Providing contact sensing on the whole body of a robot is a key feature to increase the safety level of physical human-robot interaction. In this paper, a new robot skin capable of sensing multiple contact locations is presented. The motivation behind the proposed design is to produce a relatively inexpensive skin having the capability to provide the spatial location of collisions and also to add compliance to the robot's external cover. The resulting device is a thin flexible sensor sheet made of polyimide films with electrically conductive ink and a pressure sensitive conductive rubber sheet. The problem of internal wire routing is circumvented by the use of conductive ink and a circuit is proposed to minimize the number of output wires. To provide collision absorption and mechanical robustness, the sensor is embedded in different layers of polyurethane using shape deposition manufacturing (SDM). The paper presents the design and the fabrication process of the skin but also some experimental results on the determination of the mechanical properties of the resulting sensor as well as its potential for increasing human safety during human robot interaction.

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In this paper, different measures for reducing the maximum contact force during blunt collisions between a robot and a human are evaluated using simulations. An existing collision model is adapted to include a nonlinear compliant covering, articular safety mechanisms (compliant joint and two types of torque limiters), and a collision detection system. Several scenarios are simulated in which the collision occurs at a low or high velocity, the head of the person (on which the collision occurs) is constrained by a wall or free to move and the reflected motor inertia is large or small compared to the link inertia. The results show that a torque limiter in series with each actuator has the potential to significantly improve safety without reducing the robot's performances.