Patrick Gruber

Dr Patrick Gruber


Reader in Advanced Vehicle Systems Engineering

Biography

Research interests

  • Tyre modelling
  • Friction and wear
  • Vehicle systems
  • Linear & non-linear finite element analysis

 

4th International Tyre Colloquium

The International Tyre Colloquium has a successful history in discussing the latest progress in the understanding and simulation of tyre-road-vehicle interactions. The first Tyre Colloquium was organised by Prof Pacejka in 1991 (Delft), the second one was in Berlin in 1997, organised by Prof Böhm and Prof Willumeit, and the third one was in Vienna in 2004, organised by Prof Lugner and Prof Plöchl. In line with the tradition, the 4th Tyre Colloquium was focused on topics related to modelling of tyres for vehicle dynamics analysis including:

  • Tyre measurements and measurement techniques
  • Tyre models
  • Application of tyre models to vehicle dynamics
  • Determination of tyre model parameters
  • Measurement and modelling of rubber friction
  • Tyre-road contact
  • Evaluation and verification of tyre models
  • Tyre design features and their consequences for the tyre behaviour

The Proceedings of the 4th International Tyre Colloquium are available as an OpenAccess eBook.

 

Teaching

ENG2095 Mechanics of Vehicles and Machines

ENG3162 Group Design Project (Module Leader)

ENG3166 Control and Dynamics (Module Leader)

