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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.