Geometry Control of the Deposited Layer in a Nonplanar Laser Cladding Process Using a Variable Structure Controller

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Alireza Fathi ◽  
Amir Khajepour ◽  
Mohammad Durali ◽  
Ehsan Toyserkani
Keyword(s):  
Laser Cladding ◽  
Closed Loop ◽  
Least Squares Method ◽  
Sliding Mode ◽  
Scanning Speed ◽  
Recursive Least Squares ◽  
Hammerstein Model ◽  
Model Parameters ◽  
Control Input ◽  
Laser Cladding Process

This paper presents a closed-loop laser cladding process used in nonplanar deposition of desired metallic materials. In the proposed system, the deposited layer geometry is continuously controlled via a sliding mode controller (SMC). The controller, which uses the scanning speed as the control input, is designed based on a parametric Hammerstein model. The model is a parametric dynamic model with several unknown parameters, which are identified experimentally using the recursive least squares method. The designed SMC is robust to all model parameters’ uncertainties and disturbances. The results showed that the tracking accuracy improves and the chattering effect reduces if an integrator on the scanning speed is added to the controller. It was observed that this addition decreases the response speed. The performance of the proposed controllers was verified through the fabrication of several parts made of SS303-L. This verification indicates that the developed closed-loop laser cladding process can reduce stair-step effects as well as production time in rapid prototyping of functional parts created with the adaptive slicing technique.

Height Control in Laser Cladding Using Adaptive Sliding Mode Technique: Theory and Experiment

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Meysar Zeinali ◽  
Amir Khajepour
Keyword(s):  
Laser Cladding ◽  
Closed Loop ◽  
Sliding Mode ◽  
Adaptive Sliding Mode Control ◽  
Feedback Signal ◽  
Complex Nature ◽  
Control Input ◽  
Image Processing Algorithm ◽  
Adaptive Sliding Mode ◽  
Laser Cladding Process

A closed-loop control of the laser cladding process is desired due to difficulties encountered in depositing a layer with acceptable quality from both geometrical and metallurgical point of views. One of the main parameters to achieve the desired geometry in laser cladding process is the height of the deposited layers. In this paper, a real-time measurement and control of the clad height is presented. Due to complex nature of the process and presence of uncertainties, a robust and adaptive sliding mode control is proposed and implemented to control the clad height. The velocity of the substrate is used as a control input while the molten pool height, which is obtained using a charge-coupled device (CCD) camera and an image processing algorithm is used as a feedback signal. Stability of the controller is proven in the presence of time-varying uncertainties and the performance of the closed-loop system is validated by simulation and experiments. The experimental results are promising and show that the geometrical accuracy of the deposited layers can be improved significantly.

scholarly journals Software Sensor to Enhance Online Parametric Identification for Nonlinear Closed-Loop Systems for Robotic Applications

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3653
Author(s):  
Lilia Sidhom ◽  
Ines Chihi ◽  
Ernest Nlandu Kamavuako
Keyword(s):  
Degrees Of Freedom ◽  
Closed Loop ◽  
Sliding Mode ◽  
Robot Manipulator ◽  
Parametric Identification ◽  
Recursive Least Squares ◽  
Unknown Parameters ◽  
Closed Loop Identification ◽  
Input Variables ◽  
Robotic Applications

This paper proposes an online direct closed-loop identification method based on a new dynamic sliding mode technique for robotic applications. The estimated parameters are obtained by minimizing the prediction error with respect to the vector of unknown parameters. The estimation step requires knowledge of the actual input and output of the system, as well as the successive estimate of the output derivatives. Therefore, a special robust differentiator based on higher-order sliding modes with a dynamic gain is defined. A proof of convergence is given for the robust differentiator. The dynamic parameters are estimated using the recursive least squares algorithm by the solution of a system model that is obtained from sampled positions along the closed-loop trajectory. An experimental validation is given for a 2 Degrees Of Freedom (2-DOF) robot manipulator, where direct and cross-validations are carried out. A comparative analysis is detailed to evaluate the algorithm’s effectiveness and reliability. Its performance is demonstrated by a better-quality torque prediction compared to other differentiators recently proposed in the literature. The experimental results highlight that the differentiator design strongly influences the online parametric identification and, thus, the prediction of system input variables.

