JP7725879B2 - Bus operation management system - Google Patents

Description

This disclosure relates to bus traffic management systems, and more particularly to electric bus traffic management systems.

JP 2016-181965 A (Patent Document 1) discloses an electric bus that reduces the operational burden on passengers. When the electric bus detects that at least one door is open, it issues a command to start charging the storage battery, and when it detects that all doors are closed, it issues a command to stop charging the storage battery.

Japanese Patent Application Laid-Open No. 2016-181965

In general, in electric vehicles such as electric buses, it is sometimes desirable to charge the battery (for example, fully charge) until the SOC (State Of Charge) falls within a high SOC range to avoid situations where the vehicle becomes unable to run due to a lack of power (so-called "running out of power"). However, it is known that maintaining the battery's SOC within a high SOC range can accelerate battery degradation compared to when the SOC is not maintained within the high SOC range. Patent Document 1 does not particularly take such battery degradation into consideration.

This disclosure has been made to solve the above problem, and its purpose is to suppress battery deterioration in electric buses.

A bus traffic management system according to one aspect of the present disclosure includes an electric bus including a battery that can be charged using externally supplied power, and a server that manages the operation of the electric bus. The electric bus further includes a first power receiving device configured to receive power from a charging facility installed at a first location, and a second power receiving device that can receive power wirelessly from a power transmitting device installed along the travel route from the first location to a second location. The server obtains the number of passengers on the electric bus based on the electric bus's seat reservation information or operation history, and calculates the amount of power consumed by the electric bus along the travel route based on the number of passengers. Based on the amount of power consumed, the server determines the amount of power to charge the electric bus from the charging facility and the power transmitting device so that the battery's SOC does not exceed the lower limit of the SOC range in which battery degradation accelerates while the electric bus is traveling along the travel route.

In the above configuration, the amount of charging power from the charging equipment and power transmission device to the electric bus is determined so that the battery's SOC does not exceed the lower limit of the SOC range where battery degradation accelerates (i.e., so that it does not enter the high SOC range). The electricity consumption of an electric bus varies depending on the number of passengers on the electric bus (in other words, the load weight). Therefore, in the above configuration, by determining the amount of charging power taking into account the amount of power consumed according to the number of passengers on the electric bus, it is possible to accurately determine the amount of charging power required to travel to the second location. Therefore, with the above configuration, by preventing the battery's SOC from entering the high SOC range without securing excessive charging power, it is possible to appropriately suppress battery degradation in the electric bus.

This disclosure makes it possible to suppress battery deterioration in electric buses.

1 is a diagram illustrating an overall configuration of an electric bus operation management system according to an embodiment of the present disclosure. FIG. 2 is a diagram illustrating an example of a configuration of a bus and a power transmission device. FIG. 1 is a diagram showing an example of a bus route. 10 is a time chart for explaining an example of charging control of a bus in a comparative example. 4 is a time chart for explaining an example of charging control of a bus in the present embodiment. 10 is a flowchart showing a procedure for controlling charging of a bus in the present embodiment. FIG. 4 is a conceptual diagram illustrating a map used to calculate the amount of power consumption.

Embodiments of the present disclosure will now be described in detail with reference to the drawings. Note that identical or equivalent parts in the drawings will be designated by the same reference numerals, and their description will not be repeated.

[Embodiment]
<System Configuration>
1 is a diagram illustrating a schematic diagram of the overall configuration of an electric bus traffic management system according to an embodiment of the present disclosure. The bus traffic management system 100 includes a server 1 and a plurality of electric buses (hereinafter simply referred to as "buses") 2. The server 1 includes a processor 11, a memory 12, a reservation database 13, a traffic history database 14, a communication module 15, and a data line 16.

The processor 11 is, for example, a CPU (Central Processing Unit) and is configured to execute predetermined calculations described in a program. This calculation includes formulating operation plans for multiple buses 2. Details of the operation plans will be described later.

Memory 12 includes ROM (Read Only Memory) and RAM (Random Access Memory). ROM stores programs executed by processor 11. RAM temporarily stores data generated by program execution in processor 11 and data input via communication module 15. RAM also functions as temporary data memory used as a working area.

The reservation database 13 stores data regarding the seat reservation status of each of multiple buses 2.

