NOVEL STEERING CONCEPTS FOR PERSONAL AERIAL VEHICLES B.I. Gursky and D. Müller DLR Institute of Flight Systems, German Aerospace Center Lilienthalplatz 7, 38108 Braunschweig, Germany [email protected] Abstract Against the background of constantly growing ground-based traffic and consequently increasing congestion problems, solutions have to be found for meeting the future demand of personal transportation. The European project myCopter is addressing this issue by investigating technologies for future Personal Aerial Vehicles (PAV). These rotorcraft are meant to be available to the general public with a minimal necessary amount of training. This paper is looking for answers to the question of the most suitable control concept for future PAVs. Car- like steering concepts would be a candidate for flight-naïve PAV users. Several concepts have already been designed for rotorcraft but have not further been investigated. DLR is now facing this challenge. In the paper an overview of the historical development of control devices in automobiles and helicopter is given. From this development and research results from related projects a novel control concept for PAVs is proposed. The intention is to offer a control concept that is intuitively understood by PAV users who are already used to steering automobiles. The concept as well as the underlying PAV flight dynamics are explained and a short outlook is given on the planned future research at DLR. contrary, the opposite approach has been selected. The NOMENCLATURE project goal is to develop essential technologies that will AC Attitude Command be needed for a PATS to become functional. Six partner AcC Acceleration Command institutions from Germany, Switzerland and the United ACT Active Control Technology Kingdom are conducting research in the areas of human- FHS Flying Helicopter Simulator machine interaction and handling qualities, autonomous PATS Personal Aerial Transportation System flight technologies as well as socio-economic aspects. PAV Personal Aerial Vehicle RC Rate Command RPM Revolutions Per Minute TC Turn Coordination TRC Translational Rate Command βC Sideslip Angle Command γC Flight Path Angle Command 1. INTRODUCTION The global volume of traffic is constantly growing which goes along with increasing congestion problems. It can be expected that the currently implemented ground-based transportation system will someday reach its limits. One solution to extend this limit is the extension of the currently ground-based personal transportation into the third dimension. The European project myCopter [1] is investigating the implementation of such a Personal Aerial Transportation System (PATS). The idea was original FIGURE 1. Artist’s impression of the myCopter Skyrider brought up by the ‘Out of the Box’ study funded by the PAV Concept (©Flight Stability and Control). European Commission [2]. This study was conducted in order to fructify the development of revolutionary transport In order to ensure the usability of PAVs for the general concepts to overcome the otherwise rather evolutionary public, handling of such a vehicle must become feasible trends in air transport development. also for non-professional users. PAVs must have vertical take-off and landing capabilities like helicopters in order to The myCopter project aims at enabling technologies that be manoeuvrable even in densely populated city centres. are required to provide Personal Aerial Vehicles (PAVs) to At the same time they must be as easily manoeuvrable as the general public. FIGURE 1 shows the artist’s cars in order to be flyable by the general public. It is impression of such a PAV. It is a light one- to two-seated desirable to minimize the training needed to safely rotorcraft. Nevertheless, the myCopter project is not navigate a PAV through the airspace. Additional to an concerned with actually designing such an aircraft. On the advanced flight control system and the implementation of extended automation functionalities, the human-machine control stick but his design included a hand wheel for yaw interface should be tailored towards the needs of a future control like in Pescara’s concept. PAV pilot. Flight-naïve users should be able to understand intuitively the control concept of their PAV. The first example of today’s conventional helicopter control concept was implemented in Igor Sikorsky’s VS- The control concept of automobiles is well known to the 300 in 1940 [4]. Being equipped with a piston engine, it general public. These controls have barely changed over still had a throttle in the shape of a twisting grip mounted the past century. Although new controllers like joysticks on the collective stick. This device was later abandoned in are technically feasible, all of the modern production turbine-powered designs, as they tend to have an vehicles rely on the conventional arrangement of steering automatic engine speed regulation. Apart from that, the wheel, accelerator and brake pedals, gear stick, and control