Keyboards for the handicapped

Journal of Medical Systems, Vol. 10, No. 3, 1986

Keyboards for the Handicapped

A New Concept*

Everett L. Johnson, Ph.D.

A keyboard has been designed and constructed for persons restricted to using a head or mouth stick. The keyboard is not a modification of existing keyboard technology but involves a com- pletely new concept. The keyboard, called a 2DOF keyboard, requires only two degrees of freedom motion for actuation. The problems of simultaneous key requirements, accidental key strikes, and multiple strikes of the same key have been solved. The keyboard is transparent to the personal computer to which it is connected, allowing use of any available soJbeeare.

I N T R O D U C T I O N

The availability of personal computers, PCs, increases the options for handicapped persons with regard to occupation, education, and the control of their environment. Various techniques have been designed or suggested to improve the interface between the severely handicapped and the computing power of personal computers. Prior solutions to the input problem faced by many handicapped persons involved modification of the existing keyboard. Many of the solutions eliminate the use of existing software. The approach discussed in this paper involves looking at keyboard design with the handicapped person in mind at the outset and with a primary design goal being the transparency of the new keyboard to the system software. A survey published in 19781 indicates that 1.5 million persons in the United States suffer from either complete or partial paralysis. The number of persons using head or mouth sticks is estimated to be between 200,000 and 300,000. The primary emphasis of this paper is on those forced by physical conditions to use head sticks; however, the results can be extended to mouth stick users. The work reported in this paper is research in progress, supported by the NIHR.

From The Wichita State University, Wichita, Kansas 67208. * This paper was presented at the 19th Hawaii International Conference on System Sciences, Honolulu, Ha-

waii, January 1986, and is republished here with permission.

277

0148-5598/86/0600-027%05.00/0 © 1986 Plenum Publishing Corporation

278 Johnson

THE P R O B L E M

In 1981 the Control Data Corporation gave a grant to the Cerebral Palsy Research Foundation of Kansas and Wichita State University to examine the adaptation of computer systems for severely disabled persons. As part of this grant a PLATO terminal and a link to a CDC computer was made available for a year. The PLATO educational software was used in classes offered to the handicapped who lived at The Timbers, an apartment complex for the handicapped in Wichita, Kansas. The author observed the system while it was being used by persons with different degrees of physical disability. Several diffi- culties were observed, some of which are universal:

Multiple Keys Required. Persons restricted to activating a keyboard with a single digit or stick are prevented by multiple key requirements from using the system.

Accidental Key Strikes. For persons with poor motor control, the accidental striking of keys while attempting to strike a desired key is a frustrating problem.

Multiple Key Strikes. After finding the correct key, many handicapped users strike the key more than once, giving multiple characters.

Depth perception requirements. Users of a standard keyboard are required to locate a point in three-dimensional space and then actuate a key at that point. Performing this action with a head, mouth, or hand stick is difficult even for able-bodied persons.

Attached Keyboards. The keyboard being attached to the CRT presented a problem to those in wheelchairs and those who, because of their handicap, could not orient them- selves properly to the system.

Educational software. Software that required an answer within a specific time proved difficult to those with slow motions.

Graphics. For use with some of the handicapped population, the graphics associated with educational software move too quickly.

The problems listed above prompted the author to propose a project, with the objec- tive of developing a keyboard for the handicapped, in conjunction with the Wichita State University Rehabilitation Engineering Center, to the National Institute for Handicapped Research, NIHR. This project is in the 3rd year of funding.

H E A D - M O T I O N M E A S U R E M E N T S

In order to intelligently design a keyboard for persons using a mouth or head stick, a device was designed and constructed that would determine more about the head and neck motions of handicapped persons. Figure 1 shows the head-motion test equipmen t. This research was directly in line with work done on an Available Motions Inventory, AMI, device designed by the industrial engineers on the Wichita State University REC staff. 2 The AMI is used to determine what motions a handicapped person is capable of making and strength of motion in certain axes. Resultant AMI data have been reduced, allowing the matching of motion abilities to motion requirements determined for various industrial tasks. 3

The test panel in Figure 1 consists of 65 light-emitting diodes, LEDs, which are controlled by an Apple Computer. A green LED is lit at the center of the panel at the start of each measurement. The person being tested uses a head stick with a grounded metal

Keyboards for the Handicapped 279

Figure 1. Head motion test equipment.

tip. Next to each of the LEDs is a metai contact. When the metal contact next to the green LED is touched, the green LED is turned off and one of the 64 red LEDs is turned on by the computer. The person being tested must touch the metal contact next to the active LED. An audible sound is emitted when the contact is touched and the green LED is turned on. The time required for this action is measured by the test panel electronics and sent to the computer. Tests are made at either constant or random radii. Eight lights are positioned 45 degrees apart at eight different radii: (1) .5", (2) 1.0", (3) 1.5", (4) 2 .0" , (5) 3 .0" , (6) 4 .0" , (7) 5 .0" , (8) 7 .0" .

