Tetsujiro Ninomiya

Stochastic Evaluation and Optimization of the Hierarchy- Structured Dynamic Inversion Flight Control

A flight control design methodology has been presented using the hierarchy-structured dynamic inversion (HSDI) approach, which is based on multiple time-scale separation of a general fixed-wing aircraft dynamics. HSDI approach integrates traditional guidance and control structures to realize simple, systematic, and universal design of flight control systems with a small number of design parameters. In this paper, HSDI is modified using command rate feedforward to improve control performance. Robustness of HSDI approach is then evaluated through the root sum square (RSS) analysis and Monte Carlo simulations (MCS). The design parameters are finally optimized to enhance robustness using the downhillsimplex method and MCS evaluation. The numerical simulations are based on the highly reliable 6DOF nonlinear flight simulation model of ALFLEX experimental vehicle, where the distribution data for more than 100 uncertain parameters are defined. The detailed numerical analysis discussed in this paper has shown that robustness performance of the optimized HSDI flight controller is comparable to that of the baseline linear robust controller, which is also similarly optimized.

Feedback Control of Plants Driven by Nonlinear Actuators via Input-State Linearization

A new systematic method to design a control law for a linear system with a nonlinear input is proposed. Conventionally, the inverse of the nonlinear function is often used to such problems, but it requires too much calculation to solve the nonlinear equation at each control step. Accordingly, we propose a new method that only applies the derivative of the nonlinear function. The essential idea of this method is to extend the original system with a pseudostate variable. This approach makes it possible to avoid to use the inverse of the nonlinear function and reduces the calculation load. Some numerical simulations are presented to illustrate the validity of this method.

Evaluation of Guidance and Control Systems of a Balloon-Launched Drop-Test Vehicle

T HE Japan Aerospace Exploration Agency (JAXA) has been researching key technologies for future space transportation. A series of flight experiments have been carried out to develop technologies for the planned H-II orbiting plane experimental (HOPE-X) [1] unmanned winged reentry vehicle: the orbital reentry experiment (OREX) [2], the hypersonic flight experiment (HYFLEX) [3], and the automatic landing flight experiment (ALFLEX) [4]. Following on from these earlier experiments, the two-phase high-speed flight demonstrator (HSFD) program was planned and implemented [5]. HSFD phase I aimed to inspect the environmental conditions at the designated HOPE-X landing site, whereas HSFD phase II (HSFD-II) was a drop test of an unpowered HOPE-X scale model to obtain transonic aerodynamic data on the vehicle’s configuration. After an investigation of alternatives, release from a high-altitude stratospheric balloon was selected as the launchmethod for HSFD-II [6]. This presented a couple of challenges. First, the experimental method is quite unique (as far as we are aware there have been only two similar previous experiments) and so there was a lack of experience and knowledge on which to build. At the same time, this type of experiment has a similar drawback to the testing of space systems; that is, incremental testing and flight envelope expansion, which are normal in the development of airplanes, are impossible: the vehicle must be able to fly the full mission from its very first flight. Accordingly, it is important to exhaustively evaluate the guidance and control (G&C) systems by computer simulation beforehand. Recently, a balloon launch has been considered to have great potential as a low-cost launch method for flight experiments [7–9]. This Note describes a method for evaluating the G&C systems of strongly nonlinear systems, such as a balloon-launched drop-test vehicle. It was iteratively used in the design and evaluation process to tune the theoretically designed G&C systems [10] using a statistical method [11]. This iteration was the key to establish the flight safety.

Dynamic Programming Trajectory Optimization and its application to D-SEND #2 Low Sonic-boom Research Project

JAXA develops an unmanned technology demonstrator vehicle for low sonic boom research. The research project is called D-SEND #2 (Drop test for Simplified Evaluation of Non-symmetrically Distributed sonic boom). The autonomous demonstrator vehicle will be dropped from a high altitude balloon, and it will accelerate and glide to fly over a predetermined measurement area with a supersonic cruise condition. Trajectory optimization analysis is necessary for the design of onboard reference trajectory generation logic, which is robust against the dropping point uncertainty. An easy-to-use trajectory optimization tool using dynamic programming approach has been developed in order to generate reference trajectories in the early stage of design process. This paper introduces how the dynamic programming approach is applied to the D-SEND #2 flight trajectory optimization, and it shows numerical examples, which include the maximum and minimum range problems, and range adjustment problems.

Evaluation of Guidance and Control System of High Speed Flight Demonstrator Phase II

This paper describes the results of the preflight evaluation of the guidance and control systems of the High Speed Flight Demonstrator Phase II (HSFD-II). Since the vehicle does not have a nominal trajectory because of its launch method, it is not appropriate to evaluate this system by the root sum square method. The present evaluation followed two approaches, using one standard and one custom designed analysis. The former comprised a Monte-Carlo simulation, single error analysis, sensitivity analysis, and linear analysis. The latter used emergency separation, release oscillation, and GPS receiver error. Although in some cases the Monte-Carlo simulation in the standard analysis showed a failure to satisfy mission requirements, detailed analysis indicates that the system would guide the vehicle through a successful flight experiment. This evaluation establishes that the system satisfies all mission requirements. The actual flight experiment was carried out and the guidance and control systems worked quite well. Based on the results of the preflight evaluation and the results of the flight, this paper concludes that the guidance and control systems of the vehicle was properly designed.

Neural network based adaptive control with Hierarchy-Structured Dynamic Inversion applied to nonlinear aircraft model

Japan Aerospace Exploration Agency plans a flight demonstration project for a super sonic transport. A typical supersonic transport has a larger flight envelope than conventional one, so that the flight controller is required to be more flexible to the flight environment. Therefore, the adaptive control method is a promising candidate for these flight control system. In this paper, we propose an adaptive control method which is comprised of neural networks and Hierarchical-Structured Dynamic Inversion. Its structure is clearly comprehensible to the users and numerical simulation results show that proposed method is effective even with model errors.

Linear State Feedback Control for Spacecraft with On-Off Type Reaction Control System

Abstract This paper considers design methods for controllers of linear time invariant systems that use on-off type actuators. While classical control theory uses phase-plane analysis, the describing function approach and pulse modulation technologies, these approaches do not permit the direct application of optimal controller design techniques that include non-linear effects. In this paper, we propose the application of input-state linearization theory to the general class of single on-off input plants. The resulting linearized space allows the application of any linear controller design tool. The method is further extended to be applicable to on-off controllers with a dead-band. Some numerical studies including the lunar landing problem are presented to demonstrate the effectiveness of the approach.