A sliding-mode-control-based adaptive cruise controller

This paper presents an alternative solution to the conventional cruise controller of a hybrid electric vehicle based on the sliding mode control approach. The mathematical model of a hybrid electric vehicle cruise control system is developed. Then, the sliding mode control approach is applied as the controller. The sliding mode control stability is investigated and demonstrated. Thereafter, the system is simulated and the results are presented. © 2014 IEEE.

Wear of permanent incisors with age on commercial Australian Angora goat farms

OBJECTIVE: To quantify if, and to what extent, permanent incisor wear differed with age of goat and farm of origin on commercial Australian Angora goat farms. DESIGN: Observations were made on three Angora goat farms in the wheat-sheep zone of Victoria, each managed according to the farmer's practices. Farmers provided a representative flock of does. METHODS: The proportion and pattern of wear of permanent incisors were recorded and percentage wear calculated. After log(y + 10) transformation, a parsimonious general linear model was developed to relate wear to farm and age, with age considered as a continuous variate. RESULTS: The range in wear of the permanent incisors was 0-100%. For each farm, the most parsimonious model for permanent first incisor wear and average wear of all permanent incisors was a separate straight line relating the transformed incisor wear to the age of doe. The models accounted for 66-73% of variance. On each farm the incisor wear was similar and low for ages up to approximately 4 years. On all farms, the amount of incisor wear increased dramatically with age, although the rate of increase differed with each farm. CONCLUSIONS: Permanent incisor wear increased with age of goat and differed with farm of origin. Angora goat farmers need to be aware of the potential for incisor wear to affect doe production and health.

Adaptive fuzzy multi-surface sliding control of multiple-input and multiple-output autonomous flight systems

In this study, we proposed an adaptive fuzzy multi-surface sliding control (AFMSSC) for trajectory tracking of 6 degrees of freedom inertia coupled aerial vehicles with multiple inputs and multiple outputs (MIMO). It is shown that an adaptive fuzzy logic-based function approximator can be used to estimate the system uncertainties and an iterative multi-surface sliding control design can be carried out to control flight. Using AFMSSC on MIMO autonomous flight systems creates confluent control that can account for both matched and mismatched uncertainties, system disturbances and excitation in internal dynamics. It is proved that the AFMSSC system guarantees asymptotic output tracking and ultimate uniform boundedness of the tracking error. Simulation results are presented to validate the analysis.

Multi-surface sliding control of MIMO autonomous flight systems

In this paper, a multi-surface sliding control (MSSC) is proposed for trajectory tracking of 6 degrees of freedom (6-DOF) inertia coupled aerial vehicles with multiple inputs and multiple outputs (MIMO). It is shown that an iterative MSSC design can be carried out to control flight. Using MSSC on MIMO autonomous flight systems creates confluent control that can account for model mismatches, system uncertainties, system disturbances and excitation in internal dynamics. We prove that the MSSC system guarantees asymptotic output tracking and ultimate uniform boundedness of the system. Simulation results are presented to validate the analysis.

Multi-surface sliding control of MIMO autonomous flight systems

In this paper, we present a hardware in the loop simulation of our proposed multi-surface sliding control (MSSC) for trajectory tracking of 6 degrees of freedom (6-DOF) inertia coupled aerial vehicles with multiple inputs and multiple outputs (MIMO). Using MSSC on MIMO autonomous flight systems creates confluent control that can account for both matched and mismatched uncertainties, system disturbances and excitation in internal dynamics. The control law is implemented on an onboard computer and is validated though Hardware-In-the-Loop (HIL) simulations, between the hardware and the flight simulator X-Plane, which simulates the unmanned aircraft dynamics, sensors, and actuators. Simulation results are presented to validate the analysis.

Understanding temperature and contact pressure in hot stamped channels

This paper investigates the temperature and contact pressure conditions in hot stamped channels of boron steel. Hot stamping has been used for many years to produce high strength structural auto-motive components. The high tensile strengths achievable by hot stamping is beneficial where the intrusion during a vehicle crash is not desirable – e.g. for the vehicle occupant compartment. How-ever, the high blank temperatures and high temperature cycling causes a large amount of wear in the tooling. These conditions have led to high tool failures and die maintenance costs. Thus, un-derstanding the main causes of wear behaviour in the hot stamping process is of high interest to hot stampers.
To this aim, a generic 2D thermo-mechanical finite element model of a hat-shaped crash formed hot stamped component was developed (based on the authors previous hot stamp model), and a modified phase transformation model based on Scheil’s additive principle has been applied. The model was created in the finite element software ABAQUS Standard V6.13, including convection and radiation when the component was transferred from furnace to the tool as well as the air-cooling process. A USDFLD subroutine was used to model the phase transformation and a HET-VAL subroutine was used to model the latent heat. Contact heat conductance was a function of the pressure.
The authors have used techniques from their previous work on tool wear estimation for cold stamping to estimate the contact pressure on the tooling, and the amount of sliding that occurs over the tooling, and the corresponding tooling temperature. This data provides a unique data set to understand the wear on the tooling, and will eventually lead to a model for estimating tooling life.

