Electro-hydraulic compact drive for underwater use and set of at least two electro-hydraulic compact drives

Abstract

Electro-hydraulic compact drive (10) for use under water and for driving an output element (40, 61, 62) with a hydraulic motor (31) as a component, which has an output shaft (37), with a hydraulic pump (30) as a component, from which the hydraulic motor (31) can be supplied with a hydraulic fluid via a working line (32), and with an electric motor (50) as a component, by which the hydraulic pump (30) can be driven, characterized in that the components (30, 31, 50) are located in a closed container (12) filled with hydraulic fluid and that the container (12) has an opening for coupling the output shaft (37) of the hydraulic motor (31) to the output element (40, 61, 62) and that the container (12) has a movable compensation piston (18).

Description

[0001] The invention relates to an electro-hydraulic compact drive for underwater use and a set of at least two electro-hydraulic compact drives, which are particularly, but not exclusively, suitable for underwater use and for the rotary drive of an output element, for example, a propeller, a wheel, or a cable winch. The compact unit comprises, as components, a hydraulic motor having an output shaft, a hydraulic pump, which supplies the hydraulic motor with hydraulic fluid via a working line, and an electric motor, which drives the hydraulic pump.

[0002] Many underwater activities related to the extraction of fossil energy such as oil and gas, the mining of mineral resources, natural sciences, robotics using Remote Operated Vehicles (ROVs) or Automated Underwater Vehicles (AUVs), infrastructure projects or renewable energies require special machines and equipment with underwater systems that can drive and control in the difficult environment.

[0003] Many underwater devices require one or more controllable propulsion systems, also called thrusters. These thrusters usually have a propeller as the output element. Underwater robots such as ROVs or AUVs, in particular, require one or more thrusters, for example, eight thrusters, to enable the robot's necessary mobility in all six degrees of freedom.

[0004] The output element doesn't necessarily have to be a propeller. Rather, it can also be a wheel resting on the seabed or used to drive a chain, as is the case with an underwater mining vehicle, for example. Furthermore, the compact drive can also drive a cable winch used to position ships or underwater equipment. Examples include mooring, anchoring, compensating for sea swell, or tensioning a chain underwater.

[0005] Devices specifically designed for underwater operation must function safely and reliably. The common solution is to use hydraulic motors to drive the output elements, which can be supplied with hydraulic fluid via electrically controlled underwater valves with a shared hydraulic pump. Such a device is known from GB 2 181 040 A. If the pump fails, the underwater robot or device can no longer move and must be immediately brought up for repair.

[0006] To compensate for the movements and currents of the water, an underwater drive also requires a dynamic control system. At the same time, the drive must operate with minimal energy consumption at all times. These two requirements for high dynamics and energy efficiency are difficult to achieve with the systems outlined above. Furthermore, the requirements for functional safety are increasing in order to operate safely even under complex application conditions. An example of functional safety here would be a safely reduced speed when approaching an object.

[0007] JP S61-200 096 A and US 3 764 233 A disclose electro-hydraulic compact drives for underwater use.

[0008] An electro-hydraulic drive intended for underwater use, in which a hydraulic pump driven by an electric motor and a hydraulic motor are connected in a closed hydraulic circuit, is known from DE 29 24 364 A1. The hydraulic motor drives a propeller, which serves as the output element. A total of three electro-hydraulic drives of this type are installed on a mining rig. These drives are used to move the rig underwater or to move parts of the rig relative to a frame.

[0009] The object of the invention is to design an electro-hydraulic drive which is intended for use under water and which comprises as components a hydraulic motor which has an output shaft, a hydraulic pump from which the hydraulic motor can be supplied with a hydraulic fluid via a working line, and an electric motor from which the hydraulic pump can be driven, in such a way that it is particularly suitable for use under water.

[0010] This task is solved by an electro-hydraulic compact drive in which the components are located in a closed container filled with hydraulic fluid. The container has an opening for coupling the output shaft of the hydraulic motor to the output element. The container of an electro-hydraulic compact drive has a movable compensation piston. According to the invention, the electro-hydraulic compact drive thus forms a self-contained unit containing the complete electric motor-hydraulic pump-hydraulic motor arrangement. The compact drive combines the advantages of the high power density of hydraulics with a decentralized electric direct drive. High reliability and safety are achieved. The drive is easier to handle.The electric motor, which is coupled to the hydrostatic transmission formed by the hydraulic pump and the hydraulic motor, can be a small, lightweight, and compact electric motor that operates at high speeds. Advantageously, the electric motor can be controlled at variable speeds.

