What's the best tactile feedback---LRA motor

   

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New Favorite of High end Electronic Equipment: LRA Tactile Technology

LRA motor

 

From the previous discussion, we have seen that if you need a low-cost solution, vibration motors are a good choice, but they have limited feedback quality and can produce low-end rumbling sounds, which are not clean and clear tactile effects. Therefore, advanced electronic device manufacturers have shifted their attention in recent years to another tactile technology - linear resonant actuators (LRA motor).

 

LRA is currently used in many devices to achieve better tactile feedback than ERM solutions; Compared to ERM, they have higher acceleration, faster response time, and clearer tactile feedback. LRA, like ERM motors, is also based on mass motion. The difference is that the mass hangs on the spring and moves up and down under the action of a magnetic field.

Function	ERM	LRA	piezoelectricity
Acceleration(g)	0.6	1.7	2.5
Power consumption	High	Middle	Lower
Start time（ms）	50	25	0.3
Area size	Big	Big	Micro
Integrated force sensing	No	No	Yes
HD tactile feedback	No	No	Yes

LRA has different external dimensions, some are rectangular, while others are circular; Some manufacturers even develop their own LRA versions to achieve better results (refer to tactile engine), but how do they compare to piezoelectric tactile sensors? Let's take a look!

ERM, LRA, piezoelectric tactile ratio one to one

LRA tactile solutions significantly improve performance compared to ERM motors, as they can achieve higher acceleration; Therefore, LRA can create stronger tactile feedback than ERM solutions (larger acceleration values=stronger tactile feedback). However, although the acceleration of LRA is higher than that of ERM motors, they still have the same problem compared to low-cost alternatives - they require moving mass to generate vibration.

Although LRA motors can reach their optimal frequency peak faster than ERM motors (25ms instead of 50ms), they still require some time to accelerate or decelerate to the optimal frequency peak. The piezoelectric actuator can reach its optimal peak within 2ms, and the almost instantaneous acceleration makes it better in feedback strength and more efficient than LRA. LRA used in mobile devices can achieve an acceleration of 1 to 1.7G, while piezoelectric actuators of similar sizes can achieve an acceleration of 2.5 to 5G. 

LRA consumes more power than piezoelectric actuators combined with CapDrive piezoelectric actuators.

Another advantage of LRA compared to ERM motors is its lower power consumption, which is more suitable for battery powered mobile devices. In fact, LRA has been the most effective tactile solution for many years, and before the release of CapDrive technology, LRA was even more efficient than piezoelectric tactile.

However, compared to piezoelectric actuator ICs that integrate CapDrive piezoelectric drivers, LRA consumes 4 to 10 times more power; It's time to reconsider which tactile technology will be used in battery powered devices.

LRA provides better tactile feedback than ERM motors, but does not have high-definition tactile technology

ERM motors can produce inaccurate rumbling sounds, while LRA can generate clearer tactile feedback; This is mainly because the latter has better acceleration.

LRA produces clearer tactile feedback than ERM, mainly due to their resonant frequency; Resonant frequency refers to the acceleration and displacement in a narrow frequency range where you can obtain the optimal vibration to amplify the mass of the actuator.

Although the feedback generated by LRA is clearer than that of ERM, the resonant frequency range is very narrow. Due to the limited frequency range of LRA, their bandwidth is not large and it is difficult to create different tactile effects. However, although the performance of LRA is superior to that of ERM motors, it cannot achieve the infinite frequency range of piezoelectric actuators, and you are still using a limited LRA. On the other hand, piezoelectric actuators offer infinite possibilities for various tactile effects.

LRA response time is faster than ERM motors, but slower than piezoelectric actuators

The second factor behind LRA providing better tactile performance than ERM motors is its faster response time. Like ERM actuators, LRA requires moving mass to generate tactile feedback. Although they do indeed shorten the response time compared to their low-cost alternative products, LRA still requires 25ms to reach its optimal frequency range, and the deceleration period after tactile effect is also the same.

