Attitude Control Approach Research Articles

Enhancing stability and position control of a constrained magnetic levitation system through optimal fractional-order PID controller

Magnetic levitation systems are complex and nonlinear, requiring sophisticated control methods to maintain the stability and position of the levitated object. This research presents an optimized fractional order PID (FOPID) control approach for position control of a freely-suspended ferromagnetic object. The dynamic system model is mathematically modeled in MATLAB using first-principle modeling and the grey box method. The FOPID controller has five degrees of freedom (DOFs) that allow for fine-tuning of the control gains and fractional orders, enabling the system to handle the nonlinearity inherent in the magnetic levitation system. The DOFs of FOPID and integer order PID controllers are optimized using the Artificial Bee Colony (ABC) algorithm and results are compared with state-of-the-art optimization methods. The results showed that the FOPID controller can effectively control the magnetic levitation system with constraints and outperforms other methods by up to 92.14% in terms of settling time with negligible steady-state error.

Research on UAV flight attitude control system based on simulink and genetic algorithm

With the evolution of networking and information technology, unmanned aerial vehicles (UAVs) have emerged as integral components in numerous fields, executing diverse and vital tasks. The accuracy and efficiency of UAV operations are greatly influenced by their attitude control systems, which dictate flight stability, speed, and functionality. However, traditional control methods for UAV flight stability and accuracy have become outdated, unable to meet the demands of modern applications. To address these challenges, this study introduces a novel attitude control approach based on genetic algorithms. This method utilizes the principles of natural selection and genetic traits to optimize the parameters of the attitude control system. The objective is to enhance the current control effectiveness, improve the UAV's maneuverability, and enable its versatile applications across multiple fields. Simulink tool simulations are conducted to evaluate the stability of the optimized results. This simulation tool allows for the replication of real-world flight conditions and the assessment of the attitude control system's performance under various scenarios. The results of these simulations provide valuable insights into the effectiveness of the genetic algorithm-based attitude control method. This study contributes to the advancement of UAV technology by improving the accuracy and stability of attitude control systems. It paves the way for more efficient and reliable UAV operations in various fields, from environmental monitoring to search-and-rescue missions, thus enhancing their operational capabilities and expanding their potential applications.

A Predefined-Time Extended-State Observer-Based Approach for Velocity-Free Attitude Control of Spacecraft

A Predefined-Time Extended-State Observer-Based Approach for Velocity-Free Attitude Control of Spacecraft

Designing attitude controller for nano/pico satellites at detumbling mode using magnetic sensor and actuator

Recently, satellites have been becoming economically attractive in many applications using the advanced technologies and payloads. Practically, the launching process of any satellite passes through some stages under different conditions. For example, the satellite might be uncontrollable in the detumbling mode. Thus, it might be a risk of accident with space debris and the satellite can not complete the specified mission. So it is necessary to design an attitude controller to stabilize the satellite after the separation phase, i.e., in the detumbling mode. In this paper, we design an attitude controller to bring the satellite to the desired condition with a minimum angular momentum. The magnetorquers and magnometers are an effective solution for the satellite in low-Earth orbits because they are smaller and lighter than others. Simulation studies are presented to validate the proposed attitude control approaches.

Trajectory control of a hydraulic system using intelligent control approach based on adaptive prediction model

