Optimal Design and Control of 4-IWD Electric Vehicles based on a 14-DOF Vehicle Model

A 4-independent wheel driving (4-IWD) electric vehicle has distinctive advantages with both enhanced dynamic and energy efficiency performances since this configuration provides more flexibilities from both the design and control aspects. However, it is difficult to achieve the optimal performances of a 4-IWD electric vehicle with conventional design and control approaches. This work is dedicated to investigating the vehicular optimal design and control approaches, with a 4-IWD electric race car aiming at minimizing the lap time on a given circuit as a case study. A 14-DOF vehicle model that can fully evaluate the influences of the unsprung mass is developed based on Lagrangian dynamics. The 14-DOF vehicle model implemented with the reprogrammed Magic Formula tire model and a time-efficient suspension model supports metric operations and parallel computing, which can dramatically improve the computational efficiency. The optimal design and control problems with design parameters of the motor, transmission, mass center, anti-roll bar and the suspension of the race car are successively formulated. The formulated problems are subsequently solved by directly transcribing the original problems into large scale nonlinear optimization problems based on trapezoidal approach. The influences of the mounting positions of the propulsion system, the mass and inertia of the unsprung masses, the anti-roll bars and suspensions on the lap time are analyzed and compared quantitatively. Some interesting findings that are different from the `already known facts' are presented

Multi-objective evolutionary design of an electric vehicle chassis

An iterative algorithm is proposed for determining the optimal chassis design of an electric vehicle, given a path and a reference time. The proposed algorithm balances the capacity of the battery pack and the dynamic properties of the chassis, seeking to optimize the tradeoff between the mass of the vehicle, its energy consumption, and the travel time. The design variables of the chassis include geometrical and inertial values, as well as the characteristics of the powertrain. The optimization is constrained by the slopes, curves, grip, and posted speeds of the different sections of the track. Particular service constraints are also considered, such as limiting accelerations due to passenger comfort or cargo safety. This methodology is applicable to any vehicle whose route and travel time are known in advance, such as delivery vehicles, buses, and race cars, and has been validated using telemetry data from an internal combustion rear-wheel drive race car designed for hill climb competitions. The implementation of the proposed methodology allows to reduce the weight of the battery pack by up to 20%, compared to traditional design methods

Active suspension control of electric vehicle with in-wheel motors

In-wheel motor (IWM) technology has attracted increasing research interests in recent years due to the numerous advantages it offers. However, the direct attachment of IWMs to the wheels can result in an increase in the vehicle unsprung mass and a significant drop in the suspension ride comfort performance and road holding stability. Other issues such as motor bearing wear motor vibration, air-gap eccentricity and residual unbalanced radial force can adversely influence the motor vibration, passenger comfort and vehicle rollover stability. Active suspension and optimized passive suspension are possible methods deployed to improve the ride comfort and safety of electric vehicles equipped with inwheel motor. The trade-off between ride comfort and handling stability is a major challenge in active suspension design. This thesis investigates the development of novel active suspension systems for successful implementation of IWM technology in electric cars. Towards such aim, several active suspension methods based on robust H∞ control methods are developed to achieve enhanced suspension performance by overcoming the conflicting requirement between ride comfort, suspension deflection and road holding. A novel fault-tolerant H∞ controller based on friction compensation is in the presence of system parameter uncertainties, actuator faults, as well as actuator time delay and system friction is proposed. A friction observer-based Takagi-Sugeno (T-S) fuzzy H∞ controller is developed for active suspension with sprung mass variation and system friction. This method is validated experimentally on a quarter car test rig. The experimental results demonstrate the effectiveness of proposed control methods in improving vehicle ride performance and road holding capability under different road profiles. Quarter car suspension model with suspended shaft-less direct-drive motors has the potential to improve the road holding capability and ride performance. Based on the quarter car suspension with dynamic vibration absorber (DVA) model, a multi-objective parameter optimization for active suspension of IWM mounted electric vehicle based on genetic algorithm (GA) is proposed to suppress the sprung mass vibration, motor vibration, motor bearing wear as well as improving ride comfort, suspension deflection and road holding stability. Then a fault-tolerant fuzzy H∞ control design approach for active suspension of IWM driven electric vehicles in the presence of sprung mass variation, actuator faults and control input constraints is proposed. The T-S fuzzy suspension model is used to cope with the possible sprung mass variation. The output feedback control problem for active suspension system of IWM driven electric vehicles with actuator faults and time delay is further investigated. The suspended motor parameters and vehicle suspension parameters are optimized based on the particle swarm optimization. A robust output feedback H∞ controller is designed to guarantee the system’s asymptotic stability and simultaneously satisfying the performance constraints. The proposed output feedback controller reveals much better performance than previous work when different actuator thrust losses and time delay occurs. The road surface roughness is coupled with in-wheel switched reluctance motor air-gap eccentricity and the unbalanced residual vertical force. Coupling effects between road excitation and in wheel switched reluctance motor (SRM) on electric vehicle ride comfort are also analysed in this thesis. A hybrid control method including output feedback controller and SRM controller are designed to suppress SRM vibration and to prolong the SRM lifespan, while at the same time improving vehicle ride comfort. Then a state feedback H∞ controller combined with SRM controller is designed for in-wheel SRM driven electric vehicle with DVA structure to enhance vehicle and SRM performance. Simulation results demonstrate the effectiveness of DVA structure based active suspension system with proposed control method its ability to significantly improve the road holding capability and ride performance, as well as motor performance

