Design of Under-Actuated Open-Chain Planar Robots for Repetitive Cyclic Motions

2006 ◽  
Author(s):  
Sunil K. Agrawal ◽  
Vivek Sangwan
Keyword(s):  
Numerical Methods ◽  
Industrial Robots ◽  
Differential Flatness ◽  
Open Chain ◽  
Revolute Joints ◽  
Planar Robot ◽  
Point Trajectories ◽  
Point To Point ◽  
Three Degree Of Freedom ◽  
Output Space

Under-actuated systems are unavoidable in certain applications. For example, a biped can not have an actuator between the foot and the ground. For industrial robots, underactuation is preferable due to cost considerations. A fully actuated system can execute any joint trajectory. However, if the system is under-actuated, not all joint trajectories are attainable. For such systems, it is difficult to characterize attainable joint trajectories analytically and numerical methods are generally used to characterize them. This paper investigates the property of differential flatness for under-actuated planar open chain robots and study its dependence on inertia distribution within the system. Once this property is established, trajectory between any two points in its differentially flat output space is feasible and can be shown to be consistent with the dynamics of the under-actuated system. It is shown that certain choices of inertia distributions make an under-actuated open-chain planar robot with revolute joints feedback linearizable, i.e., also differentially flat. Hence, both cyclic and point to point trajectories can be guaranteed with these under-actuated systems. The methodology proposed is demonstrated with an under-actuated three degree-of-freedom planar robot.

scholarly journals Optimizing Industrial Robots for Accurate High-Speed Applications

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Hubert Gattringer ◽  
Roland Riepl ◽  
Matthias Neubauer
Keyword(s):  
High Speed ◽  
Industrial Robot ◽  
Optimization Techniques ◽  
Industrial Robots ◽  
Industrial Control ◽  
Geometric Calibration ◽  
One Step ◽  
Point Trajectories ◽  
Optimal Efficiency ◽  
Point To Point

Today’s standard robotic systems often do not meet the industry’s demands for accurate high-speed robotic applications. Any machine, be it an existing or a new one, should be pushed to its limits to provide “optimal” efficiency. However, due to the high complexity of modern applications, a one-step overall optimization is not possible. Therefore, this contribution introduces a step-by-step sequence of multiple nonlinear optimizations. Included are optimal configurations for geometric calibration, best-exciting trajectories for parameter identification, model-based control, and time/energy optimal trajectory planning for continuous path and point-to-point trajectories. Each of these optimizations contributes to the improvement of the overall system. Existing optimization techniques are adapted and extended for use with a standard industrial robot scenario and combined with a comprehensive toolkit with discussions on the interplay between the separate components. Most importantly, all procedures are evaluated in practical experiments on a standard robot with industrial control hardware and the recorded measurements are presented, a step often missing in publications in this area.

Constrained motion planning for open-chain industrial robots

Robotica ◽  
2010 ◽  
Vol 29 (3) ◽  
pp. 403-420 ◽  
Author(s):  
Gianluca Antonelli ◽  
Cataldo Curatella ◽  
Alessandro Marino
Keyword(s):  
Motion Planning ◽  
Industrial Robots ◽  
Robot Motion ◽  
Constrained Motion ◽  
Open Chain ◽  
Physical Constraints ◽  
Industrial Manipulators ◽  
Planning Algorithm ◽  
Wide Perspective ◽  
Point To Point

SUMMARYIn the industrial environment, several constraints affect the robot motion planning. These are imposed by manufacturing considerations, such as, e.g., to strictly follow a given path, or by physical constraints, such as, e.g., to avoid torque saturation. Among the others, limitation on the velocity, acceleration, and jerk at the joints is often required by the robot manufacturers. In this paper, a motion planning algorithm for open-chain robot manipulators that takes into account several constraints simultaneously is presented. The algorithm developed approaches the motion planning algorithm from a wide perspective, solving systematically the joint as well as the Cartesian motion, both for the point-to-point and the fly movements. The validation has been performed first by numerical simulations and then by experiments on two different industrial manipulators, with different size, with and without the presence of a payload, by imposing demanding trajectories where all the constraints have been excited.

