Dr Ben Halkon is an experimental dynamicist specialising in the development of non-contact measurements techniques and technologies for the determination of structural vibration characteristics. Having recently joined UTS in the School of Mechanical and Mechatronic Engineering, Ben previously held a permanent position, ultimately as Senior Lecturer, within the Wolfson School: Mechanical, Electrical and Manufacturing Engineering at Loughborough University, U.K. from Oct 2009 to Dec 2016. During this period, Ben secured significant levels of funding (on the order of £1m over the the most recent 5yrs) from a combination of funders (including e.g. Ford Motor Company UK, Nike, Inc., HEAD Sport, the International Cricket Council, the England and Wales Cricket Board and the Great Britain Rowing Team) including, to a large extent, the sports related industry.
Ben has supervised post-doctoral researchers, three PhD students to completion and many UG/PG student research projects, often industry supported/conceived and/or in support of his funded research. Ben has authored approximately 40 peer-reviewed articles and has contributed to policy change including the topical recent revision of BS 7928:2013 - Specification for head protectors for cricketers. Furthermore, Ben has held a number of positions in industry both between completing his PhD and re-joining Loughborough University and prior to joining UTS upon arrival in Australia in early 2017. Ben is an Engineering Council accredited chartered mechanical engineer and a Fellow of the Institution of Mechanical Engineers.
- Member of the UTS Centre for Audio, Acoustics and Vibration
- Member of the UTS Human Performance Research Centre
- Fellow of Engineers Australia (application accepted)
- Fellow of the Institution of Mechanical Engineers (FIMechE)
- Engineering Council accredited Chartered Engineer (CEng)
- Fellow of the Higher Education Council UK (FHEA)
- Member of the Australasian Association for Engineering Education
- Scientific Committee 13th International Conference on Vibration Measurements by Laser and Non-contact Techniques, Ancona, Italy, 19-22th June 2018
- Invited speaker Workshop on Non-contact Techniques for Vibro-acoustics, NTU, Singapore, 29-30th November, 2017
Can supervise: YES
- The development and application of industrially relevant non-contact measurement techniques using laser Doppler vibrometry
- Laser Doppler vibrometry from vibrating platforms
- Remote condition monitoring of large infrastructure using UAV-mounted laser Doppler vibrometry
- Automated dynamic characterisation of components and systems for quality control using industrial robot-mounted laser Doppler vibrometry
- The validation and application of sports wearable sensor technology for the improvement of sports athlete performance data
- The dynamic characterisation of sports equipment
- Experimental mechanics and dynamics
- Noise, vibration and rotordynamics
- Computer-aided engineering
Halkon, BJ & Rothberg, SJ 2017, 'Restoring high accuracy to laser Doppler vibrometry measurements affected by vibration of beam steering optics', Journal of Sound and Vibration, vol. 405, pp. 144-157.View/Download from: UTS OPUS or Publisher's site
© 2017 Elsevier Ltd Laser Doppler vibrometers are now well-established as an effective non-contact alternative to traditional contacting transducers. Wide-ranging applications include those where beam steering optics are required to reach locations that are difficult to access but no attention has yet been given to measurement sensitivity to the vibration of those optics. In this paper, a thorough mathematical treatment of this sensitivity to steering optic vibration and its correction is set out. A very practical scheme requiring a single correction measurement, from the back-surface of the mirror at the incidence point and aligned with the mirror normal, delivers an error reduction typically in excess of 30 dB. After validation in the laboratory, the scheme is then applied to a genuinely challenging measurement scenario on a single cylinder racing motorcycle. Correction is theoretically perfect for translational mirror vibrations but angular mirror vibrations require an adapted scheme using a triplet of accelerometers arranged around a circular path on the mirror back-surface and this is set out theoretically.
Halkon, BJ & Rothberg, SJ 2017, 'Taking laser Doppler vibrometry off the tripod: correction of measurements affected by instrument vibration', Optics and Lasers in Engineering, vol. 91, pp. 16-23.View/Download from: UTS OPUS or Publisher's site
© 2016 Elsevier Ltd Laser Doppler vibrometers (LDVs) are now well-established as an effective non-contact alternative to traditional contacting transducers. Despite 30 years of successful applications, however, very little attention has been given to sensitivity to vibration of the instrument itself. In this paper, the sensitivity to instrument vibration is confirmed before development theoretically and experimentally of a practical scheme to enable correction of measurements for arbitrary instrument vibration. The scheme requires a pair of correction sensors with appropriate orientation and relative location, while using frequency domain processing to accommodate inter-channel time delay and signal integrations. Error reductions in excess of 30 dB are delivered in laboratory tests with simultaneous instrument and target vibration over a broad frequency range. Ultimately, application to measurement on a vehicle simulator experiencing high levels of vibration demonstrates the practical nature of the correction technique and its robustness in a challenging measurement environment.
