Coordination Control Research Articles

Interlimb coordination is not strictly controlled during walking

In human walking, the left and right legs move alternately, half a stride out of phase with each other. Although various parameters, such as stride frequency and length, vary with walking speed, the antiphase relationship remains unchanged. In contrast, during walking in left-right asymmetric situations, the relative phase shifts from the antiphase condition to compensate for the asymmetry. Interlimb coordination is important for adaptive walking and we expect that interlimb coordination is strictly controlled during walking. However, the control mechanism remains unclear. In the present study, we derived a quantity that models the control of interlimb coordination during walking using two coupled oscillators based on the phase reduction theory and Bayesian inference method. The results were not what we expected. Specifically, we found that the relative phase is not actively controlled until the deviation from the antiphase condition exceeds a certain threshold. In other words, the control of interlimb coordination has a dead zone like that in the case of the steering wheel of an automobile. It is conjectured that such forgoing of control enhances energy efficiency and maneuverability. Our discovery of the dead zone in the control of interlimb coordination provides useful insight for understanding gait control in humans.

Enhanced Hand–Eye Coordination Control for Six-Axis Robots Using YOLOv5 with Attention Module

Utilizing machine vision technology based on YOLOv5, a six-axis robot can quickly identify and classify targets. However, when the YOLOv5 model is used for the recognition and grasping of small workpieces, issues such as low precision and missed detections frequently occur. This paper proposes an enhanced object recognition algorithm, integrating a CBAM attention module and an improved loss function into YOLOv5 to control the hand–eye coordination of the six-axis robot during grasping. The CBAM attention module is incorporated into the backbone network of YOLOv5 to enhance its feature extraction capabilities, while the original loss function is modified to accelerate convergence and improve regression accuracy. An experimental platform for six-axis robot hand–eye coordination grasping was built, and grasping experiments were conducted. The proposed method significantly improves the robot’s grasping accuracy, with a 99.59% mAP0.5 and a 90.83% successful grasping rate, effectively addressing the challenges of low accuracy and missed detections in traditional systems.

Hybrid force-position coordinated control of a parallel mechanism with the number of redundant actuators equal to its DOF

To address the demands for precision and load-bearing capacity in the installation of building panels, a hybrid force-position driven robot with redundant actuation has been developed. The mechanical performance of this robot is primarily governed by its central parallel mechanism, which is equipped with redundant actuators matching the degrees of freedom. Non-redundant and redundant actuators are respectively responsible for position and force control. The inclusion of redundant force-driven joints has increased the internal coupling within the mechanism. To enhance the coordination between position and force control, a hybrid synchronized control method based on cross-coupling has been proposed. Initially, kinematic and dynamic models of the parallel structure were established. Under predefined trajectories, the theoretical inputs for each actuator were calculated using inverse kinematics and dynamics. Subsequently, employing the principle of cross-coupling, the torque output from the position actuators was used as feedback. This feedback was processed by a synchronized coordination controller to adjust the output force of the redundant force-driven joints. By adjusting the output force of the redundant actuators, the torque burden on the position actuators was effectively reduced, thereby enhancing the precision of position control. Additionally, under the same load conditions, smaller power actuators could be utilized for position control, reducing the overall weight of the robot and improving its load-to-weight ratio. To validate the effectiveness of the proposed control strategy, a robotic simulation environment was established. The simulation results demonstrated significant reductions in the average torque required by the position actuators across three different trajectories, with reductions of 91.43%, 54.56%, and 80.6% respectively. Finally, the load-bearing capacity and the load-to-weight ratio of the prototype were assessed. Experimental results confirmed that the prototype achieved a load-to-weight ratio of 15.83%, validating the effectiveness of the hybrid synchronized control method based on cross-coupling.

