A Device for Measuring Relative Angular Displacement

1998 ◽  
Vol 120 (2) ◽  
pp. 299-302 ◽  
Author(s):  
R. P. McCabe ◽  
S. S. Kohles ◽  
S. V. Chelikani ◽  
R. Vanderby
Keyword(s):  
Angular Displacement ◽  
Kinematic Chain ◽  
Displacement Transducer ◽  
Open Loop ◽  
Rotational Displacement

A simple, inexpensive, and accurate way to measure relative segmental rotations resulting from torsional loadings locally is described. To measure these rotations, we fabricated a planar spatial linkage (open-loop kinematic chain) requiring only one rotational displacement transducer. This paper describes this device, defines its kinematics, and examines its accuracy.

Design of Controllers for a Multi-Degree-of-Freedom Spherical Wheel Motor

2007 ◽  
Author(s):  
Hungsun Son ◽  
Kok-Meng Lee
Keyword(s):  
Control System ◽  
System Design ◽  
Control Structure ◽  
Angular Displacement ◽  
High Gain ◽  
Open Loop ◽  
Control System Design ◽  
Pd Controller ◽  
Rotating Shaft ◽  
Variable Reluctance

This paper presents the control system design for a particular form of variable-reluctance spherical motors, referred to here as a spherical wheel motor (SWM). Unlike most of the existing spherical motors where focuses have been on the control of the three-DOF angular displacement, the SWM offers a means to control the orientation of a continuously rotating shaft. Specifically, we demonstrate an effective method to decouple the open-loop (OL) control of the spin rate from that of the inclination, leading to a practical OL system combining a switching (spin-rate) controller and a model-based inclination controller. The OL system presented here provides the fundamental control structure for the SWM. To account for unmodeled external torques, we extend the design to allow feedback with a PD controller and a high-gain observer. The effectiveness of the controllers has been investigated by comparing their performance numerically under the influence of an unknown external torque.

The Non-Recursive Newton-Euler Formulation of the Dynamic Equation for Robotic Mechanisms

1986 ◽  
Vol 10 (1) ◽  
pp. 16-20
Author(s):  
You-Sun Li ◽  
Anastasios Kessaris
Keyword(s):  
Computer Simulation ◽  
Dynamic Equation ◽  
Kinematic Chain ◽  
Open Loop ◽  
Dynamic Equations ◽  
Design Stage ◽  
Real Time Control ◽  
Time Control ◽  
Dynamic Computer Simulation ◽  
New Formulation

A new formulation of the dynamic equations of an open loop kinematic chain is presented in this paper. This new method is based upon the composite link system concept and the dynamic equations are derived using vectorial analysis. In comparison with conventional methods, the method presented in this paper is more efficient and more explicit, hence it is applicable to both real time control and dynamic computer simulation during the design stage of new robotic mechanisms.

Rotational Displacement Transducer

1967 ◽  
Vol 38 (11) ◽  
pp. 1576-1578
Author(s):  
Jonathan E. Slater ◽  
Vadilal J. Modi
Keyword(s):  
Displacement Transducer ◽  
Rotational Displacement

Kinematic Design of a 5-DOF Hybrid Robot with Large Workspace/Limb–Stroke Ratio

2006 ◽  
Vol 129 (5) ◽  
pp. 530-537 ◽  
Author(s):  
Haitao Liu ◽  
Tian Huang ◽  
Jianping Mei ◽  
Xueman Zhao ◽  
Derek G. Chetwynd ◽  
...  
Keyword(s):  
Kinematic Chain ◽  
Open Loop ◽  
Singular Value ◽  
Dimensional Synthesis ◽  
Output Link ◽  
Design Variables ◽  
Spherical Parallel Mechanism ◽  
Symmetry Requirement ◽  
The Mean ◽  
Spherical Mechanism

This paper deals with the conceptual and kinematic designs of a 5-degree of freedom (DOF) reconfigurable hybrid robot. The robot is composed of a 2-DOF parallel spherical mechanism that is serially connected with a 3-DOF open loop kinematic chain via a prismatic joint. Somewhat similar to the well-known Tricept robot, this design has the merit that a relatively large workspace/limb–stroke ratio can be achieved thanks to the decomposition of the motions of the output link into the 2-DOF rotation and 1-DOF translation. As with the Tricept, the robot is well suited for use as a plug-and-play module to configure different machines. The dimensional synthesis of the 2-DOF spherical parallel mechanism is carried out by the monotonical analysis of the design variables versus a global conditioning index represented by the mean of the minimum singular value of the Jacobian, leading to the solution of two nonlinear equations due to the limb length constraint and nearly axial symmetry requirement of the kinematic performance. The results of the dimensional synthesis are given via examples.

