太阳能交通灯

A NEW LOGICAL CONTROL MODEL OF TRAFFIC LIGHTSSUN Xian-bo1,2, LIN Wei2, and ZHANG Nan-lun21Information Engineering School of Hubei Institute for Nationalities, Hubei, China, 4450002Automation School of Wuhan University of Technology, Hubei, China, 430070 Abstract: Based on Pan-Boolean algebra with an illustration of crossroads in the urban trunk roads, a new logical control model of the traffic light is designed in this paper. It breaks down the conventional pattern of fixed time distribution, realizes a flexible control and takes into account the combinations of various traffic lanes. Characterized by simple presentation and convenient operation, it can be clearly shown after the simulation that the model is preferable to the conventional pattern of fixed time distribution in promoting the efficiency of traveling vehicles. Since it can make the vehicles travel more efficiently, it may be employed in the near future. Key Words: traffic light, logical control model, Pan-Boolean Algebra, simulation1 IntroductionIt is of practical significance to enhance the traffic efficiency at the intersectionsto alleviate the traffic jam. Nowadays, the traffic lights are designed with certain shift cycles according to the supposed number of vehicles. However, the fixed timing has lots of demerits and greatly reduces the traffic efficiency. To improve the urban road traveling capability, reduce the delay caused by intersections, the ITS (Intelligent Transportation System) has been studied. The signal lights at intersections usually have fixed timing control, the induction-type control and the adaptive control. Since the traffic flow is complex, dynamic and random, the former two control models are not entirely satisfactory in practice. The adaptive control system represented by SCOOT(Yang Xianfu,2003) can adjust the signal timing according to the actual traffic, and hence it works well, but it needs to be more accurate. Since it is easily affected, it lacks a perfect effect on the complicated traffic situation in China. Therefore, a new logical control model of the traffic light is designed in thispaper based on Pan-Boolean algebra(Zhang Nanlun,2005) with the traveling time from all directions and enhances the flexibility and practicality of the traffic timing.2 Pan-Boolean AlgebraPan-Boolean algebra is a logical model based on the relation between input and output. The guiding principle of this algebra is that such marks as 1 2 3 x , x , x …are the1794various variables in the multi-condition system and then the total of all possible conditions of any variable i x can be referred to as its corresponding “condition number”, which can be expressed as i n (i=1,2,...). ji x (i=1,2,…; j=1,2,… i n ) isc alled the “condition variable”, that is, the jth condition corresponding to i x . Namely,when the jth condition appears, 1 is taken as its value while when there is no jth condition, 0 is taken as its value. In this multi-condition system, every variable i xin a certain case can and merely can be in one state of all i n . It means it has tosimultaneously satisfy both of the conditions:(1) 1 2 ... n 1i i i x + x + + x = ； (2)ji x ·ki x ＝0 (1≤ｊ<ｋ≤i n )Except these two conditions, all those laws including associative law, the commutative law, the distributive law and 0-1 law are similarly established as in the Boolean algebra, so it is called as Pan-Boolean algebra. The difference between logical control, traditional control and fuzzy control(CHOU Chih-Hsun,2002) is as follows: traditional control theory rests on differential equation to have an automatic control; whereas, both fuzzy control and logical control rest on the concept control. Fuzzy control is different from logical control in that the former is based on the fuzzy set theory of Charder IA and its relevant operation principle while the latter is built on the regularities Pan-Boolean algebra observes. The make-up law of fuzzy set does not work while that of Pan-Boolean algebra does work. Moreover, non-operation has diverse definitions in the two systems. It differs from fuzzy control with modification on the ground that one employs mathematics analysis formula to represent the rule of control and the response to output while the other adopts Pan-Boolean indication, which conforms to the human thinking.3 Description of a Typical Transportation SystemThis paper mainly touches on the intersections of main roads in cities. As is illustrated in Figure 1, all the traffic lanes can be divided into 12 according to such 4 directions as A, B, C and D. There are 3 traffic lanes in each direction involvingleft-turn lane, straight lane and right-turn lane. For example, A1, B4, C7 and D10 are all left-turn lanes, A2, B5, C8 and D11 are all straight lanes and A3, B6, C9, D12 are right-turn lanes. As far as the traffic regulations and vehicles safety are concerned, only two lanes without any conflict are allowed to be in operation in the same period. Since right-turn vehicles have no impact on vehicles from other directions when they pass the intersection, they are excluded from the control. The traffic flow in consideration holds 4 phases as is shown in Figure 2, which shifts from one to1795another according to the flow. Based on the specific flow of each lane, 3 types are proposed: small capacity (0-3), medium capacity (4-8) and large capacity (9-16). Thus, when the sensors from A1, A2, B4, B5, C7, C8, D10 and D11 check out the exact number of passing vehicles, the traffic lanes will be reduced to one of the above three lanes. For instance, A1 is a lane with small capacity if 2 cars are checked out on it. The maximum is 16, which is set by experience and regulated by traffic departments. It is certain that one or several more categories can be added, but there is no theoretically substantial difference except that more presentations and more designs are needed.Figure 1. Distribution Map at IntersectionFigure 2. Illustration of Phases4 Design of Control ModelOn the basis of Pan-Boolean algebra, a corresponding model is to be established, where the signals of flow from the sensors on A1, A2, B4, B5, C7, C8, D10 and D11 are combined and input. Accordingly, the