Effect of particle characteristics on the two-body abrasive wear behaviour of a pearlitic steel

The specific wear rate and friction coefficient of a pearlitic microstructure subjected to different abrasive environments (i.e. SiC and alumina) were examined. A CSM high temperature pin-on-disc tribometer was used to simulate the two-body abrasive condition (i.e. the metallic surface abrading against the abrasive particles). The characteristics of the abrasive particles (i.e. particle size and density) revealed a significant impact on the amount of material loss. The specific wear rate of the pearlitic microstructure decreased with a reduction in the abrasive particle size, irrespective of the particle type. In addition, distinct particle deterioration mechanisms were observed during the abrasion process, which was largely determined by the abrasive particle size. Attrition, shelling and fracture were some of the dominant particle deterioration mechanisms occurring in both of the abrasive environments. SEM and EDX analysis on the wear debris displayed a unique metallic chip formation with respect to the particle type. Furthermore, the abrading efficiency (i.e. threshold level) of the abrasive particles was identified by means of interrupted abrasive wear tests. The dense packing nature of the alumina abrasive particles resulted in a significantly higher material removal rate than the SiC abrasive environment.

Comparisons of the two-body abrasive wear behaviour of four different ferrous microstructures with similar hardness levels

The abrasive wear resistance of four distinct metallurgical steel microstructures - bainite, pearlite, martensite and tempered martensite, with similar hardness levels was investigated. A pin-on-disc tribometer was used to simulate the two-body abrasive condition (i.e. the metallic surface abrading against the silicon carbide abrasive particles) and evaluate the specific wear rate of the microstructures. Each microstructure had a unique response towards the abrasion behaviour and this was largely evident in the friction curve. However, the multi-phase microstructures (i.e. bainite and pearlite) demonstrated better abrasion resistance than the single-phase microstructures (i.e. martensite and tempered martensite). Abrasion induced microstructural changes at the deformed surfaces were studied using sub-surface and topographical techniques. The properties of these layers (i.e. surface profile measurements) determined the amount of material loss for each microstructure. These were directly linked to the single-wear track analysis that highlighted a marked difference in their mode of material removal. Ploughing and wedge formation modes were dominant in the case of bainite and pearlite microstructures, whereas the cutting mode could be attributed to the higher material loss in the single-phase microstructures. The combination of brittle and ductile phases in the multi-phase microstructure matrix could be one of the driving factors for their superior abrasion resistance.

Addition of low concentrations of an ionic liquid to a base oil reduces friction over multiple length scales: a combined nano- and macrotribology investigation

The efficacy of ionic liquids (ILs) as lubricant additives to a model base oil has been probed at the nanoscale and macroscale as a function of IL concentration using the same materials. Silica surfaces lubricated with mixtures of the IL trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate and hexadecane are probed using atomic force microscopy (AFM) (nanoscale) and ball-on-disc tribometer (macroscale). At both length scales the pure IL is a much more effective lubricant than hexadecane. At the nanoscale, 2.0 mol% IL (and above) in hexadecane lubricates the silica as well as the pure IL due to the formation of a robust IL boundary layer that separates the sliding surfaces. At the macroscale the lubrication is highly load dependent; at low loads all the mixtures lubricate as effectively as the pure IL, whereas at higher loads rather high concentrations are required to provide IL like lubrication. Wear is also pronounced at high loads, for all cases except the pure IL, and a tribofilm is formed. Together, the nano- and macroscales results reveal that the IL is an effective lubricant additive - it reduces friction - in both the boundary regime at the nanoscale and mixed regime at the macroscale.

Effect of retained austenite on wear resistance of nanostructured dual phase steels

Nanostructured super bainitic and quenching-partitioning (Q&P) martensitic steels with a significant amount of retained austenite obtained by low temperature bainitic transformation and Q&P respectively were studied to explore the effect of retained austenite on stirring wear resistance. The results suggest that the Q&P martensitic steel significantly enhanced the hardness of the worn surface (from 674 to 762 HV1) and increased the thickness of the deformed layer (,3.3 mm), compared to the nanostructured bainitic steel. The underlying reason is that the Q&P martensitic steel has a higher stability of retained austenite thereby providing a superior transformation induced plasticity effect to increase surface hardness and reduce wear rate during the wear process.

