Pressure controller
First Claim
1. A pressure controller having a source port, vent port and outlet port comprising:
- selection means permitting a user to select a pressure to be maintained at the outlet port;
apply and release valves for regulating gas flow, each valve having an inlet and an outlet and a control input for receiving pulse width modulated control signals;
the apply valve inlet being adapted to be connected to a source of pressurized gas, the apply valve outlet being connected to the source port, the release valve inlet being connected to the vent port, and the release valve outlet being adapted to be connected to a vent;
a pressure transducer connected to the outlet port and adapted to generate a digital signal representing the pressure;
processor means connected to the pressure transducer and selection means, and adapted to generate control signals to the apply and release valves;
valve characterization means for calibrating the controller by independently determining no for each valve for at least two predetermined pressures within the range of the controller; and
means for storing the calibration no values in the processor means for use by said processor means in generating control signals during operation of the controller;
wherein each pulse width modulated control signal has at least one period, each period having one pulse, the pulse being measured as a percentage of the period, and wherein no is the percentage of the pulse width modulated control signal received at an individual valve at which gas flow is initiated.
1 Assignment
0 Petitions
Accused Products
Abstract
A pressure controller of the type using pulse width modulated apply and release solenoid valves (80, 82) connected to an outlet port (74) of the controller overcomes the technical problem of poor control stability by using a digital control loop (98, 100, 76, 78) which utilizes stored bias characteristics representing the variation with pressure of the value (no) of the pulse width modulation signal at which each valve initiates flow (no). These values are determined in a characterisation step conducted with the controller off-line. The values may be modified during on-line operation of the controller by monitoring the stability of the controller or other signals representing the opening and closing of the valves.
-
Citations
13 Claims
-
1. A pressure controller having a source port, vent port and outlet port comprising:
-
selection means permitting a user to select a pressure to be maintained at the outlet port; apply and release valves for regulating gas flow, each valve having an inlet and an outlet and a control input for receiving pulse width modulated control signals;
the apply valve inlet being adapted to be connected to a source of pressurized gas, the apply valve outlet being connected to the source port, the release valve inlet being connected to the vent port, and the release valve outlet being adapted to be connected to a vent;a pressure transducer connected to the outlet port and adapted to generate a digital signal representing the pressure; processor means connected to the pressure transducer and selection means, and adapted to generate control signals to the apply and release valves; valve characterization means for calibrating the controller by independently determining no for each valve for at least two predetermined pressures within the range of the controller; and means for storing the calibration no values in the processor means for use by said processor means in generating control signals during operation of the controller; wherein each pulse width modulated control signal has at least one period, each period having one pulse, the pulse being measured as a percentage of the period, and wherein no is the percentage of the pulse width modulated control signal received at an individual valve at which gas flow is initiated. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
-
Specification