CONTROL DEVICE FOR A PERISTALTIC PUMP, PERISTALTIC PUMP, INJECTION APPARATUS AND METHOD FOR CONTROLLING A PERISTALTIC PUMP

Abstract

Disclosed is a control device for a peristaltic pump which delivers a medium in pulsating pressure cycles, the control device controlling a speed of the peristaltic pump in such a way that a maximum volume flow (Q.sub.max) is achieved without exceeding a pressure limit (p.sub.Grenz) in the delivery line. In certain embodiments, it is proposed to calculate a prediction pressure (p.sub.futur) for each pressure cycle (P) for an expected maximum pressure within the pressure cycle (P) on the basis of at least the pressure (p.sub.ist) in the output line and to limit the maximum volume flow (Q.sub.max) by using the prediction pressure so that the pressure (p.sub.ist) in the output line does not exceed the pressure limit (p.sub.Grenz) in the pressure cycle (P).

Claims

1. A control device for a peristaltic pump with a squeeze tube and cyclically moving conveying elements for conveying a medium guided in the squeeze tube into a discharge line connected to the squeeze tube during a conveying action with a controlled volume flow rate, wherein the conveying elements are adapted to cyclically compress the squeeze tube so that a pressure curve of a pressure (p.sub.ist) is established in the discharge line, the pressure curve having cyclically repeating pressure cycles (P), wherein each pressure cycle (P) has a pressure minimum, a pressure rise, a pressure maximum and a pressure drop, wherein the control device is adapted to controls a speed of the peristaltic pump in such a way that a maximum volume flow rate (Q.sub.max) is achieved without exceeding a pressure limit (p.sub.Grenz) in the discharge line, and wherein the control device has a first control loop for controlling the maximum volume flow rate (Q.sub.max), adapted to receives a setpoint volumetric flow (Q.sub.soll) and the pressure limit (p.sub.Grenz) as command variables, and is arranged such that for each pressure cycle (P), a prediction pressure (p.sub.futur) is calculated for an expected maximum pressure within the pressure cycle (P) on the basis of at least the pressure (p.sub.ist) in the discharge line, and the maximum volume flow rate (Q.sub.max) is limited, taking into account the prediction pressure (p.sub.futur), in such a way that the pressure (p.sub.ist) in the discharge line does not exceed the pressure limit (p.sub.Grenz) in the pressure cycle (P).

2. The control device according to claim 1, wherein the first control loop comprises a pressure phase detection which detects the end of a preceding pressure cycle (P) and the beginning of a subsequent pressure cycle (P′) on the basis of a characteristic variable, in particular a defined pressure drop relative to a pressure maximum (p.sub.max) of the preceding pressure cycle (P), in order to initiate the control of the maximum volume flow rate (Q.sub.max) for the subsequent pressure cycle (P).

3. The control device according to claim 1, wherein each pressure cycle (P) is divided into successive pressure phases (I to V) on the basis of predefined characteristics, in particular a pressure change and/or a rate of change of the pressure (p.sub.ist), and the pressure phase detection detects the start of the individual pressure phases (I to V) either on the basis of the predefined characteristics and/or on the basis of a position of the conveying elements of the peristaltic pump, and the predicted pressure (p.sub.futur) for regulating the maximum volume flow rate (Q.sub.max) in the first control loop is used only in defined pressure phases and is ignored in other pressure phases.

4. The control device according to claim 3, wherein a first pressure phase (I) is characterised by a rapid pressure loss, a second pressure phase (II) by a rapid pressure rise, a third pressure phase (III) by a mild pressure rise, a fourth pressure phase (IV) by a moderate pressure rise (IV) and a fifth pressure phase (V) by a pressure plateau with substantially constant pressure, and each pressure phase is detected by the pressure phase detection.

5. The control device according to claim 4, wherein in the first control loop, the prediction pressure (p.sub.futur) is used to limit the maximum volumetric flow rate (Q.sub.max) only in the fourth pressure phase (IV), wherein the fourth pressure phase (IV) preferably and approximately is extending in a range of the pressure cycle (P) of 50% to 80% of a phase progress of the pressure cycle (P).

