The goal of this thesis is to develop an active front steering(AFS) control system which can apply to ordinary vehicle. This AFS control system stabilizes the driving vehicle and reduces the possibility of rollover. This thesis uses magic formula tire model and constructs a vehicle model with eight degrees of freedom to study the dynamic behavior of the real driving vehicle. This thesis constructs a vehicle model with three degrees of freedom and eight degree of freedom, compare with two vehicle model, we adopt eight vehicle model in this thesis. The advantages of PI controller are low cost and easy to modify, so this thesis adopts PI controller as the control strategy. This study uses four simulate methods and compares the simulated results to develop the AFS control system which can apply to ordinary vehicle.

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The rising statistics of fatal and non-fatal injuries involving an all-terrain vehicle has called for an analysis of the accumulated data from the past years. The analysis has led to the conclusion that in the past years, the fatal and non-fatal injuries have been rising rapidly in spite of the consent decrees which were brought into effect from 1988-1998 by the consumer product safety commission. A necessity to provide increased safety while riding an all-terrain vehicle is recognized. Rollover protective structures which were used with successful results in curbing the injuries on agricultural tractors have been identified as having a potential to serve the purpose. A conceptual design of an automatically deployable rollover protective structure has been dealt with, in the thesis.

Shorter product life cycles and rapid product obsolescence provide increasing incentives to introduce newproducts to markets more quickly. As a consequence of rapidly changing market conditions, firms focus onimproving their new product development processes to reap the benefits of early market entry. Researchershave analyzed market entry, but have seldom provided quantitative approaches for the product rolloverproblem. This research builds upon the literature by using established optimization methods to examine howfirms can minimize their net loss during the rollover process. Specifically, our work explicitly optimizes thetiming of removal of old products and introduction of new products, the optimal strategy, and the magnitudeof net losses when the market entry approval date of a new product is unknown. In the first paper, we use theconditional value at risk to optimize the net loss and investigate the effect of risk perception of the manageron the rollover process. We compare it to the minimization of the classical expected net loss. We deriveconditions for optimality and unique closed-form solutions for single and dual rollover cases. In the secondpaper, we investigate the rollover problem, but for a time-dependent demand rate for the second producttrying to approximate the Bass Model. Finally, in the third paper, we apply the data-driven optimizationapproach to the product rollover problem where the probability distribution of the approval date is unknown.We rather have historical observations of approval dates. We develop the optimal times of rollover and showthe superiority of the data-driven method over the conditional value at risk in case where it is difficult to guessthe real probability distribution

Thesis(M.S.)--Auburn University, 2008. / Abstract. Vita. Includes bibliographic references (p.96-99).

Many econometric analyses of commodity futures over the years have been performed using spot or front month contract prices. Using such daily prices without the consideration of the associated contract traded volumes is slightly erroneous because, in reality, traders will typically trade the ‘most liquid’ contract, that is, the contract with the largest average daily volume (ADV). The reason for this is in order to gain the best price when buying or selling. If this ‘true’ time series is to be considered, a mapping procedure is required to account for the price jumps at the time when a trader trades out of the expiring contract and enters the new front month contract. A key finding was that this effect was significant, irrespective of the size of the price jump, sometimes referred to as basis or roll and also due to the accumulated roll over a number of years corresponding to multiple contracts. It was also found that the mapping procedure has a significant effect on the time series and should hence always be employed if the realistic traded time series is to be considered. Given this phenomenon, algorithmically-traded commodities futures must necessarily employ such time series when creating metrics or considering an econometric analysis. The key findings include the importance of diversification in algorithmically-traded portfolios, utilising the AOM and PSI metrics. The mapping of data sets to create realistic ‘live-traded’ time series was found to be significant, while the optimal day of roll over prior to contract expiry was found to be related to the trading volumes for certain commodities. Other key findings include the causalities and spillovers within the metals sector where various relationships are evident once the results were processed and analysed, both pre and post mapping. Interestingly, the key relationships including bidirectional volatility and shock spillovers between the four key metals existed when the unmapped data was used however, many of the feedbacks within these relationships was lost when the mapped data sets were considered. A significant finding was therefore the consistent differences in findings between mapped and unmapped data sets attributed to the optimisation or favourability of the models (whether econometric or algorithmic). This is due to the unmapped data including roll or basis (which the models are fitted to) taking into account the roll or basis and utilising them in finding relationships between data sets. In the mapped data set (the time series seen by traders) the roll or basis is accounted for and hence the relationships found stand in real-time trading situations. The differences in the results show how the effect of mapping can be significant with unmapped data sets displaying results which will not exist in a real time traded time series.

