Gantry Stage Research Articles

Chattering-free adaptive iterative learning control for linear-motor-driven gantry stage with initial state errors

Chattering-free adaptive iterative learning control for linear-motor-driven gantry stage with initial state errors

Adaptive Iterative Learning Constrained Control for Linear-Motor-Driven Gantry Stage

Adaptive Iterative Learning Constrained Control for Linear-Motor-Driven Gantry Stage

Adaptive Iterative Learning Constrained Control for Linear Motor-Driven Gantry Stage with Fault-Tolerant Non-Repetitive Trajectory Tracking

This article introduces an adaptive fault-tolerant control method for non-repetitive trajectory tracking of linear motor-driven gantry platforms under state constraints. It provides a comprehensive solution to real-world issues involving state constraints and actuator failures in gantry platforms, alleviating the challenges associated with precise modeling. Through the integration of iterative learning and backstepping cooperative design, this method achieves system stability without requiring a priori knowledge of system dynamic models or parameters. Leveraging a barrier composite energy function, the proposed controller can effectively regulate the stability of the controlled system, even when operating under state constraints. Instability issues caused by actuator failures are properly addressed, thereby enhancing controller robustness. The design of a trajectory correction function further extends applicability. Experimental validation on a linear motor-driven gantry platform serves as empirical evidence of the effectiveness of the proposed method.

Adaptive Wavelet Tracking Control of Dual-Linear-Motor-Driven Gantry Stage With Suppression of Crossbeam Rotation

Adaptive Wavelet Tracking Control of Dual-Linear-Motor-Driven Gantry Stage With Suppression of Crossbeam Rotation

A Composite High-Speed and High-Precision Positioning Approach for Dual-Drive Gantry Stage

A Composite High-Speed and High-Precision Positioning Approach for Dual-Drive Gantry Stage

Robust Control of Dual-Linear-Motor-Driven Gantry Stage for Coordinated Contouring Tasks Based on Feed Velocity

Contouring control is one of the most important tasks for the dual-linear-motor-driven gantry system (DLMDGS), whose control performance determines the in various precision machining equipment, mainly industrial machine tools. Nevertheless, there are some limitations in present results, including the insufficient consideration of system uncertainty and the approximation errors introduced by the computation of the path length. To overcome these issues, the effects of the rotational dynamic and uncertainties are studied and further refined in this article, and a robust control scheme with adaptive neural network identification is designed based on the desired contouring velocity. The method improves existing approaches and avoids the imperfection of the previous one, based on tracking control under global task coordinate frame. The effects of various environmental forces are considered and the B-spline wavelet neural network is employed to approximate unknown dynamic caused by the thrust ripples of the three motors. Some experiments on a real system verify the effectiveness and superiority of the proposed velocity-based contouring control method.

RBF Neural Network-Based Adaptive Robust Synchronization Control of Dual Drive Gantry Stage With Rotational Coupling Dynamics

As a typical mechatronics system, dual drive gantry stage has been widely used in high-end intelligent equipment. In this paper, an adaptive robust synchronization control scheme based on RBF neural network is presented to improve the synchronization accuracy and robust performance of dual drive gantry system. In order to overcome the limitation of system performance caused by ignoring high-frequency rotation mode in traditional modeling, a more reasonable rotational dynamic coupling model of gantry table was established. In addition, the adaptive robust control method with expected compensation is adopted to avoid the interference of measurement noise in the system and realize accurate compensation of the model. The advantages of RBF neural network infinite approximation are used to deal with the effects of model compensation residual, unmodeled dynamics and uncertain disturbances. The stability of the closed-loop system is proved by the Lyapunov theorem. Finally, different control strategies are used to conduct comparative experiments and the experimental results verify the superiority and effectiveness of the proposed control strategy. Note to Practitioners—The synchronization problem of dual drive gantry stage is a research hotspot in the industrial field and its control accuracy and robustness are important indexes that affect the system performance. In this paper, the coupled dynamics model of the gantry system is analyzed and established. In addition, an adaptive robust synchronous control strategy based on RBF neural network is presented to deal with various nonlinearities, mechanical strong coupling constraints and external unknown disturbances in the system, which improves the synchronization accuracy and anti-interference ability of the system. In practical industrial application, the designed controller can be applied to a class of dual-drive gantry systems to ensure the quality of product processing. At the same time, under the strong disturbance of complex working conditions, machine damage or more serious safety accidents caused by asynchronous movement can be avoided and the system reliability can be effectively improved, which is of great significance to industrial production.

