New York City's streets are well known—often unfairly—as dangerous places, but the city's legendary 103-mile, 110-year-old grid of underground steam pipes is far more hazardous. To fix frequent leaks in the 16-45-in. mains that move 300 °F steam at 100 mph to heat, power, and help cool about 2,000 buildings, crews must excavate and make repairs directly, compounding the city's even more frequent traffic jams.

To help Consolidated Edison repair these mains less invasively, Honeybee Robotics Ltd. (New York, N.Y.) is building a semi-autonomous robot to inspect joints, mill new grooves, and re-weld pipe flanges from inside those same pipes.

Honeybee's 8-ft, 700-pound Welding and Steam Operations Robot (WISOR) has a milling section in front, with a 360°, 6-in. extendable milling tool, and a welding section in back. These are connected by U-joints to a center indexing system that cooperates with WISOR's retractable legs to inchworm the robot along inside the pipe.

After identifying a broken pipe joint with its four on-board cameras, WISOR locks up, cuts a clean groove, retracts, moves ahead, locks up again, and lays down a new weld in the groove. At an approximate rate of four 16-in welds in six hours, WISOR's repairs are expected to cost far less than the $35,000 the utility now spends per excavated repair.

WISOR is operated via a 200-ft umbilical that delivers control signals, power, compressed air, and shielded gases from its truck-mounted control and support unit. Repair data are also transmitted to WISOR's operator at a human-machine interface above ground. Before starting a repair, the robot also self-diagnoses to learn if its compressor is on, confirms the pipe's diameter, and seeks other required data.

Honeybee used copper cable for WISOR's communication line because it required less hardware than fiber-optic, was more reliable in hot environments, and didn't require a signal converter.

Communication and control integration included tuning, debugging, and noise level testing of signal channels on WISOR's slip ring. Its cables were also checked for any signs of failure. Noise on the video signal occurred when the motors experienced load due to a common power and signal ground. Twisted-pair cable reduced noise interference.

The backbone of WISOR's control capabilities is a Local Intelligent Network Controller from Cybernetic Micro Systems (San Gregorio, Calif.). Because of tight space for on-board electronics, the controller was limited to basic functions. For example, the motor controller's loop wasn't closed because the operator above ground could fulfill that function manually using video images from the robot.

In addition, due to vibrations experienced by WISOR's circuit boards as it navigates, Honeybee's engineers decided against surface mounting the controller, and chose through-hole mounting for all the controller's electrical components.

So far, two-thirds of the robot have been delivered to Con Ed, and street trials are expected to begin in September 2001. In the future, Honeybee's engineers plan to increase the speed of WISOR's computers and increase its memory capacity, so it can operate more autonomously.

For more information, for Honeybee Robotics or visit www.hbrobotics.com.