Replacing hydrocarbon-powered off-road vehicles with hydrogen fuel cell-powered off-road vehicles can reduce carbon dioxide and criteria pollutant emissions in the agriculture, construction, and ...mining industries. Off-road vehicles perform challenging work in harsh environments that complicate deployment of their fuel cell-powered counterparts. Customers and vehicle manufacturers recognize the health and environmental benefits of emissions reductions but are compelled by the total cost of ownership of their vehicles. This study provides a novel technoeconomic comparison of hydrogen fuel cell + battery hybrid powertrains to traditional diesel powertrains for three hallmark off-road vehicles: tractors, wheel loaders, and excavators. Performance metrics include fuel cell engine power, hydrogen consumption rate, hydrogen storage system volume, energy-regenerative drivetrain efficiency, cost of capital, operating and maintenance cost, fuel cost, and fuel storage cost. Results demonstrate that state-of-the-art fuel cell-powered wheel loaders and excavators are currently cost competitive with diesel platforms by total cost of ownership: compact wheel loaders are 19% less expensive, large wheel loaders are equally expensive, mini/compact excavators are 11% more expensive, and standard/full excavators are 9% less expensive. If targeted improvements to cost, performance, and durability of fuel cell stacks and storage systems are achieved, fuel cell systems would be cost competitive for tractors and significantly lower total cost of ownership options for wheel loaders and excavators. This study also elucidates the relationship between performance, cost, and vehicle duty cycle and provides guidance for optimal deployment of fuel cell off-road vehicles.
•Performance and total cost of ownership modeling of fuel cell vehicles.•FC powertrains are currently economically viable for wheel loaders and excavators.•FC powertrains become lower cost than diesel powertrains if ultimate targets are met.
This paper presents a critical review of the drivelines in all-electric vehicles (EVs). The motor topologies that are the best candidates to be used in EVs are presented. The advantages and ...disadvantages of each electric motor type are discussed from a system perspective. A survey of the electric motors used in commercial EVs is presented. The survey shows that car manufacturers are very conservative when it comes to introducing new technologies. Most of the EVs on the market mount a single induction or permanent-magnet (PM) motor with a traditional mechanic driveline with a differential. This paper illustrates that comparisons between the different motors are difficult by the large number of parameters and the lack of a recommended test scheme. The authors propose that a standardized drive cycle be used to test and compare motors.
In this paper, a Q-learning fuzzy inference system (QLFIS)-based online control architecture is proposed and applied for the optimal control of off-road hybrid electric vehicles (HEVs) to achieve ...better dynamic performance, fuel economy and real-time performance. A dynamic model, including a hybrid system, vehicle dynamics and road model, is established to obtain the state feedback according to the current driving environment under command. The optimal control strategy and objective function are both constructed by an adaptive network fuzzy inference system (ANFIS) due to its strong approaching ability. The fuzzy rules and parameters are trained online through the Q-learning algorithm and gradient descent method. This control framework provides a new control idea for the control of off-road vehicles. Without knowing the driving cycle in advance, it achieves a good control effect for different driving environments through online data collection and training. The QLFIS-based control strategy is compared to dynamic programming (DP)-based and rule-based strategies based on two different off-road driving cycles through simulation. The simulation results show that the vehicle dynamic performance and fuel economy are improved with respect to the rule-based strategy, while the calculation time is greatly reduced compared to that of the DP-based strategy.
•Q-learning fuzzy inference system is adopted for real-time and optimum control.•An optimization model balances electric power performance and energy management.•A fuzzy controller adapts to off-road conditions with online iterative learning.•The strategy improves power and economy of vehicle, reduces elapsed time by 98%.
•Dual-motor four-wheel-drive off-road electric vehicle proposed.•Systematic methodology to optimize the drivetrain design.•Novel objective function minimizing the gap between power envelops.•Larger ...speed range, faster acceleration, better gradeability.
Electric vehicles (EVs) are a dominant transportation trend towards a low-carbon future. However, there is a lack of systematic studies for full-electric off-road vehicles in terms of drivetrain design and energy management issues. This paper proposes a novel methodology to develop a drivetrain system for a four-wheel-drive (4WD) dual-motor off-road EV. The obtained design delivers high performance in both driving performance and energy efficiency of a desired vehicle using the two electric motors with their multi-speed gearbox. The proposed approach is to minimize the power envelope (force-speed characteristic) difference between a targeted model and the system under study. As a result, the objective function finds an optimal solution for a proper set of gear ratios and constant power speed ratio (CPSR) through a two-layer hierarchical scheme. The upper layer sets the targeted power envelope based on the expected driving measures. The lower layer minimizes the gap of the power envelope characteristics between the targeted vehicle and the dual-motor vehicle. In parallel, two optimization loops are implemented at the lower layer. The outer loop determines the proper value of CPSR, meanwhile, the gear ratios corresponding to the selected CPSR are optimized by a particle swarm optimization (PSO) algorithm in the inner loop. The results verify that the dynamic and energy performances of the studied dual-motor vehicle are enhanced over critical testing scenarios. In a comparison with the single-motor single-speed gearbox configuration, the optimized design shows that the top speed is 55% higher; the acceleration time to 45 km/h is reduced by 55.83%; and the gradeability is improved by 162.5%. Moreover, the test under a typical off-road cycle reveals a 1.9% overall efficiency increase compared to the dual-motor drivetrain using the same non-optimized gear ratio. The proposed comprehensive design approach has the potential to be applied to a wide range of vehicle areas.
