Carlo Alberto Avizzano

Teaching to write Japanese characters using a haptic interface

Haptic interfaces have been used as cooperative systems to reproduce and simulate human actions. The Haptic Interface (HI) can be used as a tool capable of interacting dynamically with the operator using Reactive Robot (RR) technology. The RR systems provide to the HI the capability of interpreting the human actions and exert a more intelligent force feedback strategy. This paper deals with an application of the RR theory to leach people to write Japanese characters, using a desktop III designed at PERCRO. In this article, we will outline the main features of the RR system. Human action identification was implemented using Hidden Markov Models. The recognition system was tested using a Polhemus sensor. An initial control law to restrict the user to move along a predefined trajectory using the HI is described.

Reactive robot system using a haptic interface : an active interaction to transfer skills from the robot to unskilled persons

This paper is concerned with the reactive robot system (RRS) which has been introduced as a novel way of approaching human–robot interactions by exploiting the capabilities of haptic interfaces to transfer skills (from the robot to unskilled persons). The RRS was implemented based on two levels of interaction. The first level, which implements the first two stages of the learning process, represents the conventional control way of interchanging a set of forces in response to a static read of the contact position of some pre-defined dynamic rules (passive interaction). The second level, which implements the last stage of the learning process, represents an enhanced way of interaction between haptic interfaces and humans. This level adds to robotic system a degree of intelligence which enables the robot to dynamically adapt its behavior depending on user wishes (active interaction). In particular, in this paper, the implementation of the second level of the RRS is described in detail. A set of experiments was performed, applied to Japanese handwriting, to verify if second level of the RRS can interact with humans during the autonomous stage of the learning process. The results demonstrated that our system can still provide assistance to users on the autonomous stage while mostly respecting their intentions without significantly affecting their performance.

A virtual environment with haptic feedback for the treatment of motor dexterity disabilities

We present an immersive virtual environment (VE) including visual, auditory and haptic feedbacks, which has been designed specifically to help to recover or improve the motor dexterity of the arm and hand in patients affected by disorders of motor coordination. The realization of an effective haptic feedback on the human arm and hand is the most critical issue for such application. Innovative approaches have been followed for the monitoring of upper limb movements; the replication of forces on the human hand, the real time simulation of interactions between user upper limb and virtual objects, including the simulation of stable grasps; and the accurate synchronization of the various sensory feedbacks. The rehabilitation exercises, which have already been implemented and tested on healthy subjects are described. The major technical solutions adopted are discussed.

Design and validation of a complete haptic system for manipulative tasks

The present work deals with the design, implementation and assessment of a new haptic system specifically conceived for manipulative tasks in virtual environments. Such a system was designed by taking into account specific issues related to fine manipulation, such as multipoint haptics, coherence, transparency and physical representation. The haptic system described herein is integrated with a virtual environment engine for the simulation of multifinger manipulation. A preliminary evaluation of the system was conducted by comparing human performance in the manipulation of virtual objects with respect to real objects, according to the data available in the literature. The experiments confirm how the most relevant relationships among physiological and physical parameters involved in manipulation are also preserved during virtual manipulation. However, an in-depth analysis of the results shows that simulation parameters affect the level of force control during virtual manipulation and the quality of the perceived force feedback.

Force‐based impedance control of a haptic master system for teleoperation

This paper analyzes the design of a force‐based impedance control for a haptic interface system characterized by a parallel kinematics. By exploiting the features of parallel mechanisms, which perform better than the serial ones in terms of dynamic performance, stiffness and position accuracy, and by implementing a closed‐loop force control, the transparency of a haptic master system and the fidelity of resultant force feedback can be consistently improved. Issues for design and control as well as aspects of performance evaluation of haptic interfaces are treated within the paper and some results of the experimental characterization of a haptic interface are presented.

