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Which Exoskeleton Technology Is Easiest on Your Muscles?by@exoself

Which Exoskeleton Technology Is Easiest on Your Muscles?

by Exoself Technology ResearchJanuary 24th, 2025
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This study reveals AMTC significantly lowers oxygen uptake and interaction torque compared to other controllers during exoskeleton-assisted walking, enhancing performance and reducing user effort.
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Authors:

(1) Mohammad Shushtari, Department of Mechanical and Mechatronics Engineering, University of Waterloo ([email protected]);

(2) Julia Foellmer, Mechanics and Ocean Engineering Department, Hamburg University of Technology ([email protected]);

(3) Sanjay Krishna Gouda, Department of Mechanical and Mechatronics Engineering, University of Waterloo and Toronto Rehabilitation Institute (KITE), University Health Network ([email protected]).

Abstract and 1 Introduction

2 Results

2.1 Initial Processed Data for a Representative Participant

2.2 Overall Performance Analysis

2.3 Interaction Portrait Analysis

2.4 Individual Adaptation Strategy

3 Discussion

3.1 Human Adaptation

3.2 Importance of IP Analysis

4 Conclusion

5 Methods

5.1 Feedforward Control Strategies

5.2 Experimental Setup

5.3 Experimental Protocol

5.4 Data Analysis

Declarations

Appendix A Complementary Example Data

Appendix B Comparison with Natural Walking

References

2.1 Initial Processed Data for a Representative Participant


Fig. 2 A portion of a typical participant’s experimental data; for ease of visualization and interpretation, the interaction torque at the right hip and activation of one of the muscles are illustrated along with the relative oxygen uptake. (A) The mean absolute interaction torque at the right hip at each stride with each controller and speed for Participant #1. (B) Normal muscle activation for the Gastrocnemius Medialis at the right leg. (C) Relative oxygen uptake for each breath for each controller and speed. The oxygen uptake has increased with the increase in treadmill speed.


Fig. 3 The average performance metrics for each treadmill speed and controller across participants. (A) The sum of the relative oxygen uptake across all the strides for each speed in each controller block graphed for each participant. The bars show the average of the sum of the oxygen uptake across all participants. Similarly, the average total absolute value of the human-exoskeleton interaction and total normalized muscle effort are graphed in (B) and (C), respectively.


2.2 Overall Performance Analysis

Fig. 3A shows the sum of the oxygen uptake for participants for each of the TBC, HTC, and AMTC blocks during ultra-slow, slow, and moderate-speed walking. TBC and AMTC have the highest and lowest metabolic rate at all walking speeds, respectively. The AMTC-resultant metabolic rate is significantly less than other controllers, at ultra-slow and slow walking, where AMTC resulted in 22.9%±17.1 (Friedman: p <0.03, Wilcoxon signed rank: pT BC,AMT C <0.01) and 28.7%±12.7 (Friedman: p <0.005, Wilcoxon signed rank: pT BC,AMT C <0.003) decrease in the total oxygen uptake, respectively. The total mean absolute interaction torque is similarly illustrated for the participants in Fig. 3B. AMTC has the lowest interaction torque compared to TBC and HTC, indicating the least disagreement between the exoskeleton assistance and the user desired motion. With respect to the TBC, AMTC shows 17.1±12.5%, 12±15%, and 9.2±7.7% of reduction in human-exoskeleton total interaction in ultra-slow, slow, and moderate-speed walking, respectively. The difference is statistically significant at the ultra-slow walking (Friedman: p <0.04, Wilcoxon signed rank: pT BC,AMT C <0.01). Compared to HTC, AMTC shows 19.8±21.1%, 17.9±10.1%, and 18.1±9.9% reduction in human-exoskeleton total interaction. These differences are statistically significant in the case of slow (Fridman: p <0.03, Wilcoxon signed rank: pHT C,AMT C <0.004) and moderate-speed (Fridman: p <0.0008, Wilcoxon signed rank: pHT C,AMT C <0.004) walking. Fig. 3C shows the total muscle effort for participants’ right legs during ultraslow, slow, and moderate-speed walking across the three different controllers. Natural walking without the exoskeleton has the lowest total muscle effort compared to other cases in which the exoskeleton is involved. This is expected as wearing the exoskeleton adds about 17 kg of extra weight to the body resulting in higher muscle effort. Among the three controllers, TBC has the highest total muscular effort at all speeds. AMTC and HTC’s total muscular effort are close in all cases while AMTC is slightly lower and higher in ultra-slow and moderate speeds, respectively. None of the identified differences are statistically significant.


2.3 Interaction Portrait Analysis





Fig. 4 Comparing the Average Interaction Portrait for each Pair of Controllers. The average Interaction Portrait (IP) depicted according to the average total muscle effort and the average total human-exoskeleton interaction for each participant computed at each of the ultra-slow, slow, and moderate-speed walking for the TBC→HTC, TBC→AMTC, and HTC→AMTC illustrated in (A), (B), and (C), respectively. The yellow areas denote the area between the 25 and 75 percentiles.


2.4 Individual Adaptation Strategy





Fig. 5 Comparison of the Interaction Portrait distribution between TBC→HTC and TBC→MTBC. Interaction portrait distribution for HTC and AMTC blocks with respect to the average total muscle effort and total interaction torque across all strides during the TBC block graphed for each participant plotted for moderate speed walking. The radius of data points is normalized with respect to the maximum radius computed across all participants’ strides. Participants are arranged increasingly according to their body mass. The polar histograms show the concentration intensity of the depicted points. Each bin of the histogram covers π/6 rad.




This paper is available on arxiv under CC BY-NC-ND 4.0 DEED license.