Occlusion detection techniques for a fluid infusion device having a rotary pump mechanism and a force sensor
An embodiment of a fluid infusion device includes a fluid pump mechanism having a rotor and a stator. The rotor includes a reference surface and a cam element rising from the reference surface. The stator includes a cam element having a stator cam surface. The cam elements cooperate to axially displace the rotor as a function of rotation. A biasing element provides force to urge the cam elements together. A drive motor is coupled to actuate the rotor to pump medication fluid from a fluid cartridge module to a body, via a subcutaneous conduit. A force sensor is coupled to the rotor to generate output levels in response to force imparted thereto. The force sensor cooperates with a detection circuit that obtains and processes the output levels to detect occlusions in a fluid path downstream of the fluid pump mechanism.
1. A fluid pump mechanism comprising:
a stator comprising a stator cam element having a stator cam surface;
a rotor comprising a reference surface and a rotor cam element having a variable height rising from the reference surface, the rotor cam element cooperating with the stator cam element to axially displace the rotor, relative to the stator, as a function of angular position of the rotor;
a biasing element that provides a biasing force to urge the rotor cam element toward the stator cam element and toward the reference surface; and
a force sensor coupled to the rotor, the force sensor generating output levels in response to force imparted thereto, wherein the force imparted to the force sensor varies with axial displacement of the rotor relative to the stator, and the force sensor cooperating with a detection circuit that obtains and processes the output levels following each fluid expulsion period of the fluid pump mechanism and before each fluid intake period of the fluid pump mechanism, to detect occlusions in a fluid path downstream of the fluid pump mechanism;
wherein, under normal operating conditions:
a complete rotation of the rotor corresponds to one pumping cycle comprising a fluid intake period and a fluid expulsion period;
during the fluid intake period, the stator cam element is in contact with the rotor cam element;
during the fluid expulsion period, the rotor cam element disengages the stator cam element, and the biasing element axially displaces the rotor such that the reference surface of the rotor moves toward the stator cam element; and
after the fluid expulsion period and before a next fluid intake period, the stator cam element is in contact with the reference surface and the force sensor generates nominal output levels that fall within a range of expected output levels; and
wherein, under downstream occlusion conditions:
fluid pressure caused by an occlusion downstream of the fluid pump mechanism prevents the stator cam element from contacting the reference surface after the fluid expulsion period;
after the fluid expulsion period and before the next fluid intake period, the force sensor generates outlier output levels that fall outside the range of expected output levels and that are indicative of the occlusion; and
the detection circuit determines the presence of a downstream occlusion in response to the outlier output levels.
2. The fluid pump mechanism of claim 1 , wherein:
the detection circuit initiates an alert, alarm, or warning message in response to detecting an occlusion.
3. The fluid pump mechanism of claim 1 , wherein the force sensor is positioned between the rotor and the stator to measure force applied by the stator to the force sensor.
4. The fluid pump mechanism of claim 1 , wherein the force sensor is positioned between the rotor and the stator to measure force applied by the rotor to the force sensor.