Process for Peristaltic Pump Control

Abstract

A peristaltic pump is provided comprising squeezing elements moved by at least one actuator, which squeezing elements act on a tube in which a medium is conveyed, with the squeezing elements successively getting into and out of a squeezing engagement with the tube. A process for controlling the peristaltic pump comprises measuring over time a fluidic parameter representative for the flow rate of the medium through the tube, determining the relative undulation of the flow rate of the medium from the measured temporal course of the fluidic parameter, and smoothing the undulation by adjusting the progression speed of the squeezing elements on the basis of the determined undulation of the flow rate.

1 . A process for controlling a peristaltic pump comprising squeezing elements moved by at least one actuator, which squeezing elements act on a tube in which a medium is conveyed, with the squeezing elements successively getting into and out of a squeezing engagement with the tube, characterized by:
 measuring over time a fluidic parameter representative for the flow rate of the medium through the tube,   determining the relative undulation of the flow rate of the medium from the measured temporal course of the fluidic parameter, and   smoothing the undulation by adjusting the progression speed of the squeezing elements on the basis of the determined undulation of the flow rate.   
   
   
       2 . The process according to  claim 1 , characterized in that in peristaltic pumps with a periodical variation of the progression speed of the squeezing elements, which has been preset particularly in the factory, depending on a current position of the squeezing elements, smoothing of the undulation is performed by adjusting the preset periodical variation of the progression speed of the squeezing elements on the basis of the relative undulation of the flow rate which has been determined. 
   
   
       3 . The process according to  claim 1 , characterized in that the adjustment of the periodical variation of the progression speed of the squeezing elements comprises calculating a calibration factor from the determined undulation of the flow rate of the medium and readjusting the periodical variation of the progression speed of the squeezing elements by the calibration factor. 
   
   
       4 . The process according to  claim 3 , characterized in that the calibration factor is checked during running operation to find out if it lies within predetermined limits and a recalculation of the calibration factor is conducted if those limits are exceeded. 
   
   
       5 . The process according to  claim 1 , characterized in that the actuator is a rotor driven by a motor, from which rotor the squeezing elements are moved in a circular motion along the tube, whereby the position of the squeezing elements is detected during the rotation of the rotor and the progression speed of the squeezing elements is adjusted by controlling the angular velocity of the rotor. 
   
   
       6 . The process according to  claim 1 , characterized in that the fluidic parameter is the flow rate of the medium and is measured by detecting the time period required by medium packages or the front and end of the medium or of medium packages, respectively, for passing with a constant measuring volume through a measuring section located in the flow path of the peristaltic pump, simultaneously detecting the positions of the squeezing elements and allocating the positions of the squeezing elements to the time periods, resulting in a curve of the relative undulation of the flow rate. 
   
   
       7 . The process according to  claim 6 , characterized in that the medium packages are generated by introducing air into a medium flow, in particular that the air is introduced into the medium flow at irregular intervals. 
   
   
       8 . The process according to  claim 6 , characterized in that the measuring volume of the measuring section and the volumes of the medium packages are chosen such that the period of the undulation of the flow rate which corresponds to the distance between adjacent squeezing elements and the progression speed of the squeezing elements, in particular to the angular velocity of the rotor, is a multiple of the time period required by the medium packages for flowing through the measuring section. 
   
   
       9 . The process according to  claim 6 , characterized in that the passing of the medium packages through the measuring section is detected by optical sensors. 
   
   
       10 . The process according to  claim 1 , characterized in that the fluidic parameter is the pressure of the medium and is detected by a pressure sensor, or the fluidic parameter is the temperature of the medium and is detected by a temperature sensor, or the fluidic parameter is the relative weight change of a weighing cell into which the medium is introduced, or the flow rate is detected by a flowmeter, or the fluidic parameter is the electrical conductivity of the medium and is detected by a conductivity sensor. 
   
   
       11 . The process according to  claim 1 , characterized in that it is performed after every exchange of the tube, with the tube being designed as a replacement part or being integrated in a replacement part.