An Iterative Approach for Collision Feee Routing and Scheduling in Multirobot Stations

This work is inspired by the problem of planning sequences of operations, as welding, in car manufacturing stations where multiple industrial robots cooperate. The goal is to minimize the station cycle time, \emph{i.e.} the time it takes for the last robot to finish its cycle. This is done by dispatching the tasks among the robots, and by routing and scheduling the robots in a collision-free way, such that they perform all predefined tasks. We propose an iterative and decoupled approach in order to cope with the high complexity of the problem. First, collisions among robots are neglected, leading to a min-max Multiple Generalized Traveling Salesman Problem (MGTSP). Then, when the sets of robot loads have been obtained and fixed, we sequence and schedule their tasks, with the aim to avoid conflicts. The first problem (min-max MGTSP) is solved by an exact branch and bound method, where different lower bounds are presented by combining the solutions of a min-max set partitioning problem and of a Generalized Traveling Salesman Problem (GTSP). The second problem is approached by assuming that robots move synchronously: a novel transformation of this synchronous problem into a GTSP is presented. Eventually, in order to provide complete robot solutions, we include path planning functionalities, allowing the robots to avoid collisions with the static environment and among themselves. These steps are iterated until a satisfying solution is obtained. Experimental results are shown for both problems and for their combination. We even show the results of the iterative method, applied to an industrial test case adapted from a stud welding station in a car manufacturing line

Optimal Robot Placement for Tasks Execution

AbstractAutomotive assembly cells are cluttered environments, including robots, workpieces, and fixtures. Due to high volumes and several product variants assembled in the same cell, robot placement is crucial to increase flexibility and throughput. In this paper, we propose a novel method to optimize the base position of an industrial robot with the objective to reach all predefined tasks and minimize cycle time: robot inverse kinematics and collision avoidance are integrated together with a derivative-free optimization algorithm. This approach is successfully used to find feasible solutions on industrial test cases, showing up to 20% cycle time improvement

From attachment to parents to somatic symptoms in children: exploring the mediation role of anxiety, attachment to peers and depressive symptoms

Despite the fact that somatic symptoms are related to the quality of attachment, few studies have been conducted to explore the variables that mediate this relationship in childhood. The present study investigates the role of anxiety, attachment to peers, and depressive symptoms as mediators of the relationship between attachment to parents and somatic symptoms. 340 children (49.1% males) between the ages of 8-11 (Mean age=9.25, SD=0.89) participated in this study. They completed the Inventory of Parent and Peer Attachment-Revised (IPPA-R), the Screen for Child Anxiety Related Emotional Disorders (SCARED), the Children's Depression Inventory 2 (CDI-2) and the Children's Somatization Inventory (CSI-24). We analyzed whether the effect of attachment to parents on somatic symptoms could be explained through anxiety (mediator one), attachment to peers (mediator two) and depressive symptoms (mediator three) using the Macro PROCESS (model 6). Results show that half of the total sample (52.1%, n=177) report at least one somatic symptom during the last two weeks. According to the SCARED and CDI-2 cut-off, 34.7% (n=118) and 27.1% (n=92) of participants are at risk for anxiety and depressive disorder. The total effect of attachment to parents on somatic symptoms is significant (b=-.186, SE=.051; 95%C.I.=-.285;-.086, p<.001, R2=.08). Three indirect effect are found: through anxiety symptoms (b=-.066, Bootstrap SE=.026, 5000 bootstrap samples 95%C.I.=-.123;-.022); through anxiety and depressive symptoms (b=-.005, Bootstrap SE=.004, 5000 bootstrap samples 95%C.I.=-.016;-.001); through attachment to peers and depressive symtpoms (b=-.008, Bootstrap SE=.006, 5000 bootstrap samples 95%C.I.=-.027;-.001). After controlling for the mediators, a nonsignificant total direct effect of attachment to parents is found. Serial multiple mediation help us to clarify the link between attachment and somatic symptoms in children. Findings from this study provide evidence that somatic symptoms are associated with the quality of attachment and internalizing symptoms. Longitudinal studies are needed to test the validity of the model

Efficient sequencing of industrial robots through optimal control

In a production plant for complex assembled products there could be up to several hundred robots used for handling and joining operations. Thus, improvements in robot motion can have a huge impact on equipment utilization and energy consumption. By combining recent algorithms for collision free numerical optimal control and for optimal sequencing, we are able to cut down on energy consumption without sacrificing cycle time. The algorithm has been successfully applied to several industrial cases demonstrating that the proposed method can be used effectively in practical applications to find fast and energy efficient solutions