Systems and methods for control of pumps employing gravimetric sensing

A system for pumping a fluid comprising

• a pump having a known stroke volume (SV), which is essentially constant,
• an actuator interacting with the pump during a stroke interval (TStroke) to pump fluid through the pump at a flow rate (QActual),
• a receptacle to dispense fluid into the pump or to receive fluid pumped from the pump,
• a weigh sensor to detect changes in weight of the receptacle over a sample time period, and
• a controller coupled to the actuator and the weigh sensor and including a diagnostic function to detect abnormal operating conditions based upon a pump correction factor k, which accounts for interactions between the pump and the upstream and downstream pressures, and to generate an alarm output, the pump correction factor k being derived as follows:
• k = T Stroke × ( Q Actual SV ) .

A blood processing system coupled to a blood separation device comprising

• a cassette containing at least one pneumatically actuated pump station comprising a pump chamber having a known stroke volume (SV), which is essentially constant,
• a pneumatic actuator to hold the cassette and selectively apply pneumatic force to the pump station during a stroke interval (TStroke) to pump fluid having a density through the pump chamber,
• a receptacle to dispense fluid into the pump chamber or to receive fluid pumped from the pump chamber,
• a weigh sensor to detect changes in weight of the receptacle over a sample time period, and
• a controller coupled to the actuator and the weigh sensor and including a control function to achieve a desired flow rate (QDesired) by deriving an actual flow rate (QActual) by sensing with the weigh sensor changes in weight of the receptacle over the sample time period, taking into account the density of the fluid and adjusting the stroke interval based upon QActual so that QDesired is achieved.

A method for pumping a fluid having a density comprising the steps of

• providing a pump having a known stroke volume (SV), which is essentially constant,
• operating an actuator to interact with the pump during a stroke interval (TStroke) to pump fluid through the pump,
• coupling a receptacle to the pump to dispense fluid into the pump or to receive fluid pumped from the pump,
• detecting changes in weight of the receptacle over a sample time period, and controlling the pump to achieve a desired flow rate (QDesired) by deriving an actual flow rate (QActual) by sensing changes in weight of the receptacle over the sample time period, taking into account the density of the fluid, and adjusting the stroke interval based upon QActual so that QDesired is achieved.

A method for pumping a fluid comprising the steps of

• providing a pump having a known stroke volume (SV), which is essentially constant,
• operating an actuator to interact with the pump during a stroke interval (TStroke) to pump fluid through the pump at a flow rate (QActual),
• coupling a receptacle to the pump to dispense fluid into the pump or to receive fluid pumped from the pump,
• detecting changes in weight of the receptacle over a sample time period, and
• detecting abnormal operating conditions based upon a pump correction factor k, which accounts for interactions between the pump and the upstream and downstream pressures, and generating an alarm output, the pump correction factor k being derived as follows:
• k = T Stroke × ( Q Actual SV ) .