Manipulator tracking technology based on FSRUKF

Aiming at the shortcoming that the traditional industrial manipulator using off-line programming cannot change along with the change of external environment,the key technologies such as machine vision and manipulator control are studied,and a complete manipulator vision tracking system is designed.Firstly,Denavit-Hartenberg(D-H)parameters method is used to construct the model of the manipulator and analyze the forward and inverse kinematics equations of the manipulator.At the same time,a binocular camera is used to obtain the threedimensional position of the target.Secondly,in order to make the manipulator track the target more accurately,the fuzzy adaptive square root unscented Kalman filter(FSRUKF)is proposed to estimate the target state.Finally,the manipulator tracking system is built by using the position-based visual servo.The simulation experiments show that FSRUKF converges faster and with less error than the square root unscented Kalman filter(SRUKF),which meets the application requirements of the manipulator tracking system,and basically meets the application requirements of the manipulator tracking system in the practical experiments.

Barrier Lyapunov functions-based dynamic surface control with tracking error constraints for ammunition manipulator electro-hydraulic system

This paper focuses on the dynamic tracking control of ammunition manipulator system. A standard state space model for the ammunition manipulator electro-hydraulic system(AMEHS) with inherent nonlinearities and uncertainties considered was established. To simultaneously suppress the violation of tracking error constraints and the complexity of differential explosion, a barrier Lyapunov functionsbased dynamic surface control(BLF-DSC) method was proposed for the position tracking control of the ammunition manipulator. Theoretical analysis prove the stability of the closed-loop overall system and the tracking error converges to a prescribed neighborhood asymptotically. The effectiveness and dynamic tracking performance of the proposed control strategy is validated via simulation and experimental results.

PID Controller Optimization by GA and Its Performances on the Electro-hydraulic Servo Control System

A proportional integral derivative （PID） controller is designed and attached to electro-hydraulic servo actuator system （EHSAS） to control the angular position of the rotary actuator which control the movable surface of space vehicles. The PID gain parameters are optimized by the genetic algorithm （GA）. The controller is verified on the new state-space model of servo-valves attached to the physical rotary actuator by SIMULINK program. The controller and the state-space model are verified experimentally. Simulation and experimental results verify the effectiveness of the PID controller adaptive by GA to control the angular position of the rotary actuator as compared with the classical PID controller and the compensator controller.

New Method to Improve Dynamic Stiffness of Electro-hydraulic Servo Systems

Most current researches working on improving stiffness focus on the application of control theories.But controller in closed-loop hydraulic control system takes effect only after the controlled position is deviated,so the control action is lagged.Thus dynamic performance against force disturbance and dynamic load stiffness can’t be improved evidently by advanced control algorithms.In this paper,the elementary principle of maintaining piston position unchanged under sudden external force load change by charging additional oil is analyzed.On this basis,the conception of raising dynamic stiffness of electro hydraulic position servo system by flow feedforward compensation is put forward.And a scheme using double servo valves to realize flow feedforward compensation is presented,in which another fast response servo valve is added to the regular electro hydraulic servo system and specially utilized to compensate the compressed oil volume caused by load impact in time.The two valves are arranged in parallel to control the cylinder jointly.Furthermore,the model of flow compensation is derived,by which the product of the amplitude and width of the valve’s pulse command signal can be calculated.And determination rules of the amplitude and width of pulse signal are concluded by analysis and simulations.Using the proposed scheme,simulations and experiments at different positions with different force changes are conducted.The simulation and experimental results show that the system dynamic performance against load force impact is largely improved with decreased maximal dynamic position deviation and shortened settling time.That is,system dynamic load stiffness is evidently raised.This paper proposes a new method which can effectively improve the dynamic stiffness of electro-hydraulic servo systems.

Characteristics Prediction Method of Electro-hydraulic Servo Valve Based on Rough Set and Adaptive Neuro-fuzzy Inference System

Synthesis characteristics of the electro-hydraulic servo valve are key factors to determine eligibility of the hydraulic production. Testing all synthesis characteristics of the electro-hydraulic servo valve after assembling leads to high repair rate and reject rate, so accurate prediction for the synthesis characteristics in the industrial production is particular important in decreasing the repair rate and the reject rate of the product. However, the research in forecasting synthesis characteristics of the electro-hydraulic servo valve is rare. In this work, a hybrid prediction method was proposed based on rough set（RS） and adaptive neuro-fuzzy inference system（ANFIS） in order to predict synthesis characteristics of electro-hydraulic servo valve. Since the geometric factors affecting the synthesis characteristics of the electro-hydraulic servo valve are from workers＇ experience, the inputs of the prediction method are uncertain. RS-based attributes reduction was used as the preprocessor, and then the exact geometric factors affecting the synthesis characteristics of the electro-hydraulic servo valve were obtained. On the basis of the exact geometric factors, ANFIS was used to build the final prediction model. A typical electro-hydraulic servo valve production was used to demonstrate the proposed prediction method. The prediction results showed that the proposed prediction method was more applicable than the artificial neural networks（ANN） in predicting the synthesis characteristics of electro-hydraulic servo valve, and the proposed prediction method was a powerful tool to predict synthesis characteristics of the electro-hydraulic servo valve. Moreover, with the use of the advantages of RS and ANFIS, the highly effective forecasting framework in this study can also be applied to other problems involving synthesis characteristics forecasting.

