Improved cornering for energy-efficient vehicles
By reducing the resistance when a vehicle is turning, you save energy. That is good both for the environment and for the consumer. The energy saving is made possible by controlling each wheel individually, in terms of steering, drive, braking, wheel suspension and wheel angles.
At the Royal Institute of Technology KTH, Associate Professor Jenny Jerrelind and her colleagues in the field of Vehicle Dynamics strive to find solutions that reduce the resistance that occurs when a vehicle is turning.
“We focus on the tires’ function and their potential to contribute to more energy efficient vehicles. When a vehicle is in motion, the tire creates a resistance that must be overcome. This resistance consists partly of the rolling resistance, which is mainly due to losses when tires are deformed, and partly of the cornering resistance that arises when cornering and the tire forces create force components that act opposing the direction of travel of the vehicle. Our research is based on studying different ways to reduce the cornering resistance”, says Jenny Jerrelind.
The Vehicle Dynamics research group at KTH has studied a future vehicle concept in the form of a wheel corner model, with an electric motor integrated with an active wheel suspension. It provides the ability to individually control steering, drive, braking, wheel suspension settings and wheel angles for each wheel.
“For example, by tilting the tires outward or inward relative to the vehicle body, a so-called camber angle is created. The camber angle gives an extra side force in the direction of tilting the tire.”
KTH’s experimental vehicle RCV, Research Concept Vehicle is built at their own ITRL laboratory, Integrated Transport Research Lab. The vehicle is equipped with wheel corner functionality and has enabled researchers to test the strategies on an actual vehicle. Trials have for instance been carried out at the AstaZero test facility in Sweden.
The major challenge for the researchers is to create reliable and verified tire models:
“Optimizing the tire’s performance for energy efficiency can create conflicting requirements in terms of safety, comfort and performance. You should also try to include tire wear in the models to see how the tires are affected by electric motors and when you have camber angles on the tires.”
The simulations and tests performed by the researchers show that energy losses really can be reduced by individually controlling the camber angle, drive and steering for each wheel. Adjusting the tires’ function while driving for the sake of better energy efficiency is beneficial from a number of aspects.
“The ability to individually control steering, drive, braking and wheel suspension settings to reduce energy consumption are both good for the consumers as well as for the environment”, says Jenny Jerrelind.
Now, continued research and more real-life tests will need to be conducted:
“There is a need for research on tires wear and how to implement tire wear in the simulation models. There is also a need for more physical tests with test vehicles to evaluate the different governing strategies.”
/ Daniel Karlsson, photo: Jenny Jerrelind
Optimization design paves way for efficient freight transport
Toheed Ghandriz, a doctoral student at Chalmers University of Technology, is focused on finding the optimal distribution of propulsion over axles in long combination vehicles. The task is also to designing such a propulsion, including conceptual control design. The result: More cost- and energy-efficient transports.
Toheed, tell us more about your methods?
“The idea is that freight vehicles can be designed more cost- and energy-efficiently given operational domains and transportation use-cases. For this purpose, optimization-based methods are applied to deliver customized fleet vehicles with tailored propulsion components that fit best given transportation missions and operational environment.
“Optimization-based design of vehicle components have showed to be more effective considering optimization of transportation mission infrastructure simultaneously, including charging stations, routing and fleet composition and size, especially in case of electrified propulsion.”
What are the greatest challenges in this area?
“It is to evaluate the cost function sufficiently. Accurate models of vehicle dynamics and transportation environment are needed. The greatest challenge lies in parametrizing these models in order to reflect the real-world problems and transportation use-cases.”
“In my licentiate thesis, it was observed that by implementing integrated vehicle hardware-transportation optimization, total cost of ownership can be reduced up to 35%, in case of battery electric heavy vehicles.”
What can be the impact of the applications?
“Optimization-based design helps agile market adaption, profitable businesses specially in case of electrification and automation, as well as green transport; provided that a proper description of the use-case and system boundaries is available through clear communication between stakeholders.”
