Underwater robot local dry welding system

To satisfy the demand for good quality underwater welding and maintenance of nuclear power stations,a set of local dry automatic welding systems has been developed.These systems were based on an underwater robot that consisted of a special high-power underwater welding power supply,diving wire feeder,mini drain cap,welding robot,and special underwater welding torch.With a digital signal controller microprocessor as its core and combined with a dual inverter topology,the welding power supply was characterized by full-digital construction and multi-waveform flexible output.A compact diving wire feeding device was designed,based on the armature voltage negative feedback and high-frequency chopping pulse width modulation.This device yielded a high-efficiency seal of the driving motor with the help of dynamic and static sealing technology.To overcome the difficulty of local protection and deslagging in the welding area,a mini drain cap(with a duplexgas structure)based on the principle of the convergent nozzle was designed.The practical tests and the underwater welding experiments revealed that the underwater robotic local dry welding system is quite feasible.That is,the system could strike the arc stably and reliably in the shallow water environment,and formed beautiful welding seams.

Teleoperation strategies research for collaborative welding systems based on virtual reality

Teleoperation control strategies for collaborative welding system which is targeting at giving full play to human’s superiority is designed and the fitness for teleoperation welding task of which are studied. During the teleoperation welding process, 6-DOF controller’s signal can be converted into welding torch’s position, velocity or acceleration changing which is being controlled. For welding purposes, control strategies of four modes are designed, which are static position and posture mode, dynamic position and posture mode, velocity mode and acceleration mode. A test and analysis system for testing the tracking accuracy and reliability of control strategy based on virtual reality is developed. The tracking accuracies of the four control strategies are studied in the following tests with straight line trajectory, curve trajectory or space curve trajectory. The results show that the control strategy in dynamic position and posture mode has best stability and strong adaptability which is the most suitable for the teleoperation system.

Girth welding system for vortex type refrigeration compressor of air conditioner

According to the requirements of welding process for vortex type compressor of air conditioner manufactured in product line, a special girth welding machine with PLC as control core was developed, which had both upright and 45 ° incline service positions. And some key technologies were researched, such as structural design of machine body, reliable conduction of rotary weldments and quality control of welding process and so on. The experimental results showed that this machine could satisfy the requirements of welding quality and girth welding technology, results also proved the machine was a high-effwiency and low-cost automatic welding device.

ROBUST CONTROL OF GAS TUNGSTEN ARC WELDING SYSTEM

The robust control law for gas tungsten arc welding dynamic process, which is a typical sampled-data system and full of uncertainties, is presented. By using the Lyapunov, second method, the robust control and robust optimal control for a class of sampled-data systems whose underlying continuous-time systems are subjected to structured uncertainties are discussed in time-domain. As a result, some sufficient conditions of robust stability and the corresponding robust control laws are derived. All these results are designed by solving a class of linear matrix inequalities （LMIs） and a class of dynamic optimization problem with LMIs constraints respectively. An example adapted under some experimental conditions in the dynamic process of gas tungsten arc welding system in which the controlled variable is the backside width of weld pool and controlling variable pulse duty ratio, is worked out to illustrate the proposed results, it is shown that the sampling period is the crucial design oarameter.

Development of motion controller and its application in automatic TIG welding system

To develop a control system of cantilever arm for barrels welding, a motion controller has been developed to fit the welding procedure. The main research fields of the controller are: (1) finding effective measures to protect the controller against interferences; (2) decreasing welding current gradually in order to alleviate arc craters which are harmful to seam forming and welding quality; (3) planning the arm velocity to minimize the influence of the arm swing on arc length regulator; (4) adopting adaptive control algorithm with PD feedback and velocity feed-forward to reduce the influence of system inertia and velocity planning on the system transient performance.

Tremor suppression in master-slave robot remote welding system

Welding seam tracking precision was decreased due to human hand tremor during the master-slave welding teleoperation. To solve this problem, a master-slave robot remote welding system was built, the system consisted of a master manipulator with six degree of freedom （ DOF ） , an industrial computer control system and a slave Motoman HP3 J robot, and human hand tremor and digital filtering were discussed. An optimal digital filter was designed to clean human tremor signal for improving the welding seam tracking precision. The experimental results show that the digital filter suppresses the operator＇ s tremor signal.

Study of modeling and simulation of full digital controlled PMIG/MAG welding system based on Matlab/Simulink

This paper presents an integrated simulation model for full digital controlled PMIG/MAG welding system with Matlab/Simulink, and it consists of power inverter, digital control system and dynamic arc-load model. An integrated simulation study was done for full digital PMIG/MAG welding, and a method of connecting dynamic arc-load model to the system with controlled current source was presented, in addition, the simulation results were utilized to study the issues of digital control PMIG/MAG welding in this paper. The experimental results validated the developed simulation model, and this simulation study can be applied in implementation of the full digital PMIG/MAG welding and analysis of system dynamic process.

