Space Robotics Applications Research Articles

Shape optimization of non-rigid origami leading to emerging bistability

Origami structures are a type of thin-walled flexible structures that undergo large deformation. Their inherent non-rigid characteristic empowers them with great potential for applications in space structures, metamaterials, and robotics. To understand the large deformation of origami structures, consideration of nonlinear mechanics is necessary. However, most origami structures are still designed by pure geometric approaches without considering their non-rigid behavior. In this work, we propose a computational design framework that incorporates nonlinear mechanics into the design procedure of origami. Guided by minimization of stored energy, under prescribed displacement boundary conditions, we optimize the configuration of origami structures. Difficulties arise due to the complex energy landscape of origami structures that inevitably induces bifurcation. We develop strategies to keep track of a stable deformation branch during the optimization process. A surprising outcome is that our approach naturally leads to self-emerging bistable structures, which is demonstrated by a series of numerical examples. We believe that our new approach would make substantial contribution to computational design of non-rigid origami structures, benefiting applications in origami-inspired solutions for science and engineering.

ViT VO - A Visual Odometry technique Using CNN-Transformer Hybrid Architecture

Localization is one of the main tasks involved in the operation of autonomous agents (e.g., vehicle, robot etc.). It allows them to be able to track their paths and properly detect and avoid obstacles. Visual Odometry (VO) is one of the techniques used for agent localization. VO involves estimating the motion of an agent using the images taken by cameras attached to it. Conventional VO algorithms require specific workarounds for challenges posed by the working environment and the captured sensor data. On the other hand, Deep Learning approaches have shown tremendous efficiency and accuracy in tasks that require high degree of adaptability and scalability. In this work, a novel deep learning model is proposed to perform VO tasks for space robotic applications. The model consists of an optical flow estimation module which abstracts away scene-specific details from the input video sequence and produces an intermediate representation. The CNN module which follows next learn relative poses from the optical flow estimates. The final module is a state-of-the-art Vision Transformer, which learn absolute pose from the relative pose learnt by the CNN module. The model is trained on the KITTI dataset and has obtained a promising accuracy of approximately 2%. It has outperformed the baseline model, MagicVO, in a few sequences in the dataset.

“Space Robotics”

“Space Robotics” by Yaobing Wang belongs to the series Space Science and Technologies co-published by Beijing Institute of Technology Press, China, and Springer Nature Pte Ltd, Singapore. The Editor-in-Chief of the series, Peijian Ye, is Academician of the Chinese Academy of Sciences in Beijing and has published a collection of 10 volumes. This volume’s author, Yaobin Wang, is a research professor of Beijing Institute of Spacecraft System Engineering and Director of Beijing Key Laboratory of Intelligent Space Robotic Systems Technology and Applications. The book’s 363 pages provide a condensed combination of theory and practice as engineering guidance.

Convex Grey Optimization

Many optimization problems are formulated from a real scenario involving incomplete information due to uncertainty in reality. The uncertainties can be expressed with appropriate probability distributions or fuzzy numbers with a membership function, if enough information can be accessed for the construction of either the probability density function or the membership of the fuzzy numbers. However, in some cases there may not be enough information for that and grey numbers need to be used. A grey number is an interval number to represent the value of a quantity. Its exact value or the likelihood is not known but the maximum and/or the minimum possible values are. Applications in space exploration, robotics and engineering can be mentioned which involves such a scenario. An optimization problem is called a grey optimization problem if it involves a grey number in the objective function and/or constraint set. Unlike its wide applications, not much research is done in the field. Hence, in this paper, a convex grey optimization problem will be discussed. It will be shown that an optimal solution for a convex grey optimization problem is a grey number where the lower and upper limit are computed by solving the problem in an optimistic and pessimistic way. The optimistic way is when the decision maker counts the grey numbers as decision variables and optimize the objective function for all the decision variables whereas the pessimistic way is solving a minimax or maximin problem over the decision variables and over the grey numbers.

Real-Time Dense Stereo Matching With ELAS on FPGA-Accelerated Embedded Devices

For many applications in low-power real-time robotics, stereo cameras are the sensors of choice for depth perception as they are typically cheaper and more versatile than their active counterparts. Their biggest drawback, however, is that they do not directly sense depth maps; instead, these must be estimated through data-intensive processes. Therefore, appropriate algorithm selection plays an important role in achieving the desired performance characteristics. Motivated by applications in space and mobile robotics, we implement and evaluate a field programmable gate arrays (FPGA) accelerated adaptation of the efficient large-scale stereo (ELAS) algorithm. Despite offering one of the best tradeoffs between efficiency and accuracy, ELAS has only been shown to run at 1.5-3 fps on a high-end CPU. Our system preserves all intriguing properties of the original algorithm, such as the slanted plane priors, but can achieve a frame rate of 47 fps whilst consuming under 4 W of power. Unlike previous FPGA-based designs, we take advantage of both components on the CPU/FPGA system-on-chip to showcase the strategy necessary to accelerate more complex and computationally diverse algorithms for such low power, real-time systems.

