THEORETICAL AND EXPERIMENTAL CONTRIBUTIONS NS AT THE STUDY OF SINGLE-PHASE VIBROMOTORS WITH ROLLED STRIPS

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1 THEORETICAL AND THEORETICAL AND EXPERIMENTAL CONTRIBUTIONS NS AT THE STUDY OF SINGLE-PHASE VIBROMOTORS WITH ROLLED STRIPS Eng. Ilie ROMANIUC, PhDs, Assoc. Prof. Eng. Mihai RAŢĂ, PhD, Prof. Eng. Dorel CERNOMAZU, PhD University Ştefan cel Mare from Suceava REZUMAT. Vibromotoarele fac parte din categoria de motoare neconvenţionale, care realizează conversia mişcarii alternative de vibraţie într-o o mişcare continuă liniară sau de rotaţie. În cadrul acestui articol sunt prezentate două variante constructive de vibromotoare monofazate cu lamele roluite. Aceste tipuri de vibromotoare funcţioneaza de regulă la frecvenţă industrială, dar în acest articol se prezintă şi rezultate experimentale privind funcţionarea vibromotoarelor alimentate prin intermediul unui invertor monofazat. Acest invertor are posibilitatea modificarii atât a frecventei cât si a factorului de umplere. Cuvinte cheie: motor neconvenţional, vibromotor, mişcare de vibraţie. ABSTRACT. Vibromotors belong to the category of unconventional motors, which convert vibration alternative motion to a continuous linear or rotary motion. In this paper are presented two variants of single-phase vibromotors with rolled strips. These types of vibromotors usually work at industrial frequency, but this article also presents experimental erimental results on the operation of vibromotors powered by a single-phase inverter. This inverter has the possibility of changing both the frequency and the duty cycle. Keywords: unconventional motor, vibromotor, vibrational motion. 1. INTRODUCTION The vibromotor is a converter that converts the vibration movement produced by an electro-mechanical oscillator excited by a pulsating or alternating voltage source, into a continuous motion. After the character of the movement obtained vibromotors can be rotary or linear. In contrast to conventional electrostatic or electromagnetic motors, where the rotor and the stator are separated by a gap filled with air and where the power consumption from the source is transferred to the rotor through the electromagnetic field, at vibromotors this transfer is carried out by friction, which requires direct contact between the stator and the rotor. Vibromotors can be built without having metal parts (if we exclude the power supply cables), allowing their use in construction of magnetic or geodetic instruments with high precision. The main feature of vibromotors is the dynamic qualities those motors have in motion transient conditions (eg start-stop regimes, ie stepping scheme), as the vibrating element turns into a brake when it loses power. In many application domains, vibromotors are used as they solve various problems of positioning, uniform high-speed travel, or to achieve a required movement. Therefore in the future vibromotors will have a big share in the construction of microrobots capable to handle, with very good accuracy, small objects in confined spaces. Field applications of these microrobots is quite vast (from micro-surgery to assembling microelectronic circuits). But, vibromotors with many degrees of freedom will lead to the construction of manipulators with high accuracy. Vibromotoarele according to the mechanical oscillation frequency are classified into: vibromotors operating at frequencies of tens of khz, ie piezolelectric motors; vibromotors operating at industrial frequency. Among them can be distinguished the following types: vibromotors with rolled strips; vibromotors with tensegrity structure based on the principle of the Marinescu oscilomotor ; magnetostrictive vibromotors; electrostatic vibromotors. Buletinul AGIR nr. 4/2012 octombrie-decembrie 1 285