Grasp Planning and Visual Servoing for an Outdoors Aerial Dual Manipulator

This paper describes a system for grasping known objects with unmanned aerial vehicles (UAVs) provided with dual manipulators using an RGB-D camera. Aerial manipulation remains a very challenging task. This paper covers three principal aspects for this task: object detection and pose estimation, grasp planning, and in-flight grasp execution. First, an artificial neural network (ANN) is used to obtain clues regarding the object’s position. Next, an alignment algorithm is used to obtain the object’s sixdimensional (6D) pose, which is filtered with an extended Kalman filter. A three-dimensional (3D) model of the object is then used to estimate an arranged list of good grasps for the aerial manipulator. The results from the detection algorithm—that is, the object’s pose—are used to update the trajectories of the arms toward the object. If the target poses are not reachable due to the UAV’s oscillations, the algorithm switches to the next feasible grasp. This paper introduces the overall methodology, and provides the experimental results of both simulation and real experiments for each module, in addition to a video showing the results.

ELECTRO-HYDRAULIC SERVO SYSTEM IN THE CENTRIFUGE FIELD

The mechanical characteristics of the electro-hydraulic servo system in thecentrifuge field are analyzed. The hydraulic pressure law in the centrifuge field indicates theexistence of the centrifuge hydraulic pressure. The mechanical characteristics of the slide-valveand the dual nozzle flapper valve are studied, and it is found that the centrifuge field can notonly increase the driving force or moment of the function units, but also decrease the stability ofthe components. Finally by applying Gauss minimum constraint principle, the dynamic model of theelectro-hydraulic vibrator in the centrifuge field is established, and the mechanical restriction ofthe system is also presented. The study will be helpful for the realization of the combinedvibration and centrifuge test system.

Continuous rotary motor electro-hydraulic servo system based on the improved repetitive controller

In order to suppress the periodic interference of the continuous rotary electro-hydraulic servo motor,this paper makes the motor tracking the periodic signals with high accuracy,and improves the influence of friction interference to the performance of continuous rotary electro-hydraulic servo motor.The mathematic model of the electro-hydraulic position servo system of the continuous rotary motor was established,and the compound control method was adopted based on the repetitive control,feed forward and PID to suppress the friction interference.Through the simulation,the result confirms that the compound control method decreases the tracking error of the system,increases the robust performance of the system and improves the performance of the continuous rotary electro-hydraulic servo motor.

Self-correcting wavelet neural network control of continuous rotary electro-hydraulic servo motor

In allusion to the problem of friction,leakage,vibration and noise existing in continuous rotary motor electro-hydraulic servo system,highly nonlinearity and uncertainties affecting the system performance,based on the transfer function of electro-hydraulic servo system,a kind of Pol-Ind friction model is proposed.The parameters of Pol-Ind friction model are identified and the accurate mathematical model of friction torque is obtained by experiment.The self-correcting wavelet neural network(WNN)controller is proposed,and Adam optimization algorithm is used to perform gradient optimization on scale factor and displacement factor in wavelet basis function,so as to improve the speed and precision of parameter optimization.Through comparative simulation analysis,it is clearly that the self-correcting WNN controller can effectively improve the frequency response and tracking accuracy of continuous rotary motor electro-hydraulic servo system.

Angular Position Controller and Its Design Model Verification for the Electro-Hydraulic Servo Control System

The angular position controller is system （EHSAS） to control the output of the rotary applied to electro-hydraulic servo actuator actuator. It works as a compensator based on the frequency response of the EHSAS. Its design model is verified on the state-space model of EHSAS by using simulation program SIMULINK. Real data used to test the system. Simulation results give a good agreement for the controller and also for the state-space model.