Halkon, BJ & Rothberg, SJ 2017, 'Reprint of: Taking laser Doppler vibrometry off the tripod: Correction of measurements affected by instrument vibration', Optics and Lasers in Engineering, vol. 99, pp. 3-10.View/Download from: UTS OPUS or Publisher's site
© 2017. Laser Doppler vibrometers (LDVs) are now well-established as an effective non-contact alternative to traditional contacting transducers. Despite 30 years of successful applications, however, very little attention has been given to sensitivity to vibration of the instrument itself. In this paper, the sensitivity to instrument vibration is confirmed before development theoretically and experimentally of a practical scheme to enable correction of measurements for arbitrary instrument vibration. The scheme requires a pair of correction sensors with appropriate orientation and relative location, while using frequency domain processing to accommodate inter-channel time delay and signal integrations. Error reductions in excess of 30. dB are delivered in laboratory tests with simultaneous instrument and target vibration over a broad frequency range. Ultimately, application to measurement on a vehicle simulator experiencing high levels of vibration demonstrates the practical nature of the correction technique and its robustness in a challenging measurement environment.
Rothberg, SJ, Allen, MS, Castellini, P, Di Maio, D, Dirckx, JJJ, Ewins, DJ, Halkon, BJ, Muyshondt, P, Paone, N, Ryan, T, Steger, H, Tomasini, EP, Vanlanduit, S & Vignola, JF 2017, 'An international review of laser Doppler vibrometry: Making light work of vibration measurement', OPTICS AND LASERS IN ENGINEERING, vol. 99, pp. 11-22.View/Download from: UTS OPUS or Publisher's site
Stone, BW, Harland, AR, Jones, JA, Mitchell, SR, Sherratt, PJ, Ranson, CA & Halkon, BJ 2017, 'On the dynamic response of an instrumented headform for alternative mounting stiffnesses when subjected to ballistic impacts', Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology, vol. 231, no. 4, pp. 324-335.View/Download from: UTS OPUS or Publisher's site
© 2017, © IMechE 2017. The current British Standard for head protectors for cricketers has been recently revised to include a projectile-based battery of tests, the intention being to ensure that a certified helmet will also prevent contact of the ball or grille with the specified headform facial region. The purpose of this study was to characterise the dynamic response of the headform to direct ballistic impacts for alternative headform mounting arrangements. On one hand, and in accordance with the relevant sections of the Standard, what might be described as a 'Constrained' setup was evaluated while, on the other hand, an arrangement with significantly reduced stiffness, in line with that previously reported for the passive human neck, was subject to equivalent appraisal. For each mounting scenario, an air cannon was used to project a cricket training ball at three speeds towards the instrumented headform at three locations with five repeats per speed/location combination. High-rate/resolution video and piezoelectric accelerometer data were collected and processed to determine the headform response. While differences between specific ball impact speed and location scenarios are set out in detail later in the article, overall observations are summarised as follows. From a ball/headform contact duration standpoint, video derived results showed ranges of 1.30–1.45 ms (Constrained) versus 1.26–1.41 ms. Maximum ball deformations, the timing of which enabling the event to be subdivided into 'loading' and 'unloading' phases, were found to be 82.5%–86.2% (Constrained) versus 82.8%–86.4% of original ball diameter; mean peak headform accelerations during loading were found to be 860–1615 m/s 2 (Constrained) versus 967–1638 m/s 2 ; and headform speeds at the end of the loading phase were found to be 0.5–0.92 m/s (Constrained) versus 0.54–0.93 m/s. Differences between headform response for the two mounting arrangements were observed to be more substantial during the loadin...
Zhang, Z, Halkon, B, Chou, SM & Qu, X 2016, 'A novel phase-aligned analysis on motion patterns of table tennis strokes', INTERNATIONAL JOURNAL OF PERFORMANCE ANALYSIS IN SPORT, vol. 16, no. 1, pp. 305-316.View/Download from: UTS OPUS
Payne, T, Mitchell, S, Halkon, B, Bibb, R & Waters, M 2016, 'Development of a synthetic human thigh impact surrogate for sports personal protective equipment testing', Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology, vol. 230, no. 1, pp. 5-16.View/Download from: UTS OPUS or Publisher's site
© IMechE 2015. Synthetic impact surrogates are widely used in the sporting goods industry in the evaluation of personal protective equipment. Existing surrogates, exemplified by those used in safety standards, have many shortcomings, primarily relating to their mass, stiffness, geometries and levels of constraint which limit their biofidelity and subsequent usefulness in personal protective equipment evaluations. In sports, absence from competition is a primary severity measure for injuries; consequently, blunt trauma injuries, such as contusions and lacerations, become pertinent and serious concerns. It is important, therefore, that synthetic surrogates provide an adequate description of these soft tissues to effectively evaluate injury risk. A novel, multi-material human thigh surrogate has been presented with consideration to the tissue structures, geometries and simulant materials used. This study presents the detailed development stages undertaken to fabricate a multi-material synthetic soft tissue surrogate with skin, subcutaneous adipose and muscle tissue components. The resultant surrogate demonstrates the successful use of sequential moulding techniques to construct a full-scale anatomical human impact surrogate which can be used in personal protective equipment testing.