2 INT. SYMPOSIUM ON ELECTRICAL ENGINEERING AND ENERGY CONVERTERS ELS THE OPERATING PRINCIPLE OF VIBROMOTORS WITH ROLLED STRIPS The principle of converting vibration movement into rotation movement in a vibromotor with rolled strips is described in Figure 4.1. If the end of the vibrating plate 4 is moved with x, bent tab 3 will further describe a curve l, and thus the effect of friction, the disk 1, which is in contact with the slide will move with l in the same direction. The direction of movement of the disc is given by the direction in which the tab 3 is bented F x F l an electromagnet 7, powered by a source of alternating current of industrial frequency ~ A Fig. 1 The principle of converting vibration movement in a movement of rotation (reproduced from [2]) l A Fig. 2 Single-phase vibromotor with rolled strip (reproduced from [3]) 1 rotor; 2 shaft; 2, 2 plain bearings; 3 peripheral ring; 4 rolled strip; 5 adhesive tape; 6 ferromagnetic armature; 7 electromagnet; 8 voltage source. 3. CONTRIBUTIONS TO MAKING AND TESTING OF SINGLE-PHASE VIBROMOTORS WITH ROLLED LED STRIPS 3.1 Constructive variants and features Two solutions of single-phase vibromotors with rolled stripes are proposed; the first variant is a singlephase vibromotor with one rolled strip with protective ring of the rotor, the latter is a single-phase vibromotor with two concentrated rolled strips. 3.2 Single-phase vibromotor with one rolled strip In the first variant, the single-phase vibromotorwith one rolled strip (fig. 4.2) is made up of a rotor 1 in the form of a disc mounted on a shaft 2 which is supported in two bearings 2' and 2''. The rotor 1 is provided in the peripheral-circular part, with a ring 3 made of synthetic rubber, to which steps a rolled strip 4 made of beryllium bronze, which has in the area in contact with the ring 3, an adhesive tape 5, made of the same material. Rolled strip 4 is fixed to the free end of a ferromagnetic plate 6, made of ferromagnetic material. Ferromagnetic armature 6 is recessed at one end and is under the influence of an alternating magnetic field produced by Fig. 3 Single-phase vibromotor with rolled strip 3.3 Single-phase vibromotor with two concentrated rolled strips In the second variant, the single-phase vibromotor with two concentrated rolled strips (fig. 4.3) is made of a disk-shaped rotor 1, mounted on a shaft 2 which is supported in two sliding bearings 3 and 3'. On the surface of the rotor act two vibrating modules which constitute the stator of the motor. The action of the vibrating modules is performed through the rolled strips 4a and 4b made of cadmium bronze or beryllium 2 286

3 THEORETICAL AND EXPERIMENTAL CONTRIBUTIONS AT THE STUDY OF SINGLE-PHASE VIBROMOTORS THEORETICAL WITH AND ROLLED STRIPS bronze, and which are attached to the free ends of flexible blades, 5a and 5b, made of a ferromagnetic material. The two ferromagnetic blades are embedded at one end and are under the action of alternating magnetic fields produced by the electromagnets 6a and 6b powered by an AC power source 7. Electromagnet coil 6a is directly connected to the single-phase power source phase 7, while the electromagnet coil 6b is connected to the source by means of a phase shifter element 8 represented, where appropriate, with a capacity, through an inductance or an electric resistance. As a result, the action of the two vibrating modules, which is the stator of the vibromotor is out of phase which contributes to an increase in torque and an increase in the rotational speed of the rotor. 4. EXPERIMENTAL RESULTS The experimental data obtained in the tests carried out relate to: speed based on voltage and torque based on voltage at the single-phase vibromotor with one rolled strip with the rotor protected with three different materials; speed based on voltage and torque based on voltage at the single-phase vibromotor with two rolled strips powered by sinewave; speed based on voltage, speed based on frequency, speed based on the duty cycle and torque based on voltage at the single-phase vibromotor with two rolled strips powered by square wave; 4.1 Experimental data on the single-phase vibromotor with one rolled strip In order to verify the performance of the singlephase vibromotor with one rolled strip, various materials have been used to construct the protective ring of the rotor is to say grinding, PVC and synthetic rubber as shown in Fig. 6. a) Fig. 4 Single-phase vibromotor with two concentrated rolled strips (reproduced from [3]) 1 rotor; 2 shaft; 3, 3 plain bearings; 4a, 4b rolled strips; 5a, 5b flexible blades; 6a, 6b electromagnets; 7 AC power source; 8 out of phase element. b) c) Fig. 5 Single-phase vibromotor with two concentrated rolled strips Fig. 6 Overview of the rotor provided with different protection rings. a grinding; b PVC; c synthetic rubber