BEng/MEng Individual Project supervision

Departmental duties

Programme Leader Automotive Engineering

Year 1 Tutor

My publications

Publications

Gruber P, Sharp RS, Crocombe AD (2010) Virtual tyre testing ? experiences with an advanced FE tyre model,
De Pinto S, Camocardi P, Sorniotti A, Gruber P, Perlo P, Viotto F (2016) Torque-fill control and energy management for a 4-wheel-drive electric vehicle layout with 2-speed transmissions, IEEE Transactions on Industry Applications
This paper presents a novel 4-wheel-drive electric vehicle layout consisting of one on-board electric drivetrain per axle. Each drivetrain includes a simplified clutch-less 2-speed transmission system and an open differential, to transmit the torque to the wheels. This drivetrain layout allows eight different gear state combinations at the vehicle level, thus increasing the possibility of running the vehicle in a more energy efficient state for the specific wheel torque demand and speed. Also, to compensate the torque gap during gearshifts, a ?torque-fill? controller was developed that varies the motor torque on the axle not involved in the gearshift. Experimental tests show the effectiveness of the developed gearshift strategy extended with the torque-fill capability. Energy efficiency benefits are discussed by comparing the energy consumptions of the case study vehicle controlled through a constant front-to-total wheel torque distribution and conventional gearshift maps, and the same vehicle with an energy management system based on an off-line optimization. Results demonstrate that the more advanced controller brings a significant reduction of the energy consumption at constant speed and along different driving cycles.
Individually-controlled powertrains of fully electric
vehicles present an opportunity to enhance the steady-state and
transient cornering response of a car via continuously-acting
controllers and enable various ?driving modes? to be available.
This study investigates the associated potential for energy savings
through the minimization of power losses from the motor units
via wheel torque allocation. Power losses in straight-ahead
driving and a ramp steer maneuver for different motor types and
under different wheel torque allocation schemes are analyzed in
an offline simulation approach. Significant reductions in motor
power losses are achieved for two motor types using an
optimization scheme based on look-up tables of motor loss data.
Energy loss minimization cannot be achieved through a direct
quadratic approximation of the power losses.
De Pinto S, Sorniotti A, Gruber P, Camocardi P, Perlo P, Viotto F (2015) Gearshift control with torque-fill for a 4-wheel-drive fully electric vehicle, 2015 INTERNATIONAL CONFERENCE ON SUSTAINABLE MOBILITY APPLICATIONS, RENEWABLES AND TECHNOLOGY (SMART) IEEE
Gruber P, Sharp RS, Crocombe AD (2012) Normal and shear forces in the contact patch of a braked racing tyre Part 2: Development of a physical tyre model, Vehicle System Dynamics: international journal of vehicle mechanics and mobility 50 (3) pp. 339-356
This article is the second part of a two-part article looking at carcass deflections, contact pressure and shear stress distributions for a steady-rolling, slipping and cambered tyre. In the first part, a previously described and validated finite-element (FE) model of a racing-car tyre is developed further to extract detailed results which are not easily obtainable through measurements on an actual tyre. Generally, these results aid in the understanding of contact patch characteristics. In particular, they form a basis for the development of a simpler physical tyre model, which forms the focus of this part of the article. The created simpler tyre model has the following three purposes: (i) to reduce computational demand while retaining accuracy, (ii) to allow identification of tyre model features that are fundamental to an accurate representation of the contact stresses and (iii) to create a facility for better understanding of tyre wear mechanisms and thermal effects. Results generated agree well with the physically realistic rolling-tyre behaviour demonstrated by the FE model. Also, the model results indicate that an accurate simulation of the contact stresses requires a detailed understanding of carcass deformation behaviour.
Pennycott A, De Novellis L, Gruber P, Sorniotti A (2014) Optimal braking force allocation for a four-wheel drive fully electric vehicle, Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering
Gruber P, Sharp RS, Crocombe AD (2011) Structural influences on the contact stresses of a tyre,
De Novellis L, Sorniotti A, Gruber P, Pennycott A (2014) Comparison of Feedback Control Techniques for Torque-Vectoring Control of Fully Electric Vehicles, IEEE Transactions on Vehicular Technology
Pennycott A, de Novellis L, Sorniotti A, Gruber P (2014) The Application of Control and Wheel Torque Allocation Techniques to Driving Modes for Fully Electric Vehicles, SAE International Journal of Passenger Cars - Mechanical Systems 7 (2) pp. 488-496
The combination of continuously-acting high level controllers and control allocation techniques allows various driving modes to be made available to the driver. The driving modes modify the fundamental vehicle performance characteristics including the understeer characteristic and also enable varying emphasis to be placed on aspects such as tire slip and energy efficiency. In this study, control and wheel torque allocation techniques are used to produce three driving modes. Using simulation of an empirically validated model that incorporates the dynamics of the electric powertrains, the vehicle performance, longitudinal slip and power utilization during straight-ahead driving and cornering maneuvers under the different driving modes are compared. The three driving modes enable significant changes to the vehicle behavior to be induced, allowing the responsiveness of the car to the steering wheel inputs and the lateral acceleration limits to be varied according to the selected driving mode. Furthermore, the different driving modes have a significant impact on the longitudinal tire slip, the motor power losses and the total power utilization. The control and wheel torque allocation methods do not rely on complex and computationally demanding online optimization schemes and can thus be practically implemented on real fully electric vehicles. Copyright © 2014 SAE International.
Lenzo B, De Filippis G, Dizqah A, Sorniotti A, Gruber P, Fallah S, De Nijs W (2017) Torque Distribution Strategies for Energy-Efficient Electric Vehicles with Multiple Drivetrains, Journal of Dynamic Systems Measurement and Control: Transactions of the ASME 139 (12) 121004 American Society of Mechanical Engineers