For each person tested, 192 LEDs are turned on and must be turned off by the test subject. The time between turning off the green LED and turning off the red LED is measured and collected. This test is performed for each of the radii and for 192 LEDs at random radii. The LEDs are selected at random with 24 tests made at each angle. The controlling program allows displaying the data in both tabular and graphical form. Table 1 lists the data obtained for two clients.

Figure 2 shows graphical displays of the data. In Figure 2A the vector length indicates the velocity in each of the eight directions. The length is normalized to the maximum velocity. Figure 2B shows the normalized maximum velocity subtracted from each of the other velocities in order to accentuate the deviation from maximum. The zero length vector is in the direction of maximum velocity. Figure 3 is a time history of velocities during the test. The plot in Figure 3 allows checking for client fatigue during the test period.

Up to the present, the majority of clients have been able-bodied persons in order to establish a data base to use as a reference for evaluating the handicapped. Examination of the data for able-bodied persons, taken thus far, allows the following preliminary statements: (1) Right-handed persons have better head motion to the left (insufficient data exist for statements about left-handed persons); (2) the direction of best motion is a function of movement length; (3) the random test is an approximate average of the eight constant radii tests.

Figure 4 shows the velocity vector for a client with cerebral palsy. The client has no use of his hands. The client was sure, prior to testing, that he could control his head stick more efficiently in the horizontal direction. The resultant test indicated that if he were to

280 Johnson

Table 1. Performance Data for Two Clients

Best Worst Velocity Velocity Radius angle angle (in/sec) min/max

Client A 1 315 135 1.2 .77 2 315 135 2.1 .87 3 0 135 2.6 .63 4 315 135 3.1 .83 5 0 270 4.1 .76 6 225 90 4.2 .81 7 0 270 4.8 .91 8 180 315 5.8 .84

Random 225 135 3.48 .81

Client B 1 0 135 1.1 .83 2 225 270 1.5 .84 3 180 135 2.5 .66 4 315 270 2.4 .79 5 180 270 4.1 .71 6 180 270 4.4 .76 7 0 270 5.3 .75 8 180 90 6.1 .72

Random 225 270 3.3 .81

operate a standard keyboard, his performance might improve if the keyboard were rotated 90 degrees and positioned vertically. This repositioning of a keyboard was not tried at the time since no detachable keyboard was available at the time.

If a keyboard structure is to be developed that can be used by persons with different

A. NORMALIZEI: VELOCITY VECTORS

/ B. NORMALIZE~ DEVIATION FROM MAXIMUM

CLIENT A VELOCITY VECTORS CLIENT B VELOCITY VECTORS

Figure 2. Graphical display of performance.


VELOCITY •

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Ct . . ] : l i iNT A ( 0 DEr;.,F:EES; ) C L I i E N T B ( 1 8 0 I ] E G R E E S )

Figure 3. Time histories for R = 3.

ranges of motion, the range of extension/flexion, rotation, and lateral bending motions, as depicted in Figure 5, must be measured. As discussed in the next section, a keyboard has been designed that requires only 2 degrees of freedom to actuate. Any two of the three motions described in Figure 5 are sufficient to operate the keyboard. The range of motion ability is important for an individual given fixed keyboard dimensions. If the client has an extension/flexion motion of 0 degrees and the maximum distance the head stick must cover is D, then, as shown in Figure 6, the head stick length, L, must be

L = D/(2sin(0/2)). (1)

A device is being constructed to measure the motions shown in Figure 5. These measurements will become part of the set of ability measurements taken by the AMI. The data taken will allow determining if other abilities are correlated with head motion abilities.

TWO DEGREE OF FREEDOM KEYBOARD DEVELOPMENT

Prior to completing the collection of ability data, a keyboard was conceived that alleviates many of the problems listed previously. From observations of and conversa- tions with users, the following design goals were established: ruggedness, few or no moving parts, no double key requirements, a full range of key functions, protection

\ / / \

Figure 4. Velocity vectors for handicapped client (random radii).

282 Johnson

~ extension

.

l a te ra l bending

.--, ; .~ /

Figure 5. Measurements of the head and neck.

against accidental or multiple key hits, minimum motion and force to actuate a key, and redefinable keys. In addition, the keyboard should be transparent to the PC to which it is connected, (i.e., all software runs without modification) and it should allow flexible orientation and positioning.

Figure 7 shows the front view of the general 2 degree of freedom, 2DOF, keyboard scheme. The head stick actually penetrates the keyboard surface in which there are paths about which the keyboard head stick moves to proceed from one key to another. The keyboard shown has nine horizontal paths, or key channels, along which keys are lo-

D KEYBOARD WIDTH

Figure 6, Head motion and stick length relationship.


