| 1. |
- Di Benedetto, M. D., et al.
(författare)
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Wireless ventilation control for large-scale systems : The mining industrial case
- 2009
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Ingår i: 2009 6th IEEE Annual Communications Society Conference on Sensor, Mesh and Ad Hoc Communications and Networks Workshops. - 9781424439386
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Konferensbidrag (refereegranskat)abstract
- Mining ventilation is an interesting example of a large scale system with high environmental impact where advanced control strategies can bring major improvements. Indeed, one of the first objectives of modern mining industry is to fulfill environmental specifications [1] during the ore extraction and crushing, by optimizing the energy consumption or the production of polluting agents. The mine electric consumption was 4 % of total industrial electric demand in the US in 1994 (6 % in 2007 in South Africa) and 90 % of it was related to motor system energy [2]. Another interesting figure is given in [3] where it is estimated that the savings associated with global control strategies for fluid systems (pumps, fans and compressors) represent approximately 20 % of the total manufacturing motor system energy savings. This motivates the development of new control strategies for large scale aerodynamic processes based on appropriate automation and a global consideration of the system. More specifically, the challenge in this work is focused on the mining ventilation since as much as 50 % or more of the energy consumed by the mining process may go into the ventilation (including heating the air). It is clear that investigating automatic control solutions and minimizing the amount of pumped air to save energy consumption (proportional to the cube of airflow quantity [4]) is of great environmental and industrial interest.
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| 2. |
- D'Innocenzo, A., et al.
(författare)
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Scalable scheduling algorithms for wireless networked control systems
- 2009
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Ingår i: 2009 IEEE INTERNATIONAL CONFERENCE ON AUTOMATION SCIENCE AND ENGINEERING. - : IEEE. - 9781424445783 ; , s. 409-414
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Konferensbidrag (refereegranskat)abstract
- In this paper, we address the problem of designing scalable scheduling and routing policies over a time-triggered multi-hop control network, when closing a considerable number of control loops on the same network. The key idea is to formally define by means of regular languages the set of schedules for each control loop that satisfy a given control specification, and to exploit operators on regular languages to compute the set of schedules for the whole system. In order to test our methodology, we address a mineral floatation control problem derived from the Boliden (a swedish mining company) mine in Garpenberg, and propose a scheduling solution that can be implemented on systems compliant with communication protocols for wireless networks (e.g. the WirelessHART specification).
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| 3. |
- Witrant, E., et al.
(författare)
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Mining ventilation control : a new industrial case for wireless automation
- 2008
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Konferensbidrag (refereegranskat)abstract
- This paper describes a new industrial case on wireless automation, for a large scale system with high environmental impact: the mining ventilation. We do not pretend to solve the global control problem but rather propose a novel approach based on distributed sensing/actuation capabilities, which can be allowed by the installation of an heterogeneous network in the underground process. Several key issues, such as the centralized vs. decentralized control, the macroscopic physical models for the main components and the network structure, are introduced to motivate future research along this line. We particularly highlight new grounds for the development of global control strategies that would allow for the energy consumption optimization of this large-scale system.
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| 4. |
- Ölvander, J., et al.
(författare)
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Preface
- 2018
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Ingår i: Proceedings of NordDesign. - Linköping : Design Research Society. - 9789176851852
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Konferensbidrag (populärvet., debatt m.m.)
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| 5. |
- Dall'Ara, E., et al.
(författare)
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A practical guide for in situ mechanical testing of musculoskeletal tissues using synchrotron tomography
- 2022
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Ingår i: Journal of the Mechanical Behavior of Biomedical Materials. - : Elsevier BV. - 1751-6161. ; 133
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Forskningsöversikt (refereegranskat)abstract
- Musculoskeletal tissues are complex hierarchical materials where mechanical response is linked to structural and material properties at different dimensional levels. Therefore, high-resolution three-dimensional tomography is very useful for assessing tissue properties at different scales. In particular, Synchrotron Radiation micro-Computed Tomography (SR-microCT) has been used in several applications to analyze the structure of bone and biomaterials. In the past decade the development of digital volume correlation (DVC) algorithms applied to SR-microCT images and its combination with in situ mechanical testing (four-dimensional imaging) have allowed researchers to visualise, for the first time, the deformation of musculoskeletal tissues and their interaction with biomaterials under different loading scenarios. However, there are several experimental challenges that make these measurements difficult and at high risk of failure. Challenges relate to sample preparation, imaging parameters, loading setup, accumulated tissue damage for multiple tomographic acquisitions, reconstruction methods and data processing. Considering that access to SR-microCT facilities is usually associated with bidding processes and long waiting times, the failure of these experiments could notably slow down the advancement of this research area and reduce its impact. Many of the experimental failures can be avoided with increased experience in performing the tests and better guidelines for preparation and execution of these complex experiments; publication of negative results could help interested researchers to avoid recurring mistakes. Therefore, the goal of this article is to highlight the potential and pitfalls in the design and execution of in situ SR-microCT experiments, involving multiple scans, of musculoskeletal tissues for the assessment of their structural and/or mechanical properties. The advice and guidelines that follow should improve the success rate of this type of experiment, allowing the community to reach higher impact more efficiently.
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| 6. |
- Tiberi, Ubaldo, et al.
