Inertia and load torque estimating method and apparatus

A method for deriving a system inertia estimate and a load torque estimate in a motor controller, the method comprising using a motor controller processor to perform the steps of:

• providing a velocity command signal;
• sensing a motor position;
• using the motor position to generate a velocity feedback signal and an acceleration feedback signal;
• subtracting the velocity feedback signal from the velocity command signal to generate a velocity error signal;
• using the velocity error signal to generate an acceleration command signal;
• multiplying the acceleration feedback signal and a load torque difference signal to generate an inertia product signal;
• using the inertia product signal to generate the system inertia estimate;
• multiplying the system inertia estimate and the acceleration command signal to generate a motor torque signal;
• multiplying the acceleration feedback signal and the system inertia estimate to generate an inertia torque;
• subtracting the inertia torque from the motor torque signal to generate the load torque estimate;
• and
• filtering the load torque estimate to generate the load torque difference signal.

An apparatus for estimating a system inertia and a load torque in a motor controller, the apparatus comprising:

• a sensing device for determining a motor position;
• at least a first derivative module using the motor position to generate an acceleration feedback signal;
• a module for mathematically combining the acceleration feedback signal and a load torque signal to generate a system inertia estimate;
• a module for mathematically combining the system inertia estimate and an acceleration command signal to generate a motor torque signal;
• a module for mathematically combining the system inertia estimate and the acceleration feedback signal to generate an inertia torque;
• and
• a module for mathematically combining the inertia torque and the motor torque signal to generate the load torque estimate.