Constant low-flow air source control system and method
First Claim
1. A person-support apparatus comprisingan inflatable support structure,a variable output pump in fluid communication with the inflatable support structure, wherein the variable output pump provides a flow of fluid to the inflatable support structure, anda controller coupled to the variable output pump, the controller including a circuit having an output for controlling the output of the pump, a processor in electrical communication with the circuit and operable to vary an output of the circuit, a memory device including instructions, that when executed by the processor, cause the processor to control the circuit to vary the output of the pump to maintain a constant flow from the pump,wherein the person-support apparatus further comprises a first sensor operable to sense a pressure in the inflatable support structure and to communicate a signal indicative of the pressure in the inflatable support structure to the processor,wherein the processor includes instructions that, when executed by the processor, control the output of the pump by using the time rate of change of pressure in the inflatable support structure to determine an error term, calculate an integral term of a proportion integral control based on the error term, calculate a proportional term of a proportional integral control based on the error term, adjust the gain of the integral term if the error term has a magnitude less than a threshold, and vary the output of the pump based on the proportional integral value.
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Accused Products
Abstract
A constant low-flow air source control system and method is used to operate a pump to inflate an inflatable support structure used to support a person.
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Citations
21 Claims
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1. A person-support apparatus comprising
an inflatable support structure, a variable output pump in fluid communication with the inflatable support structure, wherein the variable output pump provides a flow of fluid to the inflatable support structure, and a controller coupled to the variable output pump, the controller including a circuit having an output for controlling the output of the pump, a processor in electrical communication with the circuit and operable to vary an output of the circuit, a memory device including instructions, that when executed by the processor, cause the processor to control the circuit to vary the output of the pump to maintain a constant flow from the pump, wherein the person-support apparatus further comprises a first sensor operable to sense a pressure in the inflatable support structure and to communicate a signal indicative of the pressure in the inflatable support structure to the processor, wherein the processor includes instructions that, when executed by the processor, control the output of the pump by using the time rate of change of pressure in the inflatable support structure to determine an error term, calculate an integral term of a proportion integral control based on the error term, calculate a proportional term of a proportional integral control based on the error term, adjust the gain of the integral term if the error term has a magnitude less than a threshold, and vary the output of the pump based on the proportional integral value.
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9. A person support apparatus comprising
an inflatable support structure, a variable output pump including an outlet in fluid communication with the inflatable support structure, a first sensor providing a signal indicative of a pressure in the inflatable support structure, a second sensor providing a signal indicative of a pressure at an outlet of the pump, and a controller operable to compare the signal from the first sensor and the signal from the second sensor to vary the output of the pump to maintain a constant flow from the pump, wherein the controller utilizes a proportional-integral-derivative control routine to vary the output of the pump, wherein an integral term of the proportional integral controller is divided by an integral gain factor if the error in the system is within a predetermined tolerance range.
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14. A person support apparatus comprising
an inflatable support structure, a variable output pump including an outlet in fluid communication with the inflatable support structure, the variable output pump including a driver responsive to a drive signal, a first sensor providing a signal indicative of a pressure in the inflatable support structure, a second sensor providing a signal indicative of a pressure at an outlet of the pump, and a processor operable to provide the drive signal to vary an output of the variable output pump, a memory device including instructions, that when executed by the processor, cause the processor to compare the pressure signal from the first sensor and the pressure signal from the second sensor to determine a pressure gradient and vary the drive signal to maintain a constant flow from the pump, wherein the variable output pump is a variable displacement pump.
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18. A person-support apparatus comprising
an inflatable support structure, a variable displacement pump in fluid communication with the inflatable support structure, wherein the variable displacement pump provides a flow of fluid to the inflatable support structure, a controller coupled to the variable displacement pump, the controller including a circuit having an output for controlling the output of the pump, a processor in electrical communication with the circuit and operable to vary an output of the circuit, a memory device including instructions, that when executed by the processor, cause the processor to control the circuit to vary the output of the pump to maintain a constant flow from the pump.
Specification