Did you forget to calibrate the sensors before the experiments? No worries!

Inertial measurement units, or IMUs, are popular and flexible tool used as a wearable and flexible device for human motion tracking.

One of the challenges of using these devices is achieving sensor-to-body alignment, or anatomical calibration (AC). Current AC methods often require extra movements or are limited to specific joints, which can be inconvenient and time-consuming. Or, even worse, sometimes you forget to do this calibration beforehand, and you think your data are lost forever.

Nothing to worry! To address this challenge, with my old group in Waseda University we proposed a novel method that can achieve AC from standard motion tests such as walking or sit-to-stand, without requiring extra movements, directly from the experimental data. Amazing, isn't it?

Our method uses the limited acceleration range on the medial-lateral direction and applies principal component analysis to estimate the sagittal plane, while the vertical direction is estimated from acceleration during quiet stance. We compared the results of our method with the AC obtained from specially designed movements and found a good correlation between the two sets of inertial measurement units placed on frontal/back and lateral sides of head, trunk, and lower limbs.

We also verified the repeatability and convergence of our method. The AC obtained from sit-to-stand and walking achieved similar results as the movements specifically designed for upper and lower body AC, respectively, except for the feet. This means that experiments performed without AC can be recovered through post-processing on the walking and sit-to-stand data. Moreover, extra movements for AC can be avoided during the experiment and achieved through our proposed method.

Our research offers a promising solution for achieving accurate and reliable motion tracking without the need for extra movements. We hope that our method will be useful for researchers and practitioners working in fields such as sports science, rehabilitation, and human-computer interaction.

Full details online at:

Kong, W, Sessa, S, Zecca, M, Takanishi, A (2016) Anatomical calibration through post-processing of standard motion tests data, Sensors (Switzerland), 16(12), ISSN: 1424-8220. DOI: 10.3390/s16122011.