Methods for parameter setting of a control system for a pressure supply system of a hydraulic system and methods for controlling a pressure supply system of a hydraulic system

Abstract

The invention relates to a method for parameter setting of a control system of a pressure supply system of a hydraulic system, wherein the pressure supply system has a motor (4) and a hydraulic machine (2) which are controlled by a manipulated variable, wherein the control (160) is implemented by a control algorithm which determines manipulated values ​​for the manipulated variable from setpoint values ​​for a variable to be controlled, wherein the control algorithm is parameterized by one or more parameters which are adjustable during operation.The procedure comprises: performing (110) during the operation of the hydraulic system an estimation procedure based on a physical model to determine an estimate for at least one characteristic of the hydraulic system, wherein the at least one characteristic includes a hydraulic capacity of the hydraulic system; determining (120) a setting time constant equal to or greater than a target time constant by which a maximum pressure build-up rate of the hydraulic system is achieved, which is determined by the estimate for the hydraulic capacity and a maximum volume flow rate of the hydraulic machine; setting (150) at least one parameter of the one or more parameters, wherein the at least one parameter is determined by a respective function dependent on the setting time constant (130, 140).

Description

[0001] The present invention relates to a method for setting the parameters of a control system for a pressure supply system of a hydraulic system and a method for controlling a pressure supply system of a hydraulic system, as well as a computer program and a computing unit for carrying them out. Background of the invention

[0002] Working machines, especially mobile working machines, or machines used in an industrial production plant, may have a hydraulic system or drive system comprising one or more hydraulic consumers (hydraulic cylinders and / or hydraulic motors) that drive the movement of coupled machine components. A hydraulic pump or hydraulic motor, driven by a motor, is typically provided in the hydraulic system to supply the hydraulic fluid. The hydraulic pump and / or motor can be controlled using a control system, where the controlled variable is, for example, a pump pressure or a pump flow rate. Disclosure of the invention

[0003] According to the invention, a method for parameter setting of a control system for a pressure supply system of a hydraulic system, a method for controlling a pressure supply system of a hydraulic system, and a computer program and a computing unit for their implementation, comprising the features of the independent claims, are proposed. Advantageous embodiments are the subject of the dependent claims and the following description.

[0004] The invention utilizes the measure of parameterizing a control system for a pressure supply system of a hydraulic system, which is achieved by a control algorithm with one or more parameters that can be set or adjusted during operation.To perform an estimation procedure during the operation of the hydraulic system using variable parameters, based on a physical model, to determine an estimated value for at least one characteristic of the hydraulic system, wherein the at least one characteristic includes a hydraulic capacity of the hydraulic system; to determine a setting time constant equal to or greater than a target time constant, by which a maximum pressure build-up rate of the hydraulic system is achieved, which is determined by the estimated value for the hydraulic capacity and a maximum volume flow rate of the hydraulic machine; and to adjust at least one parameter of the one or more parameters, wherein the at least one parameter is determined by a respective function dependent on the setting time constant. This measure results in an adaptation of the control or...The control algorithm, for example its dynamics, is adapted to the hydraulic system so that higher control accuracy can be achieved. Such an adaptation can be useful, for example, when commissioning the hydraulic system or when changes are made to the hydraulic system, such as changing an attachment or work equipment on a machine.

[0005] The controlled variable is, in particular, a pressure in the hydraulic system, e.g., the outlet pressure (pump pressure) of the hydraulic machine, which is measured by a pressure sensor. Generally, it can also be another quantity (measured or calculated from measurements) (e.g., the volume flow rate delivered by the hydraulic machine).

[0006] The one or more parameters that can be adjusted or changed during operation may, in particular, be controller parameters or controller coefficients, and furthermore, controller parameters of a proportional component (e.g., proportional gain factor), a differential component (e.g., differential gain factor, lead time), and / or an integral component (e.g., integral gain factor, reset time). Delay times and dead times are also such adjustable controller parameters.

[0007] According to one embodiment, the estimation procedure is performed if the magnitude of the rate of change of a target pressure exceeds a threshold value, and / or the estimation procedure is not performed if the magnitude of the rate of change of the target pressure is below the threshold value. This condition avoids performing the estimation during phases in which there is no or only a small pressure change and, consequently, only low sensitivity for the at least one parameter of the hydraulic system, so that the at least one parameter can be estimated with relatively high accuracy.

[0008] According to one embodiment, the setting time constant is determined to be equal to or greater than a stability time constant, which is determined by a stability criterion for the control loop formed by the controller and the hydraulic system. In particular, the setting time constant is determined to be equal to the larger of the target time constant and the stability time constant. Accordingly, according to this embodiment, the setting time constant is both equal to or greater than the target time constant and equal to or greater than the stability time constant. In other words, the setting time constant is equal to or greater than the maximum of the target time constant and the stability time constant. The phrases "equal to or greater than" essentially define conditions that the setting time constant must fulfill. The stability of the closed control loop consisting of the controller and the hydraulic system is thus ensured.The corresponding specification of poles is limited, in particular, by the phase shifts resulting, for example, from the time constants of valve control loops, torque control loops, filters, and communication dead times. For instance, the phase shifts can be summarized in an equivalent time constant, which is used in a simplified closed-loop control model. From this model, a stability condition (e.g., a pole condition) can be derived, which can then be evaluated to determine the stability time constant, optionally taking into account an additional safety factor (i.e., the time constant obtained directly from the stability condition, which corresponds approximately to a stability margin, is multiplied by a safety factor greater than one to determine the stability time constant).

