GB2210181A

GB2210181A - Adaptive control in the electro-magnetic adjustment of a flow-determining element

Info

Publication number: GB2210181A
Application number: GB8822247A
Authority: GB
Inventors: Manfred Birk; Christian Engelbrecht; R Hermann Kull
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1987-09-23
Filing date: 1988-09-22
Publication date: 1989-06-01
Anticipated expiration: 2008-09-22
Also published as: GB2210181B; DE3825138A1; GB8822247D0; JPH01112302A

Description

C' 221018 1 Method and device for the adaptive adjustment control in the

electro- magnetic adjustment of a flow-determining element

Prior art

The invention is based on a method and a device for the adaptive adjustment control of the electromagnetic adjustment of a flowdetermining element (control rod in the case of diesel injection pumps) in accordance with the precharacterizing clause of Claim 1 and of Claim 4.

In the rotary speed control of a direct current electric motor, it is known (report by G. Weihrich, in the journal REGELUNGSTECHNIK, no. 11, 1978, pages 349 to 380), to use the information for load torque, generated by simulation by a combined state and disturbance _ observer, for the disturbance feedforward, or the rotary speed difference, respectively, for damping vibrations in order to improve the dynamic control range.

The basic principle of such a state control of a direct current motor is based on the model-supported determination of particular state variables such as the speed (kinetic energy) and acceleration (force) which cannot be derived, or only with difficulty from the actual system, but which are required for improving the control loop, the accuracy of control, the speed of control the extent to which disturbances and similar are taken into consideration, if for example, the aim is a fast and accurate rotary speed control arrangement.

Thus, the state and disturbance observer is an electronic model which, in addition to the actual control value, can supply further relevant variables and informa tion for improving the control loop, namely speed and acceleration data, disturbance force influences, system 2 dynamics. Such a state and disturbance observer, which is termed the so- called Luenberger observer supplies estimated values of the speed, the acceleration and the disturbance forces acting on the system, which can then be fed, appropriately processed, to the associated state controller which controls the actual controlled system.

It is necessary here to feed both the signal fed fr-om the output of the state controller or from the output of a power regilating element to the actual sistem or the signal fed to a regulating mechanism, and the control distance to the Luenberger observer as input variables, in which arrangement the output deviation can then be used for correcting the electronic model of the observer (for exampte by weighting particular observer controller terms) in such a manner until the difference value is a minimum.

Such an observer is therefore also capable of simulating, in addition to the internal variables (state variables) of the control, external variables (distur- bances) of the controlled system which, fed back to the actual state controller, then provide the possibility for the desired accurate control.

In the normal case, such an observer, which is pilot-controlled in full order and updated in all its memory elements, is an electronic system model which can usually be verified and deposited in all its sections in a computer, the pilot control being effected either from the measurable system input and updates being derived by the abovementioned proportional weighting from the error which arises by comparing the measurable system output (control distance) with the corresponding output signal of the observer.

Generally, it is known in the case of the positioning of the control rod in the case of in-line pumps or of the control valve in the case of distributor pumps to use an operating magnet, the position of the control rod or of the control valve being controlled in a position control loop. However, such position control is made more difficult by greatly fluctuating friction and by C_ ' disturbance forces. The friction, which partly differs greatly for each in-line pump or distributor pump depends here on a large number of influence factors, for example production spreads in the case of pumps and regulation mechanisms, the respective wear phenomena, also aging and similar, on the temperature and the current control rod position. Furthermore, the disturbance forces acting on the control rod are mainly the result of control interrupting shocks, that is to say reactions from the pump mem- 0 ber on the control rod and due to shaking and vibrating of the pump housing. 1 The invention is therefore based on the object of providing the possibility of position control which is fast and accurate independent of friction and interfer- ence forces, for the magnetic adjuster of a flow-determining element (control rod, control valve) in electric diesel injection pumps.

Such a fast position control is necessary because the faster the position control loop, the faster major- loop control loops (for example the idling control loop) can be made.

In general, it is known to use so-called twoposition controllers, PID controllers with reference shaper or also PID controllers with an active filtered D component.

If a state control or cascade control is used, additional transmitters are the actual control distance or the speed of the control required that, in addition to value, the acceleration and/ rod can also be taken into consideration. This frequently gives rise to problems to measure the acceleration and speed values of the control rod correctly (sic).

