Hardware-in-the-Loop Simulation of an Extended Non-Linear Dynamic Inversion Augmented with an Immunity-Based Adaptive Control System

This paper presents a novel configuration for guidance and tracking control laws for unmanned air vehicles (UAV) based on an extended nonlinear dynamic inversion (NLDI) approach. Current outer/inner loop architectures use dynamic inversion for the outer loop controller while using linear compensation-type control for inner loops. That design, although it performs well at nominal conditions, lacks robustness under certain upset flight conditions. The design proposed in this paper includes inner and outer loop control modules that both rely on the use of an NLDI control scheme. The main objective of the control laws is to minimize forward, lateral, and vertical distances with respect to a desired trajectory, and maintain stability and adequate performance in the presence of sub-system failures and upset environmental conditions. The implementation of this control laws scheme is illustrated through a simulation example using a mathematical model of the West Virginia University (WVU) YF-22 UAV. The performance of the control laws is evaluated during autonomous flight in terms of trajectory tracking errors and control activity at nominal and abnormal conditions including actuator and sensor failures and excessive turbulence. The results obtained with the WVU UAV simulation environment show that for all cases investigated the extended NLDI approach has desirable fault tolerant capabilities.

This paper presents an advanced single network adaptive critic (SNAC) aided nonlinear dynamic inversion (NDI) approach for simultaneous attitude control and trajectory tracking of a micro-quadrotor. Control of micro-quadrotors is a challenging problem due to its small size, strong coupling in pitch-yaw-roll and aerodynamic effects that often need to be ignored in the control design process to avoid mathematical complexities. In the proposed SNAC aided NDI approach, the gains of the dynamic inversion design are selected in such a way that the resulting controller behaves closely to a pre-synthesized SNAC controller for the output regulation problem. However, since SNAC is based on optimal control theory, it makes the dynamic inversion controller to operate near optimal and enhances its robustness property as well. More important, it retains two major benefits of dynamic inversion: (i) closed form expression of the controller and (ii) easy scalability to command tracking application even without any apriori knowledge of the reference command. Effectiveness of the proposed controller is demonstrated from six degree-of-freedom simulation studies of a micro-quadrotor. It has also been observed that the proposed SNAC aided NDI approach is more robust to modeling inaccuracies, as compared to the NDI controller designed independently from time domain specifications.

In this paper the operation and control of battery-less hybrid systems for off-grid power supply is investigated. The load demand of the system is covered by a diesel-driven generator (DDG) and photovoltaic (PV) arrays. First, an overview of the features and operation of such systems is provided. Primary control of the system is investigated where the PV inverter curtails its active power in order to respect the minimum load ratio of the DDG and contribute to frequency control. Secondary control of the system is applied using the Hardware in the Loop (HIL) technique, where parts of the real-time simulation are replaced with actual physical components. Hardware controllable loads are activated by a hardware controller in order to respect the minimum load ratio of the DDG. An alternative method is applied where instead of controllable loads a hardware PV inverter curtails its active power production. The HIL simulation results show that both methods are effective to reduce the frequency deviation of the system and maintain the power output of the DDG above the predefined minimum requirement. The tests were performed with a combination of Controller HIL and Power HIL simulation leading to more realistic testing than Controller HIL simulation or pure digital simulation.

This paper presents a Hardware in the loop (HIL) simulation of a microcontroller using non-linear control implemented in PFC (Power Factor Correction) boost, buck and SEPIC converters. This is a non-conventional approach, where libraries are used to directly interface with the Texas's DSP 2812. Initially, the block diagrams that contain the control equations are constructed. Then, the codes are generated automatically. The advantages provided by the proposed method are: security, economy of development cycle time, easy understanding of the control process and programming, standardization and concurrent simulation. Three nonlinear control techniques - state feedback linearization (SFL), passivity based control (PBC) and interconnection and damping assignment passivity-based control (IDA-PBC) has been validated experimentally using HIL simulation for boost, buck and SEPIC converters.

Combining Homogeneous High Order Sliding Mode and Nonlinear Dynamic Inversion for fixed wing aircraft attitude and speed control

Since a bi-modal tram has an extended wheel base and an articulated chassis, an all-wheel steering system (AWS) is applied to it to satisfy the required steering performance. An AWS electronic control unit (ECU) controls the hydraulic actuator according to the vehicle driving environment, such as the driver steering angle, articulating angle, and vehicle velocity. In this paper, the test platform developed for the AWS ECU test in a hardware in the loop (HIL) environment is explained. Using the developed test platform, the control algorithm of the AWS ECU can be evaluated under the virtual driving condition of the bi-modal tram. Also, vehicle manoeuvrability is investigated using this test platform. The AWS system, including ECU hydraulic system and embedded software, can be verified by the hardware in the loop simulation (HILS) test results.

