Variable Impedance Control of Redundant Manipulators for Intuitive Human–Robot Physical Interaction

This paper presents an experimental study on human-robot comanipulation in the presence of kinematic redundancy. The objective of the work is to enhance the performance during human-robot physical interaction by combining Cartesian impedance modulation and redundancy resolution. Cartesian impedance control is employed to achieve a compliant behavior of the robot's end effector in response to forces exerted by the human operator. Different impedance modulation strategies, which take into account the human's behavior during the interaction, are selected with the support of a simulation study and then experimentally tested on a 7-degree-of-freedom KUKA LWR4. A comparative study to establish the most effective redundancy resolution strategy has been made by evaluating different solutions compatible with the considered task. The experiments have shown that the redundancy, when used to ensure a decoupled apparent inertia at the end effector, allows enlarging the stability region in the impedance parameters space and improving the performance. On the other hand, the variable impedance with a suitable modulation strategy for parameters' tuning outperforms the constant impedance, in the sense that it enhances the comfort perceived by humans during manual guidance and allows reaching a favorable compromise between accuracy and execution time

The Role of Impedance Modulation and Redundancy Resolution in Human-Robot Interaction

In this work, redundancy resolution and impedance modulation strategies have been employed to enhance intuitiveness and stability in physical human-robot interaction during co-manipulation tasks. An impedance strategy to control a redundant manipulator is defined in the Cartesian space. Different modulation laws for the impedance parameters are tested in combination with different strategies to solve redundancy. The stability of the coupled human-robot system is guaranteed ensuring that the impedance parameters vary in a range evaluated experimentally. Through an extensive experimental study on a 7-DOF KUKA LWR4 arm, we show that using redundancy to decouple the equivalent inertia at the end-effector enables a more flexible choice of the impedance parameters and improves the performance during manual guidance. Moreover, variable impedance is more performant with respect to constant impedance due to a favourable compromise between accuracy and execution time and the enhanced comfort perceived by humans during manual guidance

Redundancy resolution in human-robot co-manipulation with cartesian impedance control

In this paper the role of redundancy in Cartesian impedance control of a robotic arm for the execution of tasks in co-manipulation with humans is considered. In particular, the problem of stability is experimentally investigated. When a human operator guides the robot through direct physical interaction, it is desirable to have a compliant behaviour at the end effector according to a decoupled impedance dynamics. In order to achieve a desired impedance behaviour, the robot’s dynamics has to be suitably reshaped by the controller. Moreover, the stability of the coupled human-robot system should be guaranteed for any value of the impedance parameters within a prescribed region. If the robot is kinematically or functionally redundant, also the redundant degrees of freedom can be used to modify the robot dynamics. Through an extensive experimental study on a 7-DOF KUKA LWR4 arm, we compare two different strategies to solve redundancy and we show that, when redundancy is exploited to ensure a decoupled apparent inertia at the end effector, the stability region in the parameter space becomes larger. Thus, better performance can be achieved by using, e.g., variable impedance control laws tuned to human intentions

Impedance control of redundant manipulators for safe human-robot collaboration

In this paper, the impedance control paradigm is used to design control algorithms for safe human-robot collaboration. In particular, the problem of controlling a redundant robot manipulator in task space, while guaranteeing a compliant behavior for the redundant degrees of freedom, is considered first. The proposed approach allows safe and dependable reaction of the robot during deliberate or accidental physical interaction with a human or the environment, thanks to null-space impedance control. Moreover, the case of control for co-manipulation is considered. In particular, the role of the kinematic redundancy and that of the impedance parameters modulation are investigated. The algorithms are verified through experiments on a 7R KUKA lightweight robot arm

Experimental Test of Synergies Computed on the SCHUNK S5FH under-actuated Hand

In this paper, a method for synergies calculation developed for an anthropomorphic 15 DOFs hand, characterized by one to one mapping between configuration space and fingertip position in the Cartesian space, has been tested on the under-actuated SCHUNK S5FH anthropomorphic hand. The grasping capabilities of the hand controlled in a three dimension synergies subspace have been tested. The results demonstrate that the data set of grasps, measured on human hands, and the mapping method of human hand synergies, based on fingertip measurements and inverse kinematics, is efficient enough to compute suitable synergies subspace where it is possible to plan and control anthropomorphic hands for grasping actions, despite on the hand kinematics and actuation system

Cartesian impedance control of redundant manipulators for human-robot co-manipulation

