Real-Time Direct Position Analysis of Parallel Spherical Wrists by Using Extra Sensors

2005 ◽  
Vol 128 (1) ◽  
pp. 288-294 ◽  
Author(s):  
R. Vertechy ◽  
V. Parenti-Castelli
Keyword(s):  
Real Time ◽  
Measurement Errors ◽  
Degrees Of Freedom ◽  
Point Of View ◽  
The Body ◽  
Least Square ◽  
End Effector ◽  
Kinematic Chains ◽  
Position Analysis ◽  
Specialized Form

The paper presents an algorithm for the real-time evaluation of the actual end-effector orientation of general parallel spherical wrists. Conceptually, the method relies on evidence that the pose of a rigid body is defined once the location of at least two linearly independent vectors attached to the body is known. The location of these vectors of the wrist end-effector is determined by the solution of the direct position analysis of some properly chosen kinematic chains (legs) of the manipulator. In order to accomplish this analysis, extra sensors, which measure suitable non-actuated variables of the chosen legs, need to be placed in addition to the ones normally embedded in the servomotors, i.e., the sensors which measure the actuated variables. From a mathematical point of view, the algorithm is built on the polar decomposition of a matrix and has inherent least square features. Thus, together with measurement redundancy, i.e., more sensors (extra sensors) than the mechanism degrees of freedom, the method also makes it possible to minimize the influence of both round-off and measurement errors on the estimation of the location of the wrist end-effector. The method is general but, in order to prove its effectiveness, without loss of generality it has been customized to the solution of the 3(UPS)-S fully parallel wrist architecture (where U, P and S are for universal, prismatic and spherical joint, respectively). Comparison of the proposed method, in both its general and specialized form, with others from the literature is provided.

Real-Time Direct Position Analysis of Parallel Spherical Wrists by Using Extra Sensor Data

2004 ◽  
Author(s):  
R. Vertechy ◽  
V. Parenti-Castelli
Keyword(s):  
Real Time ◽  
Measurement Errors ◽  
Degrees Of Freedom ◽  
Point Of View ◽  
The Body ◽  
Least Square ◽  
Sensor Data ◽  
End Effector ◽  
Kinematic Chains ◽  
Position Analysis

The paper presents an algorithm for the real-time evaluation of the actual end-effector orientation (pose) of general parallel spherical wrists. Conceptually, the method relies on the evidence that the pose of a rigid body is defined once the location of at least two linearly independent vectors attached to the body is known. The location of these vectors of the wrist end-effector is determined by the solution of the direct position analysis of some properly chosen kinematic chains (legs) of the manipulator. In order to accomplish this analysis, extra-sensors, which measure suitable non-actuated variables of the chosen legs, need to be placed in addition to the ones normally embedded in the servo motors, i.e. the sensors which measure the actuated variables. From a mathematical point of view, the algorithm is built on the Polar Decomposition of a matrix and has inherent least square features. Thus, together with measurement redundancy, i.e. more sensors (extra-sensors) than the mechanism degrees of freedom, the method also allows minimizing the influence of both round-off and measurement errors on the estimation of the location of the wrist end-effector. The method is general but, in order to prove its effectiveness, without loss of generality it has been customized to the solution of the (3-UPS)S fully parallel wrist architecture. Comparison of the proposed method, in both its general and specialized form, with others from the literature is provided.

scholarly journals Finite-Horizon Kinetic Energy Optimization of a Redundant Space Manipulator

2021 ◽  
Vol 11 (5) ◽  
pp. 2346
Author(s):  
Alessandro Tringali ◽  
Silvio Cocuzza
Keyword(s):  
Kinetic Energy ◽  
Real Time ◽  
Inverse Kinematics ◽  
Degrees Of Freedom ◽  
Computational Time ◽  
Redundant Manipulators ◽  
Space Robotics ◽  
Optimal Method ◽  
End Effector ◽  
Global Optimal

The minimization of energy consumption is of the utmost importance in space robotics. For redundant manipulators tracking a desired end-effector trajectory, most of the proposed solutions are based on locally optimal inverse kinematics methods. On the one hand, these methods are suitable for real-time implementation; nevertheless, on the other hand, they often provide solutions quite far from the globally optimal one and, moreover, are prone to singularities. In this paper, a novel inverse kinematics method for redundant manipulators is presented, which overcomes the above mentioned issues and is suitable for real-time implementation. The proposed method is based on the optimization of the kinetic energy integral on a limited subset of future end-effector path points, making the manipulator joints to move in the direction of minimum kinetic energy. The proposed method is tested by simulation of a three degrees of freedom (DOF) planar manipulator in a number of test cases, and its performance is compared to the classical pseudoinverse solution and to a global optimal method. The proposed method outperforms the pseudoinverse-based one and proves to be able to avoid singularities. Furthermore, it provides a solution very close to the global optimal one with a much lower computational time, which is compatible for real-time implementation.

