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

Real-Time Planning with Primitives for Dynamic Walking over Uneven Terrain

We present an algorithm for receding-horizon motion planning using a finite family of motion primitives for underactuated dynamic walking over uneven terrain. The motion primitives are defined as virtual holonomic constraints, and the special structure of underactuated mechanical systems operating subject to virtual constraints is used to construct closed-form solutions and a special binary search tree that dramatically speed up motion planning. We propose a greedy depth-first search and discuss improvement using energy-based heuristics. The resulting algorithm can plan several footsteps ahead in a fraction of a second for both the compass-gait walker and a planar 7-Degree-of-freedom/five-link walker.Comment: Conference submissio

An Empirical Investigation of Legged Transitional Maneuvers Leveraging Raibert’s Scissor Algorithm

We empirically investigate the implications of applying Raibert’s Scissor algorithm to the Spring Loaded Inverted Pendulum (SLIP) model in combination with other controllers to achieve transitional maneuvers. Specifically, we are interested in how the conjectured neutral stability of Raibert’s algorithm allows combined controllers to push the system’s operating point around the state space without needing to expend limited control affordance in overcoming its stability or compensating for its instability. We demonstrate 2 cases where this facilitates the construction of interesting transitional controllers on a physical robot. In the first we use the motors in stance to maximize the rate of change of the body energy; in the second we take advantage of the local environmental energy landscape to push the robot’s operating point to a higher or lower energy level without expending valuable motor affordance. We present data bearing on the energetic performance of these approaches in executing an accelerate-and-leap maneuver on a monopedal hopping robot affixed to a boom in comparison to the cost of anchoring the robot to the SLIP template. For more information: Kod*la

Four-bar linkage synthesis using non-convex optimization

Ce mémoire présente une méthode pour synthétiser automatiquement des mécanismes articulés à quatre barres. Un logiciel implémentant cette méthode a été développé dans le cadre d’une initiative d’Autodesk Research portant sur la conception générative. Le logiciel prend une trajectoire en entrée et calcule les paramètres d’un mécanisme articulé à quatre barres capable de reproduire la même trajectoire. Ce problème de génération de trajectoire est résolu par optimisation non-convexe. Le problème est modélisé avec des contraintes quadratiques et des variables réelles. Une contrainte redondante spéciale améliore grandement la performance de la méthode. L’expérimentation présentée montre que le logiciel est plus rapide et précis que les approches existantes.This thesis presents a method to automatically synthesize four-bar linkages. A software implementing the method was developed in the scope of a generative design initiative at Autodesk. The software takes a path as input and computes the parameters of a four-bar linkage able to replicate the same path. This path generation problem is solved using non-convex optimization. The problem is modeled with quadratic constraints and real variables. A special redundant constraint greatly improves the performance of the method. Experiments show that the software is faster and more precise than existing approaches

The Penn Jerboa: A Platform for Exploring Parallel Composition of Templates

We have built a 12DOF, passive-compliant legged, tailed biped actuated by four brushless DC motors. We anticipate that this machine will achieve varied modes of quasistatic and dynamic balance, enabling a broad range of locomotion tasks including sitting, standing, walking, hopping, running, turning, leaping, and more. Achieving this diversity of behavior with a single under-actuated body, requires a correspondingly diverse array of controllers, motivating our interest in compositional techniques that promote mixing and reuse of a relatively few base constituents to achieve a combinatorially growing array of available choices. Here we report on the development of one important example of such a behavioral programming method, the construction of a novel monopedal sagittal plane hopping gait through parallel composition of four decoupled 1DOF base controllers. For this example behavior, the legs are locked in phase and the body is fastened to a boom to restrict motion to the sagittal plane. The platform's locomotion is powered by the hip motor that adjusts leg touchdown angle in flight and balance in stance, along with a tail motor that adjusts body shape in flight and drives energy into the passive leg shank spring during stance. The motor control signals arise from the application in parallel of four simple, completely decoupled 1DOF feedback laws that provably stabilize in isolation four corresponding 1DOF abstract reference plants. Each of these abstract 1DOF closed loop dynamics represents some simple but crucial specific component of the locomotion task at hand. We present a partial proof of correctness for this parallel composition of template reference systems along with data from the physical platform suggesting these templates are anchored as evidenced by the correspondence of their characteristic motions with a suitably transformed image of traces from the physical platform.Comment: Technical Report to Accompany: A. De and D. Koditschek, "Parallel composition of templates for tail-energized planar hopping," in 2015 IEEE International Conference on Robotics and Automation (ICRA), May 2015. v2: Used plain latex article, correct gap radius and specific force/torque number

The gibbon's Achilles tendon revisited: consequences for the evolution of the great apes?

