Feedback brake distribution control for minimum pitch

The distribution of brake forces between front and rear axles of a vehicle is typically specified such that the same level of brake force coefficient is imposed at both front and rear wheels. This condition is known as ‘ideal’ distribution and it is required to deliver the maximum vehicle deceleration and minimum braking distance. For subcritical braking conditions, the deceleration demand may be delivered by different distributions between front and rear braking forces. In this research we show how to obtain the optimal distribution which minimises the pitch angle of a vehicle and hence enhances driver subjective feel during braking. A vehicle model including suspension geometry features is adopted. The problem of the minimum pitch brake distribution for a varying deceleration level demand is solved by means of a model predictive control (MPC) technique. To address the problem of the undesirable pitch rebound caused by a full-stop of the vehicle, a second controller is designed and implemented independently from the braking distribution in use. An extended Kalman filter is designed for state estimation and implemented in a high fidelity environment together with the MPC strategy. The proposed solution is compared with the reference ‘ideal’ distribution as well as another previous feed-forward solution

Effect of handling characteristics on minimum time cornering with torque vectoring

In this paper, the effect of both passive and actively-modified vehicle handling characteristics on minimum time manoeuvring for vehicles with 4-wheel torque vectoring (TV) capability is studied. First, a baseline optimal TV strategy is sought, independent of any causal control law. An optimal control problem (OCP) is initially formulated considering 4 independent wheel torque inputs, together with the steering angle rate, as the control variables. Using this formulation, the performance benefit using TV against an electric drive train with a fixed torque distribution, is demonstrated. The sensitivity of TV-controlled manoeuvre time to the passive understeer gradient of the vehicle is then studied. A second formulation of the OCP is introduced where a closed-loop TV controller is incorporated into the system dynamics of the OCP. This formulation allows the effect of actively modifying a vehicle's handling characteristic via TV on its minimum time cornering performance of the vehicle to be assessed. In particular, the effect of the target understeer gradient as the key tuning parameter of the literature-standard steady-state linear single-track model yaw rate reference is analysed

Assessment of the Energy Consumption and Drivability Performance of an IPMSM-Driven Electric Vehicle Using Different Buried Magnet Arrangements

© 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/)This study investigates the influence of the buried magnet arrangement on the efficiency and drivability performance provided by an on-board interior permanent magnet synchronous machine for a four-wheel-drive electric car with two single-speed on-board powertrains. The relevant motor characteristics, including flux-linkage, inductance, electromagnetic torque, iron loss, total loss, and efficiency, are analyzed for a set of six permanent magnet configurations suitable for the specific machine, which is controlled through maximum-torque-per-ampere and maximum-torque-per-voltage strategies. Moreover, the impact of each magnet arrangement is analyzed in connection with the energy consumption along four driving cycles, as well as the longitudinal acceleration and gradeability performance of the considered vehicle. The simulation results identify the most promising rotor solutions, and show that: (i) the appropriate selection of the rotor configuration is especially important for the driving cycles with substantial high-speed sections; (ii) the magnet arrangement has a major impact on the maximum motor torque below the base speed, and thus on the longitudinal acceleration and gradeability performance; and (iii) the configurations that excel in energy efficiency are among the worst in terms of drivability, and vice versa, i.e., at the vehicle level, the rotor arrangement selection is a trade-off between energy efficiency and longitudinal vehicle dynamics.Peer reviewedFinal Published versio

On pre-emptive vehicle stability control

Future vehicle localisation technologies enable major enhancements of vehicle dynamics control. This study proposes a novel vehicle stability control paradigm, based on pre-emptive control that considers the curvature profile of the expected path ahead in the computation of the reference direct yaw moment and braking control action. The additional information allows pre-emptive trail braking control, which slows down the vehicle if the predicted speed profile based on the current torque demand is deemed incompatible with the reference trajectory ahead. Nonlinear model predictive control is used to implement the approach, in which also the steering angle and reference yaw rate provided to the internal model are varied along the prediction horizon, to account for the expected vehicle path. Two pre-emptive stability control configurations with different levels of complexity are proposed and compared with the passive vehicle, and two state-of-the-art nonlinear model predictive stability controllers, one with and one without non-pre-emptive trail braking control. The performance is assessed along obstacle avoidance tests, simulated with a high-fidelity model of an electric vehicle with in-wheel motors. Results show that the pre-emptive controllers achieve higher maximum entry speeds – up to ∼34% and ∼60% in high and low tyre-road friction conditions – than the formulations without preview.This work was supported in part by the Horizon 2020 Framework Programme of the European Commission under grant agreements no. 769944 (STEVE project) and no. 824311 (ACHILES project)

On Nonlinear Model Predictive Control for Energy-Efficient Torque-Vectoring

A recently growing literature discusses the topics of direct yaw moment control based on model predictive control (MPC), and energy-efficient torque-vectoring (TV) for electric vehicles with multiple powertrains. To reduce energy consumption, the available TV studies focus on the control allocation layer, which calculates the individual wheel torque levels to generate the total reference longitudinal force and direct yaw moment, specified by higher level algorithms to provide the desired longitudinal and lateral vehicle dynamics. In fact, with a system of redundant actuators, the vehicle-level objectives can be achieved by distributing the individual control actions to minimize an optimality criterion, e.g., based on the reduction of different power loss contributions. However, preliminary simulation and experimental studies – not using MPC – show that further important energy savings are possible through the appropriate design of the reference yaw rate. This paper presents a nonlinear model predictive control (NMPC) implementation for energy-efficient TV, which is based on the concurrent optimization of the reference yaw rate and wheel torque allocation. The NMPC cost function weights are varied through a fuzzy logic algorithm to adaptively prioritize vehicle dynamics or energy efficiency, depending on the driving conditions. The results show that the adaptive NMPC configuration allows stable cornering performance with lower energy consumption than a benchmarking fuzzy logic TV controller using an energy-efficient control allocation layer

