scholarly journals A Novel Adjustable Damper Design for a Hybrid Passive Ankle Prosthesis

Actuators ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 74
Author(s):  
Amirreza Naseri ◽  
Majid Mohammadi Moghaddam ◽  
Mohammad Gharini ◽  
Maziar Ahmad Sharbafi
Keyword(s):  
Mechanical Design ◽  
Damping Ratio ◽  
Plantar Flexion ◽  
Active Systems ◽  
Ankle Prosthesis ◽  
Prosthetic Foot ◽  
In Series ◽  
Damper Design ◽  
Compact Design ◽  
Walking Locomotion

Specifications of actuators when interacting with biological systems such as the human body are entirely different from those used in industrial machines or robots. One important instance of such applications is assistive devices and prostheses. Among various approaches in designing prostheses, recently, semi-active systems attracted the interest of researchers. Even more, some commercial systems benefit from designs such as implementing an adjustable damper in the ankle prosthesis to increase range of motion. The main reason for adding damper is to assist amputees’ walking locomotion on slopes (especially downward). In this paper, we introduce a hydraulic damper design for use in the transtibial prosthetic foot. In the fabricated hydraulic prosthetic foot, two one-way flow control valves are exploited to tune the damping ratio in the plantar flexion and dorsiflexion, independently. Using the carbon prosthetic foot in series to a damper and spring could improve mimicking intact foot movement. First, we present the details of the damper and the prosthesis mechanical design. Then, we introduce experiment-based modeling for the damper’s conceptual design in the proposed prosthesis using SIM-Hydraulic and MATLAB. This device is fabricated and tested in a pilot experiment. The compact design with reduced weight and size of the prosthetic foot are additional advantages of the proposed prosthetic foot.

Thin Thermally Efficient ICECool Defense Semiconductor Power Amplifiers

2017 ◽  
Vol 14 (3) ◽  
pp. 77-93 ◽  
Author(s):  
Sumeer Khanna ◽  
Patrick McCluskey ◽  
Avram Bar-Cohen ◽  
Bao Yang ◽  
Michael Ohadi
Keyword(s):  
Heat Flux ◽  
Structural Reliability ◽  
Mechanical Design ◽  
Substrate Thickness ◽  
Time To Failure ◽  
Failure Model ◽  
High Concentration ◽  
Element Analysis ◽  
Analysis Technique ◽  
Compact Design

Abstract Traditional power electronics for military and fast computing applications are bulky and heavy. The “mechanical design” of electronic structure and “materials” of construction of the components have limitations in performance under very high temperature conditions. The major concern here is “thermal management.” To be more specific, this refers to removal of high-concentration hotspot heat flux >5 kW/cm2, background heat flux >1 kW/cm2, and “miniaturization” of device within a substrate thickness of <100 μm. We report on the novel applications of contact-based thermoelectric cooling (TEC) to successful implementations of high-conductivity materials - diamond substrate grown on gallium nitride (GaN)/AlGaN transistors to keep the hotspot temperature rise of device below 5 K. The requirement for smarter and faster functionality along with a compact design is considered here. These efforts have focused on the removal of higher levels of heat flux, heat transfer across interface of junction and substrate, advanced packaging and manufacturing concepts, and integration of TEC of GaN devices to nanoscale. The “structural reliability” is a concern and we have reported the same in terms of mean time to failure (cycles) of SAC305 (96.5% tin, 3% silver, 0.5% cu) solder joint by application of Engelmaier's failure model and evaluation of stresses in the structure. The mathematical equation of failure model incorporates the failure phenomena of fatigue and creep in addition to the dwell time, average solder temperature, and plastic strain accumulation. The approach to this problem is a nonlinear finite element analysis technique, which incorporates thermal, mechanical, and thermoelectric boundary conditions.

scholarly journals Passive Prosthetic Foot Shape and Size Optimization Using Lower Leg Trajectory Error

