scholarly journals Computational Motor Control: Redundancy and Invariance

2007 ◽  
Vol 97 (1) ◽  
pp. 331-347 ◽  
Author(s):  
Emmanuel Guigon ◽  
Pierre Baraduc ◽  
Michel Desmurget
Keyword(s):  
Nervous System ◽  
Motor Control ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Optimal Feedback Control ◽  
Kinematic Chains ◽  
3D Space ◽  
Antagonist Muscles ◽  
Characteristic Features ◽  
System 1

The nervous system controls the behavior of complex kinematically redundant biomechanical systems. How it computes appropriate commands to generate movements is unknown. Here we propose a model based on the assumption that the nervous system: 1) processes static (e.g., gravitational) and dynamic (e.g., inertial) forces separately; 2) calculates appropriate dynamic controls to master the dynamic forces and progress toward the goal according to principles of optimal feedback control; 3) uses the size of the dynamic commands (effort) as an optimality criterion; and 4) can specify movement duration from a given level of effort. The model was used to control kinematic chains with 2, 4, and 7 degrees of freedom [planar shoulder/elbow, three-dimensional (3D) shoulder/elbow, 3D shoulder/elbow/wrist] actuated by pairs of antagonist muscles. The muscles were modeled as second-order nonlinear filters and received the dynamics commands as inputs. Simulations showed that the model can quantitatively reproduce characteristic features of pointing and grasping movements in 3D space, i.e., trajectory, velocity profile, and final posture. Furthermore, it accounted for amplitude/duration scaling and kinematic invariance for distance and load. These results suggest that motor control could be explained in terms of a limited set of computational principles.

scholarly journals Design, Fabrication, and Testing of a Novel 3D 3-Fingered Electrothermal Microgripper with Multiple Degrees of Freedom

Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 444
Author(s):  
Guoning Si ◽  
Liangying Sun ◽  
Zhuo Zhang ◽  
Xuping Zhang
Keyword(s):  
Degrees Of Freedom ◽  
Dynamic Properties ◽  
Three Dimensional ◽  
Polyimide Film ◽  
Zebrafish Embryos ◽  
Multiple Degrees Of Freedom ◽  
Electrothermal Actuator ◽  
3D Space ◽  
Pick And Place

This paper presents the design, fabrication, and testing of a novel three-dimensional (3D) three-fingered electrothermal microgripper with multiple degrees of freedom (multi DOFs). Each finger of the microgripper is composed of a V-shaped electrothermal actuator providing one DOF, and a 3D U-shaped electrothermal actuator offering two DOFs in the plane perpendicular to the movement of the V-shaped actuator. As a result, each finger possesses 3D mobilities with three DOFs. Each beam of the actuators is heated externally with the polyimide film. The durability of the polyimide film is tested under different voltages. The static and dynamic properties of the finger are also tested. Experiments show that not only can the microgripper pick and place microobjects, such as micro balls and even highly deformable zebrafish embryos, but can also rotate them in 3D space.

Design and locomotion analysis of a novel deformable mobile robot with two spatial reconfigurable platforms and three kinematic chains

2016 ◽  
Vol 231 (8) ◽  
pp. 1481-1499 ◽  
Author(s):  
Wan Ding ◽  
Qiang Ruan ◽  
Yan-an Yao
Keyword(s):  
Mobile Robot ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Three Dimensional Model ◽  
Dynamic Simulations ◽  
Gait Planning ◽  
Plane Symmetric ◽  
Kinematic Chains ◽  
Reconfigurable Platforms ◽  
Actuation Systems

A novel five degrees of freedom deformable mobile robot composed of two spatial reconfigurable platforms and three revolute–prismatic–spherical kinematic chains acting in parallel to link the two platforms is proposed to realize large deformation capabilities and multiple locomotion modes. Each platform is an improved deployable single degrees of freedom three-plane-symmetric Bricard linkage. By taking advantage of locomotion collaborating among platforms and kinematic chains, the mobile robot can fold into stick-like shape and possess omnidirectional rolling and worm-like motions. The mechanism design, kinematics, and locomotion feasibility are the main focus. Through kinematics and gait planning, the robot is analyzed to have the capabilities of rolling and turning. Based on its deformation, the worm-like motion performs the ability to overcome narrow passages (such as pipes, holes, gaps, etc.) with large range of variable size. Dynamic simulations with detailed three-dimensional model are carried out to verify the gait planning and provide the variations of essential motion and dynamic parameters in each mode. An experimental robotic system with servo and pneumatic actuation systems is built, experiments are carried out to verify the validity of the theoretical analysis and the feasibility of the different locomotion functions, and its motion performances are compared and analyzed with collected data.