FORCE FEEDBACK MODEL OF ELECTRO-HYDRAULIC SERVO TELE-OPERATION ROBOT BASED ON VELOCITY CONTROL

The tele-operation robotic system which consists of an excavator as the construction robot, and two joysticks for operating the robot from a safe place are useful for performing restoration in damaged areas. In order to accomplish a precise task, the operator needs to feel a realistic sense of task force brought about from a feedback force between the fork glove of slave robot and unfamiliar environment. A novel force feedback model is proposed based on velocity control of cylinder to determine environment force acting on fork glove. Namely, the feedback force is formed by the error of displacement of joystick with velocity and driving force of piston, and the gain is calculated by the driving force and threshold of driving force of hydraulic cylinder. Moreover, the variable gain improved algorithm is developed to overcome the defect for grasping soft object. Experimental results for fork glove freedom of robotic system are provided to demonstrate the developed algorithm is available for grasping soft object.

Numerical simulation and experimental study on the leakage of continuous rotary electro-hydraulic servo motor

In order to study the influence of inlet and outlet pressure difference and triangular buffer groove on the internal leakage of continuous rotary electro-hydraulic servo motor,the flow field model of motor with and without triangular groove is established respectively.The mesh model is divided.The pressure distribution of the internal flow field under different pressure difference is analyzed by Fluent.Then,the gap leakage under different pressure difference is calculated,and the leakage curve is obtained.Finally,continuous rotary electro-hydraulic servo motor experimental system is built to conduct the internal leakage test,and the leakage under different pressure difference is measured and compared with the simulation results.The results show that the occurrence of leakage in the motor can be reduced by setting the triangular buffer groove on the flow plate,the simulation and experimental results are consistent.It can be concluded that the larger the pressure difference between the inlet and the outlet of the motor,the larger the gap leakage.The research lays foundation for the application of continuous rotary electro-hydraulic servo motor.

Coordinating optimization-based sliding mode variable structure control for electro-hydraulic servo system

A sliding mode variable structure control （SMVSC） based on a coordinating optimization algorithm has been developed. Steady state error and control switching frequency are used to constitute the system performance indexes in the coordinating optimization, while the tuning rate of boundary layer width （BLW） is employed as the optimization parameter. Based on the mathematical relationship between the BLW and steady-state error, an optimized BLW tuning rate is added to the nonlinear control term of SMVSC. Simulation experiment results applied to the positioning control of an electro-hydraulic servo system show the comprehensive superiority in dynamical and static state performance by using the proposed controller is better than that by using SMVSC without optimized BLW tuning rate. This succeeds in coordinately considering both chattering reduction and high-precision control realization in SMVSC.

Analysis on Static Pressure Bearing Seal Characteristics of Guide Sleeve of Electro-hydraulic Servo Cylinder

As a typical bionic walking robot, hydraulic quadruped robot has attracted much attention because of its high mobility, strong load capacity and steady motion. The electro-hydraulic servo cylinder, as its power actuator, requires low friction, good lateral load resistance and high speed motion. The electro-hydraulic servo cylinder hydrostatic bearing seal guide sleeve is taken as the research object in this paper. By using Fluent software to analyze and contrast the film characteristics of rectangular and I-shaped oil chamber of hydrostatic bearing seal guide sleeve, the relationship between piston rod moving speed, eccentricity, oil film carrying capacity, friction force and leakage volume, as well as the relationship between oil feed flow and oil film bearing capacity, friction force, inlet pressure and leakage volume were analyzed. This study provides a theoretical basis for optimizing the static pressure bearing seal parameters.

Study on Oil Cavity Number of Hydrostatic Guide Sleeve of Electro-hydraulic Servo Cylinder

The electro-hydraulic servo drive hydraulic cylinder has many unique advantages, such as fast response, high load stiffness, high control power, strong anti-eccentric load ability and so on, so it has been widely used in industrial control. Based on the guide sleeve of hydrostatic seal of hydraulic cylinder, the reasonable number of oil chamber of guide sleeve is studied in this paper. ICEM CFD software and FLUENT simulation software are used to calculate and analyze the number of different oil chambers of guide sleeve of hydrostatic seal. The temperature field of piston rod with different moving speed, different initial pressure of oil chamber and oil film under different number of oil chambers is analyzed. The relationship between the pressure field and temperature field provides a better basis for optimizing the design of hydrostatic guide sleeve and helps to improve the servo drive cylinder.

