SAFETY-GUARANTEED TASK PLANNING FOR BIPEDAL NAVIGATION IN PARTIALLY OBSERVABLE ENVIRONMENTS

Bipedal robots are becoming more capable as basic hardware and control challenges are being overcome, however reasoning about safety at the task and motion planning levels has been largely underexplored. I would like to make key steps towards guaranteeing safe locomotion in cluttered environments in the presence of humans or other dynamic obstacles by designing a hierarchical task planning framework that incorporates safety guarantees at each level. This layered planning framework is composed of a coarse high-level symbolic navigation planner and a lower-level local action planner. A belief abstraction at the global navigation planning level enables belief estimation of non-visible dynamic obstacle states and guarantees navigation safety with collision avoidance. Both planning layers employ linear temporal logic for a reactive game synthesis between the robot and its environment while incorporating lower level safe locomotion keyframe policies into formal task specification design. The high-level symbolic navigation planner has been extended to leverage the capabilities of a heterogeneous multi-agent team to resolve environment assumption violations that appear at runtime. Modifications in the navigation planner in conjunction with a coordination layer allow each agent to guarantee immediate safety and eventual task completion in the presence of an assumption violation if another agent exists that can resolve said violation, e.g. a door is closed that another dexterous agent can open. The planning framework leverages the expressive nature and formal guarantees of LTL to generate provably correct controllers for complex robotic systems. The use of belief space planning for dynamic obstacle belief tracking and heterogeneous robot capabilities to assist one another when environment assumptions are violated allows the planning framework to reduce the conservativeness traditionally associated with using formal methods for robot planning.M.S

Proceedings of the NASA Conference on Space Telerobotics, volume 2

These proceedings contain papers presented at the NASA Conference on Space Telerobotics held in Pasadena, January 31 to February 2, 1989. The theme of the Conference was man-machine collaboration in space. The Conference provided a forum for researchers and engineers to exchange ideas on the research and development required for application of telerobotics technology to the space systems planned for the 1990s and beyond. The Conference: (1) provided a view of current NASA telerobotic research and development; (2) stimulated technical exchange on man-machine systems, manipulator control, machine sensing, machine intelligence, concurrent computation, and system architectures; and (3) identified important unsolved problems of current interest which can be dealt with by future research

Developing Design and Analysis Framework for Hybrid Mechanical-Digital Control of Soft Robots: from Mechanics-Based Motion Sequencing to Physical Reservoir Computing

The recent advances in the field of soft robotics have made autonomous soft robots working in unstructured dynamic environments a close reality. These soft robots can potentially collaborate with humans without causing any harm, they can handle fragile objects safely, perform delicate surgeries inside body, etc. In our research we focus on origami based compliant mechanisms, that can be used as soft robotic skeleton. Origami mechanisms are inherently compliant, lightweight, compact, and possess unique mechanical properties such as– multi-stability, nonlinear dynamics, etc. Researchers have shown that multi-stable mechanisms have applications in motion-sequencing applications. Additionally, the nonlinear dynamic properties of origami and other soft, compliant mechanisms are shown to be useful for ‘morphological computation’ in which the body of the robot itself takes part in performing complex computations required for its control. In our research we demonstrate the motion-sequencing capability of multi-stable mechanisms through the example of bistable Kresling origami robot that is capable of peristaltic locomotion. Through careful theoretical analysis and thorough experiments, we show that we can harness multistability embedded in the origami robotic skeleton for generating actuation cycle of a peristaltic-like locomotion gait. The salient feature of this compliant robot is that we need only a single linear actuator to control the total length of the robot, and the snap-through actions generated during this motion autonomously change the individual segment lengths that lead to earthworm-like peristaltic locomotion gait. In effect, the motion-sequencing is hard-coded or embedded in the origami robot skeleton. This approach is expected to reduce the control requirement drastically as the robotic skeleton itself takes part in performing low-level control tasks. The soft robots that work in dynamic environments should be able to sense their surrounding and adapt their behavior autonomously to perform given tasks successfully. Thus, hard-coding a certain behavior as in motion-sequencing is not a viable option anymore. This led us to explore Physical Reservoir Computing (PRC), a computational framework that uses a physical body with nonlinear properties as a ‘dynamic reservoir’ for performing complex computations. The compliant robot ‘trained’ using this framework should be able to sense its surroundings and respond to them autonomously via an extensive network of sensor-actuator network embedded in robotic skeleton. We show for the first time through extensive numerical analysis that origami mechanisms can work as physical reservoirs. We also successfully demonstrate the emulation task using a Miura-ori based reservoir. The results of this work will pave the way for intelligently designed origami-based robots with embodied intelligence. These next generation of soft robots will be able to coordinate and modulate their activities autonomously such as switching locomotion gait and resisting external disturbances while navigating through unstructured environments

