Electro-mechanical transmission modelling for series-hybrid tracked tanks

This paper describes a mathematical model and presents the dynamic analysis of a series-hybrid tracked tank driven by two electric motors, one devoted to propulsion (PM) and the other to steering (SM). A double differential mechanism is adopted to electrically produce the speed difference between the tracks required for skid steering. In this paper, this specific transmission is called Electro-Mechanical Transmission (EMT). The EMT model supports the steering motor control strategy definition and the electric motor size optimisation. Dynamic simulations applied to a 55 ton main battle tank are shown and discussed to validate the obtained result

transient response and frequency domain analysis of an electrically variable transmission

This article deals with the dynamic behavior of a passenger car equipped with an electrically variable transmission, which is analyzed both in time and frequency domains. After deriving the dynamic equations in the state-space form for both open- and closed-loop systems, a methodology for objectively evaluating the drivability of this over-actuated system is proposed. Several simulation results are presented with the aim of highlighting the transient response to fast engine torque changes and the effect of the generator speed controller calibration on the system dynamics. Moreover, the influence of the ratio between electrical and thermal power on the frequency response is discussed. The proposed analysis, which is based on a simple static torque split between internal combustion engine and propulsion electric motor, depicts the dynamic signature of the electrically variable transmission powertrain system, without any additional drivability filter. Hence, these results can constitute the base for the design of dynamic torque splitting aimed at optimizing the longitudinal vehicle response to the driver's acceleration demand

Drivability enhancement and transient emission reduction for a mild hybrid diesel-electric truck

This paper deals with modelling and control methodologies applied to a heavy truck equipped with a parallel hybrid electric drivetrain. The actuator redundancy, typical of the mild-hybrid vehicle configuration, allows the powertrain control system to enhance the vehicle drivability, in terms of smooth driving and promptness, while reducing transient diesel engine emissions, in comparison with conventional pure thermal engine vehicles. The electric motor, characterised by a high-bandwidth torque control, is here utilised not only to dampen the driveline oscillations that arise during rapid torque transients, e.g., when the driver accelerates the vehicle at full load in low gears, but also to keep the engine working with slow torque gradients, as required by transient emission reduction strategies. The driveline is modelled by lumped parameters, considering also the damping effects of the tyres. A detailed non-linear model is used as reference for the performance comparison of different simplified linear models. The best linear model is selected and used for the design of a LQR-based closed-loop controller aiming at reducing the driveline torsional vibrations. The regulation task (active vibration damping) is separated from the distribution task (torque splitting between the two motors

Torsional Oscillations in Automotive Transmissions: Experimental Analysis and Modelling

The paper investigates the torsional oscillations of an automotive transmission system by means of an experimental test bench used to validate the proposed lumped parameter model. The rig consists of a Dual Clutch Transmission (DCT) and a Manual Transmission (MT) connected through the respective output shafts, while the excitation is provided by two electric motors, which are controlled in speed or torque.The experimental analysis includes the measurement of the external torques, applied by the two electric motors to the mechanical system, and the measurement of the system response in terms of angular speeds at different positions along the transmission line. The frequency response of the system is estimated from the experimental data and compared with the results of a 5-degree-of-freedom lumped parameter model, which proves to be adequate to describe the dynamic behaviour of the system up to a frequency of 200 Hz.The comparison between simulated results and experimental data shows good agreement, so the model can be used to predict the torsional vibrations of the transmission system in the linear field. Moreover, the effects of the nonlinearities associated with the mean value of the excitations are shown. Finally the influence of the selected gear ratio on the experimental frequency response is discussed

Experimental analysis and modeling of transmission torsional vibrations

In this article, the torsional vibrations of a transmission system installed on a test rig are investigated. The transmission system comprises a Dual Clutch Transmission (DCT) and a Manual Transmission (MT) interconnected via their output shafts. The excitation of the dynamic system is performed by two electric motors which ensure an accurate control of the speed or torque. The analysis includes the measurement of the external torques, applied by the two electric motors to the mechanical system, and the measurement of the system response in terms of angular speeds at different positions along the transmission line. The frequency response of the system is estimated from the experimental data and compared with the simulation results of a 4-DOF lumped parameter model, which proved adequate to describe the dynamic behavior of the system up to a frequency of 100Hz. A good match between simulation and experimental results is shown. Therefore, the model can be used to predict the torsional vibration of the transmission system under test when it behaves linearly

