US4790402A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automated guided vehicle
Assignee: Tennant Co
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Filing: 1987-09-28
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Granted: 1988-12-13
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Expires: 2007-09-28
Abstract
Abstract An unmanned, self-propelled vehicle in the nature of a mobile robot has an on-board computer that stores path and machine function instructions and activates the drive and steering systems so as to cause the machine to follow a desired path. A plurality of retroreflectve targets are mounted along the desired path. They do not have to be mounted at a specific height or distance apart, nor need they be square to the path. An improved guidance system for keeping the vehicle on the prescribed path includes a laterally scanning laser transmitter-receiver mounted on the vehicle. An electromechanical tracking device controls the angle of elevation of the laser beam so as to keep it aimed at each target successively as the vehicle moves. The laser produces signals which steer the vehicle such that the laser transmitter and targets are kept aligned in a vertical plane. A positioning device can move the laser transmitter transversely on the vehicle so that the vehicle centerline may travel in the vertical plane of the laser or may travel in an offset line parallel to the vertical laser plane. Certain ones of the targets are bar coded and a target counter senses and counts them as the machine moves past them to keep track of where the vehicle is located along its desired path. A motion sensing system using reflective microwave sensors provides speed and distance information.
Inventors
- 👤 Bruce F. Field
- 👤 Joseph G. Kasper
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 04:50
CPC Classifications
G; G01; G01S; G01S17/00; G01S17/88; G01S17/93; G01S17/931; G05; G05D; G05D1/00; G05D1/02; G05D1/021; G05D1/0231; G05D1/0238; G05D1/0244
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
183 words
In an automated guided vehicle having a frame, drive means mounted on the frame for propelling the vehicle, and steering means associated with the frame for controlling the vehicle's direction of travel, an improved guidance system for controlling the drive means and steering means so as to guide the vehicle along a desired predetermined path, the guidance system comprising: a plurality of spaced retroreflective targets mounted in a sequential manner along the desired path; sighting means mounted on the vehicle including transmitting means for emitting a light beam and receiving means for detecting said emitted light beam reflected from one of said targets and defining a target-in-view signal when such light is detected; tracking means on the vehicle for controlling the angle of elevation of the transmitted light beam, with reference to a horizontal plane, so as to maintain a target-in-view signal substantially continuously as the vehicle moves by automatically tracking said targets in a sequential manner; and control means responsive to the sighting means for activating the drive means or steering means so as to keep the vehicle on the desired path.
Claim 2
Dependent Claim
183 words
In an automated guided vehicle having a frame, drive means mounted on the frame for propelling the vehicle, and steering means associated with the frame for controlling the vehicle's direction of travel, an improved guidance system for controlling the drive means and steering means so as to guide the vehicle along a desired predetermined path, the guidance system comprising: a plurality of spaced retroreflective targets mounted in a sequential manner along the desired path; sighting means mounted on the vehicle including transmitting means for emitting a light beam and receiving means for detecting said emitted light beam reflected from one of said targets and defining a target-in-view signal when such light is detected; tracking means on the vehicle for controlling the angle of elevation of the transmitted light beam, with reference to a horizontal plane, so as to maintain a target-in-view signal substantially continuously as the vehicle moves by automatically tracking said targets in a sequential manner; and control means responsive to the sighting means for activating the drive means or steering means so as to keep the vehicle on the desired path.
Claim 3
Dependent Claim
65 words
The vehicle of claim 1 wherein the receiving means detects the direction from which reflected light is received and the sighting means defines a reference line, compares the detected light direction to the reference line to determine a heading error angle, and sends signals to the control means which activates the drive or steering means so as to reduce the heading error angle to zero.
Claim 4
Dependent Claim
28 words
The vehicle of claim 2 wherein the sighting means is mounted on the vehicle frame such that the reference line is parallel to the vehicle's longitudinal center line.
Claim 5
Dependent Claim
17 words
The vehicle of claim 1 wherein the targets are mounted at non-specific elevations along the desired path.
Claim 6
Dependent Claim
25 words
The vehicle of claim 1 wherein the transmitting means further comprises a beam sweeping means for moving the transmitted light beam in a scanning plane.
Claim 7
Dependent Claim
23 words
The vehicle of claim 5 wherein the beam sweeping means moves the transmitted light beam through a scanning angle less than 180 degrees.
Claim 8
Dependent Claim
70 words
The vehicle of claim 6 wherein the receiving means detects the direction from which reflected light is received and the sighting means defines a reference line as the bisector of the scanning angle, compares the detected light direction to the reference line to determine a heading error angle, and signals the control means which activates the drive or steering means so as to reduce the heading error angle to zero.
Claim 9
Dependent Claim
12 words
The vehicle of claim 7 wherein the scanning angle is 90 degrees.
Claim 10
Dependent Claim
21 words
The vehicle of claim 1 further comprising positioning means for moving the sighting means laterally of the vehicle's longitudinal center line.
Claim 11
Dependent Claim
63 words
The vehicle of claim 9 wherein the transmitting means is pivotally mounted on the positioning means about a horizontal axis perpendicular to the vehicle's longitudinal center line, and the tracking means comprises an actuator connected between the positioning means and transmitting means, responsive to the receiving means to pivot the transmitting means as required to maintain a target-in-view signal as the vehicle moves.