Payne, T, Mitchell, S, Halkon, B & Bibb, R 2016, 'A systematic approach to the characterisation of human impact injury scenarios in sport', BMJ Open Sport & Exercise Medicine, vol. 2, no. 1, pp. e000017-e000017.View/Download from: UTS OPUS or Publisher's site
Banwell, GH, Roberts, JR, Halkon, BJ, Rothberg, SJ & Mohr, S 2014, 'Understanding the Dynamic Behaviour of a Tennis Racket under Play Conditions', EXPERIMENTAL MECHANICS, vol. 54, no. 4, pp. 527-537.View/Download from: UTS OPUS or Publisher's site
Perrin, R, Elford, DP, Chalmers, L, Swallowe, GM, Moore, TR, Hamdan, S & Halkon, BJ 2014, 'Normal modes of a small gamelan gong', JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA, vol. 136, no. 4, pp. 1942-1950.View/Download from: UTS OPUS or Publisher's site
Halkon, BJ & Rothberg, SJ 2014, 'Angular (pitch and yaw) vibration measurements directly from rotors using laser vibrometry', Mechanical Systems and Signal Processing, vol. 46, no. 2, pp. 344-360.View/Download from: UTS OPUS or Publisher's site
Parallel beam laser vibrometers offer direct measurement of pitch and yaw vibration directly from rotors. This paper, intended as an essential guide for the practical parallel beam laser vibrometer practioner, presents exact mathematical expressions for measured angular velocity in the presence of inevitable misalignments and estimates the likely measurement error levels due to such misalignments as well as to other sources of uncertainty through numerical simulation. Cross-sensitivity to the orthogonal vibration component, i.e. cross-sensitivity in a pitch measurement to yaw motion and vice-versa, is confirmed for rough rotors whereas it is shown not to be present when rotors are polished-circular. A complementary experimental investigation of the relationship between surface roughness and cross-sensitivity confirms the identification of two preferred measurement configurations: from the side of a polished-circular rotor and from the end face of a (rough) rotor coated in retro-reflective tape. Rotors with surface roughness up to 50 nm satisfy the former case provided the vibration displacement at the rotor surface does not exceed 20% beam diameter. For surfaces with roughness of 10 nm this can be extended to 50%. For rough rotor end face measurements, post-processing is required to resolve the inherent cross-sensitivity; the need for post-processing is justified quantitatively through numerical simulation. Further simulations incorporating typical levels of instrument misalignment and measurement noise are used to enable quantification of the likely errors in such angular vibration measurements. For measurements from the side of a polished-circular rotor, errors are around 1% for amplitude and 10 mrad at integer orders affected by pseudo-vibration and around one-third of these levels elsewhere. For measurements from a rough rotor end face, errors will be similar at integer orders (from 2). Errors in the rotational speed measurement, required for post-processing,...
Teng, PSP, Leong, KF, Kong, PW, Halkon, BJ & Huang, PY 2013, 'The use of rapid prototyping in the design of a customised ankle brace structure for ACL injury risk reduction: This paper explores the use of three-dimensional (3D) printing in designing a customised ankle brace structure for anterior cruciate ligament (ACL) injury risk reduction', Virtual and Physical Prototyping, vol. 8, no. 4, pp. 241-247.View/Download from: UTS OPUS or Publisher's site
Rapid prototyping, or additive manufacturing, is becoming more useful in creating functional prototypes, especially when customisation is required. This paper explores the use of three-dimensional (3D) printing in designing a customised ankle brace structure for anterior cruciate ligament (ACL) injury risk reduction. A new process is proposed to obtain ankle flexion angles and the corresponding foot surface strain associated with high ACL injury risks through motion analysis. This data is used in the design of the customised ankle brace structure and printed using rapid prototyping. One customised ankle brace structure was printed and tested to demonstrate this proposed framework. The ankle flexion range of motion (ROM) was significantly reduced in the high-risk ankle positions with the ankle brace structure. Rapid prototyping could thus be used to design customised ankle brace structures and this is useful in reducing fabrication time and complexity of customisation. © 2013 Taylor & Francis.
