There are a wide variety of driving cycles in the United States, with different uses, roughly including three systems for authentication (FTP series), research (WVU series) and short-duration (1/M series). Well-known driving cycles such as the Federal Test Program (FTP75), Los Angeles (LA92) and load simulation conditions (1M240).
(1) Suitable for driving cycles of passenger cars and light trucks
In the 1960s, the exhaust from cars used to commute to and from get off work caused very serious air pollution. Photochemical smog even appeared in the air in Los Angeles, California. In order to improve this situation, it is necessary to reduce automobile exhaust emissions. After investigation and research, the speed-time curve of a vehicle is analyzed from a representative automobile commuting route, which was used by the U.S. Environmental Protection Agency (EPA) in 1972. Used as a test program for certified vehicle emissions (referred to as FTP72, also known as UDDS). According to this procedure to control vehicle emissions, it is considered that the most stringent situation is considered.
FTP72 consists of cold transition conditions (0~505s) and steady-state conditions (506~1370s). In 1975, on the basis of FTP72, the 600s hot-soaked car and hot transitional conditions (ie repeated cold transitional conditions) were added to form the FTP75 operating condition with four stages, with a duration of 2475s; at the same time, it can be used for vehicle hot start Emission inspection. Figure 1 shows the driving cycle of the American FTP75.
Due to the development of the transportation network, many arterial lines and highways have appeared, and the high-speed operation time of vehicles accounts for an increasing proportion of the total travel time. The emission characteristics of the three main pollutants (CO, CxHx and NOx) of the engine have changed. , So the EPA issued a revised version of FTP. Researchers have developed many driving cycles that more reflect the real traffic conditions, such as the US06 that takes into account road changes, and the SC03 that the vehicle is running at full capacity with air-conditioning. As a supplementary working condition for FTP, SFTP (Supplement FTP) is formed. , And applied to the emission test of models produced after 2001. HWFET driving cycle is the operating condition used for passenger car highway fuel economy test, as shown in Figure 2. In addition, considering the impact of road gradient on vehicle fuel consumption, a variable gradient HWFET-MTN operating condition has also been developed.
In addition to the above-mentioned working conditions, there are the following typical research working conditions.
LA92: Has a higher maximum speed and average speed, less idling running time and the number of stops per unit mileage, and a higher maximum acceleration.
ARB02: A research condition developed by CARB (California Atmospheric Resources Board) based on vehicle tracking. The purpose is to test the operation of vehicles outside the edge of FTP72, including cold start and end of travel.
HL07: The engine operating conditions developed by EPA in collaboration with automobile manufacturers are designed to test a series of acceleration capabilities of vehicles beyond a certain speed range. In these acceleration situations, most vehicles must fully open the throttle. It is mainly used to develop and modify the existing driving cycle in the United States at various speed levels.
For the range of vehicle operating conditions that are not described and covered by FTP operating conditions , some driving conditions have been developed, such as REPO5 representing driving conditions and REM01 (Remainder) for starting conditions research. Working conditions, etc. They all aim at speed and acceleration, and focus on the study of more detailed transient changes.
(2) Driving Cycle for heavy vehicles
In recent years, research on driving cycle of heavy vehicles has tended to move closer to transient operating conditions. Among them, BAC is recommended as the operating procedure for testing the fuel economy of heavy-duty vehicles (SAE J1376). CBD14 is a vehicle test condition in the commercial center area. It is also a part of the BAC compound test condition, using 14 identical operating conditions Simulate bus parking-operation driving mode. CBD14 is similar to CBDBUS operating conditions, but the time step is variable.
The more famous is the city dynamometer test condition (UDDSHDV), which mainly simulates the operation of heavy-duty gasoline engines in the city. The running length is 1060s, 33% is idling, and the average speed is 30.4km/h. It is used for fuel evaporative emissions. test. New York City Operating Conditions (NYCC) represents the operating conditions of large vehicles on roads in the city. They are widely used as FTP standard operating conditions. Figure 3 and Figure 4 respectively show the UDDSHDV and NYCC driving cycles.
In order to evaluate the emission effect of buses, West Virginia University (WVU) conducted a survey on the operation and status of hybrid and conventional buses in Manhattan by covering several different and recognized busy routes. The group contains 10 short-stroke working conditions, and the idle period between short-strokes is 19s; in order to meet the energy consumption test requirements, the number of short-strokes is increased to 20, as conventional transport vehicles (trucks and city buses) in use Driving Cycle.
In addition to driving cycles for chassis dynamometers, there are also representative driving cycles used on engine benches for heavy vehicles. They are described by vehicle characteristics calculated by engine speed and torque. The test conditions include a set of stable operating items defined in accordance with the engine speed and torque (European and Japanese regulations), or transient operating conditions with instantaneous engine speed-torque indications (American regulations) at the same time.
Do you still want to see the driving cycle in other countries? You can read another article on this site-Driving Cycle in Europe.