Experimental evaluation of time-varying impulse shaping with a two-link flexible manipulator

Robotica ◽  
1996 ◽  
Vol 14 (3) ◽  
pp. 339-345 ◽  
Author(s):  
Jung-Keun Cho ◽  
Youn-Sik Park
Keyword(s):  
Vibration Reduction ◽  
Vertical Plane ◽  
Joint Stiffness ◽  
Flexible Manipulator ◽  
Input Shaping ◽  
Time Varying ◽  
Modal Properties ◽  
Revolute Joints ◽  
Point Motion ◽  
Point To Point

SUMMARYIn the authors' previous paper,10 an input shaping method was presented to reduce motion-induced vibrations effectively for various classes of flexible systems. In this paper, the effectiveness of the shaping method is experimentally demonstrated with a two-link flexible manipulator systemThe manipulator for experiments includes two revolute joints and two flexible links, and moves on a vertical plane under gravity. An analytic model is developed considering the flexibility of the system and its joint stiffness in order to derive an appropriate estimation of dynamic modal properties. The input shaping method used in this work utilizes time-varying modal properties obtained from the model instead of the conventional input shaping method which employs time-invariant modal properties. A point-to-point motion is tested in order to show the effectivess of the proposed shaping method in vibration reduction during and after a given motion. The given reference trajectories are shaped to suppress the motion induced vibration. The test results demonstrate that the link vibration can be greatly suppressed during and after a motion, and the residual vibration reduction was observed more than 90% by employing this time-varying impulse shaping technique.

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.

Kinematic Singularities of Free-Floating Open-Chain Planar Manipulators

1992 ◽  
Author(s):  
Sunil Kumar Agrawal ◽  
J. Rambhaskar
Keyword(s):  
Polynomial Equations ◽  
Joint Angles ◽  
Systematic Method ◽  
Open Chain ◽  
Singular Configurations ◽  
Revolute Joints ◽  
Planar Manipulators ◽  
Fixed Base ◽  
External Forces ◽  
Kinematic Singularities

Abstract This paper deals with Jacobian singularities of free-floating open-chain planar manipulators. The problem, in essence, is to find the joint angles where the Jacobian mapping between the end-effector rates and the joint rates is singular. In the absence of external forces and couples, for free-floating manipulators, the linear and angular momentum are conserved. This makes the singular configurations of free-floating manipulators different from structurally similar fixed-base manipulators. In order to illustrate this idea, we present a systematic method to obtain the singular solutions of a free-floating series-chain planar manipulator with revolute joints. We show that the singular configurations are solutions of simultaneous polynomial equations in the half-tangent of the joint variables. From the structure of these polynomial equations, we estimate the upper bound on the number of singularities of free-floating planar manipulators and compare these with analogous results for structurally similar fixed-base manipulators.

Generation and Evaluation of a Manipulator Workspace Based on Optimum Path Search

1985 ◽  
Vol 107 (2) ◽  
pp. 245-255 ◽  
Author(s):  
M. Cwiakala ◽  
T. W. Lee
Keyword(s):  
Comparative Study ◽  
Quantitative Evaluation ◽  
Matrix Method ◽  
Optimization Technique ◽  
Industrial Robots ◽  
Dual Number ◽  
Revolute Joints ◽  
Computational Advantage ◽  
Optimum Path ◽  
Path Search

This paper presents an algorithm using an optimization technique to outline the boundary profile of a manipulator workspace and perform quantitative evaluation of the workspace volume. The algorithm is applicable to general N-link manipulators with not only the revolute joints, but also joints of other types, such as, the prismatic and cylindrical joints. It is a partial-scanning technique which offers significant reduction on the number of scanning points to generate the workspace and the method is particularly efficient in dealing with complicated manipulator geometry. The [3 × 3] dual-number matrix method is used as the basis for analytical formulations, and consequently, computational advantage is gained. A comparative study is given with a previously used algorithm. Several specific examples involving industrial robots of various kinds are given to demonstrate the capability of the algorithm.

