Rui Esteves Araujo

Wheel Slip Control of EVs Based on Sliding Mode Technique With Conditional Integrators

This paper presents a new control system, based on field programmable gate array technology, targeting the powertrain control of multi-motor electric vehicles (EVs). The control chip builds around a reusable intellectual property core named propulsion control unit, which features motor control functions with field-orientation methods, and energy loss minimization of induction motors. In order to improve the EV safety, the control system was extended with a wheel slip controller based on the sliding mode framework. The robustness to parametric and modeling uncertainties is the main attraction in this design, thanks to a simple connection that was found between the driving torque request and the model uncertainty. To overcome the chattering issue, which arrives from the discontinuous nature of the sliding control, the conditional integrator approach was employed, enabling a smooth transition to a Proportional+Integral control law, with anti-windup, when the tire slip is close to the setpoint. The controller asymptotic stability and robustness was analytically investigated through the Lyapunov method. Experimental results, obtained with a multi-motor EV prototype under low grip conditions, demonstrate a good slip regulation and robustness to disturbances.

Torque blending and wheel slip control in EVs with in-wheel motors

Among the many opportunities offered by electric vehicles (EVs), the design of power trains based on in-wheel electric motors represents, from the vehicle dynamics point of view, a very attractive prospect, mainly due to the torque-vectoring capabilities. However, this distributed propulsion also poses some practical challenges, owing to the constraints arising from motor installation in a confined space, to the increased unsprung mass weight and to the integration of the electric motor with the friction brakes. This last issue is the main theme of this work, which, in particular, focuses on the design of the anti-lock braking system (ABS). The proposed structure for the ABS is composed of a tyre slip controller, a wheel torque allocator and a braking supervisor. To address the slip regulation problem, an adaptive controller is devised, offering robustness to uncertainties in the tyre–road friction and featuring a gain-scheduling mechanism based on the vehicle velocity. Further, an optimisation framework is employed in the torque allocator to determine the optimal split between electric and friction brake torque based on energy performance metrics, actuator constraints and different actuators bandwidth. Finally, based on the EV working condition, the priorities of this allocation scheme are adapted by the braking supervisor unit. Simulation results obtained with the CarSim vehicle model, demonstrate the effectiveness of the overall approach.

Combined Sizing and Energy Management in EVs With Batteries and Supercapacitors

This paper is concerned with the study of combined sizing and energy management algorithms for electric vehicles (EVs) endowed with batteries and supercapacitors (SCs). The main goal is to find the number of cells of each source that minimizes the installation and running costs of the EV, taking into account the performance requirements specified for the vehicle and the technical constraints of the energy sources. To tackle this problem, two methodologies will be investigated. The first considers a filter-based approach to perform the power split among the sources; it will be shown that, under some practical assumptions, the resultant sizing problem can be posed as a linear programming problem and solved using efficient numerical techniques. The second methodology employs an optimal noncausal energy management, which, when integrated with the sizing problem, yields a nonlinear optimization problem. These two methodologies will be then applied to size the storage unit of a small EV. The results indicate that the filter-based approach, although simple and numerically efficient, generally requires an oversized storage unit. Furthermore, it was also concluded that, if the range requirements of the EV are not very high (below 50 km, in our case study), the use of SCs enables energy savings of up to 7.8%.

Full and reduced order extended kalman filter for speed estimation in induction motor drives: a comparative study

This work presents a comparative study between a new approach for robust speed estimation in induction motor sensorless control, using a reduced order extended Kalman filter (EKF), and the one performed by the full order EKF. The new EKF algorithm uses a reduced order state-space model that is discretized in a particular and innovative way. In this case only the rotor flux components are estimated, besides the rotor speed, while the full order EKF also estimates stator current components. This new approach strongly reduces the execution time and simplifies the tuning of covariance matrices. The performance of speed estimation using both EKF techniques is compared with respect to computation effort, tuning of the algorithms, speed range including low speeds, load torque conditions and robustness relatively to motor parameter sensitivity.

