scholarly journals Identifying control structure of multi-joint coordination in dart throwing: the effect of distance constraint

2019 ◽  
Vol 23 (6) ◽  
pp. 267-281
Author(s):  
S.H. HosseiniZarch ◽  
S. Arsham ◽  
S.F. Tabatabaei Ghomshe ◽  
M.H. Honarvar
Keyword(s):  
Control Strategy ◽  
Center Of Mass ◽  
Joint Space ◽  
Spatial Position ◽  
Distance Constraint ◽  
Joint Configuration ◽  
Joint Coordination ◽  
Dart Throwing ◽  
Task Variables ◽  
Specific Control

Background: This study used the uncontrolled manifold (UCM) approach to study joint coordination underlying the control of task-related variables important for success at dart throwing skill. Success at a task can be achieved, in principle, by always adopting a particular joint combination. In contrast, we adopt a more selective control strategy: variations of the joint configuration that leave the values of essential task variables unchanged are predicted to be less controlled (i.e., stabilized to a lesser degree) than joint configuration changes that shift the values of the task variables. Objectives: How this abundance of motor solutions is managed by the nervous system and whether and how the throwing in different distances affects the solution to joint coordination was investigated in this study. Methods: Our experimental task involved dart throwing to a target under three conditions (standard, short and long distance) that it performed by fifteen dart professional and semiprofessional athletes. The four joint angles of the arm were obtained from the recorded positions of markers on the limb segments. The variability of joint configurations was decomposed into components lying parallel to those sets and components lying in their complement with respect to control of the path of the arm’s center of mass and spatial position of the hand. Results: When performing the task in all three different conditions, fluctuations of joint configuration that affected arm’s center of mass and spatial position variables were much reduced compared with fluctuations that did not affect these variables. The UCM principle applied to arm’s center of mass and spatial position thus captures the structure of the motor control system across different parts of joint configuration space as the movement evolves in time. Moreover, constraints representing an invariant arm’s center of mass or the spatial position structured joint configuration variability in the early and mid-portion of the movement trajectory, but not at the time of throwing. This specific control strategy indicate a target can be hit successfully also by controlling irrelevant directions in joint space equally to relevant ones. Conclusion: The results suggests a specific control strategy in which changes of joint configuration that are irrelevant to success at the task are selectively released from control. As a result, the method can be successfully used to determine the structure of coordination in joint space that underlies the control of the essential variables for a given task.

A novel active balance assistive control strategy based on virtual stiffness model of XCoM

2019 ◽  
Vol 40 (1) ◽  
pp. 132-142
Author(s):  
Wei Guo ◽  
Shiyin Qiu ◽  
Fusheng Zha ◽  
Jing Deng ◽  
Xin Wang ◽  
...  
Keyword(s):  
Control Strategy ◽  
Design Methodology ◽  
Sagittal Plane ◽  
Center Of Mass ◽  
Proof Of Concept ◽  
Disturbing Force ◽  
Content Type ◽  
Exoskeleton Robot ◽  
Stiffness Model ◽  
Virtual Stiffness

PurposeThis paper aims to propose a novel balance-assistive control strategy for hip exoskeleton robot.Design/methodology/approachA hierarchical balance assistive controller based on the virtual stiffness model of extrapolated center of mass (XCoM) is proposed and tested by exoskeleton balance assistive control experiments.FindingsExperiment results show that the proposed controller can accelerate the swing foot chasing XCoM and enlarge the margin of stability.Originality/valueAs a proof of concept, this paper shows the potential for exoskeleton to actively assist human regain balance in sagittal plane when human suffers from a forward or backward disturbing force.

CARTESIAN APPROACH FOR GAIT PLANNING AND CONTROL OF BIPED ROBOTS ON IRREGULAR SURFACES

2009 ◽  
Vol 06 (04) ◽  
pp. 675-697 ◽  
Author(s):  
S. ALI A. MOOSAVIAN ◽  
MANSOOR ALGHOONEH ◽  
AMIR TAKHMAR
Keyword(s):  
Center Of Mass ◽  
Joint Space ◽  
Computational Effort ◽  
Simulation Studies ◽  
Pd Controller ◽  
Biped Robots ◽  
Gait Planning ◽  
Trunk Motion ◽  
Planning And Control ◽  
And Control

Biped robots possess higher capabilities than other mobile robots for moving on uneven environments. However, due to natural postural instability of these robots, their motion planning and control become a more important and challenging task. This article presents a Cartesian approach for gait planning and control of biped robots without the need to use the inverse kinematics and the joint space trajectories, thus the proposed approach could substantially reduce the processing time in both simulation studies and online implementations. It is based on constraining four main points of the robot in Cartesian space. This approach exploits the concept of Transpose Jacobian control as a virtual spring and damper between each of these points and the corresponding desired trajectory, which leads to overcome the redundancy problem. These four points include the tip of right and left foot, the hip joint, and the total center of mass (CM). Furthermore, in controlling biped robots based on desired trajectories in the task space, the system may track the desired trajectory while the knee is broken. This problem is solved here using a PD controller which will be called the Knee Stopper. Similarly, another PD controller is proposed as the Trunk Stopper to limit the trunk motion. Obtained simulation results show that the proposed Cartesian approach can be successfully used in tracking desired trajectories on various surfaces with lower computational effort.

