Variable admittance control preventing undesired oscillating behaviors in physical human-robot interaction

Landi, Chiara Talignani; Ferraguti, Federica; Secchi, Cristian; Bonfè, Marcello; Fantuzzi, Cesare

doi:10.1109/iros.2017.8206207

Cited by 35 publications

(19 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It would thus be tempting to minimize or even suppress this term to decrease time lag, however, we observed empirically that both terms (inertia and damping) are required to stabilize the exoskeleton during human-robot interaction. More specifically, stability was enhanced when the ratio between inertia and damping remained constant, as shown in other studies [105][106][107]. Finally, since the worm screw can shift up relative to the worm wheel due to the oblong fixation points, our experience showed that the safety of the user's wrist and the mechanics are preserved in case of unexpected high torque.…”

Section: Design Choices and Performance Characterizationsupporting

confidence: 77%

Characterization and wearability evaluation of a fully portable wrist exoskeleton for unsupervised training after stroke

Lambelet

Temiraliuly

Siegenthaler

et al. 2020

J NeuroEngineering Rehabil

View full text Add to dashboard Cite

Background Chronic hand and wrist impairment are frequently present following stroke and severely limit independence in everyday life. The wrist orientates and stabilizes the hand before and during grasping, and is therefore of critical importance in activities of daily living (ADL). To improve rehabilitation outcomes, classical therapy could be supplemented by novel therapies that can be applied in unsupervised settings. This would enable more distributed practice and could potentially increase overall training dose. Robotic technology offers new possibilities to address this challenge, but it is critical that devices for independent training are easy and appealing to use. Here, we present the development, characterization and wearability evaluation of a fully portable exoskeleton for active wrist extension/flexion support in stroke rehabilitation. Methods First we defined the requirements, and based on these, constructed the exoskeleton. We then characterized the device with standardized haptic and human-robot interaction metrics. The exoskeleton is composed of two modules placed on the forearm/hand and the upper arm. These modules weigh 238 g and 224 g, respectively. The forearm module actively supports wrist extension and flexion with a torque up to 3.7 Nm and an angular velocity up to 530 deg/s over a range of 154∘. The upper arm module includes the control electronics and battery, which can power the device for about 125 min in normal use. Special emphasis was put on independent donning and doffing of the device, which was tested via a wearability evaluation in 15 healthy participants and 2 stroke survivors using both qualitative and quantitative methods. Results All participants were able to independently don and doff the device after only 4 practice trials. For healthy participants the donning and doffing process took 61 ±15 s and 24 ±6 s, respectively. The two stroke survivors donned and doffed the exoskeleton in 54 s/22 s and 113 s/32 s, respectively. Usability questionnaires revealed that despite minor difficulties, all participants were positive regarding the device. Conclusions This study describes an actuated wrist exoskeleton which weighs less than 500 g, and which is easy and fast to don and doff with one hand. Our design has put special emphasis on the donning aspect of robotic devices which constitutes the first barrier a user will face in unsupervised settings. The proposed device is a first and intermediate step towards wearable rehabilitation technologies that can be used independently by the patient and in unsupervised settings.

show abstract

Section: Design Choices and Performance Characterizationsupporting

confidence: 77%

Characterization and wearability evaluation of a fully portable wrist exoskeleton for unsupervised training after stroke

Lambelet

Temiraliuly

Siegenthaler

et al. 2020

J NeuroEngineering Rehabil

View full text Add to dashboard Cite

show abstract

“…A suitable control strategy for implementing desired dynamics on industrial robots is the admittance control [39]. This strategy has been exploited in many different fields, see, e.g., [23] for a surgical application, [40] for a human-robot interaction scenario, and also [12] for robotic simulators for space applications.…”

Section: Problem Statementmentioning

confidence: 99%

A Passivity-Based Approach for Simulating Satellite Dynamics With Robots: Discrete-Time Integration and Time-Delay Compensation

2020

Self Cite

View full text Add to dashboard Cite

This article proposes a passivity-based approach for simulating satellite dynamics on a position-controlled robot equipped with a force-torque sensor. Time delays intrinsic in the computational loop and discrete-time integration degrade the behavior of the satellite dynamics reproduced by the robot. These factors can generate an energy-inconsistent simulation and can even render the system unstable. In this article, time delay and discrete-time integration effects are analyzed from an energetic perspective and compensated through a passivity-based control strategy to ensure a faithful and stable dynamic simulation with position-controlled robots. The benefit of the proposed strategy is validated by simulations and experiments on the On-Orbit Servicing Simulator (OOS-SIM), a robotic facility used for simulating free-floating dynamics.

show abstract

“…Energy tanks have been used for guaranteeing a non conservative but passive behavior in interactive systems (see e.g., [19][20][21]). With the capability of storing the dissipated energy of the system, energy tanks allow to implement a passive inertia variation ( [22,23]) and a stiffness variation ( [13]) in admittance control. Nevertheless, we propose a strategy that allows to vary the stiffness parameter in admittance controlled robots.…”

Section: Introductionmentioning

confidence: 99%

A Passivity-Based Strategy for Manual Corrections in Human-Robot Coaching

et al. 2019

Self Cite

View full text Add to dashboard Cite

In recent years, new programming techniques have been developed in the human-robot collaboration (HRC) field. For example, walk-through programming allows to program the robot in an easy and intuitive way. In this context, a modification of a portion of the trajectory usually requires the teaching of the path from the beginning. In this paper we propose a passivity-based method to locally change a trajectory based on a manual human correction. At the beginning the robot follows the nominal trajectory, encoded through the Dynamical Movement Primitives, by setting high control gains. When the human grasps the end-effector, the robot is made compliant and he/she can drive it along the correction. The correction is optimally joined to the nominal trajectory, resuming the path tracking. In order to avoid unstable behaviors, the variation of the control gains is performed exploiting energy tanks, preserving the passivity of the interaction. Finally, the correction is spatially fixed so that a variation in the boundary conditions (e.g., the initial/final points) does not affect the modification.

show abstract

Variable admittance control preventing undesired oscillating behaviors in physical human-robot interaction

Cited by 35 publications

References 9 publications

Characterization and wearability evaluation of a fully portable wrist exoskeleton for unsupervised training after stroke

Characterization and wearability evaluation of a fully portable wrist exoskeleton for unsupervised training after stroke

A Passivity-Based Approach for Simulating Satellite Dynamics With Robots: Discrete-Time Integration and Time-Delay Compensation

A Passivity-Based Strategy for Manual Corrections in Human-Robot Coaching

Contact Info

Product

Resources

About