RRLAB SEA — A highly integrated compliant actuator with minimised reflected inertia

Schütz, Steffen; Mianowski, K.; Kotting, Christian; Nejadfard, Atabak; Reichardt, Max; Berns, Karsten

doi:10.1109/aim.2016.7576775

Cited by 16 publications

(7 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The reflected inertia of the motor after the transmission, which is proportional to the reduction ratio squared, is normally very high compared to the load. For example, three recent SEA designs reflect output inertia of 360, 270, and 294 kg for the UT-SEA [7], Valkyrie's SEA [20], and THOR-SEA [21], respectively, as indicated by [9]. As a consequence, the system requires a high load to backdrive.…”

Section: System Description and Modelingmentioning

confidence: 99%

See 1 more Smart Citation

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

Nieto

Rezazadeh

Gregg

2019

IEEE/ASME Trans. Mechatron.

View full text Add to dashboard Cite

Compared to rigid actuators, series elastic actuators (SEAs) offer a potential reduction of motor energy consumption and peak power, though these benefits are highly dependent on the design of the torque-elongation profile of the elastic element. In the case of linear springs, natural dynamics is a traditional method for this design, but it has two major limitations-arbitrary load trajectories are difficult or impossible to analyze and it does not consider actuator constraints. Parametric optimization is also a popular design method that addresses these limitations, but solutions are only optimal within the space of the parameters. To overcome these limitations, we propose a nonparametric convex optimization program for the design of the nonlinear elastic element that minimizes energy consumption and peak power for an arbitrary periodic reference trajectory. To obtain convexity, we introduce a convex approximation to the expression of peak power; energy consumption is shown to be convex without approximation. The combination of peak power and energy consumption in the cost function leads to a multiobjective convex optimization framework that comprises the main contribution of this paper. As a case study, we recover the elongationtorque profile of a cubic spring, given its natural oscillation as the reference load. We then design nonlinear SEAs for an ankle prosthesis that minimize energy consumption and peak power for different trajectories and extend the range of achievable tasks when subject to actuator constraints.

show abstract

Section: System Description and Modelingmentioning

confidence: 99%

“…In traditional SEAs, the motor is connected to a high-ratio linear transmission, then an elastic element connects the transmission's output to the load [7]. Designs with a low ratio transmission are less common, but still possible due to the increasing supply of high torque motors [8], [9].…”

Section: Introductionmentioning

confidence: 99%

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

Nieto

Rezazadeh

Gregg

2019

IEEE/ASME Trans. Mechatron.

View full text Add to dashboard Cite

show abstract

“…The reflected inertia of the motor after the transmission, which is proportional to the reduction ratio squared, is normally very high compared to the load. For example, three recent SEA designs reflect output inertia of 360 kg, 270 kg, and 294 kg for the UT-SEA [8], Valkyrie’s SEA [18], and THOR-SEA [19] respectively, as indicated by [10]. As a consequence, the system requires a high load to backdrive.…”

Section: System Description and Modelingmentioning

confidence: 99%

“…This architecture represents a typical implementation of SEAs [8]. Designs with a low ratio transmission are less common but still possible due to recent developments in high torque motors [9, 10]. …”

Section: Introductionmentioning

confidence: 99%

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

Bolívar

Rezazadeh

Gregg

2017

Volume 1: Aerospace Applications; Advances in Control Design Methods; Bio Engineering Applications; Advances in Non-Linear Cont

View full text Add to dashboard Cite

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.

show abstract

“…Series elastic actuators (Seas) are used to provide precise force and position control in joints. 6,7 Besides, Carl features two BiAs, to partly replicate the motor redundancy of the human leg. The energetics of actuators can be investigated specifically in case of biarticulars since the superior mechatronics of Carl allows us to accurately measure power, force and velocity of the actuators and angular velocity and torque in the joints.…”

Section: Introductionmentioning

confidence: 99%

Technical advantages and disadvantages of biarticular actuators in bipedal robots

2020

Robots in Human Life

View full text Add to dashboard Cite

The practical advantages of redundant biarticular actuators in bipedal robotic systems are demonstrated and reviewed. The major physiological role of biarticular muscles indeed can be successfully replicated in robotic systems by transferring power from heavy upper leg segments to the lower limb joints. As hypothesized in biomechanics, biarticular actuators contribute to the efficiency of explosive movements in robotic systems similar to the human body. Despite the added weight of the redundant actuators, redundancy enables the proper selection of mono-articular actuators so that all the actuators operate in their optimum working points. It is important to notice that the energetic benefits of biarticular muscles have not been identified during human walking locomotion. Therefore the efficiency gain due to the addition of biarticulars can be limited in bipedal walking. Still, the technical advantage of the bi-articulation facilitates the mass distribution of the actuators over leg segments, specifically by reducing the mass of the shank segment in the robotic leg.

show abstract

RRLAB SEA — A highly integrated compliant actuator with minimised reflected inertia

Cited by 16 publications

References 15 publications

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

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

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

Technical advantages and disadvantages of biarticular actuators in bipedal robots

Contact Info

Product

Resources

About