scholarly journals Safety Operation of n-DOF Serial Hydraulic Manipulator in Constrained Motion with Consideration of Contact-Loss Fault

2020 ◽  
Vol 10 (22) ◽  
pp. 8107 ◽  
Author(s):  
Hoai Vu Anh Truong ◽  
Hoai An Trinh ◽  
Kyoung Kwan Ahn
Keyword(s):  
Impedance Control ◽  
Constrained Motion ◽  
Control Regulation ◽  
Smooth Motion ◽  
Adaptive Laws ◽  
Energy Variable ◽  
System Robustness ◽  
Hydraulic Manipulator ◽  
Safety Operation ◽  
Further Development

In consideration of accidental contact-loss due to step-change or accidentally moving out of a constrained framework, this paper focuses on solving this problem during working processes of an n-degree-of-freedom hydraulic manipulator (n-DOF manipulator). In order to overcome this phenomenon, a fault detection methodology-based virtual energy tank is employed with a shaping function to prevent the end-effector from damage or unexpected motion. This technique helps to detect when the contact-loss happens by a virtual energy variable; thus, decoupling a force control regulation. Moreover, a new trajectory for smooth motion after contact-loss detection is also discussed to increase system robustness. Additionally, to enhance tracking performance, adaptive laws are designed to compensate for system uncertainties. Comparative simulations are given on the n-DOF hydraulic manipulator to evaluate effectiveness of the impedance-based energy tank methodology under the sudden step-changed environment. Moreover, influences of control gains and setup energy parameters to the system behaviors when contact-loss happens are remarkably discussed as indispensable criteria for further development. The simulated results certified the superior effectiveness and reliability of the suggested methodology over the conventional impedance control for safe operation.

Adaptive Sliding Mode Impedance Control of Single-Link Flexible Manipulators interacting with the Environment at an Unknown Intermediate Point

Robotica ◽  
2019 ◽  
Vol 38 (9) ◽  
pp. 1642-1664 ◽  
Author(s):  
Ali Fayazi ◽  
Naser Pariz ◽  
Ali Karimpour ◽  
V. Feliu-Batlle ◽  
S. Hassan HosseinNia
Keyword(s):  
Position Control ◽  
Sliding Mode ◽  
Impedance Control ◽  
Detection Algorithm ◽  
Reference Trajectory ◽  
Constrained Motion ◽  
Intermediate Point ◽  
Control Scheme ◽  
Single Link ◽  
Motion Mode

SUMMARYThis paper proposes an adaptive robust impedance control for a single-link flexible arm when it encounters an environment at an unknown intermediate point. First, the intermediate collision point is estimated using a collision detection algorithm. The controller, then, switches from free to constrained motion mode. In the unconstrained motion mode, the exerted force to environment is nearly zero. Thus, the reference trajectory is a prescribed desired trajectory in position control. In the constrained motion mode, the reference trajectory is determined by the desired target dynamic impedance. The simulation results demonstrate the efficiency of proposed control scheme.

scholarly journals Robust position-based impedance control of lightweight single-link flexible robots interacting with the unknown environment via a fractional-order sliding mode controller

Robotica ◽  
2018 ◽  
Vol 36 (12) ◽  
pp. 1920-1942 ◽  
Author(s):  
Ali Fayazi ◽  
Naser Pariz ◽  
Ali Karimpour ◽  
Seyed Hassan Hosseinnia
Keyword(s):  
Fractional Order ◽  
Position Control ◽  
Sliding Mode ◽  
Impedance Control ◽  
Lyapunov Theory ◽  
Reference Trajectory ◽  
Constrained Motion ◽  
Unknown Environment ◽  
Control Scheme ◽  
Single Link

SUMMARYThis paper presents a fractional-order sliding mode control scheme equipped with a disturbance observer for robust impedance control of a single-link flexible robot arm when it comes into contact with an unknown environment. In this research, the impedance control problem is studied for both unconstrained and constrained maneuvers. The proposed control strategy is robust with respect to the changes of the environment parameters (such as stiffness and damping coefficient), the unknown Coulomb friction disturbances, payload, and viscous friction variations. The proposed control scheme is also valid for both unconstrained and constrained motions. Our novel approach automatically switches from the free to the constrained motion mode using a simple algorithm of contact detection. In this regard, an impedance control scheme is proposed with the inner loop position control. This means that in the free motion, the applied force to the environment is zero and the reference trajectory for the inner loop position control is the desired trajectory. However, in the constrained motion the reference trajectory for the inner loop is determined by the desired impedance dynamics. Stability of the closed loop control system is proved by Lyapunov theory. Several numerical simulations are carried out to indicate the capability and the effectiveness of the proposed control scheme.

scholarly journals Summary (I). Experiments

1987 ◽  
Vol 5 (3) ◽  
pp. 549-550
Author(s):  
J. Pace Vandevender
Keyword(s):  
Pulse Shaping ◽  
Impedance Control ◽  
Pulsed Power ◽  
Inertial Fusion ◽  
Channel Formation ◽  
Gas Switch ◽  
Considerable Work ◽  
Further Development ◽  
Kinetics Of ◽  
Target Design

The conference has shown some important advances toward the solution of problems required for inertial fusion. We can tentatively categorize as solved, or nearly solved, the following problems: Marx prefires, Marx jitter, gas-switch prefires, gas-switch jitter, power combination of multi-modules, high-current beam divergence (in barreltype, Applied-B/MID diodes), and preheat. In addition, there are a set of mature problems with promising solutions: pulsed power accelerator efficiency, ion sources, and the electron kinetics of an extractor ion diode. Newer problems that were addressed at the meeting but still require considerable work include: impedance control of efficient ion diodes, diagnostics for both beams and targets, the further development of target design tools and their experimental verification, targetfabrication processes to make the nearly perfect targets required for inertial fusion, channel formation and beam transport in those channels at the power levels required for fusion, and pulse-shaping.

