Attitude Controller Design Research Articles

Dynamic Electromechanical Model and Position Controller Design of a New High-Precision Self-Bearing Linear Actuator

Direct drive tubular linear actuators (TLAs) may be used in various applications that require fast movements and high-precision positioning, e.g., pick-and-place robots. This article presents the analysis, dynamic electromechanical model derivation, controller design, and system operation of a TLA with integrated magnetic bearings (MBs). Furthermore, the actuator operation is verified with extensive measurements on the prototype, which include axial position step response, standard deviation of the steady-state positions and mover tilting control. Compared with any conventional TLA, which may perform only linear motion, the mover tilting control is possible due to integrated MBs. This gives the new actuator a great advantage in high-precision positioning systems, since any thermal expansions of the parallel kinematics may be compensated.

Adaptive attitude controller design for tail-sitter unmanned aerial vehicles

Tail-sitter unmanned aerial vehicles have two flight modes: they can fly long distances at high cruising speeds as fixed-wing aircrafts; or hover, take off, and land vertically as rotary-wing aircrafts. The tail-sitter dynamics involves serious nonlinearities and high uncertainties, especially in the two flight mode transitions. In this article, an adaptive control approach is proposed for a class of tail-sitter unmanned aerial vehicles to achieve the robustness properties. The control torque allocation problem is addressed based on the dynamic pressure in the transition flight. The proposed control method does not need to switch the coordinate system, the controller structure, or the controller parameters in different flight modes. It is proven that the attitude tracking errors can converge into a given neighborhood of the origin in finite time. Simulation results are presented to show the advantages of the proposed adaptive control method.

Guaranteed cost spacecraft attitude stabilization under actuator misalignments using linear partial differential equations

In this paper, the guaranteed cost spacecraft attitude stabilization problem is investigated through solving a linear partial differential equation (PDE). It is proved that the guaranteed cost spacecraft attitude controller design problem under actuator misalignments and disturbances can be reformulated into the problem of solving the linear PDE only once. It is also shown that the optimal guaranteed cost controller can be further designed through recursively solving the linear PDE. To alleviate the computational cost and implement the proposed guaranteed cost controller in higher dimensions, a nested sparse grid Chebyshev spectral collocation method is developed. Taking advantage of the designed numerical method, the resultant linear PDE is transformed into an efficiently solvable quadratic programming (QP) problem, and the controller can then be constructed analytically. Simulations show that the proposed controller successfully stabilizes the nonlinear system and also provides an upper bound for the defined performance index.

Boundary control design for vibration suppression and attitude control of flexible satellites with multi-section appendages

Attitude and vibration control of a general form of flexible satellites is addressed in this paper. Partial differential dynamic equations are derived considering new details such as multi sectioned solar panels and elastic connections between main hub and solar panels. Boundary control approach is adopted to eliminate simplification errors of discrete models, using just one actuator in the hub. Asymptotic stability of attitude dynamics is proved for a group of boundary controllers and necessary conditions for asymptotic stability of vibrations are discussed. Being independent of modeling accuracy and using easily measurable feedbacks are among advantages of the proposed class of controllers. Through simulations using FEM technique and a controller with the least number of boundary feedback parameters, good performance of the introduced method is illustrated.

PID controller for microsatellite yaw-axis attitude control system using ITAE method

The need for effective design of satellite attitude control (SAC) subsystem for a microsatellite is imperative in order to guarantee both the quality and reliability of the data acquisition. A proportional-integral-derivative (PID) controller was proposed in this study because of its numerous advantages. The performance of PID controller can be greatly improved by adopting an integral time absolute error (ITAE) robust controller design approach. Since the system to be controlled is of the 4 th order, it was approximated by its 2 nd order version and then used for the controller design. Both the reduced and higher-order pre-filter transfer functions were designed and tested, in order to improve the system performance. As revealed by the results, three out of the four designed systems satisfy the design specifications; and the PD-controlled system without pre-filter transfer function was recommended out of the three systems due to its structural simplicity, which eventually enhances its digital implementation.

