Stereotypical Fingertip Trajectories During Grasp

2003 ◽  
Vol 90 (6) ◽  
pp. 3702-3710 ◽  
Author(s):  
D. G. Kamper ◽  
E. G. Cruz ◽  
M. P. Siegel
Keyword(s):  
Logarithmic Spiral ◽  
Joint Space ◽  
Joint Angles ◽  
Object Type ◽  
Cartesian Space ◽  
Reach And Grasp ◽  
Straight Line ◽  
Hand Impairment ◽  
Finger Posture ◽  
Specific Part

The kinematics of movement of all five digits was analyzed during reach-and-grasp tasks for a variety of objects. Ten healthy subjects performed 20 trials involving the grasp of five objects of distinct size and shape. Joint angles were recorded, and digit trajectories were computed using forward kinematics. For a given subject, fingertip trajectories were consistent across trials. The different-sized objects largely produced movement along different portions of a stereotypical trajectory described by a logarithmic spiral. The spirals fit the actual finger positions with a mean error across all trials of 0.23 ± 0.25 cm and accounted for over 98% of the variance in finger position. These patterns were consistent independent of initial finger posture. Subjects did not produce straight-line movements, either in Cartesian space or joint space. The direction of the thumb trajectories exhibited a greater dependence on object type than the finger trajectories, but still utilized a small percentage (<5%) of the available workspace. These results suggest that restoration of a small but specific part of the workspace could have significant impact on function following hand impairment.

scholarly journals Kinematic analysis of a newly designed cable-driven manipulator

2018 ◽  
Vol 42 (2) ◽  
pp. 125-135 ◽  
Author(s):  
Wei Xu ◽  
Yaoyao Wang ◽  
Surong Jiang ◽  
Jiafeng Yao ◽  
Bai Chen
Keyword(s):  
Trajectory Planning ◽  
Kinematic Analysis ◽  
Joint Space ◽  
Joint Angles ◽  
Coupled Motion ◽  
Cartesian Space ◽  
The Impact ◽  
The Relationship

In this paper, the cable routing configurations for a cable-driven manipulator are introduced, and the impact of motion coupling caused by cable transmission routing of a 2n type cable-driven manipulator is analyzed in detail. Based on different configurations of cable routings, the relationship between variation of joint angles and the geometrical sizes of guide pulleys is established, represented by a matrix for coupled motion. Moreover, based on the effects of the motion coupling of a cable-driven manipulator, we propose the condition for the invariance of orientation, which can be achieved constraining of the geometrical sizes of guide pulleys and driven wheels. In addition, to identify the correctness of analysis for coupled motion, a 3-DOFs planer cable-driven manipulator prototyping model is constructed, and the kinematics and trajectory planning has been solved. Finally, the relationship among actuator space, joint space, and Cartesian space, including the mapping of the motion coupling, is experimentally validated. The property of invariance of orientation is also validated by an experiment.

scholarly journals Kinematics and control of frog hindlimb movements

1991 ◽  
Vol 65 (3) ◽  
pp. 547-562 ◽  
Author(s):  
D. J. Ostry ◽  
A. G. Feldman ◽  
J. R. Flanagan
Keyword(s):  
Nervous System ◽  
High Speed ◽  
Imaging System ◽  
Maximum Velocity ◽  
Joint Space ◽  
Motion Path ◽  
Three Dimension ◽  
Joint Angles ◽  
Joint Configuration ◽  
Straight Line

1. The determinants of the motion path of the hindlimb were explored in both intact and spinal frogs. In the spinal preparations the kinematic properties of withdrawal and crossed-extension reflexes were studied. In the intact frog the kinematics of withdrawal and swimming movements were examined. Frog hindlimb paths were described in joint angle (intrinsic) coordinates rather than limb endpoint (extrinsic) coordinates. 2. To study withdrawal and crossed-extension reflexes, the initial angles at the hip, knee, and ankle were varied. Withdrawal and crossed extension were recorded in three dimension (3-D) with the use of an infra-red spatial imaging system. Swimming movements against currents of different speeds were obtained with high-speed film. 3. Three strategies were considered related to the form of the hypothesized equilibrium paths specified by the nervous system: all trajectories lie on a single line in angular coordinates; all trajectories are directed toward a common final position; and all trajectories have the same direction independent of initial joint configuration. 4. Joint space paths in withdrawal were found to be straight and parallel independent of the initial joint configuration. The hip and knee were found to start simultaneously and in 75% of the conditions tested to reach maximum velocity simultaneously. Hip-knee maximum velocity ratios were similar in magnitude over differences in initial joint angles. This is consistent with the observation of parallel paths and supports the view that the nervous system specifies a single direction for equilibrium trajectories. 5. Straight line paths with slopes similar to those observed in withdrawal in the spinal preparation were found in swimming movements in the intact frog. Straight line paths in joint space are consistent with the idea that swimming and withdrawal are organized and controlled in a joint-level coordinate system. The similarities observed between spinal and intact preparations suggest that a common set of constructive elements underlies these behaviors. 6. Path curvature was introduced when joint limits were approached toward the end of the movement. Depending on the initial joint angles, the joint movements ended at different times. When initial joint angles were unequal, joints moving from smaller initial angles reached their functional limits earlier and stopped first. 7. In withdrawal and crossed extension in the spinal frog, velocity profiles at a given joint were similar over the initial portion of the curve for movements of different amplitude. This is consistent with the idea that withdrawal and crossed-extension movements of different amplitude are produced by a constant rate of shift of the equilibrium position.

