Research On Motion Control Strategy Of Offshore Drilling Compensation Drawworks

The floating drilling platform will heave under the influence of the waves,which will drive the hooks up and down.In serious cases,the bit will even leave the bottom of the well,which will affect the smooth progress of the drilling operation.Therefore,in order to ensure the normal operation of drilling,heave compensation device must be used.The research on this aspect of our country starts later than that of foreign countries,which causes some existing heave compensation technology and equipment in our country to lag behind the development of foreign countries.Therefore,it is of great significance for the research in this field.At present,there are many types of drill string heave compensation device,including heave compensator between travelling block and hook,crown mounted heave compensator,drawworks heave compensation system,and so on.As a new technology,which the drawworks heave compensation system has its unique performance advantages.Such as,simple transmission equipment,low barycenter of equipment,compact system structure,compensation for travel is not restricted,wide application fields and so on.Combined with the investigation of domestic and foreign data,explores the control strategy of winch heave compensation system which the subject involved.First of all,in order to study the control strategy,combined with the equipment and parameters of offshore drilling platform,the theoretical model of winch compensation system is built in this paper.The displacement control scheme of system heave compensation is analyzed.At the same time,soft start and stop control scheme is proposed to solve the problem of the fluctuation of the heave compensation when it starts and stops.And the control scheme of soft start/stop is put forward in order to solve the problem that there is fluctuation in the starting and stopping time of heave compensation.Then,the motion control method of heave compensation is selected and improved.According to the theoretical model of the system,the transfer function of the system is established.And the control algorithms such as PID control,internal model control and Smith predictor and so on are simulated and studied,the advantages and disadvantages of each method are compared and analyzed.And the control method of the system is preliminarily selected.In order to further analyze the problems existing in the control method,the overall Simulink model of the system is built,and the designed system control scheme is used to simulate and analyze the control effect.According to the problems found,the control method is improved appropriately,including the anti-interference ability of the system and the matching of the model.The existing heave compensation test rig is reformed.And the control strategy is compiled into the corresponding control program.Then,the related experiments of the control scheme,which includes the soft start/stop experiment,PID control experiment and PID-Smith control experiment,are carried out by using the test bed.Then the actual control effect of compensation winch motion control strategy is verified by experiments,which provides a theoretical basis for the design of the control scheme of the actual winch heave compensation system.