Landing Guidance Research Articles

Research on dynamic landing guidance algorithm for the maritime quadrotor

The dynamic landing guidance of the marine quadrotor is composed of trajectory guidance and landing guidance, which can't be completed by the traditional land-based landing guidance method. In addition, complex sea environment will increase the difficulty in dynamic landing guidance such as enhancing the position deviation, which will make the quadrotor unable to land accurately. To address the large trajectory tracking error when the quadrotor is flying, an adaptive step-based line-of-sight (LOS) guidance algorithm is adopted in this work to achieve dynamic three-dimensional (3D) trajectory tracking. The algorithm can not only track the trajectory of the quadrotor in a 3D space based on the position information of the wave glider, but also dynamically adjust the tracking angle and orientation in real time based on the distance and orientation information to improve the tracking accuracy. To address the low accuracy in dynamic positioning of the quadrotor while landing on the wave glider floating body, a visual landing guidance method with fused electromagnetic compensation is used. It can improve accuracy in the dynamic landing guidance of the April Tag visual reference system and reduce the interference from shaking of the wave glider floating body on landing positioning guidance of the quadrotor. The simulation results verify that the proposed algorithm can effectively reduce the trajectory tracking error of the quadrotor and accelerate trajectory convergence. The sea trial experiments prove that the trajectory tracking and landing guidance algorithm adopted in this work can well guide the quadrotor in dynamic and accurate landing on the wave glider floating body, and shorten the time.

Fixed-Time Planetary Landing Guidance With Unknown Disturbance and Thruster Constraint

This article proposes a planetary autonomous soft pinpoint adaptive fixed-time feedback landing guidance scheme based on the sliding mode control that is subject to thruster magnitude constraint, unknown control acceleration deviation, and disturbance without a priori knowledge. More specifically, a sliding surface is designed, and its gain is adjusted by the system state, increasing the convergence rate. Then, the adaptive law is proposed to compensate for the thruster magnitude constraint, unknown control acceleration deviation, and disturbance without a priori knowledge. On these bases, a thruster-magnitude-constrained feedback landing guidance is developed to ensure the fixed-time stability of the vehicle even in the presence of unknown control acceleration deviation and disturbance without priori knowledge. Furthermore, numerical simulations are performed to verify the feasibility and effectiveness of the proposed algorithms. Moreover, its near-fuel-optimal performance is illustrated by comparing it with offline fuel-optimal guidance.

Research on the Design of UAV Relay Charging High-rise Platform for Electrical Equipment Live Detection in Substation

The multi-rotor UAV inspection technology has received extensive attention in the live detection of electrical equipment in substations and has begun to be practically applied. However, due to the short endurance and the characteristics of intermittent operations, the UAV needs to frequently travel between the operational airspace and the cabin, which seriously affects the operational efficiency of the inspection. This paper first introduces the traditional substation electrical equipment live detection technology and then summarizes the application of UAV inspection in the substation electrical equipment live detection. Finally, in view of the shortcomings of the existing technology, this paper proposes a design scheme of a relay-charging high-rise platform for live detection and inspection of electrical equipment in substations. The relay charging high-rise platform can be divided into six parts according to the functional structure: high-altitude apron, UAV landing guidance system, UAV automatic binding system, high insulation strength power supply system, and platform monitoring system. In this paper, the overall structure of the relay charging high-level platform and the technical solutions of each component are described in detail. The technical solution can effectively improve the efficiency and safety of multi-rotor UAV inspection operations for live detection of electrical equipment in substations.

Real-Time Sequential Conic Optimization for Multi-Phase Rocket Landing Guidance

We introduce a multi-phase rocket landing guidance framework that can handle nonlinear dynamics and does not mandate any additional mixed-integer or nonconvex constraints to handle discrete temporal events/switching. To achieve this, we first introduce sequential conic optimization (seco), a new paradigm for solving nonconvex optimal control problems that is entirely devoid of matrix factorizations and inversions. This framework combines sequential convex programming (SCP) and first-order conic optimization and can solve unified multi-phase trajectory optimization problems in real-time. The novel features of this framework are: (1) time-interval dilation, which enables multi-phase trajectory optimization with free-transition-time; (2) single-crossing compound state-triggered constraints, which are entirely convex if the trigger and constraint conditions are convex; (3) virtual state, which is a new approach to handling artificial infeasibility in SCP methods that preserves the shapes of the constraint sets; and, (4) the use of the proportional-integral projected gradient method (pipg), a high-performance first-order conic optimization solver, in tandem with the penalized trust region (ptr) SCP algorithm. We demonstrate the efficacy and real-time capability of seco by solving a relevant multi-phase rocket landing guidance problem with nonlinear dynamics and convex constraints only, and observe that our solver is 2.7 times faster than a state-of-the-art convex optimization solver.

