【正文】 ontrol system is influenced by many factors. For example: the mechanical structure it is controlling, the human operator, effi ciency, stability, and industry regulations. Industry regulations are the first requirements that have to be addressed. Things like hose rupture protection and runaway load protection make a lot of demands on the control regulations, stability is the next most important requirement。 翻譯部分 英文原文 CONTROL OF MOBILE HYDRAULIC CRANES Marc E. M220。NZER Aalborg University Institute of Energy Technology, Pontoppidanstr230。 without stability the control system can’t be used. Once stability has been assured, the performance requirements of the control system have to be set. They are determined by the mechanical structure of the crane and the human operator. The mechanical structure of a mobile hydraulic crane is a very large flexible structure which has very low natural frequencies. To prevent oscillations it is necessary to keep the speed of the control system below this natural frequency or to develop a control system which can increase this frequency. The human operator also imposes limits on the control system. If the control system is too slow or too fast then it is impossible for a human operator to give it proper inputs. And finally, once the regulations have been met, stability is assured, and the performance is at the right level, the power efficiency of the control system has to be optimized. of Current Control Systems Before designing a new control system it is good to analyze the current control systems to find out what their problems are. Current control systems are mainly hydraulic and can suffer from three main problems: cost Instability is a serious problem as it can cause injury to human operators or damage to equipment. When a system bees unstable it usually starts to oscillate violently. To avoid instability in current systems, the designers either sacrifice certain functions which are desirable,or add plexity and cost. For example, in the crane shown in Figure 1, it would be desirable to have control over the speed. But due to the safety system that cranes are required to have, standard speed control is not stable. To add speed control requires a more plex and more expensive mechanical system. The parameters of a hydraulic system, such as temperature or load force, also affect system that is stable with one set of parameters might be unstable with another set. To ensure stability over the entire operating range of the system, performance must sometimes be sacrificed at one end of the parameter range. cost Current systems are purely hydraulicmechanical, so if the user wants a certain function, the user buys a certain hydraulicmechanical ponent. Because most users have different requirements, there are many different variations of the same basic ponent. This means that many specialized ponents must be manufactured rather than one standard drives up the cost of ponents. One form of inefficiency in current systems is due to the link between the flows of the two ports of the cylinder. This is because most valves use a single spool to control the flow in both ports. Because of this link, it is impossible to set the pressure levels in the two sides of the cylinder independently. Therefore, the outlet side will develop a back pressure which acts in opposition to the direction of travel, which increases the pressure required on the inlet side to maintain motion. Since the force generated by the actuator is proportional to the pressure dif ference between the two sides, the actual pressures in the cylinder don39。Jansson,Palmberg, 1990。jbjerg Maskinfabrik (HMF) a Danish crane manufacturer. Refer to Figure 1. Figure 1 Experimental Systems in Laboratory. Left: One DOF crane model. Right: Real Mobile Hydraulic Crane As there are currently no mercially available separate meterin/separate meterout valves,two separate valves will be used instead. A sample circuit of one cylinder is shown in Figure 2. The control algorithms which control the valves, will be programmed on a Digital Signal Processor (DSP)/Pentium dual processor system. The DSP will run the control co