Abstract: An electric multi-mode drive system (400), a method for operating the same, a vehicle (110) and a track (401). The system is arranged for operating at one part (402) of the track (401), at a station (410; 411), an electric Linear Doubly Fed Motor, LDFM, (310) for launching the vehicle (110), and for operating at another part (403) of the track (401), between stations (410; 411), a further electric motor (320; 330; 340; 350), not an LDFM, arranged for at least one of accelerating, coasting and restarting movement of the vehicle (110) after launching. Electric power for operating the further electric motor (320; 330; 340; 350), is provided by an on-board rechargeable electrical energy storage device. With the LDFM (310), sufficient power is generated for accelerating the vehicle (110), and recharging the on-board electrical energy storage device during standstill, braking and/or launching.

Abstract: A method of and a device, borehole drilling equipment and a computer program product for estimating at least one of down hole speed and down hole torque of borehole drilling equipment while drilling a borehole in an earth formation. The borehole equipment comprising a rotational drive system, a drill string, a bottom hole assembly comprising a drill bit, a top end coupled to the rotational drive system, and a speed controller arranged for controlling rotational top end drive speed by commanding a top end drive torque. The method being performed in a computer based on a two-port spectral domain transfer matrix computational model of the borehole drilling equipment. While drilling, rotational top end drive speed and top end drive torque are obtained and down hole speed and down hole torque of the borehole drilling equipment are calculated by reducing spectral bandwidth of and applying a time delay term to the calculations enabling a causal time domain solution.

Abstract: A method for mitigating stick-slip oscillations in borehole equipment while drilling a borehole in an earth formation is described. The borehole equipment is modelled by a computational model for computer simulation. The model has elements representing a particular mechanical and physical behavior of the borehole equipment. In a simulated stick mode of the borehole equipment, physical quantities are loaded to the elements, which quantities represent an initial state of the borehole equipment prior to a transition from stick mode to slip mode. From a simulation of such transition, a time response of rotational speeds of a drive system and bottom hole assembly of the borehole equipment is recorded and a lower limit of the rotational speed of the drive system is determined for which the rotational driven speed of the bottom hole assembly is zero.