- Email: [email protected]
Route Guidance System for Automobile Drivers by Speech Synthesis
CopICight
© IFA C Control
in Transportation
Systems . \ ·ie nna. Aus tria. 19H6
ROUTE GUIDANCE SYSTEM FOR AUTOMOBILE DRIVERS BY SPEECH SYNTHESIS S. Tsugawa* and S. Tabei** *.\fechalli((ll Ellgilleerillg Labora/ory. Agf llr.\' of IlId/ll/ rilll Sril'll(f alld T I'chll olog). ,\filli.I/ I), of III/ Prlla/iollal Tra df alld IlIdIlS/I ) . .\'a III iki 1- 2. Sakllra-lllllrII ..\,iiharigllll Ibaraki-kl'll. 305 ja/HIII ** A.lhikaga Dril'illg Schuol Co .. Ltd .. T allaka-lIIachi -15 9- 1. ,lIh ikaga-.I!II . T ochigikell . 326 japall
Abstract. This paper describes a route guidance system for automobile drivers by speech synthesis and road - vehi c le digital communication . The system. included in a computer - aided driving instruction system installed on a training ground. aims to guide a driving trainee along a route fixed by an instruc tor. The system consists of a personal computer in the control center. on- board computers in each automobile. and inductive loop antennas . At an inductive loop antenna buried in the road and connected to the control center. transmitting the ID numbe r. each automobile receives data code. with which speech data stored in the ROM of the on- board computer are retrieved and edited to a route guidance message. It is outputted in a synthesized f emale voice by ADPCM. The carrier frequency for the road- vehicle communication from a road is 223.2 kHz and that from a vehicle is 304.8 kHz. Data . modulated by minimum frequency shift keying . are transmitted at 9600 bps . The data frame is based on the HDLC . Experiments by trainees show that the route guidance system by speech synthesis is effective on the training ground. Keywords. Road traffic; traffic control; transportation control; route guidance; speech synthesis; vehicle monitoring.
communication technique (Tsugawa and Tabei . 1984 ) . The instruction system has been installed on a training ground for instruction and practice of automobil e driving . The route guidance system in this paper. included in the instruction system. is for a driv i ng trainee when he practices driving with a training automobile on the training ground. While the route guidance system indicates a route fixed by an instruc t or before the start of practice to him. the driving instruction system acquires his driving data along the r oute for a diagnosis of his driving. For reduc tion of the load on the visual sense of a driver . a speech synthesis technique is empl oyed in the indi cati on of the route guidance informati on.
ImRODUCfION
The road- vehicle digital communication technique has been employed in route guidance systems for automobile drivers such as Comprehensive Automobile Traffic Control System (CACS ) (one of the large- scale projects of AIST . MITI ) (Matsumoto and others. 1979 ) . -Autofahrer Leitund Informationssystem(ALl ) (Braegas . 1980 ) . and Autoscout (v. Tomkewitsch . 1984 ) . In CACS . a local and digital communication technique between a road- side computer and an on- board computer was developed and employed f or the route guidance subsystem and the driving information subsystem. The system was installed in an urban area of Tokyo and operated for one year since 1977.
PIU~IPlE
Of SYSTIli DESIGN
The objective of the r ou t e guidance system in the compute r -aided driving instruction system is to guide a driving trainee from a starting point to a goal along a route on a training ground. The route guidance system is essential t o the instruc tion system . because a driving trainee should drive along a route fixed by an instructor on the basis of a driving instruct ion curriculum. and a trainee is not accompanied by an instruc tor on board. The instruction system can probably be organized withou t the local road - vehi c le communication technique . because the r outes for instruction are fixed beforehand . However. the road - vehicle communication technique is employed in the instruc tion system. because on- board computers become simple. operations in an automobile by a driver become unnecessary. and the function of automatic vehi c le monitoring (AYM ) is introduced into the system .
All of the systems mentioned above have similar structure . though Autoscout uses infrared beacons for the road- vehicle communication. In addition. all of them employ visual display units to show the route information to a driver . It is only the recently developed -Elektronischer Yerkehrslotse fur Autofahrer- (EYA )
There 309
are
three
methods t o indicate a route to a
3\0
Cases yhen the visual indication is proper.
Cases yhen the auditory indication is proper.
-
- Messages are simple and concise.
Messages are complicated or abstract. Combination of some information is shoyn. Messages are long. Messages are referred afteryard. Messages contain spatial information. Messages are not used promptly. The auditory sense is overloaded. An operator is at a fixed station.
dri ver: the visual indication. the audi t ory indi cation . and use of the both me thods. Appli cation areas of the vis ua l indication and the auditor y indi cation are compared i n Table 1. The vis ual sense can acq uir e more data in shorter time than the auditory sense. Hoyever. yhile driving an automobil e. drivers yill york the visual sense t o confirm safety. Therefore. it is a n idea l me thod that uses the auditory sense mai nly and th en the visual sense secondarily to compensate the auditory sense. In additi on. since a drive r in the dr iv ing instruct i on system is just a beg inner. it is diffi cult or impossible for him to yatch a visual displ ay unit during driving. Consequen tly, an auditory indi cati on t echnique is employed for the route guidance in the instruction system. On the training ground. the r oad ne tYork is not complicated and the ma in corners of the r oads a r e number ed by noti ces. These ma ke it easy that the route guidance only by the a ud itory indi cation is put into practice. Thus. a speech synthes is technique is employed in the audito ry indication.
-
Messages are short . Messages are not referred afteryard. Messages indicate time. Messages are used promptly . The visual sense is overloaded. - An operator moves here and there .
d ~ \TEI<
:'l "H:--Y:-:"[ E\1
I
r
,-_._-_
...
- .-
u
--.j(ll.\l.\ll\il".\i'1!)'\ ~ C(J'\ · IJ.:lJJ. l'\IT ..
Fig. I.
