What you can learn with the collaborative robot
What a cobot is
A collaborative robot is designed to share space with people without a fence. It measures forces and speeds continuously, has rounded shapes and little mass, and its safety functions are certified. But no robot is collaborative on its own: the application is, after a risk assessment.
Hand guiding (freedrive)
The robot compensates its own weight and lets the operator move it by hand. Points are taught in seconds, without typing coordinates. That is why cobots are so quick to program in small companies.
Power and force limiting
ISO/TS 15066 gives each body region a permissible force and a stiffness. In a free impact, the peak force is F = v·√(μ·k): the higher the speed and the payload, the higher the force. That is why the same robot can move fast near a hand but must go much slower at chest height, and must never be able to hit the head.
Clamping
If the hand is trapped against the table, it can no longer back away: the force grows until the robot detects the collision. The configured force limit governs here, and it must not exceed the 140 N permitted for the hand. That is why pinch points should be avoided when designing the cell.
Payload
The robot has no force sensors on every link: it estimates the external force from the motor currents and a dynamic model that includes the payload. A misconfigured payload causes false protective stops or, worse, collisions it is slow to detect.
Speed and separation
With a laser scanner the robot can move fast when nobody is around and slow down when someone approaches. The protective zone is sized with the ISO 13855 walking speed, 1.6 m/s, multiplied by the scanner’s reaction time and the robot’s stopping time. A zone that is too small lets the person arrive before the robot has stopped.
Momentum
Many cobots can also limit momentum, p = m·v, and power. They are another way of saying the same thing: what causes injury is the energy the robot can transfer in a collision.
Other robots in the lab: KUKA arm · SCARA · Cartesian · Delta · Kinematics. More simulators in Labs. Educational simulator: the figures are representative and do not replace the manufacturer’s documentation or the risk assessment of a real installation.