# Can Ensemble Deep Learning Identify People by Their Gait Using Data Collected from Multi-Modal Sensors in Their Insole?

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## Abstract

**:**

## 1. Introduction

#### Related Work

## 2. Gait Information

#### 2.1. Data Source

#### 2.2. Data Pre-Processing

#### 2.2.1. Walking Cycle Detection

#### 2.2.2. Standard Format

## 3. Network Design

**u**:

#### 3.1. Convolutional Neural Network

#### 3.2. Recurrent Neural Network

#### 3.3. Fully Connected Network

#### 3.4. Averaging Ensemble Model

## 4. Experimental Results

#### 4.1. Datasets and Evaluation Method

#### 4.2. Latent Space and Training Time

#### 4.3. Identification Accuracy

#### 4.3.1. Tri-Modal Sensing

#### 4.3.2. Bi-Modal Sensing

#### 4.3.3. Uni-Modal Sensing

## 5. Discussion and Future Work

## 6. Conclusions

## Author Contributions

## Funding

## Conflicts of Interest

## References

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**Figure 3.**Mean of eight pressure values (blue lines) and convolution of the mean and Gaussian function with standard deviation $\sigma =0.2$ s (red lines).

**Figure 4.**The procedure of data standardization. (

**a**) Original format. (

**b**) The length of the format is fixed as $d=87$. (

**c**) The same sensing modalities of both feet are concatenated in the standard format.

**Figure 7.**t-SNE plots of the output of the fully connected layer with 256 units in the CNN and RNN architectures. (

**a**) MCCV (30%), (

**b**) Sub-MCCV (50%), (

**c**) MCCV (50%).

**Figure 8.**Identification accuracies of the proposed method using tri-modal sensing for different k-values. (

**a**) MCCV (30%), (

**b**) Sub-MCCV (50%), (

**c**) MCCV (50%).

**Figure 9.**Identification accuracies of the proposed method using bi-modal sensing for different k-values. (

**a**) Pressure - Acceleration, (

**b**) Pressure - Rotation, (

**c**) Acceleration - Rotation.

**Figure 10.**Identification accuracies of the proposed method using uni-modal sensing for different k-values. (

**a**) Pressure, (

**b**) Acceleration, (

**c**) Rotation.

**Figure 11.**Identification accuracies of the RNN with two hyper-parameters, $d=87$ and $d=43$, using tri-modal sensing for different k-values. (

**a**) MCCV (30%), (

**b**) Sub-MCCV (50%), (

**c**) MCCV (50%).

**Table 1.**The total number of samples for different k-values. MCCV stands for Monte Carlo cross-validation.

k | # of Samples | MCCV (30%) | Sub-MCCV (50%) | MCCV (50%) | |||
---|---|---|---|---|---|---|---|

Train | Test | Train | Test | Train | Test | ||

1 | 4750 | 3325 | 1425 | 2000 | 2000 | 2375 | 2375 |

2 | 2368 | 1658 | 710 | 1000 | 1000 | 1184 | 1184 |

3 | 1570 | 1099 | 471 | 600 | 600 | 785 | 785 |

4 | 1176 | 823 | 353 | 500 | 500 | 588 | 588 |

**Table 2.**Identification accuracies of the proposed method using tri-modal sensing (pressure, acceleration, and rotation) for different k-values.

Validation | k | ${\mathcal{M}}_{\mathit{cnn}}$ | ${\mathcal{M}}_{\mathit{rnn}}$ | ${\mathcal{M}}_{\mathit{ens}}$ |
---|---|---|---|---|

MCCV (30%) | 1 | 0.9896 | 0.9786 | 0.9922 |

2 | 0.9918 | 0.9676 | 0.9940 | |

3 | 0.9928 | 0.9456 | 0.9942 | |

4 | 0.9947 | 0.9395 | 0.9950 | |

Sub-MCCV (50%) | 1 | 0.9888 | 0.9754 | 0.9914 |

2 | 0.9912 | 0.9516 | 0.9921 | |

3 | 0.9915 | 0.9190 | 0.9930 | |

4 | 0.9935 | 0.9056 | 0.9946 | |

MCCV (50%) | 1 | 0.9892 | 0.9776 | 0.9926 |

2 | 0.9929 | 0.9606 | 0.9937 | |

3 | 0.9934 | 0.9378 | 0.9940 | |

4 | 0.9949 | 0.9253 | 0.9958 |

**Table 3.**Identification accuracies of the proposed method using bi-modal sensing (combinations of two of pressure, acceleration, and rotation) for k = 1.

