Coming soon: robots as parking valets.

• Author: Jean, Grace V.
• Position: INSIDE SCIENCE + TECHNOLOGY

SENDAI, Japan -- A car parked illegally on a city street comes under suspicion by law enforcement agents who believe it may be packed with explosives. They send in two robots to lift the vehicle and move it to a designated safe location where bomb disposal units can take over.

While the above scenario is fictional, it is one of the visions that Kazuhiro Kosuge of Tohoku University's bioengineering and robotics department has for his invention, the iCART--Intelligent Cooperative Autonomous Robot Transportation.

The iCART consists of two mobile robots that collaborate to carry four-wheeled vehicles to and from confined spaces. Each rectangular robot spans about the length of a small automobile and reaches a height of an average person's shins. The robots are composed of three modules: mobile base, lifter and connecting.

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The mobile base module sits on casters that can coast along the floor in all directions. It contains the lifter module that detects the center of a vehicle's wheels, positions the four lift-bars around the tires and raises and supports the weight of the car. The connecting module serves as the link between the mobile base and lifter modules and measures the pushing and pulling forces to allow for movement.

One robot grasps two wheels on one side of the vehicle, and its counterpart does the same on the other side. A motion control algorithm based on a leader-follower concept coordinates the transport of the car. The motion command is given to the first robot, and the follower robot estimates the motion given to the leader. They move in tandem, even if the casters experience slippage along the floor.

The most difficult part in designing the system was figuring out how to grasp and secure the automobile without doing damage, says Kosuge. Because there are more than 1,000 types of passenger vehicles, each with unique jack-up points on the chassis, the team determined that the simplest way to lift vehicles was to pick them up by their tires. Though wheels come in various sizes, the robots are able to detect the center points of any tires and adjust the lifting bars accordingly.

During a demonstration of the test model in the lab, one of Kosuge's graduate students controls the system with a laptop computer that is connected via a cable to the leading robot. The robots maneuver into position on either side of a four-wheeled scooter. Their lifters slide under the scooter's tires and buoy the vehicle. The iCART...