Engine Friction Torque Research Articles

Electric motor-based crankshaft stop position control to suppress range extender start vibration in electric vehicle

Range-extended electric vehicles have the most complex noise and vibration problems since certain control strategies often make range extenders (REs) shut down or restart for the sake of better fuel consumption. This paper deals with this uncomfortable riding experience, especially during the range extender start phase. A control-oriented nonlinear model for the start–stop vibration analysis, including range extender mount system, engine–clutch–motor shaft system, engine inertia torque and force, engine friction torque, engine gas torque, engine manifold pressure, electric motor torque, and range extender controller, is thus built. In the developed model, a new estimation method for gas torque is proposed, where the initial crank angle is considered and the relevant equations are simplified. The method has proven to predict gas torque accurately without using a complex calculation process. According to the developed model, the active control method, crankshaft stop position control (CSPC) has been proposed. The crankshaft stop position is analyzed as well as the crankshaft movement with different speeds at top dead center is discussed, which lead to the design of the target curves for crankshaft movement during the stop phase. Based on the set-up model, CSPC is finally applied through the cascade control of the motor to evaluate the control effectiveness. The simulation outcomes demonstrate that CSPC can help the crankshaft to finally stop at the optimal initial crank angle, which effectively lessens the vibration in the next start phase.

Gas torque compensation control for range extender start-stop vibration reduction in electric vehicle

One of the key challenges with the development of range extended electric vehicles is the noise, vibration and harshness behavior, specifically the uncomfortable ride experience during the range extender starting and stopping. This article focuses on providing an active control method to address this critical noise, vibration and harshness issue. A control-oriented nonlinear model for the start-stop vibration analysis, including range extender mount system, engine-clutch-motor shaft system, engine inertia torque and force, engine friction torque, engine gas torque, engine manifold pressure, electric motor torque and range extender controller, is thus built. In the developed model, a new estimation method for gas torque is proposed, where the initial crank angle is considered as well as the relevant equations are simplified. The method is proved to predict gas torque accurately without the expense of complex calculation process. Based on the model, the mount system vibration response has been analyzed that the excitation of range extender block on vehicle body in x-direction is the most prominent. The concept of the active control method, gas torque compensation control, is thus introduced in detail to reduce such a system vibration during start-stop phase. According to the control principle, the torque compensation coefficient for gas torque compensation control is determined and the compensation speed range is analyzed. In order to evaluate the control effectiveness, gas torque compensation control is implemented in the set-up model. The simulation outcomes demonstrate that gas torque compensation control is effective in reducing the vibration generated during start-stop transitions.

Idle speed controller based on active disturbance rejection control in diesel engines

This study proposes a design for an idle speed controller to compensate for varying engine load and friction torque in passenger car diesel engines. An active disturbance rejection control (ADRC) framework, comprised of a disturbance compensator and a feedback controller, is applied to an idle speed controller to compensate for disturbances such as engine load and friction torque. In addition, a feedforward compensator is designed into the ADRC framework to improve disturbance rejection performance. The proposed controller is validated by engine and vehicle experiments and the experiment results are compared with a commercial controller.

Combustion mode switching control in a HCCI diesel engine

HCCI (Homogeneous Charge Compression Ignition) combustion has the potential to significantly reduce NOx and PM emission of diesel engines due to its nature of even mixture and low temperature combustion. This combustion mode is only applicable in part load and low speed area so far. This range limitation results in frequently combustion mode switching from HCCI to CI and vice versa in real applications. HCCI realized by late injection with heavy EGR rate is investigated, which is also named PCCI (Premixed Charged Compression Ignition) sometimes. By changing control parameters (including injection timing, injection pressure and EGR rate) individually, the influences of these parameters on HCCI combustion and emissions are identified. Based on the evaluation of the influences, one pre-defined step-by-step air–fuel coordination strategy is presented. Additionally one hysteresis combustion mode determination method is proposed to avoid target mode fluctuation due to variation of engine speed or engine load in a small range. Torque deficiency occurs in acceleration transients as a result of fuel limitation to reduce soot emission, especially during HCCI to CI transitions. One ISG (Integrated Starter Generator) motor is applied to perform dynamic torque compensations in transient operations. Engine friction torque is estimated by means of cylinder pressure information from in-cylinder pressure sensors. On the basis of torque estimation, the difference between desired engine brake torque and actual engine brake torque is obtained. The torque output of ISG motor accounts for this torque gap and the torque pre distributed to ISG motor. The strategy is verified by engine tests. Experimental results indicate that, with the finely defined air–fuel coordination, less unstable combustion occurs and the target modes are established more quickly during transitions both in steady states and in transients. The torque deficiency during acceleration operations could be well compensated by the ISG motor.

