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Manipulation for self-Identification, and self-Identification for better manipulation
The process of modeling a series of hand-object parameters is crucial for precise and controllable robotic in-hand manipulation because it enables the mapping from the hand’s actuation input to the object’s motion to be ob-tained. Without assuming that most of these model parameters are known a priori or can be easily estimated by sensors, we focus on equipping robots with the ability to actively self-identify necessary model parameters using minimal sensing. Here, we derive algorithms, on the basis of the concept of virtual linkage-based representations (VLRs), to self-identify the underlying mechanics of hand-object systems via exploratory manipulation actions and probabilistic reasoning and, in turn, show that the self-identified VLR can enable the control of precise in-hand ma-nipulation. To validate our framework, we instantiated the proposed system on a Yale Model O hand without joint encoders or tactile sensors. The passive adaptability of the underactuated hand greatly facilitates the self-identification process, because they naturally secure stable hand-object interactions during random exploration. Relying solely on an in-hand camera, our system can effectively self-identify the VLRs, even when some fingers are replaced with novel designs. In addition, we show in-hand manipulation applications of handwriting, marble maze playing, and cup stacking to demonstrate the effectiveness of the VLR in precise in-hand manipulation control.
Calculating the Support Function of Complex Continuous Surfaces With Applications to Minimum Distance Computation and Optimal Grasp Planning
“The support function of a surface” is a fundamental concept in mathematics and a crucial operation for algorithms in robotics, such as those for collision detection and grasp planning. It is possible to calculate the support function of a convex body in closed form. However, for complex continuous surfaces, especially non-convex ones, this calculation can be far more difficult, and no general solution is available so far. This limits the applicability of related algorithms. This paper presents a branch-and-bound (B&B) algorithm to calculate the support function of complex continuous surfaces. An upper bound of the support function over a surface domain is derived. While a surface domain is divided into subdomains, the upper bound of the support function over any subdomain is proved to be not greater than the one over the original domain. Then, as the B&B algorithm sequentially divides the surface domain by dividing its subdomain having a greater upper bound than the others, the maximum upper bound over all subdomains is monotonically decreasing and converges to the exact value of the desired support function. Furthermore, with the aid of the B&B algorithm, this paper derives new algorithms for the minimum distance between complex continuous surfaces and for globally optimal grasps on objects with continuous surfaces. A number of numerical examples are provided to demonstrate the effectiveness of the proposed algorithms.