Adaptability of innate motor patterns and motor control mechanisms

1986 ◽  
Vol 9 (4) ◽  
pp. 585-599 ◽  
Author(s):  
M. B. Berkinblit ◽  
A. G. Feldman ◽  
O. I. Fukson
Keyword(s):  
Nervous System ◽  
Motor Control ◽  
Degrees Of Freedom ◽  
Behavioral Plasticity ◽  
Motor Behavior ◽  
Voluntary Control ◽  
Control Mechanisms ◽  
Motor Equivalence ◽  
Motor Patterns ◽  
Dynamic Components

AbstractThe following factors underlying behavioral plasticity are discussed: (1) reflex adaptability and its role in the voluntary control of movement, (2) degrees of freedom and motor equivalence, and (3) the problem of the discrete organization of motor behavior. Our discussion concerns a variety of innate motor patterns, with emphasis on the wiping reflex in the frog.It is proposed that central regulation of stretch reflex thresholds governs voluntary control over muscle force and length. This suggestion is an integral part of the equilibrium-point hypothesis, two versions of which are compared.Kinematic analysis of the wiping reflex in the spinal frog has shown that each stimulated skin site is associated with a group of different but equally effective trajectories directed to the target site. Such phenomena reflect the principle of motor equivalence -the capacity of the neuronal structures responsible for movement to select one or another of a set of possible trajectories leading to the goal. Redundancy of degrees of freedom at the neuronal level as well as at the mechanical level of the body's joints makes motor equivalence possible. This sort of equivalence accommodates the overall flexibility of motor behavior.An integrated behavioral act or a single movement consists of dynamic components. We distinguish six components for the wiping reflex, each associated with a certain functional goal, specific body positions, and motor-equivalent movement patterns. The nervous system can combine the available components in various ways in forming integrated behavioral sequences. The significance of command neuronal organization is discussed with respect to (1) the combinatory strategy of the nervous system and (2) the relation between continuous and discrete forms of motor control. We conclude that voluntary movements are effected by the central nervous system with the help of the mechanisms that underlie the variability and modifiability of innate motor patterns.

scholarly journals Manifold reaching paradigm: how do we handle target redundancy?

2011 ◽  
Vol 106 (4) ◽  
pp. 2086-2102 ◽  
Author(s):  
Bastien Berret ◽  
Enrico Chiovetto ◽  
Francesco Nori ◽  
Thierry Pozzo
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Degrees Of Freedom ◽  
A Priori ◽  
Movement Planning ◽  
Optimal Feedback Control ◽  
Target Redundancy ◽  
The Central Nervous System ◽  
Point To Point ◽  
Muscle Activations

How the central nervous system coordinates the many intrinsic degrees of freedom of the musculoskeletal system is a recurrent question in motor control. Numerous studies addressed it by considering redundant reaching tasks such as point-to-point arm movements, for which many joint trajectories and muscle activations are usually compatible with a single goal. There exists, however, a different, extrinsic kind of redundancy that is target redundancy. Many times, indeed, the final point to reach is neither specified nor unique. In this study, we aim to understand how the central nervous system tackles such an extrinsic redundancy by considering a reaching-to-a-manifold paradigm, more specifically an arm pointing to a long vertical bar. In this case, the endpoint is not defined a priori and, therefore, subjects are free to choose any point on the bar to successfully achieve the task. We investigated the strategies used by subjects to handle this presented choice. Our results indicate both intersubject and intertrial consistency with respect to the freedom provided by the task. However, the subjects' behavior is found to be more variable than during classical point-to-point reaches. Interestingly, the average arm trajectories to the bar and the structure of intertrial endpoint variations could be explained via stochastic optimal control with an energy/smoothness expected cost and signal-dependent motor noise. We conclude that target redundancy is first overcome during movement planning and then exploited during movement execution, in agreement with stochastic optimal feedback control principles, which illustrates how the complementary problems of goal and movement selection may be resolved at once.

Motor Control in Soft-Bodied Animals

2017 ◽  
pp. 494-510 ◽  
Author(s):  
Guy Levy ◽  
Nir Nesher ◽  
Letizia Zullo ◽  
Binyamin Hochner
Keyword(s):  
Nervous System ◽  
Motor Control ◽  
Control System ◽  
Degrees Of Freedom ◽  
Control Strategies ◽  
Highly Active ◽  
Actuation System ◽  
Controlling System ◽  
Motor Control System ◽  
Free Parameters

