A method for optimizing rescue routes of urban emergency vehicles in heavy rain

Abstract

A method for optimizing rescue routes for urban emergency vehicles in rainstorm weather, which belongs to the field of urban emergency rescue technology. The present invention solves the problem that the existing methods do not consider the continuous and dynamic effects of road water accumulation on vehicle speed in rainstorm weather, resulting in the selected emergency rescue route not being the optimal route in rainstorm weather. The method of the present invention is: step one, abstracting the urban road network into a weighted directed graph composed of nodes and edges; step two, establishing an objective function with the shortest travel time required for emergency vehicles from the departure point to the place where the emergency event occurs as the optimization goal; step three, inputting rainfall parameters into the established simulation model, obtaining the depth of water accumulation on each road section at each simulation output moment, and then calculating the average speed of emergency vehicles on each road section at each simulation output moment according to the depth of water accumulation; step four, determining the emergency rescue route according to the results of step two and step three. The method of the present invention can be applied to the field of emergency rescue technology.

Description

Technical Field

[0001] The invention belongs to the technical field of urban emergency rescue, and in particular relates to a method for optimizing a rescue path of urban emergency vehicles under heavy rain. Background Art

[0002] With the intensification of global climate change, the frequency and intensity of extreme weather events have continued to increase, seriously restricting the economic and social development of cities. The urban road network is open and complex, and is easily disturbed by external factors (such as extreme weather). Therefore, global climate change has increased the risk of urban waterlogging caused by heavy rains, leading to a further increase in the probability of traffic emergencies. Since the time and location of emergency events under heavy rain disasters are difficult to predict, optimizing the rescue routes of emergency vehicles and improving the emergency response speed is an important direction for future development.

[0003] The emergency vehicle rescue path selection problem is a special vehicle path selection problem. Current research mainly considers other factors such as the shortest travel time and path reliability to perform static optimization design of emergency vehicle rescue paths. There are also studies that consider the vehicle flow information on the road network to dynamically plan emergency vehicle rescue paths, and have achieved rich results. However, the current emergency rescue path selection model does not consider the impact of heavy rain as a continuous and dynamic disturbance factor on vehicle travel speed, resulting in the emergency rescue path obtained by the current path planning method not being the optimal path in heavy rain weather. Summary of the invention

[0004] The purpose of the present invention is to solve the problem that the existing emergency vehicle rescue path selection method does not take into account the continuous and dynamic impact of road water on vehicle speed in heavy rain weather, resulting in the selected emergency rescue path not being the optimal path in heavy rain weather, and to propose a method for optimizing the urban emergency vehicle rescue path in heavy rain weather.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: a method for optimizing the rescue path of urban emergency vehicles in rainstorm weather, the method specifically comprising the following steps:

[0006] Step 1: Take each intersection in the urban road network as a node, that is, the i-th intersection as node V i , take the jth intersection as node V j , the connection between the nodes corresponding to adjacent intersections i and j is taken as the edge, and the urban road network is abstracted into a weighted directed graph G(V,E) consisting of nodes and edges;

[0007] Among them, V represents the set of nodes in the weighted directed graph, that is, V i ∈V,V j∈V, E represents the set of edges in the weighted directed graph;

[0008] Step 2: Establish an objective function, wherein the objective function takes the shortest travel time required for emergency vehicles from the departure point to the emergency event location as the optimization goal;

[0009] Step 3: Input rainfall parameters into the established simulation model to obtain the water depth on each road section at each simulation output time, and then calculate the average speed of emergency vehicles on each road section at each simulation output time according to the water depth;

[0010] For the period between two adjacent simulation output moments, the average speed of emergency vehicles on the road section is taken as the average of the average speeds corresponding to the two adjacent simulation output moments;

[0011] Step 4: Determine the emergency rescue path based on the results of steps 2 and 3.

[0012] Furthermore, the objective function is:

[0013] C=min T

[0014]

[0015] Among them, C is the objective function value, the unit is s; T is the travel time required for the emergency vehicle to reach the emergency incident site from the departure point, the unit is s; t k is the time the emergency vehicle travels on the selected kth edge, in seconds; n is the number of edges the emergency vehicle passes through when it travels from the departure point to the node adjacent to the location where the emergency incident occurs; when the two nodes corresponding to the kth edge are V i and V j hour, Represents node V i and V j The length of the path between them, in meters; v ij Indicates that the emergency vehicle is at node V i and node V j The average speed between the nodes is in m / s; t(e) represents the travel time required for the emergency vehicle to travel from the node adjacent to the emergency event location to the emergency event location, in seconds; L e Indicates the distance from the adjacent node to the emergency event location, in meters; v e It represents the average speed of emergency vehicles on the road section from the adjacent node to the emergency site, in m / s.