[0011] To achieve particularly high drive dynamics, the hydraulic pump is advantageously adjustable in its displacement. The hydraulic motor is also preferably adjustable in its displacement, as this further increases the dynamics and energy efficiency of the electrohydraulic drive.

[0012] It is expedient if an electrical control system for supplying power to the electric motor is arranged in the container. Advantageously, the electrical control system is equipped with computing power and is programmed with algorithms for operating the components or is suitable for being programmed with algorithms for operating the components.

[0013] It is advantageous if the hydraulic motor can also be operated as a hydraulic pump, the hydraulic pump as a hydraulic motor, and the electric motor driven by the hydraulic pump operating as a hydraulic motor can also be operated as a generator. Then, driven by a propeller or wheel, electrical energy can be recovered and stored in a battery for later use. For this purpose, algorithms for energy recovery and storage are integrated into the electrical control system.

[0014] The compact drive may include an electronic control module with built-in functionality for dynamic position control of a vehicle equipped with the drive. The control module may be an integral module of the vehicle's electronic control system.

[0015] Sensors are preferred, in particular sensors such as sensors for the pressure in the hydraulic circuit, for the rotational speed, for the position, for the speed, for the acceleration, for the temperature and for the condition, for example for the degree of contamination of the hydraulic fluid and for the water depth, in particular microelectromechanical sensors (MEMS), are integrated into the electro-hydraulic compact drive. By monitoring the temperature, drive failure can be prevented if it is operated in an environment with extreme temperatures, such as those that can prevail above the water surface. Sensors can be used to record the displacement of the hydraulic units. Sensors can also be used to record the rotational speed of the components for particularly good controllability. An algorithm can be implemented to limit the output torque of the hydraulic motor in order to avoid damage to the output element, in particular a propeller.Likewise, an algorithm can be implemented to increase the pressure in the hydraulic circuit to free the propeller from an object caught in it.

[0016] Control functions can be integrated for automatically compensating for external disturbances such as water currents or counterforces when an actuator is operated. For example, sensors measure the accelerations at the drives. The propellers are then driven in such a way that the forces along the propeller's alignment axis are reduced as much as possible by generating counterforces of equal strength. Condition monitoring algorithms can also be integrated, such as operating hour counters and torque and vibration monitoring. Algorithms for maximizing dynamics and efficiency can be integrated.

[0017] An electro-hydraulic compact drive according to the invention advantageously has at least one communication interface for exchanging data with or without cables.

[0018] Safety functions can be integrated into the electronic control system as closed control loops.

[0019] In particular, the following security functions are conceivable: a) Safe Torque Off (STO): If the electrical control system receives an emergency stop command via the communication interface, the electric motor, and thus also the hydraulic pump and motor, are shut down (de-energized). The propeller will stop after an uncontrolled time and travel distance. b) Safe Stop 1 and 2 (SS1 and SS2: Safe Stop 1 & 2): When the electrical control system receives a specific command (e.g. “SS1” or “SS2” messages) via the communication interface, the electric motor and thus also the hydraulic pump and the hydraulic motor are controlled in such a way that the propeller is stopped after a controlled maximum time and a controlled maximum distance. c) Safe maximum / limited speed (SMS: Safe Max. Speed; SLS: Safe Limited Speed): The electric control system regulates the propeller's speed using appropriate sensors (such as rotary encoders) to ensure that the speed does not exceed the maximum value specified by the communication interface. If this value is exceeded, the electric motor is shut down. In addition to the maximum speed, the control system can temporarily reduce the speed to allow certain sensitive movements, for example. This function enables close approach to an object. d) Safe direction of rotation (SDI): When the electrical control system receives a command via the communication interface to safely rotate in a specific direction, a sensor monitors the propeller's rotation. If the incorrect direction of rotation is indicated, the electric motor is shut down, for example, to move away from a hazardous area. e) Safe Maximum Torque (SMT): The propeller torque is controlled by a corresponding sensor or sensors (e.g., a pressure sensor and a displacement sensor). If the torque exceeds the maximum specified value, the electric motor is shut down. f) Secure holding system in alignment with the propeller axis: The external forces acting on the drive are measured with an acceleration sensor, and the electric motor is controlled to generate a counterforce to maintain the position. If the acceleration still exceeds the specified value, an additional safety function is activated, such as "safe direction of rotation" or "safe torque off." By arranging several differently aligned compact drives on an underwater robot (e.g., AUV or ROV), the combination of these functions can control and maintain the robot's position in multiple directions. g) Secure Communication (SCO: Safe Communication): The transmission of safety-relevant data, such as commands or parameters, via the communication interface is monitored using appropriate error detection methods. If an error is detected, the electrical control system initiates a safety function, such as "safe torque off."

