Rapid inversion: running animals and robots swing like a pendulum under ledges.

Escaping from predators often demands that animals rapidly negotiate complex environments. The smallest animals attain relatively fast speeds with high frequency leg cycling, wing flapping or body undulations, but absolute speeds are slow compared to larger animals. Instead, small animals benefit from the advantages of enhanced maneuverability in part due to scaling. Here, we report a novel behavior in small, legged runners that may facilitate their escape by disappearance from predators. We video recorded cockroaches and geckos rapidly running up an incline toward a ledge, digitized their motion and created a simple model to generalize the behavior. Both species ran rapidly at 12-15 body lengths-per-second toward the ledge without braking, dove off the ledge, attached their feet by claws like a grappling hook, and used a pendulum-like motion that can exceed one meter-per-second to swing around to an inverted position under the ledge, out of sight. We discovered geckos in Southeast Asia can execute this escape behavior in the field. Quantification of these acrobatic behaviors provides biological inspiration toward the design of small, highly mobile search-and-rescue robots that can assist us during natural and human-made disasters. We report the first steps toward this new capability in a small, hexapedal robot

A Brachiating Robot Controller

We report on our empirical studies of a new controller for a two-link brachiating robot. Motivated by the pendulum-like motion of an ape\u27s brachiation, we encode this task as the output of a target dynamical system. Numerical simulations indicate that the resulting controller solves a number of brachiation problems that we term the ladder, swing-up, and rope problems. Preliminary analysis provides some explanation for this success. The proposed controller is implemented on a physical system in our laboratory. The robot achieves behaviors including swing locomotion and swing up and is capable of continuous locomotion over several rungs of a ladder. We discuss a number of formal questions whose answers will be required to gain a full understanding of the strengths and weaknesses of this approach

Experimental Implementation of a Target Dynamics Controller on a Two-link Brachiating Robot

We report on our recent empirical success in the study of a two-link brachiating robot. The target dynamics controller developed in our previous work (1997) is implemented on a physical system in our laboratory. The swing locomotion and swing-up behavior of the robot as well as continuous locomotion have been successfully attained. The experimental results illustrate the effectiveness of our control strategy

Brachiation on a Ladder with Irregular Intervals

We have previously developed a brachiation controller that allows a two degree of freedom robot to swing from handhold to handhold on a horizontal ladder with evenly space rungs as well as swing up from a suspended posture using a target dynamics controller. In this paper, we extend this class of algorithms to handle the much more natural problem of locomotion over irregularly spaced handholds. Numerical simulations and laboratory experiments illustrate the effectiveness of this generalization

Preliminary studies of a second generation brachiation robot controller

We report on our preliminary studies of a new controller for a two-link brachiating robot. Motivated by the pendulum-like motion of an ape\u27s brachiation, we encode this task as the output of a target dynamical system . Numerical simulations indicate that the resulting controller solves a number of brachiating problems that we term the ladder , swing up and rope problems. Preliminary analysis provides some explanation for this success. We discuss a number of formal questions whose answers will be required to gain a full understanding of the strengths and weaknesses of this approach

Design, modelling and control of a brachiating power line inspection robot

The inspection of power lines and associated hardware is vital to ensuring the reliability of the transmission and distribution network. The repetitive nature of the inspection tasks present a unique opportunity for the introduction of robotic platforms, which offer the ability to perform more systematic and detailed inspection than traditional methods. This lends itself to improved asset management automation, cost-effectiveness and safety for the operating crew. This dissertation presents the development of a prototype industrial brachiating robot. The robot is mechanically simple and capable of dynamically negotiating obstacles by brachiating. This is an improvement over current robotic platforms, which employ slow, high power static schemes for obstacle negotiation. Mathematical models of the robot were derived to understand the underlying dynamics of the system. These models were then used in the generation of optimal trajectories, using nonlinear optimisation techniques, for brachiating past line hardware. A physical robot was designed and manufactured to validate the brachiation manoeuvre. The robot was designed following classic mechanical design principles, with emphasis on functional design and robustness. System identification was used to capture the plant uncertainty and a feedback controller was designed to track the reference trajectory allowing for energy optimal brachiation swings. Finally, the robot was tested, starting with sub-system testing and ending with testing of a brachiation manoeuvre proving the prospective viability of the robot in an industrial environment

Robust Control Synthesis and Verification for Wire-Borne Underactuated Brachiating Robots Using Sum-of-Squares Optimization

