Joint Angle Determinants in Aimed Arm Movements With Excess Degrees of Freedom

1992 ◽  
Author(s):  
Charles E. Wright ◽  
Rebecca States
Keyword(s):  
Degrees Of Freedom ◽  
Joint Angle ◽  
Arm Movements

Alternative Inverse Kinematic Equations for General RRP and RRR Regional Structures of Manipulators

1996 ◽  
Author(s):  
Peregrine E. J. Riley
Keyword(s):  
Degrees Of Freedom ◽  
Joint Angle ◽  
Inverse Kinematic ◽  
Intersection Point ◽  
Degree Polynomial ◽  
Six Degrees Of Freedom ◽  
Common Intersection ◽  
Position And Orientation ◽  
Spatial Positioning ◽  
Orientational Structure

Abstract Many manipulators with six degrees of freedom are constructed with two distinct sections, a regional structure for spatial positioning, and an orientational structure having a common intersection point for the joint axes. With this arrangement, inverse kinematic solutions for position and orientation may be found separately. While solutions for general three link manipulators have been available since the work of Pieper in 1969, this paper presents new forms of the inverse kinematic equations for general RRP and RRR regional structures. Cartesian coordinates of the F-surface (generated by movement of the outer two joints) together with the outer joint angle are used as the equation variables. In addition, a second degree polynomial approxiamation of the equation may be used for quick iteration to a solution. It is hoped that these new equations will be useful by themselves and in workspace regions where solutions using equations in terms of the joint variables are numerically inaccurate or impossible.

Design Human-Robot Collaborative Lifting Task Using Optimization

2021 ◽  
Author(s):  
Asif Arefeen ◽  
Yujiang Xiang
Keyword(s):  
Degrees Of Freedom ◽  
Joint Angle ◽  
Joint Torque ◽  
Robotic Arm ◽  
Inverse Dynamic ◽  
Floating Base ◽  
Grasping Forces ◽  
Design Variables ◽  
Human Arm ◽  
Lifting Task

Abstract In this paper, an optimization-based dynamic modeling method is used for human-robot lifting motion prediction. The three-dimensional (3D) human arm model has 13 degrees of freedom (DOFs) and the 3D robotic arm (Sawyer robotic arm) has 10 DOFs. The human arm and robotic arm are built in Denavit-Hartenberg (DH) representation. In addition, the 3D box is modeled as a floating-base rigid body with 6 global DOFs. The interactions between human arm and box, and robot and box are modeled as a set of grasping forces which are treated as unknowns (design variables) in the optimization formulation. The inverse dynamic optimization is used to simulate the lifting motion where the summation of joint torque squares of human arm is minimized subjected to physical and task constraints. The design variables are control points of cubic B-splines of joint angle profiles of the human arm, robotic arm, and box, and the box grasping forces at each time point. A numerical example is simulated for huma-robot lifting with a 10 Kg box. The human and robotic arms’ joint angle, joint torque, and grasping force profiles are reported. These optimal outputs can be used as references to control the human-robot collaborative lifting task.

Analyzing Octopus Movements Using Three-Dimensional Reconstruction

2007 ◽  
Vol 98 (3) ◽  
pp. 1775-1790 ◽  
Author(s):  
Yoram Yekutieli ◽  
Rea Mitelman ◽  
Binyamin Hochner ◽  
Tamar Flash
Keyword(s):  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Arm Movements ◽  
Light Refraction ◽  
Video Cameras ◽  
Electrophysiological Recordings ◽  
Custom Made ◽  
Dimensional Reconstruction ◽  
Recent Developments ◽  
Computerized System

Octopus arms, as well as other muscular hydrostats, are characterized by a very large number of degrees of freedom and a rich motion repertoire. Over the years, several attempts have been made to elucidate the interplay between the biomechanics of these organs and their control systems. Recent developments in electrophysiological recordings from both the arms and brains of behaving octopuses mark significant progress in this direction. The next stage is relating these recordings to the octopus arm movements, which requires an accurate and reliable method of movement description and analysis. Here we describe a semiautomatic computerized system for 3D reconstruction of an octopus arm during motion. It consists of two digital video cameras and a PC computer running custom-made software. The system overcomes the difficulty of extracting the motion of smooth, nonrigid objects in poor viewing conditions. Some of the trouble is explained by the problem of light refraction in recording underwater motion. Here we use both experiments and simulations to analyze the refraction problem and show that accurate reconstruction is possible. We have used this system successfully to reconstruct different types of octopus arm movements, such as reaching and bend initiation movements. Our system is noninvasive and does not require attaching any artificial markers to the octopus arm. It may therefore be of more general use in reconstructing other nonrigid, elongated objects in motion.