J.()()],
;\\'I'E\\: :\
The structure of the system .
smUCI1JRE OF ruE SYSTEM
The system consists of thr ee subsystems: a cente r subsys t em, a vehi c le subsystem and a r oad - vehicl e communication subs ystem. The structure is shoyn in Fig. 1. Center Subl>Ys..tgm The center subsystem cons ists of a cente r computer shoyn in Fig. 2 . The computer is a personal computer (NEe PC9801. RAM 128 kilobytes KB : . character RAM 8 KB. graphic RAM 93 KB . It func tions as a control center of the system. In additi on . it accep t s appli ca tions of training. and outputs training routes and driving diagnoses. The input and output devices of the computer a re a col or CRI . a li ght pen. a Kanj i printer. a keyboard . a GP- IB interface a nd tyO fl oppy disc drives. The GP- IB interface is used to link the center subsystem and the r oad vehicle communication subsys t em. because the interfaci ng t o the personal computer and its programm i ng are easy. Inte rac ti on of an operator yi t h the computer is performed by pus hi ng one of the indicated points on the CRI yith the light pen. Input ope rations by the light pen are applications of training: de termination of a training au t omobil e: and display and printout of a route chart . a system mon itoring chart and a diagnosis c hart. The program is Yritten in BASIC. It is about 700 l ines long. and occupies about 22 KB in the main memo ry except yor king areas . Data from the vehi c l e subsys t em are transm itted thr ough the road-vehicle communication subsystem t o the center subsystem . Thus. the cente r subsystem can locate each automobile on the training gr ound . though the locations are quanti zed to the communication points. Therefor e. the system has the
Fig. 2.
The center computer.
fun ct i on of automati c proximity me thod.
vehi c l e
monitoring
by
a
Each training automobil e has an on- board computer. a vehi cular antenna. several kinds of vehi cu lar sensors. a push · button s yitch and a speaker as the ve hi c l e subsystem. The subsystem function s to output route guidance informat ion by speech synthesis and to acquire driving data of a driving tr ainee. The vehicu l ar antenna. mounted at the cover of the r ea r trunk . has the form of a cy linder and yorks for the r oad - vehicle comm uni cati on . The se nsors acquire driving data such as an engine stall and a shift l e ver positi on . Pushing of the the push - button syitch by a driver indicates beginning of driving to the system. The on- board computer includes a mi c roprocesso r (8 bit processor 6803. RAM 4 KB. Ra1 4 KB. a communi ca tion con tr oll er a nd a speech synthes i zing
311
unit . The unit consists of a microprocessor 8 bit processor 8748. a speech synthesizing LSI .MSM 5218 and speech data ROM. Figure 3 sho~s the on - board computer installed in the r ea r trunk of a training automobile. Figure 4 sho~s the structure of the on -board computer. Contro l in the speech synthesis ~ill be described in detail late r.
The road -vehicle communi ca ti on subsystem consists of communication control units in the contr ol center and loop antennas buri ed under the surface of roads on the t raining ground. It functions to tr ansmit information bet~een the center subsystem and the vehi c l e subsystem. Each commun icat i on control unit is controll ed by a mi crocomputer (processor 6803. RAM 4 KB. ROM 4 KB ,' and is connected to the personal compute r in the cente r subsystem thr ough the GP -lB. It has the same structure as the on · board compute r except the speech synthesizing unit. A GP- IB controller is connected to the interface controll e r in the communication control unit .
antenna. Digital data are transmitted bet~een them individually . The size of a loop antenna is 2.5 m long by 2 m ~ide . It is buried at about 4 cm from the surface of the road . Figure 5 sho~s a training automobile over an inductive loop antenna. The communication specifications are summarized in Tabl e 2. It also sho~s the specifications used in CACS for comparison. The communica tion in the instruction system is much more flexible than in CACS. Moreover. a lot of data can be transmitted at one road - vehicl e communication point. Thus. the numbe r of induc tive loop antennas can be reduced . In addition. the ne~ specifications can be applied to three types of road antennas: an inductive loop type. a side- fir e type. and an overhead type. The road vehicle communication sequence in this system is sho~n in Fig . 6. The QA frame is periodically transmitted from the road so that the sequence may begin ~ith polling from the road to the vehicle. After the vehi c le receives the QA frame . it sends back the Al frame to the road, and then the road transmits the A2 frame to the
Each inductive l oop antenna is connected to a communication contro l unit for communication ~ith the vehi cle subsystem. The road - vehicle communication empl oys induc tive radio by ~eak ~aves bet~een an induc tive l oop antenna and a vehi cular
....
Fig. 3.
\/
The on - board compu ter.
Items Carrier Frequencies
The structure of the on- board computer.
The Instructi on Sys tem
CACS
From Road To Vehicle
22.3.2 kHz
105.6 kHz
From Vehicle To Road
304.8 kHz
172.8 kHz
Baud Rate
9300 baud
4800 baud
Modulati on
Minimum Frequency Shift Keying
Phase Shift Keying
Bit Rate Transmitted Data A~ount ~h en a vehicle is running Error Detection Communication Sequence R: road. V:vehicle ' Types of Road Antennas
CTS-K
Fig. 4.
9300 bps
4800 bps
Maximum 624 bits ,variable ;
144 bits
CRC
Parity Check
R- V- R- V 1 ) Inductive Loop Type buried in the Road 2 ) Side-Fire Type 3 ) Overhead Type
\fixed )
R- V- R- V 1 ) Inductive Loop Type buried in the Road 2 ) Side- Fire Type
312
S. Tsuga\\'a and S. Tabei
,, ~OAIJ
-r-----' ----'
·\ 1 F R -\\I F
f
\
ti:\ FI< :\\IE
Fig. 6 .
\
I-.-\ ': Fk A \I E
The road- vehi c l e communication sequence.
an odometer of the training automobile. Fig. 5.
An automobile over a loop antenna.
vehi c l e. Each frame. based on the HDLC. contains the addresses of the transmitter and the r eceiver . preambl e and CRC bytes. Data for route guidance and driving da ta acquisition are included in the A2 frame. The amount of data bytes tr ans mitted at one communication point when an automobile is running is va ri ab l e. It is 78 bytes at the largest, and usua lly 17 to 49 by t es . In CACS. the amount of data was fix ed t o 18 bytes. and the contents in each data frame were also fixed . comnoL IN TIlE ROlfIE GUIDANCE SYSTEM
In CACS. the route guidance information in each road - side computer was updated periodically with new data computed in the control center on the basis of da ta from the road si de computers. Thus, the route guidance in CACS was dynami c . On the contrary. the route guidance described he re is static, because r outes are provided beforehand on the basis of a driving instruc tion curr i cu lum.
