Closed-loop Mechanism Research Articles

Exploring the nature of Parkinsonian rest tremor and the effects of common treatments on it: Stochastic process or chaotic behavior?

IntroductionParkinsonian rest tremor results in an involuntary oscillating movement with variable amplitude and frequency. The nature of rest tremor is somehow complicated and also the effects of the treatments remained obscure. Research goalThe main objective of this study is to determine the dynamic characteristic of the Parkinsonian tremor using nonlinear data processing tools including phase space reconstruction, Delay Vector Variance (DVV), delta-epsilon analysis, Higuchi fractal dimension (HFD) and approximate entropy (ApEn). ResultsDVV and delta-epsilon analyses illustrate that tremor behavior is more similar to chaotic systems. Effective treatment alters its behavior toward stochastic processes. Based on the analysis, the value of the HFD for untreated tremor is around 1.7 and effective treatments reduces the value to about 1.1. In addition, ApEn of tremor signals is around 1.3 and by effective treatment it dips to 0.7. What is more, results of statistical tests for HFD and ApEn reveals that effective treatments lead to significant differences in the dynamical behavior of tremor in subjects with high amplitude (p < 0.05). ConclusionsTo sum up, a combination of stochastic, periodic and chaotic dynamics is intrinsically present in tremor dynamic and as the severity of the disease increases, chaotic dynamics strengthen. Effective treatments weaken the chaotic dynamic, and therefore, the stochastic behavior becomes more noticeable and dominant. These results can be useful for tracking the disease progress and determining an appropriate dose of a drug for each patient. Moreover, our findings could lead to the development of a new tremor relief closed loop mechanism based on chaos to stochastic ratio.

Integrated cardiorespiratory system model with short timescale control mechanisms.

A compartmental model of the cardiorespiratory system featuring pulsatile blood flow and gas transport, as well as closed loop mechanisms of cardiorespiratory regulation is presented. Short timescale regulatory action includes baroreflex, peripheral and central chemoreflex feedback. The cardiorespiratory model is composed by compartments to describe blood flow and gas exchange in the major systemic and pulmonic regions. The control systems include formulations to afferent activity of arterial baroreceptor and peripheral and central chemoreceptors. Simulations described here include situations of hypoxia, hypercapnia, and hemorrhage. The overall responses of our simulations agree with physiological (experimental) and theoretical data. Our results suggest that the present model could be used to further understand the interplay among major regulatory mechanisms in the functioning of the cardiovascular and respiratory systems in cases of normal and abnormal physiological conditions.

Knowledge transfer strategies and practices for higher education institutions

PurposeThis study aims to identify effective strategies and practices for higher education institutions (HEIs) to enhance their knowledge recipients’ knowledge absorptive capacity.Design/methodology/approachQuestionnaire surveys and interviews were conducted to examine the effectiveness of a knowledge transfer (KT) project and these were administered by HEIs in Hong Kong. Pre- and post-test questionnaire surveys with t-tests were used to evaluate changes in the knowledge absorptive capacity of 1,014 participants from 20 schools. Qualitative interviews were conducted to investigate school leaders’ perception of the effectiveness of the KT strategies.FindingsResults revealed significant differences between the pre- and post-tests in all the elements of absorptive capacity. The processes of knowledge acquisition, contextualisation, internalisation and externalisation in a closed-loop mechanism were identified as effective KT strategies. Conducting training programmes, workshops, consultations, work-based studies and presentation seminars were found to be effective KT practices to support the recipients in acquiring, contextualising, internalising and externalising knowledge.Practical implicationsHEIs should provide consultative support to recipients by conducting work-based studies and presentations to enhance their knowledge absorptive capacities.Originality/valueThis study contributes empirical evidence to validate the application of Liyanage et al.’s (2009) KT model to HEIs’ KT model for the purpose of designing KT activities and enhancing the absorption capacities of the recipients. This research contributes an empirical closed-loop KT model, effective KT strategies and practices for HEIs to support their knowledge recipients so that they can internalise the acquired knowledge.

