The Dual Mechanical Port (DMP) electric machine has two rotors that can be set to rotate at different speeds and directions. Compared to conventional electric machines with only one rotor, the DMP machine provides higher torque density and much better control flexibility. However, the DMP machine has a relatively complex structure, which makes it a challenge to model and control. In addition, the existing model and control algorithms for single rotor machines cannot directly be applied to the DMP machine.
In this study, it has been explore that how the DMP machine can be applied to hybrid electric vehicles as an avenue for explaining the electromagnetic characteristics and functionality of this more complex mechanism. The model and the control algorithms for two different DMP machines are also investigated. The first DMP machine, which is called the PMDMP, uses two layers of permanent magnets within the outer rotor. The second one, which is referred to as the SCDMP machine, uses a single layer of squirrel cage within the outer rotor, The study of the modeling and control for the SCDMP machine is the major contribution of this work.
Compared to other DMP machines, the PMDMP machine stands out for its high torque density and high efficiency. A detailed model derivation for the PMDMP is presented later in the work. The independent control of its two rotors is investigated and verified by simulations and experiments. To overcome the problems brought about by the position sensors, the effectiveness of position sensorless control algorithms for the PMDMP is investigated. High frequency injection and sliding mode sensorless control algorithms are applied to the PMDMP machine at low speed and high speed, respectively. The performance of the sensorless control algorithms in experiments matches well with the simulation results. To verify the functionality of the DMP machine in power split hybrid application, the power flow pattern in various operational modes are discussed and simulated.
To avoid using high cost rare earth permanent magnets, the SCDMP machine is proposed. In this DMP machine, the permanent magnets in the outer rotor is replaced with a squirrel-cage. Therefore, it is referred to as the SCDMP machine. First, the electromagnetic characteristic of the SCDMP machine is analyzed. Then, the transient model and steady-state model of the SCDMP machine are derived. The proposed machine models were then verified by implementing finite element method and simulation. The results showed that the proposed models accurately represent the unique electromagnetic characteristics of the SCDMP machine.
Due to these unique characteristics, control algorithms for conventional machines cannot be applied to the SCDMP machine. The methods to calculate the correct current commands and to estimate the outer rotor flux position are proposed. Based on these two methods, a control algorithm for the SCDMP machine is proposed and estimated by simulation. The results showed that the proposed control algorithm is able to independently control the torque productions and the flux levels of the SCDMP machine's two rotors.
Keywords: Finite Element Analysis, Motor Control,Squirrel Cage Motor, Dual Mechanical Port, Electric Machine Modeling, Hybrid Electric Vehicle, Field Oriented Control, Sensorless Control, Independent Control