Animation From Instructions

We believe that computer animation in the form of narrated animated simulations can provide an engaging, effective and flexible medium for instructing agents in the performance of tasks. However, we argue that the only way to achieve the kind of flexibility needed to instruct agents of varying capabilities to perform tasks with varying demands in work places of varying layout is to drive both animation and narration from a common representation that embodies the same conceptualization of tasks and actions as Natural Language itself. To this end, we are exploring the use of Natural Language instructions to drive animated simulations. In this paper, we discuss the relationship between instructions and behavior that underlie our work and the overall structure of our system. We then describe in some what more detail three aspects of the system - the representation used by the Simulator, the operation of the Simulator and the Motion Generators used in the system

Underwater Vehicles

For the latest twenty to thirty years, a significant number of AUVs has been created for the solving of wide spectrum of scientific and applied tasks of ocean development and research. For the short time period the AUVs have shown the efficiency at performance of complex search and inspection works and opened a number of new important applications. Initially the information about AUVs had mainly review-advertising character but now more attention is paid to practical achievements, problems and systems technologies. AUVs are losing their prototype status and have become a fully operational, reliable and effective tool and modern multi-purpose AUVs represent the new class of underwater robotic objects with inherent tasks and practical applications, particular features of technology, systems structure and functional properties

Daydreaming factories

Optimisation of factories, a cornerstone of production engineering for the past half century, relies on formulating the challenges with limited degrees of freedom. In this paper, technological advances are reviewed to propose a “daydreaming” framework for factories that use their cognitive capacity for looking into the future or “foresighting”. Assessing and learning from the possible eventualities enable breakthroughs with many degrees of freedom and make daydreaming factories antifragile. In these factories with augmented and reciprocal learning and foresighting processes, revolutionary reactions to external and internal stimuli are unnecessary and industrial co-evolution of people, processes and products will replace industrial revolutions

Design and control of an origami-enabled soft crawling autonomous robot (OSCAR)

Soft mobile robots offer unique benefits as they are highly adaptable to the terrain of travel and safe for interaction with humans. However, the lack of autonomy currently limits their practical applications. Autonomous navigation has been well studied for conventional rigid-bodied robots; however, it is underrepresented in the soft mobile robot research community. Its implementation in soft robots comes with multiple challenges. However, the major challenge is the significant motion uncertainties due to the robot compliance, ground interactions, and limited available sensing. These uncertainties prevent high-level control implementation, such as autonomous navigation, to be performed successfully. Therefore, soft robots require robust design methods, as well as path following and path planning algorithms, to mitigate these uncertainties and enable autonomy. This dissertation develops and implements autonomous navigation for a novel origami-enabled soft crawling autonomous robot called OSCAR. In order to implement autonomous navigation, it first mitigates the OSCAR’s motion uncertainties by a multi-step iterative design process. Analysis has shown that OSCAR’s motion uncertainties are the result of: (i) the ground-feet interaction, (ii) effectiveness of low-level closed-loop control and, (iii) variability in the manufacturing assembly process. The iterative control-oriented design allows a robust and reliable OSCAR performance and enables high-level path following control implementation. To design and implement path following control, this research presents an idealized kinematic model and introduces an empirically based correction to make the model predictions match the experimental data. The dissertation investigates two separate path-following controllers: a model-based pure pursuit and a feedback controller. The controllers are investigated in both simulation and experiment and the need for feedback is clearly demonstrated. Finally, this research presents the path planning in order to complete OSCAR’s autonomous navigation. The simulation and experimental results show that OSCAR can accurately navigate in a 2D environment while avoiding static obstacles. Lastly, the coupled locomotion of multiple OSCARs demonstrates an extension of functionality and expands the potential design and operation space for this promising type of soft robot

