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Sytronix variable-speed pump drive

Hydraulics of the Future

Image problems notwithstanding, hydraulics is well-positioned to make the transition from dinosaur to golden unicorn.

In spite of concerted efforts to improve its image in recent decades, hydraulics is still seen as a dinosaur by many users. As a result, it is not the first choice among young recruits. Graduates tend to be drawn to start-up environments with their digital business ideas and, in the figurative sense, to the object of desire—a golden unicorn.

Internationally, the unicorn symbolizes innovation and creativity—ideas with a wow factor that make a lot of money. Regardless of how the outside world perceives hydraulics, the global economic importance of hydraulics is undisputed, with sales amounting to many tens of billions of dollars. Paradoxically, the economic importance of fluid power technology still contrasts sharply with the way it is perceived by users, the public, and the scientific community.

How can hydraulics technology transition its image to the new world? The answer is simple; the dinosaur must adapt by integrating new technologies, especially electronic control and electromechanical power transmission. By doing so, hydraulics will metamorphose into a novel, high-tech experience for users.

In specific terms, this means retaining hydraulics’ strengths and combining them with the opportunities and benefits found in the technical “IT consumer world.” Users will then perceive “hidden” hydraulics as a compact, finished functional module—simple, intuitive, connected, and quickly installed. Regardless of this vision of the future, hydraulics must maintain its position against electromechanical drives. The technological shift is already highly advanced in many sectors.

 Here, we need to defend our territory. Unlike hydraulics, easier connectivity and simpler IT connections have long been integral to the DNA of electromechanical solutions. But how can we ensure the future viability of industrial hydraulics over the next decade, and what must we do to make it more competitive? Aim for the golden unicorn!

Fig. 1
The mistaken perception of hydraulics as dinosaur technology should disappear as Industry 4.0 transforms these impressions into more of a golden unicorn.

The Industrial Environment

Industrial hydraulics is not immune to the developments taking place in a constantly changing market environment. However, hip new technology topics are not the sole factors shaping the scene in the years ahead. Several familiar trends will continue to be essential to future growth.

Energy efficiency. When considering major trends, invariably the environment and the scarcity of resources play an important role. They require more energy-efficient drive systems. In Europe for example, energy-related regulations apply on a component level (e.g., the IE3 standard for electric motors). On top of this, many standards and codes are in place for machines—efficiency labels for mass-produced machines, for example.

The importance of energy efficiency is growing beyond just industrialized nations. Energy is still far too cheap in many regions of the world, and new, innovative, approaches will only emerge from supply and price pressures. Given its specific advantages (high power density, large forces), hydraulics is predestined for powerful machines. This applies especially to pressure supply stations where energy-saving drive solutions are particularly beneficial.

Outlook. The ever-present issue of energy efficiency has sparked a steady rise in the use of speed-controlled drive systems. Highly efficient servo motors are increasingly replacing standard asynchronous motors. Technically scalable solutions are already available on the market.

Fig. 2

Sytronix variable-speed pump drive of a trend in hydraulics that combines a variable-speed electrical drive with a variable-speed electric motor and hydraulic pump into an integrated drive unit.

Environmental Challenges

Industrial hydraulic systems are used under a wide variety of environmental conditions. Governing bodies impose specific regional regulations on sustainable production, recycling, and the disposal of hydraulic products. As an indispensable pressure transmission medium and lubricant, hydraulic fluid plays a special role in terms of environmental impact and the functional safety of systems. Although rapidly biodegradable oils have been available for more than 60 years, mineral-based oils are still used most frequently. However, continuous improvement is not only pertinent to hydraulic fluids: Seals must also be further developed as regards their compatibility with hydraulic fluids, new materials, and geometric forms. Lower oil volumes are another way of reducing the environmental risk. These can be achieved through an intelligent tank design with active degassing or smaller, decentralized drive axes.

Outlook. Reducing the oil volumes used and improving environmental compatibility remain ongoing issues. Environmental regulations are expected to become more stringent in the future. As a result, oil, seal, and hydraulics manufacturers will probably form alliances in order to further improve environmental compatibility.

Safety-related requirements. In Europe, the Machinery Directive requires machines to be designed and built in such a way that potential risks to human beings are avoided. A range of European standards for the safety of hydraulic systems have been established, and these are complemented by related standards, such as the Pressure Equipment Directive.