A Motion Analysis for one D.O.F. Anthropomorphic Finger Mechanism

1998 ◽  
Author(s):  
Giorgio Figliolini ◽  
Marco Ceccarelli
Keyword(s):  
Computer Simulation ◽  
Motion Analysis ◽  
Kinematic Chain ◽  
Open Loop ◽  
Kinematic Structure ◽  
Design Considerations ◽  
Human Finger ◽  
And Control

Abstract A novel kinematic structure of a tendon-driven mechanism is proposed for an anthropomorphic finger mechanism of artificial hands. The kinematic structure is composed by three links as the three phalanges of a human finger and they are moved independently by means of suitable endless tendons. The three d.o.f.s of the proposed open-loop kinematic chain have been appropriately reduced to only one in order to simplify the actuation and control of the finger mechanism. A motion analysis has been carried out by using the polode method to obtain a suitable algorithm for computer simulation. The grasp performances of the proposed new anthropomorphic finger mechanism have been investigated and some design considerations have been pointed out.

Comparison of the contractile responses to irregular and regular trains of stimuli during microstimulation of single human motor axons

2014 ◽  
Vol 111 (7) ◽  
pp. 1499-1506 ◽  
Author(s):  
Michael Leitch ◽  
Vaughan G. Macefield
Keyword(s):  
Angular Displacement ◽  
Motor Units ◽  
Common Peroneal Nerve ◽  
Displacement Transducer ◽  
Motor Axons ◽  
Interspike Intervals ◽  
Contractile Responses ◽  
Single Motor ◽  
Single Motor Units ◽  
Voluntary Contractions

During voluntary contractions, human motoneurons discharge with a physiological variability of ∼20%. However, studies that have measured the contractile responses to microstimulation of single motor axons have used regular trains of stimuli with no variability. We tested the hypothesis that irregular (physiological) trains of stimuli produce greater contractile responses than regular (nonphysiological) trains of identical mean frequency but zero variability. High-impedance tungsten microelectrodes were inserted into the common peroneal nerve and guided into fascicles supplying a toe extensor muscle. Selective microstimulation was achieved for 14 single motor axons. Contractile responses were measured via an angular displacement transducer over the relevant toe. After the responses to regular trains of 10 stimuli extending from 2 to 100 Hz were recorded, irregular trains of 10 stimuli, based on the interspike intervals recorded from single motor units during voluntary contractions, were delivered. Finally, the stimulation sequences were repeated following a 2-min period of continuous stimulation at 10 Hz to induce muscle fatigue. Regular trains of stimuli generated a sigmoidal increase in displacement with frequency, whereas irregular trains, emulating the firing of volitionally driven motoneurons, displayed significantly greater responses over the same frequency range (8–24 Hz). This was maintained even in the presence of fatigue. We conclude that physiological discharge variability, which incorporates short and long interspike intervals, offers an advantage to the neuromuscular system by allowing motor units to operate on a higher level of the contraction-frequency curve and taking advantage of catch-like properties in skeletal muscle.

scholarly journals On the Influence of the Shoulder Kinematic Chain on Joint Kinematics and Musculotendon Lengths During Wheelchair Propulsion Estimated From Multibody Kinematics Optimization

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Pierre Puchaud ◽  
Samuel Hybois ◽  
Antoine Lombart ◽  
Joseph Bascou ◽  
Hélène Pillet ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Kinematic Chain ◽  
Joint Kinematics ◽  
Open Loop ◽  
Regression Equations ◽  
Kinematic Chains ◽  
Marker Tracking ◽  
Good Trade ◽  
Shoulder Kinematics ◽  
The Impact

Multibody kinematic optimization is frequently used to assess shoulder kinematics during manual wheelchair (MWC) propulsion, but multiple kinematics chains are available. It is hypothesized that these different kinematic chains affect marker tracking, shoulder kinematics, and resulting musculotendon (MT) lengths. In this study, shoulder kinematics and MT lengths obtained from four shoulder kinematic chains (open-loop thorax-clavicle-scapula-humerus (M1), closed-loop with contact ellipsoid (M2), scapula rhythm from regression equations (M3), and a single ball-and- socket joint between the thorax and the humerus (M4) were compared. Right-side shoulder kinematics from seven subjects were obtained with 34 reflective markers and a scapula locator using an optoelectronic motion capture system while propelling on a MWC simulator. Data were processed based on the four models. The results showed the impact of shoulder kinematic chains on all studied variables. Marker reconstruction errors were found to be similar between M1 and M2 and lower than for M3 and M4. Few degrees-of-freedom (DoF) were noticeably different between M1 and M2, but all shoulder DoFs were significantly affected between M1 and M4. As a consequence of differences in joint kinematics, MT lengths were affected by the kinematic chain definition. The contact ellipsoid (M2) was found as a good trade-off between marker tracking and penetration avoidance of the scapula. The regression-based model (M3) was less efficient due to limited humerus elevation during MWC propulsion, as well as the ball-and-socket model (M4) which appeared not suitable for upper limbs activities, including MWC propulsion.

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