[0020] The electro-hydraulic compact drive can have at least one interface through which hydraulic fluid can be refilled or replaced underwater.

[0021] Advantageously, the electrical and mechanical interfaces of an electro-hydraulic compact drive according to the invention can be decoupled underwater. This makes it possible to replace a compact drive with the help of a diver or a robot (remotely operated vehicle or autonomous underwater vehicle).

[0022] The electro-hydraulic compact drive is conveniently equipped with one or more hydraulic filters, with or without status sensors, to prevent, for example, excessive contamination of the hydraulic fluid with water or particles. The status sensors can indicate whether the hydraulic fluid needs replacing.

[0023] For use at greater depths, the tank of an electro-hydraulic compact drive features a movable compensation piston. A first surface defines the interior of the tank and a second surface, the same size as the first and opposite the first, is subjected to ambient pressure. If an additional force is exerted on the compensation piston toward the interior of the tank, for example, by a spring, the pressure inside the tank is always slightly higher than outside, preventing water from entering. By monitoring the position of the compensation piston, any hydraulic fluid leakage to the outside can be detected.

[0024] A set of at least two electro-hydraulic compact drives according to the invention can be arranged on a device to be moved, wherein the movement of the device is realized by coordinated operation of the electro-hydraulic compact units with or without a higher-level control.

[0025] If a vehicle is equipped with several electro-hydraulic compact drives according to the invention, i.e. a set of electro-hydraulic compact drives according to the invention, it is possible to compensate for the failure of one compact unit as far as possible by operating the other compact units using an intelligent algorithm or control loop.

[0026] An exemplary embodiment of an electro-hydraulic compact drive according to the invention, a set of eight electro-hydraulic compact drives according to the invention, and various output options are shown in the drawings. The invention will now be explained in more detail with reference to the figures in these drawings.

[0027] It shows Fig. 1 the embodiment as a drive of a propeller, Fig. 2 a set of eight electro-hydraulic compact drives according to the invention, Fig. 3a-3d different output options and Fig. 4 the embodiment as a drive for a cable winch.

[0028] From the electro-hydraulic compact drive 10 according to Fig. 1, only one electrical cable 11 leads to the sea surface or to another submerged higher-level electrical control system. The electro-hydraulic compact drive has a container 12 with an interior space 1 sealed off from the environment, which is filled with a hydraulic fluid as the working medium.

[0029] The container is pressure-compensated with respect to the ambient pressure prevailing underwater by a compensation device 25. For this purpose, a lid 17 is fastened by a flange 16 to a flat rim 15 surrounding an opening 14 in the container wall, and a membrane 18 is tightly clamped between the flat rim 15 and the lid 17. There are holes 19 in the lid 17 so that the space between the membrane and the lid is part of the environment and is filled with seawater. The interior 13 is thus sealed off from the environment by the membrane 18. The membrane is subjected to the pressure in the interior on its first surface facing the interior, and to the pressure in the environment on its second surface facing the lid 17, which is approximately the same size as the first surface, and always seeks to assume a position and shape in which the sum of all forces acting on it is zero.To ensure that the pressure in the interior 13 is slightly higher than the ambient pressure, the diaphragm 18 is additionally loaded against the internal pressure by a spring 20 that is clamped between a dimensionally stable, central diaphragm plate 21 and the cover 17. The force of the spring 20 is selected, taking into account the size of the pressurized surfaces of the diaphragm, so that the pressure in the interior is, for example, between 0.5 bar and 2 bar higher than the ambient pressure. A rod 22 is attached to the diaphragm plate 21 and is guided in the cover 17. This rod 22 can be provided with a measuring scale and can be part of a sensor that detects the position of the center of the diaphragm 18. According to the exemplary embodiment, the rod 22 projects beyond the diaphragm plate 21 into the interior 13 of the container 12, where it is provided with a measuring scale.A position sensor 56 detects the position of the rod 22 and thus of the diaphragm 18 and sends a corresponding signal to the electrical control unit 51. This prevents contact of the measuring scale and the position sensor 56 with seawater, increasing reliability.