Design of High Pointing Accuracy NPSAT-1 Satellite Attitude Systems of Armature Controlled DC Motor with utilization for PD Controller

An Attitude control system plays the important role to maintain the satellite to desired attitude orientations. The intended application of NANO satellite in low earth orbits (LEO) helps find transient responses with and without controllers. LEO satellites typically orbit at an altitude ranging between160-2000 km. LEO satellites are widely used for remote sensing, navigation, and military surveillance applications. The Nano NPSAT-1 satellite attitude control systems (ACS) are described in this research work. The high pointing accuracy attitude estimation and feedback control systems are presented. The design specifications have been taken to meet the accuracy requirements (desired value ≤ 0.2 seconds) of Nano satellite attitude control. The feedback signal from on-board sensors compared with reference orbit trajectory and implementation of the Proportional Derivative (PD) controller is constructed. An algorithm of Nano satellite (NPSAT-1) attitude control is implemented using MATLAB Tools. In addition, the closed loop poles help find the gain of the system using Root Locus (RL) methods. The satellite control system is used to improve the transient response like overshoot and settling time of the system. Thus, the design of attitude control to improve the rise time, the settling time, the maximum overshoot, and no steady state error was carried out.

Design of a Robust Rack Position Controller Based on 1-Dimensional AMESim Model of a Steer-by-Wire System

This paper presents a robust rack position control method based on a disturbance observer to enhance maneuverability and steering robustness during steering situation. It is shown that the rack and pinion system of Steer-by-Wire system with irregular parameters and external disturbance from the tires and mechanical elements can be modelled as a simple second-order system. In control design, robust control method, e.g., two-degree-of-freedom control (2-DOF) with a disturbance observer, is used for improving the steering robustness. Moreover, A friction compensator is designed to eliminate the friction generated by mechanical gear contact that hinders precise position control. The simulation model of the Steer-by-Wire system is designed with a permanent magnet synchronous motor (PMSM) and mechanical parts using AMESim program. The proposed controller was verified through simulation using AMESim and Matlab/Simulink cosimulation with different references.

Position controller design and implementation of ball and beam system with SMC and PD control methods

Today, several methods are proposed and tested for controlling many nonlinear and unstable systems. This study employed the sliding mode control (SMC) and proportional-derivative (PD), which are used to control the position and modeling of ball and beam system that is a fundamental system used to test the control methods. Such systems are nonlinear and unstable due to their nature. Therefore, these systems are affected by external disturbances and this leads to a decrease in the control quality. The study tested the system by utilizing the classical PD and SMC methods, and the results were assessed by employing the Integral-Square-Error (ISE) performance criterion. The system results were provided as graphics and tables. Besides, the results were compared and analyzed.

Permanent Magnet Motor Design for Satellite Attitude Control With High Torque Density and Low Torque Ripple

This paper proposes a high-precision permanent magnet (PM) motor primarily used for the satellite attitude control. Considering aerospace applications, the dynamic response, weight and torque ripple are primarily concerns. To achieve the fast response and low ripple, a stator with slotless windings is designed to achieve the ripple free torque production. However, slotless windings contain visible leakage fluxes which might decrease the torque production. In this paper, several design methods are proposed to decrease leakage fluxes by concentrating the flux linkage under slotless topology. First, leakage fluxes caused by slotless windings are minimized through the radial-flux dual-rotor topology. This topology results in the flux linkage concentration in the air gap because two rotors are used separately for flux transmitter and receiver. It is concluded that the dual-rotor is well suited for a slotless windings motor to maximize the air gap flux linkage. Second, Halbach array magnets are chosen to realize the sinusoidal flux linkage distribution. Different array angles are analyzed to minimize the torque ripple. It is shown that the 22.5deg array angle results in the lowest torque ripple among three different Halbach magnets. More importantly, the average torque output is higher comparing to conventional radial magnet magnetization. Although several optimization methods have been developed on the motor geometric design, very few researches focus on the design of dual-rotor slotless windings and air gap length. This design approach further decreases leakage fluxes. In this paper, finite element analysis (FEA) is used for the satellite motor design. In addition, a motor prototype is built for experimental tests.