Outlook. Safety issues will remain a priority in the future, too. Stricter regulations (e.g., approval checks, design guidelines) are also to be expected in other regions, especially emerging nations.

Digital Information Procurement

Industrial users are increasingly expecting the same level of convenience they are accustomed to from the consumer world—configurators, usability, mobile devices, apps, cloud solutions, etc. Depending on the requirements, products themselves will have anything from simple digital interfaces (e.g., IO-Link) to real-time-capable multi-Ethernet connections.

A new 5G communications standard will result in more private industrial networks being used in an industrial setting from 2023. With these edge cloud-based networks, sensor-actuator cycle times of less than 1 msec can be achieved. As a result, typical controller requirements in plastics processing machines can be met. Sensors and 5G communication integrated into a product will provide information for status monitoring and even data use for preventive maintenance. Consequently, a large number of data-based business models are to be expected.

Outlook. Electrohydraulic components will benefit from the technological influences of the automation and IT world. As is the case in electrical automation, hydraulic component providers are preparing to work with other relevant providers on Artificial Intelligence and cloud-based solutions. More cross-technology partnerships will be needed, especially for cutting-edge IT topics.

Individual manufacturers will no longer have all the necessary skills under one roof. Current mindsets about partnerships will also change. In certain cases, future partners will be the previous ones while some previous partners may become competitors, and new partners will come along, too. Conventional mechanical engineering and plant construction will only benefit from the much shorter innovation cycles in the IT world if the necessary structural change as regards digitalization, connectivity, and communication takes place and employees are equipped with the necessary qualifications.

Training and experience. It has been apparent for some time now that the number of potential employees with specialist hydraulic knowledge is declining. This applies to both the commercial and the engineering sector. As far as professional basic and further training are concerned, in Germany, for example, there are no recognized qualifications. At the moment, hydraulics specialists are mainly recruited from related professions, such as agricultural or construction machine fitters, industrial mechanics, or mechatronic technicians.

In fact, no specific training leads to a qualification as a fluid mechatronics specialist. Universities do not offer dedicated hydraulics courses, and hydraulics is barely a basic module in engineering courses. The situation at universities is unsatisfactory. When hydraulics is offered as a subject, the curriculum is restricted almost exclusively to standard hydraulics rather than electrohydraulics. We see a similar scenario abroad.

Reaching the Golden Unicorn requires modern, up-to-date teaching, the transfer of technologies and the creation of a new “fluid mechatronics specialist” qualification in both academic and commercial fields. This is one of the key joint tasks facing education policymakers, industry, and the national/international fluid technology associations.

In the future, two different career profiles in the field of hydraulics will be needed. One will be a component-oriented specialist with mechanical engineering skills who develops and optimizes products. The other will be a systems-oriented fluid mechatronics specialist who has a knowledge of control technology and is well versed in the toolboxes for hydraulic and electro-mechanical drives.

Outlook. Despite the effort invested, it is unlikely that the current educational situation will change much in the near future. In the years ahead, improved education leading to in-depth knowledge will be essential. This is because if knowledge is lacking in control technology, digitalization, software, or kinematics, electrohydraulic system solutions will not succeed, no matter how good the technology is.

Machine manufacturers already are outsourcing engineering work to suppliers and are increasingly procuring complete subsystems as “functional modules.” Large end-users are increasingly enlisting specialist firms to carry out maintenance work. Maintaining hydraulic systems should, therefore, be made as easy as possible for users and hydraulics should continue to offer young people an attractive future-oriented career.

Future Viability

There is surely no standard preferred technology for all applications. Whether hydraulic or electromechanical, each type of drive carries its own set of strengths and weaknesses that can only be assessed according to their suitability to specific applications. To make reliable statements regarding future viability (over a 10-year observation period), an investigation was carried out to determine whether the most important applications in 10 of the main sectors for industrial hydraulics could be substituted.

Fig. 3

Overview of important industries and applications for industrial hydraulics.

The following drive types were considered for the aforementioned main applications:

  • Linear movements: >80% of all applications
  • Hydraulics: cylinder drive via valve or pump control and compact axes
  • Electromechanics: ball or roller screw assembly
  • Rotational movements: <20% of all applications
  • Hydraulics: pump control or secondary control
  • Electromechanical: direct drive or geared motor.

