Title: "Singularity Clamping"
Here the LWRIII performs a reconfiguration from "ellbow up" to "ellbow down" while exerting quasi-static forces on a human head. The head is assumed to be clamped. This example shows the injuriy potential posed by singularities in case of clamping. This is due to the fact that the robot is theoretically able to exert very high forces which can easily lead to various fractures. As a counterbalance a collision detection based on a disturbance observer is used, leading to much lower injury potential.
Robotics: Science and Systems 2007: Manipulation Workshop
Title: "Approaching Asimov's 1st Law II"
Here the influence of the robot mass and velocity during blunt impacts with humans is shown. Several robots with weights ranging from 15-2500 kg at different impact velocities are impacted with a mechanical human head mockup. This is used to measure the so-called Head Injury Criterion, a measure for head injury caused by impacts.
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.
2007 ACM/IEEE International Conference on Human-Robot Interaction
Title: "Approaching Asimov's 1st Law"
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"
- Impact experiment with the DLR light-weight robot III hitting the outstreched arm of a human at different velocities
- Impact experiment with the DLR light-weight robot III hitting a "dumm-dummy" of the human head-neck complex at different velocities
- Impact experiment with the DLR light-weight robot III hitting a balloon at different velocities
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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