High pressure pump control

Abstract

A feedback control loop for a high pressure pump modifies the accumulator velocity and pressure during solvent transfer. The accumulator velocity is adjusted to maintain the system pressure equal to the expected pressure to thereby eliminate the effect of the flow deficit created by a thermal effect.

1 - 40 . (canceled) 
     
     
         41 . A flow control system for controlling deliver of a high pressure solvent in a chromatography system at pressures at which the effects of adiabatic heating become noticeable, the flow control system comprising:
 a high pressure pump for delivering the solvent, the high pressure pump having two interconnected pump heads with a first piston of a first pump and a second piston of a second pump;   a pump controller for setting a nominal velocity profile of the second piston which during transfer is substantially a mirror image of the first piston profile; and   a closed loop feedback control on a pressure of at least one of the first and second pumps, the closed loop feedback control being operative during a control period for compensating for a deficit in solvent delivery caused by adiabatic heating during solvent compression by modifying at least one of the nominal velocity profile of the second pump or a nominal velocity profile of the first pump during solvent transfer such that a system pressure is maintained substantially equal to a desired target pressure.   
     
     
         42 . The flow control system according to  claim 41 , wherein the control period is substantially equal to a period of transfer of the solvent. 
     
     
         43 . The flow control system according to  claim 41 , wherein the control period is longer than a period of transfer of the solvent. 
     
     
         44 . The flow control system according to  claim 41 , wherein the control period is shorter than a period of transfer of the solvent. 
     
     
         45 . The flow control system according to  claim 41 , further comprising a second piston transducer for measuring the system pressure. 
     
     
         46 . The flow control system according to  claim 41 , further comprising a first pump pressure transducer for measuring a pressure within a chamber of the first pump. 
     
     
         47 . The flow control system according to  claim 41 , further comprising a fluidic restrictor between an outlet of the high pressure pump and a solvent load of the chromatography system. 
     
     
         48 . The flow control system according to  claim 47 , wherein the fluidic restrictor is a portion of narrow inner diameter tubing. 
     
     
         49 . The flow control system according to  claim 41 , further comprising a filter for removing the second pump pressure of the high pressure pump to eliminate frequencies beyond a bandwidth of the closed loop feedback control. 
     
     
         50 . The flow control system according to  claim 41 , wherein the closed loop feedback control is based on a PID controller. 
     
     
         51 . The flow control system according to  claim 41 , further comprising a digital signal processor for performing the modification of the second piston velocity. 
     
     
         52 . The flow control system according to  claim 41 , wherein the second piston nominal velocity profile is modified by reducing a velocity of the second piston. 
     
     
         53 . The flow control system according to  claim 41 , wherein the flow control system is adapted for controlling a further high pressure pump with interconnected pump heads and wherein both high pressure pumps are connected in parallel and each high pressure pump has a pump cycle. 
     
     
         54 . The flow control system according to  claim 41 , further comprising means for monitoring position of the pistons of the first and second pumps in order to avoid control periods overlapping. 
     
     
         55 . The flow control system according to  claim 41 , further comprising means for interchanging data relating to respective positions within a pump cycle between both pumps in order to avoid control periods overlapping. 
     
     
         56 . The flow control system according to  claim 41 , further comprising means for advancing a control period with a longer pump cycle for one of the pumps when a control period collision is foreseen to thereby substantially avoid overlap with a control period of the other pump. 
     
     
         57 . The flow control system according to  claim 41 , wherein the first and second pump are connected in series. 
     
     
         58 . The flow control system according to  claim 41 , wherein the first and second pump are connected in parallel.