When a trainee does not or cannot foll ow the indicati on , he is guided to the ex it of the training ground. It is detec ted a t the next communication point on the basis of the segment number and the ID number of the automobil e. Speech Synthesis The speech synthesis in this system does not employ a spec ial coding t echnique such as PARCOR or LPC, but employs the ADPCM technique. because the coding is very simpl e and the ROM for speech data is inexpensive. Whe n stori ng speech data in the ROM, the origi nal ana log voice data were sampled at the rate of 6 kHz and quanti zed t o 4 bits in ADPCM . In this system a femal e voi ce is employed. For the route guidance. 20 elements of messages are stored in the ROM. In addition. 2 kinds of fixed messages indicating the start and end of training are stored in the ROM. The capacity of the ROM is 48 KB. Table 3 shows the elements and the fixed messages.
On output of a route guidance message.
these
elements a re edited according t o the form of 'Ielement il WO le lement jl . lelement kl'
In this route guidance system. a drive r cannot selec t his r oute a rbitrari ly . but an ins tructor selects it among some r outes provided for the instruct ion system when a driver applies driving training. Thus . a driver's r oute and the ID numbe r of his automobile are inputted to the center computer before the start of driving. Ther efore. a seri es of points for the road - vehicle communication along the r ou t e selected is known in the center computer beforehand. A part of a route between two adjacent commu ni cation points is ca lled a segment. Each comm uni cat ion control unit. corresponding to each road - vehicl e commu ni cation point. has data f or all the segments of eve ry r oute that begin from the prese nt communi ca ti on point. The data are for the route guidance and driving data acquisition. Whenever the r oad -vehi c le communi cati on is performed at an inductive l oop antenna. the ID number and the last segment numbe r of an automobile are tr ans mitted to the commun i cat i on control unit and the center computer in the AI frame . On the basis of the ID number and the route number from the center compu t e r . the communi cat ion control unit retrieves data for the next segment and transmits them to the automobile in the A2 frame. At each communication point. all the data required on the next segment are transmitted coll ect ively . In the A2 frame . each data for the route guidance or driving data acquisiti on a t one point are stored in 2 bytes . Data codes for speech synthesis or a driving data item are stored in a byte , and the distance from the communi cation point where the route guidance or da ta acquisition is operated is stored in another byte. The distance is measured by
on the basis of the data codes transmitted from a communication unit. The processor (8748 ) controls the editing and output. The e l ements in Tabl e 3 are inserted in the locati ons corresponding to the data codes i (1 ~ i ~ 12 ) . j (j = 0 or I ) . and k (0 ~ k ~ 5 ) . Some elements ar e dupli ca ted . because they are used in differ ent locat i ons in the form . When k=O. the re is no element in this l oca tion. Thus . for example. whe n i =5 . j=l. and k=2. these e l eme nts are edited to a message '00 WO HIDARI . SHUUKAI' (in English . ' Turn to the left at the corner ~ . and then enter the round road .' ) . These messages are outputted only once at predetermined points. The output of the fi xed messages is controlled by the data code 1 in Tabl e 3. A fixed message is outputted as it is . The message of 1=0 is outputted at the starting point when a driver pushes the push- button switch: that of 1=1 is at the goal after driving da ta has been transmitted to the center compute r . EXPERIMENTS OF TIlE SYSTEM
Installation of the System The instruction system has been installed on a training ground of 60 m by 80 m. Figure 7 shows the training ground where the system has been installed . The training ground has road elements essential to driving training such as S-shaped roads . crank- shaped roads and sloped roads . For the road-vehi c le communication. 9 induc tive loop antennas are buried on the training ground. The
313
Route (;uidan cc Systelll for :\utollloilile [hinTs
Elements
I
English Translation Time (s ) one t .. o three four five six seven eight nine round road
i = 1 ICHI
2 iNI 3 SAN 4 YON 5GO
I
6 l ROKU
7 jNANA 8 HACHI 9 1 KYlRJ
10 SHUUKAI
English Translation Time (s )
0.33 i =11 CHUUOH KANSEN main road 0.33 12 DEGUCHI exit WO 0.33 I (no translation ) 0.33 j = o MIGI right 0 .33 I HIDARI left 0.33 k= I KURANKU crank-shaped road 0 .33 2 SHUUKAI round road 0.33 3 CHUUOH KANSEN main road 0.33 4 HOHKOH HENKAN direction exchange 0.50 5 ESU S-shaped road
Messages 1= 0 ANZENNI CHUUISHITE HASSHINSHITE KUDASAI . 1 HANDOBlJREJ1KI, GIYA WO OTASHIKAMEKUDASAI.
Fig. 7.
Elements
0.00 0.50 0.33 0.33 0.50 0.50 0.50 0.00 0.00 0.33
English Translation
Time (s )
Start carefully and safely. Make sure of the handbrake and shift lever.
2.60 2.60
The training ground.
on-board computers are installed in 12 training automobiles. In this system 7 routes are provided for the beginner and the advanced . Up to 10 trainees can practice driving .. ith the instruction system concurrently . Ho.. ever , the number of trainees is probably limited, because the training ground is not large enough.
Fig. 8.
An example of route guidance.
TABLE 4 Route Guidance Messages along a Route in Figure 8 ' Data COOes for
Figure 8 sho..s an example of a route, points for the road - vehicle communication and locations .. here the route guidance information is outputted. Table 4 sho..s the route guidance messages that are outputted at the locations sho.. n in Fig. 8.