[0016] Furthermore, in step 3, the average speed of emergency vehicles on each road section at each simulation output moment is calculated according to the water depth; the specific process is as follows:

[0017] Step 31: At the mth simulation output moment, the average speed of emergency vehicles is:

[0018]

[0019] In the formula, Indicates the mth simulation output moment, the emergency vehicle is at node V i and V j The average speed on the road between the two, in m / s; v 0 It is the design speed when there is no water accumulation on the road section, the unit is km / h; d p The maximum depth of water that allows emergency vehicles to pass, in cm; Indicates that at the mth simulation output time, node V i and V j The depth of water in the road section between them, in cm;

[0020] Step 32: For the period between two adjacent simulation output times, the average speed of emergency vehicles on each road section is:

[0021]

[0022] In the formula, Indicates the m+1th simulation output moment, the emergency vehicle is at node V i and V j The average speed on the road section between them, in m / s; It means that between the mth simulation output time and the m+1th simulation output time, the emergency vehicle is at the node V i and V j The average speed between the two roads, in m / s.

[0023] Furthermore, when the emergency event occurs at an intersection, the end point of the emergency rescue path is node V e ; The specific process of determining the emergency rescue path is:

[0024] Step 51: Set the emergency vehicle rescue starting point V s is labeled P, and the starting point V s The label value is P(V s )=0, let all other nodes in the weighted directed graph be labeled T, and the label values ​​of other nodes are all T(V j )=∞;

[0025] Initialize the average speed v on each road segment 0 , and the node V where the emergency rescue vehicle is located i Let V be the starting point s ;

[0026] Step 52: If (V i ,V j )∈E, then according to the average speed and the length of the road section, the node V j Update the label value of node V j The updated label value T′(V j );

[0027] Step 53: Select the minimum label value minT′ (V j ), the node corresponding to the selected label value is recorded as V i , let node V i The label value P(V i )=minT′(V j );

[0028] Step 54: After updating the average speed on each road section, use the node V obtained in step 53 i and P(V i ) Return to step 52 until the node V obtained in step 53 is reached. i For node V e Stop iteration when

[0029] Step 55: Connect all nodes labeled P between the starting point and the end point to obtain an emergency rescue path.

[0030] Furthermore, the specific process of step 52 is as follows:

[0031]

[0032] Among them, T′(V j ) represents the updated node V j The label value of .

[0033] Furthermore, in step 54, the specific process of updating the average traffic speed on each road section is as follows:

[0034]

[0035]

[0036] in, represents rounding down; ε represents the time from the beginning of waterlogging on the road network to the time when the emergency vehicle receives the emergency rescue information, in seconds; t%2 represents the remainder of t divided by 2; P(V i ) represents the calculation result of step 53.

[0037] Furthermore, the emergency event occurs at node V e1The corresponding intersection and node V e2 When the corresponding intersections are between, the node V e1 and node V e2 They are respectively used as path end points, and emergency rescue paths are determined according to the two path end points;

[0038] Set the node V e1 As the end point V e , the method to determine the emergency rescue path is:

[0039] Step 51: Set the emergency vehicle rescue starting point V s is labeled P, and the starting point V s The label value is P(V s )=0, let all other nodes in the weighted directed graph be labeled T, and the label values ​​of other nodes are all T(V j )=∞;

[0040] Initialize the average speed v on each road segment 0 , and the node V where the emergency rescue vehicle is located i V s ;

[0041] Step 52: If (V i ,V j )∈E, then according to the average speed and section length, node V j Update the label value of node V j The updated label value of

[0042] Step 53: Select the minimum label value minT′ (V j ), the node corresponding to the selected label value is recorded as V i , let node V i The label value P(V i )=minT′(V j );

[0043] Step 54: After updating the average speed on each road section, use the node V obtained in step 53 i and P(V i ) Return to step 52 until the node V obtained in step 53 is reached. i For node V e1 Stop iteration when

[0044] Using the P(V calculated in the last iteration e1 ) Calculate the slave node V e1 The speed to the emergency site, P(V e1 ) is the distance from the starting point to the node V for the emergency rescue vehicle e1The shortest travel time;

[0045] Then according to the calculated slave node V e1 The speed of the emergency vehicle from node V to the emergency site is calculated. e1 The time required to travel to the emergency site t(e1);

[0046] And calculate P(V e1 ) and t(e1), and the sum is taken as the travel time required for the emergency vehicle to travel from the starting point to the place where the emergency occurs, and the sum is recorded as C 1 ;

[0047] Similarly, calculate the distance from the starting point to the node V of the emergency vehicle. e2 The shortest travel time required P(V e2 ), and the emergency vehicle from node V e2 The time t(e2) required to travel to the emergency site and calculate P(V e2 ) and t(e2), and the sum is taken as the travel time required for the emergency vehicle to travel from the starting point to the place where the emergency occurs, and the sum is recorded as C 2 ;

[0048] Step 55. Compare C 1 and C 2 size;

[0049] If C 1 Less than C 2 , then the starting point to node V e1 Connect all nodes labeled P between them, and then connect node V e1 Connect with the emergency site to obtain the emergency rescue route;

[0050] If C 1 Greater than C 2 , then the starting point to node V e2 Connect all nodes labeled P between them, and then connect node V e2 Connect with the emergency site to obtain the emergency rescue route;

[0051] If C 1 Equal to C 2 , then the starting point to node V e2 Connect all nodes labeled P between them, and then connect node V e2 Connect the line with the place where the emergency incident occurred to obtain the emergency rescue path; or connect the obtained starting point to node V e1 Connect all nodes labeled P between them, and then connect node V e1 Connect to the location where the emergency occurs and obtain the emergency rescue route.

