Nicolai Nilsen

Bio: Nicolai Nilsen is an academic researcher from Aker Solutions. The author has contributed to research in topics: Stiction & Position-sensing hydraulic cylinder. The author has an hindex of 1, co-authored 1 publications receiving 17 citations.

Reducing the static friction in hydraulic cylinders by maintaining relative velocity between piston and cylinder

Abstract: This paper is concerned with friction in hydraulic cylinders and it's influence on the performance of hydral-ically actuated system. A method for the elimination of stiction in hydraulic cylinders is presented and experimentally verified. The method utilizes the rotational degree of freedom between the piston and the cylinder to add relative velocity at the contact surfaces between piston and cylinder when the main axial motion is zero. For modeling purposes an augmentation of the Stribeck friction force equation is introduced that reflects the influence of the added motion. The possible impact of stiction elimination on the performance of heave compensation equipment is discussed and examplified via time domain simulations.

Analysis of Offshore Knuckle Boom Crane - Part One: Modeling and Parameter Identification

Abstract: This paper presents an extensive model of a knuckle boom crane used for pipe handling on oshore drilling rigs. The mechanical system is modeled as a multi-body system and includes the structural exibility and damping. The motion control system model includes the main components of the crane’s electro-hydraulic actuation system. For this a novel black-box model for counterbalance valves is presented, which uses two dierent pressure ratios to compute the ow through the valve. Experimental data and parameter identication, based on both numerical optimization and manual tuning, are used to verify the crane model. The demonstrated modeling and parameter identication techniques target the system engineer and takes into account the limited access to component data normally encountered by engineers working with design of hydraulic systems.

Full- and reduced-order model of hydraulic cylinder for motion control

Abstract: This paper describes the full- and reduced-order models of an actuated hydraulic cylinder suitable for system dynamics analysis and motion control design. The full-order model incorporates the valve spool dynamics with combined dead-zone and saturation nonlinearities — inherent for the orifice flow. It includes the continuity equations of hydraulic circuits coupled with the dynamics of mechanical part of cylinder drive. The resulted model is the fifth-order and nonlinear in states. The reduced model neglects the fast valve spool dynamics, simplifies both the orifice and continuity equations through an aggregation, and considers the cylinder rod velocity as output of interest. The reduced model is second-order that facilitates studying the system behavior and allows for direct phase plane analysis. Dynamics properties are addressed in details, for both models, with focus on the frequency response, system damping, and state trajectories related to the load pressure and relative velocity.

Experimental investigation of friction behaviors for double-acting hydraulic actuators with different reciprocating seals

Abstract: Investigation of friction force induced by seals is important in improving control accuracy and evaluating sealing performance for hydraulic actuators. An experimental apparatus was developed to measure the friction forces for hydraulic cylinders under different operating conditions based on position and chamber pressures measurements only. The effects of velocity, external load, seal diameter, and sealing profiles on steady state friction force of hydraulic cylinders were examined. In addition, the influences of amplitudes of velocity and acceleration on dynamic friction force were also highlighted. It was shown that the hydraulic actuator with combined piston seal demonstrates the highest friction force and is less sensitive to variation of load than that of Glyd ring and U-cup seal.

Hydraulic vs. Electric: A Review of Actuation Systems in Offshore Drilling Equipment

Abstract: This article presents a survey on actuation systems encountered in offshore drilling applications. Specifically, it focuses on giving a comparison of hydraulic and electric drivetrains along with detailed explanations of their advantages and drawbacks. A significant number of industrial case studies is examined in addition to the collection of academic publications, in order to accurately describe the current market situation. Some key directions of research and development required to satisfy increasing demands on powertrains operating offshore are identified. The impact of the literature and application surveys is further strengthened by benchmarking two designs of a full-scale pipe handling machine. Apart from other benefits, the electrically actuated machine reduces the total power consumption by 70 % compared to its hydraulically driven counterpart. It is concluded that electric actuation systems, among other advantages, in general offer higher efficiency and flexibility, however, in some specific applications (such as energy accumulation or translational motion control) hydraulic powertrains are favorable.

Feasibility Study of Electromechanical Cylinder Drivetrain for Offshore Mechatronic Systems

Abstract: Currently, there is an increasing focus on the environmental impact and energy consumption of the oil and gas industry. In offshore drilling equipment, electric motors tend to replace traditionally used hydraulic motors, especially in rotational motion control applications. However, force densities available from linear hydraulic actuators are still typically higher than those of electric actuators. Therefore, usually the remaining source of hydraulic power is thereby the hydraulic cylinder. This paper presents a feasibility study on the implementation of an electromechanical cylinder drivetrain on an offshore vertical pipe handling machine. The scope of this paper is to investigate the feasibility of a commercial off-the-shelf drivetrain. With a focus on the motion performance, numerical modeling and simulation are used when sizing and selecting the components of the considered electromechanical cylinder drivetrain. The simulation results are analyzed and discussed together with a literature study regarding advantages and disadvantages of the proposed solution considering the design criteria of offshore drilling equipment. It is concluded that the selected drivetrain can only satisfy the static motion requirements since the required transmitted power is higher than the recommended permissible power of the transmission screw. Consequently, based on the recommendation of the manufacturer, avoidance of overheating cannot be guaranteed for the drivetrain combinations considered for the case study presented in this paper. Hence, to avoid overheating, the average speed of the motion cycle must be decreased. Alternatively, external cooling or temperature monitoring and control system that prevents overheating could be implemented.