The operation history database 14 stores the operation history of each of the multiple buses 2, and more specifically, data on the power consumption measured while each bus 2 is traveling, for each of various operating conditions (travel route, date, day of the week, weather, temperature, etc.). The operation history database 14 may also store data on the number of passengers who have actually boarded the bus 2 in the past, for each of various operating conditions.

The communication module 15 includes a communication interface with a network such as the Internet. The communication module 15 is configured to enable bidirectional communication with external devices of the server 1 (such as multiple buses 2, multiple user terminals 9, and the charging equipment 7 and power transmission device 8 described below).

Data line 16 is configured to allow data to be exchanged between the devices that make up server 1.

Each of the multiple buses 2 is a vehicle capable of transporting multiple passengers. In this embodiment, each bus 2 is capable of contact charging via a charging cable extending from the charging equipment 7, and is also configured to be capable of contactless charging from the power transmission device 8. Hereinafter, contact charging using the charging equipment 7 will also be referred to as "contact charging," and contactless charging using the power transmission device 8 will also be referred to as "contactless charging." A more detailed configuration of the bus 2 is described in Figure 2.

The user terminal 9 is a terminal operated by passengers using the bus 2, and is, for example, a smartphone or PC (Personal Computer). By operating the user terminal 9, passengers can reserve seats on the bus 2 traveling along a desired route at a desired time. This updates the data related to seat reservation status stored in the reservation database 13.

<Contactless power transmission>
2 is a diagram schematically illustrating an example of the configuration of the bus 2 and the power transmitting device 8. The bus 2 includes a battery 21, a power receiving device 22, an inlet 23, a data communication module (DCM) 24, a global positioning system (GPS) receiver 25, and an electronic control unit (ECU) 26.

Battery 21 is a battery pack including multiple cells. Each cell is a secondary battery such as a lithium-ion battery or a nickel-metal hydride battery. Battery 21 supplies power to generate driving force for bus 2. Battery 21 also stores power generated by an on-board motor generator (not shown). Battery 21 is equipped with a voltage sensor and a current sensor (neither shown) that allow ECU 26 to calculate the SOC (State of Charge) of battery 21.

In the example shown in FIG. 2, the power receiving device 22 is disposed on the underside of a floor panel that forms the bottom surface of the bus 2. A power receiving coil 221 is housed within the power receiving device 22. The power receiving coil 221 wirelessly receives power transmitted from the power transmitting device 8. The power receiving device 22 corresponds to the "second power receiving device" according to the present disclosure.

The inlet 23 is configured to allow insertion of a charging connector of the charging equipment 7 (see Figure 3) via mechanical connection such as fitting. Inserting the charging connector electrically connects the bus 2 and the charging equipment 7, making it possible to charge the battery 21 using power supplied from the charging equipment 7. The inlet 23 corresponds to the "first power receiving device" according to the present disclosure.

The DCM 24 is configured to enable bidirectional communication between the bus 2 and the server 1. The DCM 24 is also configured to enable bidirectional communication between the bus 2 and the power transmission device 8.

The GPS receiver 25 determines the location of the bus 2 based on radio waves transmitted from an artificial satellite (not shown). The server 1 acquires the location information of each of the multiple buses 2 via communication.

The ECU 26 controls the devices based on programs stored in memory (not shown) and signals from various sensors, etc., to ensure that the bus 2 is in the desired state.

The power transmission device 8 includes multiple power transmission units 81-86 and a controller 80. Note that while Figure 2 shows an example with six power transmission units, the number of power transmission units is not particularly limited and may be greater.

The multiple power transmission units 81-86 are arranged in a row on the road surface (or sidewall) of the route along which the bus 2 travels. Each of the multiple power transmission units 81-86 includes a power transmission coil 811-861. Each of the power transmission coils 811-861 is electrically connected to an AC power source (not shown). Although not shown, each of the multiple power transmission units 81-86 is equipped with a sensor (optical sensor, weight sensor, etc.) for detecting the passage of the bus 2.

The controller 80 determines the running position of the bus 2 based on the detection signals from each sensor. The controller 80 then supplies AC power from the AC power source to the power transmission coil in the power transmission unit 81-86 above which the bus 2 is located.

