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The Influence of Autonomous Driving on Passive Vehicle Dynamics

SAE International Journal of Vehicle Dynamics, Stability, and NVH

Danisi Engineering S.r.l.-Marco Fainello, Giacomo Danisi
ETH Zürich-Alex Liniger
  • Journal Article
  • 2018-01-0551
Published 2018-04-03 by SAE International in United States
Traditional vehicles are designed to be inherently stable. This is typically obtained by imposing a large positive static margin (SM). The main drawbacks of this approach are the resulting understeering behavior of the vehicle and, often, a decrease in peak lateral grip due to oversized rear tire characteristics. On the other hand, a lower SM can cause a greater time delay in the vehicle’s response which hardens the control of a vehicle at limit handling for a human being. By introducing advanced autonomous driving features into future vehicles, the human factor can be excluded in limit handling manoeuvers (e.g., obstacle avoidance occurrences) and, consequently, the need for a high SM (i.e., high controllability for human drivers) can be avoided. Therefore, it could be possible to exploit the passive vehicle dynamics and enhance the performance, both in terms of peak grip and transient response.The goal of this article is to explore if a decrease in SM can lead to a performance advantage on an obstacle avoidance manoeuver when the vehicle is driven by a robotic controller.…
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Development of an e-LSD Control Strategy Considering the Evolution of the Friction Torque with the Wear Depth

SAE International Journal of Engines

Meccanica 42-Claudio Annicchiarico
Universita degli Studi di Firenze-Amedeo Tesi, Francesco Vinattieri, Renzo Capitani
  • Journal Article
  • 2016-01-1136
Published 2016-04-05 by SAE International in United States
The Electro actuated Limited Slip Differential (e-LSD) can help increasing the dynamic features of the vehicle, but to implement a well designed control logic it is necessary a deep knowledge of the actual friction torque built up by the differential clutch. This work presents the development of such a control law that takes into account the wear depth progression. To carry out this task, an alternative method has been used to study the clutch discs engagement depending on the wear rate.The method takes advantages from a mixed approach with a numerical and an experimental part. Using a general purpose block-on-ring test bench, the tribologic analyses were performed following the ASTM G77 standard; thus, the friction coefficient has been investigated in the contact between discs with molybdenum treatment and steel alloy discs, as well as its variation depending on the wear rate. The results were input in a numerical algorithm aimed at evaluating the friction torque of the clutch as a function of the pressure and the wear depth. The results, besides providing useful hints for…
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Target setting and structural design of an EPS-in-the-Loop test bench for steering feeling simulation

Danisi Engineering S.r.l.-Tim Wright, Giacomo Danisi
Meccanica 42 S.r.l.-Claudio Annicchiarico
Published 2016-04-05 by SAE International in United States
The adoption of Electrical Power Steering (EPS) systems has greatly opened up the possibilities to control the steering wheel torque, which is a critical parameter in the subjective and objective evaluation of a new vehicle. Therefore, the tuning of the EPS controller is not only becoming increasing complicated, containing dozens of parameters and maps, but it is crucial in defining the basic DNA of the steering feeling characteristics. The largely subjective nature of the steering feeling assessment means that EPS tuning consists primarily of subjective tests on running prototypes. On account of that, this paper presents an alternative test bench for steering feeling simulation and evaluation. It combines a static driving simulator with a physical EPS assisted steering rack. The end goal is to more accurately reproduce the tactile feedback to the driver by including a physical hardware in lieu of complicated and difficult to obtain software models. The focus of the activity in this paper was to define the specifications for this test bench and to entirely design it.The test bench contains some actuators…
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Torque Vectoring of a Formula SAE through Semi Active Differential Control

Universita degli Studi di Firenze-Claudio Annicchiarico, Renzo Capitani
Published 2014-11-11 by SAE International in United States
In a Formula SAE car, as for almost all racecars, suppressing or limiting the action of the differential mechanism is the technique mostly adopted to improve the traction exiting the high lateral acceleration corners.The common Limited Slip Differentials (LSDs) unbalance the traction torque distribution, generating as a secondary effect a yaw torque on the vehicle. If this feature is electronically controlled, these devices can be used to manage the attitude of the car.The yaw torque introduced by an electronically controlled LSD (which can also be called SAD, “Semi-Active Differential”) could suddenly change from oversteering (i.e. pro-yaw) to understeering (i.e. anti-yaw), depending on the driving conditions. Therefore, controlling the vehicle attitude with a SAD could be challenging, and its effectiveness could be low if compared with the common torque vectoring systems, which act on the brake system of the car. In addition, unlike common ESC (“Electronic Stability Control”) systems do, a SAD can modify the vehicle attitude without limiting its traction performance, which is a crucial factor for racecars.This paper shows the SAD designed at the…
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Design of an Active Vehicle System for a Hybrid Race Car

