Salvatore Strano

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 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

Fluid-Dynamic Analysis of Earthquake Shaking Table Hydraulic Circuit

This paper presents a fluid-dynamic analysis of the hydraulic circuit of a shaking table for seismic tests; the model was developed adopting a commercial code. The aim of the study is to provide useful indications for the design of a new optimized control system. The model was developed taking into account all the components of the hydraulic circuit that is made of by the following main items: the axial piston pump, the pressure relief valve, the main control valve, the accumulators, the hydraulic cylinder with variable displacement and all the connecting pipes. Particular attention was given to the modelling of internal resistance of the hydraulic system, that can greatly affect the performance of the shaking table. It has also been accurately modelled the main valve dead zone to highlight its influence on the system dynamics. The results of numerical simulations obtained for different operational conditions are reported and compared with experimental data to show the validation and the performances of the developed model.© 2012 ASME

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

Optimal power-assistance system for a new pedelec model

This paper presents an activity concerning the modeling and the control of an innovative power-assisted electric bicycle. The proposed control method is based on a torque control designed via an optimal approach to achieve multi-objective performances regarding the external disturbance input, control signal magnitude, and velocity tracking error. The performance of the methodology has been evaluated applying the proposed control to a new pedelec (pedal electric cycle) model characterized by the measurement of the total torque (rider torque and electric motor one) employed as a feedback for the control. To this aim, a mathematical model of the bicycle, equipped with the electric motor, has been developed. Simulations have been performed in order to evaluate the tracking capability and the disturbance rejection. The performances have been compared with the ones referred to a traditional assistance approach, and the results demonstrate that the proposed approach provides improvements in terms of riding comfort and energy employment.

3D Object Reconstruction Using a Robot Arm

A technique for a vision application is proposed by means of which it is possible to obtain the three dimensional reconstruction of surfaces and objects. This technique uses a number of images from a single camera that is moved around the object by a robot arm. In this way the calibration of the video system is no more necessary because the robot kinematics is known. The images are processed by an algorithm that has been developed starting from our previous investigations on computer vision applied to robotics. The reconstruction of the images can be easily used to reproduce the object itself by means of tools installed on a robot arm. Some examples are given.

A Base Isolation System for Developing Countries Using Discarded Tyres Filled with Elastomeric Recycled Materials

This article studies the performance of economic base isolators using tyres filled with elastomeric recycled materials. The research was conducted to analyze base isolators to be used in developing nations, where the application of conventional elastomeric rubber bearings due to economic reasons is limited. The tested isolators are made of kart tyres filled with different recycled elastomeric materials and aggregates. Dynamic and static tests proved acceptable vertical to horizontal stiffness ratio of the bearings and shake table tests showed an excellent enhancement of the base isolated structural response compared to the corresponding fixed base structure.

An extended Kalman Filter procedure for damage detection of base-isolated structures

Base isolation is widely adopted to mitigate earthquake effects on structures. Information concerning the status of the isolation devices is fundamental, for example, after an emergency event and, consequently, damage detection procedures have received significant attention in the recent years. Herein, an extended Kalman filter approach is developed for real-time estimation of the isolation device stiffness from acceleration measurements. Simulations have been carried out by means of a three degree of freedom model and results are illustrated. Moreover, experimental evaluations of the damage detection method have been conducted by means of a prototype structure that has been excited adopting a sequence of seismic events. The results highlight a stiffness degradation and fully agree with the measurements, allowing a validation of the technique.

Mechanical characterization and modeling of an innovative composite material for railway applications

The innovation in the railway industry is focused on the production of lightweight vehicles with high performance, in order to obtain an energy power saving and to satisfy the environmental and global community requests. To pursue this aim, new materials have been increasingly used for vehicle structures. The selection of innovative materials and the definition of the relative properties represent, however, one of the most critical aspects for the design. Several factors, such as technical requirements, strength- and stiffness-to-weight ratios, crash resistance, and cost, are involved in material selection for rail vehicles. In addition, materials have to be chosen in accordance with the reference standards concerning fire resistance. This paper describes the activity carried out in order to acquire the needed information about selected composite materials to be used in the design and validation phases for a structural rail vehicle end and a roof. The material under investigation has been manufactured in order to satisfy the strict railway light metro fire normative. Due to the novelty of the adopted composite materials, a full mechanical characterization of the lamina was needed. The orthotropic material properties were verified and tuned using further tests on laminate and sandwich configurations in order to take into account, also, the influence of manufacturing process parameters. Analytical and numerical approaches have been used to validate and optimize the structural layout. Results of the multistep material characterization, acquired during the above phases, have been used to perform computational analysis in order to further improve the component design.