6. The control device according to claim 2, wherein the pressure phase detection determines the start of at least one pressure phase of a pressure cycle (P) on the basis of a pressure change (Δp) of the pressure (p.sub.ist) and/or a pressure change rate (dp/dt) of the pressure (p.sub.ist).

7. The control device according to claim 2, wherein in the control method, the predicted pressure (p.sub.futur) is determined as a linear extrapolation of the current pressure increase (p.sub.ist) to a specific, calculated or predetermined phase progress (φ.sub.87%) of the pressure cycle (P).

8. The control device according to claim 7, wherein in the control method, the predetermined or calculated phase progress (φ.sub.87%) at which the prediction pressure (p.sub.futur) is determined does not coincide with an actual phase progress (φ.sub.81%) at which the actual maximum pressure (p.sub.max) of a pressure cycle (P) occurs.

9. The control device according to claim 1, wherein the first control circuit comprises a mean value filter which adjusts the maximum volume flow rate (Q.sub.max) as a function of a maximum pressure (p.sub.max) of a pressure cycle (P) immediately preceding the current pressure cycle (P) which is temporarily stored in the control device.

10. The control device according to claim 3, wherein the first control loop is a PID controller with a proportional element (P), an integral element (I) and a differential element (D), preferably the differential element being set to zero in certain pressure phases, in particular in the first pressure phase (I), the second pressure phase (II), the third pressure phase (III) and the fifth pressure phase (V).

11. The control device according to claim 1, wherein the control device comprises a control system for smoothing pressure peaks of the pressure curve of the pressure (p.sub.ist) in the individual pressure cycles (P), said control system being arranged as a speed adapter, such that in each case at a specific progress of the pressure cycle, a setpoint speed (ω.sub.Soll) of a conveying element of the peristaltic pump is lowered by a specific amount to a lower setpoint speed (ω−) with respect to an average setpoint speed before completion of a pressure cycle (P) and/or is increased by a specific amount to a higher setpoint speed (ω.sub.+) being higher than the average setpoint speed after completion of a pressure cycle (P), and is held for a specific holding period.

12. The control device according to claim 11, wherein the speed (ω) of a conveying element is increased abruptly by the defined amount after completion of a pressure cycle (P) and is then reduced linearly to the lower setpoint speed (ω−) of the conveying element.

13. The control device according to claim 1, wherein the conveying process comprises more than one, preferably more than 5 and particularly more than 10 pressure cycles.

14. A peristaltic pump in the form of a roller pump with a rotatable rotor and a control device according to claim 1, wherein the conveying elements are designed as rollers arranged on a rotor, the squeeze tube is supported along a tube bed with an inlet region and an outlet region, wherein the conveying elements are configures to, upon rotation of the rotor, successively compress in a fluid-tight manner a section of the squeeze tube as the conveying elements enter the hose bed at the level of the inlet region until the conveying elements exit the tube bed at the level of the outlet region and thereby the medium located in the squeeze tube is conveyed into the discharge line against a dynamic pressure arising in the discharge line, wherein each time a volume of the squeeze tube located upstream of the outlet region is compressed from a maximum volume to a minimum volume until a conveying element emerges from the tube bed at the level of the outlet region and thereby the compressed section of the squeeze tube compressed by this conveying element is released, whereby each time the volume located upstream of the outlet region of the squeeze tube is increased from the minimal volume to the maximal volume, whereby a volume reduction and a subsequent volume increase of the volume located upstream of the outlet region form a complete pressure cycle (P), wherein the roller pump has n conveying elements, so that the roller pump executes n pump strokes with n pressure cycles (P) during a complete 360° turn of the rotor, and wherein each pressure phase (I to V) of a pressure cycle (P) corresponds substantially to a certain angular range of an angular position (φ) of a conveying element.

15. The pump according to claim 14, wherein the start of at least one pressure phase (I to V) of a pressure cycle (P) is determined indirectly by the pressure phase detection via an angular position (φ) of a conveying element.

16. An injection device for injecting an injection medium into an animal or human body by means of a peristaltic pump in the form of a roller pump, wherein the injection device contains a roller pump according to claim 14.