Guidance Law for Autonomous Takeoff and Landing of Unmanned Helicopter on Mobile Platform Based on Asymmetric Tracking Differentiator

For some flight missions, such as autonomous landing on mobile platforms, the demands on indicators such as target-tracking accuracy and so on are relatively high. To achieve this, a guidance system with excellent precision is necessary. An asymmetric tracking differentiator based on a tracking differentiator is proposed to establish the guidance system. On the basis of the proposed asymmetric tracking differentiator, an altitudinal and horizontal helicopter guidance system structure is designed. In this paper, a guidance law is designed in order to meet the accuracy and precision requirements in the autonomous landing and transition process. Apart from that, a plane-motion-guidance law is also designed to realize static and dynamic point tracking, linear route tracking and circular route tracking to improve the trajectory smoothness and accuracy. Finally, simulations of the autonomous landing process on moving platforms, including three stages, namely approaching, tracking and landing, are completed. The application effects and precision of the autonomous landing guidance algorithm under different wave heights and period conditions are analyzed through the obtained simulation curves.

Automatic Landing for Carrier-Based Aircraft Under the Conditions of Deck Motion and Carrier Airwake Disturbances

This article studies the automatic landing problem for the carrier-based aircraft in the presence of deck motion and carrier airwake disturbance. First, an automatic regressive model based prediction algorithm is proposed to generate the motion information of the deck, which in turn is used to generate corrections in the commands of the aircraft's heading and flight path to guarantee landing accuracy. Then, a fast fixed-time stable system (FFSS) is proposed. Based on the FFSS, the sliding-mode-based command differentiators are designed to estimate the first-order derivatives of the reference commands in finite time. Moreover, using the modified reaching law, the incremental sliding mode control (ISMC) is presented to design the landing guidance and control system to provide fast and accurate flight control to touchdown, where the airwake disturbances are compensated by the designed adaptive super twisting extended state observers (ASTESOs). Besides, to improve the stability during the final approach, an approach power compensation subsystem maintaining the angle of attack is proposed using the ISMC and ASTESO. The stability of the closed-loop system is analyzed using the Lyapunov theorem. Finally, comparative simulation results demonstrate the effectiveness of the proposed control scheme over state-of-the-art methods on the landing accuracy and robustness.

Multi-phase and dual aero/propulsive rocket landing guidance using successive convex programming

This paper aims to suggest a new landing guidance algorithm for reusable launch vehicles (RLVs) to enable generation of fuel-efficient trajectories based on successive convex programming. To this end, a dual aero/propulsive landing guidance problem is first formulated to fully exploit the additional moment generated by the aerodynamic control to reduce the propulsion demand required for attitude control. As the result of the aerodynamic landing phase could greatly affect the fuel-optimal trajectory during the vertical landing phase, the formulation is further extended to the multi-phase optimal guidance problem using state-triggered constraints. The proposed guidance strategy is then obtained by solving the formulated optimal control problem based on the successive convex optimization framework using an interior point method The main contribution of this study lies in forming new RLV landing guidance problems to get an optimal trajectory and transforming the corresponding nonconvex problem into a convex optimization problem by introducing appropriate combinations for convexification techniques. Additionally, this paper introduces several practical constraints, such as the maximum slew rate of aerodynamic control fins and nozzle angles, which are not considered in previous works. In this paper, the performance of the proposed method with the potential for online computation is investigated through numerical simulations.

