• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.14 no.5
• /
• pp.394-401
• /
• 2004

This paper presents a study on the analysis of impact responses taking into account sensor dynamics. The contact force between impacting bodies is modelled by using Hertz force-displacement law and linear damping function. Since the real impact force and acceleration at the contact surface of two colliding bodies are measured indirectly by the sensors, the measured outputs can be a little different from the real impact responses. Therefore, in this study, the importance of consideration of sensor dynamics in the impact problems of two colliding bodies is emphasized. In order to verify the appropriateness of the proposed contact force model, the drop type impact test using two kinds of sensors is carried out. Through the numerical analysis and experiment, the effect of sensor dynamics and characteristics on the contact force model is investigated.

• Journal of Sensor Science and Technology
• /
• v.28 no.2
• /
• pp.106-112
• /
• 2019

Flexible impact force sensors composed of piezoelectric PZT/PDMS composite sandwiched between Al/PET films were fabricated and their voltage signal characteristics were evaluated under varying impact forces for electronic mitt applications. The piezoelectric impact force sensor on an ethylene-vinyl acetate (EVA) substrate exhibited an output voltage difference of no greater than 40 mV a periodical impact test in with the impact load was increased by as much as 240 N by a restoration time of 5 s in a five-time experiment, implying good sensing ability. Moreover, the impact force sensor embedded four electronic mitts showed a reliable sensitivity of less than 1 mV/N and good repeatability under 100 N-impact force during a cycle test executed 10,000 times. This indicated that the fabricated flexible piezoelectric impact sensor could be used in electronic mitt applications. However, the relatively low elastic limit of substrate material such as EVA or poly-urethane slightly deteriorated the sensitivity of the impact sensor embedded electronic mitt at over 200 N-impact forces.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.11a
• /
• pp.373.1-373
• /
• 2002

Impact is the most common type of dynamic loading conditions that give rise to impulsive forces and affects the vibrational characteristics of mechanical systems. Since the impact force and response are measured indirectly through the sensors, it is difficult to predict the impact force and acceleration. In this study, contact force model based on the Hertz law is proposed in order to predict the impact force correctly. (omitted)

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.21 no.5
• /
• pp.16-21
• /
• 2022

This study investigates the effect of the deformation on the sensitivity of a flexible polydimethylsiloxane (PDMS) membrane sensor. A PDMS membrane sensor was developed to measure the impact force of a water droplet using a silver nanowire (AgNW). The initial deformation of the membrane was confirmed with the application of a tensile force (i.e., tension) and fixing force (i.e., compressive force) at the gripers, which affects the sensitivity. The experimental results show that as the tension applied to the membrane increased, the sensitivity of the sensor decreased. The initial electrical resistance increased as the fixing force increased, while the sensitivity of the sensor decreased as the initial resistance increased. The movement of the membrane due to the impact force of the water droplet was observed with a high-speed camera, and was correlated with the measured sensor signal. The analysis of the motion of the membrane and droplets after collision confirmed the periodic movement of not only the membrane but also the change in the height of the droplet.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.11b
• /
• pp.731-736
• /
• 2002

Impact is the most common type of dynamic loading conditions that give rise to impulsive forces and affects the vibrational characteristics of mechanical systems . Since the real impact force and acceleration at the contact surface are measured indirectly through the sensors, the measured outputs can be a little different from the real impact responses. In this study, the contact force model based on the Hertz law is proposed in order to predict the impact force correctly. To investigate the influence of the position of the sensor attached to the impacting bodies, the two kinds of sensors were used. Finally, the contact force model obtained by drop test was applied to predict the impact force between the moving part and the stopper in magnetic contactor.

• Journal of Biomedical Engineering Research
• /
• v.17 no.2
• /
• pp.215-220
• /
• 1996

Impact force and strains induced by impact between the occluder and the struts have been measured with force sensor and strain gages. The maximum reaction force was about 25N, and the calculated impact force on the root of the struts amount about 9-17W. Impact force on the inlet strut is greater than that of the outlet strut, but the strain on the outlet strut is much higher than that of the inlet strut. These values might cause severe damage on the valve in the critical cases. The results of this study may be extended for the analysis of the endurance limit and optimal design of the struts and occluder.

• Composites Research
• /
• v.13 no.6
• /
• pp.47-54
• /
• 2000

One promising method for impact detection of composite structures is based on the use of piezopolymer thin fim (PVDf) sensor. In this paper, the relationship between the contact force and the signals of the attached strain gage and PVDF sensor to the composite plate subjected to low-velocity impact were derived. The relation for the open circuit and short circuit voltage of PVDF sensor was derived based on the equivalent circuit model of the piezoelectric sensor. The work was then extended to include experimental investigation into the use of short circuit voltage of PVDF sensor without using charge amplifier to detect low-velocity impact. The natural frequencies and damping ratio of the composite plate obtained from the vibration test were used to modify the analytical model and therefore the differences between measured and simulated signal of the modified analytical model in both forward and backward problem were considerably reduced. The reconstructed contact force and simulated sensor signals agreed well with the measured contact force, strain gage signal, and PVDF sensor singanl.

• Journal of Ocean Engineering and Technology
• /
• v.28 no.3
• /
• pp.209-217
• /
• 2014

In the present study, the water impact loads on two-dimensional symmetric and asymmetric wedges were mainly studied. The impact pressure and force were measured during a vertical drop of the symmetric and asymmetric wedges. The measured pressure was compared with analytic solutions. The measured force at a local area of the wedge was compared with the integrated pressures and analytic solutions. Some findings on symmetric and asymmetrical wedge drops are presented, and the reliability of the force sensor used for the measurement of the local impact force is discussed.

• International Journal of Precision Engineering and Manufacturing
• /
• v.9 no.3
• /
• pp.46-50
• /
• 2008

The present status and future prospects of the levitation mass method (LMM), a technique for precision mass and force measurement, are reviewed. In the LMM, the inertial force of a mass levitated using a pneumatic linear bearing is used as the reference force applied to the objects being tested, such as force transducers, materials, or structures. The inertial force of the levitated mass is measured using an optical interferometer. We have modified this technique for dynamic force calibration of impact, oscillation, and step loads. We have also applied the LMM to material testing, providing methods for evaluating material viscoelasticity under an oscillating or impact load, evaluating material friction, evaluating the biomechanics of a human hand, and generating and measuring micro-Newton-level forces.

• Journal of the Korean Society for Precision Engineering
• /
• v.16 no.1 s.94
• /
• pp.42-48
• /
• 1999

A control method for a robot hand grasping a object in a partially unknown environment will be proposed, where a proximate sensor detecting the distance between the fingertip and object was used. Particularly, the finger joints were driven servo-pneumatically in this study. Based on the proximate sensor signal the finger motion controller could plan the grasping process divided in three phases ; fast aproach, slow transitional contact and contact force control. That is, the fingertip approached to the object with full speed, until the output signal of the proximate sensor began to change. Within the perating range of the proximate sensor, the finger joint was moved by a state-variable feedback position controller in order to obtain a smooth contact with the object. The contact force of fingertip was then controlled using the blocked-line pressure sensitivity of the flow control servovalve for finger joint control. In this way, the grasping impact could be reduced without reducing the object approaching speed. The performance of the proposed grasping method was experimentally compared with that of a open loop-controlled one.