NHẬN THỨC VỀ NGUYÊN TẮC “QUYỀN LỰC NHÀ NƯỚC LÀ THỐNG NHẤT, CÓ SỰ PHÂN CÔNG, PHỐI HỢP VÀ KIỂM SOÁT GIỮA CÁC CƠ QUAN NHÀ NƯỚC TRONG VIỆC THỰC HIỆN CÁC QUYỀN LẬP PHÁP, HÀNH PHÁP, TƯ PHÁP” CỦA NHÀ NƯỚC PHÁP QUYỀN XÃ HỘI CHỦ NGHĨA VIỆT NAM

One of the characteristics of the Vietnamese socialist rule-of-law state that has been identified by our Party and stipulated by the Constitution as a basic principle of the organization and operation of the state apparatus is: “State power is unified, with clear division, close coordination and effective control among state agencies in the exercise of legislative, executive and judicial powers”. This article analyzes and explains this basic and important characteristic contribute to perfecting theory and unifying awareness of the Vietnamese socialist rule of law state.

Characterizing upper limb motor dysfunction with temporal and spatial distribution of muscle synergy extracted from high-density surface electromyography.

Objective.To promote the development of objective and comprehensive motion function assessment for patients, based on high-density surface electromyography (HD-sEMG), this study investigates the temporal and spatial variations of neuromuscular activities related to upper limb motor dysfunction.Approach.Patients with unilateral upper limb motor dysfunction and healthy controls were enrolled in the study. HD-sEMG was collected from both arms while they were performing eight hand and wrist movements. Muscle synergies were extracted from the HD-sEMG. Symmetry of bilateral upper limb synergies and synergy differences between motions were proposed as spatial indicators to measure alterations in synergy spatial distribution. Additionally, as a temporal characteristic, the correlation of bilateral upper limb activation coefficient was proposed to describe the coordination control of the central nervous system. All temporal and spatial indicators were compared between patients and healthy subjects.Main results.The patients showed a significant decrease (p< 0.05) in the symmetry of bilateral upper limb synergy spatial distribution and correlation of bilateral upper limb activation coefficient. Patients with motor dysfunction also showed an increase in synergy similarity between motions, indicating altered spatial distribution of muscle synergies.Significance.These findings provide valuable insights into specific patterns associated with motor dysfunction, informing motor function assessment, and guiding targeted interventions and rehabilitation strategies for neurologically disordered patients.

Temporal localization of upper extremity bilateral synergistic coordination using wearable accelerometers.

The human upper extremity is characterized by inherent motor abundance, allowing a diverse array of tasks with agility and adaptability. Upper extremity functional limitations are a common sequela to Stroke, resulting in pronounced motor and sensory impairments in the contralesional arm. While many therapeutic interventions focus on rehabilitating the weaker arm, it is increasingly evident that it is necessary to consider bimanual coordination and motor control. Participants were recruited to two groups differing in age (Group 1 (n=10): 23.4 ±2.9 years, Group 2 (n=10): 55.9 ±10.6 years) for an exploratory study on the use of accelerometry to quantify bilateral coordination. Three tasks featuring coordinated reaching were selected to investigate the acceleration of the upper arm, forearm, and hand during activities of daily living (ADLs). Subjects were equipped with acceleration and inclination sensors on each upper arm, each forearm, and each hand. Data was segmented in MATLAB to assess inter-limb and intra-limb coordination. Inter-limb coordination was indicated through dissimilarity indices and temporal locations of congruous movement between upper arm, forearm, or hand segments of the right and left limbs. Intra-limb coordination was likewise assessed between upper arm-forearm, upper arm-hand, and forearm-hand segment pairs of the dominant limb. Acceleration data revealed task-specific movement features during the three distinct tasks. Groups demonstrated diminished similarity as task complexity increased. Groups differed significantly in the hand segments during the buttoning task, with Group 1 showing no coordination in the hand segments during buttoning, and strong coordination in reaching each button with the upper arm and forearm guiding extension. Group 2's dissimilarity scores and percentages of similarity indicated longer periods of inter-limb coordination, particularly towards movement completion. Group 1's dissimilarity scores and percentages of similarity indicated longer periods of intra-limb coordination, particularly in the coordination of the upper arm and forearm segments. The Expanding Procrustes methodology can be applied to compute objective coordination scores using accessible and highly accurate wearable acceleration sensors. The findings of task duration, angular velocity, and peak roll angle are supported by previous studies finding older individuals to present with slower movements, reduced movement stability, and a reduction of laterality between the limbs. The theory of a shift towards ambidexterity with age is supported by the finding of greater inter-limb coordination in the group of subjects above the age of thirty-five. The group below the age of thirty was found to demonstrate longer periods of intra-limb coordination, with upper arm and forearm coordination emerging as a possible explanation for the demonstrated greater stability.