Electro-hydraulic actuators (EHAs) have become a preferred alternative to traditional hydraulic actuators with valve control systems due to their numerous advantages, making them an ideal choice for applications requiring high-precision force or position control. However, the highly complex nonlinear nature of EHAs makes modelling and controlling them a challenging task. To address this challenge, a new position control approach has been proposed for an EHA system using a combination of a feedforward online-tuning PID (FOPID) controller and an adaptive grey predictor (AGP), known as the feedforward online-tuning adaptive grey predictor (FOAGP). The FOPID controller is constructed based on PID controller and fuzzy logic algorithm to control the EHA system towards referred trajectory, while an updating rule that consists of robust checking terms optimizes its parameters online to minimize control error. The AGP predictor is an important aspect of the proposed approach. It consists of a self-tuning step size mechanism, which estimates the performance of the plant to tune the parameters of the controller and create an additive control signal that is used to counteract environment noises and perturbations. This approach significantly improves control performance by reducing the effect of disturbances and sensor noises on the system. The FOAGP approach was tested in simulation to investigate its effectiveness. The results showed that the proposed approach outperformed other existing control methods, with a higher accuracy and better control performance. One of the significant advantages of the FOAGP approach is its ability to learn and adapt to changing system dynamics. The learning mechanism used in the FOPID controller allows the system to optimize its parameters online, which is especially useful in systems with varying operating conditions. The AGP predictor also continuously adjusts its parameters to accurately estimate the system output, making it an effective tool for controlling EHAs. The proposed approach offers a significant improvement in control performance, making it a better alternative to traditional control methods. This approach can be applied to various EHA systems, including those used in aerospace, automobile, and robotic applications, among others.

Hybrid Position‐Compliance Control of Redundantly Actuated Parallel Kinematic Manipulators Equipped with Serial Elastic Actuators

AbstractRedundantly actuated parallel kinematic manipulators (RA‐PKM) are ideal candidates in robotic applications combining dynamic performance with high accuracy. Actuation redundancy further allows for modulation of the end‐effector (EE) stiffness. A recent trend in robotics is the use of inherently compliant and elastic components, eventually leading to soft continuum robots, which shall provide tailored solutions for human‐robot collaboration and assistance applications. One way to introduce compliance is to use serial elastic actuators (SEA). This yields two kinematically decoupled dynamic systems, the RA‐PKM mechanism and the actuation system, that are force‐coupled by (passive) elastic elements. The DOF of the actuation system exceeds the DOF of the RA‐PKM according to the degree of actuation redundancy. Due to the kinematic decoupling the RA‐PKM is underactuated. To address this issue, a flatness‐based feedback‐linearizing position control approach along with a stiffness modulation approach is proposed.

A State Observer-Based Fractional-Order Approach for Trajectory Tracking and Attitude Control of A Quadrotor

With the expanding utility base of unmanned aerial vehicles (UAVs), there comes a strong need for dedicated research towards effective control strategies for these aircraft. This paper presents a feedback control scheme for the trajectory tracking and flight control problem for quadrotor-type UAVs. In particular, a robust fractional-order sliding mode control (FOSMC) scheme based on a state observer approach, consisting of position tracking and an attitude control strategy, is proposed. The basic idea behind choosing the state observer technique is to prevent the chattering phenomenon in this highly non-linear and under-actuated dynamic structure, and preserve the robustness and finite time reachability properties of Sliding Mode controllers. The stability of the proposed control law is proved using Lyapunov’s theorem. Furthermore, a detailed performance analysis of the proposed method is presented in comparison to the existing control algorithms from the recent literature. The obtained results are found promising.

Linear Parameter Varying Controller Design For Satellite Attitude Control*

This paper presents a systematic linear parameter varying (LPV) control approach for the 3-axis attitude control of an Earth-observation satellite in a sun-synchronous orbit. The dynamics of the satellite depend on the orientation of the solar array which completes a full rotation every orbit, thus it is used as a scheduling parameter in the design. The satellite has two additional flexible appendages; these are 2 scatterometers. The control objective is to precisely track a given reference attitude using reaction wheels, while rejecting external torque disturbances and sensor noise. The design follows a mixed-sensitivity approach, applying a recently introduced weighting scheme. It allows traceable and effective controller tuning by using a low number of physically interpretable weights. The controller is synthesised by solving the induced L2-norm of the closed-loop interconnection of the controller and weighted plant. Scheduling with the solar array orientation leads to an LPV notching behaviour in the controller that effectively mitigates the effects of the array's most prominent flexible modes. This behaviour enables increased performance, when compared to a linear time invariant controller, while maintaining robustness. The pointing performance of the synthesised controller over the complete satellite lifecycle is verified using the European Space Agency's standards for spacecraft attitude control.