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Kathryn M. Olesnavage ◽  
Victor Prost ◽  
William Brett Johnson ◽  
Amos G. Winter
Keyword(s):  
Mechanical Design ◽  
Three Dimensional ◽  
Field Trials ◽  
Lower Leg ◽  
Element Analysis ◽  
Trajectory Error ◽  
Design Objective ◽  
Prosthetic Foot ◽  
Single Part ◽  
Shape And Size

A method is presented to optimize the shape and size of a passive, energy-storing prosthetic foot using the lower leg trajectory error (LLTE) as the design objective. The LLTE is defined as the root-mean-square error between the lower leg trajectory calculated for a given prosthetic foot's deformed shape under typical ground reaction forces (GRFs), and a target physiological lower leg trajectory obtained from published gait data for able-bodied walking. Using the LLTE as a design objective creates a quantitative connection between the mechanical design of a prosthetic foot (stiffness and geometry) and its anticipated biomechanical performance. The authors' prior work has shown that feet with optimized, low LLTE values can accurately replicate physiological kinematics and kinetics. The size and shape of a single-part compliant prosthetic foot made out of nylon 6/6 were optimized for minimum LLTE using a wide Bezier curve to describe its geometry, with constraints to produce only shapes that could fit within a physiological foot's geometric envelope. Given its single part architecture, the foot could be cost effectively manufactured with injection molding, extrusion, or three-dimensional printing. Load testing of the foot showed that its maximum deflection was within 0.3 cm (9%) of finite element analysis (FEA) predictions, ensuring the constitutive behavior was accurately characterized. Prototypes were tested on six below-knee amputees in India—the target users for this technology—to obtain qualitative feedback, which was overall positive and confirmed the foot is ready for extended field trials.

Dynamics Analysis of Energy Absorbing Device Based on Damped Dynamics Vibration Absorber

2015 ◽  
Vol 764-765 ◽  
pp. 254-258 ◽  
Author(s):  
Zhong Qiang Zheng ◽  
Peng Huang ◽  
Tao Yao ◽  
Zong Yu Chang
Keyword(s):  
Large Scale ◽  
Damping Ratio ◽  
Excitation Frequency ◽  
Tall Buildings ◽  
Analytical Form ◽  
Energy Absorber ◽  
In Series ◽  
Energy Transducer ◽  
Electrical Damping ◽  
Energy Absorbing

Nowadays, absorbing energy from vibration is one of the most promising technologies. In general, the vibrations may be very large, such as the vibrations of tall buildings, large flexible bridges, and ocean platform and so on in some environmental loading. With the global concern on energy and environmental issues, energy absorbing from large-scale vibrations for structural health monitoring purposes is more attractive and becomes a research frontier. A type of damped dynamics vibration energy absorber, where two masses are connected in series with the energy transducer and spring, is built and analyzed in this paper. The relationships among electrical damping ratio, excitation frequency ratio and dimensionless power are analyzed in frequency domain. The optimal parameters for maximizing the power output are discussed in analytical form while taking the parasitic mechanical damping of the system into account. In addition, the numerical simulations in time domain are calculated. The results indicate that when the system is excited by the larger peak of local optimal excitation frequency, more power can be obtained. It is helpful for design of energy absorber device.

A Control Strategy for an Active Alignment Transtibial Prosthesis

2015 ◽  
Author(s):  
Andrew LaPrè ◽  
Frank Sup
Keyword(s):  
Gait Cycle ◽  
Mechanical Design ◽  
Adaptive Controller ◽  
Residual Limb ◽  
Control Approach ◽  
Prosthetic Foot ◽  
Transtibial Prosthesis ◽  
Finite State ◽  
New Type ◽  
Walking Speeds

This paper presents a control approach for an experimental transtibial prosthesis that can actively realign the residual limb in relation to prosthetic foot during the stance phase of gait. The realignment objective is to inject positive power into the gait cycle while actively reducing the magnitude of the sagittal moment transferred to the residual limb. The altered gait dynamics of this new type of prosthesis require a control approach that coordinates its function with a user’s gait cycle. This paper overviews the mechanical design of the prosthesis development, the proposed finite-state adaptive controller, and presents experimental results for constant cadence walking and adaptation while changing walking speeds.