Quantitative Feedback Theory design of valve position control for co-ordinated superheater control of main steam temperatures of power plant boilers

This paper presents an application of a Single-Input Single-Output (SISO) controller and a Valve Position Controller (VPC) using robust Proportional-Integral (PI) controllers designed using Quantitative Feedback Theory (QFT) specifications to control superheater outlet steam temperatures of a 600MW once-through boiler. To illustrate the methodology, a dynamic model of a tower-type boiler was modelled using Flownex® to test the VPC design application with structured uncertainty under varying load and disturbance conditions. The results show that the valve position controller application is more efficient than the SISO technique, allowing the final attemperator more bandwidth to deal with unexpected temperature changes.

Adaptive Fault-Tolerant Attitude-Tracking Control of Spacecraft With Quantized Control Torque

In this article, the problem of fault-tolerant attitude-tracking control of spacecraft with quantized control torque is addressed. Actuator faults/failures, an uncertain inertia matrix and unknown disturbances are considered in the attitude controller design of the spacecraft. A dynamical quantization strategy is developed to quantize the signals of the control torque, which can reduce the data transmission rate. An adaptive fault-tolerant controller based on sliding mode techniques is constructed to address the impacts of the actuator faults/failures, quantization errors, inertia matrix uncertainties and unknown disturbances. The developed control strategy with a quantizer can ensure that the entire closed-loop system is asymptotically convergent and achieves satisfactory attitude-tracking performance. Finally, simulation results are provided to show the effectiveness of the proposed method.

Continuous Fixed-Time Sliding Mode Attitude Controller Design for Rigid-Body Spacecraft

Fast and high-precision attitude control for the rigid spacecraft is important for its broad applications in astronautics. In this paper, we address this problem via continuous nonsingular fixed-time sliding mode control approach. At first, by improving the adding power integral technique, a nonsingular nominal attitude controller is presented to achieve fixed-time convergence of the unperturbed attitude system, which underpins the basics for design of the sliding mode motion and surfaces for the subsequent proposed main results. Then, a fixed-time full-order sliding mode controller with an explicit bound of settling time is proposed to track the desire attitude even in the presence of external disturbances. However, this controller requires the angular acceleration signals which is usually unmeasurable. To this end, an integral sliding mode controller is further presented to achieve fixed-time attitude tracking without using any acceleration information. This proposed integral sliding mode controller can realize second-order sliding mode with rigorous proof of fixed-time convergence. Both the proposed fixed time full-order and integral sliding mode controller are inherent nonsingular and chattering-free. Numerical examples are illustrated to demonstrate the effectiveness of the results given herein in practical scenarios.

Stability Analysis and T-S Fuzzy Dynamic Positioning Controller Design for Autonomous Surface Vehicles Based on Sampled-Data Control

Stability Analysis and T-S Fuzzy Dynamic Positioning Controller Design for Autonomous Surface Vehicles Based on Sampled-Data Control

Advanced Autonomous Underwater Vehicles Attitude Control with L 1 Backstepping Adaptive Control Strategy.

This paper presents a novel attitude control design, which combines adaptive control and backstepping control together, for Autonomous Underwater Vehicles (AUVs) in a highly dynamic and uncertain environment. The Euler angle representation is adopted in this paper to represent the attitude propagation. Kinematics and dynamics of the attitude are in the strict feedback form, which leads the backstepping control strategy serving as the baseline controller. Moreover, by bringing fast and robust adaptation into the backstepping control architecture, our controller is capable of dealing with time-varying uncertainties from modeling and external disturbances in dynamics. This attitude controller is proposed for coupled pitch-yaw channels. For inevitable roll excursions, a Lyapunov function-based optimum linearization method is presented to analyze the stability of the roll angle in the operation region. Theoretical analysis and simulation results are given to demonstrate the feasibility of the developed control strategy.

Experimental Modelling and Control of a Tower Crane in the Frequency Domain

Abstract The laboratory tower crane by INTECO is used in research and education of control engineering for mechatronics. Its modelling and control include several subsystems. The paper deals with identification of dynamic model of trolley motion along the jib and trolley position controller design, as well as design of compensator to damp payload oscillations in the direction along the jib. A thorough frequency domain analysis of obtained results is provided.