What are the long–term benefits?
“It will give a more cost- and energy-efficient freight transport and eventually green transportation.”
Where do you see the need for further research?
“The future research includes studying the possibility and inclusion of tactical and operational levels of decision making in integrated vehicle hardware-transportation optimization. Tactical and operational decisions refer to actions taken during dynamic driving task with the time span in minutes and seconds, respectively. These actions contribute to energy consumption as well as vehicle maneuvering.”
/ Daniel Karlsson
Holistic approach increases the knowledge of hybrid vehicles and emissions
Olov Holmér is a PhD student at the Department of Electrical Engineering at Linköping University and studies hybrid vehicles together with Professor Lars Eriksson, among others.
What is unique in your research?
“In our research we look at the interaction between electrical operation, combustion engine operation and the thermally inert and slow systems in the form of aftertreatment systems with sub-components such as particle filters and catalysts. Usually, the different systems are treated quite separately, but we study the entire system as a whole, with the goal of designing control systems with more integration between the systems.”
What are the challenges in the area?
“It is building the right models that capture the most important features, so that system studies can be performed. A large part of all available models have been designed for conventional vehicles and it is not sure that these capture the phenomena that arise in a hybrid vehicle, where, for example, the engine is switched off for a long time. For science and university research it is difficult to get measured data that isolates and captures the phenomena to be modeled.
What have you done so far?
“We have developed simulation models for various vehicle components and integrated them into new complete hybrid vehicle models.”
What will this result in?
“It will be an analysis of how much you can earn in fuel consumption and reduce NOx emissions if you were to hybridize a heavy truck that runs on the Swedish highway. We have also begun looking at new control strategies to warm up the aftertreatment system as quickly as possible.
“We learn more about hybrid vehicles and emissions so that we can develop better vehicles, which will utilize the electric mobility potential and reduce emissions.”
Where are the needs of further research?
“There is a need to continue to ensure the quality of existing models and to develop new models describing new phenomena that we want to study. An important part of this is to identify the most important effects of the thermal systems.”
/ Daniel Karlsson
Stefan Pettersson brings academia and institute closer together
Stefan Pettersson, research manager of the electromobility application area at RISE Viktoria and active in the Swedish Electromobility Centre, has also become an Adjunct Professor at Chalmers University of Technology. His inauguration lecture at Chalmers is titled “Collaborative academia-institute-industry/society electromobility research”.
Stefan Pettersson has a M.Sc. in Automation Engineering and a Ph.D. in Control Engineering. He became an Associate Professor in Control Engineering at Chalmers in 2004. Since last year Stefan is an Adjunct Professor at the Department of Electrical Engineering, and a member of the departmental advisory team.
We took the opportunity to ask Stefan some questions:
In your lecture you will talk about collaborative research, engaging academia, institute, industry and society. What are the benefits of this as you see it?
“Global challenges, like the climate problem, cannot be solved by single persons or organisations. They instead require common understanding and collaboration. Sweden is on the top three list of innovative countries but the pace of other countries is high and we really need to fight hard to keep our position and climb even higher up. I strongly believe that research where different stakeholders work together solving complex problems is beneficial for Sweden’s industry and our ability to be a top research and innovation country in the world. However, more important, by collaboration we will have the ability to better solve the global challenges for the common good of our society.”
What has been the driving force for you personally to join Chalmers as an Adjunct Professor? And what advantages do you see for RISE and the department, respectively?
“I have earlier been working at Chalmers and enjoyed and appreciated being a researcher around competent colleagues. I personally enjoy being a part of Sweden’s top universities and hope that I can create natural bridges between the research at Chalmers and RISE, resulting in more collaborative research and educating more Ph.D. students. I bring to Chalmers a large network of stakeholders and insight into their challenges, many ideas and common research possibilities and can help researchers to be in contact with relevant researchers at RISE. Adjunct Professors are natural persons helping the universities with the third task to bring research results to our society. From the RISE view point, I will get to know the research and researchers better and perhaps RISE will employee some of them, it can give good ideas for common innovation projects and it can provide good opportunities for increasing the competence of RISE researchers.”