This paper presents an algorithm for overapproximating the drivable area of road vehicles in the presence of time-varying obstacles. The drivable area can be used to detect whether a feasible ...trajectory exists and in which area one can limit the search of drivable trajectories. For this purpose, we abstract the considered road vehicle by a point mass with bounded velocity and acceleration. Our algorithm calculates the reachable occupancy at discrete time steps. At each time step, the set is represented by a union of finitely many sets, which are each the Cartesian product of two 2-D convex polytopes. We demonstrate our method with three examples: i) a traffic situation with identical dynamic constraints in the x- and y-directions; ii) a highway scenario with different lateral and longitudinal constraints of the dynamics; and iii) a highway scenario with different traffic predictions. The examples demonstrate that we can compute the drivable area quickly enough to deploy our approach in real vehicles.
Volatile Organic Compounds (VOCs) source profiles of on-road vehicles were widely studied as their critical roles in VOCs source apportionment and abatement measures in megacities. Studies of VOCs ...source profiles from on-road motor vehicles from 2001 to 2016 were summarized in this study, with a focus on the comparisons among different studies and the potential impact of different factors. Generally, non-methane hydrocarbons dominated the source profile of on-road vehicle emissions. Carbonyls, potential important components of vehicle emission, were seldom considered in VOCs emissions of vehicles in the past and should be paid more attention to in further study. VOCs source profiles showed some variations among different studies, and 6 factors were extracted and studied due to their impact to VOCs source profile of on-road vehicles. Vehicle types, being dependent on engine types, and fuel types were two dominant factors impacting VOCs sources profiles of vehicles. In comparison, impacts of ignitions, driving conditions and accumulated mileage were mainly due to their influence on the combustion efficiency. An opening and interactive database of VOCs from vehicle emissions was critically essential in future, and mechanisms of sharing and inputting relative research results should be formed to encourage researchers join the database establishment. Correspondingly, detailed quality assurance and quality control procedures were also very important, which included the information of test vehicles and test methods as detailed as possible. Based on the community above, a better uncertainty analysis could be carried out for the VOCs emissions profiles, which was critically important to understand the VOCs emission characteristics of the vehicle emissions.
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•Studies of VOCs source profiles from on-road vehicles from 2001 to 2016 were summarized.•Variations of VOCs source profiles in different studies were observed.•6 factors were extracted and their impact to VOCs source profile of on-road gasoline vehicles was discussed.
Electrifying the ground vehicles is a promising approach to alleviating the energy and climate issues. The adoption of an electric vehicle (EV) and a hybrid EV (HEV) has introduced significant ...impacts on various aspects of vehicle design, especially on the chassis systems. When vehicles tend to be lighter, smarter, and autonomous, more electroactuators with a wide-bandwidth control and an energy-regeneration capability are deployed instead of traditional hydraulic ones to improve the vehicle dynamic and energy performance. In this article, an overview of the chassis electrification technologies regarding different configurations of electric/hybrid powertrains, active suspension, and steering systems, along with a comprehensive review of key research fields on the design and control of the discussed systems, is presented. For related technologies, the comparative discussions and design considerations serve as a reference for practical research and development. Although the electric solutions in different subsystems show great potential to further benefit the essential chassis functions, a fully electrified chassis still has a long way to go considering the technical maturity and the cost-performance tradeoff. This article also highlights the technical gaps and supplies future directions for the chassis electrification.
•A novel electro-hydraulic energy harvesting damper was proposed for off-road vehicles.•Unidirectional generator rotation was realized to improve energy harvesting efficiency.•Asymmetric ...rebound/compression damping force was obtained for better road-tire contact.•Damping and regenerative characteristics were studied via simulation and test.•Large controllable damping range is achieved as the basis to control active suspension.
This paper presents an electro-hydraulic semi-active damper to harvest the suspension kinetic energy for the purpose of further improving the fuel efficiency of off-road vehicles. This regenerative damper can transform the reciprocating suspension vibration into unidirectional generator rotation, and meanwhile achieve approximately asymmetric rebound/compression damping force in a wide controllable region. The working mechanism of this new damper is first elaborated, and then its dynamic model is mathematically derived based on the first-principle analysis of hydraulic and electric components. A prototyping damper is designed and manufactured, and a series of experimental tests are conducted to demonstrate its effectiveness to generate the damping characteristic and energy harvesting capability.
Hybrid and electric vehicle (HEV/EV) technology is reasonably mature at this time, with a few million vehicles around in the world, and there is a significant amount of literature in the public ...domain on this subject. However, there is not enough literature on the application of this technology for off-road vehicles, including construction equipment, other industrial utility vehicles, and nonautomotive applications, such as a locomotive, ships, or airborne vehicles. With this in mind, the author presents here the topic and its current status. In addition, the author discusses the issue related to the decision-making process before the above technology is introduced for any HEV/EV application so that one is assured that the technology will bring benefit if applied for a particular purpose.
The topic of this brief is the design and analysis of a control strategy for semi-active suspensions in road vehicles. Currently used closed-loop control strategies (like the Sky-Hook damping) ...require two sensors for each suspension. Typically, two accelerometers or an accelerometer combined with a stroke sensor are used. In this brief, a simple but innovative algorithm is proposed that is capable of providing quasi-optimal performance using a single accelerometer. The starting point of this work is the Mix-SH-ADD control algorithm, which has been recently developed and proposed. Starting from that idea, the single-sensor algorithm is derived. This algorithm pays a small price in terms of performance with respect to the mix SH-ADD algorithm, while guaranteeing cost reduction and augmented reliability.
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