Fig. 4

Drive types in hydraulic and electromechanical drive technology.

The overall assessment of the most suitable drive types for the future was based on an investigation of the following four main categories, with a total of 13 criteria for each application:

Functionality: dynamics, robustness, static power limit, accuracy, safety

Integration: installation space, flexibility, user friendliness

Cost-effectiveness: costs, efficiency, service life

Ecology: eco-friendliness, maintenance

Outlook. All in all, it is evident that electromechanical systems for linear movements max out at around 500 kN or more. For systems rated less than 100 kN, electromechanical systems hold great potential to replace hydraulics in many applications. Although slight improvements in power and speed could be achieved by further developing materials, coatings, and geometries, revolutionary jumps seem unlikely. Any further increase in power and torque through mechanical transmissions will then be limited by the masses to be accelerated.

Fig. 5

This comparison of linear motion technologies shows that hydraulic continue to outpace electromechanical actuators in both speed and force.

Hydraulic drives already transmit forces that are more than 100 times greater than in the past. As far as the physical performance limits of electromechanical systems as distinct from hydraulic systems are concerned, there is no obvious disruption. Evolutionary further developments are thus to be expected in both areas. Hydraulic systems in metal cutting machines and rotor drives will likely face even stiffer competition. However, there will be opportunities, too—through energy savings with valve control systems and more user-friendly products and systems. As far as linear applications are concerned, hydraulics will maintain and even improve its position through further innovative developments in compact axes.

Once such development is autonomous electrohydraulic axes, which are composed of a motor-pump unit, manifold, and cylinder. These axes are virtually maintenance-free and commissioned the same as with electromechanical drives. The specifics relating to hydraulics are already included in software libraries. As a result, even complex travel profiles—such as those for forming, joining, injection molding, and other large-force applications—can be parametrized very easily. Machine manufacturers and system integrators can also achieve safety levels up to SIL 3 as part of the specification process.

Fig. 6

This autonomous servohydraulic actuator is an all-in-one unit that can be commissioned using the same techniques as with electromechanical actuators.

Development Trends

The various markets, sectors, and fields of application make very different demands on industrial hydraulics. The development areas which have emerged in recent decades essentially concentrate on the following:

  • Energy efficiency (reduced flow forces, reduced pressure loss, higher efficiency)
  • Noise reduction
  • Reduced tank volumes
  • Higher pressure level and reduced installation space
  • Improved material and oil properties
  • Higher availability and predictive maintenance
  • User friendliness (onboard electronics, commissioning software)
  • Safety

Although these issues will still play a role in the future, they will no longer be sufficient on their own. Industrial trends such as 3D metal printing offer new technical opportunities for hydraulics, for example in optimized core design (sand printing procedure) to improve flow properties or in the production of servo valves.

Fig. 7

This servovalve manifold, left as an example of how 3D printing can make components more compact, lighter, and even more efficient.

Applications in Sensitive Environments

One segment of industrial hydraulics is characterized by special environmental conditions and often by continuous processes. It includes industries such as marine and offshore, steel construction for hydraulic engineering, metallurgy, foundry machines, mining, etc., where systems are installed either outdoor or similar environments. When it comes to production systems involving continual processes, the focus is on OEE (overall equipment effectiveness), whereby productivity improvements are achieved by optimizing processes, improving quality, and practicing predictive maintenance. High-performance diagnostic systems based on machine learning—such as Rexroth’s Online Diagnostics Network (ODiN)—which can already reliably predict when components will fail, are being developed in hydraulics.

Fig. 8

Current diagnostic systems based on machine learning—such as Rexroth’s Online Diagnostics Network (ODiN)—can reliably predict when components will fail, are being developed in hydraulics.

In many cases, compliance with environmental protection classes (explosion protection, for example), redundant pressure supply stations, and the use of biodegradable fluids are required. In light of the environment described here, further environmental regulations are likely to be imposed in the future. An effective method of avoiding risk from fluid spills is to reduce the volume of oil used in a system. The basis for progress is tank design that allows natural passive degassing. Using an active degassing module that includes sensors to monitor the proportion of air released in the fluid can lead to further reduction in oil volume. Compared to conventional designs, the oil volume can be reduced by as much as 70%. Other positive effects include a 50% smaller installation space and significantly reduced oil costs.