CommunIcat I on ' GUIda nce Mess a ge EdItl ng POInts LocatlOns
]
o
For the study of the auditory indication of the route guidance information, experiments ..ere conducted .. ith the aid of a number of trainees in the driving school. They included all kinds of trainees: men and ..omen of all ages. An automobile that has a speech synthesizing unit by a male voice was also prepared for comparison with a female voice. The contents of the speech in a male voice and a female voice were same . In the experiments, a pair of trainees got on an automobile. A trainee drove the automobile at the speed within 25 km/ h, and his partner brought a map of the route to indicate the route to the driver when the driver missed his .. ay. After trainees finished training by the instruction system, they were interviewed. Their impressions are summarized as follo ..s: I ) A route guidance system is necessary in the instruction system. Trainees feel uneasy when
~~DM~1
'.IQ Hi)AR!
c..~."JOI-~
CC W':::
5
,...
CHUIJI9-lITE HASSHINSHITE KtIDASAI
ICJ-I; WO
ROKt; '010 ,'1:G: !(',,'RA}..'KU KA!':S:::N '.!c r.:~AHI !1!~.G: :<"JR;8K"J
0
11
Experiments by Trainees
A~ZENN! S{~1J..
rl
10 6
Mes sage s
k
c:
(
S: ~'1.."3A. 7
Ha{KOO HE'JKAN
9 10
YOi 'of,) ~ iG! ESl.i CH'Jl.O-! KJ..N.<.D.I 'WO
11
SAN WO MI GI. ESlJ
12 13
10 2
14
A
:5
:7
10 9 :2
'8
:2
:6
9-!UUKAI
- - -- -
'.,>() ~ :G~
\ .;.";;.. ',;0 ~:::;;
'.Q
~ rGI
H: !)AR I Clf...'1...lY.
N: '-'0 i:I::AS'! 0
~
~ S."I.f,.i:_.~{A:
K'(';":
..".c
Irv V!G; ~: G:
:.o-n
!-B{o(.M-l
D--::GX:-:: '.':'!-:::::.;'::::
'9
they bring only a map of a route without a route guidance system. 2 ) The auditory indication of the route guidance information is better than the visual indication, because it is by no means easy for them to watch a visual display unit while driving. 3 ) Generally the contents of the messages and the
314
guidance locations are sufficient for the route guidance. However. some trainees said that a route guidance message is necessary even when a driver goes straight on at a junction of a straight road and a road branc hing from it. In addition. only a few trainee said that the messages should be more concise and be repea ted. 4 ) The synthesized speech in a female voice is clear enough. It is better and more comfortable than a male voice. In addition. a femal e voice is clearer than a male voi ce . 5 ) The speed of the speech is appropriate. no t fast and not slow . DISCUSSION The route guidance system by speech synthesis has been completed and installed on the training ground for the computer aided driving instruction. It was ascertained by expe riments that the subsystems and the components of the system work well . In this system. for simplicity. the communication control units and the on board computers were designed to have almost the same structure . As a result. the route guidance information was stored in the ROM of the communication control units. Howeve r. this prevents flexibility of the system. When a new route or a guidance location is added in the present system. the ROM should be replaced. For making the system flexibl e. the communi cation control units should have struc ture that enables downloading of data from the center computer. The message is outputted abruptly in the prese nt system. This surprises a driver. and it somet imes causes him to miss the message. Thus. a sound that calls a driver's attention should be outputted before a route guidance message. This functi on was provided in the visual indi cat ion of CACS. It is also required even in the auditory indi ca tion . In addition . the voca bulary in the speech synthesizi ng unit is limited because of the capacity of the ROM. Thus . it is difficult to include geographical names in the memory. unless mass storage units such as compact discs are employed. roo.USIONS The route guidance system for automobile drivers has been developed with the local road - vehi c le digital communication technique and the speech synthesis technique by ADPCM. Moreover. it has been installed on a training ground for driv i ng instruction. The system guides driving trainees along routes on the training ground in a static mode. The system has simple structure and is
inexpe nsive. The route guidance information for seve r a l guidance locations is transmitted at one road ·vehicle communication point with the improved communication spec ifica tions. The route guidance system has got a fav orabl e reception by the trainees of the driving school. The results of the experime nts by the trainees show that the contents of the messages are suffi c i ent for the route guidance. They also show that a female voice has been rated more highly than a mal e voice. However . this cannot be generalized. beca use the kind of the voi ce depends on the vari ous factors such as a speake r and an encoding method of an original voi ce. Furthe rmor e. they show that the speech synthesi s meets the indi ca tion me thod of the route guidance informa tion on the training ground. In a limited road network. the route guidance system that employs only the auditory indication is effective. Never the l ess. further studies will be required for a indi cation method of the route guidance information on urban streets and highways. ACKNOWLEDGEl1ENf We wou ld like to thank Nippon Denso Co. Ltd. for their cooperation of the de ve lopme nt of the computer aided instruc tion system of automobile driving.
Braegas. P. \1980 ·. Func tions. Equipme nt. and Field Tes ting of a Route Guidance and Information System for Drivers (ALl). IEEE Trans. on Vehiculor Technol0'l!/' VJ' - 29. 216- 225.
Matsumoto. S .. Mikami. T .. Yumoto. N.. and Tabe . T. (1 979 ), Comprehe nsi ve Automobile Traffic Control System. J. of lEa: of Jopon. 62. f370 - 887.
Pilsak . for
O. (1 984 ) . FYA:An Elec tr oni c Traffic Pilot Motorists . P, ·OC. DCa\' SYlIIpos iwH "Land Vehicle :\'m;igcliion 1984".16.1 - 16.24. Suzuki. N. (1983 1. Necessity and Method of Local Digital Communication. Proc . 2nd Sympos ium on El ec lroni cs [01 ' Improl ClIIcn t of Automobile Traffic. Assoc iolion of El ectronic Technology for Automobile Tmffi c one/ Driling . 5- 13. von Tomkewitsch. R. ( 1984 ' . AUTO-SCOUT A Universal Traffic Guidance and Informati on System. Proc . DCa\' SYlIIpos illlll "Lonci 'chicl e Sm i<)CIt ion ~ 17.1 - 17.21. Tsugawa. S. and Tabei. S. 1984 Computer - Aided Instruction System of Automobi le Driving. Proc. 1984 int er1lCl tional Conference on I ne/lis t ria I Elee lr·oni cs. Cont ro l and Ins t nml('ntot ion [ Eco.," 84 ' . 318- 323.
