Cited by 34Prosthetics and Rehabilitation RoboticsMuscle activation and electromyography studiesGait Recognition and Analysis

The DOI matches its Crossref record; 35 of the 35 references it cites were found in a registry or an index.

A Transformer-Based Neural Network for Gait Prediction in Lower Limb Exoskeleton Robots Using Plantar Force

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Abstract

Lower limb exoskeleton robots have shown significant research value due to their capabilities of providing assistance to wearers and improving physical motion functions. As a type of robotic technology, wearable robots are directly in contact with the wearer’s limbs during operation, necessitating a high level of human–robot collaboration to ensure safety and efficacy. Furthermore, gait prediction for the wearer, which helps to compensate for sensor delays and provide references for controller design, is crucial for improving the the human–robot collaboration capability. For gait prediction, the plantar force intrinsically reflects crucial gait patterns regardless of individual differences. To be exact, the plantar force encompasses a doubled three-axis force, which varies over time concerning the two feet, which also reflects the gait patterns indistinctly. In this paper, we developed a transformer-based neural network (TFSformer) comprising convolution and variational mode decomposition (VMD) to predict bilateral hip and knee joint angles utilizing the plantar pressure. Given the distinct information contained in the temporal and the force-space dimensions of plantar pressure, the encoder uses 1D convolution to obtain the integrated features in the two dimensions. As for the decoder, it utilizes a multi-channel attention mechanism to simultaneously focus on both dimensions and a deep multi-channel attention structure to reduce the computational and memory consumption. Furthermore, VMD is applied to networks to better distinguish the trends and changes in data. The model is trained and tested on a self-constructed dataset that consists of data from 35 volunteers. The experimental results show that FTSformer reduces the mean absolute error (MAE) up to 10.83%, 15.04% and 8.05% and the mean squared error (MSE) by 20.40%, 29.90% and 12.60% compared to the CNN model, the transformer model and the CNN transformer model, respectively.

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Crossref · 10.3390/s23146547

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Figures

Figure 1 The layout of the experimental scenario and position of reflective markers.
Figure 1 The layout of the experimental scenario and position of reflective markers.CC BY · PubMed Central
Figure 2 Plantar pressure.
Figure 2 Plantar pressure.CC BY · PubMed Central
Figure 3 Two-link model.
Figure 3 Two-link model.CC BY · PubMed Central
Figure 4 Moving-window-based data division.
Figure 4 Moving-window-based data division.CC BY · PubMed Central
Figure 5 Architecture of the gait prediction model.
Figure 5 Architecture of the gait prediction model.CC BY · PubMed Central
Figure 6 Convolutional diagram of the encoder module. C1 represents the one-dimensional convolutional operation performed along the temporal dimension and C2 denotes the one-dimensional convolutional operation performed along the force-space dimension. [t,t1,t2,t3] and [f,f1,f2,f3] represent the lengths of the temporal and force-space dimensions, respectively. In our research, t, t1, t2 and t3 are set as 32, 64, 128 and 256, respectively, and f,f1,f2 and f3 are designed as 6, 36, 108 and 256 in turn.
Figure 6 Convolutional diagram of the encoder module. C1 represents the one-dimensional convolutional operation performed along the temporal dimension and C2 denotes the one-dimensional convolutional operation performed along the force-space dimension. [t,t1,t2,t3] and [f,f1,f2,f3] represent the lengths of the temporal and force-space dimensions, respectively. In our research, t, t1, t2 and t3 are set as 32, 64, 128 and 256, respectively, and f,f1,f2 and f3 are designed as 6, 36, 108 and 256 in turn.CC BY · PubMed Central
Figure 7 Decomposed modes.
Figure 7 Decomposed modes.CC BY · PubMed Central
Figure 8 Multi-channel attention.
Figure 8 Multi-channel attention.CC BY · PubMed Central
Figure 9 Gait prediction results on the data of subject 1.
Figure 9 Gait prediction results on the data of subject 1.CC BY · PubMed Central
Figure 10 Gait prediction results on the data of subject 2.
Figure 10 Gait prediction results on the data of subject 2.CC BY · PubMed Central
Figure 11 Gait prediction results on the data of subject 3.
Figure 11 Gait prediction results on the data of subject 3.CC BY · PubMed Central

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Citations

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Research works printed but not linked: 4

  1. Stadler, K., Altenburger, R., Schmidhauser, E., Scherly, D., Ortiz, J., Toxiri, S., Mateos, L., and Masood, J. (2016). Advances in Cooperative Robotics, World Scientific.
  2. Borovykh, A., Bohte, S., and Oosterlee, C.W. (2017). Conditional time series forecasting with convolutional neural networks. arXiv.
  3. Vaswani, 2017, Attention is all you need, Adv. Neural Inf. Process. Syst., 30, 6000
  4. Wu, 2021, Autoformer: Decomposition transformers with auto-correlation for long-term series forecasting, Adv. Neural Inf. Process. Syst., 34, 22419

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Metadata

Authors
Ren, J., Wang, A., Li, H., Yue, X., & Meng, L.
Affiliations
  • Zhongyuan University of Technology (CN)
  • Ritsumeikan University (JP)
Corresponding author
Wang, Aihui
Venue
Sensors
Publisher
MDPI AG
Published
2023-07-20
Volume
23
Issue
14
Pages
6547
ISSN
1424-8220 (ISSN-L)
OpenAlex
W4384931412
Cited by
34
References
35
Citations by year
2026: 11 · 2025: 13 · 2024: 9 · 2023: 1
FWCI
2.69
Type
journal article
Language
en
Open access
Locations
  • Sensors (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
National Natural Science Foundation of China (62073297)
Topics
  • Physical Sciences › Engineering › Biomedical Engineering › Prosthetics and Rehabilitation Robotics
  • Physical Sciences › Engineering › Biomedical Engineering › Muscle activation and electromyography studies
  • Physical Sciences › Engineering › Biomedical Engineering › Gait Recognition and Analysis
Keywords
lower limb exoskeleton, gait prediction, plantar force, plantar pressure, transformer models, variational mode decomposition, hip joint angle, knee joint angle, multi-channel attention, wearable robotics, human-robot collaboration
MeSH terms
Exoskeleton Device, Gait, Humans, Robotics, Neural Networks, Computer, Lower Extremity

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