Traditional Walker Research Articles

Predicting fatigue life and crack growth rate of TC4 titanium alloy based on PINN before and after ultrasonic impact treatment

This study conducted fatigue crack growth rate (FCGR) experiments on TC4 titanium alloy specimens under different stress ratios (R=0.06, 0.1, 0.5) before and after ultrasonic impact treatment (UIT) conditions. Based on this, a Physics-Informed Neural Network (PINN) model was employed to predict the FCGR of TC4 titanium alloy. As a control group, the traditional Walker FCGR formula was fitted using experimental data. The results indicate that the stress ratio R does not significantly affect the FCGR of TC4 titanium alloy. Under the same range of stress intensity factor (ΔK), the FCGR (da/dN) decreases with increasing R. The FCGR prediction established by the PINN model can well reflect the nonlinear characteristics of the crack growth process rate. The coefficient of determination R2 for fitting the experimental data reached above 0.9900, generally higher than the 0.9545 of the Walker formula. Although the degree of dispersion increased after UIT, the PINN model demonstrated stable prediction accuracy compared to the Walker formula. In addition, when calculating the fatigue crack growth life using the cycle-by-cycle method, the PINN model also exhibits stable prediction accuracy compared to the Walker formula, and this advantage becomes more apparent with increased data dispersion.

Fall Detection System on Smart Walker Based on Multisensor Data Fusion and SPRT Method

Traditional walkers are commonly used for the elderly in social life, which solves the basic problem of walking, but it is difficult to ensure safety when a fall occurs, and the human-computer interaction is poor. The image recognition method or the IMU sensor method fixed on the user, such as a wearable watch, is used by most of the current fall detection methods. Wearable sensors require the user’s wearing operation, which is a little troublesome, and the detection accuracy is related to the way of wearing. The image recognition method requires a high-priced camera and a fixed installation position, which is unable to adapt to outdoor activities. We investigated a low-cost method of mounting the sensor on the body of the walker. We propose in this paper an improved fall detection method, namely Precondition and Limit Threshold SPRT (PLT-SPRT), and a novel fall detection system on the smart walker based on PLT-SPRT. The signals of the upper and lower limb sensors are fused based on the Kalman filter algorithm, and the admittance control parameters are obtained through the system identification method. In this study, the improved sequential probability ratio test algorithm is used to set the null hypothesis and the alternative hypothesis, construct the likelihood ratio and optimize the decision function, which is used to judge whether falls occur. The system is simulated by Matlab software, the user intention after fusion is more accurate, and the optimized decision function is judged accurately. Verified by the embedded system based on STM32 of the smart walker equipment in the real world, it can accurately identify the fallen state, with low detection delay, and the fallen state is detected about 160ms earlier than the traditional threshold-based detection algorithm, at the same time, the accuracy is higher than 94.9%, which meets the high real-time requirements of fall detection and is the ideal solution for smart walkers.

Design and analysis of walker with sit to stand assistance

A walker that can provide sit-to-stand assistance to the user. As the sit-to-stand motion can define the functional independence of a person, it must be considered as an important parameter in life. Currently, various types of walkers are available from traditional to smart walkers, some walkers are developed specially according to the requirement or disability of the patient. But the main problem while using the traditional walker is that the user or the patient has to lift the walker and place it forward so that he can walk this requires a considerable amount of energy of the upper extremity of a user and because of that the patient can get easily tired or feel fatigued neither the traditional walker can help the user with such kind of problem, nor the technological advance smart walkers could help. Thus, there is a requirement of a simple cost-effective walker which can address the problem. This paper provides in detail the design and analysis of such a walker.

Innovative “RK Walker”: Transdisciplinary Multiphasic Observational Experimental Trial

Activities of Daily Living (ADLs) involves several physical activities like walking, climbing, etc. However,such ADLs may get compromised because of disorders where assistive devices play a key role for functionalindependence. Walker is a device used by people with locomotor disabilities, where stair climbing remainschallenge. Objectives: To understand the process of making an innovative walker for stair climbing, totest and re-test its applicability with healthy adults and patients with locomotor disabilities, to dedicate theoutcome of research work to improve quality of care and life. Methodology: Multiphasic ObservationalExperimental Trial, Phase I: Identify the need of change in traditional walker by survey, Phase II: Designinga Walker in AutoCAD software and hardware (RK walker), Phase III: To assess the efficacy of “RK Walker”compared to Traditional Walker in healthy adults, Phase IV: With reference to data analysis from healthyadults, Traditional standard Walker and “RK Walker” was compared for walking (TUG) and “RK Walker”for Stair Climbing (SCT) on patients with partially and non-weight bearing gait due to spinal / lower limbmusculoskeletal dysfunction. Result: Outcome measures and feedback reports show significant impact withRK Walker as compared to traditional walker especially in stair climbing. Conclusion: This multiphasicobservational experimental trial and novel concept extend the functional ability for stair climbing for patientswith disability.

