Due to increased interest in comfort features, considerable effort has been spent on the modification of brake prototypes in order to suppress brake squeal. Recently, piezoelectric transducers have been investigated as an innovative way of controlling the vibrations of a brake. This paper presents an efficient mechanical model for the description of a brake with embedded transducers. Different control strategies are discussed and compared. Measurements on a brake test rig validate the obtained results.
Due to increased interest in comfort features, considerable effort is spent by brake manufacturers in order to suppress brake squeal. This process can be shortened by eliminating the remaining squealing with shunted piezoceramics that are embedded into the brake system. The piezoceramics offers the unique ability to convert mechanical energy into electrical energy and vice versa. The damping performance is determined by the connected shunt. This paper presents a multibody system model of a brake, which is capable of reproducing important features of brake squeal. It includes the dynamics of a piezoceramics that is shunted with a passive LR shunt or a negative capacitance LRC shunt. Analytical stability analysis is carried out to obtain optimal shunt parameters. The performance increase with a negative capacitance is studied in detail. The simulations are validated with measurements on an automotive disk brake.
In technical applications, Tuned Mass Dampers (TMDs) are commonly used to reduce the vibrations of a system subjected to disturbance excitations. An alternative to TMDs are passive shunted piezo elements. Because of the ability to transfer mechanical energy into electrical energy and vice versa, an electromechanical vibration damper can be created by connecting a suitable passive resonance circuit. In this paper, criterions for optimal performance of both mechanical and electromechanical systems are derived, and maximum damping performances are compared. Further, a method to increase the damping performance of piezo elements by adding a negative capacitance is examined. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The paper deals with the Engineering Design that is a general methodology of a design process. It is assumed that a designer has to solve a design task as an inverse problem in an iterative way. After each iteration, a decision should be taken on the information that is called a centre of integration in a systematic design system. For this purpose, poly-optimal solutions may be used. The poly-optimization is presented and contrasted against the Multi Attribute Decision Making, and a set of the poly-optimal solutions is defined. Then Mechatronics is defined and its characteristics given, to prove that mechatronic design process vitally needs CAD tools. Three examples are quoted to demonstrate a key role of the poly-optimization in the mechatronic design.
Damping or absorbing effect in vibration control applications with piezo elements may be customized by an external impedance shunt branch connected to the plates of the piezo element. The negative capacitance present in the shunt significantly improves the damping and absorbing performance of such systems. The circuit is built up of an electronic gyrator realized by the operational amplifier, which is in reality not the ideal element. Therefore the performance of the proposed systems is limited, concerning the maximum voltages and currents at which the operational amplifiers can operate. In the paper, the finite gain of the operational amplifier, together with the loss impedances and the feedback gain factor is studied. The influence of the certain imperfections in the design of the electronic gyrator is based on 1DOF mechanical oscillator, with a piezo stack. Vibration control with piezo elementsThe vibrating system consists of a 1DOF spring-mass-damper oscillator with a piezo stack placed between mass m and the base Fig.1a. The Piezo element influences the frequency response function (FRF) of the system according to the complex impedance of a shunt branch consisting of the inductance L, capacitance C, and the resistance R. Passive technique used in discussed system is supported by semi-active, negative capacitance elements. As the result, significantly improved damping or absorbing performance is observed with a drawback of the necessity of the inconspicuous external power supply, and possible instabilities. For the design of the negative capacitance, the maximum value of the voltage present at it's terminals has to be calculated. The appearing voltage U ZC (s) on the electrodes of the circuit in Laplace domain (s = jω) U ZC (s) = I p (s)Z C (s), where Z C (s) = 1 sC . For the proposed system, the piezo current I p (s), based on [1], reads:where: c 0 and d 0 is the external stiffness and damping in the mechanical system respectively; c 33 -the mechanical stiffness, d 33 -the charge density per unity stress under constant electric field and C ps -the capacitance of the piezo element; u pvoltage appearing on the electrodes of the piezo, and i p -the current flowing to the external shunt branch. Impedance converterNegative capacitance is realized by impedance converter build up of the operational amplifier, a passive capacitance element characterized by the complex impedance Z p (s) and the resistive voltage divider feedback loop gain c Z , where c Z ∈ (0, 1), cp. Fig.1b. The input voltage U in (s) at the terminals of the converter is summed with the portion of the output voltage of the operational amplifier. This voltage is delivered to the controlled voltage source of the amplifier, and present at the output of the amplifier. Due to the existence of the output impedance Z o , and the current loop in the circuit flowing via the positive
In this paper two different visco-elastic suspensions active system with pneumatic cylinder, and semi-active system with piezoceramics, are presented. The active suspension controls the vibration in mediumamplitude range and low frequency excitation. The semi-active suppression system controls the vibration in the audio frequency range and small amplitudes. The main aim of proposed solutions is to decrease the amplitude of vibration in resonance of conventional, passive suspensions. Both systems are worked out, especially for the better protection of the human body against harmful sounds and vibrations.
Electrical circuits that represent complex impedance connected to the plates of piezo element affect the frequency response function of compound electromechanical systems. The external network consisting of inductance results in absorbing a certain frequency of vibrations. The performance can significantly be increased using negative capacitance. All the negative impedance elements are achievable via semi‐passive way with the use of an electronic gyrator realized by operational amplifiers that require power supply. Its performance is limited due to the maximum voltage operational amplifiers can produce. The higher excitation forces require higher output voltages of amplifiers. The aim of the paper is to present the relation between the required voltage on synthetic impedance and force excitation in 1DOF vibrating system regarding parameters of piezo element and mechanical system for absorbing case. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
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