Robot combines assembly arm, AGV

Tokyo-Denso Corp. claims to have combined the flexibility and adaptability of hand labor with the productivity and reliability of automated assembly with what the company says is the world's first autonomous mobile assembly robot. Following programmed instructions, the robot automatically moves from station-to-station in accordance with changes in work flow. This enables an assembly line to be reconfigured for maximum production flexibility.

The moving robot is essentially a standard robotic assembly arm mounted on a typical automatic guided vehicle (AGV) that moves at up to 130 ft per minute. The AGV rolls on two drive wheels and two casters and follows a floor-mounted magnetic strip. Capable of carrying a 175-lb load, the robot's single arm has six degrees of freedom and can place up to 11 lbs at a maximum reach of 36 inches.

Machine vision, based on a CCD camera fitted with an iris that adjusts for ambient brightness, ensures accurate image recognition over the range of illumination found throughout an assembly plant. For safety, the robot is equipped with infrared sensors. When approached by a worker, the robot stops all operations automatically.

An on-board controller, built up of several proprietary circuit boards, runs programs written in C developed in-house. Intended to work in groups, each robot can recognize if a work station is occupied by another robot or not, and if there are parts waiting to be assembled.

During operation, each robot follows a programmed routine to assemble a given device until all the available parts have been used. It can then move to another assembly line for a different assembly operation, allowing for automatic adjustment in the number of robots running on a given line. Refinements to an assembly routine "learned" by one robot can be transmitted to other robots.

Denso put seven of the robots on one of its own automobile engine starter assembly lines in May 1998. Each robot assembled the 17 parts that go into a finished starter. During a trial period, production varied from 4,700 to 61,000 starters per month.

For more information about Denso's mobile robot: Circle 543