BIPED HOPPING CONTROL BAzSED ON SPRING LOADED INVERTED PENDULUM MODEL

2010 ◽  
Vol 07 (02) ◽  
pp. 263-280 ◽  
Author(s):  
SEYED HOSSEIN TAMADDONI ◽  
FARID JAFARI ◽  
ALI MEGHDARI ◽  
SAEED SOHRABPOUR
Keyword(s):  
Control Strategy ◽  
Inverted Pendulum ◽  
Hybrid Control ◽  
Sagittal Plane ◽  
Center Of Mass ◽  
Slip Model ◽  
Inverted Pendulum Model ◽  
Wide Range ◽  
Spring Loaded Inverted Pendulum ◽  
Mass Spring

Human running can be stabilized in a wide range of speeds by automatically adjusting muscular properties of leg and torso. It is known that fast locomotion dynamics can be approximated by a spring loaded inverted pendulum (SLIP) system, in which leg is replaced by a single spring connecting body mass to ground. Taking advantage of the inherent stability of SLIP model, a hybrid control strategy is developed that guarantees a stable biped locomotion in sagittal plane. In the presented approach, nonlinear control methods are applied to synchronize the biped dynamics and the spring-mass dynamics. As the biped center of mass follows the mass of the mass-spring model, the whole biped performs a stable locomotion corresponding to SLIP model. Simulations are done to obtain a repeatable hopping for a three-link underactuated biped model. Results show that periodic hopping gaits can be stabilized, and the presented control strategy provides feasible gait trajectories for stance and swing phases.

scholarly journals Kinematics and control of frog hindlimb movements

1991 ◽  
Vol 65 (3) ◽  
pp. 547-562 ◽  
Author(s):  
D. J. Ostry ◽  
A. G. Feldman ◽  
J. R. Flanagan
Keyword(s):  
Nervous System ◽  
High Speed ◽  
Imaging System ◽  
Maximum Velocity ◽  
Joint Space ◽  
Motion Path ◽  
Three Dimension ◽  
Joint Angles ◽  
Joint Configuration ◽  
Straight Line

1. The determinants of the motion path of the hindlimb were explored in both intact and spinal frogs. In the spinal preparations the kinematic properties of withdrawal and crossed-extension reflexes were studied. In the intact frog the kinematics of withdrawal and swimming movements were examined. Frog hindlimb paths were described in joint angle (intrinsic) coordinates rather than limb endpoint (extrinsic) coordinates. 2. To study withdrawal and crossed-extension reflexes, the initial angles at the hip, knee, and ankle were varied. Withdrawal and crossed extension were recorded in three dimension (3-D) with the use of an infra-red spatial imaging system. Swimming movements against currents of different speeds were obtained with high-speed film. 3. Three strategies were considered related to the form of the hypothesized equilibrium paths specified by the nervous system: all trajectories lie on a single line in angular coordinates; all trajectories are directed toward a common final position; and all trajectories have the same direction independent of initial joint configuration. 4. Joint space paths in withdrawal were found to be straight and parallel independent of the initial joint configuration. The hip and knee were found to start simultaneously and in 75% of the conditions tested to reach maximum velocity simultaneously. Hip-knee maximum velocity ratios were similar in magnitude over differences in initial joint angles. This is consistent with the observation of parallel paths and supports the view that the nervous system specifies a single direction for equilibrium trajectories. 5. Straight line paths with slopes similar to those observed in withdrawal in the spinal preparation were found in swimming movements in the intact frog. Straight line paths in joint space are consistent with the idea that swimming and withdrawal are organized and controlled in a joint-level coordinate system. The similarities observed between spinal and intact preparations suggest that a common set of constructive elements underlies these behaviors. 6. Path curvature was introduced when joint limits were approached toward the end of the movement. Depending on the initial joint angles, the joint movements ended at different times. When initial joint angles were unequal, joints moving from smaller initial angles reached their functional limits earlier and stopped first. 7. In withdrawal and crossed extension in the spinal frog, velocity profiles at a given joint were similar over the initial portion of the curve for movements of different amplitude. This is consistent with the idea that withdrawal and crossed-extension movements of different amplitude are produced by a constant rate of shift of the equilibrium position.

