Haptic technologies in Mobile devices

Transcription

1 1 Haptic technologies in Mobile devices Maria Paananen University of Tampere Department of Computer Sciences Computer Science / Int. Technology Seminar "Haptic Communication and Interaction in Mobile Contexts" Fall 2008

2 2 University of Tampere Department of Computer Scienses Computer Science/ Interactive Technology Haptic technologies in Mobile deivices Abstract This paper consentrates to examine most commonly used haptic technologies in mobile devices from designer point of view. How are they used and what are the benefits of each technology are the main questions handled in here. How they affect to the desing and how the knowledge of these technologies helps user interface design work. Keywords Haptics, tactile feedback, Vibra, piezo

3 3 TABLE OF CONTENT 1. Introduction Haptic technologies in mobile devices Vibra motors Rotating vibra motor Linear vibra motor Piezo element Example devices design point of view Conclution References... 9

4 4 1. INTRODUCTION The mobile world has lived through enormous changes during its economic boom. The targets have followed the global winds of change and all the mobile brands have tried to hang on to these phases. Challenge has also been the fact that all the older changes are still targets even thou the new ones arise all the time. So where are we now? Smaller phones, more powerfull, more intelligent, user friendly, accessable for everyone and now touchable screens. There has been already some touch screen phones but Apples iphone exploded the bank last year. New goal was set and all the mobile companies turned their concentration to that way. New race started to develop these small touch screens to be user friendly with all the goodies. One issue arised along touch screens in mobile devices is the luck of natural sensation of keys. The sensation of touch is maybe the most effective sense man has and flat touch screens brings new challenges to design and to technologies to compensate hardware elements for touch elements. The solution to this challenge has been haptics and its variations between technologies, design etc. Haptics is commonly known around the world as a vibrating feedback in different areas for example in entertainment industry, touch screens, devices for visually impaired people and cars, but in mobile devices it hasn t been used publically so much as a solution for usability challenges. Some of the brands have already used haptics in their devices like LG but it is predictable that in the near future all the touch screens in mobile devices uses somekind of haptic feedback. In this paper the terms haptic feedback and tactile feedback means the same thing. As a designer point of view one challenge in haptic feedback is the understanding of the technology behind these effects. For this reason this paper exists, to clarify what is behind the design and what possibilties different kind of technologies gives for designing. 2. HAPTIC TECHNOLOGIES IN MOBILE DEVICES The usage of haptics in mobile devices is solution to usalbility issues areised from touch screen devices. When there is no hardware key to handle things in mobile device the natural feeling of button is missing and the usage can be more insecure. Also blind usage is harder when there is no feedback in UI elements. In here I introduce two most commonly known and used technologies: Vibra motors and Piezo element.

5 5 2.1 Vibra motors At the moment vibra motors are most used haptic technology in mobile devices. There is different kind of vibra motors here I mention two of them, linear vibra and rotating vibra motor Rotating vibra motor Rotating vibra motor is normally 4 mm. thick and 10 mm. long object which has eccentric mass in the end of the shaft (See Figure 1.). Since the mass is eccentric it starts to vibrate when the motor is turned on [1]. The mass is often made of tungsten [2] which has higher density than iron and therefore enables the object to be smaller. This is very important in mobile industry. The shape and size of the motor is very essential: the farther the mass s midpoint is from axis the longer it takes time to start. When the motor gets voltage it starts to spin and shakes the mass in spinning direction. Therefor motor is normally placed to vibrate the phone in vertical direction. The placement and the size of motor haves an effect to the feeling of vibration. (See Figure 2.) The motor is driven at a nominal voltage of 1.5 volts and a typical current is 60 ma. The voltage can be increased to 4 volts for a short duration. This makes the start-up quicker. [2] Figure 1. Rotating vibra motor [1] Figure 2. Vibration direction Linear vibra motor Linear vibra motor is a round shape metallic can that is 8 mm in diameter and 5 mm in height. The moving mass moves up and down in the can between two springs. Next to the mass are