Global Dynamic Modeling of Electro-Hydraulic 3-UPS/S Parallel Stabilized Platform by Bond Graph

Dynamic modeling of a parallel manipulator（PM） is an important issue. A complete PM system is actually composed of multiple physical domains. As PMs are widely used in various fields, the importance of modeling the global dynamic model of the PM system becomes increasingly prominent. Currently there lacks further research in global dynamic modeling. A unified modeling approach for the multi-energy domains PM system is proposed based on bond graph and a global dynamic model of the 3-UPS/S parallel stabilized platform involving mechanical and electrical-hydraulic elements is built. Firstly, the screw bond graph theory is improved based on the screw theory, the modular joint model is modeled and the normalized dynamic model of the mechanism is established. Secondly, combined with the electro-hydraulic servo system model built by traditional bond graph, the global dynamic model of the system is obtained, and then the motion, force and power of any element can be obtained directly. Lastly, the experiments and simulations of the driving forces, pressure and flow are performed, and the results show that, the theoretical calculation results of the driving forces are in accord with the experimental ones, and the pressure and flow of the first limb and the third limb are symmetry with each other. The results are reasonable and verify the correctness and effectiveness of the model and the method. The proposed dynamic modeling method provides a reference for modeling of other multi-energy domains system which contains complex PM.

Compound Impedance Control of a Hydraulic Driven Parallel 3UPS/S Manipulator

The hydraulic parallel manipulator combines the high-power density of the hydraulic system and high rigidity of the parallel mechanism with excellent load-carrying capacity.However,the high-precision trajectory tracking control of the hydraulic parallel manipulator is challenged by the coupling dynamics of the parallel mechanism and the high nonlinearities of the hydraulic system.In this study,the trajectory control of a 3-DOF symmetric spherical parallel 3UPS/S manipulator is evaluated.Focusing on the highly coupling and nonlinear system dynamics,a compound impedance control method for a hydraulic driven parallel manipulator is proposed,which combines impedance control with the spatial motion characteristics of a parallel manipulator.The control strategy is divided into the inner and outer loops.The inner loop controls the impedance of the actuator in the joint space,and the outer loop controls the impedance of the entire platform in the task space to compensate the coupling of the actuators and improve the tracking accuracy of the moving platform.Compound impedance control does not require force or pressure sensors and is less dependent on modeling precision.The experimental results show that the compound impedance control effectively improves the tracking accuracy of the moving platform.This research proposes a compound impedance control strategy for a 3-DOF hydraulic parallel manipulator,which has high tracking precision with a simple and cheap system configuration.

Parameter-dependent vibration-attenuation controller design for electro-hydraulic actuated linear structural systems

The problem of robust active vibration control for a class of electro-hydraulic actuated structural systems with time-delay in the control input channel and parameter uncertainties appearing in all the mass, damping and stiffness matrices is investigated in this paper. First, by introducing a linear varying parameter, the nonlinear system is described as a linear parameter varying （LPV） model. Second, based on this LPV model, an LMI-based condition for the system to be asymptotically stabilized is deduced. By solving these LMIs, a parameter-dependent controller is established for the closed- loop system to be stable with a prescribed level of disturbance attenuation. The condition is also extended to the uncertain case. Finally, some numerical simulations demonstrate the satisfying performance of the proposed controller.

Study of Web-based integration of pneumatic manipulator and its vision positioning

Pneumatic driven system is widely used in industrial automation, mainly for relatively simple tasks with open-loop control. Because of the pneumatic system’s compressibility and few stop positions, it was considered hard to control in a precise motion control system. With the help of newly developed pneumatic servo control technology, using servo-pneumatic positioning controller now is just as easy as using electro-servo system. This article discusses Web-based servo-pneumatic manipulator control and object recognition and positioning. The authors built a three-degrees-of-freedom (3 DOF) pneumatic manipulator with a servo-pneumatic closed-loop control system and machine vision system in their lab. Web-based tele-operation was a basic ability in this experimental system. After installing a CCD camera, video capture card, and related software developed by the authors, the robot could recognize the user specified object through the Web page and find its position. The remote user could command the robot to move to the position and to grab the object. The critical issues of Web-based control are to integrate hybrid open-architecture mechatronic system through the Web and develop a software language environment characterized by the script. The authors’ experiment showed that pneumatic devices could serve as accurate position control and be controlled through the Web.

基于分层运动分解的飞行机械臂视觉伺服控制

飞行机械臂系统具有主动作业能力,通过搭载视觉传感器感知周围环境,系统的自主能力将进一步提高.然而,考虑到无人机的欠驱动和整个系统的非线性特性,飞行机械臂系统的视觉伺服控制仍然是一项具有挑战性的工作.本文在充分考虑机械臂对无人机的力/力矩作用后,提出了一种基于分层运动分解的飞行机械臂视觉伺服控制方案.首先,对飞行机械臂系统的运动学和动力学模型进行分析.然后,根据所得的相机运动学模型,通过基于图像的视觉伺服控制获得相机的期望速度,进而制定无人机和机械臂的速度分配策略.在考虑机械臂运动时对无人机产生的力/力矩影响,设计了底层的飞行控制器.最后,在与现有方法的仿真对比中可以看出,所提方法具有良好的控制性能,对图像特征点位置的不确定性及图像噪声也表现了较好的鲁棒性.