17. A control method for controlling a peristaltic pump with a squeeze tube and cyclically moving conveying elements for conveying a medium guided in the squeeze tube during a conveying action with a controlled volume flow rate into a discharge line connected to the squeeze tube, wherein the conveying elements cyclically compress the squeeze tube so that a pressure curve of a pressure (p.sub.ist) is established in the discharge line, and the pressure curve is having cyclically repeating pressure cycles (P), wherein each pressure cycle comprises a pressure minimum, a pressure increase, a pressure maximum and a pressure drop, wherein the control method controls a speed of the peristaltic pump in such a way that a maximum volume flow rate (Q.sub.max) is achieved without exceeding a pressure limit (p.sub.Grenz) in the discharge line, the control method is comprising a first control loop for controlling the maximum volumetric flow rate (Q.sub.max), which receives as command variables a setpoint volumetric flow rate (Q.sub.soll) and the pressure limit (p.sub.Grenz), wherein for each pressure cycle (P), a prediction pressure (p.sub.futur) is calculated for an expected maximum pressure (p.sub.max) within the pressure cycle (P) on the basis of the pressure (p.sub.ist) in the discharge line, and the maximum volume flow rate (Q.sub.max) is limited, taking into account the prediction pressure (p.sub.futur), in such a way that the pressure (p.sub.ist) in the discharge line does not exceed the pressure limit (p.sub.Grenz) in the pressure cycle (P).

Description

[0043] Thereby show

[0044] FIG. 1: a schematic representation of a contrast medium injection device with a roller pump,

[0045] FIG. 2: A detailed illustration of a roller pump with conveying elements,

[0046] FIG. 3: A diagram of a typical pressure curve of a roller pump over time, as well as the associated pressure phases and a curve of the angle of rotation of the conveying elements over time,

[0047] FIG. 4: A diagram of a typical pressure curve of a roller pump controlled according to the invention with phase detection as well as pressure prediction,

[0048] FIG. 5: A circuit diagram of a control device according to the invention,

[0049] FIG. 6: A pressure curve with occluded discharge line with control response of the control device from FIG. 5,

[0050] FIG. 7A: a diagram for a pressure phase-dependent control of a maximum volume flow rate in a control device according to the invention, as well as

[0051] FIG. 7B: A diagram of pressure curve, volume flow rate and angular velocity for a roller pump with a volume flow rate control according to FIG. 7A (left) and without volume flow rate control (right).

[0052] In the figures, identical or comparable components, functions or elements are given the same or comparable reference signs. If reference signs are used repeatedly, referral is made to the respective previous description.

[0053] FIG. 1 shows an injection device 1 for the intravenous administration of an injection agent. The injection device 1 has a base body mounted on rollers, at the upper end of which several injection agent containers 2a, 2b, 2c are arranged. Contrast media and a saline solution are stored in the injection medium containers 2a, 2b, 2c. The injection medium containers 2a, 2b, 2c are connected to a squeeze tube 4 via a supply line 3. The squeeze tube 4 is inserted into the tube bed 6 of a roller pump 5 and is connected on the outlet side to a discharge line 9, which in turn can be connected to the bloodstream of a patient via a catheter by means of an adjoining patient tube (not shown).

[0054] The roller pump 5 has three rollers 5-1, 5-2, 5-3 rotatably mounted on an electric motor-driven rotor 7, which are guided along the tube bed 6 of the peristaltic pump 5 as shown in FIG. 2, and in doing so squeeze the squeeze tube 4 in certain areas against a counter-bearing part of the tube bed 6, so that when the rotor 7 rotates about its axis of rotation, an injection medium in the squeeze tube 4 is conveyed in portions into the outlet line 9 against a back pressure in the outlet line 9. The injection device 1 has a control device 8 for controlling the roller pump 5 (and further components of the injection device 1).

[0055] FIG. 2 shows a detailed perspective view of the roller pump 5. As can be seen in FIG. 2, the squeeze tube 4 runs over an angular range of approximately 260°—with respect to the axis of rotation X of the roller pump 5—between an inlet area 6-1 of the tube bed 6 and an outlet area 6-2 of the tube bed 6. Since the three rollers 5-1, 5-2, 5-3 are arranged evenly at an angular distance of 120° each on the rotor 7, there are thus always at least two rollers between the inlet area 6-1 and the outlet area 6-2 of the tube bed 6, which compress the squeeze tube 4 against the counter bearing part of the tube bed 6. The squeeze tube 4 is therefore always compressed in at least two places during operation of the roller pump.

