BCI-Based Control for Ankle Exoskeleton T-FLEX: Comparison of Visual and Haptic Stimuli with Stroke Survivors
Abstract
:1. Introduction
2. Materials and Methods
2.1. BCI-Exoskeleton System
2.1.1. BCI Interface
2.1.2. T-FLEX Ankle Exoskeleton
2.1.3. BCI—T-FLEX System Integration
2.1.4. Stimuli Strategies
- Visual Stimulus System: The local server configured three types of instruction texts showed in a full-screen: (1) “Wait”, (2) “Idle”, and (3) “Move your feet”. On one hand, the main objective of the “Wait” text was to provide an initial 30 s waiting period to prepare the system. On the other hand, “Idle” and “Move your feet” texts, gave an explicit indication to the user to stay in a state of relaxation or a state of MI generation, with 10 s duration respectively (see Figure 3). In this way, only in the “Move your feet” stage, the local server received MI commands to activate T-FLEX.
- Haptic Stimulus System: The visual system worked with haptic one in sync with the “Move your Feet” periods to assist the patient in the MI generation (Figure 3). This haptic system, manually controlled by the supervisor, implemented the SunniMix rumble vibration motor (SM SunniMix, USA) with a vibration frequency in a range between 36 and 40 Hz (2200 to 2500 r/min). This motor attached the system through a structure made of Ethylene Vinyl Acetate (EVA), a box made of Acrylonitrile Butadiene Styrene (ABS) coated it, and finally, velcro material allowed the adhesion to the anterior tibialis muscle area.
2.2. Experimental Validation
2.2.1. Participants
- Inclusion Criteria: Patients between the ages range of 18 to 70 years with a pathology associated with the foot-ankle complex due to a neurological injury and with partial independence to mobilize.
- Exclusion Criteria: Candidates with hypertension, uncontrolled epilepsy, pain in the lower limbs, and severe spasticity (level 4 of the Ashworth Scale) were excluded from the study, as well as patients with the presence of wound or pressure ulcers that could have made nonfeasible the use of the device.
2.2.2. Experimental Setup
2.2.3. Experimental Procedure
2.2.4. Experimental Analysis
3. Results
3.1. Participants
3.2. Accuracy Results
3.3. Power Spectral Density Results
3.4. User Perception Results
4. Discussion
5. Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
Abbreviations
BCI | Brain-Computer Interface |
EEG | Electroencephalography |
MI | Motor Imagination |
MIV | Motor Imagination with Visual Stimulus |
MIVH | Motor Imagination with Visual and Haptic Stimuli |
ERP | Event-Related Potential |
PSD | Power Spectral Density |
ERS/ERD | Event-Related Desynchronization/Synchronization |
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Subject | Age (Years) | Weight (Kg) | Height (cm) | BMI | Paretic Side |
---|---|---|---|---|---|
1 | 55 | 84 | 173 | 28.1 | Right |
2 | 62 | 96 | 168 | 34 | Left |
3 | 63 | 79 | 161 | 30.5 | Right |
4 | 56 | 94 | 164 | 34.9 | Right |
5 | 61 | 69 | 166 | 25 | Left |
Subject | Threshold | MIV Detection Time | MIVH Detection Time |
---|---|---|---|
1 | 8 uV | 1798 ms | 2116 ms |
2 | 8 uV | 1272 ms | 1173 ms |
3 | 4 uV | 3326 ms | 1646 ms |
4 | 20 uV | 1226 ms | 1010 ms |
5 | 12 uV | 2418 ms | 986 ms |
PSD (dB/Hz) Mean | ||||||
---|---|---|---|---|---|---|
Test | Subject | Fcz | C1 | Cz | C2 | Cpz |
ST | 1 | 9.14 | 26.00 | 9.41 | 18.70 | 4.74 |
2 | 17.38 | 9.99 | 17.85 | 26.03 | 15.98 | |
3 | 0.86 | 1.12 | 0.97 | 4.20 | 0.86 | |
4 | 1.51 | 2.06 | 2.76 | 93.78 | NA * | |
5 | 0.52 | 0.57 | 0.56 | 0.52 | 0.36 | |
