Actuators

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391 KiB

Open AccessArticle

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

by Martin Grimmer, Mahdy Eslamy and André Seyfarth

Actuators 2014, 3(1), 1-19; https://doi.org/10.3390/act3010001 - 27 Feb 2014

Cited by 54 | Viewed by 12889

Abstract

A monoarticular series elastic actuator (SEA) reduces energetic and peak power requirements compared to a direct drive (DD) in active prosthetic ankle-foot design. Simulation studies have shown that similar advantages are possible for the knee joint. The aims of this paper were to [...] Read more.

A monoarticular series elastic actuator (SEA) reduces energetic and peak power requirements compared to a direct drive (DD) in active prosthetic ankle-foot design. Simulation studies have shown that similar advantages are possible for the knee joint. The aims of this paper were to investigate the advantages of a monoarticular SEA-driven hip joint and to quantify the energetic benefit of an SEA-driven leg (with monoarticular hip, knee and ankle SEAs), assuming that damping (negative power) is passively achieved. The hip SEA provided minor energetic advantages in walking (up to 29%) compared to the knee and the ankle SEA. Reductions in required peak power were observed only for speeds close to preferred walking speed (18% to 27%). No energetic advantages were found in running, where a DD achieved the best performance when optimizing for energy. Using an SEA at each leg joint in the sagittal plane reduced the positive work by 14% to 39% for walking and by 37% to 75% for running. When using an SEA instead of a DD, the contribution of the three leg joints to doing positive work changed: the knee contributed less and the hip more positive work. For monoarticular SEAs, the ankle joint motor did most of the positive work. Full article

(This article belongs to the Special Issue Human Centered Actuators)

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650 KiB

Open AccessArticle

Double-Acting Sleeve Muscle Actuator for Bio-Robotic Systems

by Hao Zheng and Xiangrong Shen

Actuators 2013, 2(4), 129-144; https://doi.org/10.3390/act2040129 - 25 Nov 2013

Cited by 11 | Viewed by 9926

Abstract

This paper presents a new type of muscle-like actuator, namely double-acting (DA) sleeve muscle actuator, which is suitable for the actuation of biologically-inspired and biomedical robotic systems, especially those serving human-assistance purposes (prostheses, orthoses, etc.). Developed based on the traditional pneumatic muscle [...] Read more.

This paper presents a new type of muscle-like actuator, namely double-acting (DA) sleeve muscle actuator, which is suitable for the actuation of biologically-inspired and biomedical robotic systems, especially those serving human-assistance purposes (prostheses, orthoses, etc.). Developed based on the traditional pneumatic muscle actuator, the new DA sleeve muscle incorporates a unique insert at the center. With the insert occupying the central portion of the internal volume, this new actuator enjoys multiple advantages relative to the traditional pneumatic muscle, including a consistent increase of force capacity over the entire range of motion, and a significant decrease of energy consumption in operation. Furthermore, the insert encompasses an additional chamber, which generates an extension force when pressurized. As such, this new actuator provides a unique bi-directional actuation capability, and, thus, has a potential to significantly simplify the design of a muscle actuator-powered robotic system. To demonstrate this new actuator concept, a prototype has been designed and fabricated, and experiments conducted on this prototype demonstrated the enhanced force capacity and the unique bi-directional actuation capability. Full article

(This article belongs to the Special Issue Human Centered Actuators)

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397 KiB

Open AccessArticle

Self-Sensing Control of Nafion-Based Ionic Polymer-Metal Composite (IPMC) Actuator in the Extremely Low Humidity Environment

by Minoru Sasaki, Wenyi Lin, Hirohisa Tamagawa, Satoshi Ito and Keiko Kikuchi

Actuators 2013, 2(4), 74-85; https://doi.org/10.3390/act2040074 - 1 Oct 2013

Cited by 9 | Viewed by 9771

Abstract

This paper presents feedforward, feedback and two-degree-of-freedom control applied to an Ionic Polymer-Metal Composite (IPMC) actuator. It presents a high potential for development of miniature robots and biomedical devices and artificial muscles. We have reported in the last few years that dehydration treatment [...] Read more.

This paper presents feedforward, feedback and two-degree-of-freedom control applied to an Ionic Polymer-Metal Composite (IPMC) actuator. It presents a high potential for development of miniature robots and biomedical devices and artificial muscles. We have reported in the last few years that dehydration treatment improves the electrical controllability of bending in Selemion CMV-based IPMCs. We tried to replicate this controllability in Nafion-based IPMC. We found that the displacement of a Nafion-based IPMC was proportional to the total charge imposed, just as in the Selemion-CMV case. This property is the basis of self-sensing controllers for Nafion-based IPMC bending behavior: we perform bending curvature experiments on Nafion-based IPMCs, obtaining the actuator's dynamics and transfer function. From these, we implemented self-sensing controllers using feedforward, feedback and two-degree-of-freedom techniques. All three controllers performed very well with the Nafion-based IPMC actuator. Full article

(This article belongs to the Special Issue Human Centered Actuators)

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697 KiB

Open AccessArticle

Concept of a Series-Parallel Elastic Actuator for a Powered Transtibial Prosthesis

by Glenn Mathijssen, Pierre Cherelle, Dirk Lefeber and Bram Vanderborght

Actuators 2013, 2(3), 59-73; https://doi.org/10.3390/act2030059 - 3 Jul 2013

Cited by 33 | Viewed by 11365

Abstract

The majority of the commercial transtibial prostheses are purely passive devices. They store energy in an elastic element during the beginning of a step and release it at the end. A 75 kg human, however, produces on average 26 J of energy during [...] Read more.

