Electric vehicles and vehicles systems: EV system
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Everything you should know about electric vehicle charging:
1. Electric car charging at home
With 64 percent, charging at home takes the crown of being the most popular compared to other charging locations. Not surprising, as charging at home conveniently enables electric car drivers to wake up to a fully charged vehicle every day, and ensures that they do not pay a cent more than the electricity they actually consume against the household’s electricity price.
2. Electric car charging at work
34 percent of the current EV drivers already regularly charge their car at the workplace and many more have stated that they would love to be able to do so, and who wouldn’t? I mean, driving to the office, focusing on your work during business hours, and driving home again after the day is done in a fully charged vehicle sounds super convenient. As a result, more and more workplaces are starting to install EV charging stations as part of a sustainability initiative, employee engagement strategies, and to satisfy their EV-driving visitors and partners.
3. Public charging stations
Each day, more public charging stations are popping up as cities and local governments are investing heavily in charging infrastructure. Today, 31 percent of EV drivers already gladly make use of them, and there is a ratio of 7.5 electric cars per public charging point, which is great. But, as the sales of EVs are rising, so will the number of available public charging stations in our cities.
4. EV charging at gas stations
Charging at home or at the office sounds nice, but what if you’re on the road and looking for a quick top-up? Many fuel retailers and service stations are starting to provide fast charging (also known as level 3 or DC charging) services. 29 percent of current EV drivers already charge their car there regularly. Plus, while charging at the office or at home is convenient while you do other things, it can take hours before the battery is recharged. However, with fast charging stations, you can charge your battery a lot quicker (think in minutes, not hours) and be back on the road in no time.
5. Retail locations with electric car chargers
26 percent of EV drivers charge their car at supermarkets, while 22 percent prefer shopping malls or departments stores—if the service is available to them. Think of the convenience: imagine watching a movie, having dinner, meeting a friend for a coffee, or even doing some grocery shopping and returning to a vehicle with more charge than you left it with. More and more retail locations are discovering the growing need for this service and are installing charging stations to meet the demand and acquire new customers.
EV charging levels and all types of chargers explained
Charging can be categorized in multiple ways. The most common way to think about EV charging is in terms of charging levels. There are three levels of EV charging: Level 1, Level 2, and Level 3—and generally speaking, the higher the level, the higher the power output and the faster your new vehicle will charge.
Generally speaking, the higher the level, the higher the power output and the faster your new vehicle will charge.
However, charging times are always dependent on a combination between the type of battery and charging capacity of the car, and the power output of the charging station.
Level 1 charging is when you plug your EV into the socket with a standard AC power plug. As a standard household outlet only delivers a maximum of 2.3 kW, charging via a Level 1 charger is the slowest way to charge an EV—giving only 6 to 8 kilometers of range per hour (4 to 5 miles). As there is no communication between the power outlet and the vehicle, this method is not only slow, but it can also be dangerous for your safety and your vehicle. As such, we don’t recommend relying on Level 1 charging to charge your vehicle except for in emergency circumstances.
Level 2 charger
A Level 2 charger is any standard AC charging station that you may find mounted to a wall, on a pole, or standing in the ground. Level 2 charging stations commonly deliver anywhere between 3.4 kW – 22 kW and are commonly found at residential, public parking, businesses, and commercial locations. At the maximum output of 22 kW, an hour’s charging will provide roughly 120km (75 miles) to your battery’s range. This is a lot faster than Level 1 charging. Because of this reason, combined with a range of intelligent functionalities, smart connectivity options, and a range of safety features that Level 2 chargers have to offer, many EV drivers invest in an AC charging station for home.
Level 3 charging station (DC fast charger)
Also known as DC or fast charging, Level 3 charging uses direct current (DC) to charge a vehicle’s battery directly, bypassing the AC/DC onboard converter. This allows Level 3 chargers to deliver DC power directly to the battery. As a result, Level 3 charging stations can deliver more power, faster, making them ideal for short-stop locations like gas stations and fleet depots. Charging times vary between different vehicles and power outputs, however, generally speaking, Level 3 chargers can charge a vehicle in minutes versus hours for Level 2 or days for Level 1 charging stations.
AC vs DC power
So, the higher the level, the higher the speed. All clear so far, right? But, when is something AC and when DC, and why is DC so much faster?
AC vs DC current
AC stands for “Alternating Current” and it, well, alternates as it changes direction periodically, DC stands for “Direct Current” and flows in a straight line. Without getting too technical, AC can be transported over long distances more efficiently, so this is why it flows out of your socket at your home and office. However, batteries in general are only able to store DC power.
You may have never realized it, but every time you charge your phone (or any other electrical device for that matter), the charger converts the AC power it receives from the grid into DC power to charge the battery in your device.
