Developing a model for analysis of the cooling loads of a hybrid electric vehicle by using co-simulations of verified submodels

The requirement for including the air-conditioning and the battery-cooling loads within the energy efficiency analyses of a hybrid electric vehicle is widely recognized and has promoted system-level simulations and integrated modelling, escalating the challenge of balancing the accuracy and the speed of simulations. In this paper, a hybrid electric vehicle model is created through co-simulation of the passenger cabin, the air conditioning, the battery cooling, and the powertrai. Calibration and verification of the submodels help determine their accuracy in representing the target vehicle and achieve a balance between the model fidelity and the simulation speed. The result is a model which has a higher accuracy and a higher speed than those of similar models developed previously and which provides a reliable tool for a thorough investigation of the cooling loads for different ambient conditions and different duty cycles

Co-Simulation Methods for Holistic Vehicle Design: A Comparison

Vehicle development involves the design and integration of subsystems of different domains to meet performance, efficiency, and emissions targets set during the initial developmental stages. Before a physical prototype of a vehicle or vehicle powertrain is tested, engineers build and test virtual prototypes of the design(s) on multiple stages throughout the development cycle. In addition, controllers and physical prototypes of subsystems are tested under simulated signals before a physical prototype of the vehicle is available. Different departments within an automotive company tend to use different modelling and simulation tools specific to the needs of their specific engineering discipline. While this makes sense considering the development of the said system, subsystem, or component, modern holistic vehicle engineering requires the constituent parts to operate in synergy with one-another in order to ensure vehicle-level optimal performance. Due to the above, integrated simulation of the models developed in different environments is necessary. While a large volume of existing co-simulation related publications aimed towards engineering software developers, user-oriented publications on the characteristics of integration methods are very limited. This paper reviews the current trends in model integration methods applied within the automotive industry. The reviewed model integration methods are evaluated and compared with respect to an array of criteria such as required workflow, software requirements, numerical results, and simulation speed by means of setting up and carrying out simulations on a set of different model integration case studies. The results of this evaluation constitute a comparative analysis of the suitability of each integration method for different automotive design applications. This comparison is aimed towards the end-users of simulation tools, who in the process of setting up a holistic high-level vehicle model, may have to select the most suitable among an array of available model integration techniques, given the application and the set of selection criteria

In Conversation with Professor David Greenwood

Professor David Greenwood offers insights into the challenges and current and future development trends in the automotive industry. Based on his broad experience in this sector, Professor Greenwood discusses a wide range of topics, such as global and UK automotive industry markets, emerging technologies in energy storage and its impacts on the environment and vehicle performance, and autonomous and future vehicles

Application of key-off cooling and partial charging in plug-in electric vehicles

Ambient conditions can have a significant impact on the temperature of the battery of electrified vehicles. In hot geographical locations, high battery temperatures can be experienced when the vehicle is parked and cooling is absent. This has three negative implications for the vehicle performance attributes: first, it accelerates the ageing mechanisms of the battery and leads to short battery lifetime; second, it necessitates inhibition of the battery power as a safety measure and leads to low traction in electric vehicles or poor fuel economy in hybrid electric vehicles; third, it increases the battery cooling load which reduces the cooling power available to the cabin and leads to poor passenger thermal comfort. Eliminating the high battery temperatures that result from exposure to hot ambient conditions requires a comprehensive battery cooling strategy; one in which the battery can be cooled when the vehicle is driven or when parked. In the current state of the art battery cooling strategy, cooling is only available when the vehicle is driven and when it is plugged in. Practical concerns such as the associated energy consumption have discouraged battery cooling when the vehicle is parked and not plugged in (key-off). Since passenger vehicles typically experience long key-off intervals, the existing battery cooling strategies are insufficient in hot ambient conditions. The main contribution of this research is proposing the application of key-off battery cooling and developing an underpinning methodology for evaluating the benefits of key-off cooling in a plug-in hybrid electric vehicle. Key-off cooling is defined as an optimal control problem and solved in view of the 24-hour duty cycle of the vehicle evaluated by a representative model. This new methodology enables applying key-off cooling based on the requirements of one or more of the attributes of battery lifetime, thermal comfort and fuel economy, enabling consideration of these attributes in applying battery cooling in an optimal manner. The results show that while the effectiveness of key-off cooling depends on the duty cycle of the vehicle, it generally improves the battery lifetime and benefits the thermal comfort and the fuel economy attributes. To enable further improvements in the battery lifetime, integration of key-off cooling and partial charging of the battery is proposed, advancing the existing state of the art where partial charging is optimised independently of cooling. A new methodology is developed that determines the combination of the battery charge and key-off cooling control strategy that maximises the battery lifetime, while also considering the thermal comfort and the fuel economy attributes

Improving the performance attributes of plug-in hybrid electric vehicles in hot climates through key-off battery cooling

