Hydraulic system

Abstract

The invention relates to a hydraulic system (100) comprising: - a hydraulic consumer (10); - a control pump (30); - a control valve (36); and - a system controller (40) for dynamically controlling the position of the hydraulic consumer (10), the system controller (40) having a pump controller (42) for controlling the control pump (30) and a valve controller (44) for controlling the control valve (36); wherein the valve controller (44) is designed to control the control valve (36) on the basis of a target position (46) of the hydraulic consumer (10), on the basis of a comparison (48) of the target position (46) with an actual position (28) of the hydraulic consumer (10) and on the basis of an amplification factor (50) of the control pump (30) depending on a limit value.

Description

[0001] Description

[0002] title

[0003] The invention relates to a hydraulic system with a hydraulic consumer, a control pump, a control valve and a system controller.

[0004] State of the art

[0005] In modern hydraulic engineering, the efficient and precise control of hydraulic systems plays a crucial role. One approach in this area is hydraulic primary control. This control method enables the speed of a hydraulic consumer to be controlled by adjusting the flow rate of the hydraulic pump. The advantage of this method lies in its high efficiency, achieved primarily by eliminating the need for a control valve in the main circuit. This not only leads to more efficient energy use but also to reduced complexity and potentially lower costs for the overall system.

[0006] DE 10 2014 213 264 A1 discloses a hydraulic arrangement for supplying a consumer or actuator with a first supply device comprising a pump with an adjustable displacement. A second supply device is provided parallel to the first supply device, which comprises a loadable accumulator and a digitally controlled switching valve arrangement.

[0007] The conventional control methods are not without their challenges. Particularly with longer lines between the hydraulic pump and the actuator, control inaccuracies can occur. These inaccuracies are often found in the work cycles of hydraulic machines, where general control is required, but high precision is only required at specific points or in specific positions of hydraulic cylinders.

[0008] While coarse position control may be sufficient for most of a hydraulic cylinder's cycle, the capabilities of primary control reach their limits when high accuracy is required, as is the case in specific operating areas. This results in a need for alternative control methods, whereby the choice between primary control and alternative control methods depends on the specific requirements of the respective application. A comprehensive analysis of the duty cycle and the precision requirements of the hydraulic machine or hydraulic consumer is crucial to determining the most optimal control concept for maximum efficiency and effectiveness of the hydraulic system.

[0009] It is an object of the invention to provide a hydraulic system with improved control technology.

[0010] The problem is solved by a hydraulic system according to the features of patent claim 1.

[0011] Disclosure of the invention

[0012] According to one aspect, a hydraulic system is specified. The hydraulic system has a hydraulic consumer, a control pump, a control valve, and a system controller for dynamically controlling the position of the hydraulic consumer. The system controller has a pump controller for controlling the control pump and a valve controller for controlling the control valve. The valve controller is configured to control the control valve based on a target position of the hydraulic consumer, based on a comparison of the target position with an actual position of the hydraulic consumer, and based on an amplification factor, preferably derived from the displacement of the control pump, as well as depending on a limit value. The valve controller thus preferably only assumes position control of the hydraulic consumer when the limit value condition, preferably a limit value being reached or a limit value being undershot, is met.The limit value is preferably predetermined and / or definable for the specific system and preferably indicates the dynamics and accuracy with which the position control of the hydraulic consumer can be carried out.

[0013] The hydraulic system is characterized by the hydraulic interconnection of the control pump and the control valve, as well as by the control interaction between the control pump and the control valve provided by the system controller for dynamic position control of the hydraulic actuator. The system control, or controller circuit, allows a hydraulic actuator to be precisely positioned to a target position or desired position at a fast cycle rate or high speed.

[0014] Thanks to the system control, the hydraulic axis can be moved energy-efficiently, dynamically, and precisely, even under load. Energy efficiency is achieved by using the primary control provided by the control pump in combination with the limit-dependent control valve control. With primary control, which is active over a wide operating range of the hydraulic actuator, the hydraulic cylinder(s) are directly connected to a control pump.

[0015] The control valve then only enables fine adjustment of the actual position at the end of the hydraulic actuator's operating range. The additional control valve, together with the valve controller, thus enables dynamic end-position control. When the hydraulic actuator approaches the end position of its stroke range, the control valve controls the hydraulic cylinder(s) with high precision, position-dependent control.

[0016] In other words, the control valve enables position-dependent braking of the hydraulic cylinder(s) in these end regions. The control valve is preferably a hydraulic continuous valve. The invention thus describes a combination of an energy-efficient primary control for operating ranges that do not require high accuracy with a valve control for operating ranges that require very precise and highly dynamic control. The control valve is preferably dimensioned and controlled in such a way that the energy advantages of the primary control are not negatively impacted.

[0017] By feeding back preferably the displacement volume of the control pump as a P-factor to the higher-level valve controller, which enables highly dynamic position control of the hydraulic consumer, it is possible to move the hydraulic drive at the dynamic limits of the hydraulic system.

