Capacitive sensor to detect fallen humans in conditions of low visibility

This paper examines the potential for a capacitive sensor to be used as part of a system to detect fallen humans at very close range. Previous research suggests that a robotic system incorporating a low cost capacitive sensor could potentially distinguish between different materials. The work reported in this paper stemmed from an attempt to determine the true extent to which such a system might reliably differentiate between fallen humans and other objects. The work is motivated by the fact that there are several different emergency circumstances in which such a system might save lives if it could reliably detect immobile humans. These scenarios include situations where older people have fallen and are unable to move or raise an alert, and circumstances where people have been overcome by smoke in a burning building. Current sensing systems are typically unsuitable in conditions of low visibility such as smoke filled rooms. This analysis focused specifically on the potential for a robot equipped with a capacitive sensing system to identify an immobile human in a low visibility emergency scenario. It is concluded that further work would be required to determine whether this type of capacitive sensing system is genuinely suitable for this task

Design and fabrication of force sensing robotic foot utilizing the volumetric displacement of a hyperelastic polymer

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 39-40).This thesis illustrates the fabrication and characterization of a footpad based on an original principle of volumetric displacement sensing. It is intended for use in detecting ground reaction forces in a running quadrupedal robot. The footpad is manufactured as a monolithic, composite structure composed of multi-graded polymers reinforced by glass fiber to increase durability and traction. The volumetric displacement sensing principle utilizes a hyperelastic gel-like pad with embedded magnets and Hall-effect sensors. Normal and shear forces can be detected as contact forces cause the gel-like pad to deform into rigid wells without the need to expose the sensor. A one-time training process using an artificial neural network was used to relate the normal and shear forces with the volumetric displacement sensor output. Two iterations on geometry are prototyped and tested. The first shows the ability to accurately predict normal forces in the Z-axis up to 80 N with a root mean squared error of 6% but little information about shear forces in the X an Y-axis. The second iteration demonstrates an ability to pick up the presence and direction of shear forces up to 40 N but with a root mean squared error of 70%. This project demonstrates a proof-of-concept for a more robust force sensor suitable for use in robotics that requires compliance while interacting with its environment.by Matthew A. Estrada.S.B

A Large Area Tactile Sensor Patch Based on Commercial Force Sensors

This paper reports the design of a tactile sensor patch to cover large areas of robots and machines that interact with human beings. Many devices have been proposed to meet such a demand. These realizations are mostly custom-built or developed in the lab. The sensor of this paper is implemented with commercial force sensors. This has the benefit of a more foreseeable response of the sensor if its behavior is understood as the aggregation of readings from all the individual force sensors in the array. A few reported large area tactile sensors are also based on commercial sensors. However, the one in this paper is the first of this kind based on the use of polymeric commercial force sensing resistors (FSR) as unit elements of the array or tactels, which results in a robust sensor. The paper discusses design issues related to some necessary modifications of the force sensor, its assembly in an array, and the signal conditioning. The patch has 16 × 9 force sensors mounted on a flexible printed circuit board with a spatial resolution of 18.5 mm. The force range of a tactel is 6 N and its sensitivity is 0.6 V/N. The array is read at a rate of 78 frames per second. Finally, two simple application examples are also carried out with the sensor mounted on the forearm of a rescue robot that communicates with the sensor through a CAN bus

A Distributed Tactile Sensor for Intuitive Human-Robot Interfacing

Safety of human-robot physical interaction is enabled not only by suitable robot control strategies but also by suitable sensing technologies. For example, if distributed tactile sensors were available on the robot, they could be used not only to detect unintentional collisions, but also as human-machine interface by enabling a new mode of social interaction with the machine. Starting from their previous works, the authors developed a conformable distributed tactile sensor that can be easily conformed to the different parts of the robot body. Its ability to estimate contact force components and to provide a tactile map with an accurate spatial resolution enables the robot to handle both unintentional collisions in safe human-robot collaboration tasks and intentional touches where the sensor is used as human-machine interface. In this paper, the authors present the characterization of the proposed tactile sensor and they show how it can be also exploited to recognize haptic tactile gestures, by tailoring recognition algorithms, well known in the image processing field, to the case of tactile images. In particular, a set of haptic gestures has been defined to test three recognition algorithms on a group of 20 users. The paper demonstrates how the same sensor originally designed to manage unintentional collisions can be successfully used also as human-machine interface

