Experiments on Linear and Nonlinear Control of a Multi-DOF Parallel Mechanism

2003 ◽  
Author(s):  
Sandor Riebe ◽  
Heinz Ulbrich
Keyword(s):  
Degrees Of Freedom ◽  
Motion Tracking ◽  
Parallel Robot ◽  
Parallel Kinematics ◽  
Control Laws ◽  
Six Degrees Of Freedom ◽  
Position Accuracy ◽  
Nonlinear Approach ◽  
Linear Approach ◽  
Measurement Results

Parallel kinematics with multi degrees-of-freedom (DOF), like hexapod-systems, are mostly used in applications where high demands on position accuracy are required and/or high accelerations are needed. Adequate control concepts are essential in order to achieve the desired dynamic response. This paper deals with a comparative study of two structural different control concepts applied on a parallel robot with six degrees-of-freedom. The first one is a decentral linear approach and the second one is a multivariable nonlinear approach. The two concepts are presented and implemented on an experimental hexapod-system. In order to verify the used dynamic model comparisons between simulation and measurement results are shown. Finally, experiments have been carried out to compare the control laws with respect to their motion tracking performance.

Construction of a Six-Degrees-of-Freedom Parallel Manipulator With Three Planarly Actuated Links

1996 ◽  
Author(s):  
Ronen Ben-Horin ◽  
Moshe Shoham
Keyword(s):  
Parallel Manipulator ◽  
High Performance ◽  
Degrees Of Freedom ◽  
Parallel Robot ◽  
Simple Design ◽  
Output Link ◽  
Coordinated Motion ◽  
Six Degrees Of Freedom ◽  
Work Volume ◽  
New Type

Abstract The construction of a new type of a six-degrees-of-freedom parallel robot is presented in this paper. Coordinated motion of three planar motors, connected to three fixed-length links, produces a six-degrees-of-freedom motion of an output link. Its extremely simple design along with much larger work volume make this high performance-to-simplicity ratio robot very attractive.

A Parallel Six Degrees-of-Freedom Inflatable Robot

2000 ◽  
Author(s):  
Patricia Ben-Horin (Dombiak) ◽  
Moshe Shoham ◽  
Gershon Grossman
Keyword(s):  
Path Planning ◽  
Degrees Of Freedom ◽  
Parallel Robot ◽  
Six Degrees Of Freedom ◽  
Robot Architecture

Abstract A new structure of a six degrees-of-freedom robot is described in this paper. The robot presents two new features: three inflatable links that constitute the robot structure and parallel robot architecture with large workspace. These features result in a lightweight and easy to deploy robot. The structure, kinematics and path planning of the experimental robot are presented.

Compensation of geometric and elastic errors in large manipulators with an application to a high accuracy medical system

Robotica ◽  
2002 ◽  
Vol 20 (3) ◽  
pp. 341-352 ◽  
Author(s):  
Ph. Drouet ◽  
S. Dubowsky ◽  
S. Zeghloul ◽  
C. Mavroidis
Keyword(s):  
Degrees Of Freedom ◽  
High Accuracy ◽  
Medical Robot ◽  
Serial Manipulators ◽  
High Position ◽  
Six Degrees Of Freedom ◽  
Position Accuracy ◽  
End Point ◽  
Compensation Process ◽  
Very High

A method is presented that compensates for manipulator end-point errors in order to achieve very high position accuracy. The measured end-point error is decomposed into generalized geometric and elastic error parameters that are used in an analytical model to calibrate the system as a function of its configuration and the task loads, including any payload weight. The method exploits the fundamental mechanics of serial manipulators to yield a non-iterative compensation process that only requires the identification of parameters that are function only of one variable. The resulting method is computationally simple and requires far less measured data than might be expected. The method is applied to a six degrees-of-freedom (DOF) medical robot that positions patients for cancer proton therapy to enable it to achieve very high accuracy. Experimental results show the effectiveness of the method.