A New Metamorphic Parallel Leg Mechanism with Reconfigurable Moving Platform

This paper proposes the concept of full configuration state of metamorphic mechanism. Based on the concept, the configuration synthesis principle of metamorphic parallel mechanism is put forward. Firstly, a metamorphic parallel mechanism in full configuration state is synthesized, and then full configuration state evolves into a specific configuration state by increasing constraints or decreasing degrees of freedom. A reconfigurable moving platform based on the triple symmetric Bricard spatial closed-loop mechanism with a single degree of freedom is proposed. Based on this, a new method for switching motion configuration states of the metamorphic parallel mechanism is constructed. According to the configuration synthesis principle presented above, a novel metamorphic parallel mechanism that can switch between three- and four-degree-of-freedom is synthesized, and then the triple symmetric Bricard spatial closed-loop mechanism is used as the reconfigurable moving platform (that is, the reconfigurable foot of a walking robot) of the metamorphic mechanism, and thus, a novel metamorphic parallel leg mechanism is created. The screw theory is used to verify the degrees of freedom of the new type of metamorphic parallel leg. The proposed metamorphic parallel leg mechanism is expected to improve flexibility and adaptability of walking robots in unstructured environment.

Optimization of the Rotational Asymmetric Parallel Mechanism for Hip Rehabilitation With Force Transmission Factors

Abstract An asymmetric three-degree-of-freedom parallel mechanism is adopted in rehabilitation robots for assisting patients suffering from stroke or trauma in the hip. It is necessary to keep its kinematic singularity out of the workspace of human normal gait and increase the output power efficiency. Therefore, a novel method is proposed to optimize geometrical parameters of the mechanism. To describe the kinematic singularity in a better way, the improved force transmission indexes based on previous methods are proposed using the reciprocal product and mobility condition of the closed-loop mechanism. The indexes mainly represent the force transmission performance of unactuated parts of subchains and moving platform. Together with the driving force transmission indexes and geometrical constraints, the multiobjective optimization model is established. The differential evolution algorithm, which is widely applied to mechanism optimization, is used to achieve optimal results. The Jacobian matrix singularity and output power efficiency along giving trajectory before and after optimization are compared to verify the effectiveness of the method.

Blood glucose concentration control for type 1 diabetic patients: a multiple‐model strategy

In this study, a multiple-model strategy is evaluated as an alternative closed-loop method for subcutaneous insulin delivery in type 1 diabetes. Non-linearities of the glucose-insulin regulatory system are considered by modelling the system around five different operating points. After conducting some identification experiments in the UVA/Padova metabolic simulator (accepted simulator by the US Food and Drug Administration (FDA)), five transfer functions are obtained for these operating points. Paying attention to some physiological facts, the control objectives such as the required settling time and permissible bounds of overshoots and undershoots are determined for any transfer functions. Then, five PID controllers are tuned to achieve these objectives and a bank of controllers is constructed. To cope with difficulties of the presence of delays in subcutaneous blood glucose (BG) measuring and in administration of insulin, a glucose-dependent setpoint is considered as the desired trajectory for the BG concentration. The performance of the obtained closed-loop glucose-insulin regulatory system is investigated on the in silico adult cohort of the UVA/Padova metabolic simulator. The obtained results show that the proposed multiple-model strategy leads to a closed-loop mechanism with limited hyperglycemia and no severe hypoglycemia.

Portable Forceps Manipulator with Closed Loop Mechanism using Gimbal-mounted Parallel Linkage for Endoscopic Surgery

Portable Forceps Manipulator with Closed Loop Mechanism using Gimbal-mounted Parallel Linkage for Endoscopic Surgery

Research and Application of Key Technology of Data-Driven Intelligent Manufacturing of Electronic Components

With the development of electronic equipment towards multi-function, high performance and miniaturization, the assembly density and complexity of electronic components become higher and higher. For the manufacturing characteristics of electronic components in many varieties, small batch and mixed production line, this paper uses intelligent manufacturing technology based on industrial big data, puts forward implementation architecture of electronic components digital workshop, explores the “perception - analysis - decisions” closed-loop mechanism of all data of manufacturing process of electronic component, sets up network security platform for industrial control system which ensures workshop operate transparently and safely. The necessity and feasibility of landing of data-driven intelligent workshop are verified by an application example of digital workshop of radar core microwave components, which effectively improves the production efficiency and workshop management level.