scholarly journals Simulation of Octopus Arm Based on Coupled CPGs

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Juan Tian ◽  
Qiang Lu
Keyword(s):  
Phase Diagrams ◽  
Degrees Of Freedom ◽  
Dynamic Models ◽  
Hot Spot ◽  
Central Pattern Generators ◽  
Arm Movements ◽  
Movement Control ◽  
High Dimensionality ◽  
Neuromuscular System ◽  
Pattern Generators

The octopus arm has attracted many researchers’ interests and became a research hot spot because of its amazing features. Several dynamic models inspired by an octopus arm are presented to realize the structure with a large number of degrees of freedom. The octopus arm is made of a soft material introducing high-dimensionality, nonlinearity, and elasticity, which makes the octopus arm difficult to control. In this paper, three coupled central pattern generators (CPGs) are built and a 2-dimensional dynamic model of the octopus arm is presented to explore possible strategies of the octopus movement control. And the CPGs’ signals treated as activation are added on the ventral, dorsal, and transversal sides, respectively. The effects of the octopus arm are discussed when the parameters of the CPGs are changed. Simulations show that the octopus arm movements are mainly determined by the shapes of three CPGs’ phase diagrams. Therefore, some locomotion modes are supposed to be embedded in the neuromuscular system of the octopus arm. And the octopus arm movements can be achieved by modulating the parameters of the CPGs. The results are beneficial for researchers to understand the octopus movement further.

scholarly journals The Central Nervous System Does Not Minimize Energy Cost in Arm Movements

2010 ◽  
Vol 104 (6) ◽  
pp. 2985-2994 ◽  
Author(s):  
Dinant A. Kistemaker ◽  
Jeremy D. Wong ◽  
Paul L. Gribble
Keyword(s):  
Force Field ◽  
Energy Cost ◽  
Degrees Of Freedom ◽  
Muscle Activation ◽  
Arm Movements ◽  
Dominant Factor ◽  
Minimal Energy ◽  
Null Field ◽  
Muscle Activation Patterns ◽  
Point To Point

It has been widely suggested that the many degrees of freedom of the musculoskeletal system may be exploited by the CNS to minimize energy cost. We tested this idea by having subjects making point-to-point movements while grasping a robotic manipulandum. The robot created a force field chosen such that the minimal energy hand path for reaching movements differed substantially from those observed in a null field. The results show that after extended exposure to the force field, subjects continued to move exactly as they did in the null field and thus used substantially more energy than needed. Even after practicing to move along the minimal energy path, subjects did not adapt their freely chosen hand paths to reduce energy expenditure. The results of this study indicate that for point-to-point arm movements minimization of energy cost is not a dominant factor that influences how the CNS arrives at kinematics and associated muscle activation patterns.

scholarly journals CORDIC Framework for Quaternion-based Joint Angle Computation to Classify Arm Movements

2018 ◽  
Author(s):  
Dwaipayan Biswas ◽  
Zixuan Ye ◽  
Evangelos B. Mazomenos ◽  
Michael Jobges ◽  
Koushik Maharatna
Keyword(s):  
Joint Angle ◽  
Arm Movements

Two functionally different synergies during arm reaching movements involving the trunk

1995 ◽  
Vol 73 (5) ◽  
pp. 2120-2122 ◽  
Author(s):  
S. Ma ◽  
A. G. Feldman
Keyword(s):  
Motor Control ◽  
Degrees Of Freedom ◽  
Arm Movements ◽  
The Other ◽  
Reaching Movements ◽  
Positional Error ◽  
Trunk Motion ◽  
Arm Reaching ◽  
Trunk Movements ◽  
The Right