The paper discusses novel computationally efficient torque distribution strategies for electric vehicles with individually controlled drivetrains, aimed at minimizing the overall power losses while providing the required level of wheel torque and yaw moment. Analytical solutions of the torque control allocation problem are derived and effects of load transfers due to moderate driving/braking and cornering conditions are studied and discussed in detail. Influences of different drivetrain characteristics on the front and rear axles are described. The results of the analytically-derived algorithm are contrasted with those from two other control allocation strategies, based on the off-line numerical solution of more detailed formulations of the control allocation problem (i.e., a multi-parametric non-linear programming problem). The solutions of the control allocation problem are experimentally validated along multiple driving cycles and in steady-state cornering, on an electric vehicle with four identical drivetrains. The experiments show that the computationally efficient algorithms represent a very good compromise between low energy consumption and controller complexity.
de Novellis L, Sorniotti A, Gruber P, Shead L, Ivanov V, Hoepping K (2012) Torque vectoring for electric vehicles with individually controlled motors: State-of-the-art and future developments, World Electric Vehicle Journal 5 (2) pp. 617-628
© 2012 WEVA.This paper deals with the description of current and future vehicle technology related to yaw moment control, anti-lock braking and traction control through the employment of effective torque vectoring strategies for electric vehicles. In particular, the adoption of individually controlled electric powertrains with the aim of tuning the vehicle dynamic characteristics in steady-state and transient conditions is discussed. This subject is currently investigated within the European Union (EU) funded Seventh Framework Programme (FP7) consortium E-VECTOORC, focused on the development and experimental testing of novel control strategies. Through a comprehensive literature review, the article outlines the stateof- the-art of torque vectoring control for fully electric vehicles and presents the philosophy and the potential impact of the E-VECTOORC control structure from the viewpoint of torque vectoring for vehicle dynamics enhancement.
Lu Q, Gentile P, Tota A, Sorniotti A, Gruber P, Costamagna F, De Smet J (2016) Enhancing vehicle cornering limit through sideslip and yaw rate control, MECHANICAL SYSTEMS AND SIGNAL PROCESSING 75 pp. 455-472 ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
Lenzo B, Sorniotti A, Gruber P, Sannen K (2017) On the experimental analysis of single input single output control of yaw rate and sideslip angle., International Journal of Automotive Technology 18 (5) pp. 799-811 Springer Verlag
Electric vehicles with individually controlled drivetrains allow torque-vectoring, which improves vehicle safety and drivability. This paper investigates a new approach to the concurrent control of yaw rate and sideslip angle. The proposed controller is a simple single input single output (SISO) yaw rate controller, in which the reference yaw rate depends on the vehicle handling requirements, and the actual sideslip angle. The sideslip contribution enhances safety, as it provides a corrective action in critical situations, e.g., in case of oversteer during extreme cornering on a low friction surface. The proposed controller is experimentally assessed on an electric vehicle demonstrator, along two maneuvers with quickly variable tire-road friction coefficient. Different longitudinal locations of the sideslip angle used as control variable are compared during the experiments. Results show that: i) the proposed SISO approach provides significant improvements with respect to the vehicle without torque-vectoring, and the controlled vehicle with a reference yaw rate solely based on the handling requirements for high-friction maneuvering; and ii) the control of the rear axle sideslip angle provides better performance than the control of the sideslip angle at the centre of gravity.
De Novellis, Sorniotti A, Gruber P (2013) Wheel Torque Distribution Criteria for Electric Vehicles With Torque-Vectoring Differentials, IEEE Transactions on Vehicular Technology
The continuous, precise modulation of the driving and braking torque of each wheel is considered to be the ultimate goal for controlling the performance of a vehicle in steady-state and transient conditions. To do so, dedicated torque-vectoring controllers which allow optimal wheel torque distribution under all possible driving conditions have to be developed. Commonly, vehicle torque-vectoring controllers are based on a hierarchical approach, consisting of a high-level supervisory controller which evaluates a corrective yaw moment, and a low-level controller which defines the individual wheel torque reference values. The problem of the optimal individual wheel torque distribution for a particular driving condition can be solved through an optimization-based control allocation algorithm, which must rely on the appropriate selection of the objective function. With a newly developed off-line optimization procedure, this article assesses the performance of alternative objective functions for the optimal wheel torque distribution of a four-wheel-drive fully electric vehicle. Results show that objective functions based on minimum tire slip criterion provide better control performance than functions based on energy efficiency.
Gruber P, Sharp RS (2012) Shear forces in the contact patch of a braked-racing tyre, VEHICLE SYSTEM DYNAMICS 50 (12) pp. 1761-1778 TAYLOR & FRANCIS LTD
Pennycott A, De Novellis L, Sabbatini A, Gruber P, Sorniotti A (2014) Reducing the Motor Power Losses of a Four-Wheel Drive Fully Electric Vehicle via Wheel Torque Allocation', Proceedings of the Institution of Mechanical Engineering: Part D-Journal of Automobile Engineering
Gruber P, Sharp RS, Crocombe AD (2011) Contact stresses of a braked racing tyre,
Sharp RS, Gruber P, Fina E (2016) Circuit racing, track texture, temperature and rubber friction, Vehicle System Dynamics: international journal of vehicle mechanics and mobility 54 (4) pp. 510-525 Taylor & Francis
Some general observations relating to tyre shear forces and road surfaces are followed by more specific considerations from circuit racing. The discussion then focuses on the mechanics of rubber friction. The classical experiments of Grosch are outlined and the interpretations that can be put on them are discussed. The interpretations involve rubber viscoelasticity, so that the vibration properties of rubber need to be considered. Adhesion and deformation mechanisms for energy dissipation at the interface between rubber and road and in the rubber itself are highlighted. The enquiry is concentrated on energy loss by deformation or hysteresis subsequently. Persson's deformation theory is outlined and the material properties necessary to apply the theory to Grosch's experiments are discussed. Predictions of the friction coefficient relating to one particular rubber compound and a rough surface are made using the theory and these are compared with the appropriate results from Grosch. Predictions from Persson's theory of the influence of nominal contact pressure on the friction coefficient are also examined. The extent of the agreement between theory and experiment is discussed. It is concluded that there is value in the theory but that it is far from complete. There is considerable scope for further research on the mechanics of rubber friction.
