an example in which the present invention is applied to a horseracing game machine will now be described by reference to the accompanying drawings . the overall structure of a horseracing game machine according to the embodiment is identical with that of a well - known horserace game . as shown in fig1 the horseracing game machine is a large - sized game machine having a width of about 2 . 5 m and a length of about 4 m . a plurality of satellite terminals s are provided so as to surround a racing track 1 on which miniatures 5 are to perform racing . each of the satellite terminals s has a token handling mechanism for effecting entry / payout of tokens , a control panel , such as a voting control key , and indictors for indicating various types of information items . as shown in fig2 the game machine has an upper traveling field over which miniatures are to travel ( hereinafter , referred as a racing track ), and a lower traveling field 2 over which self - propelled members are to travel ( hereinafter , simply referred as traveling field ). self - propelled members 3 , which travel over the lower traveling field 2 , attract the miniatures 5 such that the miniatures 5 are caused to compete with each other , by magnetic force originating from magnets 4 provided in the tops of respective self - propelled members 3 located below the corresponding miniatures 5 and in bottoms of the miniatures 5 . as described in , e . g ., u . s . pat . no . 2 , 188 , 619 , the basic structure of the horseracing game machine is a known structure . the horserace game machine described in the u . s . patent is a machine in which self - propelled members are caused to travel along a rail , and the traveling direction of the self - propelled members is regulated by the rail . hence , travel control to be effected for racing is limited solely to travel control that is very easy . the present embodiment is based on the game machine described in the u . s . patent , except that the guidance member using a rail is replaced with a well - known optical guidance member . as shown in fig3 and 4 , a black line ( i . e ., a guide line ) 11 having a width of 6 mm and a white line 12 having a width of 6 mm are alternately provided and printed on the traveling field 2 along a traveling direction . the only requirement for determining the width of the guide line 10 is to select an appropriate value from the range of 5 to 10 mm . the white line 12 can be taken as a guide line . in any of these two cases ; i . e ., the case where the black line 11 is taken as the guide line 10 and the case where the white line 12 is taken as the guide line 10 , the width of the guide line 10 is relevant to the layout of a detector ( e . g ., a photodiode ) 14 provided for the guide line 10 . the width of a line located on either side of the guide line 10 is selectively determined , as required , in accordance with an interval between the guide lines 10 . in the present embodiment , a pitch between the guide lines 10 is 12 mm , which accounts for about 37 % the width of the self - propelled member 3 ; that is , 33 mm . the pitch between the guide lines 10 corresponds to a path - switching width , which will be described later . if the width is too large , path - switching from one guide line to another guide line becomes less smooth . preferably , the pitch should be confined to a range in which smooth path - switching can be effected . in contrast , if the width is too small , the guide lines 10 are provided densely , and consequently the width of a change in traveling courses becomes small . in such a case , the current guide line must be switched to another guide line by skipping two or more guide lines , thereby requiring special path - switching control for specifying the number of guide lines to be skipped . moreover , if the pitch is too small , the width of each guide line 10 will become too small , thereby imposing difficulty on detecting operation performed by three or more optical sensors . for these reasons , the present embodiment needs a detection system which detects respective sides of each of the guide lines 10 through use of two optical sensors . in the embodiment , three photodiodes 14 are provided side by side on the lower face of each self - propelled member 3 in a widthwise direction , thus constituting a guide line detector . the width of a range covered by the three photodiodes 14 is 12 mm , which is double the width of the single black line ( i . e ., guide line ) 11 . further , the photodiodes 14 are spaced 6 mm from each other . if the center photodiode 14 and either the right or left photodiode 14 detect the black line and if the remaining photodiode 14 fails to detect the black line 11 , the self - propelled member 3 is determined to have deviated toward the photodiode 14 which does not detect the black line 11 . such deviation is determined by a travel controller 16 provided in each self - propelled member 3 , and the course of the self - propelled member 3 is corrected through feedback control . in this way , the self - propelled member 3 follows the guide line 10 while reliably sensing small deviations thereof . as a result , the self - propelled member 3 follows the black line ( i . e ., guide line ) 11 accurately and travels smoothly . if three optical sensors are provided in a forward portion of the self - propelled member 3 and two or three optical sensors are provided in a rear portion of the same , skewed travel of the self - propelled member 3 with reference to the guide line can also be detected . hence , the accuracy of a control operation for tracking a guide line , particularly a curved guide line , can be enhanced . in the event that the self - propelled member 3 has deviated from the guide line , course