Rothberg, SJ, Halkon, BJ, Tirabassi, M & Pusey, C 2012, 'Radial vibration measurements directly from rotors using laser vibrometry: The effects of surface roughness, instrument misalignments and pseudo-vibration', Mechanical Systems and Signal Processing, vol. 33, pp. 109-131.View/Download from: UTS OPUS or Publisher's site
Laser Doppler vibrometry (LDV) offers an attractive solution when radial vibration measurement directly from a rotor surface is required. Research to date has demonstrated application on polished-circular rotors and rotors coated with retro-reflective tape. In the latter case, however, a significant cross-sensitivity to the orthogonal radial vibration component occurs and post-processing is required to resolve individual radial vibration components. Until now, the fundamentally different behaviour observed between these cases has stood as an inconsistency in the published literature, symptomatic of the need to understand the effect of surface roughness. This paper offers the first consistent mathematical description of the polished-circular and rough rotor behaviours, combined with an experimental investigation of the relationship between surface roughness and cross-sensitivity. Rotors with surface roughness up to 10 nm satisfy the polished-circular rotor definition if vibration displacement is below 100% beam diameter, for a 90 m beam, and below 40% beam diameter, for a 520 m beam. On rotors with roughness between 10 nm and 50 nm, the polished-circular rotor definition is satisfied for vibration displacements up to 25% beam diameter, for a 90 m beam, and up to 10% beam diameter, for a 520 m beam. As roughness increases, cross-sensitivity increases but only rotors coated in retro-reflective tape satisfied the rough rotor definition fully. Consequently, when polished-circular surfaces are not available, rotor surfaces must be treated with retro-reflective tape and measurements post-processed to resolve individual vibration components. Through simulations, the value of the resolution and correction algorithms that form the post-processor has been demonstrated quantitatively. Simulations incorporating representative instrument misalignments and measurement noise have enabled quantification of likely error levels in radial vibration measurements. On a polished-ci...
Velani, N, Wilson, O, Halkon, BJ & Harland, AR 2012, 'Measuring the risk of sustaining injury in sport a novel approach to aid the re-design of personal protective equipment.', Applied ergonomics, vol. 43, no. 5, pp. 883-890.View/Download from: UTS OPUS or Publisher's site
Despite the possibilities offered by new approaches in design and advances in materials and manufacturing methods, few items of Personal Protective Equipment (PPE) used in sport have seen significant change for many decades. A major reason for this is the tradition and conservative attitudes associated with many sports, although the absence of appropriate tools and techniques to assist the design and development process has also played a large part. The aim of this study was to develop the first stage of a method of identifying specific regions of the human anatomy that are at the greatest risk of sustaining injury during participation in sports in which the player is subjected to multiple ballistic impacts. It is proposed that the findings could be used to confirm future designs of sports PPE. Previous studies have identified the amount and the location of the protection provided by current commercially available products but, until now, no evidence has been reported to determine what protection is required based on an understanding of the likely impact and the anatomy of the athlete. Using the leg and cricket as examples of an anatomical feature and a sporting application respectively, the severity and probability of injury due to ball impacts typically observed in play are quantified, with respect to their location on the leg, to estimate the level of risk in that region. Results show that the level of risk is greatest in the shin regions of the front leg, suggesting that this region should be offered the greatest degree of protection, as is generally the case in commercially available leg guard designs. Conversely, however, the inner region of the mid shin of the back leg is at the lowest risk, suggesting that protection in this region might be substantially reduced, a feature which is certainly not included in current product; such a reduction may significantly enhance the ergonomic performance of the leg guard design. The findings of this preliminary study ...
Halkon, BJ & Rothberg, SJ 2006, 'Vibration measurements using continuous scanning laser vibrometry: Advanced aspects in rotor applications', MECHANICAL SYSTEMS AND SIGNAL PROCESSING, vol. 20, no. 6, pp. 1286-1299.View/Download from: UTS OPUS or Publisher's site
Halkon, BJ & Rothberg, SJ 2006, 'Rotor vibration measurements using laser doppler vibrometry: Essential post-processing for resolution of radial and pitch/yaw vibrations', Journal of Vibration and Acoustics, Transactions of the ASME, vol. 128, no. 1, pp. 8-20.View/Download from: UTS OPUS or Publisher's site
Laser Doppler vibrometry is now a well established technique enabling noncontact vibration measurements in the most challenging of environments. Rotor vibration measurements are often highlighted as a major application of laser vibrometers due to their noncontact operation and inherent immunity to shaft runout. In such measurements, resolution of the individual axial and torsional vibration components is possible via particular arrangement of the laser beam(s). Resolution of the radial or pitch/yaw vibration components, however, can only be achieved by essential post-processing of the data from simultaneous orthogonal measurements. This paper describes the principle and rigorous examination of a novel, dedicated resolution algorithm enabling, for the first time, real-time post-processing of the outputs from standard commercial instruments. The system performed well, even in the presence of noise and other typical measurement errors, and was implemented successfully in an engine vibration study. Copyright © 2006 by ASME.
Halkon, BJ, Frizzel, SR & Rothberg, SJ 2003, 'Vibration measurements using continuous scanning laser vibrometry: Velocity sensitivity model experimental validation', Measurement Science and Technology, vol. 14, no. 6, pp. 773-783.View/Download from: UTS OPUS or Publisher's site
This paper builds on a previous study in which the theoretical description of the velocity sensed by a single laser beam incident in an arbitrary direction on a rotating target undergoing arbitrary vibration was extended to continuous scanning laser vibrometer measurements on targets with flexible cross sections. The velocity sensitivity model was written in terms of either laser beam orientation angles or deflection mirror scan angles, with the latter found to be the most useful for continuous scanning applications. The model enables the prediction of the laser vibrometer output for any measurement configuration on any target. The experimental validation presented in this paper confirms that additional components appear in rotating target measurements that are associated with both the scanning system configuration and any misalignment between the scanning system and target rotation axes. This paper will show how use of the velocity sensitivity model enables the vibration engineer to make laser Doppler vibrometry measurements with confidence.