Path Curvature in Workspace and in Joint Space: Evidence for Coexisting Coordinative Rules in Aiming

Motor Control ◽  
1998 ◽  
Vol 2 (4) ◽  
pp. 331-351 ◽  
Author(s):  
Edwin Van Thiel ◽  
Ruud G.J. Meulenbroek ◽  
Wouter Hulstijn
Keyword(s):  
Joint Space ◽  
Line Production ◽  
Vertical Movements ◽  
Space Planning ◽  
Aiming Movements ◽  
Trajectory Formation ◽  
Straight Line ◽  
Bottom Left ◽  
Path Curvature ◽  
Point To Point

In this study we tried to establish whether point-to-point aiming movements are planned in workspace, joint space, or both. Eight right-handed subjects performed horizontal, vertical, and diagonal aiming movements on a transversal plane. Movements were performed at several speeds. Curvature variations of the hand and corresponding joint-space paths were investigated as a function of position, direction, and speed. Straightness of hand paths predominated for vertical movements but was systematically violated for horizontal and top-right to bottom-left movements. Furthermore, the hand-path curvature of the latter movements increased with speed. Joint-space paths showed more deviation from a straight line than hand paths except for top-left to bottom-right movements in which the paths were equally curved. A comparison of normalized path curvatures at the hand and joint level indicated that in aiming, the coordinative rule of straight-line production seems to apply to both workspace and joint-space planning. The present findings confirm Kawato's (1996) views that optimization processes operate concurrently at the two control levels of arm-trajectory formation under study.

scholarly journals Regions of Feasible Point-to-Point Trajectories in the Cartesian Workspace of Fully-Parallel Manipulators

1999 ◽  
Author(s):  
Damien Chablat ◽  
Philippe Wenger
Keyword(s):  
Parallel Manipulator ◽  
Cartesian Product ◽  
Parallel Manipulators ◽  
Joint Space ◽  
Inverse Kinematic ◽  
Connected Components ◽  
Feasible Point ◽  
Cartesian Space ◽  
Point Trajectories ◽  
Point To Point

Abstract The goal of this paper is to define the n-connected regions in the Cartesian workspace of fully-parallel manipulators, i.e. the maximal regions where it is possible to execute point-to-point motions. The manipulators considered in this study may have multiple direct and inverse kinematic solutions. The N-connected regions are characterized by projection, onto the Cartesian workspace, of the connected components of the reachable configuration space defined in the Cartesian product of the Cartesian space by the joint space. Generalized octree models are used for the construction of all spaces. This study is illustrated with a simple planar fully-parallel manipulator.

Seismic passive earth pressure coefficients for sands

2001 ◽  
Vol 38 (4) ◽  
pp. 876-881 ◽  
Author(s):  
Jyant Kumar
Keyword(s):  
Limit Equilibrium ◽  
Earth Pressure ◽  
Logarithmic Spiral ◽  
Failure Surface ◽  
Passive Earth Pressure ◽  
Pressure Coefficients ◽  
Straight Line ◽  
Earth Pressures ◽  
Planar Failure ◽  
Seismic Forces

By taking the failure surface as a combination of the arc of a logarithmic spiral and a straight line, passive earth pressure coefficients in the presence of horizontal pseudostatic earthquake body forces have been computed for an inclined wall placed against cohesionless backfill material. The presence of seismic forces induces a considerable reduction in the passive earth resistance. The reduction increases with an increase in the magnitude of the earthquake acceleration. The effect becomes more predominant for loose sands. The obtained results compared well with those reported in the literature using curved failure surfaces. However, the results available in the literature on the basis of a planar failure surface are found to predict comparatively higher passive resistance.Key words: earth pressures, earthquakes, limit equilibrium, plasticity, retaining walls, sands.