Sliding-Mode-Control–Based Instantaneously Optimal Guidance for Precision Soft Landing on Asteroid

Precision soft landing guidance problem of a spacecraft on asteroid is addressed in this paper. Most of the methods in existing literature require linearized engagement dynamics or accurate time-to-go estimate, which is not easy to obtain in practice. To overcome these drawbacks, a heading error-dependent sliding-mode-control–based guidance approach was recently introduced in literature. However, it too suffered from disadvantages in terms of optimality and constant gravity setup-based formulation. To obviate these limitations, and, moreover, to accommodate the effect of asteroid’s angular rotation on the engagement dynamics, a sliding-mode-control–based instantaneously optimal (SMC-IO) guidance is presented in this paper, under a variable gravity setup, in which a heading-error-based sliding variable and a predefined range-dependent maximum velocity envelope profile are leveraged. A static optimization problem with square of instantaneous guidance command as the performance index and the sliding variable dynamics, velocity profile, equations of engagement, and thrust limit as constraints is solved to obtain the guidance command at every time instant. Simulation studies are presented to demonstrate the effectiveness of the presented SMC-IO guidance. An extensive comparative simulation study suggests superior performance of the SMC-IO guidance over widely referred existing landing guidance in terms of overall control effort and fuel usage.

Barrier Lyapunov Function-Based Planetary Landing Guidance for Hazardous Terrains

The landing guidance based on the barrier Lyapunov function (BLF) for hazardous terrains is investigated. Three suitable spatial geometric shapes (frustum-shape, cone-shape, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$n$</tex-math></inline-formula> -step-shape) have been chosen to describe the possible obstacles on the planetary surface. Next, a novel and general form of the barrier function (BF) has been developed using selected spatial geometric shape information, specifically designed to constrain the lateral motion. For these three different spatial geometric shapes, only the segment number of BF is different, and the segment number is determined by the spatial geometric shape. Furthermore, a fixed-time convergent function is selected as the upper boundary to coordinate the vertical motion, guaranteeing that the lander completes the landing mission within the predefined time. Next, a new nonlinear feedback guidance is designed using the asymmetric BLF constructed by the BF, keeping the lander from colliding with the obstacle and achieving the pinpoint soft landing. Finally, numerical simulations with different hazardous terrains are performed to verify the feasibility and effectiveness of the proposed algorithms.

Corrigendum to “Barrier Lyapunov Function-Based Planetary Landing Guidance for Hazardous Terrains”

In [1], the authors regret that due to the typing error and mathematical errors in the proof, three equations need to be corrected. Despite these errors, the main contributions of this article as well as the conclusions are correct.

Prediction and Compensation Model of Longitudinal and Lateral Deck Motion for Automatic Landing Guidance System

This paper mainly studies the longitudinal and lateral deck motion compensation technology. In order to ensure the safe landing of the carrier-based aircrafts on the flight decks of carriers during the landing process, it is necessary to introduce deck motion information into the guidance law information of the automatic landing guidance system when the aircraft is about to land so that the aircraft can track the deck motion. To compensate the influence of the height change in the ideal landing point on the landing process, the compensation effects of the deck motion compensators with different design parameters are verified by simulation. For further phase-lead compensation for the longitudinal automatic landing guidance system, a deck motion predictor is designed based on the particle filter optimal prediction theory and the AR model time series analysis method. Because the influence of up and down motions on the vertical motion of the ideal landing point is the largest, the compensation effects of the designed predictor and compensator are simulated and verified based on the up and down motion of the power spectrum. For the compensation for the lateral motion, a tracking strategy of the horizontal measurement axis of the inertial stability coordinate system to the horizontal axis of the hull coordinate system (center line of the deck) is proposed. The tracking effects of the horizontal measurement axis of the designed integral and inertial tracking strategies are simulated and compared. Secondly, the lateral deck motion compensation commands are designed, and the compensation effects of different forms of compensation commands are verified by simulations. Finally, the compensation effects for the lateral deck motion under integral and inertial tracking strategies are simulated and analyzed.

