Chaotification in an internal-resonance-based electromagnetic vibration energy harvester

This paper explores a 2:1 internal resonance of a bistable vibration energy harvester (BVEH) to enhance the harvesting performance. Two linear natural frequencies are tuned to meet the nearly commensurate ratio, i.e., 1:2. Thus, the 2:1 internal resonance could be activated when the first mode is directly excited under the same vibration frequency as the first linear natural frequency. The amplitude-frequency responses under small vibration amplitudes are obtained through the multi-scale method. The analytic results reveal the double-jumping characteristics, which could expand the bandwidth of the BVEH. Among them, an intriguing “flower pattern” amplitude-frequency curve is observed. Besides, the frequency spectrums are introduced to demonstrate the mode coupling and energy exchange between the first two modes. With small vibration amplitude, only intra-well responses could be obtained, and the energy exchange between modes obeys strict commensurate relation, i.e., 2:1. However, it does not obey the 2:1 ratio when the inter-well responses are activated, and the energy transfers to several low-frequency modes which results in a chaotic inter-well response. Afterward, the bifurcation diagrams and basin-of-attraction maps are explored by the numerical method to develop insights into the nonlinear responses of the BVEH. The results quantitatively prove the enhancement of the inter-well responses by internal resonance, and the chaotic inter-well response dominates the nonlinear behaviors.

THE ESTIMATION COEFFICIENT OF THE VIBRATION TRANSMISSION TO THE ENGINES´ SUPPORT STRUCTURES

The scientific paper considers the vibration calculations of the foundations in order to select its parameters (mass, size of the base flange), which provide sufficiently small vibration amplitudes. An increase in the mass of the foundation does not always lead to a decrease in the vibration amplitude. It is carried out an increase in the mass of the foundation with a constant base flange area is associated with a decrease in the frequency of natural vibrations` installation and can lead to an increase in the amplitude due to resonance.

Small plate vibration sound-absorbing device with a clearance and without surrounding restriction: Theoretical analysis and experiment

This article focuses on the theoretical analysis and experiment of a small plate vibration sound-absorbing device with a clearance and without surrounding restriction. Generally, a plate vibration sound-absorbing device absorbs sound in a frequency range lower than that of porous material, which is used as a sound-absorbing material, and its sound absorption coefficient is small. Furthermore, note that the plate is fixed at the periphery in a conventional plate vibration sound-absorbing device. Hence, when the plate is small, vibration barely occurs and effective sound-absorbing effect is not obtained. Given that the plate vibration sound-absorbing device has a restriction wherein a particular size of plate is required, it is primarily utilized for indoor finishing considering the architectural acoustics, and finding applications for small-sized machines has been challenging. Theoretical values in this work are calculated assuming that the clearance and back air layer for the small plate vibration sound-absorbing device constitute a Helmholtz resonator. Furthermore, experiments were conducted to perform comparisons against the theoretical value. The theoretical analysis was conducted by connecting the clearance and back air layer in parallel with the plate portion in the electrical equivalent circuit. By performing the experiments using various parameters, the sound absorption characteristics of the proposed plate vibration sound-absorbing device were determined. If the clearance is smaller than the boundary layer thickness, then the conventional resistive end correction cannot be applied.

Novel Haptic Device Using Jamming Principle for Providing Kinaesthetic Feedback in Glove-Based Control Interface

This paper presents a new type of wearable haptic device which can augment a sensor glove in various tasks of telemanipulation. We present the details of its two alternative designs jamming tubes or jamming pads, and their control system. These devices use the jamming phenomena to change the stiffness of their elements and block the hand movement when a vacuum is applied. We present results of our experiments to measure static and dynamic changes in stiffness, which can be used to change the perception of grabbing hard or soft objects. The device, at its current state is capable of resisting forces of up to 7 N with 5 mm displacement and can simulate hardness up to the hardness of a rubber. However, time necessary for a complete change of stiffness is high (time constant 0.5 s); therefore, additional cutaneous interface was added in a form of small vibration motors. Finally, we show an application of the haptic interface in our teleoperation system to provide the operator with haptic feedback in a light weight and simple form.

Sensory Feedback Training for Improvement of Finger Perception in Cerebral Palsy

Purpose. To develop and to test a feedback training system for improvement of tactile perception and coordination of fingers in children and youth with cerebral palsy.Methods. The fingers of 7 probands with cerebral palsy of different types and severity were stimulated using small vibration motors integrated in the fingers of a hand glove. The vibration motors were connected through a microcontroller to a computer and to a response 5-button keyboard. By pressing an appropriate keyboard button, the proband must indicate in which finger the vibration was felt. The number of incorrect responses and the reaction time were measured for every finger. The perception and coordination of fingers were estimated before and after two-week training using both clinical tests and the measurements.Results. Proper functioning of the developed system in persons with cerebral palsy was confirmed. The tactile sensation of fingers was improved in five of seven subjects after two weeks of training. There was no clear tendency towards improvement of selective use of fingers.Conclusion. The designed feedback system could be used to train tactile perception of fingers in children and youth with cerebral palsy. An extensive study is required to confirm these findings.

The Exact Linearization and LQR Control of Semiactive Connected Hydropneumatic Suspension System

Based on differential geometry theory, the nonlinear system of connected hydropneumatic suspension was transformed to a linear one. What is more, it realized the decoupling and inverter between the control variables and system outputs. With LQR (Linear Quadratic Regulator) control theory, a semiactive system has been developed for connected hydropneumatic suspension in this paper. By AMESim/Simulink cosimulation, the results show that the semiactive connected hydropneumatic suspension decreases the vibration of upper vehicle quickly and reduces the impact acceleration strongly both in displacement and inroll angle. Moreover, the semiactive suspension could increase the suspension dynamic deflection, which would make the system reach balance quickly and keep small vibration amplitude under the effect of disturbance.