Evaluation of Three Input Mechanisms for Wearable Computers
Bruce Thomas School of Computer and Information Science University of South Australia The Levels SA 5095, Australia +61883023464
[email protected]
Susan Tyerman Karen Grimmer School of Computer and School of Physiotherapy Information Science University of South Australia University of South Australia Adelaide 5000, Australia The Levels SA 5095, Australia +61883023201 +61883023969
[email protected] [email protected]
the study; the subjective portion is presented elsewhere [l].
Abstract This paper reports on an experiment investigating the functionality and usability of novel input devices on a wearable computer, for text entry tasks. Over a three week period, twelve subjects used three different input devices to create and save short textual messages. The virtual keyboard, forearm keyboard, and Kordic keypad input devices were assessed as to their eficiency and usability for simple text entry tasks. Results collected included the textual data created by the subjects, the duration of activities, the survey data and observations made by supervisors. The results indicated that the forearm keyboard is the best performer for accurate and efJicient text entry while other devices m q benefit from more work on designing specialist CUls for the wearable computer.
Keywords Input devices, wearable computers, empirical experiments
1. Introduction
Figure 1 Wearable computer system
This paper presents the experimental design and results of a study that evaluated the ease of leaming and use of a forearm mounted keyboard (FK), virtual keyboard (VK), and Kordic keypad (KK) in conjunction with a wearable computer. Twelve subjects participated in the three week experiment. The study evaluated the task of a subject entering data as an English sentence into a wearable computer. During the experiment the subjects manipulated icons, entered text and saved the files. All these tasks are requisite for text editing tasks. The data collected fell into four categories: text files created by the subjects, time logs, surveys of subjects and supervisor observations. This paper presents the results and analysis of the empirical portion of
1.1 Background A new physical form of a portable computer has emerged in
the form of a wearable computer [2,3]. Instead of the computer being hand-held, it is attached to the user on a backpack or belt, see Figure 1. This is an alternative to pen based computing[4,5], leaving the hands fiw when the computer is not in use but still allowing the user to view data in the privacy of a head mounted display. The application areas for this form of computer range from factory monitoring, stock taking, field data collection, to a soldier in the field. In the past these tasks have required at least a two stage process where the initial processing or collection is carried out via pen and paper, then entered into a computer in the second stage. This process is potentially time wasting and error prone. A wearable computer could enable this task to be compressed into a single stage and potentially save time and reduce error rates [6].
2
1.2 Aims and Objectives
(Figure 2), and belt mounted Mouse.
The aim of this study was to evaluate a set of characteristics of the three input devices; forearm mounted keyboard, virtual keyboard, and Kordic keypad, for the task of entering text based messages with a wearable computer. The set of measured characteristics were the speed of text entry and the number of errors for that entry. The textual messages were in the order of 10 to 15 English words long and contained numeric data. Elecause the computer is a general purpose computer with a windows based operating system, special attention was paid to how initiating and closing applications affited the use of the wearable computer.
Subjects consisted of both left and right hand dominant individuals. This affected their preferences for the way in which they suited up for the experiments. In this paper preferred is used to indicate the hand used on the various keyboards and the term non-preferred for the other arm and hand.
2.1 Belt mounted mouse The belt mounted mouse used was an isometric joystick device, mounted on top of the battery pack attached to the belt. A finger or thumb operates the mouse, and there is a mouse button in front of and behind the mouse. Figure 3 shows the mouse next to an index finger. All subjects positioned the mouse slightly in front of their right hip. When placed on the right hip, the subjects easily mapped the directionality of the movements of the mouse to activity on the screen. Switching the mouse to the left hip meant mentally flipping the mapping upside down which was very difficult to do. Some subjects experimented with placing the mouse in front of their abdomen but found this placement interfered with the Kordic keypad.
The study's objectives for each input device were: 1) T o determine the effort required to train a subject to the level of a proficient user. 2 ) To determine the speed at which a subject can enter alphanumeric textual data. 3 ) T o determine the number of errors a subject makes while entering alphanumeric textual data.
1.3 Structure of the Papler First a description of the wearable computer system used in the experiment is presented. This paper then describes in detail the experimental design and implementation. The third part of the paper presents the results of the study addressing the usability and functionality of the input devices. The paper finishes with a set of concluding remarks.
