system optimization by means of an integrated design

The 11th International Fluid Power Conference, 11. IFK, March 19-21, 2018, Aachen, Germany

Furthermore, nowadays in every application a large amount of work is carried out by the electronic controller. In most cases, in fact, the firmware embedded on the controller must manage all the input and output resources needed both to control the system and to assure the safety /3/. Complexity management is the key to success for mobile machinery where the variety of customers and applications requires individual solutions /4/.

This paper deals with the optimization of a complete winch system by means of the integrated design of the different components. The development is supported with the calculation results of simulation tools in order to improve the design. The various sub-systems are tested and different solutions are compared as a result of both virtual validation and real tests; Dana has different available testing facilities that allow a two-stage test, first on subsystem and then on the complete system. Finally, real field solutions will be presented and analysed, benefits highlighted in terms of performance, while also referring to minor dimensions, simple maintenance or improved safety. By referencing all the collected data, it will be possible to define an optimized total system related to the integrated design methodology /5/.

To conclude, a future outlook will be presented including new integrated approaches including condition monitoring and enhanced connectivity addressing challenges to ensure even greater benefits to the integrated-design approach.

2 Case 1: Free-wheeling winch system with hydraulic unit incorporating safety function

The first example presented is a special application of a winch and its hydraulic circuit for Anchor Handling Tug Supply. Anchor Handling Tug Supply (AHTS) vessels function is to handle anchors for oil rigs, tow them to location and anchor them; AHTS vessels are fitted with winches for towing and anchor handling, having an open stern to allow the decking of anchors, and having more power than common Platform Supply Vessels to increase the bollard pull (Figure 1).

The winches are specifically designed for anchor handling operations and, according to safety standards, must have arrangements for quick anchor release; a proportional valve has been specifically developed with free falling system that in case of danger disengage the winch releasing immediately the anchor.

The hydraulic load sensing valve is designed to fulfil all required functions; this hydraulic unit has been developed incorporating the most advanced state of the art valve element concept, where it provides velvet smooth controllability, and it can ensure trouble free operation under demanding conditions.

Figure 1: Ship equipped with Anchor Handling Tug Supply (AHTS).

The safety requirements are very strict, in emergency working condition it is necessary to unlock brake, then set hydraulic motors to minimum displacement and finally short circuit motors.


System optimization by means of an integrated design: the Dana case.

Andrea Lucchi , Federica Franzoni , Stefano Lazzaretti and Giovanni Mariech

Dana Brevini S.p.A., via Luciano Brevini 1, I-42124 Reggio Emilia, Italy E-Mail: [email protected]

The paper presents the Dana methodology to address the integrated design for winch systems. Beginning with the analysis of the generic expected performance of the system, the main issues and tasks are evaluated; moreover, the design workflow and the main benefits of integrated design are described with particular attention to the strong team working required to fulfil the defined target in the most efficient way.

Different sub-systems are analysed: the hydraulic motor-winch coupling, with particular attention to clocking speed and its relationship with motor non-uniformity grade and specific reducing gear-ratio to improve hydraulic-mechanic coupling, the hydraulic control system with the possibility to integrate several different functions in a compact and efficient solution, the winch torque sensor and motor angular sensor, which are specifically designed to merge with the components, provide fundamental information for the defined control strategy and also for safety assurance and the central control unit and its software providing an efficient-integrated control strategy and a user-oriented capability for personalization.

Keywords: Integrated design, hydraulic systems, efficiency, control strategy Target audience: Mobile Hydraulics, Design Process

1 Introduction

Today, system optimization is one of the biggest challenges and one of the keys to improve overall performance of operating machines in every field of application. It is well known that an integrated design leads to an optimization of the whole system, in terms of efficiency, packaging and overall performance.

Team working, that leads to concurrent engineering, is one of the key-points of integrated-design success. In concurrent engineering /1/, an attempt is made to perform design and other related activities simultaneously rather than in series as in the case of traditional design. This may result in a reduction of the duration of the design project, cost savings, and better quality of the final design /2/. As already said the first advantage of the team working in concurrent engineering is the significant reduction of the lead time for two main reasons: the common start and the easier and faster communications. Common start means that the kick-off meeting of the project involves all the different areas (mechanical, electronic, hydraulic and software) together. In this way, all the different matters are analysed together from the very first moment and there is no need to arrange different meetings with the different suppliers. Moreover, with this kind of approach all the different designers can start working at the same time. This assure a reduction of the lead time without any real modification of the project.

