Multi-DoF Time Domain Passivity Approach Based Drift Compensation for Telemanipulation

When, in addition to stability, position synchronization is also desired in bilateral teleoperation, Time Domain Passivity Approach (TDPA) alone might not be able to fulfill the desired objective. This is due to an undesired effect caused by admittance type passivity controllers, namely position drift. Previous works focused on developing TDPA-based drift compensation methods to solve this issue. It was shown that, in addition to reducing drift, one of the proposed methods was able to keep the force signals within their normal range, guaranteeing the safety of the task. However, no multi-DoF treatment of those approaches has been addressed. In that scope, this paper focuses on providing an extension of previous TDPA-based approaches to multi-DoF Cartesian-space teleoperation. An analysis of the convergence properties of the presented method is also provided. In addition, its applicability to multi-DoF devices is shown through hardware experiments and numerical simulation with round-trip time delays up to 700 ms.Comment: 2019 19th International Conference on Advanced Robotics (ICAR

Model Mediated Teleoperation with a Hand-Arm Exoskeleton in Long Time Delays Using Reinforcement Learning

Telerobotic systems must adapt to new environmental conditions and deal with high uncertainty caused by long-time delays. As one of the best alternatives to human-level intelligence, Reinforcement Learning (RL) may offer a solution to cope with these issues. This paper proposes to integrate RL with the Model Mediated Teleoperation (MMT) concept. The teleoperator interacts with a simulated virtual environment, which provides instant feedback. Whereas feedback from the real environment is delayed, feedback from the model is instantaneous, leading to high transparency. The MMT is realized in combination with an intelligent system with two layers. The first layer utilizes Dynamic Movement Primitives (DMP) which accounts for certain changes in the avatar environment. And, the second layer addresses the problems caused by uncertainty in the model using RL methods. Augmented reality was also provided to fuse the avatar device and virtual environment models for the teleoperator. Implemented on DLR's Exodex Adam hand-arm haptic exoskeleton, the results show RL methods are able to find different solutions when changes are applied to the object position after the demonstration. The results also show DMPs to be effective at adapting to new conditions where there is no uncertainty involved

Model Mediated Teleoperation with a Hand-Arm Exoskeleton in Long Time Delays Using Reinforcement Learning

elerobotic systems must adapt to new environmental conditions and deal with high uncertainty caused by long-time delays. As one of the best alternatives to human-level intelligence, Reinforcement Learning (RL) may offer a solution to cope with these issues. This paper proposes to integrate RL with the Model Mediated Teleoperation (MMT) concept. The teleoperator interacts with a simulated virtual environment, which provides instant feedback. Whereas feedback from the real environment is delayed, feedback from the model is instantaneous, leading to high transparency. The MMT is realized in combination with an intelligent system with two layers. The first layer utilizes Dynamic Movement Primitives (DMP) which accounts for certain changes in the avatar environment. And, the second layer addresses the problems caused by uncertainty in the model using RL methods. Augmented reality was also provided to fuse the avatar device and virtual environment models for the teleoperator. Implemented on DLR's Exodex Adam hand-arm haptic exoskeleton, the results show RL methods are able to find different solutions when changes are applied to the object position after the demonstration. The results also show DMPs to be effective at adapting to new conditions where there is no uncertainty involved

ANALOG-1 ISS - The first part of an analogue mission to guide ESA's robotic moon exploration efforts

