scholarly journals Artificial Knee Joints Actuators with Energy Recovery Capabilities: A Comparison of Performance

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Roberta Alò ◽  
Francesco Bottiglione ◽  
Giacomo Mantriota
Keyword(s):  
Electric Motor ◽  
Energy Recovery ◽  
Peak Torque ◽  
Lower Limbs ◽  
Wearable Robot ◽  
Series Elastic Actuator ◽  
Actuation System ◽  
Performance Indexes ◽  
Variable Transmission ◽  
Series Elastic

The human knee absorbs more energy than it expends in level ground walking. For this reason it would be useful if the actuation system of a wearable robot for lower limbs was able to recover energy thus improving portability. Presently, we recognize three promising technologies with energy recovery capabilities already available in the literature: the Series Elastic Actuator (SEA), the Clutchable Series Elastic Actuator (C-SEA), and the flywheel Infinitely Variable Transmission (F-IVT) actuator. In this paper, a simulation model based comparison of the performance of these actuators is presented. The focus is on two performance indexes: the energy consumed by the electric motor per gait and the peak torque/power requested to the electric motor. Both quantities are related to the portability of the device: the former affects the size of the batteries for a given desired range; the latter affects the size and the weight of the electric motor. The results show that, besides some well-explained limitations of the presented methodology, the C-SEA is the most energy efficient whereas the F-IVT allows cutting down the motor torque/peak power strongly. The analysis also leads to defining how it is possible to improve the F-IVT to achieve a reduction of the energy consumption.

Mechanical design optimization of a series elastic actuator considering the control performance

2019 ◽  
Vol 46 (2) ◽  
pp. 311-323
Author(s):  
Hanseung Woo ◽  
Kyoungchul Kong
Keyword(s):  
Design Method ◽  
Mechanical Impedance ◽  
Control Performance ◽  
Content Type ◽  
Actuation Force ◽  
Series Elastic Actuator ◽  
Actuation System ◽  
Output Torque ◽  
Performance Indexes ◽  
Series Elastic

Purpose Actuators for human-interactive robot systems require transparency and guaranteed safety. An actuation system is called transparent when it is able to generate an actuation force as desired without any actuator dynamics. The requirements for the transparent actuation include high precision and large frequency bandwidth in actuation force generation, zero mechanical impedance and so on. In this paper, a compact rotary series elastic actuator (cRSEA) is designed considering the actuation transparency and the mechanical safety. Design/methodology/approach The mechanical parameters of a cRSEA are optimally selected for the controllability, the input and output torque transmissibility and the mechanical impedance by simulation study. A mechanical clutch that automatically disengages the transmission is devised such that the human is mechanically protected from an excessive actuation torque due to any possible controller malfunction or any external impact from a collision. The proposed cRSEA with a mechanical clutch is applied to develop a wearable robot for incomplete paraplegic patients. To verify torque tracking performance and disengagement of the mechanical clutch, experiments were conducted. Findings As the effects of the gear ratio, N1, on the four control performance indexes are conflicting, it should be carefully selected such that the controllability and the output torque transmissibility are maximized, while the disturbance torque transmissibility and the mechanical impedance are minimized. When the four control performance indexes were equally weighted, N1 was selected as 30. Experimental results showed that the designed cRSEA provided good control performances and the mechanical clutch worked properly. Originality/value It is important to design the actuator so as to maximize the control performance in accordance with its purpose. This paper presents the design guidelines for the SEA by introducing four control performance indexes and analyzing how the performance indexes vary according to the change of design parameter. From the viewpoint of practicality, a mechanical clutch design method that prevents excessive torque from being transmitted to the wearer and an analysis to solve the locking phenomenon when using a worm gear are presented, and a design method of SEA satisfying both control performance and practicality is presented.

scholarly journals Design and Preliminary Results of a Reaction Force Series Elastic Actuator for Bionic Ankle Prostheses

