Q.P. Chu

Q.P. Chu

Ph.D

About

264
Publications
76,402
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
4,928
Citations

Publications

Publications (264)
Conference Paper
View Video Presentation: https://doi.org/10.2514/6.2022-0761.vid This paper presents a sampled-data form of the recently reformulated incremental nonlinear dynamic inversion (INDI) applied for robust spacecraft attitude control. INDI is a combined model- and sensor-based approach mostly applied for attitude control that only requires an accurate co...
Article
Bobbin tool friction stir welding (BT-FSW) is a promising solid-state welding process for fabricating closed or hollow profiles due to its self-supporting nature, which is achieved using a combined tool consisting of two shoulders and a penetrating pin, releasing the backing plate. The joint reliability is mainly affected by its macro-/micro-featur...
Article
Abstact The precipitation behavior and development of grain structure have been investigated to reveal their association with the microhardness and corrosion resistance of probeless friction stir spot welded (P-FSSW) joint of an Al-Li alloy. Results identified the primary strengthening phase of T1 (Al2CuLi) to be completely dissolved in the stir zo...
Article
The effect of tool morphology on the joint forming during probeless friction stir spot welding (P-FSSW) of an Al-Li alloy was evaluated with the assistance of experiments and numerical simulation. Compared to the flat tool, the surface temperature not only increased rapidly at the inner side of the shoulder periphery, but also locally appeared high...
Article
Synergetic double-sided probeless friction stir spot welding is a novel process proposed in this study, which is used to solve the contradiction between the improvement of metallurgical bonding and deterioration of hook defect. The effect of the coordinated movement of the tools on the joint formation was evaluated based on the coupled Eulerian-Lag...
Article
Full-text available
To manage air data sensor fault detection and diagnosis in the presence of atmospheric turbulence is challenging since the effects of faults and turbulence are coupled. Existing fault detection and diagnosis approaches can not decouple the faults from the turbulence. To address this challenge, this paper first proposes a novel kinematic model which...
Article
Incremental nonlinear dynamic inversion (INDI)-based controller is a promising technique that can be adopted to control dynamic systems with high nonlinearities and extended cross-coupling effects. This paper presents the incremental strategy adopted as a sensor-based controller approach for the Apache AH-64D Longbow helicopter. The strength of the...
Preprint
Full-text available
This paper proposes a novel and practical framework for safe flight envelope estimation and protection, in order to prevent loss-of-control-related accidents. Conventional analytical envelope estimation methods fail to function efficiently for systems with high dimensionality and complex dynamics, which is often the case for high-fidelity aircraft...
Article
This paper presents an agile and robust spacecraft attitude tracking controller using the recently reformulated incremental nonlinear dynamic inversion (INDI). INDI is a combined model- and sensor-based control approach that only requires a control effectiveness model and measurements of the state and some of its derivatives, making a reduced depen...
Article
This paper proposes a novel and practical framework for safe flight envelope estimation and protection, in order to prevent loss-of-control-related accidents. Conventional analytical envelope estimation methods fail to function efficiently for systems with high dimensionality and complex dynamics, which is often the case for high-fidelity aircraft...
Conference Paper
Full-text available
For mitigating the chattering effect in the sliding mode control (SMC), many adaption mechanisms have been proposed to reduce the switching gains. However, less attention is paid to the control structure, which influences the resulting uncertainty term and determines the minimum possible gains. This paper compares three control structures for induc...
Article
Recently, several insect- and hummingbird-inspired tailless flapping wing robots have been introduced. However, their flight dynamics, which are likely to be similar to that of their biological counterparts, remain yet to be fully understood. We propose a minimal dynamic model that is not only validated with experimental data, but also able to pred...
Article
Full-text available
This paper designs an incremental nonlinear dynamic inversion control law for free-flying flexible aircraft, which can regulate rigid-body motions, alleviate gust loads, reduce the wing root bending moment, and suppress elastic modes. By fully exploring the sensor measurements, the model dependency of the proposed control law can be reduced while m...
Conference Paper
This paper discusses the design, implementation and flight testing of an incremental Backstep-ping (IBS) based manual flight control law with angular accelerometer (AA) feedback. The main advantages of incremental control laws are that they only require a partial model of the system and are of low complexity. Incremental control laws for aircraft rot...
Article
High precision motion control of hydraulic manipulators is challenging due to the highly nonlinear dynamics and model uncertainties typical for hydraulic actuators. This paper addresses the implementation of a novel sensor-based Incremental Nonlinear Dynamic Inversion control technique for a high-precision hydraulic force controller in existence of...
Article
Full-text available