More specifically, for example, if a bus 2 is detected above the power transmission unit 81, the controller 80 supplies AC power to the power transmission coil 811. This causes AC current to flow through the power transmission coil 811, creating an electromagnetic field around the power transmission coil 811. The power receiving coil 221 in the power receiving device 2 receives power contactlessly through this electromagnetic field. Thereafter, when a bus 2 is no longer detected above the power transmission unit 81, the controller 80 stops the supply of AC power to the power transmission coil 811. This series of controls is performed for each of the power transmission units 81-86, allowing power to be transmitted contactlessly to a moving bus 2. Naturally, power can also be transmitted contactlessly to a bus 2 parked on a power transmission unit.

Figure 3 is a diagram showing an example of a travel route for bus 2. In this example, we assume that bus 2 travels from the current location (starting point) to the destination point via a rest point. The planned travel route for bus 2 between the current location and the rest point is denoted as R1. Contact-type charging equipment 7, for example, is installed at the current location and the rest point. The planned travel route for bus 2 between the rest point and the destination point is denoted as R2. A contactless power transmission device 8 is installed on each of the travel routes R1 and R2.

Instead of contact-type charging equipment 7, contactless power transmission devices 8 may be installed at the current location and rest areas to charge the bus 2 while it is stopped. In other words, the bus 2 may be contactlessly charged by the power transmission devices 8 before departure and while it is traveling. In this case, the power receiving device 22 corresponds to both the "first power receiving device" and the "second power receiving device" according to the present disclosure.

<Battery Deterioration>
To facilitate understanding of charging control of bus 2 in this embodiment, charging control in a comparative example will be described below. Here, an example will be described in which bus 2 travels from its current location along route R1 to a rest point. In this case, the current location corresponds to the "first location" according to the present disclosure, and the rest point corresponds to the "second location" according to the present disclosure.

Figure 4 is a time chart illustrating an example of charging control of bus 2 in a comparative example. In Figure 4 and Figure 5 described below, the horizontal axis represents elapsed time, and the vertical axis represents the SOC of battery 21.

At initial time t10, the bus is connected to the contact-type charging facility 7 at its current location. In the comparative example, the battery is fully charged using the charging facility 7 before departure (see time t12). Thereafter, while traveling along route R1, the battery is also charged using the non-contact type power transmission device 8 (see the period between time t14 and time t15).
In such a case, battery degradation may be accelerated while the battery's SOC is in the high SOC region. The high SOC region is an SOC region defined by an upper limit UL (e.g., SOC = 100%) and a lower limit LL (e.g., SOC = 80%). In the comparative example, emphasis is placed on reliably preventing battery power from running out while the vehicle is traveling, but degradation of the battery 21 is not particularly considered. It is desirable to suppress degradation of the battery 21 while preventing battery power from running out.

The inventors have noted that bus 2 has a predetermined driving route and that there is a limit on the continuous driving time. For example, if bus 2 is an express bus, it is required to avoid continuous driving for more than four hours and to take a break of at least 15 minutes, so rest stops are usually determined in advance. Furthermore, the inventors have also noted that the power consumption of bus 2 depends on the number of passengers on bus 2. The more passengers there are on bus 2, the heavier the load weight of bus 2 becomes, and therefore the power consumption of bus 2 increases. Based on this observation, the following charging control is adopted in this embodiment.

Figure 5 is a time chart illustrating an example of charging control for bus 2 in this embodiment. In this embodiment, prior to the start of contact charging using charging equipment 7, server 1 calculates the amount of power consumed (Wh3) when bus 2 travels from its current location to a rest point, taking into account the number of passengers on bus 2. Figure 5 schematically shows two SOC trends: when the number of passengers is large (see solid line) and when the number of passengers is small (see dashed line). Based on the calculated amount of power consumed (Wh3), server 1 calculates the amount of charging energy (Wh2) by contact charging before departure and the amount of charging energy (Wh1) by contactless charging while traveling along travel route R1.

As explained in detail below, the sum of these charging amounts (Wh1 + Wh2) is determined so that the SOC of the battery 21 of the bus 2 will reach a predetermined target SOC when the bus 2 is able to reach the rest point. The target SOC is lower than the lower limit LL of the high SOC region. Therefore, the SOC of the battery 21 can be prevented from entering the high SOC region while traveling along the travel route R1. Furthermore, because the target SOC is set to have a certain margin with respect to SOC = 0 when the bus 2 reaches the rest point, it is possible to prevent the battery 21 from running out of power while traveling along the travel route R1. Therefore, according to this embodiment, it is possible to prevent the battery 21 from running out of power while suppressing deterioration.

