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
- 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.
<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
- 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.
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