Estimation of the normal contact stiffness for frictional interface in sticking and sliding conditions

Modeling of frictional contact systems with high accuracy needs the knowledge of several contact parameters, which are mainly related to the local phenomena at the contact interfaces and affect the complex dynamics of mechanical systems in a prominent way. This work presents a newer approach for identifying reliable values of the normal contact stiffness between surfaces in contact, in both sliding and sticking conditions. The combination of experimental tests, on a dedicated set-up, with finite element modeling, allowed for an indirect determination of the normal contact stiffness. The stiffness was found to increase with increasing contact pressure and decreasing roughness, while the evolution of surface topography and third-body rheology affected the contact stiffness when sliding

Performance of Anti-Lock Braking Systems Based on Adaptive and Intelligent Control Methodologies

Automobiles of today must constantly change their speeds in reaction to changing road and traffic circumstances as the pace and density of road traffic increases. In sophisticated automobiles, the Anti-lock Braking System (ABS) is a vehicle safety system that enhances the vehicle's stability and steering capabilities by varying the torque to maintain the slip ratio at a safe level. This paper analyzes the performance of classical control, model reference adaptive control (MRAC), and intelligent control for controlling the (ABS). The ABS controller's goal is to keep the wheel slip ratio, which includes nonlinearities, parametric uncertainties, and disturbances as close to an optimal slip value as possible. This will decrease the stopping distance and guarantee safe vehicle operation during braking. A Bang-bang controller, PID, PID based Model Reference Adaptive Control (PID-MRAD), Fuzzy Logic Control (FLC), and Adaptive Neuro-Fuzzy Inference System (ANFIS) controller are used to control the vehicle model. The car was tested on a dry asphalt and ice road with only straight-line braking. Based on slip ratio, vehicle speed, angular velocity, and stopping time, comparisons are performed between all control strategies. To analyze braking characteristics, the simulation changes the road surface condition, vehicle weight, and control methods. The simulation results revealed that our objectives were met. The simulation results clearly show that the ANFIS provides more flexibility and improves system-tracking precision in control action compared to the Bang-bang, PID, PID-MRAC, and FLC

Quantifying non-exhaust emissions and the impact of hybrid and electric vehicles using combined measurement and modelling approaches

Road traffic is a significant emission source of urban particulate matter (PM). Due to the implementation of exhaust regulatory standards in the UK, PM emissions which arise from the wear of brakes, tyres and the road surface, together with the resuspension of road dust are now predicted to exceed tailpipe emissions. While a growing body of academic literature has developed in recent years, non-exhaust emissions (NEE) remain unregulated and largely understudied, and the impact of powertrain electrification on the vehicle fleet has not been quantified. Thus, the aim of this thesis is to improve our understanding of these important emission sources and to determine the impact of NEE on urban air pollution - both now, and in the future. A series of highly time-resolved atmospheric measurement campaigns has been undertaken at roadside and background locations to determine roadside traffic increments. These measurements provide a comprehensive dataset of traffic emissions in London, Birmingham and Manchester, incorporating locations with different vehicle mix and speed, during summer and winter periods. PM mass and elemental tracers have been used to estimate the contribution of NEE concentrations using a scaling factor approach. A novel CO2 dilution approach has been undertaken to determine average fleet emission factors (EFs), whilst the impact of electric vehicle regenerative braking has also been simulated. The results indicate that NEE concentrations and EFs are highly dependent upon meteorological conditions, traffic speed, traffic volume and vehicle class. Brake wear is the dominant source of road traffic PM emissions in congested environments, whilst for each emission source, heavy duty vehicles (HDVs) contribute an order of magnitude greater than light duty vehicles (LDVs). On the other hand, despite the predicted increase in mass, the regenerative braking simulations suggest that passenger vehicles under electric powertrains will reduce brake wear emissions by 65 – 95%. This reduction depends on the assessed drive cycle and vehicle class, highlighting the importance of driving style on future brake wear emissions. The EFs developed in this thesis have been combined with traffic forecasts to project total national emissions in the UK up to 2035 – and can be used to validate the national atmospheric emission inventory. To conclude, a number of recommendations have been made with respect to air quality measurement strategies and emission policies which are needed to further our understanding of NEE, and to reduce these traffic-related emissions. It is proposed that a multi-disciplinary study should be undertaken encompassing laboratory dynamometer testing, on-vehicle measurements and environmental atmospheric measurements.Open Acces