Redundancy utilization for obstacle avoidance of planar robot manipulators

1997 ◽  
Vol 211 (6) ◽  
pp. 463-475 ◽  
Author(s):  
U Sezgin ◽  
L D Seneviratne ◽  
S W E Earles
Keyword(s):  
Obstacle Avoidance ◽  
Computer Simulations ◽  
Redundant Manipulators ◽  
Control Points ◽  
Kinematic Redundancy ◽  
End Effector ◽  
Revolute Joints ◽  
Planar Robot ◽  
And Control ◽  
Configuration Control

Two obstacle avoidance criteria are developed, utilizing the kinematic redundancy of serial redundant manipulators having revolute joints and tracking pre-determined end effector paths. The first criterion is based on the instantaneous distances between certain selected points along the manipulator, called configuration control points (CCP), and the vertices of the obstacles. The optimized joint configurations are obtained by maximizing these distances. Thus, the links of the manipulator are configured away from the obstacles. The second criterion uses a different approach, and is based on Voronoi boundaries representing the equidistant paths between two obstacles. The optimized joint configurations are obtained by minimizing the distances between the CCP and control points selected on the Voronoi boundaries. The validities of the criteria are demonstrated through computer simulations.

Kinematic calibration of serial manipulators using Bayesian inference

Robotica ◽  
2018 ◽  
Vol 36 (5) ◽  
pp. 738-766 ◽  
Author(s):  
Elie Shammas ◽  
Shadi Najjar
Keyword(s):  
Bayesian Inference ◽  
Measurement Data ◽  
Calibration Method ◽  
Confidence Bounds ◽  
Open Chain ◽  
Robotic Arms ◽  
Serial Manipulators ◽  
Regression Methods ◽  
Three Degree Of Freedom ◽  
Inference Methods

SUMMARYIn this paper, a new calibration method for open-chain robotic arms is developed. By incorporating both prior parameter information and artifact measurement data, and by taking recourse to Bayesian inference methods, not only are the robot kinematic parameters updated but also confidence bounds are computed for all measurement data. In other words, for future measurement data not only the most likely end-effector configuration is estimated but also the uncertainty represented as 95% confidence bounds of that pose is computed. To validate the proposed calibration method, a three degree-of-freedom robotic arm was designed, constructed, and calibrated using both typical regression methods and the proposed calibration method. The results of an extensive set of experiments are presented to gauge the accuracy and utility of the proposed calibration method.

Computer Aided Synthesis of Piecewise Rational Motions for Spherical 2R and 3R Robot Arms

2008 ◽  
Vol 130 (11) ◽  
Author(s):  
Anurag Purwar ◽  
Zhe Jin ◽  
Q. J. Ge
Keyword(s):  
Motion Planning ◽  
Spline Interpolation ◽  
Robot Arm ◽  
Spherical Robot ◽  
Kinematic Constraints ◽  
Robot Arms ◽  
Revolute Joints ◽  
Computer Aided ◽  
Planar Robot ◽  
Circular Interpolation

This paper deals with the problem of synthesizing smooth piecewise rational spherical motions of an object that satisfies the kinematic constraints imposed by a spherical robot arm with revolute joints. This paper brings together the kinematics of spherical robot arms and recently developed freeform rational motions to study the problem of synthesizing constrained rational motions for Cartesian motion planning. The kinematic constraints under consideration are workspace related constraints that limit the orientation of the end link of robot arms. This paper extends our previous work on synthesis of rational motions under the kinematic constraints of planar robot arms. Using quaternion kinematics of spherical arms, it is shown that the problem of synthesizing the Cartesian rational motion of a 2R arm can be reduced to that of circular interpolation in two separate planes. Furthermore, the problem of synthesizing the Cartesian rational motion of a spherical 3R arm can be reduced to that of constrained spline interpolation in two separate planes. We present algorithms for the generation of C1 and C2 continuous rational motion of spherical 2R and 3R robot arms.

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