Applications In Bio-inspired Robotics Research Articles

Curriculum-based reinforcement learning for path tracking in an underactuated nonholonomic system

Underactuated mechanical systems with nonholonomic constraints find applications in bioinspired robotics, such as snake-like robots and more recently in fish-like aquatic robots. Animal locomotion suggests that in such bioinspired robots, gaits or cyclic changes in kinematics or shape variables lead to efficient and agile motion. Path tracking in such nonholonomic systems that are not purely kinematic can be a challenging problem. In this paper we consider the problem of path tracking by a modified Chaplygin sleigh with a ‘tail’ which is a four degree of freedom nonholonomic system, possessing a single internal reaction wheel as an actuator. We develop a curriculum based deep Reinforcement Learning (RL) optimal control approach for simultaneous velocity and path tracking for this system. The curriculum based learning approach first leads to a policy for optimal tracking of limit cycles in a reduced velocity space and then in a next step to track a path. This curriculum approach allows an RL agent to learn the ’mechanics on invariant manifolds’ of the system and can be a useful approach in the motion control of high degree of freedom robots with increasing model complexity.

Investigations on Bending Characteristics of Soft Mesh Structure using Shape Memory Alloy Spring Towards Bio-Inspired Robotic Applications

A biomimetic soft worm robot has been developed using soft mesh structured polyethylene terephthalate thermoplastic driven by shape memory alloy springs. The bending behaviour of the robot for achieving steering in peristaltic and bending for two anchor locomotion has been investigated in detail. A flex sensor is attached with the soft worm to measure the bending/steering angle. An open-loop control approach is adopted for the study of soft worm’s bending actions. In peristaltic crawling, a bending angle of 57°, 48° and 48° was achieved in upward, left and right directions, respectively. The movement of the soft worm robot has been probed towards imitating the bending action of two anchor crawling locomotion with kapton polyamide legs. In two anchor crawling, a bending angle of 60° is achieved in downward direction.

A Two-Degree of Freedom Variable Stiffness Actuator Based on the MACCEPA Concept

The current state-of-the-art of variable stiffness actuators consists mostly of different concepts for single-degree of freedom joints. However, in bio-inspired robotic applications, multiple degrees of freedom variable stiffness actuators are often desired. Currently, this is usually achieved by cascading single-degree of freedom actuators. The innovation presented in this work is a two-degree of freedom variable stiffness actuator using the mechanically adjustable and controllable equilibrium position actuator (MACCEPA) concept. The presented actuator is not a cascade of two single-degree of freedom actuators, but centralizes the two degrees of freedom in one single joint. Equilibrium position and stiffness of the actuator are, furthermore, independently controllable in both degrees of freedom. The design and experimental validation of the actuator are discussed in this work. The independence of adjusting the equilibrium position and stiffness of the actuator are experimentally validated. The results show that the measured characteristics of the actuator sufficiently match the theoretically calculated ones. Future work includes implementing the presented two-degree of freedom actuator in an application, like a bipedal robot or a robotic arm.

THE NEUROSCIENCE OF VISION-BASED GRASPING: A FUNCTIONAL REVIEW FOR COMPUTATIONAL MODELING AND BIO-INSPIRED ROBOTICS

The topic of vision-based grasping is being widely studied in humans and in other primates using various techniques and with different goals. The fundamental related findings are reviewed in this paper, with the aim of providing researchers from different fields, including intelligent robotics and neural computation, a comprehensive but accessible view on the subject. A detailed description of the principal sensorimotor processes and the brain areas involved is provided following a functional perspective, in order to make this survey especially useful for computational modeling and bio-inspired robotic applications.