The so-called "New Space era" has seen a disruptive change in the business models and manufacturing technologies of launch vehicle companies. However, limited consideration has been given to the benefits that innovation in control theory can bring; not only in terms of increasing the limits of performance but also reducing mission preparation or "missionisation" efforts. Moreover, there is a gap between the current state-of-practice that still relies on linear controls and other modern control techniques that could bring relevant improvements in launcher attitude control; this is the case for nonlinear control algorithms, especially those based on Nonlinear Dynamic Inversion (NDI). NDI is a technique that basically 'cancels' the nonlinearities of a class of nonlinear systems, allowing for a single linear control law to be applied without the need for gain-scheduling across different operational points. Incremental NDI (INDI) is a variation of NDI that generates incremental commands and employs acceleration feedback to reduce model dependency, making it easier to design, and results in being more robust in closed-loop. While INDI has been applied successfully to several aerospace applications, its applicability to launch vehicles has not yet been adequately investigated. The objective of this paper is therefore to introduce and raise awareness of the INDI method among the launcher guidance, navigation, and control (GNC) community, showcasing its implementation on a representative launch ascent application scenario which highlights INDI's strengths and challenges. We present a new, practical approach for stability analysis of INDI for attitude control, and compare INDI with scheduled PD controllers with-and without angular acceleration estimates. Results show that, while INDI controllers are generally more sensitive to sensor noise and actuator delay than linear controllers, their potential benefits outweigh these limitations in terms of robustness and performance.

The Hardware-In-the-Loop (HIL) simulation system for on-orbit docking dynamics is a large-scale complex test equipment. It establishes working conditions for the docking mechanism similar with those on orbit. The kernel of above dynamics HIL simulation system is a mechanical force and movement actions simulator. Besides the mechanical force and movement actions simulator, it also includes an environmental simulator, a microgravity simulator and so on. In a narrow mind, the HIL simulation system for on-orbit docking dynamics refers to the mechanical force and movement action simulator. It is a feedback system which consists of the dynamics simulation model and real-time simulaton computer, the hardwares under test, the force and torque sensor, the motion simulator. The research topic of this paper is limited in above narrow mind. The HIL simulation system for on-orbit docking dynamics is a key technology that played important roles in the lunar excursion of America and in the assembling and re-supplying of Russian MIR space station. Morden space programme enhance the requirements to the HIL simulation for spacecraft docking dynamics. International Space Station (ISS) program also required that the ISS Common Berthing Mechanism (CBM) testing on ground simulator should be performed under operational vacuum and thermal conditions (Office of NRBMP, 1999). In the early days, the physical simulators played main roles in docking dyniamics tests. Because of the development of computor and the complexity of modern docking mechanism, the HIL simulation technology is applied in the docking dynamics simulation. The dynamic docking test system (DDTS) is setup in US (Gates & Graves, 1974), and the integated testing system for docking mechanism was built in former Soviet (Peng et al., 1992). In1980s, docking dynamic test facility (DDTF) was created for testing the handleslatch docking mechanism (Crimbert & Marchal, 1987). National space development agency of Japan built the rendezvous and docking operation test system (RDOTS) testing threepoints handles-latch docking mechanism (Lange & Martin, 2002). The HIL simulation for spacecraft on-orbit docking is a attractive and promising research field. Lim et al. (1989) modeled and simulated the Stewart platform of DDTS. They pointed

Autonomous Underwater Glider (AUG) as a high durability underwater vehicle is typically capable of extremely long missions in the ocean by tracking the desired waypoints using guidance system. Typical AUG's guidance system development requires many costly at-sea trials to evaluate the guidance ability. Simulation provides a cost-effective measure to carry out preliminary component and system testing, thereby reducing the number of potential failures in at-sea trials. This paper presents the Hardware in the Loop (HIL) simulation development of the guidance system for a class of AUG. Guidance through waypoints using Line of Sight (LOS) method guides the AUG to desired waypoints by adjusting the yaw angle. The LOS algorithm was implemented as executable code in BeagleBone Black board. HIL simulation can be simulated using the hardware component (BeagleBone Black) along with AUG's models which were built in MATLAB/SIMULINK. It provides the verification step of the AUG's guidance system before the real deployment in the ocean. The HIL simulation showed that LOS method was able to guide the AUG to desired waypoints despite simulated using some different waypoint schemes and under the effect of ocean currents as a disturbance.