This paper addresses the problem of controlling a robot arm executing a cooperative task with a human who guides the robot through direct physical interaction. This problem is tackled by allowing the end effector to comply according to an impedance control law defined in the Cartesian space. While, in principle, the robot's dynamics can be fully compensated and any impedance behaviour can be imposed by the control, the stability of the coupled human-robot system is not guaranteed for any value of the impedance parameters. Moreover, if the robot is kinematically or functionally redundant, the redundant degrees of freedom play an important role. The idea proposed here is to use redundancy to ensure a decoupled apparent inertia at the end effector. Through an extensive experimental study on a 7-DOF KUKA LWR4 arm, we show that inertial decoupling enables a more flexible choice of the impedance parameters and improves the performance during manual guidance

Human Motion Mapping to a Robot Arm with Redundancy Resolution

The problem of image based visual servoing for robots working in a dynamic environment is addressed in this paper. It is assumed that the environment is observed by depth sensors which allow to measure the distance between any moving obstacle and the robot. The main idea is to control suitable image moments during the interaction phase to relax a certain number of robot’s degrees of freedom. If an obstacle approaches the robot, the main visual servoing task is attenuated or completely abandoned while the image features are kept in the camera field of view by controlling the image moments. Fuzzy rules are used to set the reference values for the controller. Beside that, the relaxed redundancy of the robot is exploited to avoid collisions as well. After removing the risk of collision, the main visual servoing task is resumed. The effectiveness of the algorithm is shown by several case studies on a KUKA LWR 4 robot arm

Role of narrow band imaging (NBI), in the treatment of non-polypoid colorectal lesions, with endoscopic mucosal resection (EMR). A single-center experience

BACKGROUND: In this study, the authors evaluated the role of narrow band imaging endoscopy in the early detection of infiltration of the colon wall by flat and depressed lesions, highlighted during colonoscopy, to confirm the possibility of removal with Endoscopic Mucosal Resection (EMR). METHODS: 67 patients (37 males and 30 females) with non-polypoid colorectal lesions were included in this study. The location of the lesions, the size and possible infiltration of the colon wall were performed with a colonoscopy with NBI. Lesions without massive invasion were treated with an EMR. RESULTS: NBI was found to be a sensitive, specific, and accurate technique in assessing any infiltration of the colon wall. Endoscopic resection of the mucous membrane was successfully performed in 62 patients, it was not possible to perform it in 5 patients, due to the lack of dissection, and they underwent surgery. CONCLUSIONS: Non-polypoid colorectal lesions and early tumors can be treated with EMR. Certainly, early detection with Narrow Band Imaging endoscopy and subsequent endoscopic resection can reduce colorectal cancer mortality. Many studies have confirmed that these two methods have achieved important results comparable with surgical procedures. KEY WORDS: Endoscopic Mucosal Resection, Narrow Band Imaging, Therapy

Post-operative oncological and psychological evaluation of patients with colostomy for colorectal cancer.

BACKGROUND: The therapeutic arsenal for colorectal cancer is largely made up of surgery. In digestive tumors, ostomy devices induce loss of function and control. This medical device generates changes that affect all aspects of patients’ lives. This study evaluates the postoperative follow-up from the oncological point of view and the psychological impact of colosto- my on the quality of life of patients with colorectal cancer, analyzing any complications or relapses, and the high risk of self-concept disorder and social isolation. METHODS: The aim of the work was to identify all the surgeries for colorectal cancer performed in the Federico II University Hospital of Naples, from 2018 to 2021, and among them how many had been packaged a colostomy. We then analyzed how many patients had been evaluated 12 months after surgery, with a transanal endoscopy or transto- my, and the percentage of any complications or relapses. The same patients who underwent endoscopic control were also evaluated psychologically, to analyze how they lived the packaging of the ostomy and how it had affected the quality of life. READ-ONLY COP RESULTS: At endoscopic control, diversion colitis phenomena and few cases of stoma stenosis and stomatitis were detect- PRINTING PROHIBITED ed. No case of neoplastic recurrence. From the psychological point of view, the problems detected were in particular the alteration of body image, the loss of sphincter control, embarrassment and shame for the bad smell, impairment of sex- uality and difficulties in the couple relationship and social contacts, anxiety, depression and loneliness. CONCLUSIONS: The post-operative evaluation of the ostomy patient following colorectal cancer requires endoscopic control to suddenly detect recurrences and complications and psychological support that improves their quality of life