Kinematics of a Hybrid Series-Parallel Manipulation System

1989 ◽  
Vol 111 (2) ◽  
pp. 211-221 ◽  
Author(s):  
K. J. Waldron ◽  
M. Raghavan ◽  
B. Roth
Keyword(s):  
Degrees Of Freedom ◽  
Joint Space ◽  
Degree Of Freedom ◽  
Micro Manipulator ◽  
In Series ◽  
Basic Transformation ◽  
Motion Characteristics ◽  
Six Degree Of Freedom ◽  
Three Degree Of Freedom ◽  
Force Decomposition

In this paper we first derive the coordinate transformations associated with a three-degree-of-freedom in-parallel-actuated micro-manipulator. Then we combine these results with the transformations associated with an in-series three-axis wrist on which the in-parallel micro-manipulator is mounted. The results are the basic transformation equations between joint-space position variables and end-effector (or task space) position variables for a hybrid series/parallel six-degree-of-freedom manipulator system. This structural combination results in a manipulator which exhibits desirable fine and gross motion characteristics as both a stand-alone device or as a sub-system of a more complex system with redundant degrees of freedom. The forward and inverse position kinematics and rate and force decomposition for this hybrid six-degree-of-freedom linkage are presented.

Inertial Vibration Damping Control for a Flexible Base Manipulator

2002 ◽  
Author(s):  
Lynnane E. George ◽  
Wayne J. Book
Keyword(s):  
Performance Index ◽  
Degrees Of Freedom ◽  
Position Control ◽  
Joint Space ◽  
Vibration Damping ◽  
Degree Of Freedom ◽  
Inertia Effects ◽  
Inertial Interaction ◽  
Flexible Base ◽  
Three Degree Of Freedom

A rigid (micro) robot mounted serially to the tip of a long, flexible (macro) manipulator is often used to increase reach capability, but flexibility in the macromanipulator can interfere with positioning accuracy. A rigid manipulator attached to a flexible but unactuated base was used to study a scheme to achieve positioning of the micromanipulator combined with enhanced vibration damping of the base. Inertial interaction forces and torques acting between the robot and its base were modeled and studied to determine how to use them to damp the vibration. One issue is that there are locations in the workspace where the rigid robot loses its ability to create interactions in one or more degrees of freedom. These “inertial singularities” are functions of the rigid robot’s joint variables. A performance index was developed to predict the ability of the rigid robot to damp vibration and will help ensure the robot is operating in joint space configurations favorable for inertial damping. When the performance index is used along with the appropriate choice of feedback gains, the inertia effects, or those directly due to accelerating the robot’s links, have the greatest influence on the interactions. By commanding the robot link’s accelerations out of phase with the base velocity, vibration energy will be removed from the system. This signal is then added to the rigid robot’s position control signal. Simulations of a rigid three degree of freedom anthropomorphic robot mounted on a flexible base were developed and show the effectiveness of the control scheme. In addition, experimental results demonstrating two degree of freedom vibration damping are included.

Coordinated Visual and Kinematic Servoing for Positioning Manipulating UAV End-Effectors

2014 ◽  
Author(s):  
Todd W. Danko ◽  
Paul Y. Oh
Keyword(s):  
Disaster Response ◽  
Degrees Of Freedom ◽  
Joint Space ◽  
Degree Of Freedom ◽  
Ground Vehicles ◽  
Manipulator Arm ◽  
One Step ◽  
Infrastructure Repair ◽  
End Effectors ◽  
Six Degree Of Freedom

