Search results for "nema"

973 Knee control and jump-landing technique in young basketball and floorball players

2016

Background Poor knee alignment is associated with increased loading of the joints, ligaments and tendons, and may increase the risk of injury. The study purpose was to compare differences in knee kinematics between basketball and floorball players during a vertical drop jump (VDJ) task. We wanted to investigate whether basketball players, whose sport includes frequent jump-landings, exhibited better knee control compared with floorball players, whose sport involves less jumping. Methods Players (aged 12–21 years) were recruited from six basketball and floorball clubs of the Tampere City district, Finland. Complete data was obtained from 173 basketball and 141 floorball players. Peak knee va…

A secular equation for the Jacobian matrix of certain multispecies kinematic flow models

2010

Integrated dimensional and drive-train design optimization of a light-weight anthropomorphic arm

2012

An approach to minimize the mass of robotic manipulators is developed by integrated dimensional and drive-train optimization. The method addresses the influences of dimensions and characteristics of drive-trains in the design optimization. Constraints are formulated on the basis of kinematic performance and dynamic requirements, whereas the main objective is to minimize the total mass. Case studies are included to demonstrate the application of the optimization method in the design of assistive robots.

Kinematic calibration method for a 5-DOF Gantry-Tau parallel kinematic machine

2013

In this paper a new step-wise approach to kinematic calibration of a 5-DOF Gantry-Tau parallel kinematic machine (PKM) is presented. The approach can be adapted to the modular design of the PKM and the calibration could easily perform part of the assembly instructions for the machine. By using measurements from a laser tracker and least-squares estimates of polynomial functions, a typical accuracy of about 20 micrometer was achieved for the base actuators. The remaining set of 30 general parameters for the hexapod link structure and spherical joint connections were successfully estimated using the Complex search-based evolutionary algorithm.

Nonholonomic Interpolation for Kinematic Problems, Entropy and Complexity

2008

Here we present the main lines of a theory we developed in a series of previous papers, about the motion planning problem in robotics. We illustrate the theory with a few academic examples.

Structural and functional features of human muscle-tendon unit.

2006

This paper reviews the architectural details and the in vivo behavior of the human muscle-tendon unit with the focus on the triceps surae and quadriceps femoris muscles. Recent advances in experimental techniques allow in vivo measurements of muscle-tendon architecture and function. In particular, the use of ultrasonography for measurement of tendon and muscle has expanded our knowledge in the last decade. Furthermore, the nuclear magnetic resonance imaging is opening up new insights not only for three-dimensional anatomical information but also for examining musculo-skeletal motion in vivo. While these two completely non-invasive methods provide kinematic data, in vivo force measurements s…

Optimised assembly mode reconfiguration of the 5-DOF Gantry-Tau using mixed-integer programming

2010

Pulished version of an article in the journal: Meccanica. Also available from the publisher at: http://dx.doi.org/10.1007/s11012-010-9404-y This paper presents a systematic approach based on Mixed Integer Linear Programming for finding an optimal singularity-free reconfiguration path of the 5-DOF Gantry-Tau parallel kinematic machine. The results in the paper demonstrate that singularity-free reconfiguration (change of assembly mode) of the machine is possible, which significantly increases the usable workspace. The method has been applied to a full-scale prototype and the singularity-free path has been verified both in simulations and with physical experiments using real-time control of th…

Tactile input of the hand and the control of reaching to grasp movements

1997

The role of tactile information of the hand in the control of reaching to grasp movements was investigated. The kinematics of both reaching (or transport) and grasp components were studied in healthy subjects in two experimental conditions. In one condition (control condition) subjects were required to reach and grasp an object that could have two sizes and that could be located at two distances from the viewer. In the other condition (anaesthesia condition) the same movements were executed, but anaesthesia was provided to the subjects' fingertips. In both conditions vision of the hand was prevented during movement. Anaesthesia affected mainly the kinematics of the first phase of grasping, …

Localization Based on Parallel Robots Kinematics as an Alternative to Trilateration

2022

In this article, a new scheme for range-based localization is proposed. The main goal is to estimate the position of a mobile point based on distance measurements from fixed devices, called anchors, and on inertial measurements. Due to the nonlinear nature of the problem, an analytic relation to compute the position starting from these measurements does not exist, and often trilateration methods are used, generally based on least-square algorithms. The proposed scheme is based on the modeling of the localization process as a parallel robot, thereby methodologies and control algorithms used in the robotic area can be exploited. In particular, a closed-loop control system is designed for trac…

A method for smoothly disengaging the load-holding valves of energy-efficient electro-hydraulic systems

2020

A novel self-contained, electro-hydraulic cylinder drive capable of passive load-holding, four-quadrant operations, and energy recovery was presented recently and implemented successfully. This solution improved greatly the energy efficiency and motion control in comparison to state-of-the-art, valve-controlled systems typically used in mobile or offshore applications. The passive load-holding function was realized by two pilot-operated check valves placed on the cylinder ports, where their pilot pressure is selected by a dedicated on/off electro valve. These valves can maintain the actuator position without consuming energy, as demonstrated on a single-boom crane. However, a reduced drop o…