Lateral controller design for an unmanned vehicle via Kalman filtering

This paper proposes a lateral control system for an unmanned vehicle that is designed to improve the responsiveness of the system with the use of a PD control. The vehicle heading error can be stabilized, and the transient response characteristics can be improved using the proposed controller. A mathematical model of the vehicle dynamics using two degrees of freedom was developed for the controller design. The waypoint tracking method for autonomous navigation was tested with incorporation of the Point-to-Point algorithm with position and heading measurements received from GPS receivers via Kalman filtering. The performance of the designed controller was verified through experiments with a real vehicle.     

Design optimization of an injection mold for minimizing temperature deviation

The quality of an injection molded part is largely affected by the mold cooling. Consequently, this makes it necessary to optimize the mold cooling circuit when designing the part but prior to designing the mold. Various approaches of optimizing the mold cooling circuit have been proposed previously. In this work, optimization of the mold cooling circuit was automated by a commercial process integration and design optimization tool called Process Integration, Automation and Optimization (PIAnO), which is often used for large automotive parts such as bumpers and instrument panels. The cooling channels and baffle tubes were located on the offset profile equidistant from the part surface. The locations of the cooling channels and the baffle tubes were automatically generated and input into the mold cooling computer-aided engineering program, Autodesk Moldflow Insight 2010. The objective function was the deviation of the mold surface temperature from a given design temperature. Design variables in the optimization were the depths, distances and diameters of the cooling channels and the baffle tubes. For a more practical analysis, the pressure drop and temperature drop were considered the limited values. Optimization was performed using the progressive quadratic response surface method. The optimization resulted in a more uniform temperature distribution when compared to the initial design, and utilizing the proposed optimization method, a satisfactory solution could be made at a lower cost.     

Research on the Brayton cycle design conditions for reliquefaction cooling of LNG boil off

This paper analyses the Brayton cooling cycle for the reliquefaction of the boil off on liquefied natural gas (LNG) vessels. By performing a thermodynamic study, we analysed and evaluated the conditions, parameters and energy consumption required in the process, including the influence of the choice and variation of diverse factors on the operating conditions and power.     

Control of drivers' route choice: Pipe dream or panacea?

In most large cities traffic flow is controlled or manipulated in a number of ways. The methods used are mostly negative in the sense that they restrict the driver's choice of alternative routes rather than encourage him to use a particular one. This paper reviews some of the conventional measures and goes on to consider whether a more positive approach to route control might be justified, by inducing a more efficient or acceptable pattern of traffic movement in urban areas. The principal criteria for an efficient pattern are taken to be the total rate of expenditure of vehicle mileage and the frequency of route crossings, and an attempt is made to evaluate the potential benefits of route control in these terms. Social, technical and political considerations suggest that compulsory control will not be feasible for some time (at least, in the UK), but if the benefits to drivers as individuals can be shown to be worthwhile an advisory system might be practicable. Some possible systems are briefly outlined.The author is grateful to the City Engineer of Westminster City Council, Mr A.J. Cryer, for permission to publish this paper,which, however, does not necessarily represent the views . City Council. The author is greatly indebted to E. M. Holroyd for numerous suggestions and advice.     

Study of the Impact of Single-and Double-tube Tunnel Systems on Rockburst in Deep-buried Extra-long Tunnelling北大核心CSCD

Rockburst is one of the main disasters for tunnelling under high ground stress. Taking the rockburst section of Ping'an Tunnel with high ground stress, which is located on Chengdu-Lanzhou Railway, as the study object, this paper adopts combined methods of filed measurement, numerical analysis, and laboratory test, and with respect to rockburst development mechanism, energy density change and rockburst strength it comprehensively analyzes the impact of two construction schemes (single-tube double-track tunnel system and double-tube single-track tunnel system) on the rockburst in deep-buried extra-long tunnels with high ground stress. The study results show that the order relation of maximum energy density at various locations of the tunnel is Uside wall >Uhance >Utunnel face >Uvault, and rockburst easily occurs at the working face of the tunnel section to be excavated and both side walls of excavated and supported section; compared with vault, hance, side wall and other locations, more energy would be released at the tunnel face, and the stress release holes shall be reasonably installed in the process of excavation; the doubletube single-track tunnel system scheme can effectively reduce the rockburst intensity and the rockburst hazards, so as to better avoid the occurrence of rockburst. © 2022, Editorial Office of Modern Tunnelling Technology. All right reserved.     