Manipulating objects using arms mounted to unmanned aerial vehicles (UAVs) is attractive because UAVs may access many locations that are otherwise inaccessible to traditional mobile manipulation platforms such as ground vehicles. However, the constantly moving UAV platform and compliance of manipulator arms make it difficult to position the UAV and end-effector relative to an object of interest precisely enough for reliable manipulation. Solving this challenge will bring UAVs one step closer to being able to perform meaningful tasks such as infrastructure repair, disaster response, law enforcement, and personal assistance. Toward a solution to this challenge, this paper describes an approach to coordinate the redundant degrees of freedom of a six degree of freedom gantry with those of a six degree of freedom manipulator arm. The manipulator’s degrees of freedom are visually servoed to a specified pose relative to a target while treating motions of the host platform as perturbations. Simultaneously, the host platform’s degrees of freedom are servoed using kinematic information from the manipulator. This drives the base of the manipulator to a position that allows it to assume a joint-space configuration that maximizes reachability while minimizing static torque transmitted from the arm to the host.

scholarly journals Design and Calibration of a Hall Effect System for Measurement of Six-Degree-of-Freedom Motion within a Stacked Column

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3740
Author(s):  
Olafur Oddbjornsson ◽  
Panos Kloukinas ◽  
Tansu Gokce ◽  
Kate Bourne ◽  
Tony Horseman ◽  
...  
Keyword(s):  
Hall Effect ◽  
Degrees Of Freedom ◽  
Reactor Core ◽  
Degree Of Freedom ◽  
Life Extension ◽  
Scale Model ◽  
Design Development ◽  
Seismic Safety ◽  
Six Degrees Of Freedom ◽  
Six Degree Of Freedom

This paper presents the design, development and evaluation of a unique non-contact instrumentation system that can accurately measure the interface displacement between two rigid components in six degrees of freedom. The system was developed to allow measurement of the relative displacements between interfaces within a stacked column of brick-like components, with an accuracy of 0.05 mm and 0.1 degrees. The columns comprised up to 14 components, with each component being a scale model of a graphite brick within an Advanced Gas-cooled Reactor core. A set of 585 of these columns makes up the Multi Layer Array, which was designed to investigate the response of the reactor core to seismic inputs, with excitation levels up to 1 g from 0 to 100 Hz. The nature of the application required a compact and robust design capable of accurately recording fully coupled motion in all six degrees of freedom during dynamic testing. The novel design implemented 12 Hall effect sensors with a calibration procedure based on system identification techniques. The measurement uncertainty was ±0.050 mm for displacement and ±0.052 degrees for rotation, and the system can tolerate loss of data from two sensors with the uncertainly increasing to only 0.061 mm in translation and 0.088 degrees in rotation. The system has been deployed in a research programme that has enabled EDF to present seismic safety cases to the Office for Nuclear Regulation, resulting in life extension approvals for several reactors. The measurement system developed could be readily applied to other situations where the imposed level of stress at the interface causes negligible material strain, and accurate non-contact six-degree-of-freedom interface measurement is required.

Design of a Teaching Robot with Three Degrees of Freedom

2012 ◽  
Vol 619 ◽  
pp. 325-328
Author(s):  
You Jun Huang ◽  
Ze Lun Li ◽  
Zhi Cheng Huang
Keyword(s):  
Degrees Of Freedom ◽  
Low Cost ◽  
Degree Of Freedom ◽  
Good Repeatability ◽  
Main Components ◽  
Opening And Closing ◽  
Three Degree Of Freedom ◽  
Three Degrees Of Freedom ◽  
Application Prospects

A teaching robot with three degree of freedom is designed. The three degrees of freedom are: waist rotation, lifting and stretching of the arm and opening and closing of the gripper. The designs of the main components are: a mobile chassis, parallel rails, horizontal rails and manipulator. The teaching robot designed has the features of low cost, easy to regulation, good repeatability and it has good promotion and application prospects in the field of teaching.