[0009] According to one embodiment, if the estimated value for the hydraulic capacity is below a predetermined capacity threshold, the setting time constant is determined to be equal to or greater than the target time constant plus half a substitute time constant. The substitute time constant represents a time delay or phase shift in a control loop formed by the controller and the hydraulic system. In the case of a cascaded controller, the substitute time constant specifically relates to the subordinate or inner control loop. This embodiment can increase robustness against parasitic line frequencies, to which smaller systems are more susceptible.

[0010] According to one embodiment, the at least one parameter includes at least one gain factor of one or more controllers of the control system, wherein, when the at least one parameter is set, the at least one gain factor is determined such that it decreases with increasing setting time constant. In particular, the at least one gain factor is determined as proportional to the inverse of the setting time constant and / or as proportional to the inverse of the square of the setting time constant. This embodiment enables the gain factors, and thus the dynamics of the control system, to be adapted to the setting time constant or to the size of the hydraulic system.

[0011] The two following configurations describe suitable functional dependencies on the setting time constant for gain factors of different control structures.

[0012] According to one embodiment, if the control has a parallel structure and the at least one gain factor includes a proportional gain factor and a differential gain factor, the proportional gain factor is determined as proportional to the inverse of the square of the setting time constant and / or the differential gain factor is determined as proportional to the inverse of the setting time constant.

[0013] According to one embodiment, where the control system has a cascaded structure and the at least one gain factor includes a first proportional gain factor of an external controller and / or a second proportional gain factor of an internal controller and / or a differential gain factor of the internal controller, the first and / or the second proportional gain factor is / are determined as proportional to the inverse of the setting time constant and / or the differential gain factor of the internal controller is determined as proportional to the inverse of the setting time constant. In particular, the ratio of the second proportional gain factor to the first proportional gain factor is in the range of 2 to 4 and / or a differential gain factor of the internal controller is determined as proportional to the product of the second proportional gain factor and a substitute time constant that represents a time delay or...The phase shift in a control loop formed by the control system and the hydraulic system is determined.

[0014] According to one embodiment, the control system includes trajectory planning, which, using a low-pass filter with a filter time constant, determines setpoint values ​​for a target trajectory for the controlled variable and derivative values ​​of at least one time derivative of the target trajectory from the specified values ​​for the controlled variable. The at least one parameter includes the filter time constant, and when the at least one parameter is set, the filter time constant is determined such that it increases with increasing setting time constant. In particular, the filter time constant is determined to be equal to or proportional to the setting time constant. This embodiment adapts the trajectory planning so that target trajectories determined from specified values ​​for the controlled variable can actually be realized (at least substantially) in the hydraulic system, especially according to its hydraulic capacity.

[0015] According to one embodiment, the control system includes a feedforward control element that determines feedforward control values ​​for the manipulated variable from setpoints of a target trajectory for the controlled variable and derivative values ​​of at least one time derivative of the target trajectory; wherein the feedforward control values ​​are determined as a function of the estimated value(s) of the at least one characteristic value. This feedforward control element, which is based, for example, on a physical model, can be adapted to the hydraulic system.

[0016] In one embodiment, particularly when the control system has a parallel structure, the feedforward control parameters include a term in which the estimated hydraulic capacity is divided by the maximum pressure build-up rate and multiplied by the derivatives of the second time derivative of the target trajectory. In an alternative embodiment, particularly when the control system has a cascaded structure, the feedforward control parameters include a term in which the estimated hydraulic capacity is divided by the maximum flow rate delivered by the hydraulic machine and multiplied by the derivatives of the first time derivative of the target trajectory. These terms allow for the simple implementation of feedforward control for pressure build-up under no-load conditions.

[0017] According to one embodiment, at least one parameter further includes a leakage coefficient and / or a turbulence flow coefficient, wherein a disturbance flow rate and / or its time derivative is / are determined as a function of the estimated value for the leakage coefficient and / or the estimated value for the turbulence flow coefficient, and wherein the disturbance flow rate and / or its time derivative is / are taken into account in the feedforward control. If necessary, the time derivative of the disturbance flow rate is subtracted from the maximum pressure build-up rate before division, or the disturbance flow rate is subtracted from the maximum delivered flow rate before division. This embodiment takes into account leakage or turbulence occurring at valves or similar devices in the feedforward control.

[0018] An inventive method for controlling a pressure supply system of a hydraulic system, wherein the pressure supply system comprises a motor and a hydraulic machine which are controlled by a manipulated variable, wherein the control is implemented by a control algorithm which is parameterized by one or more parameters which are adjustable or changeable during operation, comprises carrying out an inventive method for parameter setting of the control in order to set at least one parameter of the control algorithm; determining manipulated values ​​for the manipulated variable based on setpoint values ​​for the quantity to be controlled by executing the control algorithm; and controlling the pressure supply system with the manipulated values.

[0019] The methods according to the invention and their embodiments are in particular computer-implemented methods.

[0020] A computing unit according to the invention, e.g. a control unit of a hydraulic system or of a mobile working machine with a hydraulic system, is, in particular in terms of programming, equipped to carry out a method according to the invention.