Halkon, B, Rauter, A, Oberst, S & Marburg, S 2019, 'Research and development of an air-puff excitation system for lightweight structures', 8th International Operational Modal Analysis Conference 2019, Copenhagen.View/Download from: UTS OPUS
Lightweight, thin-walled structures appear in numerous engineering and natural structures. Due to their sensitivity, vibration excitation by, now traditional, contacting techniques, such as modally-tuned impact hammers or electrodynamic shakers, to investigate their dynamics is challenging since it typically adds substantial mass and/or stiffness at the excitation location. The research presented in this article, therefore, is intended to yield a system for the non-contact excitation of thin-walled structures through small, controlled blasts of air. An air-puff system, consisting of two fast-acting solenoid controlled valves, a small air outlet nozzle and bespoke control software with a programmable valve control sequence, is researched and developed. The excitation impulse characteristics are investigated
experimentally and described in detail for varying input control parameters. Ultimately, suitability of the system for the excitation of thin-walled structures is explored, for both a 3D-printed micro-satellite panel and a natural bee honeycomb, with promising results when compared to that of an impact hammer.
Halkon, BJ & Chapman, C 2018, 'On the development and characterisation of a synchronised-scanning laser Doppler vibrometer system', International Congress on Sound and Vibration, Hiroshima, Japan.View/Download from: UTS OPUS
Halkon, BJ & Rothberg, S 2018, 'Towards laser Doppler vibrometry from unmanned aerial vehicles', 13th Intl CONFERENCE on VIBRATION MEASUREMENTS by LASER and NONCONTACT TECHNIQUES, Ancona, Italy.View/Download from: UTS OPUS
Halkon, B & Rothberg, S 2015, 'Correction of laser Doppler vibrometry measurements affected by steering mirror vibration', OPTICAL MEASUREMENT TECHNIQUES FOR STRUCTURES & SYSTEMS III, 6th International Conference on Optical Measurement Techniques for Structures and Systems III (OPTIMESS2015), SHAKER PUBLISHING BV, Univ Antwerp, Antwerp, BELGIUM, pp. 117-126.View/Download from: UTS OPUS
© 2016 The Authors. Published by Elsevier Ltd. The current British Standard for head protectors for cricketers specifies a projectile test to ensure that a helmet can prevent the ball penetrating the peak-grille gap and deformation of the grille onto the face. For practical reasons, it is specified that the headform is mounted onto a grounded frame. This study aims to determine whether this "Fixed" mounting technique influences the response of the headform relative to a theoretically preferable "Free" suspension. A pressurised air cannon was used to project a "BOLA"TM ball at three nominal speeds (22, 25 and 28 m/s) and at three target impact locations (136 (Top), 108 (Middle) and 80 (Bottom) mm from the base). High speed video was used to identify the contact duration and accelerometer data were used to assess the peak resultant headform acceleration and velocity during this period. Generally, good agreement between the two scenarios was found in regard to peak resultant headform acceleration, particularly at the 25 and 28 m/s impact speeds. In terms of headform velocity, the two scenarios showed greater variation when the full contact duration was considered, with root mean square deviations ranging from 1.77-5.6 in all testing conditions. However, some portions of the impact were considerably more consistent than others. These initial results indicate that the result of the penetration test, as specified in BS 7928:2013, would be independent of the suspension technique particularly given the convergence of results at the specified standard velocity (28 m/s). Future work should look to identify the loading and unloading phases of an impact, and use this to compare headform response. Thus allowing a more in-depth investigation of headform mounting performance and provide more clarity on the use of the Fixed technique in cricket standard tests.