Universita degli Studi di Firenze-Claudio Annicchiarico, Silvano Cappelli, Lorenzo Gasperini, Tommaso Innocenti, Renzo Capitani
Published 2011-09-11 by SAE International in United States
The aim of this work is to define the core of a stability control, called Active Vehicle System, for a hybrid Formula SAE car that will compete in the next season in the upcoming Alternative Energies (Class 1A) class. The vehicle on which the control system will act is equipped with two electric motors on the front axle and an internal combustion engine connected to the rear axle by the way of a semi-active differential. The layout of the car under consideration has been defined with the purpose of getting the most effectiveness by the Active Vehicle System, whose role is to define a yaw torque to be applied to the vehicle in order to correct its behavior during each maneuver. The results of the Upper Controller will be actuated by two Lower Controllers, one dedicated to the electric motors and one to the semi-active differential. On such controlled vehicle some testing maneuvers have been performed, in order to check its functionality. The analyses have been done with a mathematical model of the vehicle, in…
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Stress Analysis of a CVT Belt Transmission

Piaggio & C. S.p.A.-Riccardo Testi
Università degli Studi di Firenze-Claudio Annicchiarico, Renzo Capitani
Published 2010-09-28 by SAE International in United States
The paper is focused on the stress field acting on a continuously variable transmission (CVT) mechanism used on the high displacement scooters produced by Piaggio & C. S.p.A. The most important results of the analysis have been extrapolated with the aim of providing the designers with some guidelines useful to reduce the design error occurrence. In detail, in the paper is described the behavior of the belt and of the driven pulley, that are the critical parts of the assembly. The analysis has been conducted with a full MultiBody model of the mechanism combined with the Finite Element analysis of both the belt and the pulley. The output data so obtained have been used in a fatigue analysis in order to define the reliability of these parts. This paper could serve as a base to define a new proportioning method, that should be based on the whole stress history of each part of the assembly, computed with the aid of some numerical tools.
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Experimental Analysis of the Handling Behaviour of a Two-Wheeled Vehicle

Piaggio & C. S.p.A.-Claudio Limone
Università degli Studi di Firenze-Renzo Capitani, Andrea Meneghin, Daniele G. Rosti
Published 2004-09-27 by SAE International in United States
An experimental analysis of the handling behaviour of a two-wheeled vehicle was realized in order to define and quantify the most important forces and torques needed to drive the vehicle, and to find the driving method applied by the driver. To acquire all the data, a scooter was instrumented and tested under some codified maneuvers. In addition to the usual instrumentation (speed sensor, inertial sensor, linear and angular transducers) a load cell was installed under the saddle to measure the forces and torques applied by the driver. The experimental analysis was focused on the interaction between the driver and the vehicle. The main signals, quantifying the driver actions, were obtained via the load cell and the steering axis. These data were analyzed in order to verify that the most common two-wheeled vehicle driving method, known as “counter-steering”, is not sufficient to explain the handling behaviour but it has to be taken into account with the torso movement and the driver position. For each tested maneuver an explanation of the driving method is given, supplied by…
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Virtual Prototyping of a Two Wheeled Vehicle

Università di Firenze-Renzo Capitani, Andrea Meneghin, Daniele G. Rosti
Published 2003-03-03 by SAE International in United States
The virtual protoype of a two wheeled vehicle (Piaggio Liberty 150 4T) was realized in order to simulate the behavior of a scooter during some codified maneuvres. A virtual driver was realized to conduct the virtual prototype. The obtained results were compared with the data acquired with the instrumented vehicle during the same maneuvres. In addition to the usual instrumentation (speed sensor, inertial sensor, linear and angular transducers) a load cell was installed under the saddle to measure the forces and torques applied by the driver. All the data were evaluated in order to define the real driving style. These data were used to enhance the virtual driver that conducts the virtual prototype as a human driver conducts the real vehicle.
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