The METERON project is a European initiative to prepare for future human-robotic exploration missions to the Moon, Mars and other celestial bodies. The project aims to implement infrastructure and tools to test and evaluate communications, operations and robotic control strategies in the context of future exploration missions. It is in collaboration between three directorates of the European Space Agency (ESA); Human and Robotic Exploration (HRE), Technology, Engineering and Quality (TEC), Operations (OPS). This paper presents the first part of the on-going ANALOG-1 experiment which is the culmination of the METERON project, implementing the knowledge gained in the 12 distinct METERON experiments between 2011 and 2020. These all address aspects of teleoperating a robotic asset from an orbital platform, i.e. technical implementation, user interfaces, autonomy and operations. The ANALOG-1 technology demonstration and operations concept experiment is based upon the surface mission scenario segment of the notional EL3 sample return mission. This segment focuses on the control of a lunar surface robotic asset from the Earth and from the Lunar Gateway. In November 2019, the first part of this experiment was successfully completed from the ISS. It assessed the effectiveness of a state-of-the-art robotic control interface to control a complex mobile robot from orbit, as well as evaluating the scientific interactions, during robotic-assisted geology exploration, between crew in orbit and scientists on the ground. Luca Parmitano drove this robot in a lunar analogue site in the Netherlands, and controlled its arms, while he was on the ISS. For this experiment, a complex control station had been installed on the ISS, including a sigma.7 haptic device. This device allowed the astronaut to feel forces felt by the robotic arm. The experiment demonstrated the advantage of having an immersive control station and high level of robotic dexterity, with Luca finishing all his assigned and secondary geology targets ahead of time. The second part of Analog-1 extends the ISS experiment with a full ground-based analogue, in which further technical experiments and a full mission scenario will be played out. The analogue is in cooperation with the DLR ARCHES space demo mission, and includes a rover operations centre based at ESOC as well as an outdoor lunar analogue site on Mount Etna. The astronaut, in this case, is on ground. We expect to further demonstrate the advantages of a state-of-the art interface for both fully teleoperated and semi-autonomous rover and robotic arm control for lunar missions, in order to guide ESA's Moon exploration efforts

Preliminary Insights From the METERON SUPVIS Justin Space-Robotics Experiment

As the human race expands its horizon toward a multiplanetary existence, infrastructures on the target planets have to be constructed and maintained to pave the way for humans. The support of robotic coworkers plays a key role in setting up habitats, energy supplies, and return vehicles, until the completion of such infrastructures in the hazardous planetary environment. The operation of these robots require capabilities including autonomy, communication, and human-robot interface design to meet the challenges of the harsh conditions in space deployment. This letter examines these topics through German Aerospace Center (DLR) and European Space Agency's METERON SUPVIS Justin space telerobotics experiments, during that astronauts on-board the International Space Station command DLR's humanoid robot Rollin' Justin to survey and maintain a simulated Martian solar farm on Earth. Based on the first experiments conducted on August 25, 2017, this letter discusses several astronaut-robot collaboration concepts in real space-to-ground deployment and provides preliminary insights for future manned Mars missions

Robotic Manipulation and Capture in Space: A Survey

Space exploration and exploitation depend on the development of on-orbit robotic capabilities for tasks such as servicing of satellites, removing of orbital debris, or construction and maintenance of orbital assets. Manipulation and capture of objects on-orbit are key enablers for these capabilities. This survey addresses fundamental aspects of manipulation and capture, such as the dynamics of space manipulator systems (SMS), i.e., satellites equipped with manipulators, the contact dynamics between manipulator grippers/payloads and targets, and the methods for identifying properties of SMSs and their targets. Also, it presents recent work of sensing pose and system states, of motion planning for capturing a target, and of feedback control methods for SMS during motion or interaction tasks. Finally, the paper reviews major ground testing testbeds for capture operations, and several notable missions and technologies developed for capture of targets on-orbit

The Shape of Damping: Optimizing Damping Coefficients to Improve Transparency on Bilateral Telemanipulation