Chatzikomis C, Sorniotti A, Gruber P, Shah M, Bastin M, Orlov Y (2017) Torque-vectoring control for an autonomous and driverless electric racing vehicle with multiple motors, SAE International Journal of Vehicle Dynamics, Stability and NVH 1 (2) SAE International
Electric vehicles with multiple motors permit continuous direct yaw moment control, also called torque-vectoring. This allows to significantly enhance the cornering response, e.g., by extending the linear region of the vehicle understeer characteristic, and by increasing the maximum achievable lateral acceleration. These benefits are well documented for human-driven cars, yet limited information is available for autonomous/driverless vehicles. In particular, over the last few years, steering controllers for automated driving at the cornering limit have considerably advanced, but it is unclear how these controllers should be integrated alongside a torque-vectoring system. This contribution discusses the integration of torque-vectoring control and automated driving, including the design and implementation of the torque-vectoring controller of an autonomous electric vehicle for a novel racing competition. The paper presents the main vehicle characteristics and control architecture. A quasi-static model is introduced to predict the understeer characteristics at different longitudinal accelerations. The model is coupled with an off-line optimization for the a-priori investigation of the potential benefits of torque-vectoring. The systematic computation of the achievable cornering limits is used to specify and design realistic maps of the reference yaw rate, and a non-linear feedforward yaw moment contribution providing the reference cornering response in quasi-static conditions. A gain scheduled proportional integral controller increases yaw damping, thus enhancing the transient response. Simulation results demonstrate the effectiveness of the proposed approach.
De Novellis L, Sorniotti A, Gruber P (2013) Design and comparison of the handling performance of different electric vehicle layouts, PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART D-JOURNAL OF AUTOMOBILE ENGINEERING Sage
In contrast with conventional vehicles driven by an internal-combustion engine, the number of motors in fully electric cars is not fixed. A variety of architectural solutions, including from one to four individually controlled electric drive units, is possible and opens up new avenues in the design of vehicle characteristics. In particular, individual control of multiple electric powertrains promises to enhance the handling performance in steady-state and dynamic conditions. For the analysis and selection of the best electric powertrain layout based on the expected vehicle characteristics and performance, new analytical tools and metrics are required. This article presents and demonstrates a novel offline procedure for the design of the feedforward control action of the vehicle dynamics controller of a fully electric vehicle and three performance indicators for the objective comparison of the handling potential of alternative electric powertrain layouts. The results demonstrate that the proposed offline routine allows the desired understeer characteristics to be achieved with any of the investigated vehicle configurations, in traction and braking conditions. With respect to linear handling characteristics, the simulations indicate that the influence of torque-vectoring is independent of the location of the controlled axles (front or rear) and is considerably affected by the number of controlled axles.
Fina E, Gruber P, Sharp RS (2014) Hysteretic Rubber Friction: Application of Persson's Theories to Grosch's Experimental Results, JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME 81 (12) ARTN 121001 ASME
Sharp RS, Gruber P, Fina E (2015) Circuit racing, track texture, temperature and rubber friction, pp. 21-30
De Novellis L, Sorniotti A, Gruber P, Shead L, Ivanov V, Hoepping K Torque Vectoring for Electric Vehicles with Individually Controlled Motors: State-of-the-Art and Future Developments, 26th Electric Vehicle Symposium 2012 Curran Associates
Dizqah AM, Lenzo B, Sorniotti A, Gruber P, Fallah S, De Smet J (2016) A Fast and Parametric Torque Distribution Strategy for Four-Wheel-Drive Energy-Efficient Electric Vehicles, IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS 63 (7) pp. 4367-4376 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Pennycott A, De Novellis L, Gruber P, Sorniotti A (2014) Sources of power loss during torque?vectoring for fully electric vehicles, International Journal of Vehicle Design pp. 157-177
De Novellis L, Sorniotti A, Gruber P (2013) Optimal Wheel Torque Distribution for a Four-Wheel-Drive Fully Electric Vehicle, SAE International Journal of Passenger Cars: Mechanical Systems 6 (1) pp. 128-136
Vehicle handling in steady-state and transient conditions can be significantly enhanced with the continuous modulation of the driving and braking torques of each wheel via dedicated torque-vectoring controllers. For fully electric vehicles with multiple electric motor drives, the enhancements can be achieved through a control allocation algorithm for the determination of the wheel torque distribution. This article analyzes alternative cost functions developed for the allocation of the wheel torques for a four-wheel-driven fully electric vehicle with individually controlled motors. Results in terms of wheel torque and tire slip distributions among the four wheels, and of input power to the electric drivetrains as functions of lateral acceleration are presented and discussed in detail. The cost functions based on minimizing tire slip allow better control performance than the functions based on energy efficiency for the case-study vehicle.
De Novellis L, Sorniotti A, Gruber P (2014) Driving modes for designing the cornering response of fully electric vehicles with multiple motors, Mechanical Systems and Signal Processing 64-65 pp. 1-15
© 2015 The Authors.Abstract Fully electric vehicles with multiple drivetrains allow a significant variation of the steady-state and transient cornering responses through the individual control of the electric motor drives. As a consequence, alternative driving modes can be created that provide the driver the option to select the preferred dynamic vehicle behavior. This article presents a torque-vectoring control structure based on the combination of feedforward and feedback contributions for the continuous control of vehicle yaw rate. The controller is specifically developed to be easily implementable on real-world vehicles. A novel model-based procedure for the definition of the control objectives is described in detail, together with the automated tuning process of the algorithm. The implemented control functions are demonstrated with experimental vehicle tests. The results show the possibilities of torque-vectoring control in designing the vehicle understeer characteristic.
