Dynamic Systems Analysis (Canada)

The constantly increasing needs for astronomical imaging of ever fainter objects as well as for imaging the Earth from space require much higher angular resolution and dynamic range than current optical telescopes can deliver. Mirrors are the key elements of these systems; but they are technologically difficult to improve because they must maintain an exceedingly precise shape while resisting deformations (for example from gravity and/or variable wind loads) in the open environments in which they must operate. Our interdisciplinary novel technology will establish a new paradigm: we will shape thin, very smooth, “fire-polished,” lightweight glass to a predetermined curvature and generate dynamically controlled stiffness by using the addressable energy of electroactive polymers (EAPs) to resist environmental deformations – making what we call a “Live” Mirror.

In the cast house, from the raw materials to the finished products, aluminium undergoes a series of treatments ranging from furnace charging and alloying, degassing, filtration, and casting. One common denominator between all these treatments is that molten metal must be transferred in a way or another. Sometimes the transfer method is obvious but there are many occasions where there are different methods available. Open launders, covered launders, pouring, multi-level launders are common open channel methods for transferring molten metal. Gravity siphoning, aspiration siphoning, and pressure siphoning are less common but increasingly used in the industry. All have different influences on molten metal temperature, oxidation, and cleanliness. The purpose of this paper is to compare different molten metal transfer methods and provide guidelines to select and size the most appropriate method according to the process requirements.

Abstract On an increasingly frequent basis, pipeline operators are using risk-based decision making to prioritize cross-company expenditures. Due to the long-term mitigation benefits of Cathodic Protection (CP), when planning external corrosion mitigation activities, pipeline operators typically prioritize mitigation of deeper anomalies for integrity expenditures due to their higher Probability of Failure (PoF). However, anomalies that are not receiving adequate CP or those experiencing electrical interference may remain unaddressed using this rationale. This paper presents both a qualitative and semi-quantitative approach to support the quantification of the risk reduction benefits gained from external corrosion prevention on pipelines. This can help in the efficient prioritization of both pro-active and re-active integrity repair activities. Supporting examples are also discussed to help explain the intended use of the methodology and the interpretation of the results.

Robots and automated systems are increasingly being introduced to unknown and dynamic environments where they are required to handle disturbances, unmodeled dynamics, and parametric uncertainties. Robust and adaptive control strategies are required to achieve high performance in these dynamic environments. In this paper, we propose a novel adaptive model predictive controller that combines model predictive control (MPC) with an underlying $\mathcal{L}_{1}$ adaptive controller to improve trajectory tracking of a system subject to unknown and changing disturbances. The $\mathcal{L}_{1}$ adaptive controller forces the system to behave in a predefined way, as specified by a reference model. A higher-level model predictive controller then uses this reference model to calculate the optimal reference input based on a cost function, while taking into account input and state constraints. We focus on the experimental validation of the proposed approach and demonstrate its effectiveness in experiments on a quadrotor. We show that the proposed approach has a lower trajectory tracking error compared to non-predictive, adaptive approaches and a predictive, nonadaptive approach, even when external wind disturbances are applied.

Development of wave energy conversion systems may yield many key benefits for society such as the production of electrical power or fresh water for remote communities. However, complex ocean dynamics make it difficult for technology developers to not only address the stability and survivability of their systems, but also to establish energy conversion rates that are fundamental to proving economic viability. Building physical prototypes presents many challenges in terms of cost, accessible facilities, and time requirements. The use of accurate numerical modelling and computer simulation can help guide design and significantly reduce the number of physical prototype tests required and as a result play a primary role in the development of wave energy conversion systems that have to operate in challenging marine environments. SurfPower is an ocean wave energy converter (WEC) that converts wave motion into useful energy through surge and heave motion of a point absorber. The system pumps seawater into a high pressure hydraulic network that generates electricity via a turbine or freshwater via desalination at a facility onshore. The system is nonlinear due to the significant change in draft and mooring reaction load through the energy capture cycle of the device. This makes the use of nonlinear time domain simulation ideal for analysis and design of the system. Furthermore, utilizing a simplified nonlinear hydrodynamic model available in the time domain results in a practical early-stage design tool for system refinement. The focus of this work is to compare the results of scale model testing completed at the Institute for Ocean Technology in St. John’s, Newfoundland, with results produced from an equivalent system simulated in the time domain simulation software ProteusDS. The results give an assessment of the range of error that can be used to assess other experiments of the SurfPower WEC at full scale.

Over half of the seafood in the world today is produced through aquaculture. Many finfish species, such as Atlantic salmon, are farmed in permeable net pens in the ocean. Traditionally, these sites have been located in regions protected from high energy ocean swell, current, and wind. However, in areas such as Nova Scotia, Canada, there is a declining number of such protected locations available and so aquaculturists are moving into exposed sites. To safely operate at these sites, it is necessary to engineer the pens to withstand the forces of the open ocean. To conclusively assess finfish aquaculture equipment and moorings in open ocean conditions, Dynamic Systems Analysis Ltd. (DSA) has developed a finite-element net model (FENM) to interface with the dynamics simulation software ProteusDS. The following paper presents the development of the FENM and demonstrates the capability of the FENM to model wave and current loadings by comparing FENM simulations with published results from tank tests. In addition, the results of simulations of a full scale finfish aquaculture site in hurricane conditions are presented. The conditions were collected with an acoustic Doppler current profiler during hurricane Earl on September 4, 2010. The mooring line tensions from the ProteusDS simulation are compared against tensions measured during the storm with a Submersible Tension Logger (STL).

<div class="htmlview paragraph">In crash analyses, components or component assemblies are evaluated to identify if they were damaged as a result of the crash or if they lost function prior to the crash. Determining the circumstances that cause a component to become disabled can be useful when evaluating the cause of a crash. This study focuses on spherical ball joints commonly used in automotive suspension systems. Analyses can include the evaluation of the ball joint itself, the surrounding components, evidence at the scene, and the circumstances of the specific crash. In this study, the causes and conditions for a ball joint separation are analyzed, in part, through both component level testing and full vehicle testing. Laboratory tests were performed on upper ball joint assemblies where loads were applied in multiple directions and the residual damage to the components was measured and documented. Full vehicle testing was performed to analyze vehicle response to suspension ball joint separations on independent front suspensions. A lower ball joint separation test was conducted with the staged ball joint separation occurring as the vehicle was being operated. An upper ball joint separation test was conducted by disconnecting the upper ball joint prior to testing and evaluating the modified vehicle response to driver inputs. Residual damage to suspension, components, and the test surface were analyzed as well. Case studies of ball joint separations are presented and compared to the controlled test results.</div>

A demonstration ocean wave energy project is planned for Hesquiaht Sound, British Columbia, Canada in 2010. This project is led by SyncWave Systems and involves the University of Victoria, Dynamic Systems Analysis Ltd. and Marinus Power. The design process for this demonstration wave energy converter (WEC) including site selection, linear dynamics, control system scheduling and non-linear dynamics modelling is presented. The WEC is a heaving point absorber that extracts energy through the relative motion between two axisymmetric bodies and utilizes an internally housed mechanical system with adjustable inertia characteristics for frequency response tuning. Site selection for the device was completed by using an established wave propagation model to translate off-shore sea conditions calculated from WAVEWATCHIII (WW3) into near-shore conditions. By analysis of the predicted near-shore conditions a suitable location with a frequently energetic sea state was chosen. The design process of the WEC consists of a linearized dynamics model to optimize the controller and a nonlinear dynamics model to analyze the mooring and hull components. The resulting unit effectively captures energy from the prevailing sea-states while ensuring adequate survival capability.