© IFA C Control
in Transportation
Systems . \ ·ie nna. Aus tria. 19H6
ROUTE GUIDANCE SYSTEM FOR AUTOMOBILE DRIVERS BY SPEECH SYNTHESIS S. Tsugawa* and S. Tabei** *.\fechalli((ll Ellgilleerillg Labora/ory. Agf llr.\' of IlId/ll/ rilll Sril'll(f alld T I'chll olog). ,\filli.I/ I), of III/ Prlla/iollal Tra df alld IlIdIlS/I ) . .\'a III iki 1- 2. Sakllra-lllllrII ..\,iiharigllll Ibaraki-kl'll. 305 ja/HIII ** A.lhikaga Dril'illg Schuol Co .. Ltd .. T allaka-lIIachi -15 9- 1. ,lIh ikaga-.I!II . T ochigikell . 326 japall
Abstract. This paper describes a route guidance system for automobile drivers by speech synthesis and road - vehi c le digital communication . The system. included in a computer - aided driving instruction system installed on a training ground. aims to guide a driving trainee along a route fixed by an instruc tor. The system consists of a personal computer in the control center. on- board computers in each automobile. and inductive loop antennas . At an inductive loop antenna buried in the road and connected to the control center. transmitting the ID numbe r. each automobile receives data code. with which speech data stored in the ROM of the on- board computer are retrieved and edited to a route guidance message. It is outputted in a synthesized f emale voice by ADPCM. The carrier frequency for the road- vehicle communication from a road is 223.2 kHz and that from a vehicle is 304.8 kHz. Data . modulated by minimum frequency shift keying . are transmitted at 9600 bps . The data frame is based on the HDLC . Experiments by trainees show that the route guidance system by speech synthesis is effective on the training ground. Keywords. Road traffic; traffic control; transportation control; route guidance; speech synthesis; vehicle monitoring.
communication technique (Tsugawa and Tabei . 1984 ) . The instruction system has been installed on a training ground for instruction and practice of automobil e driving . The route guidance system in this paper. included in the instruction system. is for a driv i ng trainee when he practices driving with a training automobile on the training ground. While the route guidance system indicates a route fixed by an instruc t or before the start of practice to him. the driving instruction system acquires his driving data along the r oute for a diagnosis of his driving. For reduc tion of the load on the visual sense of a driver . a speech synthesis technique is empl oyed in the indi cati on of the route guidance informati on.
ImRODUCfION
The road- vehicle digital communication technique has been employed in route guidance systems for automobile drivers such as Comprehensive Automobile Traffic Control System (CACS ) (one of the large- scale projects of AIST . MITI ) (Matsumoto and others. 1979 ) . -Autofahrer Leitund Informationssystem(ALl ) (Braegas . 1980 ) . and Autoscout (v. Tomkewitsch . 1984 ) . In CACS . a local and digital communication technique between a road- side computer and an on- board computer was developed and employed f or the route guidance subsystem and the driving information subsystem. The system was installed in an urban area of Tokyo and operated for one year since 1977.
PIU~IPlE
Of SYSTIli DESIGN
The objective of the r ou t e guidance system in the compute r -aided driving instruction system is to guide a driving trainee from a starting point to a goal along a route on a training ground. The route guidance system is essential t o the instruc tion system . because a driving trainee should drive along a route fixed by an instructor on the basis of a driving instruct ion curriculum. and a trainee is not accompanied by an instruc tor on board. The instruction system can probably be organized withou t the local road - vehi c le communication technique . because the r outes for instruction are fixed beforehand . However. the road - vehicle communication technique is employed in the instruc tion system. because on- board computers become simple. operations in an automobile by a driver become unnecessary. and the function of automatic vehi c le monitoring (AYM ) is introduced into the system .
All of the systems mentioned above have similar structure . though Autoscout uses infrared beacons for the road- vehicle communication. In addition. all of them employ visual display units to show the route information to a driver . It is only the recently developed -Elektronischer Yerkehrslotse fur Autofahrer- (EYA )
There 309
are
three
methods t o indicate a route to a
3\0
Cases yhen the visual indication is proper.
Cases yhen the auditory indication is proper.
-
- Messages are simple and concise.
Messages are complicated or abstract. Combination of some information is shoyn. Messages are long. Messages are referred afteryard. Messages contain spatial information. Messages are not used promptly. The auditory sense is overloaded. An operator is at a fixed station.
dri ver: the visual indication. the audi t ory indi cation . and use of the both me thods. Appli cation areas of the vis ua l indication and the auditor y indi cation are compared i n Table 1. The vis ual sense can acq uir e more data in shorter time than the auditory sense. Hoyever. yhile driving an automobil e. drivers yill york the visual sense t o confirm safety. Therefore. it is a n idea l me thod that uses the auditory sense mai nly and th en the visual sense secondarily to compensate the auditory sense. In additi on. since a drive r in the dr iv ing instruct i on system is just a beg inner. it is diffi cult or impossible for him to yatch a visual displ ay unit during driving. Consequen tly, an auditory indi cati on t echnique is employed for the route guidance in the instruction system. On the training ground. the r oad ne tYork is not complicated and the ma in corners of the r oads a r e number ed by noti ces. These ma ke it easy that the route guidance only by the a ud itory indi cation is put into practice. Thus. a speech synthes is technique is employed in the audito ry indication.
-
Messages are short . Messages are not referred afteryard. Messages indicate time. Messages are used promptly . The visual sense is overloaded. - An operator moves here and there .
d ~ \TEI<
:'l "H:--Y:-:"[ E\1
I
r
,-_._-_
...
- .-
u
--.j(ll.\l.\ll\il".\i'1!)'\ ~ C(J'\ · IJ.:lJJ. l'\IT ..
Fig. I.