<Control flow>
6 is a flowchart showing the processing procedure for charging control of the bus 2 in this embodiment. This flowchart is called from a main routine (not shown) and executed, for example, when a predetermined condition is met. In the figure, the processing executed by the server 1 (processor 11) is shown on the left side, and the processing executed by the bus 2 (ECU 26) is shown on the right side. Each step is realized by software processing by the server 1 or the ECU 26, but may also be realized by hardware such as an LSI (Large Scale Integration) arranged in the server 1 or the ECU 26. Hereinafter, steps are abbreviated as "S."

In S21, the bus 2 determines whether it is ready for contact charging by the charging equipment 7. The bus 2 can determine that it is ready for contact charging, for example, when the bus 2 and the charging equipment 7 are connected by a charging cable (not shown). If it is not ready for contact charging (NO in S21), the bus 2 returns to the main routine without executing any further processing. If it is ready for contact charging (YES in S21), the bus 2 outputs a request to calculate the amount of power to the server 1 (S22). Note that the rest points for the bus 2 may be predetermined, or information specifying the rest points may be output from the bus 2 to the server 1.

In S11, the server 1 determines whether or not a calculation request has been received from the bus 2. If a calculation request has not been received (NO in S11), the server 1 returns processing to the main routine. If a calculation request has been received (YES in S11), the server 1 proceeds to S12.

In S12, server 1 obtains the number of passengers on bus 2 along route R1 by referencing data related to seat reservation status for bus 2 stored in reservation database 13. Note that if reservation database 13 is not provided on server 1, server 1 may refer to bus 2's operation history database 14 to use the number of passengers on buses that have previously traveled under the same operating conditions as bus 2.

In S13, the server 1 calculates the amount of power consumed by the bus 2 to the rest point (or the destination point in another example of traveling from the rest point to the destination point in Figure 3) based on the number of passengers acquired in S12 and the route the bus 2 is traveling. For this calculation, for example, a map MP as described below can be used.

Figure 7 is a conceptual diagram illustrating map MP used to calculate power consumption Wh3. Map MP defines the power consumption Wh3 for each travel route according to the number of passengers. The power consumption Wh3 can be the actual measured value obtained when the target bus 2 (which may be the same type of bus as bus 2) previously traveled the planned travel route (R1 in this example). As shown in Figure 7, the power consumption Wh3 for the same travel route is set to be larger the greater the number of passengers.

Note that while Figure 7 shows an example in which the relationship between the number of passengers and the amount of power consumption Wh3 is determined, Map MP may be a multidimensional map that includes parameters other than the number of passengers. In other words, Map MP may further include parameters such as the temperature along the travel route and an index that indicates the degree of traffic congestion along the travel route.

Referring again to FIG. 6, in S14, the server 1 calculates the amount of charging energy Wh1 by contactless charging up to the rest point. Since it is known what type of power transmission device 8 is installed on the travel route R1, the server 1 can read out the amount of charging energy Wh1 corresponding to the travel route R1, for example, by referring to a map (not shown). The server 1 may also use the actual measured value of the amount of charging energy when the target bus 2 (or a bus of the same type) previously traveled along the travel route by referring to the operation history database 14. The server 1 transmits the calculated amount of charging energy Wh1 to the bus 2.

In S15, the server 1 calculates the amount of energy Wh2 to be charged by contact charging so that the SOC of the battery 21 at the rest point will be the target SOC. More specifically, the server 1 calculates the amount of energy Wh0 stored in the battery 21 at the current point from the SOC at the current point. The server 1 also calculates the target amount of energy Wh(tag) corresponding to the target SOC. As mentioned above, the target SOC is lower than the lower limit LL of the high SOC region, but is set high enough to prevent the bus 2 from running out of power before reaching the rest point.

As shown in the following formula (1), the target energy amount Wh(tag) is obtained by adding the energy amount Wh0 at the current location, the energy amount Wh1 charged by contactless charging, and the energy amount Wh2 charged by contact charging, and subtracting the energy consumption Wh3 while traveling. Therefore, server 1 can calculate the energy amount Wh2 charged by contact charging based on the above formula (1). Server 1 transmits the calculated energy amount Wh2 charged to bus 2.

