Feedback control System for position and velocity control of load

[gitanjali]

Hi,

I'm facing difficulty in designing a Control System for load as it contains mechanical system(mathematical modelling)also.

A dc motor is coupled to gearbox which is further connected to load.Speed and position of load is to be controlled.

i have made a model the snapshot are attached.As the stiffness and damping value of gearbox and load are very high the feedback torque to gearbox or the dc motor reaches infinity.

Please if any one can suggest if some problem is there in the modelling of gearbox, load or their interconnection(feedback).

Thanks Gitanjali