Gruber P, Fina E, Sharp RS (2013) Friction mechanisms of high-performance tyres,
Gruber P, Sharp R, Crocombe A (2008) Friction and camber influences on the static stiffness properties of a racing tyre, PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART D-JOURNAL OF AUTOMOBILE ENGINEERING 222 (D11) pp. 1965-1976 PROFESSIONAL ENGINEERING PUBLISHING LTD
Gruber P, Sharp RS (2016) Special issue on the 4th International Tyre Colloquium PREFACE, VEHICLE SYSTEM DYNAMICS 54 (4) pp. 445-447 TAYLOR & FRANCIS LTD
Goggia T, Sorniotti A, De Novellis L, Ferrara A, Gruber P, Theunissen J, Steenbeke D, Knauder B, Zehetner J (2014) Integral sliding mode for the torque-vectoring control of fully electric vehicles: Theoretical design and experimental assessment, IEEE Transactions on Vehicular Technology 64 (5) pp. 1701-1715
© 2014 IEEE.This paper presents an integral sliding mode (ISM) formulation for the torque-vectoring (TV) control of a fully electric vehicle. The performance of the controller is evaluated in steady-state and transient conditions, including the analysis of the controller performance degradation due to its real-world implementation. This potential issue, which is typical of sliding mode formulations, relates to the actuation delays caused by the drivetrain hardware configuration, signal discretization, and vehicle communication buses, which can provoke chattering and irregular control action. The controller is experimentally assessed on a prototype electric vehicle demonstrator under the worst-case conditions in terms of drivetrain layout and communication delays. The results show a significant enhancement of the controlled vehicle performance during all maneuvers.
Lu Q, Sorniotti A, Gruber P, Theunissen J, De Smet J (2016) H-infinity loop shaping for the torque-vectoring control of electric vehicles: Theoretical design and experimental assessment, MECHATRONICS 35 pp. 32-43 PERGAMON-ELSEVIER SCIENCE LTD
De Novellis L, Sorniotti A, Gruber P, Orus J, Rodriguez Fortun J-M, Theunissen J, De Smet J (2014) Direct yaw moment control actuated through electric drivetrains and friction brakes: Theoretical design and experimental assessment, Mechatronics
A significant challenge in electric vehicles with multiple motors is how to control the individual drivetrains in order to achieve measurable benefits in terms of vehicle cornering response, compared to conventional stability control systems actuating the friction brakes. This paper presents a direct yaw moment controller based on the combination of feedforward and feedback contributions for continuous yaw rate control. When the estimated sideslip exceeds a pre-defined threshold, a sideslip-based yaw moment contribution is activated. All yaw moment contributions are entirely tunable through model-based approaches, for reduced vehicle testing time. The purpose of the controller is to continuously modify the vehicle understeer characteristic in quasi-static conditions and increase yaw and sideslip damping during transients. Skid-pad, step-steer and sweep steer tests are carried out with a front-wheel-drive fully electric vehicle demonstrator with two independent drivetrains. The experimental test results of the electric motor-based actuation of the direct yaw moment controller are compared with those deriving from the friction brake-based actuation of the same algorithm, which is a major contribution of this paper. The novel results show that continuous direct yaw moment control allows significant "on-demand" changes of the vehicle response in cornering conditions and to enhance active vehicle safety during extreme driving maneuvers.
Goggia T, Sorniotti A, Gruber P (2015) Integral Sliding Mode for the Torque-Vectoring Control of Fully Electric Vehicles,
Gruber P, Sharp RS, Crocombe AD (2012) Normal and shear forces in the contact patch of a braked racing tyre Part 1: Results from a Finite Element model, Vehicle System Dynamics: international journal of vehicle mechanics and mobility 50 (2) pp. 323-337
Fallah S, Sorniotti A, Gruber P (2014) A novel robust optimal active control of vehicle suspension systems, IFAC Proceedings Volumes (IFAC-PapersOnline) 19 pp. 11213-11218
© IFAC.Using Lyapunov theory, Pontryagin's minimum principle, and affine quadratic stability, a novel robust optimal control strategy is developed for active suspension systems to enhance vehicle ride comfort and handling performance. The controller has a simple structure, making its suitable for real-time implementation. The required sensor configuration includes a six-axis IMU and four LVDTs. The proposed controller is suitable for on-road commercial vehicles where ride comfort over bump disturbances and handling performance are the most concerns. The effectiveness of the controller is verified through simulation results using IPG CarMaker software.
Chatzikomis C, Sorniotti A, Gruber P, Shah M, Bastin M, Orlov Y (2017) Torque-vectoring control for an autonomous and driverless electric racing vehicle with multiple motors, SAE Int. J. Veh. Dyn., Stab., and NVH 1 (2) pp. 338-351
Electric vehicles with multiple motors permit continuous direct yaw moment control, also called torque-vectoring. This allows to significantly enhance the cornering response, e.g., by extending the linear region of the vehicle understeer characteristic, and by increasing the maximum achievable lateral acceleration. These benefits are well documented for human-driven cars, yet limited information is available for autonomous/driverless vehicles. In particular, over the last few years, steering controllers for automated driving at the cornering limit have considerably advanced, but it is unclear how these controllers should be integrated alongside a torque-vectoring system. This contribution discusses the integration of torque-vectoring control and automated driving, including the design and implementation of the torque-vectoring controller of an autonomous electric vehicle for a novel racing competition. The paper presents the main vehicle characteristics and control architecture. A quasi-static model is introduced to predict the understeer characteristics at different longitudinal accelerations. The model is coupled with an off-line optimization for the a-priori investigation of the potential benefits of torque-vectoring. The systematic computation of the achievable cornering limits is used to specify and design realistic maps of the reference yaw rate, and a non-linear feedforward yaw moment contribution providing the reference cornering response in quasi-static conditions. A gain scheduled proportional integral controller increases yaw damping, thus enhancing the transient response. Simulation results demonstrate the effectiveness of the proposed approach.
de Filippis G, Lenzo B, Sorniotti A, Gruber P, Sannen K, De Smet J (2016) On the energy efficiency of electric vehicles with multiple motors, IEEE Vehicle Power and Propulsion Conference (VPPC), 2016