Moreover, Dana has a team of experts, inside the same company, for each component of the system (mechanics, hydraulics, electronics, software) leading to a significant reduction in communication intervals and enabling the increasing of shared technical knowledge information leading to an easier and faster communication.

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torque has been increased of 30%. Obviously, the operator of the crane noticed the correspondent reduction of winch speed, but it was evaluated as still acceptable. The pressure setting of the motor control was set to 150 bar; this value corresponds to rise 2 ton with direct line pull at the minimum motor displacement.

The motor displacement is adjusted to Vg min when the solenoid valve is switched on and if the operating pressure rises beyond the pressure setting (150 bar), the pressure limiting device overrides the electric two position control and the motor swivels out to the max motor displacement Vg max. This assures a completely safe lifting of the load.

The overload transducers and the position transducer, together with the electronic controller, mounted on the winch enable to know the torque transmitted on the drum – motor axis and an approximation of the load being lifted. Moreover, the speed sensor which is mounted on the motor, once defined on the electronic controller the system geometry, can provide information also on the winch control direction. When all these sensors are redundant and correctly connected with the electronic controller also the CAT 3 safety requirements are achieved (see Figure 3).

Figure 3: System architecture with redundant sensor for safety requirements.

Moreover, the case of the motor has been modified in order to directly connect the drain hoses between motor and valve; in this way there are no external hoses, the apparatus is more compact thus the installation and the maintenance of the whole system is easier.

The whole system has been tested on the testing tower (Figure 4), a specific experimental equipment where test engineers can reproduce different working conditions, even tougher than the real ones, and evaluate the complete system behavior in order to optimize it.

Figure 4: Testing tower and its technical features.

4 Case 3: Winch with integrated motor also for extreme environment

Integrated design is one of the key to guarantee the correct functioning of complex systems also in extreme environmental condition (i.e. very low temperature). After a first design phase, performance and quality are improved by a consistent concept and guidelines for testing and reliability. Standardized test procedures with improved effectiveness cover the complete range of functional, endurance and environment testing. Oil contaminations, aeration as well as performance at very low temperature are considered.


More in details, the proportional valve designed to control the winches has been splitted in modular blocks which have the following characteristics:

• The basic hydraulic winch block contains the most commonly used functions. The counterbalance should have a cavity that allows a dummy (bypass) cartridge so one or both counterbalance valves can be replaced if function is not needed.

• The special functions block is separated in to 3 different blocks that fulfil the special/experimental functions in addition to the Basic block:

o Hoisting winch, emergency lowering, mooring, constant tension o Anchor handling winch (variable pump) o Anchor handling winch (fixed pump)

The different parts of the system, in particular the winch and the hydraulic part, are developed in parallel by engineers who works side by side; this lead to a great advantage because the whole system has been thought out as a whole and thus all the performance have been optimized.

The other big advantage for the customer is that he receives the complete system and not two, or more, separate parts that must be assembled: if a customer has to fulfill a specific function or overcome a specific problem he can demand all the design to our engineers that will decompose it in two or more parts, develop each part and then recompose all the parts before giving the complete solution to the customer.

3 Case 2: High power to move the world (Bent axis motor for gearboxes & winches)

The advantage of axial piston units is the high nominal pressure level, variability of the displacements, beneficial efficiencies, through drive capability and low mass of inertia /6/. Typically, axial units are used in applications with high technical requirements, for example construction, agricultural, offshore and industrial machinery /7/.

In the specific application reported in Figure 2 the hydraulic motor-winch coupling has been developed, with particular attention to clocking speed and its relationship with motor non-uniformity grade and dedicated reducing gear-ratio to improve hydraulic-mechanic coupling. Integrated in the winch there is also an overload transducer that, once known the geometry of the machine, is used to monitor and control the generated torque.

Figure 2: Mobile Crane equipped with Dana motor – winch system.