Kinematic Synthesis of a Spatial 3-RPS Parallel Manipulator

2003 ◽  
Vol 125 (1) ◽  
pp. 92-97 ◽  
Author(s):  
Han Sung Kim ◽  
Lung-Wen Tsai
Keyword(s):  
Parallel Manipulator ◽  
Degrees Of Freedom ◽  
Parallel Manipulators ◽  
Point Of View ◽  
Dimensional Synthesis ◽  
Kinematic Synthesis ◽  
End Effector ◽  
Solution Methods ◽  
Moving Platform ◽  
At Will

This paper presents the design of spatial 3-RPS parallel manipulators from dimensional synthesis point of view. Since a spatial 3-RPS manipulator has only 3 degrees of freedom, its end effector cannot be positioned arbitrarily in space. It is shown that at most six positions and orientations of the moving platform can be prescribed at will and, given six prescribed positions, there are at most ten RPS chains that can be used to construct up to 120 manipulators. Further, solution methods for fewer than six prescribed positions are also described.

scholarly journals Polynomial Solution to the Position Analysis of Two Assur Kinematic Chains With Four Loops and the Same Topology

2009 ◽  
Vol 1 (2) ◽  
Author(s):  
Júlia Borràs ◽  
Raffaele Di Gregorio
Keyword(s):  
Polynomial Solution ◽  
Large Family ◽  
The Other ◽  
End Effector ◽  
Closed Loops ◽  
Kinematic Chains ◽  
Position Analysis ◽  
One To One ◽  
Actuated Joints

The direct position analysis (DPA) of a manipulator is the computation of the end-effector poses (positions and orientations) compatible with assigned values of the actuated-joint variables. Assigning the actuated-joint variables corresponds to considering the actuated joints locked, which makes the manipulator a structure. The solutions of the DPA of a manipulator one to one correspond to the assembly modes of the structure that is generated by locking the actuated-joint variables of that manipulator. Determining the assembly modes of a structure means solving the DPA of a large family of manipulators since the same structure can be generated from different manipulators. This paper provides an algorithm that determines all the assembly modes of two structures with the same topology that are generated from two families of mechanisms: one planar and the other spherical. The topology of these structures is constituted of nine links (one quaternary link, four ternary links, and four binary links) connected through 12 revolute pairs to form four closed loops.

Singularity Analysis of Closed Kinematic Chains

1999 ◽  
Vol 121 (1) ◽  
pp. 32-38 ◽  
Author(s):  
F. C. Park ◽  
J. W. Kim
Keyword(s):  
Configuration Space ◽  
Degrees Of Freedom ◽  
Geometric Analysis ◽  
Singularity Analysis ◽  
Geometric Framework ◽  
End Effector ◽  
Kinematic Chains ◽  
Closed Chain ◽  
High Level ◽  
Kinematic Singularities

This paper presents a coordinate-invariant differential geometric analysis of kinematic singularities for closed kinematic chains containing both active and passive joints. Using the geometric framework developed in Park and Kim (1996) for closed chain manipulability analysis, we classify closed chain singularities into three basic types: (i) those corresponding to singular points of the joint configuration space (configuration space singularities), (ii) those induced by the choice of actuated joints (actuator singularities), and (iii) those configurations in which the end-effector loses one or more degrees of freedom of available motion (end-effector singularities). The proposed geometric classification provides a high-level taxonomy for mechanism singularities that is independent of the choice of local coordinates used to describe the kinematics, and includes mechanisms that have more actuators than kinematic degrees of freedom.

scholarly journals Kinematic Synthesis and Analysis of the RoboMech Class Parallel Manipulator with Two Grippers

Robotics ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 99
Author(s):  
Zhumadil Baigunchekov ◽  
Med Amine Laribi ◽  
Azamat Mustafa ◽  
Abzal Kassinov
Keyword(s):  
Parallel Manipulator ◽  
Degrees Of Freedom ◽  
Geometric Parameters ◽  
Geometric Constraints ◽  
Least Square ◽  
Kinematic Synthesis ◽  
Serial Manipulators ◽  
Kinematic Chains ◽  
End Effectors ◽  
Cold Stamping

In this paper, methods of kinematic synthesis and analysis of the RoboMech class parallel manipulator (PM) with two grippers (end effectors) are presented. This PM is formed by connecting two output objects (grippers) with a base using two passive and one negative closing kinematic chains (CKCs). A PM with two end effectors can be used for reloading operations of stamped products between two adjacent main technologies in a cold stamping line. Passive CKCs represent two serial manipulators with two degrees of freedom, and negative CKC is a three-joined link with three negative degrees of freedom. A negative CKC imposes three geometric constraints on the movements of the two output objects. Geometric parameters of the negative CKC are determined on the basis of the problems of the Chebyshev and least-square approximations. Problems of positions and analogues of velocities and accelerations of the PM with two end effectors have been solved.

scholarly journals Exoskeleton kinematic design robustness: An assessment method to account for human variability

2020 ◽  
Vol 1 ◽  
Author(s):  
Matteo Sposito ◽  
Christian Di Natali ◽  
Stefano Toxiri ◽  
Darwin G. Caldwell ◽  
Elena De Momi ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Pilot Trial ◽  
Kinematic Model ◽  
Assessment Method ◽  
Point Of View ◽  
Systematic Method ◽  
Kinematic Chains ◽  
Subject Variability ◽  
Anchor Points ◽  
Human Joints

Abstract Exoskeletons are wearable devices intended to physically assist one or multiple human joints in executing certain activities. From a mechanical point of view, they are kinematic structures arranged in parallel to the biological joints. In order to allow the users to move while assisted, it is crucial to avoid mobility restrictions introduced by the exoskeleton’s kinematics. Passive degrees of freedom and other self-alignment mechanisms are a common option to avoid any restrictions. However, the literature lacks a systematic method to account for large inter- and intra-subject variability in designing and assessing kinematic chains. To this end, we introduce a model-based method to assess the kinematics of exoskeletons by representing restrictions in mobility as disturbances and undesired forces at the anchor points. The method makes use of robotic kinematic tools and generates useful insights to support the design process. Though an application on a back-support exoskeleton designed for lifting tasks is illustrated, the method can describe any type of rigid exoskeleton. A qualitative pilot trial is conducted to assess the kinematic model that proved to predict kinematic configurations associated to rising undesired forces recorded at the anchor points, that give rise to mobility restrictions and discomfort on the users.

A Momentum-Based Algorithm for Identifying the Inertia Properties of a Human Body: A Preliminary Study

2010 ◽  
Author(s):  
Qi Lu ◽  
Ou Ma
Keyword(s):  
Human Body ◽  
Measurement Errors ◽  
Equations Of Motion ◽  
Least Square Method ◽  
Internal Force ◽  
Momentum Equation ◽  
The Body ◽  
Least Square ◽  
Identification Algorithm ◽  
Force Data

The body segment parameters (BSP) of a human body are critical information for modeling, simulating, and understanding human dynamics. The determination of BSPs of human bodies has received increasing attention in biomechanics, sport science, ergonomics, rehabilitation and other fields. This paper presents a momentum-based identification algorithm for dynamically estimating the BSPs of a human body. The human body is modeled as a multibody dynamical system, and the momentum equation of the system can be derived by applying the principle of impulse and momentum. It is possible to formulate the momentum equations corresponding to a set of experiment tests into a linear regression form with respect to the unknown BSPs, which then can be solved using the least square method or other methods. The momentum-based algorithm requires inputting position, velocity, and external force data only. Since acceleration and all the internal force data is not needed, the algorithm is less demanding on measurements and is also less sensitive to measurement errors. As a result, it is practically more appealing than the algorithms depending on the equations of motion. The paper presents the momentum-based inertia identification algorithm along with a simulation study of the algorithm using a simplified trunk-leg model representing a main portion of a human body.

scholarly journals Voluntary performance

Medicina ◽  
2010 ◽  
Vol 46 (9) ◽  
pp. 581 ◽  
Author(s):  
Guy Van Orden
Keyword(s):  
Degrees Of Freedom ◽  
Human Performance ◽  
Motor Coordination ◽  
Direct Consequence ◽  
Present Knowledge ◽  
Repeated Measurements ◽  
Point Of View ◽  
The Body ◽  
Direct Coupling ◽  
Dynamical Disease

Will, purpose, and volition have long been viewed as either causes of behavior or of no direct consequence to behavior. In this essay, volition affects a flexible direct coupling of participant to task, modulating the degrees of freedom for kinematics in action, a point of view first introduced in theories of motor coordination. The consequence is an explanation consistent with present knowledge about involuntary and voluntary sources of control in human performance, and also the changes of the body expressed in aging and dynamical disease. Specifically, this view explains how tradeoffs between sources of overly regular versus overly random dynamics change the structure of variability in repeated measurements of voluntary performance.

Real-Time Motion Capture for a Human Body using Accelerometers

Robotica ◽  
2001 ◽  
Vol 19 (6) ◽  
pp. 601-610 ◽  
Author(s):  
Jihong Lee ◽  
Insoo Ha
Keyword(s):  
Real Time ◽  
Motion Capture ◽  
Human Body ◽  
Degrees Of Freedom ◽  
Low Cost ◽  
Human Motion ◽  
The Body ◽  
Sensor Data ◽  
Time Motion ◽  
Gravity Acceleration

In this paper we propose a set of techniques for a real-time motion capture of a human body. The proposed motion capture system is based on low cost accelerometers, and is capable of identifying the body configuration by extracting gravity-related terms from the sensor data. One sensor unit is composed of 3 accelerometers arranged orthogonally to each other, and is capable of identifying 2 rotating angles of joints with 2 degrees of freedom. A geometric fusion technique is applied to cope with the uncertainty of sensor data. A practical calibration technique is also proposed to handle errors in aligning the sensing axis to the coordination axis. In the case where motion acceleration is not negligible compared with gravity acceleration, a compensation technique to extract gravity acceleration from the sensor data is proposed. Experimental results not only for individual techniques but also for human motion capturing with graphics are included.

Sign in / Sign up

Export Citation Format

Share Document