Electric Vehicles (EVs) with multiple motors permit to design the steady-state cornering response by imposing reference understeer characteristics according to expected vehicle handling quality targets. To this aim a direct yaw moment is generated by assigning different torque demands to the left and right vehicle sides. The reference understeer characteristic has an impact on the drivetrain input power as well. In parallel, a Control Allocation (CA) strategy can be employed to achieve an energy-efficient wheel torque distribution generating the reference yaw moment and wheel torque. To the knowledge of the authors, for the first time this paper experimentally compares and critically analyses the potential energy efficiency benefits achievable through the appropriate set-up of the reference understeer characteristics and wheel torque CA. Interestingly, the experiments on a four wheel-drive EV demonstrator show that higher energy savings can be obtained through the appropriate tuning of the reference cornering response rather than with an energy efficient CA.
Gruber P, Sorniotti A, Lenzo B, De Filippis G, Fallah S (2016) Energy efficient torque vectoring control, Advanced Vehicle Control (Proceedings of AVEC'16) CRC Press (Taylor & Francis Group)
Tire forces are at the heart of the dynamic qualities of vehicles. With the advent of electric vehicles the precise and accurate control of the traction and braking forces at the individual wheel becomes a possibility and a reality outside test labs and virtual proving grounds. Benefits of individual wheel torque control, or torque-vectoring, in terms of vehicle dynamics behavior have been well documented in the literature. However, very few studies exist which analyze the individual wheel torque control integrated with vehicle efficiency considerations. This paper focuses on this aspect and discusses the possibilities and benefits of integrated, energy efficient torque vectoring control. Experiments with a four-wheel-drive electric vehicle show that considerable energy savings can be achieved by considering drivetrain and tire power losses through energy efficient torque vectoring control.
Sorniotti A, Gruber P, Lenzo B, De Filippis G, Fallah S (2017) Energy efficient torque vectoring for electric vehicles with multiple drivetrains,
The benefits of individual wheel torque control, or torque vectoring, in terms of vehicle dynamics behaviour have been well documented in the literature. However, few studies analyse individual wheel torque control integrated with electric vehicle efficiency considerations. The possibilities and benefits of energy efficient torque vectoring control for electric vehicles with multiple drivetrains are discussed. In particular, energy consumption reductions can be obtained through specific design of the wheel torque control allocation algorithm and the reference yaw rate characteristics. Experiments with a four-wheel-drive electric vehicle demonstrate considerable energy savings.
Lenzo B, De Filippis G, Sorniotti A, Gruber P, Sannen K (2016) Understeer characteristics for energy-efficient fully electric vehicles with multiple motors, EVS29 International Battery, Hybrid and Fuel Cell Electric Vehicle Symposium Proceedings
Electric vehicles with multiple motors allow torque-vectoring, which generates a yaw moment by assigning different motor torques at the left and right wheels. This permits designing the steady-state cornering response according to several vehicle handling quality targets. For example, as widely discussed in the literature, to make the vehicle more sports-oriented, it is possible to reduce the understeer gradient and increase the maximum lateral acceleration with respect to the same vehicle without torque-vectoring. This paper focuses on the novel experimentally-based design of a reference vehicle understeer characteristic providing energy efficiency enhancement over the whole range of achievable lateral accelerations. Experiments show that an appropriate tuning of the reference understeer characteristic, i.e., the reference yaw rate of the torque-vectoring controller, can bring energy savings of up to ~11% for a case study four-wheel-drive electric vehicle demonstrator. Moreover, during constant speed cornering, it is more efficient to significantly reduce the level of vehicle understeer, with respect to the same vehicle with even torque distribution on the left and right wheels.
Theunissen J, Sorniotti A, Gruber P, Fallah S, Dhaens M, Reybrouck K, Lauwerys C, Vandersmissen B, Sakka M, Motte K Explicit model predictive control of active suspension systems,
Vacca F, Pinto De S, Hartavi Karci A, Gruber P, Viotto F, Cavallino C, Rossi J, Sorniotti A (2017) On the Energy Efficiency of Dual Clutch
Transmissions and Automated Manual Transmissions,
Energies 10 (10) 1562 pp. 1-22 MDPI
The main benefits of dual clutch transmissions (DCTs) are: (i) a higher energy efficiency
than automatic transmission systems with torque converters; and (ii) the capability to fill the torque
gap during gear shifts to allow seamless longitudinal acceleration profiles. Therefore, DCTs are viable
alternatives to automated manual transmissions (AMTs). For vehicles equipped with engines that
can generate considerable torque, large clutch-slip energy losses occur during power-on gear shifts
and, as a result, DCTs need wet clutches for effective heat dissipation. This requirement substantially
reduces DCT efficiency because of the churning and ancillary power dissipations associated with
the wet clutch pack. To the knowledge of the authors, this study is the first to analyse the detailed
power loss contributions of a DCT with wet clutches, and their relative significance along a set of
driving cycles. Based on these results, a novel hybridised AMT (HAMT) with a single dry clutch
and an electric motor is proposed for the same vehicle. The HAMT architecture combines the high
mechanical efficiency typical of AMTs with a single dry clutch, with the torque-fill capability and
operational flexibility allowed by the electric motor. The measured efficiency maps of a case study
DCT and HAMT are compared. This is then complemented by the analysis of the respective fuel
consumption along the driving cycles, which is simulated with an experimentally validated vehicle
model. In its internal combustion engine mode, the HAMT reduces fuel consumption by >9% with
respect to the DCT.
Gruber P (2017) Tyres and Roads: Predicting Friction, Vehicle Ride and Handling: Specialist engineering for an improved experience Institution of Mechanical Engineers
Zanchetta Mattia, Tavernini Davide, Sorniotti Aldo, Gruber Patrick, Lenzo B., Ferrara A., De Nijs W., Sannen K., De Smet J. (2018) On the Feedback Control of Hitch Angle through Torque-Vectoring, 2018 IEEE 15th International Workshop on Advanced Motion Control (AMC) pp. 535-540 Institute of Electrical and Electronics Engineers (IEEE)
This paper describes a torque-vectoring (TV)
algorithm for the control of the hitch angle of an articulated
vehicle. The hitch angle control function prevents trailer
oscillations and instability during extreme cornering maneuvers.
The proposed control variable is a weighted combination of terms
accounting for the yaw rate, sideslip angle and hitch angle of the