Christensen, J, Rasmussen, J, Halkon, B & Koike, S 2016, 'The Development of a Methodology to Determine the Relationship in Grip Size and Pressure to Racket Head Speed in a Tennis Forehand Stroke', Procedia Engineering, pp. 787-792.View/Download from: UTS OPUS or Publisher's site
© 2016 The Authors. Published by Elsevier Ltd. This study developed a methodology to examine the effects of grip size and grip firmness on the kinematic contribution of angular velocity (KCAV) to the generation of racket head speed during a topspin tennis forehand. The KCAV is subdivided into kinematic contribution of joint angular velocity and kinematic contribution of the body segments in the upper trunk translational and angular velocities. Two Babolat Pure Storm GT rackets, with grip sizes 2 and 4 respectively, were used with Tekscan 9811E pressure sensors applied to the handles to examine pressure distribution during the stroke. Upper body kinematic data taken from the racket arm and trunk were obtained by means of a Vicon motion capture system. One elite male tennis player was recruited. Fifty topspin forehand strokes per grip at two nominal grip pressures were performed in a laboratory environment with balls being tossed towards the player and struck on the bounce towards a target on a net in as consistent a way as practically achievable. Processing of the results showed that the firm grip condition led to a significant (p<0.001) increase in average racket head speed compared to a normal grip condition. The normal gripping condition resulted in a significant (p<0.001) increase in average racket head speed for grip size 2 compared to grip size 4. A trend in negative linear relationships was found between upper trunk and shoulder joint in KCAV across conditions. Using the smaller grip also led to a trend in negative linear relationship between shoulder joint and wrist joint in KCAV across grip conditions. Grip pressure for grip size 2 showed the same pattern across gripping conditions. From 50-75% of completion in forward swing, the pressure difference due to grip firmness decreased. This feasibility study managed to quantify the KCAV while performing a topspin forehand, with respect to changing of grip size and grip pressure in an elite male tennis player f...
Oldham, KM, Chung, PWH, Edirisinghe, EA & Halkon, BJ 2016, 'Table tennis and computer vision: A monocular event classifier', Advances in Intelligent Systems and Computing, pp. 29-32.View/Download from: UTS OPUS or Publisher's site
© Springer International Publishing Switzerland 2016. Detecting events in table tennis using monocular video sequences for match-play officiating is challenging. Here a low-cost monocular video installation generates image sequences and, using the Horn-Schunck Optical Flow algorithm, ball detection and location processing captures sudden changes in the ball's motion. It is demonstrated that each abrupt change corresponds to a distinct event pattern described by its combined velocity, acceleration and bearing. Component motion threshold values are determined from the analysis of a range of table tennis event video sequences. The novel event classifier reviews change in motion data against these thresholds, for use in a rules based officiating decision support system. Experimental results using this method demonstrate an event classification success rate of 95.9%.
Stone, BW, Halkon, BJ & Harland, AR 2016, 'An explorative study into the mechanics of projectile impacts to the head', 2016 IRCOBI Conference Proceedings - International Research Council on the Biomechanics of Injury, pp. 369-380.View/Download from: UTS OPUS
There has been little research focused on the mechanics of high-velocity, low-mass projectile impacts to the head. The little work that has been conducted has focused solely on linear acceleration, despite the evidence linking rotational acceleration to the development of brain injury. The aim of this study was to explore the presence of rotational acceleration in projectile impacts and investigate the influence of impact location. A pressurised air cannon was used to project a BOLATM ball at 22 and 28 m.s-1 towards a BSEN 960:2006 headform positioned to elicit impacts at frontal and lateral locations. High-speed video and accelerometer measurements were used to investigate differences in contact duration, ball deformation and average linear and rotational acceleration during loading. Contact duration was found to be independent of impact location or speed. Greater ball deformation was observed in frontal impacts, despite no differences in time to maximum deformation. Average linear acceleration was observed to be greater during the loading phase in the frontal impacts then in the lateral impacts, potentially due to differences in surface geometry, resulting in differences in ball deformation. Average rotational acceleration was greater in lateral impacts potentially due to differences in the moments of inertia of the headform. Rotational acceleration was found to be higher than previously published injury thresholds for concussion and therefore a potentially important factor in projectile impacts, warranting further research.
Halkon, BJ & Rothberg, SJ 2015, 'A practical guide to laser Doppler vibrometry measurements directly from rotating surfaces', IMechE Vibrations in Rotating Machinery, University of Manchester, UK.View/Download from: UTS OPUS
Oldham, KM, Chung, PWH, Edirisinghe, EA & Halkon, BJ 2014, 'Experiments in the Application of Computer Vision for Ball and Event Identification in Indoor Sports', COMPUTATIONAL INTELLIGENCE IN INFORMATION SYSTEMS, 4th INNS Symposia on Computational Intelligencein Information Systems (INNS-CIIS), SPRINGER-VERLAG BERLIN, Inst Teknologi Brunei, Bandar Seri Begawan, BRUNEI, pp. 275-284.View/Download from: Publisher's site
Sykora, M, Chung, PWH, Folland, JP, Halkon, BJ & Edirisinghe, EA 2014, 'Advances in Sports Informatics Research', COMPUTATIONAL INTELLIGENCE IN INFORMATION SYSTEMS, 4th INNS Symposia on Computational Intelligencein Information Systems (INNS-CIIS), SPRINGER-VERLAG BERLIN, Inst Teknologi Brunei, Bandar Seri Begawan, BRUNEI, pp. 265-274.View/Download from: UTS OPUS or Publisher's site
Zhang, Z, Halkon, B, Chou, SM & Qu, X 2015, 'Shoulder Joint Angle Errors Caused by Marker Offset', IMPACT OF TECHNOLOGY ON SPORT VI' 7TH ASIA-PACIFIC CONGRESS ON SPORTS TECHNOLOGY, APCST2015, 'The Impact of Technology on Sport VI' 7th Asia-Pacific Congress on Sports Technology, APCST, ELSEVIER SCIENCE BV, Barcelona, SPAIN, pp. 479-484.View/Download from: UTS OPUS or Publisher's site
Despite significant advances in materials and manufacturing techniques applied to sports protective equipment in recent years, sports injuries due to impact, contusions in particular, continue to occur. In this paper, a test methodology aimed at collecting data from laboratory-simulated human-on-human impacts in Basketball is presented. The study was executed in three stages with data being collected from: i) human on instrumented bag; ii) impactor on instrumented bag and iii) impactor on instrumented human impacts. In all cases, high-speed video and/or kinematic motion data capture systems were used to obtain parameters such as inbound/outbound velocities, contact durations while resistive ink technology pressure sensing films were used to estimate parameters such as pressure distributions, peak pressures, contact areas, impact forces. Elite-level athletes were used in all human trials to ensure that impact techniques and levels representative of the elite game were obtained and that tolerance to impacts was similarly representative. Two common strikes were simulated: knee on thigh and elbow on rib/torso. Five participants were used to collect the human-on-bag data while 12 participants were used to collect the impactor-on-human data. Between three and five impacts per scenario were performed to enable noise averaging and, importantly, likely injurycausing outlier capture. © 2014 Published by Elsevier Ltd.
