Method of maintaining a position of an airflow-direction control element of a HVAC system

1. A method of maintaining a position of an airflow-direction control element of a HVAC system, comprising the steps of:

a] monitoring an angular position of a rotor of an electric motor of an airflow- direction-controller actuator of the HVAC system, the airflow-direction-controller actuator comprising a reversible gear train engaged with the electric motor, and the airflow-direction control element being driven by the rotor via the reversible gear train;

b] calculating a position of the airflow-direction control element according to the monitored angular position of the rotor;

c] determining whether the airflow-direction control element maintains at a target position, and if not, activating the airflow-direction-controller actuator of the HVAC system to effect a change in the angular position of the rotor;

d] monitoring the changed angular position of the rotor following actuation of the airflow-direction-controller actuator;

e] calculating a new position of the airflow-direction control element according to the changed angular position of the rotor;

f] comparing the new position and the target position of the airflow-direction control element, and

i] if the airflow-direction control element is at the target position, deactivating the airflow-direction-controller actuator, otherwise

ii] activating the airflow-direction-controller actuator of the HVAC system, and returning to the step d].

2. The method as claimed in claim 1 , wherein during step a], using a position sensor to monitor the angular position of the rotor.

3. The method as claimed in claim 1 , wherein during step a], using a Hall sensor to monitor the angular position of the rotor.

4. The method as claimed in claim 1 , wherein the airflow-direction control element is a vent flap of the HVAC system.

5. The method as claimed in claim 1 , wherein, during step c], a current to the airflow-direction-controller actuator is ramped until reaching a threshold current for forcing a change in the position of the airflow-direction control element.

6. The method as claimed in claim 5 , wherein the current to the airflow-direction- controller actuator is smoothly ramped.

7. The method as claimed in claim 1 , further comprising a step prior to the step c] of monitoring the current to the airflow-direction-controller actuator to determine a minimum current required to cause an actuation of the rotor.

8. The method as claimed in claim 1 , wherein the monitoring of the angular position of the rotor is continuous.

9. The method as claimed in claim 1 , wherein during step c], the actuator is only activated if the position of the airflow-direction control element differs from the target position by more than a threshold value.

10. A HVAC system comprising:

an airflow-direction-controller actuator comprising an electric motor, and a reversible gear train engaged with the electric motor;

an airflow-direction control element driven by the electric motor via the reversible gear train;

an actuator position sensor associated with the airflow-direction-controller actuator for monitoring an angular position of a rotor of the electric motor; and

a controller associated with the actuator position sensor, and arranged to determine whether the rotor maintains at a required angular position corresponding to a target position of the airflow-direction control element, and activate the airflow-direction-controller actuator to effect a change in the angular position of the rotor thereby bringing the airflow-direction control element to or towards the target position when the rotor does not maintain at the required angular position.

11. The HVAC system as claimed in claim 10 , wherein the actuator position sensor is a Hall sensor, and the airflow-direction control element is a vent flap.

12. The HVAC system as claimed in claim 10 , wherein when the controller activates the airflow-direction-controller, a current to the airflow-direction-controller actuator is ramped until reaching a threshold current for forcing a change in the position of the airflow-direction control element.

13. The HVAC system as claimed in claim 10 , further comprising a current monitor arranged to monitor a current passed to the actuator.

14. A method of maintaining a position of an airflow-direction control element of a HVAC system, comprising the steps of:

a] monitoring an angular position of a rotor of an electric motor of an airflow-direction-controller actuator of the HVAC system, the airflow-direction-controller actuator comprising a reversible gear train engaged with the electric motor, and the airflow-direction control element being driven by the rotor via the reversible gear train; and

b] determining whether the rotor maintains at a required angular position corresponding to a target position of the airflow-direction control element; if not, activating the airflow-direction-controller actuator to effect a change in the angular position of the rotor thereby bringing the airflow-direction control element to or towards the target position.

15. The method as claimed in claim 14 , wherein the method further comprises steps following the step b] of:

c] monitoring a changed angular position of the rotor following actuation of the airflow-direction-controller actuator;

d] comparing the changed angular position of the rotor to the required angular position, and

i] if the rotor is at the required angular position, deactivating the airflow- direction-controller actuator, otherwise

ii] activating the airflow-direction-controller actuator of the HVAC system, and returning to the step c].

16. The method as claimed in claim 14 , wherein during step b], a current to the airflow-direction-controller actuator is ramped until reaching a threshold current for forcing a change in the position of the airflow-direction control element.