Experimental Study on Road Friction Variation and Stopping Distance Uncertainty using ABS Braking Data

This paper investigates the remaining fluctuation of road friction and stopping distance when the contribution from known sources has been removed. This fluctuation can serve as uncertainty for active safety functions relying on friction estimates. Data from repeated ABS brake maneuvers on several uniform road conditions, including high and low friction surfaces, is analyzed. Road friction estimates are obtained and used to estimate the uncertainty in road friction and stopping distance. Measurements from the same road segment show a friction uncertainty of less than 0.1 with the presented procedure. The stopping distance uncertainty becomes considerable at high speeds and low friction for the intended use in emergency brake functions. Especially for low friction, high estimate accuracy is motivated

Enhanced Sliding Mode Wheel Slip Controller for Heavy Goods Vehicles

This paper introduces an improved version of a sliding mode slip controller for pneumatic brake system ofheavy goods vehicles, HGVs. Using the Fast Actuating Brake Valve, FABV, allows to adopt advance control approaches forwheel-slip controllers which provide features such as fast dynamic response, stability and robustness. In this paper, the slidingmode algorithm which was developed for the speed dependent wheel slip control using the FABV hardware is analysed andimproved. The asymptotic convergence properties of the control algorithm are proven using Lyapunov stability theory and therobustness of the method is investigate

Simulation of the Thermal Behavior of Cast Iron Brake Block during Braking Maneuvers

In recent years, the interest in monitoring the operating conditions of freight wagons has grown significantly to improve the safety of railway vehicles. The railway research group of the Politecnico di Torino has been working for years on the development of solutions to effectively monitor the operating conditions of passenger and freight rail vehicles. As part of the national Cluster ITS Italy 2020 project funded by Italian ministry of education, university and research (MIUR), the Politecnico di Torino has collected a considerable amount of data thanks to the wired and wireless prototypes developed. The data obtained are used in this paper for the validation and calibration of a finite element (FE) model that simulates the temperature variation of a cast iron brake block due to braking operations of an intermodal freight wagon. The developed model can be a useful tool to predict the temperature at the wheel–shoe interface as a function of the current operating conditions since a direct measurement is not easy to perform

Design and Characterization of a Single Lever Bicycle Brake with Hydraulic Pressure Proportioning

Featured Application: The work described here aims to design and characterize a more efficient bicycle braking system. In 2019, the Centers for Disease Control and Prevention estimated that 329,000 Americans were injured in cycling-related incidents. Since the first bicycle brake in 1817, there has been an individual brake lever for decelerating each wheel, while on cars, there has been a single control lever for decelerating multiple wheels since 1921. To perform an emergency stop on a bicycle, the rider must proportion hand pressure on each brake lever and simultaneously vary hand pressure throughout the duration of the maneuver to match the variations of normal force on each tire. Only highly skilled riders, with years of training and practice, can correctly proportion brake pressure to maximize available traction and thus minimize stopping distances. The objective of this study is to simulate and prototype a hydraulic, single-lever bicycle brake system, integrating front and rear brake proportioning, which minimizes stopping distance compared to dual-lever simulations. A design is developed to address the brake proportioning issue. Based on the simulations and physical model, the prototype proportioning valve decreased simulated stopping distances up to 18%. Exploring a range of bike types and scenarios, stopping distances were decreased between 13% and 26%. Simulating an ideal proportioning valve, stopping distances were further decreased between 4% and 40%. These results show that there can be an advantage to brake proportioning technologies in bicycles

The Influence of Propyl gallate Antioxidant on the Performance and Emission Characteristics of a Diesel Engine Fueled with Blends of khaya senegalensis (Mahogany) Biodiesel