The well-developed Achilles tendon in humans is generally interpreted as an adaptation for mechanical energy storage and reuse during cyclic locomotion. All other extant great apes have a short tendon and long-fibred triceps surae, which is thought to be beneficial for locomotion in a complex arboreal habitat as this morphology enables a large range of motion. Surprisingly, highly arboreal gibbons show a more human-like triceps surae with a long Achilles tendon. Evidence for a spring-like function similar to humans is not conclusive. We revisit and integrate our anatomical and biomechanical data to calculate the energy that can be recovered from the recoiling Achilles tendon during ankle plantar flexion in bipedal gibbons. Only 7.5% of the required external positive work in a stride can come from tendon recoil, yet it is delivered at an instant when the whole-body energy level drops. Consequently, an additional similar amount of mechanical energy must simultaneously dissipate elsewhere in the system. Altogether, this challenges the concept of an energy-saving function in the gibbon's Achilles tendon. Cercopithecids, sister group of the apes, also have a human-like triceps surae. Therefore, a well-developed Achilles tendon, present in the last common 'Cercopithecoidea-Hominoidea' ancestor, seems plausible. If so, the gibbon's anatomy represents an evolutionary relict (no harm-no benefit), and the large Achilles tendon is not the premised key adaptation in humans (although the spring-like function may have further improved during evolution). Moreover, the triceps surae anatomy of extant non-human great apes must be a convergence, related to muscle control and range of motion. This perspective accords with the suggestions put forward in the literature that the last common hominoid ancestor was not necessarily great ape-like, but might have been more similar to the small-bodied catarrhines

Bio-Inspired Robotics

Modern robotic technologies have enabled robots to operate in a variety of unstructured and dynamically-changing environments, in addition to traditional structured environments. Robots have, thus, become an important element in our everyday lives. One key approach to develop such intelligent and autonomous robots is to draw inspiration from biological systems. Biological structure, mechanisms, and underlying principles have the potential to provide new ideas to support the improvement of conventional robotic designs and control. Such biological principles usually originate from animal or even plant models, for robots, which can sense, think, walk, swim, crawl, jump or even fly. Thus, it is believed that these bio-inspired methods are becoming increasingly important in the face of complex applications. Bio-inspired robotics is leading to the study of innovative structures and computing with sensory–motor coordination and learning to achieve intelligence, flexibility, stability, and adaptation for emergent robotic applications, such as manipulation, learning, and control. This Special Issue invites original papers of innovative ideas and concepts, new discoveries and improvements, and novel applications and business models relevant to the selected topics of ``Bio-Inspired Robotics''. Bio-Inspired Robotics is a broad topic and an ongoing expanding field. This Special Issue collates 30 papers that address some of the important challenges and opportunities in this broad and expanding field

Origins of vocal-entangled gesture

Gestures during speaking are typically understood in a representational framework: they represent absent or distal states of affairs by means of pointing, resemblance, or symbolic replacement. However, humans also gesture along with the rhythm of speaking, which is amenable to a non-representational perspective. Such a perspective centers on the phenomenon of vocal-entangled gestures and builds on evidence showing that when an upper limb with a certain mass decelerates/accelerates sufficiently, it yields impulses on the body that cascade in various ways into the respiratory–vocal system. It entails a physical entanglement between body motions, respiration, and vocal activities. It is shown that vocal-entangled gestures are realized in infant vocal–motor babbling before any representational use of gesture develops. Similarly, an overview is given of vocal-entangled processes in non-human animals. They can frequently be found in rats, bats, birds, and a range of other species that developed even earlier in the phylogenetic tree. Thus, the origins of human gesture lie in biomechanics, emerging early in ontogeny and running deep in phylogeny

Utvärdering av precisionen i en autonom terrängfordonsplattforms kranspetspositionering