[0021] Implementing a method according to the invention in the form of a computer program or computer program product with program code for carrying out all method steps is also advantageous, as this incurs particularly low costs, especially if an executing control unit is already available for other tasks. Suitable data carriers for providing the computer program are, in particular, magnetic, optical, and electrical storage media, such as hard drives, flash memory, EEPROMs, DVDs, etc. Downloading a program via computer networks (Internet, intranet, etc.) is also possible.

[0022] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawing.

[0023] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0024] The invention is schematically illustrated in the drawing using exemplary embodiments and is described in detail below with reference to the drawing. Character description Fig. Figure 1 shows a sketch of a hydraulic system in which a method according to the invention can be applied. Fig. Figure 2 shows a flowchart of a method according to embodiments of the invention. Detailed description of the drawing

[0025] Fig. Figure 1 shows a sketch of a hydraulic system in which a method according to the invention can be applied.

[0026] The hydraulic system (or drive system) comprises a hydraulic machine 2 (also referred to simply as a hydraulic pump or pump in the figure description) and a motor 4, which is coupled to the hydraulic machine 2 to drive it, for example, by a rotationally fixed coupling via a shaft and / or a gearbox. The motor 4 is, for example, an internal combustion engine, in particular a diesel engine, or an electric drive comprising an inverter and an electric motor. The motor 4 and the hydraulic machine 2 form a pressure supply system for the hydraulic system.

[0027] The hydraulic machine 2 is equipped with a tank for hydraulic fluid (i.e., hydraulic fluid, in particular hydraulic oil) and a hydraulic line 6 and, in particular, pumps hydraulic fluid from the tank into the hydraulic line 6. The pressure (also referred to as pump pressure) of the hydraulic fluid at the port of the hydraulic machine 2 connected to the hydraulic line 6 or in the hydraulic line 6 is measured, for example, by a pressure sensor 8 or pump pressure sensor.

[0028] As shown, the hydraulic machine 2 can be a variable displacement hydraulic machine, i.e., it has an adjustable swivel angle or displacement (volume of hydraulic fluid delivered per revolution), or it can be a constant displacement machine, i.e., it has a constant displacement. In the first case, the volume flow rate delivered by the hydraulic machine 2 can be changed by changing the swivel angle and, optionally, also by changing the rotational speed of the hydraulic machine or motor. In the second case, the volume flow rate delivered by the hydraulic machine can be changed by changing the rotational speed of the hydraulic machine or motor.

[0029] The hydraulic line 6 is connected to a hydraulic consumer 10 (for example, a hydraulic cylinder) via a valve 10, a nozzle, or similar device. The valve 10 (e.g., a directional control valve) can, for example, control the flow of hydraulic fluid to and from the hydraulic consumer 10. Contrary to the illustration, the hydraulic line can also be directly connected to the hydraulic consumer, for example, in a so-called compact axis, in which hydraulic fluid is pumped back and forth between chambers of a hydraulic cylinder depending on the direction of flow of the hydraulic machine.

[0030] Furthermore, a computing unit 14 (control unit or electronic control) is shown, which can implement control of the pressure supply system, in particular by means of a corresponding control algorithm, for example by executing a computer program. At least partial implementation of the control algorithm in the form of hardware circuits, e.g., using an ASIC or FPGA, is also possible. The computing unit 14 can be configured to control or actuate the pressure medium supply system, i.e., the motor 4 and / or the hydraulic machine 2, using a manipulated variable. The computing unit 14 can also be configured to receive measured values ​​from the pressure sensor 8. Electrical control and / or signal lines for transmitting control signals (e.g., with manipulated values) and / or measurement signals (e.g., with pump pressure readings) are shown as dashed lines.The computing unit 14 is specifically designed to carry out a method according to the invention.

[0031] The control system for the pressure supply, or the control algorithm, can include a pressure regulator, a flow rate controller, or a combination of both (so-called pQ control). In particular, a parallel or a cascaded structure can be used for the control. In the parallel structure, a pressure regulator is used to determine the manipulated values ​​(e.g., pilot valve voltage for a pilot valve of an adjustable hydraulic machine and / or torque to be applied by the motor) for the hydraulic fluid supply system. The chain of elements or parameters of the pressure supply system—i.e., the adjusting mechanism of the hydraulic machine and / or the motor (e.g., the inverter of an electric machine), and subsequently the swivel angle and / or the rotational speed (or, taken together, the delivered flow rate), as well as the resulting actual pressure value—are considered and controlled simultaneously or in parallel, specifically through pure pressure control.In the cascaded structure, an external (or higher-level) pressure regulator and a subordinate (or inner) flow regulator are used. The pressure regulator's manipulated variable is, for example, a target flow rate or swivel angle, while the flow regulator determines the manipulated values ​​(e.g., pilot valve voltage and / or required torque) for the pressure supply system so that the target flow rate or swivel angle is achieved. The higher-level pressure regulator uses measured values ​​from a pressure sensor as actual pressure values, and the flow regulator uses measured values ​​from a swivel angle sensor as actual swivel angle values. From these values, the actual flow rate can also be determined if the rotational speed (e.g., measured rotational speed) is known.