2. The wearable computer system The wearable computer is designed to be wom by a user on a belt with cable connections to a headset, see Figure 1. All the hardware and software are offthe shelf products. Suiting up takes approximately three to ten minutes with assistance. The weight of the whole system sits comfortably on the hips and is not particularly noticeable after a short time.
Figure 3 Belt Mount Mouse
2.2 Private Eye Display The Private Eye was mounted on a headset with microphone and earphone. All devices were on the right side of the head. This was awkward and the headset tended to slide down to the right. The Private Eye also partially occluded the vision, but the blind spot was not a danger to the subjects. Software to convert the Private Eye to left eye use was not available so it was necessary to restrict the subjects to those who did not have a strong left eye dominance.
2.3 Text Entry Using the Forearm Keyboard When using the forearm keyboard all left handed people chose the left hand as the preferred hand and all right handed people chose the right hand for typing on the forearm keyboard. The forearm keyboard was strapped to the subjects non-preferred forearm using elasticised Velcro straps. The back of the keyboard is slightly curved and fits comfortably on the arm. The rubberised keys have clear white characters. The keys of the forearm keyboard are easy to depress and placed well apart. In use, the keys have a
Figure 2 Kordic Keypad The hardware used in the experiment was as follows: The Phoenix 2 computer, headset with earphone, microphone, and Private Eye display, forearm keyboard, Australian Institute of Marine Science (AIMS) Kordic keypad [7]
3
definite resistance and click that cnsure the subject knows that the key has been successfully engaged. The foremn keyboard has standard QWERTY layout.
session. subjects became acquainted with the hardware and software for each device, by entering three to five word text messays in the same procedure as the six final tasks.
2.4 T e x t E n t r y Using t h e V i r t u a l K e y b o a r d Entering text with the virtual keyboard involvcs the ClickPad [SI program and use of the belt mounted mouse. Subjects select the characters and operations they want with the belt mounted mouse from the ClickPad application displayed in n nindow. see Figure 1. The selected characters appeared in the ClickPad editing window, on the right side of the window. The ClickPad has clear lettering set out in the standard QWERTY keyboard layout and is implemented in colour. On the monochrome Private Eye the icons are difficult to distinguish due to the lack of appropriate greyscale mapping and colour. HoLvever. the characters are all clear and unambi,ouous.
3.2 Subject Task S e s s i o n s The subjects performed six sessions each lasting a duration of one hour over a three week time frame. The study mapped the progress of sub-jects over the length of the study, and determined the amount of efort required to train a subject in the three different input devices. For each of the sessions the subjects performed the following tasks: 1) The subject was first asked to don, with assistance, the computer and all the input devices described in the previous section. 2 ) The subject performed nine tasks, three tasks for each of the three input devices: forearm keyboard, Kordic keypad, and virtual keyboard. 3) The subject removed the computer from themselves with assistance. 4) The subject performed one text entry task with the standard keyboard, at a desk. 5 ) The subject completed the survey.
Figure 4 ClickPad Window
2.5 Text Entry Using the Kordic Keypad The Kordic keypad is a hand sized, five button device that is used to enter chords of key combinations. The chords are entered on release rather than depression of the keys. Some commands require one chord and others two chords within a set space of time. The Kordic Note [ 7 ] , software for the Kordic keypad was written for the Hercules graphics card and utilised the wide screen. It displayed an edit window, under which there are pages of buttons labelled with the chord sequence and the word for that button. Subjects moved from page to page to select whole words to include in the message. Subjects enter entire words with an ending space character with a chord combination.
3. Research
method
and
Figure 5 Text entry task with a forearm keyboard
design
considerations A pilot study prior to the main study enabled the
experimental design to be modified. The experiment was broken down into three phases: firstly, an initial subject interview; secondly, a subject training session; and thirdly, subject task sessions. The interview involved explaining the experiment to the subjects in a standard way, obtaining their consent and
Figure 6 Room configuration for experiment
establishing a timetable for participation. The rest of this section describes the training and task phases of the experiment.
3.1 Subject Training Session In the week preceding the start of the experiment, there was a one hour training session for each of the subjects to become familiar with the wearable computer. During this
4
standard QWERTY keyboard for one text entry task. The subjects performed these trials one at a time in the laboratory with a supervisor.