concept remained the same from 1940 until today: optionally clutch pedal for manual transmission. A driver’s a control stick for cyclic pitch angle control, mounted license holder can intuitively connect the usage of these between the pilot’s legs, a collective lever on the pilot’s controls to the movement of any typical car. On the other side for collective pitch angle control and pedals for yaw hand, conventional helicopter controls are not at all control. intuitive for non-expert pilots. The question is now how this intuitively understood concept can be transferred to a However, research on helicopter controls shows that there helicopter-like PAV. Some inventors have already are promising alternatives to conventional controls, such proposed car-like steering concepts for rotorcraft but as sidesticks. Among others, Landis and Aiken have these concepts have not been further investigated. DLR is assessed the applicability of various sidestick now facing this challenge. configurations in the 1980s [5]. One of the most recent examples can be seen in DLR’s Active Control This paper first gives an overview of the development of Technology Flying Helicopter Simulator (ACT/FHS) [6]. control devices in rotorcraft and automobiles and then This unique Eurocopter 135 modification is equipped with describes already existing steering concepts for PAVs. Fly-by-Wire and Fly-by-Light technology, which is crucial Furthermore, the development of a novel car-like control for flexible implementation and fast evaluation of concept together with connection to the underlying flight innovative control devices. It has been equipped with two dynamics is explained. Finally, an outlook is given on how active sidesticks [7]. Among DLR’s current research this steering concept will be further refined and tested. activities is the development of haptic pilot assistance functions based on these active sidesticks [8]. 2. HISTORICAL DEVELOPMENT OF CONTROL CONCEPTS 2.2. Automobile Controls After the early years of development today’s conventional Having been built in 1886, Carl Benz’s “Motorwagen control concepts have been well established for both Nummer 1” is considered to be the world’s first helicopters and automobiles separately. automobile. It had a crank handle for steering and a long hand lever that combined the functions of a clutch, a brake and a gear switch [9]. Pushed forward, it moved the 2.1. Helicopter Controls driving belt onto a pulley on the axle and thus connected Soon after the first motorized flights of the Wright brothers wheels and engine. In the middle position, the belt hung in 1903, helicopter prototypes also began to successfully loose and the wheels were free to move, whereas pulling take off. In those early days of rotary wing technology, back the lever activated the brake. leaving the ground was the major concern of the aviation Later in 1886, Daimler and Maybach revealed their pioneers. This can be derived from the fact that the first “Motorkutsche” (motor carriage). Steering was enabled by two machines to take off vertically had almost no means a star handle that directly turned the front axle [10]. to influence the direction of their movement. The Another design from 1889, the so called “Stahlradwagen” “Breguet-Richet No. 1” had to be stabilized by several (steel wheel car), featured a tiller for the steering task. men once it lost ground contact. The pilot could only control the rotational speed of the rotors by changing the The disadvantage of these steering concepts became RPM of the engine [3]. Paul Cornu’s helicopter prototype apparent when more powerful engines were developed of 1907 was at least equipped with one control surface in and precise steering became more difficult as driving the downwash of each of the two rotors, which were speeds increased. In 1894 Alfred Vacheron participated in supposed to make longitudinal movement possible. They the “Competition for Horseless Carriages” from Paris to were controlled by the pilot with the help of two handles Rouen with a “Panhard et Levassor 4HP”, which he had but proved to be not effective for control [3]. equipped with a steering wheel. The idea is likely to have been inspired by the helms of ships. Although Vacheron Raul Pescara was more successful in 1925 when he had did not win, the benefits of his modification had been found a way to manipulate the cyclic pitch of the blades noticed and by 1898, all Panhard et Levassor models on his coaxial rotors. He used a control stick for this task were built with a wheel as the steering control [11]. that was mounted in front of the pilot. It was similar to the one found in airplanes with an additional small hand In the following years other automobile manufacturers wheel on top of it. That wheel’s purpose was to control the followed. When the Ford Model T was released in 1908, yawing movement by differential adjustment of the the steering wheel had already been accepted by the collective pitch angles of the two rotors [3].