[0056] The rotor 7 of the peristaltic pump rotates in a direction of rotation—clockwise in the illustration of FIG. 2—so that the compressed areas of the squeeze tube 4 with the rollers 5-1, 5-2, 5-3 move in the direction of rotation. Between two compressed areas, a fluid-tight tube section with a certain volume is formed in each case, so that injection medium contained therein is encapsulated between two rollers 5-1, 5-2, 5-3 and moved in the direction of rotation to the outlet area 6-2. When in the outlet area 6-2 a roller 5-1 starts to lift off from the tube bed 6, the injection medium can be conveyed in the tube section against the back pressure prevailing in the remaining part of the discharge line 9. In FIG. 2, the roller 5-1 has already completely left the outlet area 6-2 in the direction of rotation (the squeeze tube 4 is therefore no longer compressed by the roller 5-1), and the injection agent is conveyed in the tube section against the dynamic pressure prevailing in the remaining part of the discharge line 9.

[0057] A pressure sensor 9-1 shown in FIG. 5 is arranged in the discharge line 9, which continuously measures the pressure p.sub.ist prevailing therein and transmits it to the control device 8.

[0058] The cyclically exiting of a roller 5-1 in the outlet area 6-2 results in a characteristic pressure curve of the pressure p.sub.ist with cyclically repeating pressure cycles P in the discharge line 9. A characteristic pressure curve p.sub.ist with several pressure cycles P, P′, P″ is exemplarily shown in FIG. 3 at the top in its temporal course. During a pressure cycle P, the pressure fluctuates between a pressure minimum p.sub.min at the beginning of the pressure cycle P, rises rapidly at first, then passes into a range with a moderate pressure increase and reaches a brief pressure plateau or pressure maximum p.sub.max before the pressure drops rapidly and the next pressure cycle P′ begins.

[0059] The beginning of a pressure cycle P correlates with the exit of the first roller 5-1 from the tube bed 6 in the outlet area 6-2, at which time a second roller 5-2 is in the angular position marked in FIG. 2 with the reference sign φ.sub.0° This second roller 5-2 represents the leading roller at this moment (and until it exits via the exit area 6-2) and, with further rotation, continues to reduce the tube volume of the squeeze tube 4 in front of it against a back pressure in the discharge line 9, which leads to the characteristic pressure increase. When this second roller leaves the tube bed 6 in the outlet area 6-2, i.e. approximately at an angular position which is provided with the reference sign φ.sub.120° in FIG. 2, the compression of the squeeze tube 4 at this region is terminated, so that the volume increases approximately abruptly up to the subsequent third roller 5-3. This leads to the characteristic pressure drop at the end of a pressure cycle P.

[0060] As can be seen in FIG. 3, the pressure curve at the beginning of the pressure cycle is comparatively steep (range II) as long as a non-return valve 9-2 (see FIG. 5) in the discharge line 9 is still closed. As soon as the closing pressure of the non-return valve 9-2 is reached, the non-return valve 9-2 opens and the pressure increase drops (range III). At this point, the liquid column of the injection medium present in the discharge line 9 and the patient tube following downstream must be set in motion against the mass inertias as well as further throttle resistances, which is responsible for the further pressure increase. A further pressure increase occurs in range IV, which is due to another non-return valve in a catheter. After the pressure resistances have been overcome, a quasi-static flow state with an approximately constant pressure (range V) is established before the pressure drops again when a roller exits the tube bed 6 (range I).

[0061] During a complete revolution of the rotor 7, each of the three rollers 5-1, 5-2, 5-3 will therefore pass once through the angular range designated φ.sub.P between φ.sub.0° and φ.sub.120° and cause a pressure cycle P. The angular range φ.sub.P thus comprises angles φ.sub.i° between 0° and 120°, designated here as the pressure phase angle, where the subscript i stands for the angle. It is evident that the pressure phase angle φ.sub.i° is directly related to the angular position φ of the rotor 7 or the individual rollers via the modulo relationship φ.sub.i°=φ mod 120°.

[0062] For clarification, a time course of the pressure phase angle φ.sub.i° is drawn in FIG. 3 below.

