Performance Analysis and Flexible Control of a Novel Ball Double-screw Hydraulic Robot Knee Joint

Focusing on the ball double-screw hydraulic knee joint as the research object,this paper analyzes the load driving performance of the hydraulic knee joint.Taking the posture data of the human body such as walking,squatting and landing buffer as initial learning objects,motion features are extracted.By simplifying the trajectories of different motion actions into key feature control points and flexible trajectory fitting,the trajectory of joint actions is optimized.This method can realize the adaptability of the hydraulic robot knee joint in different movements,and take the flexible action as the optimization goal under the condition of ensuring the movement performance,so as to reduce the damage to the knee joint caused by the foot impact in motion.The simulation model was built by Adams and Matlab to complete the performance analysis and motion optimization experiment of the knee joint.The simulation results show that the foot impact force of the experimental model decreases gradually through optimization.Finally,the method is applied to the hydraulic joint experimental prototype to prove its load capacity and flexible motion control performance.

A Flexible Hingeless Control Surface Inspired by Aquatic Animals

A flexible hingeless control surface model was proposed for motion control of Underwater Vehicles (UVs),which is inspiredby the flexible bending control surfaces of underwater creatures,such as fish and squid.Computational Fluid Dynamics(CFD) simulation demonstrates that,in comparison with the hinged or rigid control surface,the proposed flexible bendingcontrol surface can suppress the flow separation so as to improve the turning performance.A prototype of the flexible controlsurface was fabricated,in which Shape Memory Alloy (SMA) wires were selected as the actuators.The elastic energy storageand exchange mechanism was incorporated into the actuation of the control surface to improve the efficiency.Thermal analysisof SMA wires was performed to find proper actuating condition.Open-loop bending experiments were carried out.The resultsshow that the proposed control surface can achieve the maximum bending angle of 104°.Moreover,the power and energyconsumption under different pulse conditions were compared.

Effects of Joint Controller on Analytical Modal Analysis of Rotational Flexible Manipulator

Modal analysis is a fundamental and important task for modeling and control of the flexible manipulator. However, almost all of the traditional modal analysis methods view the flexible manipulator as a pure mechanical structure and neglect feedback action of joint controller. In order to study the effects of joint controller on the modal analysis of rotational flexible manipulator, a closed-loop analytical modal analysis method is proposed. Firstly, two exact boundary constraints, namely servo feedback constraint and bending moment constraint, are derived to solve the vibration partial differential equation. It is found that the stiffness and damping gains of joint controller are both included in the boundary conditions, which lead to an unconventional secular term. Secondly, analytical algorithm based on Ritz approach is developed by using Laplace transform and complex modal approach to obtain the natural frequencies and mode shapes. And then, the numerical simulations are performed and the computational results show that joint controller has pronounced influence on the modal parameters： joint controller stiffness reduces the natural frequency, while joint controller damping makes the shape phase non-zero. Furthermore, the validity of the presented conclusion is confirmed through experimental studies. These findings are expected to improve the performance of dynamics simulation systems and model-based controllers.

Precision and Flexible Bending Control Strategy Based on Analytical Models and Data Models

Forming of various customized bending parts,small batches,as well as numerous types of materials is a new challenges for Industry 4.0,the current control strategies can not meet the precision and flexibility requirement,expected control strategy of bending processes need to not only resist unknown interferences of process condition and models,but also produce various new parts automatically and efficiently.In this paper,a precision and flexible bending control strategy based on analytical models and data models is proposed to build adaptive bending systems.New analytical prediction models for loading and unloading are established and suitable for various materials,a sequential identification strategy is proposed to search nominal properties using the four sub-optimization models.A data-based feedback model is established to prevent over-bending and eliminate online deviation.Above models are merged into a precision and flexible control strategy.The system firstly uses sub-optimization models to search the nominal point which is near to target point,secondly the system further uses feedback model to eliminate residual error between the nominal point and target point.Compared with four kinds sheet metals,the allowable ranges for variables are determined for a good convergence.The target bending angles were set to 20°,40°,and 60°.Forty parts were tracked for each kind material,the adaptive bending system converged after one iteration,and exhibited better performances.