Rocket landing guidance using convex optimization and proportional navigation considering performance-limited engine

In recent years, convex optimization has been widely applied in aircraft trajectory optimization and guidance. For rocket vertical landing, the dynamics are highly nonlinear, which easily causes convergence issues in convex optimization. Moreover, for the existing convex optimization methods, it is difficult to implement landing guidance with a performance-limited engine in which the thrust cannot be continuously and instantly regulated. To address these two issues, a novel rocket vertical landing guidance method is developed, in which the guidance in the normal and tangential planes with respect to the rocket velocity is separated to enhance the convergence property of convex optimization. Normal guidance adopts biased proportional navigation to easily satisfy the pinpoint landing with the required attitude angles. For tangential guidance, convex optimization and model predictive control are employed to optimize the thrust command that satisfies the landing velocity limit. Based on this, an impulse equivalent transformation method is designed to derive thrust commands that satisfy the engine limits. Simulation results indicate that the proposed guidance method can achieve precise landing and satisfy various constraints while being highly robust to uncertainties. Moreover, the efficiency, convergence property, and control smoothness are significantly improved.

Aircraft Carrier Pose Tracking Based on Adaptive Region in Visual Landing

Due to its structural simplicity and its strong anti-electromagnetic ability, landing guidance based on airborne monocular vision has gained more and more attention. Monocular 6D pose tracking of the aircraft carrier is one of the key technologies in visual landing guidance. However, owing to the large range span in the process of carrier landing, the scale of the carrier target in the image variates greatly. There is still a lack of robust monocular pose tracking methods suitable for this scenario. To tackle this problem, a new aircraft carrier pose tracking algorithm based on scale-adaptive local region is proposed in this paper. Firstly, the projected contour of the carrier target is uniformly sampled to establish local circular regions. Then, the local area radius is adjusted according to the pixel scale of the projected contour to build the optimal segmentation energy function. Finally, the 6D pose tracking of the carrier target is realized by iterative optimization. Experimental results on both synthetic and real image sequences show that the proposed method achieves robust and efficient 6D pose tracking of the carrier target under the condition of large distance span, which meets the application requirements of carrier landing guidance.

Autonomous deck landing of a vertical take-off and landing unmanned aerial vehicle based on the tau theory

The research on autonomous landing of vertical take-off and landing (VTOL) unmanned aerial vehicles (UAVs) is well established. However, the research on autonomous deck landing using visual methods is relatively not so mature and many of them require the support of ground infrastructures. In order to reduce such dependencies, a ship landing guidance strategy based on on-board vision is studied. Considering the characteristics of the ship landing issue, we propose a three-phase landing scheme and a decision-making method to ensure landing safety is also studied. For improving the traditional two-dimensional (2D) optical-flow method, a three-dimensional (3D) velocity vector estimation method using image spherical optical flow is studied. Furthermore, a guidance law based on the tau theory is employed by only using the visual information of the line of sight to the target. In this phase, a trajectory-tracking controller is applied to generate the velocity commands of the UAV. Finally, the whole algorithm is validated by simulation in different wave conditions developed with Unity3D. Compared with traditional trajectory planning methods, our method does not require complex optimization iterations and can meet both the real-time and accuracy requirements of deck landing. The average tracking error of our method maintains in 0.2 m. Moreover, the whole algorithm runs efficiently at around 30 fps on a Raspberry-Pi 3B+ microcomputer which meets the real-time requirements.

Nonlinear homotopy interior-point algorithm for 6-DoF powered landing guidance

The six-degree-of-freedom (6-DoF) powered landing guidance problem usually is difficult to solve for several reasons. First, this problem coupled with low-frequency translational and high-frequency rotational equations of motion is naturally large-scale. Second, the constraints enforced into the problem are highly coupled, nonlinear and non-convex, which makes the problem quite sensitive to the initial value guesses. Third, the initial position, velocity and attitude of the landing vehicle is quite difficult to forecast due to the complex endo-atmospheric environment, thus the traditional guidance methods are difficult to obtain a predetermined trajectory. In this paper, for the first time we proposed a nonlinear homotopy interior-point optimization algorithm (NHOPT) for solving the 6-DoF powered landing guidance problem. Different from general external homotopy strategies, we embed the concept of homotopy methods into the barrier line-search interior-point method. Using vertical landing without position and velocity offset, it is easy to provide initial guesses, which we define as the initial homotopy subproblem. Then a class of related homotopy subproblems is solved along a homotopy path using the algorithm until the original problem is converged. Numerical results demonstrate that the algorithm has high performance in terms of convergence and computational efficiency.