Robots with increased number of degree-of-freedom with single exciting force

This paper presents the results of the development and investigation of a new class of novel multi-degree-of-freedom robots based on a new concept – the application of kinematic pairs with alternating degree-of-freedom (DOF) controlled by a single force or moment, changing its direction in space. The number of DOF of the kinematic pairs is controlled periodically from 0 to 3, exploiting the dependence of frictional forces on the oscillation in the contact zone of links. The advantages of this new class of robots include significant weight reduction, simple design and control, and specific applications in space robotics and soft robotic spines. In more complicated cases of trunk robots, elastic kinematic pairs are used with a number of DOF controlled by electro- or magneto-rheological fluids with viscosities that change as a result of applied electric or magnetic fields. Expressions for the generalized inertia matrix of the robots with a large number of joints have been derived using the computer algebra technique with the subsequent automatic program code generation. As shown in this paper, such an application could drastically reduce the number of floating point product operations for an efficient numerical simulation of robots.

Design and Development of Hexapod using Nitinol Actuator Wire

Objectives: This research work involves the design and implementation of Hexapod robot which is a small, inexpensive, six-legged robot. Methods/Statistical Analysis: Hexapod robots from decennium have gained considerable attention in various research and development sectors. This research work involves the design and implementation of Hexapod robot which is a small, inexpensive, six-legged robot intended to replace huge and heavy robotic that are used in space applications, industries for lifting purpose containing solenoids and servo motors. Findings: Initial stage of research work involves design and construction of the structure of Hexapod. Plastic material is used for the construction of body and a Nitinol actuator wire is used to drive the Hexapod’s legs. The final stage involves Hexapod interfacing with Arduino and HBridge module for supply to achieve proper locomotion of the Hexapod. Specifically, real element like mechanical structure, legs arrangement, impelling, payload, movement condition and waking walk are considered in proposed system design. In this work, a novel robot is constructed and found that conservative, and lightweight Hexapod robot demonstrates guarantee for use in space, therapeutic, and other large scale robotic applications. Application/Improvements: Due to the unique actuating mechanism of nitinol wire the proposed and developed model has the impact significance in many application fields.

Cooperative Relative Navigation for Space Rendezvous and Proximity Operations using Controlled Active Vision

This work aims to solve the problem of relative navigation for space rendezvous and proximity operations using a monocular camera in a numerically efficient manner. It is assumed that the target spacecraft has a special pattern to aid the task of relative pose estimation, and that the chaser spacecraft uses a monocular camera as the primary visual sensor. In this sense, the problem falls under the category of cooperative relative navigation in orbit. While existing systems for cooperative localization with fiducial markers allow full six‐degrees‐of‐freedom pose estimation, the majority of them are not suitable for in‐space cooperative navigation (especially when involving a small‐size chaser spacecraft), due to their computational cost. Moreover, most existing fiducial‐based localization methods are designed for ground‐based applications with limited range (e.g., ground robotics, augmented reality), and their performance deteriorates under large‐scale changes, such as those encountered in space applications. Using an adaptive visual algorithm, we propose an accurate and numerically efficient approach for real‐time vision‐based relative navigation, especially designed for space robotics applications. The proposed method achieves low computational cost and high accuracy and robustness via the following innovations: first, an adaptive visual pattern detection scheme based on the estimated relative pose is proposed, which improves both the efficiency of detection and the accuracy of pose estimates; second, a parametric blob detector called Box‐LoG is used, which is computationally efficient; and third, a fast and robust algorithm is introduced, which jointly solves the data association and pose estimation problems. In addition to having an accuracy comparable to state‐of‐the‐art cooperative localization algorithms, our method demonstrates a significant improvement in speed and robustness for scenarios with large range changes. A vision‐based closed‐loop experiment using the Autonomous Spacecraft Testing of Robotic Operations in Space (ASTROS) testbed demonstrates the performance benefits of the proposed approach.