Design of Attitude Controller of Two-Dimensional Correction Projectile Based on UAS-SMC Method

For the spin stabilized two-dimensional trajectory correction projectiles with utation and precession phenomenon, an attitude controller with sliding mode control method and unidiational auxilairy surfaces (UAS-SMC) is proposed in this paper. And the underactuated control allocation in two-dimensional trajectory correction projectile with UAS-SMC controller is also discussed here. Simulation results show that the proposed controller can effectively control the attitude of the projectile and has strong robustness, which provides reference for engineering applications.

Regressor-free adaptive fuzzy force tracking control of redundant robot manipulator for task space

In this study, an adaptive fuzzy force control of a redundant robot manipulator experiencing system uncertainties and operating in an unknown environment is proposed. This is important not only to provide additional control flexibility for complicated tasks but also to avoid the joint limit of a robot in implementing better dynamics and kinematics. The relation between the task and joint spaces is discussed to derive a dynamic model for force tracking controller design. To treat the system uncertainties, an adaptive fuzzy system approach is established to achieve the adaptive position and force controller design based on a regressor-free approach. Considering that the stiffness coefficient of the environment is assumed to be unknown, the gradient descent method is used to estimate this coefficient to achieve adaptive force tracking. A stability analysis of the closed-loop system and the corresponding update laws are given by the Lyapunov stability theorem. Finally, several apposite simulations using the KUKA lightweight robot are performed to validate our approach and demonstrate the performance and effectiveness of the proposed regressor-free adaptive fuzzy force controller.

Fixed-time attitude stabilization for a rigid spacecraft

This paper mainly investigates the problem of the attitude stabilization for a rigid spacecraft based on the model of Modified Rodriguez Parameters. A fixed-time attitude stabilization controller is designed to guarantee that the attitude of the rigid spacecraft will be stabilized to the equilibrium in a fixed time which is independent of any initial condition. The design of fixed-time attitude controller is mainly based on improved backstepping method. The proposed fixed-time attitude control scheme can deal with not only the parameters’ uncertainties but also the external disturbances. Reliability and effectiveness of the proposed approach are proved by simulations.

Beyond Snap-In: A Hybrid Nonlinear Control Approach for Actuators Possessing a Square-Law Characteristic

The undesired square-law characteristics in micro-electrostatic actuators and magnetic solenoids results in a limited stable range, which reduces their application fields and performance. This research investigated the isomorphic dynamics in these actuators and observed that the nonlinear drive force and the uncertain time delay are the challenges for the full range position controller design. A hybrid nonlinear control scheme includes an input–output linearization controller and a feedback posicast compensator for targeting these problems with abundant stability margin. The experimental results show that the stable range has been extended from 33% to 80%. Furthermore, it is the first literature report of this type of actuator that can track sinusoidal motion beyond the conventional stable range with an amplitude of 70% of the total range. This contribution can significantly enhance the performance of micro-sensors or expand the usage of electrostatic/magnetic actuators in motion-control systems.

Attitude controller design for the aerial trees-pruning robot based on nonsingular fast terminal sliding mode

In this article, the attitude control problem of a new-designed aerial trees-pruning robot is addressed. During the tree cutting process, the aerial trees-pruning robot will be disturbed by unknown external disturbances. At the same time, the model uncertainties will also affect the attitude controller. To overcome the above problems, an attitude controller is designed with a nonsingular fast terminal sliding mode method. First, the extended state observer is designed to estimate the modeling uncertainties and unknown disturbances. Then, the extended state observer-based nonsingular fast terminal sliding mode controller can make the tracking error of the attitude converge to zero in a finite time. Finally, a control allocation matrix switching strategy is proposed to solve the problem of the change of the aerial robot model in the cutting process. The final simulation and experimental results show that the extended state observer-based nonsingular fast terminal sliding mode controller designed in this article has good attitude control performance and can effectively overcome the modeling uncertainties and unknown disturbances. The attitude controller and control allocation matrix switching strategy ensure that the attitude angles of the aerial robot can quickly track the reference signals.