Composite Adaptive Synchronous Control of Dual-Drive Gantry Stage With Load Movement

In gantry systems, load usually moves according to different production tasks. The continuous change of the beam centroid position is a non-negligible factor for achieving high-performance synchronous control. Therefore, it cannot be simply treated as an external disturbance. In addition, advanced controller design and model parameter identification are very important for precision motion control systems. This article addresses the synchronous control of dual-drive gantry platforms with load movement to improve their steady-state and transient performance. Based on the analysis of the rigid and flexible characteristics of gantry mechanical components, a rigid-flexible coupling dynamic model is proposed, which provides a theoretical basis for the control system design. To ensure zero steady-state tracking error and parameter convergence in the presence of parameter uncertainties and unknown disturbances, a composite adaptive control method integrating excellent output tracking performance and parameter estimation is presented. Furthermore, the bridge between load movement and centroid position is established through frequency domain identification, which facilitates reasonable thrust distribution. Comparative experimental results are presented that confirm the effectiveness and advantages of the proposed synchronous control scheme.

Master-Slave Synchronous Control of Dual-Drive Gantry Stage With Cogging Force Compensation

Dual-drive gantry stage has been widely applied to various industrial manufacturing fields with its unique structural advantages, and the synchronous control accuracy of the platform is crucial to the performance of the whole motion system. Therefore, an adaptive robust synchronous control scheme based on an improved master-slave structure is proposed, which is not only simple in structure but also easy to implement in engineering. The error dynamics model established in this article makes up for the lag of response of traditional master-slave control and improves the stability of closed-loop system. Online parameter adaptive algorithms deal with parameter uncertainties in the system, while robust control deals with unmodeled dynamics and external disturbances. In addition, nonlinear cogging force compensation is applied to the gantry biaxial system to further improve the control accuracy of tracking and synchronization. Finally, a dual-drive gantry stage system with good tracking and synchronization performance is obtained. The effectiveness and superiority of the proposed control strategy are verified by the comparison of several groups of experiments.

Modeling Dual-Drive Gantry Stages with Heavy-Load and Optimal Synchronous Controls with Force-Feed-Forward Decoupling

The application of precision dual-drive gantry stages in intelligent manufacturing is increasing. However, the loads of dual drive motors can be severely inconsistent due to the movement of heavy loads on the horizontal crossbeam, resulting in synchronization errors in the same direction movement of dual-drive motors. This phenomenon affects the machining accuracy of the gantry stage and is an critical problem that should be immediately solved. A novel optimal synchronization control algorithm based on model decoupling is proposed to solve the problem. First, an accurate physical model is established to obtain the essential characteristics of the heavy-load dual-drive gantry stage in which the rigid-flexible coupling dynamic is considered. It includes the crossbeam’s linear motion and rotational motion of the non-constant moment of inertia. The established model is verified by using the actual system. By defining the virtual centroid of the crossbeam, the cross-coupling force between dual-drive motors is quantified. Then, the virtual-centroid-based Gantry Synchronization Linear Quadratic Regulator (GSLQR) optimal control and force-Feed-Forward (FF) decoupling control algorithm is proposed. The result of the comparative experiment shows the effectiveness and superiority of the proposed algorithm.

Compliant Joints with Remote Centre of Compliance for the Improvement of the Motion Accuracy of a Gantry Stage

Compliant Joints with Remote Centre of Compliance for the Improvement of the Motion Accuracy of a Gantry Stage

Compliant joints for the improvement of the dynamic behaviour of a gantry stage with direct drives

1. BELL D.J., LU T.J., FLECK N.A., SPEARING S. M., 2005, MEMS Actuators and Sensors: Observations on Their Performance and Selection for Purpose, Journal of Micromechanics and Microengineering, 15/7, 153–164. Google Scholar

Disturbance Observer-Based Modeling and Parameter Identification for Synchronous Dual-Drive Ball Screw Gantry Stage

A novel algorithm is proposed to identify the parameters of a synchronous dual-drive ball screw gantry system in this paper. The modeling of the gantry system is described in this paper, and dynamic equations are used to derive the relationship from the motor to the coupling mechanism. The modeling results are used to design the algorithm used to identify the model parameters. The proposed algorithm uses two disturbance observers (DOB) to identify the parameters for the coupling mechanism and sliding stages. The sinusoidal position and velocity commands for the proposed identification algorithm are relatively smooth to avoid damaging the mechanism. The proposed method is easy to implement in the position control loop and velocity control loop. Finally, simulation and experimental results show that the proposed DOBs can accurately estimate the parameters for a gantry system, and the estimated results can be further used to design a corresponding controller for the gantry stage.

