Offsetting the course of a laser guided vehicle

• US 5,020,620 A
• Filed: 09/28/1989
• Issued: 06/04/1991
• Est. Priority Date: 09/28/1989
• Status: Expired due to Fees

• Current Assignee: Tennant Company
• Original Assignee: Tennant Company
• Inventors: Field, Bruce F.
• Primary Examiner(s): Mitchell, David M.
• Application Number:
  US07/413,631
• Time in Patent Office: 614 Days
• Field of Search: 180/167, 180/168, 180/169, 318/587, 356/141, 364/424.02, 250/221
• US Class Current: 180/169
• CPC Class Codes: G01S 17/06 Systems determining position data of a target
• CPC Class Codes: G05D 1/0231 using optical position detecting means position-fixing by using electromagnetic waves other than radio waves, e.g. optical position detecting means G01S5/16
• CPC Class Codes: G05D 1/0234 using optical markers or beacons optical beacons per se G01S1/70
• CPC Class Codes: G05D 1/024 in combination with a laser lasers per se H01S
• CPC Class Codes: G05D 1/0244 using reflecting strips

Abstract

This is an improved apparatus and method for guiding an automated guided vehicle, particularly a floor maintenance machine. This invention discloses electronic means which permit guiding the vehicle toward a point that is laterally offset a desired distance from a retroreflective target, generally in front of the machine, by reference to that target. A series of targets may be sequentially referenced in this manner. A floor area of extended width relative to the width of the machine can be treated by causing the machine to traverse the floor area in a series of passes from one end of the area to the other. The machine is guided during each pass by reference to each one in turn of a series of retroreflective targets located generally ahead of it, and maintains a selected lateral offset from each target. Changing the offset distance during successive passes allows treatment of the area while guiding off a single series of targets.

Claims

1. A method of automatically guiding a floor maintenance machine so as to treat a floor area of extended width relative to the machine width, comprising the steps of:

placing a plurality of retroreflective targets at nonspecific distances in a row relative to the floor area to be treated;

causing the floor maintenance machine to traverse the floor area in a pass from one end of the floor area to the other;

guiding the machine during the pass with reference to each target successively to maintain a predetermined offset distance from the row of targets; and

successively changing the predetermined offset distance after completion of at least one pass so as to make the offset distance either more or less than the width of the machine, and;

making additional passes at the successive offset distance until the enter floor area has been treated.

2. The method of claim 1 further including the steps of turning the machine around at the end of a pass and changing the offset distance an amount substantially equal to the width of the machine'"'"'s floor treating apparatus.

3. The method of claim 1 further characterized in that there is only a single row of targets in a given direction.

4. The method of claim 1 further comprising the step of changing the predetermined offset distance from time to time during a pass so that the vehicle may move by or around a fixed obstacle in its path.

5. The method of claim 1 further including the steps of placing a marker target to define the end of a pass and sensing the arrival of the machine at a marker target.

6. The method of claim 1 further characterized in that the floor maintenance machine includes a light source thereon located in the vertical plane containing the longitudinal centerline of the machine and including the steps of:

placing the retroreflective targets in successive locations offset a desired distance from each of the desired passes, the targets being located higher than the light source;

traversing a light beam from said light source through a scanning plane;

controlling the angle of elevation of the scanning plane such that the scanning plane substantially continuously intersects one of the targets to maintain a target in view;

sensing the actual angle in the scanning plane between the vertical plane containing the longitudinal axis of the machine and a light beam from the light source to the target in view;

sensing the range from the light source to the target in view;

using the desired offset distance and the sensed range from the light source to the target in view to determine the desired angle in the scanning plane between the vertical plane containing the longitudinal axis of the machine and a light beam from the light source to the target in view;

steering the machine such that the actual angle equals the desired angle; and

repeating this procedure with each target successively during the execution of each pass until the entire floor area has been treated.

7. The method of claim 6 further characterized in that there is only a single row of targets.

8. A method for controlling an automated guided vehicle such that the vehicle travels along a desired path, comprising the steps of:

placing a light source on the vehicle;

placing a plurality of retroreflective targets laterally offset a desired distance from the desired path, the targets being located higher than the light source;

traversing a light beam from the light source through a scanning plane;

controlling the angle of elevation of the scanning plane such that the scanning plane substantially continuously intersects one of the targets to maintain a target in view;

sensing the actual angle in the scanning plane between a reference line in the scanning plane passing through the light source parallel to or in the vertical plane containing the longitudinal centerline of the vehicle and a light beam from the light source to the target in view;

sensing the range from the light source to the target in view;

using the desired offset distance and the sensed range of the target in view to determine the desired angle in the scanning plane between the reference line and a light beam from the light source to the target in view;

comparing the actual angle with the desired angle; and

steering the machine such that, at any given time, the actual angle equals the desired angle.

9. The method of claim 8 wherein the step of placing a light source on the vehicle is characterized by locating said light source in the vertical plane of the longitudinal centerline of the vehicle.

10. A guidance system for an automated guided vehicle, comprising sensing means on the vehicle for emitting a light beam and traversing the light beam through a scanning plane, a plurality of spaced retroreflective targets arranged in successive locations and placed higher than the height of the sensing means, tracking means for controlling the angle of elevation of tho scanning plane such that the scanning plane substantially continuously intersects one of the targets to maintain a target in view, the sensing means including means for repeatedly detecting light reflected from the target in view and providing successive signals representing the changing range from the sensor to the target and the changing angle in the scanning plane between the vertical plane containing the longitudinal axis of the vehicle and a light beam from the sensor to the target in view, and means for utilizing the range and angle signals to provide a steering signal to maintain vehicle movement along a path which is a desired offset distance from each of the targets in succession.

11. The guidance system of claim 10 wherein said plurality of targets includes first targets of a first width which will cause the sensing means to provide a first signal representing the range from the sensor to the target and produce a corresponding steering signal, and at least one second target of a second width which will produce a correspondingly different range signal and cause a correspondingly different steering signal.