High‐temperature LCF life estimation based on stress gradient effect of notched GH4169 alloy specimens

AbstractBased on the Neuber's rule and Walker equation, a new measurement method considering the influence of mean stress and stress gradient is proposed. A stress gradient factor is defined to correct the traditional Walker equation; thus, it is easy to estimate the life of the structural components only based on the purely elastic finite element analysis. The low‐cycle fatigue experiment was carried out by using the direct aging GH4169 notched specimen with different stress concentration factors under evaluated temperature. The fracture morphology of specimens was analyzed to determine the crack initiation position and the damage mechanism. The data points of the experiment life and the estimation life are correlated well within a three times scatter band. It indicates that the Walker equation corrected by introducing a new kind of measurement of stress gradient is reliable to estimate the notched specimen fatigue life.

A Robotic Walker Based on a Two-Wheeled Inverted Pendulum

This paper presents the design and control of a robotic walker based on a two-wheeled inverted pendulum (TWIP) developed to assist mobility-impaired users with balance and stability. Traditional walkers use three or more contact points to create a solid base to augment a user's balance. A TWIP walker can support a user's balance through balance control. A robotic walker prototype has been developed to illustrate its ability to assist human gait and exploit the maneuverability of a two-wheeled mobile platform compared to multi-wheeled system. Presented is a linearized mathematical model of the two-wheeled system using Newtonian mechanics. A control strategy consisting of a decoupled linear quadratic regulator (LQR) controller and two state variable controllers is developed to stabilize the platform and regulate its behavior with robust disturbance rejection performance. Results are shown using a physical prototype to demonstrate the ability of the decoupled LQR controller to robustly balance the platform while the state variable controllers regulate the platform's position with smooth, minimum jerk, control when used by a person during standing and walking.

Some remarks on the engineering application of the fatigue crack growth approach under nonzero mean loads

The well-known fatigue crack growth (FCG) curves are two-parameter dependents. The range of the stress intensity factor ΔK and the load ratio R are the parameters normally used for describing these curves. For engineering purposes, the mathematical representation of these curves should be integrated between the initial and final crack sizes in order to obtain the safety factors for stresses and life. First of all, it is necessary to reduce the dependence of the FCG curves to only one parameter. ΔK is almost always selected and, in these conditions, considered as the crack driving force. Using experimental data from literature, the present paper shows how to perform multiple regression analyses using the traditional Walker approach and the more recent unified approach. The correlations so obtained are graphically analyzed in three dimensions. Numerical examples of crack growth analysis for cracks growing under nominal stresses of constant amplitude in smooth and notched geometries are performed, assuming an identical material component as that of the available experimental data. The resulting curves of crack size versus number of cycles (a vs. N) are then compared. The two models give approximately the same (a vs. N) curves in both geometries. Differences between the behaviors of the (a vs. N) curves in smooth and notched geometries are highlighted, and the reasons for these particular behaviors are discussed.

Development and Evaluation of Rollator for Elderly Farmers

Objective: This study aims to develop and evaluate a multi-purpose rollator, which may be used as a seat, as a traditional walker, or as a storage basket for elderly farmers. Background: The rollators on the market are not user-friendly designed and seen inconvenient for elderly farmers to use, although they are sold at considerably high price. Since they lack enough space to load stuffs and are not durable or stable enough, they do not seem to be suitable for elderly farmers to use in rural areas. Method: Two types of methods were used in this study. First, the survey consisted of 19 questions was conducted among elderly farmers in rural areas, after using the developed rollator, to evaluate the usability of the rollator developed in this study. Second, EMG experiment was conducted to compare the existing rollator and developed rollator quantitatively. Through this experiment, we tried to verify the differences of muscle responses, when using the traditional and the developed ones, which have their own brake system, in the ramp. Results: The developed rollator was highly evaluated in most of the questions in the usability survey, except for the Weight category in which the opinions were divided into three different types (Worse: 31%, Similar: 30%, Better: 36%). The result of EMG experiment showed that the existing rollator (7.4%MVC) demands more muscle strength than the developed rollator (5.5%MVC) does. By statistically analyzing the results of upper limb and lower limb respectively, we found out that all the muscles except deltoid in upper limb showed statistically significant differences in muscle activity when using the existing and the developed rollator. However, there was no statistical difference in lower limb muscles. Conclusion: The developed rollator in this study has maximized the functionality of the brake system, the storage and the chair, which were pointed out as the weaknesses of existing rollators. Furthermore, the developed rollator is designed to be more user-friendly, safe, durable, and effective for elderly farmers to use in rural areas, where roads are rough and bumpy. Application: We expect that the emergency brake system developed in this study would be utilized for other convenience equipment, such as strollers and carts, and that it would be able to develop and produce more secure and reliable equipment in the future.