MIV | 1 | 18.30 | 53.39 | 20.89 | 36.79 | 10.03 |
2 | 8.26 | 4.10 | 7.67 | 15.25 | 6.36 | |
3 | 0.17 | 0.24 | 0.15 | 0.16 | 0.13 | |
4 | 2.19 | 20.03 | 4.25 | 172.11 | NA * | |
5 | 6.07 | 6.55 | 7.78 | 6.47 | 5.42 | |
MIVH | 1 | 8.98 | 13.30 | 10.17 | 24.89 | 6.19 |
2 | 24.45 | 12.35 | 24.89 | 55.95 | 21.41 | |
3 | 3.43 | 0.96 | 3.52 | 28.29 | 1.69 | |
4 | 7.95 | 2.99 | 16.55 | 85.16 | NA * | |
5 | 4.52 | 4.04 | 4.04 | 5.00 | 4.03 | |
ST | 1 | 9.67 | 27.83 | 10.57 | 19.63 | 5.07 |
2 | 19.65 | 11.95 | 20.28 | 31.00 | 18.51 | |
3 | 1.05 | 1.15 | 1.11 | 4.29 | 1.05 | |
4 | 1.73 | 2.49 | 3.11 | 121.08 | NA * | |
5 | 0.79 | 0.80 | 0.90 | 0.81 | 0.51 | |
MIV | 1 | 19.56 | 55.74 | 23.22 | 38.74 | 11.23 |
2 | 9.85 | 4.86 | 9.04 | 19.86 | 7.34 | |
3 | 0.18 | 0.29 | 0.17 | 0.19 | 0.15 | |
4 | 2.56 | 25.21 | 5.24 | 185.08 | NA * | |
5 | 8.86 | 10.06 | 11.75 | 9.84 | 8.02 | |
MIVH | 1 | 9.91 | 13.26 | 10.96 | 26.81 | 7.31 |
2 | 21.93 | 13.43 | 21.76 | 65.34 | 24.11 | |
3 | 4.13 | 1.24 | 4.77 | 33.19 | 2.24 | |
4 | 7.62 | 2.92 | 18.40 | 110.69 | NA * | |
5 | 4.30 | 4.38 | 3.97 | 4.78 | 3.63 |
Test Comparison | Fcz | C1 | Cz | C2 | Cpz |
---|---|---|---|---|---|
ST vs. MIV vs. MIVH | 0.704 | 0.498 | 0.562 | 0.549 | 0.368 |
ST vs. MIV | 0.737 | 0.218 | 0.645 | 0.437 | 0.999 |
ST vs. MIVH | 0.039 | 0.699 | 0.074 | 0.184 | 0.100 |
MI vs. MIVH | 0.532 | 0.300 | 0.509 | 0.999 | 0.530 |
QUEST Survey Responses | ||||||
---|---|---|---|---|---|---|
Criteria | S1 | S2 | S3 | S4 | S5 | Average |
Dimensions | 4.00 | 5.00 | 3.00 | 4.00 | 5.00 | 4.20 |
Weight | 5.00 | 5.00 | 5.00 | 5.00 | 5.00 | 5.00 |
Adjustment | 5.00 | 5.00 | 4.00 | 5.00 | 5.00 | 4.75 |
Safety | 5.00 | 5.00 | 4.00 | 5.00 | 5.00 | 4.75 |
Ease of use | 5.00 | 5.00 | 5.00 | 4.00 | 5.00 | 4.75 |
Effectiveness | 5.00 | 5.00 | 5.00 | 4.00 | 5.00 | 4.75 |
Information/Instuctions | 5.00 | 5.00 | 5.00 | 5.00 | 5.00 | 5.00 |
QUEST Total Score | 4.85 | 5.00 | 4.42 | 4.57 | 5.00 | 4.76 |
Extended QUEST Survey Responses | ||||||
Reliability | 5.00 | 5.00 | 4.00 | 5.00 | 5.00 | 4.75 |
Speed | 4.00 | 4.00 | 4.00 | 4.00 | 4.00 | 4.00 |
Learning | 4.00 | 5.00 | 5.00 | 5.00 | 5.00 | 4.75 |
Aesthetic design | 4.00 | 5.00 | 4.00 | 5.00 | 5.00 | 4.25 |
Added Items Total Score | 4.25 | 4.75 | 4.25 | 4.75 | 4.75 | 4.55 |
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Barria, P.; Pino, A.; Tovar, N.; Gomez-Vargas, D.; Baleta, K.; Díaz, C.A.R.; Múnera, M.; Cifuentes, C.A. BCI-Based Control for Ankle Exoskeleton T-FLEX: Comparison of Visual and Haptic Stimuli with Stroke Survivors. Sensors 2021, 21, 6431. https://doi.org/10.3390/s21196431
Barria P, Pino A, Tovar N, Gomez-Vargas D, Baleta K, Díaz CAR, Múnera M, Cifuentes CA. BCI-Based Control for Ankle Exoskeleton T-FLEX: Comparison of Visual and Haptic Stimuli with Stroke Survivors. Sensors. 2021; 21(19):6431. https://doi.org/10.3390/s21196431
Chicago/Turabian StyleBarria, Patricio, Angie Pino, Nicolás Tovar, Daniel Gomez-Vargas, Karim Baleta, Camilo A. R. Díaz, Marcela Múnera, and Carlos A. Cifuentes. 2021. "BCI-Based Control for Ankle Exoskeleton T-FLEX: Comparison of Visual and Haptic Stimuli with Stroke Survivors" Sensors 21, no. 19: 6431. https://doi.org/10.3390/s21196431
APA StyleBarria, P., Pino, A., Tovar, N., Gomez-Vargas, D., Baleta, K., Díaz, C. A. R., Múnera, M., & Cifuentes, C. A. (2021). BCI-Based Control for Ankle Exoskeleton T-FLEX: Comparison of Visual and Haptic Stimuli with Stroke Survivors. Sensors, 21(19), 6431. https://doi.org/10.3390/s21196431