In this paper the problem of computing a rigid object trajectory in an environment populated with deformable objects is addressed. The problem arises in Minimally Invasive Robotic Surgery (MIRS) from the needs of reaching a point of interest inside the anatomy with rigid laparoscopic instruments. We address the case of abdominal surgery. The abdomen is a densely populated soft environment and it is not possible to apply classical techniques for obstacle avoidance because a collision free solution is, most of the time, not feasible. In order to have a convergent algorithm with, at least, one possible solution we have to relax the constraints and allow collision under a specific contact threshold to avoid tissue damaging. In this work a new approach for trajectory planning under these peculiar conditions is implemented. The method computes offline the path which is then tested in a surgical simulator as part of a pre-operative surgical plan.

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.

In this paper a force scaling function for an haptic system is the output of the psychophysics experiments that have been carried out with the aim of better understanding the human perception capabilities. The experimental work consists in measuring the differential thresholds of force perception applied to the hand-arm system. These findings support our claim that the human perception of forces and torques depends on force intensity and works differently along different directions, thus suggesting that perception can be enhanced by suitable scaling. We have identified a scaling function for each direction and we have shown that this variable scalings can be safely embedded in a passivity based teleoperation system in order to improve the feeling perceived by the user during the interaction with remote environments.

In this paper a perceptual model of the interaction with pliable surface is presented. The aim of this work is to evaluate those human factors most relevant to surface contact task in a bilateral teleoperation system characterized by a low stiffness environment. Three psychophysical experiments are conducted using an high performance haptic device and a virtual environment. In the first experiment we measure the capability of the human hand in terms of absolute force detection. The second experiment takes into account the time required by the neuro-muscular-skeletal system to stabilize the hand displacement in the presence of an external force. In the third one, a task of surface detection is involved to measures the smallest penetration depth that can be used to reliably perceive the contact surface. These perceptual factors are evaluated to build a perceptual model of a surface detection task. Results show the effectiveness of our model, which can be useful in applications where it is crucial to be aware of the interplay among perceptual factors.

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 theCPUto theGPUtaking 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 onGPUand the results are asyncronously transferred to theCPU. 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.

In the last few years, robotics education has been proposed in Universities and High Schools, to take advantage of the appeal of this discipline to teach scientific subjects. Robotics education is greatly improved when classroom teaching is supported by adequate laboratory courses and experiments following the "learning by doing" paradigm. However, cost of robotic laboratory equipment is an important issue, and several low cost instruments have been developed to permit an effective teaching in robotics at an affordable cost. These learning tools have demonstrated the importance and effectiveness of hand-on experiences and of group work in robotics learning. Among the best known and most used tools for robotics teaching, there is the Legocopy Mindstormtrade set, which is normally used to develop and program mobile robots, often biologically inspired and cooperating. In this paper however, we describe our experience with using LEGO kits in the development of teaching curricula for fixed robot manipulators. We found that the LEGO set is also an excellent tool to analyze robot kinematics and trajectory planning, and we describe our experience with a laboratory course designed to address kinematic properties of fixed robots

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

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

This paper presents theoretical and experimental results of robot interaction control schemes for a teleoperation system whose slave end effector comes in contact with a compliant surface. A salient feature of this work is a comparison of different control schemes implemented on a system whose slave consists of an industrial robot with an open software architecture and equipped with a wrist force sensor. Three control strategies are considered; one based on a single regulator PID giving a nominal performance, the second based on impedance control, and the last one based on a hybrid system approach. The performance of the various schemes is compared on a contact and puncturing task of an elastic membrane. The comparison is first carried out in simulation and then the simulations are validated with experiments. Quantitative as well as subjective performance measures are compared to assess the performance of the different control schemes.

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.

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.