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Designing Fast Switching Valves (FSVs) for digital displacement units is a complicated process pushing the technology to the limit. The system dynamics and the interaction of the fluid, mechanical structure, actuator and control hence calls for advanced modelling, including CFD and FEA, to capture, e.g. fluid stiction effects, end-damping and impact contact stresses. Unfortunately, this essentially renders optimization processes infeasible due to the computational burden involved, although this is precisely what is required for this type of complex multi-domain problem. Therefore, the focus of the current article is on how a complex mechatronic design problem, like designing an FSV, may be aided by considering decomposing and simplification through sensitivity analysis and analyzing correlations between the design and output parameters. This is done to significantly reduce the original design problem without compromising the investigated design space. The paper focuses specifically on the results related to an FSV and the flow delivering part of this, showing the influence of the various design parameters. However, the approach and considerations may be generalized to an other areas as well.

Hydraulic servo systems are characterized by nonlinear dynamics that can render control design challenges. Controllers for a linearized model will typically be conservative, and the stability of the closed loop system, in the Lyapunov sense, may be difficult to prove. On the contrary, the backstepping technique can lead to control algorithms for which stability margins can be estimated. However, these tend to be complex algorithms that are difficult to apply. In this paper, the backstepping control design procedure is applied to a hydraulically actuated robot. A sliding mode disturbance observer is utilized to avoid the high complexity of the backstepping algorithm. The paper’s primary focus is hence on proving the stability of the proposed algorithm and its applicability to a laboratory setup. However, ways to improve performance are also discussed. Finally, results are presented where the designed controller is tested in both simulations and applied to the laboratory setup, and compared to linear controllers.

This paper investigates a new asymmetric steering concept within orbital steering units called OSPS, which asymmetry enables new steering features for the operator of the vehicle compared to traditional OSP variants. A traditional orbital steering unit functions as a proportional valve system with a certain overlap, where the operator input to the steering wheel will initiate the rotation of the wheels with a small dead-band of 2–3 degrees. The new asymmetric unit functions instead as a proportional valve system with a certain under-lap, where the operator will initiate the rotation of the wheels directly related to the steering wheel rotation instead. The objective with this paper is to evaluate the closed loop performance for the new asymmetric concept, because the right and left control loop is changed compared to a tradional OSP unit.

This paper investigates the steering performance of an articulated vehicle with a hydrostatic steering circuit, where the objective is to evaluate the steering performance and comfort level of the vehicle with and without active damping. The steering system is based on a hydraulic actuated system, which response often is underdamped. The operator of such a vehicle is placed on top of the articulation point and the hydraulic cylinders, which then directly translates the underdamped cylinder oscillations into undesired lateral motion of the operator. Active damping is therefore a promising concept for increasing the comfort level of the hydraulic steering circuit.

Typical propellers today are the fixed pitch (FP) and controllable pitch (CP) propeller. With the CP propeller it is possible to pitch all the blades of the propeller at the same time. A cyclic varying pitch (CVP) propeller for commercial vessels is a modification of a CP propeller. With the CVP propeller it is possible to control the pitch of the propeller blades individually. Having the possibility of making a cyclic variation to the blade pitch can yield performance improvements with respect to: efficiency, cavitation, vibrations, pressure pulses and noise. This is because the propeller operates in the wake of the ship. The inflow into the propeller is therefore non-uniform distributed over the propeller, making the operation condition of the individual blade change depending on the blades position in the wake field. In this paper a review and discussion of the research made so far for the CVP propeller is made. The challenges in realizing the CVP propeller for commercial vessels are identified which constitutes the foundation for future researchof the CVP propeller

This paper aims to evaluate the benefits and disadvantages of applying a digital hydraulic concept to actuate a knuckle boom crane. The standard cylinders of the knuckle boom crane will be substituted with multi-chamber cylinders of comparable size. The performance of one of the multi-chamber cylinders will be compared with the standard differential cylinder. The standard cylinder will be actuated with a constant pressure supply, a proportional directional valve and a proportional controller. Control performance and energy consumption for the two configurations have been considered. It is concluded that more research is needed into the control strategies in order to improve robustness and performance.

Digital hydraulic piston pumps and motors have shown the potential of improving efficiency in hydraulic systems. Two independently controlled fast switching on/off valves are connected to each piston chamber and allows for optimal valve timing and independent piston control. Each piston chamber is only pressurized when necessary, resulting in losses that almost scale with motor and pump displacement. This simulation study investigates the potential of using digital hydraulic pumps and motors to increase efficiency in a hydraulic offshore auxiliary winch with a safe working load equal to 20000 kg. Onedigital hydraulic winch drive system and one conventional hydraulic winch drive system are simulated hoisting two different loads. The payload in the first load case is 18000 kg and the payload in the second load case is 4000 kg. The efficiency and control performance of the two different winch drive systems are then evaluated. The simulation results show that digital hydraulic winch drive systems have the potential of increasing efficiency of hydraulic offshore winches.

The offshore oil and gas industry has traditionally used hydraulically driven applications. Hydraulic systems are known to suffer from relatively low efficiency. Due to environmental issues, more efficient systems are now required. Today, the offshore oil and gas industry is experiencing a shift in driveline systems; high efficient electric motors tend to replace low efficient hydraulic systems. In addition to the electric motors, a new alternative to the conventional hydraulic system is digital hydraulic machines. This paper investigates the feasibility of using a digital hydraulic winch drive system and presents a new digital hydraulic winch drive control system. The simulated system is based on a 20000 kg hydraulic offshore auxiliary winch with a drum capacity of 3600 m of wire. The digital hydraulic winch drive system is a closed-circuit system with one high-speed digital pump and one low-speed high-torque digital motor. One of the biggest challenges in digital hydraulic pump/motor technology is the fast switching on/off valves. The valvesmust have high durability, low power consumption, zero leakage and low response time. The on/off valves in this study are modeled with an ideal behavior. The simulation results show that the payload follows the reference trajectory when using a digital hydraulic winch drive system for a wide range of loads and speeds.