2019 ◽  
Author(s):  
Matt Carney ◽  
Tony Shu ◽  
Roman Stolyarov ◽  
Jean-Francois Duval ◽  
Hugh Herr
Keyword(s):  
Energy Storage ◽  
Mechanical Design ◽  
Mechanical Energy ◽  
Reaction Force ◽  
Electrical Energy ◽  
Peak Torque ◽  
Walking Gait ◽  
Series Elastic Actuator ◽  
Hardware Specification ◽  
Series Elastic

The TF8 actuator is an untethered, lower-extremity powered-prostheses designed to replicate biological kinetic and kinematic function of ankles. An energy optimal hardware specification was found by kinematically clamping walking gait data to the dynamic model of a series elastic actuator (SEA). We searched for a minimal electrical energy configuration of motor, reduction ratio, and spring, subject to specified constraints and ultimately discretely available components. The outcome translated into a mechanical design that heavily weighted the importance of mechanical energy storage in springs. The resulting design is a moment-coupled cantilever-beam reaction-force SEA (RFSEA) that has a nominal torque rating of 85Nm, peak torque of 175Nm, 105 degree range of motion, and a hardware mass of 1.6kg.

An Innovative Design of Artificial Knee Joint Actuator With Energy Recovery Capabilities

2015 ◽  
Vol 8 (1) ◽  
Author(s):  
Roberta Alò ◽  
Francesco Bottiglione ◽  
Giacomo Mantriota
Keyword(s):  
Knee Joint ◽  
Human Locomotion ◽  
Lower Limbs ◽  
Great Effort ◽  
Innovative Design ◽  
Actuation System ◽  
Variable Transmission ◽  
Infinitely Variable Transmission ◽  
Actuation Systems ◽  
Powertrain Configuration

The actuation systems of lower limbs exoskeletons have been extensively investigated and, presently, a great effort is aimed at reducing the weight and improving the efficiency, thus increasing the operating range for battery-operated devices. In this work, an innovative and more efficient actuation system to power the knee joint is proposed. The key and nonconventional elements of this alternative design are a flywheel and a micro infinitely variable transmission (IVT). This particular powertrain configuration permits to exploit efficiently the dynamics of human locomotion, which offers the possibility to recover energy. By means of simulations of level ground walking and running, it is here demonstrated how storing energy in the flywheel permits to reduce the energy consumption and to downsize the electric motor.

A Compact, Modular Series Elastic Actuator

2016 ◽  
Vol 8 (4) ◽  
Author(s):  
Jonathan P. Cummings ◽  
Dirk Ruiken ◽  
Eric L. Wilkinson ◽  
Michael W. Lanighan ◽  
Roderic A. Grupen ◽  
...  
Keyword(s):  
High Performance ◽  
Negative Impact ◽  
Peak Torque ◽  
Mobile Manipulator ◽  
Brushless Motors ◽  
Hall Effect Sensor ◽  
Series Elastic Actuator ◽  
Wide Range ◽  
Active Impedance ◽  
Series Elastic

This paper presents the development of a compact, modular rotary series elastic actuator (SEA) design that can be customized to meet the requirements of a wide range of applications. The concept incorporates flat brushless motors and planetary gearheads instead of expensive harmonic drives and a flat torsional spring design to create a lightweight, low-volume, easily reconfigurable, and relatively high-performance modular SEA for use in active impedance controlled devices. The key innovations include a Hall effect sensor for direct spring displacement measurements that mitigate the negative impact of backlash on SEA control performance. Both torque and impedance controllers are developed and evaluated using a 1-degree-of-freedom (DoF) prototype of the proposed actuator package. The results demonstrate the performance of a stable first-order impedance controller tested over a range of target impedances. Finally, the flexibility of the modular SEA is demonstrated by configuring it for use in five different actuator specifications designed for use in the uBot-7 mobile manipulator requiring spring stiffnesses from 3 N · m/deg to 11.25 N · m/deg and peak torque outputs from 12 N · m to 45 N · m.

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