IP Controller Design for Uncertain Two‐Mass Torsional System Using Time‐Frequency Analysis

Abstract

With the development of industrial production, drive systems are demanded for larger inertias of motors and load machines, whereas shafts should be lightweight. In this situation, it will excite mechanical vibrations in load side, which is harmful for industrial production when the motor works. Because of the complexity of the flexible shaft, it is often difficult to calculate stiffness coefficient of the flexible shaft. Furthermore, only the velocity of driving side could be measured, whereas the driving torque, the load torque, and the velocity of load side are immeasurable. Therefore, it is inconvenient to design the controller for the uncertain system. In this paper, a low-order IP controller is designed for an uncertain two-mass torsional system based on polynomial method and time-frequency analysis (TFA). IP controller parameters are calculated by inertias of driving side and load side as well as the resonant frequency based on polynomial method. Therein, the resonant frequency is identified using the time-frequency analysis (TFA) of the velocity step response of the driving side under the open-loop system state, which can not only avoid harmful persistent startstop excitation signal of the traditional method, but also obtain high recognition accuracy under the condition of weak vibration signal submerged in noise. The effectiveness of the designed IP controller is verified by groups of experiments. Experimental results show that good performance for vibration suppression is obtained for uncertain two-mass torsional system in a medium-low shaft stiffness condition.

Optimal IP Current Controller Design Based on Small Signal Stability for THD Reduction of High-Power Density PFC Boost Converter

“…Another important issue at the choosing of the output bulk capacitor, the capacitor series equivalent resistance (ESR) should be very low, which it is effects in circuit efficiency and the output voltage regulations. Also, higher ESR causes more ripple, influencing stability of the control loops [25]. Table 1 shows the designed specification and results for the 2500 W PFC boost converter employed in this work.…”

“…Diode current is the sum of two components, load current ( ) and the output capacitor current ( ), which it can expressed as (25).…”

“…Applying the averaged small signal perturbation to (25) with the resistive load case give expression in (26).…”

“…This paper presents the small signal stability modeling of the conventional PFC boost converter proposed, and based on the signal stability model, an optimal integral-proportional (IP) current controller consists of double loop control strategy, where the integral gain feed forward to return the inductor current back to the reference set point, and the proportional gain implemented in the feedback path to increase the controller response. IP controller usually used in the control circuits of the DC-DC converters and the DC motor drive systems [25][26][27], as compared with the PI controller, the IP controller have less overshoot and fast dynamic response [28]. So, IP current controller with fast dynamic response has been designed to let the inductor current track the reference current, removing the total distortion occurred around the zero-crossing point and increase the power factor.…”

Optimal IP Current Controller Design Based on Small Signal Stability for THD Reduction of a High-Power-Density PFC Boost Converter

“…Based on the signal stability model, the optimal integral-proportional (IP) current controller consists of a double-loop control strategy, where the integral gain feedforward returns the inductor current to the reference set point, and the proportional gain implemented in the feedback path increases the controller response. The IP controller is usually used in the control circuits of DC/DC converters and DC motor drive systems [25][26][27]. Compared with the PI controller, the IP controller has less overshoot and a fast-dynamic response [27].…”