Validation | Sensing | ${\mathcal{M}}_{\mathit{cnn}}$ | ${\mathcal{M}}_{\mathit{rnn}}$ | ${\mathcal{M}}_{\mathit{ens}}$ |
---|---|---|---|---|

MCCV (30%) | ${\mathbf{x}}_{p}\left(t\right),{\mathbf{x}}_{a}\left(t\right)$ | 0.9888 | 0.9762 | 0.9919 |

${\mathbf{x}}_{a}\left(t\right),{\mathbf{x}}_{r}\left(t\right)$ | 0.9823 | 0.9512 | 0.9853 | |

${\mathbf{x}}_{r}\left(t\right),{\mathbf{x}}_{p}\left(t\right)$ | 0.9886 | 0.9732 | 0.9916 | |

Sub-MCCV (50%) | ${\mathbf{x}}_{p}\left(t\right),{\mathbf{x}}_{a}\left(t\right)$ | 0.9893 | 0.9651 | 0.9917 |

${\mathbf{x}}_{a}\left(t\right),{\mathbf{x}}_{r}\left(t\right)$ | 0.9825 | 0.9412 | 0.9836 | |

${\mathbf{x}}_{r}\left(t\right),{\mathbf{x}}_{p}\left(t\right)$ | 0.9887 | 0.9603 | 0.9908 | |

MCCV (50%) | ${\mathbf{x}}_{p}\left(t\right),{\mathbf{x}}_{a}\left(t\right)$ | 0.9884 | 0.9697 | 0.9910 |

${\mathbf{x}}_{a}\left(t\right),{\mathbf{x}}_{r}\left(t\right)$ | 0.9831 | 0.9459 | 0.9844 | |

${\mathbf{x}}_{r}\left(t\right),{\mathbf{x}}_{p}\left(t\right)$ | 0.9893 | 0.9688 | 0.9918 | |

MCCV (30%) | ${\mathbf{x}}_{p}\left(t\right)$ | 0.9847 | 0.9673 | 0.9885 |

${\mathbf{x}}_{a}\left(t\right)$ | 0.9808 | 0.9086 | 0.9798 | |

${\mathbf{x}}_{r}\left(t\right)$ | 0.9821 | 0.9173 | 0.9824 | |

Sub-MCCV (50%) | ${\mathbf{x}}_{p}\left(t\right)$ | 0.9818 | 0.9559 | 0.9867 |

${\mathbf{x}}_{a}\left(t\right)$ | 0.9808 | 0.8860 | 0.9789 | |

${\mathbf{x}}_{r}\left(t\right)$ | 0.9796 | 0.9004 | 0.9800 | |

MCCV (50%) | ${\mathbf{x}}_{p}\left(t\right)$ | 0.9777 | 0.9580 | 0.9851 |

${\mathbf{x}}_{a}\left(t\right)$ | 0.9801 | 0.9139 | 0.9796 | |

${\mathbf{x}}_{r}\left(t\right)$ | 0.9808 | 0.9130 | 0.9808 |

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**MDPI and ACS Style**

Moon, J.; Minaya, N.H.; Le, N.A.; Park, H.-C.; Choi, S.-I. Can Ensemble Deep Learning Identify People by Their Gait Using Data Collected from Multi-Modal Sensors in Their Insole? *Sensors* **2020**, *20*, 4001.
https://doi.org/10.3390/s20144001

**AMA Style**

Moon J, Minaya NH, Le NA, Park H-C, Choi S-I. Can Ensemble Deep Learning Identify People by Their Gait Using Data Collected from Multi-Modal Sensors in Their Insole? *Sensors*. 2020; 20(14):4001.
https://doi.org/10.3390/s20144001

**Chicago/Turabian Style**

Moon, Jucheol, Nelson Hebert Minaya, Nhat Anh Le, Hee-Chan Park, and Sang-Il Choi. 2020. "Can Ensemble Deep Learning Identify People by Their Gait Using Data Collected from Multi-Modal Sensors in Their Insole?" *Sensors* 20, no. 14: 4001.
https://doi.org/10.3390/s20144001