Protection of aperture plate during aerosol generation
An aerosol delivery system has an aerosol generator with a vibrating aperture plate ( 10 ) and an actuator ( 11, 16, 17, 19 ), a controller ( 18, 19 ). The controller in real time monitors ( 201 ) the aerosol generator as it is driven for vibration of the aperture plate, and detects ( 202 ) a change in an electrical characteristic in response to a transition from a wet state to a dry state of the aperture plate. It automatically modifies ( 203, 205, 206 ), during the transition, operation of the aerosol generator in response to the detected change. The modification includes reducing applied power ( 203 ). The controller continues ( 204 ) to monitor during the transition, including monitoring the aperture plate for presence of residual liquid on the aperture plate first surface. The controller monitors at a number of drive frequencies and maintains data representing trends in a combination of the electrical characteristic signals at the different frequencies, and identifies a start of a transition if a calculated value rises above a threshold. There is one threshold for triggering a check scan for residual volume and a higher threshold to trigger an immediate shut down.
1 . An aerosol delivery system comprising:
an aerosol generator comprising a vibrating aperture plate and an actuator including a resistor for determining a power requirement of the actuator, wherein the aperture plate has a plurality of apertures extending between a first surface which is adapted to receive a liquid to be aerosolised and a second surface at which an aerosol is generated, and
a controller for controlling operation of the aerosol generator, wherein the controller is configured to perform steps comprising:
monitoring a voltage across the resistor as the vibrating aperture plate is vibrated at one or more drive frequencies;
determining a first power consumption requirement of vibrating the vibrating aperture plate at a first drive frequency of the one or more drive frequencies based on the voltage across the resistor; and
automatically modifying operation of the aerosol generator in response to an output based on the first power consumption requirement crossing a transition threshold, wherein modifying operation of the aerosol generator includes reducing power applied to the aerosol generator to a non-zero power level.
2 . The aerosol delivery system of claim 1 , wherein the vibrating aperture plate is vibrated at a second drive frequency and at a third drive frequency, wherein the controller is further configured to determine a second power consumption requirement of vibrating the vibrating aperture plate at the second drive frequency and a third power consumption requirement of vibrating the vibrating aperture plate at the third drive frequency, and wherein the output is based on the first, second, and third power consumption requirements.
3 . The aerosol delivery system of claim 2 , wherein the first drive frequency is a middle frequency, the second drive frequency is a high frequency, and the third drive frequency is a low frequency.
4 . The aerosol delivery system of claim 3 , wherein a magnitude of difference between the middle frequency and the high frequency is equivalent to a magnitude of difference between the middle frequency and the low frequency.
5 . The aerosol delivery system of claim 4 , wherein the magnitude of difference between the middle frequency and the high frequency is 1 kHz.
6 . The aerosol delivery system of claim 2 , wherein the vibrating aperture plate is driven at each of the first, second, and third drive frequencies for a drive time.
7 . The aerosol delivery system of claim 6 , wherein the drive time at each of the first, second, and third drive frequencies is equivalent.
8 . The aerosol delivery system of claim 7 , wherein the drive time is between 1 and 5 ms.
9 . The aerosol delivery system of claim 1 , wherein the first power consumption requirement is monitored at each of the one or more drive frequencies in a time division multiplexed manner.
10 . The aerosol delivery system of claim 9 , wherein the output is further based at least in part on one or more prior power consumption requirements determined of vibrating the vibrating aperture plate at the one or more drive frequencies in one or more prior instances.
11 . An aerosol delivery system comprising:
an aerosol generator comprising:
a vibrating aperture plate including a plurality of apertures extending between a first surface which is adapted to receive a liquid to be aerosolised and a second surface at which an aerosol is generated; and
an actuator including a resistor for determining a power requirement of the actuator; and
a controller for controlling operation of the aerosol generator, wherein the controller is configured to perform steps comprising:
monitoring a voltage across the resistor as the vibrating aperture plate is vibrated at one or more drive frequencies;
determining a power consumption requirement of vibrating the vibrating aperture plate based on the voltage across the resistor;
automatically reducing power applied to the aerosol generator to a first power level in response to an output based on the power consumption requirement crossing a transition threshold; and
automatically reducing power applied to the aerosol generator to a second power level in response to the output based on the power consumption requirement crossing an immediate shutdown threshold.
12 . The aerosol delivery system of claim 11 , wherein the immediate shutdown threshold is a greater power consumption than the transition threshold.
13 . The aerosol delivery system of claim 11 , wherein the second power level is lower than the first power level.
14 . The aerosol delivery system of claim 11 , wherein the controller is further configured to identify a start of a transition if a trend in the output increases above a transition trend line.
15 . The aerosol delivery system of claim 11 , wherein the vibrating aperture plate is driven at three different drive frequencies.
16 . The aerosol delivery system of claim 15 , wherein the vibrating aperture plate is driven at each of the three different drive frequencies for a drive time between 1 and 4 ms.