Harfield, P, Halkon, B, Mitchell, S, Phillips, I & May, A 2014, 'A novel, real-time biomechanical feedback system for use in rowing', ENGINEERING OF SPORT 10, 10th Conference of the International-Sports-Engineering-Association, ELSEVIER SCIENCE BV, Sheffield Hallam Univ, Sheffield, ENGLAND, pp. 126-131.View/Download from: UTS OPUS or Publisher's site
Udeshi, A, Halkon, B & Coupland, J 2013, 'An alternative technique for investigating fluid flow around the hand during front crawl', Procedia Engineering, pp. 176-181.View/Download from: UTS OPUS or Publisher's site
This paper presents the novel application of a technique for measuring flow around the hand during a simulated swim stroke with a view to enable a better understanding of propulsion generation in swimming. The technique relies on the instantaneous, non-intrusive, volumetric measurement of 3D velocity fields using a commercially available optical measurement system. A hand and forearm model was towed through a water tank to replicate the pull phase with fluid flow data being captured at regular intervals in a fixed volume through which the model moved. The measurement system included a single body, three-sensor probe for capturing pairs of images which were then processed to determine particle velocities and to characterise the flow. The results were used to investigate changes in mean velocity for six experimental cases based on three different angles of attack and two towing speeds. The results showed that the V3V system could be used to capture velocity data around the hand and for a 45° increase in angle of attack, the velocity magnitude of the flow reduced by half, indicating the presence of lift forces. © 2013 The Authors.
Velani, N, Harland, AR & Halkon, BJ 2013, 'The development of a test methodology for the determination of cricket batting helmet performance when subjected to ballistic impacts', 2013 IRCOBI Conference Proceedings - International Research Council on the Biomechanics of Injury, pp. 424-430.View/Download from: UTS OPUS
The study presented in this paper was conducted in support of the development of a proposed revision to a cricket helmet certification test standard. Helmets were impacted between the peak and faceguard by 'projecting' balls at them at velocities up to 80 mph. The velocity at which the balls penetrated between the peak and the faceguard (or grille) for the various permissible peak-grille gap settings for each helmet was recorded. The study progressed to compare these penetration velocities against the equivalent found when 'game-aligned' alternate (drop) test methodologies were used. The results demonstrate that the penetration velocities are considerably lower than those that might be observed in play. As peak-grille gap settings were reduced, penetration velocities increased as expected but, significantly, balls were able to penetrate despite gap settings, on occasion being considerably smaller than the ball diameter. The penetration velocity was also found, as expected, to vary with the stiffness of the ball with increased ball stiffness leading to reduced penetration velocities. When comparing penetration velocities against those found using the alternate methodologies, significant differences were found, suggesting that such methodologies cannot be used to reliably evaluate the performance of helmets to ball impacts occurring in this particular region.
Halkon, B, Webster, J, Mitchell, S & Mientjes, M 2012, 'Development of a test methodology for the assessment of human impacts in sport', ENGINEERING OF SPORT CONFERENCE 2012, 9th Conference of the International-Sports-Engineering-Association (ISEA), ELSEVIER SCIENCE BV, Univ Massachusetts Lowell, Lowell, MA, pp. 813-818.View/Download from: UTS OPUS or Publisher's site
Rothberg, S & Halkon, B 2004, 'Laser Vibrometry meets laser speckle', Proceedings of SPIE - The International Society for Optical Engineering, pp. 280-291.View/Download from: UTS OPUS or Publisher's site
This paper begins with a review of the fundamental mechanism by which speckle noise is generated in Laser Vibrometry before describing a new numerical simulation of speckle behaviour for prediction of noise level in a real measurement. The simulation data provides real insight into the phase and amplitude modulation of the Doppler signal as a result of speckle changes. The paper also includes experimental data looking at the influence of speckle noise in measurements on rotors with a selection of surface treatments and in scanning and tracking configurations.
