Leonardo Meli

Two finger grasping simulation with cutaneous and kinesthetic force feedback

This paper presents an experiment of two finger grasping. The task considered is the peg-in-hole and the simulated force feedback is cutaneous or kinesthetic. The kinesthetic feedback is provided by a commercial haptic device while the cutaneous one is provided by a new haptic display proposed in this work, which allows to render at the fingertip a wide range of contact forces. The device consists of a mobile surface, which interacts with the fingertip, actuated by three wires directly connected to the motors placed on the grounded structure of the display. This work summarizes the design of the proposed display and presents the main relationships which describe its kinematics and dynamics. Results showed that cutaneous feedback exhibits improved performances when compared to visual feedback only.

Sensory Subtraction in Robot-Assisted Surgery: Fingertip Skin Deformation Feedback to Ensure Safety and Improve Transparency in Bimanual Haptic Interaction

This study presents a novel approach to force feedback in robot-assisted surgery. It consists of substituting haptic stimuli, composed of a kinesthetic component and a skin deformation, with cutaneous stimuli only. The force generated can then be thought as a subtraction between the complete haptic interaction, cutaneous, and kinesthetic, and the kinesthetic part of it. For this reason, we refer to this approach as sensory subtraction. Sensory subtraction aims at outperforming other nonkinesthetic feedback techniques in teleoperation (e.g., sensory substitution) while guaranteeing the stability and safety of the system. We tested the proposed approach in a challenging 7-DoF bimanual teleoperation task, similar to the Pegboard experiment of the da Vinci Skills Simulator. Sensory subtraction showed improved performance in terms of completion time, force exerted, and total displacement of the rings with respect to two popular sensory substitution techniques. Moreover, it guaranteed a stable interaction in the presence of a communication delay in the haptic loop.

Cutaneous haptic feedback to ensure the stability of robotic teleoperation systems

Cutaneous haptic feedback can be used to enhance the performance of robotic teleoperation systems while guaranteeing their safety. Delivering ungrounded cutaneous cues to the human operator conveys in fact information about the forces exerted at the slave side and does not affect the stability of the control loop. In this work we analyze the feasibility, effectiveness, and implications of providing solely cutaneous feedback in robotic teleoperation. We carried out two peg-in-hole experiments, both in a virtual environment and in a real (teleoperated) environment. Two novel 3-degree-of-freedom fingertip cutaneous displays deliver a suitable amount of cutaneous feedback at the thumb and index fingers. Results assessed the feasibility and effectiveness of the proposed approach. Cutaneous feedback was outperformed by full haptic feedback provided by grounded haptic interfaces, but it outperformed conditions providing no force feedback at all. Moreover, cutaneous feedback always kept the system stable, even in the presence of destabilizing factors such as communication delays and hard contacts.

Wearable haptics and hand tracking via an RGB-D camera for immersive tactile experiences

In 1997 Sony revolutionized the gaming industry by introducing a simple but effective vibrotactile feedback in its DualShock controller for PlayStation. By 2013, more than 400M units have been sold. Nowadays, the game interface Wii Remote motion controller provides a similar feature, but wirelessly, and can be considered the most popular portable haptic interface, with over 100M sales. However, its force feedback is still limited to vibrations, reducing the possibility of simulating any rich contact interaction with virtual and remote environments. Towards a more realistic feeling of interacting with virtual objects, researchers focused on glove-type haptic displays such as the Rutgers Master II and the CyberGrasp, which provide force sensations to all the fingers of the hand simultaneously. However, although they provide a compelling force feedback, these displays are complex and very expensive the CyberGrasp, for instance, costs more than 60,000 US dollars! Thus, it becomes crucial to find a trade-off between a realistic feeling of touch and cost/portability of the system. In this regard, we found tactile technologies very promising. Tactile devices are haptic interfaces able to provide tactile force feedback only (they do not provide any kind of kinesthetic force). This property makes possible to dramatically simplify their form factor and provide a compelling and realistic feeling of touching virtual objects [Pacchierotti et al. 2014].

Using the robotic sixth finger and vibrotactile feedback for grasp compensation in chronic stroke patients

This paper presents a wearable robotic extra finger used by chronic stroke patients to compensate for the missing hand functions of the paretic limb. The extra finger is worn on the paretic forearm by means of an elastic band, and it is coupled with a vibrotactile ring interface worn on the healthy hand. The robotic finger and the paretic hand act like the two parts of a gripper working together to hold an object. The human user is able to control the flexion/extension of the robotic finger through a switch placed on the ring, while being provided with vibrotactile feedback about the forces exerted by the robotic finger on the environment. To understand how to control the vibrotactile interface to evoke the most effective cutaneous sensations, we carried out perceptual experiments to evaluate its absolute and differential thresholds. Finally, we performed a qualitative experiment, the Franchay Arm Test, with a chronic post-stroke patient presenting a partial loss of sensitivity on the paretic limb. Results show that the proposed system significantly improves the performance of the considered test.

Object-based bilateral telemanipulation between dissimilar kinematic structures

This paper presents a bilateral telemanipulation framework where the master and slave sub-systems have different kinematic structures. A virtual object is defined on the master and slave sides and used to capture the human hand motion and to compute the related force feedback. The force feedback is determined imposing that the same wrench acts on the master and slave virtual objects. An abstraction from the sub-system structures is obtained focusing on the effects produced on the manipulated object. The proposed approach has been tested with an experimental setup consisting of two haptic interfaces able to capture index and thumb motions on the master side and a DLR-HIT Hand II as slave sub-system.

Vibrotactile haptic feedback for intuitive control of robotic extra fingers

Wearable robots have been mostly designed as exoskeletons, with segments and joints corresponding to those of the person they are coupled with. Exoskeletons are mainly employed to augment human body force and precision capabilities, or for rehabilitation purposes. More recently, new wearable robots resembling additional robotic limbs have been developed thanks to the progress in miniaturization and efficiency of mechanical and sensing components. However, wearable robotic extra limbs presented in the literature lack of effective haptic feedback systems. In this paper, we present a robotic extra finger coupled with a vibrotactile ring interface. The human user is able to control the motion of the robotic finger through a switch placed on the ring, while being provided with vibrotactile feedback about the forces exerted by the robotic finger on the environment. To understand how to control the vibrotactile interface to evoke the most effective cutaneous sensations, we executed perceptual experiments to evaluate its absolute and differential thresholds. We also carried out a pick-and-place experiment with ten subjects. Haptic feedback significantly improved the performance in task execution in terms of completion time, exerted force, and perceived effectiveness. All subjects preferred experimental conditions employing haptic feedback with respect to those not providing any force feedback.

Experimental evaluation of magnified haptic feedback for robot-assisted needle insertion and palpation

Haptic feedback has been proven to play a key role in enhancing the performance of teleoperated medical procedures. However, due to safety issues, commercially‐available medical robots do not currently provide the clinician with haptic feedback.

Digital Handwriting with a Finger or a Stylus: A Biomechanical Comparison

In this paper, we present a study concerning the human hand during digital handwriting on a tablet. Two different cases are considered: writing with the finger, and writing with the stylus. We chose an approach based on the biomechanics of the human hand to compare the two different input methods. Performance is evaluated using metrics originally introduced and developed in robotics, such as the manipulability indexes. Analytical results assess that writing with the finger is more suitable for performing large, but not very accurate motions, while writing with the stylus leads to a higher precision and more isotropic motion performance. We then carried out two experiments of digital handwriting to support the approach and contextualize the results.

Multicontact Bilateral Telemanipulation With Kinematic Asymmetries

We propose a novel bilateral telemanipulation framework to tame master and slave devices having different structures. This condition applies to multicontact teleoperation scenarios where the number of contact points on the slave side and the number of interaction points on the master side are different. An example is a master device interacting with the thumb and the index fingertips of the human operator, and as slave device, a robotic arm with a multifingered robotic hand. In case of a manipulation task, it is not straightforward to transmit motion commands and reflect forces from the interaction with the environment. A general telemanipulation framework, that does not consider the specific kinematics of the devices involved, is needed. The main idea of this study is to take advantage of a virtual object as a mediator between the master and slave side. The arising forward and backward mapping algorithms are able to relate the motions and the exerted forces of very dissimilar systems. The approach has been evaluated in a case study consisting of two haptic interfaces used both to track the index and thumb motions and to render forces on the master side and a robotic arm with a multifingered hand as end effector on the slave side. The results presented in this paper can be extended to cooperative grasping scenarios where multiple robots telemanipulate the same object.