HEAD STICK PENETRATES KEYBOARD.

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~~ I[ ~ [ I[ i --I [ ~ ~

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Figure 7. General 2DOF keyboard.

KEY CHANNELS

cated. The user can use the lower part of each horizontal path as a support for the head stick while the next key is sought.

Figure 8 shows a detailed picture of what constitutes a single key. There are two keyboards involved--one keyboard enables the other. A key activation requires making contact with the grounded head stick at point A1 (key A of keyboard 1), which enables point A2 (key A of keyboard 2). Making contact with A2 after it is enabled causes an output of an 8-bit binary code unique to key A. This A1, A2 sequence causes only one output to occur. Each desired output of key A requires the A1, A2 sequence. Bouncing on A1 then bouncing on A2 causes just one A key output; i .e . , the sequence A1 ,A1,A2,A2,A2 causes only one A code output. Only the corresponding key is enabled on k e y b o a r d 2 w h e n a k e y is e n a b l e d on k e y b o a r d 1. The s e q u e n c e A1,A1,A1,B1,A2,A2,B2 will output only the code for B.

Figure 9 shows the complete keyboard structure connected to a PC. A detailed description of the function of each of the components shown in Figure 9 follows.

S c a n n e r

The scanner uses two keyboard scanner chips, KR3600-PRO, each capable of scan- ning a 9 × 10 switch matrix. For the scanner designed for the 2DOF keyboard, an 8 × 8 matrix is scanned. The intersection points in the matrix shown in Figure 10A must be connected to cause a key input. The connection is usually made mechanically with a switch. Figure 10B shows the circuit used to make the connection electrically when the grounded head stick makes contact with the keyboard switch contact. The KR3600-PRO chip has an on-board read-only memory, ROM, which outputs a distinct binary code for

~ m ~ ~ . ~ , ~ _ _

> I'IETAL CONTACTS CONNECTED KEY CHANNEL A 2 B - - TO SCANNER

~ ~ ~

A 1 gl

Figure 8. Details of key contacts in key channels.

284 Johnson

I I l,. i r - - - 1 L IT I f - - l t - - 1 I - - I I - - I

i ~ I I - - I

I I ' L__4 ,~__~ 2DOF K E B ~

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INTELLIGENT KEYBOARD

Figure 9. Intelligent 2DOF keyboard.

I PERSONAL (~Or,'~UTER . .---

the connection of each of the matrix intersections. Two chip inputs, shift and control, allow selecting 4 different sets of key codes. In the 2DOF scanner built, 4 sets of 64 keys are selectable, as shown in Table 2.

The user selects the desired key set by touching the head stick to one of four key set select contacts on the 2DOF keyboard. These contacts are single-hit contacts not re- quiring any initialization. Circuitry in the scanner selects the key set corresponding to the last grounded contact. The scanner also has a control circuit that notifies the intelligence portion (microprocessor) of the 2DOF keyboard whenever a key is initialized and whenever the proper initialize/select sequence occurs. The processor returns an acknowledge signal when it has accepted the key code. Figure 11 contains a flow chart that explains the function of the scanner.

I n t e l l i g e n c e

The VIC-20 in Figure 9 translates the 8-bit code from the scanner to the desired key code for the PC to which the keyboard is connected. The VIC-20 outputs a serial bit stream with the timing characteristics expected by the PC from its own keyboard. The control program and code translation table occupies 2K bytes, which are stored in an Intel 2732A-4KX8 EPROM. The VIC-20 user's port is used for the data and control interface,

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. . . . . . . 1 - - ~- ' \ ~ o -

~ o , ~°~%~0 t ~ , ~ ~ , ~ T ~ , ~ T , , ~ NIN CONNE~S NW ~ COL~.

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ELECTNIIC NITCH

Figure 10. Key matrix scanner.


Table 2. 2DOF Selectable Key Sets

Control Shift Key set

0 0 Standard 64-key set 0 I Shifted 64-key set 1 0 Control and 64-key set 1 1 Wordstar control,

strings, and special keys

as shown in Figure 12. The EPROM is positioned in memory space such that when inserted in the expansion port, the program is entered, upon power-up, as if a game cartridge were inserted.

The control program displays an enlarged character on the VIC-20 CRT indicating which key is initialized. As the head stick is moved across the keys that make up the initializing keyboard, the last key touched by the head stick is displayed. When the initialized key contact is touched, the CRT changes color and a "beep" is generated by the VIC-20. When special keys of key set No. 3 (shift = control = 1) are selected, the function or phrase is printed in large letters on the screen, such as RESET, PAUSE, BASIC, HOME, PG UP, PG DN, etc. A phrase table can be branched to by placing any code in the translation table that ends in 1. The control program then branches to the phrase table and sends the table characters until a stop code is encountered (hexidecimat FF).