A Direct Contour Control Method for Free-Form Surface Machining Trajectories Based on Coordinate Transformation

The requirement for high-speed and high-precision contouring with free-form surfaces in the CNC machining process is increasing. The contour error is an essential criterion for the quality of CNC machining. For the problem of contour error control, the present research is mainly based on position tracking, and the control method directly aiming at contour control has not been well studied. This paper proposed a new type of coordinate transformation-based direct contour control method (CT-DCC) for free-form surface machining trajectories. By real-time monitoring of the contour error and the foot point of the free-form parametric trajectory, the contouring task is decomposed into the contour error control task in the normal direction and the velocity control problem in the feed direction. Using coordinate transformation, the output commands of the two tasks are converted to the axial motion command. CT-DCC completely eliminates position tracking in the traditional control to achieve direct control of the contour error, which provides a new solution for the contour control problem of free-form surface machining. Both the axial velocity control and the axial torque control-based CT-DCC scheme were studied, and the two-axis and three-axis direct contour controllers were tested. The simulation and experiment results show the feasibility of the proposed method.

Resilient Neuroadaptive Distributed Fixed-Time Attitude Coordination Control for Multiple Spacecraft.

This work studies the attitude coordination tracking problem for multiple spacecraft with consideration of unintended faults (communication link faults and actuator faults), inertial uncertainties, and external disturbances under a directed communication graph. A resilient neuroadaptive distributed fixed-time control scheme is investigated to solve this challenging problem. First, an improved adaptive distributed observer is established for followers to estimate the states of the leader when considering communication link faults. The proposed observer improves the resilience against communication link faults. Subsequently, to further cope with the problem of actuator faults, inertial uncertainties, and external disturbances, based on the proposed observer and the technique of adding a power integrator, a neuroadaptive distributed fixed-time attitude coordination controller is developed. Unlike the existing controllers, the proposed one requires less information when dealing with faults and lumped uncertainties, and has a lower-computational cost. Moreover, the fixed-time stability of the closed-loop system is ensured under the designed resilient neuroadaptive distributed control scheme. Finally, comparative simulations are carried out to manifest the effectiveness of the investigated coordination control method.

Intelligent mission planning for autonomous distributed satellite systems

System autonomy plays a critical role in the success of next generation Distributed Satellite Systems (DSS) mission architectures, enabling the inference of external and internal environment conditions to support system adaptation in unexpected and unfamiliar situations. Artificial Intelligence (AI) based techniques show promise in achieving this desired self-adaptive capability by offering on-board predictive real time analytics, supporting an evolution towards Trusted Autonomous Satellite Operations (TASO). In parallel, TASO requires an evolution of the control and coordination of increasingly autonomous large scale DSS, achieved in the design and operation of intelligent Mission Planning Systems (MPS). In this paper, we focus on intelligent mission planning functionality problem utilising a distributed ant colony optimisation approach to achieve local task allocation and platform coordination. The approach is implemented in the context of a Space-Based Space Surveillance (SBSS) mission architecture that considers self-adaptive capabilities, global coordination and supervisory control aspects. The effectiveness of the approach is shown, demonstrating that the proposed solution based on metaheuristics supports an efficient and pervasive SBSS capability.