1. To address the problem of the coordination of a redundant number of degrees of freedom in motor control, we analyzed the influence of voluntary trunk movements on the arm endpoint trajectory during reaching. 2. Subjects made fast noncorrected planar movements of the right arm from a near to a far target located in the ipsilateral work space at a 45 degrees angle to the sagittal midline of the trunk. These reaching movements were combined with a forward or a backward sagittal motion of the trunk. 3. The direction, positional error, curvature, and velocity profile of the endpoint trajectory remained invariant regardless of trunk movements. Trunk motion preceded endpoint motion by approximately 175 ms, continued during endpoint movement to the target, and outlasted it by 200 ms. This sequence of trunk and arm movements was observed regardless of the direction of the endpoint trajectory (to or from the far target) or trunk movements (forward or backward). 4. Our data imply that reaching movements result from two control synergies: one coordinates trunk and arm movements leaving the position of the endpoint unchanged, and the other produces interjoint coordination shifting the arm endpoint to the target. The use of functionally different synergies may underlie a solution of the redundancy problem.

Optimization-Based Digital Human Dynamics: Santos™ Walking Backwards

2007 ◽  
Author(s):  
Hyun Jung Kwon ◽  
Yujiang Xiang ◽  
Salam Rahmatalla ◽  
R. Timothy Marler ◽  
Karim Abdel-Malek ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Optimization Problem ◽  
Joint Angle ◽  
Spline Interpolation ◽  
Performance Measure ◽  
Degree Of Freedom ◽  
Human Model ◽  
Entire Body ◽  
Joint Torques ◽  
Digital Human

An objective of this study is to simulate the backward walking motion of a full-body digital human model. The model consists of 55 degree of freedom – 6 degrees of freedom for global translation and rotation and 49 degrees of freedom representing the kinematics of the entire body. The resultant action of all the muscles at a joint is represented by the torque for each degree of freedom. The torques and angles at a joint are treated as unknowns in the optimization problem. The B-spline interpolation is used to represent the time histories of the joint angles and the well-established robotics formulation of the Denavit-Hartenberg method is used for kinematics analysis of the mechanical system. The recursive Lagrangian formulation is used to develop the equations of motion, and was chosen because of its known computational efficiency. The backwards walking problem is formulated as a nonlinear optimization problem. The control points of the B-splines for the joint angle profiles are treated as the design variables. For the performance measure, total dynamic effort that is represented as the integral of the sum of the squares of all the joint torques is minimized using a sequential quadratic programming algorithm. The solution is simulated in the Santos™ environment. Results of the optimization problem are the torque and joint angle profiles. The torques at the key joints and the ground reaction forces are compared to those for the forward walk in order to study the differences between the two walking patterns. Simulation results are approximately validated with the experimental data which is motion captured in the VSR Lab at the University of Iowa.

A preferred pattern of joint coordination during arm movements with redundant degrees of freedom

2014 ◽  
Vol 112 (5) ◽  
pp. 1040-1053 ◽  
Author(s):  
Natalia Dounskaia ◽  
Wanyue Wang
Keyword(s):  
Degrees Of Freedom ◽  
Feedforward Control ◽  
Arm Movements ◽  
Joint Control ◽  
Movement Execution ◽  
Joint Coordination ◽  
Human Movements ◽  
Drawing Task ◽  
Control Research ◽  
Control Pattern

Redundancy of degrees of freedom (DOFs) during natural human movements is a central problem of motor control research. This study tests a novel interpretation that during arm movements, the DOF redundancy is used to support a preferred, simplified joint control pattern that consists of rotating either the shoulder or elbow actively and the other (trailing) joint predominantly passively by interaction and gravitational torques. We previously revealed the preference for this control pattern during nonredundant horizontal arm movements. Here, we studied whether this preference persists during movements with redundant DOFs and the redundancy is used to enlarge the range of directions in which this control pattern can be utilized. A free-stroke drawing task was performed that involved production of series of horizontal center-out strokes in randomly selected directions. Two conditions were used, with the arm's joints unconstrained (U) and constrained (C) to the horizontal plane. In both conditions, directional preferences were revealed and the simplified control pattern was used in the preferred and not in nonpreferred directions. The directional preferences were weaker and the range of preferred directions was wider in the U condition, with higher percentage of strokes performed with the simplified control pattern. This advantage was related to the usage of additional DOFs. We discuss that the simplified pattern may represent a feedforward control strategy that reduces the challenge of joint coordination caused by signal-dependent noise during movement execution. The results suggest a possibility that the simplified pattern is used during the majority of natural, seemingly complex arm movements.

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