Morten Kjeld Ebbesen

Design Optimization of Conveyor Systems

In this paper an approach to the design of conveyor systems and particular the design of tracks suited for luggage handling systems in airports is presented. The considered system consists of a closed track with a closed loop of carts carrying the luggage for different flight destinations. The track is a 3 dimensional structure assembled of both straight and arc segments as well as level changes of different kinds. The loop of carts is considered as a multibody system including joint flexibility and the stationary track as a guiding frame. While the track forms a continuous line the closed loop of carts approximates the same geometry in a piecewise linear discretized form. Due to geometric effects caused by the use of straight and arc segments the required length of the discretized line varies in order to remain closed when the system is in service. Since the length variation is one of the principal factors in the resulting load spectrum for the carts in the system the aim of the presented work is to reduce this length variation and thereby reduce the fatigue load on the carts.

Novel concept for stabilising a hydraulic circuit containing counterbalance valve and pressure compensated flow supply

Abstract In this paper, a novel concept for stabilising a hydraulic system containing a counterbalance valve and a pressure compensated flow supply is presented. The concept utilizes a secondary circuit where a low-pass filtered value of the load pressure is generated and fed back to the compensator of the flow supply valve. The novel concept has been investigated theoretically and experimentally. A linear model has been developed to verify the improved stability conditions. The novel concept has been implemented on a single boom actuated by a cylinder. The results show that the pressure oscillations in an otherwise unstable system can be suppressed with the novel concept. This happens without any compromise on the load independence of the flow supply but with some limitations on response time.

Bearing Fault Detection in Induction Motor-Gearbox Drivetrain

The main contribution in the hereby presented paper is to investigate the fault detection capability of a motor current signature analysis by expanding its scope to include the gearbox, and not only the induction motor. Detecting bearing faults outside the induction motor through the stator current analysis represents an interesting alternative to traditional vibration analysis. Bearing faults cause changes in the stator current spectrum that can be used for fault diagnosis purposes. A time-domain simulation of the drivetrain model is developed. The drivetrain system consists of a loaded single stage gearbox driven by a line-fed induction motor. Three typical bearing faults in the gearbox are addressed, i.e. defects in the outer raceway, the inner raceway, and the rolling element. The interaction with the fault is modelled by means of kinematical and mechanical relations. The fault region is modelled in order to achieve gradual loss and gain of contact. A bearing fault generates an additional torque component that varies at the specific bearing defect frequency. The presented dynamic electromagnetic dq-model of an induction motor is adjusted for diagnostic purpose and considers such torque variations. The bearing fault is detected as a phase modulation of the stator current sine wave at the expected bearing defect frequency.

Time domain simulation of large-scale material handling chains using an unconstrained formulation

This article presents a dynamic time domain simulation model of loop-sortation systems. Loop-sortation systems for sortation of medium-size items are designed as a closed chain of carts guided in a closed loop track with a view to meet customers’ requirements of capacity and space available. Loop-sortation systems are complex mechatronic systems which require the use of simulation models in order to analyse, predict, and improve the dynamic performance in a cost efficient way. The model utilizes theory for unconstrained rigid multibody dynamics where contact between carts and between cart and track are modelled through the use of force elements. To determine contact between the track and the chain of carts, a rapid and robust contact search formulation has been developed and implemented in the model. Comparisons of main forces of the chain model are made with experimental measurements on three different test layouts. Verification results show that the normalized root mean square deviations are generally less than 10 per cent.

Optimal Tool Point Control of Hydraulically Actuated Flexible Multibody System With an Operator-in-the-Loop

The paper is on automated tool point path and velocity control of a loader crane. A two step approach is used that combines a direct computation of the optimal cylinder velocities with a general procedure that includes the different saturation phenomena encountered in a hydraulically actuated mobile machine. The two step procedure is envoked at each sampling instant during operation and returns the desired valve control signals. The first step of the procedure involves a direct computation of the optimal cylinder velocities for all possible combinations of active and non active cylinders. Among the configurations that may produce the exact velocity reference, the one requiring the least hydraulic power is chosen. Some simulation examples of the proposed procedure are shown and dynamic simulation based on the computed control signals is applied taking into account the finit bandwith of the hydraulic control valves and the flexibility of the hydraulic fluid and the mechanical structure, respectively..

Multi Criteria Design Improvement of Commercial Loader Crane

An approach to systematically deriving the optimal use of operator-in-the-loop machinery is presented. The operation is considered as a set of design variables that similarly to classical design variables such as geometry and materials may be manipulated with a view to reach certain performances. The emphasis of the paper is on mobile loader cranes and an example on the development of the lifting capacity diagram of such a crane is used to illustrate the potential benefits of employing the presented approach. In general, physical data is not given for the loader crane due to limited space, however, the authors will be happy to provide more details for anyone interested.Copyright

Comparative analysis of numerical models of pipe handling equipment used in offshore drilling applications

Design of offshore drilling equipment is a task that involves not only analysis of strict machine specifications and safety requirements but also consideration of changeable weather conditions and harsh environment. These challenges call for a multidisciplinary approach and make the design process complex. Various modeling software products are currently available to aid design engineers in their effort to test and redesign equipment before it is manufactured. However, given the number of available modeling tools and methods, the choice of the proper modeling methodology becomes not obvious and – in some cases – troublesome. Therefore, we present a comparative analysis of two popular approaches used in modeling and simulation of mechanical systems: multibody and analytical modeling. A gripper arm of the offshore vertical pipe handling machine is selected as a case study for which both models are created. In contrast to some other works, the current paper shows verification of both systems by benchmarking ...

A Tire Model for Off-Highway Vehicle Simulation and Comfort Evaluation

Manufacturers of construction machinery are challenged to accommodate legal requirements on the vibration exposure associated with their products. Hence, the ability to evaluate ride comfort by virtual prototyping is needed. One of the derived necessities is a modeling approach that can handle big off-road tires on irregular terrain and even the passing of sharp corner obstacles. In this paper a simple tire model combining the well known slip theory and a displaced volume approach is presented. A non-gradient optimization routine is applied for parameter identification by minimizing the difference between simulated data and experimental data obtained from a full vehicle model passing a set of well defined obstacles. The two most important deviations have been identified as frequency and force amplitude response because comfort is computed as a frequency weighted acceleration of the operator. Based on the obtained agreement between simulated and measured results the tire model is considered as well suited for comfort evaluation and, subsequently, reliable model based design.Copyright

Proceedings of the ASME 2009 International Design Engineering Technical Conferences & Computer and Information in Engineering Conference: CD-ROM

Manufacturers of construction machinery are challenged to accommodate legal requirements on the vibration exposure associated with their products. Hence, the ability to evaluate ride comfort by virtual prototyping is needed. One of the derived necessities is a modeling approach that can handle big off-road tires on irregular terrain and even the passing of sharp corner obstacles. In this paper a simple tire model combining the well known slip theory and a displaced volume approach is presented. A non-gradient optimization routine is applied for parameter identification by minimizing the difference between simulated data and experimental data obtained from a full vehicle model passing a set of well defined obstacles. The two most important deviations have been identified as frequency and force amplitude response because comfort is computed as a frequency weighted acceleration of the operator. Based on the obtained agreement between simulated and measured results the tire model is considered as well suited for comfort evaluation and, subsequently, reliable model based design.Copyright