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Identifier 000460369
Title Adaptive control of body posture and movement in quadruped robots
Alternative Title Προσαρμοστικός έλεγχος πόζας σώματος και κίνησης τετράποδων ρομπότ
Author Αργυροπούλου, Δέσποινα Αικατερίνη Ε.
Thesis advisor Τραχανιάς, Παναγιώτης
Reviewer Παπαγεωργίου, Δημήτριος
Αργυρός, Αντώνιος
Abstract One of the primary advantages of legged robots lies in their ability to navigate through complex and unstructured environments, such as outdoor fields, sewers and construction sites, which often feature a variety of challenging terrains. This capability opens the door to employing legged robots in applications that might pose risks to humans, including search and rescue missions, inspection tasks and maintenance in critical infrastructure facilities. In addition to the structural intricacies of these environments, they also present dynamic challenges, with varying terrain friction being a prominent concern. Legged robots frequently encounter the issue of partially or globally slippery terrains, which can result from conditions like mud, wet surfaces, oil or ice. The slippage of any leg relative to the supporting surface can introduce unpredictable and unmodeled dynamics, potentially compromising trajectory tracking performance or even leading to the robot’s instability from loss of contact with the supporting surface. In such conditions, maintaining stability and precise control becomes paramount. Ensuring that the robot follows desired trajectories with accuracy is not only essential for its own safety but also critical for successfully executing dexterous maneuvers in these challenging settings. Task space trajectory tracking plays a central role in achieving these objectives, as it enables the robot to adapt to the dynamic nature of its surroundings, react to unanticipated disturbances, and minimize the risk of falls or instability. By focusing on accurate tracking of task space trajectories, we aim to equip quadruped robots with the capability to operate with confidence and reliability in the face of environmental uncertainties. Driven by the challenges posed by agile maneuvers and locomotion in rough and slippery terrains, we introduce an adaptive controller termed as the Body Posture and Movement Controller (BPMC) designed specifically for such conditions. BPMC comprises two key components: an adaptive trajectory tracking controller, referred to as “Body Posture”, and an adaptive reaching-target controller that initiates locomotion, called “Body Movement”. The former, namely Body Posture controller, comprises a robust adaptive trajectory tracking controller that consists of two prioritized layers of adaptation aimed at maintaining stability during dynamic contact events of one or more supporting legs. The main objective of the proposed adaptive controller is to induce a robust reactive behaviour of a quadruped robot when it experiences unstable contacts while executing a trajectory without sacrificing the spatial properties of the task. The Body Movement controller, serving as an adaptive reaching controller, plays a pivotal role in initiating locomotion tasks and executing agile maneuvers, particularly in challenging terrains marked by slipperiness and dynamic obstacles. The core of the Body Movement controller lies in its initial layer, in which the control effort is distributed among all stance legs, meaning all legs except the swinging leg. The latter is accomplished by assigning an exceptionally high weight to a specific leg, designated as the swinging leg. In that way, the swinging leg task is attained while, at the same time, the robot keeps its stability and controllability during locomotion. On top of that, the Body Movement controller offers an additional layer that can be activated at the user’s discretion, taking into account the probability of detecting slip events. This extra layer draws inspiration from the approach used in the first layer of the Body Posture controller. It dynamically adjusts the effort distribution among all legs based on the slip probability of each foot. This multifaceted approach not only introduces innovative concepts for agile movements but also ensures the stability of the robot’s dynamic maneuvers. It represents a crucial step in advancing the adaptability and robustness of the overall system. The proposed methods constitute novel, lightweight analytical solutions that assume no prior knowledge of the friction properties of the supporting surface. This is accomplished by considering the slippage probability as extracted by our previous work on contact state estimation in order to avoid non-controllable conditions. Our experimental outcomes, stemming from both simulations and real-world tests, highlight the approach’s effectiveness. It substantially enhances system robustness, minimizing leg slippage while maintaining robot stability and control even in challenging conditions. These advances mark significant milestones in enhancing quadruped robot capabilities for diverse real-world scenarios.
Language English
Subject Locomotion
Slip detection and recovery
Trajectory tracking
Αναγνώριση και προσαρμογή
Βάδιση
Παρακολούθηση τροχιάς
Τετράποδα ρομπότ
Issue date 2023-12-01
Collection   School/Department--School of Sciences and Engineering--Department of Computer Science--Post-graduate theses
  Type of Work--Post-graduate theses
Permanent Link https://elocus.lib.uoc.gr//dlib/1/0/b/metadata-dlib-1699954808-379533-15292.tkl Bookmark and Share
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