[0063] In order to guide an actual volume flow rate Q.sub.ist in the discharge line 9 as close as possible to a specified target volumetric flow, it is necessary to guide the actual pressure curve of the pressure p.sub.ist as close as possible to the pressure limit p.sub.Grenz that is still permissible. In the present embodiment example of the invention, the roller pump 5 is to be controlled to a maximum volume flow rate Q.sub.max without exceeding the still permissible pressure limit p.sub.Grenz. The pressure limit p.sub.Grenz can therefore also be understood as the (maximum) set pressure for the pressure p.sub.ist. Above the limit value p.sub.Grenz. FIG. 3 also shows a hazard pressure p.sub.Gefährdungsdruck, at which irreparable damage to the device or patient occurs. It must therefore be ensured that the hazard pressure p.sub.Gefährdungsdruck is not exceeded under any circumstances.

[0064] Unlike syringe pumps, where a piston is pushed into a cylinder at a controlled speed, it is much more difficult to maintain the pressure limit p.sub.Grenz with roller pumps because of the pressure pulsations. For this reason, high safety buffers (distance between p.sub.Grenz and p.sub.Gefährdungsdruck) must be usually incorporated in known roller pumps in order to prevent the hazard pressure p.sub.Gefährdungsdruck from being reached or even exceeded in the further course of a pressure cycle if the pressure limit p.sub.Grenz is already exceeded at the beginning of a pressure cycle.

[0065] To compensate for this system-related disadvantage, the control device 8 of this embodiment provides a control according to the control scheme shown in FIG. 5. The control device 8 comprises a second control loop 10 for controlling the rotational (angular) speed ω of the rotor 7 of the roller pump 5, the pump speed PID controller, which receives the maximum volume flow rate Q.sub.max as a command variable and converts this into a set rotational (angular) speed ω.sub.Soll or a corresponding rotating field for controlling the roller pump. The actual rotational (angular) speed ω.sub.ist is fed back as a measured variable and a control deviation between the set and actual rotational (angular) speed is minimised by feedback.

[0066] To determine the maximum volume flow rate Q.sub.max, a first control loop 11 is connected upstream of the second control loop 10, to which a setpoint volumetric flow rate Q.sub.Soll and a permissible pressure limit p.sub.Grenz are externally specified as command variables. The setpoint volumetric flow rate Q.sub.Soll (unchanged), the pressure p.sub.ist measured in the discharge line 9 and the angular speed ω.sub.ist of the rotor 7 of the roller pump 5 measured at the roller pump 5 enter the first control loop 11 as feedback variables. The measurement and feedback of an actual volume flow rate Q.sub.ist in the discharge line 9 can be dispensed with.

[0067] The first control loop 11 is designed as a discontinuous PID controller that regulates the controlled variable of the maximum volume flow rate Q.sub.max differently depending on the pressure phase of a pressure cycle.

[0068] The first control loop 11 comprises a pressure phase detection 12 including a pressure phase commutation detector 12-1 and a pressure phase switch 12-2, a pressure prediction 13, and a first control component 14 and a second control component 15.

[0069] The pressure phase commutation detector 12-1 is used to detect the start of a pressure phase. For this purpose, it continuously compares the current pressure p.sub.ist with a reference value, namely a temporarily stored pressure maximum p.sub.max of a previous pressure cycle P, and sets the start of a pressure cycle P to the point in time at which a pressure drop of the pressure p.sub.ist in the discharge line 9 of more than ⅙, when compared to the temporarily stored pressure maximum p.sub.max, occurs. At this time, one of the rollers 5-1, 5-2, 5-3 of the roller pump 5 is approximately in the angular position marked φ.sub.0° in FIG. 2. The pressure phase angle φ.sub.i° is set to zero, i.e. φ.sub.0°=0°, and serves in the further course of the pressure cycle P as a reference value for determining subsequent pressure phases. “Phase I” is set as the current pressure phase.

[0070] The pressure phase switch 12-2 switches or counts up the individual pressure phases II to V. The individual pressure phases or the start of the individual pressure phases are determined via the angle φ.sub.i°. The pressure phase angle φ.sub.i° in turn is detected or approximated—starting from the reference value φ.sub.0°—via a time integration of the actual angular velocity of rotation of the roller pump.

