Debora Botturi

Hybrid HMM/SVM model for the analysis and segmentation of teleoperation tasks

The automatic execution of a complex task requires the identification of an underlying mental model to derive a possible task control sequence. The model aims at analysing and segmenting the task in simpler sub-tasks. As an example of a complex task, in this paper we consider teleoperation where a person commands a remote robot. This paper presents a new modeling approach using hidden Markov models (HMM) and support vector machines (SVM) to analyse the force/torque signals of a teleoperation task. The task is divided into simpler sub-tasks and the model is used to segment the signals in each sub-task. The segmentation gives informations on the system behavior identifying the changes of the model states. Peg in hole force/torque data are used for testing the model. The results are consistent with the literature with respect to off-line analysis, whereas a significant increase of performance is achieved for on-line analysis.

Evaluation of force and torque magnitude discrimination thresholds on the human hand-arm system

This article reports on experiments about haptic perception aimed at measuring the force/torque differential thresholds applied to the hand-arm system. The experimental work analyzes how force is sent back to the user by means of a 6 degrees-of-freedom haptic device. Our findings on force perception indicate that the just-noticeable-difference is generally higher than previously reported in the literature and not constant along the stimulus continuum. We found evidence that the thresholds change also among the different directions. Furthermore, asymmetries in force perceptions, which were not described in previous reports, can be evinced for most of the directions. These findings support our claim that human beings perceive forces differently along different directions, thus suggesting that perception can also be enhanced by suitable signal processing, that is, with a manipulation of the force signal before it reaches the haptic device. We think that the improvement of the user perception can have a great impact in many applications and in particular we are focusing on surgical teleoperation scenarios.

Simulation of deformable environment with haptic feedback on GPU

Interactive simulations of deformable bodies are a growing research area with possible applications in several fields, i.e. computer aided surgery. The main implementation issue is to mimic the real behavior of the body at the extremely high rates required by haptic devices. Since even high-end computers have inadequate performance, one possible solution is to exploit the parallelism of modern Graphics Processing Units. In this paper we present our research aiming at moving the whole computational process from the CPU to the GPU taking advantage of the computational power of the graphics hardware. We use a mass-spring model, augmented with local damping coefficients and volume preservation forces. Collision detection is performed against external rigid bodies with high complexity mesh, such as the skeletonpsilas one. The user interacts with the model by controlling virtual tools, i.e. probes or tweezers. Haptic forces are computed on GPU and the results are asyncronously transferred to the CPU. Our approach can simulate the deformation of complex models with gravity and interaction with environment and tools at a frame rate higher than 1 KHz, making it suitable for visual rendering and haptic feedback.

GPU-based physical cut in interactive haptic simulations

PurposeInteractive, physics based, simulations of deformable bodies are a growing research area with possible applications to computer-aided surgery. Their aim is to create virtual environments where surgeons are free to practice. To ensure the needed realism, the simulations must be performed with deformable bodies. The goal of this paper is to describe the approach to the development of a physics-based surgical simulator with haptic feedback.MethodThe main development issue is the representation of the organ behavior at the high rates required by haptic realism. Since even high-end computers have inadequate performance, our approach exploits the parallelism of modern Graphics Processing Units (GPU). Particular attention is paid to the simulation of cuts because of their great importance in the surgical practice and the difficulty in handling topological changes in real time.ResultsTo prove the correctness of our approach, we simulated an interactive, physically based, virtual abdomen. The simulation allows the user to interact with deformable models. Deformable models are updated in real time, thus allowing the rendering of force feedback to the user. The method is optimized to handle high quality scenes: we report results of interactive simulation of two virtual tools interacting with a complex model.ConclusionsThe integration of physics-based deformable models in simulations greatly increases the realism of the virtual environment, taking into account real tissue properties and allowing the user to feel the actual forces exerted by organs on virtual tools. Our method proves the feasibility of exploiting GPU to simulate deformable models in interactive virtual environments.

