This study aims at understanding the perception of city bus users in selected Indian cities under given operating conditions. A questionnaire form was designed for capturing the socio-economic ...characteristics, trip characteristics, satisfaction, and preferences of the bus users. This questionnaire includes seven service quality attributes namely in-vehicle travel time, bus stop waiting time, bus on-time performance, riding comfort, safety, end-to-end connectivity, providing reliable information on the bus stops, and providing reliable information on the smartphone. Personal Interview Surveys were conducted to collect the responses from the city bus users. Total 613 samples were considered for analysis in Hyderabad, 707 samples in Navi Mumbai and 590 samples from Surat BRTS users, 505 samples from Surat city bus users. Further, Garret ranking technique was also employed to analyze the priority preferences based on the sample’s responses. Based on Garret’s weightages, weighted average satisfaction ratings were evaluated. Based on the results, it was found that females have given more priority for safety attributes. Bus on-time performance, bus reliability, bus stop waiting time and on time performance were given the highest priority and reliable information at bus stops and online sources were given the least priority.
•A new Coherence-PPI method for practical drive-by bridge inspection is proposed.•Effects of road roughness, noise, and vehicle parameter variations are eliminated.•The algorithm encourages ...measurement variability to filter bridge frequencies.•The method is validated through numerical studies and field tests using city buses.
Recently, drive-by-bridge inspection methods have attracted substantial scholarly interest; however, their practical implementation has encountered significant challenges. In engineering practice, even simply extracting bridge frequencies from ordinary or commercial vehicles appears to be difficult; components related to factors such as road roughness often dominate vehicle vibration responses. This study proposes a novel coherence-PPI (Prominent Peak Identification) algorithm based on the Bayesian framework and applies it to city bus bridge monitoring to extract bridge frequencies. The fundamental idea is to recognize the bridge frequency as a common vibration component across various vehicle runs. The algorithm comprises the following three steps: First, coherences were computed for all vehicle runs to interpret the signal relationships. Second, a Bayesian framework was established to statistically determine the threshold that can maximize the occurrence of bridge frequency. Third, the prominent peaks (PPs) were selected based on the threshold, and their distribution was counted to identify the fundamental frequency of the bridge. In contrast to the previous studies that focused on avoiding differences (e.g., by trying to reduce variation, driving in the same lane, and using the same speed), this methodology encourages the introduction of variability in drive-by measurements to filter bridge frequencies, rendering it particularly compelling for practical engineering applications. The proposed methodology was validated through numerical studies, including the Monte Carlo method, and field tests using city buses. The results demonstrated that the method can effectively eliminate the effects of road roughness, environmental noise, and vehicle parameter variations and accurately identify the bridge frequency.
The key challenge in energy management of plug-in hybrid electric vehicles is how to macroscopically plan the battery energy considering trip information while microscopically distributing the torque ...between power sources to improve the energy efficiency of the hybrid propulsion system. Nowadays, future partial trip information can be obtained from an intelligent transportation system and a navigation system when traveling starts. But how to use these trip information sufficiently remains to be further studied. Moreover, the online energy management strategy should not take up too many resources of micro-controller. Based on these conditions, we proposed a novel energy management strategy for plug-in hybrid electric city buses. First, Pontryagin's minimum principle was used to obtain the optimal results of different driving cycles. Then, a neural network module was designed and trained to learn the mechanisms of optimal state-of-charge (SOC) curves. When trip starts, the neural network module can be used to generate a reasonable battery SOC reference curve according to the partial trip information available. Finally, an adaptive fuzzy logic controller was applied to follow the trend of the SOC reference curve. The main contribution of this paper is that the effectiveness of battery energy planning by comprehensively considering the future partial trip information and historical optimal SOC curves is verified, which provides a new perspective for real vehicle energy management. Simulation results show 4.61%-13.49% fuel savings on the trained and untrained driving cycles as compared with the charge-depleting and charge-sustaining strategy.
Fuel cell hybrid electric vehicles are attracting increasing attention and research. However, the durability of fuel cell systems (FCS) is the main bottleneck in commercial application. A plug-in ...fuel cell city bus was developed by our group, and it completed several months of demonstration operation. A two-stage flowchart was proposed to clarify the FCS degradation analysis. The average cell voltage decline rate is approximately 346 μV/h at a current density of 120 A, under which the initial voltage is about 0.7 V. The estimated lifetime in the third stage reaches the design target. The final electrochemically active surface areas are approximately 80% of the initial value. A detailed degradation analysis of fuel cell voltage uniformity is presented, and a five-region degradation otherness analysis is proposed for performance uniformity analysis. The difference of equivalent resistance has been verified to be the main factor in degradation otherness of the regions and in system performance degradation.
•A two-stage flowchart is proposed for performance degradation analysis of fuel cell vehicles.•A detailed on-road fuel cell stack performance degradation analysis is presented.•The voltage declines of different degradation mechanisms are compared.•The performance degradation otherness in five regions of a fuel cell stack is analyzed.
Prognostics and Health Management (PHM) is among the most significant and effective technologies to improve the durability of a proton exchange membrane (PEM) fuel cell system. This paper deals with ...the prediction issues of the degradation trend for PEM fuel cells equipped in a city bus. First, three aging parameters are extracted from a multi-parameter voltage model, and two of them are selected to represent the degradation of electronic and ionic resistance separately for the first time. Then the parameters are initialized by harmony search (HS) algorithm with an improved objective function, and updated by resorting to the particle filtering (PF) algorithm. Subsequently, Bayesian ridge regression (BRR) and Gaussian progress regression (GPR) are utilized to establish the relationship between the operating time and aging parameters. We categorized the input of the regression models into two classes: the total operating time and the cumulative time of four operating conditions. The results indicate that the latter performs better than the former in characterizing the future trend of aging parameters. Moreover, it is observed that BRR is more attractive since its computational time is far less than that of GPR while the mean absolute error (MAE) is no more than 8.5 mV.
