Xin Gao

3D augmented reality teleoperated robot system based on dual vision

Abstract A 3D augmented reality navigation system using stereoscopic images is developed for teleoperated robot systems. The accurate matching between the simulated model and the video image of the actual robot can be realized, which helps the operator to accomplish the remote control task correctly and reliably. The system introduces the disparity map translation transformation method to take parallax images for stereoscopic displays, providing the operator an immersive 3D experience. Meanwhile, a fast and accurate registration method of dynamic stereo video is proposed, and effective integration of a virtual robot and the real stereo scene can be achieved. Preliminary experiments show that operation error of the system is maintained at less than 2.2 mm and the average error is 0.854 7, 0.909 3 and 0.697 2 mm at x, y, z direction respectively. Lots of experiments such as pressing the button, pulling the drawer and so on are also conducted to evaluate the performance of the system. The feasibility studies show that the depth information of structure can be rapidly and recognized in remote environment site. The augmented reality of the image overlay system could increase the operating accuracy and reduce the procedure time as a result of intuitive 3D viewing.

Study on the perception mechanism and method of virtual and real objects in augmented reality assembly environment

Augmented reality assembly, is a promising application of virtual reality in design and manufacturing and has drawn much more and more attentions from industries and research institutes. The foucs of this study are as follows. (1) using the agent-oriented modeling for subassembly object and the behavior reasoning based on petri net model of environment, to build the system model of augmented reality assembly environment and construct the percepting mechanism of the virtual and real objects; (2) based on above percepting mechanism, to solve the epipolar geometry constraint by least robustness square estimation model, and to sense the depth of the occluded virtual objects or real objects in the environment through assembly scene recognizing, background eliminating and geometrical features restructuring of product contour; (3) combining awareness process of object features matching, constrained motion and features fitting with image based visual hull generating and volume querying, to detect the collision of virtual and real objects, including the dynamic deformable objects. The reseach results is of very important academic and applicative interest in the field of digital design, assembly and maintenace. It would be helpful to promote the application research of augemented reality and virtual reality technology.

Dynamic Obstacle Avoidance Algorithm for Redundant Robots with Pre-selected Minimum Distance Index

A pre-selected minimum distance index is presented considering the real-time performance of dynamic obstacle avoidance for redundant robots.The OBB(oriented bounding box) is applied to modeling robot,and safe links are removed by intersection test before calculating real-time distance.The real-time minimum distance is calculated by local mapping based distance calculation method according to the coordinates of objective points.Based on that,avoidance factor and escaping velocity related to minimum distance are built and then mapping matrix in zero space of redundant robots is utilized to accomplish obstacle avoidance path planning.Finally,the validity and efficiency of pre-selected minimum distance index for dynamic obstacle avoidance are manifested by simulation.Compared with traditional path planning methods,the overall planning time is reduced by 15.5%.

Simultaneous positioning and non-minimum phase vibration suppression of slewing flexible-link manipulator using only joint actuator

This paper presents a new global terminal sliding mode control (GTSMC) methodology for the simultaneous positioning and vibration suppression of slewing a flexible-link manipulator. The proposed control scheme is realized using only a joint actuator without an extra actuator (for example, the widely used piezoelectric zirconate titanate), and the non-minimum phase vibration control problem is solved. Firstly, based on the differential geometry method, the initial dynamic system is decomposed into two subsystems, namely an input-output subsystem and a zero-dynamics subsystem. Secondly, a continuous GTSMC strategy without chattering phenomenon is designed for the input-output subsystem, and the limited convergence time is deduced. Moreover, the eigenvalues of the zero-dynamics subsystem can be pointed by setting proper controller parameters for Lyapunov asymptotical stability. Finally, simulation and experimental results demonstrated the efficacy and feasibility of the proposed control methodology.

Design and implementation of the teleoperation platform based on augmented reality

Predictive display based on virtual environment models is an effective method of solving the problem of time delay in teleoperation. However, this method will not work well without the precise virtual environment model. Thus, it is of great significance that augmented reality with video feedback is introduced into teleoperation, instead of the virtual environment models. A teleoperation system platform based on augmented reality was developed to improve system stability and enhance system telepresence, facilitating the operators observation and operation. The improved algorithm ARToolkit-based made the system adaptable to many types of lighting environments. This paper introduces system structure and the realization of key modules. Lots of experiments such as pressing the button, pulling the drawer and so on are also conducted to evaluate the system performance. The simulation results indicate that the proposed system can compensate the defect of prediction and improve teleoperation system reliability.