High-speed flight in GPS-denied environments is currently an important frontier in the research on autonomous flight of micro air vehicles. Autonomous drone races stimulate the advances in this area by representing a very challenging case with tight turns, texture-less floors, and dynamic spectators around the track. These properties hamper the use...
Article
AA2198 joints were produced using the probeless friction stir spot welding (P-FSSW). Numerical modeling of the process based on the Coupled Eulerian-Lagrangian technique was developed to investigate the material flow. The modeling and experimental observations provide a consistent interpretation of the circumferential material flow which has some i...
Article
Full-text available
To explore the aerodynamic effects on a quadrotor in the high-speed flight regime and establish an accurate nonlinear model, free-flight tests with a quadrotor are carried out in a large-scale wind tunnel. The flight data reveal that complex aerodynamic interactions could appear and significantly influence the forces and moments acting on the quadr...
Article
Double-side probeless friction stir spot welding (DP-FSSW) of AA2198 alloy was conducted to investigate the microstructure and mechanical properties. Compared with common single-side probeless friction stir spot welding (P-FSSW), the plastic strain during DP-FSSW is nearly symmetrical with respect to the bondline to suppress the extension of hook d...
Article
Full-text available
Sheets of AA2198 alloy with various surface conditions were welded with probeless friction stir spot welding (P-FSSW). Results show that the oxide layer on the original lap-weld surface produces continuously distributed oxide impurities at the interface of the P-FSSWed joint with a large amount of voids. The visual flow at the interface provides a...
Article
The precipitate evolution and material flow visualization during probeless friction stir spot welding (P-FSSW) of an Al-Li alloy has been investigated experimentally and numerically in this work. Due to severe heat input during welding, the main strengthening phases of T1 fully dissolved in the stir zone followed by the re-precipitation of GP zone...
Article
Full-text available
A finite element model based on software Abaqus/Explicit and experimentation was established to describe the probeless friction stir spot welding process of 2198-T8 aluminium alloy. An Arbitrary Lagrangian–Eulerian method was adopted in this model in which the Johnson–Cook equation was used to describe the flow stress depending on temperature, plas...
Article
Full-text available
This paper presents the cascaded integration of Incremental Nonlinear Dynamic Inversion (INDI) for attitude control and INDI for position control of micro air vehicles. Significant improvements over a traditional Proportional Integral Derivative (PID) controller are demonstrated in an experiment where the quadrotor flies in and out of a 10 m/s wind...
Article
Full-text available
Dual heuristic programming has gained an increasing interest in recent years because it provides an effective process for optimal adaptive control of uncertain nonlinear systems. However, it requires an off-line stage to train a global system model from a representative model, which is often infeasible to obtain in practice. This paper presents a n...
Article
In this work, a third generation Al-Li alloy has been successfully spot welded with probeless friction stir spot welding (P-FSSW), which is a variant of conventional friction stir welding. The Box-Behnken experimental design in response surface methodology (RSM) was applied to optimize the P-FSSW parameters to attain maximum tensile/shear strength...
Article
Full-text available
The research presented in this paper focuses on the effects of structural failures on the safe flight envelope of an aircraft, which is the set of all the states in which safe maneuver of the aircraft can be assured. Nonlinear reachability analysis based on an optimal control formulation is performed to estimate the safe flight envelope using actua...
Conference Paper
This paper describes the design, implementation and flight testing of flight control laws based on Incremental nonlinear Dynamic Inversion (INDI). The method compares commanded and measured accelerations to compute increments on the current control deflections. This results in highly robust control solutions with respect to model uncertainties as w...
Conference Paper
This paper presents the design and implementation of incremental backstepping (IBS) flight control laws for the attitude control and stabilization on a fixed-wing aircraft. The design consists of multiple functionalities such as command-filtered backstepping, angle of attack control and body attitude control, that are based around an incremental co...
Chapter
Full-text available
An adaptive Backstepping attitude control law based on Immersion and Invariance (I&I) is developed for the TU Delft FAST-D micro-satellite. Tackling both system uncertainties and disturbances, a general additively disturbed rotational dynamics model is considered. In the I&I framework the parameters to be estimated are typically constant. Here, how...
Conference Paper
Full-text available
This paper presents an adaptive control technique to deal with spacecraft attitude tracking and disturbance rejection problems in the presence of model uncertainties. Approximate dynamic programming has been proposed to solve adaptive, optimal control problems without using accurate systems models. Within this category, linear approximate dynamic p...
Conference Paper
Full-text available
A self-learning controller which makes quick and successful adaptations to new conditions can considerably benefit autonomous operations of launch vehicles. To provide a model-free, adaptive process for optimal control, approximate dynamic programming has been introduced to aerospace engineering. A widely used structure of approximate dynamic progr...