How do electric cars charge?
The same principle goes for electric cars. The difference between AC and DC charging all depends on whether there is a conversion process or not. No matter how you charge it though, at the end of the day, the battery in the car is always charged with DC.
With a DC charger, the direct current can flow into the battery directly, while with an AC charger, the electricity has to be converted to DC first. This process will always take more time as the onboard charger can only take so much electricity at a time.
Electric Vehicle technology
With the rapid development of the smartphone market, future cars seem to have more connections with intelligent cell phone and Internet. Intelligent transportation system (ITS) and telematics system have become research focus in recent years. There is an increasing demand for remote monitoring and diagnostic system as the further research of hybrid electric vehicle (HEV) goes on. In this paper, a remote controller area network bus (CAN-Bus) data monitor and diagnostic system for HEV is presented using on board diagnostic version-II (OBD-II) and Android-based smartphone. It is low-cost, convenient, and extensible with smartphone used in the system to realize communication with ELM327 and remote monitoring center wirelessly. The prototype of client and server is developed in Java language, and it is proved by the test that the system works stably and the collected data have practical values.
In the past decades, as environmental protection and energy saving have been greatly concerned, automobile manufacturers and well-known universities are active to research and develop new technologies to improve fuel efficiency, in which hybrid electric vehicles (HEVs) have been adopted as a commercial technology. Nowadays, various HEV topologies have been developed, such as parallel HEVs, series HEVs, and power-split HEVs [1–6].
As HEVs become increasingly popular, the demand for HEVs remote monitoring systems is growing [6–10]. First, there are more than two power units (engine and motors) installed in the same vehicle. In order to improve fuel efficiency of the vehicle, an optimized energy management control strategy must be used [1–5]. Then a remote monitoring system is needed to provide the running parameters of the HEV. Second, in order to improve efficiency of transportation, an intelligent transportation system and an on-board telematics system are needed to share the information in vehicles and remote service center [11–16]. Third, taking the public transportation into consideration, it is very important to improve the traffic safety by monitoring the running status and performance parameters of hybird buses and taxies in real time. These tasks can be quickly realized by online diagnosis and troubleshooting based on remote monitoring and diagnostic system [17–21].
Much research about remote monitoring system has been carried out. With a digital signal processor (DSP) used as a central processor, Fang et al. designed an on-board data acquisition system of hybrid electric vehicle . Aljaafreh et al. designed a system based on wireless networking technology (WiFi), in which, without a base station to upload the collected data to a web server, the data acquisition system is placed onboard, together with database server and web interface for fleet management automation . Kucera et al. developed a vehicle data acquisition system to reduce hazardous situations on the roads by analyzing driver and identifying the degradation of driver’s abilities . Dow et al. developed a dedicated short-range communications (DSRC) vehicular warning and notification system. It was capable of detecting road hazards and transmitting traffic information to the Internet through intervehicular communications via DSRC . Montazeri-Gh and Asadi designed a vehicle telematics system to receive traffic data and also built a genetic-fuzzy controller that considered the influence of traffic condition on the controller parameters. The traffic data received from the telematics system was used to tune the proposed intelligent controller . Lin et al. developed a vehicle online diagnosis and real-time early warning system to acquire OBD signals that is transmitted to a Server of Maintenance Center via General Packet Radio Service (GPRS) mobile communication for immediate actions .
However, the proposed solutions and systems need external dedicated hardware, network, or specialized software. Moreover, most of them are running on a desktop, and the associated high costs restrict their development and promotion.
With the rapid development of smartphones, its hardware configurations are becoming increasingly powerful, and its applications tend to be diversified. Nowadays, smartphone is widely used around the world, and it can also be used as controller/multimedia/data collector/mobile localizer except for mobile phone [11, 12, 27–32]. With the development of ITS and ecological electric vehicle, to develop a vehicle remote monitoring system is of great significance. In this paper, a HEVs CAN-Bus data monitor and diagnostic system based on OBD-II and Android-based smartphones is presented. It is low-cost, convenient, and practicable to use smartphones in the system to implement communication with ELM327 and remote monitoring center wirelessly. There are two key problems that need to be solved: (1) how to program to acquire vehicle real-time status information on Android platform; (2) how to integrate different functions such as vehicle positioning, route tracking, user chatting, and information sharing.
2. System Structure
2.1. Powertrain Structure of HEV
Since Toyota Hybrid System (THS) was equipped on Prius in 1997, the electric variable transmission (EVT) had been widely accepted with its good performance in fuel consumption and emission. After Changan New Energy Automobile (CNEA) Co. finished their Integrated Starter and Generator (ISG) HEV project, the ISG HEV appeared in the market. In order to obtain better fuel efficiency, CNEA started a new EVT HEV project.
