System and method for measuring pressure applied by a piezo-electric pump

Abstract

A system and method for measuring the pressure provided by a disc pump is disclosed. The disc pump comprises an actuator mounted within the disc pump on a flexible skirt that allows the actuator to oscillate for generating air flow through the cavity of the pump and allows the actuator to be displaced with increasing pressure to a load. The actuator moves from a rest position when air begins flowing through the cavity to a biased position when the load is fully pressurized or depressurized depending on the direction of fluid flow through the cavity. The pump further comprises a sensor which measures the displacement of the actuator at any position between the rest position and the biased position as fluid begins flowing through the cavity to pressurize or depressurize the load. The pressure being delivered by the disc pump is determined as a function of the displacement of the actuator.

1 . A pump comprising:
 a pump body having a substantially elliptical shaped side wall closed at one end by a base wall and the other end by a pair of interior plates to form a cavity within said pump body for containing a fluid, wherein a first one of the interior plates adjacent the cavity includes a center portion and a peripheral portion;   an actuator formed by the end plates wherein the second one of the interior plates is operatively associated with the central portion of the first interior plate to cause an oscillatory displacement motion thereby generating radial pressure oscillations of the fluid within the cavity in response to a drive signal being applied to said actuator when in use;   a skirt flexibly connected between the side wall and the peripheral portion of the first interior plate to facilitate the oscillatory displacement motion;   a first aperture extending through said actuator to enable fluid to flow through the cavity;   a second aperture extending through the base wall to enable fluid to flow through the cavity;   a valve disposed in at least one of said first aperture and second apertures and is adapted to permit the fluid to flow through the cavity in substantially one direction to pressurize or depressurize a load as fluid begins flowing through the cavity, thereby causing said actuator to move toward the base wall from a rest position to a biased position with increasing pressure and flexing of the skirt; and,   a sensor mounted outside the cavity in a fixed position with respect to said pump body for measuring the displacement of said actuator at any position between the rest position and the biased position as fluid begins flowing through the cavity to pressurize or depressurize the load.   
     
     
         2 . The pump of  claim 1  wherein the ratio of the radius of the cavity (r) extending from the longitudinal axis of the cavity to the side wall to the height of the side wall of the cavity (h) is greater than or equal to 1.2. 
     
     
         3 .- 9 . (canceled) 
     
     
         10 . The pump of  claim 1  wherein said skirt is a flexible membrane. 
     
     
         11 . The pump of  claim 10  wherein the flexible membrane is formed from plastic. 
     
     
         12 . The pump of  claim 11  wherein the annular width of flexible membrane is between about 0.5 and 1.0 mm and the thickness of the flexible membrane is less than about 200 microns. 
     
     
         13 . The pump of  claim 10  wherein the flexible membrane is formed from metal. 
     
     
         14 . The pump of  claim 13  wherein the annular width of flexible membrane is between about 0.5 and 1.0 mm and the thickness of the flexible membrane is less than about 20 microns. 
     
     
         15 .- 20 . (canceled) 
     
     
         21 . The pump of  claim 1  further comprising an electronic circuit in communication with said sensor and configured to calculate the pressure at the load as a function of the displacement of said actuator. 
     
     
         22 . The pump of  claim 21  wherein the electronic circuit is further, configured to calculate the rate of change of the pressure at the load. 
     
     
         23 . The pump of  claim 1  wherein said sensor is an optical sensor configured to illuminate and measure the displacement of said actuator. 
     
     
         24 . The pump of  claim 23  wherein the optical sensor illuminates an annular displacement node of the oscillatory displacement motion of said actuator. 
     
     
         25 . The pump of  claim 23  wherein said optical sensor comprises an optical transmitter and an optical receiver. 
     
     
         26 . The pump of  claim 25  wherein the optical transmitter includes a light emitting diode that illuminates said actuator with an optical beam, and wherein the optical receiver includes a light sensor array of pixel elements that sense reflections of the optical beam as of the reflections move along the array of pixel elements corresponding to the displacement of said actuator as said actuator moves from the rest position to the biased position. 
     
