Tactile Sensors For Robotic Applications PDF Download

Despite an important role and being a component of robotics roughly as long as vision, the use of touch sensing in robots is lesser than other sensory modalities e.g. vision and auditory sensing, thereby restricting the cognitive capabilities of the robots and strongly limiting their real world interaction capabilities. The lesser usage of touch sensing could partly be attributed to the complex and distributed nature of tactile sensing and partly also to the non availability of satisfactory tactile sensors. The physical problems like placement, robustness of sensors, wiring complexity etc. also pose a hurdle in effective utilization of tactile sensors. The interaction of robots with environment through tactile sensing has largely been limited to the measurement of static interaction forces whereas real world interaction involves both static and dynamic forces. Similarly, most of the sensors are designed to measure static pressure or forces from which it is difficult to obtain information like friction, stickiness, texture, hardness and elasticity. In real world, one needs to measure all these contact parameters which may require use of more than one transduction method simultaneously. As an example measurement of stress and stress rate can be done by having capacitive and piezoelectric transducers. Thus, more and more multifunctional tactile sensors? very few of which have been reported (Engel, Chen et al. 2005) - are required for real world interaction. The pursuit of tactile sensing for robotic applications, in the last two decades, has resulted in the development of many touch sensors - exploring nearly all modes of transduction -but; none could produce a tactile analog of CMOS optical arrays. Clearly, the emphasis, `only' on the sensor development has resulted in a large number of `bench top' sensors? suitable in a laboratory environment, and having limited practical usage in the robotic systems. This is surprising, considering the long history of gripper design for manipulative tasks. It is believed that the lack of the system approach has rendered many of them unusable, despite having a good design and performance (Dahiya, Valle et al. March, 2008). It is evident from the fact that very few works on tactile sensing have taken into account system constraints, like those posed by other sensors or by the robot controller, processing power etc. As an example, large numbers of tactile sensors put a pressure on the computing power required to process large number of data, whereas same can be solved (or at least reduced) by having distributed computing starting right from the transducer level (Dahiya, Valle et al. March, 2008). A system approach for the tactile sensing can be helpful in filling the gaps between tactile sensing and other sense modalities.