This paper presents an observer-based sliding mode control concept with chattering reduction, generally applicable for position tracking control of electro-hydraulic valve-cylinder drives (VCD's). The proposed control concept requires only common data sheet information and no knowledge on load characteristics. Furthermore the proposed scheme only employ pistonand valve spool positions- and pressure feedback, commonly available in industry. The main target is to overcome problems with linear controllers deteriorating performance due to the inherent nonlinear nature of such systems, without requiring extensive knowledge on system parameters nor advanced control theory. In order to accomplish this task, an integral sliding mode controller designed for the control derivative employing state observation is proposed, based on a generalized reduced order model structure of a VCD with unmatched valve ow- and cylinder asymmetries. It is shown that limited attention can be given to bounds on parameter estimates, that chattering is reduced and the number of tuning parameters is reduced to the level seen in conventional PID schemes. Furthermore, simulation results demonstrate a high level of robustness when subjected to strong perturbations in supply pressure and coulomb friction force, and that tracking accuracy may be reduced to the level of noise. Furthermore, the proposed controller tolerates signicant noise levels, while still remaining stable and accurate.

This paper presents a new adaptive sliding mode controller generally applicable for position tracking control of electro-hydraulic valve-cylinder drives (VCD’s). The proposed control scheme requires limited knowledge on system parameters, and employs only piston- and valve spool position feedback. The main target is to overcome problems with linear controllers deteriorating performance due to the inherent nonlinear nature of such systems, without requiring extensive knowledge on system parameters nor advanced control theory. In order to accomplish this task, an integral sliding mode controller employing parameter adaption through a recursive algorithm is presented. This is based on a reduced order model approximation of a VCD with unmatched valve flow- and cylinder asymmetries. Bounds on parameters are obtained despite lack of parameter knowledge, and the proposed controller demonstrates improved position tracking performance and robustness / adaptability compared with a conventional feedforward-PI controller, when subjected to perturbations in supply pressure and coulomb friction.

As a result of the increasing use of sensors in mobile hydraulic equipment, the need for hydraulic pilot lines is decreasing, being replaced by electrical wiring and electrically controllable components. For controlling some of the existing hydraulic components there are, however, still a need for being able to generate a hydraulic pilot pressure. In this paper controlling a hydraulic variable pump is considered. The LS-pressure is measured electrically and the hydraulic pilot pressure is generated using a small spool valve. From a control point of view there are two approaches for controlling this system, by either generating a copy of the LS-pressure, the LS-pressure being the output, or letting the output be the pump pressure. The focus of the current paper is on the controller design based on the first approach. Specifically a controlled leakage flow is used to avoid the need for a switching control structure. As a result of the increasing use of sensors in mobile hydraulic equipment, the need for hydraulic pilot lines is decreasing, being replaced by electrical wiring and electrically controllable components. For controlling some of the existing hydraulic components there are, however, still a need for being able to generate a hydraulic pilot pressure. In this paper controlling a hydraulic variable pump is considered. The LS-pressure is measured electrically and the hydraulic pilot pressure is generated using a small spool valve. From a control point of view there are two approaches for controlling this system, by either generating a copy of the LS-pressure, the LS-pressure being the output, or letting the output be the pump pressure. The focus of the current paper is on the controller design based on the first approach. Specifically a controlled leakage flow is used to avoid the need for a switching control structure.

Mechatronics is a field of multidisciplinary engineering that not only requires knowledge about different technical areas, but also insight into how to combine technologies optimally, to design efficient products and systems.This paper addresses the group project based and problem-oriented learning approach in relation to a mechatronic education, which makes it possible for the student to get in-depth skills in the area of mechatronics very fast. The trends and applications of mechatronic engineering and research are illustrated. Control engineering plays a central role in this context, where the well established methods from control engineering form very powerful techniques in both analysis and synthesis of mechatronic systems. The necessary skills for mechatronic engineers are outlined followed up by a discussion on how problem oriented project based learning is implemented. A complete curriculum named Mechatronic Control Engineering is presented, which is started at Aalborg University, Denmark, and the content of the semesters and projects are described. The projects are all characterized by the use of simulation and control for the purpose of analyzing and designing complex commercial systems of a strongly dynamic nature. Mechatronics is a field of multidisciplinary engineering that not only requires knowledge about different technical areas, but also insight into how to combine technologies optimally, to design efficient products and systems.This paper addresses the group project based and problem-oriented learning approach in relation to a mechatronic education, which makes it possible for the student to get in-depth skills in the area of mechatronics very fast. The trends and applications of mechatronic engineering and research are illustrated. Control engineering plays a central role in this context, where the well established methods from control engineering form very powerful techniques in both analysis and synthesis of mechatronic systems. The necessary skills for mechatronic engineers are outlined followed up by a discussion on how problem oriented project based learning is implemented. A complete curriculum named Mechatronic Control Engineering is presented, which is started at Aalborg University, Denmark, and the content of the semesters and projects are described. The projects are all characterized by the use of simulation and control for the purpose of analyzing and designing complex commercial systems of a strongly dynamic nature.

The envisaged objective of this paper project is to extend the current state of the art regarding the design of complex mechatronic systems utilizing an optimisation approach. We propose to investigate a novel framework for mechatronic system design. The novelty and originality being the use of optimisation techniques. The methods used to optimise/design within the classical disciplines will be identified and extended to mechatronic system design.