A Study of Fuel Economy Additive Formulation Technology for Passenger Car Motor Oil and Development of a Screener Test for Fuel Economy

The motored engine friction torque test has been developed for the purpose of evaluating various additive formulations. Difference in frictional behavior using different additive chemistries were observed and the importance of the additive chemistry for fuel economy was indicated. Sequence VID engine testing was conducted and the correlation between the motored engine friction torque test and Sequence VID was considered. Excellent correlation between the motored friction torque tests and Sequence VID FEI 1 was demonstrated. However, excellent correlation with FEI 2 was not observed at any conditions of the motored engine friction torque test. Also, the motored engine friction torque test correlates with vehicle fuel consumption with JC08H and 10.15 modes on a chassis dynamometer test.

A Reverse Driving Control Method for Hydrostatic Double-drum Vibratory Rollers

A reverse driving control method for hydrostatic double-drum vibratory rollers is devised in this paper. Based on the analysis of dynamic characteristics of stopping process, the relationship equation between engine speed and pump displacement is established. To restrict the peak value of engine overspeed within the allowable region, an offline parameter determination approach complied with the requirements of average stopping deceleration is developed. The online control method using the selected parameter is presented. Approaches are derived to determine the two key parameters of the control methods, i.e., the critical deceleration value and the coefficient of relationship equation of the engine friction torque and the engine speed. The control method can also be applied to one type of hydrostatic machinery with their engine throttle position unchangeable in stopping process in addition to the double-drum vibratory roller.

Data-driven algorithm to estimate friction in automobile engine

Algorithms based on the oscillations of the engine angular rotational speed under fuel cutoff and no-load were proposed for estimation of the engine friction torque. The recursive algorithm to restore the periodic signal is used to calculate the amplitude of the engine speed signal at fuel cutoff. The values of the friction torque in the corresponding table entries are updated at acquiring new measurements of the friction moment. A new, data-driven algorithm for table adaptation on the basis of stepwise regression was developed and verified using the six-cylinder Volvo engine.

Data-driven algorithms for engine friction estimation

Errors in the estimation of friction torque in modern spark ignition automotive engines necessitate the development of real-time algorithms for adaptation of the friction torque. Friction torque in the engine control unit is presented as a look-up table with two input variables (the engine speed and indicated engine torque). The algorithms proposed in this paper estimate the engine friction torque via the crankshaft speed fluctuations at the fuel cut-off state and at idle. A computationally efficient filtering algorithm for reconstruction of the first harmonic of a periodic signal is used to recover an amplitude which corresponds to engine events from the noise-contaminated engine speed measurements at the fuel cut-off state. The values of the friction torque at the nodes of the look-up table are updated, when new measured data of the friction torque are available. New data-driven algorithms which are based on a stepwise regression method are developed for adaptation of look-up tables. The algorithms are verified by using a spark ignition six-cylinder prototype engine.

Discussion on: “Adaptive Estimation of the Engine Friction Torque”

The paper by A. Stotsky introduces an algorithm for real-time estimation of the engine friction torque, capable to achieve a dynamic adaptation of the static maps widely used in the engine control functionality. This adaptation of the friction map allows a better vehicle driveability performance and an enhanced control by the driver of the vehicle longitudinal transients. There are several interesting features of the approach proposed by the Author, while the discussion will focus on four issues that may be seen as suggestions for further development: (i) analysis of cold start condition, (ii) accessories torque; (iii) working condition other than idling; (iv) effects of engine wear. As first, since the method aims to improve the vehicle comfort and driver’s control, the possibility to get friction torque assessment during cold start with consequent map and look-up table adaption is given by the theoretical models and experimental outcomes in [1,2]. The conclusions of these papers underline that, for some tribological pairs, the friction mean effective pressure (fmep ¼ 4� Tf,avr/V; V is the engine displacement) during cold transient is up to three or four times higher than fmep at warmed up condition. The piston assembly and the crankshaft main bearings contribute significantly to the total engine fmep and the changes in the oil viscosity produced by changes in film temperature are the most substantial influence on friction during cold start and cold running at constant speed. The use of theoretical models for fmep evolution as function of engine average temperature may improve the controller performance during cold start phases. The ECU friction map could be updated by acquiring some points (e.g., 2 � 4 points as proposed by the Author) during the cold start. The second point deals with accuracy of the instantaneous accessories torque estimate, since some devices can account for up to 40% of the whole Tloss þ Tacs torque, in some conditions [3]. Therefore, the uncertainty on the Tacs has momentous influence on Tloss (and its Tf share calculation); this effect is clearly shown taking into account the relationship for the friction torque deviation evaluation (see Eq (4)):