某富水断层隧道涌水治理方案优化分析及工程应用北大核心CSCD

以武九高速高楼山公路隧道为例,针对以断层破碎带为主控因素的隧道突水治理问题展开数值分析研究。基于FLAC 3D有限差分法及流固耦合分析原理,研究了导水洞排水、注浆堵水和排堵结合等不同治理方式对隧道涌水量及围岩稳定性的影响。结果表明:对于富水断层隧道发生A、B级别的大量涌水时,建议同时采取导水洞排水、注浆堵水的排堵结合措施,导水洞设置在近断层处,且与隧道相对距离为0.75(D+l),注浆圈厚度控制在7 m以内,注浆圈相对渗透系数比不超过10,既能降低涌水量,又能保证围岩的稳定性;对于C级涌水隧道,可采取注浆措施,注浆厚度不低于3 m,相对渗透系数不低于20;对于D级及以下涌水隧道,采取常规抽排水措施即可。     

Facing the realities of non-motorized transportation in developing countries

The objective of this paper is to assess issues concerning non-motorized transportation in developing countries. This assessment is done through an examination of three topics: a brief overview of the transportation picture in developing countries; a study of city size and city form vis-a-vis pedestrian movement; and, a look at the characteristics of non-motorized modes, including their capacities. An analysis and discussion attempt to sort out the crucial issues connected with pedestrian planning in particular, and non-motorized transport in general. It is concluded (1) that special attention be paid to space/time capacity/cost issues connected with non-motorized modes (2)that some of the low-cost intermediate technology modes be examined for possible inclusion in traffic streams (3)that land-use patterns need to be rearranged keeping in mind the limitations of non-motorized modes, and (4)that the extent to which physical trip-making can be substituted by telecommunication needs to be examined very critically. An agenda for action reflects these concerns.     

A Methodology for estimating traffic safety improvements at intersections

Intersection accidents represent a significant proportion of overall motor vehicle accidents. More accurate estimates of the actual effectiveness of intersection safety improvements are required. This study develops an improved methodology for post-implementation evaluation of safety countermeasures at intersections. Accidents are random, rarely occurring events. For a given time period, this leads to random fluctuations in accident frequencies, which suggests that statistical analysis employing confidence intervals, rather than point estimates, is required. Two technical problems complicate this treatment of accident occurrence as a random variable. The first problem is that identifying of hazardous locations is generally based on above-average accident frequency during the most recent period(s) for which data is available. The second problem arises from changes in external factors such as traffic volume, motor vehicle safety standards, etc., during the period of analysis, which may also affect traffic safety. A “combined” approach which addresses these technical issues is developed. Empirical Bayesian methodology is combined with regression techniques to derive a more accurate measure of the effect of safety treatments. An important consideration is the derivation of the variance of this measure, so that appropriate confidence intervals may be constructed. The approach is then applied to a sample of locations that underwent treatment by the Massachusetts Department of Public Works (MDPW). We compare our results to those which might be obtained using alternative methodologies that correct for neither or only one of the technical problems. We also illustrate how preliminary conclusions may be drawn regarding the effectiveness of broad categories of treatments, and how individual sites requiring further investigation may be identified.     

Freight Transport Deceleration: Its Possible Contribution to the Decarbonisation of Logistics

The paper challenges the conventional view that the movement of goods through supply chains must continue to accelerate. The compression of freight transit times has been one of the most enduring logistics trends but may not be compatible with governmental climate change policies to cut greenhouse gas emissions by 60–80% by 2050. Opportunities for cutting CO₂ emissions by ‘despeeding' are explored within a freight decarbonisation framework and split into three categories: direct, indirect and consequential. Discussion of the direct carbon savings focuses on the trucking and deep-sea container sectors, where there is clear evidence that slower operation cuts cost, energy and emissions and can be accommodated within current supply chain requirements. Indirect emission reductions could accrue from more localised sourcing and a relaxation of just-in-time (JIT) replenishment. Acceleration of logistical activities other than transport could offset increases in freight transit times, allowing the overall carbon intensity of supply chains to reduce with minimal loss of performance. Consequential deceleration results from other decarbonisation initiatives such as freight modal split and a shift to lower carbon fuels. Having reviewed evidence drawn from a broad range of sources, the paper concludes that freight deceleration is a promising decarbonisation option, but raises a number of important issues that will require new empirical research.