What has made you specially interested in research on electromobility?
“After my quite theoretical Ph.D. studies at Chalmers I shifted the research more into the automotive application area. I worked with energy management problems in industry a couple of years before I moved to RISE Viktoria and became responsible for the electromobility application area. I personally like to do and contribute to research that is relevant and where you quite easily see the result of the research in society. Electric vehicles are part of the future transportation system and I am glad to contribute to the shift from fossil fuelled vehicles to a sustainable future with electrified vehicles.”
Text: Yvonne Jonsson, Chalmers
Algorithms provide faster and more efficient electric vehicle charging
As electric cars become more common, charging large numbers of electric vehicles could cause problems with the stability of the local electricity grid. This could be avoided by utilizing smart control charging, wherein the charging power is altered over time by some algorithm. It is also possible to use the grid more effectively by using smart charging. With the right algorithms for charging, researchers want to ensure that the power grid can be kept in balance.
Joakim Munkhammar is an associate professor, research leader of the Electric Transport Group, Uppsala University and involved in Swedish Electromobility Centre. He and his research colleagues are working to find the optimum models for smart charging of electric vehicles.
“Smart” in this case means charging is controlled via algorithms, to achieve a variation in the otherwise expected charge pattern. The advantage is that smart electric car charging could minimize the risk of overloading the local power grid, while during low load times, the charging model will be able to utilize more capacity for charging, compared to standard charging without control.
“Conventional uncontrolled electric car charging can lead to problems with the local power grid. Alternatively, it may be suboptimal not to use remaining resources in the local power grid for electric car charging. This research project is based on developing models or algorithms for smart electric car charging that will allow the charging to avoid local problems in the grid, while at other times they can charge cars faster than with uncontrolled charging”, says Joakim Munkhammar.
The major challenge in the field is to create algorithms that work well and are robust, and that connect directly to existing industry technology. Therefore, the research is closely linked to both the energy and automotive industry, in the form of Vattenfall RnD and CEVT.
“The idea is to link this closer to the industry than before, and connect to CEVT and Vattenfall RnD by creating algorithms that can be implemented in existing technology. The way forward is to create models or algorithms for this, validate them against data and try to implement in actual systems.”
The hope is that the smart charge algorithms developed by the researchers will be used directly in the automotive industry. In this particular study, focus is on passenger cars and home charging, but Joakim Munkhammar points out that the algorithms can also prove useful for other vehicle types.
What are the results from the research so far?
“In a study, presented at the E-mobility Symposium in Stockholm in October, we have found that the amount of problems with the local power grid expected to occur with home charging is minimal. Therefore, the need for smart charging here is largely non-existent. The results, which are preliminary, are calculated based on electricity consumption without heating and are a comparison between electricity consumption from households with or without electric car charging and a given fuse level. Later, we will calculate what happens with the power grid. It may be particularly interesting on block level or city level.”
“We also found that electric car charging could be done faster for most of the year’s days, for virtually all simulated cases with different installed charging power.”
The results can consequently be of importance to the individual car owner, but also in a broader perspective.
“Smart electric car charging is designed to utilize resources more efficiently, in this case the local power grid. Therefore, all parties could win by implementing such algorithms. For society, range anxiety for electric car drivers can decrease by shorter charging time and for electricity grid providers the stability of the local grid could be enhanced, and it could also help to keep the local power grid in balance, even with for example local solar production, which could otherwise create problems.”
What are the needs of further research?
Aside from neighborhood and city level of home-charging public and workplace charging are the next challenges in the research. Then, research on the power grid’s impact from electric car charging is required, and the combination of electric car charging and intermittent sources of energy, such as wind or solar power, is important to determine how the algorithms are to be designed. Furthermore, it is a challenge to create transports for future smart cities, where this is only the first step”, concludes Joakim Munkhammar.
/ Daniel Karlsson