Design of a series elastic actuator for a compliant parallel wrist rehabilitation robot

Sergi, Fabrizio; Lee, Melissa M.; O’Malley, Marcia K.

doi:10.1109/icorr.2013.6650481

Cited by 26 publications

(19 citation statements)

References 19 publications

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“…The resultant bandwidth, highlighted in Fig. 6, is approximately 9.5 Hz, which is comparable to similar devices [22]. The compliance of the actuator acts to lessen the force bandwidth of the system as compared to a rigid actuator [24].…”

Section: A Force Controlmentioning

confidence: 80%

“…The design of the sensor is an extension of the Hall effect based sensor presented by Sergi et al [22]. To design the custom Hall effect sensor, we simulated the magnetic fields using the 2D freeware magnetic simulator FEMM.…”

Section: B Actuator Componentsmentioning

confidence: 99%

“…To read the full spring compression, the sensor needs a range of 21.6 mm. For sensor error, similar sensor designs have used 3−5% of full state output as an acceptable error limit [22]. To achieve this optimization, the magnetic field and the 1D slice read by a single sensor were designed.…”

Section: B Actuator Componentsmentioning

confidence: 99%

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A cable-based series elastic actuator with conduit sensor for wearable exoskeletons

Blumenschein

McDonald

O’Malley

2017

2017 IEEE International Conference on Robotics and Automation (ICRA)

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Abstract-There is currently a scarcity of wearable robotic devices that can practically provide physical assistance in a range of real world activities. Soft wearable exoskeletons, or exosuits, have the potential to be more portable and less restrictive than their rigid counterparts. In this paper, we present the design of an actuation system that has been optimized for use in a soft exosuit for the human arm. The selected design comprises a DC motor and gearbox, a flexible cable conduit transmission, and a custom series elastic force sensor. Placed in series with the transmission conduit, the custom compliant force sensor consists of a translational steel compression spring with a pair of Hall effect sensors for measuring deflection. The custom sensor is validated as an accurate means of measuring cable tension, and it is shown that it can be used in feedback to control the cable tension with high bandwidth. The dynamic effect of the cable-conduit transmission on the force felt at the user interface is characterized by backdriving the system as it renders a range of virtual impedances to the user. We conclude with recommendations for the integration of such an actuation system into a full wearable exosuit.

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Section: A Force Controlmentioning

confidence: 80%

Section: B Actuator Componentsmentioning

confidence: 99%

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A cable-based series elastic actuator with conduit sensor for wearable exoskeletons

Blumenschein

McDonald

O’Malley

2017

2017 IEEE International Conference on Robotics and Automation (ICRA)

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“…The ease with which impedance controlled SEAs can actively render low output impedances is also particularly valuable in haptics, rehabilitation robotics, and human augmentation systems (e.g. [7], [8], and [9]) where importance is placed on achieving both safety and device transparency for the user. A variety of impedance control architectures have been proposed for series elastic actuators.…”

Section: Introductionmentioning

confidence: 99%

Leveraging disturbance observer based torque control for improved impedance rendering with series elastic actuators

Mehling

Holley

O’Malley

2015

2015 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)

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The fidelity with which series elastic actuators (SEAs) render desired impedances is important. Numerous approaches to SEA impedance control have been developed under the premise that high-precision actuator torque control is a prerequisite. Indeed, the design of an inner torque compensator has a significant impact on actuator impedance rendering. The disturbance observer (DOB) based torque control implemented in NASA's Valkyrie robot is considered here and a mathematical model of this torque control, cascaded with an outer impedance compensator, is constructed. While previous work has examined the impact a disturbance observer has on torque control performance, little has been done regarding DOBs and impedance rendering accuracy. Both simulation and a series of experiments are used to demonstrate the significant improvements possible in an SEA's ability to render desired dynamic behaviors when utilizing a DOB. Actuator transparency at low impedances is improved, closed loop hysteresis is reduced, and the actuator's dynamic response to both commands and interaction torques more faithfully matches that of the desired model. All of this is achieved by leveraging DOB based control rather than increasing compensator gains, thus making improved SEA impedance control easier to achieve in practice.

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“…Parallel robots with flexure joints have also been studied, including and flexure-jointed 6 DOF platforms [18]- [21], high-precision robots [22], [23], mechanisms for micro/nano-manipulation [24], [25], and 3 DOF translation platforms [26]. In medical robotics, parallel robots with elastic actuation and flexure joints have been developed for rehabilitation [27], [28], and capsule endoscopy [29]. Parallel continuum robots differ in that they exhibit large, nonlinear, link deflections by design, and bending is distributed along the entire link rather than lumped at a specific a point.…”

Section: Introductionmentioning

confidence: 99%

Toward parallel continuum manipulators

Bryson

Rucker

2014

2014 IEEE International Conference on Robotics and Automation (ICRA)

113

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In this paper, we investigate continuum manipulators that are analogous to conventional rigid-link parallel robot designs. These "parallel continuum manipulators" have the potential to inherit some of the compactness and compliance of continuum robots while retaining some of the precision, stability, and strength of rigid-link parallel robots, yet they represent a relatively unexplored area of the broad manipulator design space. We describe the construction of a prototype manipulator structure with six compliant legs connected in a parallel pattern similar to that of a Stewart-Gough platform. We formulate the static forward and inverse kinematics problems for such manipulators as the solution to multiple Cosserat-rod models with coupled boundary conditions, and we test the accuracy of this approach in a set of experiments, including the prediction of leg buckling. An inverse kinematics simulation of slices through the 6 degree-of-freedom (DOF) workspace illustrates the kinematic mapping, range of motion, and force required for actuation, which sheds light on the potential advantages and tradeoffs that parallel continuum manipulators may bring. Potential applications include miniature wrists and arms for endoscopic medical procedures, and lightweight compliant arms for safe interaction with humans.

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Design of a series elastic actuator for a compliant parallel wrist rehabilitation robot

Cited by 26 publications

References 19 publications

A cable-based series elastic actuator with conduit sensor for wearable exoskeletons

A cable-based series elastic actuator with conduit sensor for wearable exoskeletons

Leveraging disturbance observer based torque control for improved impedance rendering with series elastic actuators

Toward parallel continuum manipulators

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