Giuseppe De Maria

Innovative Technologies for the Next Generation of Robotic Hands

With the aim of reproducing the grasping and manipulation capabilities of humans, many robotic devices have been developed all over the world in more than 50 years of research, starting from very simple grippers, normally used in industrial activities, to very complex anthropomorphic robotic hands. Unfortunately, the reduced functionality and/or reliability of the devices developed so far prevent, together with the cost, their usability in unstructured environments, and in particular in human everyday activities. The adoption of design solutions inherited from conventional mechanics and the lack of purposely developed sensors and actuators are among the main causes of the partial fail in achieving the final goal of reproducing human manipulation capabilities. Our research activity aims at developing innovative solutions concerning the mechanical design, the sensory equipment and the actuation system for the implementation of anthropomorphic robotic hands with improved reliability, functionality and reduced complexity and cost, considering also aspects related to safety during human–robot interaction, paving the way toward the next generation of robotic hands.

ROBUST FLIGHT CONTROL SYSTEMS : A PARAMETER SPACE DESIGN

This paper deals with the longitudinal dynamics stabilization, around a trim condition, of an aircraft with unsatisfactory longitudinal stability characteristics. This problem is a single-input control problem because only elevator and canards deflections are used as control inputs, and they are simultaneously driven by the same control signal. To this aim, a new linear parameterization of all compensators stabilizing a given single-input plant is proposed, along with a design method based on a computationally tractable procedure for the robust stability analysis of polynomials with at finely dependent coefficient perturbations. Since scale factor sensor changes are perturbations entering affinely the characteristic polynomials coefficients of the closed-loop system, a controller will be synthesized in order to guarantee that the closed-loop poles lie in a specified domain of the complex plane prescribed by MIL specifications, and to achieve robustness against scale factor sensor failures. An application of the proposed procedure to the F4-E military aircraft is presented.

Integrated force/tactile sensing: The enabling technology for slipping detection and avoidance

This paper proposes an experimental study of slipping avoidance algorithms based on force/tactile perception data. The claim is that contact force measurements alone or tactile data alone are not sufficient for an effective slipping avoidance strategy in real world conditions. Integrated force/tactile sensors able to provide measurements of both the contact force vector and spatially distributed tactile maps are the key enabling technology for efficient slipping avoidance control algorithms that can actually work with real world objects under no restricting assumption on the contact geometry or with unknown physical properties of the objects. The paper proposes a new slipping avoidance control scheme, which usefully exploits an integrated force/tactile sensor mounted on the parallel gripper of a Kuka youBot. The results show how the strategy successfully allows the robot to safely manipulate real-world objects, both rigid and compliant, in various friction conditions of their surface, both stable and slippery.

Attitude control for low lift/drag re-entry vehicles

We propose an attitude control system for a re-entry capsule with a low lift/drag ratio (0.3). The control law is based on quaternions and on a sliding manifold approach. By using the singular perturbation theory, a feedback controller is designed with robustness properties with respect to structural parametric uncertainties and environmental disturbances. The system state remains in a neighborhood of a reference attitude and the control signal is close to the well-defined equivalent control. The reference attitude is commanded by a trajectory controller that steers the vehicle on a reference precalculated path. This controller is based on a time-varying linear quadratic and a variable structure system strategy to meet landing accuracy requirements. Moreover, a new modulator scheme is proposed to modulate the thrust torque commanded by the attitude controller. The overall control law is tested by using a six-degree-of-freedom model of the capsule, taking into account an oblate rotating Earth, and gravitational field, aerodynamics, propulsive forces, and moments. Simulation results show the effectiveness of the proposed control strategy in meeting the requirements on landing accuracy and on heating and load factor limits.

Data Fusion Based on Optical Technology for Observation of Human Manipulation

The adoption of human observation is becoming more and more frequent within imitation learning and programming by demonstration approaches (PbD) to robot programming. For robotic systems equipped with anthropomorphic hands, the observation phase is very challenging and no ultimate solution exists. This work proposes a novel mechatronic approach to the observation of human hand motion during manipulation tasks. The strategy is based on the combined use of an optical motion capture system and a low-cost data glove equipped with novel joint angle sensors, based on optoelectronic technology. The combination of the two information sources is obtained through a sensor fusion algorithm based on the extended Kalman filter (EKF) suitably modified to tackle the problem of marker occlusions, typical of optical motion capture systems. This approach requires a kinematic model of the human hand. Another key contribution of this work is a new method to calibrate this model.

