Photodetector system for detecting obstacles in aisles between mobile shelving carriages
First Claim
1. A self-calibrating photodetector protection system comprising:
- a radiation beam transmitter having an input for electric driving pulses and operative to project a beam of radiation pulses corresponding substantially in width to the width of the driving pulses,a radiation receiver spaced from the transmitter and arranged for receiving the pulsed radiation beam, the receiver having an output and is adapted to respond to receiving radiation pulses of a minimum width and greater than a minimum width by issuing from its output electric pulses corresponding substantially to the width of the received radiation pulses,a digital processor having an electric pulse output coupled to the input of the transmitter and having an input coupled to the output of the receiver,the processor responding to an initializing signal by functioning in a calibration mode wherein the processor is operative to output a series of electric pulses to the input of the transmitter, the first corresponding radiation pulse output in the series by a properly operative transmitter having a preset minimum width and following pulses having successively greater widths up to a predetermined limit to determine the least pulse width in the series that has sufficient width to exceed the pulse width sensitivity threshold of the receiver, which if exceeded, will cause a properly operating receiver to output an electric pulse signal to said input of the processor, said processor having an output and responding to said input of electric pulses by changing the logic level voltage state of said last named output.
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Accused Products
Abstract
Obstacles are protected against collision in aisles adjacent mobile storage units with an IR transmitter mounted in spaced apart relation to an IR receiver on a unit. For initializing and calibrating the system a microcomputer controls the transmitter to emit IR pulses of increasing width at a uniform repetition rate. If there is no defect in the system the receiver responds with output electric pulses after the IR pulse width is reached that has the minimum integrated energy to exceed the input signal threshold of the receiver. The minimum energy pulse width is stored in the microcomputer and the system switches to a run mode allowing storage units to move when commanded. The computer responds to the absence of returned pulses from the receiver by inhibiting the system so the mobile unit will not run. If returned pulses are not in the proper phase relationship the system goes into a diagnostic mode wherein the interval between transmitted IR pulses is reduced in increments for reasons including determining if there may only be temporary ambient IR interference. If the problem does not clear up by the time the interval is reduced to one-half normal interval the system locks out.
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Citations
18 Claims
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1. A self-calibrating photodetector protection system comprising:
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a radiation beam transmitter having an input for electric driving pulses and operative to project a beam of radiation pulses corresponding substantially in width to the width of the driving pulses, a radiation receiver spaced from the transmitter and arranged for receiving the pulsed radiation beam, the receiver having an output and is adapted to respond to receiving radiation pulses of a minimum width and greater than a minimum width by issuing from its output electric pulses corresponding substantially to the width of the received radiation pulses, a digital processor having an electric pulse output coupled to the input of the transmitter and having an input coupled to the output of the receiver, the processor responding to an initializing signal by functioning in a calibration mode wherein the processor is operative to output a series of electric pulses to the input of the transmitter, the first corresponding radiation pulse output in the series by a properly operative transmitter having a preset minimum width and following pulses having successively greater widths up to a predetermined limit to determine the least pulse width in the series that has sufficient width to exceed the pulse width sensitivity threshold of the receiver, which if exceeded, will cause a properly operating receiver to output an electric pulse signal to said input of the processor, said processor having an output and responding to said input of electric pulses by changing the logic level voltage state of said last named output. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. Mobile storage apparatus and a self calibrating photoelectric protective system therefor, comprising:
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at least one movable unit movable in at least one direction and comprised of a carriage having wheels and a storage structure mounted to the carriage, an electric motor mounted to the carriage and operatively coupled to the wheels for moving the movable unit, a transmitter of an infrared radiation beam mounted to said movable unit and a receiver of said beam mounted to said unit in spaced relation to the transmitter to provide for preventing the unit from moving when the beam is interrupted, the transmitter having an input for electric pulse signals and is adapted for emitting a beam of infrared radiation pulses having a pulse width or duration corresponding substantially to the width or duration of the input electric pulse signals, the receiver having an input for the infrared radiation pulses and an output for electric pulse signals, the receiver is adapted to output electric pulse signals corresponding substantially to the width or duration of the input infrared radiation pulses provided the input infrared radiation pulses have sufficient width to equal or exceed the sensitivity threshold of the receiver, a digital processor having a plurality of inputs and outputs including an electric pulse output coupled to said input of the infrared beam transmitter and having an input coupled to the electric pulse output of the receiver, the processor responding to an initializing signal by functioning in a calibration mode wherein the processor is operative to output a series of electric pulse signals to the input of the transmitter, the first corresponding infrared radiation output pulse from a properly operating transmitter having a preset minimum width and following pulses having successively greater widths to determine the pulse width in the series that has at least sufficient width to exceed the pulse width sensitivity threshold of the receiver, which if exceeded, causes a properly operating receiver to output an electric pulse signal to said input of the processor, the processor responding to receiving the electric pulse signal by providing control signals at an output of the processor, a motor controller aboard said movable storage unit having input means, said motor controller responding to input of a signal representative of a control signal from the processor by becoming enabled to energize said motor for moving the mobile unit. - View Dependent Claims (10, 11, 12, 13)
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14. A method of preventing a motor driven carriage from colliding with a person or object, comprising:
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having an infrared (IR) beam pulse transmitter and an IR pulse receiver mounted on the carriage with the transmitter aimed at the receiver, initiating a calibration mode by generating under control of a computer electric pulses at constant periodicity but successively increasing width and applying the electric pulses to the transmitter to cause it to project IR pulses having corresponding periodicity and width to identify the minimum IR pulse width that has sufficient energy to evoke a first corresponding electric pulse output from the IR receiver, storing in memory data representative of the width of the minimum pulse if one is identified and switching to a run mode wherein electric signals are produced under control of the computer for enabling the motor to be energized, continuing to project said pulses of minimum width to maintain the run mode. - View Dependent Claims (15, 16, 17, 18)
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Specification