Enhancement of the accuracy of the ( P–ω) method through the implementation of a nonlinear robust observer

The ( P–ω) method is a model-based approach developed for determining the instantaneous friction torque in internal combustion engines. This scheme requires measurements of the cylinder gas pressure, the engine load torque, the crankshaft angular displacement and its time derivatives. The effects of the higher order dynamics of the crank-slider mechanism on the measured angular motion of the crankshaft have caused the ( P–ω) method to yield erroneous results, especially, at high engine speeds. To alleviate this problem, a nonlinear sliding mode observer has been developed herein to accurately estimate the rigid and flexible motions of the piston-assembly/connecting-rod/crankshaft mechanism of a single cylinder engine. The observer has been designed to yield a robust performance in the presence of disturbances and modeling imprecision. The digital simulation results, generated under transient conditions representing a decrease in the engine speed, have illustrated the rapid convergence of the estimated state variables to the actual ones in the presence of both structured and unstructured uncertainties. Moreover, this study has proven that the use of the estimated rather than the measured angular displacement of the crankshaft and its time derivatives can significantly improve the accuracy of the ( P–ω) method in determining the instantaneous engine friction torque.

EFFECTS OF FILTERING THE ANGULAR MOTION OF THE CRANKSHAFT ON THE ESTIMATION OF THE INSTANTANEOUS ENGINE FRICTION TORQUE

The focus of this study is to investigate the effects of filtering the actual angular displacement, velocity and acceleration of the crankshaft on the computation of the instantaneous engine friction torque. These effects are isolated from those of measurement errors and/or noise by relying on a detailed model of the crank-slider mechanism to generate the rigid and flexible motions of the piston/connecting-rod/crankshaft mechanism along with the engine friction torque. The (P−ω) method is used herein to estimate the instantaneous engine friction torque based on the actual and the filtered angular displacement, velocity and acceleration of the crankshaft. The digital simulation results have demonstrated that the (P−ω) method cannot produce an acceptable estimation of the instantaneous engine friction torque in spite of filtering the actual angular motion of the crankshaft. It should be mentioned that the low-pass filter is commonly implemented to attenuate the measurement noise and the effects of structural deformations on the measured angular velocity of the crankshaft. However, the ineffectiveness of the low-pass filter stems from the non-linearities of the crank-slider mechanism that induced superharmonic and combination resonance frequencies in the angular displacement, velocity and acceleration of the crankshaft. The filter has severely attenuated some of the superharmonic resonance frequencies, which constitute an important part of the rigid-body behavior of the crankshaft that is needed by the (P−ω) method to accurately predict the engine friction torque. Moreover, the filtered signals would still be contaminated by the combination resonance frequencies that may appear in the low-frequency range commonly assumed to be dominated by the frequency components of the rigid-body motion of the crankshaft.

EFFECTS OF STRUCTURAL DEFORMATIONS OF THE CRANK-SLIDER MECHANISM ON THE ESTIMATION OF THE INSTANTANEOUS ENGINE FRICTION TORQUE

The focus on the current study is to assess the effects of structural deformations of the crankshaft/connecting-rod/piston mechanism on the computation of the instantaneous engine friction torque. This study is performed in a fully controlled environment in order to isolate the effects of structural deformations from those of measurement errors or noise interference. Therefore, a detailed model, accounting for the rigid and flexible motions of the crank-slider mechanism and including engine component friction formulations, is considered in this study. The model is used as a test bed to generate the engine friction torque,Tfa, and to predict the rigid and flexible motions of the system in response to the cylinder gas pressure. The torsional vibrations and the rigid body angular velocity of the crankshaft, as predicted by the detailed model of the crank-slider mechanism, are used along with the engine load torque and the cylinder gas pressure in the (P–ω) method to estimate the engine friction torque,Tfe. This method is well suited for the purpose of this study because its formulation is based on the rigid body model of the crank-slider mechanism. The digital simulation results demonstrate that the exclusion of the structural deformations of the crank-slider mechanism from the formulation of the (P–ω) method leads to an overestimation of the engine friction torque near the top-dead-center (TDC) position of the piston under firing conditions. Moreover, for the remainder of the engine cycle, the estimated friction torque exhibits large oscillations and takes on positive numerical values as if it is inducing energy into the system. Thus, the adverse effects of structural deformations of the crank-slider mechanism on the estimation of the engine friction torque greatly differ in their nature from one phase of the engine cycle to another.