High speed fluttering skids with elastic suspensions

In a recent project, named SEALAB, a novel marine vehicle has been developed. Its main characteristic is the presence of special skid surfaces surfing over rough water. A suspension system controls the vertical motion of the skid, softening the sequential impacts and vibrations induced by the water, similarly to a wheeled vehicle in off-road trials. The hull-skid-suspension set is modeled by prototypical equations. The system undergoes special regimes when the vessel speed at sea is varied. In particular, for some combinations of the forward speed and sea-state, the skid still maintains the contact with the water. In other navigation conditions the skid indeed jumps out the water with a complete different average transmitted force and vibration characteristics of the hull. This paper presents a theory that outlines these phenomena identifying conditions that lead to the jumping skid condition

On line estimation of rolling resistance for intelligent tires

The analysis of a rolling tire is a complex problem of nonlinear elasticity. Although in the technical literature some tire models have been presented, the phenomena involved in the tire rolling are far to be completely understood. In particular, small knowledge comes even from experimental direct observation of the rolling tire, in terms of dynamic contact patch, instantaneous dissipation due to rubber-road friction and hysteretic behavior of the tire structure, and instantaneous grip. This paper illustrates in details a new powerful technology that the research group has developed in the context of the project OPTYRE. A new wireless optical system based on Fiber Bragg Grating strain sensors permits a direct observation of the inner tire stress when rolling in real conditions on the road. From this information, following a new suitably developed tire model, it is possible to identify the instant area of the contact patch, the grip conditions as well the instant dissipation, which is the object of the present work

Energy exchange between nonlinear oscillators: An entropy foundation

In the field of vibrations of complex structures, energy methods like SEA and a series of mid-frequency methods, represent an important resource for computational analysis. All these methods are based in general on a linear formulation of the elastic problem. However, when nonlinearities are present, for example related to clearance or stiffening of joints, these methods, in principle, cannot be applied. This paper, on the basis of a theory presented recently by one of the authors, proposes a foundation of a new energy method able to deal with nonlinearities when studying the energy exchange between subsystems. The idea relies on the concept of a thermodynamic vibroacoustic temperature, that can be directly defined when introducing the entropy of a vibrating structure. The theory is introduced in general, and examples of calculation of the power flow between nonlinear resonators are presented introducing stiffening and clearences for systems with many degrees of freedom

Prototyping a new car semi-active suspension by variational feedback controller

New suspension systems electronically controlled are presented and mounted on board of a real car. The system consists of variable semi-active magneto-rheological dampers that are controlled through an electronic unit that is designed on the basis of a new optimal theoretical control, named VFC-Variational Feedback Controller. The system has been mounted on board of a BMW Series 1 car, and a set of experimental tests have been conducted in real driving conditions. The VFC reveals, because of its design strategy, to be able to enhance simultaneously both the comfort performance as well as the handling capability of the car. Preliminary comparisons with several industrially control methods adopted in the automotive field, among them skyhook and groundhook, show excellent results

Car collision avoidance with velocity obstacle approach

The obstacle avoidance maneuver is required for an autonomous vehicle. It is essential to define the system's performance by evaluating the minimum reaction times of the vehicle and analyzing the probability of success of the avoiding operation. This paper presents a collision avoidance algorithm based on the velocity bstacle approach that guarantees collision-free maneuvers. The vehicle is controlled by an optimal feedback control named FLOP, designed to produce the best performance in terms of safety and minimum kinetic collision energy. Dimensionless accident evaluation parameters are proposed to compare different crash scenarios

A multisensing setup for the intelligent tire monitoring

The present paper offers the chance to experimentally measure, for the first time, the internal tire strain by optical fiber sensors during the tire rolling in real operating conditions. The phenomena that take place during the tire rolling are in fact far from being completely understood. Despite several models available in the technical literature, there is not a correspondently large set of experimental observations. The paper includes the detailed description of the new multi-sensing technology for an ongoing vehicle measurement, which the research group has developed in the context of the project OPTYRE. The experimental apparatus is mainly based on the use of optical fibers with embedded Fiber Bragg Gratings sensors for the acquisition of the circumferential tire strain. Other sensors are also installed on the tire, such as a phonic wheel, a uniaxial accelerometer, and a dynamic temperature sensor. The acquired information is used as input variables in dedicated algorithms that allow the identification of key parameters, such as the dynamic contact patch, instantaneous dissipation and instantaneous grip. The OPTYRE project brings a contribution into the field of experimental grip monitoring of wheeled vehicles, with implications both on passive and active safety characteristics of cars and motorbikes

Aeroelastic dynamic feedback control of a Volterra airfoil

The work aims to develop a novel optimal control algorithm for integral differential equations which includes the first kind Volterra’s integral. An indirect and analytical solution of Pontryagin’s problem for Volterra equations permits to find an explicit feedback control solution here called PI(N). Numerical simulations are performed to validate the proposed algorithm with a classical test case in aerodynamic: the motion control of a moving airfoil modelled with the Wagner time-varying theory. The wings are characterized by memory effects, due to aeroelastic phenomena, which are usually difficult to incorporate in optimal control logics unless quantized numerical solvers are used, which require onerous computational efforts

Processing of logical-physical rules in the control of the autonomous vehicle

Recent advances in intelligent vehicles imply more sophisticated control laws. The standard concept of objective function and models of vehicle and driver represented by differential equations, are not anymore sufficient tools in a future scenario. The capability of reasoning of the machines imposes the use of logic as a fundamental tool to describe requirements of the behavior of the vehicle, and to characterize their response. However, logical statements exhibit a difficulty of integration with the differential physic laws to which the vehicle obeys. There is a clear heterogeneity between mathematics and logic, especially when they must fuse into a single model. The paper proposes an integrated model in which the physics and the logic fuse into a common model, able to generate a meaningful objective function to optimize the behavior through a physical-logic model of the vehicle in the context of control of hybrid dynamical systems. Not negligibly, a logic-statement design helps the autonomous driving to be more acceptable and comprehensible in an insurance and court law context