[0018] In a preferred aspect, the control valve is designed as a throttle valve.

[0019] The throttle valve is located in the main hydraulic flow. The throttle valve receives a control signal from the valve controller, which allows the opening cross-section of the throttle valve to be continuously adjusted. The throttle valve can be continuously adjusted between a fully open position, in which the throttle valve is preferably considered to be free of flow resistance in the main flow, and reduced throttle positions, in which the cross-section of the throttle valve is reduced depending on the control signal. The throttle valve also preferably enables a reversal of the flow direction in the main flow for highly dynamic position control of the hydraulic actuator.

[0020] In a preferred aspect, the pump controller is configured to control the control pump based on a volume flow setpoint and / or a pressure setpoint and / or a power setpoint.

[0021] The pump controller therefore preferably receives the flow rate setpoint and / or the pressure setpoint and / or the power setpoint as control inputs. The primary control operates as a back-up pressure and flow rate control with power limitation. "Back-up" in this context means that all controllers are always active, and when the pressure, flow, or power setpoint is reached, the respective controller determines the primary control.

[0022] In a preferred aspect, the valve controller comprises a position controller (P controller) configured to compare the desired position with the actual position and to multiply a difference between the desired position and the actual position by the gain factor and provide it as a control output. The valve controller further comprises a limiter configured to limit the control output or to keep it within certain limits.

[0023] The limiter, for example, limits the control output to ± 100%. The valve controller can further comprise a negator, which can negate the limiter's output or change its sign, preferably based on a negation signal. The control output is then output depending on the actual position and / or the target position of the hydraulic consumer, which are preferably determined by a position sensor, and taking the negation signal into account.

[0024] In a preferred aspect, the limit value can be set based on the target position.

[0025] In principle, the limit value can also be set based on the dynamic requirements of the hydraulic system. Multiple limit values ​​are also conceivable.

[0026] In a preferred aspect, the pump controller is configured to execute the position control of the hydraulic consumer by controlling the control pump when the limit value is exceeded. The valve controller is configured to execute the position control of the hydraulic consumer (only) when the limit value is reached or undershot.

[0027] During primary control, the position of the hydraulic consumer is controlled by controlling the flow rate of the control pump. The cylinder(s) are therefore moved into position by the control pump. The setpoints for the position of the hydraulic cylinders are process-specific. Above a predefined control deviation, which preferably corresponds to the limit value, the valve controller is in saturation. This activates the limiter and sets the setpoint of the control valve to the maximum valve opening specified by the limiter. When the control valve is at its maximum opening, the hydraulic consumer is moved solely by primary control. If the control deviation falls below a defined value or is at least equal to this value, the position controller is no longer in saturation. As a result, the limiter is no longer active and the control valve takes over control of the hydraulic consumer.

[0028] Particularly preferably, the control valve can be reset to maximum opening via the system controller or by setting a position setpoint with a resulting large control deviation, which makes the primary control active again.

[0029] In a preferred aspect, the gain factor is calculable based on the swivel angle of the control pump.

[0030] The swivel angle of a variable-speed pump is a key element in the primary hydraulic control, which directly controls the pump's power and flow rate. In hydraulic systems, especially those with variable displacement, the pump's swivel angle enables precise control of the hydraulic flow to the hydraulic consumer(s). By adjusting the swivel angle, the pump can continuously adjust its flow rate and, consequently, dynamically adjust the speed of the hydraulic consumer without any throttling loss.

[0031] In a preferred aspect, the control pump has a pump drive. The pump drive has an asynchronous motor, a servo motor, or a variable-speed drive.

[0032] Other pump drives are also conceivable, so this list is not intended to be limiting. In a preferred aspect, the hydraulic consumer comprises a gas compressor, preferably a hydrogen compressor.

[0033] The hydraulic system is particularly suitable as a control system for driving compressors.

[0034] In a preferred aspect, the hydraulic consumer comprises a cylinder drive with one or more piston rods or a hydraulic motor with an eccentric drive.

[0035] Other hydraulic consumers that need to be moved dynamically, with high precision and energy efficiency are also conceivable, so the list should not be understood as limiting.

[0036] The described designs and further training courses can be combined as desired.

[0037] Further possible embodiments, further developments and implementations of the invention also include combinations of features of the invention described previously or below with regard to the embodiments that are not explicitly mentioned.

[0038] Short description of the drawings

[0039] The accompanying drawings are intended to provide a further understanding of embodiments of the invention. They illustrate embodiments and, in conjunction with the description, serve to explain principles and concepts of the invention.

[0040] Other embodiments and many of the aforementioned advantages will become apparent upon review of the drawings. The elements illustrated in the drawings are not necessarily drawn to scale.

[0041] It shows: Fig. 1 an exemplary hydraulic system.

[0042] In the figures of the drawings, the same reference symbols designate the same or functionally equivalent elements, parts or components, unless otherwise stated.