4 INT. SYMPOSIUM SYMPOSIUM ON ON ELECTRICAL ELECTRICAL ENGINEERING ENGINEERING AND AND ENERGY ENERGY CONVERTERS CONVERTERS ELS ELS INT. Fig. 7 Speed and torque experimental characteristics of the singlephase vibromotor with one rolled strip Fig. 9 Experimental characteristics of the single-phase vibromotor with two rolled strips 4.2 Experimental data on single-phase vibromotor with two rolled strips powered by sinewave 4.3 Experimental data on single-phase vibromotor with two rolled strips powered by square wave In Fig. 8 is presented the stand for the study of the performance characteristics of the vibromotor with two concentrated rolled strips powered by sinewave. To supply with a square wave was used the IGBT inverter built in the Research Center EMAD, which provides to its output an alternative rectangular voltage. This inverter allows adjustements in both frequency and duty cycle in the range 0 100%. Fig. 8 Stand for the study of the performance characteristics when powered by sinewave a) 4 288

5 THEORETICAL AND EXPERIMENTAL CONTRIBUTIONS AT THE STUDY OF THEORETICAL ANDROLLED STRIPS SINGLE-PHASE VIBROMOTORS WITH b) Fig. 10 Inverter for powering vibromotors with square wave a inverter; b PWM control module. Fig. 11 presents the stand for the study of the performance characteristics of the vibromotor with two rolled strips powered by square wave. Fig. 11 Stand for the study of the performance characteristics when powered by square wave b) c) The stand consists of a power supply, an IGBT inverter, a PWM control module, a phase encoder and the vibromotor with two concentrated rolled strips being analyzed. d) Fig. 12 Experimental speed and torque characteristics of singlephase vibromotor with two rolled strips a speed voltage characteristic; b torque voltage characteristic; c speed frequency characteristic; d speed duty cycle characteristic. a) 5 289

6 INT. SYMPOSIUM ON ELECTRICAL ENGINEERING AND ENERGY CONVERTERS ELS CONCLUSIONS Vibromotors and unconventional motors are an efficient alternative compared to classical solutions based on the magnetic effect; Vibromotors with rolled strips are characterized by increased power and torque at low speeds. Experimental tests carried out in order to protect the rotor by attaching a protective ring on the contact surface between the rotor and rolled strip showed that while the higher speed which was achieved with protective rubber ring, the couple was highest obtained with abrasive protective ring. From the point of view of the shape of the signal applied to power the vibromotor, the best results of speed and torque were obtained when powered by sinewave. Experimental tests on powering the vibromotor with rectangular signal power showed that the best results were obtained at 50 Hz with 50% duty cycle. ACKNOWLEDGMENT This paper was supported by the project "Improvement of the doctoral studies quality in engineering science for development of the knowledge based society-qdoc contract no. POSDRU/107/1.5/S/78534, project cofunded by the European Social Fund through the Sectorial Operational Program Human Resources BIBLIOGRAPHY [1] Ragulskis K., Bansevicius R., Barauscas R.,Kulvietis G., Vibromotors for Precision Microrobots, Hemispher Publishing Corporation, ISBN: , 1988; [2] Cernomazu, D.; Simion, Al.; Daniela, I., Baciu, I.; Vibromotor. Cerere de brevet de invenţie nr. A/00203 din , OSIM Bucureşti; [3] Romaniuc, I.; Niţan, I.; Raţă, M.; Milici, M.R.; Milici, D.L.; David, C.; Raţă, G. Vibromotor. Cerere de Brevet de Invenţie nr. A/00257 din , Publicat în B.O.P.I. 9/2012, O.S.I.M. Bucureşti. [4] Cernomazu, D.; Raţă, M.; Raţă, G.; David, C.; Milici, M. R.; Milici, L. D.; Olariu, E. D.; Niţan, I. Vibromotor. Cerere de Brevet de Inventie nr. A00865 din , Publicat în B.O.P.I. 4/2012, O.S.I.M., Bucureşti