Wh0+Wh1+Wh2-Wh3=Wh(tag)...(1)
In S23, the bus 2 is contact-charged by the charging facility 7 so that the amount of charging energy calculated in S15 is charged to the bus 2. When contact-charging is completed and the departure time arrives, the bus 2 starts traveling toward the rest point (S24).

When the bus 2 is traveling, it adjusts the amount of power charged by the power transmission device 8 through contactless charging so that the SOC of the battery 21 does not enter the high SOC range. More specifically, if the SOC of the battery 21 approaches the high SOC range, the bus 2 requests the power transmission device 8 to set the power supply to zero. If the amount of power actually charged to the bus 2 through contactless charging exceeds the amount of charging power Wh1 received from the server 1, the bus 2 may also request the power transmission device 8 to set the power supply to zero. This prevents excessive power, which could accelerate deterioration of the battery 21, from being transmitted from the power transmission device 8 to the power receiving device 22, even when the bus 2 travels above the power transmission device 8.

Note that power transmission devices 8 may be installed in only some of the multiple travel lanes. The bus 2 may notify the driver to avoid traveling above the power transmission devices 8 (to travel in a travel lane where no power transmission devices 8 are installed).

Until it arrives at a rest point (NO in S26), bus 2 continues to adjust the amount of charging energy through contactless charging. Once it arrives at a rest point (YES in S26), bus 2 ends the series of processes and returns to the main routine.

As described above, in this embodiment, the amount of charging energy Wh1 by contactless charging and the amount of charging energy Wh2 by contact charging are determined so that the SOC of the battery 21 of the bus 2 does not exceed the lower limit LL of the high SOC range while the bus 2 is traveling along the travel route R1 from the current location to the rest point. At this time, the power consumption of the bus 2 is strongly affected by the number of passengers (load weight) on the bus 2. By taking into account the amount of power consumption Wh3 based on the number of passengers on the bus 2, the amount of charging energy (Wh1 + Wh2) required for traveling to the rest point can be determined with high accuracy. This prevents the SOC of the battery 21 from falling into the high SOC range, thereby suppressing deterioration of the battery 21. Furthermore, in this embodiment, the target SOC at the rest point is set to a value high enough to prevent the bus 2 from running out of power while traveling to the rest point. Therefore, this embodiment can suppress deterioration of the battery 21 while preventing the bus 2 from running out of power.

The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present disclosure is indicated by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims.

1 Server, 2 Bus, 11 Processor, 12 Memory, 13 Reservation database, 14 Operation history database, 15 Communication module, 16 Data line, 21 Battery, 22 Power receiving device, 221 Power receiving coil, 23 Inlet, 24 DCM, 25 Receiver, 26 ECU, 7 Charging equipment, 8 Power transmitting device, 9 User terminal, 80 Controller, 81-86 Power transmitting units, 811-861 Power transmitting coils, 100 Operation management system.

Claims (1)

an electric bus including a battery that can be charged by an externally supplied power;
a server that performs operation management of the electric bus,
The electric bus is
a first power receiving device configured to be able to receive power from a charging facility provided at a first location;
a second power receiving device capable of receiving power in a wireless manner from a power transmitting device provided on a travel route from the first point to the second point,
Before the electric bus travels along the travel route, the server
Acquire the number of passengers on the electric bus based on seat reservation information or operation history of the electric bus;
calculating an amount of power consumption Wh3 of the electric bus along the travel route according to the number of passengers;
calculating a first amount of charging energy Wh1 from the power transmission device to the electric bus along the travel route according to the travel route;
determining a second amount of energy Wh2 to be charged from the charging facility to the electric bus based on the amount of consumed energy Wh3, the first amount of charged energy Wh1, the amount of energy Wh0 stored in the battery at the first location, and a target amount of energy Wh(tag) corresponding to a target SOC that is set lower than a lower limit value of an SOC region in which deterioration of the battery is accelerated, so as to satisfy the following formula (1):
The bus operation management system adjusts the amount of power charged from the power transmission device to the electric bus while the electric bus is traveling on the travel route so that the SOC of the battery does not fall within the SOC range.
Wh0+Wh1+Wh2-Wh3=Wh(tag)...Formula (1)