[0052] Furthermore, the specific process of step 52 is as follows:

[0053]

[0054] Among them, T′(V j ) represents the updated node V j The label value of .

[0055] Furthermore, in step 54, the specific process of updating the average traffic speed on each road section is as follows:

[0056]

[0057]

[0058] in, represents rounding down; ε represents the time from the beginning of waterlogging on the road network to the time when the emergency vehicle receives the emergency rescue information, in seconds; t%2 represents the remainder of t divided by 2; P(V i ) represents the calculation result of step 53.

[0059] Furthermore, the calculation method of t(e1) and t(e2) is:

[0060]

[0061]

[0062]

[0063]

[0064]

[0065] Among them, L e1 is node V e1 Distance to the emergency site, L e2 is node V e2 The distance to the site of the emergency.

[0066] The beneficial effects of the present invention are:

[0067] The present invention comprehensively considers the travel characteristics of emergency vehicles and the dynamic impact of road waterlogging caused by heavy rain on vehicle travel speed, and proposes a method for optimizing the rescue path of urban emergency vehicles under heavy rain weather. In the same emergency rescue scenario (intersection emergency event), the emergency rescue path is solved using the traditional static shortest path solution algorithm and the method proposed in the present invention. The results show that the travel time of the emergency rescue path solved by the method proposed in the present invention is reduced by 58.94s, and the time required is reduced by 25.52% year-on-year; the emergency rescue efficiency is higher and the reliability is stronger, so the emergency rescue path is better.

[0068] The present invention also realizes the allocation of emergency rescue tasks by considering the emergency rescue material reserves, thus expanding the application scenarios of the present invention. It also solves the optimal emergency rescue path for different emergency rescue scenarios (intersection emergency events, road section emergency events), and forms a scientific and effective emergency rescue plan in rainstorm weather. It is helpful to improve the emergency response speed and guide the emergency rescue practice. The method proposed by the present invention is highly portable and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 It is a flow chart of a method for optimizing rescue routes of urban emergency vehicles in rainstorm weather according to the present invention;

[0070] Figure 2 Schematic diagram of the road network for the experimental part;

[0071] Figure 3 This is a result diagram of the rescue path optimization of intersection emergency events using the method of the present invention;

[0072] Figure 4 This is the result diagram of the rescue path optimization for intersection emergency events using the traditional static shortest path algorithm;

[0073] Figure 5 Assign a flowchart to emergency rescue tasks;

[0074] C 3 It is the starting point V s1 The corresponding emergency vehicle travel time, C 4 It is the starting point V s2 The corresponding emergency vehicle travel time. DETAILED DESCRIPTION

[0075] Specific implementation method 1: Combination Figure 1 This embodiment describes a method for optimizing the rescue path of urban emergency vehicles in rainstorm weather, and the method specifically includes the following steps:

[0076] Step 1: Take each intersection in the urban road network as a node, that is, the i-th intersection as node Vi , take the jth intersection as node V j , the connection between the nodes corresponding to adjacent intersections i and j is taken as the edge, and the urban road network is abstracted into a weighted directed graph G(V,E) consisting of nodes and edges;

[0077] Among them, V represents the set of nodes in the weighted directed graph, that is, V i ∈V,V j ∈V, E represents the set of edges in the weighted directed graph;

[0078] Step 2: Establish an objective function, wherein the objective function takes the shortest travel time required for emergency vehicles from the departure point to the emergency event location as the optimization goal;

[0079] Step 3: Input rainfall parameters into the established simulation model to obtain the water depth on each road section at each simulation output time, and then calculate the average speed of emergency vehicles on each road section at each simulation output time according to the water depth;

[0080] For the period between two adjacent simulation output moments, the average speed of emergency vehicles on the road section is taken as the average of the average speeds corresponding to the two adjacent simulation output moments;

[0081] Step 4: Determine the emergency rescue path based on the results of steps 2 and 3.

[0082] The present invention takes into account the continuous and dynamic impact of road waterlogging on vehicle travel speed during rainstorms, and constructs a speed dynamic change matrix, which can ensure that the emergency rescue path obtained is optimal.

[0083] The rainstorm intensity w (mm / min) is:

[0084]

[0085] Therefore, by inputting the design return period Q, rainfall duration d, and rainfall parameters A, C, b, and p into the simulation model, the intensity of the rainstorm can be simulated and the depth of water accumulation on each road section at each simulation output time can be obtained. Among them, A = 1600, C = 0.846, b = 0.70, and p = 0.656.

