Apparatus for temperature control using a cycle rate control algorithm
The present invention controls a room temperature by controlling an environmental control unit. A total span about a setpoint temperature is adjusted in accordance with a previous total span and a multiplicative factor. The multiplicative factor is periodically updated from a desired cycle time and a previous cycle time. The room temperature may also be controlled by adjusting a duty cycle for controlling an environmental control unit. The duty cycle is adjusted based on an error associated with a previous control cycle and an attenuation factor. A new control cycle may be started by cutting the previous control cycle or a current control cycle may be extended if a predetermined condition is detected. The control mode is selected based on environmental characteristics and room characteristics. The control mode may include a span control mode and a duty cycle control mode that is selected from the cycle rate.
1. An apparatus that controls a temperature of a room, the apparatus comprising:
a temperature sensor that measures the temperature; and
a processing unit that controls an environmental control unit and that is configured to perform:
(a) determining a control mode;
(b) if the control mode equals a span control mode, adjusting a current total span of a current control cycle based on a desired cycle time and a previous cycle time; and
(c) if the control mode equals a duty cycle control mode, adjusting a duty cycle of the current control cycle based on an error of a previous control cycle.
2. The apparatus of claim 1 , wherein the processing unit is further configured to perform:
(b)(i) obtaining a previous total span of the previous control cycle; and
(b)(ii) multiplying the previous total span by a multiplicative factor.
3. The apparatus of claim 1 , wherein the multiplicative factor is determined from a ratio equal to the desired cycle time divided by the previous cycle time.
4. The apparatus of claim 1 , wherein the processing unit is further configured to perform:
(c)(i) determining the error from a setpoint temperature and a predicted temperature.
5. The apparatus of claim 4 , wherein the predicted temperature is based on an average temperature and a temperature change of the previous control cycle.
6. The apparatus of claim 4 , wherein the processing unit is further configured to perform:
(c)(ii) multiplying the error by an attenuation factor.
7. The apparatus of claim 6 , wherein the processing unit is further configured to perform:
(c)(iii) adjusting the attenuation factor to match a characteristic of the room.
8. The apparatus of claim 1 , wherein the environmental control unit comprises a heating unit.
9. The apparatus of claim 1 , wherein the environmental control unit comprises a cooling unit.
10. The apparatus of claim 1 , wherein the processing unit is further configured to perform:
(a)(i) if a cycle rate exceeds a predetermined limit, setting the control mode to the duty cycle control mode; and
(a)(ii) if the cycle rate is less than or equal to the predetermined limit, setting the control mode to the span control mode.