Block Vibration Research Articles

Closed-form rocking vibration of rigid block under critical and non-critical double impulse

Closed-form rocking vibration of rigid block under critical and non-critical double impulse

Real time identification of the internal combustion engine combustion parameters based on the vibration velocity signal

Accurate combustion parameters are the foundations of effective closed-loop control of engine combustion process. Some combustion parameters, including the start of combustion, the location of peak pressure, the maximum pressure rise rate and its location, can be identified from the engine block vibration signals. These signals often include non-combustion related contributions, which limit the prompt acquisition of the combustion parameters computationally. The main component in these non-combustion related contributions is considered to be caused by the reciprocating inertia force excitation (RIFE) of engine crank train. A mathematical model is established to describe the response of the RIFE. The parameters of the model are recognized with a pattern recognition algorithm, and the response of the RIFE is predicted and then the related contributions are removed from the measured vibration velocity signals. The combustion parameters are extracted from the feature points of the renovated vibration velocity signals. There are angle deviations between the feature points in the vibration velocity signals and those in the cylinder pressure signals. For the start of combustion, a system bias is adopted to correct the deviation and the error bound of the predicted parameters is within 1.1°. To predict the location of the maximum pressure rise rate and the location of the peak pressure, algorithms based on the proportion of high frequency components in the vibration velocity signals are introduced. Tests results show that the two parameters are able to be predicted within 0.7° and 0.8° error bound respectively. The increase from the knee point preceding the peak value point to the peak value in the vibration velocity signals is used to predict the value of the maximum pressure rise rate. Finally, a monitoring frame work is inferred to realize the combustion parameters prediction. Satisfactory prediction for combustion parameters in successive cycles is achieved, which validates the proposed methods.

Unified approach to engine cylinder pressure reconstruction using time-delay neural networks with crank kinematics or block vibration measurements

Closed-loop combustion control in gasoline engines can improve efficiency, calibration effort, and performance using different fuels. Knowledge of in-cylinder pressures is a key requirement for closed-loop combustion control. Adaptive cylinder pressure reconstruction offers a realistic alternative to direct sensing, which is otherwise necessary as legislation requires continued reductions in CO2 and exhaust emissions. Direct sensing, however, is expensive and may not prove adequately robust. A new approach is developed for in-cylinder pressure reconstruction on gasoline engines. The approach uses time-delay feedforward artificial neural networks trained with the standard Levenberg–Marquardt algorithm. The same approach can be applied to reconstruction via measured crank kinematics obtained from a shaft encoder or measured engine cylinder block vibrations obtained from a production knock sensor. The basis of the procedure is initially justified by examination of the information content within measured data, which is considered to be equally important as the network architecture and training methodology. Key hypotheses are constructed and tested using data taken from a three-cylinder (direct injected spark ignition) engine to reveal the influence of the data information content on reconstruction potential. The findings of these hypotheses tests are then used to develop the methodology. The approach is tested by reconstructing cylinder pressure across a wide range of steady-state engine operation using both measured crank kinematics and block accelerations. The results obtained show a very marked improvement over previously published reconstruction accuracy for both crank kinematics and cylinder block vibration–based reconstruction using measurements obtained from a multi-cylinder engine. This article shows that by careful processing of measured engine data, a standard neural network architecture and a standard training algorithm can be used to very accurately reconstruct engine cylinder pressure with high levels of robustness and efficiency.

Closed-Form Overturning Limit of Rigid Block under Critical Near-Fault Ground Motions

A closed-form limit on the input level of the double impulse as a substitute of a near-fault ground motion is derived for the overturning of a rigid block. The rocking vibration of the rigid block is formulated by using the conservation law of angular momentum and the conservation law of mechanical energy. The initial rotational velocity after the first impulse and the rotational velocity after the impact are determined by the conservation law of angular momentum. The velocity change after the second impulse is also characterized by the conservation law of angular momentum. The maximum angles of rotation of the rigid block in both the clockwise and anti-clockwise directions, which are needed for the computation of the overturning limit, are derived by the conservation law of mechanical energy. This enables us to avoid the computation of complicated non-linear time-history responses. The critical timing of the second impulse to the first impulse is characterized by the time of impact after the first impulse. It is clarified that the action of the second impulse just after the impact corresponds to the critical timing. It is derived from the closed-form expression of the critical velocity amplitude limit of the double impulse that its limit is proportional to the square root of size, i.e. the scale effect.

