Abstract: A combination crane A is formed by connecting two crawler cranes 1L and 1R. Each crawler crane is provided with at least a lower propelling body 3 which can be propelled by crawlers 2, an upper revolving body 5 rotatably mounted on the lower propelling body 3 by a swing unit 4 provided between them, a boom 6 whose base section is tiltably supported on the upper revolving body, a tilting mechanism 10 that raises and lowers the boom and a hoist mechanism that hoists and lowers the lifting members 12 hung by a hoist rope 11 from the top of the boom. Both upper swing bodies of two cranes are connected together with a connecting beam 20. Swing motion is performed by driving the one crawler crane to move around the other crawler crane which is free to rotate and is locked against propulsion.

Abstract: A combination crane A is formed by connecting two crawler cranes 1L and 1R. Each crawler crane is provided with at least a lower propelling body 3 which can propel by crawlers 2, an upper revolving body 5 rotatably mounted on the lower propelling body 3 by a swing unit 4 provided between them, a boom 6 of which base section is tiltably supported on the upper revolving body, a tilting mechanism 10 that raises and lowers the boom and a hoist mechanism that hoists and lowers the lifting members 12 hung by a hoist rope 11 from the top of the boom. Both upper swing bodies of two cranes are connected together with a connecting beam 20. Swing motion is performed by driving the one crawler crane to propel around the other crawler crane which is free to rotate and is locked to propel. The combination crane can change the direction of the body, and can increase the lifting capacity twice as much without troubles, and can be embodied easily.

Abstract: In a neutral range preset, there are set a zone for stopping and holding a rotating body only by a mechanical brake, a zone for holding the body only by performing position holding control, and a zone for simultaneously exerting both effects, i.e., the effect of the mechanical brake and the effect of the holding control. On-the-spot holding torque generated when the position holding control is performed is stored. The higher of the on-the-spot holding torque stored and accelerating torque according to an operation amount of the body at a rotation starting time is set as electric motor torque for acceleration. When performing a pressing work including pressing a bucket against an object for work, torque control is carried out according to the operation amount.

Abstract: In a neutral range preset, there are set a zone for stopping and holding a rotating body only by a mechanical brake, a zone for holding the body only by performing position holding control, and a zone for simultaneously exerting both effects, i.e., the effect of the mechanical brake and the effect of the holding control. On-the-spot holding torque generated when the position holding control is performed is stored. The higher of the on-the-spot holding torque stored and accelerating torque according to an operation amount of the body at a rotation starting time is set as electric motor torque for acceleration. When performing a pressing work including pressing a bucket against an object for work, torque control is carried out according to the operation amount.

Abstract: In a construction machine comprising an electric motor 6 for driving a rotational system, an operating member for instructing an operation of the electric motor 6, and a controller 9 for controlling the electric motor 6 according to an operation command from the operating member, the controller 9 has an emulation model 9a for simulating dynamic characteristics of a hydraulic rotation driving device in real time, and a target value for control is calculated from the emulation model 9a according to the operation command from the operating member to control the electric motor 6. Accordingly, the electric motor can mildly respond to the operation of a lever in an intermediate range and swiftly respond to a quick operation of the lever.