Control of A High Performance Bipedal Robot using Viscoelastic Liquid Cooled Actuators

This paper describes the control, and evaluation of a new human-scaled biped robot with liquid cooled viscoelastic actuators (VLCA). Based on the lessons learned from previous work from our team on VLCA [1], we present a new system design embodying a Reaction Force Sensing Series Elastic Actuator (RFSEA) and a Force Sensing Series Elastic Actuator (FSEA). These designs are aimed at reducing the size and weight of the robot's actuation system while inheriting the advantages of our designs such as energy efficiency, torque density, impact resistance and position/force controllability. The system design takes into consideration human-inspired kinematics and range-of-motion (ROM), while relying on foot placement to balance. In terms of actuator control, we perform a stability analysis on a Disturbance Observer (DOB) designed for force control. We then evaluate various position control algorithms both in the time and frequency domains for our VLCA actuators. Having the low level baseline established, we first perform a controller evaluation on the legs using Operational Space Control (OSC) [2]. Finally, we move on to evaluating the full bipedal robot by accomplishing unsupported dynamic walking by means of the algorithms to appear in [3].Comment: 8 pages, 8 figure

Reliability assessment approach through geospatial mapping for offshore wind energy

To meet the increased energy demands, uphold commitments made in the Paris agreement and provide energy security to its consumers, the United Kingdom is rapidly expanding its wind energy industry at offshore locations. While harnessing the improved wind resource further offshore, the industry has faced reliability challenges in the dynamic marine environment which contribute to an increase in the cost of energy. This thesis promotes the argument for location - intelligent decisions in the industry by developing a methodology to allocate a combined risk - return performance metric for offshore locations. In the absence of comprehensive spatially distributed field reliability data for offshore wind turbines, the limit state design methodology is employed to model structural damage. Exposed to stochastic loading from wind and wave regimes, offshore wind turbines are fatigue-critical structures. The aero- and hydro-dynamic loads at representative sites across eight sub-regions in the UK continental shelf are quantified by processing modelled metocean data through established aero-hydro-servo-elastic design tools. These simulated loads and the inherent material fatigue properties provide site-specific lifetime accumulated damage. Normalising this damage based on the potential energy production at each site provides an improved understanding of the feasibility of the sub-region for offshore wind deployment. Results indicate that although sheltered sub-regions display lower resource potential, they have the benefit of the reduced associated structural damage compared to more dynamic locations. A similar observation is made when the methodology is employed on a larger scale incorporating the UK continental shelf and its adjoining areas. Furthermore, not only the energy potential displays an increase with an increase in distance-to-shore, but also the damage per unit energy produced. The research outcomes of this project are useful for identifying the potential of structural reserves for lifetime extension considerations as more turbines reach their design lifetimes. Additionally, it may be used to inform design parameters, optimise siting of future installations and determine suitable maintenance strategies to improve the economic viability of offshore wind