Development of a Quality Indicator System for Haptic Exoskeleton Modules

The accuracy of outer space robotic applications using haptic devices requires high performance of the haptic device connected with the remote robot. The paper introduces and develops a quality indicator system, able to give overall information on the performances of the haptic device. The authors define several categories of indicators, such as the geometric, kinematic and dynamic. The geometric category comprises the position and orientation accuracy, the repeatability, the trajectory fluctuation, the resolution, the working space and the static relaxation. The kinematic indicators category comprises the speed fluctuation, the maximal acceleration and time accuracy. The dynamic indicators category comprises the force and torque fluctuation, the vibration amplitude and acceleration. All above-mentioned simple indicators open the path to complex indicators such as the pose accuracy in relation with the working space or the maximum force/torque in respect with the total weight. By introducing moderated indicators, the authors consider the specificity of each group of tasks or applications and in the end, they introduce a global moderated indicator in order to quantify rapidly the general performance level of a certain haptic device.

Comprehensive Characterization of Large Piezoresistive Variation of Ni-PDMS Composites

This work presents a comprehensive investigation of the piezoresistive response of a metal-polymer composite for robotic tactile sensor application. Composite samples, based on nickel nanostructured conductive filler in a polydimetihylsiloxane (PDMS) insulating elastomeric matrix, were prepared changing several process parameters like thickness, composition of the polymer and nickel filler content. A variation of electric resistance up to nine orders of magnitude under applied uniaxial load was measured in the fabricated samples. Cost efficient materials, simplicity of the process, large sensibility, and harsh environment compatibility make this quantum tunnelling composite adapted to be integrated as sensing coating in space robotic applications.

Nonholonomic motion planning based on optimal control for flight phases of planar bipedal running

Presented is a novel approach for online trajectory modification of joint motions to transfer a free open kinematic chain, undergoing flight phase, from a specified initial configuration to a specified final configuration. Formally, it is assumed that a nominal trajectory, computed offline, can reorient the kinematic chain (reconfiguration problem) for a given angular momentum on a time interval. A modification algorithm of body joints, based on optimal control, is developed such that for different angular momentums and time intervals, the same reconfiguration problem can be solved online. This approach can be utilised for space robotics applications and online computation of planar running trajectories during flight phases.

Bond Graph Modeling of an Internally Damped Nonideal Flexible Spinning Shaft

The rotating internal damping or nonconservative circulatory force in a rotor shaft system causes instability beyond a certain threshold rotor spinning speed. However, if the source loading of the drive is considered, then the rotor spin is entrained at the stability threshold and a stable whirl orbit is observed about the unstable equilibrium. As we move toward the use of more and more lightweight rotor dynamic components such as the shaft and the motor, overlooking this frequency entrainment phenomenon while sizing the actuator in the design stage may lead to undesirable performance. This applies to many emerging areas of strategic importance such as in vivo medical robots where flexible probes are used and space robotics applications involving rotating tools. We analyze this spin entrainment phenomenon in a distributed parameter model of a spinning shaft, which is driven by a nonideal dc motor. A drive whose dynamics is influenced by the dynamics of the driven system is called a nonideal source and the whole system is referred to as a nonideal system. In particular, we show the advantages of representing such nonideal drive-system interactions in a modular manner through bond graph modeling as compared to standard equation models where the energetic couplings between dynamic variables are not explicitly shown. The developed modular bond graph model can be extended to include rotor disks and bearings placed at different locations on the shaft. Moreover, the power conserving property of the junction structure of the bond graph model is exploited to derive the source loading expressions, which are then used to analytically derive the steady-state spinning frequency and whirl orbit amplitude as functions of the drive and the rotor system parameters. We show that the higher transverse modes may become unstable before the lower ones under certain parametric conditions. The shaft spinning speed is entrained at the lowest stability threshold among all transverse modes. The bond graph model is used for numerical simulation of the system to validate the steady-state results obtained from the theoretical study.

Adaptive Reaction Control for Space Robotic Applications with Dynamic Model Uncertainty

This paper proposes adaptive control methods based on reaction dynamics for different types of space robotic systems. Reaction dynamics feature the dynamic coupling between an actively operated part and a passively moving part in a multibody robotic system. The reaction dynamics have been used to develop trajectory tracking control of a free-floating space robot or vibration suppression control of a flexible-structure-based manipulator system. However, the presence of dynamic parameter uncertainties degrades the control performance of the above-mentioned methods, since the methods require accurate values of both kinematic and dynamic parameters. To resolve such parameter uncertainties, practical adaptive control methods are proposed in this study. The proposed methods overcome two inherent difficulties in the adaptive control design of space robotic systems, such as nonlinear parameterization of the dynamic equation and uncertainties in coordinate mapping from Cartesian space to joint space. To confirm the validity of the proposed methods, numerical simulations are carried out using three-dimensional realistic models of two types of space robotic systems.

