Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2022 Oct 7;22(19):7605.
doi: 10.3390/s22197605.

Motion Sensors for Knee Angle Recognition in Muscle Rehabilitation Solutions

Tiago Franco  1 , Leonardo Sestrem  1 , Pedro Rangel Henriques  2 , Paulo Alves  1 , Maria João Varanda Pereira  1 , Diego Brandão  3 , Paulo Leitão  1 , Alfredo Silva  4
Affiliations

Motion Sensors for Knee Angle Recognition in Muscle Rehabilitation Solutions

Tiago Franco et al. Sensors (Basel). .

Abstract

The progressive loss of functional capacity due to aging is a serious problem that can compromise human locomotion capacity, requiring the help of an assistant and reducing independence. The NanoStim project aims to develop a system capable of performing treatment with electrostimulation at the patient's home, reducing the number of consultations. The knee angle is one of the essential attributes in this context, helping understand the patient's movement during the treatment session. This article presents a wearable system that recognizes the knee angle through IMU sensors. The hardware chosen for the wearables are low cost, including an ESP32 microcontroller and an MPU-6050 sensor. However, this hardware impairs signal accuracy in the multitasking environment expected in rehabilitation treatment. Three optimization filters with algorithmic complexity O(1) were tested to improve the signal's noise. The complementary filter obtained the best result, presenting an average error of 0.6 degrees and an improvement of 77% in MSE. Furthermore, an interface in the mobile app was developed to respond immediately to the recognized movement. The systems were tested with volunteers in a real environment and could successfully measure the movement performed. In the future, it is planned to use the recognized angle with the electromyography sensor.

Keywords: IMU sensor; algorithmic complexity; knee angle; muscle rehabilitation; wearable system.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
IMU acquisition system diagram.
Figure 2
Figure 2
The electronic components soldered inside the case.
Figure 3
Figure 3
Δ Time of IMU samples collected by the wearable system.
Figure 4
Figure 4
Sensors with the reference coordinate system.
Figure 5
Figure 5
(a) Frame representation with respect to a reference frame. (b) Linear mapping of a frame to another.
Figure 6
Figure 6
Sensors with the angles representation. Adapted from [21].
Figure 7
Figure 7
Complementary Filter applied to IMU sensor, adapted from [27].
Figure 8
Figure 8
Wearable modules attached to the UR3 robot.
Figure 9
Figure 9
Movement performed by the UR3 robot.
Figure 10
Figure 10
Wearable system raw data synchronized with UR3 data.
Figure 11
Figure 11
Optimal points of the adjustable filters parameters.
Figure 12
Figure 12
CF filter implemented in wearable embedded system.
Figure 13
Figure 13
Knee angle recognition app interface.
Figure 14
Figure 14
Wearable system and mobile app recognizing the movement of a volunteer’s leg.
Figure 15
Figure 15
Knee angle acquired by the wearable system.
See this image and copyright information in PMC

References

    1. Cruz-Jentoft A.J., Sayer A.A. Sarcopenia. Lancet. 2019;393:2636–2646. doi: 10.1016/S0140-6736(19)31138-9. - DOI - PubMed
    1. World Health Organization . Decade of Healthy Ageing: Baseline Report. World Health Organization; Geneva, Switzerland: 2020.
    1. Ambrose A., Paul G., Hausdorff J. Risk factors for falls among older adults: A review of the literature. Maturitas. 2013;75:51–61. doi: 10.1016/j.maturitas.2013.02.009. - DOI - PubMed
    1. Franco T., Henriques P.R., Alves P., Varanda Pereira M.J., Pedrosa T., Silva F., Leitão P., Oliveira L. System Architecture for Home Muscle Rehabilitation Treatment; Proceedings of the 10th World Conference on Information Systems and Technologies (WorldCIST’22); Budva, Balkans. 12–14 April 2022; pp. 305–315. - DOI
    1. Lou Z., Wang L., Jiang K., Wei Z., Shen G. Reviews of wearable healthcare systems: Materials, devices and system integration. Mater. Sci. Eng. Rep. 2020;140:100523. doi: 10.1016/j.mser.2019.100523. - DOI

LinkOut - more resources