Die doel van die navorsing wat in hierdie verslag bespreek word, was om ondersoek in te stel na die omrolgedrag van veldvoertuie. Die studie is gedoen deur gebruik te maak van ʼn Land Rover Defender 110 sport nutsvoertuig as eksperimentele voertuig, en ADAMS View as sagteware pakket Die sogenaamde “vishoektoets” is met die basislynvoertuig uitgevoer. Daar is korrelasie verkry tussen die data wat tydens die toetse opgeneem is, en ʼn volledige drie-dimensionele model van die voertuig in ADAMS View. Die basislynsuspensie op die voertuig is vervolgens vervang met ʼn vier toestand semi-aktiewe hidropneumatiese suspensiestelsel of 4S4. Die toetse is herhaal, en korrelasie verkry tussen die toetsdata en die rekenaarmodel. Die rekenaarmodel, met die basislyn suspensiekarakteristieke vervang met die hidropneumatiese suspensiekarakteristieke, is teen hierdie toetsdata geverifieer. Die rekenaarmodel is na korrelasie gebruik om te bepaal watter veer- en demperstellings die effektiefste sal wees om omrol te voorkom. Verder is die model ook gebruik om die effek van rithoogteverlaging op omrolgeneigdheid te bepaal. Die hoeveelheid wat die wiele oplig, is as norm vir omrolgeneigdheid gebruik. Ander parameters, soos giersnelheid, rolsnelheid en rolhoek is ook ondersoek. Uit die studie is dit duidelik dat die 4S4, met die moontlikheid van verstelling aan rithoogte, sinvol aangewend kan word om omrolgeneigdheid te verminder. / Dissertation (MEng (Mechanical Engineering))--University of Pretoria, 2008. / Mechanical and Aeronautical Engineering / unrestricted