Comparison of ductile damage models during scratch tests - a numerical study

The ‘wear mode diagram’ has been commonly used to classify the deformation regime of the soft work-piece during scratching, into three modes: ploughing, wedge formation and cutting. The scratch test is usedto evaluate wear modes and material removal associated with wear. There are different damage models in the literature used for the description of material behaviour after damage initiation under different loadingconditions. However, there has been little analysis to compare damage models during scratch test conditions. The first aim of this work is first to use a finite element modelling package (Abaqus/Explicit) to build a 3Dmodel to capture deformation modes during scratching with indenters with different attack angles. Three different damage models are incorporated into the model and patterns of damage initiation and propagation arecompared with experimental results from the literature. This work highlights the role of the damage model in accurately capturing wear modes and material removal during two body sliding interactions.

The impact of retained austenite characteristics on the two-body abrasive wear behavior of ultrahigh strength bainitic steels

In the current study, a high-carbon, high-alloy steel (0.79 pct C, 1.5 pct Si, 1.98 pct Mn, 0.98 pct Cr, 0.24 pct Mo, 1.06 pct Al, and 1.58 pct Co in wt pct) was subjected to an isothermal bainitic transformation at a temperature range of 473 K to 623 K (200 °C to 350 °C), resulting in different fully bainitic microstructures consisting of bainitic ferrite and retained austenite. With a decrease in the transformation temperature, the microstructure was significantly refined from ~300 nm at 623 K (350 °C) to less than 60 nm at 473 K (200 °C), forming nanostructured bainitic microstructure. In addition, the morphology of retained austenite was progressively altered from film + blocky to an exclusive film morphology with a decrease in the temperature. This resulted in an enhanced wear resistance in nanobainitic microstructures formed at low transformation temperature, e.g., 473 K (200 °C). Meanwhile, it gradually deteriorated with an increase in the phase transformation temperature. This was mostly attributed to the retained austenite characteristics (i.e., thin film vs blocky), which significantly altered their mechanical stability. The presence of blocky retained austenite at high transformation temperature, e.g., 623 K (350 °C) resulted in an early onset of TRIPing phenomenon during abrasion. This led to the formation of coarse martensite with irregular morphology, which is more vulnerable to crack initiation and propagation than that of martensite formed from the thin film austenite, e.g., 473 K (200 °C). This resulted in a pronounced material loss for the fully bainitic microstructures transformed at high temperature, e.g., 623 K (350 °C), leading to distinct sub-surface layer and friction coefficient curve characteristics. A comparison of the abrasive behavior of the fully bainitic microstructure formed at 623 K (350 °C) and fully pearlitic microstructure demonstrated a detrimental effect of blocky retained austenite with low mechanical stability on the two-body abrasion.

Tool wear and surface integrity analysis of machined heat treated selective laser melted Ti-6Al-4V

In this study, the tool wear and surface integrity during machining of wrought and Selective LaserMelted (SLM) titanium alloy (after heat treatment) are studied. Face turning trails were carried out onboth the materials at different cutting speeds of 60,120 and 180 m/min. Cutting tools and machinedspecimens collected are characterized using scanning electron microscope, surface profiler and opticalmicroscope to study the tool wear, machined surface quality and machining induced microstructuralalterations. It was found that high cutting speeds lead to rapid tool wear during machining of SLMTi-6Al-4V materials. Rapid tool wear observed at high cutting speeds in machining SLM Ti-6Al-4Vresulted in damaging the surface integrity by 1) Deposition of chip/work material on the machinedsurface giving rise to higher surface roughness and 2) Increasing the depth of plastic deformationon the machined sub surface.

Impacts of wear and geometry response of the cutting tool on machinability of super austenitic stainless steel

This paper presents a study of tool wear and geometry response whenmachinability tests were applied under milling operations onthe Super Austenitic Stainless Steel alloy AL-6XN. Eight milling trials were executed under two cutting speeds, two feed rates, andtwo depths of cuts. Cutting edge profile measurements were performed to reveal response of cutting edge geometry to the cuttingparameters and wear. A scanning electron microscope (SEM) was used to inspect the cutting edges. Results showed the presenceof various types of wear such as adhesion wear and abrasion wear on the tool rake and flank faces. Adhesion wear represents theformation of the built-up edge, crater wear, and chipping, whereas abrasion wear represents flank wear.Thecommonly formed wearwas crater wear. Therefore, the optimum tool life among the executed cutting trails was identified according to minimum lengthand depth of the crater wear.The profile measurements showed the formation of new geometries for the worn cutting edges due toadhesion and abrasion wear and the cutting parameters.The formation of the built-up edge was observed on the rake face of thecutting tool. The microstructure of the built-up edge was investigated using SEM. The built-up edge was found to have the austeniteshear lamellar structure which is identical to the formed shear lamellae of the produced chip.