Maximum Adhesion Control of Railway Based on Sliding Mode Control System

2011 ◽  
Vol 383-390 ◽  
pp. 5242-5249 ◽  
Author(s):  
Yun Feng Li ◽  
Xiao Yun Feng ◽  
Rui Kuo Liu
Keyword(s):  
Least Squares Method ◽  
Sliding Mode ◽  
Reference Value ◽  
Variable Structure ◽  
Recursive Least Squares ◽  
Adhesion Coefficient ◽  
Reference Velocity ◽  
Torque Transmission ◽  
Vehicle Velocity ◽  
Recursive Least Squares Method

The wheels will idle when the relative slipping speed between the wheel and rail exceeds the reference slipping speed. In order to avoid this phenomenon, the simplified model of wheel-rail traction torque transmission was established. And the adhesion coefficient and vehicle velocity are got through the disturbance observer. Then the recursive least squares method was used to forecast the slope of the adhesion-slip curve. Sliding variable structure controller was used to control the error of wheel velocity and reference velocity. From the results of simulation, this method can be effective to maintain the adhesion coefficient around the maximum. And the slipping speed approached the reference value, so the damage for wheel and rail was effectively prevented which achieved the desired effect.

scholarly journals Optimization of laser cladding process for additive repair of high temperature and high pressure valve sealing surface

2019 ◽  
Author(s):  
Lei Che
Keyword(s):  
High Pressure ◽  
Corrosion Resistance ◽  
High Temperature ◽  
Laser Cladding ◽  
Laser Power ◽  
Feeding Rate ◽  
Scanning Speed ◽  
Alloy Layer ◽  
Laser Cladding Process ◽  
Valve Sealing

Laser cladding technology is highly suitable for the remanufacturing of thin-walled and easily deformable parts due to its concentrated energy density. Due to the high temperature and high pressure corrosion environment, the valve sealing surface is prone to corrosion, wear and other failures. A nickel-based tungsten carbide alloy layer was prepared on the valve sealing surface substrate material by laser cladding process. By designing orthogonal experiments, the effects of laser power (P), scanning speed (Vb), powder feeding rate (Vf), and WC content (wt%) on the alloy layer were investigated. A fuzzy comprehensive evaluation method including macroscopic quality, microstructure, microhardness, anti-wear performance, oxidation resistance, compactness and corrosion resistance was proposed. The experimental results showed that the hardness, oxidation resistance and corrosion resistance of the laser alloy layer are significantly improved compared with the matrix; the optimum process parameters and the addition ratio of WC powder are laser power (P) of 1.1 kW and scanning speed (Vb) of 800 mm/min. The powder feeding rate (Vf) was 20%, and the WC content was 20% by weight.

Feedforward model-inverse position control of three-stage servo-valve using zero magnitude error tracking control

2018 ◽  
Vol 233 (7) ◽  
pp. 2340-2348 ◽  
Author(s):  
Kyeong Ha Lee ◽  
Seung Guk Baek ◽  
Hyouk Ryeol Choi ◽  
Hyungpil Moon ◽  
Sang-Hoon Ji ◽  
...  
Keyword(s):  
Flow Rate ◽  
Tracking Control ◽  
Closed Loop ◽  
Position Control ◽  
Control Method ◽  
Least Squares Method ◽  
Flow Direction ◽  
Recursive Least Squares ◽  
Servo Valve ◽  
Model Inverse

Three-stage servo-valves are popularly used in hydraulic systems that require large flow rate and high pressure. For a proper control of flow direction and flow rate fed into a hydraulic actuator, securing a proper position control bandwidth is a critical task for the servo-valve. In this paper, a set of popular control methods are systematically studied and a control method is selected. It is proven that the feedforward model-inverse control is the most effective method in terms of the control bandwidth. In the present work, the feedforward closed-loop architecture is adopted and the closed-loop system is estimated in a linear discrete-time transfer function by recursive least squares method. On recognizing a nonminimum phase zero problem, this work implements the zero magnitude error tracking control, an approximate model-inverse technique, in order to overcome the problem. As a result, the effectiveness of the proposed feedforward model-inverse position control strategy is verified.

Practical Considerations for Sliding Mode Observers for High-Rate Structural Health Monitoring

2018 ◽  
Author(s):  
Bryan Joyce ◽  
Jacob Dodson ◽  
Jonathan Hong ◽  
Simon Laflamme
Keyword(s):  
Structural Health Monitoring ◽  
Health Monitoring ◽  
Sliding Mode ◽  
State Parameter ◽  
High Rate ◽  
Recursive Least Squares ◽  
Model Parameters ◽  
Structural Health ◽  
Disturbance Estimation ◽  
Sliding Mode Observers

Structural health monitoring (SHM) of high-rate, mechanical systems in dynamically harsh environments presents many challenges over traditional SHM applications. Damage in these systems must be detected and quantified in tens to hundreds of microseconds in order to have sufficient time to react and mitigate damage. The computation speeds and robustness of sliding mode observers (SMOs) for state, parameter, and disturbance estimation for linear and nonlinear systems make them an attractive approach for real-time SHM of high-rate systems. This paper investigates a novel SMO combined with a recursive least squares parameter estimator to detect and track changing system parameters. The observer is simulated on a one degree-of-freedom system with time-varying model parameters to mimic damage. This paper focuses on practical considerations for SMOs for high-rate systems, such as the effects of measurement noise and sampling rates on the estimator’s accuracy and convergence speeds.