Design of Fully Automatic Specification Selection System for Resistance Welding Equipment

A system for fully automatic selection of welding specifications in resistance welding equipment has been developed to address the problem of workers frequently choosing the wrong specifications during manual welding of multiple parts on a single machine in automobile factories. The system incorporates an automatic recognition system for different workpiece materials using the added machine fixture,visual detection system for nuts and bolts,and secondary graphical confirmation to ensure the correctness of specification calling. This system achieves reliable,fully automatic selection of welding specifications in resistance welding equipment and has shown significant effects in improving welding quality for massproduced workpieces,while solving the problem of specification calling errors that can occur with traditional methods involving process charts and code adjustments. This system is particularly suitable for promoting applications in manual welding of multiple parts on a single machine in automobile factories,ensuring correct specification calling and welding quality.

Omnidirectional simulation analysis of thermomechanical coupling mechanism in inertia friction welding of Ni-based superalloy

The coupling between heat and pressure is the kernel of inertia friction welding(IFW)and is still not fully understood.A novel 3D fully coupled finite element model based on a plastic friction pair was developed to simulate the IFW process of a Ni-based superalloy and reveal the omnidirectional thermo-mechanical coupling mechanism of the friction interface.The numerical model successfully simulated the deceleration,deformation processes,and peak torsional moments in IFW and captured the evolution of temperature,contact pressure,and stress.The simulated results were validated through measured thermal history,optical macrography,and axial shortening.The results indicated that interfacial friction heat was the primary heat source,and plastic deformation energy only accounted for 4%of the total.The increase in initial rotational speed and friction pressure elevated the peak temperature,reaching a maximum of 1525.5K at an initial rotational speed of 2000 r/min and friction pressure of 400 MPa.The interface heat generation could form an axial temperature gradient exceeding 320K/mm.The radial inhomogeneities of heat generation and temperature were manifested in a concentric ring distribution with maximum heat flux and temperature ranging from 2/5 to 2/3 radius.The radial inhomogeneities were caused by increasing linear velocity along the radius and an opposite distribution of contact pressure,which could reach 1.7 times the set pressure at the center.The circumferential inhomogeneity of thermomechanical distribution during rotary friction welding was revealed for the first time,benefiting from the 3D model.The deflection and transformation of distribution in contact pressure and Mises stress were indicators of plastic deformation and transition of quasi-steady state welding.The critical Mises stress was 0.5 times the friction pressure in this study.The presented modeling provides a reliable insight into the thermo-mechanical coupling mechanism of IFW and lays a solid foundation for predicting the microstructures and mechanical properties of inertia friction welded joints.

Plastic flow and interfacial bonding behaviors of embedded linear friction welding process:Numerical simulation combined with thermophysical experiment

In this study,a new linear friction welding(LFW)process,embedded LFW process,was put forward,which was mainly applied to combination manufacturing of long or overlong loadcarrying titanium alloy structural components in aircraft.The interfacial plastic flow behavior and bonding mechanism of this process were investigated by a developed coupling EulerianLagrangian numerical model using software ABAQUS and a novel thermo-physical simulation method with designed embedded hot compression specimen.In addition,the formation mechanism and control method of welding defects caused by uneven plastic flow were discussed.The results reveal that the plastic flow along oscillating direction of this process is even and sufficient.In the direction perpendicular to oscillation,thermo-plastic metals mainly flow downward along welding interface under coupling of shear stress and interfacial pressure,resulting in the interfacial plastic zone shown as an inverted“V”shape.The upward plastic flow in this direction is relatively weak,and only a small amount of flash is extruded from top of joint.Moreover,the wedge block and welding components at top of joint are always in un-steady friction stage,leading to nonuniform temperature field distribution and un-welded defects.According to the results of numerical simulation,high oscillating frequency combined with low pressure and small amplitude is considered as appropriate parameter selection scheme to improve the upward interfacial plastic flow at top of joint and suppress the un-welded defects.The results of thermo-physical simulation illustrate that continuous dynamic recrystallization(CDRX)induces the bonding of interface,accompanying by intense dislocation movement and creation of many low-angle grain boundaries.In the interfacial bonding area,grain orientation is random with relatively low texture density(5.0 mud)owing to CDRX.

High cycle fatigue performance at 650℃and corresponding fracture behaviors of GH4169 joint produced by linear friction welding

GH4169 joints manufactured by Linear Friction Welding(LFW)are subjected to tensile test and stair-case method to evaluate the High Cycle Fatigue(HCF)performance at 650℃.The yield and ultimate tensile strengths are 582 MPa and 820 MPa,respectively.The HCF strength of joint reaches 400 MPa,which is slightly lower than that of Base Metal(BM),indicating reliable quality of this type of joint.The microstructure observation results show that all cracks initiate at the inside of specimens and transfer into deeper region with decrease of external stress,and the crack initiation site is related with microhardness of matrix.The Electron Backscattered Diffraction(EBSD)results of the observed regions with different distances to fracture show that plastic deformation plays a key role in HCF,and the Schmid factor of most grains near fracture exceeds 0.4.In addition,the generation of twins plays a vital role in strain concentration release and coordinating plastic deformation among grains.