Electronic Chassis Stability Control Systems for Electric Vehicles with IWD/IWB

Práca sa zaoberá analýzou, návrhom a výskumom nového riešenia pre redundantné laterálne riadenie vozidiel pomocou selektívnej distribúcie hnacieho a brzdného momentu jednotlivých kolies. V práci je popísaný rozbor súčasne využívaných aktívnych systémov jazdnej stability, podobne ako niektorými limitujúcimi faktormi pre ich funkcie. V úvode je popísaná motivácia pre vznik systému redundantného laterálneho riadenia a je zmienený state of art zavedených prístupov k riešeniu zmieneného systému. V práci je zachytený popis experimentálneho vozidla Democar 2, ktoré slúži ako platforma pre vývoj automobilových elektronických systémov, detailnejšie sú popísané systémy IWD, IWB, SbW a systém trakčnej batéria a napájacej siete vozidla. Ďalšia kapitola sa zaoberá simulačným modelom vozidla, ktorý slúži k výskumu a optimalizácii riadiacich algoritmov systémov IWB a IWD a ich kooperácii. Nasledujúca kapitola rozoberá návrh systému redundantného laterálneho riadenia. V poslednej časti sú uvedené simulované a reálne jazdné testy, zachytávajúce funkčnosť systému.The work deals with an analysis and design of a new solution for redundant lateral steering of vehicles by using selective distribution of driving and braking torque of individual wheels. The paper describes the analysis of currently used active driving stability systems, as well as some limiting factors for their functions. In the introduction, the motivation for the emergence of a system of redundant lateral control is described and the state of art of established approaches to the solution of the mentioned system is described. The description of the experimental vehicle Democar 2, which serves as a platform for the development of automotive electronic systems, captures the IWD, IWB, SbW systems and the traction battery and vehicle power supply network system in more detail. The next chapter involves the simulation model of the vehicle, which is used to research and optimize the control algorithms of the IWB and IWD systems and their cooperation. The following part deals with description of the proposed redundant lateral control system. The last part contains simulated and real driving tests, capturing the operation of the system.430 - Katedra elektronikyvyhově

Analysis of different powertrain configurations for a formula style electric racecar

The aim of this thesis is to provide useful framework for the design of the upcoming electric race car of Lund Formula Student Team. The thesis intends to find the different powertrain concepts on the state of the art. From the configurations, the thesis should provide outcomes of the performance, efficiency, complexity design and cost. Furthermore, the best concept should be find and a simple preliminary design is made.To compare the different concepts developed, a Matlab code was used, which simulates the vehicle dynamics of the race cars. A Simulink model wasbe used to analyse the different electric systems and come up with the most efficient solution. The results of the thesis show that the powertrain configuration that should perform better in a real competition is the design with four motors actuating one in each wheel. The reason behind it, is the abilty of the system to provide different torque at each wheel, known as torque vectoring. By distributing different torque at each wheel the race car is able to create a yaw movement to the body, allowing it to make turns at a higher velocity. The design shows the different parts composing the powertrain, and how each of the parts was chosen. To conclude the thesis, the four motor’s configuration is compared to the LFS20 design in order to explain how this powertrain improves the car results in the overall competitionOutgoin