It is also known to use adaptive control arrange ments which are adapted via an identification of the system.

Advantages of the invention The invention achieves the above object by means C'

Claims

of the characterizing features of Claim 1 and of subclaim 4 and has the

advantage that due to the operation of the electronic obscrvation model on the flow-determining element driven by an operating magnet, that is to say control rod or control valve, a particularly effective suppression of the influence factors acting on the system, frictions and disturbance forces, is achieved in the case of-electronic diesel injection pumps.

The invention enables further variables such as -speed, acceleration, disturbance forces, friction, system dynamics to be utilized for the position cdntrol from on-tine identification; these variables are determined as estimated variables in the electronic model of the observer and fed forward to the state controller controlling the system. However, another controller having an corresponding characteristic, for example PID or PIDD2 can alsobe used here.

A particular advantage of the present invention is also obtained by virtue of the fact that the electronic model of the observer can only enable the system to be simulated with certain tolerances which necessarily lead to a steady-state error when the observer variables are output for the feedforward. Due to the feedforward, made possible by the invention, of the disturbances, friction and other influences via a high-pass filter to the con- trotler. or the current control loop following the latter the steady- state errors attributable to model tolerances are eliminated and therefore also do not reach the system. This results in an improved system behaviour which, in turn, reacts on the electronic observer model so that, overall, the overall operation of such a state controller for the control rod or the control valve can be improved by means of reference shaper and friction feedforward. 35 Advantageous further developments and improvements of the invention are pos-sible by means of the measures quoted in the subclaims.

is Drawing An illustrative embodiment of the invention is shown in the drawing and is explained in greater detail 5 in the description following.

Figure 1 shows a block diagram of the structure of-the arrangement with state controller, friction observation and friction feedforward and Figure 2 shows an illustrative representation of the structure of the system, of the state controller with reference s"haper and friction and disturbance feedforward by the observer.

Description of the illustrative embodiments The basic concept of the present invention consists in allocating to the control loop for adjusting the ftow-determining element, that is to say the control rod or the control valve in the case of an electric diesel injection pump, an observer which is capable to provide in addition to information on the acceleration and the speed of the control rod for the state control, information on the influencing disturbance forces such as friction, control-interrupting shocks, shaking of the pump and similar for the purpose of disturbance feedforward, the disturbance feedforward particularly being effected via a high-pass fitter as a result of which all steady state errors attributable to observed tolerances can be eliminated.

In the structure diagram of the arrangement accor ding to Figure 1, the control loop comprises a state con troller 10 which is fed with estimated values on the con trol speed of v and the magnetic force F of the magnetic adjuster via lines 1.1 and L2. Furthermore the measured control distance x at the output of the regulating mechanism 11 is also made available to the state controller as input variable and fed forward via the line L3. The observer 12 also supplies an estimated variable Fstor for the disturbance forces caused by friction and other disturbances. Via a disturbance feedforward block 13, the processed disturbance value which is a summing circuit point P1 which is fed with the output signal of the state controller 10 in addition to the disturbance and which drives the current control loop 14 which follows the state controller 10.

In the current control loop, the current I in the solenoid coil of the magnetic adjuster (regulating mecha- nism 11) is regulated to the setpoint Isoll. A two position current controller with hysteresis is preferably used as current controller, which is driven with a clock frequency of, for example 1000 Hz. This drive clock frequency can be so high because the disturbance influence in the control structure forming the basis of the inven- tion is kept small due to the particular feedforward from the observer so that low-frequency pulsing of the coil voltage, by means of which the influence of friction can be somewhat minimized in other cases, can be omitted. 20 The current loop 14 also largely speedproportionally compensates for the counter voltage induced in the solenoid coil, which reaches the loop as disturbance EMF, which wilt still be explained with reference to the representation of Figure 2. 25 -The observer 12 is supplied with the magnetic current I supplied from the current control 1. oop 14 to the regulating mechanism 11 via the line L4 and with the control distance x via the line L5 as input variables. The system observer provides the possibility of disturbance feedforward by the observed friction force Fstor. When the system is in the friction hysteresis, a set jump at the controller input causes a steep change in the observed friction force Fstor because the friction force and the magnetic force change at the same rate as long as the arrangement is in static friction mode. In the case of great friction, the set jumps also result in a greater deviation in the observed friction force than in the case of little friction.

