Message #3556 - comp.ai Date : 05-Aug-91 15:42 From : Rick Schlichting To : All Subject : Kahaner Report: Fuzzy Helicopter Flight Control ------------------------------------------------------------------------------- @PTH 1:124/2206.0@fidonet @Newsgroups: comp.ai @Message-ID: <5906@optima.cs.arizona.edu> @Date: 5 Aug 1991 15:42:01 GMT @ @ [Dr. David Kahaner is a numerical analyst visiting Japan for two-years under the auspices of the Office of Naval Research-Asia (ONR/Asia). The following is the professional opinion of David Kahaner and in no way has the blessing of the US Government or any agency of it. All information is dated and of limited life time. This disclaimer should be noted on ANY attribution.] [Copies of previous reports written by Kahaner can be obtained from host cs.arizona.edu using anonymous FTP.] To: Distribution From: David K. Kahaner, ONR Asia [kahaner@xroads.cc.u-tokyo.ac.jp] Daniel Schwartz, Florida State Univ [schwartz@.cs.fsu.edu] Re: Fuzzy Helicopter Flight Control 5 August 1991 This file is named "helicopt" ABSTRACT. A summary of research on helicopter flight control in Japan based on fuzzy logic techniques. During the past year I have circulated several reports on research in fuzzy systems (control.34, 1 Aug 1990), (takagi, 7 Aug 1990), (fuzzy, 24 Aug 1990), (fuzzy.gmd, 21 Jan 1991), (klir, 12 Apr 1991), and (fuzzy1.gmd, 17 May 1991). During this summer, the Office on Naval Research has been supporting Professor Daniel Schwartz, Dept of Computer Science, Florida State University, Tallahassee FL 32306-4019, to analyze Japanese research in this area. Schwartz will be preparing a report that I will circulate as soon as it is complete. However, the following material is interesting enough that we felt it was appropriate to circulate quickly. More details will follow as part of Schwartz's report. This report concerns three projects related to helicopter control which use fuzzy logic; we are not aware of any comparable research in the US. There seems to be some sense among Japanese researchers that research on fuzzy theory (basic science) may be losing some of its momentum but applications (engineering) are still very active. It is our opinion that in the US, applications of fuzzy control to real problems are far behind the work in Japan. In several of the earlier reports we mentioned research on the use of fuzzy control for helicopter applications. For example, at the 1989 Japan electronics show, a small model helicopter with several rotors was demonstrated. This was developed as a LIFE (Laboratory for International Fuzzy Engineering Research) project. However the model was very small, and most of the information was obtained by cameras on the ground, which were then fed to a ground based control system helping a human operator who held a set of wireless controls. Professor Michio Sugeno Department of Systems Science Tokyo Institute of Technology 4259 Nagatsuta Midori-ku Yokohama 227 Japan Tel: +81-45-922-1111, x 2641, Fax: +81-25-921-1485 described three more recent projects of his, in this general area. (1) Radio control of helicopter by oral instructions (2) Automatic helicopter autorotation entry (3) Unmanned helicopter for sea rescue The projects have some overlap. In 1989, the Science and Technology Agency (Part of the Prime Minister's office) began a five year program, Fuzzy Systems Research Projects, covering three major areas. * Basic theory (inference, fuzzy computer, operating system, etc.) * Engineering * Applications of fuzzy theory to social and natural science In total, there are 20-25 projects supported and about 60 researchers at 19 different organizations, roughly one third each at academic, industrial, and government laboratories. Its total budget is about 0.8B Yen for five years, about $1M US/year. Sugeno explained to us that this program is actually larger than LIFE's, as it does not have to cover salaries, and because there is no central facility to be operated. There was a closed symposium last year and he has promised to send us a copy of the proceedings, although it will be in Japanese. There will be another symposium this year, after an international meeting on Fuzzy systems in Japan (Nov 1991) and we were told that at least one day of that will be open. Sugeno's projects are being supported as follows. (1) 1989-1993, Tokyo Institute of Technology (TIT) and STA. There are two graduate students working on this. Until recently the project was conducted at TIT, although it has recently moved to a site near Osaka. (2) 1989-1993, Tokyo Institute of Technology, STA, and Kawasaki Heavy Industry. There are 5 or six engineers working on this at Kawasaki. This is the company that manufactures the body for Boeing's 747 and also builds at least one large helicopter (BK117). (3) 1990-1991, Tokyo Institute of Technology, Tokimec and the Ministry of Transportation. Tokimec is a large instrument company (sensors). Project 1 and 2 are supported under the engineering part of the STA program. Project 3 is supported by the Ministry of Transportation. Project (1). The goal is to be able to use simple language "fly straight", "turn left", "hover", "land", etc., for control. Sugeno had already done this with a car more than 5 years ago. Of course, the current project is vastly more complex. They developed a 1 meter model which was able to correctly respond to "take off", and "hover". They are now using a 3.5 meter model (adapted from Kawasaki's R50) and they have been able to make this respond stably to "hover"; this month they will also be testing it's ability to respond to commands to fly straight. Sugeno explained that the model cost about 12M Yen (almost $120K US), of which about 7M Yen are sensors, and that the size, danger and cost of the system required them to move the project out of the university. Sugeno explained that there are 15 state variables for the helicopter; three spatial coordinates, their velocities and accelerations, three angular coordinates and their speeds. Of these, currently only nine can be measured on the helicopter; spatial position and velocity need to be measured from Global Positioning System (GPS) satellite data that is not yet readily available in Japan, although he claims that within three years there will be enough of these satellites in orbit to provide the additional needed data. Motion of the helicopter comes from making adjustments to collective pitch level, longitudinal stick, lateral stick, and directional pedal. General linguistic (high level) rules can be formulated such as "while hovering if the body rolls, then control the lateral in reverse", etc, and that these can then be converted into a number of fuzzy rules, such as "if delta x is Forward then delta longitudinal stick is Pull". In all, they generated about 120 rules which then replaced the usual PID controllers in the helicopter. As described above they have run actual tests with the models using several (not all) of the voice controls. In addition, they have simulated all the controls that they plan to implement using a Silicon Graphics 3D workstation. Sugeno displayed some of the simulation results showing plots of air speed, altitude, pitch, etc., during various situations such as variable wind 7-13m/sec from one side while hovering, and claimed that the plots were as good as would be obtained from manual control with an experienced pilot. Sugeno is confident that the project will eventually be able to actually operate a real helicopter using these techniques. (2) As Sugeno explained, when a helicopter has an engine failure the pilot must decide if he should (a) try to restart the engine, or (b) abandon the attempt. In the latter case he must disconnect the engine from the rotor to allow it to rotate freely and then dive forward in an appropriate manner to generate force on the rotor to keep it spinning. If this is done correctly, then near the ground he can straighten out and there will be enough lift on the rotors to allow a safe landing. Sugeno explained that all pilots must have this skill to obtain a license. A key aspect of this is "autorotation entry," the period between straight flight when the engine fails and initializing the dive, and that pilots at Kawasaki told him they did not think it could be automated. However, again using a fuzzy control system he claimed that it had been done, and in fact was going to be installed on the company's large units. (We did not obtain any of the details of the fuzzy rules.) (3) This project is much larger than either 1 or 2 and will not be finished in the allowed time; Sugeno is expecting that it will be continued. The main goal is to allow a helicopter to fly from a mother ship to another location, for example, where a ship is on fire, and perform various operations, such as rescue. The original project was to combine GPS satellite data with other video information to generate traditional control instructions from the mother ship, but Sugeno is anticipating that the project follow-on will replace this with fuzzy control. Sugeno explained that the Japanese feel they have worked out all the necessary theory associated with fuzzy control; of course there are many applications yet to be developed. He felt that there were two major problem areas to be studied in future (a) control of unstable systems of which the helicopter is a prime example, and (b) control of "ill structured" systems, those too large or poorly defined to be amenable to traditional methods (he specifically mentioned control of water turbidity in a filtration plant, and some biomedical systems). In response to a query about chaining of fuzzy inferences, Sugeno explained that while this is not done formally it is done in practice by first using what he termed fuzzy-sensors followed by a fuzzy inference. Fuzzy-sensors refers to making decisions about sensor inputs by fuzzy reasoning, such as "why is the water turbid" (oil, dirt, etc). ------------------------END OF REPORT------------------------------------- --- Fred-Uf 1.8h(L)[BETA] * Origin: Dallas/Ft-Worth Usenet Gateway (1:124/2206.0) @PID: FredMail 1.8-BETA @ @PATH: 124/9999 @