Zhili Zhang

Collaborative virtual maintenance training system of complex equipment based on immersive virtual reality environment

Purpose – The paper aims to provide an integrated system for collaborative maintenance training of complex equipment based on virtual maintenance and immersive virtual reality environment.Design/methodology/approach – An integrated platform for collaborative virtual maintenance operation and training of complex equipment is developed. The simulation supporting platform for collaborative virtual maintenance is designed with the combined hierarchical structure and modularized members to support the interactive communication of heterogeneous data and information. By analyzing the collaboration mode of multi operators, the maintenance task allocation model, maintenance operation model and Extensible Markup Language‐based object information template are presented.Findings – The research finds that the proposed system is an efficient platform for collaborative maintenance training of complex equipment.Practical implications – Appropriate and efficient maintenance task allocation and collaborative maintenance op...

Nonsingular Fast Terminal Sliding Mode Control with Extended State Observer and Tracking Differentiator for Uncertain Nonlinear Systems

A continuous nonsingular fast terminal sliding mode (NFTSM) control scheme with the extended state observer (ESO) and the tracking differentiator (TD) is proposed for second-order uncertain SISO nonlinear systems. The system’s disturbances and states can be estimated by introducing the ESO, then the disturbances are compensated effectively, and the ideal transient process of the system can be arranged based on TD to provide the target tracking signal and its high-order derivatives. The proposed controller obtains finite-time convergence property and keeps good robustness of sliding mode control (SMC) for disturbances. Moreover, compared with conventional SMC, the proposed control law is continuous and no chattering phenomenon exists. The property of system stability is guaranteed by Lyapunov stability theory. The simulation results show that the proposed method can be employed to shorten the system reaching time, improve the system tracking precision, and suppress the system chattering and the input noise. The proposed control method is finally applied for the rotating control problem of theodolite servo system.

Research on fault diagnosis of hydraulic system in missile armament simulation system based on HLA

Hydraulic system is the important component of missile armament system, and its performance has determined the viability and reliability of the armament system. So it is very significant to diagnose its faults during its working period. But it will cause the substantive training expense to carry out the study in the actual equipment, and it is disadvantageous to the study of fault diagnosis technique. In this paper the models of hydraulic system using the missile armament simulation system based on HLA is proposed, and then they are partitioned into different subsystems according to their functions and the detection points are set among them. The faults are located and classified by the neural network, the simulation model of diagnosis system and the faults repository, thereby their locations and causes are detected. The simulation result validates the feasibility and validity of this method.

Finite Time Proportional-Integral Sliding Mode Control of Theodolite Aiming Chaotic Motor with Time Varying Parameters

In the angle measuring using theodolite, the telescope is driven by the aiming motor to sight the target automatically. The parameters of aiming motor will vary with duty conditions to bring about aiming control system chaotic, which is harmful for the aiming system and the aiming results. The aiming motor control system exist the time-varying load and the inside disturbances, the dynamic model is established and analyzed. The behavior of chaos is proved. Due to terminal sliding control with good robustness, fast dynamic response, finite time convergence and high tracking precision, The finite time proportional-integral (PI) sliding mode structure and control strategy are given, and the system stability is analyzed. The chaotic orbits of the aiming motor control system are stabilized to arbitrary chosen the fixed points and periodic orbits by means of sliding mode method. Simulation results show that finite time PI sliding mode control can realize the stability and accuracy of aiming motor control system, and overcome the negative influence of the chaos for the aiming system.

A real-time interaction strategy for virtual maintenance based on motion capture

This paper presents a real-time interaction strategy for virtual maintenance based on motion capture system. The strategy has integrated the real-time control function of motion capture systems and reusable function of motion capture data to solve the limited captured-domain problem in the motion capture system. The main techniques for this cross boundary research include maintenance feature matrix calculation, collision detection, interpolation algorithm, oriented switch, data glove and path planning, which have overcome a number of critical issues, such as data storage, automotive generation of transition frames, transformation of operation location and shifting of control approaches. Further the research has implemented the real-time interaction control of large-domain virtual maintenance operation.

An approach to solving the inverse kinematics problem of virtual human’s lower limbs kinematic chain

The lower limbs kinematic chain (LLKC) is the important part of human body. It contains two joints with four degrees of freedom (DOF). As it is difficult to compute LLKC’s inverse kinematic solution quickly and accurately by using neural network or genetic algorithm (GA) due to its high degree of freedom, we proposed a BP-GA approach by combining BP neural network and GA to resolve it. Firstly, the mathematical model of LLKC was built based on D-H method. Then BP neural network output a local optimal solution, which could be served as an individual of GA initial population. And the searching domain of GA could be determined by local optimal solution. Finally, the high-accuracy solution was searched by using the adaptive GA. The actions of walking, squatting and seated position were simulated and results showed that the precise solution could be calculated efficiently by using the proposed approach with the BP neural network high-speed and GA high-accuracy.