Advanced Sensing and Control for Connected and Automated Vehicles

Connected and automated vehicles (CAVs) are a transformative technology that is expected to change and improve the safety and efficiency of mobility. As the main functional components of CAVs, advanced sensing technologies and control algorithms, which gather environmental information, process data, and control vehicle motion, are of great importance. The development of novel sensing technologies for CAVs has become a hotspot in recent years. Thanks to improved sensing technologies, CAVs are able to interpret sensory information to further detect obstacles, localize their positions, navigate themselves, and interact with other surrounding vehicles in the dynamic environment. Furthermore, leveraging computer vision and other sensing methods, in-cabin humans’ body activities, facial emotions, and even mental states can also be recognized. Therefore, the aim of this Special Issue has been to gather contributions that illustrate the interest in the sensing and control of CAVs

Fast performance assessment of mechatronic designs integrating CAD and dynamical models with application on servo actuated designs

In this paper an approach is presented that allows to investigate, in a systematic way, how design parameters of a servo actuated system modeled in CAD influence the dynamic behaviour and performance of the system. This is achieved by extracting physical quantities such as mass and inertia in part designs as these are difficult to model analytically when having irregular part shapes. These values are then employed in a symbolic dynamic model to assess the behavior and associated performance through numerical integration. To illustrate the effectiveness of the integrated approach, different slider-crank designs are evaluated for a given motion path. A sensitivity analysis is performed on the basis of gradients extracted from the introduced symbolic dynamical model through algorithmic differentiation. Our approach is flexible and enables precise motion study of actuated mechanisms with calculation times improved by an order of magnitude compared to other methods. In addition, this novel approach depends only on open source software

Analytical study to define a helicopter stability derivative extraction method, volume 1

A method is developed for extracting six degree-of-freedom stability and control derivatives from helicopter flight data. Different combinations of filtering and derivative estimate are investigated and used with a Bayesian approach for derivative identification. The combination of filtering and estimate found to yield the most accurate time response match to flight test data is determined and applied to CH-53A and CH-54B flight data. The method found to be most accurate consists of (1) filtering flight test data with a digital filter, followed by an extended Kalman filter (2) identifying a derivative estimate with a least square estimator, and (3) obtaining derivatives with the Bayesian derivative extraction method

Integrated vehicle dynamics control using active steering, driveline and braking

This thesis investigates the principle of integrated vehicle dynamics control through proposing a new control configuration to coordinate active steering subsystems and dynamic stability control (DSC) subsystems. The active steering subsystems include Active Front Steering (AFS) and Active Rear Steering (ARS); the dynamic stability control subsystems include driveline based, brake based and driveline plus brake based DSC subsystems. A nonlinear vehicle handling model is developed for this study, incorporating the load transfer effects and nonlinear tyre characteristics. This model consists of 8 degrees of freedom that include longitudinal, lateral and yaw motions of the vehicle and body roll motion relative to the chassis about the roll axis as well as the rotational dynamics of four wheels. The lateral vehicle dynamics are analysed for the entire handling region and two distinct control objectives are defined, i.e. steerability and stability which correspond to yaw rate tracking and sideslip motion bounding, respectively. Active steering subsystem controllers and dynamic stability subsystem controller are designed by using the Sliding Mode Control (SMC) technique and phase-plane method, respectively. The former is used as the steerability controller to track the reference yaw rate and the latter serves as the stability controller to bound the sideslip motion of the vehicle. Both stand-alone controllers are evaluated over a range of different handling regimes. The stand-alone steerability controllers are found to be very effective in improving vehicle steering response up to the handling limit and the stand-alone stability controller is found to be capable of performing the task of maintaining vehicle stability at the operating points where the active steering subsystems cannot. Based on the two independently developed stand-alone controllers, a novel rule based integration scheme for AFS and driveline plus brake based DSC is proposed to optimise the overall vehicle performance by minimising interactions between the two subsystems and extending functionalities of individual subsystems. The proposed integrated control system is assessed by comparing it to corresponding combined control. Through the simulation work conducted under critical driving conditions, the proposed integrated control system is found to lead to a trade-off between stability and limit steerability, improved vehicle stability and reduced influence on the longitudinal vehicle dynamics