Sensors for Robotic Hands: A Survey of State of the Art

Recent decades have seen significant progress in the field of artificial hands. Most of the surveys, which try to capture the latest developments in this field, focused on actuation and control systems of these devices. In this paper, our goal is to provide a comprehensive survey of the sensors for artificial hands. In order to present the evolution of the field, we cover five year periods starting at the turn of the millennium. At each period, we present the robot hands with a focus on their sensor systems dividing them into categories, such as prosthetics, research devices, and industrial end-effectors.We also cover the sensors developed for robot hand usage in each era. Finally, the period between 2010 and 2015 introduces the reader to the state of the art and also hints to the future directions in the sensor development for artificial hands

Composite force sensing foot utilizing volumetric displacement of a hyperelastic polymer

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (p. 65-67).In this thesis, I will describe the fabrication and characterization of a footpad based on an original principle of volumetric displacement sensing. It is intended for use in detecting ground contact forces in a running quadrupedal robot. The footpad is man- ufactured as a monolithic, composite structure composed of multi-graded polymers which are reinforced by glass fiber to increase durability and traction. The volumetric displacement sensing principle utilizes a hyperelastic gel-like pad with embedded magnets that are tracked with Hall-effect sensors. Normal and shear forces can be detected as contact with the ground which causes the gel-like pad to deform into rigid wells. This is all done without the need to expose the sensor. A one-time training process using an artificial neural network was used to relate the normal and shear forces with the volumetric displacement sensor output. The sensor was shown to pre- dict normal forces in the Z-axis up to 80N with a root mean squared error of 6.04% as well as the onset of shear in the X and Y-axis. This demonstrates a proof-of-concept for a more robust footpad sensor suitable for use in all outdoor conditions.by Meng Yee (Michael) Chuah.S.M

Study and development of stretchable sensors for flexible surgical instrumentation.

Recently, attention has been focused to minimize the invasiveness of existing minimally invasive surgery (MIS) approaches: one example is the development of continuum-like and soft robots that can bend, extend, contract at any point along their length. This provides them with capabilities well beyond those of their rigid-link counterparts, thus allowing to perform whole arm manipulation. One recent approach to soft and modular systems is represented by the on-going EU project STIFF-FLOP (www.stiff-flop.eu). The STIFF-FLOP arm is not fabricated by rigid structures, but soft ones showing advanced manipulation capabilities for surgical applications, with multiple degrees of freedom (DOFs), and ability of multi-bending. Ideally, the entire robotic structure should safely move with contact and bend detection and the embedded sensors should not interfere with the movements: the use of small sensors, both soft and stretchable, which remain functional when deformed, becomes necessary. For the aforementioned reasons, we introduce a small, low-cost, soft and stretchable sensor composed of a silicone rubber (EcoFlex0030, SmoothOn), integrating a conductive liquid channel filled with biocompatible Sodium Chloride (NaCl) solution. By stretching the sensor the cross-section of the channel deforms, thus leading to a change in electrical resistance. The functionality of the sensor has been proved through testing: changes in electrical resistance are measured as a function of the applied strain. The advantage of using silicone rubber is its mechanical durability and high flexibility, non-toxicity, chemical stability and low cost. Furthermore, liquid conductors eliminate the need for rigid electronics and preserve the natural elasticity of the sensor, and the NaCl solution fulfills the need for a biocompatible liquid. Differently from existing solutions that are not truly stretchable and biocompatible, the contribution of this work is an effort for improving the current soft sensors technologies through the demonstration that NaCl filled channel rubbers represent a valid solution for measuring deformations in flexible surgical instrumentation