Interaction forces between a robotic cuff and the skin during assisted walking with a lower limb exoskeleton may cause skin injuries over time, such as blisters and ulcers. This study proposes a sensing cuff that can monitor the contact behavior between the exoskeleton and skin during assisted walking, and a functional test and assisted walking experiments were conducted to evaluate the performance of the proposed device. The functional test of the sensing cuff showed good performance of capturing the contact behavior for safety evaluation. The walking experiment involved subjects walking on a treadmill with a lower limb exoskeleton under different conditions (i.e., walking speed and clothing), and the sensing cuff attached to the exoskeleton measured the interaction forces and slip velocity. The magnitude of shear force in the movement direction peaked near the beginning and within 40 – 50% of the gait cycle. The contact safety of the lower limb exoskeleton during assisted walking was then evaluated based on the calculated shear stress. The designed sensing cuff could provide sufficient information regarding contact behavior and contact safety during assisted walking.

The field of spatial cognitive training and evaluation has rapidly evolved. However, the low learning motivation and engagement of the subjects hinder the widespread use of spatial cognitive training. This study designed a home-based spatial cognitive training and evaluation system (SCTES), which aimed to train subjects on spatial cognitive tasks for 20 days, and compared the brain activities before and after the training. This study also evaluated the feasibility of using a portable all-in-one prototype for cognitive training that combined a virtual reality (VR) head-mounted display with high-quality electroencephalogram (EEG) recording. During the course of training, the length of the navigation path and the distance between the starting position and the platform position revealed significant behavioral differences. In the testing sessions, the subjects showed significant behavioral differences in the time it took to complete the test task before and after training. After only four days of training, the subjects demonstrated significant differences in the Granger causality analysis (GCA) characteristics of brain regions in the δ, θ, α ₁ , β ₂ , and γ frequency bands of the EEG, as well as significant differences in the GCA of the EEG in the β ₁ , β ₂ , and γ frequency bands between the two test sessions. The proposed SCTES used a compact and all-in-one form factor to train and evaluate spatial cognition and collect EEG signals and behavioral data simultaneously. The recorded EEG data can be used to quantitatively assess the efficacy of spatial training in patients with spatial cognitive impairments.

Measurement of the internal stress and strain distributions within soft materials is necessary in the field of skin contact safety. However, conventional interactive force sensors cannot efficiently obtain or estimate these distributions. Herein, a shear strain sensor system consisting of distributed built-in piezoelectric polyvinylidene fluoride (PVDF) polymer films was developed to measure the internal shear strain field of a soft material. A shear strain sensing model was mathematically established, based on the piezoelectricity and mechanical behavior of a bending cantilever beam, to explain the sensing principle. An experiment in three-dimensional measurement of the shear strain distribution within an artificial skin was designed and conducted to assess the sensitivity of the sensing model. This sensor system could visualize the shear strain field and was sensitive to different contact conditions. The measurement results agreed well with the results of numerical simulation of the substrate, based on contact mechanics. The proposed sensor system was confirmed to provide a new sensing method for the field of shape analysis. The sensor system can be applied to develop sufficiently sensitive electronic skin and can significantly contribute to skin damage analysis and skin contact safety assessment.

This paper aimed to identify the effects of a robotic walker on gait dynamics during assisted walking via the analysis of acceleration data. Walking experiments were conducted with eleven healthy young subjects under different conditions, including normal, rollator-assisted, and robotic-walker-assisted walking. We collected acceleration data of trunk and pelvis to extract measures for evaluating the properties of gait dynamics, including periodicity, complexity, and determinism. These measures include maximum Lyapunov exponent (MLE), multiscale entropy (MSE), multiscale permutation entropy (MPE), correlation dimension (CD), and percentage of determinism (%DET, from recurrence plot). Significant differences in the complex measures, MSE and MPE, between normal and walker-assisted walking for trunk acceleration data in anteroposterior (AP) and mediolateral (ML) directions were observed. The determinism measures, CD and %DET, demonstrated significant differences between normal and robotic-walker-assisted walking for trunk acceleration data in AP direction, while significant differences in the periodicity measures, MLE, were not observed between the three conditions. These results imply mostly unchanged local dynamic stability, reduced deterministic patterns, and increased complexity in the gait dynamics of healthy young subjects, especially for the upper body. The robotic walker’s assistance is considered appropriate because of no significant difference between rollator-assisted and robotic-walker-assisted walking. This study provides a new insight into biomechanical effects of robotic walker on gait. It also suggests that the used methods can be applied to the assistance evaluation of walking assistive devices like lower-limb exoskeletons, and assess the ability of resisting perturbations with a robotic walker for rehabilitation applications such as perturbation-based gait training.

In this paper, we propose two control methods for driving a power-assisted cart made for walking assistance for the elderly. The optimal assistance ratio (OAR) and disturbance observer-based (DOB) methods properly adjust the motor output of the cart with high operational efficiency in response to changes in the environment. Healthy subjects walked with the cart on several road surfaces under various conditions, and the experimental results indicate the high operational efficiency of the two proposed methods. Meanwhile, their drawbacks are also discussed herein. The two methods can be used separately or combined according to the application. The OAR method is more suitable for indoor use, while the DOB method is applicable for outdoor applications. Combining these two methods could overcome the mentioned drawbacks.

Soft robotics require flexible sensors that can realize sensitive measurements for which rigid sensors are not viable. Precise and quantitative measurement of the mechanical phenomena is necessary in all the sensors; however, in the field of soft robotics, the complex structure and physical properties of composite materials complicate the construction of a precise sensing model. In this study, a built-in sensor system for internal shear strain and stress distribution measurement is developed by embedding piezoelectric polyvinylidene fluoride polymer films within the objective soft material. Shear-strain sensing models are established by relating the piezoelectricity and cantilever bending mechanics. For validation, experiments are conducted in which the deflection of the embedded film sensors is monitored and digitized using a video camera. The shear-strain sensing model is validated by evaluating the agreement between the modeled and measured physical variations, and a high coefficient of determination of 0.974 is obtained. In addition, based on the linear relation of the arithmetic expression of each sensing model, calibrated results for internal shear strain and stress sensing are successfully obtained. Furthermore, the measurement effect of this type of flexible sensor and its potential applications are discussed.