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Projects / Programmes source: ARIS

Biologically inspired synthesis of periodic movement for a robotic humanoid leg

Research activity

Code Science Field Subfield
2.10.04  Engineering sciences and technologies  Manufacturing technologies and systems  Robotics 

Code Science Field
T125  Technological sciences  Automation, robotics, control engineering 

Code Science Field
2.11  Engineering and Technology  Other engineering and technologies 
Keywords
motion synthesis, periodic movements, central pattern generators, nonlinear oscillators, humanoid robots, biarticular tendon, vertical jump, bipedal walking
Evaluation (rules)
source: COBISS
Researchers (1)
no. Code Name and surname Research area Role Period No. of publicationsNo. of publications
1.  25638  PhD Andrej Gams  Manufacturing technologies and systems  Head  2010 - 2012  238 
Organisations (1)
no. Code Research organisation City Registration number No. of publicationsNo. of publications
1.  0106  Jožef Stefan Institute  Ljubljana  5051606000  91,044 
Abstract
The proposed research deals with a new approach to the synthesis of periodic motion of a robotic humanoid leg. The idea is based on imitating biological systems with nonlinear oscillators. The final goal is the development and implementation of periodic motion of a lower extremity of a humanoid robot with the use of a novel method for motion synthesis. The method must ensure the balance of the system and allow the transition from periodic to aperiodic motion that concludes with a vertical jump. By refitting the experimental mechanism into a bipedal mechanism we wish to apply the same method for bipedal walking. The proposed research is based on the results of research, which were published in journals with highest impact factors in their fields. The idea for controlling the lower extremity of a humanoid mechanism derives from controlling a planar robotic mechanism that models a snake. Besides the similarities in the mechanical structure between the snake and a robotic leg (despite differences in the number and length of segments) we also derive from the possibility to use nonlinear oscillators to synthesize periodic motion of separate segments, from the properties of the oscillators to synchronize and the usage of pairs of oscillators to model antagonistic virtual muscles. The main problem of the research is vertical stability while performing a periodic task in the vertical plane. Also very demanding is the mechanical structure. Researchers have shown that a human leg has biarticular tendons, which allow for more efficient use of energy when walking and performing vertical jumps. The task demands a modification of the existing robotic mechanism with a biarticular tendon, which acts only when the knee is extending. This introduces a nonlinear and unilateral mechanical coupling, which is superior to the mathematical coupling of the oscillators and therefore demands new approaches to deal with such interaction. The main goal is the development and implementation of periodic motion for a robotic humanoid lower extremity with the use of nonlinear oscillators. The control has to ensure the stability of the mechanism. The motion synthesis must allow human-like motion with better results than model based approaches. The system of control has to include mechanical coupling of a biarticular tendon and achieve energetically efficient motion as it has to ensure controlled behavior also in the dynamical phases of motion. An upgrade of the mechanism to a bipedal version will allow the use of the developed method for dynamical bipedal walking. Nonlinear oscillators have never been applied to such a task on a humanoid mechanism in the described sense. Available mechanisms also do not include the biarticular tendon, which is crucial for efficient walking and vertical jump. To achieve the goal, we will also have to perform measurements on human subject with a motion capture system, measure the activation of muscles and the reacting forces. A mathematical model of the mechanism has to be derived. The actual mechanism demands an upgrade with a biarticular tendon. We have adequate knowledge and equipment to perform the task. We have gained substantial knowledge and experience in using and designing nonlinear oscillators. We (co)authored several methods for control of periodic robotic motion. We have the required measuring and mechanical equipment: A robotic humanoid lower extremity, a motion capture system, a force plate and a system to measure muscle activation. Bipedal walking is a demanding process, which requires innovative, partially structurally intelligent and autonomous processes for the synthesis of the controlling signals. The use of coupled nonlinear oscillators for modeling of antagonistic muscles and for synchronized movement of separate segments, combined with a mechanical structure that accounts for the biarticular tendon can lead to a crucial break-through in the field of controlling lower extremities of humanoid robots.
Significance for science
The developed method of control of periodic robotic tasks using nonlinear oscillators is a clear improvement of previously published methods, as it allows explicit determination of the base frequency and the phase of the periodic signal in question and therefore allows straightforward execution of periodic tasks on the robot. The method of stability control builds on the well-researched mathematical principles of prioritizing tasks. The implemented upgrade gives for the first time easy and direct means of applying and exploiting the proposed method for a wide set of tasks, from obstacle avoidance and stability control to any prioritized task with several subtasks.
Significance for the country
The methods developed during the course of the project have again reaffirmed Slovenia among the countries that perform state-of-the-art research in the area of robotics, which was confirmed with publications in the highest ranking journals of Robotics and the most competitive and acknowledged conferences. Indirectly, this improves the position of the researchers when applying for funding and gives them an overall better position when looking for project partners worldwide.
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