PASSIVE-ACTIVE CONTROL OF A FLEXIBLE ISOLATI0N SYSTEM

Passive-active control of a flexible isolation system is investigated from the viewpoint ofpower flow. Dynamic transfer equations of the system are deduced based on a matrix method whichuses mobility or impedance representations of three substrictures: the source of vibration, the receiverand the mounting system which connects the source to the receiver The cancellation of axial inputforces to the receiver is considered as the active control strategy and its effects are discussed. Theresults of the study show that the strategy adopted herein can effectively reduce the power transmittedto the receiver.

OPTIMUM CONTROL OF VIBRATION AND STRUCTURE－BORNE NOISE FOR MACHINERY ON FLEXIBLE FOUNDATION

Faced with the key problems of machinerv- induced vibration and structure-borne noise when dynamic machines are mounted on flexible foundations such as upper floors of facto- ry buildings, the vibration and noise transmission mechanism and optimal control for the flexible system are systematically studied by the novel approach of power flow. A more general system of machinery-isolators一flexible foundation is modelled. Based on substructure transfer matrix tech- nique the power flow input and transmitted are formulated in closed forms, and the effects that the flexibility of foundation and the asymmetricity of system have upon the power flow transmis- sion spectra are revealed, Also the inverse problems of isolation design are discussed by using an optimum method. Optimum design for a typical example about a force fan mounted on a con- crete building floor is successfully performed to show that the model is practical, the theory and the optimisation developed are reasonable and effective. Thereby, theoretical bases for accurate prediction of isolation effectiveness and an optimum method for practical design of a general flexi- ble isolation system are provided.

NEW OPTIMAL LARGE ANGLE MANEUVER STRATEGY FOR SINGLE FLEXIBLE LINK

A component synthesis vibration suppression (CSVS) method for flexible structures is put forward. It can eliminate any unwanted orders of flexible vibration modes while achieves desired rigid motion. This method has robustness to uncertainty of frequency, which makes it practical in engineering. Several time optimal and time-fuel optimal control strategies are designed for a kind of single flexible link. Simulation results validate the feasibility of our method.

A NEW MODELING METHOD FOR MACHINE-FOUNDATION COUPLING SYSTEM AND ITS APPLICATION TO THE CONTROL OF POWER FLOW

A new concept, namely, the equivalent mobility matrix of coupling subsystem is proposed, and the corresponding threesubsystem coupling progressive approach is explored. With the new efficient approach presented, the complexity in dealing with a more complicated dynamic coupling system is greatly reduced. The new modeling method is then combined with the theory of power flow to investigate the dynamics of the overall non rigid isolation system from the viewpoint of energy. The interaction between the resilient machine of its main modes and the resonant behavior of the flexible foundation on power flow transmission is studied. Taking a machine tool mounted on a multi story working plant as an example, the dynamic characteristics of the machine foundation coupling system are analyzed, and their effects on power flow transmission are revealed under various service frequency bands. Some advisable control strategies and the design principle for machinery mounted on flexible structure are proposed.

Compliant Control of Lower Limb Rehabilitation Exoskeleton Robot Based on Flexible Transmission

To ensure the safety, comfort, and effectiveness of lower limb rehabilitation exoskeleton robots in the rehabilitation training process, compliance is a prerequisite for human–machine interaction safety. First, under the premise of considering the mechanical structure of the lower limb rehabilitation exoskeleton robot (LLRER), when conducting the dynamic transmission of the exoskeleton knee joint, the soft axis is added to ensure that the rotation motion and torque are flexibly transmitted to any position to achieve flexible force transmission. Second, to realize the active compliance control of LLRER, the sliding mode impedance closed-loop controller is developed based on the kinematics and dynamics model of LLRER, and the stability of the designed control system is verified by Lyapunov method. Then the experiment is designed to track the collected bicycle rehabilitation motion data stably, and the algorithm and dynamic model are verified to satisfy the experimental requirements. Finally, aiming at the transmission efficiency and response performance of the soft shaft in the torque transmission process of the knee joint, the soft shaft transmission performance test is carried out to test the soft shaft transmission performance and realize the compliance of the LLRER, so as to ensure that the rehabilitation training can be carried out in a safe and comfortable interactive environment. Through the design of rehabilitation exercise training, it is verified that the LLRER of flexible transmission under sliding mode impedance control has good adaptability in the actual environment, and can achieve accurate and flexible control. During the experiment, the effectiveness of monitoring rehabilitation training is brought through the respiratory belt.