The majority of the commercial transtibial prostheses are purely passive devices. They store energy in an elastic element during the beginning of a step and release it at the end. A 75 kg human, however, produces on average 26 J of energy during one stride at the ankle joint when walking at normal cadence and stores/releases 9 J of energy, contributing to energy efficient locomotion. According to Winter, a subject produces on average of 250W peak power at a maximum joint torque of 125 Nm. As a result, powering a prosthesis with traditional servomotors leads to excessive motors and gearboxes at the outer extremities of the legs. Therefore, research prototypes use series elastic actuation (SEA) concepts to reduce the power requirements of the motor. In the paper, it will be shown that SEAs are able to reduce the power of the electric motor, but not the torque. To further decrease the motor size, a novel human-centered actuator concept is developed, which is inspired by the variable recruitment of muscle fibers of a human muscle. We call this concept series-parallel elastic actuation (SPEA), and the actuator consists of multiple parallel springs, each connected to an intermittent mechanism with internal locking and a single motor. As a result, the motor torque requirements can be lowered and the efficiency drastically increased. In the paper, the novel actuation concept is explained, and a comparative study between a stiff motor, an SEA and an SPEA, which all aim at mimicking human ankle behavior, is performed. Full article

(This article belongs to the Special Issue Human Centered Actuators)

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9391 KiB

Open AccessArticle

Optimal Passive Dynamics for Physical Interaction: Catching a Mass

by Kevin Kemper, Hamid Reza Vejdani, Brent Piercy and Jonathan Hurst

Actuators 2013, 2(2), 45-58; https://doi.org/10.3390/act2020045 - 2 May 2013

Cited by 3 | Viewed by 7100

Abstract

For manipulation tasks in uncertain environments, intentionally designed series impedance in mechanical systems can provide significant benefits that cannot be achieved in software. Traditionally, the design of actuated systems revolves around sizing torques, speeds, and control strategies without considering the system’s passive dynamics. [...] Read more.

For manipulation tasks in uncertain environments, intentionally designed series impedance in mechanical systems can provide significant benefits that cannot be achieved in software. Traditionally, the design of actuated systems revolves around sizing torques, speeds, and control strategies without considering the system’s passive dynamics. However, the passive dynamics of the mechanical system, including inertia, stiffness, and damping along with other parameters such as torque and stroke limits often impose performance limitations that cannot be overcome with software control. In this paper, we develop relationships between an actuator’s passive dynamics and the resulting performance for the purpose of better understanding how to tune the passive dynamics for catching an unexpected object. We use a mathematically optimal controller subject to force limitations to stop the incoming object without breaking contact and bouncing. The use of an optimal controller is important so that our results directly reflect the physical system’s performance. We analytically calculate the maximum velocity that can be caught by a realistic actuator with limitations such as force and stroke limits. The results show that in order to maximize the velocity of an object that can be caught without exceeding the actuator’s torque and stroke limits, a soft spring along with a strong damper will be desired. Full article

(This article belongs to the Special Issue Human Centered Actuators)

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617 KiB

Open AccessArticle

Analysis and Modeling of Linear-Switched Reluctance for Medical Application

by Jean-Francois Llibre, Nicolas Martinez, Pascal Leprince and Bertrand Nogarede

Actuators 2013, 2(2), 27-44; https://doi.org/10.3390/act2020027 - 22 Apr 2013

Cited by 15 | Viewed by 10667

Abstract

This paper focuses on the analysis, the modeling and the control of a linear-switched reluctance motor. The application under consideration is medical, and the actuator is to be used as a left ventricular assist device. The actuator has a cylindrical or tubular shape, [...] Read more.