Considering Link Flexibility in the Dynamic Synthesis of Closed-Loop Mechanisms: A General Approach

Abstract This paper has focused on the dynamic analysis of mechanisms with closed-loop configuration while considering the flexibility of links. In order to present a general formulation for such a closed-loop mechanism, it is allowed to have any arbitrary number of flexible links in its chain-like structure. The truncated assumed modal expansion technique has been used here to model link flexibility. Moreover, due to the closed nature of the mentioned mechanism, which imposes finite holonomic constraints on the system, the appearance of Lagrange multipliers in the dynamic motion equations obtained by Lagrangian formulation is unavoidable. So, the Gibbs-Appell (G-A) formulation has been applied to get rid of these Lagrange multipliers and to ease the extraction of governing motion equations. In addition to the finite constraints, the impulsive constraints, which originate from the collision of system joints with the ground, have also been formulated here using the Newton's kinematic impact law. Finally, to stress the generality of the proposed formulation in deriving and solving the motion equations of complex closed-loop mechanisms in both the impact and non-impact conditions, the computer simulation results for a mechanism with four flexible links and closed-loop configuration have been presented.

A novel chemosensor for Fe3+ based on open–closed-loop mechanism and imaging in living cells

In this paper, a novel chemosensor (named L1) for Fe3+ based on the rhodamine 6G and o-vanillin has been synthesized, which can selectively recognize Fe3+. The L1 solution showed a distinguishable colour change by naked eye, and the fluorescence turns on response after the addition of Fe3+. In addition, the experimental results showed that the spirocyclic of L1 was opened by cooperation between L1 and Fe3+, and then the fluorescence emission after excitation of the mixture solution was detected with the change in solution colour. The complexation coefficient of L1 towards Fe3+ was 1:1. Furthermore, L1 for Fe3+ sensing had a remarkable low detection limit of 427 nM (UV) and 130 nM (fluorescence), which is far below the drinking water standards (0.3 mg/L) of China. Meanwhile, the in vivo imaging and cell viability assay experiments demonstrated that L1 could be used for sensing Fe3+ in vivo.

An Approach to Modeling Closed-Loop Kinematic Chain Mechanisms, Applied to Simulations of the da Vinci Surgical System

Open-sourced kinematic models of the da Vinci Surgical System have previously been developed using serial chains for forward and inverse kinematics. However, these models do not describe the motion of every link in the closed-loop mechanism of the da Vinci manipulators; knowing the kinematics of all components in motion is essential for the foundation of modeling the system dynamics and implementing representative simulations. This paper proposes a modeling method of the closed-loop kinematics, using the existing da Vinci kinematics and an optical motion capture link length calibration. Resulting link lengths and DH parameters are presented and used as the basis for ROS-based simulation models. The models were simulated in RViz visualization simulation and Gazebo dynamics simulation. Additionally, the closed-loop kinematic chain was verified by comparing the remote center of motion location of simulation with the hardware. Furthermore, the dynamic simulation resulted in satisfactory joint stability and performance. All models and simulations are provided as an open-source package.

A Simple Approach to Enhance the Effectiveness of Passive Currents Balancing in an Interleaved Multiphase Bidirectional DC–DC Converter

This paper studies the high power density bidirectional dc–dc converter with interleaving, soft-switching, and near critical conduction mode (near-CRM) operation. Systematic design and control methods are proposed to enhance the effectiveness of passive currents balancing between multiple interleaved phases without using individual phase current feedbacks. This paper first analyzes the zero voltage turn- on operation, including the turn- off energy diversion by the added snubber capacitor and the turn- off resonance models. Second, the intrinsic inverse co-relation between the phase current deviation and the resulting effective duty cycles variation is quantitatively formulated and modeled as a closed-loop mechanism that balances the currents passively. Then, the design constraints of the system parameters including the snubber capacitance, dead time, and valley currents of the near-CRM mode are formulated to guarantee the effectiveness of counteracting the current unbalance. Finally, a variable switching frequency control is proposed to actively control the valley current and maintain the current balancing effectiveness throughout the operating range. An IGBT-based 20-kW three-phase interleaved prototype with the maximum efficiency of 99.1% is constructed to verify the proposed design and control methods.

