Featured Research

from universities, journals, and other organizations

Motion control keeps electric car's four wheels -- and four motors -- on the road

Date:
January 23, 2013
Source:
Ohio State University
Summary:
It weighs half as much as a sports car, and turns on a dime —- so its no surprise that a new electric car needs an exceptional traction and motion control system to keep it on the road.

An experimental electric car under development at Ohio State University.
Credit: Photo by Junmin Wang, Courtesy of Ohio State University

It weighs half as much as a sports car, and turns on a dime -- so its no surprise that the electric car being developed at Ohio State University needs an exceptional traction and motion control system to keep it on the road.

Related Articles


With four wheels that turn independently, each with its own built-in electric motor and set of batteries, the experimental car is the only one of its kind outside of commercial carmakers' laboratories.

"It is considered one of the promising future vehicle architectures," said Junmin Wang, assistant professor of mechanical engineering and Director of the Vehicle Systems and Control Laboratory at Ohio State. "It would make a good in-city car -- efficient and maneuverable, with no emissions. Our task is to make a robust control system to keep it safe and reliable."

In a paper in the January 2013 issue of the journal Control Engineering Practice, his team described the car's ability to follow a specific trajectory.

In tests on good road conditions at the Transportation Research Center in East Liberty, Ohio, the car followed a driver's desired path within four inches (10 cm). To test slippery road conditions, the researchers took the car to an empty west campus parking lot on a snowy day. There, the car maneuvered with an accuracy of up to eight inches (20 cm), and the vehicle traction and motion control system prevented "fishtailing" through independent control of the left and right sides of the car.

Wang characterized these results as more accurate than a conventional car, though the comparison is hard to make, given that conventional cars are much more limited in maneuverability by the transmission and differential systems that link the wheels together mechanically. The four independent wheels of the electric car give drivers greater control and more freedom of movement.

The experimental car also weighs half as much as a conventional car -- only 800 kg, or a little over 1,750 pounds -- because it contains no engine, no transmission, and no differential. The researchers took a commercially available sport utility vehicle chassis and removed all those parts, and added a 7.5 kW electric motor to each wheel and a 15 kW lithium-ion battery pack. A single electrical cable connects the motors to a central computer.

One hundred times a second, the onboard computer samples input data from the steering wheel, gas pedal and brake and calculates how each wheel should respond. Because the wheels are independent, one or more can brake while the others accelerate, providing enhanced traction and motion control.

In fact, a driver who is accustomed to conventional cars would have a difficult time driving a car of this experimental design, known as a "four-wheel independently actuated" (FIWA) car without the help of the vehicle motion and traction control system. With its ability to turn sharply and change direction very quickly, the car could be hard to control. Wang has tried it.

"Without the controller, it's very hard to drive. With the controller, it's quite nice -- quiet, and better control than commercial four-wheel drive," he said.

The main challenge for his team -- which consists of bachelor's, master's, and doctoral students as well as a few local high school students -- is to make the whole traction and motion control system energy-efficient and fault-tolerant, so if one wheel, motor or brake malfunctions, the others can compensate for it and maintain safety. It's a situation analogous to a multi-engine plane losing an engine: the other engines have to adjust thrust and angle to keep the plane safe and on course.

Future work will concern the FIWA car's energy efficiency for increasing its travel range in urban environments, and optimizing the weight distribution in the car.

Wang estimates that we won't see a FIWA car on the road for another 5-10 years, as researchers continue to develop new algorithms to control the car more efficiently and add more safety features.

The coauthor on the paper was Rongrong Wang, a doctoral student in mechanical engineering, and the team's high school participants came from the Columbus Metro School, a state of Ohio public STEM (science, technology, engineering, math) high school open to students from around the state.

This research was supported by Junmin Wang's awards from the Office of Naval Research Young Investigator Program (2009) and the National Science Foundation's Faculty Early Career Development Program (2012); the Honda-OSU Partnership program; and the OSU Transportation Research Endowment Program.


Story Source:

The above story is based on materials provided by Ohio State University. The original article was written by Pam Frost Gorder. Note: Materials may be edited for content and length.


Journal Reference:

  1. Rongrong Wang, Junmin Wang. Tire–road friction coefficient and tire cornering stiffness estimation based on longitudinal tire force difference generation. Control Engineering Practice, 2013; 21 (1): 65 DOI: 10.1016/j.conengprac.2012.09.009

Cite This Page:

Ohio State University. "Motion control keeps electric car's four wheels -- and four motors -- on the road." ScienceDaily. ScienceDaily, 23 January 2013. <www.sciencedaily.com/releases/2013/01/130123164902.htm>.
Ohio State University. (2013, January 23). Motion control keeps electric car's four wheels -- and four motors -- on the road. ScienceDaily. Retrieved October 25, 2014 from www.sciencedaily.com/releases/2013/01/130123164902.htm
Ohio State University. "Motion control keeps electric car's four wheels -- and four motors -- on the road." ScienceDaily. www.sciencedaily.com/releases/2013/01/130123164902.htm (accessed October 25, 2014).

Share This



More Matter & Energy News

Saturday, October 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

IKEA Desk Converts From Standing to Sitting With One Button

IKEA Desk Converts From Standing to Sitting With One Button

Buzz60 (Oct. 24, 2014) IKEA is out with a new convertible desk that can convert from a sitting desk to a standing one with just the push of a button. Jen Markham explains. Video provided by Buzz60
Powered by NewsLook.com
Ebola Protective Suits Being Made in China

Ebola Protective Suits Being Made in China

AFP (Oct. 24, 2014) A factory in China is busy making Ebola protective suits for healthcare workers and others fighting the spread of the virus. Duration: 00:38 Video provided by AFP
Powered by NewsLook.com
Real-Life Transformer Robot Walks, Then Folds Into a Car

Real-Life Transformer Robot Walks, Then Folds Into a Car

Buzz60 (Oct. 24, 2014) Brave Robotics and Asratec teamed with original Transformers toy company Tomy to create a functional 5-foot-tall humanoid robot that can march and fold itself into a 3-foot-long sports car. Jen Markham has the story. Video provided by Buzz60
Powered by NewsLook.com
Police Testing New Gunfire Tracking Technology

Police Testing New Gunfire Tracking Technology

AP (Oct. 24, 2014) A California-based startup has designed new law enforcement technology that aims to automatically alert dispatch when an officer's gun is unholstered and fired. Two law enforcement agencies are currently testing the technology. (Oct. 24) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins