A foot contact model is an important component of any forward-dynamic human gait simulation. This work presents a preliminary experimental validation of a three-dimensional (3D) foot contact model that represents the ...
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ISBN:
(纸本)9783319107233;9783319107226
A foot contact model is an important component of any forward-dynamic human gait simulation. This work presents a preliminary experimental validation of a three-dimensional (3D) foot contact model that represents the heel and forefoot using a pair of contact disks. The disk elements are well-suited to modeling the foot because they are computationally efficient and are mechanically stable when flat on the ground. We evaluated the foot model by comparing its ankle position to the subject's ankle position (measured using skin-mounted reflective markers and infrared cameras) when both feet developed the same ground reaction force (GRF) and center-of-pressure (COP) profiles (measured using a force plate). We used this novel approach because the experimental GRF and COP measurements are accurate, but the kinematic data is usually corrupted with 1 cm of skin-movement error at the foot. The results indicate that the disk-based foot model is an accurate representation of the subject's barefoot except during toe-off, and when the COP is on the extreme medial boundaries of the foot. The experimental data and foot model presented in this work is provided as supplementary material online.
Maintaining the efficiency of AC motors in site equipment is important, given the increasing cost of energy. Reduction of motor efficiency from baseline manufacturer data can go undetected until total failure of the e...
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ISBN:
(纸本)9783319099170
Maintaining the efficiency of AC motors in site equipment is important, given the increasing cost of energy. Reduction of motor efficiency from baseline manufacturer data can go undetected until total failure of the equipment is experienced. This paper introduces motor current signature analysis methods used to detect the early onset of motor efficiency reduction in AC motors controlled by modern Sensorless-Vector Variable Speed Control inverters. A step increase in the resistance of one stator winding is simulated in stages. Off-line processing of motor current data signals using data analysis methods developed for the MATLAB platform is used to identify imbalances caused by subtle stator resistance increases. Initial results indicate that small increases in stator resistances can be observed in the motor current signals received after data processing techniques have been used on the measured signals. The test results are presented herein along with details on the research work to be continued.
This paper focuses on cable-suspended parallel robots (CSPRs), a subclass of cable-driven parallel robots, and particularly on the analysis of their workspace. CSPRs present, among other interesting characteristics, l...
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ISBN:
(纸本)9783319094892;9783319094885
This paper focuses on cable-suspended parallel robots (CSPRs), a subclass of cable-driven parallel robots, and particularly on the analysis of their workspace. CSPRs present, among other interesting characteristics, large workspaces and high reconfigurability, which make them attractive for a large variety of applications, especially for pick and place operations over wide spaces. This paper is based on the assumption that the safest (and cheapest) control scheme for a redundant CSPR consists, at the current state of development, in actuating only 6 cables at a time. This paper shows how, under this assumption, it is still possible to take advantage of redundancy to enhance the workspace and eventually reduce the maximal tension among cables. A simple interval-analysis routine is presented as a tool for the workspace and trajectory analysis of a redundant CSPR, and the results of a case study on an existing prototype are discussed.
In this paper three groove semi kinematic mounting has been designed and analyzed its the stability in micro milling operational conditions, employed in a specific modular reconfigurable micro factory test bed develop...
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ISBN:
(纸本)9783319158624;9783319158617
In this paper three groove semi kinematic mounting has been designed and analyzed its the stability in micro milling operational conditions, employed in a specific modular reconfigurable micro factory test bed developed at authors group. While various kinds of kinematic couplings, which are popular for their high repeatability and interchangeability, are considered for the modular machine design, Gothic arch and Maxwell coupling designs were compared. In this evaluation process, first the maximum preload, which can resist the induced contact stresses, is determined. Then the static stiffness matrices are evaluated for each case and compared as a measure of their relative stability. Maxwell coupling which was found to be best was adopted for the machine stage and experiments were performed to know the coupling stability with varying load.
Any crack in a beam-like structure creates a local reduction in the stiffness which in turn, affects the dynamics of the structure. This local reduction in stiffness generates small discontinuities in the modal displa...
