High speed robotic weighing system
First Claim
Patent Images
1. A system for weighing items while they are moving, the system comprising:
- a scale conveyor (400) disposed adjacent to an infeed conveyor and arranged to receive a parcel (410) from the infeed conveyor, the scale conveyor including a drive axle (412);
a servo motor (430) having a shaft (436);
a servo drive system coupled to the server motor to drive the motor responsive to a command velocity input signal;
a motor mount (440) arranged for connecting the servo motor shaft to the drive axle (412) of the scale conveyor, the motor mount comprising a viscous rotary damper, a rotary spring and a shaft coupler, so as to connect the servo motor shaft (436) to the drive axle (412) by way of the rotary damper viscosity;
a velocity encoder (450) coupled to the scale conveyor to generate velocity signals during operation responsive to velocity of the scale conveyor; and
a processor configured tomonitor at least one of (a) a frequency of oscillation and (b) a phase response to detect a variation;
responsive to detecting the variation, analyzing the variation of frequency of oscillation and or the phase response; and
infer a mass of the parcel on the scale conveyor based on the analysis.
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Abstract
This disclosure pertains to weighing a physical item while it is moving in a servo-driven conveyor system for e-commerce, logistics, manufacturing and other applications. The introduction of an unknown mass to an electro-mechanical feedback or filter network controlling a conveyance system will modify the steady state behavior of that system in such a way that measuring the phase or frequency shift of an input signal or oscillation will enable us to infer the magnitude of that mass.
164 Citations
18 Claims
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1. A system for weighing items while they are moving, the system comprising:
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a scale conveyor (400) disposed adjacent to an infeed conveyor and arranged to receive a parcel (410) from the infeed conveyor, the scale conveyor including a drive axle (412); a servo motor (430) having a shaft (436); a servo drive system coupled to the server motor to drive the motor responsive to a command velocity input signal; a motor mount (440) arranged for connecting the servo motor shaft to the drive axle (412) of the scale conveyor, the motor mount comprising a viscous rotary damper, a rotary spring and a shaft coupler, so as to connect the servo motor shaft (436) to the drive axle (412) by way of the rotary damper viscosity; a velocity encoder (450) coupled to the scale conveyor to generate velocity signals during operation responsive to velocity of the scale conveyor; and a processor configured to monitor at least one of (a) a frequency of oscillation and (b) a phase response to detect a variation; responsive to detecting the variation, analyzing the variation of frequency of oscillation and or the phase response; and infer a mass of the parcel on the scale conveyor based on the analysis. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of weighing a parcel comprising the steps of:
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providing a mechanical conveyor having a drive shaft for moving the parcel; providing a servo motor having a motor shaft for driving the conveyor; coupling the servo motor shaft to the conveyor drive shaft by means of a viscous damper; providing a servo system for driving the servo motor, and arranging the servo system to drive the motor responsive to a time-varying velocity command input signal; providing a motor shaft encoder coupled to the servo motor shaft to generate motor velocity signals; providing a velocity encoder coupled to the conveyor to generate conveyor velocity signals; driving the conveyor responsive to the time-varying velocity command input signal; receiving the parcel onto the moving conveyor; and determining a mass of the parcel based on a phase angle between the motor velocity signals and the conveyor velocity signals. - View Dependent Claims (11, 12, 13, 14, 15)
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16. A method of weighing a parcel comprising the steps of:
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providing a mechanical conveyor having a drive shaft for moving the parcel; providing a servo motor having a motor shaft for driving the conveyor; coupling the servo motor shaft to the conveyor drive shaft by means of a viscous damper and a rotary spring; providing a servo system for driving the servo motor, and arranging the servo system to drive the motor responsive to a velocity command input signal, the input signal selected to drive the motor at a predetermined nominal constant velocity; providing a velocity encoder coupled to the conveyor to generate conveyor velocity signals; superimposing the conveyor velocity signals on to the velocity command input signal to so as to form a positive feedback loop that supports natural self-exciting oscillation, the feedback loop including a feedback network comprising the viscous damper, the rotary spring, and the conveyor, so that the feedback loop oscillates at a resonant frequency of the feedback network while the conveyor is unloaded; measuring the resonant frequency while the conveyor is unloaded; receiving a parcel onto the moving conveyor; and determining a mass of the parcel based measuring a change in the oscillation frequency relative to the unloaded state. - View Dependent Claims (17, 18)
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Specification