MECANT I: A zyxwv Six Legged Walking Machine zyx for Research Purposes in Outdoor Environment zyxw K. K. Hartikainen A. J. Halme H. Lehtinen K. 0. Koskinen Automation Technology Laboratory Helsinki University of Technology ESPOO, Finland SF-02150 Laboratory of Electrical and Automation Engineering Technical Research Centre of Finland ESPOO, Finland SF-02150 Abstract zyxwvuts This paper deals with the ovemll structural design of a self-contained hydraulic si2 legged machine, called MECANT I, which has been constructed for studying possible applications of legged vehicles in natural en- vironments, like forest. First the main mechanical so- lutions and control hardware of the machine are pre- sented. The systematic approach to the motion plan- ning of a legged vehicle and some algorithmical fea- tures are discussed. The special features of the leg control are presented. Nezt the use of a simulator in the design work is discussed and the main principles of the control software structure, which supports fast soft- ware design and testing, are presented. Finally some continuing Tesearch topics and present situation are discussed. 1 Introduction Legged locomotion provides certain clear advan- tages when considering vehicle movement in uneven natural terrain like. forest ground. When compared to more classical wheeled or tracked locomotion the legged machines can step over minor obstacles and thus obtain a much smoother movement. Moreover, the large number of degree of freedoms makes the ma- chine more flexible to move and easier to stabilize at uneven terrains. An interesting property is also that legged locomotion has smaller impact on the ground because moving needs only discrete foot places instead of continuous tracks. Those properties make legged lo- comotion an interesting alternative in many outdoor work machine applications, for example in future for- est harvesting machines. Reader who is not familiar with the legged machines can be referred to the works zyxwvu 157 in the area [5],[6]. This research project aims to develope and test the fundamental properties needed for a six legged work machine capable to move in a highly unstructured en- vironment such as typical forest environment. The main theoretical challenges include: zyxw 0 Vehicle motion planning and execution in natural terrain without apriori knowledge of the terrain using the standard sensor technology with contact and inertia sensing. 0 Gait planning using flexible gaits, e.g. free gait. 0 Integration of feet and manipulator control dur- ing work periods. 2 General Design Philosophy A test bed, called MECANT I, has been designed and constructed. MECANT I is a hydraulic, combus- tion engine driven six legged machine shown in Fig. 1. The machine weights about 1050 kg and can be used for testing purposes both indoor and outdoor environ- ments. It carries all the computer power needed and is independent from external energy sources. It is con- trolled remotely by the operator via radio link. The machine is comparable to the well-known Adaptive Suspension Vehicle (ASV) constructed at the Ohio University [4], but it is smaller in size and designed on different bases to serve rather as a work machine platform than a transportation vehicle. The leading principle when designing MECANT I was modularity and distribution. The design started from leg construction. A two degree of freedom pan- tograph with separated horizontal and vertical move- ments was selected because of its well-known good 0-8186-27"2 $3.00 81992 IEE zyxwvutsrqpo -~--______