Semi-Analytical Planetary Landing Guidance with Constraint Equations Using Model Predictive Control

With the deepening of planetary exploration, rapid decision making and descent trajectory planning capabilities are needed to cope with uncertain environmental disturbances and possible faults during planetary landings. In this article, a novel decoupling method is adopted, and the analytical three-dimensional constraint equations are derived and solved, ensuring real-time guidance computation. The three-dimensional motion modes and thrust profiles are analyzed and determined based on Pontryagin’s minimum principle, and a supporting semi-analytical reachability judgment method is presented, which can also be used to determine controllability. The algorithm is embedded in the model predictive control (MPC) framework, and several techniques are adopted to enhance stability and robustness, including thrust averaging, thrust correction after ignition, thrust reservation, and open-loop terminal guidance. Numerical simulations demonstrate that the proposed algorithm can guarantee real-time trajectory generation and meanwhile maintain considerable optimality. In addition, the MPC simulation shows that the algorithm can maintain a good accuracy under external disturbances.

Visual-based Landing Guidance System of UAV with Deep Learning Technique for Environments of Visual-detection Impairment

Visual-based Landing Guidance System of UAV with Deep Learning Technique for Environments of Visual-detection Impairment

Visual Landing Based on the Human Depth Perception in Limited Visibility and Failure of Avionic Systems.

This paper introduces a novel visual landing system applicable to the accurate landing of commercial aircraft utilizing human depth perception algorithms, named a 3D Model Landing System (3DMLS). The 3DMLS uses a simulation environment for visual landing in the failure of navigation aids/avionics, adverse weather conditions, and limited visibility. To simulate the approach path and surrounding area, the 3DMLS implements both the inertial measurement unit (IMU) and the digital elevation model (DEM). While the aircraft is in the instrument landing system (ILS) range, the 3DMLS simulates more details of the environment in addition to implementing the DOF depth perception algorithm to provide a clear visual landing path. This path is displayed on a multifunction display in the cockpit for pilots. As the pilot's eye concentrates mostly on the runway location and touch-down point, “the runway” becomes the center of focus in the environment simulation. To display and evaluate the performance of the 3DMLS and depth perception, a landing auto test is also designed and implemented to guide the aircraft along the runway. The flight path is derived simultaneously by comparison of the current aircraft and the runway position. The Unity and MATLAB software are adopted to model the 3DMLS. The accuracy and the quality of the simulated environment in terms of resolution, the field of view, frame per second, and latency are confirmed based on FSTD's visual requirements. Finally, the saliency map toolbox shows that the depth of field (DOF) implementation increases the pilot's concentration resulting in safe landing guidance.

Free Final-Time Fuel-Optimal Powered Landing Guidance Algorithm Combing Lossless Convex Optimization with Deep Neural Network Predictor

The real-time guidance algorithm is the key technology of the powered landing. Given the lack of real-time performance of the convex optimization algorithm with free final time, a lossless convex optimization (LCvx) algorithm based on the deep neural network (DNN) predictor is proposed. Firstly, the DNN predictor is built to map the optimal final time. Then, the LCvx algorithm is used to solve the problem of fuel-optimal powered landing with the given final time. The optimality and real-time performance of the proposed algorithm are verified by numerical examples. Finally, a closed-loop simulation framework is constructed, and the accuracy of landing under various disturbances is verified. The proposed method does not need complex iterative operations compared with the traditional algorithm with free final time. Therefore, the computational efficiency can be improved by an order of magnitude.

Semi-analytical adaptive guidance computation for autonomous planetary landing

A novel algorithm for autonomous landing guidance computation is presented. The trajectory is expressed in polynomial form of minimum order to satisfy a set of 17 boundary constraints, depending on 2 parameters: time-of-flight and initial thrust magnitude. The consequent control acceleration is expressed in terms of differential algebraic (DA) variables, expanded around the point of the domain along the nominal trajectory followed at the retargeting epoch. The DA representation of the objective and constraints gives additional information about their sensitivity to variations of the optimization variables, which is exploited to find the desired fuel minimum solution (if existing) robustly and with a very light computational effort.