correction control for rendering smooth travel of the self - propelled member 3 should be gentle . the order of arrival in the racing game cannot be taken care of themselves in view of the odds of the game . for this reason , at least a miniature for the first place and a miniature for the second place must be determined before a game is started . in other words , determination of miniatures for the first and second places is sufficient . effecting control such that the thus - determined miniatures gain scheduled places and sequentially ascertaining the condition of a group of horses makes detection of progress in respective horses from the start is important . to this end , as shown in fig5 a , progress lines 15 orthogonal to the guide lines are provided on the track at high density . the progress lines 15 are detected by a hole sensor 9 provided in the lower face of each self - propelled member 3 . the number of progress lines 15 which the self - propelled member 3 has run across is counted , to thereby detect progress . the width of the progress line 15 may be selected from the range of 5 to 10 mm , as required . in the present embodiment , an n - pole magnetic line 15 a having a width of 6 mm and an s - pole magnetic line 15 b having a width of 6 mm are provided alternately . when the self - propelled member 3 runs across these magnetic lines , the hole sensor 9 detects the lines as a detection signal , such as that shown in fig5 b . as a result of the detection signal being converted through analog - to - digital conversion , the number of progress lines 15 which the self - propelled member 3 has run across can be detected . the thus - detected progress information is transmitted from each self - propelled member 3 to a central controller 20 ( see fig6 ). the central controller 20 acquires progress information from all the self - propelled members 3 , thereby ascertaining the positions of the self - propelled members 3 and the condition of a group of horses on the basis of the positional relationship between the miniatures 5 ( in reality the positional relationship between the self - propelled members 3 ). the principal traveling speed of each self - propelled member 3 is controlled on the basis of a speed control program assigned to a travel controller 16 of the self - propelled member 3 before a game is started , and in accordance with the characteristics of the self - propelled member 3 ( e . g ., a shake - off type , a last - spurt type , a sprinter type , or a long - distance runner type ) and the strengths , weaknesses , and peculiarities of a jockey ( the self - propelled members 3 assigned to win and place are controlled by a special speed control program after they have substantially passed by the third corner ). under the ever - changing condition of a group of horses , and under central control a determination is made as to whether to change the current guide line to another guide line , on the basis of conditions for determination ; that is , the presence or absence of orientation of the self - propelled member toward the inner or outer side of the traveling course , and the presence or absence of the chance of the self - propelled member interfering with an adjacent self - propelled member . a path - switching signal is sent to the self - propelled member which satisfies any one of the above conditions so that the traveling path of the subject self - propelled member is switched to an inner guide line or an outer guide line . in the present embodiment , if a self - propelled member is oriented ( programmed ) toward an inner side of the traveling path , priority is placed on path - switching to the inner side . in contrast , if a self - propelled member is oriented toward an outer side of the traveling course , priority is placed on path - switching toward the outer side . if no chance of the self - propelled member interfering with an adjacent self - propelled member is ascertained , an instruction for path - switching the course to a required direction is immediately issued . although the principal traveling speed is taken as a basic speed , a deceleration instruction is issued if there is a chance of occurrence of collision . a determination is made as to whether or not collision is impending , on the basis of a difference in the speed of a self - propelled member of interest and the speed of a self - propelled member running ahead or behind , and a distance between the self - propelled members . here , a speed signal indicating a decelerated speed or a signal for instructing a reduction in speed may be issued . moreover , principal traveling speed signals to be sent to the travel controllers 16 of the respective self - propelled members 3 may be transmitted collectively or in several transmissions on a per - segment basis . in reality , path - switching control and deceleration control are performed on the basis of sequential determination operation allowing for various requirements set forth . in principle , one race is carried out through path - switching control and deceleration control on the basis of the above - described requirements . the functions of the travel controller 16 of the self - propelled member 3 and those of the central controller 20 are shown in fig6 . the signal transmitted from the central controller 20 to the travel controller 16 of the self - propelled member 3 includes principal speed data corresponding to the characteristic of each miniature to be transmitted before a race is started , a signal for steering the self - propelled member at the start of a race , and path - switching and deceleration signals to be issued during a race . data pertaining to the principal speed to be employed for one race are output as principal traveling speeds