Fractional‐order sliding mode attitude coordinated control for spacecraft formation flying with unreliable wireless communication

This paper investigates the coordinated attitude control problem with fractional order sliding mode control theory for spacecraft formation flying by considering of unknown disturbance, inertia uncertainty, partial loss of actuators, and communication delay. Two types of fractional order sliding mode control laws are proposed to solve the considered design problem. The first one is based on the Chebyshev neural network technique, and the second one is involved with the integral-type and super-twisting sliding mode control methods. Compared to traditional sliding mode control methods, the developed fractional order sliding mode control strategies can achieve a faster convergence speed. Simulation results based on a group of three spacecrafts are presented to demonstrate the performance of the proposed coordinated attitude control approaches.

Visual servoing for coordinated precise attitude control in the TOM small satellite formation

Formations of multiple satellites observe target areas on the Earth’s surface from different perspectives, enabling construction of 3D surface maps by photogrammetric methods. The main objective of TOM (Telematics Earth Observation Mission) is to monitor ash clouds during Volcanic Eruptions with a satellite formation consisting of three CubeSats. TOM is Bavaria’s contribution to the multi-national Telematics International Mission (TIM), composed of 7 satellites by partners from 4 continents. To achieve sufficient overlap of the images for the usage of photogrammetric methods, very precise and coordinated attitude control of the satellites is necessary. This paper presents a vision-based attitude control approach using image data to calculate the control input, also referred to as visual servoing. Thus, the cameras and data processing capacity onboard the CubeSats will be used for both image acquisition and attitude determination, eliminating the need for additional precise attitude sensors like star trackers. To perform visual servoing, highly distinctive features are identified and tracked in the images. The control input for reaction wheels is calculated from the movement of the features between consecutive images. To ensure that the images captured by the different satellites overlap sufficiently for photogrammetric processing, the satellites track the same target area based on feature data exchange directly between the satellites. Simulations of realistic scenarios based on the TOM project show the applicability of the presented attitude control approach. In a first step, a software-based Earth observation simulator generates the acquired images, demonstrating feasibility to compute and track features in satellite images to compute the AOCS (Attitude and Orbit Control System) input. In the second step, hardware-in-the-loop (HiL) simulations allow to realistically characterize the performance of this approach. This HiL environment utilizes two high-precision/high-dynamics turntables as 3-axis attitude simulators, where the satellites with their cameras are mounted, while the observation target is mounted on a mobile robot to simulate the relative orbit motion.

Fractional-order nonsingular terminal sliding mode controller for a quadrotor with disturbances

This paper proposes a finite-time controller for an unmanned aerial vehicle in the presence of Figures/uncertainties using fractional-order terminal sliding mode. First, contrary to existing fractional-order backstepping sliding mode controllers, this paper introduces a new control approach for quadrotor position control, which is based on fractional-order fast terminal backstepping sliding mode control. Using an appropriate sliding surface, the position tracking error converges to zero in finite time while providing good robustness properties in different complex path scenarios under unknown disturbances. Then, a novel fractional-order fast terminal sliding mode control scheme is developed for quadrotor attitude control, which provides good properties in terms of robustness against unknown disturbances, and in terms of convergence time, etc. Finally, simulation results are presented to discuss the advantages of the hybrid control approach proposed in this work for quadrotors under unknown disturbances compared to other existing controllers.

Tip Position Control and Vibration Suppression of a Planar Two-Link Rigid-Flexible Underactuated Manipulator.

When a flexible link manipulator lacks a joint motor, how to use the remaining motors to achieve the control objective is a challenge, and the research in this direction is limited. This article presents a tip position control and vibration suppression approach for a planar two-link rigid-flexible (TLRF) underactuated manipulator with a passive first joint. First, we establish a dynamic model of the system by using the assumed mode method (AMM) and the Lagrangian modeling method. Then, we obtain the dynamic coupling relationship of the two links based on the dynamic model. According to this dynamic coupling relationship, we find that the passive rigid link can be controlled indirectly by controlling the active flexible link. Thus, we calculate the target angles of the two links by using the inverse kinematic method and design a controller for the active flexible link to stabilize it at its target angle and to suppress its vibration. Next, we optimize the parameters of this controller by using the genetic algorithm (GA). GA helps us simultaneously stabilize the passive rigid link at its target angle while realizing the control objective of the active flexible link. The simulation results demonstrate the effectiveness of the proposed control approach.

