IROS 2021 论文列表

Origami robots–often called "printable" robots– created using folding processes have gained extensive attention due to their potential for rapid and accessible design and fabrication through simple structures with complex functionalities. However, almost all origami robots require conventional rigid electronics for control, which may hinder the integration and restrict the potential of these origami systems. Here we introduce origami logic gates that can be built through folding. The major enabling technology is a bistable switch that can switch between two different circuits to control the electrical flow. Based on the origami switch, we develop NOT, AND, and OR logic gates (showing functional completeness) and demonstrate these logic gates through sufficiently powering low-current LEDs. These logic gates are fabricated using cut-and-fold manufacturing and offer a potential way of integrating logic functions directly into origami machines without electronics.

Omni-directional mobile robot (OMR) systems have been very popular in academia and industry for their superb maneuverability and flexibility. Yet their potential has not been fully exploited, where the extra degree of freedom in OMR can potentially enable the robot to carry out extra tasks. For instance, gimbals or sensors on robots may suffer from a limited field of view or be constrained by the inherent mechanical design, which will require the chassis to be orientation-aware and respond in time. To solve this problem and further develop the OMR systems, in this paper, we categorize the tasks related to OMR chassis into orientation transition tasks and position transition tasks, where the two tasks can be carried out at the same time. By integrating the parallel task goals in a single planning problem, we proposed an orientation-aware planning architecture for OMR systems to execute the orientation transition and position transition in a unified and efficient way. A modified trajectory optimization method called orientation-aware timed-elastic-band (OATEB) is introduced to generate the trajectory that satisfies the requirements of both tasks. Experiments in both 2D simulated environments and real scenes are carried out. A four-wheeled OMR is deployed to conduct the real scene experiment and the results demonstrate that the proposed method is capable of simultaneously executing parallel tasks and is applicable to real-life scenarios.

Human touching the robot to convey intentions or emotions is an essential communication pathway during physical Human-Robot Interaction (pHRI). Therefore, advanced service robots require superior tactile intelligence to guarantee naturalness and safety when making physical contact with human subjects. Tactile intelligence is the capability to percept and recognize tactile information from touch behaviors, in which understanding the physical meaning of touching actions is crucial. For this purpose, this report introduces a recently collected and organized dataset "TacAct" that encloses real-time tactile information when human subjects touched the test device mimicking a robot forearm. The dataset contains 12 types of 24,000 touch actions from 50 subjects. The dataset details are described, the data are preliminarily analyzed, and the validity of the dataset is tested through a convolutional neural network LeNet-5 which classifying different types of touch actions. We believe that the TacAct dataset would be beneficial for the community to understand the touch intention under various circumstances and to develop learning-based intelligent algorithms for different applications.

Adjustable Autonomy is gaining interest as it alleviates robot management costs, which often restrain non-routine applications. Whereas it seems straightforward to account for the availability of helpers when making plans that involve being granted for support in the future, no existing research covers this issue. As a solution, we formalize the first human-centric model that accounts for operator support dynamics when generating adjustable-autonomy plans. We formalize Restricted Autonomy Levels (RAL) within a Markov-based framework for representing when and what level of support the robot should ask for. This model is combined with a formalization of usual aspects of man-machine collaboration: operator availability, risk of denial and withdrawal, effect of teleoperation, risks and consequences for violating RAL restrictions and backup procedures, should violations occur. We empirically demonstrate, through a detailed example and the deployment on a professional-grade security robot, that the generated plans deeply combine the problem-solving activities of the robot with the management of requested human support, leading to improved performance and decreased operator effort. We also analyse the computational costs of computing policies that ensure a zero-chance of RAL violation.

Exploring robots may fail due to environmental hazards. Thus, robots need to account for the possibility of failure to plan the best exploration paths. Optimizing expected utility enables robots to find plans that balance achievable reward with the inherent risks of exploration. Moreover, when robots rendezvous and communicate to exchange observations, they increase the probability that at least one robot is able to return with the map. Optimal exploration is NP-hard, so we apply a constraint-based approach to enable highly-engineered solution techniques. We model exploration under the possibility of robot failure and communication constraints as an integer, linear program and a generalization of the Vehicle Routing Problem. Empirically, we show that for several scenarios, this formulation produces paths within 50% of a theoretical optimum and achieves twice as much reward as a baseline greedy approach.