[0071] The different pressure phases I to V are defined as follows:

[0072] The beginning of the first pressure phase I is defined by a pressure drop of more than ⅙ compared to the pressure maximum of the previous pressure cycle. The beginning of the second pressure phase II is set to the point in time at which or after a pressure increase is certain. The third pressure phase III corresponds to a first compression phase, the beginning of which is defined at a pressure phase angle of 45° (this corresponds to a phase progress of 37.5% of the complete angular range φ.sub.P). A fourth pressure phase IV is defined at a pressure phase angle of 60° (phase progress of 50%). The beginning of the fifth pressure phase V is set at a pressure phase angle of 97.2° (phase progress of 81%).

[0073] The individual pressure phases I to V of several successive pressure cycles P, P′, P″ can be taken from FIG. 4.

[0074] The first control component 14 is activated via the pressure phase detection 12 when the current pressure cycle P is in the fourth pressure phase IV. In all other pressure phases (I to III and V), the first control component 14 is deactivated, i.e. set to zero.

[0075] The first control component 14 is the differential element of the PID controller. In it, a correction factor Q.sub.D is calculated, which is deducted from the target volume flow rate Q.sub.Soll. It is calculated as the ratio of a predicted pressure p.sub.futur (or p.sub.forecast) and the pressure limit p.sub.Grenz multiplied by the currently calculated maximum volume flow rate Q.sub.max according to the formula

[00001]$Q_D=K_D\frac{p_{\mathrm{futur}}}{p_{\mathrm{Grenz}}}{Q}_{\max },$

[0076] where K.sub.D is a fixed gain factor.

[0077] The predicted pressure p.sub.futur is continuously provided by the pressure prediction 13. The predicted pressure p.sub.futur is determined as a linear extrapolation of the current pressure p.sub.ist to a defined pressure phase angle of 105° (or a phase progress of 87.5%) according to the formula

[00002]$p_{\mathrm{futur}}=p_{\mathrm{ist}}\frac{{\mathrm{dp}}_{\mathrm{ist}}}{\mathrm{dt}}\frac{\phi t}{\mathrm{\phi 87},5\%},$$\mathrm{where}$$\frac{{\mathrm{dp}}_{\mathrm{ist}}}{\mathrm{dt}}$

is the time derivative of the measured pressure p.sub.ist and

[00003]$\frac{\phi }{\mathrm{\phi 87},5\%}$

determines the ratio of the current pressure phase angle φ.sub.i=t at time t and the pressure phase angle at a phase progress of 87.5% (this corresponds to a pressure phase angle of 105° for a complete angular range φ.sub.P of 120°). The predicted pressure represents a forecast for the expected pressure maximum in the current pressure cycle at the defined pressure phase angle. The predicted pressure p.sub.futur is plotted in its temporal course in FIG. 4.

[0078] The terms “prediction pressure” and “predicted pressure” are to be understood synonymously.

[0079] The second control component 15 is the proportional and integral element of the PID controller. In it, a correction factor Q.sub.I is calculated, which is deducted from the setpoint volume flow rate Q.sub.Soll and is calculated via three components α, β, γ:

[0080] The first component α of the second control component 15 is a mean value filter which adjusts the maximum volume flow rate Q.sub.max via the ratio of the maximum pressure p.sub.max of the immediately preceding pressure cycle P compared to the pressure limit p.sub.Grenz, multiplied by a gain factor K.sub.I, according to the formula

[00004]$\alpha =K_I\frac{p_{\max }}{p_{\mathrm{Grenz}}}{Q}_{\max }.$

[0081] The maximum pressure p.sub.max of each pressure cycle is temporarily stored in a memory in the control unit 8 for this purpose. Measurement errors of the pressure p.sub.ist can be smoothed via the mean value filter.

[0082] The second component β of the second control component 15 is a proportional element which increases the correction factor Q.sub.D calculated in the previous pressure cycle P by the first control component 14 by a gain factor K.sub.D.fwdarw.I according to the formula

β=K.sub.D.fwdarw.IQ.sub.D.