This paper focuses on the analysis, the modeling and the control of a linear-switched reluctance motor. The application under consideration is medical, and the actuator is to be used as a left ventricular assist device. The actuator has a cylindrical or tubular shape, with a mechanical unidirectional valve placed inside the mover, which provides a pulsatile flow of blood. The analytical expression of the effort based on the linear behavior of the actuator is given. The identification of the characteristics of the prototype actuator and the principle of position control is performed. A modeling of the actuator is proposed, taking into account the variation of inductance with respect to the position. The closed-loop position control of the actuator is performed by simulation. A controller with integral action and anticipatory action is implemented in order to compensate the effects of disturbing efforts and tracking deviations. Moreover, a magic switch is performed in the controller to avoid overshoots. The results show that the closed-loop response of the actuator is satisfactory. Full article

(This article belongs to the Special Issue Human Centered Actuators)

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855 KiB

Open AccessArticle

Optically Driven Mobile Integrated Micro-Tools for a Lab-on-a-Chip

by Yi-Jui Liu, Yi-Hsiung Lee, Yu-Sheng Lin, Chingfu Tsou, Patrice L. Baldeck and Chih-Lang Lin

Actuators 2013, 2(2), 19-26; https://doi.org/10.3390/act2020019 - 11 Apr 2013

Cited by 12 | Viewed by 8515

Abstract

This study proposes an optically driven complex micromachine with an Archimedes microscrew as the mechanical power, a sphere as a coupler, and three knives as the mechanical tools. The micromachine is fabricated by two-photon polymerization and is portably driven by optical tweezers. Because [...] Read more.

This study proposes an optically driven complex micromachine with an Archimedes microscrew as the mechanical power, a sphere as a coupler, and three knives as the mechanical tools. The micromachine is fabricated by two-photon polymerization and is portably driven by optical tweezers. Because the microscrew can be optically trapped and rotates spontaneously, it provides driving power for the complex micro-tools. In other words, when a laser beam focuses on the micromachine, the microscrew is trapped toward the focus point and simultaneously rotates. A demonstration showed that the integrated micromachines are grasped by the optical tweezers and rotated by the Archimedes screw. The rotation efficiencies of the microrotors with and without knives are 1.9 rpm/mW and 13.5 rpm/mW, respectively. The micromachine can also be portably dragged along planed routes. Such Archimedes screw-based optically driven complex mechanical micro-tools enable rotation similar to moving machines or mixers, which could contribute to applications for a biological microfluidic chip or a lab-on-a-chip. Full article

(This article belongs to the Special Issue Human Centered Actuators)

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369 KiB

Open AccessArticle

State Space System Identification of 3-Degree-of-Freedom (DOF) Piezo-Actuator-Driven Stages with Unknown Configuration

by Yu Cao and Xiongbiao Chen

Actuators 2013, 2(1), 1-18; https://doi.org/10.3390/act2010001 - 8 Mar 2013

Cited by 5 | Viewed by 8849

Abstract

Due to their fast response, high accuracy and non-friction force, piezo-actuators have been widely employed in multiple degree-of-freedom (DOF) stages for various nano-positioning applications. The use of flexible hinges in these piezo-actuator-driven stages allows the elimination of the influence of friction and backlash [...] Read more.

Due to their fast response, high accuracy and non-friction force, piezo-actuators have been widely employed in multiple degree-of-freedom (DOF) stages for various nano-positioning applications. The use of flexible hinges in these piezo-actuator-driven stages allows the elimination of the influence of friction and backlash clearance, as observed in other configurations; meanwhile it also causes more complicated stage performance in terms of dynamics and the cross-coupling effect between different axes. Based on the system identification technique, this paper presents the development of a model for the 3-DOF piezo-actuator-driven stages with unknown configuration, with its parameters estimated from the Hankel matrix by means of the maximum a posteriori (MAP) online estimation. Experiments were carried out on a commercially-available piezo-actuator-driven stage to verify the effectiveness of the developed model, as compared to other methods. The results show that the developed model is able to predict the stage performance with improved accuracy, while the model parameters can be well updated online by using the MAP estimation. These capabilities allow investigation of the complicated stage performance and also provide a starting point from which the mode-based control scheme can be established for improved performance. Full article

(This article belongs to the Special Issue Human Centered Actuators)

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Review

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417 KiB

Open AccessReview

Overview of Actuated Arm Support Systems and Their Applications

by B. Van Ninhuijs, L.A. Van der Heide, J.W. Jansen, B.L.J. Gysen, D.J. Van der Pijl and E.A. Lomonova

Actuators 2013, 2(4), 86-110; https://doi.org/10.3390/act2040086 - 2 Oct 2013

Cited by 20 | Viewed by 15521

Abstract

Arm support systems provide support throughout daily tasks, training or in an industrial environment. During the last decades a large diversity of actuated arm support systems have been developed. To analyze the actuation principles in these systems, an overview of actuated arm support [...] Read more.

Arm support systems provide support throughout daily tasks, training or in an industrial environment. During the last decades a large diversity of actuated arm support systems have been developed. To analyze the actuation principles in these systems, an overview of actuated arm support systems is provided. This overview visualizes the current trends on research and development of these support systems and distinguishes three categories. These categories depend mainly on the functional status of the user environment, which defines the specifications. Therefore, the actuated arm support systems are classified according to their user environment, namely: ambulatory, rehabilitation and industrial. Furthermore, three main actuation principles and three mechanical construction principles have been identified. Full article

(This article belongs to the Special Issue Human Centered Actuators)

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