CHI 2001 • 31 MARCH- 5 APRIL Interactive Posters Active Click: Tactile Feedback for Touch Panels FUKUMOTO, Masaaki fukumoto @ mml.yrp.nttdocomo.co.jp SUGIMURA, Toshiaki sugi @mml.yrp.nttdocomo.co.jp NTT DoCoMo Multimedia Labs. 3-5 Hikari-no-oka, Yokosuka-shi Kanagawa-ken, 239-8536 JAPAN Fax: +81 468 40 3788 ABSTRACT "Active Click" is a new interface mechanism for addling tac- tile feedback to touch panels. A small actuator is attached to a body of PDA or the backside of a touch panel. The tactile feedback, created by driving the actuator with a short pulse, is perceived by the grasping hand or tapping finger-tip when the panel is tapped. Active Click is effective in improving the input speed of touch panel operation especially in noisy situa- tions. Active click is also useful for large touch panel devices such as public information terminals or ArMs. Keywords touch panel, crick, PDA, interface device INTRODUCTION Touch panel displays are commonly used for PDAs because they are suitable for graphical and direct operation, and dis- play size can also be increased through the deletion of key- board buttons. However, ordinary touch panel devices fail to achieve comfortable and accurate operation because they do not provide the click feel when tapping. In many cases, a short beep sound is used to simulating the tactile click. However, this mechanism has many problems; for example, input mode (tactile tapping) differs from output mode (audible beep), and the beep sound may not be heard in noisy situations such as outdoor use. "UnMouse"[1] is one solution for adding tactile feedback to touch panels. It uses the whole touch panel as a large push switch, however, nimble operation is difficuk because the in- ertia of the push switch is large. "CC Click"[2] places trans- parent switch mechanisms over the display panel. The mov- able parts are small enough to operate airily, but switch posi- tion and display design are restricted. CONCEPT "Active Click" is a new mechanism that allows any touch panel device to provide tactile feedback. An actuator (elec- tric to vibration transducer) is attached to a body of the PDA or the backside of the touch panel (Figure 1). When tac- Figure 1: Example of actuator mounting Putting actuator on the back panel of PDA. T= ;/to T= ~/to Single Pulse Short Burst Figure 2: Example of driving signal for click feel. fo = natural frequency of the actuator. tile feedback is desired such as tapping action by finger-tip, a short pulse signal is supplied to the actuator for making the actuator vibrate. The vibration is conveyed to the grasping hand or tapping finger-tip. One commonly used vibrating device is a small motor that rotates an eccentrically weighted shaft. This approach cannot offer subtle control; only continuous vibration is well gen- erated such as silent alarm of cellular phones. On the other hand, the structure of Active Click's actuator i is similar to a magnetic speaker, and delicate control is possible. For exam- ple, click feel is expressed by adding a single pulse or a short burst signal (Figure 2). Large vibration levels can be ob- tained using a small amplitude input signal if the pulse width or signal frequency equals the natural frequency of the actua- tor. In addition, the actuator can be used as speaker if the in- put signal contains audible frequency range. Therefore, both tactile feedback and audible output can be generated from just one device. iTOKIN "MultiActor" [http://www.tokin.com] © Copyright on this material is held by the Author(s). anyone, anywhere. 121
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`Inferaclive Posters CHI 2001 * 31 MARCH - 5 APRIL ~ .~ PDA Body (a) Body mounted actuator for PDA. Tactile information is conveyed to grasping hand. -~ Display Panel .o a (b) Panel mounted actuator for PDA. Tactile information directly reaches tapping finger-tip. Clay Panel Public I~lormation ~"mlnal / / (c) Panel mounted actuator for large display. Large or multiple actuators are used. Figure 3: Mechanism of Active Click VARIATION Active Click has several variations according to the attach- ing position of the actuator. Figure 3-(a) shows the body mounted actuator for PDAs. Tactile feedback is conveyed to the grasping hand. Large feedback can be achieved with small amplitude input signal by attaching the actuator to the contact position of the grasping hand. This style is suitable for PDAs that requires low power operation. Figure 3-(b) shows the panel mounted actuator for PDAs. The actuator is attached to the backside of the touch panel display. Tactile feedback is conveyed to the tapping finger- tip directly, so this style can express most natural click feel. However, power consumption is higher since the whole touch panel must be vibrated. Figure 3-(c) shows the panel mounted actuator for large dis- Error Bar=: 51amdird Olmi|ioctll 14o f • ; - ' ....... ~ ......... i / r Operation tirol k ilanchlrdlzed as OS=lOOm£,, for = lubjicL i I '+°! !+ 120 ,0ol i I . oo I : + i O0 1 i i ; BS C$ ON CN CondRlae, J Figure 4: Time to perform calculating task. Active Click is effective in reducing operation time. plays such as public information terminals or ATMs. In this case, power consumption is insignificant therefore adequate tactile feedback can be realized by using large or multiple ac- tuator(s). EVALUATION Simple calculation task ii was set to verify Active Click's per- formance. Palm compatible PDA iii and Palm-OS standard Calculator application were used in the evaluation. Both op- eration time and correct answer rate were measured using ei- ther Active Click feedback (body mounted actuator) or or- dinary beep feedback. Two noise levels iv were set to check the influence of environmental noise. Four situations ( [BS]: Beep&Silent, [CS]: Click&Silent, [BN]: Beep&Noisy and [CN]: Click&Noisy ) were tested for each subject. Presen- tation order was randomized to eliminate any learning effect; the number of subjects was I0. Difference in operation time is shown in Figure 4 v. This graph shows that Active Click can reduce the operation time by about 5% (in silent situation) and 15% (in noisy situa- t.ion) ~. CONCLUSION Active Click can improve the usability of touch panels, espe- cially in noisy situation, even though its mechanism is simple and easily implemented in ordinary PDAs. We are planning to create various tactile information by controlling the actu- ator's input signal, and to handle the feedback position by using plural actuators. REFERENCES [1 ] "UnMouse" by MicroTouch Systems Inc. [http://www.microtouch.com] [2] "CC Click" by IDEC Corp. [http://www.idec.com] iiOne question: adding 5 pairs of 4-digit numbers. 20 questions in one task. iiiTRG Pro [http://www.trgnet.com] iV40dB(A) corresponds to a silent room, and 70dB(A) corresponds to an urban street. Pink noise was used as the signal source. VOperation time was standardized as [BS] = 100% for each subject. ~iNo significant difference was observed in the correct answer rate. 122 CH12001
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