Method for Improving Metering Profiles of Displacement Pumps

Abstract

The invention relates to a method for determining hydraulic parameters in a displacement pump, wherein the displacement pump has a movable displacement element, which bounds the metering chamber, which is connected to a suction and pressure line by means of valves, wherein a drive is provided for the oscillating motion of the displacement element. In order that pumped fluid can be alternately sucked into the metering chamber via the suction line and pressed from the metering chamber via the pressure line by means of an oscillating motion of the displacement element, a physical model having hydraulic parameters according to the invention is established for the hydraulic system, the force exerted by the displacement element on the fluid located in the metering chamber or the pressure in the metering chamber is determined and the position of the displacement element is determined, and at least one hydraulic parameter is calculated by means of an optimization calculation.

1 .- 18 . (canceled) 
     
     
         19 . A method of optimizing metering profiles of positive displacement pumps, in which a moveable displacer element delimits a metering chamber which is connected by way of valves to a suction and a pressure line so that delivery fluid can alternately be sucked into the metering chamber by way of the suction line and urged out of the metering chamber by way of the pressure line by an oscillating movement of the displacer element, wherein the delivery fluid flow into the pressure line represents the metering profile and there is provided a drive for the oscillating movement of the displacer element, characterised in that a model-based closed-loop control is used for the drive. 
     
     
         20 . A method as set forth in  claim 19  characterized in that the method is used for optimizing metering profiles of electromagnetically driven metering pumps. 
     
     
         21 . A method as set forth in  claim 20  characterized in that the position of the displacer element and a state space model is used for the model-based closed-loop control, which state space model uses the position of the displacer element and/or the current through the electromagnetic drive as measurement variables. 
     
     
         22 . A method as set forth in one of  claim 19  characterized in that a differential equation is used for the model-based closed-loop control. 
     
     
         23 . A method as set forth in  claim 22  characterized in that displacement pump-specific forces acting on the pressure portion are modeled in the differential equation. 
     
     
         24 . A method as set forth in  claim 19  characterized in that a non-linear state space model is selected as the state space model, wherein the non-linear closed-loop control is effected by way of control-Lyapunov functions, by way of flatness-based closed-loop control methods with flatness-based precontrol, by way of integrator backstepping methods, by way of sliding mode methods or by way of predictive closed-loop control. 
     
     
         25 . A method as set forth in  claim 20  characterized in that the difference between the detected actual position profile of the displacer element and a predetermined target position profile of the displacer element is detected during a suction-pressure cycle and the difference of at least a part of the detected difference and the predetermined target position profile is used as the target value profile for the next suction-pressure cycle. 
     
     
         26 . A method as set forth in  claim 22  characterized in that a physical variable is determined in the displacement pump by means of the differential or movement equation. 
     
     
         27 . A method as set forth in claim  8  characterized in that the fluid pressure p of a delivery fluid disposed in a metering chamber of a displacement pump is determined as a physical variable. 
     
     
         28 . A method as set forth in  claim 26  characterized in that if the actual fluid pressure reaches or exceeds a predetermined maximum value a warning signal is output. 
     
     
         29 . A method as set forth in  claim 26  characterized in that for a movement cycle of the displacer element at least one of a target fluid pressure curve, a target position curve of the displacer element and the target current pattern through the electromagnetic drive is stored, and the actual fluid pressure is compared to at least one of the target fluid pressure, the actual position of the displacer element is compared to the target position of the displacer element and a warning signal is output if the differences between the actual and target values satisfy a predetermined criterion. 
     
     
         30 . A method as set forth in  claim 29  characterized in that a weighted sum of the relative deviations from the target value is determined and the criterion is so selected that a warning signal is output if the weighted sum exceeds a predetermined value. 
     
     
         31 . A method as set forth in  claim 29  characterized in that a plurality of criteria are predetermined, a fault event is associated with each criterion and, if a criterion is fulfilled, the associated fault event is diagnosed. 
     
     
         32 . A method as set forth in  claim 26  characterized in that at least one of the mass m of the displacer element, the spring constant k of the spring prestressing the displacer element, the damping d and the electrical resistance R Cu  of the electromagnetic drive is determined as the physical variable. 
     
     
         33 . A method as set forth in  claim 19  through  14  characterized in that hydraulic parameters in the positive displacement pump are determined, for the hydraulic system a physical model is established with hydraulic parameters, the force exerted by the displacer element on the fluid in the metering chamber or the pressure in the metering chamber as well as the position of the displacer element is determined and at least one hydraulic parameter is calculated by means of an optimization calculation. 
     
     
         34 . A method as set forth in  claim 33  characterized in that at least one of the density of the fluid in the metering chamber and the viscosity of the fluid in the metering chamber is determined as the hydraulic parameter. 
     
     
         35 . A method as set forth in  claim 33  characterized in that the physical model is set up for the situation where the valve to the suction line is opened and the valve to the pressure line is closed and/or for the situation where the valve to the suction line is closed and the valve to the pressure line is opened, wherein if the physical model is set up both for the situation where the valve to the suction line is opened and the valve to the pressure line is closed and also for the situation where the valve to the suction line is closed and the valve to the pressure line is opened, the valve opening times are determined, and the physical model is selected in dependence on the result of determining the valve opening times. 
     
     
         36 . A method as set forth in  claim 33  characterized in that after determination of the hydraulic parameter same and the physical model is used for determining the force exerted by the delivery fluid on the displacer element and the force determined in that way is used in a closed-loop control of the movement of the displacer element. 
     
     
         37 . A method as set forth in  claim 20  characterized in that the current through the electromagnetic drive is measured and a state space model is used for the model-based closed-loop control, which state space model uses the position of the displacer element and/or the current through the electromagnetic drive as measurement variables. 
     
     
         38 . A method as set forth in  claim 26  characterized in that if the actual fluid pressure reaches or exceeds a predetermined maximum value a warning signal is output and the warning signal is sent to an automatic shut-down arrangement which shuts down the metering pump in response to reception of the warning signal.