Proceedings of the Institution of Mechanical Engineers,Part D: Journal of Automobile Engineering

A study was performed to investigate the human ability to detect road surface type on the basis of the associated steering wheel vibration feedback. Tangential direction acceleration time histories measured during road testing of a single mid-sized European automobile were used as the basis for the study. Scaled and frequency-filtered copies of two base stimuli were presented to test subjects in a laboratory setting during two experiments that each involved 25 participants. Theory of signal detection (TSD) was adopted as the analytical framework, and the results were summarized by means of the detectability index d' and as receiver operating curve (ROC) points. The results of the experiment to investigate the effect of scaling suggested monotonic relationships between stimulus level and detection for both road surfaces. Detection of the tarmac surface improved with reductions in acceleration level, while the opposite was true of the cobblestone surface. The ROC points for both surfaces were characterized by gradual increases in detectability as a function of acceleration level, obtaining hit rates of nearly 100 per cent at optimum. The results of the experiment to investigate the effect of frequency bandwidth suggested a monotonically increasing relationship between detectability and the bandwidth of the vibration stimuli. Detection of both road surfaces improved with increases in bandwidth. Average hit rates exceeded 80 per cent for stimuli covering the frequency range from 0 to 80 Hz. Human detection of road surface type appears to depend on the long-term memory model, or cognitive interpretation mechanism, associated with each surface. The complexity of the measured response suggests the need to categorize and classify incoming data before an optimal choice of feedback stimuli can be made in automotive steering systems.

Since it is difficult to establish an accurate dynamic model of a physical active suspension system for a model-based control design, various model-free approaches have been introduced in this field of application. This paper proposes a functional approximation-based adaptive sliding controller with fuzzy compensation for a quarter-car active suspension system. The functional approximation technique is employed to represent the unknown function and release the model-based requirement of a sliding mode control. In addition, a self-tuning fuzzy scheme is introduced to compensate the model approximation error for improving the control performance. The update laws for the coefficients of the Fourier series functions and the fuzzy tuning parameters can be derived from the Lyapunov function directly for guaranteeing the system stability. The simulation results show that the proposed control approach can suppress effectively the vibration amplitude of this suspension system under severe external uncertainties. The dynamic performance of this proposed controller is compared with that of the adaptive sliding controller without fuzzy compensation to show the performance improvement of the inducing of fuzzy control loop.

Multidisciplinary design optimization based on independent subspaces (MDOIS), which is a multidisciplinary design optimization (MDO) algorithm, has been recently proposed. Since MDOIS is relatively simple compared with other MDO algorithms, it is easy to apply MDOIS to practical engineering problems. In this research, an MDO problem is defined for the design of a belt-integrated seat (BIS) while considering crashworthiness. The crash model consists of an airbag, a BIS, an energy-absorbing steering system, and a safety belt. It is found that the current design problem has two disciplines - structural non-linear analysis and occupant analysis. The interdisciplinary relationship between the disciplines is identified. Interdisciplinary variables between the two disciplines are stiffness of the seat back frame and the belt load. The interdisciplinary relationship is addressed in the system analysis step in MDOIS. Prior to each independent subspace design, values of interdisciplinary variables at a given design point are determined in the system analysis step. The determined values are passed to corresponding subspaces, and the subspaces treat the received values of the interdisciplinary variables as constant parameters throughout the subspace design. For the present example, the belt load is passed to the structural analysis subspace and the stiffness of the seat back frame is passed to the occupant analysis subspace. Determined design variables in each subspace are passed to the system analysis step. In this way, the design process iterates until the convergence criterion is satisfied. As a result of the design, the weight of the BIS and the head injury criterion (HIC) of an occupant are reduced while the specified constraints are satisfied. Since the system analysis cannot be formulated in an explicit form in the current example, an optimization problem is formulated to solve the system analysis. The results from MDOIS are discussed.

Car-rear-impact-induced cervical spine injuries present a serious burden on society and, in response, seats offering enhanced protection have been introduced. Seats are evaluated for neck protection performance but only at one specific backrest angle, whereas in the real world this varies greatly owing to the variation in occupant physique. Changing the backrest angle modifies the seat geometry and thereby the nature of its interaction with the occupant.

Low-velocity rear-impact tests on a BioRID II anthropomorphic test dummy (ATD) have shown that changes in backrest angle have a significant proportionate effect on dummy kinematics. A close correlation was found between changes in backrest angle and the responses of neck injury predictors such as lower neck loading and lower neck shear but not for the neck injury criterion NIC_max. Torso ramping was evident, however, with negligible effect in low-velocity impacts.