Washout filter design for a motorcycle simulator

Many motion based simulators have been developed for many different types of vehicles. In order to make a simulation more realistic, linear accelerations and angular rates are exerted on the pilot by moving the platform on which the mock-up vehicle is located. This has to be accomplished without driving the simulator out of its work-space. The software component that is in charge of this is commonly referred to as the washout filter. Washout filters have been widely investigated in the past, mainly in the field of flight simulators. We present a washout filter designed for a motorcycle simulator. The solution is preliminary and follows, as a reference point, techniques previously adopted for large aircraft simulators. Differences between motorcycle and aircraft simulation are analyzed and a preliminary customized solution is proposed. The washout filter, which will be used to drive a motorcycle simulator, currently being built at PERCRO, has been tested off-line showing good results and will soon be tested on real riders.

A multi-finger haptic interface for visually impaired people

The present paper deals with a novel type of dual point haptic system. The system exploits a novel kind of kinematics to achieve a high isotropy which improves the force rendering. Other features of the system are its high stiffness, high peak forces together with a zero backlash cable based transmission. The device can be used by means of a set of sizeable thimbles by any pairs of users fingertips. Such a device has been developed within the EU GRAB project, for testing a novel set of application with blind users. Such a project investigates to which extent a purely haptic environment can be employed from users with visual impairments in terms of the effective capabilities of the device to exchange high level information with the users; the real degree of interaction which can be achieved in this type of system; the effective opportunity for the user to profit from the system using just this type of interaction. The basic system concepts, the application environment and the system performances are given in the following.

Technological approach for cultural heritage: augmented reality

Augmented reality (AR) systems allow the user to see a combination of a mixed scenario, generated by a computer, in which virtual objects are merged with the real environment. The calibration between the two frames, the real world and the virtual environment, and the real time tracking of the user are the most important problems for the AR application implementations. Augmented reality systems are proposed as solutions in many application domains. In this paper we addressed the aspect related to the development of AR applications in the cultural heritage field. Possible future applications are described, including the use of haptic interfaces in AR systems, designed at PERCRO.

Real-Time Gesture Recognition, Evaluation and Feed-Forward Correction of a Multimodal Tai-Chi Platform

This paper presents a multimodal system capable to understand and correct in real-time the movements of Tai-Chi students through the integration of audio-visual-tactile technologies. This platform acts like a virtual teacher that transfers the knowledge of five Tai-Chi movements using feed-back stimuli to compensate the errors committed by a user during the performance of the gesture. The fundamental components of this multimodal interface are the gesture recognition system (using k-means clustering, Probabilistic Neural Networks (PNN) and Finite State Machines (FSM)) and the real-time descriptor of motion which is used to compute and qualify the actual movements performed by the student respect to the movements performed by the master, obtaining several feedbacks and compensating this movement in real-time varying audio-visualtactile parameters of different devices. The experiments of this multimodal platform have confirmed that the quality of the movements performed by the students is improved significantly.

The hand force feedback: analysis and control of a haptic device for the human-hand

The hand force feedback system is an anthropomorphic haptic interface for the replication of the forces arising during grasping and fine manipulation operations. It is composed of four independent finger dorsal exoskeletons which wrap up four fingers of the human hand (the little finger is excluded). Each finger possesses three electrically actuated DOF placed in correspondence with the human finger flexion axes and a passive DOF allowing finger abduction movements. Each exoskeleton finger has three points of attachment to the operators finger (two for the thumb) at the middle of the phalanges. Mechanical fixtures guarantee that just a force perpendicular to the finger and in its sagittal plane is exchanged at each point of attachment. Such force component is sensed and it is actively controlled in feedback. The paper illustrates the design and testing of the controller for the thumb exoskeleton. First the mechanical system is analyzed and the features which influence the controller design, such as the presence of unidirectional tendon transmission, are modeled. Then haptic controllers, i.e. feedback controllers aiming at improving the performance of the device when used as a haptic interface for virtual environments or telemanipulation, are designed and tested experimentally. Finally the experimental results are discussed.