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ISBN:
(纸本)9783319099170
Any crack in a beam-like structure creates a local reduction in the stiffness which in turn, affects the dynamics of the structure. This local reduction in stiffness generates small discontinuities in the modal displacements of the beam at the crack locations. However, these discontinuities cannot be visually observed in the modal displacement plots. Therefore, the identification of cracks is performed by decomposing the modal displacements using the stationary wavelet transform (SWT). This paper investigates identification of multiple cracks in simply-supported beams using the SWT. The SWT decomposes a signal into two components that are known as the detail and the approximate coefficients. These coefficients can be viewed as the results of passing the signal through low-pass and high-pass filters. The approximate coefficient gives the low frequency components of the signal which in this case is the overall shape of the signal (mode shapes) and the detail coefficient gives the high frequency components of the signal which in this case contains any high frequency noise or effects of small structural discontinuities present in the signal. The detail coefficients of the SWT detect the existence of cracks by showing high values at the crack locations. The method presented can detect both single and multiple symmetric and non-symmetric cracks with high accuracy in beam-like structures. The modal displacement data of the cracked simply supported beams used are obtained from the finite element method. The results are validated experimentally.
The static stiffness of incompletely restrained cable-driven robot (IRCR) is studied and its theoretical formulation of the calculation model is derived. The analysis shows that the static stiffness matrix is a sum of...
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ISBN:
(纸本)9783319094892;9783319094885
The static stiffness of incompletely restrained cable-driven robot (IRCR) is studied and its theoretical formulation of the calculation model is derived. The analysis shows that the static stiffness matrix is a sum of two components. The first part K-1 results from the change of position and orientation of end-effector which is proportional to cable tensions, while the second K-2 is caused by the deformation and deflection of cables. The study shows that K-2 is not only affected by material performances of all cables but by cable tensions. For the IRCR, however, the static stiffness correlates both parts because of the existence of cable catenaries. Two examples concerning the static stiffness are given for verification. Finally a few improvements are proposed for robot design based on stiffness analysis.
Crawling mechanical structures with energetic autonomy and remote control may move and steer by sliding on the ground. The paper presents a study on simple possibilities to achieve sliding movement with a crawling tet...
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ISBN:
(纸本)9783319158624;9783319158617
Crawling mechanical structures with energetic autonomy and remote control may move and steer by sliding on the ground. The paper presents a study on simple possibilities to achieve sliding movement with a crawling tetrahedral structure and studies their movement capabilities both analytically and by MBS simulation. The structures are analyzed using an equivalent plane model and a 3d model, respectively. The analysis is structural, kinematical, static and dynamic.
The problem of grasping with robots is solved by using suitable finger mechanisms that are inspired from structures in nature. A variety of solutions have been experienced and are used in a variety of designs all arou...
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ISBN:
(纸本)9783319181264;9783319181257
The problem of grasping with robots is solved by using suitable finger mechanisms that are inspired from structures in nature. A variety of solutions have been experienced and are used in a variety of designs all around the world. This paper discusses a survey of possibilities by addressing attention to characteristics and problems in the design and operation of those finger mechanisms. The author's experience with LARM hand is reported to show practical results in attaching the problem of improving efficient solutions with better finger mechanisms.
This work is aimed at a comprehensive discussion of experiments and numerical procedures for the open-loop geometric calibration of the KUKA LWR4+ redundant robotic arm, when a full 6D end-effector's pose is measu...
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ISBN:
(纸本)9783319181264;9783319181257
This work is aimed at a comprehensive discussion of experiments and numerical procedures for the open-loop geometric calibration of the KUKA LWR4+ redundant robotic arm, when a full 6D end-effector's pose is measured using Nikon K610 optical coordinate measuring machine (CMM). The later includes a comparative analysis of three different conjugate-type and meta-heuristic iterative algorithms used for numerical optimization of two observability indexes associated with Jacobian properties of the manipulator kinematics. While the former is based an original LEDs fixture design, which geometry is important for organization of the experiment. To the best of our knowledge, such integrated efforts are new for the KUKA robot widely used in robotics research community.
For cable-driven parallel robots elastic cables are used to manipulate the end-effector in the workspace. In this paper we present a hybrid position/force control which allows for applying defined forces on the enviro...
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ISBN:
(纸本)9783319094106
For cable-driven parallel robots elastic cables are used to manipulate the end-effector in the workspace. In this paper we present a hybrid position/force control which allows for applying defined forces on the environment and simultaneous movement along the surface. We propose a synchronous control of the cable forces to ensure the stability of the end-effector during movement. The performance of the controller is experimentally presented regarding contact establishment and dynamic behaviour during a motion on the cable robot IPAnema 3.
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