【正文】 lemented on mercial machinery, much emphasis will be placed on experimental results. Experimental results will be obtained from two systems. The first, a simple one degree of freedom crane,was designed as an experimental platform. The second is a real crane which was donated to the University by H248。t affect the action of the cylinder. For example, the action of the cylinder for 0psi/600 psi would be the same as 1000psi/1600psi. However, in the second case, the power supply would have to supply much more power. This extra power is wasted. Options for Control Systems Current control systems use hydraulic actuators with directional/proportional valves to control the movement. However there are many different options for controlling a cylinder. Options range from new high performance electrohydraulic valves, to separate meter in / separate meter out (SMISMO) valves, to hydraulic bus systems, to intelligent actuators with built in power supplies, to pump based control strategies. These systems all have advantages and disadvantages which need to be analyzed if the most optimum solution is to be chosen. Near Future Solution It is expected that even if it is proven that a pletely new system topology is the optimum configuration, the crane manufacturers and ponent manufacturers will not accept the new technology overnight. This will most likely take time, so an interim solution will be developed. This solution will be made up of micro puter controlled Separate Meter In / Separate Meter Out (SMISMO) valves (Elfving,Palmberg 1997。de 101 DK9220 Aalborg, Denmark The goal of the thesis described in this paper is to improve the control of mobile hydraulic cranes. The thesis is split into five parts: a requirements analysis, an analysis of the current systems and their problems, an analysis of different possibilities for system topologies, development of a new control system for the near future based on electrohydraulic separate meter in / separate meter out valves, and finally an analysis of more advanced and plex solutions which can be applied in the more distant future. The work of the thesis will be done in cooperation with industry so the thesis will have more of an industrial focus than a purely theoretical focus. Key words: Mobile Hydraulic Cranes, Control Strategies, Separate Meterin/Separate Meterout. 1 INTRODUCTION The goal of the thesis described in this paper is to improve the control of mobile hydraulic cranes. A mobile hydraulic crane can be thought of as a large flexible mechanical structure which is moved by some sort of control system. The control system takes its input from a human operator and translates this mand into the motion of actuators which move the mechanical structure. The definition of this control system is purposely left vague in order not to impose any constraints on its design. The control system consists of actuators which move the mechanical structure, a means of controlling the actuators, a means of supplying power to the actuators,and a way of accepting inputs from the operator. It is this control system which is the target of this thesis. The goal is to analyze the requirements made on the control system and present guidelines for the design of new control systems. The thesis will be split into five parts: of the requirements of the control system, from the perspective of the operator, the mechanical system, efficiency, stability, and safety requirements. of current control systems and what their problems are. of the different options for the control system: different types of actuators,different types of control strategies, and different ways of organizing ponents. of a new type of control system, which is mercially implementable. A system that will meet the needs of industry in the near future. of more optimized systems, with higher performance, better efficiency, more flexible control, etc. This will be less mercially applicable but will be a starting point for more research. 2 SECTIONS OF THE THESIS Analysis of the Control System Before starting detailed work on developing new control systems, it is important to analyze what the exact demands are on the control system. The c