Skogsbranschen har möjlighet att fortsätta den teknologiska utvecklingen för att höja produktiviteten i skogen, men det krävs innovation, utveckling och investering. I de nordiska länderna bedrivs skogsbruk med kortvirkesmetoden, där en skördare och en skotare används. Kortvirkesmetoden har många arbetsmoment som skulle kunna autonomiseras, vilket skulle innebära ekologiska-, ekonomiska och sociala fördelar. Ett tidskrävande arbetsmoment för skotaren är kranarbetet, som består av att förflytta kranen, gripa stockar och lasta dessa i skotarens lastutrymme. Dessa arbetsmoment kräver hög noggrannhet och precision för att genomföras lyckosamt. I den här studien används en terrängfordonsplattform som har utvecklats för att autonomisera en skotares arbete. Syftet med studien var att undersöka precision och noggrannhet i terrängfordonsplattformens kranspetspositionering. Positioneringen utfördes på olika avstånd och vinklar från terrängfordonsplattformen samt med och utan last i gripen. Variansanalyser i programvaran Minitab gjordes för att fastställa om det fanns skillnader i kranspetspositioneringen beroende de testade behandlingarna. Kranspetsen positionerade sig 31 till 44 centimeter ifrån målpositionen, vilket var kranspetspositioneringens noggrannhet. Kranspetsen kunde genomföra återkommande positioneringar inom 2 centimeter till 3 centimeter från tidigare positioneringar, vilket var kranspetspositioneringens precision. Resultatet från variansanalysen visade signifikanta huvudeffekter av avstånd, vinkel och last. Det innebär att terrängfordonsplattformens kranspetspositioneringens noggrannhet och precision påverkades av olika avstånd och vinklar samt om gripen är lastad eller inte. Noggrannheten försämrades på längre avstånd och om gripen var lastad. De tio första och sista kranspetspositioneringarna utfördes med samma målposition för att utvärdera terrängfordonsplattformens maskininlärning för förbättrad kranspetspositionering. Det konstaterades det att under datainsamlingens gång hade terrängfordonsplattformen förbättrat kranspetspositioneringen med 1 cm. Studien visar att terrängfordonsplattformen kan autonomt placera kranspetsen vid en målposition med bra precision men med mindre bra noggrannhet. Detta är framsteg för den teknologiska utvecklingen inom skogsbruket och utveckling inom autonomisering.The forest industry has the opportunity to continue the technological development to increase productivity in the forest, but innovation, development and investment are required. In the Nordic countries, forestry is conducted using the cut-to-length method, where a harvester and a forwarder are used. The cut-to-length method has many work elements that could be autotomized, which would mean ecological, economic and social benefits. A time-consuming work element for the forwarder is the crane work, which consists of moving the crane, gripping logs and loading them into the forwarder's load space. These steps require high accuracy and precision to be completed successfully. This study uses an off-road vehicle platform that has been developed to autotomize a forwarder's work. The purpose of this study was to investigate the precision and accuracy of the off-road vehicle platform’s crane tip positioning. The crane tip positioning was performed at different distances and angles from the off-road vehicle platform and with and without load in the grapple. Analysis of variance in the Minitab software was done to determine if there was a difference in the crane tip positioning depending on the tested treatments. The crane tip was positioned 31 to 44 centimeter from the target position, which was the accuracy of the crane tip positioning. The crane tip could perform recurring positioning’s within 2 to 3 centimeter from previous positioning’s, which was the precision of the crane tip positioning. The results from the analysis of variance showed significant main effects of distance, angle and load. This means that the off-road vehicle platform's crane tip positioning accuracy and precision are affected by different distances and angles and whether the grapple is loaded or not. Accuracy deteriorated over longer distances and with load. The first ten and the last crane tip positioning’s were performed with the same target position to evaluate the off-road vehicle platform’s machine learning for improved crane tip positioning. It was found that during the data collection, the off-road vehicle platform had improved the crane tip positioning by 1 cm. The study shows that the off-road vehicle platform can autonomously place the tip of the crane at a target position with a good precision but with less good accuracy. Thi

Sample-based motion planning in high-dimensional and differentially-constrained systems

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student submitted PDF version of thesis.Includes bibliographical references (p. 115-124).State of the art sample-based path planning algorithms, such as the Rapidly-exploring Random Tree (RRT), have proven to be effective in path planning for systems subject to complex kinematic and geometric constraints. The performance of these algorithms, however, degrade as the dimension of the system increases. Furthermore, sample-based planners rely on distance metrics which do not work well when the system has differential constraints. Such constraints are particularly challenging in systems with non-holonomic and underactuated dynamics. This thesis develops two intelligent sampling strategies to help guide the search process. To reduce sensitivity to dimension, sampling can be done in a low-dimensional task space rather than in the high-dimensional state space. Altering the sampling strategy in this way creates a Voronoi Bias in task space, which helps to guide the search, while the RRT continues to verify trajectory feasibility in the full state space. Fast path planning is demonstrated using this approach on a 1500-link manipulator. To enable task-space biasing for underactuated systems, a hierarchical task space controller is developed by utilizing partial feedback linearization. Another sampling strategy is also presented, where the local reachability of the tree is approximated, and used to bias the search, for systems subject to differential constraints. Reachability guidance is shown to improve search performance of the RRT by an order of magnitude when planning on a pendulum and non-holonomic car. The ideas of task-space biasing and reachability guidance are then combined for demonstration of a motion planning algorithm implemented on LittleDog, a quadruped robot. The motion planning algorithm successfully planned bounding trajectories over extremely rough terrain.by Alexander C. Shkolnik.Ph.D