エンジンのギアケーシングへの制振処理の適用

As the diesel engine used for the forklift and construction machineries is operated at the continuous heavy duty condition, it employs the gear train to drive the fuel injection pump and valve train. When the driving torque acting on the rotating shaft is decreased in the idling condition, separation of gear tooth and rattle noise are induced. Moreover, torsional vibration of crankshaft increases the impact vibration between the gear train. This gear train is commonly installed at the pulley side of the crankshaft and the gear casing is attached to an engine block to cover the gear train. Vibration level of this gear casing is often magnified due to the engine block vibration and consequently the engine noise is increased at the pulley side. The effects of changing the structure of gear casing and noise radiation from the gear casing are evaluated by use of the modal synthesis method which employs the vibratory characteristics of each structure and static deformation caused by the displacement of the connecting points. The rubber pasting on the gear casing is carried out to reduce engine noise. A modal damping ratio of coupled system after pasting rubber on the gear casing evaluated by use of modal analysis technique and its validity is confirmed by vibration experiment of a box model which imitates engine block and gear casing. Change of actual engine noise level by rubber pasting on gear casing is also discussed in detail.

Knock Detection in Spark Ignition Engines Base on Complementary Ensemble Empirical Mode Decomposition-Hilbert Transform

In spark ignition engines, knock onset limits the maximum spark advance. An inaccurate identification of this limit penalises the fuel conversion efficiency. Thus knock feature extraction is the key of closed-loop control of ignition in spark ignition engine. This paper reports an investigation of knock detection in spark ignition (SI) engines using CEEMD-Hilbert transform based on the engine cylinder pressure signals and engine cylinder block vibration signals. Complementary Ensemble Empirical Mode Decomposition (CEEMD) was used to decompose the signal and detect knock characteristic. Hilbert transform was used to analyze the frequency information of knock characteristic. The result shows that, for both of cylinder pressure signals and vibration signals, the CEEMD algorithm could extract the knock characteristic, and the Hilbert transform result shows that the energy of knock impact areas has the phenomenon of frequency concentration in both cylinder pressure signal and cylinder block vibration signal. At last, the knock window is then determined, based on which a new knock intensity evaluation factorKis propose, and it can accurately distinguish between heavy knock, light knock, and normal combustion three states.

冷却水音場を考慮したエンジン連成振動とキャビテーションの予測（解析法の提案とモデル試験による検証）

Liner cavitation induced by piston slap in the diesel engine is caused by the water pressure fluctuation when its negative pressure is reduced to the saturated vapor pressure or less. Cavitation erosion of the cylinder liner is thought to be generated by the impulsive pressure or jet flow impingement following the collapse of cavitation bubble. As the measured results have shown that the water coolant passage of actual engine block has the resonant frequencies, this study presents the numerical method to predict the water pressure fluctuation in the water coolant passage considering vibration of the engine block and rotating shafts induced by engine exciting forces like combustion pressure, piston slap and so on. To examine the validity of this method, rectangular tank model containing the water is used to measure the response of water pressure fluctuation and structural vibration induced by the impulsive force acting on the structure. Measured water pressure response and structural vibration of rectangular tank model agreed well with the analytical results and the validity of the analytical method was confirmed. In this impact vibration experiment, high frequency components of the water pressure were observed just after the water pressure reaches to the saturated vapor pressure or less. These high frequency components seem to show the occurrence of the cavitation. Moreover, it was revealed that water pressure response is affected by the proximity of the natural frequencies of water acoustic field and structural vibration.

On the identification of piston slap events in internal combustion engines using tribodynamic analysis

Piston slap is a major source of vibration and noise in internal combustion engines. Therefore, better understanding of the conditions favouring piston slap can be beneficial for the reduction of engine Noise, Vibration and Harshness (NVH). Past research has attempted to determine the exact position of piston slap events during the engine cycle and correlate them to the engine block vibration response. Validated numerical/analytical models of the piston assembly can be very useful towards this aim, since extracting the relevant information from experimental measurements can be a tedious and complicated process.In the present work, a coupled simulation of piston dynamics and engine tribology (tribodynamics) has been performed using quasi-static and transient numerical codes. Thus, the inertia and reaction forces developed in the piston are calculated. The occurrence of piston slap events in the engine cycle is monitored by introducing six alternative concepts: (i) the quasi-static lateral force, (ii) the transient lateral force, (iii) the minimum film thickness occurrence, (iv) the maximum energy transfer, (v) the lubricant squeeze velocity and (vi) the piston-impact angular duration.The validation of the proposed methods is achieved using experimental measurements taken from a single cylinder petrol engine in laboratory conditions. The surface acceleration of the engine block is measured at the thrust- and anti-thrust side locations. The correlation between the theoretically predicted events and the measured acceleration signals has been satisfactory in determining piston slap incidents, using the aforementioned concepts. The results also exhibit good repeatability throughout the set of measurements obtained in terms of the number of events occurring and their locations during the engine cycle.

