Mario Terzo

Design of an adaptive control for a magnetorheological fluid brake with model parameters depending on temperature and speed

This paper describes experimental/theoretical activities carried out on a magnetorheological fluid brake (MRFB) prototype. A device model is derived and a detailed evaluation of the influence of temperature and speed on its parameters is performed. It can be seen that temperature and speed act as modifying inputs for the system model and change the value of some of its parameters. More specifically, time constant and torque/current gain are affected by velocity whereas fluid viscosity is only affected by temperature. The presence of the above modifying input suggests the employment of an adaptive approach for MRFB feedback control based on the torque measurement only. Starting from the proposed model, a model reference adaptive control is designed, ensuring that the tracking error converges to zero as time t →∞ . Simulation activity, carried out on the device validated model, confirms the effectiveness of the proposed adaptive controller. (Some figures in this article are in colour only in the electronic version)

A mixed approach for the control of a testing equipment employed for earthquake isolation systems

This paper presents an activity concerning the modelling and control of a system adopted to perform shear tests on seismic isolators. The test rig consists of a hydraulic actuation system that drives a sliding table mounted on linear bearings. The system is characterized by non-linearities such as hydraulic proportional valve dead zone and frictions. A non-linear model is derived and then employed for parameter identification procedure. The test rig needs a suitable controller able to guarantee the desired table displacement in presence of unknown reaction force of the device under test. The proposed approach consists of a feedforward control integrated with a feedback one. The feedforward control law takes the form of a non-linear inverse model of the system. In this way, it is possible to obtain the desired target without affecting the stability of the test rig. The feedback control has the function to compensate for tracking error due to the model uncertainties and the unknown isolator reaction force. Therefore, the feedback control is not required to compensate for the large non-linearities: in this manner, it is possible to obtain good tracking results without the increasing of the feedback control gain that would change the stability properties of the plant. Numerical simulations have been performed in order to evaluate the goodness of the designed control with and without the specimen under test. Experimental tests show that the controlled system simulations are able to predict the controller performance. The experimental results also confirm that the performance of the proposed controller fully satisfy the standards concerning the testing procedure of seismic isolators.

Modelling, parameter identification, and control of a shear mode magnetorheological device

This paper describes theoretical and experimental studies of a shear mode magnetorheological fluid device. A testing procedure is used to measure the fundamental quantities needed to define a state space non-linear model and to identify its parameters. The obtained model is then validated by means of comparisons between modelling results and measurements. Finally, the model is used in the development of a time domain control scheme to regulate the transmitted torque.

A combined use of phase plane and handling diagram method to study the influence of tyre and vehicle characteristics on stability

This paper deals with in-curve vehicle lateral behaviour and is aimed to find out which vehicle physical characteristics affect significantly its stability. Two different analytical methods, one numerical (phase plane) and the other graphical (handling diagram) are discussed. The numerical model refers to the complete quadricycle, while the graphical one refers to a bicycle model. Both models take into account lateral load transfers and nonlinear Pacejka tyre–road interactions. The influence of centre of mass longitudinal position, tyre cornering stiffness and front/rear roll stiffness ratio on vehicle stability are analysed. The presented results are in good agreement with theoretical expectations about the above parameters influence, and show how some physical characteristics behave as saddle-node bifurcation parameters.

Modelling and Control of a Hydraulically Actuated Shaking Table Employed for Vibration Absorber Testing

This paper presents an activity concerning the modelling and control of an unidirectional electro-hydraulically actuated table adopted to test vibration isolators. The test rig consists of a hydraulic actuation system that drives a sliding table mounted on linear bearings. The system is characterized by nonlinearities such as valve dead zone and frictions. A nonlinear model is derived and then employed for parameters identification procedure. The results concerning the model validation are illustrated. They fully confirm the effectiveness of the proposed model able to capture the system behavior.The testing procedure of the isolation systems is based on the definition of a target displacement time history of the table and, consequently, the precision of the table positioning is of primary importance. In order to minimize the positioning error, a suitable control system has to be adopted. The system non-linearities limit highly the performances of the classical linear control, so a non-linear one is proposed. The sliding table mathematical model is employed for a non-linear control design able to minimize the error between the target position and the current one. The controller synthesis is made taking into account no isolator under test. The proposed approach consists in a non-linear optimal control based on the state-dependent Riccati equation (SDRE). Numerical simulations have been performed in order to evaluate the goodness of the designed control with and without the specimen under test. The results confirm that the performances of the proposed non-linear controller are not invalidated because of the presence of the specimen and highlight the controller robustness.Copyright