FPGA-based Controller for Haptic Devices

Teleoperation with force feedback is a complex task and a good haptic device is a key element. In this paper we present an innovative hardware/software structure used to control an actuated 6 dof joystick in a teleoperation task. To increase speed and reliability, parts of the kinematic calculation are embedded into the joystick controller. To implement this idea we used an FPGA to handle both the low level tasks and the algorithmic part of the approach. This speedup does not preclude the possibility of changing the control strategies, the parameters and the feedback calculations as well, necessary to carry out experiments about human perception. Thus the need of flexibility and performance, and the choice of an FPGA. We tested the setup proposed in a real teleoperation task within our software framework (Penelope) collecting data of speed, precision and reliability

Introducing service robotics to the pharmaceutical industry

In this paper, we present the development of a prototype of service robot for the pharmaceutical industry. First, the paper describes the analysis of functional and economical justifications of a service robot in this manufacturing segment. The warehouse of the Parma (Italy) GSK plant was identified as suitable, and goods transportation as the highest impact application. Then, the paper describes some of the key technologies of mobile manipulation proposed for this service robot. We summarize the functional aspects of the system, and its main control elements. The project produced a feasibility proof of safe and efficient goods transportation in a partially structured, dynamic and public environment, with minimal impact on the manufacturing plant. We conclude the paper by summarizing the validation steps needed to make these technologies accepted by the pharmaceutical industry.

Advanced Teleoperation Architecture

In this paper we report on the efforts carried out at the Robotics Laboratory ALTAIR of the University of Verona (Italy) towards the development of a high performance architecture for bilateral, i.e. force reflecting, teleoperation system. This architecture, called Penelope, takes into account the main features of a haptics system: real-time behavior, distributed resources, general purpose structure and safe exchange of data. The emphasis here is on heterogeneous hardware and software within the same structure

Human factors in haptic contact of pliable surfaces

This paper considers relevant human factors to interact with a pliable body in a teleoperation surgical environment. Our aim is to identify the human capabilities, in terms of penetration depth and responsiveness, in a task of pliable surface contact, where surgeons are required to adopt a specific behavior immediately after the contact. A psychophysical experiment is conducted using virtual surfaces rendered with two different force-feedback devices. The results show that impact velocity affects performance in surface contact perception. In a second experiment where different postures are used, we examine whether the previous results hold for the particular ergonomic configuration employed. The results show that posture affects performance especially in expert users. Our findings underscore the importance of understanding the interplay of human perceptual parameters in the surgical teleoperation framework.

Laboratory tools for robotics and automation education

This paper describes our efforts and plans to develop a Virtual Laboratory for the education in Robotics and Automation. These efforts are characterized by the need of blending R&A subjects into a traditional Computer Science curriculum, thus forcing a specific selection of development topics. In this context, the Robotics Laboratory must provide the basic as well as advanced experiments, to address the needs of students at different education levels. In this paper, we present the development of three main applications, to support Control Systems and Robotics classes, as well as the thesis and dissertation research. Of particular interest is the effort in the area of teleoperation, preliminary to the opening (next year) of a new curriculum on Medical Informatics, in which Computer Assisted Surgery will play an important role.

Perceptual Issues Improve Haptic Systems Performance

Since its introduction in the early 50s, teleoperation systems have expanded their reach, to address micro and macro manipulation, interaction with virtual worlds and the general field of haptic interaction. From its beginnings, as a mean to handle radioactive materials and to reduce human presence in dangerous areas, teleoperation and haptics have also become an interaction modality with computer generated objects and environments. One of the main goals of teleoperation is to achieve transparency, i.e. the complete perception by the human operator of the virtual or remote environment with which he/she is interacting (Lawrence, 1993). The ability of a teleoperation system to provide transparency depends upon the performance of the master and the slave, and of its control system. Ideally, the master should be able to emulate any environment, real or simulated, from freespace to infinitely stiff obstacles. The design of a transparent haptic interface is a quite challenging engineering task, since motion and sensing capabilities of the human hand/arm system are difficult to match. Furthermore, recent studies are providing more and more evidence that transparency is not only achieved by a good engineering design, but also by a combination of perceptual and cognitive factors that affect the operator ability to actually perceive the stimuli provided. The current knowledge on operator models reflects two separate groups of results. On one hand, there are guidelines for the design of an effective interface, from a human factors points of view, which include perceptual issues related to the cognitive and information processing of the human operators (see Subsection 2.4). On the other hand, there are several operator models related to biomechanical, bandwidth and reaction time issues (see Subsection 2.5). In this work we survey the main human factors that concur to the effectiveness of a haptic interface, and we present a series of psychophysical experiments, which can enrich performance in haptic systems, by measuring the mechanical effectiveness of the interface, providing a measure of the perception of a human operator. In addition the experiments are useful to represent the complex behavior of the human perception capabilities, and to propose new ways for enhancing the transparency of the virtual environment, by proposing suitable force scaling functions. In addition, our experience with psychophysics procedures highlights the needs of non-classical approaches to the problem, but the design of this type of experiments is not trivial, thus the need of a dedicated software tool or library arises. 22