6 6 magnetic coil and when voltage is conducted to this coil it makes the mass vibrate [2]. The working principle is similar with a loudspeaker. 2.2 Piezo element Piezo element consists of two layers. First one is a brass layer and other one is somekind of ceramic layer (See Figure 3.). It is called piezoelectronics. When voltage is conducted to this element it deflects the whole element. Usually the piezo element is placed between devices frame and display. When the element deflects it lifts the display up giving tactile feedback to the Figure 3. Piezo element [3] user. Piezo element is faster than vibra motors and that s why wanted haptic technology. When vibra can take ms. to start, the piezo element can do it with 0.5 ms. Piezo element also allows controlling both the amplitude and the frequency of the tactile feedback at the same time [3], which makes the usage more flexible from vibra motors. These elements can be used with multiple layers. 2.3 Example devices Using vibra motors and piezo elements in mobile devices gives opprturnities, but also limitations to design work. Starting times and accuracy of different effects are dependent of used technologie, the size of a device and other things which have to be taken into account. There are already some devices on the market using vibra motors. Most known company making these haptic technologies to mobile devices is Immersion [5].The Company has contracts with mobile brands like Nokia [7] and LG [6]. The VibeTonz technology used in phones is giving more opportunities for vibra usage. Another reason for using their technology might be the fact that Immerison owns most of the haptic patents. Figure 4. LG KU990 uses VibeTonz technology [8]

7 7 Figure 5. Nokias new touch phone 5800 Xpress Music Phone uses vibra motors to give haptic feedback. This model does not have Immersion VibeTonz Technology. For the meantime there are no pure mobile devices on the market which uses piezo element. The piezo is wanted technology because of its fastness and accuracy of feedbacks, but the maturity of mobile technology hasn t been good enough yet. 3. DESIGN POINT OF VIEW There is some design rules made for haptics in mobile devices. Kaaresoja and Linjama have tested what would be the best duration of tactile feedback from user point of view and the result was between 50 and 200 ms [9]. Also others have made these technical point of view quidelines, but eventually designing the haptic feedback to mobile device starts from imagination and end for testing. The sense of touch is something we all have our own. Somebody feels it more sensitive than others; some one gets irritated even from a small vibration when somebody wants to have it strong. There are cultural differences, differences between genders and other human based issues which all set challenges to designers. Designing mobile phones, which are everyday devices for people, the variation of best solution design is impossible. Settings are commonly known problem to users, so the default effects designed for UI have to be somehow globally good. Because of the newness of haptics in mobile phones used with touch events we need more testing, more reseach and more technologies to make better and better haptic feedback to these devices. In the meanwhile we need to proseed through trial and error.

8 8 4. CONCLUTION Like many researchers have proved Tactile feedback improves the usage of touch screens [4, 10]. This is because of the missing natural feedback can be produced with haptics technologies. The right solutions of technologies are dependent of the maturity of hardware, software design, devices size, and code limitations etc. which all need to be thought when designing haptic feedback to mobile phones. Still we need creativity not to think always the limitations, because eventually everything is possible. We just need more time to develop more flexible more accurate and more easy to use technologies. Good haptic design and implementation needs knowledge of these different technology backgrounds, usability studies and still creativity to make consistent, user friendly and still working haptic feedback to mobile devices, and that means team work.

9 9 5. REFERENCES [1] T. Kaaresoja and J. Linjama, Perception of Short Tactile Pulses Generated by a Vibration Motor in a Mobile Phone, WHC, 2005, [2] M. Nisula, Thesis: Actuators For Haptic Feedback in Mobile Phones, University of Oulu, 2008 [3] E. Koskinen, Thesis: Optimizing Tactile Feedback for VirtualButtons in Mobile Devices, Helsinki Univerxity of Technology, 2008 [4] E. Hoggan, S.A.Brewster and J.Johnston, Investigating the effectiveness of tactile feedback for mobile touchscreens, CHI 2008 Proceedings [5] VibeTonz System, Immersion Corporation, 2007, [6] reuters, LG and VibeTonz technology BW [7] Mobile Tech News [8] LG KU990 Finnish Homepage, ryid=0701&categoryid=0701&parentid=07&modelcodedisplay=ku990&unit=noth ING&model=Select+a+model [9] T. Kaaresoja and J.Lilnjama, Perception of Short Tactile Pulses Generated by a Vibration Motor in a Mobile Phone, Proceedings of the First Joint Eurohaptics Conference and Symposium on Haptic Interfaces for Virtual Environment and

10 10 Teleoperator Systems, [10] T.Kaaresoja, L.M.Brown and J. Linjama, Snap-Crackle-Pop: Tactile Feedback for Mobile Touch Screens, Euro Haptics, t.com/~lornab/publications/kaaresoja_eh06.pdf+snap+crackle+pop+kaaresoja