[0032] The control variables or setpoints of the pressure supply system depend on its design. If a constant displacement hydraulic machine is used, the control variable for the motor in a parallel structure is, for example, the rotational speed or the torque to be applied, where the motor is, in particular, an electric machine. In a cascaded structure, in the case of a constant displacement hydraulic machine, the control variable for the higher-level pressure regulator can be, for example, the rotational speed or, equivalently, the flow rate, and the control variable for the lower-level flow regulator can be the torque to be applied by the motor. If a variable displacement hydraulic machine is used, for example...In a cascaded structure, the swivel angle is a control variable for the higher-level pressure regulator, and the pilot valve voltage is a control variable for the lower-level flow regulator. Similarly, in a parallel structure, the pilot valve voltage is a control variable for the pressure regulator. The swivel angle or the pilot valve voltage can be the sole control variable, for example, if the engine (which in this case is an internal combustion engine, particularly a diesel engine) operates at a constant speed. Alternatively, the swivel angle and a control variable for the engine (speed or torque) can be combined to act as a control variable for the pressure supply system.

[0033] Fig. Figure 2 shows a flowchart of a method according to embodiments of the invention. The flowchart relates to the parameter setting of a control system for a pressure supply system of a hydraulic system, such as in Fig.Figure 1 illustrates this. Furthermore, the flowchart relates to the control of such a hydraulic system. The pressure supply system comprises a motor and a hydraulic pump, which are controlled by a manipulated variable. The control is implemented by a control algorithm that determines manipulated values ​​for the manipulated variable from setpoint values ​​for the variable to be controlled (in particular, the pump pressure). The control algorithm is parameterized by one or more parameters (i.e., dependent on one or more parameters) that can be set or changed during operation. Methods according to embodiments of the invention can be carried out, in particular, by a computing unit or a control unit of the hydraulic system.

[0034] In step 110, an estimation procedure based on a physical model is performed to determine an estimated value for at least one parameter of the hydraulic system. This at least one parameter includes the hydraulic capacity of the hydraulic system. In principle, any suitable estimation procedure can be used, e.g., a recursive estimation method, in particular a Kalman filter. An observer can also be used. Below, a physical model is first described, followed by a recursive least-squares method as the estimation procedure.

[0035] A time discretization is used, where the index k denotes the time t to which a quantity, e.g., p, refers (in the case of measured values, specifically a measurement time). Given a sample time T (the time interval between two points in time in the discretization), t = kT, so that, for example, p k= p(kT) is.

[0036] The following applies to the pressure build-up (a dot above a quantity denotes, as usual, the derivative of the quantity with respect to time): p˙k=1CH(Qk−pkCl)

[0037] Here, p is the pressure in the hydraulic system under consideration, C is... H the hydraulic capacity of the hydraulic system under consideration, Q k the pump flow rate (without considering leakage), C l a leakage coefficient.

[0038] With the discretization p k+1 = ṗ k T + p k (Euler discretization) the difference equation follows from this: pk+1=TCHQk+(1−ClTCH)pk

[0039] Using the parameters a and b, and with suitable parameter identification, this results in: pk+1=bQk+apk

[0040] This model can be expanded if a load valve or nozzle is present in the hydraulic system: p˙k=1CH(Qk−pkCl−pkCt) pk+1=TCHQk+(1−ClTCH)pk−pkCtTCH pk+1=bQk+apk−cpk

[0041] Here is C t A turbulent flow coefficient (through the load valve or nozzle). Also known as the turbulence flow coefficient.

[0042] In the equations above, p k and Q k Quantities that are measurable or observable (directly, e.g., by a pressure sensor, or indirectly, e.g., from the rotational speed and / or swivel angle of the hydraulic pump). Parameters a, b, and, if applicable, c are quantities that can be estimated using a suitable estimation method.

[0043] For example, as described below, a recursive estimation can be performed using a recursive least squares method. Of course, other estimation methods are also conceivable.

[0044] The prediction equation is in vectorized form, where Θ is a parameter vector. k, which includes the quantities to be estimated, a regressor ϕ k , which contains the known quantities or their measured values, and a covariance matrix C k to be used for the respective times: y^k=p^k=Θk−1T⋅ϕk=(ab)(pk−1Qk−1)

[0045] For the extended model with load valve or nozzle: y^k=p^k=Θk−1T⋅ϕk=(abc)(pk−1Qk−1−pk−1)

[0046] The updates or revisions of the parameter vector Θ k and the covariance matrix C k Each time step is performed by: Θk=Θk−1+Ck−1⋅ϕk1+ϕkT⋅Ck−1⋅ϕk⋅(yk−Θk−1T⋅ϕk) Ck=Ck−1−Ck−1⋅ϕk⋅ϕkT⋅Ck−11+ϕkT⋅Ck−1⋅ϕk

[0047] The estimation procedure yields estimated values ​​for the parameters a, b, and optionally c, from which, by resubstitution, estimated values ​​for the desired quantities, also known as characteristic values, are obtained. Accordingly, an estimated value ĈH for the hydraulic capacity, an estimated value Ĉ l , for the leakage coefficient and, if applicable, an estimated value Ĉ t The turbulent flow coefficient or turbulence flow coefficient can be obtained as follows: C^H=Tb C^l=C^H(1−a)T=(1−a)b C^t=C^HcT=cb

[0048] The most important parameter for controller setting is the hydraulic capacity. To prevent the process from being identified during a static pressure holding phase, in which the parameter sensitivity for Ĉ H If the value is low, a criterion corresponding to high parameter sensitivity can be used to increase the accuracy of the parameter estimation, especially of the hydraulic capacity. Specifically, it can be checked whether the magnitude of the rate of change or the first time derivative of a target pressure exceeds a threshold (|ṗ). soll | > ṗ LimThis prevents the process from being carried out during a static pressure holding phase, in which, for example, the sensitivity to hydraulic capacity is low, provided the threshold is appropriately chosen. The time derivative of the target pressure can be generated, for example, by a DT1 element from a time sequence of (external) pressure setpoints. If the time derivative of the target pressure exceeds the threshold, the estimation process can be triggered. This allows the time window width to be automatically adjusted to the excitation level.