The configuration is further completed by an I 1 5 bypass (element with integrating action), the input of which is supplied with the control deviation from the control distance x and the set po,,nt W, which is,processed via a reference shaper 16, and the output of which is compared with the setpoint W at a summation point P2 Located at the input of the state controller 10. The I bypass 15 forces the steady-state accuracy of the control Loop.

The more detailed structure of the state controller, shown in the representation of Figure,2, with refereye shaper and friction feedforward, shows the system complete with all disturbance influences, embedded in the_ adjustment control loop with detailed configuration of the electronic observer corresponding to the system.

The individual blocks or statements in the representation of Figure 2 in this case represent not only circuit functions but also generally physical variables. and parameters and it must also be pointed out that the blocks specifying discreet circuit or operating stages used for the subsequent explanation of the invention do not restrict the invention but are only aids for itlus'trating the basic functional effects of the invention and representing particular functional sequences in an illustrative embodiment. Naturally, the individual modules and blocks can be constructed in analog digital or also hybrid technology or can also be correspon,ding areas of program-controlled digital systems, for example, computers, microprocessors, digital or analog logic circuits and similar in complete or partial combination. The invention is therefore only specified with respect to the functional overall and time sequence, the action achieved by the blocks discussed in each case, and with respect to the relevant interaction of the subfunctions represented by the individual components with reference to the block diagrams of Figure 1 and 2, in which connection references to the individual circuit or function blocks must not be understood to be restricting but are only intended to be used for better understanding.

To facilitate identification, the basic blocks of c Figure 1 are again shown in Figure 2 within a dashed boundary.

The reference variable, that is to say the position setpoint W which is the first summing circuit area or circuit point P2 which is also fed with the output signal of the I bypass 15 having the integration time constant TI.

A further addition area as circuit point P3 at the input of the state controller with current control loop 10, 14 is fed with the state variables,v and F supplied by the observer and to this extent to be termed estimated values from summation or comparator areas (circuit points P4 and P5) via coefficient elements K1 and K3 containing amplifiers and with the controlled variable (control distance x) via the coefficient K2. Naturally, the circuit points mentioned.now and still to be mentioned hereinafter, can also be combined or are simply areas at which the variables supplied are compared and correspondingly processed in a different design of the analog circuit area or also in a digital implementat i o n.

At the input of the integrating bypass 15, a further summation or comparison point P6 is also formed which supplies the control deviation e from the controlled variable x and the position setpoint W processed via the reference shaper 16 to the input of the 1 bypass 15.

Via a coefficient element KO, a corresponding current setpoint Isoll reches the input of the current control Loop area with proportional control component P.

Before that, a comparison with the current I (correcting variable, by means of which the subsequent magnetic regutating mechanism KI is driven as transmission factor from current to force, is still effected via the feedback block KMES (steady-state transmission factor) at the cur- rent controller. The comparison is effected at the circuit point Pl', the disturbance Fstor originating from the observer still being fedforward at the preceding circuit point Pl. This will still be discussed below. The current control loop also comprises some integration time constant elements and circuit elements, PBM, KMS and TM, which are of no significance for the general configuration of the state controller with system and observer which is here only considered in principle. The speeddependant armature reaction is also indicated as EMF feedback via the block KV at P7.

At the output of the magnetic adjuster KI the fo-rce F generated by it is obtained, to which the spring pretension FO of the pretensioning spring acting on the armature or the regulating element (control rod) is also added at P8.

A further effect characterizing the physical configuration of the state controller with system results from block M from which the spring constant of the restoring spring appears at the circuit point P9 in depenence on the control distance x. The circuit points P9 and P10 are force influence points which, as far as this is concerned, naturally do not exist in reality - it has already been mentioned above that the state controller has been specified with its physical variables and parameters in Figure 2. This also results in a further feedback which is speed dependent in this extent in the area P10 via the block KR, which feedback corresponds to the P coefficient for speed-proportional friction. Incidentally, a large number of these blocks from a previous and subsequent explanation also appear in the.discussion of the basic configuration of the observer where they must be provided with an index "B" in order to distinguish them from the corresponding blocks, physical variables and parameters of the state controller with system.