This thesis presents a novel optimization-based passivity control algorithm for hapticenabled bilateral teleoperation systems involving multiple degrees of freedom. In particular, in the context of energy-bounding control, the contribution focuses on the implementation of a passivity layer for an existing time-domain scheme, ensuring optimal transparency of the interaction along subsets of the environment space which are preponderant for the given task, while preserving the energy bounds required for passivity. The involved optimization problem is convex and amenable to real-time implementation. The effectiveness of the proposed design is validated via an experiment performed on a virtual teleoperated environment. The interplay between transparency and stability is a critical aspect in haptic-enabled bilateral teleoperation control. While it is important to present the user with the true impedance of the environment, destabilizing factors such as time delays, stiff environments, and a relaxed grasp on the master device may compromise the stability and safety of the system. Passivity has been exploited as one of the the main tools for providing sufficient conditions for stable teleoperation in several controller design approaches, such as the scattering algorithm, timedomain passivity control, energy bounding algorithm, and passive set position modulation. In this work it is presented an innovative energy-based approach, which builds upon existing time-domain passivity controllers, improving and extending their effectiveness and functionality. The set of damping coefficients are prioritized in each degree of freedom, the resulting transparency presents a realistic force feedback in comparison to the other directions. Thus, the prioritization takes effect using a quadratic programming algorithm to find the optimal values for the damping. Finally, the energy tanks approach on passivity control is a solution used to ensure stability in a system for robotics bilateral manipulation. The bilateral telemanipulation must maintain the principle of passivity in all moments to preserve the system\u2019s stability. This work presents a brief introduction to haptic devices as a master component on the telemanipulation chain; the end effector in the slave side is a representation of an interactive object within an environment having a force sensor as feedback signal. The whole interface is designed into a cross-platform framework named ROS, where the user interacts with the system. Experimental results are presented

Compliant and stable robot control for physical human-robot cooperation

The main goal of this thesis is to accomplish a compliant and stable closed-loop physical human-robot cooperation by guaranteeing the safety metrics for all of the agents in a shared-working environment. There is increasing interest in control frameworks capable of moving robots from industrial cages to unstructured environments and coexisting with humans. Initially, having robots capable of safely interacting with humans was of interest for medical applications (e.g., rehabilitation, surgical). Despite significant improvement in some specific applications like medical robotics, there is still the need for a general control framework that improves interaction robustness and motion dynamics. Passive controllers show promising results in this direction; however, they often rely on virtual energy tanks that can guarantee passivity as long as they do not run out of energy. In this thesis, a fractal attractor is proposed to implement a variable impedance controller that can retain passivity without relying on energy tanks. The controller generates a fractal attractor around the desired state using an asymptotic stable potential field, making the controller robust to discretization and numerical integration errors. Thus, the proposed Fractal Impedance Controller (FIC) in this thesis is robust for low-bandwidth applications. I have tested this controller with a torque controlled 7-DoF manipulator. The results prove that it can accurately track both trajectories and end-effector forces during interaction. Furthermore, it can automatically deal with the extra energy introduced by changes in interaction conditions, null-space controller and environment. Therefore, on the one hand these properties make the controller ideal for applications where the dynamic interaction at the end-effector is challenging to be characterized a priori, such as proximate physical human-robot cooperation and unknown dynamics. On the other hand in remote human-robot cooperation, robotic teleoperation provides human-in-the-loop capabilities of complex manipulation tasks in dangerous or remote environments, such as planetary exploration or nuclear decommissioning. This thesis proposes a novel bilateral telemanipulation architecture using the proposed passive FIC, which does not depend upon an active viscous component for guaranteeing stability. Compared to a traditional impedance controller in ideal conditions (no delays and maximum communication bandwidth), the proposed method yields higher transparency in interaction and demonstrates superior dexterity and capability in my telemanipulation test scenarios. I also validate its performance with extreme delays up to 1s and communication bandwidths as low as 10Hz. The results of the carried out experiments validate a consistent stability when using the proposed controller in challenging conditions, regardless of operator expertise. The proposed fractal impedance controller in this thesis exploits its non-linear stiffness to adapt to multiple cooperative scenarios without tuning the controller. Furthermore, the FIC has an intuitive method to adjust the impedance that can be performed online without affecting stability. The experimental results, carried out using 2 torque controlled 7-DoF manipulators and the Sigma.7 haptic device, also show that the proposed method can perform tasks such as drilling, moving objects with unknown dynamics, and interacting with humans without re-tuning the controller's impedance in a tele-cooperative manner consisting of multi-agents in the loop. The FIC also allows identifying the highest impedance profile for a robot experimentally, and it bounds the maximum momentum generated while moving. Thus, it opens new possibilities for developing better adaptive controllers by coupling the proposed method with learning and optimisation algorithms to modulate its behaviour without the risk of incurring instability issues.YOUTUBE links to Chapters 3,4 & 5 below