Current Loop-Free Observer-Based Double Integral Positioning for Servo Drive Applications via High-Order Pole-Zero Cancellation Method

The output feedback system proposed in this article robustly regulates the position of the servo drives independent from the current loop and true system parameters and load information, forming a simple structure that is similar to a proportional–integral–derivative controller. The contributions of this article are threefold: 1) a high-order pole-zero cancellation (PZC) observer that estimates the speed and acceleration without the use of a system model; 2) an observer-based proportional–double-integral–derivative (PDID) controller that employs the active damping term as the feed-forward compensator while only using nominal system parameters; and 3) special structures of the PDID and active damping gains that trigger the high-order PZC to ensure a second-order transfer function with the multiple poles. The proposed solution is implemented using QUBE-servo2 to experimentally validate the practical merits of the proposals.