Safety Mechanisms

Safety Mechanisms

• • Research Background

    • Safety is one of the key issues in real environments where humans and service robots coexist. 

    • A safety mechanism based on passive compliance is desirable since no sensors or actuators are required.

                                                                                      <Human-robot safety>

• • Research Objectives

    • Safety mechanisms using only mechanical elements (spring, link, cam-camfollower, etc..): Fast response, high reliability and low cost 

    • Nonlinear spring system: Both collision safety and positioning accuracy

      • Sustained rigidity of the mechanism below the prescribed level of threshold force.

      • Sharp increased in compliance of the mechanism above the prescribed threshold force.

                                                    <Nonlinear stiffness of safety mechanism>

Safe Joint Mechanism (SJM)

• • Construction of SJM

    • Composed of an inclined link, linear guide, roller and springs 

    • Capable of adjusting compliance level of the mechanism using the angle of inclination of an inclined link and changing the spring constant and length.

                                                                        <Structure and operational principle of SJM III>

• • Features of SJM

    • High stiffness of the robot joint can be sustained during tasks subject to forces less than the threshold force.

    • The level of the threshold force can be easily adjusted.

    • Highly responsive, reliable, no sensors or actuators, and no need for control scheme by using only the passive compliance method

    • A small size, light weight, low price safety mechanism

• Research output

• • Collision experiments of SJM

    • Dynamic collision experiments for the robot arm with and without SJM

    • Higher safety for human-robot contact than robot arm without SJM

Safe Link Mechanism (SLM)   Safety link mechanism 내용 삭제

• • Construction of SLM

    • Composed of double-slider mechanism, spring, wire and shock-absorbing module.

    • Capable of adjusting compliance level of the mechanism using the transmission angle of the double slider mechanism and the resistive force of a spring.

                                                           <Structure and operational principle of SLM>

• • Features of SJM

    • Capable of absorbing the impact forces in all directions.

    • High stiffness of the mechanism can be sustained during the tasks subject to forces less than the threshold force.

    • The level of the threshold force can be easily adjusted.

    • Highly responsive, reliable, no sensors or actuators, and no need for a control scheme.

    • A small size, light weight, low price safety mechanism.

  • Research output

                                            <Safe Link Mechanism(SLM)>

• • Collision experiments of SLM

    • Dynamic collision experiments for robot arms equipped with and without SLM

    • Higher safety for human-robot contact than robot arm without SJM

Safe Joint Module

• • Construction of Safe joint module

    • Combination of passive and active compliance method

    • Safety mechanism for collision absorption with passive compliance method

    • Embedded joint torque sensor for collision detection with active compliance method

    • Modular type design composed of safety device, gear reducer and bearing

                                                         <Structure of Safe joint module>

• • Features of SJM

    • Collision absorption using safety mechanism based on cam-cam follower mechanism.

    • Collision detection with embedded torque sensor

    • Low-cost force control system using embedded torque sensor

    • High gear reduction and low backlash with harmonic drive

    • Support of moment load by cross-roller bearing

    • Hollow shaft for wiring

    • Modular type design to construct various types robots 

  • Research output

• • Collision and force control experiments of safety joint module

    • Dynamic collision experiments for the robot arm constructed of safe joint modules

    • Force control: Wall-following experiment using 3-DOF robot arm constructed using 3 safe joint modules.