In this project hydraulic, mechanic and electronic engineers worked together on the entire system. This co-design has allowed to modify the characteristics of all the different components of the system and thus to include different features that have improved the efficiency and the usability of the machine.

More in detail, to achieve the regular rotation of the drum, with the minimum possible speed, the minimum displacement of the hydraulic motor was increased of 8%; with the new setting of the minimum motor displacement the speed at which the vibration of the drum starts (clocking) had a significant drop and the starting

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Figure 7: Pressure needed to run the motor and winch at -46°C (CCW and CW rotation).

Looking at graph of Figure 7 it can be seen that, in the worst condition (CW rotation), after 10s all the cold oil present inside the circuit is replaced by hot oil. This means that the volume of oil V necessary to warm up the system is:

𝑉𝑉 = 𝑄𝑄𝑝𝑝 ∙ 𝑡𝑡= 2.75l (1)

Where Qp is the flow rate addressed by the external pump and t is the time.

Another test has been performed in order to determine the torque needed to make a complete rotation of the winch as a function of the temperature. From a standard motor – winch coupling the internal part of the motor has been removed and has been substituted by a special shaft which allow to measure the torque by means of a torque-wrench. The measurements have been performed at different temperature as reported in Figure 8.

Figure 8: Torque needed to make a complete rotation of the winch as a function of the temperature.

Motor & winch – T=-46°C – CCW rotation

Motor & winch – T=-46°C – CW rotation

T [Nm]


A challenging example is a winch with integrated motor that could work at -46°C (Figure 5). This system has been co-designed starting from the standard winch EP1524, to offer same external dimensions and layout than the standard product.

Thanks to the synergies and collaboration established between the Power Transmission team with the Hydraulic and Electronic team, it has been possible to determine the critical parts and to improve them. The possibility to work on each single components of the whole system allow us to validate, in a very short time, each component within our specialized test department, reducing the overall time needed for the project. In this way, the trial and error has been eliminated because the different problems have been solved by the single specialist.

For example, steel instead of cast iron has been chosen in order to improve the impact strength at low temperature and for an easy manufacturability a two-parts construction spindle has been adopted. Moreover, PTFE and PU oil seals specific for low temperature have been adopted. The case of the motor has been modified thus the system is ready to be connected with an oil heating flushing system.

Figure 5: Truck equipped with winch for very extreme environment.

Dana has several test benches and testing tower simulating real working conditions. The first tests are carried out in the Fluid Power test lab, in which the system composed by motor and winch has been run at very low temperature in order to determine the maximum pressure, and thus the maximum torque and power, needed to start the winch-motor coupling. Different kind of oil are evaluated in order to determine the best tradeoff between the behavior at low and standard temperature. Within the same test also the volume of oil necessary to warm up the system has been determined. To do that, the motor – winch coupling has been connected with an external pump, which supply oil at environmental temperature (25 °C).

Figure 6: Test bench for test at low temperature.

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Figure 10: Mobile telehandler and a simplified electronic structure.

With a traditional approach, to control a whole machine it is necessary to determine the architecture of the control, write the firmware with a mid-level programming language (i.e. C++ language), debug the software and upload it on the master controller of the machine. Using the Brevini® Electronics Bricks it is still necessary to determine the architecture of the control but there is no need to have a programmer that knows the mid-level programming language because the firmware can directly be built with the graphical interface and the single App doesn’t need to be debugged (because they are already debugged). The firmware has to be uploaded on the master controller. Consequently, using the Brevini® Electronics Bricks the system engineer could directly prepare the firmware to be uploaded on the master controller reducing the development time of about 25%.

6 Summary and Conclusion - Integrated design evaluation

The Dana approach to the system optimization by means of integrated design has been described. Dana, with its broad expertise in complementary fields of engineering – mechanics, electronics, hydraulics and software – has the capability to improve the performance of each single component of the complete system. With this kind of approach, it is possible to obtain an overall improvement of the system performance without the need to stress only a single part. High quality and performance are ensured by a team of experts supported with means of simulation and testing.

As an example, by means of the co-design of the winch and the motor for the mobile crane application, the minimum torque has been increased of 30% and the vibrations had a significant drop.

