In this paper, we discuss a human-robot (H-R) coexistent system which allows H-R contact actions in the safeguarding space mechanically bounded by the human pain tolerance limit. The first half of this paper describes our study on the evaluation of the human pain tolerance limit which determines an individual's safeguarding space. We also show the human-safety-oriented design of a robot. The robot is covered with a viscoelastic material to achieve both impact force attenuation and contact sensitivity, keeping within the human pain tolerance limit. The robot, with simple direct-drive (DD) motor torque detection and emergency stop capabilities, automatically stops whenever any severe H-R contact occurs. In the second half of the paper, we propose a more efficient H-R system, which allows H-R contact for improving work efficiency, as long as the contact does not exceed the human pain tolerance limit. For this purpose, a robot is controlled to reduce its velocity with high reliability at an incipient stage of its contact with a human. Through experiments, we demonstrate the validity and efficient utility of the safeguarding space. The first experiment verifies that the developed robot exerts a contact force less than the human pain tolerance limit establishing the safeguarding space. The second experiment comparatively shows the robot's velocity reduction to accept a safe contact with the human in the space.

Human-robot contact in the safeguarding space

The safety of humans who work with robots is an important issue. Many studies have addressed related methods, but fundamental limits to meet safety requirements have been encountered owing to the absence of compliance in robot actuators. Pneumatic muscle is considered to be a basic actuator and offers the advantage of intrinsic elasticity to achieve joint compliance. In this study, joint compliance actuated by pneumatic muscle is actively utilized to enhance human safety during collisions. To this end, the authors present a novel approach to control compliance and associated positions independently with no cross-performance effects using pneumatic muscles. The proposed method is verified by simulation and experiments using a physical robot.

Position and Compliance Control of a Pneumatic Muscle Actuated Manipulator for Enhanced Safety

Position and compliance control of manipulator using pneumatic muscles for enhanced safety = 안전성 강화를 위한 인공 근육에 기반한 매니퓰레이터의 위치 및 컴플라이언스 제어

Safety of humans who work with robots is an important issue. Many studies have addressed related methods, but fundamental limits to meet safety requirements have been encountered owing to the absence of compliance in robot actuators. Pneumatic muscle (PM) is considered to be a basic actuator and offers the advantage of intrinsic elasticity to achieve joint compliance. In this paper, joint compliance actuated by PM is actively utilized to enhance human safety during collisions. To this end, the authors present a novel approach to control compliance and associated positions independently with no cross-performance effects using PMs. The proposed method is verified by experiments using a physical robot. In addition, methods to decrease damage from collisions between robots and humans due to operational faults are evaluated through experiments. The effectiveness of the proposed method is verified by measuring the impact impulse in collisions.

Control of Manipulator Using Pneumatic Muscles for Enhanced Safety

This paper presents a review of published literature on robot reliability and safety. The literature is classified into three main categories: robot safety; robot reliability; and miscellaneous. Robot safety is further categorized into six classifications: general; accidents; human‐factors; safety standards; safety methods; and safety systems/technologies. The period covered by the review is from 1973 to 2001.

Robot systems reliability and safety: a review

As more and more robots are installed in the industrial sector, the statistical likelihood for accidents involving robots increases unless careful design and implementation of safety features occurs. Some worker deaths related to robot accidents have been reported in Japan. Most workers and users of robots have embarked on a safety program depending on personnel training, preventative maintenance, and perimeter barriers and/or interlocks. Most of these necessary methods still do not address the issue of personnel required to be close to a robot during teaching, maintenance, and troubleshooting. The results of a research project underway at Rensselaer Polytechnic Institute to develop a computer controlled sensor system that will monitor the working envelope of a robot are discussed. If an dangerous situation occurs, this system will cause the robot to take corrective action to avoid personnel injury or damage to the robot or equipment.

John F. Meagher

Papers

A Safety and Collision Avoidance System for Industrial Robots