•Electronic and ionic resistances are studied separately in the voltage model.•A penalty coefficient is deployed in the objective function of HS algorithm.•The prognosis method can predict the degradation of PEMFC integrated to a city bus.
•Optimization and selection study for the input power split configuration applied in PHEV buses.•One-dimensional direction search ECMS method is provided to decrease the on-line calculation in real ...application.•Proper input split configuration decreases fuel consumption and battery degradation in plug-in hybrid electric buses.•Only 4 of 6 possible input power split configurations are suitable for use.
Power split configurations exhibit potential on decreasing fuel consumption. However, how to select the best power split configuration among all the possible configurations still need to be explored. In this paper, a one-dimensional searching ECMS (Equivalent Consumption Minimization Strategy) is developed to evaluate fuel consumption for input power split configuration. Additionally, a battery degradation model based on experimental data is applied to evaluate the battery degradation for input power split configuration. According to one-dimensional searching ECMS and battery degradation model, the impact of different input power split configurations on fuel consumption and battery degradation is investigated. Simulations show that configuration T1 has fuel consumption and battery degradation advantages for PHEV city bus application in China. These advantages are observed because the system efficiency operation points of configuration T1 are closer to the high efficiency area than the system efficiency operation points of other input power split configurations. Furthermore, according to the lever model and one-dimensional searching ECMS method, a power split configuration selection method is provided in this paper. The simulation results based on configuration selection method still indicate that configuration T1 appears to have the best fuel economy for PHEV city bus application. Moreover, configuration T5, with a lever length close to 0, exhibits the worst fuel consumption and battery degradation.
In this work, a permanent magnet synchronous motor is designed for an electric city bus. The unit winding factor is considered for torque capability enhancement and completely open slots are adopted ...for low‐cost rectangular wire winding implementation. Accordingly, extremely large pulsating torques that are predictable should be mitigated through the rotor design possibilities. In this regard, a modified Halbach pole configuration, named axially segmented Halbach, that is capable of producing considerably smooth torque as well as retaining the large mean torque is proposed. First, an optimised conventional Halbach array is calculated as the initial design. Then, following a detailed introduction to the new design concept, the modified Halbach pole parameters are obtained through the proposed 2D model‐based optimisation algorithm. A rotor step skewing scheme is also evaluated to make the final comparisons, which are carried out via 3D FE models. The results demonstrate the admirable performance of the proposed Halbach configuration as an effective solution for torque profile improvement.
Fuel cell vehicles are becoming more popular and attracting more attention from industries, but stability and reliability of the fuel cell system (FCS) are still problems for its commercial progress. ...Therefore, a fault diagnosis system is essential for a reliable and long working lifetime FCS. In this work, a fault diagnosis method based on multi-sensor signals and principle component analysis (PCA) is proposed to improve FCS performance. By using this method, the correlation among different sensor signals are analyzed based on multi-sensor signals, and a simplified statistic index for fault diagnosis is deduced based on the PCA. The FCS operation conditions are monitored online, and faults in sensor and system levels are diagnosed. Experimental results show that, two typical fault scenarios, i.e., a single sensor fault and a serious system failure, can be successfully diagnosed and distinguished. For the single sensor fault, the sensor signal is reconstructed immediately to ensure that fuel cell vehicles operate normally. For the system failure, the fault can be detected in 17 s and the fault source signals can be located in 31 s, so the fuel cell stack can be protected timely. The main contribution of this work is to deduce a simplified statistic index for fault diagnosis based on multi-sensor signals and PCA method, and to provide an experimental study on identifying faults in sensor and system levels of a PEM fuel cell system.
•One online diagnosis method for PEM fuel cell system is explored.•A simplified statistics index for fault diagnosis based on multi-sensor signals and PCA method is deduced.•Experimental study on identifying faults in sensors and system levels of a PEM fuel cell system is carried out.•Fault-tolerant strategies corresponding to sensor fault and system failure have been proposed.
The pre-determined city bus routes and the availability of partial-trip information obtained through vehicular connectivity provides new opportunities for plug-in vehicles to plan electric energy ...reasonably. This paper presents a data-driven hierarchical control method for online energy management of plug-in hybrid electric city buses, which can learn from globally optimal solutions based on historical accumulated cycles while taking advantage of connectivity-enabled partial-trip information. The devised scheme comprises two levels of control modules. The upper battery state-of-charge planner trained using historical optimal data is employed for deriving a reference state-of-charge based on the current battery state, remaining trip length, and low/high speed ratios. The lower powertrain controller is then applied to regulate the engine operation according to the reference state-of-charge and powertrain states. This article presents two contributions: (1) both accumulated historical optimal data and partial-trip information are assimilated to augment the applicability of the control hierarchy, thus achieving better resilience to “unseen” driving patterns; (2) given limited resources of micro-controllers, the control strategy is proven to be a real-time implementable, close-to-optimal solution. A variety of results show that the proposed approach can achieve significant fuel savings (4.99%–14.80%) as compared to the charge depleting and charge sustaining strategy.
•Data driven hierarchical control is presented for online energy management.•The upper state-of-charge planner is employed for planning battery state-of-charge.•The lower powertrain controller is applied to regulate the engine operation.•The strategy can achieve better resilience to “unseen” driving patterns.•The strategy is proven to be a real-time implementable, close-to-optimal solution.
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