Ilse Cervantes

Stability of an Electric Differential for Traction Applications

The use of an electric differential (ED) constitutes a technological advance in vehicle design along the concept of more electric vehicles (MEVs). EDs have the advantage of replacing loose and heavy mechanical differentials and transmissions with lighter and smaller electric motors directly coupled to the wheels via a single gear or an in-wheel motor. To date, EDs have been proposed for two- and four-wheeled vehicles. Despite its long reported success and possible advantages in terms of flexibility and direct torque control of the wheels during cornering and risky maneuvers, the ED has several problems that have limited its applicability, for instance, an increment of control loops and an increase of computational effort. Therefore, the main purpose of this paper is to present a simple and easy-to-implement ED that ensures both reliability and good path tracking. The proposed strategy has the advantage of being linear and, therefore, easy to implement. Furthermore, a rigorous proof of stability is presented, and connections with other controllers are discussed. Features and advantages of the proposed scheme are illustrated via numerical simulations in a 4-kW system, which is able to handle 500-kg mass and deliver peak power up to 10 kW during transit periods.

On the Design of Robust Energy Management Strategies for FCHEV

In this paper, we analyze the limitations that impose the presence of uncertainty in the design of optimal energy management strategies (EMSs) for fuel cell (FC) hybrid electric vehicles. Using an electric powertrain constituted by a hydrogen FC and a battery bank, the fuel consumption minimization problem is analyzed in the presence of parametric uncertainty. The conditions that ensure that the nominal optimization problem matches the solution of the real (unknown) optimization problem are clearly stated. By observing that the uncertainty will limit the feasible solutions of the minimization consumption problem, supervisory control constituted by heuristic rules is proposed to face such limitations, resulting in a mixed optimal-heuristic EMS. The effect of the powertrain design, driving cycle, and initial conditions in the proposed strategy is discussed. Numerical simulations provide evidence of the advantages and features of the supervisory control strategy.

Robust Switched Predictive Braking Control for Rollover Prevention in Wheeled Vehicles

The aim of this paper is to propose a differential braking rollover mitigation strategy for wheeled vehicles. The strategy makes use of a polytopic (piecewise linear) description of the vehicle and includes translational and rotational dynamics, as well as suspension effects. The braking controller is robust and the system states are predicted to estimate the rollover risk up to a given time horizon. In contrast to existing works, the switched predictive nature of the control allows it to be applied only when risk of rollover is foreseen, interfering a minimum with driver’s actions. The stability of the strategy is analyzed and its robustness is illustrated via numerical simulations using CarSim for a variety of vehicles.

Stability of Gain Scheduling Control for Aircraft with Highly Nonlinear Behavior

The main goal of this work is to study the stability properties of an aircraft with nonlinear behavior, controlled using a gain scheduled approach. An output feedback is proposed which is able to guarantee asymptotical stability of the task-coordinates origin and safety of the operation in the entire flight envelope. The results are derived using theory of hybrid and singular perturbed systems. It is demonstrated that both body velocity and orientation asymptotic tracking can be obtained in spite of nonlinearities and uncertainty. The results are illustrated using numerical simulations in F16 jet.

Switched control for power management in hybrid propulsion schemes

This paper proposes an improved operation strategy for hybrid propulsion systems based on a switched control scheme. The goal is to investigate the role of switching criterion on fuel economy, based on a switched description of a fuel cell (FC) — batteries (B) propulsion scheme. Stability conditions of the closed-loop system are derived. A 1KW propulsion system is taken as a benchmark to illustrate the features of the proposed controller. The results show that by defining switching surfaces conveniently, similar results to those involving optimization can be obtained; simplifying in this way, the fuel economy problem to the election of off-line switching criterion parameters.

Hybrid control technique applied in a FC-SC electric vehicle platform

A Fuel Cell-Supercapacitor Electric Vehicle (FC-SC-EV) with only one power converter generally uses the FC as an average power unit and the SC as a peak power unit. This array requires operating the power converter linked to the FC in operation regions rather than single operation point; as a result traditional averaged modeling and control methods are no longer valid. In this paper, a hybrid control technique is proposed to control the power converter, which is cable to work in operation regions and it can use any inductor current in the converter as a feedback; meanwhile it achieves an excellent output voltage control under disturbances either from supply voltage, load voltage or other perturbations. Experimental results are given for a 1kW Nexa® power module and interleaved boost converter taken as a benchmark.

Switched control of interleaved converters

In this paper, a time varying switching control of interleaved converters is proposed. The controller has the feature of being simple and it is able to guarantee global voltage regulation. The controller is based on the piece-continuous model of the converter and it works by switching between performance surfaces that depends on the state vector. The switching surfaces are chosen differently for each cell of the interleaved converter in order to guarantee, both maximum current and voltage ripple. Furthermore, a given phase between current signals can also be guaranteed. The switched control is illustrated in a 2-cell 2kw boost converter: however, it can be applied directly in any interleaved converter independently of the number of cells.

Hybrid multi-objective control of DC-DC converters

The highly need of flexibility and more robust controllers in areas such as motor controllers, renewable energy, and power electronics have opened the niche for applying and developing a new family of more active controllers such as: fuzzy, linear quadratic, passivity, pulse adjustment, etc. All these controllers are able to work in operations regions rather than at a single operation point and they make use, for practical implementation purposes, at least one DSP or FPGA. Following this trend, the main purpose of this work is to propose a new hybrid controller, which is able to work in several operation regions while having the feature of being of simple structure and easy to implement. In addition, the proposed strategy has several advantages that makes it attractive, (i) the controller is able to solve a multi-objective problem (i.e. voltage regulation and current limitation), (ii) it is robust against parameter uncertainty (i.e. the controller does not make use of knowledge of system parameters), and (iii) the controller operates at constant frequency. Controller description, numerical simulations and experimental work in a boost converter are presented.

On the predictive rollover detection in wheeled vehicles

This paper is aimed at proposing a predictive rollover detection strategy for wheeled vehicles. The strategy makes use of a nonlinear description of the vehicle that includes translational and rotational dynamics, as well as suspension dynamic effects. A hybrid control strategy to avoid rollover is also proposed based on the vehicle model, a predictive time horizon and a predictive estimation of the steering. A feature of the proposed strategy is its simplicity. Numerical simulations allow us to show the performance of the estimation as well as of the proposed control strategy.

Test-bed to implement energy management strategies in PHEV

This paper describes a powertrain test-bed platform for Plug-In Hybrid Electric Vehicles (PHEVs) that can be used to evaluate energy management strategies. The hardware-in-the-loop (HIL) simulation platform comprises two parts: 1) the simulation of the vehicles electric powertrain, 2) the monitoring and control of the vehicle through the use of an ad hoc data administration and communication system that uses CAN bus. Evaluation of the test platform is performed using an urban driving cycle, which also allows the illustration of the starting and emergency protocols.