Moreover, the improvements are not only in the overall performance of the system but also in the compactness and in the simpler maintenance of the system: the different parts have been engineered in order to be directly connected between themselves, without external hoses. This lead to a reduction of both the installation time and of the possible future maintenance and in a more compact system.

Finally, the possibility to use a customized control design made with Brevini® Electronics Bricks has been shown. With this new approach the development time could be further reduced of about 25%.

In the next months the Dana integrated approach will be expanded to include condition monitoring and enhanced connectivity. In this way it will be possible to ensure even greater benefits to the integrated-design approach.


5 Case 4: Smart and scalable system control design

Manufacturers of mobile machinery require components that have been optimized to their specific application and to do that a large amount of work is carried out by the electronic controller. The firmware embedded on the controlle, in fact, must manage all the input and output resources needed both to control the system and to assure the safety.

Brevini® Electronics Bricks is a firmware development tool studied for a fast development of the application; it is a user-friendly interface, based on NetBean IDE, that can be used to build a specific firmware application. It is based on an intuitive graphical approach thus no programming skills are required (see Figure 9).

Some specific libraries, called Apps, are already available, such as the ones for the area limitation, the load limitation for mobile cranes, the outrigger self-levelling, the solenoid valves PWM outputs management, the analogic and CANopen transducers management, while an infinity of customized libraries can be developed for each specific application.

The control strategy already developed and implemented are “plug and play” with the other Dana components (such as directional control valve, MAV board, …) thus the start-up time is further reduced.

Figure 9: Brevini® Electronics Bricks.

The challenge is to define different customized control strategy, with customized firmware, test them directly on the customer machine and thus to optimize the whole functioning in a shorter time.

An example in which the Brevini® Electronics brick is used is the mobile telehandler reported in Figure 10. With Brevini® Electronics Bricks a customized firmware that can handle multiple controllers and several transducers is generated and then loaded via serial port on the master controller. In this application, a large number of sensor are used to correctly control both the functioning and the safety of the machine. More in detail, in this application, the master controller, which is a multifunctional modular electronic controller, communicates via CAN bus with two slave controllers and with several transducers such as tilt devices, angle, length and pressure transducers. Using these transducers and knowing the machine geometry, without a load cell, it is possible to determine a load estimation which is used by the load limiter.

This architecture lead to high performance because the load limiter can communicate with the master controller via CAN bus and before stopping the detrimental movements it starts to slow down them while approaching to the limit.

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Nomenclature

Variable Description Unit

𝑄𝑄p Pump flow rate [l/min]

t time [s]

𝑇𝑇 Temperature [°C]

𝑉𝑉 Volume [l]

References

/1/ A. Kusiak and J. Wang, Decomposition of the Design Process, J. Mech. Des 115(4), 687-695 (Dec 01, 1993).

/2/ Talukdar, S., Elfes, A., Papanikolopoulos, N., Concurrent Design, Simultaneous Engineering and Distributed Problem Solving, Technical Report, Engineering Design Research Center, Carnegie Mellon, 1988

/3/ Lautner, E., Körner, D., An integrated system development approach for mobile machinery in consistence with functional safety requirements, In: 10th International Fluid Power Conference, 10. IFK, Dresden, Germany, pp. 439-450, March 8-10, 2014

/4/ Krüẞmann, M., Tischler, K., Complexity management to design and produce customer-specific hydraulic controls for mobile applications, In: 10th International Fluid Power Conference, 10. IFK, Dresden, Germany, pp. 477-488, March 8-10, 2014

/5/ Hentschel, T., Schramm, C., Resource and energy efficient process integrated development with virtual prototypes for mobile machinery, In: 8th International Fluid Power Conference, 8. IFK, Dresden, Germany, March 26-28, 2012

/6/ Ivantysyn, J., Ivantysynova, M., Hydrostatic Pumps and Motors, abi vogel, New Delhi, India, 2001

/7/ Mohn, G., Nafz, T., Swash plate pumps – the key to the future, In: 10th International Fluid Power Conference, 10. IFK, Dresden, Germany, pp. 139-150, March 8-10, 2014

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system optimization by means of an integrated design

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