This paper presents a Single Network Adaptive Critic (SNAC) aided Nonlinear Dynamic Inversion (NDI) optimization controller with a Proportional-Derivative (PD) based Optimal Control Modification (OCM) design for fast pitch rate adaptation in an MRAC flight control system. The advantages of adding SNAC to the NDI MRAC controller with OCM adaptation are presented. It is seen from simulation results that the SNAC aided NDI controller with the OCM adaptation has fewer high frequency oscillations and increased robustness to the different network architectures of the OCM. Three variations of OCM uncertainty estimation basis functions, namely the OCM – Linear (OCM-L), OCM – Bias (OCM-B) and OCM Linear and Bias (OCM-LB) are included in this paper. The responses of the SNAC aided NDI and traditional NDI controllers, using the same OCM adaptation technique are compared. Simulation results run on a nonlinear model of a small single piston engine are included for demonstration.

High performance aircraft of the future will be designed to be lighter, more maneuverable, and operate over an ever expanding flight envelope. This set of conditions will necessarily mean highly flexible vehicles operating in nonlinear regimes. A methodology proposed to better optimize their responses to both pilot input and external disturbances, as well as to decrease the cost of vehicle design is the novel dynamic inversion. The attractiveness of this methodology lies in the fact that the inherent nonlinearities of the problem and the coupled nature of flexible dynamics are explicitly considered. The contribution of this work to the state of the art is predicated on the development and application of the novel dynamic inversion methodology to handle highly flexible aircraft in an integrated flight/structural mode control manner. The unprecedented small separation between rigid body and flexible dynamics as well as the reciprocal interaction between them due to flight control action are the key elements of the aircraft model. The novel approach to the nonlinear dynamic inversion allows the methodology to more intelligently handle flexible dynamics in the context of the dual objectives of integrated flight/SMC control by altering flexible mode damping without cancellation; thus, improving disturbance response and avoiding the potentially destabilizing effect of pole cancellation close to the j-omega-axis in case of modeling uncertainty. The necessary level of model complexity for design has been established with particular attention given to understanding physics. The effect of uncertainty in the structural mode dynamics has been addressed. Further contribution of this work addresses the issue of stability of the dynamic systems driven by nonlinear controllers. One result shows how assessing stability of an n-dimensional system can be reduced to checking stability of a two-dimensional one using algebraic expressions that are based on the vehicle characteristics such as aerodynamic coefficients. This reduces a complicated dynamical problem to something purely algebraic and manageably complex. Another approach is based on algorithmically finding a local Lyapunov function using sum of squares. The presented results are the first to address the question of stability for the nonlinear dynamic inversion in the presence of flexible dynamics.

Hardware in the loop simulation for homing missiles

In this paper, we deal with the development of a HIL (Hardware-in-the-Loop) simulator for BLDC motor driving using a microcontroller. We propose a modified BLDC model for the simulation of a BLDC motor using a microcontroller. The proposed HIL simulator is developed using various peripherals of STM32F407 (ARM cortex-M4 based microcontroller). The proposed HIL simulator consists of three parts. First, the part simulating the inverter analyzes the input PWM signals to calculate the corresponding input voltage. This part detects wrong PWM signals or shoot-throughs of the half-bridge. Second, the BLDC motor part is implemented by solving the modified model equations in real time. Finally, the third part generates the output of the BLDC motor. The HIL simulator generates the Back Electromotive Force (BEMF) waveform and signals of a rotary encoder and a hall sensor. Sensor signals are generated using a timer interrupt. The BEMF waveform is implemented using DAC. Moreover, a generation method using PWM and RC filter is presented. Through experiments, we illustrate that the developed HIL simulator accurately simulates the BLDC motor. Furthermore, we confirm that the BLDC motor drive algorithm designed with the developed HIL simulator can be successfully applied to real BLDC motor driving systems.

This paper presents a numerical impedancemeter which allows the electric impedance of a piezoelectric transducer Z(f) to be estimated both in real time and in situ. Authors’ method is based on SOPC and hardware in the loop (HIL) techniques. The system comprises two principal modules: a direct digital synthesizer (DDS) and a chain actuator with a numerical resistive network and a transducer. Feedback control of the excitation voltage is carried out by regulating the resistive network. Z(f) modulus is estimated from the values obtained by the resistive network during a fast frequential sweep. The analogical part is modeled by using Matlab SimPower Syst and the numerical architecture is built by DSP Builder. The architecture is then implemented in a FPGA Stratix II board and validated by HIL simulation, in which the transducer is modeled by a Butterworth van Dycke structure. The system is tested within the bandwidth 1.8 MHz - 2.8 MHz with a 20 mm square transducer resonant at 2 MHz. We have determined all the relations which allow the parameters of the numerical functions to be set. The parameters take into account the range of excitation, the quality factor of the transducer and the resolution, speed and duration of the analysis. The results show how accurate Z(f) estimation is and the duration of the analysis, which does not exceed 10 ms.

Hardware-in-the-loop simulator for research on fault tolerant control of electrohydraulic actuators in a flight control application