A single motor speed coupling hybrid system has been developed; the structure of the powertrain is shown in Figure 1. The powertrain configuration of the HEV includes an internal combustion engine, a One Way Clutch (OWC), a multi-disc wet clutch, a planetary gearset (PGS), an ISG motor, an automatic mechanical transmission (AMT), and NiMH-battery [33–35]. The PSG has a sun gear, a carrier with planetary gears, and a ring gear. The sun gear and the ring gear are the input elements. The sun gear is connected to the motor and the ring gear is connected to the engine shaft. The carrier is the output element and is connected to the input shaft of the transmission. The OWC and the multi-disc wet clutch inner part are mounted to the engine shaft. In this way, the OWC allows the engine to rotate forwards freely and prevents the engine from rotating backward. The multi-disc wet clutch is disengaged when it is in electric drive mode; when multi-disc is engaged, it will help to start the engine with motor or to lock the PGS. The ISG motor is used to assist the engine or to recover braking power. The AMT is used to expand the speed ratio of the system. It also can change the rotating direction of the output shaft to fulfill the reverse function of the vehicle.
The powertrain system has the following work modes: pure electric driving, power boosting, regenerative braking, normal engine driving, electric variable transmission, and so forth. The driving modes are listed in Table 1; the red lines in Figure 2 show the power flows of different driving modes. In order to acquire the source data to optimize the control strategy, a remote monitoring and diagnostic system is developed through ELM327 and Android-based smartphones.
2.2. System Structure
Telematics is a compound word of Telecommunications and informatics; it is an integrated information service system. It provides traffic information, emergency response strategy, remote vehicle diagnosis, and internet services to both driver and passengers by integrating GPS, wireless voice, digital communication, and satellite navigation [11, 12, 24–27, 36–39]. Telematics system is also known as Internet of Vehicles (IOV) in a narrow sense, and it makes up an important part of ITS. The HEV CAN-Bus data monitor and diagnostic system proposed in this paper can be seen as a simplified telematics system.
The system presented in this paper consists of HEV, ELM327, an Android smartphone, and a remote monitoring center; the system structure is shown in Figure 3. ELM327 interacts with the HEV through OBD-II interface, the Android smartphone is used as the client to complete data acquisition and data transmission, and the remote monitoring center realizes data reception and real-time monitoring.
3. Technical Details
There were two hardware solutions to perform vehicle data acquisition, accident warning, trouble diagnosis, and remote monitoring: (1) embedded system with CAN interface or OBD port, GPS module, and wireless communication module; (2) take advantage of smartphone, ELM327 or OBDLink and Bluetooth technology. Furmanczyk et al. designed the Vyatta hardware device which consisted of an ELM327 to interface with the OBD port, an ATmega644 microcontroller to facilitate communication, and a Bluetooth module to interface with the smart phone . Lin et al. proposed the on-board computer of the remote online diagnostic system, which was mainly comprised of OBD-II to RS232 adapter, GPS receiver, encoder, 3G module, and so forth . Lin et al. developed the G3 client hardware using an ARM CPU, a GPS module for positioning data, and a GPRS module for mobile communication . Al-Taee et al. presented a distributed system for remote monitoring of vehicle diagnostics and geographical position by using On-Board Smart Box (OBSB); it was installed inside the vehicle and equipped with an integrated GPS receiver and a GPRS communication module . Cabala and Gamec analyzed vehicle communication through diagnostic interface OBDII and designed and implemented an application on Android system, which can obtain real-time data from ECU . Tahat et al. provided a vehicle diagnostic and tracking system utilizing OBD and Bluetooth .
Compared with the first solution, the second solution is low-cost, easy to operate, and more convenient. Consider that ELM327 equips OBD interface and Bluetooth module as shown in Figure 4; smartphone integrates GPS and GPRS/3G; the second solution is adopted in this paper. We cannot only collect the location information, running parameters, and trouble codes, but also interact with other cars and remote server.
3.1. OBD System
On-Board Diagnostics (OBD) is a computer-based system originally designed to reduce emissions by monitoring the performance of major components such as the engine, catalytic converter, particulate filter, oxygen sensor, emission control system, fuel system, and exhaust gas recirculation (EGR). Its schematic diagram is shown in Figure 5. A basic OBD system consists of an ECU, which uses input signals from various sensors to control the actuators to get the desired performance [28, 31]. The “Check Engine Light,” also known as the malfunction indicator lamp (MIL), provides an early warning of malfunctions to the driver. A modern vehicle supports hundreds of parameters, which can be accessed via the diagnostic link connector (DLC) by using external diagnostic devices.