traffic lights will be varied due to different traffic flows and lanes will be shifted as Figure 2 illustrates, which ensures two lanes are always in operation and also optimizes the road resources. Meanwhile, the waiting time for pass must be above a minimum (10s is supposed here) to ensure pedestrians and non-motor vehicles have enough time and below a maximum (80s is supposed here) to ensure vehicles from opposite directions do not wait for too long. The combinations of A2 and C8, B5 and D11, A1 and C7, B4 and D10, as separately input condition variables, are marked respectively as X1 (flow of straight vehicles from east and west), X2 (flow of straight vehicles from north and south), X3 (flow of left-turn vehicles from east and west) and X4 (flow of right-turn vehicles from north and south). The condition values of the variables are respectivelyn1 = 3，3 2 n = ，3 3 n = ，3 4 n = . That is to say, the following will be input systematically as condition variables: 11 x （a small flow of straight vehicles from eastand west），21 x （a medium flow of straight vehicles from east and west），31 x （a large1796flow of straight vehicles from east and west），12 x （a small flow of straight vehiclesfrom north and south），22 x （a medium flow of straight vehicles from north andsouth），32 x （a large flow of straight vehicles from north and south），13 x（a small flowof left-turn vehicles from east and west），23 x （a medium flow of left-turn vehiclesfrom east and west），33 x （a large flow of left-turn vehicles from east and west），14 x（a small flow of left-turn vehicles from north and south），24 x （a medium flow ofleft-turn vehicles from north and south）and 34 x （a large flow of left-turn vehiclesfrom north and south）. In addition, this system is made up of 4 output variables: 1 Y （traffic lights for passing straight from east and west），2 Y （traffic lights for passing straight from north and south），3 Y （traffic lights for left-turn from east and west），4 Y （traffic lights for left-turn from north and south）. The state number of the fouroutput variables are respectively n1 = 2 ，n2 = 2，n3 = 2，n4 = 2 . That is, all the output variables include: 11 y （red light for passing straight from east and west），21 y（green light for passing straight from east and west），12 y （red light for passingstraight from north and south），22 y （green light for passing straight from north andsouth），13 y （red light for left turn from east and west），23 y （green light for left-turnfrom east and west），14 y （red light for left-turn from north and south），24 y （greenlight for left-turn from north and south）.Suppose the traffic lights only shift among the above-mentioned 4 phases and inthe same situation straight way is prior to turning left and east - west is prior to north –south. 2 F stands for the output of succession and 12 f (23)2 f represent thedifferent output signals of 23kinds of successions（the outputs of succession vary on different supposals.）.Table 1 shows the logical diagram.1797Table 1. The Logical Diagram of Traffic Light Control at the IntersectionA logical diagram of traffic lights control at the intersection is available, but the specific control steps in one succession are not offered. The outputs concern with succession. Take 12 f for example, which involves 4 phases in succession and can beshown as 12 f (1), 12 f (2), 12 f (3), 12 f (4). The whole output is the logical total of 4 phases:12 f ＝12 f (1)+ 12 f (2)+ 12 f (3)+ 12 f (4)It can be described in details as:12 f (1) ＝21 y 1y2 1y3 1y4It means “keeping the green light on A2 and C8 on for 10 seconds, the red lighton B5 and D11 on for 10 seconds, the red light for left-turn on A1 and C7 on for 10 seconds, the red light for left-turn on B4 and D10 for 10 seconds.”12 f (2) ＝1y1 12 y 23 y 14 yIt means “keeping green light for left-turn on A1 and C7 on for 10 seconds, redlight for left-turn on B4 and D10 on for 10 seconds, red light on A2 and C8 on for 10 seconds, red light on B5 and D11 on for 10 seconds”.12 f (3) ＝1y1 22 y 1y3 1y4It means “keeping green light on B5 and D11 on for 10 seconds, red light on A2and C8 on for 10 seconds, red light for left-turn on A1 and C7 on for 10 seconds, red light for left-turn on B4 and D10 on for 10 seconds”.12 f (4) ＝1y1 1y2 1y3 2y4It means “keeping green light for left-turn on B4 and D10 on for 10 seconds, red1798light for left-turn on A1 and C7 on for 10 seconds, red light on A2 and C8 on for 10 seconds, red light on B5 and D11 on for 10 seconds”.These are the output succession of 12 f . Other variables from 22 f to 232 f include4 steps similar to it, which will not be introduced here.5 SimulationsTo testify the priority of logical control model, the software MATLAB is employed to simulate the fixed timing and the logical control. Supposing the intersection is as in Figure 1 and the 12 traffic lanes from 4 directions are considered and Supposing the lanes for right-turn are not put under control and only lanes forleft-turn and straight passing are considered, the traffic lights on each lane will be shifted dynamically as is shown in Figure 2. In the random situations, two models of M are used to simulate the process, the result of which is displayed in Figure 3: Figure 3. Simulated Result6 ConclusionsThe new logical control model based on Pan-Boolean algebra here is practicaland easy to handle, which surpasses the conventional model of fixed timing for traffic lights and is suitable for controlling the traffic lights in usual cases. 4 phases are considered because it can prevent the traffic flows from different directions from conflicting with each other. Furthermore, since it conforms to the present traffic rule, it is easy to be publicized and improve the traffic efficiency. As is shown in the simulation, this model is applicable and effective, which is worth developing. ReferencesCHOU Chih-Hsun,TENG Jen-Chao. A fuzzy logic controller for traffic junction signals[J].Information Sciences,2002,143 (1):73-97YANG Xianfu, The adaptive system of traffic lights based on EDA [J], the Journal of Chengdu University (natural science version), 2003，22（3）：19～24ZHANG Nanlun, A new control theory [M], Beijing: State Defense Industry Press, 2005, 11799。