A Real-Time Display for Tactile Images

The tactile array sensor is a key component of the multi-sensory integration work at the General Robotics and Active Sensory Perception Laboratory (GRASP Lab) at the University of Pennsylvania. In our work, tactile sensors provide information about the nature of the contact between an actuated tool, such as a robotic gripper, and its physical domain. This information is used for feedback control of the gripper and robot manipulator to which it is attached, and for tactile perception. The sensor we currently use, LTS-200 from Lord Corp. [r@. I], consists of a two separate modules (see figure 1): • a 10 x 16 tactile array, which measures displacement (or deflection) via optical technology. • a 6 degree of freedom force/torque module using strain gauge technology. The force/ torque module is mounted under the tactile array. This is not an array, its output is scalar. The interface and signal processing circuitry is located in an external box. The data obtained from the LTS-200 tactile array describes the amount of deformation of the sensor cover. The sensor cover, made from a synthetic rubber, can deform, up to a point, to comply with the surface of the object under investigation (see figure 2). The sensing array samples this surface and data is obtained describing the texture and local shape of the contact area. This tactile sensor can be compared to a range finder, but with very limited span. The second module of the LTS-200 provides overall force, in x, y and z direction, and overall moments, around the x, y and z direction, which result from pressing the sensor against an object. In the course of using the LTS-200, or evaluating new sensors, we felt a need for visualizing the tactile information obtained. We looked for a format that provides insight into the tactile image and is suitable for further post-processing.