(författare)
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Dead-band self-triggered PI control for processes with dead-time
- 2012
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Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). - : Elsevier BV. ; , s. 442-447, s. 442-447
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Konferensbidrag (refereegranskat)abstract
- Current implementations of digital controllers assume that sensing, control and actuation are performed in a periodic fashion. In classic control schemes, where sensors and controllers are directly connected, periodicity does not provide particular drawbacks, but, in the case of wireless sensor networks, such a choice may be questionable. One of the driving constraints in the design of wireless sensor networks is represented by its energy efficiency, and it has been shown that the main cause of energy consumption is due to the radio activities of the sensor nodes. By using periodic implementations, the sensor nodes are enforced to keep on transmitting measurements to the controller even if it is not really needed, thus wasting energy. To cope with these problems, self-triggered control was recently introduced. This technique aims at reducing the conservativeness of periodic implementations providing an adaption of the inter-sampling intervals based on the current output of the system. Existing work on self-triggered control considers linear systems controlled by state feedback controllers under the assumption of small time-delays. In this paper the problem of designing a self-triggered control scheme that applies to first-order processes with large dead-times controlled by PI controllers is addressed. Moreover, the proposed self-triggered scheme is robust with respect to set-point changes and external disturbances, which are typical in process industry. The results are validated by simulations.
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| 7. |
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| 8. |
- Ghandour, Salim, et al.
(författare)
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A model for the biomechanical assessment of discoplasty in a laboratory setting
- 2021
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Percutaneous cement discoplasty is a spinal surgical technique which has been rarely tested outside the clinical setting. This study aimed at developing an ovine model framework to allow testing and optimization of discoplasty in a lab-controlled environment.
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| 9. |
- Grassi, Lorenzo, et al.
(författare)
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Experimental Validation Of Finite Element Model For Proximal Composite Femur Using Optical Measurements
- 2013
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Ingår i: Journal of the Mechanical Behavior of Biomedical Materials. - : Elsevier BV. - 1751-6161. ; 21, s. 86-94
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Tidskriftsartikel (refereegranskat)abstract
- Patient-specific finite element models have been used to predict femur strength and fracture risk in individuals. Validation of the adopted finite element modelling procedure against mechanical testing data is a crucial step when aiming for clinical applications. The majority of the works available in literature used data from strain gages to validate the model, thus having up to 15 experimental measurements. Optical techniques, such as Digital Image Correlation, can help to improve the models by providing a continuous field of deformation data over a femoral surface. The main objective of this study was to validate finite element models of six composite femora against strain data from digital image correlation, obtained during fracture tests performed in quasi-axial loading configuration. The finite element models were obtained from CT scans, by means of a semi-automatic segmentation. The principal strains both during the elastic phase and close to the fracture were compared, and showed a correlation coefficient close to 0.9. In the linear region, the slope and intercept were close to zero and unity, while for the case when fracture load was simulated, the slope decreased somewhat. The accuracy of the obtained results is comparable with the state-of-the-art literature, with the significant improvement of having around 50000 data points for each femur. This large number of measurements allows a more comprehensive validation of the predictions by the finite element models, since thousand of points are tracked along the femoral neck and trochanter region, i.e., the sites that are most critical for femur fracture. Moreover, strain measurement biases due to the strain gage reinforcement effect, were avoided. The combined experimental-numerical approach proved to be ready for application to in-vitro tests of human cadaver femurs, thus helping to develop a suitable mechanistic fracture risk criterion.
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| 10. |
- Grassi, Lorenzo, et al.
(författare)
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Full-field Strain Measurement During Mechanical Testing of the Human Femur at Physiologically Relevant Strain Rates
- 2014
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Ingår i: Journal of Biomechanical Engineering. - : ASME International. - 0148-0731 .- 1528-8951. ; 136:11
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the mechanical properties of human femora is of great importance for the development of a reliable fracture criterion aimed at assessing fracture risk. Earlier ex vivo studies have been conducted by measuring strains on a limited set of locations using strain gauges. Digital Image Correlation (DIC) could instead be used to reconstruct the full-field strain pattern over the surface of the femur. The objective of this study was to measure the full-field strain response of cadaver femora tested at a physiological strain rate up to fracture in a configuration resembling single stance. The three cadaver femora were cleaned from soft tissues, and a white background paint was applied with a random black speckle pattern over the anterior surface. The mechanical tests were conducted up to fracture at a constant displacement rate of 15 mm/s, and two cameras recorded the event at 3000 frames per second. DIC was performed to retrieve the full-field displacement map, from which strains were derived. A low-pass filter was applied over the measured displacements before the crack opened in order to reduce the noise level. The noise levels were assessed using a dedicated control plate. Conversely, no filtering was applied at the frames close to fracture to get the maximum resolution. The specimens showed a linear behavior of the principal strains with respect to the applied force up to fracture. The strain rate was comparable to the values available in literature from in-vivo measurements during daily activities. The cracks opened and fully propagated in less than 1 ms, and small regions with high values of the major principal strains could be spotted just a few frames before the crack opened. This corroborates the hypothesis of a strain-driven fracture mechanism in human bone. The data represents a comprehensive collection of full-field strains, both at physiological load levels and up to fracture. About 10000 measurements were collected for each bone, providing superior spatial resolution compared to ~15 measurements typically collected using strain gauges. These experimental data collection can be further used for validation of numerical models, and for experimental verification of bone constitutive laws and fracture criteria.
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