[0083] Since the first control component 14 calculates the correction factor Q.sub.D only in pressure phase IV, the second component β of the second control component 15 is zero when the pressure cycle is outside pressure phase IV.

[0084] The third component γ of the second control component 15 is an integral element that is calculated from the sum of the previous volume flow rate corrections Q.sub.I n-1 of the individual pressure phases of the current pressure cycle, according to the formula

γ=Σ.sub.n-1Q.sub.I n-1,

[0085] where n is the number of pressure cycles and Q.sub.I n-1 is the volume flow rate correction of successive pressure cycles.

[0086] The three components α, β, γ of the second control component are added up to a correction variable Q.sub.I (Q.sub.I=α+β+γ) and the correction variable Q.sub.I is subtracted from the setpoint volume flow rate Q.sub.Soll.

[0087] Thus, the maximum setpoint volume flow rate Q.sub.max results from the setpoint volume flow rate Q.sub.soll minus the correction variables Q.sub.D and Q.sub.I of the first and second control components 14 and 15 (Q.sub.max=Q.sub.Soll−Q.sub.I−Q.sub.D).

[0088] Via the control device 8 designed in this way, the output of the roller pump 5 or its rotational speed ω can be regulated and adjusted in a prospective manner. Since the maximum volume flow rate Q.sub.max is calculated differently in pressure phases I to III and V than in pressure phase IV, this is a discontinuous control.

[0089] A control response for the case of a pinched-off, fluid-impermeable discharge line 9 is shown in the diagram of FIG. 6 with six successive pressure cycles A to F showing the measured pressure p.sub.ist, the predicted pressure p.sub.futur calculated by the pressure prediction 13 and the associated pressure phases I to V of the individual pressure cycles A to F. As a result of the disconnected discharge line 9, the absolute pressure maximum p.sub.max increases steadily in each pressure cycle: p.sup.A.sub.max<p.sup.B.sub.max<p.sup.C.sub.max<p.sup.D.sub.max etc.

[0090] The predicted pressure p.sub.futur exceeds the pressure limit p.sub.Grenz for the first time in a fourth pressure phase IV in pressure cycle F. The other exceedances of the predicted pressure p.sub.futur beyond the pressure limit p.sub.Grenz in other phases, e.g. in pressure cycle D in pressure phase II, are irrelevant, since the control device 8 only takes the predicted pressure p.sub.futur into account in pressure phase IV via the control component 14.

[0091] Since every fourth pressure phase IV already begins at a pressure phase angle of 60° (or a phase progress of 50%), the maximum setpoint volume flow rate Q.sub.max in the pressure cycle F and thus also the rotational speed ω.sub.ist are reduced by the control device 8 with the onset of the pressure phase IV in the pressure cycle F. The throttling of the rotational speed ω at the beginning of phase IV is clearly visible in FIG. 6. The pressure limit p.sub.Grenz is not exceeded due to the sufficient lead time between the detection of an imminent exceeding of the pressure limit p.sub.Grenz and the occurrence of the pressure maximum p.sup.F.sub.max<p.sub.Grenz.

[0092] In order to achieve a levelling of the pressure curve of the pressure p.sub.ist, i.e. a reduction of the amplitude, the control device 8 of the embodiment example according to FIG. 5 can also be supplemented by a control system not shown in FIG. 5, which increases or decreases the maximum setpoint volume flow rate Q.sub.Soll depending on the phase progress. This control manipulates the command variable of the setpoint volumetric flow rate Q.sub.Soll in such a way that the setpoint volumetric flow rate Q.sub.Soll is increased by 30% to an increased setpoint volumetric flow rate Q.sub.+ at the beginning of a pressure cycle and is reduced by 30% to a reduced setpoint volumetric flow Q.sub.− towards the end of a pressure cycle. The changed setpoint flow rate Q.sub.Soll is held for a holding time of x-hold. The holding time x-hold can correspond to a certain phase progress, such as e.g. 25% or the duration of phase I. Due to the opposite adjustment to the increased or decreased setpoint volumetric flow rate Q.sub.+ or Q.sub.−, the average setpoint volumetric flow rate over a pressure cycle P remains unchanged. The corresponding presetting of the target volumetric flow rate is shown in FIG. 7A for a pressure cycle P with pressure phases I to V. As can be seen in FIG. 7A, the set volumetric flow rate Q.sub.Soll is suddenly increased to the set volumetric flow Q.sub.+ at the beginning of the pressure cycle P and then decreases linearly to the reduced set volumetric flow rate Q.sub.−. The command variable of the setpoint volumetric flow rate Q.sub.Soll changed in this way, which is now variable in time over a pressure cycle P, is fed into the first control loop 11.

