Section: New Results

Shared Control Architectures

• in [51] we proposed a shared control algorithm for remote telemanipulation of redundant robots able to fuse the task-prioritized control architecture (for handling the concurrent realization of multiple tasks) with haptic guidance techniques. In particular, we developed a suitable passivity-preserving strategy based on energy tanks for always guaranteeing stability despite the possible presence of autonomous tasks that could generate an increase of energy during operation. The approach has been validated with extensive simulative results in a realistic environment.

• in [6] we have considered a shared control algorithm for telemanipulation that embeds the presence of a grasping planner for guiding the operator towards suitable grasping poses. The operator retains control of the end-effector motion and eventual grasping location, but she/he is assisted by the autonomy (via force cues) in navigating towards good grasps, as classified by the grasping planner that takes as input a RGBD image of the scene and computes a set of grasping poses along the object contour.

• in [50] we have presented two haptic shared-control approaches for robotic cutting. They are designed to assist the human operator by enforcing different nonholonomic-like constraints representative of the cutting kinematics. To validate this approach, we carried out a human-subject experiment in a real cutting scenario. We compared our shared-control techniques with each other and with a standard haptic teleoperation scheme. Results show the usefulness of assisted control schemes in complex applications such as cutting.

Needle insertion procedures under ultrasound guidance are commonly used for diagnosis and therapy. This kind of intervention can greatly benefit from robotic systems to improve their accuracy and success rate. In the past years, we have developed a robotic framework dedicated to 3D steering of beveled-tip flexible needle in order to autonomously reach a desired target in the tissues by ultrasound visual servoing using a 3D ultrasound probe. This year we have proposed a real-time semi-automatic teleoperation framework that enables the user to directly control the trajectory of the needle tip during its insertion via a haptic interface [38]. The framework enables the user to intuitively guide the trajectory of the needle tip in the ultrasound 3D volume while the controller handles the complexity of the 6D motion that needs to be applied to the needle base. A mean targeting accuracy of 2.5 mm has been achieved in gelatin phantoms and different ways to provide the haptic feedback as well as different levels of control given to the user on the tip trajectory have been compared. Limiting the user input to the insertion speed while automatically controlling the trajectory of the needle tip seems to provide a safer insertion process, however it may be too constraining and can not handle situations where more control over the tip trajectory is required, for example if unpredicted obstacles need to be avoided. On the contrary, giving the full control of the 3D tip velocity to the user and applying a haptic feedback to guide the user toward the target proved to maintain a low level of needle bending and tissue deformation.

The objective of this work is to provide assistance during manual needle steering for biopsies or therapy purposes (see Section 7.2.3). At the difference of our work presented in Section 6.4.2 where a robotic system is used to steer the needle, we propose in this study another way of assistance where the needle is collaboratively manipulated by the physician and a haptic device. The principle of our approach is to provide haptic cue feedback to the clinician in order to help him during his manual gesture [43]. We elaborated 5 different haptic-guidance strategies to assist the needle pre-positioning and pre-orienting on a pre-defined insertion point, and with a pre-planned desired incidence angle. The haptic guides rely on the position and orientation errors between the needle, the entry point and the desired angle of incidence toward the target, which are computed from the measurements provided by an electromagnetic tracker. Each of the guide implements a different Guiding Virtual Fixture producing haptic cues that attract the needle towards a point or a trajectory in space with different force feedback applied on the user's hand manipulating the needle. A two-step evaluation was conducted to assess the performance and ergonomy of each haptic guide, and compare them to the unassisted reference gesture. The first evaluation stage [44] involved two physicians both experts in needle manipulation at Rennes University Hospital. The performance results showed that, compared to the unassisted gesture, the positioning accuracy was enhanced with haptic guidance. The second evaluation stage [43] was a user study with twelve participants. From this second study it results that the most constraining guide allows to perform the gesture with the best accuracy, lower time duration and highest level of ergonomy.

Power wheelchairs allow people with motor disabilities to have more mobility and independence. However, driving safely such a vehicle is a daily challenge particularly in urban environments while navigating on sidewalks, negotiating curbs or dealing with uneven grounds. Indeed, differences of elevation have been reported to be one of the most challenging environmental barrier to negotiate, with tipping and falling being the most common accidents power wheelchair users encounter. It is thus our challenge to design assistive solutions for power wheelchair navigation in order to improve safety while navigating in such environments. To this aim, we proposed a shared-control algorithm which provides assistance while navigating with a wheelchair in an environment consisting of negative obstacles. We designed a dedicated sensor-based control law allowing trajectory correction while approaching negative obstacles e.g. steps, curbs, descending slopes. This shared control method takes into account the humanin-the loop factor. In this study, our solution the ability of our system to ensure a safe trajectory while navigating on a sidewalk is demonstrated through simulation, thus providing a proof-of-concept of our method [42].

We then conducted experiments with Results show that walkers set more conservative strategies when interacting with a power wheelchair. These results can then be linked to the difference in the physical characteristics of the walkers and power wheelchairs where asymmetry in the physical risks raised by collisions influence the strategies performed by the walkers in comparison with a similar walker-walker situation. This gives interesting insights in the task of modeling such interactions, indicating that geometrical terms are not sufficient to explain behaviours, physical terms linked to collision momentum should also be considered [49][62].

Power wheelchair driving is a challenging task which requires good visual, cognitive and visuo-spatial abilities. Besides, a power wheelchair can cause material damage or represent a danger of injury for others or oneself if not operated safely. Therefore, training and repeated practice are mandatory to acquire safe driving skills to obtain power wheelchair prescription from therapists. However, conventional training programs may reveal themselves insufficient for some people with severe impairments. In this context, Virtual Reality offers the opportunity to design innovative learning and training programs while providing realistic wheelchair driving experience within a virtual environment. We then proposed a user-centered design of a multisensory power wheelchair simulator [59][58]. This simulator addresses classical virtual experience drawbacks such as cybersickness and sense of presence by combining 3D visual rendering, haptic and vestibular feedback. It relies on a modular and versatile workflow enabling not only easy interfacing with any virtual display, but also with any user interface such as wheelchair controllers or feedback devices. First experiments with able-bodied people shown that vestibular feedback activation increases the Sense of Presence and decreases cybersickness [54].