[0030] In the interior 13 of the container 12, all mechanical, electrical and hydraulic components that are necessary or advantageous for controlling the electro-hydraulic compact drive 10 are accommodated, with the exception of the source of electrical power energy and higher-level electrical control signals.

[0031] The interior 13 of the tank 12 contains a hydraulic pump 30 and a hydraulic motor 31, which are connected to one another via two working lines 32 and 33 and are arranged together in a closed hydraulic circuit. Both the hydraulic pump 30 and the hydraulic motor 31 are adjustable in their displacement. The hydraulic motor can be adjusted between a maximum value and a displacement of zero or close to zero. The hydraulic pump 30 is always driven in the same direction and its displacement can be adjusted between a maximum positive value and a maximum negative value. Accordingly, the working line 32 is the high-pressure line and the working line 33 is the low-pressure line, or vice versa, depending on the direction in which the hydraulic pump is adjusted from a neutral or zero position.By adjusting the hydraulic pump above zero, the direction of rotation of the hydraulic motor can be reversed while maintaining the direction of rotation of the electric motor and hydraulic pump. The pressure prevailing in the working line 32 is detected by a pressure sensor 34. Accordingly, the pressure prevailing in the working line 33 can also be detected by a pressure sensor. In the working line 33 there is a throttle 35, to which a device 36 for separating water contained in the hydraulic fluid, which is usually an oil, is connected in parallel. Due to the throttle 35, a portion of the hydraulic fluid flowing back from the hydraulic motor 31 to the hydraulic pump 30 flows via the separating device 36, so that a portion of the returning oil is always cleaned. The device 36 can also be combined with a filter for cleaning the hydraulic fluid of solid particles.

[0032] The hydraulic motor 31 has an output shaft 37, which is rotationally fixedly coupled to a propeller 40 located outside the container 13, which forms the output element of the electrohydraulic drive. A central drive shaft 41 of the propeller is tightly guided through a wall of the container 13 and is connected internally to the output shaft 37 of the hydraulic motor 31. The speed of the output shaft of the hydraulic motor and the drive shaft of the propeller is detected by a speed sensor 42 arranged inside the container.

[0033] The hydraulic pump 30 is driven by an electric motor 50, whose speed is adjustable and connected to an electrical control unit 51, which is also housed in the interior 13 and connected to an electrical power source at the sea surface and possibly also to a higher-level electrical control system located underwater via the cable 11, which extends sealed from the container 12. The speed of the electric motor 50 and the hydraulic pump 30 is detected by a speed sensor 52 and processed by the control unit 51.

[0034] In addition to the sensors already mentioned, there is also a temperature sensor 53 for detecting the temperature of the hydraulic fluid in the tank and an acceleration sensor 54 for detecting accelerations of the compact drive.

[0035] The electric motor 50 can also be operated as a generator, the hydraulic pump 30 can also be operated as a hydraulic motor, and the hydraulic motor 31 can also be operated as a hydraulic pump. Driven by the propeller, the pump 30, which functions as a hydraulic motor, supplies hydraulic fluid to the pump 30, which functions as a hydraulic motor. The electric motor 50, in turn, can be driven as a generator by the pump 30, which functions as a hydraulic motor. In this way, electrical energy can be recovered from the rotational movement of the propeller and stored, for example, in a battery.

