WO2006128516A1

WO2006128516A1 - Regulator device and method for operating a regulator device

Info

Publication number: WO2006128516A1
Application number: PCT/EP2006/003186
Authority: WO
Inventors: Joachim Morsch; Franz Fuchshumer; Andreas Kugi
Original assignee: Hydac Electronic Gmbh
Priority date: 2005-06-03
Filing date: 2006-04-07
Publication date: 2006-12-07
Also published as: DE102005025590A1; US20090304523A1; EP1886022A1; CN101189433A

Abstract

The invention relates to a regulator device, preferably as a component of a hydraulic circuit, in particular for regulating fluid-bearing units or units that are driven using a fluid, such as adjustable fluid pumps, which respectively co-operate with at least one actuator, which can be controlled by means of at least one governor in accordance with a predefinable guide variable (pd), said governor detecting output variables (α,pI) at least partially via a recirculation line. The fact that at least one recirculation line comprises at least one monitor (estimator), which estimates the output variables (condition x) that are at least in part unknown for the assignable governor, enables the provision of a regulator device, in which the governor comprises a linear or non-linear monitor for estimating the unknown load. Said regulator device continuously monitors the load, (load volumetric flow), independently of the regulation type, (volumetric and/or pressure regulation) and its implementation, (in analogous or discrete form), in order to regulate the operation in a dynamic, precise manner (devoid of spikes).

Description

HYDAC ELECTRONIC GmbH, Hauptstraße 27, 66128 Saarbrücken

Regulating device and method for operating a control device

The invention relates to a control device, preferably as part of a hydraulic circuit, and to a method for operating a control device, in particular for controlling fluid-conveying or driven by a fluid devices, such as adjustable fluid pumps, each interacting with an actuator, in response to a predetermined reference variable can be controlled by at least one controller, which detects at least partially feedback output variables of the controlled system via at least one feedback.

From DE 41 35 277 C2 a control device for an adjustable hydraulic pump is known in which the delivery rate of the hydraulic pump is variable by an adjusting device and the control device has at least two actuators controlling the actuator and wherein at least one hydraulic switching element is provided, which automatically connects the regulator to the actuator that provides the highest or lowest control pressure. The pertinent control device has in an embodiment of the known solution to a pressure-volume regulator, which essentially comprises a mounted on the pump unit switching valve plate, an adjustable orifice unit and a flow regulator plate, which is mounted independently of a pressure regulator plate as well as this plate on the switching valve comprises. According to the known solution, at a connection of the local pump inlet A control pressure is applied, namely either a control pressure supplied by the quantity regulator plate or a control pressure supplied by the pressure regulator plate. In this case, it is decided on the switching valve plate, whether the flow regulator plate or pressure regulator plate supplies a corresponding control signal to said port. In the known solution, the two controllers, ie the flow regulator and the pressure regulator work independently and do not affect each other directly. Properties of the volume and pressure regulators to be designated as standard regulators are retained in the known solution, and a cost-effective solution for the known control device is achieved through the use of these standard controllers, which can be produced inexpensively and in large numbers.

In particular, the known solution allows a volume flow controlled operation with pressure limiting function. This type of regulation of an adjustable pump is also known under the name "LOAD SENSING." In this operating mode, the pump is regulated to a certain volume flow, whereas the load pressure is defined by the "constitutive law" of the load. In order to prevent damage to the pump or the elements in the hydraulic circuit, the "LOAD SENSING" concept includes a so-called pressure limiting function, that is, from reaching a certain pressure level is switched from the volume flow-controlled operation in the pressure-controlled operation.

The problem of the currently known method for the volume flow regulated operation with pressure limiting function is when switching from the volume flow in the pressure-controlled operation. This switching is to be carried out, for example, so that regardless of the (unknown) load the desired pressure is adjusted without overshoot. This is especially true for applications in the field of injection molding and / or In this context, the pressure often has to be compensated for on a precisely defined level without overshoot, due to a sudden change in the load.

US Pat. No. 6,468,046 B1 discloses a device and a method for pressure regulation in a hydraulic pump which use the PID control concepts known from the prior art. In the known solution, in one embodiment, in an axial piston pump, a pivot plate pivotally connected to the pump is changed by a control valve at its relative angle to the pump. The pertinent regulation allows control of the control valve solely as a function of the load pressure of the pump.

US 6,375,433 B1 discloses a method and a device for controlling the load pressure in a hydraulic pump. In this solution, a non-linear method is used using two control laws (First Feedback Linearization Control Law, Second Feedback Linearization Control Law), whereby an accurate input and output linearization of the pressure flow on the load side takes place.