Nonlinear Synchronous Control for H-Type Gantry Stage Used in Electric Vehicles Manufacturing

The H-type gantry stage (HGS) is widely used in electric vehicle manufacturing and other fields. However, resulting from the existence of mechanical coupling, the synchronous control problem of HGS always troubles many engineers. Most synchronization schemes were either engaged in improving each motor’s tracking performance or committed to pure motion synchronization only. However, tracking and synchronous performance are interconnected, because of the mechanical coupling. In this paper, a rigid assumed system model of HGS, concerning the effects of mid-beam rotary inertia, mid-beam stiffness, and end-effector movement, is presented. Based on the proposed model, an adaptive robust synchronous control based on a rigid assumed model (ARSCR) is proposed to improve both synchronous and tracking performance of the HGS. From the Lyapunov analysis, the proposed ARSCR can achieve the convergence of synchronous error and tracking error, simultaneously. An HGS driven by dual linear motors is built and used to perform the experimental verification. The experimental results indicate the effectiveness of the proposed method.

Parameter space optimization towards integrated mechatronic design for uncertain systems with generalized feedback constraints

There is an increasing trend to apply integrated mechatronic design approaches in precision engineering to synthesize key mechanical and controller parameters simultaneously. However, such technique is yet to be mature, due to the constraints imported by mechanical design and feedback control, as well as the existence of model uncertainties. In this work, we treat the integrated mechatronic design problem as a controller optimization problem with structural constraints. We start from the case when the composite feedback gain matrix (CFGM) has some elements either being zero or with equal or opposite relationships. First, algorithms are proposed to factorize the CFGM. Secondly, the feedback constraints are transformed from the state space to an extended parameter space. In this way, the design problem is reformulated as minimizing the ℋ2-norm upper bound of the closed-loop system transmittance from the exogenous disturbance to the regulated variables over the intersection of convex and non-convex domains. Eventually, cutting-plane-based numerical procedures are developed to obtain a global optimal solution, and the closed-loop robust stability is ensured with guaranteed performance. An illustrative example on a flexure-linked biaxial gantry stage is presented to reveal the practical appeal of the proposed approach. This approach is extensively applicable to a class of optimal control problems, such as controller synthesis problem with prescribed sparsity pattern, decentralized control problem with/without structural constraints, etc.

Modeling and Synchronization Control of a Dual Drive Industrial Gantry Stage

Dual drive gantry mechanisms, in which two actuators are physically connected through a crossbeam to provide a joint thrust for higher acceleration, are widely used in high-speed or heavy payload precision motion control applications. Synchronizing motions of the two actuators and avoiding excessive internal forces are both essential to the smooth operation of these systems. This paper presents a novel synchronization control scheme with thrust allocation that achieves not only better motion synchronization of the two actuators but also simultaneous regulation of internal forces. With decreased internal forces, lesser wear in sliding parts, lower energy consumption, and higher performances can be achieved for dual drive gantry stages. In contrast, existing synchronization control approaches mainly focus on pure motion compensation and synchronization of the two actuators only. Due to the near-rigid physical coupling between the two actuators, excessive internal forces or the “pull and drag” phenomena could still exhibit under existing approaches even when their motions are quite well synchronized. Comparative experimental results are also obtained to show the superiority of the proposed synchronization controller over existing ones in practical applications.