[0036] The compact drive also includes an electronic control module 55, which is a component of a control system used to control a vehicle equipped with the compact drive and has built-in functionality for dynamic position control of the vehicle. Modifications of an electrohydraulic system according to the invention are also possible compared to the illustrated embodiment.

[0037] The container has two interfaces 56 which are used to refill or replace hydraulic fluid underwater.

[0038] In its simplest form, the electrical control system comprises a DC motor, an electrical control unit with corresponding analog and digital input and output interfaces, and a suitable power supply.

[0039] In its advanced form, the electrical control system includes a three-phase motor with the appropriate drive and frequency converter, an electrical control unit with the appropriate analog and digital input and output interfaces, as well as a suitable power supply and network interfaces, including LAN, bus systems, fiber optic cables, or wireless LAN.

[0040] In addition to the power supply, the electrical cable also includes the electrical signals for control communication, such as setpoints, actual values ​​and error messages.

[0041] Condition monitoring of the electrohydraulic system can be implemented in the electrical control system by evaluating all sensor signals using appropriate algorithms implemented in software. In the event of a malfunction, the control system can autonomously place the compact drive into a safe idle state and inform the higher-level control system. Preventive and reactive maintenance measures can be communicated to the higher-level control system.

[0042] Out of Fig. 2 shows a set of eight electro-hydraulic compact drives 10 according to the invention, each of which, like the electro-hydraulic compact drive from Fig. 1 and which are all located on the same underwater vehicle. The electrical controls 51 of the compact drives are connected to a central master control 60, which controls the individual compact drives according to the movement pattern specified for the vehicle. Two of the compact drives are responsible for opposite movements of the vehicle along an x-axis. Two further compact drives are responsible for opposite movements of the vehicle along a y-axis. Another compact drive is responsible for movement of the vehicle in the direction of a z-axis, whereby it is assumed that movement in one direction of the z-axis occurs due to gravity. Of the three further compact drives, one is responsible for rotations around the x-axis, one for rotations around the y-axis and one for rotations around the z-axis.

[0043] In case of failure of one or more of the Fig. In the electro-hydraulic compact drives 10 shown in Figure 2, the failure is compensated as far as possible by an intelligent algorithm or control circuit, so that essential movement sequences can still be carried out in an emergency.

[0044] Of the four in Fig. 3 shown output options corresponds to that according to Fig. 3a of the Fig. 1 and Fig. 2. A propeller 40 is driven directly by a hydraulic motor via a central drive shaft 41.

[0045] Fig. Figure 3b shows a propeller 40 whose central drive shaft 41 is arranged parallel to the output shaft 37 of a hydraulic motor, but is spaced apart from the shaft 37. The output shaft of the hydraulic motor and the drive shaft of the propeller are coupled to each other via a traction drive.

[0046] According to the execution according to Fig. 3c, a single wheel 61 can also be directly driven by the hydraulic motor of an electro-hydraulic compact drive according to the invention. The wheel can be Fig. 3d part of a crawler track.

[0047] Fig. Figure 4 shows a cable winch 62, which is driven directly by the hydraulic motor 31 via a central drive shaft 41. Typical control algorithms for controlling a cable winch are then implemented in the electrical control unit, for example, to control the position of a ship or an underwater machine, to move an actuator, or to lower or raise a load. Cable winches are used on ships for many applications. For many applications, it is advantageous to implement algorithms for heave compensation (heave compensation system).

[0048] In summary, the invention creates an electro-hydraulic compact drive with low total operating costs, high energy efficiency, high reliability, and a high level of safety, which is easy to maintain, and delivers high performance. The compact design reduces the weight of the entire drive system compared to a separate design.

