An experimental study on touch-driven robot control, or tactile-servo, is presented in this paper. The tactile servo scheme uses a tactile feature Jacobian matrix to relate the differential change in tactile feature space to that in the robot task space. Tactile Jacobian matrices are constructed through a finite element (FE) model of the tactile sensor. Detailed implementation of the control scheme and experimental results are presented.

Studies on contact problems such as shape recovery from tactile sensing involve complex geometrics and kinematics. In the first part of the paper we introduce a convenient matrix expression of 3-D surfaces, which can be easily applied to manipulate contact constraints and kinematics equations using homogeneous transformation. In the second part of the paper we apply the notation introduced in the first part and derive an active tactile sensing strategy which consists of a shape sensing algorithm and a touch-based robot control scheme.

A real-time tactile image processing algorithm for edge contact is presented in this paper. Based on basic elasticity results, closed-form solutions for calculating contact force and local contact geometries (i.e., location and orientation of the line of contact) from the first three moments of a tactile image are derived. Computational complexity of the proposed algorithm and those of the previous approaches are compared, and passive tactile sensing experiments are performed. It is shown that the proposed algorithm has the advantage of persevering force information and is more consistent and computationally efficient.

A novel method to perform edge tracking using tactile sensors is presented in this paper. Using the tactile servo scheme, a robot manipulator is driven only by real-time tactile feedback from the array tactile sensors mounted directly on the robot end-effector. Compared with previous approaches, the control scheme presented in this paper is consistent and more efficient. Real-time edge tracking experiments are conducted using an experimental system consisting of a PUMA 260, a single rigid finger and a planar array tactile sensor. Experimental results show satisfactory control speed and accuracy for both straight and curved edge tracking. An example of active tactile sensing of a unknown object using edge tracking is also demonstrated.

A three-alternative step-function process on two dimensions, with step size constrained in both directions, is considered. The maximum specific entropy is found to be only 1.02 bits/interval, compared with the 1.59 bits/interval that would be obtained if step size were constrained in only one direction.