scholarly journals Minimizing Energy Consumption and Peak Power of Series Elastic Actuators: A Convex Optimization Framework for Elastic Element Design

2019 ◽  
Vol 24 (3) ◽  
pp. 1334-1345 ◽  
Author(s):  
Edgar A. Bolivar Nieto ◽  
Siavash Rezazadeh ◽  
Robert D. Gregg
Keyword(s):  
Energy Consumption ◽  
Convex Optimization ◽  
Elastic Element ◽  
Peak Power ◽  
Optimization Framework ◽  
Series Elastic Actuators ◽  
Series Elastic

A convex optimization framework for robust-feasible series elastic actuators

Mechatronics ◽  
2021 ◽  
Vol 79 ◽  
pp. 102635
Author(s):  
Edgar A. Bolívar-Nieto ◽  
Tyler Summers ◽  
Robert D. Gregg ◽  
Siavash Rezazadeh
Keyword(s):  
Convex Optimization ◽  
Optimization Framework ◽  
Series Elastic Actuators ◽  
Series Elastic

scholarly journals A General Framework for Minimizing Energy Consumption of Series Elastic Actuators With Regeneration

2017 ◽  
Author(s):  
Edgar Bolívar ◽  
Siavash Rezazadeh ◽  
Robert Gregg
Keyword(s):  
Energy Consumption ◽  
Elastic Element ◽  
Close Contact ◽  
Reference Trajectory ◽  
Ankle Motion ◽  
Natural Motion ◽  
Actuator Constraints ◽  
Natural Dynamics ◽  
Series Elastic Actuators ◽  
Series Elastic

The use of actuators with inherent compliance, such as series elastic actuators (SEAs), has become traditional for robotic systems working in close contact with humans. SEAs can reduce the energy consumption for a given task compared to rigid actuators, but this reduction is highly dependent on the design of the SEA’s elastic element. This design is often based on natural dynamics or a parameterized optimization, but both approaches have limitations. The natural dynamics approach cannot consider actuator constraints or arbitrary reference trajectories, and a parameterized elastic element can only be optimized within the given parameter space. In this work, we propose a solution to these limitations by formulating the design of the SEA’s elastic element as a non-parametric convex optimization problem, which yields a globally optimal conservative elastic element while respecting actuator constraints. Convexity is proven for the case of an arbitrary periodic reference trajectory with a SEA capable of energy regeneration. We discuss the optimization results for the tasks defined by the human ankle motion during level-ground walking and the natural motion of a single mass-spring system with a nonlinear spring. For all these tasks, the designed SEA reduces energy consumption and satisfies the actuator’s constraints.

Design of a Compact, Lightweight, Electromechanical Linear Series Elastic Actuator

2014 ◽  
Author(s):  
Coleman Knabe ◽  
Bryce Lee ◽  
Viktor Orekhov ◽  
Dennis Hong
Keyword(s):  
Elastic Element ◽  
Load Capacity ◽  
Ball Screw ◽  
Leaf Spring ◽  
Load Range ◽  
Compression Load ◽  
Design Changes ◽  
Series Elastic Actuators ◽  
Future Work ◽  
Series Elastic

Series Elastic Actuators (SEAs) have several benefits for force controlled robotic applications. Typical SEAs place an elastic element between the motor and the load, increasing shock tolerance, allowing for more accurate and stable force control, and creating the potential for energy storage. This paper presents the design of a compact, lightweight, low-friction, electromechanical linear SEA used in the lower body of the Tactical Hazardous Operations Robot (THOR). The THOR SEA is an evolutionary improvement upon the SAFFiR SEA [1]. Design changes focused on reducing the size and fixed length of the actuator while increasing its load capacity. This SEA pairs a ball screw-driven linear actuator with a configurable elastic member. The elastic element is a titanium leaf spring with a removable pivot, setting the compliance to either 650 or 372 [kN/m]. The compliant beam is positioned parallel to the actuator, reducing overall packaging size by relocating the space required for spring deflection. Unlike typical SEAs which measure force through spring deflection, the force applied to the titanium beam is measured through a tension/compression load cell located in line with each actuator, resulting in a measurable load range of +/−2225 [N] at a tolerance of +/−1 [N]. A pair of universal joints connects the actuator to the compliant beam and to the robot frame. As the size of each universal joint is greatly dependent upon its required range of motion, each joint design is tailored to fit a particular angle range to further reduce packaging size. Potential research topics involving the actuator are proposed for future work.

