Motor Electrical Damping for Back-Drivable Prosthetic Knee

The paper presents a model and analysis of a backdrivable knee prosthesis. In this context, the investigation into the design, modelling and analysis of a back-drivable semiactive prosthetic knee is presented. A mathematical model has been developed for evaluating the electrical damping characteristics of the DC motor in passive mode. The analysis shows that a single actuator could be suitable to work in active mode to provide mechanical power and in passive mode as a damper dissipating energy

Portable haptic device for lower limb amputee gait feedback: Assessing static and dynamic perceptibility

Loss of joints and severed sensory pathway cause reduced mobility capabilities in lower limb amputees. Although prosthetic devices attempt to restore normal mobility functions, lack of awareness and control of limb placement increase the risk of falling and causing amputee to have high level of visual dependency. Haptic feedback can serve as a cue for gait events during ambulation thus providing sense of awareness of the limb position. This paper presents a wireless wearable skin stretch haptic device to be fitted around the thigh region. The movement profile of the device was characterized and a preliminary work with able-bodied participants and an above-knee amputee to assess the ability of users to perceive the delivered stimuli during static and dynamic mode is reported. Perceptibility was found to be increasing with stretch magnitude. It was observed that a higher magnitude of stretch was needed for the stimuli to be accurately perceived during walking in comparison to static standing, most likely due to the intense movement of the muscle and increased motor skills demand during walking activity

A Wearable Skin Stretch Haptic Feedback Device: Towards Improving Balance Control in Lower Limb Amputees

Haptic feedback to lower limb amputees is essential to maximize the functionality of a prosthetic device by providing information to the user about the interaction with the environment and the position of the prostheses in space. Severed sensory pathway and the absence of connection between the prosthesis and the Central Nervous System (CNS) after lower limb amputation reduces balance control, increases visual dependency and increases risk of falls among amputees. This work describes the design of a wearable haptic feedback device for lower limb amputees using lateral skin-stretch modality intended to serve as a feedback cue during ambulation. A feedback scheme was proposed based on gait event detection for possible real-time postural adjustment. Preliminary perceptual test with healthy subjects in static condition was carried out and the results indicated over 98% accuracy in determining stimuli location around the upper leg region, suggesting good perceptibility of the delivered stimuli

Real-time gait event detection for transfemoral amputees during ramp ascending and descending

Events and phases detection of the human gait are vital for controlling prosthesis, orthosis and functional electrical stimulation (FES) systems. Wearable sensors are inexpensive, portable and have fast processing capability. They are frequently used to assess spatio-temporal, kinematic and kinetic parameters of the human gait which in turn provide more details about the human voluntary control and ampute-eprosthesis interaction. This paper presents a reliable real-time gait event detection algorithm based on simple heuristics approach, applicable to signals from tri-axial gyroscope for lower limb amputees during ramp ascending and descending. Experimental validation is done by comparing the results of gyroscope signal with footswitches. For healthy subjects, the mean difference between events detected by gyroscope and footswitches is 14 ms and 10.5 ms for initial contact (IC) whereas for toe off (TO) it is -5 ms and -25 ms for ramp up and down respectively. For transfemoral amputee, the error is slightly higher either due to the placement of footswitches underneath the foot or the lack of proper knee flexion and ankle plantarflexion/dorsiflexion during ramp up and down. Finally, repeatability tests showed promising results

Prediction of gait events in walking activities with a Bayesian perception system

In this paper, a robust probabilistic formulation for prediction of gait events from human walking activities using wearable sensors is presented. This approach combines the output from a Bayesian perception system with observations from actions and decisions made over time. The perception system makes decisions about the current gait events, while observations from decisions and actions allow to predict the most probable gait event during walking activities. Furthermore, our proposed method is capable to evaluate the accuracy of its predictions, which permits to obtain a better performance and trade-off between accuracy and speed. In our work, we use data from wearable inertial measurement sensors attached to the thigh, shank and foot of human participants. The proposed perception system is validated with multiple experiments for recognition and prediction of gait events using angular velocity data from three walking activities; level-ground, ramp ascent and ramp descent. The results show that our method is fast, accurate and capable to evaluate and adapt its own performance. Overall, our Bayesian perception system demonstrates to be a suitable high-level method for the development of reliable and intelligent assistive and rehabilitation robots

A Real-Time Gait Event Detection for Lower Limb Prosthesis Control and Evaluation

