Equilibrium-point-based synergies that encode coordinates in task space: A practical method for translating functional synergies from human to musculoskeletal robot arm

A practical method for exploiting the neuromuscular coordination in a human arm posture to control a musculoskeletal robotic arm is proposed. The method enables the low-dimensional control of multiple muscles in the arm robot without considering the differences in the size and force balance between the human and artificial muscles. The central idea is based on the assumption that the equilibrium point (EP) of an arm is always located at its endpoint position while maintaining the posture on the horizontal plane. The mathematical formulation obtained using this physical constraint leads to the EP-based synergies that encode the polar coordinates in the task space. We tested this theory by extracting EP-based synergies from electromyography activities during human posture maintenance and implementing them for a musculoskeletal robotic arm. The results suggest EP-based synergies could be functional modules of muscle mechanical impedance which is an essential primitive for human motor control.

[1]  Hermano Igo Krebs,et al.  On the Origin of Muscle Synergies: Invariant Balance in the Co-activation of Agonist and Antagonist Muscle Pairs , 2015, Frontiers in Bioengineering and Biotechnology.

[2]  Francesco Lacquaniti,et al.  Control of Fast-Reaching Movements by Muscle Synergy Combinations , 2006, The Journal of Neuroscience.

[3]  Fumio Miyazaki,et al.  A novel muscle synergy extraction method to explain the equilibrium-point trajectory and endpoint stiffness during human upper-limb movements on a horizontal plane , 2014, 5th IEEE RAS/EMBS International Conference on Biomedical Robotics and Biomechatronics.

[4]  A. d’Avella,et al.  Locomotor Primitives in Newborn Babies and Their Development , 2011, Science.

[5]  David Ilngle.  The Co-ordination and Regulation of Movements. Papers translated from Russian and German. N. Bernstein. Pergamon, New York, 1967. xii + 196 pp., illus. $8 , 1968 .

[6]  Fumio Miyazaki,et al.  Extraction and implementation of muscle synergies in neuro-mechanical control of upper limb movement , 2014, Adv. Robotics.

[7]  Fumio Miyazaki,et al.  Tacit representation of muscle activities during coordination training: Muscle synergy analysis to visualize motor enhancement in virtual trajectory of multi-joint arm movement , 2014, 5th IEEE RAS/EMBS International Conference on Biomedical Robotics and Biomechatronics.

[8]  M. Latash,et al.  Testing hypotheses and the advancement of science: recent attempts to falsify the equilibrium point hypothesis , 2005, Experimental Brain Research.

[9]  Emilio Bizzi,et al.  The neural origin of muscle synergies , 2013, Front. Comput. Neurosci..

[10]  F. Miyazaki,et al.  A feasibility study to assess intralimb coordination in stroke rehabilitation: two indices of mechanical impedance by coactivation of agonist muscles , 2015, 2015 IEEE International Conference on Rehabilitation Robotics (ICORR).

[11]  Dagmar Sternad,et al.  Dynamic primitives of motor behavior , 2012, Biological Cybernetics.

[12]  R. Buschbacher.  Anatomical Guide for the Electromyographer: The Limbs and Trunk , 2007 .