The continuous rise in the total earth’s atmospheric temperature is basically attributed to the greenhouse effects occasioned by increased levels of CO2 and other air pollutants. The objective of this study was to investigate the Influence of propyl gallate antioxidant on the performance and emission characteristics of a diesel engine fueled with blends of khaya senegalensis (Mahogany) biodiesel on a TD 110-TD 115 single cylinder four-stroke internal combustion diesel engine under constant speed (1500 rpm) and varying load (L1, L2, L3 and L4) conditions coupled with SV 5Q automobile exhaust gas analyser. Khaya senegalensis biodiesel was produced at optimized reaction conditions using reaction variables, viz, 6:1 methanol/oil molar ratio, 0.84 wt. % catalyst concentration, 70◦C temperature and 60 min reaction time. Selected physicochemical properties of the biodiesel blends were determined using American Society for Testing and Materials (ASTM) standard procedures. The fuels used in the analyses are B0, B20, B30 and B100. Propyl gallate antioxidant were added at 1000 ppm concentration to B20, B30 and B100 to study their effect. The results showed that the PG-treated B20, B30 and B100 blend decreased the BP by 21.94%, 12.12% and 36.17% as compared to B20, B30 and B100 fuel blends, but increase by 0.99% for B20PG at L4, and increased BSFC by 21.47%, 15.42% and 22.63%. At load L4, the BSFC increase for B20PG and B100PG by 12.70% and 1.35%, and reduces for B20PG by 8.09%. BTE decreases for B20 and B100 by 28.39%, 18.63% and 34.42%, while B30PG show an increase of 8.02%. Also, B20PG recorded a drop in EGT by 15.40%, while B30PG and B100PG had 1.90% and 3.33% increases at a higher load. It is noted that the addition of PG to diesel–biodiesel blend caused to lower emissions (CO, CO2, HC, and NOx).CO reduces by 0.02 and 0.01% for B30 and B100, CO2 emission reduces by 2.13%, 2.26% and 15.0%, while, HC emission reduce by 12.73, 18.18 and 25.45% respectively at engine load L1 and 14.81, 20.37 and 24.07% at engine load L4 and NOx decreases by B20 (13.85%), B30 (21.54%), B100 (41.54%) compared to that of diesel (B0). The utilization of KSO biodiesel for engine application and the reduction in exhaust emissions was found to be a viable means of heightening adoption of sustainable biofuels and minimizing pollutant emissions from the combustion of fossil fuels. However, further research to incorporate the use of this additive in actual automobile applications is recommended to be carry out

Interfacial Dissipative Phenomena in Tribomechanical Systems

The book is a collection of articles on the themes of contact mechanics and non-linear dynamics. In particular, the contribution focus on the mechanisms that lead to interfacial energy dissipation, which is a crucial quantity to determine in order to correctly predict the non-linear dynamic response of mechanical systems. The book is a collection of nine journal papers, among those one editorial, one review paper, and seven articles. The papers consider different dissipative mechanisms, such as Coulomb friction, interfacial adhesion, and viscoelasticity, and study how the system response and stability is influenced by the interfacial interactions. The review paper describes old and recent test rigs for friction and wear measurements, focusing on their performance and range of operability

Full-scale dynamometer tests of composite railway brake shoes including latxa sheep wool fibers

The main target of the present work is to characterize the effect of the inclusion of natural sheep wool (SW) into a railway brake block composition and then to compare it to that of a set of three organic fibers commonly used in the friction material industry: aramid fiber (AF), cellulose fiber (CF) and polyacrylonitrile fiber (PAN). In order to achieve this, 4 versions of the same friction material with a fixed amount of each organic fiber were produced and one more sample was manufactured including no organic fibers. The characterization work consisted of friction tests on a full-scale railway test rig. Then, the samples were SEM analyzed in order to characterize the tested surface microstructure. It was found that all organic fibers helped achieve a more stable bedding, and showed lower friction in wet conditions. They also affected the recovery %. Pictures of the blocks were taken after certain phases of the test and, although the failure sequence remained the same for all samples, the organic fibers very much influenced the magnitude of the wear rates. Sheep wool led to better results than cellulose. No final conclusions could be drawn with respect to metal pick-up. SEM analysis evidenced primary and secondary plateaus, but no significant differences were observed depending on the fiber nature. Finally, a Life Cycle Assessment with a “from cradle to gate” perspective was carried out. Ecoinvent v3.5 database and CML and ReCiPe Endpoint methodologies were used to evaluate the environmental impact create by the five brake block materials. Overall, cellulose, PAN and sheep wool brake blocks show slightly lower environmental impacts that the base material or than aramid fibers. Therefore, Latxa sheep wool offers a good balance between low cost, adequate wear rates and environmental impact, making it a compelling substitute for cellulose fibers