Research on Control Method Based on Real-Time Operational Reliability Evaluation for Space Manipulator

A control method based on real-time operational reliability evaluation for space manipulator is presented for improving the success rate of a manipulator during the execution of a task. In this paper, a method for quantitative analysis of operational reliability is given when manipulator is executing a specified task; then a control model which could control the quantitative operational reliability is built. First, the control process is described by using a state space equation. Second, process parameters are estimated in real time using Bayesian method. Third, the expression of the systems real-time operational reliability is deduced based on the state space equation and process parameters which are estimated using Bayesian method. Finally, a control variable regulation strategy which considers the cost of control is given based on the Theory of Statistical Process Control. It is shown via simulations that this method effectively improves the operational reliability of space manipulator control system.

Survey a of virtual assembly system

Based on the structure of virtual assembly system, a comprehensive survey and analysis of the recent research in the field are given, which include assembly modeling, constraint recognizing and solving, collision detection, assembly plans and evaluation and so on. The future research trends are presented.

On-line parameter identification and control parameters optimization of robot joints with unknown load torque

An online identification method based on discrete model reference adaptive identification is presented in this paper. First, the algorithm obtains the difference equation of the reference mode, which includes both load inertia and damping coefficient, by dispersing the mechanical movement equation of motion of motor. Landaus discrete time-recursive parameter identification is used to reduce the adaptation mechanism. Then, the control parameters are optimized on-line on the base of the estimation result and the error threshold. This method can estimate the load inertia and damping coefficient at the same time which are used to optimize the speed PI regulator parameters and improve the performance for speed control. The simulation and experiment results prove the effectiveness of the proposed method.

A Hierarchical Reliability Control Method for a Space Manipulator Based on the Strategy of Autonomous Decision-Making

In order to maintain and enhance the operational reliability of a robotic manipulator deployed in space, an operational reliability system control method is presented in this paper. First, a method to divide factors affecting the operational reliability is proposed, which divides the operational reliability factors into task-related factors and cost-related factors. Then the models describing the relationships between the two kinds of factors and control variables are established. Based on this, a multivariable and multiconstraint optimization model is constructed. Second, a hierarchical system control model which incorporates the operational reliability factors is constructed. The control process of the space manipulator is divided into three layers: task planning, path planning, and motion control. Operational reliability related performance parameters are measured and used as the system’s feedback. Taking the factors affecting the operational reliability into consideration, the system can autonomously decide which control layer of the system should be optimized and how to optimize it using a control level adjustment decision module. The operational reliability factors affect these three control levels in the form of control variable constraints. Simulation results demonstrate that the proposed method can achieve a greater probability of meeting the task accuracy requirements, while extending the expected lifetime of the space manipulator.

Research on the operational reliability system control methodology and its application for aerospace mechanism

According to the characteristics of space missions and space environment, to slow performance deterioration and possible reliability attenuation for aerospace mechanisms, an operational reliability system control methodology is proposed in this article. A space manipulator – a kind of typical complicated aerospace mechanism – is chosen as the research object. First, considering relevant materials and structure mechanism of joint and link parts, the influence factors of operational reliability for space manipulator are divided. Then, by introducing the responding layer factors, a mapping relationship between the influence factors of operational reliability and control variables is analysed. On this basis, a new method to build a hierarchical control system of operational reliability for the aerospace mechanisms is proposed. In this method, the mechanism how the influence factors of operational reliability are introduced into the control system is defined, and an operational reliability system control model is built, which is made up of task planning, path planning, and motion control. Finally, the proposed methodology is further explained with the operational stability of a space manipulator as an example. After analysing the mapping relationship among the influence factors of operational reliability, the factors of responding layer and control variables, a multi-objective optimization method based on Nondominated Sorting Genetic Algorithm II (NSGA-II) is proposed to ensure the operation stability for a space manipulator. These optimization objectives are introduced into the optimized control model at path planning level as constraints. According to these constraints, the optimized control system can be adjusted to improve the operation stability of the manipulator, and the operational reliability is also improved during this process correspondingly. Simulation results prove the effectiveness of the proposed method.