The system has been constructed and is being tested. Head stick users can use all of the software available to the able-bodied, and they have the facility to input selected

- - l " ~ - ~ _ _ _ ~ _ ~ .

INITIALIZING KEY HIT TARGET IKEY HIT

l BiGNAL VIC-20 AND I5 INITIALIZE OUTPUT 8-BIT CODE FLAG O~?ES|Y NO FOR INITIALIZED KEY

1 ' i TURN ON INITIALIZE IS THE TARGET KEY FLAG [ INITIALI~ZED?Es - NO

SIGNAL VIE-20 AND OUTPUT 8-BIT CODE TO BE USED FOR KEY TRANSLATION TABLE

+ TURN OFF INITIALIZE FLAG ~

INITIALIZE KEY--INITIALIZES CORRESPONDING KEY ON TARGET KEYBOARD

TARGET KEY--OUTPUTS THE CODE TO BE USED BY THE VIC-20 TRANSLATION TABLE IF THE KEY HAS BEEN INITIALIZED

Figure i i . Scanner flow cha~.

286 Johnson

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2DOF CONNECTOR

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Figure 12. VIC-20 control interface.

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CONNECTOR - - -~

commands, phrases, or character strings with a single key-stroke. Phrases for a particular user may be stored in the remaining memory in the EPROM. Figure 13 shows the form of the initial keyboard built for testing. A stand has been built that allows 5 degrees of positioning freedom.

KEY POSITIONS

Much has been written about the inefficient placement of keys on the standard QWERTY keyboard. Montgomery 4 has proposed a keyboard layout and a keyboard actuated by wiping a finger or stylus across the keys. From analysis of most frequent words and trigrams (3 letter groups), he suggests key placement that allows the typing of many words by a single wiping process. Sha 5 performed a simulation of a standard keyboard operated by a person using a single digit as a key actuator. The purpose was to determine distance traveled while typing typical English text for different key arrangements. Using frequency of occurrence of letter pairs, Sha proposed key layouts that decreased the distance of travel for single-digit typing by 40%. He also analyzed the frequency of occurence of character pairs for FORTRAN and proposed a key layout that decreased distance traveled by 30% when typing FORTRAN statements.

Using the work of Montgomery and Sha, an attempt will be made to position keys on the 2DOF keyboard in a way that will minimize the distance the end of the head stick will have to travel to input control and data characters. The 2DOF key actuation concept allows the same character to be included as many times as required for efficient use; i.e., a space key could be included next to all characters that have a high frequency of use as word endings, or a period could be included in each key channel. All keys with the same


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I0 KEY CHANNELS ~ 9 KEYS/CHANNEL Figure 13. Pictorial view of 2DOF keyboard.

function would be wired together, with the key being actuated when any one of them is grounded by the head stick.

The initial key layout can be changed for experimental purposes by software in the VIC-20. Two types of periods are available. Each channel has a period-space-space key, and a period is positioned in the numerical character channel. A total of 90 physical keys are available. Those having the same function are connected by removable jumpers.

SUMMARY AND COMMENTS

A unique approach has been taken to design keyboards for the handicapped in that the design was begun from scratch instead of attempting to modify a conventional keyboard. A 2DOF keyboard that uses a double-scan process to eliminate unwanted key inputs has been designed and is in use. The 2DOF keyboard has given a head-stick user the ability to use the complete software complement of a PC without modification. Data are being taken to include the head motion abilities of handicapped users in determining key layout, structure, and positioning of the keyboard. Many human factor problems must be resolved.

The VIC-20 will be replaced with a microprocessor-based circuit in future models. The VIC-20 CRT will be replaced with a line display that will inform the user as to what key or phrase is activated and the selected key set. A detailed description of the circuitry and software is available in rough draft form. 6

288 Johnson

REFERENCES

1. Firing, M., The Physically Impaired Population of the United States, Firing and Associates, San Francisco, 1978.

2. Rahimi, M., and Malzahn, D. E., Task design and modification based on physical ability measurement. Hum. Factors 26:715-726, 1984.

3. Malzahn, D. E., Functional evaluation for task modification using the available motions inventory. Func- tional Assessment in Rehabilitation (A. S. Halpren and M. J. Fuhrer, eds.), Brooks Publishing, Baltimore, 1984, pp. 131-144.

4. Montgomery, E. B., Bringing manual input into the twentieth century. IEEE MICRO, March 1982. 5. Sha, W., Keyboard Optimization for Single Digit Typists. Directed Studies Report, Wichita State Univer-

sity, Wichita, Kansas, 1980. 6. Weber, Holt, and Johnson, An intelligent two degree of freedom keyboard for head and mouth stick users.

Rough draft available from EE Department, Wichita State University, Wichita, Kansas.

Documents

Keyboards for the handicapped