Control of wire-borne underactuated brachiating robots requires a robust feedback control design that can deal with dynamic uncertainties, actuator constraints and unmeasurable states. In this paper, we develop a robust feedback control for brachiating on flexible cables, building on previous work on optimal trajectory generation and time-varying LQR controller design. We propose a novel simplified model for approximation of the flexible cable dynamics, which enables inclusion of parametric model uncertainties in the system. We then use semidefinite programming (SDP) and sum-of-squares (SOS) optimization to synthesize a time-varying feedback control with formal robustness guarantees to account for model uncertainties and unmeasurable states in the system. Through simulation, hardware experiments and comparison with a time-varying LQR controller, it is shown that the proposed robust controller results in relatively large robust backward reachable sets and is able to reliably track a pre-generated optimal trajectory and achieve the desired brachiating motion in the presence of parametric model uncertainties, actuator limits, and unobservable states.Comment: 8 pages, 12 figures, 2020 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS

A Hybrid Swing up Controller for a Two-link Brachiating Robot

In this paper, we report on a hybrid scheme for regulating the swing up behavior of a two degree of freedom brachiating robot. In this controller, a previous target dynamics controller and a mechanical energy regulator are combined. The proposed controller guarantees the boundedness of the total energy of the system. Simulations suggest that this hybrid controller achieves much better regulation of the desired swing motion than the target dynamics method by itself

Brachiating power line inspection robot: controller design and implementation

The prevalence of electrical transmission networks has led to an increase in productivity and prosperity. In 2014, estimates showed that the global electric power transmission network consisted of 5.5 million circuit kilometres (Ckm) of high-voltage transmission lines with a combined capacity of 17 million mega-volt ampere. The vastness of the global transmission grid presents a significant problem for infrastructure maintenance. The high maintenance costs, coupled with challenging terrain, provide an opportunity for autonomous inspection robots. The Brachiating Power Line Inspection Robot (BPLIR) with wheels [73] is a transmission line inspection robot. The BPLIR is the focus of this research and this dissertation tackles the problem of state estimation, adaptive trajectory generation and robust control for the BPLIR. A kinematics-based Kalman Filter state estimator was designed and implemented to determine the full system state. Instrumentation used for measurement consisted of 2 Inertial Measurement Units (IMUs). The advantages of utilising IMUs is that they are less susceptible to drift, have no moving parts and are not prone to misalignment errors. The use of IMU's in the design meant that absolute angles (link angles measured with respect to earth) could be estimated, enabling the BPLIR to navigate inclined slopes. Quantitative Feedback Control theory was employed to address the issue of parameter uncertainty during operation. The operating environment of the BPLIR requires it to be robust to environmental factors such as wind disturbance and uncertainty in joint friction over time. The resulting robust control system was able to compensate for uncertain system parameters and reject disturbances in simulation. An online trajectory generator (OTG), inspired by Raibert-style reverse-time symmetry[10], fed into the control system to drive the end effector to the power line by employing brachiation. The OTG produced two trajectories; one of which was reverse time symmetrical and; another which minimised the perpendicular distance between the end gripper and the power line. Linear interpolation between the two trajectories ensured a smooth bump-less trajectory for the BPLIR to follow

Learning Algorithm for a Brachiating Robot

If charity begins at home, scholarship on the charitable deduction has stayed at home. In the vast legal literature, few authors have engaged the distinction between charitable contributions that are meant to be used within the United States and charitable contributions that are meant to be used abroad. Yet these two types of contributions are treated very differently in the Code and raise very different policy issues. As Americans\u27 giving patterns and the U.S. nonprofit sector grow increasingly international, the distinction will only become more salient. This Article offers the first exploration of how theories of the charitable deduction apply to internationally targeted donations. In so doing, the Article aims to contribute not only to a methodological shift in nonprofit tax scholarship (a strategic remapping), but also to a reappraisal of the deduction literature (an analytic remapping): just as existing theories of the deduction can inform our understanding of foreign charity, considerations of foreign charity can shed light back on the existing theories. I argue that the standard rationales are underdetermined and undertheorized, and propose a new, integrated approach to the charitable deduction. Internationally targeted donations emerge from the analysis holding a strong claim to deductibility – often a stronger claim than domestically targeted donations hold – on almost every relevant dimension, which calls into question current regulations that privilege domestic giving. Oversight and foreign policy concerns, however, complicate the ideal of geographic neutrality and illuminate the charitable deduction\u27s role as an instrument of statecraft. Admitting foreign charity into the debate over the deduction thus changes the debate\u27s terms; it gives deduction theory new urgency as well as new complexity