[0093] Such control results in a smoother pressure curve with fewer pressure fluctuations and, in particular, flattened pressure peaks. This is shown in FIG. 7B: FIG. 7B shows a pressure curve for several pressure cycles A to F, whereby the setpoint volume flow rate Q.sub.Soll in the pressure cycles A to C and the beginning of the pressure cycle D was adjusted according to the variable setpoint volume flow rate Q.sub.Soll according to FIG. 7A, and a constant setpoint volume rate flow was specified in the subsequent pressure cycles. As can be seen in FIG. 7B, the pressure peaks p.sub.max of the pressure cycles A, B and C can thus be reduced compared to the pressure peaks p.sub.max of the pressure cycles D, E and F.

[0094] Another effect of this control is also that a motor power of the peristaltic pump 5 after the sudden pressure drop at the end of a pressure cycle P does not have to be abruptly reduced or even slowed down to keep the volume flow rate constant. This can save energy and reduce motor noise.

[0095] Since the setpoint volumetric flow rate Q.sub.Soll is approximately directly proportional to the angular velocity ω.sub.ist of the peristaltic pump 5, the angular velocity ω.sub.ist of the peristaltic pump 5 (discounting for measurement inaccuracies and the influence of the controlled system) has a comparable curve to the target volume flow rate Q.sub.Soll. It is therefore possible to increase the angular velocity ω.sub.Soll of the peristaltic pump to an increased setpoint velocity ω.sub.+ at the beginning of a pressure cycle and/or to decrease it to a lower setpoint velocity ω.sub.− towards the end of the pressure cycle instead of the setpoint volumetric flow rate.

[0096] The invention exemplified in the described embodiments enables safer operation of a peristaltic pump with higher media throughput and lower pressure fluctuations.

[0097] In addition to peristaltic pumps, the control device can also be used for other pumps with cyclically repeating pressure curves, such as diaphragm pumps with an oscillating diaphragm, piston pumps with reciprocating pistons, sine pumps or gear pumps. The control device is particularly suitable for application purposes in which overpressure valves, over which medium is set free, are incompatible with the system to be used in.

LIST OF REFERENCE SIGNS

[0098] I to V Pressure phases of a pressure cycle [0099] p.sub.Grenz Pressure limit (target pressure) [0100] p.sub.futur Prediction pressure [0101] p.sub.Gefährdungsdruck Hazard pressure [0102] P Pressure cycle (period) [0103] Q.sub.max maximum volume flow rate [0104] Q.sub.soll Target volume flow rate/setpoint volumetric flow rate [0105] X Rotary axis (roller pump) [0106] φ.sub.i° Pressure phase angle (at an angle i) [0107] ω.sub.ist Rotation angle speed of the roller pump/rollers 5-1.5-2, 5-3 (actual value) [0108] ω.sub.soll Angular velocity of rotation (set point) [0109] 1 Injection device [0110] 2a-c Injection medium container [0111] 3, 3′, 3″ Supply line [0112] 4 Squeeze tube [0113] 5 Peristaltic pump (roller pump) [0114] 5-1 Roll (squeeze roll) [0115] 5-2 Roll (squeeze roll) [0116] 5-3 Roll (squeeze roll) [0117] 5′ leading roll [0118] 6 Tube bed [0119] 6-1 Inlet area [0120] 6-2 Outlet area [0121] 7 Rotor [0122] 8 Control device [0123] 9 Discharge line [0124] 9-1 Pressure sensor (injection line) [0125] 9-2 Non-Return valve (injection line) [0126] 10 Second control loop (pump speed controller) [0127] 11 First control loop [0128] 12 Pressure phase detection [0129] 12-1 Pressure phase commutator [0130] 12-2 Pressure phase switch [0131] 13 Pressure predictor [0132] 14 first control component [0133] 15 second control component