Publicação
Intelligent gait motion for all-terrain hexapods
| Resumo: | Hexapod locomotion shows noteworthy stable navigation across controlled environments. With irregularities in terrain topology, the variation of the center of mass position decreases this motion stability, which remains a challenge for performing rescue and exploratory missions, where prior knowledge of the environment is not accessible. In this context, proprioceptive information, in particular contact forces, is crucial to estimate the hexapod’s interactions with the environment and adjust motion. Given the necessity of gait adjustment with terrain topology, this thesis presents a comprehensive methodology for designing adaptive locomotion control of a hexapod to navigate across complex environments. In what concerns locomotion, foot-ground interaction is essential to understand stability. Thus, the hexapod’s physical properties are incorporated into a three-dimensional multibody robot representation for contact resolution. Distinct approaches based on Coulomb’s and Hunt and Crossley’s work are examined to represent the normal and tangential components of contact motion. Building upon dynamic analysis, stability and energy enhancement with focus on contact force interaction is discussed. In this process, limb activation is adjusted to decrease the foot’s pre-contact velocity during transition between gait phases. Given the obtained torque reduction at the actuators level, an optimization of the limbs’ stride is proposed, considering the gait energetic cost, velocity and stability. The novel limb trajectory exhibited significant stability improvements in different contact properties. Limb trajectory optimization serves as groundwork for adaptive motion design. Gait adjustment requires precepting the hexapod’s surroundings for stability maximization. Thus, a strategy for identifying the type of terrain using proprioceptive data of the hexapod robot is proposed. Behavior recognition in distinct conditions allows to adjust gait according to the severity of the disturbances caused by the type of terrain. For this purpose, posture control is crucial to adjust the robot’s center of mass position, being this proposed by estimating the ground’s slope to control the hexapod’s height and posture. According to the results, this method compensates for motion disturbances caused by the contact forces, ensuring a stable position of the torso throughout locomotion. Given the concern of continuously adjusting motion to the terrain topology, the incorporation of learning methodologies as optimization tool of the control system is discussed. A new control policy for hexapod’s height adjustment that considers ground slope is assessed. The implementation of the proposed methodology shows significant stability improvements for irregular terrains. |
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| Autores principais: | Coelho, Joana Sofia Falcato Pereira Lima |
| Assunto: | Adaptive locomotion Contact detection Foot-ground interaction Hexapod robots Legged robotics dynamics. Deteção de contacto Dinâmica de robôs com pernas Interação pé-solo Locomoção adaptativa Robôs hexápodes |
| Ano: | 2025 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | Hexapod locomotion shows noteworthy stable navigation across controlled environments. With irregularities in terrain topology, the variation of the center of mass position decreases this motion stability, which remains a challenge for performing rescue and exploratory missions, where prior knowledge of the environment is not accessible. In this context, proprioceptive information, in particular contact forces, is crucial to estimate the hexapod’s interactions with the environment and adjust motion. Given the necessity of gait adjustment with terrain topology, this thesis presents a comprehensive methodology for designing adaptive locomotion control of a hexapod to navigate across complex environments. In what concerns locomotion, foot-ground interaction is essential to understand stability. Thus, the hexapod’s physical properties are incorporated into a three-dimensional multibody robot representation for contact resolution. Distinct approaches based on Coulomb’s and Hunt and Crossley’s work are examined to represent the normal and tangential components of contact motion. Building upon dynamic analysis, stability and energy enhancement with focus on contact force interaction is discussed. In this process, limb activation is adjusted to decrease the foot’s pre-contact velocity during transition between gait phases. Given the obtained torque reduction at the actuators level, an optimization of the limbs’ stride is proposed, considering the gait energetic cost, velocity and stability. The novel limb trajectory exhibited significant stability improvements in different contact properties. Limb trajectory optimization serves as groundwork for adaptive motion design. Gait adjustment requires precepting the hexapod’s surroundings for stability maximization. Thus, a strategy for identifying the type of terrain using proprioceptive data of the hexapod robot is proposed. Behavior recognition in distinct conditions allows to adjust gait according to the severity of the disturbances caused by the type of terrain. For this purpose, posture control is crucial to adjust the robot’s center of mass position, being this proposed by estimating the ground’s slope to control the hexapod’s height and posture. According to the results, this method compensates for motion disturbances caused by the contact forces, ensuring a stable position of the torso throughout locomotion. Given the concern of continuously adjusting motion to the terrain topology, the incorporation of learning methodologies as optimization tool of the control system is discussed. A new control policy for hexapod’s height adjustment that considers ground slope is assessed. The implementation of the proposed methodology shows significant stability improvements for irregular terrains. |
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