"Experimental results for Correlative Correction of Current Measurement Errors for Quad-Motor Drives Experiment (Nominal and EMI)"

"Quad-motor drive (QMD) systems enable fully independent torque control at each wheel and are increasingly adopted in high-performance electric vehicles (EVs). However, compared with single-motor drives, current measurement errors (CMEs) in QMD architecture accumulate across multi-motor subsystems, leading to amplified torque and speed ripple as well as asymmetric current sharing.  This paper proposes a correlative correction strategy for QMDs based on a distributed calibration approach (DCA). In the proposed method, each motor subsystem is calibrated independently while the remaining motors are temporarily disabled via software, eliminating inter-motor interference. By exploiting inherent correlations between phase currents and DC-bus currents at selectively chosen midpoint sampling instants within a five-segment PWM scheme, both offset and scaling errors are estimated and compensated for without observers, additional sensors, or increased sampling frequency. Experimental validation on a quad-motor platform demonstrates that the proposed method reduces the RMS ripple of the torque-producing current by approximately 78\u201388% under non-EMI conditions across steady-state, step-torque, and step-speed operating scenarios. Under electromagnetic interference (EMI), dominant harmonic components are suppressed by 60\u201371%, confirming robust time-domain correction with partial spectral attenuation. The results verify that the proposed correlative correction strategy provides a scalable, low-complexity solution for accurate CME compensation in QMDs operating under both nominal and electromagnetically harsh conditions."