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Universal joint

About: Universal joint is a research topic. Over the lifetime, 8937 publications have been published within this topic receiving 39113 citations. The topic is also known as: universal coupling & U-joint.


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Journal ArticleDOI
TL;DR: Quantitative comparisons between model and experiment indicate that the model reproduces the kinematic, kinetic, and muscle-coordination patterns evident when humans jump to their maximum achievable heights.
Abstract: A three-dimensional model of the human body is used to simulate a maximal vertical jump. The body is modeled as a 10-segment, 23 degree-of-freedom (dof), mechanical linkage, actuated by 54 muscles. Six generalized coordinates describe the position and orientation of the pelvis relative to the ground; the remaining nine segments branch in an open chain from the pelvis. The head, arms, and torso (HAT) are modeled as a single rigid body. The HAT articulates with the pelvis via a 3 dof ball-and-socket joint. Each hip is modeled as a 3 dof ball-and-socket joint, and each knee is modeled as a 1 dof hinge joint. Each foot is represented by a hindfoot and toes segment. The hindfoot articulates with the shank via a 2 dof universal joint, and the toes articulate with the hindfoot via a 1 dof hinge joint. Interaction of the feet with the ground is modeled using a series of spring-damper units placed under the sole of each foot. The path of each muscle is represented by either a series of straight lines or a combination of straight lines and space curves. Each actuator is modeled as a three-element, Hill-type muscle in series with tendon. A first-order process is assumed to model muscle excitation-contraction dynamics. Dynamic optimization theory is used to calculate the pattern of muscle excitations that produces a maximal vertical jump. Quantitative comparisons between model and experiment indicate that the model reproduces the kinematic, kinetic, and muscle-coordination patterns evident when humans jump to their maximum achievable heights.

572 citations

Journal ArticleDOI
TL;DR: In this article, the drawbacks of typical flexure connectors are investigated and cataloged, and several new designs for highly effective, kinematically-behaved compliant joints are proposed.
Abstract: Flexure joints are widely used to approximate the function of traditional mechanical joints, while offering the benefits of high precision, long life, and ease of manufacture. This paper investigates and catalogs the drawbacks of typical flexure connectors and presents several new designs for highly-effective, kinematically-behaved compliant joints. A revolute and a translational compliant joint are proposed (Figure 1), both of which offer great improvements over existing flexures in the qualities of (1) large range of motion, (2) minimal axis drift, (3) increased off-axis stiffness, and (4) reduced stress-concentrations. Analytic stiffness equations are developed for each joint and parametric computer models are used to verify their superior stiffness properties. A catalog of design charts based on the parametric models is also presented, allowing for rapid sizing of the joints for custom performance. Finally, two multi-degree-of-freedom joints are proposed as modifications to the revolute joint. These include a compliant universal joint and a compliant spherical joint, both designed to provide high degrees of compliance in the desired direction of motion and high stiffness in other directions.Copyright © 2002 by ASME

339 citations

Patent
05 Feb 1998
TL;DR: In this paper, an actively controlled rotary steerable drilling system for directional drilling of wells having a tool collar rotated by a drill string during well drilling is presented, where an electric motor provides rotation to the offsetting mandrel with respect to the tool collar and is servo-controlled by signal input from position sensing elements such as magnetometers, gyroscopic sensors, and accelerometers.
Abstract: An actively controlled rotary steerable drilling system for directional drilling of wells having a tool collar rotated by a drill string during well drilling. A bit shaft has an upper portion within the tool collar and a lower end extending from the collar and supporting a drill bit. The bit shaft is omni-directionally pivotally supported intermediate its upper and lower ends by a universal joint within the collar and is rotatably driven by the collar. To achieve controlled steering of the rotating drill bit, orientation of the bit shaft relative to the tool collar is sensed and the bit shaft is maintained geostationary and selectively axially inclined relative to the tool collar during drill string rotation by rotating it about the universal joint by an offsetting mandrel that is rotated counter to collar rotation and at the same frequency of rotation. An electric motor provides rotation to the offsetting mandrel with respect to the tool collar and is servo-controlled by signal input from position sensing elements such as magnetometers, gyroscopic sensors, and accelerometers which provide real time position signals to the motor control. In addition, when necessary, a brake is used to maintain the offsetting mandrel and the bit shaft axis geostationary. Alternatively, a turbine is connected to the offsetting mandrel to provide rotation to the offsetting mandrel with respect to the tool collar and a brake is used to servo-control the turbine by signal input from position sensors.

307 citations

Book ChapterDOI
01 Jan 1996
TL;DR: A three degree-of-freedom manipulator that has a fairly large translational workspace is presented and both the direct and inverse kinematics are investigated.
Abstract: A three degree-of-freedom manipulator that has a fairly large translational workspace is presented. The mechanism consists of a fixed base, a moving platform, and three extensible limbs. Each limb consists of a prismatic joint and two universal joints connecting the moving platform to the fixed base. Both the direct and inverse kinematics are investigated. The inverse kinematics problem yields two equal and opposite limb lengths for each limb while the direct kinematics problem is reduced to a second-degree polynomial in one unknown. Further, the workspace and singular conditions of the manipulator are discussed.

238 citations

Journal ArticleDOI
TL;DR: In this paper, a theoretical model of a complete motor-flexible coupling-rotor system capable of describing the mechanical vibration resulting from misalignment and unbalance was developed.

229 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202310
202224
202154
2020182
2019251
2018365