Parameter optimization of controllable local degree of freedom for reducing vibration of flexible manipulator

Parameter optimization of the controllable local degree of freedom is studied for reducing vibration of the flexible manipulator at the lowest possible cost. The controllable local degrees of freedom are suggested and introduced to the topological structure of the flexible manipulator, and used as an effective way to alleviate vibration through dynamic coupling. Parameters introduced by the controllable local degrees of freedom are analyzed and their influences on vibration reduction are investigated. A strategy to optimize these parameters is put forward and the corresponding optimization method is suggested based on Particle Swarm Optimization （PSO）. Simulations are conducted and results of case studies confirm that the proposed optimization method is effective in reducing vibration of the flexible manipulator at the lowest possible cost.

AN OPTION PRICING MODEL UNDER FUTURE REVENUE UNCERTAINTY

The purpose of this paper is to discuss how the value of high-tech firm can be rationally valued by taking into account managerial flexibility when its future revenue is uncertain,thereby the firm's manager can make rational investment decisions.Using stochastic control theory,the paper will present that the firm's value satisfies a partially differentiate equation,and analyze the managerial flexibility value within a framework of real-option analytic theorey.Finally,the comparative static analysis and the model's simple application are given.

Sliding Mode and PI Controllers for Uncertain Flexible Joint Manipulator

This paper is dealing with the problem of tracking control for uncertain flexible joint manipulator robots driven by brushless direct current motor(BDCM). Flexibility of joint in the manipulator constitutes one of the most important sources of uncertainties. In order to achieve high performance, all parts of the manipulator including actuator have been modeled. To cancel the tracking error, a hysteresis current controller and speed controllers have been developed. To evaluate the effectiveness of speed controllers, a comparative study between proportional integral(PI) and sliding mode controllers has been performed. Finally, simulation results carried out in the Matlab simulink environment demonstrate the high precision of sliding mode controller compared with PI controller in the presence of uncertainties of joint flexibility.

A flexible and high-performance bidirectional optical amplifier with all-optical gain control using ASE noise path through multi-port circulators

We report a flexible all-optical gain controlled bidirectional optical amplifier. The device achieves constant gain and low noise figure over a large input power range. Moreover, the device removes Rayleigh backscattered light and amplifier noise.

A novel ADRC-based design for a kind of flexible aerocraft

The paper presents a novel control design,which is based on the idea of active disturbance rejection control(ADRC),for a kind of flexible aerocraft whose contolled variable cannot be measured directly.Since the original frame of ADRC can-not be directly applied,the paper puts forward a new extended state observer(ESO)and the corresponding ADRC law.In order to assign the poles of the closed loop system to ideal positions such that the vibration can be quickly suppressed,an elastic damping term is added into feedback law.The advantages of the new ESO for fectively estimating both the rigid mode and elastic mode from the measurements are discussed.Moreover,the analysis on the stabiliy.the relative stability and the steady state of the closed-loop system is given.Finally,the efectiveness and robustness of the proposed ADRC are verified by simulations.

Analysis and Control of MVDC Demonstration Project in the UK:ANGLE-DC

The emerging medium voltage direct current(MVDC)distribution networks are becoming more attractive due to their flexible power flow control and lower losses compared to traditional AC networks.This will significantly increase the wide uptake of renewable energy sources.The optimum utilization of the existing assets is an important aspect in grid upgrading and planning.One feasible option is to convert existing MVAC lines into MVDC operation.One of the practical demonstrations is the“ANGLE-DC”project which is also the first MVDC link in the UK.This paper highlights the innovative approach,challenges and key benefits delivered by the ANGLE-DC project.

