Dewen Jin

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.

An electrorheological fluid damper for robots

A new electrorheological fluid damper has been developed to control the elastic vibrations of robotic mechanisms. The damper is capable of providing a continuously variable damping torque in response to an electric field. In the absence of an electric field the device acts like a normal fluid damper that produces a viscous damping torque. When the field is energized the device develops a Coulomb damping torque that is much greater then that produced by conventional viscous damping. The influence of model parameters on the damping torques is analyzed in this paper. Simulation results show that this damper can cause joint vibrations to quickly decay.

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.

An intelligent above-knee prosthesis with EMG-based terrain identification

Gait analyses show that knee moments are considerably different when walking on different terrain. To accommodate changing conditions, prostheses should provide a means for adjusting the knee moments by identifying conditions of the terrain. In this research, terrain identification is obtained by the use of electromyographic (EMG) signals that are used to control resistive moments of an above-knee prosthesis. Results from laboratory experiments demonstrate that the technique is effective for identification and adaptable to different terrain.

Effect of noise-enhanced on the balance control ability in older adults

Somatosensory function declines with age, and such changes have been associated with diminished motor performance. Noise input can enhance sensory and motor function. We tested the effects of the vibrating stimulation applied at the feet on balance control of 6 healthy elderly and 8 young volunteers. Balance performance was characterized using a FASTRAK System. We calculated four traditional measures of postural sway parameters and five stabilogram-diffusion analysis variables. Among the 14 participants, application of noise resulted in a reduction of seven of nine sway parameters in young participants and eight of nine sway variables in elderly participants. The results suggested that the imperceptible noise, when applied to the feet, could enhance the balance performance of healthy older adults. Therefore, using the noise-based devices may be an effective way to improve the balance control of elderly people.

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.

Vibration control of a redundant robot for grinding

Research on robotic grinding has emphasized process parameter control. When an industrial robot is used to remove excess material from castings, grinding weld beads, or welded surfaces, excessive vibrations often occur. Methods based on force control can improve the response. In this paper, we present practical methods for vibration reduction, feed-speed/force control, and an optimal configuration of a 4-DOF redundant robotic manipulator for grinding welded surfaces. An optimal configuration of the robotic manipulator is derived to minimize the arm compliance. The proposed method maximizes the robotic arm stiffness to reduce vibrations. The arm, parameters, and PID control were simulated using ADAMS/view and ADAMS/controls under MATLAB. The grinding force was considered as an input to the dynamical system in addition to the torque/force inputs at each joint. DC servomotors were modeled for actuation of each joint and the PID controller was tuned by the Ziegler-Nichols second rule. Simulation results demonstrate that feed speed/force control reduces vibrations, and provides the capability to use the robotic manipulator for profiling.

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