Piezoelectric actuators can begin to exert their tactile effect within 2ms, providing the possibility of creating clearer and more precise tactile feedback.

Utilizing Piezoelectric Integrated Pressure Sensing to Save Hardware

Another advantage of the CapDrive piezoelectric tactile driver architecture is the integrated piezoelectric pressure sensing. BOS1901 piezoelectric driver IC can sense pressure from the same piezoelectric actuator and generate tactile feedback; This means that when your application requires pressure sensing (such as button replacement), you can remove the previously used pressure sensing hardware from the design.

LRA occupies more space than piezoelectric actuators

LRAs are smaller in size than piezoelectric actuators and are generally considered more suitable for small devices, but when considering the size of the actuator, they are completely different. 

Like ERM actuators, LRA sizes are larger than piezoelectric actuators with similar acceleration (feedback strength), and the space saved by piezoelectric actuators will far exceed the space lost by integrating piezoelectric actuators. For example, BOS1901 only requires 7 passive components to operate.

CapDrive piezoelectric IC vs. LRA (* mass is 100 grams. Acceleration is related to feedback strength. Higher numbers=stronger feedback)

 

With better performance technologies such as piezoelectric tactile technology, tactile technology is entering a new era.

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What's the best tactile feedback---Piezoelectric

 

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http://www.coin-motor.com/mod_article-article_content-article_id-215.html

Piezoelectric tactile vs ERM tactile sensation

The acceleration in haptics is related to the intensity of tactile feedback you feel; The higher the acceleration that the actuator can achieve, the stronger the tactile feedback it generates.

The acceleration that the ERM system can achieve is quite limited, and the reason is easy to understand: the vibration motor needs to accelerate the mass to generate vibration. Therefore, it needs to break the mass inertia and increase the speed to the optimal frequency. However, the acceleration of the mass is not instantaneous, which is why the ERM motor emits a rumbling sound due to inaccuracy.

 

On the other hand, piezoelectric actuators have no mechanical limitations. Due to the fact that vibration does not rely on mass rotation, once high pressure reaches the piezoelectric material, the actuator will vibrate. Therefore, piezoelectric actuators can generate stronger and clearer feedback than ERM motors. In addition, taking Bor é as Technologies' piezoelectric CapDrive technology as an example, the ERM solution consumes 20 times more energy Power consumption: ERM vs. CapDrive technology piezoelectric tactile.

The main advantage of piezoelectric tactile technology in other fields is total power consumption. The performance of piezoelectric actuators is very high, but unfortunately, the low power consumption of the actuators is offset by the poor performance of piezoelectric actuators. The situation has changed since the release of CapDrive technology. The first piezoelectric tactile drive IC (BOS1901) using CapDrive technology is claimed to be the most efficient piezoelectric driver on the market. If you want to integrate touch control into devices with limited power consumption (such as mobile devices), piezoelectric tactile technology is a better choice than ERM solutions.

 

Piezoelectric almost instantaneous response, vibration motor response time is slower。

 

Tactile feedback requires perfect timing to generate the best feedback, and the faster the response time, the clearer and more accurate tactile feedback can be transformed. A vibrating motor requires a longer time to accelerate the rotational mass and reach its peak frequency (optimal feedback area); In addition, after achieving the effect, they need to slow down the quality. ERM usually takes up to 50 milliseconds (ms) to reach the peak frequency, and the delay in acceleration and deceleration will produce slight adverse vibrations at the beginning and end of reaching the peak.

 

The real-time response time of the piezoelectric actuator is less than 2 ms, which means you can hardly feel the slight adverse tactile feedback generated during acceleration and deceleration. Piezoelectric tactile feedback produces clearer and more accurate feedback, and the limiting factor of piezoelectric actuators is actually the response time of piezoelectric actuators. The response time of the BOS1901 piezoelectric driver is less than 6ms.

Piezoelectric tactile technology saves a lot of space compared to ERM systems.