A Coordination Control Method for Current Stress Reduction in High-Frequency Link Matrix Converter

A Coordination Control Method for Current Stress Reduction in High-Frequency Link Matrix Converter

Optimization research on control strategies for photovoltaic energy storage systems considering multi-mode operation

In this paper, a selective input/output strategy is proposed for improving the life of photovoltaic energy storage (PV-storage) virtual synchronous generator (VSG) caused by random load interference, which can sharply reduce costs of storage device. The strategy consists of two operating modes and a power coordination control method for the VSGs. Firstly, a selective VSG input strategy is proposed based on the magnitude of disturbances, a method of offline solving model equation is used for determine the VSG input time. An online method is used for matching the disturbance frequency variations, which enables a selective VSG startup method, allowing the grid to prioritize the utilization of the generator's physical inertia. Secondly, a dynamic VSG exit strategy is developed based on dynamic frequency characteristics to prevent secondary oscillations in the frequency recovery phase of the PV-storage VSG following grid disturbances. This strategy is crucial as grid variations may affect energy storage lifespan and reduce frequency recovery speed. Finally, the proposed approach is validated for correctness and effectiveness through computer simulations and semi-physical experiments using the NI-PXI + LabVIEW platform. Through the above optimization and research, the selective start of VSG is realized, the energy storage life is improved, the capacity of charge and discharge cycles is reduced by 37.82 % compared with the strategy without investment and withdrawal, and the life loss in the secondary charge and discharge process of PV-storage VSG is avoided, which is conducive to frequency recovery.

Dynamic control of His-hemin coordination and catalysis by reversible host–guest inclusion in peptide assemblies

Dynamic self-assembly has significant implications in the regulation of the enzyme activities. In this study, we present a histidine-based enzyme-mimicking catalyst, formed by the self-assembly of carefully-engineered FH-based short peptides with hemin, showcasing switchable catalytic activity of hemin due to externally induced reversible inclusion of a cucurbit[7]uril-peptide hybrid. 1H NMR, ITC and theoretical simulation are employed to examine the binding affinity between the guest and host components, and UV–vis spectra are used to investigate changes in the hemin coordination environment. The histidine segment of the short peptide can be partially shielded by the cucurbituril and released following addition of the azo compound, leading to a decrease and subsequent restoration of the histidine-hemin coordination affinity and hemin activity. The photoisomeriziable nature of the azo compound enabled the activation of FHH/hemin activity to be switched on and off by exposure to different wavelengths of light. During the operation, the Phe residue remained within the cucurbituril, allowing reversible inclusion and exposure of the histidine residues. The hemin stayed connected to FHH/cucurbit[7]uril hybrid, preventing the severe aggregation of hemin and irreversible deactivation. This work may provide insights into engineering the dynamic behaviors of the cofactor-dependent catalytic assemblies.

Dynamic mater-slave control strategy for transient coordination of inverter based microgrids under asymmetric faults

The ever-expanding inverter-based microgrids (MGs) require the grid-forming distributed renewable energy resources (DERs) to enhance the system safety. However, the different types of grid-forming DERs are prone to have transient conflicts with each other under short circuit faults, leading to unexpected outage or even system collapse. The fast response and poor overcurrent capability of DERs make transient coordination a challenge. This paper proposes a dynamic master–slave architecture for transient coordination control in islanded MGs under asymmetric faults. A dynamic reconfigurable voltage reference unit (DVRU) is designed according to the real faults. In this manner, the other DERs could comply with this DVRU to achieve both system voltage support, inrush current restraining, and power oscillation suppression. It is action signals instead of phase signals need to be transferred by the communication bus with the proposed local fault current differential time delay method (FCDDM). Thus, the low-bandwidth and the enhanced robust communication could be met under transient state. Additionally, the feasibility of the proposed method to combined with relay protection is analyzed. Finally, case study results on islanded MGs consisting of various grid-forming and grid-following DERs demonstrate the effectiveness and robustness of the proposed method under short circuit faults as well as communication failures.

