programming motor to operate to work in milli meter/ hour.

[jembola747]

Here is the existing syringe driver pics. hope you guys get some idea how it works.
will upload the inside pics later.

 

[MaxHeadRoom78]

First you need to measure the pitch of the screw in order to calculate rev's or fractions of/min.
Max.

 

[Tony Stewart]

Inputs:
door latch sensor for IV
Battery Voltage and current sense for Coulomb count of battery load
Air-in-Line sensor (optical)
Pressure sensor
Motor drive signals from uC
Power On Self Test Processor status
User interface with switches; flow rate, duration, etc...
Temperature sensor
Power Management state
Fluid in hose

To perform the actual flow rate, the transfer function of the Infusion pump must be well defined for all situations. Pinched hose ( very common nuicance), air in hose, empty bag, type of fluid, temperature, pressure. An ALGORITHM MUST BE DEFINED BY YOU.

It is not acceptable always to simply apply DC to motor and coast, but rather compute from algorithm and sensor inputs, apply DC, count coulombs, open DC, short motor (stop quickly) , rest. repeat.


From MAXIM....

All infusion pumps must perform power-on self-test (POST) to meet FDA requirements. This includes tests of all critical processors, critical circuitry, indicators, displays, and alarm functionality. Some POST operations can require user observations, but additional circuitry is used for self-checking to reduce the risk of undetected failures.

For example, some models use a safety processor to monitor the performance of the main processor and to generate an alarm if unexpected behavior is detected. Another example of self-test is the simple monitoring of current through light-emitting diodes (LEDs) as they are turned on and off. If currents fall outside the acceptable range, a fault is indicated. Probably the most common self-test is the watchdog timer (WDT). Microprocessor supervisors with WDT functions are commonly used to ensure that the processor executes within proper code boundaries. In medical devices, it is usually not acceptable to have the supervisor on the same IC as the microprocessor, as this approach would subject the supervisor to the same transient errors as the microprocessor.

Supervisory functions are critical for ensuring that the pump is operating properly during patient use. Microcontrollers (of which there are often several in a single pump) must be held in reset until all power supplies are within tolerance and stable. All power supplies are monitored with voltage supervisors for undervoltage and overvoltage conditions. Motor loading is monitored and motor-stall detection is provided. (Motor stall is a critical failure causing a top-priority alarm.) Because of the criticality of the system, often power-supply voltages are monitored with ADCs so that their exact value can be recorded periodically. ADCs are also needed for sensor readings, such as temperature, motor loading, IV line pressure, and battery voltage.

Temperature sensing is implemented in the battery pack, the power supply, the motor, and the display. Due to the high efficiency of these designs, fans are usually not needed. These pumps must be splash-proof, so it is difficult to put in openings for airflow.

 

[KeepItSimpleStupid]

What I thought. You need to measure displacement per time and time. RPM is very influenced by load. Shaft displacement can be measured by the sensors.

I don;t think it's as simple as turning the motor on/off for a certain time, if you want accuracy.

 

[Tony Stewart]

Having seen worm gear syringe drive and stepper motor drive pump on a fixed hose diameter , the trend today is towards pulsed DC motor driven pumps apply pressure to an elastic hose with a cam driven impeller.
This can be very precise if properly characterized as a "Transfer Function" from current to torque to acceleration to velocity to rotation to linear hose flow to volumetric flow.

It is like worm gear current * time to torque to acceleration to rotation to linear displacement to syringe incremental volume displacement is a "transfer function"

 

[Tony Stewart]

Keep in mind there are many types of infusion pumps, rotary, linear etc.

The smallest infusion pump I can think of is the piezo-ceramic ink-jet pump, where a uC counts ink drops from pulses and is either internal to cartridge or external. This would be a linear pump, but same style used for medical purposes. These are more precise for low flow rates than rotary cam driven tubes.

It would be wise if the designer learnt from the mistakes of others and think of every possible test to ensure reliability from the design stage thru DVT testing .

https://www.fda.gov/MedicalDevices/...evicesandSupplies/InfusionPumps/ucm202496.htm