5 Task5
6 Task6
7 lark7
8
9 'Task8
1 Task9
The text entry data for tasks 1 through 9 and the standard keyboard task had all ten digits in each message. In addition this text entry data was o f a length between 50 and 65 characters. The data recorded for each trial was the start, stop and elapsed times from the electronic stop watch, and the textual information entered by the subject. Times were recorded on the pressing of the Start and Stop on the stopwatch and the textual data was saved on exiting the application. An example of the S t o p button is shown in Figure 4.
0 Tjsklfl
I
Figure 7 Icons t o start tasks The tasks the subjects performed were attached to the wall under numbered signs in order 1 through 9, starting with 1. To simulate the mobility of a wearable computer system, the subjects stood while performing the tasks and walked between the task stations. Fi!gures 5 and 6 show the configuration of the signs in the laboratory. Tasks 1 through 9 utilised the f o r e m keyboard, Kordic keypad. and virtual keyboard. With these first nine tasks, there were three forms of the tasks: 1) Open und Shzrt Task - The subjects started an application,, entered a single character and closed the application. 2 ) Messuge 1 Task - The subjects started an application, entered a text message with an input device for the first time, and closed the application. 3) Message 2 Task - This task was the same as Message 1, but the input device was used for the second time. The applications were started with an icon labelled with the task number. Figure 7 shows the window presented to the subjects to start the applications. Task I O recorded typing speed using a standard QWERTY keyboard.
Errors were counted by comparing the expected textual data with the actual data the subject entered. One error is defined as a character in the wrong position. One error was counted for the following reasons: a missing character, an e m character, or a wrong character. With the Kordic keypad, every wrong character of a wrong word was counted.
3.3 Stat is t ical Con side ra t ions There were twelve subjects. The three input devices were presented in a random order to overcome ordering effects. Data for each of the input devices was obtained from each subject to allow for inter-subject, intra-subject, inter-session and intra-session analysis. The subjects were selected fnrm a pool of computer-literate people. To obtain this pool, students were recruited from the undergraduate and postgraduate students of the School of Computer and Information Science, and other Schools based at the Levels campus, University of South Australia. The selection process was on a first-come-first-served basis and specified that subjects must be able to walk, have the full use of both their arms and must not have left eye dominant vision. Cf the twelve subjects there were two female subjects and ten male subjects, all university students in the age range 19 to 42 with an average age of 23.8 years.
Figure 8 shows an example of the signs for the Message 1 and 2 tasks. The Open and %ut task was in the same format but simply asked the subject to enter any single character. Subjects were given directions to not correct any mistakes that occurred during text entry and told to enter any single character of their choice for the opedclose operation. Not correcting mistakes is a standard method fcr typing speed tests. The purpose of the Open and Shut task was to measure the time it took to operate the stopwatch and change focus back to the editor, so the particular character chosen was not important.
4. Results of the study n e results presented here are drawn from times recorded by the stop watch and from the saved textual data. Analysis cf the devices was carried out within sessions, between sessions, by subject and across subjects. To lend some perspective to the times for each of the devices the standard keyboard data for task 10 of each session is included in Table 1. The test number indicates which of six sessions.
Kordic keypad Read this page before editing Click on icon 4 The task is to enter the following text
I1 Mean I 0.65 Test
the 3 children were late at 845~171 to 60 people street in 1972 1. When you are ready to star;t editing click on the Start 2. Carry out the task 3. Click on the Stop 4. Quit the application
2
3
4
5
6
0.73
0.44
0.45
0.62
0.45
I
Table 1 Average typing speed in characters per second The next four sections present the results and analysis for the Open and Shut, Message 1, and Message 2 tasks.
Figure 8 Sign for a. text entry task The device type used in the first nine tasks were randomised, with the condition that adjacent tasks used different input devices. New data and a new random order were used for each of the six sessions. Task 10 used a
4.1 OPEN AND SHUT TASK The Open and Shut task was included in the experiment to gauge the influence of the opening and closing of the editor applications on the results. The total task time results fm
5
device and the virtual keyboard device performed similarly, with the time over the six tests ranging from four to eight seconds for both devices, see Figure 9. The Kordic keypad time ranged from 12 to 38 seconds. There was a significant diff?rence(p