Robust multi-objective optimization design of active tuned mass damper system to mitigate the vibrations of a high-rise building

2014 ◽  
Vol 229 (1) ◽  
pp. 26-43 ◽  
Author(s):  
S Pourzeynali ◽  
S Salimi
Keyword(s):  
Damping Ratio ◽  
Tuned Mass Damper ◽  
Robust Design Optimization ◽  
Design Parameters ◽  
Control Force ◽  
Multi Objective ◽  
High Rise ◽  
High Rise Building ◽  
Mass Damper ◽  
Damper Design

In engineering applications, many control devices have been developed to reduce the vibrations of structures. Active tuned mass damper system is one of these devices, which is a combination of a passive tuned mass damper system and an actuator to produce a control force. The main objective of this paper is to present a practical procedure for both deterministic and probabilistic design of the active tuned mass damper control system using multi-objective genetic algorithms to mitigate high-rise building responses. For this purpose, extensive numerical analyses have been performed, and optimal robust results of the active tuned mass damper design parameters with their effectiveness in reducing the example building responses have been presented. Uncertainties, which may exist in the system, have been taken into account using a robust design optimization procedure. The stiffness matrix and damping ratio of the building are considered as uncertain random variables; and using the well-known beta distribution, 50 pairs of these variables are generated. This resulted in 50 buildings with different stiffness matrices and damping ratios. These simulated buildings are used to evaluate robust optimal values of the active tuned mass damper design parameters. Four non-commensurable objective functions, namely maximum displacement, maximum velocity, maximum acceleration of each floor of the building, and active control force produced by the actuator are considered, and a fast and elitist non-dominated sorting genetic algorithm approach is used to find a set of pareto-optimal solutions.

Design and analysis of magnetorheological damper based ankle-foot prosthesis prototype

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Sachin Negi ◽  
Ujjwal Sagar ◽  
Vijay Kumar Nautiyal ◽  
Neeraj Sharma
Keyword(s):  
Computer Aided Design ◽  
Dynamic Range ◽  
Plantar Flexion ◽  
Mr Damper ◽  
Magnetorheological Damper ◽  
Heel Strike ◽  
Leaf Spring ◽  
Content Type ◽  
Prosthetic Foot ◽  
Fused Deposition

Purpose This paper aims to design and analyze a controlled magnetorheological damper-based ankle-foot prosthesis prototype. Design/methodology/approach The ankle-foot prostheses prototype is proposed using the lightweight three dimensional (3 D)-printed parts, MR damper and digital servomotor. Initially, the computer-aided design (CAD) model of the prosthetic foot, leaf spring, retention spring and the various connecting parts required to connect the pylon and damper actuator assemblies are designed using CAD software. Later, the fused deposition modeling 3 D printer-based technique prints a prosthetic foot and other connecting parts using Acrylonitrile Butadiene Styrene filament. The prototype consists of two control parts: the first part controls the MR actuator that absorbs the impacts during walking. The second part is the control of the electric actuator intended to generate the dorsiflexion and plantar flexion movements. Finally, the prototype is tested on a transtibial amputee under the supervision of a prosthetist. Findings The ANalysis SYStems software-based analysis has shown that the prosthetic foot has a factor of safety values between 4.7 and 8.7 for heel strike, mid-swing and toe-off; hence, it is safe from mechanical failure. The designed MR damper-based ankle-foot prosthesis prototype is tested on an amputee for a level-ground walk; he felt comfortable compared to his passive prosthesis. Originality/value The design of an MR damper-based prosthesis prototype offers a better dynamic range for locomotion than passive prostheses. It reduces the injuries and provides relief to the transtibial amputees.

