Sensing a status of an infuser based on sensing motor control and power input
A status of a battery operated infuser may be detected by measuring a controlled input parameter. The measurement may be used to determine a magnitude of the input parameter and a parameter of the control. For example, control of power input to a motor may be by pulse density modulation. An integral of current over time may serve as a measure of current magnitude and pulse density. The result of the integral may be used to determine the status of the injector. The status may include normal functions for example start of pumping and/or malfunctions such as occlusion or drive disengagement.
1. A method of determining a status of a battery operated drug infusing device having an actuator, the method comprising:
measuring an initial input energy level;
determining whether the initial energy level is below a minimum threshold, above a maximum threshold, or represents a steady input energy state between the minimum and maximum thresholds;
when the initial energy level is above the maximum threshold, triggering an alarm;
when the initial energy level is below the minimum threshold, determining whether the initial energy level remains below the minimum threshold for a predetermined period of time, and if so, triggering an alarm;
when the initial energy level is determined to be at the steady input energy state:
establishing the steady input energy state as a baseline input energy; and
controlling the actuator based on a performance of the actuator as determined by:
(1) measuring an input parameter to the actuator, the input parameter including at least a magnitude of a current input to the actuator, and
(2) ascertaining a status of the device by integrating a magnitude of said current input over a time corresponding to said current input to the actuator and comparing the integrated current input over time with the baseline input energy-inserted therein.
2. The method of claim 1 , wherein
said performance of the actuator includes a cumulative movement of the actuator, and
said controlling includes limiting a time of current input to the actuator.
3. The method of claim 2 , wherein said cumulative movement includes a number of revolutions by the actuator during a time period.
4. The method of claim 3 , wherein said limiting includes limiting a pulse density of said current input in said time period.
5. The method of claim 1 , wherein said controlling affects said input parameter.
6. The method of claim 5 , wherein a result of said measuring serves as a proxy for a parameter of said controlling.
7. The method of claim 6 , wherein a time dependence of said measured input parameter serves as said proxy for said parameter of said controlling.
8. The method of claim 1 , wherein said controlling includes pulse density modulation and said ascertaining depends on said pulse density.
9. The method of claim 1 , wherein said status includes at least one element selected from the group consisting of, a blockage, a disengagement, changing of an active mechanical part, discharging medicine, and not discharging.
10. The method of claim 1 , wherein said controlling includes:
counting a number of rotations by the actuator wherein said number of rotations is proportional to a cumulative discharge of the device, and
cutting off said current when said number reaches a threshold.
11. The method of claim 10 , wherein a rate of said counting is less than four times a sampling rate of said measuring.
12. The method of claim 1 , wherein said input parameter is unregulated.
13. The method of claim 1 , wherein said controlling includes temporarily cutting off said input parameter.