[0049] In step 120, a setting time constant, hereinafter also referred to as the effective time constant, is determined. This time constant is defined as equal to or greater than a target time constant that achieves a maximum pressure build-up rate of the hydraulic system. The maximum pressure build-up rate is determined by the estimated value for the hydraulic capacity and a maximum flow rate of the hydraulic machine, i.e., according to the definition of hydraulic capacity as the quotient of the flow rate and the pressure build-up rate.

[0050] For controller design, i.e., setting the parameters of the control system, the target time constant T is first determined. d determined, at which, given a maximum volume flow rate Q Lthe pump (for a variable displacement pump, the maximum flow rate at a given speed is that obtained at maximum swivel angle; for a constant displacement pump driven at variable speed, the maximum flow rate is, for example, the flow rate at a maximum speed for the constant displacement pump or motor) and estimated hydraulic capacity Ĉ H a maximum pressure build-up rate ṗ L = Q L / Ĉ H of the hydraulic system. In particular, the target time constant T is achieved. d The time constant or time interval of a PT2 element is determined, after which the maximum pressure build-up rate is reached. The step response (to a step in the pressure value at the input of the PT2 element) of a critically damped PT2 element is given by, where K is the step height: h(t)=K(1−e−tTd(tTd+1))

[0051] Setting the second derivative of the step response to zero h¨(t)=Ke−tTd(Td−t)Td3=0 This yields the time of the extremum of the first derivative (i.e., the maximum of the pressure build-up rate): t ṗmax = T d .

[0052] This point in time can be the first derivative of the step response h˙(t)=Kte−tTdTd2 are used and deliver: p˙max,PT2=Ke−1Td

[0053] By equating this expression with ṗ max = Q L / Ĉ H and solving for T d The target time constant is obtained as: Td=C^HKe−1QL

[0054] The step height K can be selected depending on the specific hydraulic system, for example, as a typical step height occurring during operation or as the maximum step height occurring (e.g., equal to the difference between the maximum pressure of the hydraulic system or pump and the idling pressure). Corresponding pressure values ​​for the step height can, for example, range between 50 bar and 300 bar, and particularly between 100 bar and 200 bar.

[0055] In hydraulic systems with a variable displacement pump and variable speed of the pump or motor, where the control essentially involves changing the swivel angle as the manipulated variable and the speed is set to a constant value or changed only slowly for at least a certain period of time (e.g., by a higher-level control system), the target time constant can be determined as a function of the speed (and subsequently used), since the maximum volume flow QL the pump depends on the speed (Q L = nV G α max in a variable displacement pump with maximum swivel angle α max For example, several rotational speeds can be used. i (Support points) respective target time constants T d,i The values ​​can be determined and stored, and during operation the appropriate target time constant can be selected or determined from it for currently used rotational speeds (e.g. by interpolation between the support points).

[0056] Furthermore, a stability criterion can be considered for the control system. One factor that can be taken into account when specifying poles for the transfer function is the phase shift or time delay, which results, for example, from time constants of valve or torque control loops, filters, and communication dead times. These effects can be represented in a substitute time constant T. E to be summarized.

[0057] A simplified design model (for the control system) is a double integrator with the equivalent time constant. This results in the following differential equation for the closed-loop control system: TEp⃛+p¨+KDp˙+KPp=0

[0058] According to the Hurwitz criterion, as a stability criterion, for a third-order polynomial P(s) = a3s 3 + a2s 2 + a1s + a0 the condition a1 a2 - a3 a0 > 0 must be satisfied.

[0059] For the reinforcements K D , K P The target time constant and target damping can be used. Comparing coefficients yields the following condition: 2DdTd−TE1Td2>0

[0060] Here is D d (e.g. 1) the target damping of the closed-loop control system. Solving this expression for the target time constant and introducing a safety factor K, StabTo ensure a certain distance from the stability limit, a stability time constant results: Td,crit=TE2DdKStab

[0061] For controller design, if the stability criterion is taken into account (otherwise, the target time constant T is used). d used), the larger of the target time constants and the stability time constants is used (as the effective time constant T). d,eff (also called the setting time constant, as it is involved in determining and setting parameters of the control system): Td,eff=max{Td,krit,Td}

[0062] For systems with small hydraulic capacities, i.e., H < C H,Lim , where C H,Lim If a predetermined threshold (referred to as the capacity threshold) exists, the effective time constant can be chosen to be larger (especially since smaller systems are more susceptible to instabilities such as oscillations): Td,eff,C={C^H>CH,Lim:Td,eff,C=Td,effC^H <CH,Lim:Td,eff,C=Td,eff+TE,F / 2

[0063] Here is T d,eff,C the effective time constant of the cascaded control and T E,F is the equivalent time constant for the inner control loop, which is controlled by the subordinate volume flow controller.