Application of multiple robotic manipulators in a shared workspace is still restricted to repetitive tasks limiting their flexible deployment for production systems. Still, existing motion control algorithms cannot be performed online for arbitrary environments in case of multiple manipulators cooperating with each other. In this work we propose a scalable and real-time capable motion control algorithm based on non-cooperative distributed model predictive control. Furthermore, we propose an optimal scheduling algorithm, which provides optimal setpoints to each robot’s motion controller that prevents possible deadlocks beforehand. We validate our approach on a simulative setup of four robotic manipulators for multiple pick and place scenarios.

Control of tetherless magnetically actuated helical robots using rotating dipole fields has a wide variety of medical applications. The most promising technique in manipulation of these robots involves a rotating permanent magnet controlled by a robotic manipulator. In this work, we study the open-loop response of helical robots (in viscous fluids characterized by low Reynolds numbers) in the presence of position constraints on the actuating rotating permanent magnet. We first derive a mapping between the space of the manipulator’s joints, the produced magnetic fields in three-dimensional space, and the translational and rotational velocities of the helical robot. Then, we constrain the 3D position of the rotating dipole field and predict the response of the helical robot by controlling its angular velocity using the constrained mapping. We demonstrate open-loop control and gravity compensation of the robot using the angular velocities of the actuating permanent magnet while enforcing constraints on the end-effector position.

When an autonomous robot learns how to execute actions, it is of interest to know if and when the execution policy can be generalised to variations of the learning scenarios. This can inform the robot about the necessity of additional learning, as using incomplete or unsuitable policies can lead to execution failures. Generalisation is particularly relevant when a robot has to deal with a large variety of objects and in different contexts. In this paper, we propose and analyse a strategy for generalising parameterised execution models of manipulation actions over different objects based on an object ontology. In particular, a robot transfers a known execution model to objects of related classes according to the ontology, but only if there is no other evidence that the model may be unsuitable. This allows using ontological knowledge as prior information that is then refined by the robot’s own experiences. We verify our algorithm for two actions - grasping and stowing everyday objects - such that we show that the robot can deduce cases in which an existing policy can generalise to other objects and when additional execution knowledge has to be acquired.

Humans must remain unharmed during their interaction with robots. We present a new method guaranteeing impact force limits when humans and robots share a workspace. Formal guarantees are realized using an online verification method, which plans and verifies fail-safe maneuvers through predicting reachable impact forces by considering all future possible scenarios. We model collisions as a coupled human-robot dynamical system with uncertainties and identify reachset-conforming models based on real-world collision experiments. The effectiveness of our approach for human-robot co-existence is demonstrated for the human hand interacting with the end effector of a six-axis robot manipulator with force sensing. By integrating a human pose detection system, the efficiency of robot movements increases.

The combination of ultrawideband (UWB) radios and inertial measurement units (IMU) can provide accurate positioning in environments where the Global Positioning System (GPS) service is either unavailable or has unsatisfactory performance. The two sensors, IMU and UWB radio, are often not co-located on a moving system. The UWB radio is typically located at the extremities of the system to ensure reliable communication, whereas the IMUs are located closer to its center of gravity. Furthermore, without hardware or software synchronization, data from heterogeneous sensors can arrive at different time instants resulting in temporal offsets. If uncalibrated, these spatial and temporal offsets can degrade the positioning performance. In this paper, using observability and identifiability criteria, we derive the conditions required for successfully calibrating the spatial and the temporal offset parameters of a tightly-coupled UWB-IMU system. We also present an online method for jointly calibrating these offsets. The results show that our calibration approach results in improved positioning accuracy while simultaneously estimating (i) the spatial offset parameters to millimeter precision and (ii) the temporal offset parameter to millisecond precision.