Motor Control is essentially the computations required for producing coordinated sequences of commands from the controlling system (i.e., nervous system) to the actuation system (i.e., muscles) to generate efficient motion. The level of motor control complexity depends on the number of free parameters (degrees of freedom) that have to be coordinated. This number is much smaller in skeletal animals because they have a rather limited number of joints. In soft bodied animals, like the octopus, this number is virtually infinite. Here we show that the efficient motor control system of the octopus uses solutions that are very different from those of articulated animals, and it involves embodied co-evolution of the unique morphology together with the organization of the nervous and muscular systems to enable control strategies that are best suited for a highly active soft-bodied animal like the octopus.

scholarly journals The Autonomic Nervous System Differentiates between Levels of Motor Intent and End Effector

2020 ◽  
Vol 10 (3) ◽  
pp. 76
Author(s):  
Jihye Ryu ◽  
Elizabeth Torres
Keyword(s):  
Nervous System ◽  
Motor Control ◽  
Autonomic Nervous System ◽  
Cognitive Science ◽  
Embodied Cognition ◽  
Degrees Of Freedom ◽  
The Body ◽  
End Effector ◽  
Nervous Systems ◽  
Autonomic Nervous

While attempting to bridge motor control and cognitive science, the nascent field of embodied cognition has primarily addressed intended, goal-oriented actions. Less explored, however, have been unintended motions. Such movements tend to occur largely beneath awareness, while contributing to the spontaneous control of redundant degrees of freedom across the body in motion. We posit that the consequences of such unintended actions implicitly contribute to our autonomous sense of action ownership and agency. We question whether biorhythmic activities from these motions are separable from those which intentionally occur. Here we find that fluctuations in the biorhythmic activities of the nervous systems can unambiguously differentiate across levels of intent. More important yet, this differentiation is remarkable when we examine the fluctuations in biorhythmic activity from the autonomic nervous systems. We find that when the action is intended, the heart signal leads the body kinematics signals; but when the action segment spontaneously occurs without instructions, the heart signal lags the bodily kinematics signals. We conclude that the autonomic nervous system can differentiate levels of intent. Our results are discussed while considering their potential translational value.

scholarly journals The Autonomic Nervous System Differentiates Between Levels of Motor Intent and Hand Dominance

2020 ◽  
Author(s):  
Jihye Ryu ◽  
Elizabeth Torres
Keyword(s):  
Nervous System ◽  
Motor Control ◽  
Autonomic Nervous System ◽  
Cognitive Science ◽  
Embodied Cognition ◽  
Degrees Of Freedom ◽  
The Body ◽  
Hand Dominance ◽  
Nervous Systems ◽  
Autonomic Nervous

AbstractWhile attempting to bridge motor control and cognitive science, the nascent field of embodied cognition has primarily addressed intended, goal-oriented actions. Less explored however, have been unintended motions. Such movements tend to occur largely beneath awareness, while contributing to the spontaneous control of redundant degrees of freedom across the body in motion. We posit that the consequences of such unintended actions implicitly contribute to our autonomous sense of action ownership and agency. We question whether biorhythmic activities from these motions are separable from those which intentionally occur. Here we find that fluctuations in the biorhythmic activities of the nervous systems can unambiguously differentiate across levels of intent. More important yet, this differentiation is remarkable when we examine the fluctuations in biorhythmic activity from the autonomic nervous systems. We find that when the action is intended, the heart signal leads the body kinematics signals; but when the action segment spontaneously occurs without instructions, the heart signal lags the bodily kinematics signals. We posit that such differentiation within the nervous system, may be necessary to acquire the sense of action ownership, which in turn, contributes to the sense of agency. We discuss our results while considering their potential translational value.

Learning to balance an NAO robot using reinforcement learning with symbolic inverse kinematic

2016 ◽  
Vol 39 (11) ◽  
pp. 1735-1748 ◽  
Author(s):  
Onder Tutsoy ◽  
Duygun Erol Barkana ◽  
Sule Colak
Keyword(s):  
Reinforcement Learning ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Inverse Kinematic ◽  
Lower Body ◽  
3D Space ◽  
Nao Robot ◽  
Standing Up ◽  
And Control ◽  
Autonomous Humanoid

An autonomous humanoid robot (HR) with learning and control algorithms is able to balance itself during sitting down, standing up, walking and running operations, as humans do. In this study, reinforcement learning (RL) with a complete symbolic inverse kinematic (IK) solution is developed to balance the full lower body of a three-dimensional (3D) NAO HR which has 12 degrees of freedom. The IK solution converts the lower body trajectories, which are learned by RL, into reference positions for the joints of the NAO robot. This reduces the dimensionality of the learning and control problems since the IK integrated with the RL eliminates the need to use whole HR states. The IK solution in 3D space takes into account not only the legs but also the full lower body; hence, it is possible to incorporate the effect of the foot and hip lengths on the IK solution. The accuracy and capability of following real joint states are evaluated in the simulation environment. MapleSim is used to model the full lower body, and the developed RL is combined with this model by utilizing Modelica and Maple software properties. The results of the simulation show that the value function is maximized, temporal difference error is reduced to zero, the lower body is stabilized at the upright, and the convergence speed of the RL is improved with use of the symbolic IK solution.