Kinematic Analysis and Simulation of the Tri-Prism Deployable Structure

2015 ◽  
Vol 799-800 ◽  
pp. 1183-1187
Author(s):  
Huai Dong Zhou ◽  
Peng Zhen ◽  
Wu Sheng Chou
Keyword(s):  
Kinematic Analysis ◽  
Screw Theory ◽  
Mechanical Design ◽  
Complex Mechanism ◽  
Drive Mode ◽  
Kinematic Equation ◽  
Deployable Structure ◽  
In Series ◽  
The Relationship ◽  
Theoretical Results

The Tri-prism deployable structure is a complex mechanism which consists of six deployable structure units in series. All deployable structure units have the similar movements; the screw theory is used to establish the kinematic equation of each unit and the entire tri-prism deployable structure. Meanwhile, the motion stability, drive mode and mechanical design of the tri-prism deployable structure have been comprehensively researched. Finally, extensive simulations in ADAMS have been conducted to obtain the relationship between the motions of ends and inputs, which are further compared with theoretical results.

Rotational Stiffness Adjustability of a Prototype Foot/Ankle Prosthesis

1999 ◽  
Author(s):  
Peter M. Quesada ◽  
John A. Hays ◽  
Mark R. Pitkin ◽  
James M. Colvin
Keyword(s):  
Mechanical Testing ◽  
Loading Rate ◽  
Rotational Stiffness ◽  
Ankle Prosthesis ◽  
Loading Rates ◽  
Prosthetic Foot ◽  
Quantitative Manner ◽  
Prototype Design

Abstract Mechanical testing was conducted for a prototype prosthetic foot/ankle component to assess the potential for being able to adjust dynamic rotational stiffness of the prototype in a simple but quantitative manner. The tested prototype has been dubbed the rolling joint ankle (RJA) prosthesis. The RJA prototype design is based on a concept in which rotational stiffness is lower with the ankle position closer to neutral, and increases as ankle rotation moves away from neutral. Adjustment of the RJA prototype’s stiffness involved systematic tightening and loosening of two set screws. Two sets of mechanical testing were conducted at each of three different loading rates to evaluate repeatability of rotational stiffness and to examine the effects of loading rate on RJA stiffness.

Methodology for Modeling of Passive Shunt Damping of Systems With Bonded Piezocomposites

2005 ◽  
Author(s):  
Anil Saigal ◽  
Robert Greif ◽  
Jane Ng
Keyword(s):  
Finite Element ◽  
Boundary Conditions ◽  
Cantilever Beam ◽  
Loss Factor ◽  
Heat Dissipation ◽  
Damping Ratio ◽  
Modeling Tools ◽  
Simply Supported ◽  
In Series ◽  
The Impact

An aluminum cantilever beam bonded with 1-3 piezocomposite dampers is modeled by means of ANSYS finite element and SIMULINK simulation softwares. ANSYS currently cannot account for heat dissipation in piezoelectric materials. As such, ANSYS is used to obtain strain energies to be input into the SIMULINK model to investigate the dynamic behavior of the system and calculate the damping ratio. The impact of two different shunting arrangements, a damper in conjunction with a simple resistive electrical circuit in series and parallel, is investigated. In addition, a simply supported beam and a simply supported straight pipe are also analyzed for their wide applications in industry, and as an indication of the utility of this methodology to analyze complex structural configurations. For a typical cantilever beam, energy dissipation and transient analysis are used to calculate the tip displacement as a function of time and the damping ratio. Then using ANSYS, with the parameter BETAD to incorporate damping as a stiffness multiplier, a comparison of the transient results is used to quantify the damping response of aluminum beams with bonded 1-3 piezocomposite dampers. The system loss factor due to the piezoelectric damping is also compared to the inherent loss factor of different beam materials. The results show that circuits in series provides a better damping ratio (0.000581) as compared to circuits in parallel (0.000374). In addition, for different boundary conditions (cantilever, simply supported), the damping ratios (0.000581, 0.000202) and the BETAD values (6.3 E-6, 0.7 E-6), respectively, are functions of the boundary conditions and are not directly related to each other. Finally, damping using 1-3 piezocomposites effectively increases the overall system loss factor by at least 100% to almost 300% as compared to the inherent material damping. In general, this methodology of combining finite element method (ANSYS) and transient modeling tools (SIMULINK) can be used to study damping characteristics of any structural system damped with 1-3 piezocomposites.

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