An important problem in designing human-robot systems is the integration of human intent and performance in the robotic control loop, especially during complex tasks. Bimanual coordination is a complex human behavior that is critical in many fine motor tasks, including robot-assisted surgery. To fully leverage the capabilities of the robot as an intelligent and assistive agent, online recognition of bimanual coordination could be important. Robotic assistance for a suturing task, for example, will be fundamentally different during phases when the suture is wrapped around the instrument (i.e., making a c-loop), than when the ends of the suture are pulled apart. In this study, we develop an online recognition method of bimanual coordination modes (i.e., the directions and symmetries of right and left hand movements) using geometric descriptors of hand motion. We (1) develop this framework based on ideal trajectories obtained during virtual 2D bimanual path following tasks performed by human subjects operating Geomagic Touch haptic devices, (2) test the offline recognition accuracy of bimanual direction and symmetry from human subject movement trials, and (3) evalaute how the framework can be used to characterize 3D trajectories of the da Vinci Surgical System’s surgeon-side manipulators during bimanual surgical training tasks. In the human subject trials, our geometric bimanual movement classification accuracy was 92.3% for movement direction (i.e., hands moving together, parallel, or away) and 86.0% for symmetry (e.g., mirror or point symmetry). We also show that this approach can be used for online classification of different bimanual coordination modes during needle transfer, making a C loop, and suture pulling gestures on the da Vinci system, with results matching the expected modes. Finally, we discuss how these online estimates are sensitive to task environment factors and surgeon expertise, and thus inspire future work that could leverage adaptive control strat... Show More

During deployment, an object detector is expected to operate at a similar performance level reported on its testing dataset. However, when deployed onboard mobile robots that operate under varying and complex environmental conditions, the detector’s performance can fluctuate and occasionally degrade severely without warning. Undetected, this can lead the robot to take unsafe and risky actions based on low-quality and unreliable object detections. We address this problem and introduce a cascaded neural network that monitors the performance of the object detector by predicting the quality of its mean average precision (mAP) on a sliding window of the input frames. The proposed cascaded network exploits the internal features from the deep neural network of the object detector. We evaluate our proposed approach using different combinations of autonomous driving datasets and object detectors.

One of the main challenges in underwater robot localization is the scarcity of external positioning references. Therefore, accurate inertial localization in between external position updates is crucial for applications such as underwater environmental sampling. In this paper, we present a framework for estimating kinematic and dynamic model parameters used for inertial navigation. Accurate values of these parameters result in better trajectory estimation. Our approach can run online as well as offline, with either choice providing different advantages. Further, our framework can correct errors in the past trajectory at each estimation step. By doing so, we are able to provide improved geo-references for past as well as future spatial measurements made by the robots. This has an impact on adaptive sampling methods, which use geo-tagged measurements for building local spatial distributions and choose future sampling points. We present results from field experiments and demonstrate improvement in trajectory estimation accuracy. We also experimentally show that with optimal parameter estimates, robots can tolerate longer intervals in external positioning updates for a specified acceptable level of estimation error.

Space free-flyers like the Astrobee robots currently operating aboard the International Space Station must operate with inherent system uncertainties. Parametric uncertainties like mass and moment of inertia are especially important to quantify in these safety-critical space systems and can change in scenarios such as on-orbit cargo movement, where unknown grappled payloads significantly change the system dynamics. Cautiously learning these uncertainties en route can potentially avoid time- and fuel-consuming pure system identification maneuvers. Recognizing this, this work proposes RATTLE, an online information-aware motion planning algorithm that explicitly weights parametric model-learning coupled with real-time replanning capability that can take advantage of improved system models. The method consists of a two-tiered (global and local) planner, a low-level model predictive controller, and an online parameter estimator that produces estimates of the robot’s inertial properties for more informed control and replanning on-the-fly; all levels of the planning and control feature online update-able models. Simulation results of RAT-TLE for the Astrobee free-flyer grappling an uncertain payload are presented alongside results of a hardware demonstration showcasing the ability to explicitly encourage model parametric learning while achieving otherwise useful motion.