Design and control of a gravity-assisted underactuated snake robot with application to aircraft wing assembly

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.Includes bibliographical references (p. 108-111).We present the design and control of a hyper-articulated robot arm comprising just a few active joints driving a multitude of passive joints. This underactuated arm design was motivated by the need for a compact snake-like robot for assembly operations inside an aircraft wing. The interior of the wing is accessible only through small access portholes distributed along the length. Currently, such assembly operations are performed by human operators who crawl into the wing through its access portholes. The working conditions are ergonomically challenging and result in frequent injuries. The conflicting requirements of small form factor and high payload carrying capacity have been the primary bottlenecks in the development of assembly robots. We propose a nested-channel serial linkage structure for the hyper-articulated arm. When fully contracted, the arm is extremely compact and can access the interior of the wing through its access porthole. Once inside the wing, the arm may be expanded to access distal assembly locations. However, it is impossible to package current actuator technology to meet the payload requirements within the limited size of the robot arm. The joints of the hyper-articulated arm have no dedicated actuators. Instead, they are deployed by modulating gravitational torques. By tilting the base link appropriately, the gravitational torque drives each unactuated link to a desired angular position. With simple, compact locking mechanisms, the arm can change its configuration using the actuated base placed outside the wing. We analyze the system dynamics to gain physical insight into the interaction between the actuated and unactuated degrees of freedom. We make important approximations to capture the dominant effects in the system dynamics so as to facilitate control design.(cont.) The dynamics (actual, as well as approximate) of the unactuated links are essentially 2nd order non-holonomic constraints, for which there are no general control techniques. We present several motion planning algorithms for sequential positioning of the free joints of the robot arm. The motion planning algorithms are formulated as parameterized non-linear two point boundary value problems. These algorithms demonstrate reasonable performance in the absence of disturbances. However, the end-effecter requires accurate positioning to perform assembly operations. To address this issue, we present a sequential closed-loop control algorithm for accurate positioning of the free joints. We synthesize a Lyapunov function to prove the convergence of this control scheme and to generate estimates of the domain of convergence. For faster deployment of the robot arm, multiple free links must move concurrently. We also present several motion planning algorithms to address this problem. We built two prototypes to illustrate the design and actuation concepts. The first prototype has 3 links and has a fixed axis of tilt in the horizontal plane. The second prototype has 4 links and may be tilted about an arbitrary axis in the horizontal plane. The motion planning and closed-loop control algorithms were implemented on both prototypes. The experimental results indicate the efficacy of such control schemes.by Binayak Roy.Ph.D

A Foot Placement Strategy for Robust Bipedal Gait Control

This thesis introduces a new measure of balance for bipedal robotics called the foot placement estimator (FPE). To develop this measure, stability first is defined for a simple biped. A proof of the stability of a simple biped in a controls sense is shown to exist using classical methods for nonlinear systems. With the addition of a contact model, an analytical solution is provided to define the bounds of the region of stability. This provides the basis for the FPE which estimates where the biped must step in order to be stable. By using the FPE in combination with a state machine, complete gait cycles are created without any precalculated trajectories. This includes gait initiation and termination. The bipedal model is then advanced to include more realistic mechanical and environmental models and the FPE approach is verified in a dynamic simulation. From these results, a 5-link, point-foot robot is designed and constructed to provide the final validation that the FPE can be used to provide closed-loop gait control. In addition, this approach is shown to demonstrate significant robustness to external disturbances. Finally, the FPE is shown in experimental results to be an unprecedented estimate of where humans place their feet for walking and jumping, and for stepping in response to an external disturbance