A Different Kind of Green Robotics

To serve high-end golf courses striving for smooth manicured greens, Precise Path Robotics has combined a variety of sensing technologies, a maintenance application based on Linux, Ethernet, and an electric engine to create a robotic motor for greenskeepers.

In a clear example of no niche being too small for robotics, Precise Path's $30,000 RG3 mower is designed to cut the grass on golf greens as neatly and consistently as possible, sometimes as low as one-tenth of an inch. The company unveiled the mower, which is 3 ft long, 4 ft high and 2 ft wide, at the 2009 Golf Industry Show which opened Feb. 5 in New Orleans. The mower was designed using Solidworks 3D CAD for the mechanical engineering and Cadsoft Eagle for the electronics. Linux is the operating system, and the application was written in C++.

Robotics brings a level of precision golf courses are willing to invest in when it comes to the course they offer. "Golf courses have become more competitive," says Traster. "The level of perfection has gone up and up, and it's difficult for human beings to maintain the level of quality that golf courses have come to expect. It's a battle of inches."

Developing the RG3 presented some interesting technical challenges, according to Doug Traster, president of Indianapolis-based Precise Path. "A key element in robotic technology for outdoor environments is that the robot must always know where it is and where it's going," he says, (adding that) this is especially important on a golf green, which has very specific boundaries and characteristics different from the other side of those boundaries in terms of the grass length.

While some robotic mowers targeted at consumers use buried wire to delineate boundaries, it represents a huge infrastructure cost of golf courses. In other applications where highly precise robotics are necessary, the cost of those devices can be as high as $500,000, according to Traster, which is also not financially feasible.

To keep costs down, Traster says his company's system uses a combination of ultrasonic and infrared devices to guide the mower. "They're mature technologies used in high volume, and they allow us with near-millimeter accuracy to know locations in space and angle to known locations." Four beacons, each four inches in diameter and 18 inches tall, sit anywhere from one to six yards outside the mowing space, and exchange location information.

From a mechanical standpoint, Precise Path's designers avoided using a gasoline engine to avoid possible dripping of fluids on the green. As a result, the RG3 uses an electric motor. The operation of the blades is run by a servo-driven motor, and coordinated with the forward motion of the mower so that the blades cut the grass at regular intervals.

The RG3 also incorporates optical sensors both to ensure precise motion and to watch for obstacles on the grass, such as sticks, coins or if the flag has been left in the hole. Vibration, temperature and voltage sensors send information to a small two-line display on the motor, but Traster says you can also plug a laptop into the mower's Ethernet port to run diagnostics.

Finally, the mower contains sensors that track movement around the device itself. "If somebody approaches the mower, like a child, it'll shut down or provide a warning," says Traster. "But if its operator is walking beside it, it will ignore that person."

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