Slope predictive control and digital PID control for a variable temperature control system
First Claim
1. A method for controlling a flow of a non-solid substance in a Variable Temperature Control (VTC) box in a temperature control system, wherein the VTC box comprises a heat exchange device under control of a regulation device, comprising:
- receiving an indication of a temperature setpoint;
measuring a discharge air temperature of the VTC box and calculating an error between the temperature setpoint and the measured discharge air temperature; and
until a new temperature setpoint indication is received, repeating the steps comprising;
based on the error, predicting a regulation device position adjustment to actuate the regulation device to achieve the temperature setpoint, if the predicted regulation device position adjustment is less than a minimum position adjustment, not actuating the regulation device and measuring the discharge air temperature to calculate an average discharge air temperature over a period of time, if the predicted regulation device position adjustment is not less than the minimum position adjustment, measuring the discharge air temperature in the VTC box while actuating the regulation device the predicted position adjustment or until the discharge air temperature is measured to have crossed the temperature setpoint, in response to actuating the regulation device, measuring the discharge air temperature to calculate the average discharge air temperature, and based on the average discharge air temperature, recalculating the error.
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Abstract
The present invention applies a slope predictive control method to a Variable Temperature Control (VTC) system, measuring the slope of the discharge temperature as a function of flow regulation device position, and using this slope to predict the position of the flow regulation device needed to achieve the desired discharge temperature. The present invention also monitors the response of the VTC over time and utilizes a self-learning algorithm to predict the response time of the system in order to determine when further control adjustments need to be taken.
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Citations
20 Claims
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1. A method for controlling a flow of a non-solid substance in a Variable Temperature Control (VTC) box in a temperature control system, wherein the VTC box comprises a heat exchange device under control of a regulation device, comprising:
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receiving an indication of a temperature setpoint;
measuring a discharge air temperature of the VTC box and calculating an error between the temperature setpoint and the measured discharge air temperature; and
until a new temperature setpoint indication is received, repeating the steps comprising;
based on the error, predicting a regulation device position adjustment to actuate the regulation device to achieve the temperature setpoint, if the predicted regulation device position adjustment is less than a minimum position adjustment, not actuating the regulation device and measuring the discharge air temperature to calculate an average discharge air temperature over a period of time, if the predicted regulation device position adjustment is not less than the minimum position adjustment, measuring the discharge air temperature in the VTC box while actuating the regulation device the predicted position adjustment or until the discharge air temperature is measured to have crossed the temperature setpoint, in response to actuating the regulation device, measuring the discharge air temperature to calculate the average discharge air temperature, and based on the average discharge air temperature, recalculating the error. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A Variable Temperature Control (VTC) temperature control system comprising:
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a VTC box including a heat exchange device and a discharge air temperature sensor for measuring the discharge air temperature;
a flow regulation device for controlling a volume of non-solid substance delivered to the heat exchange device; and
a micro-controller configured for executing computer-executable instructions for;
receiving a discharge temperature setpoint, receiving a discharge air temperature measurement from the temperature sensor and calculating an error between the discharge temperature setpoint and the discharge air temperature measurement, and until a new discharge temperature setpoint is received, repeating the steps comprising;
based on the error, predicting a flow regulation device position adjustment to actuate the flow regulation device in the VTC box to achieve the temperature setpoint, if the predicted flow regulation device position adjustment is less than a minimum position adjustment, not generating a signal for actuating the flow regulation device and receiving discharge air temperature measurements from the discharge air temperature sensor to calculate an average temperature over a period of time, if the predicted flow regulation device position adjustment is not less than the minimum position adjustment, receiving discharge air temperature measurements from the discharge air temperature sensor while generating the signal for actuating the flow regulation device the predicted flow regulation device position adjustment or until one of the temperature measurements is determined to have crossed the temperature setpoint, in response to actuation of the flow regulation device, receiving discharge air temperature measurements from the discharge air temperature sensor to calculate the average temperature, and based on the average discharge air temperature, recalculating the error. - View Dependent Claims (9, 10, 11, 12)
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13. A method for controlling a Variable Temperature Control (VTC) box in a temperature control system, wherein the VTC box comprises a heat exchange device under control of a regulation device, comprising:
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receiving an indication of a temperature setpoint;
measuring a discharge air temperature of the VTC box and calculating an error between the temperature setpoint and the measured discharge air temperature; and
until a new temperature setpoint indication is received, repeating the steps comprising;
based on the error, predicting a regulation device setting to which the regulation device is actuated to achieve the temperature setpoint, if the predicted regulation device setting requires less than a minimum setting change, not actuating the regulation device and measuring the discharge air temperature to calculate an average discharge air temperature over a period of time, if the predicted regulation device setting does not require less than the minimum setting change, measuring the discharge air temperature in the VTC box while actuating the regulation device to the predicted regulation device setting or until the discharge air temperature is measured to have crossed the temperature setpoint, in response to actuating the regulation device, measuring the discharge air temperature to calculate the average discharge air temperature, and based on the average discharge air temperature, recalculating the error. - View Dependent Claims (14)
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15. A new method for implementing PID control having a proportional term, an integral term, and a derivative term, the method comprising:
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receiving a controlled variable measurement and calculating an error between the controlled variable measurement and a desired condition;
defining at least two distinct regions of operation based at least in part on the error, wherein each region has a predetermined gain set;
based on the error, (i) determining a region of operation, (ii) calculating a PID output using a gain set associated with that region;
after the expiration of a time increment, re-measuring the controlled variable, re-calculating the error and repeating steps (i)-(iii). - View Dependent Claims (16, 17, 18, 19, 20)
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Specification