[0064] In step 130, one or more controller parameters or gain factors are determined for at least one controller included in the control system, such that the one or more controller parameters or gain factors (which are the parameters of the control algorithm) depend on the effective time constant. In particular, the one or more controller parameters K are determined such that they increase with increasing effective time constant T. d,eff or T d,eff,CThe controller parameters decrease or decrease. For example, one or more controller parameters can be chosen to be inversely proportional to the effective time constant or inversely proportional to the square of the effective time constant. Of course, other functional relationships for the decrease with increasing effective time constant are also conceivable. Different controller parameters can exhibit different functional relationships. Examples of controller parameter determination for control systems with parallel and cascaded structures are described below.

[0065] For a parallel control structure with a controller C^HQ˙L[KP+KDs] This applies in simplified terms to the closed control loop: p¨+2DdTdp˙+1td2p=p¨+KDp˙+KPp

[0066] By comparing coefficients, controller parameters or gain factors to be used in the control system, with differential (D) and proportional (P) components, can be determined. This results in... KD=2DdTd,eff for the D component and KP=1Td,eff2

[0067] For any low-pass filter time constant of the D component that may be used, the following applies: TF,D=0.1KD / KP

[0068] For a cascaded control structure with a higher-level pressure regulator CH[KP,K(1+1sTN,K)] and subordinate volume flow controller KP,F+KD,Fs can KP,K=1Td,eff,C as proportional amplification for the pressure regulator, TN,K=4Td,eff,C as the adjustment time for the pressure regulator, KP,F=3Td,eff,C=3KP,K as proportional amplification for the volume flow controller and KD,F=KP,FTE can be used as differential amplification for the volume flow controller.

[0069] In optional step 140, if trajectory planning or a trajectory filter is used in the control system, parameters for this, also known as trajectory filter parameters, can be determined or set depending on the estimated characteristic values. A trajectory filter is used, for example, to smooth out jumps in setpoint values ​​(e.g., from a higher-level controller or a user interface) for the controlled variable. Accordingly, a target trajectory is determined that includes setpoints for the controlled variable (pressure or volume flow), i.e., a temporal sequence of setpoints. Furthermore, the trajectory filter can determine one or more time derivatives of the target trajectory, for example, for use in feedforward control.The trajectory filter determines values ​​referred to as target trajectory values, which include a temporal sequence of target values ​​and may include one or more temporal sequences of derivative values ​​for one or more temporal derivatives of the target trajectory.

[0070] The trajectory filter parameters (which are the parameters of the control algorithm) can, in particular, include at least one filter limit value and / or a filter time constant. The at least one filter limit value can be a maximum permissible rate of change for the first and / or the second time derivative of the desired trajectory. For example, the first time derivative for the desired pressure based on the estimated hydraulic capacity Ĉ H by means of an equation for leak-free pressure build-up through a maximum pressure change rate ṗ d,L be limited: p˙d,L=QL / C^H

[0071] Differentiating with respect to time allows for a limitation p̈ d,L to be determined for the second derivative: p¨d,L=Q˙L / C^H

[0072] For systems with constant rotational speed and variable swivel angle α, the following applies: Q˙L=nVGα˙ where the time derivative of the swivel angle is particularly relevant for the maximum swivel angle α̇ max is evaluated (Q̇̇ L = nV G α̇ max For systems with variable rotational speed and constant swivel angle α, the following applies: Q˙L=n˙VGα

[0073] The time derivatives of the desired trajectory can be determined, particularly up to the second time derivative, since, for example, physical inverse plant models used in feedforward control include the second derivatives of the pressure. A second-order (low-pass) filter, such as a second-order PT2 filter or two first-order PT1 filters in series, can be used for this purpose. Such a filter can be described by the following differential equation: p¨d=1τ2pcmd−2τp˙d−1τ2p˙d

[0074] Here is p cmd the pressure setpoint to be filtered, i.e., a temporal sequence of pressure setpoint values, and p d is the desired pressure, i.e., the target trajectory for the pressure. The filter time constant τ can be determined as a function of the effective time constant T. d,eff , or T d,eff,C In the case of a cascaded structure, parameterization can be achieved, e.g., as equal to this τ = T d,eff or τ = T d,eff,C .

[0075] Such a filter can be implemented by a controller, where, corresponding to the fact that the above differential equation is a second-order differential equation, a chain with two integrators is used. The output values ​​of the second integrator are the setpoints of the desired trajectory, the input values ​​of the second integrator are the derivatives of the first time derivative of the desired trajectory, and the input values ​​of the first of the two integrators are the derivatives of the second time derivative of the desired trajectory. Elements can be provided that adjust the input values ​​of the second integrator to the maximum pressure change rate ṗ. d,L limit and / or restrict the input values ​​of the first integrator to the limit ṗ d,LLimit the second derivative so that the above limitations are taken into account in the filter. Of course, other filters and / or other methods for trajectory planning are also possible, whereby the limitations and the effective time constant can be taken into account analogously.

[0076] In step 150, the specific parameters of the control system, i.e., the specific controller parameter(s) or gain factors (from step 130) and, if applicable, the trajectory filter parameter(s) (from step 140), are set in the control system or the control algorithm. For example, the corresponding values ​​are written to memory locations or registers that are read by the control algorithm.

