Passive elasto-magnetic suspensions: nonlinear models and experimental outcomes

The paper presents a passive elasto-magnetic suspension based on rare-earth permanent magnets: the dynamical system is described with theoretical and numerical nonlinear models, whose results are validated through experimental compar- ison. The goal is to minimize the dependence on mass of the natural frequency of a single degree of freedom system. For a system with variable mass, static configuration and dynamical behaviour are compared for classic linear elastic systems, for purely magnetic suspensions and for a combination of the two. In particular the dynamics of the magneto-mechanic inter- action is predicted by use of nonlinear and linearised models and experimentally observed through a suitable single degree of freedom test ri

A model for a flywheel automatic assistedmanual transmission

This paper is focused on the model and dynamical analysis of a flywheel assisted transmis- sion aiming at reducing the torque gap during gear shift manoeuvres. A completely passive device, consisting of a planetary gear set mounting a flywheel on the sun gear shaft, allows to continuously connect the engine to the load shaft. Depending on the operating condi- tions, it can either absorb energy from the engine or deliver the previously stored kinetic energy to the wheels when the clutch is disengaged, thus allowing better vehicle performances and/or ride comfort through a suitable coordinated control of engine and clutc

Experimental device to identify friction levels for airport applications

This paper presents an experimental device aimed at identifying different road friction levels; it has been designed at the Politecnico di Torino as part of the research program AWIS (Airport Weather Information System: study and realisation of a system for the prediction, monitoring and management of meteorological winter emergencies in airports) funded by Regione Piemonte

Identification Techniques Applied to a Passive Elasto-magnetic Suspension

The paper presents an experimental passive elasto-magnetic suspension based on rare-earth permanent magnets, characterized by negligible dependence on mass of its natural frequency. The nonlinear behaviour of this system, equipped with a traditional linear elastic spring coupled to a magnetic spring, is analysed in time domain, for non-zero initial conditions, and in frequency domain, by applying sweep excitations to the test rig base. The dynamics of the system is very complex in dependence of the magnetic contribution, showing both hardening behaviour in the elasto-magnetic setup, and softening motion amplitude dependent behaviour in the purely magnetic case. Hence it is necessary to adopt nonlinear identification techniques, such as non-parametric restoring force mapping method and direct parametric estimation technique, in order to identify the system parameters in the different configurations. Finally, it is discussed the ability of identified versus analytical models in reproducing the nonlinear dependency of frequency on motion amplitude and the presence of jump phenomen

Adaptive Equivalent Consumption Minimization Strategy with Rule-based Gear Selection for the Energy Management of Hybrid Electric Vehicles Equipped with Dual Clutch Transmissions

Based on observations of the behaviour of the optimal solution to the problem of energy management for plug-in hybrid electric vehicles, a novel real-time Energy Management Strategy (EMS) is proposed. In particular, dynamic programming results are used to derive a set of rules aiming at reproducing the optimal gearshift schedule in electric mode while the Adaptive Equivalent Consumption Minimization Strategy (A-ECMS) is employed to decide the powertrain operating mode and the current gear when power from the internal combustion engine is needed. In terms of total fuel consumption, simulations show that the proposed approach yields results that are close to the optimal solution and also outperforms those of the A-ECMS, a well-known EMS. One of the main aspects that differentiates the strategy here proposed from previous works is the introduction of a model to use physical considerations to estimate the energy consumption during gearshifts in dual-clutch transmissions. This, together with a series of properly tuned fuel penalties allows the controller to yield results in which there is no gear hunting behaviour

Energy Management Strategy for Hybrid Multimode Powertrains: Influence of Inertial Properties and Road Inclination

Multimode hybrid powertrains have captured the attention of automotive OEMs for their flexible nature and ability to provide better and optimized efficiency levels. However, the presence of multiple actuators, with different efficiency and dynamic characteristics, increases the problem complexity for minimizing the overall power losses in each powertrain operating condition. The paper aims at providing a methodology to select the powertrain mode and set the reference torques and angular speeds for each actuator, based on the power-weighted efficiency concept. The power-weighted efficiency is formulated to normalize the efficiency contribution from each power source and to include the inertial properties of the powertrain components as well as the vehicle motion resistance forces. The approach, valid for a wide category of multimode powertrain architectures, is then applied to the specific case of a two-mode hybrid system where the engagement of one of the two clutches enables an Input Split or Compound Split operative mode. The simulation results obtained with the procedure prove to be promising in avoiding excessive accelerations, drift of powertrain components, and in managing the power flow for uphill and downhill vehicle conditions

On the model-based design of front-to-total anti-roll moment distribution controllers for yaw rate tracking

In passenger cars active suspensions have been traditionally used to enhance comfort through body control, and handling through the reduction of the tyre load variations induced by road irregularities. However, active suspensions can also be designed to track a desired yaw rate profile through the control of the anti-roll moment distribution between the front and rear axles. The effect of the anti-roll moment distribution relates to the nonlinearity of tyre behaviour, which is difficult to capture in the linearised vehicle models normally used for control design. Hence, the tuning of anti-roll moment distribution controllers is usually based on heuristics. This paper includes an analysis of the effect of the lateral load transfer on the lateral axle force and cornering stiffness. A linearised axle force formulation is presented, and compared with a formulation from the literature, based on a quadratic relationship between cornering stiffness and load transfer. Multiple linearised vehicle models for control design are assessed in the frequency domain, and the respective controllers are tuned through optimisation routines. Simulation results from a nonlinear vehicle model are discussed to analyse the performance of the controllers, and show the importance of employing accurate models of the lateral load transfer effect during control design

An ABS control logic based on wheel force measurement

The paper presents an anti-lock braking system (ABS) control logic based on the measurement of the longitudinal forces at the hub bearings. The availability of force information allows to design a logic that does not rely on the estimation of the tyre-road friction coefficient, since it continuously tries to exploit the maximum longitudinal tyre force. The logic is designed by means of computer simulation and then tested on a specific hardware in the loop test bench: the experimental results confirm that measured wheel force can lead to a significant improvement of the ABS performances in terms of stopping distance also in the presence of road with variable friction coefficien

Malignancy in Guillain-Barré syndrome:A twelve-year single-center study

The relationship between Guillain-Barré syndrome (GBS) and malignancy is uncertain. We retrospectively analyzed data of 118 consecutive patients admitted with GBS from Birmingham, U.K. (2001 − 2012). We calculated relative cancer risk using different definitions and determined characteristics of malignancy-associated GBS. Malignancy was globally commoner in our GBS cohort compared to the general population (odds ratio: 2.08; CI: 1.06–3.71; p = 0.036). However, this was unconfirmed if paraneoplastic criteria were applied. GBS patients with cancer were significantly more likely to be older (p = 0.043), hyponatremic (p = 0.037) and demonstrate more axonal loss (p < 0.05). Cerebrospinal fluid (CSF) protein levels were lower in the malignancy group (p = 0.002) and neurological improvement less likely (p = 0.023). In-patient mortality was significantly higher in patients with malignancy (p < 0.01). We conclude global cancer risk is higher in GBS than in the general population, although definition-dependent. Malignancy requires consideration in elderly, hyponatremic subjects with normal CSF protein, severe axonal loss, who fail to improve post-treatment