Rudder/Fin Roll Stabilization of the USCG WMEC 901 Class Vessel

1999 ◽  
Vol 36 (03) ◽  
pp. 157-170
Author(s):  
Jerrold N. Sgobbo ◽  
Michael G. Parsons
Keyword(s):  
Degrees Of Freedom ◽  
Multiple Input Multiple Output ◽  
Cross Coupling ◽  
Degree Of Freedom ◽  
Rolling Motion ◽  
Rolling Moment ◽  
Multiple Input ◽  
Input Multiple Output ◽  
Three Degree Of Freedom ◽  
The U.S

The U.S. Coast Guard's 270-ft Medium Endurance Cutter (WMEC) operates with an active fin stabilization system. This system was designed using a one-degree-of-freedom (1-DOF) model in the roll direction. The controller was designed separate from the heading autopilot. The effects of the rudders and their ability to produce a significant rolling moment were also neglected as well as the cross coupling of roll motions into other degrees of freedom. This paper studies the effects of the rudders on the rolling motion of the ship using a three-degree-of-freedom (3-DOF) model. A simple optimal heading autopilot is designed and combined with the existing fin roll controller to investigate the effects of the rudders on the roll motions of this class of vessel. A rudder roll controller and a multiple input-multiple output (MIMO) rudder/fin controller are designed as well. Significant roll reduction can be achieved using the MIMO rudder/fin controller.

Regulating a Formation of a Large Number of Vehicles

2005 ◽  
Author(s):  
Akira Okamoto ◽  
Dean B. Edwards
Keyword(s):  
Control Problem ◽  
Coordinate System ◽  
Formation Control ◽  
Control Algorithm ◽  
Degrees Of Freedom ◽  
Degree Of Freedom ◽  
Relative Distance ◽  
Control Algorithms ◽  
Distance Measurements ◽  
Six Degree Of Freedom

Various control algorithms have been developed for fleets of autonomous vehicles. Many of the successful control algorithms in practice are behavior-based control or nonlinear control algorithms, which makes analyzing their stability difficult. At the same time, many system theoretic approaches for controlling a fleet of vehicles have also been developed. These approaches usually use very simple vehicle models such as particles or point-mass systems and have only one coordinate system which allows stability to be proven. Since most of the practical vehicle models are six-degree-of-freedom systems defined relative to a body-fixed coordinate system, it is difficult to apply these algorithms in practice. In this paper, we consider a formation regulation problem as opposed to a formation control problem. In a formation control problem, convergence of a formation from random positions and orientations is considered, and it may need a scheme to integrate multiple moving coordinates. On the contrary, in a formation regulation problem, it is not necessary since small perturbations from the nominal condition, in which the vehicles are in formation, are considered. A common origin is also not necessary if the relative distance to neighbors or a leader is used for regulation. Under these circumstances, the system theoretic control algorithms are applicable to a formation regulation problem where the vehicle models have six degrees of freedom. We will use a realistic six-degree-of-freedom model and investigate stability of a fleet using results from decentralized control theory. We will show that the leader-follower control algorithm does not have any unstable fixed modes if the followers are able to measure distance to the leader. We also show that the leader-follower control algorithm has fixed modes at the origin, indicating that the formation is marginally stable, when the relative distance measurements are not available. Multi-vehicle simulations are performed using a hybrid leader-follower control algorithm where each vehicle is given a desired trajectory to follow and adjusts its velocity to maintain a prescribed distance to the leader. Each vehicle is modeled as a three-degree-of-freedom system to investigate the vehicle’s motion in a horizontal plane. The examples show efficacy of the analysis.

Research of Nanometer Positioning Stage With Six Degree of Freedom Based on Binary Actuation Principle

2007 ◽  
Author(s):  
Shufeng Sun
Keyword(s):  
Feedback Control ◽  
Theoretical Calculation ◽  
Degree Of Freedom ◽  
Element Analysis ◽  
Positioning Stage ◽  
In Series ◽  
Ultra Precision ◽  
New Type ◽  
Six Degree Of Freedom ◽  
Development Tendency

To adapt the miniaturized development tendency of nanometer positioning devices, a new type of micro-displacement stage with six degree of freedom, which can implement nanometer-level ultra-precision positioning without feedback control is designed. It takes a group of piezoelectric ceramics actuators (PZTAs) connected in series as actuation unit, takes flexure hinges as elastic guide rail. To overcome the non-linearity and hysteresis of PZTAs, binary actuation principle is adopted to control a group of actuators that work together to output many discrete, repeatable displacements. If these displacements are distributed within a scope of several microns, only simple on and off actuator commands may obtain nanometer-level repeatable positioning without feedback control. Theoretical calculation and finite element analysis (FEA) are used to design and simulate the stage. Expressions of rigidity and stress are obtained by theoretical calculation. FEA and experimental results verify the rationality and feasibility of the stage.

