scholarly journals Integration of intrinsic muscle properties, feed-forward and feedback signals for generating and stabilizing hopping

2012 ◽  
Vol 9 (72) ◽  
pp. 1458-1469 ◽  
Author(s):  
D. F. B. Haeufle ◽  
S. Grimmer ◽  
K.-T. Kalveram ◽  
A. Seyfarth
Keyword(s):  
Muscle Activation ◽  
Contractile Element ◽  
Muscle Properties ◽  
Type Representation ◽  
Feed Forward ◽  
Intrinsic Muscle ◽  
Individual Type ◽  
The Stability ◽  
Map Analysis ◽  
Hopping Model

It was hypothesized that a tight integration of feed-forward and feedback-driven muscle activation with the characteristic intrinsic muscle properties is a key feature of locomotion in challenging environments. In this simulation study it was investigated whether a combination of feed-forward and feedback signals improves hopping stability compared with those simulations with one individual type of activation. In a reduced one-dimensional hopping model with a Hill-type muscle (one contractile element, neither serial nor parallel elastic elements), the level of detail of the muscle's force–length–velocity relation and the type of activation generation (feed-forward, feedback and combination of both) were varied to test their influence on periodic hopping. The stability of the hopping patterns was evaluated by return map analysis. It was found that the combination of feed-forward and proprioceptive feedback improved hopping stability. Furthermore, the nonlinear Hill-type representation of intrinsic muscle properties led to a faster reduction of perturbations than a linear approximation, independent of the type of activation. The results emphasize the ability of organisms to exploit the stabilizing properties of intrinsic muscle characteristics.

scholarly journals Mass Imbalance Compensation Control for Stabilized Platform Based on UKF Identification

2018 ◽  
Vol 198 ◽  
pp. 01005
Author(s):  
WeiMing Zhang ◽  
ZeLin Shi
Keyword(s):  
Mean Squared Error ◽  
Unscented Kalman Filter ◽  
Parameters Estimation ◽  
Feed Forward ◽  
Mass Imbalance ◽  
Feed Forward Control ◽  
Nonlinear Compensation ◽  
The Stability ◽  
Stabilized Platform ◽  
Platform System

Due to the mass imbalance about the center of rotation, the stability of stabilized platform system degrades with carrier’s disturbances. Various feed-forward control methods are provided by reaserchers to solve this problem, however these methods are not well applied because the eccentricity of stabilized platform could not be measured directly. The dynamics model of a typical 2-axis stabilized platform is given. The eccentricity vector is identified through Unscented Kalman Filter(UKF) algorithm. Imbalance torque is precisely observed so that the real-time nonlinear compensation for mass imbalance is achieved through a feed-forward loop. The simulation result indicates that the Root Mean Squared Error (RMSE) of parameters estimation is 0.024 after convergence. the LOS stabilization with carrier’s 2.5Hz vibration is 0.04 rad/s, which improves 78% compared to conventional feed-back control.

Design of an adaptive control law using trigonometric functions for robot manipulators

Robotica ◽  
2005 ◽  
Vol 23 (1) ◽  
pp. 93-99 ◽  
Author(s):  
Recep Burkan
Keyword(s):  
Adaptive Control ◽  
Robot Manipulators ◽  
Tracking Error ◽  
Uncertain System ◽  
Control Law ◽  
Trigonometric Functions ◽  
Feed Forward ◽  
Inertia Parameters ◽  
The Stability ◽  
Adaptive Control Law

In this study, a new approach of adaptive control law for controlling robot manipulators using the Lyapunov based theory is derived, thus the stability of an uncertain system is guaranteed. The control law includes a PD feed forward part and a full dynamics feed forward compensation part with the unknown manipulator and payload parameters. The novelty of the obtained result is that an adaptive control algorithm is developed using trigonometric functions depending on manipulator kinematics, inertia parameters and tracking error, and both system parameters and adaptation gain matrix are updated in time.

Use of a new index to study relaxation in a vascular model of anaphylactic shock

1993 ◽  
Vol 74 (6) ◽  
pp. 2621-2626 ◽  
Author(s):  
X. Liu ◽  
H. Jiang ◽  
N. L. Stephens
Keyword(s):  
Saphenous Vein ◽  
Anaphylactic Shock ◽  
Muscle Activation ◽  
Muscle Relaxation ◽  
Contractile Element ◽  
Time Index ◽  
Muscle Shortening ◽  
Cross Bridges ◽  
And Control ◽  
Relaxation Index

We have reported increased smooth muscle shortening ability in ragweed pollen-sensitized saphenous vein (SSV). This may account for the vascular hyperreactivity of anaphylactic shock. We have now investigated relaxation in SSV. Because isotonic relaxation is load and initial contractile element length dependent, we developed an adjusted half-relaxation time index, which was independent of these variables. Muscle activation state was monitored by measuring maximum unloaded velocity. The relaxation index showed no difference between SSV and control saphenous vein after 2.5, 10, and 15 s of electrical stimulation; however, after 1 s of stimulation it was prolonged significantly in SSV. We concluded that the cross bridges activating early in contraction demonstrated prolonged relaxation. Activation state during muscle relaxation spontaneously increased toward the end of relaxation, coincident with a slowing in isotonic re-elongation rate. This was seen only in muscles relaxing from 15 s of stimulation. Our results indicate that 1) the relaxation properties of early cycling (1 s) cross bridges are altered after sensitization; and 2) toward the end of isotonic relaxation, cross-bridge cycling rate increases spontaneously, a phenomenon not previously reported. We speculate that the rapid re-elongation in late relaxation may reactivate muscle.

