Shiva, Ali

English

This thesis investigates active and/or passive utilization of robot morphology to achieve effective and safe interaction with its environment. The proposed approach is based on replicating certain morphological features observed in nature to enhance robotic performance during contact. The term morphology herein refers not only to the shape, but also physical properties such as stiffness, as well as actuator and sensor distribution. Within the context of “Soft Robotics”, two paradigms entailing contact are considered: a soft continuum manipulator for soft interaction and haptic perception; and a rigid-link arm with internal actuator compliance for potential industrial collaborative tasks. Firstly, A fluid-actuated intrinsically-soft continuum robot is proposed as a bioinspired finger-like appendage. A novel analytical model is presented to solve the continuum kinematics based on the Cosserat Beam Theory and the Principle of Virtual Work, yielding complete pose and force data across the backbone hence attaining embodied sensory information. In addition, elasticity versus hyperelasticity considerations are discussed, showing the validity of elastic assumptions within its operational range. Secondly, for the first time, the soft robotic appendage is used for haptic perception in soft tissue palpation for anomaly detection. Using Silicone as a tissue phantom, different actuation pressures are applied to the robot for mapping the tissue surface and detecting a hard nodule embedded in the phantom while estimating the tip force of the robotic appendage. Thirdly, an innovative design is introduced to generate variable impedance for the soft robotic appendage. Inspired by muscular movement in nature, a hybrid actuation scheme is proposed by introducing embedded tendons inside the manipulator’s wall to enable stiffness adjustment, which also improves manoeuvrability. Experiments are carried out by applying an external force in different configurations while changing the stiffness by the two actuation mechanisms, demonstrating that dual antagonistic actuation increases load bearing capacities in this class of manipulators. Subsequently, the tendon-augmented robotic appendage is enhanced by multiplying the tendons to produce a more uniform longitudinal tension distribution. Sweeping tests of a Silicone phantom with an embedded nodule are again carried out with different actuation pressures and tendon tensions. Utilising force sensors placed at the tip and at the base (representing tactile and proprioceptive cues, respectively), the behaviour of selected sensing modalities are investigated and compared. This novel setting delivers insights into the role of internal impedance regulation in perceptive exploration and how the tactile and proprioceptive sensory cues evolve by alteration in the morphology of the appendage. The final outcome of this stage presents a soft robotic appendage which emulates some biological morphology in being intrinsically soft and safe by its passive conformity, benefiting from embodied action-perception coupling, while enabling antagonistic actuation for actively adjusting internal impedance to arbitrate information gain. Finally, the concept of exploiting variable impedance for safe interaction is extended to a rigid link robotic arm. A novel active approach is presented by employing a fuzzy inference mechanism to generate a decision for actively adjusting the overall stiffness of the robotic arm in the task-space direction(s) along the trajectory that is assumed to lead to a collision between the human and the robot, while not affecting the stiffness in other direction(s). It is shown that the torque experienced by the actuators in the joints have the potential to be used as a “stiffness” index for the arm in a coupled action/perception setting

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Towards safe &amp; soft robotic perception &amp; interaction via situated morphological control

https://kclpure.kcl.ac.uk/ws/files/125062547/2020_Shiva_Ali_1451256_ethesis.pdf

Towards safe & soft robotic perception & interaction via situated morphological control

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King's Research Portal

Towards safe &amp; soft robotic perception &amp; interaction via situated morphological control

Abstract

Similar works

Full text

Available Versions

King's Research Portal

Towards safe & soft robotic perception & interaction via situated morphological control