The Research on Fault Diagnosis of Diesel Engine Based on EMD

In view of the superiority of support vector machine and the fault characteristic of diesel engine, a classify method for diesel engine fault based on support vector machine is presented in this paper. First the cylinder block vibration signal on different condition was measured by the simulation test of diesel engine fuel injection system fault, then the feature parameter was extracted by empirical mode decomposition and the most impactful parameter was selected to be the input of support vector machine. The result shows that this method has fine classified ability and precision.

Determination of TDC in a hydraulic free-piston engine by a novel approach

In indicator diagram analysis, precise determination of the top dead center (TDC) position is vital. However, in a hydraulic free-piston engine (HFPE), the piston is not restricted by any mechanism, and it is in the “free” state. This means that the methods used to determine the TDC position in a conventional engine are not applicable to an HFPE because its different structures. Thus, an HFPE indicator diagram has been developed on the basis of the piston displacement and in-cylinder gas pressure measured with respect to time. However, the vibration of engine block during the HFPE operation will lead to the errors between the real minimal volume of cylinder and the measurement TDC position by measuring the piston displacement. Therefore, it is necessary to find a new approach for determining the TDC position for indicator diagram analysis of an HFPE. In this paper, we discuss a novel solution to the problem for determining the TDC position using a one-to-one correspondence between the geometrical characteristics of the pressure diagram and the maximum pressure point position relative to the TDC position. The results of the experiments we conducted show that the proposed method can determine the TDC position.

Combustion diagnosis via block vibration signal in common rail diesel engine

This article presents a diagnostic technique in which nonintrusive measurements are used with the aim of indirect characterization of the combustion process of an internal combustion diesel engine. The developed technique is based on the vibration signal coming from a mono-axial accelerometer placed in a selected location of the engine block. Such a location is able to guarantee high sensitivity to vibration caused by forces directly linked to the combustion process and low sensitivity to all the other excitation sources. The technique is applied to the signals acquired during two series of experimental tests, carried out on the same kind of engine (multi-cylinder diesel engine, equipped with common rail injection system), in two separate engine test facilities in order to test the engine stand-alone and the engine dressed up with the integrated automatic transmission, aimed at reproducing its real operation condition (it is mainly employed in mini-car sector application). The obtained results suggest the potential applicability of the technique both in the laboratory, during the tuning between the injection parameter settings and the engine, and in the regular running condition of the engine for combustion process diagnosis.

Investigation of piston slap induced vibration of IC engine considering the coupled vibration of connecting rod, crankshaft and engine block

Piston slap is a major cause of the complex transient vibration response related to the impact excitation inside the engine. In the conventional analytical model of piston slap, the coupled vibration of piston and cylinder liner was taken into consideration only. In order to estimate the piston slap induced vibration of IC engine accurately, a theoretical model of piston slap which considering the movement and coupled vibration of piston, connecting rod, crankshaft and engine block was proposed. Based on this model, the piston slap and vibration response of some type of 3.5 L diesel engine were predicted. Then the comparison of rotate angle of piston, impact force induced by piston slap, torsional vibration of crankshaft, reaction force acting on main bearing and the vibration response of engine block between the present method and conventional method have been discussed in details. Research results revealed that the coupled vibration takes seriously influence on piston slap and the piston slap also influences the characteristic of crankshaft torsional vibration, reaction force at main bearing and vibration response of engine block inverse.

