Motor control of a hub motor for electric skateboard propulsion : a thesis presented in partial fulfilment of the requirements for the degree of Masters in Engineering at Massey University, Palmerston North, New Zealand

Redacted for copyright reasons: Appendix A - Journal Article Published in IEEE International Instrumentation and Measurement Technology Conference (I2MTC 2012). Rowe, A. & Sen Gupta, G. (2012). Instrumentation and control of a high power BLDC motor for small vehicle applications.An electric powered skateboard was designed and built for testing and development of an innovative hub motor propulsion system and motor controller. The electric skateboard prototype is able to reach speeds of over 50km/h and achieve a range of over 35km on a single battery charge. The prototype weighs 8.6kg and can easily be carried by the user. This mode of transport has potential uses in recreational use, motor sports (racing), short commutes, and most notably, in ‘the last mile’ of public transport – getting to and from a train station, bus stop, etc. to the user’s final destination. Typical electric powered skateboards use external motors(s) requiring a power transmission assembly to drive the wheels. The hub motor design places the motor(s) inside the skateboard wheels and drives the wheels directly. This removes the need for power transmission assemblies therefore reductions in size, weight, cost, audible noise, and maintenance are realised. The hub motor built for this prototype has proven to be a highly feasible option over typical drive systems and further improvements to the design are discussed in this report. Advances in the processor capability of low cost microcontrollers has allowed for advanced motor control techniques to be implemented on low cost consumer level motor controllers which, until recent times, have been using the basic ‘Six-Step Control’ technique to drive Permanent Magnet Synchronous Motors. The custom built motor controllers allow for firmware to be flashed to the microcontroller. Firmware was written for the basic motor control technique, Six-Step Control and for the advanced motor control technique, ‘Field Oriented Control’ (FOC). This allowed for the two control techniques to be tested and compared using identical hardware for each. Six-Step Control drives a three phase motor by controlling the inverter output to six discrete states. The states are stepped through sequentially. This results in a square wave AC waveform. Theory shows that this is not optimal as the magnetic flux produced in the stator is not always perpendicular to the magnet poles but rather aligned to the nearest 60°. FOC addresses this by controlling the magnetic flux to always be perpendicular to the magnet poles in order to maximise torque. The inverter is essentially controlled to produce a continuously variable voltage vector output in terms of both magnitude and direction (vector control). Bench testing of the control techniques was performed using two motors coupled together with one motor driving and the other motor running as a generator. The generator motor was shown to provide a highly consistent and repeatable load on the driving motor under test and therefore comparisons could be made between the performance of the motor while controlled under Six-Step Control and FOC. This test indicated that FOC was able to drive the motor more efficiently than Six-Step Control, however the FOC implementation requires further development to achieve greater efficiency under high load demands. Furthermore, on-road testing was performed using the motor controllers in the electric skateboard prototype to compare the performance of the two control techniques in a real world application. The results from this test were inconclusive due to large variation in the results between repeated tests

Effect of Single Vs Accumulated Bouts of Exercise on Body Composition, Fitness, and Resting Metabolic Rate

PURPOSE: To examine how the effects of accumulated exercise compare to continuous exercise on body composition, VO2max, and metabolic rate. METHODS: Mildly active males (n = 4) and females (n = 5) were randomly selected to perform either 1) continuous exercise consisting of one 30-minute bout of Tabata (1-bout), 2) accumulated exercise consisting of two 15-minute bouts of Tabata (2-bout), or 3) no exercise (control). Both exercise groups performed Tabata three times per week for 4 weeks. Each group had three participants (2 males and 1 female) with the exception of the 2-bout group which had 3 female participants. Changes in body composition (i.e., body mass (kg) and percent body fat (BF%)) were assessed using Dual-Energy X-Ray Absorptiometry (DXA) measurements taken at baseline and after 4 weeks of training. VO2max (ml/kg/min) and resting metabolic rate (kcal/day) were assessed at baseline and after 4 weeks of training using open spirometry on a ParvoMedics True Max 2400 Oxygen Uptake system. For the female participants, both the baseline and 4-week measurements were assessed in the mid-follicular phase of the menstrual cycle. Participants maintained their normal diet throughout the study. Participants were provided with Fitbit watches to keep track of their activity (avg. heart rate & steps per day) during the study. Significant differences (pRESULTS: No significant changes in body mass were detected within the groups (p \u3e .05) or between the groups (p =.72). No significant changes in fat mass were detected within the groups (p \u3e .05) or between the groups (p =.22). With that being said, there was a trend towards a decrease in fat mass within the 2-bout group (1.2 ± .45 kg; p=.061; ES= -.22). No significant changes in BF% (p\u3e.05) were detected within the control or 1-bout group. There was a significant reduction in BF% within the 2-bout group (1.43 ± 0.38%; p=.03; ES= -.63) and there was a significant difference in the change in BF% between the 3 groups (p=.048; ES= -1.2 and -1.8). No significant changes in muscle mass muscle (kg) were detected within the groups (p\u3e.05) or between the groups (p = .17). With that being said, there was a trend towards an increase in muscle mass within the 2-bout group (.77 ± .27kg; p=.059; ES= -.14). No significant changes (p\u3e.05) in resting metabolic rate or VO2max were reported within the groups or between the groups. CONCLUSION: Four weeks of accumulated exercise reduced BF% when compared to no exercise and continuous exercise. Despite the absence of improvement in VO2max and metabolic rate, accumulated exercise throughout the day may still be a valuable exercise mode as it could help people with busy schedules achieve minimum exercise recommendations. Future studies should include 1) a larger sample size, 2) a greater volume of exercise, or 3) a longer period of observation. These modifications may lead to a more valid evaluation of how metabolic health and fitness are influenced by accumulated and continuous exercise