Lower extremity amputees suffer from mobility limitations which will result in a degradation of their quality of life. Wearable sensors are frequently used to assess spatio-temporal, kinematic and kinetic parameters providing the means to establish an interactive control of the amputee-prosthesis-environment system. Gait events and the gait phase detection of an amputee’s locomotion are vital for controlling lower limb prosthetic devices. The paper presents an approach to real-time gait event detection for lower limb amputees using a wireless gyroscope attached to the shank when performing level ground and ramp activities. The results were validated using both healthy and amputee subjects and showed that the time differences in identifying Initial Contact (IC) and Toe Off (TO) events were larger in a transfemoral amputee when compared to the control subjects and a transtibial amputee (TTA). Overall, the time difference latency lies within a range of ± 50 ms while the detection rate was 100% for all activities. Based on the validated results, the IC and TO events can be accurately detected using the proposed system in both control subjects and amputees when performing activities of daily living and can also be utilized in the clinical setup for rehabilitation and assessing the performance of lower limb prosthesis users

Real-time gait event detection for lower limb amputees using a single wearable sensor

This paper presents a rule-based real-time gait event/phase detection system (R-GEDS) using a shank mounted inertial measurement unit (IMU) for lower limb amputees during the level ground walking. Development of the algorithm is based on the shank angular velocity in the sagittal plane and linear acceleration signal in the shank longitudinal direction. System performance was evaluated with four control subjects (CS) and one transfemoral amputee (TFA) and the results were validated with four FlexiForce footswitches (FSW). The results showed a data latency for initial contact (IC) and toe off (TO) within a range of ± 40 ms for both CS and TFA. A delay of about 3.7 ± 62 ms for a foot-flat start (FFS) and an early detection of -9.4 ± 66 ms for heel-off (HO) was found for CS. Prosthetic side showed an early detection of -105 ± 95 ms for FFS whereas intact side showed a delay of 141 ±73 ms for HO. The difference in the kinematics of the TFA and CS is one of the potential reasons for high variations in the time difference. Overall, detection accuracy was 99.78% for all the events in both groups. Based on the validated results, the proposed system can be used to accurately detect the temporal gait events in real-time that leads to the detection of gait phase system and therefore, can be utilized in gait analysis applications and the control of lower limb prostheses

Estimation of Actuation System Parameters for Lower Limb Prostheses

This paper provides guidelines to estimate the kinematics, energy and torque requirements for lower limb prosthetic actuation systems during daily living activities. These parameters are estimated based on human biomechanical data from different sources to consider the variability due to the assumptions and errors in the analysis and data collection. The results showed that the powered actuation source is important at the ankle joint in the stance phase during level ground walking while it is more important at knee joint during stair ascending. These estimated parameters can be used as guidelines to design and select proper actuation systems

Effect of Different Prosthetic Knees/feet on the Roll-Over Shape

Roll-over shape (ROS) of knee-ankle-foot (KAF) is a scientific method which has been used to compare performance and design of the different prosthetic foot. In the current study, however, we aimed to understand the influence of the prosthetic components (i.e. knee and foot) on the knee-ankle-foot roll-over shape in a unilateral transfemoral amputee. We performed a case study based on series of experiments with repeated measures on single amputee wearing two different commercially available microprocessor prosthetic knees, during two weeks adaptation period to understand the influence of the prosthetic knee/foot using KAF ROS as an objective measure during level ground walking. The kinematics of the center of pressure (COP), lateral knee and ankle markers were collected and processed to obtain ROS and the results were used to fit a circular shape arc to obtain radius of curvature (ROC). The results indicated that the prosthetic knees have influenced ROC outcomes. The analysis of variance (ANOVA) and post hoc test of the normalized radius of curvature showed the mean of ROC were significantly different between Rheo3 knee, Orion2 and Orion2 with Echelon foot. The amputee reflected his comfort with Rheo3 plus College park foot and Orion with Echelon foot. A conclusion is drawn that multiple comfort zones may exists based on amputee’s ROS metrics. This finding suggests that the design of prosthetic knee should not be considered as a single component but rather as part of a whole system with different comfort zones

Investigation into Energy Efficiency and Regeneration in an Electric Prosthetic Knee

Powered lower limb prosthesis are facing energy and efficiency challenges. This article presents an investigation into reducing the energy losses and increasing the efficiencies of energy regeneration for a powered prosthetic knee during level ground walking. The results showed that the regeneration and overall system efficiencies would dramatically increase if the negative mechanical load in the braking quadrants are within the regenerative zone of the motor. This approach reduced the energy losses in the stance and swing phases and increased the possibility of harvesting more negative mechanical energy during level ground walking