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Ivancevic_Applied-Diff-Geom

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1046 <strong>Applied</strong> <strong>Diff</strong>erential <strong>Geom</strong>etry: A Modern Introductionto contraction. Stretch and unloading reflexes are mediated by combinedactions of several autogenetic neural pathways, forming the motor servo.In other words, branches of the afferent fibers also synapse with with interneuronsthat inhibit motor neurons controlling the antagonistic muscles– reciprocal inhibition. Consequently, the stretch stimulus causes the antagoniststo relax so that they cannot resists the shortening of the stretchedmuscle caused by the main reflex arc. Similarly, firing of the Golgi tendonreceptors causes inhibition of the muscle contracting too strong andsimultaneous reciprocal activation of its antagonist. Both mechanisms ofreciprocal inhibition and activation performed by the autogenetic circuits+F −1 and -F −1 , serve to generate the well–tuned EMA–driving torquesT i .Now, once we have properly defined the symplectic musculo–skeletal dynamics[<strong>Ivancevic</strong> (2004)] on the biomechanical (momentum) phase–spacemanifold T ∗ M N , we can proceed in formalizing its hierarchical subcorticalneural control. By introducing the coupling Hamiltonians H m = H m (q, p),selectively corresponding only to the M ≤ N active joints, we define theaffine Hamiltonian control function H aff : T ∗ M N → R, in local canonicalcoordinates on T ∗ M N given by (adapted from [Nijmeijer and van derSchaft (1990)] for the biomechanical purpose)H aff (q, p) = H 0 (q, p) − H m (q, p) T m , (m = 1, . . . , M ≤ N), (6.78)where T m = T m (t, q, p) are affine feedback torque one–forms, different fromthe initial driving torques T i acting in all the joints. Using the affine Hamiltonianfunction (6.78), we get the affine Hamiltonian servo–system [<strong>Ivancevic</strong>(2004)],˙q i = ∂H 0(q, p)∂p i− ∂Hm (q, p)∂p iT m , (6.79)ṗ i = − ∂H 0(q, p)∂q i + ∂Hm (q, p)∂q i T m ,q i (0) = q i 0, p i (0) = p 0 i , (i = 1, . . . , N; m = 1, . . . , M ≤ N).The affine Hamiltonian control system (6.79) gives our formal descriptionfor the autogenetic spinal motor–servo for all M ≤ N activated (i.e., working)EMAs.

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