MEMS Gyro Random Drift Model Parameter Identification Based on Two-Stage Recursive Least Squares Method

2012 ◽  
Vol 220-223 ◽  
pp. 1044-1047 ◽  
Author(s):  
Zhao Hua Liu ◽  
Jia Bin Chen ◽  
Yu Liang Mao ◽  
Chun Lei Song
Keyword(s):  
Least Squares ◽  
Least Squares Method ◽  
Moving Average ◽  
Recursive Least Squares ◽  
Model Parameters ◽  
Random Drift ◽  
Two Stage ◽  
Autoregressive Moving Average Model ◽  
Drift Model ◽  
Recursive Least Squares Method

Autoregressive moving average model (ARMA) was usually used for gyro random drift modeling. Because gyro random drift was a non-stationary, weak non-linear and time-variant random signal, model parameters were random and time-variant, too. For improving precision of gyro and reducing effects of random drift, this paper adopted two-stage recursive least squares method for ARMA parameter estimation. This method overcame the shortcomings of the conventional recursive extended least squares (RELS) algorithm. At the same time, the forgetting factor was introduced to adapt the model parameters change. The simulation experimental results showed that this method is effective.

Model Parameter Identification and Simulation of Ship Power System Based on Recursive Least Squares Method

2012 ◽  
Vol 220-223 ◽  
pp. 482-486 ◽  
Author(s):  
Jin Hui Hu ◽  
Da Bin Hu ◽  
Jian Bo Xiao
Keyword(s):  
Mathematical Model ◽  
Power Systems ◽  
Parameter Identification ◽  
Least Squares ◽  
Least Squares Method ◽  
Recursive Least Squares ◽  
Design Parameters ◽  
Model Parameters ◽  
Model Parameter ◽  
Model Parameter Identification

According to the lack of the part of the equipment design parameters of a certain type of ship power systems, the algorithm of recursive least squares for model parameter identification is studied. The mathematical model of the propulsion motor is established. The model parameters are calculated and simulated based on parameter identification method of recursive least squares. The simulation results show that a more precise mathematical model can be simple and easily obtained by using of the method.

scholarly journals Probabilistic Control for Uncertain Systems

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Randa Herzallah
Keyword(s):  
Control Algorithm ◽  
Probabilistic Models ◽  
Closed Loop ◽  
Inverse Dynamics ◽  
Loop System ◽  
Model Parameters ◽  
Control Input ◽  
Closed Loop System ◽  
Optimal Control Strategy ◽  
Mixture Density

In this paper a new framework has been applied to the design of controllers which encompasses nonlinearity, hysteresis and arbitrary density functions of forward models and inverse controllers. Using mixture density networks, the probabilistic models of both the forward and inverse dynamics are estimated such that they are dependent on the state and the control input. The optimal control strategy is then derived which minimizes uncertainty of the closed loop system. In the absence of reliable plant models, the proposed control algorithm incorporates uncertainties in model parameters, observations, and latent processes. The local stability of the closed loop system has been established. The efficacy of the control algorithm is demonstrated on two nonlinear stochastic control examples with additive and multiplicative noise.

Research on Optimization of Laser Cladding Process Parameters Based on Orthogonal Experimental Method

2020 ◽  
Vol 866 ◽  
pp. 72-81
Author(s):  
Da Shu ◽  
Si Chao Dai ◽  
Ji Chao Sun ◽  
Feng Tao ◽  
Ping Xiao ◽  
...  
Keyword(s):  
Dilution Rate ◽  
Laser Cladding ◽  
Process Parameters ◽  
Orthogonal Experiment ◽  
Scanning Speed ◽  
Optimum Level ◽  
Scoring Method ◽  
Laser Cladding Process ◽  
Potential Applications ◽  
Orthogonal Experiment Method

The orthogonal experiment method is used in optimal design of laser cladding, such as laser power (P), scanning speed (SS), powder feeding rate (PFR) and shielding gas velocity (SGV) etc. Both the dilution rate and the aspect ratio are investigated by comprehensive scoring method, which transforms multi-index into single index. In view of the nonlinear characteristics of laser cladding process parameters, the optimum level of each factor based on interaction effect is obtained by analyzing binary tables. Finally, the relationship between the laser cladding process parameters and the two indexes (the dilution rate and the ratio of width to height of coating) is obtained. This method has potential applications for the further investigating on the laser cladding process rules.

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