The Coordinated Control Strategy of Engine Starting Process in Power Split Hybrid Electric Vehicle Based on Load Observation

During the process of moving, the power splitting hybrid vehicle is required to start the engine to transfer from pure electric mode to hybrid drive mode. According to the structural characteristics of the system, the engine starting process was divided into four stages, the engine starting process was established, and a multi-stage engine starting coordination control strategy was designed. In the engine reverse-drag process, the coordination control strategy was transformed into the optimal rotation rate tracker problem. In order to solve the load torque required in the tracking problem, a reduced-order observer was designed. Finally, the validity of the coordination control strategy was verified on the simulation platform of the electro-mechanical composite transmission system. The feasibility of the coordination control strategy was verified by hardware-in-the-loop simulation. The results show that the engine start coordination control strategy could achieve steady and fast engine start control. The maximal impact of the whole vehicle is reduced from 30 to 2.5 m/s3.

Velocity‐free attitude coordination control of multiple rigid spacecraft with practical predefined‐time convergence

Velocity‐free attitude coordination control of multiple rigid spacecraft with practical predefined‐time convergence

Ballet practice improves neuromuscular and biomechanical responses to an unexpected standing-slip in older adults.

Falls and fall-induced injuries are common and consequential in older adults. Ballet emphasizes full-body coordination, leg strength, and postural control. However, it remains unknown whether ballet can indeed reduce falls in older adults. This study examined biomechanical and neuromuscular responses of older recreational ballet dancers to an unexpected standing-slip. Twenty older ballet dancers (17 females, 3 males) and 23 age- and sex-matched nondancers (19 females, 4 males) were exposed to an unexpected slip during treadmill standing. The slip-faller rate was the primary outcome. The secondary outcomes were kinematic measurements, including dynamic gait stability, slip distance, and recovery stepping performance (step latency, duration, length, and speed). The tertiary outcome was the electromyography latency of leg muscles (bilateral tibialis anterior, medial gastrocnemius, rectus femoris, and biceps femoris). Fewer dancers fell than nondancers after the standing-slip (45% vs. 83%, P = 0.005, d = 0.970). Dancers displayed better stability at recovery foot liftoff (P = 0.006) and touchdown (P = 0.012), a shorter step latency (P = 0.020), shorter step duration (P = 0.011), faster step speed (P = 0.032), and shorter slip distance (P = 0.015) than nondancers. They also exhibited shorter latencies than nondancers for the standing leg rectus femoris (P = 0.028) and tibialis anterior (P = 0.002), and the stepping leg biceps femoris (P = 0.031), tibialis anterior (P = 0.017), and medial gastrocnemius (P = 0.030). The results suggest that older ballet dancers experience a lower fall risk and are more stable than nondancers following an unexpected standing-slip. The greater stability among dancers could be attributed to more biomechanically effective recovery stepping, possibly associated with the ballet-induced neuromuscular benefit-an earlier leg muscle activation.NEW & NOTEWORTHY This is the first study to examine how older ballet dancers respond to an unexpected external slip perturbation while standing. The results suggest that older ballet dancers experience a reduced fall risk after the slip than their nondancer counterparts. The lower fall risk can be accounted for by dancers' quicker neuromuscular reactions to the slip that result in a more effective recovery step and thus higher stability against backward falls due to the slip.

The Coordination Control Strategy for Improving Systems Frequency Stability Based on HVDC Quota Power Support

This paper aims to improve the recovery characteristics of the receiving grid during DC blocking failures through DC emergency power support, revealing the mechanism of improving the power angle stability of the receiving grid through timely DC power increase and decrease. Based on the transmission pattern of “north-to-south power transmission” in a certain provincial power grid, the actual maximum long-term overload capacity of multiple DC lines is calculated, considering multiple constraints such as the strength of the receiving grid, the stability limit of AC evacuation channels, and DC overload capacity. A multi-DC emergency power support strategy after DC blocking is developed, avoiding the risk of AC transmission channel overload caused by power flow transfer, reducing the impact of large-capacity DC blocking and inappropriate DC power increases on the receiving grid, and achieving coordination between AC and DC systems. The effectiveness of the proposed strategy is verified through simulation.

