Abstract
Tracking performance and stability play a major role in observer design for speed estimation purpose in motor drives used in vehicles. It is all the more prevalent at lower speed ranges. There was a need to have a tradeoff between these parameters ensuring the speed bandwidth remains as wide as possible. This work demonstrates an improved static and dynamic performance of a sliding mode state observer used for speed sensorless 3 phase induction motor drive employed in electric vehicles (EVs). The estimated torque is treated as a model disturbance and integrated into the state observer while the error is constrained in the sliding hyperplane. Two state observers with different disturbance handling mechanisms have been designed. Depending on, how they reject disturbances, based on their structure, their performance is studied and analyzed with respect to speed bandwidth, tracking and disturbance handling capability. The proposed observer with superior disturbance handling capabilities is able to provide a wider speed range, which is a main issue in EV. Here, a new dimension of model based design strategy is employed namely the Processor-in-Loop. The concept is validated in a real-time model based design test bench powered by RT-lab. The plant and the controller are built in a Simulink environment and made compatible with real-time blocksets and the system is executed in real-time targets OP4500/OP5600 (Opal-RT). Additionally, the Processor-in-Loop hardware verification is performed by using two adapters, which are used to loop-back analog and digital input and outputs. It is done to include a real-world signal routing between the plant and the controller thereby, ensuring a real-time interaction between the plant and the controller. Results validated portray better disturbance handling, steady state and a dynamic tracking profile, higher speed bandwidth and lesser torque pulsations compared to the conventional observer.
Highlights
Electric vehicles (EVs) have come to occupy considerable space in the transportation sector owing to less harmful emissions, better energy profile, lesser noise and cheaper maintenance and operating costs
The use of the speed sensor adds to the non-linearity of the system by means of the sensor noise, which may affect the gain and dynamic performance of the motor used in the EV [3]
The disturbance handling method in SMLO1 is similar to many disturbance observers where the estimated disturbance is integrated into the state dynamic equation
Summary
Electric vehicles (EVs) have come to occupy considerable space in the transportation sector owing to less harmful emissions, better energy profile, lesser noise and cheaper maintenance and operating costs. LabVIEW permit the creation of computer models, which can be connected to real‐time embedded systems or electronic control units through digital and analog I/O (input/output) cards. As part of the model based design strategy for testing computer models, there are several testing levels namely the software in loop (SIL), model in which can be connected to real-time embedded systems or electronic control units through digital and analog I/O (input/output) cards. Existing disturbance observers have short comings in terms of speed bandwidth, parameter estimation, torque profile and stability issues. In a new real-time PIL platform, the plant and the controller are made to interact through digital and analog I/O cards by providing a real-time link This testing is based on a model based design paradigm and has not been performed in the existing literature. The conclusion section emphasizes the importance of the findings to the existing literature and its significance with respect to vehicle performance and dynamics
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