On the Feedback Control of Hitch Angle through Torque-Vectoring

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

Sport vehicles and virtual riders modeling

The Optimal Maneuver Method is a package for optimal control problem simulations based on the mathematical formulation of a vehicle model capable of getting the dynamics of the system and on the concept of ideal rider. The work presented in this thesis covers different purposes: the development of the current methodology applied to motorcycles in order to improve matching between experimental evidence results and lap-time simulations, second to formulate different single, two, four-wheeled vehicle models for different application cases. Third to create flexible libraries to manage components that are communal between the different models and require a particular formulation. Fourth to apply the Optimal Maneuver Method for studying the optimality of some specialized driving techniques that are nowadays under investigation, as aggressive maneuvers outside the linear behavior of tires, which knowledge are at the base of modern active chassis control systems.Il Metodo della Manovra Ottima è un pacchetto software per simulazioni basate su problemi di controllo ottimo. Esso consiste nella formulazione matematica di un modello di veicolo capace di cogliere la dinamica del sistema a cui è associato e si basa sul concetto di pilota ideale. Il lavoro presentato in questa tesi copre diversi aspetti: lo sviluppo della già esistente metodologia applicata in campo motociclistico al fine di migliorare la corrispondenza tra prove sperimentali e risultati delle simulazioni, secondo la formulazione di diversi modelli di veicolo ad una, due e quattro ruote per diverse applicazioni. Terzo lo sviluppo di un pacchetto di librerie in grado di gestire alcuni componenti comuni a più modelli di veicolo che richiedono una particolare formulazione. Quarto l’applicazione del Metodo della Manovra Ottima per lo studio dell’ottimalità di certe tecniche di guida adottate da piloti professionisti che sono al momento oggetto di studio, come manovre aggressive oltre il comportamento lineare degli pneumatici, la cui comprensione è alla base dei moderni sistemi di controllo attivo del veicolo

Sport vehicles and virtual riders modeling

The Optimal Maneuver Method is a package for optimal control problem simulations based on the mathematical formulation of a vehicle model capable of getting the dynamics of the system and on the concept of ideal rider. The work presented in this thesis covers different purposes: the development of the current methodology applied to motorcycles in order to improve matching between experimental evidence results and lap-time simulations, second to formulate different single, two, four-wheeled vehicle models for different application cases. Third to create flexible libraries to manage components that are communal between the different models and require a particular formulation. Fourth to apply the Optimal Maneuver Method for studying the optimality of some specialized driving techniques that are nowadays under investigation, as aggressive maneuvers outside the linear behavior of tires, which knowledge are at the base of modern active chassis control systems.Il Metodo della Manovra Ottima è un pacchetto software per simulazioni basate su problemi di controllo ottimo. Esso consiste nella formulazione matematica di un modello di veicolo capace di cogliere la dinamica del sistema a cui è associato e si basa sul concetto di pilota ideale. Il lavoro presentato in questa tesi copre diversi aspetti: lo sviluppo della già esistente metodologia applicata in campo motociclistico al fine di migliorare la corrispondenza tra prove sperimentali e risultati delle simulazioni, secondo la formulazione di diversi modelli di veicolo ad una, due e quattro ruote per diverse applicazioni. Terzo lo sviluppo di un pacchetto di librerie in grado di gestire alcuni componenti comuni a più modelli di veicolo che richiedono una particolare formulazione. Quarto l’applicazione del Metodo della Manovra Ottima per lo studio dell’ottimalità di certe tecniche di guida adottate da piloti professionisti che sono al momento oggetto di studio, come manovre aggressive oltre il comportamento lineare degli pneumatici, la cui comprensione è alla base dei moderni sistemi di controllo attivo del veicolo

Feedback brake distribution control for minimum pitch

The distribution of brake forces between front and rear axles of a vehicle is typically specified such that the same level of brake force coefficient is imposed at both front and rear wheels. This condition is known as ‘ideal’ distribution and it is required to deliver the maximum vehicle deceleration and minimum braking distance. For subcritical braking conditions, the deceleration demand may be delivered by different distributions between front and rear brak- ing forces. In this research we show how to obtain the optimal distribution which minimises the pitch angle of a vehicle and hence enhances driver subjective feel during braking. A vehi- cle model including suspension geometry features is adopted. The problem of the minimum pitch brake distribution for a varying deceleration level demand is solved by means of a model predictive control technique. To address the problem of the undesirable pitch rebound caused by a full-stop of the vehicle, a second controller is designed and implemented independently from the braking distribution in use. An extended Kalman filter is designed for state esti- mation and implemented in a high fidelity environment together with the model predictive control strategy. The proposed solution is compared with the reference ‘ideal’ distribution as well as another previous feed-forward solution

Evaluation of optimal yaw rate reference for electric vehicle torque vectoring

This work evaluates the intrinsic contribution of the yaw rate reference to the overall handling performance of an electric vehicle with torque vectoring control - in terms of minimum-time manoeuvring. A range of yaw rate references are compared through optimal control simulations incorporating closed-loop controller dynamics. Results show yaw rate reference has a significant effect on manoeuvre time