of applied research, and work closely with engineering teams to be able to match the right component to each application. Bestarsensor also provides suitable haptic feedback solutions for you, welcome to contact Bestarsensor.

Step 5: Selection Checklist
Use this as a quick reference before finalizing your actuator choice. You don't need exact numbers at this stage — just a clear answer for each dimension.

Conclusion: Going From Hardware Selection to Haptic Feedback Design
The solution to the hardware problem is to choose the correct piezo actuator. But hardware is just the beginning.
The difference between a product that vibrates and a product that talks to you through touch is the layer of haptic feedback design which made up of the choices about when to provide feedback to a user, the waveform used, the duration of the feedback and how it changes from one situation to the next. This is where good products are transformed into memorable products.
Start with a clear use case. Select an actuator and driver that can deliver quality that is expected by your users. Then invest in the design work getting that hardware to be something creative and expressive.
If you are anywhere in this process, from the initial feasibility to the integration with production. Bestarsensor's engineering team is willing to discuss your unique requirements, suggest components and aid in waveform development from the initial prototype to production.