[0043] Figure 1 shows an exemplary hydraulic system 100. The hydraulic system 100 has a hydraulic consumer 10. In Fig. 1, three different hydraulic consumers 10 are shown by way of example, namely a cylinder drive 12 with a cylinder 14 and several piston rods 16, a hydraulic motor 18 with an eccentric drive 20, and a single-cylinder drive 22 with only one piston rod 24. A respective actual position 28 of the respective, in particular cyclically moved, component of the hydraulic consumer is preferably detected via a position and / or position sensor 26. The hydraulic consumer 10 has a gas compressor, preferably a hydrogen compressor.

[0044] The hydraulic system 100 further includes a control pump 30. The control pump 30 includes a pump drive 32, which can be configured as an asynchronous motor, a servo motor, or a variable-speed drive. The control pump 30 also includes a pump control 34, which can receive control signals and adjust the drive or the control pump based on the control signals.

[0045] The hydraulic system 100 further includes a control valve 36, which is designed as a throttle valve. The hydraulic system 100 further includes a pressure relief valve 38 or a safety valve.

[0046] The hydraulic system 100 further comprises a system controller 40 for dynamic position control of the hydraulic consumer 10.

[0047] The system controller 40 comprises a pump controller 42 for controlling the control pump 30 and a valve controller 44 for controlling the control valve 36. The valve controller 44 is configured to control the control valve 36 based on a target position 46 of the hydraulic consumer 10, based on a comparison 48 of the target position 46 with the actual position 28 of the hydraulic consumer 10, and based on a gain factor 50 of the control pump 30 as a function of a limit value. The limit value can be set based on the target position 46. The gain factor 50 is calculated based on a swivel angle of the control pump 30.

[0048] The valve controller 44 has a position controller 52 configured to compare the target position 46 with the actual position 28, and to multiply a difference between the target position 46 and the actual position 28 by the gain factor 50 and provide it as a control output 54 to a limiter 56. The limiter 56 is configured to limit the control output 54. The valve controller 44 further includes a negator 58, which can negate the output of the limiter or the control output 54 based on a negation signal 60.

[0049] The pump controller 42 is configured to control the control pump 30 based on a volume flow setpoint 62 and / or a pressure setpoint 64 and / or a power setpoint 66. For this purpose, the pump controller 42 comprises a power controller 68, a pressure controller 70, and a volume flow controller 72. The output of the power controller 68 is connected to a minimum value former 74, which receives the volume flow setpoint 62 as a further input. The output of the pressure controller 70 and an output of the volume flow controller 72 are connected to another minimum value former 76.

Claims

Claims 1. A hydraulic system (100), comprising: a hydraulic consumer (10); a control pump (30); a control valve (36); and a system controller (40) for dynamically controlling the position of the hydraulic consumer (10), the system controller (40) comprising a pump controller (42) for controlling the control pump (30) and a valve controller (44) for controlling the control valve (36); wherein the valve controller (44) is configured to control the control valve (36) based on a target position (46) of the hydraulic consumer (10), based on a comparison (48) of the target position (46) with an actual position (28) of the hydraulic consumer (10), and based on an amplification factor (50) of the control pump (30) as a function of a limit value.

2. Hydraulic system according to claim 1, wherein the control valve (36) is designed as a throttle valve.

3. Hydraulic system according to claim 1 or 2, wherein the pump controller (42) is configured to control the control pump (30) on the basis of a volume flow setpoint (62) and / or a pressure setpoint (64) and / or a power setpoint (66).

4. Hydraulic system according to one of the preceding claims, wherein the valve controller (44) has a position controller (52) which is configured to compare the desired position (46) with the actual position (28) and to multiply a difference between the desired position (46) and the actual position (28) by the gain factor (50) and to output it as a control output (54); and wherein the valve controller (44) has a limiter (56) configured to limit the control output (54).

5. Hydraulic system according to one of the preceding claims, wherein the limit value can be set on the basis of the desired position (46).

6. Hydraulic system according to one of the preceding claims, wherein the pump controller (42) is configured to carry out the position control of the hydraulic consumer (10) by controlling the control pump (30) when the limit value is exceeded, and wherein the valve controller (44) is configured to carry out the position control of the hydraulic consumer (10) when the limit value is reached or undershot.

7. Hydraulic system according to one of the preceding claims, wherein the amplification factor (50) is calculable on the basis of a pivot angle of the control pump (30).

8. Hydraulic system according to one of the preceding claims, wherein the control pump (30) has a pump drive (32), and wherein the pump drive (32) has an asynchronous motor or a servo motor or a variable speed drive.

9. Hydraulic system according to one of the preceding claims, wherein the hydraulic consumer (10) comprises a gas compressor, preferably a hydrogen compressor.

10. Hydraulic system according to one of the preceding claims, wherein the hydraulic consumer (10) comprises: a cylinder drive (12) with a cylinder (14) and a plurality of piston rods (16); or a hydraulic motor (18) with an eccentric drive (20); or a cylinder drive (22) with a piston rod (24).

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