The backrest angle ranged from 20° to 30° whereas the BioRID II spine was adapted to a range from 20° to 26.5°. Nevertheless, in general, instrumentation outputs correlated well, indicating that this ATD could be used for evaluating seats over a 20–30° range rather than solely at 25° as required by current approval test specifications.

Numerical and experimental investigations shed light on the root causes leading to the emergence and persistence of an acute metallic noise in rear wheel drive light truck drivelines. Sudden demands in engine output torque combined with the presence of lash zones give rise to a phenomenon that is onomatopoeically referred to as clonk. Its multi physics nature requires a comprehensive study, which includes rigid multi-body dynamics, flexible body oscillations, and noise radiation computation. The verification of numerical results is achieved through the design and implementation of a transient dynamic experimental rig, which comprises the complete drivetrain from the engine flywheel to the rear axle. Parametric studies reveal high-frequency contributions in the driveline vibration response of certain structural modes of the driveshaft pieces, which are induced by remote impact of meshing transmission teeth through backlash. The numerically predicted spectrum of vibration is in good qualitative agreement with the experimental measurements. Combined study of the aforementioned results reveals the components that amplify the clonk noise.

Combining both launch and reverse drive functions with the ratio change function in a geared neutral continuously variable transmission (GN-CVT), thus making a launch device like a torque converter and a drive-neutral-reverse (DNR) set obsolete, is attracting considerable attention. This paper covers the modelling and simulation of a V-belt geared neutral transmission in and around the geared neutral point. Owing to the specific nature of the geared neutral state, conventional driveline simulation models are shown to be inadequate. Experimental results are presented, allowing a more detailed description of the functional properties of the V-belt variator, especially those related to small amounts of slip between the belt and the pulleys. The measured data will be analysed to obtain grey model fitting parameters, which allow the data to be used in a simulation program based on a dynamic driveline model. It will be shown that, with a GN-CVT, stall and launch performance can be considerably better than that achieved with a driveline with a torque converter (TC).

Having in mind con-rods for motorbike and car engines, and spurred by the disagreements evidenced in the pertinent literature, the maximum circumferential stresses within the small end are investigated analytically, photoelastically, and numerically. The analytical models are based upon a plane assumption, and they adopt both beam and theory of elasticity idealizations. The plane photoelastic study concentrates on small ends with outer to inner radii ratios ranging from 1.2 to 1.5. A plane numerical model aimed at thoroughly mimicking the pin ovalization is developed, and a design chart of the peak hoop stress within the small end is provided for a wide spectrum of small end and pin geometries, for zero initial clearance. Such diagrams allow a prompt preliminary dimensioning of the small end to be carried out, which may be refined by effecting a three-dimensional finite element study of the specific con-rod geometry. The consequences of an initial clearance between small end bore and gudgeon pin are examined for selected geometries, and three-dimensional aspects are explored for specific con-rod shapes.

This paper provides an adaptive technique for the control of a variable geometry turbine (VGT) in a turbocharged compression ignition engine. The adaptive control is based on a fuzzy logic control scheme and a least-squares parameter estimator algorithm. In order to test the performance of the proposed control technique, a numerical model of the engine has been used, which employs a thermodynamic (zero-dimensional) approach. The paper will show that the fuzzy logic control technique is able to take into account the non-linearity of the controlled system and to reject white noise affecting the measurement chain.

This paper addresses the problem of controlling a turbocharged diesel engine so as to minimize NO_x and smoke emissions while ensuring that the driver's torque demands are met. A diesel engine equipped with a variable-geometry turbocharger (VGT) and an exhaust gas recirculation (EGR) valve is considered. The technical challenges in the control design task include the multivariable non-linear dynamics of the system and the unavailability of key states for feedback. A control strategy based on non-linear control synthesis is developed and shown accurately to control the air-fuel ratio (AFR) and the burned gas fraction in the intake manifold, F ₁, to desired values in the presence of changing operating conditions. The variables F ₁ and AFR are shown to be crucial for feedback. Since neither of these variables can be measured, an observer based on flow and pressure sensor measurements is developed for their real-time estimation. Lyapunov theory is used to show that the developed observer is asymptotically stable. Simulation results confirm the performance of the observer and the observer-based feedback controller. The importance of the developed observer extends beyond the application discussed in this paper. It could be useful for a wide variety of different control and diagnostic applications in diesel engines.