Position Controller for a Flapping-Wing Drone Using UWB

This paper proposes an integral approach for accurate ultra-wideband indoor position control of flapping-wing micro-air vehicles. Three aspects are considered to achieve a reliable and accurate position controller. The first aspect is a velocity/attitude flapping-wing model for drag compensation. The model is compared with real flight data and shown to be applicable for more than one type of flapping-wing drone. The second improvement regards a voltage-dependent thrust control. Lastly, a characterisation of ground effects in flapping-wing flight is obtained from hovering experiments. The proposed controller improves position control by a factor [Formula: see text], reaching a mean absolute error of 10[Formula: see text]cm for the position in [Formula: see text] and [Formula: see text], and 4.9[Formula: see text]cm for the position in [Formula: see text].

Pose Tracking Control for Spacecraft Proximity Operations Using the Udwadia–Kalaba Framework

This paper develops an analytical dynamics-based approach for simultaneous position and orientation tracking control of a chaser spacecraft with respect to an uncontrolled target. The control requirements are formulated as holonomic or nonholonomic constraints, which are expressed as linear and angular acceleration constraints. The complete six-degree-of-freedom formulation of the Udwadia–Kalaba-based pose tracking controller generating exact real-time control forces and torques is presented. For design purposes, the method assumes a precise knowledge of the system parameters and states, along with perfect control action by the actuators. The exponential convergence of the constraint dynamics is proven using the Lyapunov stability theory. Simulation results demonstrate exponentially stable position and orientation tracking for close-proximity operations in perturbed low Earth orbits. Finally, the controller is experimentally validated using the Spacecraft Proximity Operations Testbed at Carleton University.

A Simple Structure Constrained Attitude Control for Rigid Bodies: A PD-Type Control

This study investigates the challenging and complicated issue of full-state constraint attitude control for rigid bodies under actuators physical limitation. Using the concept of prescribed performance control (PPC), a novel proportional-derivative (PD)-type control is introduced by which both the attitude quaternion and the rotation velocity of the rigid body are enforced to possess specific behaviors in transient and steady state. To this end, a prescribed performance function (PPF) with finite-time convergence is first defined as the predefined boundaries for the quaternion and rotation velocity. Subsequently, a constrained PD-type attitude control for rigid body attitude system is developed. The significant difference between the proposed methodology and the PPC is the simple structure of the controller making it more applicable from practical implementation point of view. Indeed, due to the use of error transformation in the PPC, the controller contains partial derivative terms and complicated functions even for only constraining the attitude quaternion. When it comes to angular velocity constraint as well, the complexity of the control design procedure is doubled. It is rigorously proved that the suggested control framework can successfully satisfy constraints not only on the quaternion but also on the angular velocity, simultaneously. These interesting results are obtained even when the actuator saturation is considered. The simulation results conducted on a rigid spacecraft verify the efficacy and applicability of the suggested constrained attitude control approach.

Robust finite-time control design for attitude stabilization of spacecraft under measurement uncertainties

This paper investigates the finite-time attitude stabilization of spacecraft under multiple uncertainties. Besides inertia uncertainties, external disturbances, and actuator faults, the measurement uncertainties are particularly considered. When including the measurement uncertainties, the spacecraft attitude control system becomes a mismatching system, which brings a great challenge to the control design. To resolve this problem, a novel robust finite-time attitude control approach is proposed by using a dual-disturbance-observer-based structure. First, two finite-time disturbance observers are developed to estimate the mismatched and matched lumped disturbances in the spacecraft attitude kinematics and dynamics, respectively. Then, the robust finite-time attitude controller is synthesized by incorporating the two finite-time disturbance observers into the adding a power integrator technique. It is strictly proved that the proposed robust finite-time attitude controller can ensure the actual attitude and angular velocity stabilize to the small neighborhoods around the origin in finite time even subject to multiple uncertainties. Benefiting from the feedforward disturbance compensation, the proposed controller is not only robust against inertia uncertainties, external disturbances, and actuator faults, but also insensitive to measurement uncertainties. Lastly, the effectiveness and advantages of the proposed control approach are validated through simulations and comparisons.