J.()()],
;\\'I'E\\: :\
The structure of the system .
smUCI1JRE OF ruE SYSTEM
The system consists of thr ee subsystems: a cente r subsys t em, a vehi c le subsystem and a r oad - vehicl e communication subs ystem. The structure is shoyn in Fig. 1. Center Subl>Ys..tgm The center subsystem cons ists of a cente r computer shoyn in Fig. 2 . The computer is a personal computer (NEe PC9801. RAM 128 kilobytes KB : . character RAM 8 KB. graphic RAM 93 KB . It func tions as a control center of the system. In additi on . it accep t s appli ca tions of training. and outputs training routes and driving diagnoses. The input and output devices of the computer a re a col or CRI . a li ght pen. a Kanj i printer. a keyboard . a GP- IB interface a nd tyO fl oppy disc drives. The GP- IB interface is used to link the center subsystem and the r oad vehicle communication subsys t em. because the interfaci ng t o the personal computer and its programm i ng are easy. Inte rac ti on of an operator yi t h the computer is performed by pus hi ng one of the indicated points on the CRI yith the light pen. Input ope rations by the light pen are applications of training: de termination of a training au t omobil e: and display and printout of a route chart . a system mon itoring chart and a diagnosis c hart. The program is Yritten in BASIC. It is about 700 l ines long. and occupies about 22 KB in the main memo ry except yor king areas . Data from the vehi c l e subsys t em are transm itted thr ough the road-vehicle communication subsystem t o the center subsystem . Thus. the cente r subsystem can locate each automobile on the training gr ound . though the locations are quanti zed to the communication points. Therefor e. the system has the
Fig. 2.
The center computer.
fun ct i on of automati c proximity me thod.
vehi c l e
monitoring
by
a
Each training automobil e has an on- board computer. a vehi cular antenna. several kinds of vehi cu lar sensors. a push · button s yitch and a speaker as the ve hi c l e subsystem. The subsystem function s to output route guidance informat ion by speech synthesis and to acquire driving data of a driving tr ainee. The vehicu l ar antenna. mounted at the cover of the r ea r trunk . has the form of a cy linder and yorks for the r oad - vehicle comm uni cati on . The se nsors acquire driving data such as an engine stall and a shift l e ver positi on . Pushing of the the push - button syitch by a driver indicates beginning of driving to the system. The on- board computer includes a mi c roprocesso r (8 bit processor 6803. RAM 4 KB. Ra1 4 KB. a communi ca tion con tr oll er a nd a speech synthes i zing
311
unit . The unit consists of a microprocessor 8 bit processor 8748. a speech synthesizing LSI .MSM 5218 and speech data ROM. Figure 3 sho~s the on - board computer installed in the r ea r trunk of a training automobile. Figure 4 sho~s the structure of the on -board computer. Contro l in the speech synthesis ~ill be described in detail late r.
The road -vehicle communi ca ti on subsystem consists of communication control units in the contr ol center and loop antennas buri ed under the surface of roads on the t raining ground. It functions to tr ansmit information bet~een the center subsystem and the vehi c l e subsystem. Each commun icat i on control unit is controll ed by a mi crocomputer (processor 6803. RAM 4 KB. ROM 4 KB ,' and is connected to the personal compute r in the cente r subsystem thr ough the GP -lB. It has the same structure as the on · board compute r except the speech synthesizing unit. A GP- IB controller is connected to the interface controll e r in the communication control unit .
antenna. Digital data are transmitted bet~een them individually . The size of a loop antenna is 2.5 m long by 2 m ~ide . It is buried at about 4 cm from the surface of the road . Figure 5 sho~s a training automobile over an inductive loop antenna. The communication specifications are summarized in Tabl e 2. It also sho~s the specifications used in CACS for comparison. The communica tion in the instruction system is much more flexible than in CACS. Moreover. a lot of data can be transmitted at one road - vehicl e communication point. Thus. the numbe r of induc tive loop antennas can be reduced . In addition. the ne~ specifications can be applied to three types of road antennas: an inductive loop type. a side- fir e type. and an overhead type. The road vehicle communication sequence in this system is sho~n in Fig . 6. The QA frame is periodically transmitted from the road so that the sequence may begin ~ith polling from the road to the vehicle. After the vehi c le receives the QA frame . it sends back the Al frame to the road, and then the road transmits the A2 frame to the
Each inductive l oop antenna is connected to a communication contro l unit for communication ~ith the vehi cle subsystem. The road - vehicle communication empl oys induc tive radio by ~eak ~aves bet~een an induc tive l oop antenna and a vehi cular
....
Fig. 3.
\/
The on - board compu ter.
Items Carrier Frequencies
The structure of the on- board computer.
The Instructi on Sys tem
CACS
From Road To Vehicle
22.3.2 kHz
105.6 kHz
From Vehicle To Road
304.8 kHz
172.8 kHz
Baud Rate
9300 baud
4800 baud
Modulati on
Minimum Frequency Shift Keying
Phase Shift Keying
Bit Rate Transmitted Data A~ount ~h en a vehicle is running Error Detection Communication Sequence R: road. V:vehicle ' Types of Road Antennas
CTS-K
Fig. 4.
9300 bps
4800 bps
Maximum 624 bits ,variable ;
144 bits
CRC
Parity Check
R- V- R- V 1 ) Inductive Loop Type buried in the Road 2 ) Side-Fire Type 3 ) Overhead Type
\fixed )
R- V- R- V 1 ) Inductive Loop Type buried in the Road 2 ) Side- Fire Type
312
S. Tsuga\\'a and S. Tabei
,, ~OAIJ
-r-----' ----'
·\ 1 F R -\\I F
f
\
ti:\ FI< :\\IE
Fig. 6 .
\
I-.-\ ': Fk A \I E
The road- vehi c l e communication sequence.
an odometer of the training automobile. Fig. 5.
An automobile over a loop antenna.
vehi c l e. Each frame. based on the HDLC. contains the addresses of the transmitter and the r eceiver . preambl e and CRC bytes. Data for route guidance and driving da ta acquisition are included in the A2 frame. The amount of data bytes tr ans mitted at one communication point when an automobile is running is va ri ab l e. It is 78 bytes at the largest, and usua lly 17 to 49 by t es . In CACS. the amount of data was fix ed t o 18 bytes. and the contents in each data frame were also fixed . comnoL IN TIlE ROlfIE GUIDANCE SYSTEM
In CACS. the route guidance information in each road - side computer was updated periodically with new data computed in the control center on the basis of da ta from the road si de computers. Thus, the route guidance in CACS was dynami c . On the contrary. the route guidance described he re is static, because r outes are provided beforehand on the basis of a driving instruc tion curr i cu lum.