The main problem lies in the currently known methods for pressure-controlled operation in that due to the load changes, the gain of the open circuit changes significantly, which can lead to the instability of the closed loop in the previously existing concepts. In most cases, high demands are placed on the control quality over the entire operating range of the pump, which can not be satisfactorily covered by these methods. Based on this prior art, the present invention seeks to further improve the known solutions to the effect that, in particular when switching from a volume flow operation in the pressure-controlled operation regardless of the unknown load situation, the desired pressure is adjusted without overshoot. Furthermore, the solution according to the invention should be characterized by a stable control behavior and enable dynamic adjustment operations to a high degree. This object is achieved by a control device having the features of patent claim 1 and a method having the features of patent claim 11.

The fact that according to the characterizing part of claim 1 at least one feedback at least one observer (estimator), which makes an estimate of at least partially unknown output variables (state x) for the assignable controller, a control device is provided in which the Regulator includes a linear or possibly non-linear observer for estimating the unknown load, which regardless of the type of control - volume and / or pressure control - and the implementation - analog or discrete - continuously monitored the load (Lastvoiumenstrom) in such a way with high dynamics and accuracy (overshoot free) to make the scheme. In this way, a very accurate adjustment can be made to a constant flow rate of the pump and / or to a constant pressure on the load side of the control device. The method according to the invention refers insofar to the pertinent operation of the control device. Including the above-mentioned variables (state x), there is also the possibility of adjusting to a constant power for the fluid-conveying device, for example in the form of a fluid pump. Overall, with the invention, a large number of individual control variant of a fluid-conveying device, for example, achieved in the form of a hydraulic motor.

Further advantageous embodiments of the control device according to the invention are the subject of the other dependent claims.

In the following, the control device according to the invention and a method for its operation with reference to two embodiments will be explained in more detail according to the drawing.

In principle, and not to scale, the two figures in the form of circuit diagrams show the basic structure of the control device according to the invention.

If the solution according to the invention is to be used for a so-called pressure-controlled operation, the regulator shown in the figures is designed in the form of a linear or a nonlinear regulator, and preferably provided with a disturbance input and executed with a nonlinear and linear observer (load estimator). As state variables of a simplified model with an adjustable by means of an adjusting axial pump as a fluid pump (state x) are output variables such as p _actor , α, tu, p, where p _actor should correspond to the pressure in the adjusting _cylinder , α is the swivel angle, tσ the swivel angular velocity and pι corresponds to the pump or load pressure at the output of the intended consumption load. P _aktor can provide a proportionality factor corresponding to the fluid _quantity q _aktor , which is passed according to the representations of the actuator coming via a spring-loaded actuating cylinder (not shown) to the axial piston pump. Preferably, this is an axial piston pump with adjustable swash plate The axial piston pumps designed for this purpose are disclosed by way of example in the Mannesmann Rexroth publication Fundamentals and Components of Fluidtechnik Hydraulik (1991) in a pressure-controlled operation such as Particularly if the control arrangement according to FIG. 1 is low-priced, the advantages are in particular the better guidance pressure regulation, since in this control concept the dynamic behavior can be predetermined arbitrarily and independently of the respective operating point.

By applying the so-called "adaptive backstepping" method (M. Krstic, I. Kanellakopoulos, P. Kokotovic, Nonlinear and Adaptive Control Design, John Wiley & Sons, Incorporation New York, NY, 1995), the law of control results for one Load case according to the constitutive law (K ₁ is constant but unknown, K, corresponds to the estimated value of K)

with the controller parameters k _p and C ₂ , the measured variables p, (load pressure) and α (swivel angle), the desired load pressure p _d and the pump and load-specific parameters V ,, ß and K _q . The observer (load estimator) surrenders

lacto,

with the adjustable parameter.Y. The structure resulting from the control law and the observer is reproduced by way of example in FIG. In the _pertinent embodiment, not the manipulated variable u but q _{aktor was selected} as a manipulated variable for the pump, since the actuator is usually assumed to be ideal fast in the form of a switching valve (not shown) and thus only an algebraic between q _actuator and the other manipulated variable u (non-linear) relationship that can be integrated into the law of law (servo compensation).

The control circuit according to FIG. 1 is characterized in that, in the sense of a vector signal, the swivel angle α of the pump and the load pressure p, behind the load are combined into one (state x), which is given once directly to the controller and once to the observer / estimator. In the feedback, the latter then carries out a disturbance variable connection of the estimated load (K,) for the controller, which also receives on the input side as a reference variable p _d .