Manipulation of flexible objects is one of the major challenges in robotics as the nonlinear dynamics of the high-dimensional object structure makes it difficult to apply current control methods. A previous simulation study showed that control with few pre-structured joint trajectories coupled with joint impedance (dynamic primitives) could control a 25-dimensional whip to hit a target. This was possible even though the impedance values were constant. This paper explores whether time-varying impedance throughout the movement may further enhance performance. We present an online impedance adaptation (OIA) controller that modulates the joint impedances of a two-joint actuator in real time for the same task. Results showed that the OIA control method increased the speed of optimization and resulted in smaller deviation from the zero-torque joint trajectories compared to the controller with constant joint impedances. This novel way to modulate both motion and impedance of a manipulator may facilitate the control of flexible objects with significant dynamics.

We would like to enable a robot to navigate efficiently and robustly in known, structured environments that are large enough to cause traditional planning approaches to incur considerable computational cost. Hierarchical planners are a promising way to increase planning efficiency in such environments because high-level abstract plans can be used to reduce the size of the search space over which detailed planning occurs. However, useful high-level representations of planning problems can be challenging to generate without prior domain knowledge. In this work, we propose a high-level planning representation which can be learned from previous plans considered in the environment and used online during hierarchical, multi-query robot navigation. We treat previous planning results as noisy measurements of high-level navigation properties, then update these properties over time using recursive estimation. We test our approach in standard and risk-aware hierarchical planning schemes, and demonstrate up to an 86% decrease in the number of nodes expanded and a 66% decrease in wallclock time as compared to a baseline A* planner while finding plans that are only 2-10% more expensive.

We propose a new algorithm to simplify the controller development for distributed robotic systems subject to external observations, disturbances, and communication delays. Unlike prior approaches that propose specialized solutions to handling communication latency for specific robotic applications, our algorithm uses an arbitrary centralized controller as the specification and automatically generates distributed controllers with communication management and delay compensation. We formulate our goal as nonlinear optimal control— using a regret minimizing objective that measures how much the distributed agents behave differently from the delay-free centralized response—and solve for optimal actions w.r.t. local estimations of this objective using gradient-based optimization. We analyze our proposed algorithm’s behavior under a linear time-invariant special case and prove that the closed-loop dynamics satisfy a form of input-to-state stability w.r.t. unexpected disturbances and observations. Our experimental results on both simulated and real-world robotic tasks demonstrate the practical usefulness of our approach and show significant improvement over several baseline approaches.

We propose an extension to the segment-based global localization method for LiDAR SLAM using descriptors learned considering the visual context of the segments. A new architecture of the deep neural network is presented that learns the visual context acquired from synthetic LiDAR intensity images. This approach allows a single multi-beam LiDAR to produce rich and highly descriptive location signatures. The method is tested on two public datasets, demonstrating an improved descriptiveness of the new descriptors, and more reliable loop closure detection in SLAM. Attention analysis of the network is used to show the importance of focusing on the broader context rather than only on the 3-D segment.

Many safety critical scenarios, including post-disaster areas, or military fields, require prompt area monitoring and fast detection of events of interest. Flying Ad-hoc Networks (FANETs) provide a powerful tool to search the area, and locate anomalies. Nevertheless, wide-area deployment of FANETs poses a number of challenges. Existing long range communication technologies are inadequate to meet the data rate and delay requirements of a safety critical application. To face this challenge, we formulate the connected deployment problem, where we require the FANET to create connected formations to ensure multi-hop low-latency communications while performing the monitoring task. We show that addressing the above problem with the aim of maximizing event coverage is NP-hard. We propose a polynomial time solution, called Greedy Connected Deployment (GCD), based on a two phase approximation of the problem. By means of extensive simulations and real field experiments, we show that our approach outperforms existing solutions to related problems, both in terms of monitoring accuracy and system responsiveness.