FLUID CONTROLLER AND A METHOD OF DETECTING AN ERROR IN A FLUID CONTROLLER
First Claim
1. A fluid controller operable to control a flow of a fluid from a source of pressurized fluid to a pressure operated device, the controller comprising:
- a housing defining an inlet port connected to the source and an outlet port connected to the pressure operated device, a valve member movable within the housing and cooperating therewith to provide the flow between the inlet port and the outlet port at a flow rate which depends on the position of the valve member relative to the housing, a processor providing a reference which is indicative of a desired position of the valve member relative to the housing an actuator adapted to move the valve member in accordance with a reference received from the processor, a sensor adapted to provide an output indicative of an obtained position of the valve member relative to the housing, an observer adapted, based on a reference, to determine a model output which is indicative of a theoretically correct position of the valve member relative to the housing, and to determine a residual value indicative of a difference between the output and the model output, and a fault detection system adapted to compare the residual value with a threshold value, wherein the fluid controller is adapted to provide a gradient of the reference and to scale the threshold value based on the gradient.
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Accused Products
Abstract
The invention provides a fluid controller for controlling a machine, e.g. for steering a vehicle. The controller comprises a housing defining an inlet port connected to the source and an outlet port connected to the pressure operated device. The flow rate is controlled by movement of a valve member within the housing, and a processor provides a reference which is indicative of a desired position of the valve member relative to the housing. The fluid controller comprises a fault detection system based on an observer. The observer calculates a theoretically correct position of the valve member relative to the housing for a given reference, and compares this position to an obtained position of the valve member relative to the housing. The difference between the positions is compared with a threshold value. In order to dynamically change the sensitivity of the system, the threshold value is scaled based on a gradient of the reference.
27 Citations
8 Claims
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1. A fluid controller operable to control a flow of a fluid from a source of pressurized fluid to a pressure operated device, the controller comprising:
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a housing defining an inlet port connected to the source and an outlet port connected to the pressure operated device, a valve member movable within the housing and cooperating therewith to provide the flow between the inlet port and the outlet port at a flow rate which depends on the position of the valve member relative to the housing, a processor providing a reference which is indicative of a desired position of the valve member relative to the housing an actuator adapted to move the valve member in accordance with a reference received from the processor, a sensor adapted to provide an output indicative of an obtained position of the valve member relative to the housing, an observer adapted, based on a reference, to determine a model output which is indicative of a theoretically correct position of the valve member relative to the housing, and to determine a residual value indicative of a difference between the output and the model output, and a fault detection system adapted to compare the residual value with a threshold value, wherein the fluid controller is adapted to provide a gradient of the reference and to scale the threshold value based on the gradient. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An error detection method for a fluid controller of the kind comprising:
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a housing defining an inlet port connected to a source of pressurised fluid and an outlet port connected to a pressure operated device, a valve member movable within the housing and cooperating therewith to provide a flow between the inlet port and the outlet port at a flow rate which depends on the position of the valve member relative to the housing, an actuator adapted to move the valve member in accordance with a reference received from the processor, and a sensor adapted to provide an output indicative of an actual position of the valve member relative to the housing, said method comprising the steps of;
providing a reference which is indicative of a desired position of the valve member relative to the housing, based on the reference, determining a model output which is indicative of a theoretically correct position of the valve member relative to the housing, determining a residual value indicative of a difference between the output and the model output, and providing a threshold value, determining a gradient of the reference, scaling the threshold value based on the gradient, and comparing the residual value with the scaled threshold value.
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8. A steering system for a vehicle, said system comprising a fluid controller operable to control a flow of a fluid from a source of pressurized fluid to a pressure operated device, the controller comprising:
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a housing defining an inlet port connected to the source and an outlet port connected to the pressure operated device, a valve member movable within the housing and cooperating therewith to provide the flow between the inlet port and the outlet port at a flow rate which depends on the position of the valve member relative to the housing, a processor providing a reference which is indicative of a desired position of the valve member relative to the housing an actuator adapted to move the valve member in accordance with a reference received from the processor, a sensor adapted to provide an output indicative of an obtained position of the valve member relative to the housing, an observer adapted, based on a reference, to determine a model output which is indicative of a theoretically correct position of the valve member relative to the housing, and to determine a residual value indicative of a difference between the output and the model output, and a fault detection system adapted to compare the residual value with a threshold value, wherein the fluid controller is adapted to provide a gradient of the reference and to scale the threshold value based on the gradient.
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Specification