 

Compared to piezoelectric tactile solutions, ERM vibration motor tactile systems are larger and occupy more space. Although ERM actuators are indeed smaller than piezoelectric actuators, the biggest difference lies in the size of the actuator. Piezoelectric actuators are smaller than ERMs and provide greater tactile feedback.

 

If you need a compact solution, piezoelectric touch is a better choice than vibration motors.

 

The advantages of piezoelectric effect.

 

The piezoelectric effect is reversible. You can apply high voltage to a piezoelectric material to make it move, but when the piezoelectric material deforms, it generates an electric charge. When you press the piezoelectric actuator, the piezoelectric material will deform slightly and the actuator will generate current. Piezoelectric drives using CapDrive technology can detect current, and they can detect pressure and trigger feedback from the same actuator.

 

The eccentric rotating mass tactile scheme can only trigger tactile feedback, so if pressure detection is required, in addition to the tactile system, a complete pressure sensing hardware system is also required.

 

This means that if you need a tactile solution that triggers when applying pressure (such as replacing mechanical buttons), you can cancel the sensing hardware and rely solely on one piezoelectric actuator and one CapDrive piezoelectric driver. This can significantly save space; This is what a SmartClik buttonless phone prototype does.

 

High resolution tactile technology vs. basic technology solutions

 

Piezoelectric actuators can produce more advanced tactile effects. Like speakers, they use electrical waveform signals from amplifiers (piezoelectric drivers) and can operate over a wide range of frequencies and amplitudes, producing various tactile effects. You can customize tactile feedback based on your application to create rich and detailed feedback. This is what we call high-definition tactile feedback.

On the other hand, the frequency range of ERM solutions is quite limited and cannot create the best feedback effect. This means that your tactile effect range is quite limited, and ERM motors are limited to low-quality applications.

 

Piezoelectric tactile technology brings the possibility of higher-level effects that ERM cannot replicate. 

Piezoelectric tactile technology is very suitable for various applications that require different tactile effects, such as AR/VR, vehicle safety alarms, button replacement, etc.

CapDrive Piezoelectric Tactile Technology vs ERM technology

Function	ERM	Capdrive TM
Acceleration(g)	0.6	2.5
Power consumption	High	Low
Start time（ms）	50	0.3
Area size	Big	Micro
Integrated force sensing	No	Yes
HD tactile feedback	No	yes
Calculated with a mass of 100 grams, the acceleration is related to the feedback intensity, and the larger the number, the stronger the feedback

------------------------------------To be continued---------------------------------

What’s the best tactile feedback?-ERM motor

                   What’s the best tactile feedback?

    

Compare three mainstream tactile feedback technologies: 

1. ERM,
2. LRA
3. piezoelectric

Haptic feedback is not a new technology. We can go back to the 1960s and discover the first device changes that used vibration feedback to send information to users.

The systems used to generate vibration in the past are still being used in low-cost equipment to generate basic tactile feedback. 

A vibration feedback solution with a long history and low cost Eccentric rotating mass (ERM motor) is commonly referred to as a vibration motor, and this tactile system consists of a high-frequency motor that rotates the eccentric mass. Since the 1960s, the same concept has still been in use, but this technology has been miniaturized to accommodate smaller devices.

With its low-cost advantage, eccentric rotating mass actuators (ERM motor)are still used in many devices to generate tactile feedback, but they are beginning to be replaced by more efficient technologies. Nowadays, we live in a digital world surrounded by various devices with touch screens. In order to improve the user experience of devices, companies around the world are developing new technologies, so better touch technology is also developing.

Piezoelectric haptic actuator is one of the high-efficiency technologies. Based on the piezoelectric effect of certain materials, this technology has more advantages than ERM motors. The piezoelectric solution does not require rotating the eccentric mass, but requires the use of a piezoelectric actuator, which sends high-voltage power through the actuator material of the piezoelectric actuator, causing it to deform and generate tactile feedback. Next, we will discuss the differences between decompression and ERM tactile techniques, as well as the tactile techniques you should use in your application.

-----to be continued and refer to JI FEI HOLDING LIMITED