[0086] Specific implementation method 2: This implementation method is different from the specific implementation method 1 in that the objective function is:

[0087] C=min T

[0088]

[0089] Among them, C is the objective function value, the unit is s; T is the travel time required for the emergency vehicle to reach the emergency incident site from the departure point, the unit is s; tk is the time the emergency vehicle travels on the selected kth edge (each edge corresponds to a road section), in seconds; n is the number of edges the emergency vehicle passes through when it travels from the departure point to the node adjacent to the emergency event location (first determine the node corresponding to the emergency event location; if the emergency event location is located at an intersection, the node corresponding to the emergency event location is the node corresponding to the intersection; if the emergency event location is located on a road section, the nodes at both ends of the road section where the emergency event location is located are the nodes corresponding to the emergency event location; the nodes corresponding to the emergency event location are called nodes adjacent to the emergency event location; then determine the number of edges passed from the departure point to the node adjacent to the emergency event location); when the two nodes corresponding to the kth edge are V i and V j hour, Represents node V i and V j The length of the path between them, in meters; v ij Indicates that the emergency vehicle is at node V i and node V j The average speed between the nodes is in m / s; t(e) represents the travel time required for the emergency vehicle to travel from the node adjacent to the emergency event location to the emergency event location, in seconds; L e Indicates the distance from the adjacent node to the emergency event location, in meters; v e It represents the average speed of emergency vehicles on the road section from the adjacent node to the emergency site, in m / s.

[0090] The other steps and parameters are the same as those in the first embodiment.

[0091] In the present invention, if it is an intersection emergency event, the intersection where the emergency event occurs is directly used as the end point V e If it is a road section emergency event, the intersection nodes at both ends of the road section where the emergency event occurs are recorded as V e1 and V e2 , V e1 and V e2 As the end point, a path is planned according to each end point, and then the path with the shortest time is selected from the two paths. It should be noted that since the departure point of the emergency vehicle is the fire rescue station, the distance between the fire rescue station and the intersection node is relatively close, and the time required for the emergency vehicle to travel between the fire rescue station and the intersection adjacent to it is very short, assuming that the emergency vehicle departs from the intersection for emergency rescue and does not affect the selection of subsequent emergency rescue paths, the departure point of the emergency vehicle is set to the intersection node closest to the fire rescue station.

[0092] Specific implementation method three: This implementation method is different from the specific implementation method two in that: in step three, the average speed of emergency vehicles on each road section at each simulation output moment is calculated according to the depth of water accumulation; the specific process is:

[0093] Step 31: At the mth simulation output moment, the average speed of emergency vehicles is:

[0094]

[0095] In the formula, Indicates the mth simulation output moment, the emergency vehicle is at node V i and V j The average speed on the road between the two, in m / s; v 0 It is the design speed when there is no water accumulation on the road section, the unit is km / h; d p The maximum depth of water that allows emergency vehicles to pass, in cm; Indicates that at the mth simulation output time, node V i and V j The depth of water accumulation in the road section between them, in cm; m is a non-negative integer;

[0096] The above calculation shows that when the water level on the road exceeds the maximum water depth for emergency vehicles to pass, emergency vehicles cannot pass, that is, the passing speed drops to 0.

[0097] Step 32: For the period between two adjacent simulation output times, the average speed of emergency vehicles on each road section is:

[0098]

[0099] In the formula, Indicates the m+1th simulation output moment, the emergency vehicle is at node V i and V j The average speed on the road section between them, in m / s; It means that between the mth simulation output time and the m+1th simulation output time, the emergency vehicle is at the node V i and V j The average speed between the two roads, in m / s.

[0100] The other steps and parameters are the same as those in the second specific implementation manner.

[0101] The present invention records the time when water begins to accumulate on the road surface as time 0, and constructs a speed dynamic change matrix as shown in Table 1 based on the average travel speed of emergency vehicles on each road section in different time periods.

[0102] Table 1 Speed ​​dynamic change matrix

[0103]

[0104]

[0105] Specific implementation method 4: This implementation method is different from the specific implementation method 3 in that: when the emergency event occurs at an intersection, the end point of the emergency rescue path is node V e ; The specific process of determining the emergency rescue path is:

[0106] Step 51: Set the emergency vehicle rescue starting point V s is labeled P, and the starting point V s The label value is P(V s )=0, let all other nodes in the weighted directed graph be labeled T, and the label values ​​of other nodes are all T(V j )=∞;

[0107] As shown in Table 2, the average speed v on each road segment is initialized. 0 , and the node V where the emergency rescue vehicle is located i Let V be the starting point s ;

[0108] Table 2 Design average speed of different sections of the city

[0109]

