1,720,972 research outputs found
Motion planning and control of redundant manipulators for dynamical obstacle avoidance
Full text linkThis paper presents a framework for the motion planning and control of redundant manipulators with the added task of collision avoidance. The algorithms that were previously studied and tested by the authors for planar cases are here extended to full mobility redundant manipulators operating in a three-dimensional workspace. The control strategy consists of a combination of off-line path planning algorithms with on-line motion control. The path planning algorithm is used to generate trajectories able to avoid fixed obstacles detected before the robot starts to move; this is based on the potential fields method combined with a smoothing interpolation that exploits Bézier curves. The on-line motion control is designed to compensate for the motion of the obstacles and to avoid collisions along the kinematic chain of the manipulator; this is realized using a velocity control law based on the null space method for redundancy control. Furthermore, an additional term of the control law is introduced which takes into account the speed of the obstacles, as well as their position. In order to test the algorithms, a set of simulations are presented: The redundant collaborative robot KUKA LBR iiwa is controlled in different cases, where fixed or dynamic obstacles interfere with its motion. The simulated data show that the proposed method for the smoothing of the trajectory can give a reduction of the angular accelerations of the motors of the order of 90%, with an increase of less than 15% of the calculation time. Furthermore, the dependence of the on-line control law on the speed of the obstacle can lead to reductions in the maximum speed and acceleration of the joints of approximately 50% and 80%, respectively, without significantly increasing the computational effort that is compatible for transferability to a real system
A human-oriented design process for collaborative robotics
Full text linkThe potential of collaborative robotics often does not materialize in an efficient design of the human-robot collaboration. Technology-oriented approaches are no longer enough in the Industry 4.0 era. This work proposes a set of methods to support manufacturing engineers in the human-oriented design process of integrated production systems to obtain satisfactory performance in the mass customization paradigm, without impacting the safety and health of workers. It founds the design criteria definition on five main pillars (safety, ergonomics, effectiveness, flexibility, and costs), favors the consideration of different design alternatives, and leads their selection. The dynamic impact of the design choices on the various elements of the system prevails over the static design constraints. The method has been experimented in collaboration with the major kitchen manufacturer in Italy, which introduced a collaborative robotics cell in the drawers' assembly line. It resulted in a more balanced production line (10% more), a verified risk minimization (RULA score reduced from 5 to 3 and OCRA score from 13.30 to 5.70), and a greater allocation of operators to high added value activities
Experimental Evaluation of Collision Avoidance Techniques for Collaborative Robots
Full text linkThis paper presents the implementation of an obstacle avoidance algorithm on the UR5e collaborative robot. The algorithm, previously developed and verified in simulation, allows one to modify in real time the trajectory of the manipulator with three different modalities to avoid obstacles. Some test cases with fixed or dynamic obstacles affecting the robot’s motion were first simulated and then experimented on. The paper describes the hardware/software architecture of the robotic system: an external controller is realized by a standard PC that communicates with the robot controller by a TCP/IP protocol; algorithms and data processing are executed by Python/Matlab software that guarantees a duty cycle of at least 100 Hz. The error analysis between simulated and real data allows one to conclude that the developed algorithms revealed to be effectively applied to a real robotic system, showing behavior similar to what is expected by simulations
Experimental Assessment of a Vision-Based Obstacle Avoidance Strategy for Robot Manipulators: Off-line Trajectory Planning and On-line Motion Control
Full text linkHuman-Robot Interaction is an increasingly important topic in both research and industry fields. Since human safety must be always guaranteed and accidental contact with the operator avoided, it is necessary to investigate real-time obstacle avoidance strategies. The transfer from simulation environments, where algorithms are tested, to the real world is challenging from different points of view, e.g., the continuous tracking of the obstacle and the configuration of different manipulators. In this paper, the authors describe the implementation of a collision avoidance strategy based on the potential field method for off-line trajectory planning and on-line motion control, paired with the Motion Capture system Optitrack PrimeX 22 for obstacle tracking. Several experiments show the performance of the proposed strategy in the case of a fixed and dynamic obstacle, disturbing the robot’s trajectory from multiple directions. Two different avoidance modalities are adapted and tested for both standard and redundant robot manipulators. The results show the possibility of safely implementing the proposed avoidance strategy on real systems