scholarly journals Energy Implications of Torque Feedback Control and Series Elastic Actuators for Mobile Robots

2018 ◽  
Author(s):  
Stephen P. Buerger ◽  
Anirban Mazumdar ◽  
Steven J. Spencer
Keyword(s):  
Energy Consumption ◽  
Feedback Control ◽  
Best Practices ◽  
Energy Efficient ◽  
Mechanical Impedance ◽  
Gear Ratio ◽  
Spring Stiffness ◽  
Feedback Analysis ◽  
Series Elastic Actuators ◽  
Series Elastic

Torque feedback control and series elastic actuators are widely used to enable compact, highly-geared electric motors to provide low and controllable mechanical impedance. While these approaches provide certain benefits for control, their impact on system energy consumption is not widely understood. This paper presents a model for examining the energy consumption of drivetrains implementing various target dynamic behaviors in the presence of gear reductions and torque feedback. Analysis of this model reveals that under cyclical motions for many conditions, increasing the gear ratio results in greater energy loss. A similar model is presented for series elastic actuators and used to determine the energy consequences of various spring stiffness values. Both models enable the computation and optimization of power based on specific hardware manifestations, and illustrate how energy consumption sometimes defies conventional best-practices. Results of evaluating these two topologies as part of a drivetrain design optimization for two energy-efficient electrically driven humanoids are summarized. The model presented enables robot designers to predict the energy consequences of gearing and series elasticity for future robot designs, helping to avoid substantial energy sinks that may be inadvertently introduced if these issues are not properly analyzed.

scholarly journals Energetic and Peak Power Advantages of Series Elastic Actuators in an Actuated Prosthetic Leg for Walking and Running

Actuators ◽  
2014 ◽  
Vol 3 (1) ◽  
pp. 1-19 ◽  
Author(s):  
Martin Grimmer ◽  
Mahdy Eslamy ◽  
André Seyfarth
Keyword(s):  
Peak Power ◽  
Series Elastic Actuators ◽  
Series Elastic

Design of Elastic Element and Controller Algorithm

2014 ◽  
Author(s):  
Zhuohua Shen ◽  
Junming Zhang ◽  
Manish Anand ◽  
Jared Schwartzentruber ◽  
Justin Seipel
Keyword(s):  
Elastic Element ◽  
Dynamic Properties ◽  
Steel Strip ◽  
Low Cost ◽  
Spring Steel ◽  
Control Series ◽  
Series Elastic Actuators ◽  
Strip Length ◽  
Elastic Elements ◽  
Series Elastic

Recent development of series elastic actuators have revealed a capability to mimic muscle-like properties and achieve accurate force control. Series elastic actuators have also been widely used in humanoid and surgical robotic devices. The design of the elastic elements are critical and complex. This tends to increase costs and complexity of designing and controlling series elastic actuators. Here, we present a novel low cost and easy-to-fabricate design for a series elastic element that also has adjustable stiffness. The design consists of simple shaft couplers and spring steel plates. During the test, the stiffness of the designed elastic elements is very close to linear (R2 = 0.999) when the clamped spring-steel strip length is sufficiently long. As the clamped strip length shortens, the resulting torque deflection curve becomes slightly quadratic but remains largely linear. Also, the designed elastic element exhibits little hysteresis during loading and unloading. The stiffness of the designed elastic element can be tuned to achieve a range of stiffness values, thus it is suitable for different applications with different stiffness requirements. We also design a simple control algorithm and develop a simulation based on the dynamic properties of the designed elastic element. In simulation, the controller is able to accurately track the commanded torque values. Overall, this design could help reduce the cost and development time required for series elastic actuators.

Hopping frequency influences elastic energy reuse with joint series elastic actuators

2021 ◽  
Vol 119 ◽  
pp. 110319
Author(s):  
A. Mohammadi Nejad Rashty ◽  
M. Grimmer ◽  
A. Seyfarth
Keyword(s):  
Elastic Energy ◽  
Series Elastic Actuators ◽  
Series Elastic
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