Micro Trip Method
The Philippines, especially urban areas such as Metro Manila, has a heavy volume
of traffic at almost any time of the day. In fact, CBS News ranked Philippines as number
one with the worst traffic in the world tied to India, in which the congestion level of Manila
between 2018 and 2019 was recorded to be at 71%. Therefore, whether it may be for
private or public vehicles, adjacent stops are expected for every vehicle in the road.
According to a study conducted by Engr. Corpus, the Micro trip method based cycle
construction is best used for the drive cycle generation in the country as it consists of
many stops in between the origin and destination, for the most part, more stop-go
conditions are considered for public utility vehicles (PUVs) because of passenger
boarding and alighting.
There are two types of driving cycles, the Model Driving Cycle and the Transient
Driving Cycle. The Model Driving cycle comprises constant speed and does not represent
a real driving pattern of a vehicle. These driving cycles will be used for specific
applications such as an emission test. While the Transient Driving Cycle represents an
actual pattern of a vehicle which contains acceleration, deceleration, constant speed, and
other parameters necessary for the purpose of the drive cycle generation. According to
an article from EV Projects by Krishnan, vehicle manufacturers use standard driving
cycles which have already been developed for the performance analysis of vehicle. But
then, those values might not match with the actual results from a real vehicle since the
test driving cycle are extremely different from the actual pattern of the drive. Thus, using
methods such as the micro trip method which can be considered as a transient driving
cycle is used for drive cycle generation for Metro Manila because of the aforementioned
factors.
Drive cycle generation is done with the proper data acquisition instruments such
as a fuel flow meter to measure the fuel consumption, and a magnetic pick up sensor to
measure the vehicle’s velocity. An on-board computer to process, convert and display the
signals from the flow meter and magnetic sensor, and a data logger with the proper
software to store the speed data with respect to time. As standard operation before
conducting an experiment, calibration should be done between the instruments. Then,
the vehicle must be mounted to a chassis dynamometer to calibrate the sensors until the
on-board computer and the chassis dynamometer gives out the same values.
For the drive cycle generation itself, according to Huertas, the micro trips are the
speed-time data, collected during the vehicle monitoring campaign, partitioned in
segments of trips bounded generally by vehicle speed equal to 0 kph. Based from an
investigation by Engr. Corpus, a micro trip is a 0 kph to 0 kph two-minute trip or more.
The micro trips are randomly selected to form a drive cycle which has an approximate
duration of twenty minutes. His study elaborated a step-by-step process of using the
micro trip method for a drive cycle generation from a public utility vehicle, specifically an
Isuzu Crosswind, which is a UV express. The first step includes the generation of speed
acceleration probability matrix which needs the parameters such as maximum, average,
and minimum acceleration and speed, and class width for both velocity and acceleration.
Step 2 instructs for a random selection of ten micro tips at least minutes in length. The
number of micro trips selected depends on the desired duration of the drive cycle. For the
third step, step 1 is repeated to establish the characteristic parameters for the candidate
driving cycle. And finally, the generated matrices were normalized and the difference of
the characteristic perimeters are less than the established limits.
As part of the experimentation, evaluation of the driving cycle representative shall
be considered. To validate, the generated drive cycle shall be tested on a chassis
dynamometer, which was calibrated to mimic on-road conditions, to be compared with
the on-road values. In this validation, fuel consumption of the drive cycles generated
through the micro trip method were measured using the same instruments used in the
on-board road data gathering. Finally. for each drive cycle generated, certain number of
runs shall be made for the data such as average fuel consumption may be compared to
the on-road fuel consumption where the tested drive cycle was obtained.
References
Corpus, R. Q. (2020). A Preliminary Comparison of Fuel Economy Estimates from
Driving Cycles Developed Using Road Load Energy-Based and Microtrip
Methods. Retrieved from SAE International: https://doi.org/10.4271/2020-011281
Huertas, J. I. (2019). Comparison of driving cycles obtained by the Micro-trips, Markovchains and MWD-CP methods. International Journal of Sustainable Energy
Planning and Management. Retrieved from International Journal of Sustainable
Energy Planning and Management: https://doi.org/10.5278/ijsepm.2554
Krishnan, S. (2018). What are Driving Cycles and How to Develop One for Electric
Vehicle Simulation? Retrieved from Get Electric Vehicle:
https://getelectricvehicle.com/driving-cycle/
Vasquez, P. Q. (2021, July 22). AN INVESTIGATION OF THE FUEL ECONOMY OF A
DRIVE CYCLE DEVELOPED USING . Retrieved from ASME Digital Collection:
https://doi.org/10.1115/ES2021-62790