Bridge weigh-in-motion system
First Claim
1. A self-operating apparatus for weighing a moving vehicle, comprising:
- a plurality of strain gauges adapted to be attached to existing bridge structures, each of said strain gauges adapted to sense strain sustained by said bridge structure when a vehicle passes thereover, and outputting an analog strain signal in response to said strain;
at least one pair of axle sensors, each of said axle sensors adapted to automatically sense a vehicle axle passing thereover and output an axle sense signal in response thereto;
means for converting said analog strain signal to a digital strain signal;
central processing circuitry adapted to (i) perform first computations on said axle sense signal to determine vehicle speed and vehicle axle spacing, and (ii) perform second computations on said digital strain signal and said axle sense signal to determine vehicle weight, said central processing circuitry further adapted to output results of said first and second computations;
random access memory circuitry directly accessible by a digital computer and adapted to receive and retain said results of said first and second computations;
means to supply power to said strain gauges, said axle sensors, said signal converting means, said central processing circuitry, and said random access memory circuitry; and
electrical interconnection means for electronically interconnecting said means to supply power, said strain gauges, said axle sensors, said signal converting means, said central processing circuitry and said random access memory circuitry.
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Accused Products
Abstract
An apparatus and method are provided for calculating the speed and weight of a vehicle as it passes over an existing bridge. The apparatus includes a number of strain gages attachable to existing bridge girders or support members each of which outputs an analog strain signal in response to strain sustained by the bridge when a vehicle passes thereover. An analog front end circuit card amplifies the analog strain signal and converts it into digital format. A pair of axle sensors installed in or on the pavement before the bridge each output an axle sense signal in response to a vehicle axle passing thereover. A central processing unit receives the axle sense signals and the digitally formatted strain signals and performs calculations necessary to determine vehicle speed and weight. A static random access memory card is used to retain the results of these calculations for retrieval at a later time. A power supply provides electrical power to the system components. The method comprises the steps of providing axle sense signals generated by a pair of axle sensors in response to a vehicle passing thereover, providing an analog strain signal generated by a strain gage attached to a bridge structure, converting the analog strain signal to digital format, determining the vehicle speed and axle spacings, relating the position of every axle on the bridge to the strain record, and calculating axle weights using a least squares error minimization algorithm.
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Citations
26 Claims
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1. A self-operating apparatus for weighing a moving vehicle, comprising:
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a plurality of strain gauges adapted to be attached to existing bridge structures, each of said strain gauges adapted to sense strain sustained by said bridge structure when a vehicle passes thereover, and outputting an analog strain signal in response to said strain; at least one pair of axle sensors, each of said axle sensors adapted to automatically sense a vehicle axle passing thereover and output an axle sense signal in response thereto; means for converting said analog strain signal to a digital strain signal; central processing circuitry adapted to (i) perform first computations on said axle sense signal to determine vehicle speed and vehicle axle spacing, and (ii) perform second computations on said digital strain signal and said axle sense signal to determine vehicle weight, said central processing circuitry further adapted to output results of said first and second computations; random access memory circuitry directly accessible by a digital computer and adapted to receive and retain said results of said first and second computations; means to supply power to said strain gauges, said axle sensors, said signal converting means, said central processing circuitry, and said random access memory circuitry; and electrical interconnection means for electronically interconnecting said means to supply power, said strain gauges, said axle sensors, said signal converting means, said central processing circuitry and said random access memory circuitry. - View Dependent Claims (2, 3, 4, 5, 12)
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6. A self-operating apparatus for weighting a moving vehicle, comprising:
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a plurality of strain gauges adapted to be attached to existing bridge structures, each of said strain gauges adapted to sense the strain sustained by said bridge structure when a vehicle passes thereover, and outputting an analog strain signal in response to said strain; at least one pair of axle sensors, each of said axle sensors in said pair of axle sensors being positioned with a predetermined distance between each axle sensor in said pair of axle sensors and being adapted to automatically sense a vehicle axle passing thereover and output axle sense signals in response thereto; analog front end circuitry adapted to receive and amplify a plurality of analog strain signals, convert said analog strain signals to digital strain signals, using conversion means, and output said digital strain signals; central processing circuitry adapted to receive said digital strain signals and said axle sense signals, perform first computations on said axle sense signals to determine vehicle speed and vehicle axle spacing, perform second computations on said digital strain signals and said axle sense signals to determine vehicle weight, and output results of said first and second computations; random access memory circuitry adapted to receive and retain said results of said first and second computations, said random access memory circuitry directly accessible by a digital computer; an electrical power supply adapted to supply power to said strain gages, said axle sensors, said analog front end circuitry, said central processing circuitry, and said random access memory circuitry; and electrical interconnection means adapted to electrically interconnect said electrical power supply, said strain gauges, said axle sensors, said analog front end circuitry, said central processing circuitry, and said random access memory circuitry. - View Dependent Claims (7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A method of weighing a vehicle in motion using a digital computer controlled by a microprocessor operating at a clock rate, comprising the steps of:
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attaching at least one strain gage to an existing bridge structure spanning two sections of roadway, said strain gauge adapted to sense strain sustained by said structure when a vehicle passes thereover and output a strain signal in response thereto; placing at least one pair of axle sensors on or in one of said two sections of roadway before said bridge, each axle sensor in said pair of axles sensors being positioned with a predetermined distance between each axle sensor in said pair of axle sensors, and being adapted to automatically sense a vehicle axle passing thereover and output an axle sense signal in response thereto; providing said microprocessor with data including said predetermined distance between axle sensors, said axle sense signal and said strain signal; performing first calculations with he microprocessor using said axle sense signal and said predetermined distance between axle sensors to determine a vehicle velocity and vehicle axle spacings and output first results of said first calculations; storing said first results in a semiconductor memory device which is directly accessible by a digital computer; performing second calculations with the microprocessor using said strain signal and said axle sense signal to relate a position of very vehicle axle on the bridge to said strain signal and thereby determine an individual weight carried by each individual axle of said vehicle and output second results of said second calculations; determining a gross vehicle weight by summing said individual weights; and storing said second results and said gross vehicle weight in said semiconductor memory device. - View Dependent Claims (24, 25, 26)
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Specification