Ambient conditions can have a significant impact on the average and maximum temperature of the battery of electric and plug-in hybrid electric vehicles. Given the sensitivity of the ageing mechanisms of typical battery cells to temperature, a significant variability in battery lifetime has been reported with geographical location. In addition, high battery temperature and the associated cooling requirements can cause poor passenger thermal comfort, while extreme battery temperatures can negatively impact the power output of the battery, limiting the available electric traction torque. Avoiding such issues requires enabling battery cooling even when the vehicle is parked and not plugged in (key-off), but the associated extra energy requirements make applying key-off cooling a non-trivial decision. In this paper, a representative plug-in parallel hybrid electric vehicle model is used to simulate a typical 24-h duty cycle to quantify the impact of hot ambient conditions on three performance attributes of the vehicle: the battery lifetime, passenger thermal comfort and fuel economy. Key-off cooling is defined as an optimal control problem in view of the duty cycle of the vehicle. The problem is then solved using the dynamic programming method. Controlling key-off cooling through this method leads to significant improvements in the battery lifetime, while benefiting the fuel economy and thermal comfort attributes. To further improve the battery lifetime, partial charging of the battery is considered. An algorithm is developed that determines the optimum combination of key-off cooling and the level of battery charge. Simulation results confirm the benefits of the proposed method

Theoretical and experimental investigation of magneto-rheological damper based semi-active suspension systems

Semi-active vehicle suspension systems with Magneto-Rheological (MR) dampers have recently received an increasing attention. Satisfactory performance of these systems is highly dependent on the adopted control method. This paper offers theoretical and experimental investigation of the control of vehicle suspension systems using a quarter car suspension equipped with a MR damper. To achieve the best performance, a control method made of two nested controllers is used. Fuzzy logic, skyhook and On-Off control techniques are studied as system controllers in conjunction with a Heaviside step function as the damper controller. For the theoretical study, the modified Bouc-Wen model of MR dampers is used to calculate the damping force and a mathematical model of the semi-active quarter car suspension is derived and used in the simulation. To prove the applicability of the proposed fuzzy logic controller in a real suspension system, a two degrees of freedom quarter car test rig is designed and used. To quantify the effectiveness of the system under bump and random road disturbance, various performance criteria are evaluated based on the dynamic response of the quarter car suspension system in time and frequency domains,. Simulation and experimental results from the system with the fuzzy logic controllers are compared to the results from the system with skyhook controller, On-Off controller, a passive MR damper and a conventional passive damper

Passengers vs. battery : calculation of cooling requirements in a PHEV

The power demand of air conditioning in PHEVs is known to have a significant impact on the vehicle’s fuel economy and performance. Besides the cooling power associated to the passenger cabin, in many PHEVs, the air conditioning system provides power to cool the high voltage battery. Calculating the cooling power demands of the cabin and battery and their impact on the vehicle performance can help with developing optimum system design and energy management strategies. In this paper, a representative vehicle model is used to calculate these cooling requirements over a 24-hour duty cycle. A number of pre-cooling and after-run cooling strategies are studied and effect of each strategy on the performance of the vehicle including, energy efficiency, battery degradation and passenger thermal comfort are calculated. Results show that after-run cooling of the battery should be considered as it can lead to significant reductions in battery degradation. Results also show that despite the impact on energy consumption, pre-cooling the cabin and battery in extreme climate conditions is inevitable to achieve the required comfort levels

Screening, isolation and molecular identification of biodegrading mycobacteria from Iranian ecosystems and analysis of their biodegradation activity

Abstract Anthropogenic origin pollutants including pesticides, heavy metals, pharmaceuticals and industry chemicals impose many risks to human health and environment and bioremediation has been considered the strategy of choice to reduce the risk of hazardous chemicals. In the current study, we aimed to screen and characterize mycobacteria from the diverse range of Iranian aquatic and terrestrial ecosystems with harsh and unfavorable environmental conditions that can be utilized for biodegradation of target pollutants. Mycobacteria were isolated from a collection of 90 environmental samples and identified to the species level using conventional microbiological and molecular methods including the PCR amplification of hsp65 and sequence analysis of, 16S rRNA genetic markers. The growth rate of the isolates in presence of pollutants, chromatography, Gibbs and turbidometric methods were used to assess their biodegradation activity. A total of 39 mycobacterial isolates (43.3%) were recovered from 90 samples that belonged to 21 various species consisting of M. fortuitum; 6 isolates, M. flavescens and M. paragordonae; 4 isolates each, M. monacense, M. fredriksbergense and M. aurum; 2 isolates each, 7 single isolates of M. conceptionense, M. porcinum, M. simiae, M. celeriflavum, M. novocastrense, M. neoaurum, M. obuense and 12 isolates that belonged to 8 unknown potentially novel mycobacterial species. The isolates were categorized in three groups based on their bioremediation activity, i.e., 5 (12.8%) organisms without biodegradation activity, 20 (51.2%) organisms with previously reported biodegradation activity, and 14 (35.9%) organisms that showed biodegradation activity but not previously reported. Our results showed that the Iranian ecosystems harbor a good reservoir of diverse mycobacterial species with biodegrading potentiality for neutralizing environmental chemical pollutants

Modelling the electric air conditioning system in a commercially available vehicle for energy management optimisation

Among the auxiliary systems on electric and hybrid electric vehicles the electric air conditioning (eAC) system causes the largest load on the high voltage battery and can significantly impact the energy efficiency and performance of the vehicle. New methods are being investigated for effective management of air conditioning loads through their integration into vehicle level energy management strategies. For this purpose, a fully integrated vehicle model is developed for a commercially available hybrid vehicle and used to develop energy management algorithms. In this paper, details of the eAC model of this vehicle are discussed, including steady state component validation against rig data. Also results of simulating the cabin pull-down are included