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Mobile Manipulation

Di Wang, Joshua Southerland, Charles de Granville, Andrew H. Fagg

Redundant Array of Inexpensive Digits

Brian Watson, Di Wang, Andrew H. Fagg

Commercially available robot hands (in particular, those equipped with sophisticated sensors) are expensive to purchase and maintain. Our lab is exploring the possibility of constructing hands from inexpensive components. Although this approach limits the capabilities of the individual fingers that make up a hand, it allows one to achieve capability through the redundancy that is possible with a large number of fingers.
One key component of this approach is that of accurately sensing the contact location between a finger of a robot hand and an object. Our approach is to embed a six-axis force/torque sensor within the finger. Given the sensed forces and torques, and knowledge of the finger geometry, one can infer the location of a contact. However, sensing is limited to contacts that are distal from the sensor. We have been developing a hand testbed in which we move the force/torque sensor from the finger tip (the typical configuration) to the base of the finger. This approach allows for the sensing of contacts across the entire surface of the finger, but dramatically increases the complexity of the sensor interpretation problem. Problems that we are addressing include:

  • distinguishing between contact and gravitational forces (in a configuration-dependent manner),
  • separating the real from "ghost" contacts that arise from the redundant solution problem, and
  • dealing with multiple, simultaneous contacts between finger and object.

Force & Torque Based Grasping Controller

Di Wang, Brian Watson, Andrew H. Fagg

The F/T grasp controller is a series of control algorithms used to control the "Redundant Array of Inexpensive Digits". We have developed a simulation environment using VTK. In this environment, the contact force direction is simulated using the normal of the contact point. The controller program can either be used to control the real finger using a server- client manner or just to do simulated grasp by itself.
In this research, we mainly focused on the following problems:

  • finding contact location using data from F/T sensor and eliminating "ghost" contacts,
  • reducing F/T residual by using some clean rules directly derived in Cartesian space, and
  • dealing with both convex and concave objects using multiple fingers.


di[at]cs[dot]ou[dot]edu

Last modified: 10-01-2009