[0110] Step 52: If (V i ,V j )∈E, then according to the average speed (because the moment when the road surface begins to accumulate water is recorded as the 0th simulation output moment, the speed at the 0th simulation output moment is the initial speed, and after the road surface begins to accumulate water, the emergency vehicle will start the rescue only after receiving the emergency rescue information. Therefore, there is a certain time interval between the time of starting the rescue and the moment when the road surface begins to accumulate water, and the time interval is If the time interval t is between the 0th simulation output moment and the 1st simulation output moment, the first iteration needs to use the initialization speed and the speed at the 1st simulation output moment to calculate the average speed of each section; starting from the second iteration, if the total time required to pass all previous sections is t′, and time t′ is between the mth simulation output moment and the m+1th simulation output moment, then the average speed on each section is calculated based on the speed on each section at the mth simulation output moment and the m+1th simulation output moment; if time t′ is directly a certain simulation output moment, then the speed on each section at the simulation output moment is directly used for calculation) and the length of the section for node V j Update the label value of node V j The updated label value T′(Vj );

[0111] Step 53: Select the minimum label value minT′ (V j ), the node corresponding to the selected label value is recorded as V i , let node V i The label value P(V i )=minT′(V j );

[0112] Step 54: After updating the average speed on each road section, use the node V obtained in step 53 i and P(V i ) Return to step 52 until the node V obtained in step 53 is reached. i For node V e Stop iteration when

[0113] Step 55: Connect all nodes labeled P between the starting point and the end point to obtain an emergency rescue path.

[0114] The other steps and parameters are the same as those in the third specific implementation manner.

[0115] The P(V e ) is the calculated objective function value, which is the shortest driving time required for the emergency vehicle to reach the location of the emergency.

[0116] Specific implementation method 5: This implementation method is different from the specific implementation method 4 in that the specific process of step 52 is:

[0117]

[0118] Among them, T′(V j ) represents the updated node V j The label value of .

[0119] The other steps and parameters are the same as those in the fourth embodiment.

[0120] Specific implementation method 6: This implementation method is different from the specific implementation method 5 in that: in step 54, the specific process of updating the average traffic speed on each road section is:

[0121]

[0122]

[0123] in, represents rounding down; ε represents the time from the beginning of waterlogging on the road network to the time when the emergency vehicle receives the emergency rescue information, in seconds; t%2 represents the remainder of t divided by 2; P(V i ) represents the calculation result of step 53.

[0124] The other steps and parameters are the same as those in the fifth embodiment.

[0125] The first formula of this embodiment can be used to calculate the simulation period corresponding to the time required for the emergency vehicle to pass before selecting the next sub-path. The second formula can be used to determine the time required for the emergency vehicle to pass at the node V in the corresponding period. i With V j The average speed of traffic on the road section between.

[0126] Specific implementation method 7: This implementation method is different from the specific implementation method 3 in that: the emergency event occurs at node V e1 The corresponding intersection and node V e2 When the corresponding intersections are between, the node V e1 and node V e2 They are respectively used as path end points, and emergency rescue paths are determined according to the two path end points;

[0127] Set the node V e1 As the end point V e , the method to determine the emergency rescue path is:

[0128] Step 51: Set the emergency vehicle rescue starting point V s is labeled P, and the starting point V s The label value is P(V s )=0, let all other nodes in the weighted directed graph be labeled T, and the label values ​​of other nodes are all T(V j )=∞;

[0129] Initialize the average speed v on each road segment 0 , and the node V where the emergency rescue vehicle is located i V s ;

[0130] Step 52: If (V i ,V j )∈E, then according to the average speed and section length, node V j Update the label value of node V j The updated label value of

[0131] Step 53: Select the minimum label value minT′ (V j ), the node corresponding to the selected label value is recorded as Vi , let node V i The label value P(V i )=minT′(V j );

[0132] Step 54: After updating the average speed on each road section, use the node V obtained in step 53 i and P(V i ) Return to step 52 until the node V obtained in step 53 is reached. i For node V e1 Stop iteration when

[0133] Using the P(V calculated in the last iteration e1 ) Calculate the slave node V e1 The speed to the emergency site, P(V e1 ) is the distance from the starting point to the node V for the emergency rescue vehicle e1 The shortest travel time;

[0134] Then according to the calculated slave node V e1 The speed of the emergency vehicle from node V to the emergency site is calculated. e1 The time required to travel to the emergency site t(e1);

[0135] And calculate P(V e1 ) and t(e1), and the sum is taken as the travel time required for the emergency vehicle to travel from the starting point to the place where the emergency occurs, and the sum is recorded as C 1 ;

[0136] Similarly, calculate the distance from the starting point to the node V of the emergency vehicle. e2 The shortest travel time required P(V e2 ), and the emergency vehicle from node V e2 The time t(e2) required to travel to the emergency site and calculate P(V e2 ) and t(e2), and the sum is taken as the travel time required for the emergency vehicle to travel from the starting point to the place where the emergency occurs, and the sum is recorded as C 2 ;

[0137] Step 55. Compare C 1 and C 2 size;

[0138] If C 1 Less than C 2 , then the starting point to node V e1 Connect all nodes labeled P between them, and then connect node V e1 Connect with the emergency site to obtain the emergency rescue route;

[0139] If C 1 Greater than C 2 , then the starting point to node V e2 Connect all nodes labeled P between them, and then connect node V e2 Connect with the emergency site to obtain the emergency rescue route;

[0140] If C 1 Equal to C 2 , then the starting point to node V e2 Connect all nodes labeled P between them, and then connect node V e2 Connect the line with the place where the emergency incident occurred to obtain the emergency rescue path; or connect the obtained starting point to node V e1 Connect all nodes labeled P between them, and then connect node V e1 Connect to the location where the emergency occurs and obtain the emergency rescue route.

[0141] The other steps and parameters are the same as those in the third specific implementation manner.

[0142] Specific implementation eight: This implementation differs from specific implementation seven in that the specific process of step five-two is as follows:

[0143]

[0144] Among them, T′(V j ) represents the updated node V j The label value of .

[0145] The other steps and parameters are the same as those in the seventh embodiment.

[0146] Specific implementation method 9: This implementation method is different from specific implementation method 8 in that: in step 54, the specific process of updating the average traffic speed on each road section is:

[0147]

[0148]

[0149] in, represents rounding down; ε represents the time from the beginning of waterlogging on the road network to the time when the emergency vehicle receives the emergency rescue information, in seconds; t%2 represents the remainder of t divided by 2; P(V i ) represents the calculation result of step 53.

[0150] The other steps and parameters are the same as those in the eighth embodiment.

[0151] Specific implementation method 10: This implementation method is different from specific implementation method 9 in that the calculation method of t(e1) and t(e2) is:

[0152]

[0153]

[0154]

[0155]

[0156]

[0157] Among them, L e1 is node V e1 Distance to the emergency site, L e2 is node V e2 The distance to the site of the emergency.

[0158] The other steps and parameters are the same as those in the ninth embodiment.

[0159] Experimental Section

[0160] For intersection emergencies, the traditional static shortest path solving algorithm and the method proposed in the present invention are used to solve the emergency rescue path.

[0161] Set emergency scene: The location of the emergency event is V 25 , the emergency vehicle receives the emergency rescue information 1 minute after water appears on the road network, that is, the emergency vehicle sets out 1 minute after water appears on the road.

[0162] Set the starting point to V 9 (i.e. V s =V 9 ), the end point is set to V 25 (i.e. V e =V 25 ), let ε = 60, and solve the emergency rescue path. The location of the emergency rescue path in the urban road topology network solved by the method proposed by the present invention is as follows: Figure 3 In the same emergency scenario, the position of the emergency rescue path obtained by the traditional static shortest path solution algorithm in the urban road topology network is shown in Figure 4 shown.

[0163] By comparing the results obtained by the two methods, it can be seen that the travel distance of the emergency rescue path solved by the dynamic shortest path optimization algorithm of the present invention increased by 0.9 km, an increase of 52.63% year-on-year, but the travel time was shortened by 58.94 s, a decrease of 25.52% year-on-year. The comparison of travel time and travel distance is shown in Table 3. The emergency rescue path solved by the method proposed by the present invention has a shorter travel time and higher reliability. It can be seen that the method proposed by the present invention is more suitable for solving emergency rescue paths in rainstorm weather.

[0164] Table 3 Comparison of characteristics of two methods for solving emergency rescue paths

[0165]

[0166]

[0167] For road emergency events, the method proposed in the present invention is used to solve the emergency rescue path.

[0168] Set up emergency scenarios: The emergency event occurs at V 25 and V 33 and the emergency incident location is between V 25 The distance is 200m, and V 33 The distance is 240m; the emergency vehicle receives the emergency rescue information 1 minute after water appears on the road network.

[0169] First, set the starting point to V 9 (i.e. V s =V 9 ), set the end points to V 25 (i.e. V e1 =V 25 ) and V 33 (i.e. V e2 =V 33 ), let ε=60. Solve the equations for V 9 To V 25 The emergency rescue path and the 9 To V 33 The emergency rescue path is calculated and the time required for the passage is calculated. The results are: V 9 →V 10 →V 13 →V 14 →V 15 →V 16 →V 19 →V 25 , the time required to choose this path is 172.03s; V 9 →V 28 →V 29 →V30 →V 31 →V 32 →V 33 , the time required to choose this path is 154.93s. Next, calculate V 25 and V 33 The time required to travel to the emergency location is 19.70s and 23.65s respectively. 9 Via V 25 The shortest time to reach the emergency event point is 191.73s. 9 Via V 33 The shortest time to reach the emergency event point is 178.58s. From the objective function, we can see that the solution of the emergency rescue path is “V 9 →V 28 →V 29 →V 30 →V 31 →V 32 →V 33 →The place where the emergency incident occurs". Comparing the results obtained by the two methods, it can be seen that the emergency rescue path solved by the method proposed in the present invention takes less time to pass in rainstorm weather, which is more in line with the actual requirements of emergency rescue.