Claim 12
Dependent Claim
61 words
The vehicle of claim 1 wherein the transmitting means is pivotally connected to the frame about a horizontal axis perpendicular to the vehicle's longitudinal center line, and the tracking means comprises an actuator connected between the frame and transmitting means, responsive to the receiving means to pivot the transmitting means as required to maintain a target-in-view signal as the vehicle moves.
Claim 13
Dependent Claim
14 words
The vehicle of claim 11 wherein the actuator is operable at two different speeds.
Claim 14
Dependent Claim
13 words
The vehicle of claim 11 wherein the actuator includes an electronic dynamic brake.
Claim 15
Dependent Claim
22 words
The vehicle of claim 11 wherein the tracking means further comprises means defining upper and lower limits for the angle of elevation.
Claim 16
Dependent Claim
18 words
The vehicle of claim 14 wherein the means for defining the upper and lower limits are proximity switches.
Claim 17
Dependent Claim
166 words
In an automated guided vehicle having a frame, drive means mounted on the frame for propelling the vehicle, and steering means associated with the frame for controlling the vehicle's direction of travel, an improved method of controlling the drive means and steering means so as to guide the vehicle along a desired predetermined path, the method comprising the steps of: placing a plurality of spaced retroreflective targets in a sequential manner along the desired path; transmitting a light beam from the vehicle; detecting at the vehicle transmitted light reflected from one of said targets and defining a target-in-view signal when such light is detected; controlling the angle of elevation of the transmitted light beam, with reference to a horizontal plane, so as to maintain a target-in-view signal substantially continuously as the vehicle moves by automatically tracking said targets in a sequential manner; and activating the drive means or steering means in response to detected light signals so as to keep the vehicle on the desired path.
Claim 18
Dependent Claim
166 words
In an automated guided vehicle having a frame, drive means mounted on the frame for propelling the vehicle, and steering means associated with the frame for controlling the vehicle's direction of travel, an improved method of controlling the drive means and steering means so as to guide the vehicle along a desired predetermined path, the method comprising the steps of: placing a plurality of spaced retroreflective targets in a sequential manner along the desired path; transmitting a light beam from the vehicle; detecting at the vehicle transmitted light reflected from one of said targets and defining a target-in-view signal when such light is detected; controlling the angle of elevation of the transmitted light beam, with reference to a horizontal plane, so as to maintain a target-in-view signal substantially continuously as the vehicle moves by automatically tracking said targets in a sequential manner; and activating the drive means or steering means in response to detected light signals so as to keep the vehicle on the desired path.
Claim 19
Dependent Claim
55 words
The method of claim 16 further comprising the steps of detecting the direction from which reflected light is received, defining a reference line, comparing the detected light direction to the reference line to determine a heading error angle, and activating the drive or steering means so as to reduce the heading error angle to zero.
Claim 20
Dependent Claim
19 words
The method of claim 16 further comprising the step of sweeping the transmitted light beam in a scanning plane.
Claim 21
Dependent Claim
14 words
The method of claim 18 wherein the scanning angle is less than 180 degrees.
Claim 22
Dependent Claim
70 words
The method of claim 19 further comprising the steps of detecting the direction from which reflected light is received, defining a reference line through the optical center of the transmitter and parallel to the longitudinal axis of the vehicle, comparing the detected light direction to the reference line, determining a heading error angle, and activating the drive or steering means so as to reduce the heading error angle to zero.
Claim 23
Dependent Claim
12 words
The method of claim 20 wherein the scanning angle is 90 degrees.
Claim 24
Dependent Claim
26 words
The method of claim 20 further comprising the step of laterally moving the location on the venicle from which the light beam is transmitted and detected.
Claim 25
Dependent Claim
20 words
The method of claim 16 further characterized in that the targets are placed at non-specific elevations along the desired path.
Claim 26
Dependent Claim
75 words
The method of claim 16 wherein the step of controlling the angle of elevation is further characterized in that when the target-in-view signal is lost the angle of elevation is corrected so as to regain the target-in-view signal by increasing the angle if the vehicle is moving forwardly at the time the signal loss occurs and by decreasing the angle of elevation if the vehicle is moving backwardly at the time of the signal loss.
Claim 27
Dependent Claim
59 words
The method of claim 24 further including the steps of defining upper and lower limits for the angle of elevation, releasing tracking of a first target when one of the limits is exceeded and searching for a second target by changing the angle of elevation in the sense opposite the angle correction which produced the overreaching of the limit.
Claim 28
Dependent Claim
63 words
The method of claim 24 further comprising the steps of defining upper and lower limits for the angle of elevation, releasing tracking of a first target when one of the limits is exceeded and searching for a second target by changing the angle of elevation at a rate higher than that used when changing the angle of elevation under a lost target-in-view condition.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-12-13 | 1992-06-13 | 1992-12-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-12-13 | 1996-06-13 | 1996-12-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-12-13 | 2000-06-13 | 2000-12-13 | $7700.00 | Window Closed / Lapsed |