Study on the noise and vibration of engine block coupled with the rotating crankshaft and gear train (Effect of the torsional vibration of crankshaft)

Study on the noise and vibration of engine block coupled with the rotating crankshaft and gear train (Effect of the torsional vibration of crankshaft)

The Mechanical Model of the Dynamic Characteristics of the Bituminous Concrete Compaction Mechanism

In view of the industry status that the working performance of domestic bituminous concrete paver is not ideal and corresponding design theory is lack, this paper proposes the compaction system structures of screeding devices, sets up differential equations of vibration system of the freedom degree of the double eccentric block vibration compaction mechanism, sets up the mechanical model of dynamic characteristics of ironing compaction mechanism. With computer simulation, it studies the problems of dynamics of ironing compaction mechanism, analyzes the influence of changes of dynamical parameters of the ironing compaction mechanism on the dynamic characteristics of the system. The study of the dynamic response of ironing compaction systems and dynamic design has important theoretical significance and engineering application value.

An Intelligent Tire Based Tire-Road Friction Estimation Technique and Adaptive Wheel Slip Controller for Antilock Brake System

The contact between the tire and the road is the key enabler of vehicle acceleration, deceleration and steering. However, due to changes to the road conditions, the driver's ability to maintain a stable vehicle may be at risk. In many cases, this requires intervention from the chassis control systems onboard the vehicle. Although these systems perform well in a variety of situations, their performance can be improved if a real-time estimate of the tire-road friction coefficient is available. Existing tire-road friction estimation approaches often require certain levels of vehicle longitudinal and/or lateral motion to satisfy the persistence of excitation condition for reliable estimations. Such excitations may undesirably interfere with vehicle motion controls. This paper presents a novel development and implementation of a real-time tire-road contact parameter estimation methodology using acceleration signals from an intelligent tire. The proposed method characterizes the terrain using the measured frequency response of the tire vibrations and provides the capability to estimate the tire road friction coefficient under extremely lower levels of force utilization. Under higher levels of force excitation (high slip conditions), the increased vibration levels due to the stick/slip phenomenon linked to the tread block vibration modes make the proposed tire vibrations based method unsuitable. Therefore for high slip conditions, a brush model-based nonlinear least squares (NLLS) parameter estimation approach is proposed. Hence an integrated approach using the intelligent tire based friction estimator and the model based estimator gives us the capability to reliably estimate friction for a wider range of excitations. Considering the strong interdependence between the operating road surface condition and the instantaneous forces and moments generated; this real time estimate of the tire-road friction coefficient is expected to play a pivotal role in improving the performance of a number of vehicle control systems. In particular, this paper focuses on the possibility of enhancing the performance of the ABS control systems. In order to achieve the aforementioned objectives, the design and implementation of a fuzzy/sliding mode/proportional integral (fuzzy-SMC-PI (FSP)) control methodology is proposed. The results show significant improvements in the stopping distance of a vehicle equipped with an intelligent tire based FSP controller as compared to a vehicle equipped with a standard ABS.

Enhancement of Collision Mitigation Braking System Performance Through Real-Time Estimation of Tire-road Friction Coefficient by Means of Smart Tires

In the case of modern day vehicle control systems employing a feedback control structure, a real-time estimate of the tire-road contact parameters is invaluable for enhancing the performance of the chassis control systems such as anti-lock braking systems (ABS) and electronic stability control (ESC) systems. However, at present, the commercially available tire monitoring systems are not equipped to sense and transmit high speed dynamic variables used for real-time active safety control systems. Consequently, under the circumstances of sudden changes to the road conditions, the driver's ability to maintain control of the vehicle maybe at risk. In many cases, this requires intervention from the chassis control systems onboard the vehicle. Although these systems perform well in a variety of situations, their performance can be improved if a real-time estimate of the tire-road friction coefficient is available. Existing tire-road friction estimation approaches often require certain levels of vehicle longitudinal and/or lateral motion to satisfy the persistence of excitation condition for reliable estimations. Such excitations may undesirably interfere with vehicle motion controls. This paper presents a novel development and implementation of a real-time tire-road contact parameter estimation methodology using acceleration signals from a smart/intelligent tire. The proposed method characterizes the terrain using the measured frequency response of the tire vibrations and provides the capability to estimate the tire road friction coefficient under extremely lower levels of force utilization. Under higher levels of force excitation (high slip conditions), the increased vibration levels due to the stick/slip phenomenon linked to the tread block vibration modes make the proposed tire vibrations based method unsuitable. Therefore for high slip conditions, a tire-road friction model-based parameter estimation approach is proposed. Hence an integrated approach using the smart/intelligent tire based friction estimator and the model based estimator gives us the capability to reliably estimate friction for a wider range of excitations. Considering the strong interdependence between the operating road surface condition and the instantaneous forces and moments generated; this real time estimate of the tire-road friction coefficient is expected to play a pivotal role in improving the performance of a number of vehicle control systems. In particular, this paper focuses on the possibility of enhancing the performance of collision mitigation braking systems. Language: en