Trajectory Tracking of 3D Autonomous Vehicles Using Backstepping Control

2019 ◽  
Author(s):  
Karl Ludwig Fetzer ◽  
Sergey G. Nersesov ◽  
Hashem Ashrafiuon
Keyword(s):  
Autonomous Vehicles ◽  
Degrees Of Freedom ◽  
3D Model ◽  
Autonomous Vehicle ◽  
Backstepping Control ◽  
Reference Trajectory ◽  
Control Laws ◽  
Six Degrees Of Freedom ◽  
Error Dynamics ◽  
Dynamics Stability

Abstract In this paper, the authors derive backstepping control laws for tracking a time-based reference trajectory for a 3D model of an autonomous vehicle with two degrees of underactuation. Tracking all six degrees of freedom is made possible by a transformation that reduces the order of the error dynamics. Stability of the resulting error dynamics is proven and demonstrated in simulations.

scholarly journals Studies Evaluating Measurement Accuracy of CMS-JAW, a Jaw Motion Tracking Device with Six Degrees of Freedom Using an Ultrasonic Recording System

2008 ◽  
Vol 52 (3) ◽  
pp. 350-359 ◽  
Author(s):  
Takashi Uchida ◽  
Jun Sakai ◽  
Yasuhiro Okamoto ◽  
Tsukasa Watanabe ◽  
Tsuyoshi Kitagawa ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Motion Tracking ◽  
Measurement Accuracy ◽  
Recording System ◽  
Six Degrees Of Freedom ◽  
Tracking Device

The Wide-Open Three-Legged Parallel Robot for Long-Bone Fracture Reduction

2017 ◽  
Vol 9 (1) ◽  
Author(s):  
Mohammad H. Abedinnasab ◽  
Farzam Farahmand ◽  
Jaime Gallardo-Alvarado
Keyword(s):  
Bone Fracture ◽  
Degrees Of Freedom ◽  
Experimental Tests ◽  
Parallel Robot ◽  
High Accuracy ◽  
Fracture Reduction ◽  
Long Bone ◽  
Long Bones ◽  
Six Degrees Of Freedom ◽  
Long Bone Fracture

Robotic reduction of long bones is associated with the need for considerable force and high precision. To balance the accuracy, payload, and workspace, we have designed a new six degrees-of-freedom three-legged wide-open robotic system for long-bone fracture reduction. Thanks to the low number of legs and their nonsymmetrical configuration, the mechanism enjoys a unique architecture with a frontally open half-plane. This facilitates positioning the leg inside the mechanism and provides a large workspace for surgical maneuvers, as shown and compared to the well-known Gough–Stewart platform. The experimental tests on a phantom reveal that the mechanism is well capable of applying the desired reduction steps against the large muscular payloads with high accuracy.

Reconfiguration Analysis of a Fully Reconfigurable Parallel Robot

2013 ◽  
Vol 5 (4) ◽  
Author(s):  
Allan Daniel Finistauri ◽  
Fengfeng (Jeff) Xi
Keyword(s):  
Comparative Study ◽  
Degrees Of Freedom ◽  
Parallel Robot ◽  
Passive State ◽  
Limited Mobility ◽  
Six Degrees Of Freedom ◽  
Revolute Joints ◽  
Six Degree Of Freedom ◽  
The Comparative Study ◽  
Selection Of

This paper presents a new method for the combined topological and geometric reconfiguration of a parallel robot to achieve task-based reconfiguration. Using the existing structure of a six degree-of-freedom (DOF) parallel robot, reconfiguration to limited mobility modes, a configuration with less than six degrees-of-freedom, can be achieved easily without the need to remove branches from the robot structure. Branch modules are instead, reconfigured from an unconstrained-active to a constrained-passive state by means of hybrid active/passive motors and reconfigurable universal-to-revolute joints. In doing so, the robot is capable of assuming a configuration in which the number of task-based degrees-of-freedom match the number of controllable actuators within the robot structure. The selection of branch modules for reconfiguration is independent of the limited mobility mode required and leads to multiple isomorphic configurations. A comparative study is thus needed to understand not only the implication of morphing, but also the capabilities of the reconfigured robot. For this purpose, a branch-based mobility analysis is performed and isomorphic configurations are identified. These isomorphic configurations are then compared based on their workspace and kinematic capabilities for which a parametric kinematic constraint formulation is developed. The comparative study evaluates the abilities of each configuration and is used for guidance in selecting an appropriate configuration for a particular task. The developed tools can also be used for design evaluation purposes.

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