[0077] In step 160, control is performed using the respective set parameters (controller parameters or gain factors, and, if applicable, the trajectory filter parameter(s)). The control is carried out in particular according to the parallel or cascaded structure described above. The control includes at least one controller, where the setpoint values ​​of the desired trajectory or, if no trajectory planning is performed, the target values ​​themselves are used as the reference input values. The control system or the control algorithm determines the manipulated values ​​for the manipulated variable.

[0078] In optional step 165, which can be considered a sub-step of the control process in step 160, feedforward control can be performed. In this step, feedforward control determines values ​​for the manipulated variable, referred to as feedforward control values, which are then added to the values ​​for the manipulated variable determined by the at least one controller (controller control values) to obtain the control values ​​used to operate the pressure supply system. The feedforward control is based on the setpoint trajectory and, in particular, on the setpoint trajectory values ​​up to the second time derivative.

[0079] The feedforward control parameters u ff can be determined depending on the estimated values ​​for the key figures.

[0080] For example, for a parallel control structure, the feedforward control input can be used as follows: uff,P=C^HQ˙Lp¨d

[0081] Similarly, for example, the feedforward control value can be used for a cascaded control structure as follows: uff,C=C^HQLp˙d

[0082] Here are ṗ d and p̈ d the first and second time derivatives of the target trajectory, as determined by the trajectory filter (as sequences of derivative values).

[0083] In the parallel structure, pressure acts as a disturbance variable on the system. This can be illustrated by the following contribution to the feedforward control signal (e.g., to the above u). ff,P (added) are compensated: ud=pd,F1JC^H(VG2π)2

[0084] Here, J is the moment of inertia of the motor plus pump, and p is the moment of inertia of the pump. d,F is a pressure setpoint that is determined by a pre-filter with a PT1 filter as a model for the closed control loop and is the setpoint p d follows: pd,F=pd(Td,effs+1)

[0085] The above terms for u ff can be adjusted to pre-control hydraulic disturbance flow rates. For this purpose, the above terms for u can be used. ff instead of Q L an effective volume flow Q L - Q dist can be used, which is defined by the following equation: p˙=1 / CH(Q−pkCl−pkCt)=1 / CH(Q−Qdist)

[0086] In the cascaded structure, Q is therefore L through Qdist=pdC^l+pdQ^t changed and in the parallel structure Q̇ L through Q˙dist=p˙dC^l+p˙d2pdC^t changed.

[0087] The control system may include filters to filter specific signals. For example, Butterworth filters and / or notch filters (band-stop filters) may be used to eliminate certain interference frequencies. Notch filters can be used, for instance, to eliminate interference in a known narrow frequency band. The parameters of such filters may also depend on the estimated values ​​of the characteristic values ​​and, in particular, on the effective time constant T. d,eff , or T d,eff,C be determined.

[0088] For example, the control system can include a Butterworth filter to remove high-frequency disturbances from the actual signal, i.e., from the sequence of actual values. The target dynamics of the system can be expressed as a target frequency ω. d The effective time constant T will be specified. d,eff or T d,eff,C , corresponds: ωd=2π / Td,eff or 2π / Td,eff,C

[0089] The cutoff frequency ω c The cutoff frequency should be higher than the target frequency ω by a certain factor b, which should be between 3 and 7, or between 4 and 6, or between 4.5 and 5.5, and is, for example, equal to or approximately equal to 5. d be. On the other hand, the cutoff frequency ω should be c do not exceed the Nyquist frequency. The cutoff frequency ω c can be defined accordingly as: ωc=max{bωd,π / T}

[0090] Here, the sampling time T introduced above is used, which determines the Nyquist frequency.

[0091] In step 170, the pressure supply system, i.e. the motor and / or the hydraulic machine, is controlled with the setpoints determined in step 160.

[0092] Step 110 can be performed once, e.g., during commissioning of the hydraulic system, or repeatedly, particularly also in parallel with the execution of the control process (step 160, and optionally step 165, step 170). The execution of step 110, especially when performed repeatedly, can be triggered manually (e.g., by an operator of a machine in which the hydraulic system is used) or automatically (e.g., by a control unit or a computing unit). Automatic triggering can occur, for example, regularly or in response to predetermined events (e.g., when using feedforward control, if it is determined that the remaining control deviation, which is corrected by a controller, or a time average, exceeds a predetermined threshold).If step 110 is performed for the first time, or if a change in the estimated value of a parameter is detected during repeated execution of step 110 compared to a previous estimate, the subsequent steps 120, 130, and, if applicable, 140, and 150 are performed. Step 110 is performed while the hydraulic system is operating. The subsequent steps 120, 130, and, if applicable, 140, and 150 can also be performed during operation.