Article
Full-text available
Safe flight-envelope prediction is essential for preventing aircraft loss of control after the occurrence of sudden structural damage and aerodynamic failures. Considering the unpredictable nature of such failures, many challenges remain in the process of implementing such a prediction system. In this paper, an approach to online safe flight-envelo...
Conference Paper
Full-text available
Maintaining stable flight during high turbulence intensities is challenging for fixed-wing micro air vehicles (MAV). Two methods are proposed to improve the disturbance rejection performance of the MAV: incremental nonlinear dynamic inversion (INDI) control and phase-advanced pitch probes. INDI uses the angular acceleration measurements to countera...
Article
Recently, multivariate simplex B-splines (MVSB) function approximators have been investigated with the aim of providing accurate global aerodynamic models for use in adaptive flight control systems. In this paper, a new approach for constructing multivariate spline models is presented in the form of the tensor-product MVSB (TP-MVSB) that consists o...
Article
A third generation Al-Li alloy has been successfully welded by probeless friction stir spot welding (P-FSSW). The joints presented symmetrical ‘basin’ shapes and two distinct regions were observed: the stir zone (SZ) and the thermo-mechanically affected zone (TMAZ), which were characterized by recrystallized grains and deformed grains, respectively...
Conference Paper
Full-text available
Previous results reported in the robotics literature show the relationship between time-delay control (TDC) and proportional-integral-derivative control (PID). In this paper, we show that incremental nonlinear dynamic inversion (INDI) - more familiar in the aerospace community - are in fact equivalent to TDC. This leads to a meaningful and systemat...
Article
Hydraulic driven manipulators face serious control problems due to the nonlinear system dynamics and model and parametric uncertainties of hydraulic actuators. In this paper, a novel sensor-based Incremental Nonlinear Dynamic Inversion controller is applied to force tracking control of hydraulic actuators of a hexapod flight simulator motion system...
Article
Full-text available
Accurate and reliable estimation of the kinematic state of a six degrees-of-freedom Stewart platform is a problem of interest in various engineering disciplines. Particularly so in the area of flight simulation, where the Stewart platform is in widespread use for the generation of motion similar to that experienced in actual flight. Accurate measur...
Conference Paper
An adaptive Backstepping attitude control law based on Immersion and Invariance (I&I) is developed for the TU Delft FAST-D micro-satellite. Tackling both system uncertainties and disturbances, a general additively disturbed rotational dynamics model is considered. In the I&I framework the parameters to be estimated are typically constant. Here, how...
Article
Full-text available
Monocular vision is increasingly used in micro air vehicles for navigation. In particular, optical flow, inspired by flying insects, is used to perceive vehicle movement with respect to the surroundings or sense changes in the environment. However, optical flow does not directly provide us the distance to an object or velocity, but the ratio of the...
Article
Self-learning approaches, such as reinforcement learning, offer new possibilities for autonomous control of uncertain or time-varying systems. However, exploring an unknown environment under limited prediction capabilities is a challenge for a learning agent. If the environment is dangerous, free exploration can result in physical damage or in an o...
Article
Full-text available
Previous results reported in the robotics literature show the relationship between $\textit{time-delay control}$ (TDC) and $\textit{proportional-integral-derivative control}$ (PID). In this paper, we show that $\textit{incremental nonlinear dynamic inversion}$ (INDI) $-$ more familiar in the aerospace community $-$ are in fact equivalent to TDC. Th...
Conference Paper
An Angular Accelerometer Measurement Unit can be constructed from three single-axis angular acceleration sensors, established on a 3-axes oriented mounting block. Investigating the cross-axis sensitivity and input axis misalignment characteristics are critical when considering the unit’s role as a basis for an inertial reference system, or for prov...
Conference Paper
Full-text available
Monocular vision is increasingly used in Micro Air Vehicles for navigation. In particular, optical flow, inspired by flying insects, is used to perceive vehicles' movement with respect to the surroundings or sense changes in the environment. However, optical flow does not directly provide us the distance to an object or velocity, but the ratio of t...
Conference Paper
Full-text available
A self-learning adaptive flight control design allows reliable and effective operation of flight vehicles in a complex environment. Reinforcement Learning provides a model-free, adaptive, and effective process for optimal control and navigation. This paper presents a new and systematic approach combining Q-learning and hierarchical reinforcement le...
Conference Paper
Full-text available
This paper presents a new and effective approach , incremental model based heuristic dynamic programming, to design an adaptive near-optimal controller without a-prior knowledge of the dynamic model. Both traditional heuristic dynamic programming algorithm and incremen-tal model based heuristic dynamic programming algorithm are provided and applied...