Vehicle sensor monitoring system

• US 4,411,577 A
• Filed: 03/03/1981
• Issued: 10/25/1983
• Est. Priority Date: 03/07/1980
• Status: Expired due to Fees

• Current Assignee: Rapistan Division Lear Siegler Incorporated
• Original Assignee: Rapistan Division Lear Siegler Incorporated
• Inventors: Shearer, James T. Jr.
• Primary Examiner(s): Reeves, Robert B.
• Assistant Examiner(s): WACYRA, EDWARD MICHAEL
• Application Number:
  US06/240,172
• Time in Patent Office: 966 Days
• Field of Search: 414/273-275, 340/686, 340/679, 364/426, 364/478, 364/551, 364/552, 364/550, 371/25
• US Class Current: 414/274
• CPC Class Codes: B65G 1/0421 with control for stacker crane operations
• CPC Class Codes: B65G 2203/042 Sensors
• CPC Class Codes: G05D 1/0234 using optical markers or beacons optical beacons per se G01S1/70
• CPC Class Codes: G05D 1/0244 using reflecting strips
• CPC Class Codes: G05D 1/0259 using magnetic or electromagnetic means
• CPC Class Codes: G05D 1/0272 comprising means for registering the travel distance, e.g. revolutions of wheels measuring distance traversed on the ground by vehicles, e.g. using odometers G01C22/00

Abstract

In a system for controlling the horizontal and vertical alignment of a materials handling vehicle and for transferring articles to and from storage locations of a warehousing system in which several control sensors are positioned on the materials handling vehicle, a monitoring method and circuit for determing the operational status of the sensors by monitoring their status during a selected portion of a cycle of operation when their output is known. In one embodiment sensor outputs are cross checked against each other during a portion of an operating cycle in which the sensors outputs will be at a predetermined relationship to one another.

Claims

1. A system for checking the operation of one or more sensors used for controlling a vehicle employed for transferring articles into or out of storage locations of a warehousing system comprising:

first sensing means associated with the vehicle for providing signals employed in controlling the vehicle during a load transferring cycle of operation and which has a predictable operational status when detecting a predetermined condition normally encountered during a selected portion of each load transferring cycle of operation;

monitoring circuit means coupled to said first sensing means for determining the operational status of said first sensing means during said selected portion of each load transferring cycle of operation and for generating a fault control signal in the event the status of said first sensing means indicates that the predetermined condition is not sensed;

control circuit means coupled to said first sensing means and responsive to signals therefrom for providing vehicle controlling signals; and

second sensing means which provides a predetermined output signal during said selected portion of each load transferring cycle of operation and logic circuit means coupled to said first sensing means and to said second sensing means to provide a fault control signal in the event that the predictable operational status of said first sensing means does not occur in the desired relationship to said predetermined output signal from said second sensing means.

2. The system as defined in claim 1 wherein said vehicle includes load handling means extendable into and out of a storage location of the warehousing system for transferring articles between the vehicle and a storage location and wherein said first sensing means comprises an overhung load sensor for detecting the presence of an article extending laterally to a side of the vehicle an excessive amount, said overhung load sensor providing a predictable operational status when said load handling means are extended into a storage location.

3. The system as defined in claim 2 wherein said second sensing means comprises a switch which engages the frame forming the storage location when said load handling means are extended into the storage location to provide a predetermined output signal.

4. The system as defined in claim 1 wherein said vehicle includes load handling means extendable into and out of a storage location of the warehousing system for transferring articles between the vehicle and a storage location and wherein said first sensing means comprises a storage location full sensor for detecting the presence of an article in a storage location and employed for preventing the extension of a loaded load handling means into a full bin and wherein the operational status of said storage location full sensor is checked when picking an article from a storage location and therefore the storage location will have an article therein which actuates said storage location full sensor;

and

wherein said second sensing means comprises an article on-board sensor associated with said load handling means for detecting the presence of an article on said load handling means.

5. The system as defined in claim 1 wherein said vehicle includes load handling means extendable from side to side on said vehicle and means movably supporting said load handling means along a laterally extending track, said first and second sensing means comprises switch means located at opposite ends of said track for providing control signals indicating when said load handling means are at one side or the other of said vehicle during a load transferring function, and wherein only one of said switch means are actuated when said load handling means are centered for vehicle travel, and wherein said monitoring circuit means determines that only one of said switch means are actuated during vehicle motion.

