Design and Evaluation of Swing Phase Controllers for Single-axis Knee (original) (raw)
Related papers
Design and Implementation of a Swing Phase Control System for a Prosthetic Knee
2008
Lower limb prostheses for above knee (AK) amputees require very challenging technology. All prosthetic knees require some degree of swing phase control to maintain a smooth gait. Swing control designs differ in complexity according to the mechanism used to change the rate of motion of the knee. The simplest knees use mechanical friction at the axis of rotation and only allow a constant walking speed. The more complex knees use fluid dynamics to provide variable resistance and the most complex knees use microprocessor technology to allow the knee to respond instantly to the amputees desired changes in speed. However, this superior gait performance comes at an extremely high financial cost to the amputee. In this work, a low cost swing phase control system for a prosthetic knee is designed, implemented and tested. The control system continuously monitors the subject's gait, detects the maximum hip flexion angle and recognizes his desired walking speed before the end of each gait cycle. It then outputs a trigger signal to the knee unit to adjust the damping coefficient accordingly, thus permitting fast automatic matching of the desired slow, normal or fast walking speed. The results show the ability of the system to recognize the required speeds after a sufficient training period for the subject.
Techniques for Dynamic Damping Control in Above Knee Prosthesis
2018
The paper presents a new technique for dynamic damping control based on natural humanoid walk for above knee prosthesis. It has been observed that natural humanoid walking is not solely relied on sensory feed back but also on Central Pattern Generators (CPG) and this CPG produces variation in joint trajectories based on task. Developing task oriented active prosthesis exploiting biologically inspired CPG patterns are of main focus of the paper. Task oriented stable gaits were synthesized using ZMP (Zero Moment Point) approach and the results were compared to kinematics of subjects captured by video streaming. Initial results suggest a feasible solution to gait pattern generation and adjustment of damping profile of prosthetic knee joints to achieve normal humanoid walking.
Design and Evaluation of a Magnetorheological Damper Based Prosthetic Knee
International Journal of Engineering, 2019
In this work, a magnetorheological (MR) damper based above-knee prosthesis is design and evaluated based on its performance in swing phase and in stance phase. Initially, a dynamic system model for swing phase of a prosthetic leg incorporating a single-axis knee with ideal MR damper was built. The dynamic properties of the damper are represented with Bingham parametric model. From Bingham model, governing damper parameters that determine the damping force and piston displacement of the damper are identified and optimized so as to enable the single-axis knee to nearly mimick the natural swing phase trajectory of a healthy person for level-ground walking as obtained from experimental data. Then, with the optimal damper parameters, an MR damper valve constrained in a desired cylindrical volume is developed. Finally, the prosthetic knee with the MR damper is evaluated for its performance during stance phase, based on ISO standard loading condition for the intended application. The results show that, compare to Rheo knee ® , the MR damper based prosthetic knee has achieved up to 68% reduction by volume and 40% reduction by weight.
A study on damping profile for prosthetic knee
Proceedings of the …, 2012
An intelligent prosthetic leg for above knee amputee person has been developed by Indian Institute of Information Technology -Allahabad. The leg has been called as Adaptive Modular Active Leg (AMAL). The main aim of this paper was to generate suitable damping profiles required for above knee prosthetic patients for locomotion. A detailed analysis of human gait cycle is needed to provide damping profiles to the prosthetic knee. This information is obtained from the healthy leg. A simple potentiometer sensor is fitted beside the healthy knee to measure the knee angle and strain gauges mounted below the heel, in the shoe to measure gait strain. These signals from the knee and the heel are the input that describe the gait cycle of the patient. These two signal values are cleaned using Kalman filter to reduce the sensory noise for providing better performance to our system. Human gait cycle is divided into six different phases to evaluate damping profiles. In this paper, we formulate six different damping equations to produce damping profiles for prosthetic knee. The Artificial Neural Network has been used to classify different phase of walking cycle with suitable damping value.
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2020
Improving the gait of transfemoral amputees and making it biomimetic and stable has always been a major effort. A dynamic model of the prosthetic device can predict the kinetic and kinematic performances, when incorporated with a musculoskeletal model. In this regard, a dynamic model of a recent trend of variable damping technology will help a great deal in evaluating the performance of the prosthetic device and also in studying the effect of various parameters on the prostheses. The current paper presents the dynamic model of a single axis two segmental prosthetic knee implemented with a magneto-rheological (MR) damper as a variable damping element. The MR damper is modeled mathematically using Bouc-Wen model with model parameters evaluated by minimizing the error norms for time, displacement and velocity between the experimental and the model-generated results using a genetic algorithm. Two different experimental data sets are used, one for mathematical modeling and other to assess the accuracy of the fit model. A Proportional Derivative plus Controlled Torque controller is employed, and the parameters are tuned to minimize the error between the desired and control input torques. Further, an inverse dynamic model using Bouc-Wen model variables is assumed and validated later. This model predicts the current directly and avoids the necessity of solving any quadratic equation, which is required in the case of inverse models based on modified Bouc-Wen. The dynamic model of the prosthesis is analyzed for the swing phase alone, and the results show that the model traces the desired knee angle and also the shank reaches full knee extension at the end of this phase with terminal velocity small enough to be handled by an extension stop.