The Laser Vibrometer constitutes a potentially powerful vibration transducer for measurements directly from rotating components. Radial, axial, pitch/yaw and torsional vibrations can all be measured using either single beam or parallel beam Laser Vibrometers. Successful application, however, requires a clear appreciation of the effects of laser speckle and of how radial and pitch/yaw vibration measurements from rotors contain significant cross-sensitivities to motion perpendicular to the intended measurement. Making use of two orthogonal vibration measurements and an independent speed measurement it is possible to eliminate cross-sensitivity from measured data at all non-synchronous frequencies but a convenient, practical means to undertake the necessary data processing has not been available until now. A Lab VIEW based real-time version of this essential resolution technique will be presented for the first time in this paper. This paper describes a number of example measurements. Radial and pitch/yaw vibration measurements will demonstrate the use of the resolution technique to show effects such as the excitation of the first bending mode of the crankshaft. A torsional vibration measurement on a crankshaft pulley will show the influence of speckle noise and alignment issues will be discussed to limit the pitch/yaw vibration sensitivity. Differential torsional measurements on rotating components can be used to examine, for example, the twisting across a flexible coupling and the stretching of a drive belt; speckle effects are again important. © IMechE 2004.
Halkon, B & Rothberg, S 2004, 'Synchronised-scanning laser vibrometry', SIXTH INTERNATIONAL CONFERENCE ON VIBRATION MEASUREMENTS BY LASER TECHNIQUES: ADVANCES AND APPLICATIONS, 6th International Conference on Vibration Measurements by Laser Techniques, SPIE-INT SOC OPTICAL ENGINEERING, Ancona, ITALY, pp. 260-271.View/Download from: UTS OPUS or Publisher's site
Halkon, B & Rothberg, S 2003, 'Continuous scanning laser vibrometry for measurements on rotating structures', MODERN PRACTICE IN STRESS AND VIBRATION ANALYSIS, 5th International Conference on Modern Practice in Stress and Vibration Analysis, TRANS TECH PUBLICATIONS LTD, GLASGOW, SCOTLAND, pp. 245-252.View/Download from: UTS OPUS or Publisher's site
Halkon, B & Rothberg, S 2002, 'A comprehensive velocity sensitivity model for scanning and tracking laser Doppler vibrometry on rotating structures', Proceedings of SPIE - The International Society for Optical Engineering, pp. 9-21.View/Download from: UTS OPUS or Publisher's site
Recent work set out a comprehensive analysis of the velocity sensed by a single laser Doppler vibrometer beam incident in an arbitrary direction on a target that is of substantial interest in engineering - a rotating, shaft requiring three translational and three rotational co-ordinates to describe its vibratory motion fully. Six separate "vibration sets", each a combination of motion parameters, appeared in the full expression for vibration velocity sensitivity and the difficulties associated with resolving individual vibration components within a complex motion were highlighted. The velocity sensitivity model can incorporate time dependent beam orientation and this is described in this paper with reference to scanning laser Doppler vibrometry. Continuously scanning strategies, in which the laser beam orientation is a continuous function of time, have recently received considerable attention, including a tracking profile in which the probe laser beam remains fixed on a single point on a target such as a rotating disc. Typically, one beam deflection mirror is driven using a cosine function whilst the other is driven with a sine function, resulting in a slightly elliptical beam trajectory. This and other more significant issues such as the effects of misalignment are easily accommodated in the velocity sensitivity model and a thorough analysis of their influence on the measured vibration signal is reported in this paper.
Halkon, B & Rothberg, S 2002, 'Comprehensive velocity sensitivity model for scanning and tracking laser vibrometry', Proceedings of SPIE - The International Society for Optical Engineering, pp. 1166-1170.View/Download from: UTS OPUS
Recent work set out a comprehensive analysis of the velocity sensed by a single laser vibrometer beam incident in an arbitrary direction on a target that is of substantial interest in engineering - a rotating shaft requiring three translational and three rotational co-ordinates to describe its vibratory motion fully. Six separate "vibration sets", each a combination of motion parameters, appeared in the full expression for vibration velocity sensitivity and the difficulties associated with resolving individual vibration components within a complex motion were highlighted. One specific way in which the model has been extended is the subject of this paper. The scanning laser Doppler vibrometer has become an increasingly popular instrument especially for experimental modal analysis. Continuously scanning strategies, in which the laser beam orientation is a continuous function of time, have received considerable attention. Researchers have reported use of several different types of scan profile including a tracking profile in which the probe laser beam remains fixed on a single point on a target such as a rotating disc. When the velocity sensitivity model was originally reported, it was stated that it could be used with such applications and this is shown explicitly, for the first time, in this paper.