An alternative method for order tracking using autopower spectrum

Order tracking is a method of analysis used by engineers in the diagnosis of rotating machinery. In many applications, order analysis of non-stationary signals is required. The direct extraction of the amplitude information from the shorttime Fourier transform may lead to inaccurate vibration-level estimation in the case of fast changes in the signal frequency content. This article discusses spectral smearing, which is the main reason of the problem, and its sensitivity to the characteristics of the signal (frequency and amplitude variations) and to the input parameters of discrete Fourier transform analysis (window size and type). Through the years, many different approaches to perform order analysis have been developed; this article introduces a novel method for order tracking based on the short-time Fourier transform, which applies a compensation of the smearing effect based on an invariant information contained in autopower spectrum. The limitations and capabilities of the proposed method with respect to other existing techniques are discussed: considering the accuracy of the results, low requirements of computational resources, and ease of implementation, this method proves a valid alternative to currently used techniques

Development and experimental validation of a low-frequency dynamic model for a Hybrid Electric Vehicle

This paper describes the development and experimental validation of a high-fidelity Hybrid Electric Vehicle (HEV) simulator that enables testing and calibration of energy management and driveline control strategies. The model is capable of predicting longitudinal vehicle responses that affect energy consumption and drivability in the low-to-mid frequency region (up to 10 Hz). The simulator focuses primarily on the drivetrain dynamics, while the dynamics of the actuators are represented by simplified models. The vehicle simulator is validated by a number of experiments that include electric only, engine only and hybrid operating conditions. The test vehicle has a through-the-road parallel hybrid architecture that utilises a dual electric machine configuration. Experimental results confirm that important driveline phenomena such as shunt, shuffle, torque holes and other transient disturbances related to operating mode changes are accurately predicte

Torque Allocation of Hybrid Electric Trucks for Drivability and Transient Emissions Reduction

This paper aims at investigating powertrain behaviour, especially in transient dynamic responses, using a nonlinear truck vehicle dynamic model with a parallel hybrid configuration. A power split control was designed to achieve the desired drivability performance, with a focus on NOx emissions. The controller was characterized by high-level model-based logic used to elaborate the total powertrain torque required, and a low-level allocation strategy for splitting power between the engine and the electric motor. The final task was to enhance vehicle drivability based on driver requests, with the goal of reducing-in a hybrid configuration-transient diesel engine emissions when compared to a conventional pure thermal engine powertrain. Different parameters were investigated for the assessment of powertrain performance, in terms of external input disturbance rejection and NOx emissions reduction. The investigation of torque allocation performance was limited to the simulation of a Tip-in manoeuvre, which showed a satisfying trade-off between vehicle drivability and transient emissions

Drivability analysis of through-the-road-parallel hybrid vehicles

In the last decade, Hybrid Electric Vehicles (HEVs) have spread worldwide due to their capability to reduce fuel consumption. Several studies focused on the optimisation of the energy management system of hybrid vehicles are available in literature, whilst there are few articles dealing with the drivability and the dynamics of these new powertrain systems. In this paper a ‘Through-the-Road-Parallel HEV' is analysed. This architecture is composed of an internal combustion engine mounted on the front axle and an electric motor powering the rear one. These two powertrains are not directly connected to each other, as the parallel configuration is implemented through the road-tyre force interaction. The main purpose of this paper is the drivability analysis of this layout of HEVs, using linearised mathematical models in both time (i.e. vehicle response during tip-in tests) and frequency domain (i.e. frequency response functions), considering the effect of the engaged gear ratio. The differences from a traditional Front-Wheel-Drive (FWD) configuration are subsequently highlighted. Furthermore, the authors compare different linearised dynamic models, with an increasing number of degrees of freedom, in order to assess which model represents the best compromise between complexity and quality of the results. Finally, a sensitivity analysis of the influence of the torque distribution between the front (thermal) and rear (electric) axles on vehicle drivability is carried out and presented in detai

Passenger car active braking system: Pressure control design and experimental results (part II)

This paper deals with the design of a brake caliper pressure controller for a conventional anti-lock braking system/electronic stability control system and the experimental validation of its tracking performances. The analysis of the hydraulic plant, carried out in part I of this two-part study, is here utilized to develop the control algorithm. The control strategy is based on a feed-forward and a proportional integral controller through pulse width modulation with a constant frequency and variable duty cycle. The feed-forward contribution requires modeling of the nonlinear openloop system behavior which has been experimentally identified and described through two-dimensional maps: the inputs are the duty cycle applied to the electrovalves and the pressure drop across their orifice, while the output is the pressure gradient in the brake caliper. These maps, obtained for inlet and outlet valves, are used to set the feed-forward term. Finally a proportional integral controller is designed to reject external disturbances and compensate for model uncertainties. A brake system test rig, described in part I, is used for building inverse maps and validating the proposed control logic. Different reference pressure profiles are used to experimentally verify the control tracking performances