     
         27 . The pump of  claim 25  further comprising an electronic circuit in communication with the optical receiver and configured to calculate the pressure at the load as a function of the displacement of said actuator. 
     
     
         28 . The pump of  claim 23  wherein the optical sensor comprises an illumination source for providing an optical beam having a multi-frequency spectrum, a diffraction grating disposed on said actuator for reflecting the optical beam as a plurality of reflected beams at different wavelengths within the multi-frequency spectrum, and an optical receiver for receiving the reflected beams, each of which corresponds to a different displacement of said actuator as said actuator moves from the rest position to the biased position. 
     
     
         29 . The pump of  claim 1  wherein said sensor is a magnetic sensor. 
     
     
         30 . The pump of  claim 1  wherein said sensor is and RF sensor. 
     
     
         31 . A method for measuring pressure generated for a load by a pump having an actuator mounted within the pump on a flexible skirt that allows the actuator to oscillate for generating air flow through a cavity of the pump and allows the actuator to be displaced with increasing pressure to the load, said method comprising:
 driving the actuator to cause an oscillatory displacement motion of the actuator to generate radial pressure oscillations of fluid within the cavity;   measuring the displacement of the actuator as fluid begins flowing through the cavity causing the actuator to move from a rest position to a biased position with increasing pressure at the load and flexing of the skirt; and   calculating the pressure at the load based on the displacement of the actuator.   
     
     
         32 .- 43 . (canceled) 
     
     
         44 . A disc pump comprising:
 a pump body having an end wall closing one end of the pump body, the end wall having an aperture for airflow through the aperture;   an actuator having a peripheral portion and a flexible skirt portion extending from the peripheral portion to the pump body wherein the actuator closes the other end of the pump body to form a cavity therein, the actuator including an aperture for airflow through the aperture, and configured to vibrate in an oscillatory motion to generate airflow from one aperture to the other aperture for building pressure at a load;   a valve disposed in one of the apertures and adapted to permit airflow through the cavity in substantially in one direction to pressurize or depressurize the load thereby causing the actuator to move from a rest position to a biased position with increasing pressure at the load; and   a sensor configured to measure the displacement of the actuator as the pressure builds within the load and to calculate the pressure as a function of the displacement.   
     
     
         45 . A disc pump according to  claim 44 , wherein the sensor is mounted outside the cavity in a fixed position with respect to said pump body. 
     
     
         46 . The pump of  claim 44  wherein said sensor is an optical sensor configured to illuminate and measure the displacement of the actuator. 
     
     
         47 . The pump of  claim 46  wherein the optical sensor illuminates an annular displacement node of the oscillatory motion of the actuator. 
     
     
         48 . The pump of  claim 47  wherein said optical sensor comprises an optical transmitter and an optical receiver. 
     
     
         49 . The pump of  claim 48  wherein the optical transmitter includes a light emitting diode that illuminates the actuator with an optical beam, and wherein the optical receiver includes a light sensor array of pixel elements that sense reflections of the optical beam as of the reflections move along the array of pixel elements corresponding to the displacement of the actuator as the actuator moves from the rest position to the biased position. 
     
     
         50 . The pump of  claim 48  further comprising an electronic circuit in communication with the optical receiver and configured to calculate the pressure at the load as a function of the position of said actuator. 
     
     
         51 . The pump of  claim 46  wherein the optical sensor comprises an illumination source for providing an optical beam having a multi-frequency spectrum, a diffraction grating disposed on said actuator for reflecting the optical beam as a plurality of reflected beams at different wavelengths within the multi-frequency spectrum, and an optical receiver for receiving the reflected beams, each of which corresponds to a different position of said actuator. 
     
     
         52 . The pump of  claim 44  wherein said sensor is a magnetic sensor. 
     
     
         53 . The pump of  claim 44  wherein said sensor is an RF sensor. 
     
     
         54 . The pump of  claim 44  wherein said sensor is an ultrasonic sensor. 
     
     
         55 . The pump of  claim 44  wherein the load is calculated as a function of the average position of a sensed part of the actuator.