In addition to the speed-proportional friction, the force influences resulting from the friction hysteresis, which are also speed-dependent and the respective occurence of which is indicated by the small table 18, are also obtained in the area P10. Thus, depending on whether the speed of the control rod is equal to zero or greater than or less than zero, three switching cases 1, 2, 3 are obtained in accordance with the table, static friction FRH existing in the switching case 1 (v = 0), c v indicated by the small diagram 19 and the switch position for the friction information at point 1.

If accordingly the speed of the control rod is greater than or less than zero (v > 0; v < 0), approximately constant friction variables FRG and FRG are obtained.

This "force area" is also followed by integration time constants T1 for the integration of the magnetic force (results in speed of the control rod) and integra- tion time constant T2 for the integration of the control rod speed (results in control distance).

This adequately describes the model of the moving control rod which represents a third-order system (third order because there are three energies stores, namely the magnetic energy, the spring energy and kinetic energy corresponding to the speed of the moving mass - with the state variables control distance x, speed v and (magnetic) force F).

The controller design can then be implemented via network terminal selection in that the transfer function of the closed loop is determined and carried out by means of a coefficient comparison with the standard transfer function. This does not need to be discussed in greater detail since these are essentially mathematical deriva- tions and calculations and the same correspondingly applies to the observer design whi.ch is also established by means of network terminal selection.

The part of the structure of the observer 12 in Figure 2 corresponding to the regulating mechanism com- prises the blocks T2E;, T18 M, TV), KIB and KCXB.

The observer thus represents an electronic simulation of the remaining system, the current I measured by a shunt being fed to it as input variable (Line L4). Instead of the coil current, the coil voltage could also be selected as input variable for the observer in which case the induced counterv^oltage EMF must be simulated in the observer. However, the coil inductants depends on the control distance so that its accurate implementation in the electronic model is difficult. For this reason, c having regard to a desired simulation of the system which is as accurate as possible, it makes sense to simulate only this remaining system in the observer, the nonlinear friction not being taken into consideration in the simulation of the system. This is why the dead zone and the speeddependent friction feedforward are omitted. Blocks GB, GA and TIB used for calibrating the observer model in such a way that x = X holds true. This is why the blocks GA, GB and TIS are the desing parameters of the observer. Since, as mentioned, neither the nonlinear friction nor other disturbances are included in the observer, the integrator must compensate the control deviation between model and sytem, caused by the disturbance and the friction, with the time constant TIB since it is only then that x holds true. If the system observer is sufficiently fast, the output fR,stor Of this integrator is therefore a measure of the resultant disturbance force occuring (friction, control-interrupting variables and similar). The variable FR,stor is there- fore utilised for disturbance feedforward to the state controller, the observer also supplying, in addition to this variable, estimated variables 1v and ? for the speed v and the magnetic force F which are needed as input variables for the state controller and reach the circuit point P3 via K1 and K3 as previously mentioned.

The integral bypass 15 in the input area of the state controller is divided since the state controller itself does not have an I component and the steadystate accurate regulation of the control distance is effected by the integrator.

The reference shaper 16 is provided to achieve a faster reaction to a setpoint change. The reference shaper is a DT1 element, that is to say to this extent a real differentiator, as, of course, the diagrammatic curve characteristics within the blocks also specify the category or function blocks to which the respective ment belongs. It is also possible to place the reference shaper 16 directly into the branch for the setpoint feed w which leads to the state controller.

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A further advantage of the high-pass feedforward of the observer disturbance information FR,stor has already been mentioned above and consists in the fact that steady-state errors attributable to tolerances in the observer are not also fedforward to the state obser- ver, but are eliminated right from the start.

A particularly simple development of the invention is obtained if the observer 12 only determines the disturbance forces FR,st16r, mainly caused by friction. Instead of the state controller 10, only a controller exhibiting, for example, PID characteristics is needed. The disturbance forces FR,stbr are fedforward to the output signal of this controller by virtue of the fact that a state and disturbance observer is fed with the measurable input variable as pitot-controlled and updated system model and the updating is performed by at least one proportional andlor in.tegral weighting up from the error which arises from a comparison of the system output x with the corresponding signal X of the observer 12. In this connection, the observer supplies at least one esti- mated variable FR,st6r for disturbance forces caused by friction and other disturbances. This disturbance force is fedforward to the output signal of a controller 10 following the actual-vatuelsetpoint comparison P2 via a high-pass filter which exhibits, for example, DT1 or PTDT1 characteristics. The control current for the operating magnet and the actual control distance x are used as input variables for the observer.