Modelling and simulation of a gripper with Dymola

As an opportunity to show the evolution of the state of the art in modular physical modelling, the model of a gripper for space robotics applications, already developed in the MOSES environment, has been re-implemented in the Dymola environment, adopting the new Modelica multibody library recently developed. The new library allows a truly object-oriented approach, while being efficient from a computational point of view.

3D MAP BUILDING FOR PLANETARY ROVER LOCALIZATION AND PATH PLANNING

This paper considers the problem of constructing a 3D environment model for space robotics applications. We presented our approach to 3D environment reconstruction from large sparse range data sets. In space robotics applications an accurate and up-to-date model of the environment is very important for variety of reasons. In particular, the model can be used for safe tele-operation, path planning and mapping of points of interest. We propose an on-line reconstruction of the environment using data provided by an on-board 3D range sensor LIDAR. The experiment results demonstrated the effectiveness of our approach in localization, path planning and following scenario on the Mars Yard located at Canadian Space Agency.

Literature survey of contact dynamics modelling

Impact is a complex phenomenon that occurs when two or more bodies undergo a collision. This phenomenon is important in many different areas––machine design, robotics, multi-body analysis are just a few examples. The purpose of this manuscript is to provide an overview of the state of the art on impact and contact modelling methodologies, taking into account their different aspects, specifically, the energy loss, the influence of the friction model, solution approaches, the multi-contact problem and the experimental verification. The paper is intended to provide a review of results presented in literature and some additional insights into existing models, their interrelationship and the use of these models for impact/contact scenarios encountered in space robotic applications.

NASDA/DLR Joint Robot Experiment on ETS-VII.

This paper describes the GETEX (German ETS-VII EXperiments) joint robotics experiments, which has been conducted in April '99 at the first free-floating space robot on NASDA's ETS-VII satellite [1] . All the experiments have been performed and controlled from DLR's ground control system for space robotics applications which was connected to NASDA's ground station in Tsukuba. The telerobotic system combines sensor-based task-level teleprogramrning (as the basis for autonomy) with the features of teleoperation and shared autonomy. The hierarchical system structure is shown as well as the flexibility in programming and controlling each kind of space robotics application. This approach has led to a modular task-directed programming scheme, called Modular A & R Controller (MARCO), which provides a very flexible architecture to adapt the application-specific requirements to a given controlling scheme. A peg-in-hole experiment, using VR methods and the “vision & force” control scheme, by closing sensor control loops directly on-board (force) and via the ground control system (vision) is explained. During GETEX we conducted experiments with relevance to the behavior of ETS-VII in free motion mode in order to verify the existing dynamic models.

Vision-based sensing and control for space robotics applications

The following problems arise in the precise positioning of payloads by space manipulators: (1) the precise measurement of the relative position and motion of objects in the workspace of the robot; (2) the design of a control system, which is robust and performs well in spite of the effects of structural flexibility and oscillations typically associated with space robots. This paper discusses the solution to the measurement problem by a vision system using photogrammatic image processing to determine the motion of objects in real time. Performance characteristics are presented. The control problem is addressed by a new technique dealing effectively with the challenge posed by the noncollocated sensor/actuator configuration on the flexible robot structure. The laboratory implementation of the measurement and control concepts is discussed. Preliminary results validate the concepts.

Modular dynamic virtual-reality modeling of robotic systems

This article presents the results of research into the field of dynamic simulation of mechanical and robotic systems. The main goal of the whole project is to achieve an efficient modular approach to modeling, in order to make the modeling process easier, ensure its traceability and inspectability, and support model reuse. This is achieved through the declarative definition of models, the standardization of model interfaces, and the object-oriented approach to model development and model data management. The article presents the specific features ofa general-purpose simulation environment, including an overview of the 3D solid modeling software interfaces. The modeling and simulation of a 3-DOF gripper designed for Space robotics applications is also discussed to show the performance of the whole simulation environment in terms of complexity management, efficiency, and accuracy.

Near-optimal nonholonomic motion planning for a system of coupled rigid bodies

How does a falling cat change her orientation in midair without violating angular momentum constraint? This has become an interesting problem to both control engineers and roboticists. In this paper, we address this problem together with a constructive solution. First, we show that a falling cat problem is equivalent to the constructive nonlinear controllability problem. Thus, the same principle and algorithm used by a falling cat can be used for space robotic applications, such as reorientation of a satellite using rotors and attitude control of a space structure using internal motion, and other robotic tasks, such as dextrous manipulation with multifingered robotic hands and nonholonomic motion planning for mobile robots. Then, using ideas from Ritz approximation theory, we develop a simple algorithm for motion planning of a falling cat. Finally, we test the algorithm through simulation on two widely accepted models of a falling cat. It is interesting to note that one set of simulation results closely resembles the real trajectories employed by a falling cat. >