This paper presents modeling, simulation and control architecture for implementing biped gait in an active lower limb exoskeleton. A lower body biped structure has been modeled in MATLAB Sim Mechanics according to ant...
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This paper addresses the topic of industrial robots built for handling processes used in cutting machining applications. The study discourses the machining of a globe calotte made of komatex using a Yamaha YK 400 SCAR...
This paper addresses the topic of industrial robots built for handling processes used in cutting machining applications. The study discourses the machining of a globe calotte made of komatex using a Yamaha YK 400 SCARA robot. Are presented aspects regarding the capabilities of Yamaha YK 400 robot, the development of the robot program, analyses of the proposed system and methods of improvement. A set of experimental analyses was conducted in order to identify correlations between the robot speed variation and distance between the points that describe the trajectory of the motion.
The original version of this article unfortunately contained a mistake. In Eqs. (1) to (3), the gas constant 'R' should be replaced with Boltzmann constant 'k .' This change accompanies the change in t...
The original version of this article unfortunately contained a mistake. In Eqs. (1) to (3), the gas constant 'R' should be replaced with Boltzmann constant 'k .' This change accompanies the change in the paragraph following Eq. (3) as below.
Legged robots based on one degree-of-freedom reconfigurable planar leg mechanisms, that are capable of generating multiple useful gaits, are highly desired due to the possibility of handling environments and tasks of ...
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Legged robots based on one degree-of-freedom reconfigurable planar leg mechanisms, that are capable of generating multiple useful gaits, are highly desired due to the possibility of handling environments and tasks of high complexity while maintaining simple control schemes. An essential consideration in these reconfigurable legged robots is to attain stability in motion, at rest as well as while transforming from one configuration to another with the minimum number of legs as long as the full range of their walking patterns, resulting from the different gait cycles of their legs, is achieved. To this end, in this paper, we present a method for the generation of input joint trajectories to properly synchronize the movement of quadruped robots with reconfigurable legs. The approach is exemplified in a four-legged robot with reconfigurable Jansen legs capable of generating up to six useful different gait cycles. The proposed technique is validated through simulated results that show the platform's stability across its six feasible walking patterns and during gait transition phases, thus considerably extending the capabilities of the non-reconfigurable design.
A locomotion control of a snake-like robot on geometrically smooth surface is developed. To design the motion control, a mathematical model of the snake-like robot is derived by Projection Method (PJ method). Utilizin...
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This manuscript presents the estimation of both position and velocity of Stewart manipulator using leg length measurements and MEMS inertial sensors. The estimation by using Unscented Kalman Filter (UKF) is based on t...
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ISBN:
(纸本)9781509025367
This manuscript presents the estimation of both position and velocity of Stewart manipulator using leg length measurements and MEMS inertial sensors. The estimation by using Unscented Kalman Filter (UKF) is based on the combination of different sensors. UKF is used as a nonlinear state estimator to the Stewart platform which is modeled as a stochastic differential equation due to measurement noise. The experimental results of the UKF are verified on the Stewart platform DELTALAB EX800 using LABVIEW real time software. The desired trajectories are compared with the estimated states (position and orientation) obtained using UKF. Moreover, the estimated leg lengths are compared with the real measured output from the potentiometer sensors of the six legs of the parallel manipulator. The experimental results show that the estimation error is bounded with small bound depending on the covariance matrices. This proves the effectiveness of the proposed Unscented Kalman Filter (UKF) as a nonlinear estimator with integration between inertial sensors and leg potentiometers.
This paper describes the development and control of a series elastic actuator based myoelectric knee exoskeleton which can be used for gait rehabilitation and load augmentation purposes. The device consists of a motor...
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This paper presents the estimation of both position and velocity of Stewart Manipulator by means of limbs potentiometer measurements and MEMS inertial sensors. The estimation used the Extended Kalman Filter (EKF) and...
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ISBN:
(纸本)9781509009374
This paper presents the estimation of both position and velocity of Stewart Manipulator by means of limbs potentiometer measurements and MEMS inertial sensors. The estimation used the Extended Kalman Filter (EKF) and H ∞ optimal filtering technique based on the combination of these sensors. The two types of filters are used as nonlinear state estimators to the Stewart platform which is modeled as a stochastic differential equations due to measurement noise in case of EKF and as a continuous time system model in case of H ∞ filtering technique. The results of the both filters are compared with each other on the Stewart platform DELTALAB EX800 using MATLAB SimMechanics toolbox. The simulation results show that Kalman filters are not the best choice for parallel manipulator state estimation as they bear from the hypothesis of statistical noise with zero mean as well as known noise covariance, which may reduce its performance. For these reasons, H ∞ filter may be the alternative of Kalman filter.
The pipelines for fluids transport have usually to support variable loadings, because of fluid pressure and temperature variation, but also as a result of some environmental effects. On the other hand, some possible e...
The pipelines for fluids transport have usually to support variable loadings, because of fluid pressure and temperature variation, but also as a result of some environmental effects. On the other hand, some possible errors in the use of equipments and machinery, around the pipes, may lead to accidentally introducing of stress raisers, having different types and sizes, on the pipe surfaces. The presence of stress raisers may lead to significant decreases of pipe lifetime duration. The paper is focused on some fatigue tests, made on specimens that were longitudinally cut from a steel pipe, used for oil transport. Three types of stress raisers were artificially introduced on the specimen surfaces, with spherical, conical, and respectively pyramidal shape, and with three different values of depth (obtained for different levels of down force on the corresponding indenter). The fatigue tests were conducted, using pulsating loading cycles, with the same maximum stress level, situated below the yield point of the steel. The number of loading cycles to failure was established, for each tested specimen, and on this basis it was possible to distinguish the influence of both the type and size of stress raiser, on the remaining lifetime duration, for the studied pipeline.
There have been few studies on the effects of stress raisers on the parts that are plastically deformed, at least into a certain extent of their volume. Such a situation may arrive near a stress raiser, when the peak ...
There have been few studies on the effects of stress raisers on the parts that are plastically deformed, at least into a certain extent of their volume. Such a situation may arrive near a stress raiser, when the peak stress value rises over the material yield stress limit. Some tensile tests are described in the paper, on flat aluminum specimens, with and without the presence of a stress raiser on their surface, namely a through frontal hole, at the center of their calibrated region. Some of the mechanical characteristics (yield limit, elongation at break, Young's modulus) were affected by the stress raiser presence, but its ductile behavior and tensile strength were not. The effective values of stress and strain concentration coefficients were calculated using the Neuber's rule, but the results may be considered as overestimated. The plastic strain enlargement in the specimen volume was also evaluated by measuring the Vickers microhardness values in the stress raiser vicinity. The tests results were shown that the plastic deformation is more pronounced for the measuring points that are closer to the hole's edge; that fact was confirmed by the specimens appearance, after the material failure. A hardness values ratio is finally proposed as an evaluation of the effective stress concentration coefficient.
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