The potential injury occurring during the actual impact will saturate with increasing robot mass and is from a certain point on only depending on the impact velocity. Furthermore, it will be confirmed that Severity Indices focusing just on the moment of impact like the Head Injury Criterion are not an appropriate measure of injury severity in robotics because no robot exceeds their safety critical thresholds. This is due to the usually significantly lower velocities of the robots compared to impact tests carried out in automobile crash-testing.
From the presented impact tests, the rarely analyzed injury source clamping is motivated by the breaking distance of the investigated robots.
Especially for larger robots clamping is an injury source one has to focus on and for which countermeasures have to be found.
The desired coexistence of robotic systems and humans in the same physical domain, by sharing the same workspace and actually cooperating in a physical manner, poses the very fundamental problem of ensuring safety to the user and the robot. In order to quantify the potential danger emanating from the DLR lightweight-robot (LWRIII), impact tests at the Crash Test Center of the German Automobile Club ADAC were conducted and evaluated.
A collision detection and reaction scheme, based on a disturbance observer is used. It utilizes only the proprioceptive capabilities of the robot and provides a filtered version of the external torque.
The outcome of the dummy crash-tests indicated a very low injury risk posed by rigid impacts with the DLR LWRIII. This was confirmed by real human-robot impacts at robot velocities up to 2.5m/s. Based on this experimental evaluation generalizations to robots of arbitrary mass can be drawn.
Real Robot-Human Impacts
Title: "Physical Interaction and Impact Experiments"
In order to ultimatively prove that the impact experiments conducted at the ADAC are reasonable, several human-robot impacts were carried out. The impacted body parts were the head, chest, shoulder and abdomen.
The torque estimation is, apart from being used as a collision detection mechanism, utilized as an adaptive scaling of time increments in the trajectory generation and allows the user to intuitively push the robot forth and back along its desired trajectory. Combined, these mechanisms are used to distinguish between desired cooperation and collision in physical human-robot interaction.
Initial Impact Experiments,Collision Detection & Reaction
Title: "Criteria and Control Structures for safe Human-Robot Interaction"
When a collision is detected, several reaction strategies can be activated sich as switching to gravity compensation mode or simply stopping the robot.
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