scholarly journals Statistical determinants of visuomotor adaptation in a virtual reality three-dimensional environment

2021 ◽  
Author(s):  
E. Ferrea ◽  
P. Morel ◽  
J. Franke ◽  
A. Gail
Keyword(s):  
Virtual Reality ◽  
Motor Control ◽  
Three Dimensional ◽  
Motor Adaptation ◽  
Sensory Perception ◽  
Visuomotor Adaptation ◽  
The Body ◽  
Integration Theory ◽  
Motor Deficits ◽  
3D Space

AbstractRecent advances in virtual reality (VR) technology allow motor control studies to investigate movement variety in a controlled 3D environment. However, visuomotor adaptation paradigms for arm reaches in a 3D space are still scarcely investigated. Elucidating these adaptations is important to further our understanding, predicting and hence, rehabilitating everyday movement behavior in humans suffering from motor deficits. We test how well optimal integration theory that was extrapolated from 1D and 2D settings extends to movements in 3D space; specifically, if and how a subject’s variability in planning and sensory perception will influence motor adaptation. We test this hypothesis without introducing artificial (experimentally induced) variability. Instead, we exploit the natural anisotropy in sensory performance along different dimensions relative to the body. We use a virtual reality (VR) setup to compare the subject’s adaptation of their 3D movements to perturbations applied separately in sagittal, coronal and horizontal planes. We found that subjects adapt best to perturbations in the coronal plane, i.e. when the depth component of the movement is unaffected, followed by sagittal then horizontal perturbations. To characterize how the adaptation rate selectively depends on planning and sensory uncertainty along different body axes, we developed a novel hierarchical two-state space model using Bayesian modeling via Hamiltonian Monte Carlo procedures to fit visuomotor adaptation profiles. Our hierarchical model reconstructs learning parameters from surrogate data better than a state-of-the-art expectation-maximization (EM) algorithm. Modeling revealed that differences in adaptation rate of movement among the three planes are explained from the Kalman gain, i.e. the relative variability associated with planning and sensory perception. The developed method allowed us to show that the motor behavior is in line with optimal integration theory when considering adaptation rate variation between the different planes.Author SummaryThe process of neurorehabilitation in human patients suffering from motor deficits could be considered as a process of relearning or re-adapting motor skills. Virtual reality is already used to drive motor rehabilitation. However, the majority of motor learning theories were developed under one or two-dimensional experimental paradigms and it is assumed that the general findings apply to motor control in three-dimensional movements. To test whether these theories are also compatible with more naturalistic movements performed in a three-dimensional space, we used a new statistical method to identify the dynamics of motor adaptation in virtual reality. We found that in a three-dimensional environment, there are differences in how the subject will correct and adapt their movement based on which orientation relative to the body the movement needs to be corrected. These differences come from the statistical variability associated with unperturbed movements in the different directions. These findings provide clues on how therapeutic regimens in virtual reality should be adapted, i.e. physical reorientation of the body, to improve rehabilitation of certain movements.

scholarly journals Analysis of Three-Dimensional Circular Tracking Movements Based on Temporo-Spatial Parameters in Polar Coordinates

2020 ◽  
Vol 10 (2) ◽  
pp. 621 ◽  
Author(s):  
Woong Choi ◽  
Jongho Lee ◽  
Liang Li
Keyword(s):  
Motor Control ◽  
Sagittal Plane ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Frontal Plane ◽  
Polar Coordinates ◽  
Target Velocity ◽  
Healthy Human ◽  
3D Space ◽  
Tracking Movements

Motor control characteristics of the human visuomotor control system need to be analyzed in the three-dimensional (3D) space to study and imitate human movements. In this paper, we examined circular tracking movements on two planes in 3D space from a motor control perspective based on three temporospatial parameters in polar coordinates. Sixteen healthy human subjects participated in this study and performed circular target tracking movements rotating at 0.125, 0.25, 0.5, and 0.75 Hz in the frontal or sagittal planes in three-dimensional space. The results showed that two temporal parameter errors on each plane were proportional to the change in the target velocity. Furthermore, frontal plane circular tracking errors without depth for a spatial parameter were lower than those for sagittal plane circular tracking with depth. The experimental protocol and data analysis allowed us to analyze the motor control characteristics temporospatially for circular tracking movement with various depths and speeds in the 3D VR space.

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