Semi-Autonomous Control of a Multi-Arm Telemanipulator With Adaptive Impedance

2009 ◽  
Author(s):  
Jae H. Chung ◽  
Norman P. Coleman ◽  
Yushing Cheung
Keyword(s):  
Impedance Control ◽  
Time Varying ◽  
Communication Delays ◽  
Constrained Motion ◽  
Bilateral Control ◽  
Contact Stability ◽  
Switching Functions ◽  
Haptic Simulations ◽  
Amount Of Knowledge ◽  
Unconstrained Motion

This paper addresses problems to achieve transparency and contact stability for Single Master Multi-Slave telemanipulation that consists of unconstrained and constrained motions. The adaptive bilateral control with a local force compensator is developed based on adaptive impedance control and contact force driven compensation with auto-switching functions. With a limited amount of knowledge about robotic and environment dynamics and a time-varying communication delay, the developed method guarantees good adaptive tracking performance in unconstrained motion and reduction of oscillating contacts to keep a balance of the system in constrained motion. Based on an actual haptic device and virtual robots, haptic simulations are presented to demonstrate adaptive transparency and contact stability in the presence of communication delays.

Adaptive force reflecting teleoperation with local force compensators

Robotica ◽  
2007 ◽  
Vol 25 (4) ◽  
pp. 433-444 ◽  
Author(s):  
Yushing Cheung ◽  
Jae H. Chung ◽  
Daehie Hong
Keyword(s):  
Contact Force ◽  
Impedance Control ◽  
Communication Delay ◽  
Constrained Motion ◽  
Bilateral Control ◽  
Contact Stability ◽  
Switching Functions ◽  
Haptic Simulations ◽  
Adaptive Impedance Control ◽  
Unconstrained Motion

SUMMARYThis paper addresses problems to achieve transparency and contact stability for teleoperation that consists of unconstrained and constrained motions. The adaptive bilateral control with a local force compensator is developed, based on adaptive impedance control and contact force driven compensation with auto-switching functions. Without any knowledge about robotic and environment dynamics and with a communication delay, the developed method guarantees good adaptive tracking performance in unconstrained motion and reduction of oscillating contacts in constrained motion. Based on an actual haptic device and a virtual manipulator, haptic simulations are presented to demonstrate adaptive transparency and contact stability in the presence of communication delay.

Application of TEM to Deformation, Wear, and Fracture of Ceramics

1974 ◽  
Vol 32 ◽  
pp. 472-473
Author(s):  
B. J. Hockey
Keyword(s):  
Wear Resistance ◽  
High Temperature ◽  
Mechanical Behavior ◽  
Brittle Materials ◽  
High Temperature Strength ◽  
Wide Range ◽  
Corrosive Environments ◽  
Further Development

Ceramics, such as Al2O3 and SiC have numerous current and potential uses in applications where high temperature strength, hardness, and wear resistance are required often in corrosive environments. These materials are, however, highly anisotropic and brittle, so that their mechanical behavior is often unpredictable. The further development of these materials will require a better understanding of the basic mechanisms controlling deformation, wear, and fracture.The purpose of this talk is to describe applications of TEM to the study of the deformation, wear, and fracture of Al2O3. Similar studies are currently being conducted on SiC and the techniques involved should be applicable to a wide range of hard, brittle materials.

The stability of dislocation networks under various oxygen-doping conditions in superconducting Bi2Sr2CaCu2Oy single crystals and their influence on the flux pinning properties

1994 ◽  
Vol 52 ◽  
pp. 802-803
Author(s):  
Y. Feng ◽  
X. Y. Cai ◽  
R. J. Kelley ◽  
D. C. Larbalestier
Keyword(s):  
Single Crystals ◽  
Oxygen Content ◽  
Basal Plane ◽  
Flux Pinning ◽  
Pinning Centers ◽  
Before And After ◽  
Anomalous Peak ◽  
Basal Plane Dislocation ◽  
The Stability ◽  
Further Development

The issue of strong flux pinning is crucial to the further development of high critical current density Bi-Sr-Ca-Cu-O (BSCCO) superconductors in conductor-like applications, yet the pinning mechanisms are still much debated. Anomalous peaks in the M-H (magnetization vs. magnetic field) loops are commonly observed in Bi2Sr2CaCu2Oy (Bi-2212) single crystals. Oxygen vacancies may be effective flux pinning centers in BSCCO, as has been found in YBCO. However, it has also been proposed that basal-plane dislocation networks also act as effective pinning centers. Yang et al. proposed that the characteristic scale of the basal-plane dislocation networksmay strongly depend on oxygen content and the anomalous peak in the M-H loop at ˜20-30K may be due tothe flux pinning of decoupled two-dimensional pancake vortices by the dislocation networks. In light of this, we have performed an insitu observation on the dislocation networks precisely at the same region before and after annealing in air, vacuumand oxygen, in order to verify whether the dislocation networks change with varying oxygen content Inall cases, we have not found any noticeable changes in dislocation structure, regardless of the drastic changes in Tc and the anomalous magnetization. Therefore, it does not appear that the anomalous peak in the M-H loops is controlled by the basal-plane dislocation networks.

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