6. The system as defined in claim 1 in which said first and second sensing means comprises a pair of address reading sensors positioned on said vehicle in spaced relationship such that as the vehicle moves along an access aisle of the warehouse system each sensor will successively detect an address indicia associated with the warehouse storage locations and wherein said monitor circuit is coupled to said address sensors to determine if both sensors simultaneously detect an address indicia and provide said fault control signal in the event of such detection.

7. The system as defined in claim 1 wherein said first and second sensing means comprise a plurality of sensors positioned on said vehicle to be actuated by actuators near the ends of access aisles in the warehousing system for controlling the vehicle speed near the aisle ends and wherein said monitoring circuit is coupled to each of said plurality of sensors to test for an abnormal combination of sensor states and provide a fault control signal in the event an abnormal combination is detected.

8. A method of testing the operation of a vehicle controlling sensor of a warehousing vehicle employed for transferring articles into and out of storage locations and providing a fault control signal output if an abnormal condition exists comprising:

monitoring the operational status of a pair of functionally related sensors against each other during a portion of each load transferring cycle in which each sensor has a predictable operational status with respect to the other sensor of the pair; and

providing a fault control output signal in response to sensor output signals not corresponding to the predictable outputs.

9. In a system for controlling the alignment of an article handling vehicle which traverses an access aisle of a storage system, a detection system which detects storage location address indicia on the framework defining the storage locations of the system comprising:

a pair of detectors positioned on the vehicle to successively scan address indicia spaced at pre-determined intervals of the storage system as the vehicle travels along an access aisle, said detectors spaced from one another a distance to assure that both detectors will not be simultaneously aligned with a pair of adjacent indicia; and

circuit means coupled to said detectors for providing a fault control signal in the event signals from said detectors indicate simultaneous alignment with indicia thereby indicating a system failure.

10. In a warehousing system in which a load handling vehicle travels along an access aisle which includes actuators along the aisle and vehicle sensors responsive to the actuators for limiting and controlling the speed of the vehicle as it approaches an aisle end, a safety circuit comprising:

monitor circuit means coupled to said sensors for monitoring the status of the vehicle sensors and for providing a fault control signal if an abnormal combination of sensor states exists;

vehicle control circuit means coupled to said monitor circuit means and responsive to the fault control signal to stop the vehicle upon receipt of said fault control signal; and

wherein said sensors include two detectors which detect forward and reverse vehicle intermediate speed actuators spaced a first predetermined distance from opposite ends of an aisle for slowing the vehicle as it approaches an aisle end.

11. The system as defined in claim 10 wherein said monitor circuit means provides a fault control signal in the event both of said intermediate speed detectors are actuated.

12. The system as defined in claim 11 wherein said sensors include an additional detector which detects vehicle creep speed actuators spaced a second predetermined distance from opposite ends of an aisle, said second predetermined distance being less than said first predetermined distance.

13. In a vehicle control system in which a speed tachometer is employed to control the speed of the vehicle, and a speed actuated safety switch is provided to provide a vehicle control signal in the event the vehicle is moving at an excessive speed near an aisle end of a warehousing system, a system for providing a test of the operational status of the speed actuated switch comprising:

a speed actuated switch set to change from a first state to a second state at a predetermined vehicle speed; and

a monitor circuit coupled to said speed switch and to said speed tachometer for testing the state of said speed switch when said tachometer indicates the vehicle is below and above said predetermined speed to ascertain whether or not said speed switch is in said first or second states respectively, and for providing a fault control signal for stopping said vehicle in the event the proper switch state is not detected.

14. A system for controlling the alignment of an article transporting vehicle with respect to storage locations of an article storage system comprising:

a storage structure for receiving and storing articles, said structure including a framework of vertical and horizontal support members defining an array of storage locations;

target means positioned at a predetermined location with respect to each storage location;

an article transporting vehicle including drive means for moving said vehicle to any of the storage locations in said storage structure, said vehicle including target sensing means having three detectors positioned in a triangular pattern and responsive to the alignment of said detectors with said target means to provide predetermined control signals therefrom;

at least one sensing means associated with the vehicle for providing signals employed in controlling the vehicle during a load transferring cycle of operation and which has a predictable operational status when detecting a predetermined condition normally encountered during a selected portion of each load transferring cycle of operation;

monitoring circuit means coupled to said at least one sensing means for determining the operational status of said at least one sensing means during said selected portion of each load transferring cycle of operation and for generating a fault control signal in the event the status of said at least one sensing means indicates that the predetermined condition is not sensed; and

control circuit means coupled to said target sensing means and to said at least one sensing means and responsive to said control signals therefrom to provide vehicle control signals applied to said drive means for actuating said drive means to position said vehicle in alignment with a storage location for the transfer of articles between said vehicle and said storage location.