A Distributed Tactile Sensor for Intuitive Human-Robot Interfacing

Safety of human-robot physical interaction is enabled not only by suitable robot control strategies but also by suitable sensing technologies. For example, if distributed tactile sensors were available on the robot, they could be used not only to detect unintentional collisions, but also as human-machine interface by enabling a new mode of social interaction with the machine. Starting from their previous works, the authors developed a conformable distributed tactile sensor that can be easily conformed to the different parts of the robot body. Its ability to estimate contact force components and to provide a tactile map with an accurate spatial resolution enables the robot to handle both unintentional collisions in safe human-robot collaboration tasks and intentional touches where the sensor is used as human-machine interface. In this paper, the authors present the characterization of the proposed tactile sensor and they show how it can be also exploited to recognize haptic tactile gestures, by tailoring recognition algorithms, well known in the image processing field, to the case of tactile images. In particular, a set of haptic gestures has been defined to test three recognition algorithms on a group of users. The paper demonstrates how the same sensor originally designed to manage unintentional collisions can be successfully used also as human-machine interface.

A FE analysis of a silicone deformable interface for distributed force sensors

The authors propose a novel modular artificial skin sensor, based on optoelectronic technology, able to estimate both normal and shear contact force components. The skin is constituted by sensor modules, each one characterized by four sensing elements that consist of a couple of infrared Light Emitting Diode and Photo-Detector covered by a silicone layer that transduces the external force in a mechanical deformation, measured by the four photodetectors. The skin prototype is obtained from the interconnection of several sensing modules and a single deformable layer is obtained with the use of two different silicone materials that differ for the shore hardness. Several FEM simulations have been carried out in order to demonstrate that the use of the two materials allows to obtain a single silicone structure with a very low coupling between two adjacent sensing modules.

Force/Tactile Sensors Based on Optoelectronic Technology for Manipulation and Physical Human–Robot Interaction

Design and realization of autonomous robotic platforms require crucial information on their surroundings especially when robots should interact with the environment and humans. In many cases, perception is necessary to correctly accomplish tasks in a dynamic environment where a model is hard to obtain. Grasping and fine manipulation of objects with different shapes and surface characteristics as well as detection of contacts between the robot and the environment are easily enabled by tactile sensing. The sense of touch represents the most natural way to obtain relevant information during an interaction task, such as parameters like surface friction, exchanged forces and torques, object shape. This chapter provides an overview of the authors’ work on force/tactile sensors development. By exploiting optoelectronic technology, the authors designed and realized two tactile sensors that can be used to execute both fine manipulation of objects and safe interaction tasks with humans. The chapter describes both sensors in detail and provides an experimental validation of their capabilities.

Customization of low-cost hexapod robots based on optimal design through inverse dynamics computation

The Stewart parallel mechanism is used in various applications due to its high load-carrying capacity, accuracy and stiffness, such as flight simulation, spaceship aligning, radar and satellite antenna orientation, rehabilitation applications, parallel machine tools. The dissemination of such parallel robots is however limited by three factors: the limited workspace, the singularity configurations existing inside the workspace, and the high cost. In this work, a simulation environment to support the design of a cost-effective Stewart Platform-based mechanisms for specific applications and to facilitate the choice of suitable components, e.g., linear actuators, plate sizes, is presented. The optimal design here presented has multiple objectives. It intends to maximize the payload and minimize the forces at each leg needed to counteract external forces applied to the mobile platform during positioning or manufacturing applications. These objectives can be achieved through a dynamic optimization. It also aims at avoiding reduction of the robot workspace through a kinematic optimization.

Experimental Modal Analysis based on a Gray-box Model of Flexible Structures

The main objective of this paper is to propose an experimental modal analysis procedure, based on the use of a gray-box model for flexible structures. The described approach presents interesting advantages with respect to commercial solutions: ease of use due to the low number of parameters to set for an identification session; no need for expert users, even in the presence of particular cases such as double modes, since it does not use a stabilization diagram to be elaborated; use of a gray-box model whose unknown parameters have a clear physical meaning. All these characteristics are discussed in the paper, and the performance of the proposed procedure has been evaluated by using experimental data available from a non-trivial standard benchmark. The results have been compared with those obtained by using a commercial tool.