Large-Amplitude, Pair-Creating Oscillations in Pulsar and Black Hole Magnetospheres

A time-dependent model for pair creation in a pulsar magnetosphere is developed. It is argued that the parallel electric field that develops in a charge-starved region (a gap) of a pulsar magnetosphere oscillates with large amplitude. Electrons and positrons are accelerated periodically and the amplitude of the oscillations is assumed large enough to cause creation of upgoing and downgoing pairs at different phases of the oscillation. With a charge-starved initial condition, we find that the oscillations result in bursts of pair creation in which the pair density rises exponentially with time. The pair density saturates at $N_\pm\simeq E_{0}^2/(8\pi m_ec^2\Gamma_{\rm thr})$, where $E_0$ is the parallel electric field in the charge-starved initial state, and $\Gamma_{\rm thr}$ is the Lorentz factor for effec tive pair creation. The frequency of oscillations following the pair creation burst is given roughly by $\omega_{\rm osc}=eE_0/(8m_ec\Gamma_{\rm thr})$. A positive feedback keeps the system stable, such that the average pair creation rate balances the loss rate due to pairs escaping the magnetosphere.Comment: 21 pages, 6 figures, ApJ submitte

Is operationalising natural capital risk assessment practicable?

Financial institutions are indirectly exposed to risks associated with the impacts and dependencies on natural capital and ecosystem services of the companies that they invest in, lend to, and insure. This is particularly true for banks lending to agriculture: a sector with both significant impacts and critical dependencies on natural capital. Bank lending is a vital source of new finance for the sector, which is essential to achieve sustainable intensification targets. Yet current credit decision-making practice is still based on conventional financial and management indicators, lacking any systematic assessment of natural capital risks, especially those associated with dependencies. Operationalising natural capital risk assessment requires practicable indicators and data to evaluate the most material natural capital risks for a given sub-sector and geography, but it is unclear to what extent these are available. We assess the practicability of natural capital dependency risk indicators and data sources for a critical case study of Australian sheep production. We find that at least moderately practicable indicators and data sources are available to assess the 11 major dependency risks that are material for this industry. Challenges remain in determining risk thresholds for most indicators, and quantifying risk impacts on profitability. © 2021 Elsevier B.V

Editorial: From Pedagogic Research to Embedded E-Learning

This Special Issue of Reflecting Education arises from the work of the PREEL project (From Pedagogic Research to Embedded e-Learning) at the Institute of Education from 2006-2008. This project was one of nine HEA/JISC (Higher Education Academy and Joint Information Systems Committee) Pilot Pathfinder Projects and followed on from our involvement in the Pilot Benchmarking of e-Learning Programme. In the benchmarking exercise we identified a lack of coordination between research and practice in e-learning at the IoE as one of our crucial weaknesses, and so our Pilot Pathfinder project concentrated on this theme of building links between e-learning research and practice

Visual Function Questionnaire as an outcome measure for homonymous hemianopia: subscales and supplementary questions, analysis from the VISION trial