This arrangement has the advantage that a fast position control is possible independently of and disturban-ce forces with ininimum expenditure, the control rod speed JV" and the magnetic force IF' is not calculated and the reference shapers 16 and the I bypass 15 are omitted.

All features represented in the description, the subsequent claims and the drawing can be essential to the invention both individually and in any arbitrary combination with one another.

C.

C 1 a i m s 1. Method for the adaptive adjustment control etectro-magnet ic adjustment of a f low-determining element, characterized in that the measurable input variable is fed as pilot-controlled and updated system model to a state and disturbance observer and the updating is performed by at least proportional andlor int4gral weighting from the error which arises from a comparison of the system output (x) with the corresponding signal (X) of the observer (12), the observer supplying at least one estimated variable (FR,st6r) for disturbance forces caused by friction and other disturbances, which is fedforward via a high-pass filter (DT1, PTDT1) to the output signal of a controller (10) following the actualvalue/setpoint comparison.
2. Method for the adaptive adjustment control of the electromagnetic adjustment of a flow-determining element, characterized in that the measurable input variable is fed as Pilot-controlled and updated system model to a state and disturbance observer and the updating is per- formed by the proportional weightings from the error which arises by compArison of the system output (x) with the corresponding signal (X) of the observer (12), the estimated variables for control rod speed (v) and magnetic force (F), supplied by the observer, being fed to the state controller for current setpoint processing and furthermore supplies (sic) the estimated variable (FR,st6r) supplied at the same time by the observer, for distur bance forces caused by friction and other disturbances, which is also fedforward to the state controller (10) via a high-pass filter (DT1, PTDT1).
3. Method according to Claim 2, characterized in that the observed estimated variables for control rod speed (AV) and magnetic force (^F) are fedforward to the input of the state controller (10) via coefficient C_ elements (K1, K3) containing gain factors.
4. Method according to Claim 2 or 3, characterized in that reference variable (position signal w) is fed to the input of the state controller directly and via an integrating bypass (15).
5. Device for the adaptive adjustment control in the electro-magnetic adjustment of a ftow-determining element in the case of diesel injection pumps, characterized in that a controtter (10) is associated with a pilotcontrolled and updated system model as observer which is fed with the measurable input variable and 'the control distance (x) for updating from the error which arises from a comparison with the system output with the corresponding signal of the observer, a high-pass fitter pos- sibty with proportional element (DT1; PDT1) being provided via which the estimated variable (FR,stor) for the disturbance forces caused by friction and other disturbance, supplied by the observer, is connected to the output of the controtter (10) fottowing the actuat-vatuel setpoint comparison.
6. Device for the adaptive adjustment control in the etectro-magnetic adjustment of a ftow-determining element in the case of diesel injection pumps, characterized in that the state controtter (10) is associated with a pilot- controtted and updated system model as observer which is fed with the measu.rabte input variable and the controt distance (x) for updating from the error which arises from a comparison of the system output with the corresponding signal of the observer, the estimated variables for control rod speed (v) and magnetic force (F), supplied by the observer (12), being fed to the input of the state controtter (10) via coefficient elements (K1, K3) provided with gain factors, and furthermore, a high-pass fitter possibly with proportional element (DT1; PDT1) being provided via which the estimated variable (FR,st6r) for the disturbance forces caused by friction and other disturbance, supptied by the observer, is connected to the output of the state controtter (10).
7. A mthod for the adaptive adjustment control of the electro-magnetic adjustment of a flow-determining element substantially as herein described with reference to the accompanying drawings.
8. A device for the adaptive adjustment control in the electro-magnetic adjustment of a flow-determining element substantially as herein described with reference to the accompanying drawings.

Published 1988 at le Pater! ".,ce- S:Zte Housc 66 71 HiC! London WC1R 4TP llur-her cepies Tnky be obtained frc=, The Paten, Wice.

SAles Branch, St Mary Cray, Orpington. Kent BR$ 3RD. Printed by Multiplex techniques ltd, St M ary Cray, Kent. Con. 1, 87.