Outlook. In addition to the further development of the technology and fluids to help improve environmental compatibility, these industries will undergo a transformation process prompted by digitalization, for example with smart mining, metallurgy 4.0, or autonomous ships.

Production Applications

The other market segment is influenced by developments and trends from the factory of the future. This relates, for example, to presses, plastics processing machines, assembly systems, machine tools, testing machines, and similar machines installed in modern factories. The factory of the future must be described before we can identify the requirements imposed on industrial hydraulics. The main aim will be to increase productivity and efficiency through transparency.

The factory of the future will be highly agile. High flexibility and adaptability are key objectives, while transparency will help to avoid unplanned, costly downtimes. The walls, the floor, and the ceiling will remain in place—everything else will be mobile. Assembly lines will have a modular design and machines will be restructured to create new lines for new purposes. They will communicate wirelessly with each other via 5G and will be supplied with power by an inductive charging system in the floor.

Fig. 9

High flexibility and adaptability are key objectives of the factory of the future, with transparency to help avoid unplanned, downtime. The walls, the floor, and the ceiling will remain in place—everything else will be mobile.

In the factory of the future, everything will be connected—from field level to cloud-based IT systems. Automation and drive solutions will only fit into this environment with open-standard communication. They will be easily configurable, with features and classes stored in the device data and controlled or managed by the firmware. Industrial hydraulics must adapt to this world by adopting open standards such as multi-Ethernet and IO-Link, which are already in use. With real-time extensions, all components, modules, and machines will share information.

Outlook. These data then need to be implemented in all future product generations because value stream mapping in the factories of the future will be digitalized. Digital business models will continue to be based on prepared operating data from all actuators, modules, sensors, and machines that make up both new and existing infrastructure.

Fig. 10

Pressure valve with IO-Link/ Bluetooth (left) and high-response valve with multi-Ethernet interface for positional, pressure, and force control as well as closed-loop control (right).

One these is the CytroBox from Bosch Rexroth, our latest generation of hydraulic power units. The CytroBox is a decentralized unit that is both mobile and flexible. It has a plug-and-run concept and decentralized intelligence, offering machine manufacturers a ready-made drive controller with numerous built-in functions. Key safety functions and drive controls are included and, therefore, can be easily integrated and configured to suit a specific application. Integrated and wired sensors provide information on the filter, fluid, and drive conditions. The collected sensor data are bundled via IO-Link and preprocessed by the drive controller to network with modern machine designs.

Similar machines and their modules will be wireless, will exchange information and instructions via open interfaces, and monitor themselves continuously. With its multi-Ethernet interface and open core engineering, the CytroBox offers this future viability. Like modern electromechanical drives, the unit is IoT-ready using Bosch Rexroth’s CytroConnect. All information on the unit–from component and operating status or scheduled maintenance work to predictive maintenance analyses from Rexroth’s Online Diagnostics Network (ODiN)—is conveniently available. Depending on requirements, other additional packages for the maintenance function, fault detection, and predictive maintenance are available as an add-on services.

Fig. 12

The CytroBox is an all-in-one hydraulic power unit containing a variable-speed pump drive, reduced-size reservoir, and advanced electronics for monitoring, control, diagnostics, and communication.

Wrapping It Up

Conventional hydraulics will change significantly over the next 10 years. Intelligence, sensors, electronics, and software will increasingly be incorporated into steel and cast iron. This will be strongly influenced by IT and automation trends. Users will experience industrial hydraulics as a ready-made functional module with the same level of user-friendliness they are accustomed to in the IT consumer world. Although it is currently perceived as a dinosaur by many, industrial hydraulics will gradually evolve into an attractive unicorn—the industrial hydraulics of tomorrow. New developments in electrical automation and IT technology will make it easier to integrate industrial hydraulics and will make it more competitive.

Areas that offer industrial hydraulics potential for development include compact axes, energy efficienc,y and user friendliness. Developments from the new IT-based world of automation will complement previous key areas in hydraulics. Digitalization (software, connectivity, private networks, apps, etc.) as well as data use (sensors, web servers, data analytics, IoT services, cloud solutions, etc.) will inevitably conquer the world of industry.

Dr. Steffen Haack is head of the Industrial Hydraulics Business Unit, Bosch Rexroth AG, Lohr am Main, Germany. Click here for details on Bosch Rexroth’s vision of the future of industrial hydraulics.

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