A numerical control algorithm for navigation of an operator-driven snake-like robot with 4WD-4WS segments

This paper presents a new algorithm for the control of a snake-like robot with passive joints and active wheels. Each segment has four autonomously driven and steered wheels. The algorithm approximates the ideal solution in which all wheels on a segment have the same centre of curvature with wheel speeds, providing cooperative redundancy. Each hitch point joining segments traverses the same path, which is determined by an operator, prescribing the path curvature and front hitch speed. The numerical algorithm developed in this paper is simulation tested against a previously derived analytical solution for a predetermined path. Further simulations are carried out to show the effects of changing curvature and front hitch speed on hitch path, wheel angles and wheel speeds for a one, two and three segment robot

A numerical control algorithm for a B-double truck-trailer with steerable trailer wheels and active hitch angles

This paper presents a new algorithm for the control of a B-double truck–trailer with steerable trailer wheels and active hitch angles, designed to minimize both off-tracking and scuffing. Each trailer has six autonomously steered double wheels, although each double wheel is modelled by a centrally placed single wheel. Each hitch point, joining truck to first trailer and first trailer to second trailer, as well as a nominated point central to the axles of the second trailer, traverses the same path which is determined by an operator controlling the path curvature and truck speed. The algorithm approximates the ideal solution in which all wheels on each trailer have the same centre of curvature. The actively controlled hitch angles, satisfying the path-following constraints, provide a further level of cooperative redundancy of steering systems. Simulations are carried out to show the effects of changing curvature and front hitch speed on hitch path, wheel angles, and hitch angles as well as the accuracy of the algorithm. Further simulation is carried out to show the improvement in off-tracking of the new control system over current B-double fixed-wheel systems

A numerical control algorithm for a B-double truck-trailer with steerable trailer wheels and active hitch angles. Part 2: reversing

The authors have previously proposed a solution to the twin problems of wheel scuffing and off-tracking of B-double truck–trailer vehicles thereby reducing tyre wear and environmental damage as well as improving maneuverability. The solution to the scuffing problem requires that trailer axles in excess of one per trailer must have steerable wheels. However, if all trailer wheels are steerable, then the off-tracking problem can also be solved. The previous work devised an algorithm for a B-double in forward motion, whereby an on-board computer would be used to calculate the correct wheel and hitch angles and a control system would implement these angles. The purpose of the present technical note is to complete the study of a numerical algorithm for navigating a B-double truck–trailer vehicle by considering travel in the reverse direction. In this case the angle of the front wheels of the truck must also be controlled by the on-board computer. The algorithm for determining the effective angle of the truck’s steerable wheels is derived using an innovative combination of vector geometry and calculus and completes the total control system for these B-double vehicles. The paper concludes with a simulation study of the control algorithm demonstrating its versatility for reversing along twisting paths and effectiveness in reducing off-tracking

Vehicles with cooperative redundant multiple steering systems: Alternative driver interfaces

This paper presents the results of calculations of the wheel angles and the drive wheel speeds to ensure that the steering effect of the wheel angles and the steering effect of the speeds of the drive wheels are identical. These calculations are general insofar as the centre of curvature of the path of the centre of the vehicle can lie anywhere in the 'horizontal' plane, including within the plan view of the vehicle. These minimal turning circles at times require large wheel angles and large differences in the drive wheel speeds. When the driver selects a centre of curvature inside the rectangle defined by the wheelbase and the track, problems arise owing to the multiple solutions of the arctan function. This problem is solved so that flipping of the wheels through 180° is avoided. Similar problems can arise in the calculation of the correct wheel speed because of the ambiguity of the square root function, which has both positive and negative roots. This problem is also solved. Alternative driver interfaces are described in detail. Vehicles with cooperative redundant multiple steering systems promise safety benefits relative to vehicles with a single non-redundant steering system and environmental benefits relative to vehicles with conflicting redundant multiple steering systems. The safety benefits result from increased traction, stability and manoeuvrability (especially on hills). The environmental benefits include reduced ground damage, tyre wear and fuel wastage on turning. These vehicles would be used to best advantage as extreme off-road vehicles. The general case of vehicles described is capable of both pure rotation and pure translation in any direction, and all motion in between. This maximized manoeuvrability also makes the system ideal for vehicles operating in confined spaces, such as forklift trucks

Data Mining of Telematics Data: Unveiling the Hidden Patterns in Driving Behaviour

With the advancement in technology, telematics data which capture vehicle movements information are becoming available to more insurers. As these data capture the actual driving behaviour, they are expected to improve our understanding of driving risk and facilitate more accurate auto-insurance ratemaking. In this paper, we analyze an auto-insurance dataset with telematics data collected from a major European insurer. Through a detailed discussion of the telematics data structure and related data quality issues, we elaborate on practical challenges in processing and incorporating telematics information in loss modelling and ratemaking. Then, with an exploratory data analysis, we demonstrate the existence of heterogeneity in individual driving behaviour, even within the groups of policyholders with and without claims, which supports the study of telematics data. Our regression analysis reiterates the importance of telematics data in claims modelling; in particular, we propose a speed transition matrix that describes discretely recorded speed time series and produces statistically significant predictors for claim counts. We conclude that large speed transitions, together with higher maximum speed attained, nighttime driving and increased harsh braking, are associated with increased claim counts. Moreover, we empirically illustrate the learning effects in driving behaviour: we show that both severe harsh events detected at a high threshold and expected claim counts are not directly proportional with driving time or distance, but they increase at a decreasing rate

Assessment of wound healing: validity, reliability and sensitivity of available instruments

Objectives: If wound assessment instruments are to be used in the periodic assessment of wound healing, they must prove to be valid, reliable and sensitive measures of wound healing. Thus, this systematic literature review aims to examine available wound healing instruments in terms of these parameters. Method: Only instruments able to measure changes in wound healing were included in this review and not those used to predict healing, classify wounds, or measure wound characteristics per se. All wound types were suitable for inclusion. Results: A total of 20 articles were found, evaluating the validity of 10 instruments used to monitor wound healing. No instrument satisfied all criteria required for instrument validation. Instruments used to assess pressure ulcers, notably the Pressure Ulcer Scale for Healing (PUSH) and Pressure Sore Status Tool (PSST), had been validated to the greatest extent, whilst those describing healing in leg ulcers and general or surgical wounds tended to lack comprehensive and quality evaluation. Conclusion: This review identified substantial gaps in the literature with regard to validation of existing wound healing instruments. Future studies are needed to comprehensively validate these instruments

A Posteriori Risk Classification and Ratemaking with Random Effects in the Mixture-of-Experts Model

A well-designed framework for risk classification and ratemaking in automobile insurance is key to insurers' profitability and risk management, while also ensuring that policyholders are charged a fair premium according to their risk profile. In this paper, we propose to adapt a flexible regression model, called the Mixed LRMoE, to the problem of a posteriori risk classification and ratemaking, where policyholder-level random effects are incorporated to better infer their risk profile reflected by the claim history. We also develop a stochastic variational Expectation-Conditional-Maximization algorithm for estimating model parameters and inferring the posterior distribution of random effects, which is numerically efficient and scalable to large insurance portfolios. We then apply the Mixed LRMoE model to a real, multiyear automobile insurance dataset, where the proposed framework is shown to offer better fit to data and produce posterior premium which accurately reflects policyholders' claim history