A collision avoidance strategy for redundant manipulators in dynamically variable environments: On-line perturbations of off-line generated trajectories
No full textIn this work, a comprehensive control strategy for obstacle avoidance in redundant manipulation is presented, consisting of a combination of off-line path planning algorithms with on-line motion control. Path planning allows the avoidance of fixed obstacles detected before the start of the robot’s motion; it is based on the potential fields method combined with a smoothing process realized by means of interpolation with Bezier curves. The on-line motion control is designed to compensate for the motion of the obstacles and to avoid collisions along the kinematic chain of the manipulator; it is realized by means of a velocity control law based on the null space method for redundancy control. A new term is introduced in the control law to take into account the speed of the obstacles as well as their position. Simulations on a simplified planar case are presented to assess the validity of the algorithms and to estimate the computational effort in order to verify the transferability of our approach to a real system
Collaborative robot sensorization with 3D depth measurement system for collision avoidance
No full textHuman-Robot Collaboration (HRC) and Machine Vision are some of the most promising technologies of Industry 4.0. Collaborative robots are quickly gaining ground in the industrial network, due to their possibility of working side by side with humans, in a shared space, without physical barriers. However, the knowledge of the environment is required to adapt the robot motion and guarantee the operator safety. This paper presents a preliminary study for a bigger project regarding the implementation of a full obstacle avoidance strategy into a robotic system for industrial purposes. The system adopted consists of a vision system based on Intel Realsense cameras, an algorithm providing obstacle representation as elementary geometric shapes and an obstacle avoidance strategy used for the motion control of the robot. The continuous monitoring of the operators, objects and robots present in the workstation with the vision system ensures the stability and security of the system
Design of a Labriform-Steering Underwater Robot Using a Multiphysics Simulation Environment
Full text linkBio-inspired solutions devised for Autonomous Underwater Robots are currently investigated by researchers as a source of propulsive improvement. To address this ambitious objective, the authors have designed a carangiform swimming robot, which represents a compromise in terms of efficiency and maximum velocity. The requirements of stabilizing a course and performing turns were not met in their previous works. Therefore, the aim of this paper is to improve the vehicle maneuvering capabilities by means of a novel transmission system capable of transforming the constant angular velocity of a single rotary actuator into the pitching–yawing rotation of fish pectoral fins. Here, the biomimetic thrusters exploit the drag-based momentum transfer mechanism of labriform swimmers to generate the necessary steering torque. Aside from inertia and encumbrance reduction, the main improvement of this solution is the inherent synchronization of the system granted by the mechanism’s kinematics. The system was sized by using the experimental results collected by biologists and then integrated in a multiphysics simulation environment to predict the resulting maneuvering performance
Design of a human-robot collaborative system: Methodology and case study
No full textHuman-machine collaboration is one of the key drivers of the Industry 4.0 paradigm. The recent advances in collaborative robotics led to the effective implementation of various control strategies able to improve interactions between robots and humans in unstructured environments. This represents an important socio-economic aspect: the robot does not replace the human being, but supports them in carrying out repetitive or dangerous tasks. In this scenario it is necessary to take into account different contrasting issues that derive from the necessity to grant the high performance typical of a robotic installation together with the safety levels required by a manual operation. In this paper we analyse the use case of a famous kitchen industry that decided to test the introduction of collaborative robotics to increase the flexibility and productivity of their production lines. A method, to define the design criteria of the Human-Robot Collaboration system (HRC), is proposed taking into account aspects related to both the safety and the ergonomics of the human operator, using a real-time mapping of the work area and the management of operations. The collaboration between robot and operator can be facilitated thanks to the use of an assistive device which, through the recognition of gestures, allows easy communication. Therefore, this paper aims to combine: operator safety and ergonomics, study of the workstation, sensor technologies, identification and tracing of gestures. Several simulations have been performed to evaluate the proposed collaborative workstation
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