ELECTRONIC CONTROL UNIT, HYDRAULIC SYSTEM, AND METHOD FOR CONTROLLING A HYDRAULIC SYSTEM

Abstract

The disclosure concerns an electronic control unit for a hydraulic system, the hydraulic system comprising a pump drivingly coupled to a motor, the pump configured to provide a supply pressure in a supply line of the hydraulic system. The electronic control unit is configured to receive a load sensing signal corresponding to a sensed load measure of the hydraulic system; determine, based on the load sensing signal and a predetermined pump margin, a target torque parameter for the motor; and adjust the motor based on the target torque parameter. The disclosure further concerns a hydraulic system and a method for controlling a hydraulic system.

Claims

1. An electronic control unit for a hydraulic system, the hydraulic system comprising a pump drivingly coupled to a motor, the pump configured to provide a supply pressure in a supply line of the hydraulic system; wherein the electronic control unit is configured to receive a load sensing signal corresponding to a sensed load measure of the hydraulic system; determine, based on the load sensing signal and a predetermined pump margin, a target torque parameter for the motor; and adjust the motor based on the target torque parameter.

2. The electronic control unit according to claim 1, wherein the sensed load measure is a load sensing pressure, including a hydraulic and/or electric load sensing pressure, and the pump margin corresponds to a pressure differential between the supply pressure and the load sensing pressure.

3. The electronic control unit according to claim 1, further configured to determine the predetermined pump margin, as a variable pump margin, based on a variable fluid flow rate in the supply line.

4. The electronic control unit according to claim 1, wherein the predetermined pump margin is a maximum pump margin corresponding to a maximum fluid flow in the supply line.

5. The electronic control unit according to claim 1, further comprising a closed-loop controller configured to determine a closed-loop target torque parameter based on a supply pressure signal corresponding to the supply pressure in the supply line.

6. The electronic control unit according to claim 1, further comprising a closed-loop controller configured to determine a closed-loop target torque parameter based on a current speed of the motor.

7. A hydraulic system, comprising a pump configured to provide a supply pressure in a supply line of the hydraulic system; a motor drivingly coupled to the pump; and an electronic control unit according to claim 1.

8. The hydraulic system according to claim 7, wherein the pump is a fixed-displacement pump.

9. The hydraulic system according to claim 7, wherein the motor is an electric motor.

10. The hydraulic system according to claim 7, further comprising a directional control valve with at least two load supply paths selectively connectable with the supply line and a pressure sensor configured to sense, as the sensed load measure, a pressure in at least one of the at least two load supply paths.

11. The hydraulic system according to claim 7, comprising a load sensing line with a load sensing orifice, wherein the hydraulic system is a working hydraulic system of an off-highway vehicle.

12. A method for controlling a hydraulic system, the hydraulic system comprising a pump drivingly coupled to a motor, the pump configured to provide a supply pressure in a supply line of the hydraulic system, comprising: receiving a load sensing signal corresponding to a sensed load measure of the hydraulic system; determining, based on the load sensing signal and a predetermined pump margin of the pump, a target torque parameter for the motor; and adjusting the motor based on the target torque parameter.

13. The method of claim 12 wherein the hydraulic system is a working hydraulic system of an off-highway vehicle.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0046] FIG. 1 shows, schematically, a hydraulic system.

[0047] FIG. 2 shows a control scheme of an ECU for a hydraulic system such as, e.g., the hydraulic system of FIG. 1.

[0048] FIG. 3 shows a graph representing a relation between a pump margin and a fluid flow rate in a supply line of a hydraulic system.

[0049] FIG. 4 shows a further example of a control scheme of an ECU for a hydraulic system.

[0050] FIG. 5 shows, schematically, a further example of a hydraulic system.

[0051] Recurring and similar features in the drawings are provided with identical reference numerals.

DETAILED DESCRIPTION

[0052] The hydraulic system 1 shown in FIG. 1 comprises a pump 2 configured to provide a supply pressure in a medium (such as oil, though a different fluid may be used) in a supply line 3 of the hydraulic system 1, a motor 4 drivingly coupled to the pump 2 via a rotatable shaft 13, and an ECU 5.

[0053] The pump 2 is a fixed-displacement pump. However, a variable-displacement pump may instead be provided. The motor 4 is an electric motor, though other types of motors, such as a combustion engine, may also be used. The pump 2 comprises a suction port connected to a reservoir 12 (fluid reservoir) via a pump inlet line 14.

[0054] The hydraulic system 1 comprises a directional control valve 6 with two load supply paths connected to respective supply paths 7a, 7b, the load supply paths 7a, 7b selectively connectable with the supply line 3. The load supply paths 7a, 7b are connected to a load 8, in the illustrated example a hydraulic cylinder of a working hydraulic system of a vehicle. The hydraulic system 1 may comprise different and/or additional loads. A different number of load supply paths may be provided.

[0055] A load pressure sensor 9 is provided to sense, as a sensed load measure of the hydraulic system 1, a pressure in a load sensing line 10 connected to one of the load supply paths 7a, 7b (hydraulic load sensing pressure P.sub.ls). The load sensing line 10 comprises a load sensing orifice 11 and is connected to reservoir 12. The illustrated example shows an exemplary design of a load sensing path, but alternative designs, such as those known in the art or described above, may be provided.