Rainbow:reliable personally identifiable information retrieval across multi-cloud

Personally identifiable information(PII)refers to any information that links to an individual.Sharing PII is extremely useful in public affairs yet hard to implement due to the worries about privacy violations.Building a PII retrieval service over multi-cloud,which is a modern strategy to make services stable where multiple servers are deployed,seems to be a promising solution.However,three major technical challenges remain to be solved.The first is the privacy and access control of PII.In fact,each entry in PII can be shared to different users with different access rights.Hence,flexible and fine-grained access control is needed.Second,a reliable user revocation mechanism is required to ensure that users can be revoked efficiently,even if few cloud servers are compromised or collapse,to avoid data leakage.Third,verifying the correctness of received PII and locating a misbehaved server when wrong data are returned is crucial to guarantee user’s privacy,but challenging to realize.In this paper,we propose Rainbow,a secure and practical PII retrieval scheme to solve the above issues.In particular,we design an important cryptographic tool,called Reliable Outsourced Attribute Based Encryption(ROABE)which provides data privacy,flexible and fine-grained access control,reliable immediate user revocation and verification for multiple servers simultaneously,to support Rainbow.Moreover,we present how to build Rainbow with ROABE and several necessary cloud techniques in real world.To evaluate the performance,we deploy Rainbow on multiple mainstream clouds,namely,AWS,GCP and Microsoft Azure,and experiment in browsers on mobile phones and computers.Both theoretical analysis and experimental results indicate that Rainbow is secure and practical.

An Immersive Virtual Reality System for Rodents in Behavioral and Neural Research

Context cognition involves abstractly deriving meaning from situational information in the world and is an important psychological function of higher cognition. However, due to the complexity of contextual information processing, along with the lack of relevant technical tools, little remains known about the neural mechanisms and behavioral regulation of context cognition. At present, behavioral training with rodents using virtual reality techniques is considered a potential key for uncovering the neurobiological mechanisms of context cognition. Although virtual reality technology has been preliminarily applied in the study of context cognition in recent years, there remains a lack of virtual scenario integration of multi-sensory information, along with a need for convenient experimental design platforms for researchers who have little programming experience. Therefore, in order to solve problems related to the authenticity, immersion, interaction, and flexibility of rodent virtual reality systems, an immersive virtual reality system based on visual programming was constructed in this study. The system had the ability to flexibly modulate rodent interactive 3 D dynamic experimental environments. The system included a central control unit, virtual perception unit, virtual motion unit, virtual vision unit, and video recording unit. The neural circuit mechanisms in various environments could be effectively studied by combining two-photon imaging and other neural activity recording methods. In addition, to verify the proposed system′s performance, licking experiments were conducted with experimental mice. The results demonstrated that the system could provide a new method and tool for analyzing the neural circuits of the higher cognitive functions in rodents.

Cross-seam Hybrid MTDC System for Integration and Delivery of Large-scale Renewable Energy

To better utilize the diversity of renewable energies in the U. S., this paper proposes a cross-seam hybrid multi-terminal high-voltage direct current(MTDC) system for the integration of different types of renewable energies in the U. S.Based on a developed station-hybrid converter design, the proposed hybrid MTDC system further investigates the connection methods of renewable energies and develops novel flexible power flow control strategies for realizing uninterrupted integration of renewable energies. In addition, the frequency response control of the hybrid MTDC system is proposed by utilizing the coordination between the converters in the hybrid MTDC system.The feasibility of the hybrid MTDC system and the performance of its corresponding control strategies are conducted in the PSCAD/EMTDC simulation. The simulation results indicate that the proposed hybrid MTDC system could realize the uninterrupted integration of renewable energies and flexible power transmission to both coasts of U.S.