Software-in-the-loop development and validation of a Cornering Brake Control logic

In this article, a logic for vehicle dynamics control during partial braking while turning a corner is presented, which only requires knowledge of the instantaneous speed of the four wheels. For this reason, the proposed control algorithm can be adopted on all ABS equipped cars. A scheme of the simulation program for logic validation is described, which is constituted by a loop of software models of the principal vehicle subsystems which are singly illustrated. The proposed logic has been tested both in closed and open-loop maneuvers. The results are provided in the form of time histories of the principal analyzed quantities. The analysis of the results confirms the goodness of the proposed control strategy.

Optimisation of handling and traction in a rear wheel drive vehicle by means of magneto-rheological semi-active differential

This paper presents a semi-active differential, magneto-rheological fluid limited slip differential, which allows us to bias the torque between the driving wheels. It is based on the magneto-rheological fluid employment, by which it is possible to change, in a controlled manner, the internal friction torque and, consequently, the torque bias ratio. This device is an adaptive one and allows us to obtain an asymmetric torque distribution in order to improve vehicle handling. The device modelling and the control algorithm, realised for this activity, are described. The illustrated results highlight the advantages that are attainable regarding directional behaviour, stability, and traction.

Ph.An.Ty.M.H.A.: a physical analytical tyre model for handling analysis – the normal interaction

A new analytical–physical tyre model for which the paternity has to be ascribed to Professor Giuseppe Capone was developed at the Department of Mechanical Engineering for Energetics at Naples University ‘Federico II’ with the support of the Bridgestone Technical Centre Europe. The whole model allows to obtain the road–tyre interactions so it can be used in vehicle dynamic simulations. The model has been named Ph.An.Ty.M.H.A., acronym of ‘PHysical ANalytical TYre Model for Handling Analysis’ and it includes the normal, longitudinal and lateral tyre–road interaction. Considering that Ph.An.Ty.M.H.A. is an analytical ‘deductive’ model, it is necessary to develop it starting just from the normal interaction, described in this paper, and then the other ones will be described in future papers. In fact, the normal interaction, i.e. the relationship between the normal load and the normal deflection, influences the tangential (longitudinal plus lateral) one, which determines the vehicle handling behaviour. The parameters used in this model are physical and geometrical so they can be measured on the real tyre. This property allows to better understand the tyre–road interaction mechanism. The tyre behaviour is modelled by analytical expressions based on equilibrium conditions and geometrical relations. To reproduce the experimental normal interaction and the pressure distribution, once the tyre geometrical quantities are known, it is necessary to identify some parameters, related to the tyre structure, by a comparison with the experimental data. Moreover, the predictive ability of the whole model, combined with a vehicle model, is very careful in analysing the vehicle handling [J.C. Dixon, Tyres, Suspensions and Handling, Cambridge University Press, Cambridge, 1991].

Analysis of a New Measurement System of the Chain Strength for Electrically Assisted Bicycles

This paper presents an activity concerning a theoretical/experimental analysis of a new measurement system of the chain strength functional for the control of the electrically assisted bicycles. Such systems are characterized by a driving torque due to the contribution of an electric motor and of the rider. The electrical assistance is commonly regulated taking into account informations such as chain ring rotation, bicycle speed and/or the torque given by the rider. As a consequence, suitable measurements have to be made on board in order to handle the assistance performances and to improve drivability.Copyright

Performance Evaluation and Environmental Analysis of an Electrically Assisted Bicycle Under Real Driving Conditions

This paper describes the on-road test program that was used for a performance study and environmental analysis of an electrically assisted bicycle in the urban area of Naples. For this purpose, the vehicle was tested on different test tracks, cycling over 2000 km, and then making a general assessment about the driving behavior under real conditions.Based on the findings obtained during the different test samples, an appraisal of the electric traction offered by this bicycle on the driving comfort was evaluated for different conditions: electrical assistance at start, on a flat road and when riding uphill. The power requirements in different typical riding situations were also calculated: these results were estimated by experimental kinematic parameters that describe the driving dynamics collected during the real-life applications. An environmental analysis was made and also put against the environmental impact of a thermal moped.Copyright