Combined effects of inertia and pressure on engine vibration

The present paper describes a methodology devised to study the engine block displacement of an internal combustion engine in the radial direction due to combustion force and inertia forces. The combustion force produced in in-cylinder is a substantial function of angular displacement and then correlated with pressure and temperature. Other than the substantial function, combustion force depends on chamber design, injection parameters, flow patterns and fuels. But inertia is a function of angular displacement and a mass of reciprocating parts. Speed is directly related to combustion by means of indicated pressure and the indicated torque respectively. The engine was taken for an analysis along with speed and load as the design variables. The engine block displacement, time-domain frequency, wave form, side thrust and in-cylinder force were examined for the analysis. The results obtained provide the combined effect of combustion force and inertia force induced displacement, uncertainty in combustion processes, nonlinear vibration of the engine block, and vibration spectra. This new approach in engine parameter design bestows insight with the combustion force and inertia induced vibration and source of noise in the diesel engine.

Dynamic Response of the Foundations Resting on a Two-layered Soil Underlain by a Rigid Layer

The present experimental investigations study the effect of layering over rigid base on the dynamic behavior of foundation under vertical mode of vibration. Model block vibration tests were conducted on a rigid surface footing resting on different layered soil systems underlain by rigid base. The rigid base was used to simulate the presence of bedrock. The tests were carried out in a pit of size 2.0 m × 2.0 m × 1.9 m (deep) using a concrete footing of size 0.4 m × 0.4 m × 0.1 m. A rotating mass type mechanical oscillator was used for inducing vibration in vertical direction. Different layered soil systems were prepared within the total depth of 1,200 mm over the rigid base. Locally available gravel and fly ash were used to form different layered soil systems. In total, 132 nos. model block vibration tests in vertical mode were conducted for different layering and loading combinations. The experimentally obtained results are also compared with the results obtained from the analysis by mass-spring-dashpot and equivalent half-space theory.

Characterization on the rocking vibration of rigid blocks under horizontal harmonic excitations

This investigation deals with characteristics of rocking vibration of rigid block subjected to the horizontal harmonic excitations. Nonlinear rocking system may include minute changes of system parameters, such as friction and restitution coefficients depending on contact conditions between the block and the base, and friction force that may vary as the block moves. This paper is the first part of the examination how minute changes of the above system parameters are related with minute changes of friction coefficients. A numerical analysis program has been developed to solve nonlinear motion equations for rocking motion of a rigid block subjected to horizontal base excitation. Natural changes of friction coefficient are simulated by random numbers with a normal probability distribution. Analytical results have shown that rocking responses are very sensitive to small changes of friction conditions between the block and the base. Minute changes of the friction coefficients make rocking response unstable and greatly change the response distribution itself. Because of the dynamic nature of friction coefficients changes, experimental rocking responses are not recurring.

Dynamic Behavior of Fibre Reinforced Sand

Fibre reinforcement has more or less established itself as a composite civil engineering material having significant effect in improving the static strength characteristics of granular soil like sand. However the dynamic behavior of fibre reinforced sand as far as large scale model tests are concerned is rarely discussed in the literature. The present study illustrates the effect of randomly distributed polypropylene fibrillated fibre reinforcement in modifying the dynamic characteristics of locally available sand (Solani River, Roorkee, India). Block resonance tests (BRT) for low-medium strain levels and Cyclic plate load tests (CPLT) for high strain level have been conducted both on un-reinforced and fiber reinforced sand in the laboratory to study its dynamic characteristics. In BRT, the magnitude of resonant frequency and maximum amplitude of vibration of the test block have been recorded at different excitation levels in vertical mode of vibration at a particular percentage of fiber content, thus establishing the effect of dynamic loading or in turn the effect of strain level. The dynamic response was evaluated in terms of coefficient of elastic uniform compression and damping ratio. Where as, in CPLT, settlement and pressure values have been recorded to calculate coefficient of elastic uniform compression at two different strain levels. It was observed that there was no significant effect of fibre reinforcement on the dynamic behavior of sand contrary to the static loading condition.