Usefulness of INTELLiVENT-ASV for postoperative ventilator-associated pneumonia: a case report

BackgroundINTELLiVENT®-ASV (iASV) is a respiration mode on the Hamilton G5. The ventilator uses a closed-loop mechanism that automatically adjusts settings related to oxygenation and ventilation.Case presentationA 47-year-old man underwent reconstruction surgery with free musculocutaneous flap for tongue resection. After surgery, the patient entered the ICU, and the iASV, which automatically changed only the percent minute volume (%MV) in respiration mode, was selected. On the second day, ventilator-associated pneumonia (VAP) was diagnosed, and the antibiotic treatment was changed. Using the settings of the iASV, automated FiO2 and positive end-expiratory pressure (PEEP) control were added to the ventilator mode. The patient’s oxygenation was improved.ConclusionsIn a patient who developed VAP after surgery, ventilation was continued using iASV, and automated changes in PEEP and FiO2 settings were successfully made according to the open lung strategy, under short-staffed circumstances.

Kinematic and dynamic analysis of a serial manipulator with local closed loop mechanisms

This paper addresses the kinematic and dynamic modelling and analysis for a robot arm consisting of two hydraulic cylinders driving two revolute joints of the arm. The two cylinders and relevant links of the robot constitute two local closed kinematic chains added to the main robot mechanism. Therefore, the number of the generalized coordinates of the mechanical system is increased, and the mathematical modelling is more complex that requires a formulation of constraint equations with respect to the local closed chains. By using the Lagrangian formulation with Lagrangian Multipliers, the dynamic equations are first derived with respect to all extended generalized coordinates. Then a compact form of the dynamic equations is yielded by canceling the Multipliers. Since the obtained dynamic equations are expressed in terms of independent generalized coordinates which are selected according to active joint variables of the arm, the equations could be best suitable for control law design and implementation. The simulation of the forward and inverse kinematics and dynamics of the arm demonstrates the motion behavior of the robot system.

Elements of the theory of closed-loop mechanisms formed by rolling bodies without kinematic sliding

Elements of the theory of closed-loop mechanisms formed by rolling bodies without kinematic sliding

A Robust Indoor Localization System Integrating Visual Localization Aided by CNN-Based Image Retrieval with Monte Carlo Localization.

This paper proposes a novel multi-sensor-based indoor global localization system integrating visual localization aided by CNN-based image retrieval with a probabilistic localization approach. The global localization system consists of three parts: coarse place recognition, fine localization and re-localization from kidnapping. Coarse place recognition exploits a monocular camera to realize the initial localization based on image retrieval, in which off-the-shelf features extracted from a pre-trained Convolutional Neural Network (CNN) are adopted to determine the candidate locations of the robot. In the fine localization, a laser range finder is equipped to estimate the accurate pose of a mobile robot by means of an adaptive Monte Carlo localization, in which the candidate locations obtained by image retrieval are considered as seeds for initial random sampling. Additionally, to address the problem of robot kidnapping, we present a closed-loop localization mechanism to monitor the state of the robot in real time and make adaptive adjustments when the robot is kidnapped. The closed-loop mechanism effectively exploits the correlation of image sequences to realize the re-localization based on Long-Short Term Memory (LSTM) network. Extensive experiments were conducted and the results indicate that the proposed method not only exhibits great improvement on accuracy and speed, but also can recover from localization failures compared to two conventional localization methods.

