Jichuan Zhang

Kinematic and dynamic performance of prosthetic knee joint using six-bar mechanism

Six-bar linkages have been used in some prosthetic knees in the past years, but only a few publications have been written on the special functions of the mechanism as used in transfemoral prosthesis. This paper investigates the advantages of the mechanism as used in the prosthetic knee from the kinematic and dynamic points of view. Computer simulation and an experimental method were used in the investigation. The results show that the six-bar mechanism, as compared to the four-bar mechanism, can be designed to better achieve the expected trajectory of the ankle joint in swing phase. Moreover, a six-bar linkage can be designed to have more instant inactive joints than a four-bar linkage, hence making the prosthetic knee more stable in the standing phase. In the dynamic analysis, the location of the moment controller was determined for minimum value of the control moment. A testing prosthetic knee mechanism with optimum designed parameters was manufactured for experiments in the laboratory. The experimental results have verified the advantage revealed in the analyses.

Terrain identification for prosthetic knees based on electromyographic signal features

The features of electromyographic (EMG) signals were investigated while people walking on dif- ferent terrains, including up and down slopes, up and down stairs, and during level walking at different speeds. The features were used to develop a terrain identification method. The technology can be used to develop an intelligent transfemoral prosthetic limb with terrain identification capability. The EMG signals from 8 hip muscles of 13 healthy persons were recorded as they walked on the different terrains. The sig- nals from the sound side of a transfemoral amputee were also recorded. The features of these signals were obtained using data processing techniques with an identification process developed for the identification of the terrain type. The procedure was simplified by using only the signals from three muscles. The identifica- tion process worked well in an intelligent prosthetic knee in a laboratory setting.

A finite element 3D model of in vivo human knee joint based on MRI for the tibiofemoral joint contact analysis

The contact behaviors of in vivo knee during weight bearing were quantified using MRI-based 3D knee model. The model included the cortical and trabecular bone of the femur and tibia, cartilage of the femoral condyles and tibial plateau, both the medial and lateral menisci with their horn attachments. Explicit dynamic nonlinear finite element techniques were discussed to simulate biomechanical features of tibio-femeral joint under different loads condition, considering the relative slide and friction existing in the knee. The simulating results show that the contact area increased while the loads increased. Both the ratio of the contact area and the ratio of contact force of medial and laterial tibial plateau were almost constant under the different loads along the axis of the tibia during the supporting phase in a gait, and yet the contact points of the compressive force were changed.

Finite element analysis of a six-component force sensor for the trans-femoral prosthesis

It is significant to detect and analyze its mechanical property for the design of the artificial knee joint, especially for the design of an osseointegrated prosthetic limb. Since normal six-component force sensors are unsuitable for detecting the mechanical property of the lower limb prosthesis, a novel sensor is presented in this paper. It can be easily fixed between the artificial knee joint and the stump of the patient to detect the load condition during walking. The mathematic model of the sensor is analyzed, and strength check, stiffness design and the linearity of the sensor were studied with FEA. Finally, the Transmission Matrix is calculated. This kind of sensor can help us to get academic foundations for the designment and the evaluation of the limb prosthesis and its performance.

DEVELOPMENT OF A TACTILE AND SLIP SENSOR CONTROLLED PROSTHETIC HAND SYSTEM

Supported by the latest sensor and microcontroller technologies, prosthetic hands have been widely used to reclaim the human functionaries. Among these, the most advanced prosthetic hand was controlled by the tactile and EMG singles. However, for a slippery object, attention has to be taken for the inexperienced users who need to control the shrinkage of the wrist flexor carefully. In this paper, the authors presented a prosthetic hand control system using PVDF film sensor to provide both tactile and slip force feedback signals to operate the hand. The PVDF film sensor used for this control system was specifically developed to detect both tactile and slip force between the prosthetic finger and object. The method of distinguishing two signals was described. A prototype system was constructed using a microcontroller to process the signal from the sensor and provide control signal to the motors operate the prosthetic hand. The test result of the prototype device shown that comparing with the one without sli...

The Investigation on sEMG of Lower Extremity When a Slip Occurs in Level Walking

The purpose of the present study was to determine the relationship between the surface electromyography (sEMG) variables and slip events using principal component analysis (PCA). Ten healthy young adults were required to walk on the oily surface on a self-selected comfortable pace. The sEMG signals of lower extremity muscles were recorded and analyzed, while kinematics data was recorded to assist slip definitions. When ten variables (seven in time domain and three in frequency domain) were considered in the PCA, the results indicated that 1) three most important principal components could explain more than 85% of the variation in the entire data set; 2) some variables should be especially noticed such as muscle power, the mean frequency, the median frequency and the amplitude amount exceeding the mean value

A hybrid AB-RBF classifier for surface electromyography classification

In this paper, we aim to classify surface electromyography (sEMG) by using Attribute Bagging-Radial Basis Function (AB-RBF) hybrid classifier. Eight normally-limbed individuals were recruited to participate in the experiments. Each subject was instructed to perform six kinds of finger movements and each movement was repeated 50 times. Features were extracted using wavelet transform and used to train the RBF classifier and the AB-RBF hybrid classifier. The experiment results showed that AB-RBF hybrid classifier achieved higher discrimination accuracy and stability than single RBF classifier. It proves that integrating classifiers using random feature subsets is an effective method to improve the performance of the pattern recognition system.

The influence of shoe-heel height on knee muscle activity of transtibial amputees during standing

In order to access the effects of shoe-heel height on knee muscle activity for transtibial amputees during standing, five male subjects volunteered for the study. Three pairs of shoes with zero, 20 mm and 40 mm heel height were used during normal standing. Surface EMG of 10 muscles was recorded by the Noraxon surface EMG collection system. EMG-MAV of the medial and lateral gastrocnemius of the sound leg almost change double with increase in heel height from zero to 40 mm, and EMG-MAV of the rectus fomris, vastus lateralis and vastus medialis of prosthetic side became larger to different extent. The finding in this paper suggested that an alignment change was necessary to accommodate the heel height change and the prostheses users should be cautious to choose shoes in daily life.

An inverse dynamical model for slip gait

A inverse dynamical model for slip gait developed by using Kanes method of dynamics is described in this paper. The modeling was based on two separate sub-systems: anti-slip and anti-fall. Both sub-systems were modeled as an open kinematic chain and formulated using the same equations, so that the whole slip and fall process could be simulated using the same equations by switching input data. In the simulation, only kinematic data need to be input to obtain the joint moments and horizontal ground reaction force in the whole slip and fall process. The kinematic input data were acquired from one health male subject who was asked to perform the normal and slip gait. The anthropometric data for each body segment in the skeletal model was calculated using the body height, weight and the national standards on inertia parameters regression equations. The kinematic and kinetic results from the simulation are discussed in the paper which are well consistent with the conclusions in previous studies.