articulated vehicle. The novel control variable formulation results
in a single-input single-output (SISO) feedback controller. In the
specific application a simple proportional integral (PI) controller
with gain scheduling on vehicle velocity is developed. The TV
system is implemented and experimentally tested on a fully electric
vehicle with four on-board drivetrains, towing a single-axle passive
trailer. Sinusoidal steer test results show that the proposed
algorithm significantly improves the behavior of the articulated
vehicle, and justify further research on the topic of hitch angle
control through TV.
De Filippis Giovanni, Lenzo Basilio, Sorniotti Aldo, Gruber Patrick, De Nijs Wouter (2018) Energy-Efficient Torque-Vectoring Control of Electric Vehicles with Multiple Drivetrains, Proceedings of the IEEE 67 (6) pp. 4702-4715 Institute of Electrical and Electronics Engineers (IEEE)
The safety benefits of torque-vectoring control of electric vehicles with multiple drivetrains are well known and extensively discussed in the literature. Also, several authors analyze wheel torque control allocation algorithms for reducing the energy consumption while obtaining the wheel torque demand and reference yaw moment specified by the higher layer of a torque-vectoring controller. Based on a set of novel experimental results, this study demonstrates that further significant energy consumption reductions can be achieved through the appropriate tuning of the reference understeer characteristics. The effects of drivetrain power losses and tire slip power losses are discussed for the case of identical drivetrains at the four vehicle corners. Easily implementable yet effective rule-based algorithms are presented for the set-up of the energy-efficient reference yaw rate, feedforward yaw moment and wheel torque distribution of the torque-vectoring controller.
Tota Antonio, Lenzo Basilio, Lu Qian, Sorniotti Aldo, Gruber Patrick, Fallah Saber, Velardocchia Mauro, Galvagno Enrico, De Smet Jasper (2018) On the experimental analysis of integral sliding modes for yaw rate and sideslip control of an electric vehicle with multiple motors, International Journal of Automotive Technology 19 (5) pp. 811-823 Springer Verlag
With the advent of electric vehicles with multiple motors, the steady-state and transient cornering responses can be designed based on high-level reference targets, and implemented through the continuous torque control of the individual wheels, i.e., torque-vectoring or direct yaw moment control. The literature includes several papers describing the application of the sliding mode control theory to torque-vectoring. However, the experimental implementations of sliding mode controllers on real vehicle prototypes are very limited at the moment. More importantly, to the knowledge of the authors, there is lack of experimental assessments of the performance benefits of direct yaw moment control based on sliding modes, with respect to other controllers, such as the proportional integral derivative controllers or linear quadratic regulators currently used for stability control in production vehicles. This paper aims to reduce this gap by presenting an integral sliding mode controller for concurrent yaw rate and sideslip control. A new driving mode, the Enhanced Sport mode, is proposed, inducing sustained high values of sideslip angle, which can be safely limited to a specified threshold. The system is experimentally assessed on a four-wheel-drive electric vehicle along a wide range of maneuvers. The performance of the integral sliding mode controller is compared with that of a linear quadratic regulator during step steer tests. The results show that the integral sliding mode controller brings a significant enhancement of the tracking performance and yaw damping with respect to the more conventional linear quadratic regulator based on an augmented single-track vehicle model formulation.
Metzler Mathias, Tavernini Davide, Sorniotti Aldo, Gruber Patrick (2018) Explicit nonlinear model predictive control for vehicle stability control, Proceedings of 9th International Munich Chassis Symposium 2018, chassis.tech plus Springer Vieweg
Nonlinear model predictive control is proposed in multiple academic studies as an ad-vanced control system technology for vehicle operation at the limits of handling, allow-ing high tracking performance and formal consideration of system constraints. How-ever, the implementation of implicit nonlinear model predictive control (NMPC), in which the control problem is solved on-line, poses significant challenges in terms of computational load. This issue can be overcome through explicit NMPC, in which the optimization problem is solved off-line, and the resulting explicit solution, with guar-anteed level of sub-optimality, is evaluated on-line. Due to the simplicity of the explicit solution, the real-time execution of the controller is possible even on automotive control hardware platforms with low specifications. The explicit nature of the control law fa-cilitates feasibility checks and functional safety validation. This study presents a yaw and lateral stability controller based on explicit NMPC, actuated through the electro-hydraulically controlled friction brakes of the vehicle. The controller performance is demonstrated during sine-with-dwell tests simulated with a high-fidelity model. The analysis includes a comparison of implicit and explicit implementations of the control system.
Lenzo B, Sorniotti Aldo, Gruber Patrick (2018) A Single Input Single Output Formulation for Yaw Rate and Sideslip Angle Control via Torque-Vectoring, AVEC 2018 Proceedings
Many torque-vectoring controllers are based on the concurrent control of yaw rate and sideslip angle through complex multi-variable control structures. In general, the target is to continuously track a reference yaw rate, and constrain the sideslip angle to remain within thresholds that are critical for vehicle stability. To achieve this objective, this paper presents a single input single output (SISO) formulation, which varies the reference yaw rate to constrain sideslip angle. The performance of the controller is successfully validated through simulations and experimental tests on an electric vehicle prototype with four drivetrains
Tavernini Davide, Metzler Mathias, Gruber Patrick, Sorniotti Aldo (2018) Explicit non-linear model predictive control for electric vehicle traction control, IEEE Transactions on Control Systems Technology IEEE