The St. Petersburg Wrist: A Prototype Powered Flexion Wrist Unit

2008 ◽  
Author(s):  
Kathryn J. De Laurentis ◽  
Sam L. Phillips
Keyword(s):  
Degrees Of Freedom ◽  
Degree Of Freedom ◽  
Six Degrees Of Freedom ◽  
Important Addition ◽  
Powered Prosthesis ◽  
Six Degree Of Freedom ◽  
Flexion And Extension

This is the presentation of a prototype wrist, which has powered rotation and flexion. Powered flexion is an important addition to an externally powered prosthesis. Flexion and extension, along with rotation give the prosthesis two additional degrees of freedom, which when added to degrees of freedom for the shoulder and elbow yield a six-degree of freedom system. Six-degrees of freedom are important because they allow placement of the hand throughout the entire workspace. Without flexion, amputees cannot reach some positions, and must use compensatory motions for many other movements.

scholarly journals Feedback Linearisation for Nonlinear Vibration Problems

2014 ◽  
Vol 2014 ◽  
pp. 1-16 ◽  
Author(s):  
S. Jiffri ◽  
P. Paoletti ◽  
J. E. Cooper ◽  
J. E. Mottershead
Keyword(s):  
Degrees Of Freedom ◽  
Nonlinear Problems ◽  
Second Order ◽  
Degree Of Freedom ◽  
Sensors And Actuators ◽  
Order Matrix ◽  
Problem Class ◽  
Aeroelastic Model ◽  
Matrix Differential ◽  
Three Degree Of Freedom

Feedback linearisation is a well-known technique in the controls community but has not been widely taken up in the vibrations community. It has the advantage of linearising nonlinear system models, thereby enabling the avoidance of the complicated mathematics associated with nonlinear problems. A particular and common class of problems is considered, where the nonlinearity is present in a system parameter and a formulation in terms of the usual second-order matrix differential equation is presented. The classical texts all cast the feedback linearisation problem in first-order form, requiring repeated differentiation of the output, usually presented in the Lie algebra notation. This becomes unnecessary when using second-order matrix equations of the problem class considered herein. Analysis is presented for the general multidegree of freedom system for those cases when a full set of sensors and actuators is available at every degree of freedom and when the number of sensors and actuators is fewer than the number of degrees of freedom. Adaptive feedback linearisation is used to address the problem of nonlinearity that is not known precisely. The theory is illustrated by means of a three-degree-of-freedom nonlinear aeroelastic model, with results demonstrating the effectiveness of the method in suppressing flutter.

Collision Avoidance for a Multiple-DOF Manipulator Based on Empty Space Analysis of the 3-D Real World

1992 ◽  
Vol 4 (5) ◽  
pp. 430-436 ◽  
Author(s):  
Hiromu Onda ◽  
◽  
Tsutomu Hasegawa ◽  
Toshihiro Matsui ◽  
Keyword(s):  
Collision Avoidance ◽  
Real World ◽  
Degrees Of Freedom ◽  
Empty Space ◽  
Joint Space ◽  
Degree Of Freedom ◽  
New Method ◽  
Promising Direction ◽  
Space Analysis ◽  
Path Search

This paper describes a new method for finding collisionfree paths for a multiple-degree of freedom (DOF) manipulator with rotational joints and a grasped object. The method first analyzes the structure of empty space in the 3-D workspace. Based on this space analysis, the path search is divided and direction which appears to be most promising is determined in the 3-D workspace. Finally, the path search is systematically executed in the joint space in the direction equivalent to the promising direction. This method is applicable to various problems regardless of the number of degrees of freedom of the manipulator, its structure, and the presence of a grasped object.

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