[0056] The hydraulic system 1 further comprises an inlet pressure sensor 15 configured to measure a pressure in the pump inlet line 14 (inlet pressure P.sub.t) and a supply pressure sensor 16 configured to measure the supply pressure P.sub.p in the supply line 3. A temperature sensor (not shown) to sense a temperature of the medium in the supply line (supply temperature T.sub.p) is also provided. In some embodiments, the inlet pressure sensor 15 and/or the supply pressure sensor 16 and/or the temperature sensor may be omitted. In some embodiments, for instance if the medium in the pump inlet line is pressurized, the inlet pressure P.sub.t may be assumed to be constant.

[0057] The ECU 5 is configured to

[0058] receive a load sensing signal corresponding to the load sensing pressure sensed by load pressure sensor 9;

[0059] determine, based on the load sensing signal and a predetermined pump margin P.sub.m, a target torque parameter for the motor 4; and

[0060] adjust the motor 4 based on the target torque parameter.

[0061] The ECU 5 may be thus configured to carry out a method for controlling the hydraulic system 1 (or another hydraulic system such as the hydraulic system 1′ described further below) comprising at least the aforementioned steps. For example, the ECU may include a processor and memory holding code for carrying out the actions described herein. In an example, the ECU receives data and/or information from sensors, such as the sensors described herein, and generates control signals and/or instructions sent to actuators for adjusting the various parameters described herein, such as the pump via the torque.

[0062] In the following, aspects of the operation of the ECU 5 and the hydraulic system 1 are described in further detail with reference to the control scheme shown in FIG. 2.

[0063] The ECU 5 determines the predetermined pump margin P.sub.m as a variable pump margin based on a variable fluid flow rate Q in the supply line, wherein a pre-established relation between the predetermined pump margin Pm and the fluid flow rate Q in the supply line (as illustrated in the graph shown in FIG. 3) is taken into account. The fluid flow rate Q may be determined, for instance, using an optional flow sensor or based on Equation 4, i.e.

Q=V.sub.p×ω×η.sub.v.

[0064] Here, the pump rotational speed w is equal to the known motor rotational speed, the displacement volume V.sub.p is a known property of the pump, and the volumetric efficiency η.sub.v (as well as the hydro-mechanical efficiency η.sub.hm) of the pump is known based on a pump efficiency map, wherein the pump efficiency map specifies the pump efficiency depending on the supply pressure P.sub.p, the supply temperature T.sub.p, and/or the pump rotational speed ω).

[0065] Returning to FIG. 2, the ECU 5 comprises a feedforward controller block 17, which determines an open-loop target torque parameter T according to Equation 2 or 3, i. e.

[00003]$T=V_p\times \frac{P_p-P_t}{{\eta }_{\mathrm{hm}}}\mathrm{or}T=V_p\times \frac{P_{\mathrm{ls}}+P_m-P_t}{{\eta }_{\mathrm{hm}}}.$

[0066] The ECU 5 further comprises a closed-loop controller block 18, which determines a closed-loop target torque parameter T* based on a supply pressure signal corresponding to the measured supply pressure P.sub.p in the supply line 3 (here, P.sub.p* denotes the actual value of the supply pressure P.sub.p).

[0067] In the following, operation of the ECU 5 according to the further example of a control scheme shown in FIG. 4 is described.

[0068] In this case, the ECU 5 determines the predetermined pump margin as a maximum pump margin P.sub.m′ corresponding to a maximum fluid flow in the supply line. The control scheme according to FIG. 4 may be suited for a hydraulic system wherein a supply pressure sensor is not provided.

[0069] The ECU 5 comprises a feedforward controller block 17′, which determines an open-loop target torque parameter T according to Equation 2 or 3. An achieved pump rotational speed in the case of the maximum pump margin P.sub.m′ is denoted with ω′.

[0070] The ECU further comprises a closed-loop controller block 18′, which determines a closed-loop target torque parameter T* based on based on the current rotational speed of the motor (here, ω* denotes the actual value of the supply pressure ω). By providing this control scheme, P.sub.m can be intrinsically reduced up to the minimum value required to guarantee the required oil flow rate.

[0071] It is noted that various components of the different control schemes/the ECU 5 (such as the feedforward and/or closed-loop controller block) may be implemented as dedicated circuitry and/or as software running on multi-purpose digital circuitry. In FIG. 2 and FIG. 4, the term “plant” refers to the common meaning in control theory, i.e. it represents the underlying physical system, such as in terms of a system transfer function relating an input of the physical system to a corresponding output.

[0072] As a further example of the subject matter of the present disclosure, hydraulic system 1′ is shown in FIG. 5. The hydraulic system 1′ is largely similar to the hydraulic system 1 described above. Accordingly, only the differences are described here.

[0073] Whereas the directional control valve 6 of hydraulic system 1 is a conventional load sensing directional control valve, the load sensing pressure being provided as a hydraulic load sensing pressure, the hydraulic system 1′ comprises an electric load sensing directional control valve 6′ (such as with an integrated load pressure sensor), and the load sensing pressure is provided to the ECU 5 as a load sensing signal corresponding to an electric load sensing pressure, foregoing the need for a dedicated load sensing path connected to the reservoir 12.

[0074] For instance, the hydraulic system 1′ shown in FIG. 5—in contrast to hydraulic system 1 shown in FIG. 1—does not require the load sensing line 10 comprising load sensing orifice 11 and “external” load pressure sensor 9 (otherwise used to “translate” a hydraulic load sensing pressure into a load sensing signal).

[0075] The hydraulic system 1′ may be operated using an ECU as described above, for instance according to any of the control scheme examples provided above.