Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Automatic route guidance vehicle
Reexamination Certificate
2001-11-20
2003-11-18
Black, Thomas G. (Department: 3663)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Automatic route guidance vehicle
C701S002000, C701S209000, C342S357490, C056S01020A, C056S01020F
Reexamination Certificate
active
06650975
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
REFERENCE TO A MICROFICHE APPENDIX
Not Applicable
BACKGROUND OF THE INVENTION
People who own lawns, or are tasked with maintaining them, continually struggle to keep them aesthetically trimmed. The patent record documents many attempts to simplify the task of lawn mowing, but very few innovations have had enough merit to be widely adopted. Today, lawn mowing is still largely a hot, exhausting labor that requires the use of noisy, polluting, dangerous equipment.
The members of a typical yard-owning family would be delighted to wake up each morning and find their grass precisely trimmed to a desired height without any effort on their part, with no related air or noise pollution, with no threat of injury (even to children or pets), with no need to hire mowing personnel who would invade their privacy, and even, with no visible sign of a mower. The present invention can satisfy each of these desires and do so at low cost.
The prior art illustrates a long history of attempts to automate lawn mowing. Almost all of these designs continued the mindset of mowing as a periodic process where a user brings the automatic mower into the area to be mown and returns it to storage after the mowing is completed.
One proposed method of controlling the movement of the mower (U.S. Pat. No. 4,347,908, Anderson; U.S. Pat. No. 4,831,813, Jones et al.) was to connect it to a physical track that would guide it around the lawn. Another method would use a buried wire for the same purpose (U.S. Pat. No. 4,180,964, Pansire; U.S. Pat. No. 4,919,224, Shyu et al.). Both approaches are expensive, labor intensive and disruptive to the lawn.
Other designs would require the user to start the mower in exactly the same spot each time and let a storage medium direct the mower to repeat a set of motions made during a recording run. The storage media referenced include magnetic (U.S. Pat. No. 3,789,939, Geislinger), plastic tape (U.S. Pat. Nos. 3,650,097 & 4,354,339, Nokes), or paper tape (U.S. Pat. No. 4,694,639, Chen, et al.). Each of these designs suffers from the amplification of small positional errors. Such errors may be introduced by variations in the mower's starting location and rotation, by changes in motor efficiency or by wheel slippage caused by such things as variations in grass height, moisture conditions, or temperature.
Noonan, et al., in U.S. Pat. No. 5,204,814, recognized the need to adjust for such variations. He proposed burying metal reference points at various locations along the mower path. The mower would detect these reference points as it passed and use them to correct for any deviations from its desired path. This greatly complicates the initial site preparation and the complexity of the routing algorithm. Instead of just playing back a set of wheel-drive commands recorded by the user, the invention must now know how to interpret sensor data related to the buried metal and override the command playback. The buried markers also make it difficult for the user to modify the mowing geometry after making landscaping changes.
Many of the prior-art patents depend on a pre-defined perimeter only. The perimeter may be a physical barrier, a manually mown strip, or a buried wire. The user must expend considerable effort creating any of these perimeters.
Where there is a manually mown strip, the automatic mower generally uses some form of edge detection to follow the inside edge of the mown strip. It will then spiral inward to the center of the lawn area. The edge detection method could be a mechanical arm with an electrical switch (U.S. Pat. No. 3,924,389, Kita; U.S. Pat. No. 4,184,559, Rass; U.S. Pat. No. 4,887,415, Martin; U.S. Pat. No. 5,507,137, Norris), the breaking of a light beam (U.S. Pat. Nos. 4,133,404, Griffin; U.S. Pat. No. 4,603,753, Yoshimura; U.S. Pat. No. 4,777,785, Rafaels), or a change in motor load (U.S. Pat. Nos. 5,007,234 Shurman, et al.; U.S. Pat. No. 5,444,965 Colens). Manufacturers have a hard time making either the mechanical switches or the light beams rugged enough for a mowing environment. They are susceptible to bending and corrosion, clogging with plant debris and juices, and errors caused by changes in moisture content. The systems that search for increased motor loading can be misdirected by non-uniform grass growth rates and moisture content.
Many designs that incorporate a buried perimeter wire (U.S. Pat. Nos. 3,550,714, 3,570,227 & 3,698,523, Bellinger) or a fixed barrier wall (U.S. Pat. No. 5,323,593, Cline, et al.) have used a random mowing pattern. The random-walk approach will significantly extend the time required for all of the grass to be cut.
The concept of using wireless triangulation (U.S. Pat. No. 4,700,301, Dyke) for navigation has been applied to the control of farming equipment. Similarly, satellite navigation using the Global Positioning System [GPS] has been used for utility right-of-way clearing (U.S. Pat. No. 5,666,792, Mullins), rice farming (U.S. Pat. No. 5,438,817 & U.S. Pat. No. 5,606,850, Nakamura), and the mowing of fields (U.S. Pat. No. 5,528,888, Miyamoto, et al.). For national security reasons, the accuracy of the GPS available to the public was purposefully limited to approximately 100 meters by its administrator, the United States Department of Defense (USDOD). This intentional signal corruption is known as Selective Availability (SA) [see U.S. Pat. No. 5,838,562, Gudat, et al., or U.S. Pat. No. 5,684,696, Rao, et al., for a detailed description of GPS]. Much of the introduced error can be eliminated using a technique known as differential GPS (DGPS) which compares data from the roving receiver to the same satellite data received at a known fixed location nearby. The most accurate DGPS receiver, however, still has an inherent error of considerably more than one meter and this is not sufficiently accurate for most home, yard, or industrial appliances. The term appliance, as used in this document, is inclusive of mobile machines that perform a wide range of repetitive operations or tasks over a defined work area.
Recently, the traditional concept of mowing as a periodic process has begun to yield to the idea of letting an autonomous mower continually perform the mowing task for the duration of the growing season (U.S. Pat. No. 5,323,593, Cline; U.S. Pat. No. 5,444,965 Colens). Such an approach has the advantage of further minimizing the amount of user interface required. It also enables the ideal condition of having the lawn always trimmed to the same desired height. Because the incremental amount of grass removed becomes very small, the mower is inherently mulching, so there is no need for the user to be concerned about raking or removing the cut grass. Also, a motor designed to cut off a small increment of grass can be smaller and quieter than a motor designed to wade through tall grass.
Because mowers have traditionally been dangerous appliances, one can see an obvious problem with allowing a mower to continuously mow a lawn. Many toes and fingers have been cut off inadvertently by mower users. Most prudent users would consider it unwise to allow a robotic lawnmower to wander around their lawn continually while their children and pets played in that same yard. At least two inventors have proposed the idea of using thin, razor-blade-like cutting blades that are free to rotate away if they impact something more massive than grass (U.S. Pat. No. 4,777,785, Rafaels; U.S. Pat. No. 5,444,965 Colens), such as a human hand. While this feature might keep the blade from severing fingers, there is no questioning that a razor blade spinning at thousands of revolutions per minute will do serious damage to an errant hand or foot.
Other automated, or robotic, appliances have gone through an evolution similar to the mowers. Principal among these are floor maintenance appliances which may perform a task such as vacuuming, waxing, or polishing.
As with the mower technology, most of the floor-maintenance prior art approaches the task as a periodic one. T
Black Thomas G.
Diller Ramik & Wight
To Tuan C
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