Stereodivergency in Copper-Catalyzed Borylative Difunctionalizations: The Impact of Boron Coordination.

A reagent-controlled diastereodivergent copper-catalyzed borylative difunctionalization is reported. The formation of Lewis adducts that guide selectivity is commonly invoked in organic reaction mechanisms. Using density functional theory calculations, we identified BpinBdan as a sterically similar and less Lewis acidic alternative to B2pin2. Using a newly developed borylative aldol domino reaction as the proof-of-concept, we demonstrate a change in stereochemical outcome by a simple change of borylating reagent-B2pin2 affords the diastereomer associated with coordination control while BpinBdan overturns this mode of binding. We show that this strategy can be generalized to other scaffolds and, more importantly, that BpinBdan does not alter the diastereomeric outcome of the reaction when coordination is not involved. BpinBdan can be viewed as a mechanistic probe for coordination in future copper-catalyzed borylation reactions.

The Effect of Neuromuscular Fatigue on the Spatiotemporal Coordination of Rowing

Within rowing, lower back disorders (LBDs) are common, but the mechanisms underpinning LBDs are poorly understood. Considering this, it is essential to understand how coordination and motor control change under different constraints such as ergometer rowing and fatigue. This can help better inform movement features linked to LBDs. Measurement of the continuous relative phase (CRP) is a method used to quantify body segment and joint coordination, as CRP measures the spatiotemporal control of multi-joint movement. The purpose of this study was twofold: to examine the general spatiotemporal coordination aspects of ergometer rowing in an unfatigued state, and to quantify how the spatiotemporal coordination of a rowing movement changes in response to a fatigue-inducing rowing trial. Wearable IMUs monitored 20 participants’ movement during a 2000 m ergometer row. The Borg-10 Rating of Perceived Exertion (RPE) scale was used to quantify perceived fatigue. Despite significant RPE increases across all athletes, the spatiotemporal coordination of rowing revealed prevailing strategies for the lumbar spine and lower extremity but no significant effects (α = 0.05) of fatigue on CRP outcomes (MARP, DP), cross-correlation lag (RXY), or range of motion. These findings provide further insight into rowing movements and support the idea that heterogeneous responses to fatigue may exist, requiring further study.

Frequency Coordination Control Strategy for Large-Scale Wind Power Transmission Systems Based on Hybrid DC Transmission Technology with Deep Q Network Assistance

Wind power is currently the most mature representative of sustainable energy generation technology, which has been developed and utilized on a large scale worldwide. The random and fluctuating nature of wind power output poses a threat to the secure and stable operation of the system. Consequently, the transmission of wind power has garnered considerable attention as a crucial factor in mitigating the challenges associated with wind power integration. In this paper, an artificial-intelligence-aided frequency coordination control strategy applicable to wind power transmission systems based on hybrid DC transmission technology is proposed. The line commutated converter (LCC) station at the sending end implements the strategy of auxiliary frequency control (AFC) and automatic generation control (AGC) to cooperate with each other in order to assist the system frequency regulation. The AFC controller is designed based on the variable forgetting factor recursive least squares (VFF-RLS) algorithm for system identification. First, the VFF-RLS algorithm is used to identify the open-loop transfer function of the system. Then, the AFC controller is designed based on the root locus method to achieve precise control of the system frequency. The DC line power modulation quantity is introduced in the AGC to automatically track the active power fluctuation and frequency deviation of the system. The AGC utilizes the classical proportional-integral (PI) control. By selecting the integrated time absolute error (ITAE) performance index to construct the reward function, and using a deep Q-network (DQN) for controller parameter optimization, it achieves improved regulation performance for the AGC. The voltage source converter (VSC) station at the receiving end implements an adaptive DC voltage droop control (ADC)strategy. Finally, the effectiveness and robustness of the proposed frequency control strategy are verified through simulation experiments.