A general procedure for collision detection between an industrial robot and the environment

Development of a Virtual Collision Sensor for Industrial Robots

“…The solution proposed in [ 15 ] and here revised is given by the introduction of a threshold varying function, defined as: the first term, , represents an estimate of the absolute value of the model error in absence of collisions. Such an estimate is determined using the only available information, i.e., the current residue computed inside the virtual collision sensor as in ( 1 ).…”

“…In [ 15 ], was assumed as constant for all of the joints, simply leaving the user the possibility of changing it, if necessary. In practice, a unique value was adopted for all of the joints and maintained for any robot to which the collision detection procedure was applied.…”

“…The results were satisfactory, but open to possible improvements, in particular with reference to robustness and speed in detecting a collision. In this paper, the algorithms used in [ 15 ] for the computation of are only slightly modified, since they allowed good results even for the simplistic choice of a constant vector, while an automatic learning and adaptation process of the entries of is now proposed, to enhance the robustness of the procedure and the speed in detecting a collision, as well as to cope with possible slow variations of the robot behavior. The model error estimation process is described in Sub Section 3.1 , while the automatic adaptation of the sensor sensitivity will be developed in Section 4 , after having illustrated in Sub Section 3.2 the FSM used to monitor the currents behavior.…”

“…The flowchart representing the virtual collision sensor block was already presented in [ 15 ], but here, some modifications are introduced in order to implement the learning and adaptation of the sensor sensitivity. The workflow of the new virtual collision sensor block ( Figure 12 b) is presented using the graphical representation provided by the activity diagrams, which allows defining additional characteristics like the parameters involved in the activities and the sets of activities that can be executed in parallel (fork/joint statement).…”

“…The solution proposed in this paper is constituted by a virtual collision sensor for industrial manipulators, which has been developed through a research activity carried on by the collaboration of Politecnico di Torino and COMAU SpA, and motivated by critical situations that occurred in some factories and production lines using COMAU manipulators, as well as by the goal of improving a previous COMAU software solution for collision detection, which required a high level of customization and long warm up phases. The core of the virtual collision sensor is given by the collision detection procedure that was proposed in [ 15 ], which is here revised and enhanced, introducing the possibility of automatically customizing the sensor sensitivity for a specific robotic application and, subsequently, slowly adapting it. This new functionality enhances the sensor ability of recognizing even light collisions while avoiding the risk of generating false collision alarms and allows coping with possible slow variations of the robot behavior.…”