Dynamic modeling and analysis of flexible H-type gantry stage

Conventionally, the dynamic modeling of H-type gantry stage(HGS) assumes that the stiffness of mid-beam is extremely high so that its deformation is ignorable. This assumption apparently simplifies the study, but unavoidably compromises the modeling precision as it is not consistent with the real working status especially at high frequency motion. Comparing with similar studies on moving mass problems, the beam vibration of HGS is excited not only by the moving mass and system acceleration but also by the non-synchronized motion of the two moving ends of mid-beam. Therefore, the objective of this paper is to propose an assumed mode method based on simplified mode shapes(AMM-SMS) by simultaneously considering the lateral flexibility and the motion of the ends of mid-beam. The proposed AMM-SMS adopts the mode shapes of a simplified system, which has the same geometry boundary condition(BC) with the investigated system, to discretize the nonlinear kinematic equations of the proposed system. This method improves the modeling precision with low complexity, and can be applied in different BCs of FHGS. The proposed method is verified by various comparisons with the finite element method. Based on the AMM-SMS, the first three natural frequencies and mode shapes are studied. The open-loop responses of the system are obtained to analyze the effects of different BCs, of the motion of end-effector and of the external exciting force on the vibratory behavior.

Adaptive thrust allocation based synchronization control of a dual drive gantry stage

In order to take full advantage of the hardware benefits by using redundant drive mechanisms, both synchronizing motions of the two actuators and avoiding excessive internal forces are vital to the smooth operations of dual drive gantry systems. However, almost all existing control schemes focus on pure motion synchronization only and the latter has been essentially ignored. Thus, even if the synchronization errors are kept within a small enough range, “pull and drag” phenomena could still exhibit due to the near-rigid physical coupling crossbeam and the consequent large internal forces. In this paper, a three-level synchronization control scheme based on adaptive thrust allocation is proposed to achieve not only better synchronized motion performance but also simultaneous regulation of internal forces. The overall control algorithm is composed of the motion tracking (Level I), the adjustable thrust allocation (Level II) and the on-line recursive least squares estimation (Level III), which is capable of achieving excellent internal force regulation and synchronization performance even when the distribution of system load cannot be priori known exactly in implementation or suffers from variations. Simulation and experimental results verify the effectiveness of the proposed synchronization control scheme based on adaptive thrust allocation in practical applications.

Integrated Mechatronic Design in the Flexure-Linked Dual-Drive Gantry by Constrained Linear–Quadratic Optimization

A dual-drive H-gantry is commonly used in many industrial processes to meet the requirement of high-precision Cartesian motion. Unlike the rigid-linked gantry stage, the flexure-linked counterpart allows a small degree of rotation of the crossarm to prevent possible damages. However, by this design, the chattering of control signals and inappropriate stiffness of the flexure may induce the resonant modes of the gantry. Hence, to maintain the precision tracking of the midpoint position and the orientation of the gantry, as well as to minimize the vibration on the end effector, we seek the most suitable flexure stiffness and controller parameters by formulating a constrained linear–quadratic optimization problem. Since such a mechatronic design problem is not solvable via standard linear–quadratic regulator formulas, we convert it to a constrained projection gradient-based optimization problem, which can be efficiently solved by direct computation of projection gradient and line search of optimal step length. A fast convergence of parameters is achieved after first several iterations. Through a series of comparative experiments, the effectiveness of the proposed method is validated.

The application of proportional–integral–derivative–type fuzzy controller for synchronized XY motion gantry stage system

Gantry systems in which two linear motors are used to drive a single axis provide flexible and efficient solutions for a wide range of material handling applications. It is an important issue to find a way to drive the parallel stage to achieve a synchronous motion effectively and precisely. In this research, the proportional–integral–derivative–type fuzzy controller structure is presented for precision trajectory tracking control in synchronized XY motion gantry stage system. Three proportional–integral–derivative–type fuzzy controllers are designed for each axis, and the complete membership functions and rule table are developed to fulfill the better tracking capability. The controller parameters, which include the scaling factor of fuzzy rules and proportional–integral structures, are searched using the cross-mixing global artificial bee colony algorithm. The algorithm can optimize these parameters based on the integral of the time-weighted absolute error criterion. MATLAB system identification tool is used to find the equivalent coupled transfer functions of the gantry system. The proposed cross-mixing global artificial bee colony algorithm is utilized to offer the better convergence speed and avoid the local optimal solution in the searching process. The simulation results and experimental results on star and circle reference contours are presented to show that the proposed cross-mixing global artificial bee colony–based fuzzy controller indeed accomplish the better tracking performances in motion control application.