This study presents a traction control system for electric vehicles with in-wheel motors, based on explicit non-linear model predictive control. The feedback law, available beforehand, is described in detail, together with its variation for different plant conditions. The explicit controller is implemented on a rapid control prototyping unit, which proves the real-time capability of the strategy, with computing times in the order of microseconds. These are significantly lower than the required sampling time for a traction control application. Hence, the explicit model predictive controller can run at the same frequency as a simple traction control system based on Proportional Integral (PI) technology. High-fidelity model simulations provide: i) a performance comparison of the proposed explicit non-linear model predictive controller with a benchmark PI-based traction controller with gain scheduling and anti-windup features; and ii) a performance comparison among two explicit and one implicit non-linear model predictive controllers based on different internal models, with and without consideration of transient tire behavior and load transfers. Experimental test results on an electric vehicle demonstrator are shown for one of the explicit non-linear model predictive controller formulations.
Theunissen Johan, Sorniotti Aldo, Gruber Patrick, Fallah Saber, Dhaens M, Reybrouck K, Lauwerys C, Vandersmissen B, Al Sakka M, Motte K (2018) Explicit model predictive control of an active suspension system, chassis.tech plus 2018 ? 9th International Munich Chassis Symposium pp. 201-214 Springer Fachmedien Wiesbaden GmbH
Model predictive control (MPC) is increasingly finding its way into industrial applications, due to its superior tracking performance and ability to formally handle system constraints. However, the real-time capability problems related to the conventional implicit model predictive control (i-MPC) framework are well known, especially when targeting low-cost electronic control units (ECUs) for high bandwidth systems, such as automotive active suspensions, which are the topic of this paper. In this context, to overcome the real-time implementation issues of i-MPC, this study proposes explicit model predictive control (e-MPC), which solves the optimization problem off-line, via multi-parametric quadratic programming (mp-QP). e-MPC reduces the on-line algorithm to a function evaluation, which replaces the computationally demanding on-line solution of the quadratic programming (QP) problem. An e-MPC based suspension controller is designed and experimentally validated for a case study Sport Utility Vehicle (SUV), equipped with the active ACOCAR suspension system from the Tenneco Monroe product family. The target is to improve ride comfort in the frequency range of primary ride ( 40% compared to the passive vehicle set-up for frequencies
Chatzikomis Christoforos, Sorniotti Aldo, Gruber Patrick, Zanchetta Mattia, Willans D, Balcombe B (2018) Comparison of Path Tracking and Torque-Vectoring Controllers for Autonomous Electric Vehicles, IEEE Transactions on Intelligent Vehicles IEEE
Steering control for path tracking in autonomous vehicles is well documented in the literature. Also, continuous direct yaw moment control, i.e., torque-vectoring, applied to human-driven electric vehicles with multiple motors is extensively researched. However, the combination of both controllers is not yet well understood. This paper analyzes the benefits of torque-vectoring in an autonomous electric vehicle, either by integrating the torque-vectoring system in the path tracking controller, or through its separate implementation alongside the steering controller for path tracking. A selection of path tracking controllers is compared in obstacle avoidance tests simulated with an experimentally validated vehicle dynamics model. A genetic optimization is used to select the controller parameters. Simulation results confirm that torque-vectoring is beneficial to autonomous vehicle response. The integrated controllers achieve the best performance if they are tuned for the specific tire-road friction condition. However, they can also cause unstable behavior when they operate in lower friction conditions without any re-tuning. On the other hand, separate torque-vectoring implementations provide consistently stable cornering response for a wide range of friction conditions. Controllers with preview formulations, or based on appropriate reference paths with respect to the middle line of the available lane, are beneficial to the path tracking performance.
Metzler Mathias, Tavernini Davide, Sorniotti Aldo, Gruber Patrick (2018) An Explicit Nonlinear MPC Approach to Vehicle Stability Control, Proceedings of The 14th International Symposium on Advanced Vehicle Control Tsinghua University
Nonlinear model predictive control (NMPC) is proposed in multiple academic studies as an advanced control system technology for vehicle operation at the limits of handling, allowing high tracking performance and formal consideration of system constraints. However, the implementation of implicit NMPC, in which the control problem is solved on-line, poses significant challenges in terms of computational load. This issue can be overcome through explicit NMPC, in which the optimization problem is solved off-line, and the resulting explicit solution, with guaranteed level of sub-optimality, is evaluated on-line. This study presents a yaw and lateral stability controller based on explicit NMPC, actuated through the friction brakes of the vehicle. The controller performance is demonstrated during sine-with-dwell tests simulated with a high-fidelity model. The analysis investigates the influence of the weights in the cost function formulation and includes a comparison of different settings of the optimal control problem.
Chatzikomis C., Zanchetta M., Gruber P., Sorniotti A., Modic B., Motaln T., Blagotinsek L., Gotovac G. (2019) An energy-efficient torque-vectoring algorithm for electric vehicles with multiple motors, Mechanical Systems and Signal Processing 128 pp. 655-673 Elsevier
In electric vehicles with multiple motors, the individual wheel torque control, i.e., the so-called torque-vectoring, significantly enhances the cornering response and active safety. Torque-vectoring can also increase energy efficiency, through the appropriate design of the reference understeer characteristic and the calculation of the wheel torque distribution providing the desired total wheel torque and direct yaw moment. To meet the industrial requirements for real vehicle implementation, the energy-efficiency benefits of torque-vectoring should be achieved via controllers characterised by predictable behaviour, ease of tuning and low computational requirements. This paper discusses a novel energy-efficient torque-vectoring algorithm for an electric vehicle with in-wheel motors, which is based on a set of rules deriving from the combined consideration of: i) the experimentally measured electric powertrain efficiency maps; ii) a set of optimisation results from a non-linear quasi-static vehicle model, including the computation of tyre slip power losses; and iii) drivability requirements for comfortable and safe cornering response. With respect to the same electric vehicle with even wheel torque distribution, the simulation results, based on an experimentally validated vehicle dynamics simulation model, show: a) up to 4% power consumption reduction during straight line operation at constant speed; b) >5% average input power saving in steady-state cornering at lateral accelerations >3.5/m/s2; and c) effective compensation of the yaw rate and sideslip angle oscillations during extreme transient tests.