This is an important sensing modality for robotic systems, especially those involved in the grasping, recognition and precise manipulation of objects. Tactile sensing is not as well developed as computer vision, in part, because of the lack of suitable sensors. I have designed a number of highly compliant tactile sensors using the following principles:
* Fluid resistance (electrical resistance), and
* Strain sensitive rubber.
Giving a tactile sensor a compliant surface enlarges the area of contact and thus increases the information that can be gathered from non-planer surfaces. I have also developed tactile sensors to determine the thermal properties of touched objects and whisker proximity sensors.
The processing of tactile sensory data and sensory control of robotic mechanisms are other current research topics. Sensory manipulation and object recognition experiments are performed using the Monash Dexterous Gripper shown below. The gripper has two 6-degree-of-freedom fingers which are each actuated by a Stewart platform mechanism. A 6-axis force/torque sensor detects forces acting on the work-surface and load cells in the root of each finger detect gripping forces. The fingers also incorporate tactile sensor arrays.
The Monash Dexterous Gripper
Shape and force displays provide the natural complement to tactile sensors and allow tactile information (either real or synthetic) to be displayed. The following picture shows an 8 by 8 array shape display. Each of the 64 rods can be set to a height within a 5 cm range.
A prototype tactile shape display
Quite a number of animals and insects mark their environment with traces of chemicals. Territorial animals deposit pheromone markings to indicate the boundaries of their territory and to warn off competitors. Foraging ants lay trails for worker ants to follow. Having deposited an odour mark the stored information that it represents is available to be read at a later time by the creature that made the marking or by others of the same species. These markings can be used as an aid to navigation or to help coordinate the actions of a group of creatures. To perform useful tasks in an unconstrained environment mobile robots have to solve similar navigational and organizational problems to those that challenge insects and other simple creatures. I have called any method of storing information in the environment in a form that dissipates over time a short-lived navigational marker. The following picture shows a miniature robot equipped to detect odour marking on the ground.
Miniature robot equipped to follow chemical trail trails on the ground
Many of the potential applications for chemical sensing robots involve locating the source of a chemical plume released into the air. With this kind of capability a mobile robot could perform some of the tasks that we currently assign to sniffer dogs including the detection of::
o plant matter, drugs and other materials important to the customs service,
o victims of avalanches and earthquakes,
o escaped prisoners,
o chemical leaks, and
o mines and unexploded bombs.
In most cases vast improvements will be required in chemical sensing technologies before robots can perform these tasks. However, even without improved sensors it is still possible to make progress in areas such as robot design and control algorithms.
A robot equipped with two conducive polymer chemical sensors and a wind vane
locates the source of a plume of ammonia
Robot learning is a very appealing area of research that has a number of potential benefits. A robot with the ability to learn would require less application-specific programming to customize it for performing a particular operation. If the environment changed then a learning robot may also be able to adapt appropriately without external guidance.
For me this is a new area of research and consequently there are only a few publications as of yet. The current project focuses on the transition between an organism whose genetically evolved competence is purely inherited and one with the added ability to learn from its environment. The framework of the project draws on Rolf Pfeifer's ideas about building complete autonomous systems that he calls "Fungus Eaters". For this project a self-contained environment EDEN has been constructed to act as an ecological niche for a mobile robot (ADAM Robot). It is anticipated that the robot will be able to improve its performance by learning from its interactions with this environment.
ADAM Robot feeds from a 'flower' in EDEN
In order to build the robotic platforms necessary to try out new robotic sensors I also maintain an interest in robotic mechanisms and novel robotic actuators such as shape-memory alloy, electrorheological fluid clutches, magnetic fluids, etc.
Some Media Coverage: