Autonomous lawnmower

A guidance apparatus for a semi-autonomous or autonomous vehicle, the guidance apparatus comprising:

• a plurality of rotatable contact members on a rotating shaft;
• a plurality of slip clutches, each slip clutch associated with a contact member coupling said shaft to said contact member in rotating engagement;
• a sensor configured to detect a boundary by detecting impeded rotation of said rotatable contact members relative to said rotating shaft due to slippage of one or more of said slip clutches in response to contact with a relatively higher surface, but not contact with a relatively lower surface, without stoppage of the said rotating shaft;
• and
• a controller configured to produce one or more guidance signals to steer said semi-autonomous or autonomous vehicle along said boundary detected by said sensor.

A semi-autonomous or autonomous mowing vehicle having a body and at least one cutting blade under said body, the mowing vehicle comprising:

• a plurality of rotatable contact members on a rotating shaft;
• a plurality of slip clutches, each slip clutch associated with one of said rotatable contact members, thereby coupling said shaft to a contact member in rotating engagement;
• a sensor configured to detect impeded rotation of said rotatable contact members relative to said rotating shaft due to slippage of said clutches in response to contact with a first, relatively higher surface, but not contact with a second, relatively lower surface without stoppage of the rotating shaft;
• and
• a controller configured to produce one or more guidance signals to steer said mowing vehicle along said boundary.

A method for controlling steering of a vehicle having at least one cutting blade for mowing a field, the method comprising:

• measuring, with distance sensors, wherein said sensors are infrared, ultrasonic, capacitance, microwave, or vision, spaced closely together with no moving components that are fixed in a physical orientation with respect to the vehicle, a plurality of vertical distances directly above the vegetation to an approximate top of vegetation in the field so as to result in a respective plurality of measured distances,
• wherein the plurality of vertical distances comprise a first vertical distance to a relatively higher top level of the vegetation and a second vertical distance to a relatively lower top level of the vegetation, wherein the relatively higher top level is associated with un-mowed vegetation, and the relatively lower top level is associated with mowed vegetation, and
• wherein the plurality of measured distances are measured at points having known relative positions in a direction that is transverse to the direction of the distances and also generally transverse to a direction in which the vehicle is configured to move across the field during mowing,
• wherein measuring the plurality of vertical distances is accomplished without contacting the vegetation and comprises transmitting a respective plurality of distance-measuring signals and estimating respective distances based on processing of the distance-measuring signals;
• determining, based on the plurality of distances and the known relative positions of the points of distance measurement, an approximate boundary without movement of the vehicle between mowed vegetation and unmowed vegetation;
• and
• controlling said vehicle to steer said vehicle based on said boundary.