Feasibility of novel four degrees of freedom capacitive force sensor for skin interface force

BioMedical Engineering OnLine

Makoto Takahashi²  Yusuke Ishikuro¹  Chisato Murakami² 

[1]Hokkaido Electric Power Co., Inc., Hokkaido, Japan

[2]Division of Biomedical Systems Engineering, Graduate School of Information Science and Technology, Hokkaido University, Hokkaido, Japan

关键词: Capacitance;    Skin surface;    Four DOF;    Force sensor;    Capacitive sensor;   

Others  :  797977
DOI  :  10.1186/1475-925X-11-90

 received in 2012-08-01, accepted in 2012-11-19,  发布年份 2012

【 摘 要 】

Background

The objective of our study was to develop a novel capacitive force sensor that enables simultaneous measurements of yaw torque around the pressure axis and normal force and shear forces at a single point for the purpose of elucidating pressure ulcer pathogenesis and establishing criteria for selection of cushions and mattresses.

Methods

Two newly developed sensors (approximately 10 mm×10 mm×5 mm (10) and 20 mm×20 mm×5 mm (20)) were constructed from silicone gel and four upper and lower electrodes. The upper and lower electrodes had sixteen combinations that had the function as capacitors of parallel plate type. The full scale (FS) ranges of force/torque were defined as 0–1.5 N, –0.5-0.5 N and −1.5-1.5 N mm (10) and 0–8.7 N, –2.9-2.9 N and −16.8-16.8 N mm (20) in normal force, shear forces and yaw torque, respectively. The capacitances of sixteen capacitors were measured by an LCR meter (AC1V, 100 kHz) when displacements corresponding to four degrees of freedom (DOF) forces within FS ranges were applied to the sensor. The measurement was repeated three times in each displacement condition (10 only). Force/torque were calculated by corrected capacitance and were evaluated by comparison to theoretical values and standard normal force measured by an universal tester.

Results

In measurements of capacitance, the coefficient of variation was 3.23% (10). The Maximum FS errors of estimated force/torque were less than or equal to 10.1 (10) and 16.4% (20), respectively. The standard normal forces were approximately 1.5 (10) and 9.4 N (20) when pressure displacements were 3 (10) and 2 mm (20), respectively. The estimated normal forces were approximately 1.5 (10) and 8.6 N (10) in the same condition.

Conclusions

In this study, we developed a new four DOF force sensor for measurement of force/torque that occur between the skin and a mattress. In measurement of capacitance, the repeatability was good and it was confirmed that the sensor had characteristics that enabled the correction by linear approximation for adjustment of gain and offset. In estimation of forces/torque, we considered accuracy to be within an acceptable range.

【 授权许可】

   
2012 Murakami et al.; licensee BioMed Central Ltd.

【 图 表 】

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