COMPUTER SIMULATION OF NEURAL NETWORK CONTROL SYSTEM FOR CO_2 WELDING PROCESS

In this paper, neural network control systems for decreasing the spatter of CO2 welding have been created. The Generalized inverse Learning Architecture(GILA), the SPecialized inverse Learning Architecture(SILA)-I & H and the Error Back Propagating Model(EBPM) are adopted respectively to simulate the static and dynamic welding control processes. The results of simulation and experiment show that the SILA-I and EBPM have betted properties. The factors affecting the simulating results and the dynamic response quality have also been analyzed.

SPOT WELDING QUALITY FUZZY CONTROL SYSTEM BASED ON MULTISENSOR INFORMATION FUSION

The multisensor information fusion technology is adopted for real time measuring the four parameters which are connected closely with the weld nugget size（welding current, electrode displacement, dynamic resistance, welding time）, thus much more original information is obtained. In this way, the difficulty caused by measuring indirectly weld nugget size can be decreased in spot welding quality control, and the stability of spot welding quality can be improved. According to this method, two-dimensional fuzzy controllers are designed with the information fusion result as input and the thyristor control signal as output. The spot welding experimental results indicate that the spot welding quality intelligent control method based on multiscnsor information fusion technology can compensate the influence caused by variable factors in welding process and ensure the stability of welding quality.

Research of chamber local dry underwater welding system and drainage properties

Because of relatively large protective area and good underwater welding quality, chamber underwater welding has a great using prospect in spent fuel pool maintenance at nuclear power plant. A chamber local dry automatic underwater welding test system with a data acquisition platform is developed, drainage seal tests in a water tank are carried out and the data acquired from the tests are analyzed. The results show that the chamber local dry underwater welding test system can achieve good drainage seal, the drainage effect is enhanced with the increase of the drainage gas flow rate and the drainage time. The results establish the foundation of the research of chamber local dry underwater welding.

A computer-based control system for keyhole plasma arc welding

A new kind of control system for keyhole plasma arc welding （K-PAW） was developed based on the computer and the Graphics Language--LabVIEW. It can set and output the required current waveforms with desired decreasing slopes so that the corresponding ＂opening and closing＂ of keyhole can occur periodically. With this control strategy of welding current waveforms, the workpiece is fully penetrated while no burn-through Occurs. Keyhole plasma arc welding experiments were conducted to verify the stability and reliability of the developed system.

Weldability evaluation and tensile strength estimation model for aluminum alloy lap joint welding using hybrid system with laser and scanner head

Aluminum welding using a hybrid system with a laser and scanner welding head was performed under various welding conditions to verify the feasibility of applying an aluminum alloy to a car body.The experimental material was 5J32 aluminum alloy,and the laser power,welding speed,and laser incidence angle were used as the control variables.The weld bead shape and the tensile shear strength were evaluated in order to understand the aluminum lap joint weld characteristics.Analysis of variance (ANOVA) was conducted to identify the effect of the process variables on the tensile shear strength.Tensile strength estimation models using three different regression models were also suggested.The input variables were the laser power,welding speed,and laser incidence angle,and the output was the tensile shear strength.Among the models,the second-order polynomial estimation model had the best estimation performance,and the average error rate of this model was 0.058.

Development of underwater wet welding experimental and divers training system

Compared to traditional welding methods, the underwater wet welding is special with many different characteristics due to the unique aqueous environment. It is conducted completely under water by divers and unique welding technology is required in the special operation environment. The operating levels of the divers are the key factor to acquire high quality welded joints. In this paper, an underwater wet welding experimental and divers training system is developed to serve divers training and conducting welding experiments. The system consists of life support system, signals real-time monitoring system and communicating system, etc. An underwater butt welding experiment based on welding electrodes is conducted, and the system works well. It proves that the system can guarantee divers welding safely and successfully and high quality weld seam is expected to be acquired.

A time-dependent measuring system for welding deformation

In this paper the establishment and application of a time dependent measuring system for welding deformation are presented which is established with high quality sensors shielded from strong welding interference. By using this system, vertical and horizontal displacements of the high temperature area are surveyed at the same time. And this system is also used for monitoring and controlling the deformation of real welded structures.

A high-precision control system for robotic welding positioner

Aiming at the robotic welding positioner with characteristic of parameter change, load change, nonlinearity, and an intelligent control system was researched and developed. This control system used a two-mode controller that based on Fuzzy and PID control method. The results of simulation show that the dynamic and steady performances of the intelligent controller are better than that of single PID or Fuzzy controller. This paper has made a detail theoretical analysis of the constitution design and real-time controlled software and brought up the design and fulfillment method of multi-task real-time control software of high precisely and numerically controlled welding positioner, which has a good result in practice.

Dynamic and control system analysis of two-wheeled robot for welding application

Aiming at the welding condition of space complex seam is uncertain and the intelligence of welding robot is unideal, a two-wheeled mobile robot is developed. It not only has the capacity of autonomous decision and avoiding obstacles, but also can flexibly move and strongly adapt variable environment. The composition of the welding robot is described and the dynamic model is established. The feasible control strategy and control algorithm is put forward. The simulation experiments of real world are conducted, the results are satisfying.