[0170] like Figure 5 As shown, for intersection emergency events, the method proposed by the present invention is used to allocate emergency rescue tasks.

[0171] Under the condition that emergency rescue materials are not restricted (all rescue teams in the study area can perform emergency rescue tasks), the emergency scenario is set: the location of the emergency event is V 25 , emergency rescue information was received 1 minute after water accumulation appeared on the road network.

[0172] Set the end point to V 25 (i.e. V e =V 25 ), set the starting point to V 9 (i.e. V s =V 9 ) and V 45 (i.e. V s =V 45 ) Let ε = 60. The method proposed in the present invention is used to solve the emergency rescue path, and the result obtained is: V 9 →V 10 →V 13 →V 14 →V 15 →V 16 →V 19 →V 25 and V 45 →V46 →V 47 →V 32 →V 33 →V 25 The time required for the paths obtained is 172.03s and 95.81s respectively. According to the objective function of the optimization model, without considering the limited conditions of emergency rescue materials, the emergency rescue task is assigned to the starting point V 45 By using the method proposed in the present invention, the paths and travel time of different emergency rescue teams to the location where the emergency incident occurs can be solved, and emergency rescue tasks can be allocated more scientifically.

[0173] In summary, if we ignore the continuous and dynamic impact of heavy rain on the speed of emergency vehicles, and use the traditional method to solve the static shortest path, we will not be able to solve the optimal emergency rescue path in heavy rain. It is even possible that due to the excessive depth of water accumulation, emergency vehicles cannot pass normally on some sections of the selected path, and emergency rescue work cannot be carried out smoothly and quickly, thus affecting the response speed of emergency rescue. Therefore, in heavy rain, the emergency rescue path solved by the method proposed in the present invention is better and more in line with the actual requirements of emergency rescue.

[0174] The above calculation examples of the present invention are only used to explain the calculation model and calculation process of the present invention in detail, and are not intended to limit the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for optimizing rescue routes of urban emergency vehicles in rainstorm weather, characterized in that: The method specifically comprises the following steps: Step 1: Take each intersection in the urban road network as a node, that is, the i-th intersection as node V i , take the jth intersection as node V j , the connection between the nodes corresponding to adjacent intersections i and j is taken as the edge, and the urban road network is abstracted into a weighted directed graph G(V,E) consisting of nodes and edges; Among them, V represents the set of nodes in the weighted directed graph, that is, V i ∈V,V j ∈V, E represents the set of edges in the weighted directed graph; Step 2: Establish an objective function, wherein the objective function takes the shortest travel time required for emergency vehicles from the departure point to the emergency event location as the optimization goal; The objective function is: C=min T Among them, C is the objective function value, the unit is s; T is the travel time required for the emergency vehicle to reach the emergency incident site from the departure point, the unit is s; t k is the time the emergency vehicle travels on the selected kth edge, in seconds; n is the number of edges the emergency vehicle passes through when it travels from the departure point to the node adjacent to the location where the emergency incident occurs; when the two nodes corresponding to the kth edge are V i and V j hour, Represents node V i and V j The length of the path between them, in meters; v ij Indicates that the emergency vehicle is at node V i and node V j The average speed between the nodes is in m / s; t(e) represents the travel time required for the emergency vehicle to travel from the node adjacent to the emergency event location to the emergency event location, in seconds; L e Indicates the distance from the adjacent node to the emergency event location, in meters; v e It represents the average speed of emergency vehicles on the road section from the adjacent node to the emergency site, in m / s. Step 3: Input rainfall parameters into the established simulation model to obtain the water depth on each road section at each simulation output time, and then calculate the average speed of emergency vehicles on each road section at each simulation output time according to the water depth; For the period between two adjacent simulation output moments, the average speed of emergency vehicles on the road section is taken as the average of the average speeds corresponding to the two adjacent simulation output moments; The specific process of calculating the average speed of emergency vehicles on each road section at each simulation output time according to the depth of water accumulation is as follows: Step 31: At the mth simulation output moment, the average speed of emergency vehicles is: In the formula, Indicates the mth simulation output moment, the emergency vehicle is at node V i and V j The average speed on the road section between the two, in m / s; v0 is the design speed when there is no water accumulation on the road section, in km / h; d p The maximum depth of water that allows emergency vehicles to pass, in cm; Indicates that at the mth simulation output time, node V i and V j The depth of water in the road section between them, in cm; Step 32: For the period between two adjacent simulation output times, the average speed of emergency vehicles on each road section is: In the formula, Indicates the m+1th simulation output moment, the emergency vehicle is at node V i and V j The average speed on the road section between them, in m / s; It means that between the mth simulation output time and the m+1th simulation output time, the emergency vehicle is at the node V i and V j The average speed between the two is in m / s; When the emergency event occurs at an intersection, the end point of the emergency rescue path is node V e ; The specific process of determining the emergency rescue path is: Step 51: Set the emergency vehicle rescue starting point V s is labeled P, and the starting point V s The label value is P(V s )=0, let all other nodes in the weighted directed graph be labeled T, and the label values ​​of other nodes are all T(V j )=∞; Initialize the average speed v0 on each road section and set the node V where the emergency rescue vehicle is located i Let V be the starting point s ; Step 52: If (V i ,V j )∈E, then according to the average speed and the length of the road section, the node V j Update the label value of node V j The updated label value T′(V j ); Step 53: Select the minimum label value minT′ (V j ), the node corresponding to the selected label value is recorded as V i , let node V i The label value P(V i )=minT′(V j ); Step 54: After updating the average speed on each road section, use the node V obtained in step 53 i and P(V i ) Return to step 52 until the node V obtained in step 53 is reached. i For node V e Stop iteration when Step 55: connect all nodes labeled P between the starting point and the end point to obtain an emergency rescue path; Step 4: Determine the emergency rescue path based on the results of steps 2 and 3.