In this paper, ELM327 is used to connect with OBD-II interface and convert the OBD signals into series signals, which are used to communicate with the upper machine. OBD-II interface has sixteen pins as shown in Figure 6. The OBD communication protocol differs from automobile manufacturers in that it includes ISO 9141-2, ISO 14230-4 (KWP2000), ISO 15765-4 (CAN), SAE J1850 PWM, and SAE J1850 VPM [40, 41]. Which protocol the vehicle uses can be determined by pin connections; the corresponding relation is shown in Table 2.
3.2. GPS and Network Communication
Global Positioning System (GPS) is convenient and practical and allows the vehicle to be positioned and navigated on a global scale by using GPS positioning satellite [13, 15]. Assisted GPS (A-GPS) is a technology combining network base station and GPS information; it is widely used on the smartphone to improve positioning accuracy and shorten positioning time. With the rapid development of network technology, GPRS/3G has been widely used and 4G network has also entered trial period. So mobile network can be used to ensure the efficiency of data transmission.
3.3. Data Transmission
The open source project HttpClient is utilized in this paper to complete the communication between Android client and Web server. After the client, based on Hyper Text Transfer Protocol (HTTP), sends request to the server each time, the server will return response messages (including the request is correct or not and the requested data) to the client. The server will shut down the network connection after the client has received the response messages.
3.4. Data Storage
Key-value table is used as data transmission format between client and server; the acquired data are stored on the server via SQL Sever2005, which also used to complete the management of driver information and vehicle information.
4. System Design and Implementation
The main function of the proposed system is wireless data acquisition and transmission of HEV operation parameters. Considering the demand for rapid vehicle positioning, the vehicle positioning and trajectory tracking function are added [15, 21]. The system is developed with Client/Server (C/S) mode, the Android application acts as a client, and the Web application acts as a server. Modular programming is adopted in the development process; the system will be integrated and completed after the basic function modules of client and server are built.
4.1. Vehicle Positioning and Trajectory Tracking
Android Software Development Kit (SDK) contains basic location Application Programming Interface (API) which interacts with GPS hardware ; the API and Baidu map are used to accomplish vehicle positioning in this paper; the flowchart is shown in Figure 7.
In order to embed Baidu map in the application, we first need to apply for a Baidu map API key, then finish the project configuration, and finally execute according to the following steps:
- add internet access permission and positioning function usage permission in the file AndroidManifest.xml,
- create layout for activity, and add widgets in the layout file to show Baidu map,
- create activities, initialize the map, set the zoom level, and add the function button,
- program to realize the function.
We can complete the related operation by adding buttons on the MapView. When the “Location” button is triggered, we can obtain the longitude and latitude of current position and display it by the way of Toast. When the “Track” button is triggered, we can start tracking with the current position as the starting point, then draw the route on the map with the change of location information; the ending point will be drawn until the “Stop” button is clicked.
4.2. Vehicle State Information Collection
ELM327 communicates with ECUs via OBD protocol; ELM327 can be set by AT commands and the real-time data are acquired by OBD commands. A kind of format named “Mode plus Parameter Identification (PID)” is used as OBD command; the nine diagnostic modes and all PIDs are described in detail in international standard such as SAE J1979 and ISO 15031-5. The diagnostic modes defined in ISO 9141-2, ISO 14230-4, and SAE J1850 are slightly different from ISO 15765-4 [40, 41]. In this paper, data such as engine Revolutions Per Minute (RPM), engine load, throttle position, mass air flow (MAF), diagnostic trouble code (DTC), and vehicle speed, can be obtained. The relative OBD commands are listed in Table 3.
ELM327 connects with the car through OBD-II, and smartphone connects with ELM327 via Bluetooth. Smartphone sends OBD commands and reads the response; the data flow of whole process is shown in Figure 8. The programming method is as follows: ObdCommand class is created as a parent class according to SAE J1979, and other child classes which are defined to acquire specific data inherit the parent class. After the successful connection of Bluetooth, it will always work as a background service. The queue technology is adopted in the process of data acquisition and a buffer is used to store data temporarily.
The flowchart of data acquisition is shown in Figure 9.
4.3. Data Transmission
After the location information and vehicle state information are collected successfully, the data will be transmitted to the remote server. When the menu “Upload data” is clicked, data are submitted to the specified server by means of POST, and the request of POST is sent through HttpClient.
5. System Testing
5.1. Vehicle Positioning Test
After acquiring the latitude and longitude information through GPS embedded in the smartphone, the position of the vehicle is monitored on the Baidu map. A Samsung S5660 is used in this test; it can be seen from Figure 10 that the vehicle location is accurate and the moving route is clear.