[0049] A compact drive according to the invention is therefore particularly suitable for use in new vehicles and machines for the deep sea, such as underwater robots ROVs and AUVs or underwater machines, for example for raw material extraction, which are thus more technically and economically feasible. List of reference symbols 10 Compact drive 11 electrical cable 12 containers 13 interior of 12 14 Opening 15 flat edges of 12 16 flange 17 lids 18 Membran 19 holes in 17 20 springs 21 diaphragm plates 22 Rod with measuring scale 25 Pressure compensation device 30 hydraulic pump 31 hydraulic motor 32 Work management 33 Work management 34 Pressure sensor 35 Throttle 36 Separator 37 output shaft of 31 40 propellers 41 Drive shaft 42 Speed ​​sensor 50 electric motor 51 electrical control unit 52 speed sensors 53 Temperature sensor 54 Accelerometer 55 electronic control module 56 Position sensor 60 electrical control 61 wheels 62 cable winch

Claims

[1] Electro-hydraulic compact drive (10) for use underwater and for driving an output element (40, 61, 62) comprising a hydraulic motor (31) as a component having an output shaft (37), a hydraulic pump (30) as a component from which the hydraulic motor (31) can be supplied with hydraulic fluid via a working line (32), and an electric motor (50) as a component from which the hydraulic pump (30) can be driven, characterized by , that the components (30, 31, 50) are located in a closed container (12) filled with hydraulic fluid, and that the container (12) has an opening for coupling the output shaft (37) of the hydraulic motor (31) with the output element (40, 61, 62), and that the container (12) has a movable compensation piston (18). [2] Electro-hydraulic compact drive according to claim 1, wherein the electric motor (50) is adjustable in its speed. [3] Electro-hydraulic compact drive according to claim 1 or 2, wherein an electrical control (51) for supplying power to the electric motor (50) is arranged in the container (12). [4] Electro-hydraulic compact drive according to claim 3, wherein the electrical control (51) is equipped with computing power and is programmed with algorithms for operating the components (30, 31, 50) or is suitable for being programmed with algorithms for operating the components. [5] Electro-hydraulic compact drive according to claim 3 or 4, wherein the hydraulic motor (31) can also be operated as a hydraulic pump, the hydraulic pump (30) can also be operated as a hydraulic motor and the electric motor (50) can also be operated as a generator driven by the hydraulic pump operating as a hydraulic motor and wherein algorithms for energy recovery and storage are integrated into the electrical control (51). [6] Electro-hydraulic compact drive according to a preceding claim, wherein the hydraulic pump (30) is adjustable in its stroke volume. [7] Electro-hydraulic compact drive according to a preceding claim, wherein the hydraulic motor (31) is adjustable in its stroke volume. [8] Electrohydraulic compact drive according to a preceding claim, wherein sensors (34, 42, 53, 54), in particular sensors for pressure, rotational speed and position, velocity and acceleration, temperature and water depth, in particular microelectromechanical sensors (MEMS), are integrated. [9] Electro-hydraulic compact drive according to a preceding claim, wherein control functions for automatic compensation of external disturbances such as water flows or counterforces when actuating an actuator are integrated. [10] Electro-hydraulic compact drive according to a preceding claim, wherein it has at least one communication interface for exchanging data with or without cables. [11] Electro-hydraulic compact drive according to a preceding claim, wherein safety functions are integrated as closed control loops. [12] Electro-hydraulic compact drive according to a preceding claim, wherein algorithms for condition monitoring are integrated. [13] Electro-hydraulic compact drive according to a preceding claim, wherein algorithms for controlling a winch are integrated. [14] Electro-hydraulic compact drive according to a preceding claim, wherein it has at least one interface (56) through which hydraulic fluid can be refilled or replaced underwater. [15] Electro-hydraulic compact drive according to a preceding claim, wherein its electrical and mechanical interfaces can be disconnected underwater. [16] Electro-hydraulic compact drive according to a preceding claim, wherein it comprises a hydraulic filter and / or a device (36) for separating contamination of the hydraulic fluid with water and dirt particles with or without status sensors. [17] Electro-hydraulic compact drive according to a preceding claim, wherein the movable compensation piston (18) has a first surface that defines the interior (13) of the container (12) and is subjected to ambient pressure at a second surface which is the same size as the first surface and is directed opposite to it. [18] Set of at least two electro-hydraulic compact drives according to a preceding claim, wherein the electro-hydraulic compact units (10) are arranged on a device to be moved and wherein the movement of the device is realized by coordinated operation of the electro-hydraulic compact units (10) with or without a higher-level control (60). [19] Set of at least two electro-hydraulic compact drives according to claim 18, wherein an intelligent algorithm or control loop compensates for the failure of one compact unit (10) as far as possible by operating the other compact units (10).

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