Reinforcement learning-based dynamic position control of mobile node for ocean sensor networks

In this paper, a novel dynamic position control (PC) approach for mobile nodes (MNs) is proposed for ocean sensor networks (OSNs) which directly utilizes a neural network to represent a PC strategy. The calculation of position estimation no longer needs to be carried out in the proposed scheme, so the localization error is eliminated. In addition, reinforcement learning is used to train the PC strategy, so that the MN can learn a more highly accurate and fast response control strategy. Moreover, to verify its applicability to the real-world environment, we conducted field experiment deployment in OSNs consisting of a MN designed by us and some fixed nodes. The experimental results demonstrate the effectiveness of our proposed control scheme with impressive improvements on PC accuracy by more than 53% and response speed by more than 15%.

Task-Based Design Approach: Development of a Planar Cable-Driven Parallel Robot for Upper Limb Rehabilitation

This paper deals with the optimal design of a planar cable-driven parallel robot (CDPR), with three degrees of freedom, intended for assisting the patient’s affected upper limb along a prescribed movement. A Qualisys motion capture system was used to record the prescribed task performed by a healthy subject. For each pose taken by the center of mass of the end-effector, the cable tensions, the elastic stiffness and the dexterity were optimized while satisfying a set of constraints. First, a multiobjective formulation of the optimization problem was adopted. Since selecting a single solution among the multiple ones given by the Pareto front presents an issue, a mono-objective formulation was chosen, where the objective function was defined as a weighted sum of the chosen criteria. The appropriate values of the weighted coefficients were studied with the aim of identifying their influence on the optimization process and, thus, a judicious choice was made. A prototype of the optimal design of the CDPR was developed and validated experimentally on the prescribed workspace using the position control approach for the motors. The tests showed promising reliability of the proposed design for the task.

Velocity-Free Attitude Control of Quadrotors: A Nonlinear Negative Imaginary Approach.

In this paper, we propose a new approach to the attitude control of quadrotors, by which angular velocity measurements or a model-based observer reconstructing the angular velocity are not needed. The proposed approach is based on recent stability results obtained for nonlinear negative imaginary systems. In specific, through an inner-outer loop method, we establish the nonlinear negative imaginary property of the quadrotor rotational subsystem. Then, a strictly negative imaginary controller is synthesized using the nonlinear negative imaginary results. This guarantees the robust asymptotic stability of the attitude of the quadrotor in the face of modeling uncertainties and external disturbances. First simulation results underline the effectiveness of the proposed attitude control approach are presented.

LSTM-Based Output-Constrained Adaptive Fault-Tolerant Control for Fixed-Wing UAV with High Dynamic Disturbances and Actuator Faults

The unknown disturbances and the changing uncertainties bring difficulties for designing a stable attitude controller for UAV. In this paper, a novel adaptive fault-tolerant attitude control approach is designed based on the long short-term memory (LSTM) network for the fixed-wing UAV subject to the high dynamic disturbances and actuator faults. Firstly, the high dynamic disturbances can be compensated by the adaptive laws. Meanwhile, the actuator faults can be handled by the proposed adaptive fault-tolerant control (AFTC) scheme. Moreover, the LSTM network is introduced to approximate the unknown and time-accumulating nonlinearities. With the introduction of the one-to-one nonlinear mapping (NM), the output constraints in the control system can be guaranteed. Additionally, it can be demonstrated that the boundness of all the signals can be assured. At last, numerical simulation results are provided to illustrate the effectiveness of the proposed method.