A Virtual Pressure and Force Sensor for Safety Evaluation in Collaboration Robot Application

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.

Evaluation of force pain thresholds to ensure collision safety in worker-robot collaborative operations

“…Comprehensive specification of biomechanical limitations that are inherently involved in collaborative operation of human workers and robots can help verify the safety of robot operation through collision tests or simulation methods ( Robotic Industries Association, 2018 ; Shin et al, 2019 ). For example, although the biomechanical limitations specified in ISO/TS 15066 can be used to validate the collision safety of industrial robots in collaborative workspaces, this standard states that the operational speed of the robot must not exceed the specified limits which may cause the robots to be too slow to be effectively used.…”

“…Moreover, the biophysical property of body location in contact or collision could be examined from measured data, such as contact force and displacement of tissue, from clinical trials. Biophysical properties can potentially be utilized for human-robot contact modeling to verify collision safety in advance ( Shin et al, 2019 ). These improvements are expected to contribute to the development of technologies needed to establish safer human-robot interactions.…”

“…To evaluate the safety, it is necessary to assess the level of injury. As a representative technique for such assessments, virtual contact sensors were used to evaluate the contact force and pressure before implementation of collaborative operations ( Shin et al, 2019 ). Moreover, as mentioned previously, clinical trials were conducted to measure the pain initiation thresholds in pinching situations.…”

Bioinspired Multifunctional E‐skin for Robot Dynamic Tactile Real‐Time Feedback Systems Using Triboelectric Sensors and Electrochromic Devices

“…Different force sensing systems based on different force sensing mechanisms have been reported. [5][6][7][8] However, pressure sensor-based robot feedback systems mostly display pressure-related information on the display interface of the back-end signal processing system. The feedback system needs a hard data processing process assisting with manual work since the robots working in a dynamic environment often output mass data when interacting with a complicated environment.…”

Effect of Joints’ Configuration Change on the Effective Mass of the Robot

“…They built on the methods of the augmented robot-object dynamics models and the effective mass. In [26], a virtual sensor approach was proposed to compute the collision peak force and the pressure that results from the human-robot collision at a given time using an analytical contact model. The collision safety was evaluated using the conventional finite element simulation for particular collision conditions with the given parameters, which include the effective mass, the collision velocity and direction, and the impactor shape.…”