A new bi-directional charger for vehicle-to-grid integration

Bidirectional and efficient on-board charger systems for electric vehicles is a challenge nowadays. This paper describes a novel power converter system that implements bidirectional flow between the grid and an electric vehicle battery, where a dual active bridge is advantageous. With a bidirectional topology and proper control all the major grid constraints, such as power quality, harmonic rejection, active and reactive power control, and others, can be easily satisfied. A hardware prototype of the power converter is built. Experimental results from this hardware prototype verify the preliminary operation and claims of the V2G power interface.

Assisted Assignment of Automotive Safety Requirements

ISO 26262, a functional-safety standard, uses Automotive Safety Integrity Levels (ASILs) to assign safety requirements to automotive-system elements. System designers initially assign ASILs to system-level hazards and then allocate them to elements of the refined system architecture. Through ASIL decomposition, designers can divide a functions safety requirements among multiple components. However, in practice, manual ASIL decomposition is difficult and produces varying results. To overcome this problem, a new tool automates ASIL allocation and decomposition. It supports the system and software engineering life cycle by enabling users to efficiently allocate safety requirements regarding systematic failures in the design of critical embedded computer systems. The tool is applicable to industries with a similar concept of safety integrity levels.

Microgrid Service Restoration: The Role of Plugged-in Electric Vehicles

The development of the microgrid (MG) concept endows distribution networks with increased reliability and resilience and offers an adequate management and control solution for massive deployment of microgeneration and electric vehicles (EVs). Within an MG, local generation can be exploited to launch a local restoration procedure following a blackout. EVs are flexible resources that can also be actively included in the restoration procedure, thus contributing to the improvement of MG operating conditions. The feasibility of MG service restoration, including the active participation of EVs, is demonstrated in this article through extensive numerical simulation and experimentation in a laboratorial setup.

A new approach for speed estimation in induction motor drives based on a reduced-order extended Kalman filter

This paper presents and proposes a new approach to achieve robust speed estimation in induction motor sensorless control. The estimation method is based on a reduced-order extended Kalman filter (EKF), instead of a full-order EKF. The EKF algorithm uses a reduced-order state-space model structure that is discretized in a particular and innovative way proposed in this paper. With this model structure, only the rotor flux components are estimated, besides the rotor speed itself. Important practical aspects and new improvements are introduced that enable us to reduce the execution time of the algorithm without difficulties related to the tuning of covariance matrices, since the number of elements to be adjusted is reduced.

Automatic decomposition and allocation of safety integrity levels using a penalty-based genetic algorithm

Automotive Safety Integrity Levels (ASILs) are used in the new automotive functional safety standard, ISO 26262, as a key part of managing safety requirements throughout a top-down design process. The ASIL decomposition concept, outlined in the standard, allows the safety requirements to be divided between multiple components of the system whilst still meeting the ASILs initially allocated to system-level hazards. Existing exhaustive automatic decomposition techniques drastically reduce the effort of performing such tasks manually. However, the combinatorial nature of the problem leaves such exhaustive techniques with a scalability issue. To overcome this problem, we have developed a new technique that uses a penalty-based genetic algorithm to efficiently explore the search space and identify optimum assignments of ASILs to the system components. The technique has been applied to a hybrid braking system to evaluate its effectiveness.

Procedural knowledge, decision-making and game performance analysis in Female Volleyball’s attack according to the player’s experience and competitive success

The purpose of this study was to analyse procedural knowledge, decision-making and game performance of the zone 4 attackers in Volleyball, according to the players’ experience and competitive performance. A verbal interview protocol was implemented immediately after randomly chosen live game actions to analyze procedural knowledge. Decision-making and players’ performance were analyzed by video images. Oneway Anova, Independent Samples t-Test, and Pearson Chi-Square were applied to data analysis. The results showed that more experienced and more successful players play more under goal concepts than condition concepts and concern more often with the opponent. Specifically, more experienced players mentioned more goal concepts and less sophisticated conditions, as more successful players mentioned more action concepts. More experienced players also presented fewer condition concepts than the less experienced ones. Successful players tended to make more appropriate decisions. However, as player’s experience and competitive success are multidimensional variables they might not be fully well characterized by the number of years of practice and competitive results. Therefore, future research is required, and it should include other criteria to characterize both variables. Moreover, qualitative analysis is needed, since it will allow a deeper understanding of the tactical development of the players according to the specific nature of the training process, and also considering the competitive success and the player’s experience as multidimensional variables.