Virtual Constraints and Hybrid Zero Dynamics for Realizing Underactuated Bipedal Locomotion

Underactuation is ubiquitous in human locomotion and should be ubiquitous in bipedal robotic locomotion as well. This chapter presents a coherent theory for the design of feedback controllers that achieve stable walking gaits in underactuated bipedal robots. Two fundamental tools are introduced, virtual constraints and hybrid zero dynamics. Virtual constraints are relations on the state variables of a mechanical model that are imposed through a time-invariant feedback controller. One of their roles is to synchronize the robot's joints to an internal gait phasing variable. A second role is to induce a low dimensional system, the zero dynamics, that captures the underactuated aspects of a robot's model, without any approximations. To enhance intuition, the relation between physical constraints and virtual constraints is first established. From here, the hybrid zero dynamics of an underactuated bipedal model is developed, and its fundamental role in the design of asymptotically stable walking motions is established. The chapter includes numerous references to robots on which the highlighted techniques have been implemented.Comment: 17 pages, 4 figures, bookchapte

The European Reference Genome Atlas: piloting a decentralised approach to equitable biodiversity genomics.

ABSTRACT: A global genome database of all of Earth’s species diversity could be a treasure trove of scientific discoveries. However, regardless of the major advances in genome sequencing technologies, only a tiny fraction of species have genomic information available. To contribute to a more complete planetary genomic database, scientists and institutions across the world have united under the Earth BioGenome Project (EBP), which plans to sequence and assemble high-quality reference genomes for all ∼1.5 million recognized eukaryotic species through a stepwise phased approach. As the initiative transitions into Phase II, where 150,000 species are to be sequenced in just four years, worldwide participation in the project will be fundamental to success. As the European node of the EBP, the European Reference Genome Atlas (ERGA) seeks to implement a new decentralised, accessible, equitable and inclusive model for producing high-quality reference genomes, which will inform EBP as it scales. To embark on this mission, ERGA launched a Pilot Project to establish a network across Europe to develop and test the first infrastructure of its kind for the coordinated and distributed reference genome production on 98 European eukaryotic species from sample providers across 33 European countries. Here we outline the process and challenges faced during the development of a pilot infrastructure for the production of reference genome resources, and explore the effectiveness of this approach in terms of high-quality reference genome production, considering also equity and inclusion. The outcomes and lessons learned during this pilot provide a solid foundation for ERGA while offering key learnings to other transnational and national genomic resource projects.info:eu-repo/semantics/publishedVersio

Planning and obstacle avoidance for mobile robots

A planning methodology for nonholonomic mobile manipulators that employs smooth and continuous functions such as polynomials is developed. The method decouples kinematically the manipulator from the platform by constructing admissible paths that drive it to a final configuration and is based on mapping the nonholonomic constraint to a space where it can be trivially satisfied. In addition, the method allows for direct control over the platform orientation. The developed transformation also maps Cartesian space obstacles to transformed ones and allows for obstacle avoidance by increasing the order of the polynomials that are used in planning trajectories. The additional parameters required are computed systematically. It is shown how the method can be extended for avoiding obstacles of any number. 1

On path planning and obstacle avoidance for nonholonomic platforms with manipulators: A polynomial approach

A planning methodology for nonholonomic mobile platforms with manipulators in the presence of obstacles is developed that employs smooth and continuous functions such as polynomials. The method yields admissible input trajectories that drive both the manipulator and the platform to a desired configuration and is based on mapping the nonholonomic constraint to a space where it can be satisfied trivially. In addition, the method allows for direct control over the platform orientation. Cartesian space obstacles are also mapped into this space in which they can be avoided by increasing the order of the polynomials employed in planning trajectories. The additional parameters required are computed systematically, while the computational burden increases linearly with the number of obstacles and the system elements taken into account. Illustrative examples demonstrate the planning methodology in obstacle-free and obstructed environments. I

Opportunities for Adaptation and Learning In Dynamically Stable Legegd Robots

This paper addresses the control and aspects of modeling for Scout II, an autonomous four-legged robot with only one actuator per compliant leg. The running controller requires minimal task level feedback, yet achieves reliable, efficient and fast running up to 1.2 m/s - apparently complex dynamically dexterous tasks may be controlled via simple control laws. We demonstrate the need to model the actuators and the power source of the robot system carefully in order to obtain experimentally valid models for simulation and analysis. The availability of validated models and the small number of controller parameters, makes this type of robot a good candidate for further performance improvements based on adaptation and learning

Quadruped Robot Running With a Bounding Gait

Abstract: Scout II, an autonomous four-legged robot with only one ac-tuator per compliant leg is described. We demonstrate the need to model the actuators and the power source of the robot system carefully in or-der to obtain experimentally valid models for simulation and analysis. We describe a new, simple running controller that requires minimal task level feedback, yet achieves reliable and fast running up to 1.2 m/s. These results contribute to the increasing evidence that apparently complex dynamically dexterous tasks may be controlled via simple control laws. An energetics analysis reveals a highly eÆcient system with a specic resistance of 0.32 when based on mechanical power dissipation and of 1.0 when based on total electrical power dissipation. 1