New sensor gives robot unprecedented dexterity

Researchers, including one of Indian-origin, have equipped a robot with a new tactile sensor that gives it unprecedented dexterity, letting it grasp a USB cable draped freely over a hook and insert it into a port.
The sensor is an adaptation of a technology called GelSight, which was developed by the lab of Edward Adelson from Massachusetts Institute of Technology (MIT).
The sensor small enough to fit on a robot's gripper and its processing algorithm is faster, so it can give the robot feedback in real time.
According to Robert Platt, an assistant professor of computer science at Northeastern University and the research team's robotics expert, for a robot taking its bearings as it goes, this type of fine-grained manipulation is unprecedented.

The MIT team - which consists of Adelson; first author Rui Li, a PhD student; Wenzhen Yuan, a master's student; and Mandayam Srinivasan, a senior research scientist in the Department of Mechanical Engineering - designed and built the sensor. Platt's team at Northeastern developed the robotic controller and conducted the experiments.
Whereas most tactile sensors use mechanical measurements to gauge mechanical forces, GelSight uses optics and computer-vision algorithms.

A GelSight sensor consists of a slab of transparent, synthetic rubber coated on one side with a metallic paint.
The rubber conforms to any object it's pressed against, and the metallic paint evens out the light-reflective properties of diverse materials, making it much easier to make precise optical measurements.

In the new device, the gel is mounted in a cubic plastic housing, with just the paint-covered face exposed. The four walls of the cube adjacent to the sensor face are translucent, and each conducts a different colour of light - red, green, blue, or white - emitted by light-emitting diodes at the opposite end of the cube.
When the gel is deformed, light bounces off of the metallic paint and is captured by a camera mounted on the same cube face as the diodes.
From the different intensities of the different-coloured light, the algorithms developed by Adelson's team can infer the three-dimensional structure of ridges or depressions of the surface against which the sensor is pressed.

In Platt's experiments, a Baxter robot from MIT spin-out Rethink Robotics was equipped with a two-pincer gripper, one of whose pincers had a GelSight sensor on its tip. Using conventional computer-vision algorithms, the robot identified the dangling USB plug and attempted to grasp it.
It then determined the position of the USB plug relative to its gripper from an embossed USB symbol. Although there was a 3-millimetre variation, in each of two dimensions, in where the robot grasped the plug, it was still able to insert it into a USB port that tolerated only about a millimetre's error.