Theodora Kastritsi

Conjoined collaborative robots, functioning as supernumerary robotic bodies (SRBs), can enhance human load tolerance abilities. However, in tasks involving physical interaction with humans, users may still adopt awkward, non-ergonomic postures, which can lead to discomfort or injury over time. In this paper, we propose a novel control framework that provides kinesthetic feedback to SRB users when a non-ergonomic posture is detected, offering resistance to discourage such behaviors. This approach aims to foster long-term learning of ergonomic habits and promote proper posture during physical interactions. To achieve this, a virtual fixture method is developed, integrated with a continuous, online ergonomic posture assessment framework. Additionally, to improve coordination between the operator and the SRB, which consists of a robotic arm mounted on a floating base, the position of the floating base is adjusted as needed. Experimental results demonstrate the functionality and efficacy of the ergonomics-driven control framework, including two user studies involving practical loco-manipulation tasks with 14 subjects, comparing the proposed framework with a baseline control framework that does not account for human ergonomics.

The primary issue in bilateral teleportation setups is the existence of communication delays, which can destabilize the system. We are addressing this challenge in the case of a bilateral leader–follower surgical setup, where the surgeon uses a haptic device as the leader robot to manipulate the surgical instrument held by a general-purpose manipulator, the follower robot. The follower robot is equipped with an elongated tool that through a small incision passes inside the patient's body, where sensitive structures may exist. These structures may include organs, arteries, or veins that require protection during surgery. To address this challenge, we propose a bilateral control framework that is proven to maintain passivity, ensure bounded tracking errors between the leader and follower robots, and impose remote center of motion and spatial constraints related with the sensitive structures, all in the presence of constant and variable communication delays. Experimental results in a virtual intraoperative environment, using a point cloud of a kidney and its surrounding vessels, demonstrate the effectiveness of our control scheme under various communication delay scenarios.

Mobile robotic platforms have gained increasing popularity across various fields; however, achieving intuitive physical interaction between these robots and humans remains an ongoing area of exploration. In this study, we proposed a novel variable admittance model designed for robotic mobile platforms. The proposed admittance model achieves the decoupling of the desired dynamics related to the intended motion direction from that of the unintentional motion, ensuring that changes in one space do not affect the other. In the unintentional space, the admittance parameters remain constant, while the inertia and damping gains along the intended motion direction are adjusted to provide compliance to the human user. The design of these variable terms was performed to ensure a consistent response, aiming to offer a perceived consistent behavior to the human user and to guarantee strict passivity under human force input, ensuring manipulation stability. In addition to theoretical proof of passivity, we validate the effectiveness and performance of the proposed control scheme through experimental results using an omni-directional robotic mobile platform.

In robotic assisted surgeries, surgical tools are inserted into the human body via an incision point in the abdominal wall, which is imposed as a remote center of motion (RCM). The selection of the incision's point location in the human body is critical for the success of the surgical procedure. In this paper, we propose a simulation tool for finding the optimal incision point location, which can be utilized by the surgeon during the preoperative stage. The surgeon can plan the path/region of intervention as well as sensitive regions which should be protected from unintentional damage by the surgical tool on the preoperative images of internal organs. A target admittance model that enforces a candidate incision as a RCM is utilized in the simulation enhanced by a term for following the planned path. We propose a cost evaluation function taking into account metrics involving the distance of the tool from sensitive areas, the tool links maximum pressure on tumors and the robot's dexterity measure. The example of a tumor resection task is used with the simulation tool to demonstrate its use in finding the incision points that ensures minimal intraoperative risks and accurate task execution.

We consider the problem of controlling a bilateral leader-follower robotic surgical set-up to allow kinesthetic haptic feedback to the user when the instrument approaches a forbidden area like sensitive organs arteries or veins that should be protected from injuries during surgery. The leader is a haptic device while the follower is a general purpose manipulator holding an elongated tool with an articulated instrument that should be manipulated through an entry port. We propose a control framework that is proved passive, incorporating a target admittance model for the follower that is designed in a way to impose a remote center of motion (RCM) while being subject to repulsive forces generated by properly designed artificial potentials associated with forbidden areas. Simulation and experimental results utilizing a virtual intraoperative environment provided as a point cloud of a kidney and its surrounding vessels characterized as forbidden areas, validate and demonstrate the performance of the proposed control scheme.

In this work, the problem of cooperative human-robot manipulation of an object with large inertia is addressed, considering the availability of a kinematically controlled industrial robot. In particular, a variable admittance control scheme is proposed, where the damping is adjusted based on the power transmitted from the human to the robot, with the aim of minimizing the energy injected by the human while also allowing her/him to have control over the task. The proposed approach is evaluated via a human-in-the-loop setup and compared to a generic variable damping state-of-the-art method. The proposed approach is shown to achieve significant reduction of the human’s effort and minimization of unintended overshoots and oscillations, which may deteriorate the user’s feeling of control over the task.

In robot assisted minimally invasive surgery long instruments are inserted inside the patient's body through tiny incisions in the patient's skin. During surgery, it is important to constraint the motion of the instrument not to stress the incision wall to avoid injuring the patient. Hence the incision point is desired to act like a remote center of motion (RCM). The breathing or/and heartbeat function means that the incision point is time-varying. With a general purpose manipulator such desired RCM should be actively imposed by the control function. In this work, we propose a control scheme that achieves this objective for hands-on procedures in which the robot is directly manipulated by the surgeon. The proposed control scheme is proved to satisfy the moving RCM constraint while the controlled robot is passive under the exertion of a human generalized force. Simulation and experimental results are given utilizing a KUKA LWR4+.