On the Stability Analysis of the Human Spine

2003 ◽  
Author(s):  
M. El-Rich ◽  
A. Shirazi-Adl
Keyword(s):  
Stability Analysis ◽  
Material Handling ◽  
Muscle Activation ◽  
The Body ◽  
Abdominal Pressure ◽  
Human Spine ◽  
Manual Material Handling ◽  
The Stability ◽  
Force Relationship

The stability of the human spine in compression has attracted a considerable amount of attention in recent years. The passive ligamentous thoracolumbar and lumbar spines are known to exhibit large displacements or hypermobility (i.e., instability in an imperfect column) under compression loads <100N. Since such compression loads are only a small fraction of those supported by the spine even in regular daily activities, let aside the manual material handling tasks, the question arises as to how the spine is stablized in vivo? Various stabilizing mechanisms have been proposed and investigated; wrapping loading [Shirazi-Adl and Parnianpour, 2000], postural adaptations [Shirazi-Adl and parnianpor, 1999], intra-abdominal pressure [Cholewicki et al, 1999] and muscle activation/coactivation [Bergmark, 1989; Crisco and Panjabi, 1991]. In this work, a novel kinematics-based methad [Shirazi-Adl et al., 2002] is first applied to compute muscle forces and internal loads in standing postures under gravity with or without 200N loads held either on sides or close to the body in front. The stability of the system under given loads and prescribed postures is sudsequently examined using both linear bucking analysis based on the deformed configurations and nonlinear analysis while employing a liner stiffness-force relationship for muscules [Bergmark, 1989; Crico and Panjabi, 1991]. The relative accuracy of foregoing methods in stability analysis of some sample structures is also investigated. Moreover, the effect of co-activity on stability of the spine in neutral postures is studied.

Intrinsic Muscle Properties Of The M. Quadriceps Femoris After Subacute Stroke

2009 ◽  
Vol 41 ◽  
pp. 528
Author(s):  
Astrid M. Horstman ◽  
Karin H. Gerrits ◽  
Thomas W. Janssen ◽  
Arnold de Haan
Keyword(s):  
Quadriceps Femoris ◽  
Muscle Properties ◽  
Intrinsic Muscle ◽  
Subacute Stroke

Central Representation of Dynamics When Manipulating Handheld Objects

2006 ◽  
Vol 95 (2) ◽  
pp. 893-901 ◽  
Author(s):  
Theodore E. Milner ◽  
David W. Franklin ◽  
Hiroshi Imamizu ◽  
Mitsuo Kawato
Keyword(s):  
Motor Cortex ◽  
Internal Model ◽  
Muscle Activation ◽  
Primary Motor Cortex ◽  
Small Region ◽  
Unstable State ◽  
Moment Control ◽  
Central Representation ◽  
The Stability ◽  
The Moment

To explore the neural mechanisms related to representation of the manipulation dynamics of objects, we performed whole-brain fMRI while subjects balanced an object in stable and highly unstable states and while they balanced a rigid object and a flexible object in the same unstable state, in all cases without vision. In this way, we varied the extent to which an internal model of the manipulation dynamics was required in the moment-to-moment control of the object's orientation. We hypothesized that activity in primary motor cortex would reflect the amount of muscle activation under each condition. In contrast, we hypothesized that cerebellar activity would be more strongly related to the stability and complexity of the manipulation dynamics because the cerebellum has been implicated in internal model-based control. As hypothesized, the dynamics-related activation of the cerebellum was quite different from that of the primary motor cortex. Changes in cerebellar activity were much greater than would have been predicted from differences in muscle activation when the stability and complexity of the manipulation dynamics were contrasted. On the other hand, the activity of the primary motor cortex more closely resembled the mean motor output necessary to execute the task. We also discovered a small region near the anterior edge of the ipsilateral (right) inferior parietal lobule where activity was modulated with the complexity of the manipulation dynamics. We suggest that this is related to imagining the location and motion of an object with complex manipulation dynamics.

Local Dynamic Stability of Spine Muscle Activation and Stiffness Patterns During Repetitive Lifting

2014 ◽  
Vol 136 (12) ◽  
Author(s):  
Ryan B. Graham ◽  
Stephen H. M. Brown
Keyword(s):  
Dynamic Stability ◽  
Muscle Activation ◽  
Muscle Force ◽  
Local Dynamic ◽  
Rotational Stiffness ◽  
Physiological Variables ◽  
Repetitive Lifting ◽  
Local Dynamic Stability ◽  
Muscle Activations ◽  
The Stability

To facilitate stable trunk kinematics, humans must generate appropriate motor patterns to effectively control muscle force and stiffness and respond to biomechanical perturbations and/or neuromuscular control errors. Thus, it is important to understand physiological variables such as muscle force and stiffness, and how these relate to the downstream production of stable spine and trunk movements. This study was designed to assess the local dynamic stability of spine muscle activation and rotational stiffness patterns using Lyapunov analyses, and relationships to the local dynamic stability of resulting spine kinematics, during repetitive lifting and lowering at varying combinations of lifting load and rate. With an increase in the load lifted at a constant rate there was a trend for decreased local dynamic stability of spine muscle activations and the muscular contributions to spine rotational stiffness; although the only significant change was for the full state space muscle activation stability (p < 0.05). With an increase in lifting rate with a constant load there was a significant decrease in the local dynamic stability of spine muscle activations and the muscular contributions to spine rotational stiffness (p ≤ 0.001 for all measures). These novel findings suggest that the stability of motor inputs and the muscular contributions to spine rotational stiffness can be altered by external task demands (load and lifting rate), and therefore are important variables to consider when assessing the stability of the resulting kinematics.

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