Background: We conduct supplementary analyses of the NEI VFQ-25 data to evaluate where changes occurred within subscales of the NEI VFQ-25 leading to change in the composite scores between the three treatment arms, and evaluate the NEI VFQ-25 with and without the Neuro 10 supplement. Methods: A prospective, multicentre, parallel, single-blind, three-arm RCT of fourteen UK acute stroke units was conducted. Stroke survivors with homonymous hemianopia were recruited. Interventions included: Fresnel prisms for minimum 2 h, 5 days/week over 6-weeks (Arm a), Visual search training for minimum 30 min, 5 days/week over 6-weeks (Arm b) and standard care-information only (Arm c). Primary and secondary outcomes (including NEI VFQ-25 data) were measured at baseline, 6, 12 and 26 weeks after randomisation. Results: Eighty seven patients were recruited (69% male; mean age (SD) equal to 69 (12) years). At 26 weeks, outcomes for 24, 24 and 22 patients, respectively, were compared to baseline. NEI VFQ-25 (with and without Neuro 10) responses improved from baseline to 26 weeks with visual search training compared to Fresnel prisms and standard care. In subscale analysis, the most impacted across all treatment arms was ‘driving’ whilst the least impacted were ‘colour vision’ and ‘ocular pain’. Conclusions: Composite scores differed systematically for the NEI VFQ-25 (Neuro 10) versus NEI VFQ-25 at all time points. For subscale scores, descriptive statistics suggest clinically relevant improvement in distance activities and vision-specific dependency subscales for NEI VFQ-25 scores in the visual search treatment arm. Trial Registration: Current Controlled Trials ISRCTN05956042

Interventions for visual field defects in people with stroke

BACKGROUND:Visual field defects are estimated to affect 20% to 57% of people who have had a stroke. Visual field defects can affect functional ability in activities of daily living (commonly affecting mobility, reading and driving), quality of life, ability to participate in rehabilitation, and depression and anxiety following stroke. There are many interventions for visual field defects, which are proposed to work by restoring the visual field (restitution); compensating for the visual field defect by changing behaviour or activity (compensation); substituting for the visual field defect by using a device or extraneous modification (substitution); or ensuring appropriate diagnosis, referral and treatment prescription through standardised assessment or screening, or both. OBJECTIVES:To determine the effects of interventions for people with visual field defects after stroke. SEARCH METHODS:We searched the Cochrane Stroke Group Trials Register, the Cochrane Eyes and Vision Group Trials Register, CENTRAL, MEDLINE, Embase, CINAHL, AMED, PsycINFO, and PDQT Databse, and clinical trials databases, including ClinicalTrials.gov and WHO Clinical Trials Registry, to May 2018. We also searched reference lists and trials registers, handsearched journals and conference proceedings, and contacted experts. SELECTION CRITERIA:Randomised trials in adults after stroke, where the intervention was specifically targeted at improving the visual field defect or improving the ability of the participant to cope with the visual field loss. The primary outcome was functional ability in activities of daily living and secondary outcomes included functional ability in extended activities of daily living, reading ability, visual field measures, balance, falls, depression and anxiety, discharge destination or residence after stroke, quality of life and social isolation, visual scanning, adverse events, and death. DATA COLLECTION AND ANALYSIS:Two review authors independently screened abstracts, extracted data and appraised trials. We undertook an assessment of methodological quality for allocation concealment, blinding of outcome assessors, method of dealing with missing data, and other potential sources of bias. We assessed the quality of evidence for each outcome using the GRADE approach. MAIN RESULTS:Twenty studies (732 randomised participants, with data for 547 participants with stroke) met the inclusion criteria for this review. However, only 10 of these studies compared the effect of an intervention with a placebo, control, or no treatment group, and eight had data which could be included in meta-analyses. Only two of these eight studies presented data relating to our primary outcome of functional abilities in activities of daily living. One study reported evidence relating to adverse events.Three studies (88 participants) compared a restitutive intervention with a control, but data were only available for one study (19 participants). There was very low-quality evidence that visual restitution therapy had no effect on visual field outcomes, and a statistically significant effect on quality of life, but limitations with these data mean that there is insufficient evidence to draw any conclusions about the effectiveness of restitutive interventions as compared to control.Four studies (193 participants) compared the effect of scanning (compensatory) training with a control or placebo intervention. There was low-quality evidence that scanning training was more beneficial than control or placebo on quality of life, measured using the Visual Function Questionnaire (VFQ-25) (two studies, 96 participants, mean difference (MD) 9.36, 95% confidence interval (CI) 3.10 to 15.62). However, there was low or very-low quality evidence of no effect on measures of visual field, extended activities of daily living, reading, and scanning ability. There was low-quality evidence of no significant increase in adverse events in people doing scanning training, as compared to no treatment.Three studies (166 participants) compared a substitutive intervention (a type of prism) with a control. There was low or very-low quality evidence that prisms did not have an effect on measures of activities of daily living, extended activities of daily living, reading, falls, or quality of life, and very low-quality evidence that they may have an effect on scanning ability (one study, 39 participants, MD 9.80, 95% CI 1.91 to 17.69). There was low-quality evidence of an increased odds of an adverse event (primarily headache) in people wearing prisms, as compared to no treatment.One study (39 participants) compared the effect of assessment by an orthoptist to standard care (no assessment) and found very low-quality evidence that there was no effect on measures of activities of daily living.Due to the quality and quantity of evidence, we remain uncertain about the benefits of assessment interventions. AUTHORS' CONCLUSIONS:There is a lack of evidence relating to the effect of interventions on our primary outcome of functional ability in activities of daily living. There is limited low-quality evidence that compensatory scanning training may be more beneficial than placebo or control at improving quality of life, but not other outcomes. There is insufficient evidence to reach any generalised conclusions about the effect of restitutive interventions or substitutive interventions (prisms) as compared to placebo, control, or no treatment. There is low-quality evidence that prisms may cause minor adverse events