Minimizing drum-shaped inaccuracy in high-speed wire electrical discharge machining after multiple cuts

Drum-shaped inaccuracy increases dramatically in high-speed wire electrical discharge machining (HS-WEDM) after multiple cuts when very thick workpiece (> 100 mm) are used. To tackle this problem, a positional change model of the wire electrode was established to analyze the main causes of the drum-shaped inaccuracy. In HS-WEDM, the conductivity of the working fluid is very high. As the workpiece thickness increases, the “leakage current” at the machining gap increases, and more energy is required for the trim cuts. In addition, to maintain stable trim cuts, a long pulse-on time is needed. As a result, the high discharge energy inevitably results in a large explosive force, which increases the wire bending deformation due to long durations under this force. To solve these problems, novel measures were taken in this study. First, an improved working fluid was proposed to reduce the conductivity so that the energy loss between the electrodes can be decreased. The discharge energy used for the trim cuts was diminished to reduce the impact of the discharge explosive force. Second, a short pulse-on time and a high peak current were utilized for the trim cuts to reduce the impulse from the effect of the discharge explosive force on the wire electrode. Third, a closed-loop tension mechanism was designed to increase the wire tension, thereby improving the stability and rigidity of wire electrode. Finally, the rigidity of wire electrode was further improved by utilizing a unique trim-cut method proposed in this study. The experimental results showed that the drum-shaped inaccuracy of a workpiece with a thickness of 150 mm was reduced to 10 μm from 25 μm after three cuts (one roughing cut and two finish/trim cuts) under normal machining and the quality and uniformity of the machined surface were improved.

Motion analysis of flexible spatial closed loop mechanism made of a certain thin elastic plate

Motion analysis of flexible spatial closed loop mechanism made of a certain thin elastic plate

Investigation on the impact of nongeometric uncertainty in dynamic performance of serial and parallel robot manipulators

Uncertainty in robot manipulations is a fundamental source of inaccuracy. Most nongeometric uncertainties is caused by the mechanical components of robot manipulators such as gear transmission systems and joints. This study integrates existing uncertainty models for practical applications of both three-degrees-of-freedom serial robot and parallel robot (closed-loop 5R mechanism). We first review the literature on uncertainty and existing methods for improving the precision of robot manipulation. For existing methods for uncertainty modeling: (1) the mathematical model of a harmonic drive considering kinematic error and compliance is derived; (2) joint clearance analysis that includes models of contact force and friction force is presented; (3) Archard’s wear model is used to estimate the effect of joint wear, based on which the geometry of joints is updated. Computer simulation is then used to demonstrate the application of the proposed method for serial and parallel robot manipulators. Simulations are used to examine the behavior of robot manipulators operating under uncertainty, with performance-evaluated positional error and trajectory error. The proposed method can provide some insight into nongeometric uncertainty in robot manipulations. The proposed methodology can be further used to improve the accuracy of robot manipulation under uncertainty by identifying uncertainty parameters.

Toward Emotionally Adaptive Virtual Reality for Mental Health Applications.

Here, we introduce the design and preliminary validation of a general-purpose architecture for affective-driven procedural content generation in virtual reality (VR) applications in mental health and wellbeing. The architecture supports seven commercial physiological sensing technologies and can be deployed in immersive and non-immersive VR systems. To demonstrate the concept, we developed the "The Emotional Labyrinth," a non-linear scenario in which navigation in a procedurally generated three-dimensional maze is entirely decided by the user, and whose features are dynamically adapted according to a set of emotional states. During navigation, affective states are dynamically represented through pictures, music, and animated visual metaphors chosen to represent and induce affective states. The underlying hypothesis is that exposing users to multimodal representations of their affective states can create a feedback loop that supports emotional self-awareness and fosters more effective emotional regulation strategies. We carried out a first study to, first, assess the effectiveness of the selected metaphors in inducing target emotions, and second, identify relevant psycho-physiological markers of the emotional experience generated by the labyrinth. Results show that the Emotional Labyrinth is overall a pleasant experience in which the proposed procedural content generation can induce distinctive psycho-physiological patterns, generally coherent with the meaning of the metaphors used in the labyrinth design. Furthermore, collected psycho-physiological responses such as electrocardiography, respiration, electrodermal activity, and electromyography are used to generate computational models of users' reported experience. These models enable the future implementation of the closed loop mechanism to adapt the Labyrinth procedurally to the users' affective state.