Modelling, Optimization and Control of Biomorphic Hands

In this thesis, we present a general framework to model and control a class of biomorphically designed systems for robotic manipulation. Such system, are composed of a set of rigid bodies, interacting through unilateral rolling contact, and are actuated by a net of elastic tendons. Method based on convex analysis are applied to study this class of mechanisms, and are shown to provide a basis for the dynamic control of co-contraction and internal forces that guarantee the correct operation of the system, despite limited friction between contacting surfaces or object fragility. An algorithm is described and tested that integrate a computed torque law, and allows to control tendon actuators to optimally comply with the prescribed constraints

Modeling Compliant Grasps Exploiting Environmental Constraints

In this paper we present a mathematical framework to describe the interaction between compliant hands and environmental constraints during grasping tasks. In the proposed model, we considered compliance at wrist, joint and contact level. We modeled the general case in which the hand is in contact with the object and the surrounding environment. All the other contact cases can be derived from the proposed system of equations. We performed several numerical simulation using the SynGrasp Matlab Toolbox to prove the consistency of the proposed model. We tested different combinations of compliance as well as different reference inputs for the hand/arm system considered. This work has to be intended as a tool for compliant hand designer since it allows to tune compliance at different levels before the real hand realization. Furthermore, the same framework can be used for compliant hand simulation in order to study the interaction with the environmental constrains and to plan complex manipulation tasks

NEW METHODS OF UNDERACTUATED ROBOT ANALYSIS, DESIGN AND CONTROL FOR CYCLIC TASKS

Ph.DDOCTOR OF PHILOSOPH

Analysis and optimization of tendinous actuation for biomorphically designed robotic systems

We present a general framework for modeling a class of mechanical systems for robotic manipulation, consisting of articulated limbs with redundant tendinous actuation and unilateral constraints. Such systems, that include biomorphically designed devices, are regarded as a collection of rigid bodies, interacting through connections that model both joints and contacts with virtual springs. Methods previously developed for the analysis of force distribution in multiple whole-limb manipulation are generalized to this broader class of mechanisms, and are shown to provide a basis for the control of co–contraction and internal forces that guarantee proper operation of the system. In particular, in the presence of constraints such as those due to limited friction between surfaces or object fragility, the choice of tendon tensions is crucial to the success of manipulation. An algorithm is described that allows to evaluate efficiently set–points for the control of tendon actuators that “optimally ” (in a sense to be described) comply with the given constraints. I