2. The method for optimizing the rescue path of urban emergency vehicles in rainstorm weather according to claim 1 is characterized in that: The specific process of step 52 is as follows: Among them, T′(V j ) represents the updated node V j The label value of .

3. The method for optimizing the rescue path of urban emergency vehicles in rainstorm weather according to claim 2 is characterized in that: In step 54, the specific process of updating the average speed on each road section is as follows: in, represents rounding down; ε represents the time from the beginning of waterlogging on the road network to the time when the emergency vehicle receives the emergency rescue information, in seconds; t%2 represents the remainder of t divided by 2; P(V i ) represents the calculation result of step 53.

4. The method for optimizing the rescue path of urban emergency vehicles in rainstorm weather according to claim 1 is characterized in that: The emergency event occurs at node V e1 The corresponding intersection and node V e2 When the corresponding intersections are between, the node V e1 and node V e2 They are respectively used as path end points, and emergency rescue paths are determined according to the two path end points; Set the node V e1 As the end point V e , the method to determine the emergency rescue path is: Step 51: Set the emergency vehicle rescue starting point V s is labeled P, and the starting point V s The label value is P(V s )=0, let all other nodes in the weighted directed graph be labeled T, and the label values ​​of other nodes are all T(V j )=∞; Initialize the average speed v0 on each road section and set the node V where the emergency rescue vehicle is located i Let V be the starting point s ; Step 52: If (V i ,V j )∈E, then according to the average speed and section length, node V j Update the label value of node V j The updated label value of Step 53: Select the minimum label value minT′ (V j ), the node corresponding to the selected label value is recorded as V i , let node V i The label value P(V i )=minT′(V j ); Step 54: After updating the average speed on each road section, use the node V obtained in step 53 i and P(V i ) Return to step 52 until the node V obtained in step 53 is reached. i For node V e1 Stop iteration when Using the P(V calculated in the last iteration e1 ) Calculate the slave node V e1 The speed to the emergency site, P(V e1 ) is the distance from the starting point to the node V for the emergency rescue vehicle e1 The shortest travel time; Then according to the calculated slave node V e1 The speed of the emergency vehicle from node V to the emergency site is calculated. e1 The time required to travel to the emergency site t(e1); And calculate P(V e1 ) and t(e1), the sum is taken as the travel time required for the emergency vehicle to travel from the starting point to the place where the emergency occurs, and the sum is recorded as C1; Similarly, calculate the distance from the starting point to the node V of the emergency vehicle. e2 The shortest required travel time P(V e2 ), and the emergency vehicle from node V e2 The time t(e2) required to travel to the emergency site and calculate P(V e2 ) and t(e2), and the sum is taken as the travel time required for the emergency vehicle to travel from the starting point to the place where the emergency occurs, and the sum is recorded as C2; Step 55: Compare the sizes of C1 and C2; If C1 is less than C2, the starting point to node V e1 Connect all nodes labeled P between them, and then connect node V e1 Connect with the emergency site to obtain the emergency rescue route; If C1 is greater than C2, the starting point to node V e2 Connect all nodes labeled P between them, and then connect node V e2 Connect with the emergency site to obtain the emergency rescue route; If C1 is equal to C2, then the starting point to node V e2 Connect all nodes labeled P between them, and then connect node V e2 Connect the emergency incident site to obtain the emergency rescue path; or connect the obtained starting point to node V e1 Connect all nodes labeled P between them, and then connect node V e1 Connect to the location where the emergency occurs and obtain the emergency rescue route.

5. The method for optimizing the rescue path of urban emergency vehicles in rainstorm weather according to claim 4 is characterized in that: The calculation method of t(e1) and t(e2) is: Among them, L e1 is node V e1 Distance to the emergency site, L e2 is node V e2 The distance to the site of the emergency.

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