Abstract
Recent developments in robotics have resulted in implementations that have drastically increased collaborative interactions between robots and humans. As robots have the potential to collide intentionally and/or unexpectedly with a human during the collaboration, effective measures to ensure human safety must be devised. In order to estimate the collision safety of a robot, this study proposes a virtual sensor based on an analytical contact model that accurately estimates the peak collision force and pressure as the robot moves along a pre-defined path, even before the occurrence of a collision event, with a short computation time. The estimated physical interaction values that would be caused by the (hypothetical) collision were compared to the collision safety thresholds provided within ISO/TS 15066 to evaluate the safety of the operation. In this virtual collision sensor model, the nonlinear physical characteristics and the effect of the contact surface shape were included to assure the reliability of the prediction. To verify the effectiveness of the virtual sensor model, the force and pressure estimated by the model were compared with various experimental results and the numerical results obtained from a finite element simulation.
Highlights
As the robotics field experiences exponential growth in use, instances in which robots are installed or operated in the vicinity of human activity, to improve productivity by directly aiding humans with tasks, have increased
A human–robot collision dynamic model consists of a two-mass human–robot collision event, it is necessary to calculate the contact force and pressure at a low system given by the equation below: computational cost for the safety evaluation in real-time
As we evaluate the robot collision safety assuming that the robot has the possibility of colliding with the forehead in an unconstrained transient contact, Mh is set to 4.4 kg [6]
Summary
As the robotics field experiences exponential growth in use, instances in which robots are installed or operated in the vicinity of human activity, to improve productivity by directly aiding humans with tasks, have increased. This paper proposes a virtual sensor approach that computes the expected collision peak force and pressure that would result from a collision between a robot and a human at a given time using an analytical contact model. That varying the effective mass of the robot as the robot moves, and considering all the shapes of the contact surface, which change depending on the collision direction, leads to difficulty in modeling the FE model, the previously proposed numerical estimation methods are not adequate as a virtual collision sensor for the posture changing robot. In order to use the virtual sensors as a safety sensor, the computation time for estimating the collision pressure and force should be fast To satisfy this requirement and to reduce the computational costs, a mathematical contact model based on the Hertz contact model has been proposed for use as a virtual sensor. This paper presents several simulations for evaluating robot safety
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