In the embodiment according to FIG. 2, the first described solution has been changed insofar as the parameters panning angle α and load pressure p combined in the sum vector signal are supplied to the controller as an input variable, namely in the form of a sum signal Factor k1 is evaluated and is composed of the load pressure and the reference variable p _d and the further sum size is formed from the swivel angle and the estimated load (or estimated swivel angle) of the observer / estimator, which in turn provided with a factor k2 of the controller together with the Value after k1 forms a total signal as control value u for the actuator. In order to be able to realize a volume-flow-controlled operation with a pressure-limiting function and to make the transition from volume-controlled operation to pressure-controlled operation (and vice versa) as smooth and free from overshoot as possible, the concept described so far is the concept of so-called flatness (see MJ Fliess et al, Flatness and Defect of Non-Linear Systems, Introductory Theory and Examples, Int.J. Control, Vol. 61, No. 6, pp. 1327-1361, 1995), ie a specific pressure and / or pressure gradient is exceeded or In this case, "soft" means in this case that a trajectory for the load pressure is generated starting from the changeover point in such a way that at the switchover time the absolute value of the pressure and at least the first derivative of the pressure at the switching time are identical. The switching time is determined (application-specific) as a function of the pressure level and the pressure gradient; (z. _B.. is the maximum allowable pressure gradient is a function of the pressure level). This method also has the advantage that the pressure can be controlled overshoot-free to a certain level.

Given the same conditions as for the pressure-controlled operation described above, the extended control law results

, * - -

and the load estimator is through

specified with the at least twice continuously differentiable pressure reference specification p _d .

The combined volumetric flow and pressure regulator can be realized either as a cascade regulator or as a linear or nonlinear state controller with or without feedforward control and with an observer (estimator). The detectable means of the respective observer output quantities of the controlled system form x a state in which in addition to the already erwähn- ^• ten sizes of the state can be also x tet observed on the basis of other measured variables. The output variable of the observer (load estimator) can correspond to the load volume flow and can thus be designed as a function of the adjustment path (in the case of an adjustable axial piston pump, the adjustment path essentially corresponds to the angle α of the swash plate).

Practical tests have shown that even with a very large jump in load, the load pressure can be adjusted to the desired set value, for example from 180 bar without overshoot, so that a large number of applications are possible, in particular in the field of injection molding and / or machine tools.

Claims

Patent claims

1. Control device, preferably as part of a hydraulic circuit, in particular for controlling fluid-conveying or by means of a fluid driven devices, such as adjustable

Fluid pumps, each cooperating with at least one actuator, depending on a predetermined reference variable. (p _d ) is controllable by means of at least one controller which at least partially detects output variables (α, p,) of the controlled system via at least one feedback, characterized in that at least one feedback has at least one observer (estimator), which estimates at least partially unknown output variables (state x) makes for the assignable controller.

2. Control device according to claim 1, characterized in that the means of the respective observer detectable outputs (α, P |) of the controlled system form a state x, which is at least partially describable as a vector signal system state descriptive fed to the observer.

3. Control device according to claim 2, characterized in that in the respective vector signal at least one pivot angle (α) of the fluid pump and / or the respective pressure value (P,) received by the subsequent load on the fluid pump.

4. Control device according to one of claims 1 to 3, characterized in that the respective vector signal can be supplied to the one observer and on the other hand as a whole or at least one one or more components of the vector signal is the input to the assignable controller.

5. Control device according to claim 3 or 4, characterized in that it is designed for a pressure-controlled or a volume flow controlled operation.

6. Control device according to one of claims 1 to 5, characterized in that the pending at the output of the observer estimated value (K,) as input value for the assignable controller corresponds to the respective load related load volume, which can be evaluated as a function of the adjustment path for the fluid pump is.

7. Control device according to claim 6, characterized in that the respective controller undergoes a feedforward control by the detectable or known load volume flow.

8. Control device according to one of claims 1 to 7, characterized in that the respective controller is designed as a cascade controller or as a linear or non-linear state controller with or without feedforward.

9. Regulating device according to one of claims 1 to 8, characterized in that the fluid pump is an axial piston pump whose detectable output variable refers to the pivot angle (α).

10. Control device according to one of claims 2 to 9, characterized in that at least one controller on the input side at least receives two sum signals, wherein a sum signal is formed from the reference variable (p _d ) and at least one component of the vector signal, and a further sum signal is formed from the estimated value of the observer and at least one further component of the vector signal.

1. A method for operating a control device, in particular for. Control of fluid-conveying or fluid-drivable devices, such as adjustable fluid pumps, each of which interacts with at least one actuator which is controlled as a function of a predeterminable reference variable (p _d ) by means of at least one controller which has at least one observer (estimator) having at least partially output variables (α, pι) of the controlled system detected, characterized in that a transition in a switching from a volume flow-controlled and pressure-limited operation in the pressure-controlled operation, and preferably vice versa, characterized preferably carried out gently that at the switching time a steady Course of at least serving as a part of the vector signal pressure value (p,) and its first derivative takes place after the time.