25,082 research outputs found
A Passivity-based Nonlinear Admittance Control with Application to Powered Upper-limb Control under Unknown Environmental Interactions
This paper presents an admittance controller based on the passivity theory
for a powered upper-limb exoskeleton robot which is governed by the nonlinear
equation of motion. Passivity allows us to include a human operator and
environmental interaction in the control loop. The robot interacts with the
human operator via F/T sensor and interacts with the environment mainly via
end-effectors. Although the environmental interaction cannot be detected by any
sensors (hence unknown), passivity allows us to have natural interaction. An
analysis shows that the behavior of the actual system mimics that of a nominal
model as the control gain goes to infinity, which implies that the proposed
approach is an admittance controller. However, because the control gain cannot
grow infinitely in practice, the performance limitation according to the
achievable control gain is also analyzed. The result of this analysis indicates
that the performance in the sense of infinite norm increases linearly with the
control gain. In the experiments, the proposed properties were verified using 1
degree-of-freedom testbench, and an actual powered upper-limb exoskeleton was
used to lift and maneuver the unknown payload.Comment: Accepted in IEEE/ASME Transactions on Mechatronics (T-MECH
Comfort-Centered Design of a Lightweight and Backdrivable Knee Exoskeleton
This paper presents design principles for comfort-centered wearable robots
and their application in a lightweight and backdrivable knee exoskeleton. The
mitigation of discomfort is treated as mechanical design and control issues and
three solutions are proposed in this paper: 1) a new wearable structure
optimizes the strap attachment configuration and suit layout to ameliorate
excessive shear forces of conventional wearable structure design; 2) rolling
knee joint and double-hinge mechanisms reduce the misalignment in the sagittal
and frontal plane, without increasing the mechanical complexity and inertia,
respectively; 3) a low impedance mechanical transmission reduces the reflected
inertia and damping of the actuator to human, thus the exoskeleton is
highly-backdrivable. Kinematic simulations demonstrate that misalignment
between the robot joint and knee joint can be reduced by 74% at maximum knee
flexion. In experiments, the exoskeleton in the unpowered mode exhibits 1.03 Nm
root mean square (RMS) low resistive torque. The torque control experiments
demonstrate 0.31 Nm RMS torque tracking error in three human subjects.Comment: 8 pages, 16figures, Journa
Collision Detection and Reaction: A Contribution to Safe Physical Human-Robot Interaction
In the framework of physical Human-Robot Interaction
(pHRI), methodologies and experimental tests are
presented for the problem of detecting and reacting to collisions
between a robot manipulator and a human being. Using a
lightweight robot that was especially designed for interactive
and cooperative tasks, we show how reactive control strategies
can significantly contribute to ensuring safety to the human
during physical interaction. Several collision tests were carried
out, illustrating the feasibility and effectiveness of the proposed
approach. While a subjective “safety” feeling is experienced by
users when being able to naturally stop the robot in autonomous
motion, a quantitative analysis of different reaction strategies
was lacking. In order to compare these strategies on an objective
basis, a mechanical verification platform has been built. The
proposed collision detection and reactions methods prove to
work very reliably and are effective in reducing contact forces
far below any level which is dangerous to humans. Evaluations
of impacts between robot and human arm or chest up to a
maximum robot velocity of 2.7 m/s are presented
A flexible sensor technology for the distributed measurement of interaction pressure
We present a sensor technology for the measure of the physical human-robot interaction pressure developed in the last years at Scuola Superiore Sant'Anna. The system is composed of flexible matrices of opto-electronic sensors covered by a soft silicone cover. This sensory system is completely modular and scalable, allowing one to cover areas of any sizes and shapes, and to measure different pressure ranges. In this work we present the main application areas for this technology. A first generation of the system was used to monitor human-robot interaction in upper- (NEUROExos; Scuola Superiore Sant'Anna) and lower-limb (LOPES; University of Twente) exoskeletons for rehabilitation. A second generation, with increased resolution and wireless connection, was used to develop a pressure-sensitive foot insole and an improved human-robot interaction measurement systems. The experimental characterization of the latter system along with its validation on three healthy subjects is presented here for the first time. A perspective on future uses and development of the technology is finally drafted
An advanced telerobotic system for shuttle payload changeout room processing applications
To potentially alleviate the inherent difficulties in the ground processing of the Space Shuttle and its associated payloads, a teleoperated, semi-autonomous robotic processing system for the Payload Changeout Room (PCR) is now in the conceptual stages. The complete PCR robotic system as currently conceived is described and critical design issues and the required technologies are discussed
Folding Assembly by Means of Dual-Arm Robotic Manipulation
In this paper, we consider folding assembly as an assembly primitive suitable
for dual-arm robotic assembly, that can be integrated in a higher level
assembly strategy. The system composed by two pieces in contact is modelled as
an articulated object, connected by a prismatic-revolute joint. Different
grasping scenarios were considered in order to model the system, and a simple
controller based on feedback linearisation is proposed, using force torque
measurements to compute the contact point kinematics. The folding assembly
controller has been experimentally tested with two sample parts, in order to
showcase folding assembly as a viable assembly primitive.Comment: 7 pages, accepted for ICRA 201
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