When a trainee does not or cannot foll ow the indicati on , he is guided to the ex it of the training ground. It is detec ted a t the next communication point on the basis of the segment number and the ID number of the automobil e. Speech Synthesis The speech synthesis in this system does not employ a spec ial coding t echnique such as PARCOR or LPC, but employs the ADPCM technique. because the coding is very simpl e and the ROM for speech data is inexpensive. Whe n stori ng speech data in the ROM, the origi nal ana log voice data were sampled at the rate of 6 kHz and quanti zed t o 4 bits in ADPCM . In this system a femal e voi ce is employed. For the route guidance. 20 elements of messages are stored in the ROM. In addition. 2 kinds of fixed messages indicating the start and end of training are stored in the ROM. The capacity of the ROM is 48 KB. Table 3 shows the elements and the fixed messages.
On output of a route guidance message.
these
elements a re edited according t o the form of 'Ielement il WO le lement jl . lelement kl'
In this route guidance system. a drive r cannot selec t his r oute a rbitrari ly . but an ins tructor selects it among some r outes provided for the instruct ion system when a driver applies driving training. Thus . a driver's r oute and the ID numbe r of his automobile are inputted to the center computer before the start of driving. Ther efore. a seri es of points for the road - vehicle communication along the r ou t e selected is known in the center computer beforehand. A part of a route between two adjacent commu ni cation points is ca lled a segment. Each comm uni cat ion control unit. corresponding to each road - vehicl e commu ni cation point. has data f or all the segments of eve ry r oute that begin from the prese nt communi ca ti on point. The data are for the route guidance and driving data acquisition. Whenever the r oad -vehi c le communi cati on is performed at an inductive l oop antenna. the ID number and the last segment numbe r of an automobile are tr ans mitted to the commun i cat i on control unit and the center computer in the AI frame . On the basis of the ID number and the route number from the center compu t e r . the communi cat ion control unit retrieves data for the next segment and transmits them to the automobile in the A2 frame. At each communication point. all the data required on the next segment are transmitted coll ect ively . In the A2 frame . each data for the route guidance or driving data acquisiti on a t one point are stored in 2 bytes . Data codes for speech synthesis or a driving data item are stored in a byte , and the distance from the communi cation point where the route guidance or da ta acquisition is operated is stored in another byte. The distance is measured by
on the basis of the data codes transmitted from a communication unit. The processor (8748 ) controls the editing and output. The e l ements in Tabl e 3 are inserted in the locati ons corresponding to the data codes i (1 ~ i ~ 12 ) . j (j = 0 or I ) . and k (0 ~ k ~ 5 ) . Some elements ar e dupli ca ted . because they are used in differ ent locat i ons in the form . When k=O. the re is no element in this l oca tion. Thus . for example. whe n i =5 . j=l. and k=2. these e l eme nts are edited to a message '00 WO HIDARI . SHUUKAI' (in English . ' Turn to the left at the corner ~ . and then enter the round road .' ) . These messages are outputted only once at predetermined points. The output of the fi xed messages is controlled by the data code 1 in Tabl e 3. A fixed message is outputted as it is . The message of 1=0 is outputted at the starting point when a driver pushes the push- button switch: that of 1=1 is at the goal after driving da ta has been transmitted to the center compute r . EXPERIMENTS OF TIlE SYSTEM
Installation of the System The instruction system has been installed on a training ground of 60 m by 80 m. Figure 7 shows the training ground where the system has been installed . The training ground has road elements essential to driving training such as S-shaped roads . crank- shaped roads and sloped roads . For the road-vehi c le communication. 9 induc tive loop antennas are buried on the training ground. The
313
Route (;uidan cc Systelll for :\utollloilile [hinTs
Elements
I
English Translation Time (s ) one t .. o three four five six seven eight nine round road
i = 1 ICHI
2 iNI 3 SAN 4 YON 5GO
I
6 l ROKU
7 jNANA 8 HACHI 9 1 KYlRJ
10 SHUUKAI
English Translation Time (s )
0.33 i =11 CHUUOH KANSEN main road 0.33 12 DEGUCHI exit WO 0.33 I (no translation ) 0.33 j = o MIGI right 0 .33 I HIDARI left 0.33 k= I KURANKU crank-shaped road 0 .33 2 SHUUKAI round road 0.33 3 CHUUOH KANSEN main road 0.33 4 HOHKOH HENKAN direction exchange 0.50 5 ESU S-shaped road
Messages 1= 0 ANZENNI CHUUISHITE HASSHINSHITE KUDASAI . 1 HANDOBlJREJ1KI, GIYA WO OTASHIKAMEKUDASAI.
Fig. 7.
Elements
0.00 0.50 0.33 0.33 0.50 0.50 0.50 0.00 0.00 0.33
English Translation
Time (s )
Start carefully and safely. Make sure of the handbrake and shift lever.
2.60 2.60
The training ground.
on-board computers are installed in 12 training automobiles. In this system 7 routes are provided for the beginner and the advanced . Up to 10 trainees can practice driving .. ith the instruction system concurrently . Ho.. ever , the number of trainees is probably limited, because the training ground is not large enough.
Fig. 8.
An example of route guidance.
TABLE 4 Route Guidance Messages along a Route in Figure 8 ' Data COOes for
Figure 8 sho..s an example of a route, points for the road - vehicle communication and locations .. here the route guidance information is outputted. Table 4 sho..s the route guidance messages that are outputted at the locations sho.. n in Fig. 8.
