Design Of State Observer For Two-mass Drive System

In electric drive system, drive shaft, gear reducer, and coupling are alwaysused to connect motor and load. Under certain conditions, the transmission isrigid; but in many cases, the elasticity of transmission device have to be takeninto consider. The existence of elasticity leads to mechanical resonancephenomenon in drive system. It will reduce the system dynamic and staticcharacteristics, influence the production quality, and even make the system loststability.In order to suppress resonance, it is necessary to feedback some or all of thesystem state to the controller. To some system state (such as load torque, loadspeed, shaft torque, etc.), the direct measurement is difficult. so it is needed todesign state observer to estimate the state value. Before designing the stateobserver, to make sure inherent parameters of the two-mass torsional systemmodel is necessary, such as the inertia of the drive side and load side, the shaftstiffness coefficient, etc. If the inertia of the load side is unknown, it is necessaryto identify the load inertia, and then develop the correct model of the observer.This paper studied the inertia identification principle firstly，and designedpassive-online inertia identification method. In the case of does not affect thenormal operation of the system, it can get load inertia identification value. Itdetermined the corresponding parameters of the two-mass torsional system.On the base of studied the structure and the existence conditions ofLuenberger observer, the state equation of two-mass torsional system isestablished, and the observability of the system is verified. The state observermodel is designed to estimate the system state (load torque and speed, shafttorque). The observer’s poles location is configured.At last, the condition and accuracy of inertia identification is tested. Themeasured value of the system state (load torque and speed, shaft torque) iscompared with the estimated value by observer. With the suitable pole position,the result of observation is satisfied.