User‐adaptive control of a magnetorheological prosthetic knee
Industrial Robot: An International Journal, 2003
A magnetorheological knee prosthesis is presented that automatically adapts knee damping to the gait of the amputee using only local sensing of knee force, torque, and position. To assess the clinical effects of the user‐adaptive knee prosthesis, kinematic gait data were collected on four unilateral trans‐femoral amputees. Using the user‐adaptive knee and a conventional, non‐adaptive knee, gait kinematics were evaluated on both affected and unaffected sides. Results were compared to the kinematics of 12 age, weight and height matched normals. We find that the user‐adaptive knee successfully controls early stance damping, enabling amputee to undergo biologically‐realistic, early stance knee flexion. These results indicate that a user‐adaptive control scheme and local mechanical sensing are all that is required for amputees to walk with an increased level of biological realism compared to mechanically passive prosthetic systems.
Optimal design of an MR damper valve for prosthetic knee application
Journal of Mechanical Science and Technology, 2018
In this work, a magnetorheological (MR) damper valve is designed with the primary objective of controlling swing-phase damping in an above-knee prosthesis. Initially, a swing phase model of the desired single axis knee incorporating MR damper was modelled. The control parameters that govern damping force and displacement of the damper were identified and optimized to enable the prosthetic knee to produce near normal swing phase trajectory for ground walking as obtained from experimental data. Then, the MR damper valve is optimally designed by selecting typical performance indices of the damper for the intended application. A multi-objective optimization problem is formulated where the MR damper valve is constrained in a desired cylindrical volume defined by its radius and height. Effects of the geometrical design variables of the valve are analytically investigated by mapping finite element analysis (FEA) numerical responses with response surface method (RSM). The results show that the MR damper with designed damper valve enables the prosthetic knee to achieve near to normal swing phase trajectory, and compare to the existed MR damper, up to 71 % reduction by weight has been achieved.
Proceedings of the ... IEEE/RSJ International Conference on Intelligent Robots and Systems. IEEE/RSJ International Conference on Intelligent Robots and Systems, 2016
This paper presents the experimental validation of a novel control strategy that unifies the entire gait cycle of a powered knee-ankle prosthetic leg without the need to switch between controllers for different periods of gait. Current control methods divide the gait cycle into several sequential periods each with independent controllers, resulting in many patient-specific control parameters and switching rules that must be tuned for a specific walking speed. The single controller presented is speed-invariant with a minimal number of control parameters to be tuned. A single, periodic virtual constraint is derived that exactly characterizes the desired actuated joint motion as a function of a mechanical phase variable across walking cycles. A single sensor was used to compute a phase variable related to the residual thigh angle's phase plane, which was recently shown to robustly represent the phase of non-steady human gait. This phase variable allows the prosthesis to synchronize...
Estimating Transfer Function of Below-Knee Prosthesis at Two Phases of Gait Cycle
The modern development in prosthetics field demand the evaluation of the dynamical behavior and automatic control .The key process in the design and implement of these devices is the determination of the model parameters inherited with the transfer function .In such complicated structures it is so difficult to evaluate transfer function analytically ,however experimental approaches can serve as a simple and effective tool for estimating transfer function and model parameters .In this regard computer software such as Matlab is used .System Identification SID refers to the method for estimating the system transfer function from experimental tests by using computer .In the present paper; SID method is employed for analyzing below-knee prosthesis leg .In order to simulate with the practical requirement for design and evaluation ,two phases of human gait are considered ,namely; swing phase and single support of stance phase .The validity of this method is firstly checked by applying it on clamped-clamped beam model where the required parameters are evaluated and compared theoretically (via modal analysis) and experimentally (via System identification) .It is found that ; the error in estimating the transfer function parameter of beam is not exceeded 6%. Then the transfer function of the prosthesis are estimated for two phases of gait cycle .It is found that; the estimated transfer function of the prosthesis leg is highly affected by the phase type of gait cycle , where ;the natural frequency highly increases, the static gain decrease for support phase as compared with the swing phase ,however the damping ratio does not affected .