for respective segments , provided that a race track is divided into a plurality of segments . in the present embodiment , the entire race track for one race is divided into seven segments ; namely , a straight segment between a starting line and the first corner ; the first corner ; the second corner ; a straight segment between the second and third corners ; the third corner ; the fourth corner ; and a segment between the fourth corner and a finish line . the principal traveling speed of the self - propelled member 3 does not always differ from one segment to another segment . the characteristic of a horse is represented by the number of segments . in view of simulation of a real horserace , provision of seven segments is sufficient . a single principal traveling speed may be assigned to an individual self - propelled member . in this embodiment , the speeds of the self - propelled members are controlled separately on a per - segment basis in accordance with the characteristics of the miniatures . the information transmitted from the travel controller 16 of the self - propelled member 3 to the central controller 20 constitutes progress information . the travel controller 16 of the self - propelled member 3 controls rotational speeds of right and left wheel drive motors 19 so as to cause the self - propelled member 3 to travel while tracking a guide line 10 on the basis of the principal traveling speed signal . in response to a path - switching or deceleration instruction output from the central controller 20 , the travel controller 16 accelerates or decelerates the wheel drive motors 19 . if no path - switching or deceleration instruction is issued , the self - propelled member travels at the traveling speed matching the principal traveling speed data on the basis of the characteristics of the self - propelled member 3 from the start to the finish while following a single guide line . the travel controller 16 has memory 16 a for storing information output from the central controller 20 , a driver 16 c for controlling and activating an arithmetic processor 16 b and the drive motors 19 , and a progress processor 16 d . the signal output from the central controller 20 is received by a receiver 17 , and required data are saved in the memory 16 a . the travel controller 16 receives guide line detection signals output from the three photodiodes 14 of the self - propelled member 3 . in accordance with the detection signals , the travel controller 16 detects a rightward or leftward deviation from the guide line 10 . the travel controller 16 causes the self - propelled member to travel and follow the guide line 10 while correcting deviations therefrom . on the other hand , the progress processor 16 d computes progress from a progress line 15 based on detection signal output from the hole sensor 9 . the resultant progress information is sent to the central controller 20 by way of a transmitter 18 . on the basis of the progress information items sent from the respective self - propelled members 3 , the central controller 20 successively ascertains the condition of a group of horses and , in accordance with the predetermined conditions for determination , makes a determination as to a necessity for path - switching a guide line or deceleration , thereby sequentially sending path - switching and deceleration signals to the respective self - propelled members 3 . the central controller 20 successively ascertains the condition of a group of horses and controls required path - switching operation or traveling speed on the basis of the thus - ascertained condition . feedback of information about progress in a self - propelled member to progress control is not required ; the only requirement for enhancing the accuracy of progress tracking is to cause the central controller 20 or the controller provided in the self - propelled member to perform feedback control . although the present invention has been shown and described with reference to specific preferred embodiments , various changes and modifications will be apparent to those skilled in the art from the teachings herein . such changes and modifications as are obvious are deemed to come within the spirit , scope and contemplation of the invention as defined in the appended claims .
a plurality of guide lines are provided on a lower traveling field . a first detector is provided with each self - propelled member to detect at least one of the guide lines optically or magnetically . a second detector is provided with each self - propelled member to output a displacement signal which indicates a displaced distance from a predetermined position . a travel controller is provided with each self - propelled member , and performs a feedback control such that the self - propelled member travels on the lower traveling field while tracing the at least one guide line . a plurality of miniature members , each associated with one self - propelled member are placed on a upper traveling field extending above the lower traveling field . the miniature members travel thereon in accordance with the traveling of the self - propelled members through magnetic force . a central controller collectively monitors the displacement signal of each self - propelled member to recognize relative position relationship among the self - propelled members , and issues at least a speed changing instruction and a path - switching instruction for each self - propelled member , based on the relative position relationship . the travel controller of each self - propelled member changes a traveling speed thereof according to the speed changing instruction , and switches a traveling path thereof from the traced guide line to another guide line , according to the path - switching instruction .