Assessing the Impact of Suboptimal Donor Characteristics on Mortality After Liver Transplantation: A Time-dependent Analysis Comparing HCC With Non-HCC Patients.

BACKGROUND: Patients who receive a liver transplant for hepatocellular carcinoma (HCC) often receive poorer-quality livers. Tumor recurrence also has a negative effect on posttransplant outcomes. We compared mortality of HCC and non-HCC recipients in different posttransplant time periods (epochs) to separate the impact of these different risk factors on short-term and longer-term posttransplant survival. METHODS: We identified a population-based cohort of first-time liver transplant recipients (aged ≥16 years) between 2008 and 2016 in the United Kingdom. We used Cox regression to estimate hazard ratios (HRs) comparing posttransplant mortality between HCC and non-HCC patients in 3 posttransplant epochs: 0 to 90 days, 90 days to 2 years, and 2 to 5 years, with adjustment first for recipient and later also for donor characteristics. RESULTS: One thousand two hundred seventy HCC and 3657 non-HCC transplant recipients were included. Five-year posttransplant survival was 74.5% (95% confidence interval [CI] 71.2%-77.5%) in HCC patients and 84.6% (83.0%-86.1%) in non-HCC patients. With adjustment for recipient characteristics only, mortality of HCC patients was lower but not statistically significantly different in the first 90 days (HR, 0.76; 95% CI, 0.53-1.09; P = 0.11), but significantly higher thereafter (90 days to 2 years: HR, 1.99; 95% CI, 1.48-2.66; P < 0.001; 2 to 5 years HR, 1.77; 95% CI, 1.30-2.42; P < 0.001). Further adjustment for donor characteristics had little impact on these results. CONCLUSIONS: HCC recipients have poorer 5-year posttransplant survival than non-HCC recipients, most likely because of tumor recurrence. The more frequent use of poorer-quality donor organs for HCC does not explain this difference

West End Walkers 65+: using programme theory to enhance outcome assessment in a randomised controlled trial

Background: Walking has great potential to engage people in physical activity (PA), and could address health problems associated with sedentary living. Previous research showed increasing walking behaviour in inactive adults aged 18-65 years is feasible 1. However, a systematic review showed that evidence on how to encourage older adults to increase walking is lacking 2. This study aims to test a pedometer-based walking programme in combination with a PA consultation with adults aged 65 years+ in a primary care setting and to design a study protocol that enables shared learning outcomes. Methods: Over 12 months, West End Walkers 65+ will recruit 46 participants, aged 65 years+. Participants will be allocated to: Group 1 PA consultation, individualised walking programme and pedometer; or Group 2 a waiting list control group. Step counts, activity patterns and psychological measures will be assessed pre and post intervention. Focus groups and interviews will be completed with participants and stakeholders post intervention. Programme Theory: Feasibility of the intervention will be assessed using a programme theory. A programme’s theory conceptualises what must be done to bring about desired outcomes. This allows comparison between project planning and design and programme processes3. A triangulation of qualitative and quantitative research measures will inform this assessment. Feasibility will be assessed using goals designed to promote shared and transferrable learning outcomes