Rethink Robotics Sawyer, Original Instructions Manual, Page: 144 / 220

137
Intera 5.3
Sawyer and Safety
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Moderate velocity: Sawyer operates at human-equivalent speeds which are
limited by the power limits of the inherent design, which makes it easier for
nearby people to avoid any unintended contact with the robot.
2. Machine Safety: Rethink's Collaborative Robots are designed with many protective features
which govern operation and protect those working around them.
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E-Stop: When actuated, the emergency stop function directly removes power to
actuators and applies brakes (Category 0 protective stop per IEC 60204-1).
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Brake Applied at Joints on Power Loss: When experiencing a power loss,
Sawyer will brake using residual power to slow to a stop. Sawyer’s small joints
will slowly return to a gravity-neutral position. Sawyer also has physical brakes
that hold the position of the shoulder and elbow joints, yet can be released
simply by pressing a button to allow manual re-positioning of the robot arm.
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Over-Temperature Shutdown: Operating temperatures are internally monitored
and Sawyer(TM) will shut down if overheating is detected.
3. Contact Detection: Sawyer has Series Elastic Actuators that directly measure torque at every
joint, allowing the robots to detect and respond to contact.
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Clamping Detection: Monitors torque at all joints for a steady obstruction or
resistance and pauses robot motion, preventing Sawyer from applying
continuous or excessive force.
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Impact Detection: Monitors torque at all joints to sense sharp contact with a hard
surface and pauses motion.
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End Effector Force/Torque Detection: If excess force or torque is detected at the
tool tip, the robot will pause motion.
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Over-Torque Detection: If torques in excess of joint limits are detected, the arms
disable and apply brakes to prevent damage.
4. Diverse Checking Subsystems: Diverse subsystems leverage and control the “heartbeat” signals
to enable joint brakes, and disable motor power if a control error or failure is detected.
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Heartbeats:
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Commanded Stop via “Heartbeat” Signal: Hardware “Heartbeat” signal
that can be interrupted by external control, an internal failure, or by any
internal subsystem resulting in stopping all joints, engaging brakes and
disabling motor power.
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Communications Heartbeat: A second “heartbeat” stops all joints,
engages brakes, and disables motor power in response to detecting
internal communication issues.