The Control of Hexapod Parallel Mechanism

2012 ◽  
Vol 195-196 ◽  
pp. 1030-1034
Author(s):  
Chun Ping Pan ◽  
Hsin Guan
Keyword(s):  
Tracking Error ◽  
Joint Space ◽  
Variable Load ◽  
Phase Lag ◽  
Parallel Mechanisms ◽  
Nonlinear Controller ◽  
Cartesian Space ◽  
Motion System ◽  
Wide Range ◽  
System Output

In order to enhance the innervations fidelity of simulators, an adaptive nonlinear controller is developed, which guarantees parallel mechanisms closed loop system global asymptotical stability and the convergence of posture tracking error in Cartesian space. The problem of rapid tracking under the condition of the wide range, nonlinear and variable load is solved. After the adaptive nonlinear controller is actually applied to the hexapod parallel mechanisms of simulator, the dynamic-static capabilities of motion system is tested by amplitude-frequency response and posture precision. The experimental results show that the static precision improves ten times and system output amplitude increase and the phase lag reduce with respect to the same input signal in Cartesian space in comparison with the traditional proportional and derivative controlling method in joint space. Therefore the adaptive nonlinear controller can effectively improve the dynamic-static response performance of the hexapod parallel mechanisms of simulators in Cartesian space.

scholarly journals Optimal Trajectories for Flexible-Link Manipulator Slewing Using Recursive Quadratic Programming: Experimental Verification

1997 ◽  
Vol 119 (4) ◽  
pp. 833-836 ◽  
Author(s):  
G. G. Parker ◽  
G. R. Eisler ◽  
R. D. Robinett ◽  
J. T. Feddema
Keyword(s):  
Experimental Verification ◽  
Tracking Error ◽  
Minimum Time ◽  
Flexible Link ◽  
Flexible Robot ◽  
Joint Angles ◽  
Actuator Dynamics ◽  
Straight Line ◽  
Servo Actuator ◽  
Line Tracking

Experimental verification of minimum time, straight-line tracking using a two-link planar flexible robot is presented. Previously reported minimum-time angle histories are precompensated to account for joint servo-actuator dynamics. Using the precompensated joint commands, the optimal joint angles are tracked with such fidelity that the tip tracking error is less than 1.8 percent of the tip travel distance.

Nine Degree-of-Freedom Kinematic Modeling of the Upper-Limb Complex for Constrained Workspace Evaluation

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Brayden DeBoon ◽  
Ryan C. A. Foley ◽  
Scott Nokleby ◽  
Nicholas J. La Delfa ◽  
Carlos Rossa
Keyword(s):  
Upper Limb ◽  
Evaluation Method ◽  
Kinematic Model ◽  
Joint Space ◽  
Inverse Kinematic ◽  
Degree Of Freedom ◽  
Kinematic Modeling ◽  
Joint Angles ◽  
Rehabilitative Treatment ◽  
Rehabilitation Devices

Abstract The design of rehabilitation devices for patients experiencing musculoskeletal disorders (MSDs) requires a great deal of attention. This article aims to develop a comprehensive model of the upper-limb complex to guide the design of robotic rehabilitation devices that prioritize patient safety, while targeting effective rehabilitative treatment. A 9 degree-of-freedom kinematic model of the upper-limb complex is derived to assess the workspace of a constrained arm as an evaluation method of such devices. Through a novel differential inverse kinematic method accounting for constraints on all joints1820, the model determines the workspaces in which a patient is able to perform rehabilitative tasks and those regions where the patient needs assistance due to joint range limitations resulting from an MSD. Constraints are imposed on each joint by mapping the joint angles to saturation functions, whose joint-space derivative near the physical limitation angles approaches zero. The model Jacobian is reevaluated based on the nonlinearly mapped joint angles, providing a means of compensating for redundancy while guaranteeing feasible inverse kinematic solutions. The method is validated in three scenarios with different constraints on the elbow and palm orientations. By measuring the lengths of arm segments and the range of motion for each joint, the total workspace of a patient experiencing an upper-limb MSD can be compared to a preinjured state. This method determines the locations in which a rehabilitation device must provide assistance to facilitate movement within reachable space that is limited by any joint restrictions resulting from MSDs.

A 3-ṞPR Parallel Mechanism With Singularities That are Self-Motions

2010 ◽  
Vol 2 (3) ◽  
Author(s):  
Novona Rakotomanga ◽  
Ilian A. Bonev
Keyword(s):  
Parallel Mechanism ◽  
Control Strategies ◽  
Joint Space ◽  
Degree Of Freedom ◽  
Parallel Mechanisms ◽  
Active Joint ◽  
Cartesian Space ◽  
Three Degree Of Freedom

The Cartesian workspace of most three-degree-of-freedom parallel mechanisms is divided by Type 2 (also called parallel) singularity surfaces into several regions. Accessing more than one such region requires crossing a Type 2 singularity, which is risky and calls for sophisticated control strategies. Some mechanisms can still cross these Type 2 singularity surfaces through “holes” that represent Type 1 (also called serial) singularities only. However, what is even more desirable is if these Type 2 singularity surfaces were curves instead. Indeed, there exists at least one such parallel mechanism (the agile eye) and all of its singularities are self-motions. This paper presents another parallel mechanism, a planar one, whose singularities are self-motions. The singularities of this novel mechanism are studied in detail. While the Type 2 singularities in the Cartesian space still constitute a surface, they degenerate into lines in the active-joint space, which is the main result of this paper.

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