Some of the results of an extensive track testing program at the Center for Vehicle Systems and Safety (CVeSS) at Virginia Tech for evaluating the roll stability of commercial trucks with 33-ft A-double trailers are evaluated. The study includes straight-rail trailers with heavy and light loading conditions. Commercial trucks are more susceptible to rollovers than passenger cars because of their higher center of gravity relative to their track width. Multi-trailer articulated heavy vehicles, such as A-doubles, are particularly prone to rollovers because of their articulation and rearward amplification. Electronic stability control (ESC) has been mandated by the National Highway Safety Administration (NHSTA) for Class 8 trucks and busses since 2017. When detecting oversteer or understeer, ESC automatically activates the brakes at the correct side of the steer and/or drive axle(s) to regain steering stability. ESC, however, often cannot sense the likelihood of trailer rollover in multi-trailer articulated heavy vehicles because of the articulation between the trailers and tractors. As a result of this, trailers are often equipped with roll stability control (RSC) systems to mitigate speed-induced rollovers. Sensing the trailer lateral acceleration, RSC activates the trailer brakes to reduce speed and lower the likelihood of rollover. However, a limited number of past studies have shown that the trailer roll angle may provide an earlier indication of a pending rollover than the lateral acceleration. This study intends to provide further analysis in this regard in an effort to improve the effectiveness of RSC systems for trailers. An extensive amount of data from track testing with a 33-ft A-double under heavy and light loading is evaluated. Particular attention is given to lateral accelerations and trailer roll angles prior to rollover and relative to RSC activation time. The study's results indicate that the trailer roll angle provides a slightly earlier indication of rollover than lateral acceleration during dynamic driving conditions, potentially resulting in a timelier activation of RSC. Of course, detecting the roll angle is often more challenging than lateral acceleration, which can be detected with an accelerometer. Additionally, the roll angle measurement may be subjected to errors and possibly unwanted RSC engagement. The study's results further indicate that the trailer-based RSC systems effectively mitigate rollovers in both quasi-steady-state and dynamic driving conditions. / Master of Science / Some of the results of an extensive track testing program at the Center for Vehicle Systems and Safety (CVeSS) at Virginia Tech for evaluating the roll stability of commercial trucks with 33-ft A-double trailers are evaluated. "33-ft A-doubles" commonly refer to a commercial truck that has a tractor with two trailers (in this case 33-ft in length) that are connected by an A-dolly. Their modularity and ease of connecting and disconnecting at various drop stations have made such commercial vehicles a common scene on U.S. highways due to the proliferation of e-commerce cargo. Compared to a single-unit or tractor semi-trailer combination, the double- or triple-trailer configurations offer several logistical benefits that make them more advantageous. The multi-trailer vehicles can carry more cargo per driver, lowering driver, fuel, and equipment costs significantly. There are, however, some challenges to operating multi-trailer articulated vehicles. On average, their accidents are more expensive than single-trailer or single-unit trucks. Additionally, they are more susceptible to rolling over and causing property damage, injuries, and at times fatalities. To reduce rollovers, systems with automated braking, called roll stability control (RSC), are often installed on the trailers. RSC applies the trailer brakes if it senses that the vehicle speed — the primary cause of most commercial vehicle accidents — exceeds the safe limit for negotiating a turn. In this study, we intend to evaluate the effectiveness of roll stability control (RSC) systems for reducing the likelihood of speed-induced rollovers. We will also explore ways of improving their performance. Namely, we will evaluate whether sensing the lateral acceleration of the trailer or its roll angle would provide a better means for timely activation of RSC. The study's results indicate that, although more challenging to measure, the trailer roll angle provides a slightly sooner indication of a pending rollover than lateral acceleration. The results also suggest that RSC systems vastly reduce the number of speed-induced rollovers in trucks with 33-ft A-double trailers under different trailer configurations and cargo weights.

Light vehicle rollover accidents on soft surfaces can be modeled assuming constant drag with linear motion equations and other engineering principles. The concept of using segment average results to evaluate roll mechanics parameters throughout a roll sequence, and specifically, segment duration to evaluate vehicle trajectory between ground impacts is developed. The trajectory model is presented, explained and compared to values obtained by analyzing digital video of rollover crash tests. Detailed film analysis procedures are developed to obtain data from rollover crash tests that are not otherwise documented. Elevation of the center of gravity of vehicles is obtained where instrumentation does not explicitly yield this data. Instantaneous center of gravity elevation data throughout a roll sequence provides the opportunity to calculate descend distances as a vehicle travels from one ground contact to another. This data is used to quantify severity of ground impacts as a vehicle interact with the ground throughout a roll sequence. Segment average analysis is a reasonable method for determining general roll mechanics parameters. Because of the chaotic nature of rollover accidents, the range of effective drag factors for a given roll surface may be quite large. Choosing an average of typical drag factors is a reasonable approach for a first-order approximation although certain parameters may be predicted less accurately than if actual values were known. The trajectory results demonstrate the influence of drag factor descent height calculations. Typical constant drag factors tend to overestimate descent height early in a roll sequence and underestimate descent height later in the sequence. The trajectory model is a useful tool to aid in understanding rollover mechanics although a rolling vehicle may be in contact with the ground for a significant fraction of a roll segment. The model should not be used at locations in roll sequences where there are extremes in translational center of gravity decelerations. These extremes include the segments immediately following overturn where there are large angular accelerations and large differences between the tangential velocity of the vehicle perimeter and the translational velocity of the center of gravity, as well as segments that include vehicle impacts with irregular topography.