ZMP Tracking Control of an Android Robot Leg on Slope-Changing Ground Using Disturbance Observer and Dual Plant Models

2016 ◽  
Vol 13 (03) ◽  
pp. 1550043 ◽  
Author(s):  
Jung-Yup Kim ◽  
Young-Seog Kim
Keyword(s):  
Control Strategy ◽  
Tracking Control ◽  
Disturbance Observer ◽  
Balance Control ◽  
Control Strategies ◽  
Center Of Mass ◽  
Model Inversion ◽  
Slope Change ◽  
Ground Slope ◽  
Android Robot

This paper describes a novel zero moment point (ZMP) tracking control strategy using a disturbance observer (DOB) in the presence of ground slope change for balance control of an android robot. With regard to conventional ZMP controls, many researchers have studied ZMP tracking control strategies using an inverted pendulum model on flat level ground, and they have solved a slow response problem of nonminimum phase systems by using suitable feedforward motions called walking patterns. However, the conventional methods lead to ZMP offset errors in the presence of ground slope change; it is hence necessary to quickly eliminate the ZMP offset errors to realize robust balance control. In this paper, we rapidly eliminate the ZMP offset errors through a DOB using a model inversion for robust balance control in the presence of ground slope change. In particular, a dynamic model that uses the projected center of mass (CoM) position on the ground is additionally used as an output to solve a problem that generates an unstable pole during model inversion. Finally, the proposed control strategy is verified through MATLAB simulations and experiments using a real android leg.

scholarly journals A Novel Balance Control Strategy Based on Enhanced Stability Pyramid Index and Dynamic Movement Primitives for a Lower Limb Human-Exoskeleton System

2021 ◽  
Vol 15 ◽  
Author(s):  
Fashu Xu ◽  
Jing Qiu ◽  
Wenbo Yuan ◽  
Hong Cheng
Keyword(s):  
Control Strategy ◽  
Lower Limb ◽  
Balance Control ◽  
Control Strategies ◽  
Center Of Mass ◽  
Movement Primitives ◽  
Dynamic Movement ◽  
Cord Injury ◽  
Dynamic Movement Primitives ◽  
Enhanced Stability

The lower limb exoskeleton is playing an increasing role in enabling individuals with spinal cord injury (SCI) to stand upright, walk, turn, and so on. Hence, it is essential to maintain the balance of the human-exoskeleton system during movements. However, the balance of the human-exoskeleton system is challenging to maintain. There are no effective balance control strategies because most of them can only be used in a specific movement like walking or standing. Hence, the primary aim of the current study is to propose a balance control strategy to improve the balance of the human-exoskeleton system in dynamic movements. This study proposes a new safety index named Enhanced Stability Pyramid Index (ESPI), and a new balance control strategy is based on the ESPI and the Dynamic Movement Primitives (DMPs). To incorporate dynamic information of the system, the ESPI employs eXtrapolated Center of Mass (XCoM) instead of the center of mass (CoM). Meanwhile, Time-to-Contact (TTC), the urgency of safety, is used as an automatic weight assignment factor of ESPI instead of the traditional manual one. Then, the balance control strategy utilizing DMPs to generate the gait trajectory according to the scalar and vector values of the ESPI is proposed. Finally, the walking simulation in Gazebo and the experiments of the human-exoskeleton system verify the effectiveness of the index and balance control strategy.

2A1-I01 Elucidation of Joint Coordination with UCM Analysis during Dart Throwing Motion in Healthy People(Mobiligence and Embodiment)

2013 ◽  
Vol 2013 (0) ◽  
pp. _2A1-I01_1-_2A1-I01_4
Author(s):  
Junki NAKAGAWA ◽  
AN Qi ◽  
Yuki ISHIKAWA ◽  
Hiroyuki OKA ◽  
Hiroshi YAMAKAWA ◽  
...  
Keyword(s):  
Healthy People ◽  
Joint Coordination ◽  
Dart Throwing ◽  
Throwing Motion

scholarly journals Modal Decoupled Dynamics Feed-Forward Active Force Control of Spatial Multi-DOF Parallel Robotic Manipulator

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Xinjian Niu ◽  
Chifu Yang ◽  
Bowen Tian ◽  
Xiang Li ◽  
Junwei Han
Keyword(s):  
Control Strategy ◽  
Force Control ◽  
Parallel Mechanism ◽  
Control Method ◽  
Intelligent System ◽  
Joint Space ◽  
Active Force ◽  
Feed Forward ◽  
Electric Actuator ◽  
Active Force Control

According to the parallel mechanism theory, this paper proposes a novel intelligent robotic spine brace for the treatment of scoliosis. Nevertheless, this type of parallel mechanism has the following disadvantages: strong dynamic coupling in task space or joint space, adverse effect of system’s gravity, and lower response frequency in roll and pitch orientations, which seriously affect the performance of the system. In order to solve those boring problems, this paper presents a novel active force control structure, modal space dynamic feed-forward (MSDF) force control strategy. Besides, this paper expresses the intelligent robotic brace system model including the dynamic and kinematic models and the electric actuator model with Kane strategy. The stability of the intelligent system with the novel control strategy is proved. In order to evaluate the performance of the presented MSDF force control method, this paper builds the parallel mechanism experimental platform. It can be seen from experimental results that the proposed motion control method solves these boring problems well.

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