Claims

[1] Method for parameter setting of a control of a pressure supply system of a hydraulic system, wherein the pressure supply system has a motor (4) and a hydraulic machine (2) which are controlled by a manipulated variable, wherein the control (160) is implemented by a control algorithm which determines manipulated values ​​for the manipulated variable from setpoint values ​​for a variable to be controlled, wherein the control algorithm is parameterized by one or more parameters which are adjustable or changeable during operation, wherein the method comprises: Performing (110) during the operation of the hydraulic system an estimation procedure based on a physical model to determine an estimate for at least one characteristic of the hydraulic system, wherein the at least one characteristic includes a hydraulic capacity of the hydraulic system; Determine (120) a setting time constant as equal to or greater than a target time constant by which a maximum pressure build-up rate of the hydraulic system is achieved, which is determined by the estimated value for the hydraulic capacity and a maximum volume flow rate of the hydraulic machine; Setting (150) at least one parameter of the one or more parameters, wherein the at least one parameter is determined by a respective function dependent on the setting time constant (130, 140). [2] Method according to claim 1, wherein the estimation method is carried out (110) when the magnitude of a rate of change of a target pressure is above a threshold; and / or wherein the estimation method is not carried out when the magnitude of the rate of change of the target pressure is below the threshold. [3] Method according to one of the preceding claims, wherein the setting time constant is determined to be equal to or greater than a stability time constant determined by means of a stability criterion for the control loop formed by the control system and the hydraulic system; wherein the setting time constant is determined in particular to be equal to the greater of the target time constant and the stability time constant. [4] Method according to any of the preceding claims, wherein, if the estimated value for the hydraulic capacity is below a predetermined capacity threshold, the setting time constant is determined to be equal to or greater than the target time constant plus half of a substitute time constant; wherein the substitute time constant combines a time delay or phase shift in a control loop formed by the controller and the hydraulic system; wherein, in the case of a cascaded controller, the substitute time constant relates in particular to the subordinate or inner control loop. [5] Method according to one of the preceding claims, wherein the at least one parameter includes at least one gain factor of one or more controllers of the control system; wherein when setting (150) the at least one parameter, the at least one gain factor is determined (140) such that it decreases with increasing setting time constant; wherein, in particular, the at least one gain factor is determined as being proportional to the inverse of the setting time constant and / or as being proportional to the inverse of the square of the setting time constant. [6] Method according to claim 5, wherein, if the control (160) has a parallel structure and the at least one gain factor includes a proportional gain factor and a differential gain factor, the proportional gain factor is determined as being proportional to the inverse of the square of the setting time constant and / or the differential gain factor is determined as being proportional to the inverse of the setting time constant. [7] Method according to claim 5, wherein, if the control (160) has a cascaded structure and the at least one gain factor includes a first proportional gain factor of an outer controller and / or a second proportional gain factor of an inner controller and / or a differential gain factor of the inner controller, the first and / or the second proportional gain factor is determined as being proportional to the inverse of the setting time constants, respectively.are determined and / or the differential gain factor of the internal controller is determined as proportional to the inverse of the setting time constant, wherein in particular a ratio of the second proportional gain factor to the first proportional gain factor is in the range of 2 to 4 and / or wherein in particular a differential gain factor of the internal controller is determined as proportional to the product of the second proportional gain factor with an equivalent time constant that summarizes a time delay or phase shift in a control loop formed by the control system and the hydraulic system. [8] A method according to any of the preceding claims, wherein the control includes trajectory planning which, from the setpoint values ​​for the quantity to be controlled, determines setpoint values ​​of a target trajectory for the quantity to be controlled and derivative values ​​of at least one time derivative of the target trajectory using a low-pass filter having a filter time constant; wherein the at least one parameter includes the filter time constant; wherein when setting (150) the at least one parameter, the filter time constant is determined (140) such that it increases with increasing setting time constant; wherein the filter time constant is determined, in particular, to be equal to or proportional to the setting time constant. [9] Method according to one of the preceding claims, wherein the control (160) includes a feedforward control (165) which determines feedforward control values ​​for the manipulated variable from setpoint values ​​of a setpoint trajectory for the variable to be controlled and derivative values ​​of at least one time derivative of the setpoint trajectory; wherein the feedforward control values ​​are determined as a function of the estimated value or values ​​of the at least one characteristic value. [10] Method according to claim 9, wherein, in particular if the control (160) has a parallel structure, the input control values ​​include a term in which the estimated hydraulic capacity is divided by the maximum pressure build-up rate and multiplied by the derivative values ​​of the second time derivative of the desired trajectory; or wherein, in particular if the control (160) has a cascaded structure, the input control values ​​include a term in which the estimated hydraulic capacity is divided by a maximum volume flow delivered by the hydraulic machine and multiplied by the derivative values ​​of the first time derivative of the desired trajectory. [11] Method according to claim 9 or 10, wherein the at least one parameter further includes a leakage coefficient and / or a turbulence flow coefficient; wherein a disturbance flow rate and / or its time derivative is / are determined as a function of the estimated value for the leakage coefficient and / or the estimated value for the turbulence flow coefficient; and wherein the disturbance flow rate and / or its time derivative is / are taken into account in the feedforward control (165); wherein, if dependent on claim 10, the time derivative of the disturbance flow rate is subtracted from the maximum pressure build-up rate before division or the disturbance flow rate is subtracted from the maximum delivered volume flow rate before division. [12] Method for controlling a pressure supply system of a hydraulic system, wherein the pressure supply system comprises a motor (4) and a hydraulic machine (2) which are controlled by a manipulated variable, and wherein the control is implemented by a control algorithm which is parameterized by one or more parameters which are adjustable or changeable during operation, the method comprising, Performing (110-150) the method according to one of the preceding claims to adjust at least one parameter of the control algorithm; Determining (160) setpoints for the manipulated variable based on setpoints for the controlled variable by executing the control algorithm; and Controlling (170) the pressure supply system with the setpoints. [13] Computing unit (14) comprising a processor configured to perform the method according to any of the preceding claims. [14] Computer program comprising instructions which, when the program is executed by a computer, cause it to execute the method according to claims 1 to 12. [15] Computer-readable data carrier on which the computer program according to claim 14 is stored.

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