Michał Mańka

Numerical Modelling and Experimental Verification of Interdigital Transducers for Lamb Wave Generation

Recently, intensive research activity in the application of guided waves (GWs) for structural health monitoring (SHM) has been observed. Interdigital Transducer (IDT) is one of the types of transducers used for generating GWs. The main advantages of such transducers include their ability in generating directional and mode-selective waves. The parameters of IDTs have to be adjusted for the excited wavelength. Some geometric parameters as well as the properties of materials used for manufacturing transducers may be defined using widely known analytical relationships [1]. However, in order to accurately determine the parameters of the IDT, numerous simulations and their experimental verification are required [2]. The paper presents a novel, time efficient approach to the virtual prototyping of complex shaped transducers. The proposed procedure consists of the following four steps: (1) designing a transducer based on analytical relations, (2) approximate numerical simulations of designed transducers with a custom-made, computationally efficient code for screening tests, (3) detailed numerical tests employing the multiphysics Finite Element Method (FEM) for the developed IDT design and (4) experimental tests.

Review of the modular self reconfigurable robotic systems

Modular Self-Reconfigurable robot (MSR) is a system composed of a group, connected together identical modules, resulting structure can carry out specific, even complicated tasks. Such design allows for easy reconfiguration of the robot and its structure in order to continuously adapt it to the current needs or tasks, without the use of additional tools. Currently, the use of MSRs is very limited due to the early stage of technology development. In the future this type of robots will probably be widely used in industry and leisure activities. This paper describes the challenges and opportunities facing the modular robots, an explanation of key terms and the latest designs of artificial cell.

Improving the Design of Capacitive Micromachined Ultrasonic Transducers Aided with Sensitivity Analysis

The paper presents the results of analysis performed to search for feasible design improvements for capacitive micromachined ultrasonic transducer. Carried out search has been aided with the sensitivity analysis and the application of Response Surface Method. The multiphysics approach has been taken into account in elaborated finite element model of one cell of described transducer in order to include significant physical phenomena present in modelled microdevice. The set of twelve input uncertain and design parameters consists of geometric, material and control properties. The amplitude of dynamic membrane deformation of the transducer has been chosen as studied parameter. The objective of performed study has been defined as the task of finding robust design configurations of the transducer, i.e. characterizing maximal value of deformation amplitude with its minimal variation.

Co-Simulations of Motorcycle-Rider System in Road Behaviour Simulations

This paper presents the research results of the first stage of the Marie Curie Project, MYMOSA (MotorcYcle and MOtorcyclist SAfety). One of the aims of MYMOSA is increasing safety of motorcycle’s rider by better understanding of its road behaviour. It can be achieved by simulations of the motorcycle-rider system during road manoeuvres and pre-/crash scenarios. The process of the motorcycle-rider system development and initial results of the road behaviour simulations are presented. The system is divided into three separate elements: controller, motorcycle and rider’s body models. The co-simulations of motorcycle, rider and controller, are performed to determine the behaviour of the system on the road. Obtained simulation results are compared with results from the system without multibody rider’s model. During further work, kinematic and dynamic properties of the rider’s body parts will be used as inputs for crash simulations with detailed rider’s model to determine positions and severity of injuries caused by crash.Copyright

Elastic Interdigital Transducers for Lamb Wave Generations

During recent years structural health monitoring (SHM) systems have gained growing attention. Widely applied methods in SHM are methods based on the ultrasonic Lamb waves (LWs) which are also known as plate waves. LWs may be generated and sensed using different types of transducers and their selection is essential for the SHM systems performance. Among transducers used for generation and sensing of such waves, Interdigital Transducers (IDTs) are ones of the most promising types. Their main advantages are: mode selectivity, high excitation strength, wave directivity, small sizes and relatively low cost. In most cases IDTs are made of piezoceramics or piezoelectric polymers what makes them stiff and fragile. Contrary to the piezoceramic transducers, the ones based on piezocomposites (i.e.: macro-fiber composite) are flexible with the comparable efficiency of piezoelectric effects. The MFC transducers are usually optimized as actuators and they are not designed to any specific frequency. It appears, however, that sparse comb-like electrodes used in interdigital transducers create very interesting properties of mode selectivity. In the paper, after the introduction and short discussion about advantages and disadvantages of the IDTs, a novel type of the interdigital transducer, based on elastic macro-fiber composite, is presented. Next, the results of the numerical and experimental tests of the MFC based IDT designed for the A0 mode excitation in a 4mm-thick aluminium plate is presented. In the final part of the paper advantages and disadvantages of the investigated transducer are discussed.

Design Process of IDT Aided by Multiphysics FE Analyses

Presented work is devoted to a design process performed for the interdigital transducer, which is a perspective application for the area of structural health monitoring. In order to obtain the desirable characteristic of the transducer fully coupled numerical analyses were performed in ANSYS Multiphysics software. Utilised finite element models considered both structural dynamics and properties of used piezoelectric material. The process of design improvement was preceded by the sensitivity analysis. In order to search for the best electrode pattern selected geometrical features of the transducer were assumed to vary within allowed ranges. The design parameters, which were taken into account, related to the efficiency of proposed transducer design for the emission of acoustic waves in the monitored structure. The search objectives considered the criteria related to the shape of the beampattern and amplitudes of generated Lamb waves. As a result of the optimization procedure, the simultaneous increase of anti-symmetric mode amplitude and the reduction of undesirable symmetric mode amplitude of generated Lamb waves in the direction perpendicular to the transducer fingers was expected. Another aim of the optimization was to minimize the main lobe width and undesirable contribution of both symmetric and anti-symmetric waves in the parallel direction to the transducer fingers. The response surface method and genetic algorithms were used for fast and effective search through the input design domain.

A “corner solver” for motorcycles as a tool for the development of a virtual rider

In this paper, a solver for the cornering analysis of motorcycles is presented. Its main outcome is the trim condition of the vehicle accelerating through a corner. There are several advantages of using this approach over a dynamic solution. Firstly, a controller is not needed to stabilize the motorcycle under the desired conditions and, secondly, the solution is much faster. The exploration of the motorcycle equilibrium points and their dependence on the speed and the corner radius will give a useful insight for the design of a virtual rider.

Motorcycle Dynamic Models for Virtual Rider Design and Cornering Analysis

In this paper, three motorcycle models of increasing complexity are introduced. The first, and most simple, can be considered an extension of the model developed by Neil Getz in which the non-holonomic constraints have been removed to take into account the sideslip in tires. Also, this model can be viewed as an extension of the popular bicycle model, widely used in analyzing car dynamics. It has been extended with an additional degree of freedom essential to study motorcycle dynamics: the roll angle. Such a model, simple yet detailed enough, will be used as the basis in the development of a virtual rider. The second model is much more complex than the previous one. It includes the real geometry of the steering system and circular tire profiles which greatly increases the size of the equations. This is a multibody model of a complete rigid motorcycle (i.e. it has no suspensions) consisting of 4 bodies: rear wheel, main frame, fork and front wheel. The last model incorporates the front and rear suspensions together with all the features of its predecessor. It has 13 degrees of freedom, 11 of the mechanical system and 2 of the tire relaxation equations. It will be used as a full model for simulation and rider validation. The models presented in this article have been developed using Maple mathematical software which allows symbolic manipulation of equations. Thus, with this set of models, one can study in depth the phenomena that govern motorcycle dynamics since all the equations are available symbolically.Copyright