CommunIcat I on ' GUIda nce Mess a ge EdItl ng POInts LocatlOns
]
o
For the study of the auditory indication of the route guidance information, experiments ..ere conducted .. ith the aid of a number of trainees in the driving school. They included all kinds of trainees: men and ..omen of all ages. An automobile that has a speech synthesizing unit by a male voice was also prepared for comparison with a female voice. The contents of the speech in a male voice and a female voice were same . In the experiments, a pair of trainees got on an automobile. A trainee drove the automobile at the speed within 25 km/ h, and his partner brought a map of the route to indicate the route to the driver when the driver missed his .. ay. After trainees finished training by the instruction system, they were interviewed. Their impressions are summarized as follo ..s: I ) A route guidance system is necessary in the instruction system. Trainees feel uneasy when
~~DM~1
'.IQ Hi)AR!
c..~."JOI-~
CC W':::
5
,...
CHUIJI9-lITE HASSHINSHITE KtIDASAI
ICJ-I; WO
ROKt; '010 ,'1:G: !(',,'RA}..'KU KA!':S:::N '.!c r.:~AHI !1!~.G: :<"JR;8K"J
0
11
Experiments by Trainees
A~ZENN! S{~1J..
rl
10 6
Mes sage s
k
c:
(
S: ~'1.."3A. 7
Ha{KOO HE'JKAN
9 10
YOi 'of,) ~ iG! ESl.i CH'Jl.O-! KJ..N.<.D.I 'WO
11
SAN WO MI GI. ESlJ
12 13
10 2
14
A
:5
:7
10 9 :2
'8
:2
:6
9-!UUKAI
- - -- -
'.,>() ~ :G~
\ .;.";;.. ',;0 ~:::;;
'.Q
~ rGI
H: !)AR I Clf...'1...lY.
N: '-'0 i:I::AS'! 0
~
~ S."I.f,.i:_.~{A:
K'(';":
..".c
Irv V!G; ~: G:
:.o-n
!-B{o(.M-l
D--::GX:-:: '.':'!-:::::.;'::::
'9
they bring only a map of a route without a route guidance system. 2 ) The auditory indication of the route guidance information is better than the visual indication, because it is by no means easy for them to watch a visual display unit while driving. 3 ) Generally the contents of the messages and the
314
guidance locations are sufficient for the route guidance. However. some trainees said that a route guidance message is necessary even when a driver goes straight on at a junction of a straight road and a road branc hing from it. In addition. only a few trainee said that the messages should be more concise and be repea ted. 4 ) The synthesized speech in a female voice is clear enough. It is better and more comfortable than a male voice. In addition. a femal e voice is clearer than a male voi ce . 5 ) The speed of the speech is appropriate. no t fast and not slow . DISCUSSION The route guidance system by speech synthesis has been completed and installed on the training ground for the computer aided driving instruction. It was ascertained by expe riments that the subsystems and the components of the system work well . In this system. for simplicity. the communication control units and the on board computers were designed to have almost the same structure . As a result. the route guidance information was stored in the ROM of the communication control units. Howeve r. this prevents flexibility of the system. When a new route or a guidance location is added in the present system. the ROM should be replaced. For making the system flexibl e. the communi cation control units should have struc ture that enables downloading of data from the center computer. The message is outputted abruptly in the prese nt system. This surprises a driver. and it somet imes causes him to miss the message. Thus. a sound that calls a driver's attention should be outputted before a route guidance message. This functi on was provided in the visual indi cat ion of CACS. It is also required even in the auditory indi ca tion . In addition . the voca bulary in the speech synthesizi ng unit is limited because of the capacity of the ROM. Thus . it is difficult to include geographical names in the memory. unless mass storage units such as compact discs are employed. roo.USIONS The route guidance system for automobile drivers has been developed with the local road - vehi c le digital communication technique and the speech synthesis technique by ADPCM. Moreover. it has been installed on a training ground for driv i ng instruction. The system guides driving trainees along routes on the training ground in a static mode. The system has simple structure and is
inexpe nsive. The route guidance information for seve r a l guidance locations is transmitted at one road ·vehicle communication point with the improved communication spec ifica tions. The route guidance system has got a fav orabl e reception by the trainees of the driving school. The results of the experime nts by the trainees show that the contents of the messages are suffi c i ent for the route guidance. They also show that a female voice has been rated more highly than a mal e voice. However . this cannot be generalized. beca use the kind of the voi ce depends on the vari ous factors such as a speake r and an encoding method of an original voi ce. Furthe rmor e. they show that the speech synthesi s meets the indi ca tion me thod of the route guidance informa tion on the training ground. In a limited road network. the route guidance system that employs only the auditory indication is effective. Never the l ess. further studies will be required for a indi cation method of the route guidance information on urban streets and highways. ACKNOWLEDGEl1ENf We wou ld like to thank Nippon Denso Co. Ltd. for their cooperation of the de ve lopme nt of the computer aided instruc tion system of automobile driving.
Braegas. P. \1980 ·. Func tions. Equipme nt. and Field Tes ting of a Route Guidance and Information System for Drivers (ALl). IEEE Trans. on Vehiculor Technol0'l!/' VJ' - 29. 216- 225.
Matsumoto. S .. Mikami. T .. Yumoto. N.. and Tabe . T. (1 979 ), Comprehe nsi ve Automobile Traffic Control System. J. of lEa: of Jopon. 62. f370 - 887.
Pilsak . for
O. (1 984 ) . FYA:An Elec tr oni c Traffic Pilot Motorists . P, ·OC. DCa\' SYlIIpos iwH "Land Vehicle :\'m;igcliion 1984".16.1 - 16.24. Suzuki. N. (1983 1. Necessity and Method of Local Digital Communication. Proc . 2nd Sympos ium on El ec lroni cs [01 ' Improl ClIIcn t of Automobile Traffic. Assoc iolion of El ectronic Technology for Automobile Tmffi c one/ Driling . 5- 13. von Tomkewitsch. R. ( 1984 ' . AUTO-SCOUT A Universal Traffic Guidance and Informati on System. Proc . DCa\' SYlIIpos illlll "Lonci 'chicl e Sm i<)CIt ion ~ 17.1 - 17.21. Tsugawa. S. and Tabei. S. 1984 Computer - Aided Instruction System of Automobi le Driving. Proc. 1984 int er1lCl tional Conference on I ne/lis t ria I Elee lr·oni cs. Cont ro l and Ins t nml('ntot ion [ Eco.," 84 ' . 318- 323.