scholarly journals Adaptive Obstacle Avoidance for a Class of Collaborative Robots

Machines ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 113
Author(s):  
Giorgia Chiriatti ◽  
Giacomo Palmieri ◽  
Cecilia Scoccia ◽  
Matteo Claudio Palpacelli ◽  
Massimo Callegari
Keyword(s):  
Collision Avoidance ◽  
Computational Effort ◽  
Control Law ◽  
Cylindrical Shape ◽  
Control Techniques ◽  
Planar Manipulators ◽  
Collision Avoidance Control ◽  
Avoidance Control ◽  
Human Robot Collaboration ◽  
Operator Safety

In a human–robot collaboration scenario, operator safety is the main problem and must be guaranteed under all conditions. Collision avoidance control techniques are essential to improve operator safety and robot flexibility by preventing impacts that can occur between the robot and humans or with objects inadvertently left within the operational workspace. On this basis, collision avoidance algorithms for moving obstacles are presented in this paper: inspired by algorithms already developed by the authors for planar manipulators, algorithms are adapted for the 6-DOF collaborative manipulators by Universal Robots, and some new contributions are introduced. First, in this work, the safety region wrapping each link of the manipulator assumes a cylindrical shape whose radius varies according to the speed of the colliding obstacle, so that dynamical obstacles are avoided with increased safety regions in order to reduce the risk, whereas fixed obstacles allow us to use smaller safety regions, facilitating the motion of the robot. In addition, three different modalities for the collision avoidance control law are proposed, which differ in the type of motion admitted for the perturbation of the end-effector: the general mode allows for a 6-DOF perturbation, but restrictions can be imposed on the orientation part of the avoidance motion using 4-DOF or 3-DOF modes. In order to demonstrate the effectiveness of the control strategy, simulations with dynamic and fixed obstacles are presented and discussed. Simulations are also used to estimate the required computational effort in order to verify the transferability to a real system.

Collision-avoidance control for redundant articulated robots

Robotica ◽  
1995 ◽  
Vol 13 (2) ◽  
pp. 159-168 ◽  
Author(s):  
N. Rahmanian-Shahri ◽  
I. Troch
Keyword(s):  
Collision Avoidance ◽  
Degrees Of Freedom ◽  
Mathematical Formulation ◽  
Arbitrary Point ◽  
Convex Polygons ◽  
Planar Manipulators ◽  
Collision Avoidance Control ◽  
On Line ◽  
Avoidance Control ◽  
Articulated Robots

SummaryA new mathematical formulation of robot and obstacles is presented such that for on-line collision recognition only robot joint positions in the workspace are required. This reduces calculation time essentially because joint positions in workspace can be computed every time from the joint variables through robot geometry. It is assumed that the obstacles in the workspace of the manipulator are represented by convex polygons. For every link of the redundant robot and every obstacle a boundary ellipse is defined in workspace such that there is no collision if the robot joints are outside this ellipsis.In addition to this, a collision avoidance method is presented which allows the use of redundant degrees of freedom such that a manipulator can avoid obstacles while tracking the desired end-effector trajectory. The method is based on the generalized inverse with boundary ellipse functions as optimization criteria. The method permits the tip of the hand to approach any arbitrary point in the free space while the kinematic control algorithm maximizes the boundary ellipse function of the critical link. The effectiveness of the proposed methods is discussed by theoretical considerations and illustrated by simulations of the motion of three- and four-link planar manipulators between obstacles.

scholarly journals Collision avoidance for multiple Lagrangian dynamical systems with gyroscopic forces

2017 ◽  
Vol 14 (1) ◽  
pp. 172988141668710 ◽  
Author(s):  
Lorenzo Sabattini ◽  
Cristian Secchi ◽  
Cesare Fantuzzi
Keyword(s):  
Collision Avoidance ◽  
Control Strategy ◽  
Three Dimensional ◽  
Control Law ◽  
Convergence Properties ◽  
Gyroscopic Force ◽  
Collision Avoidance Control ◽  
Avoidance Control ◽  
Gyroscopic Forces ◽  
Simulation Results

This article introduces a novel methodology for dealing with collision avoidance for groups of mobile robots. In particular, full dynamics are considered, since each robot is modeled as a Lagrangian dynamical system moving in a three-dimensional environment. Gyroscopic forces are utilized for defining the collision avoidance control strategy: This kind of forces leads to avoiding collisions, without interfering with the convergence properties of the multi-robot system’s desired control law. Collision avoidance introduces, in fact, a perturbation on the nominal behavior of the system: We define a method for choosing the direction of the gyroscopic force in an optimal manner, in such a way that perturbation is minimized. Collision avoidance and convergence properties are analytically demonstrated, and simulation results are provided for validation purpose.

scholarly journals Fuzzy Risk Evaluation and Collision Avoidance Control of Unmanned Surface Vessels

2021 ◽  
Vol 11 (14) ◽  
pp. 6338
Author(s):  
Yung-Yue Chen ◽  
Ming-Zhen Ellis-Tiew ◽  
Wei-Chun Chen ◽  
Chong-Ze Wang
Keyword(s):  
Optimal Control ◽  
Collision Avoidance ◽  
Trajectory Tracking ◽  
Nonlinear Optimal Control ◽  
Control Law ◽  
Risk Indicator ◽  
Collision Avoidance Control ◽  
Surface Vessels ◽  
Tracking Ability ◽  
Avoidance Control

In this investigation, a smart collision avoidance control design, which integrates a collision avoidance navigation and a nonlinear optimal control method, is developed for unmanned surface vessels (USVs) under randomly incoming ships and fixed obstacle encounter situations. For achieving collision avoidance navigation, a fuzzy collision risk indicator and a fuzzy collision avoidance acting timing indicator are developed. These two risk indicators can offer effective pre-alarms for making the controlled USVs to perform dodge actions in time when obstacles appear. As to nonlinear optimal control law, it provides a precise trajectory tracking ability for the controlled USVs to follow a collision avoidance trajectory, which is generated via a smart collision avoidance trajectory generator. Finally, a power allocation method is used to transform the desired control law into available actuator outputs to guide the USVs to follow a desired collision avoidance trajectory. From simulation results, the proposed collision avoidance strategy reveals a promising collision avoidance performance and an accurate trajectory tracking ability with respect to fixed objects and randomly moving ships under the effect of environmental ocean disturbances.

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