Abstract: This paper proposes a rotor field-oriented vector control method for induction motors based on the voltage flux linkage equation in a synchronous shaft system. The motor speed is estimated using the error signal of the q-axis current in the synchronous shaft system. In this sensorless vector control system, the use of a classic PI controller simplifies the control system. Finally, a simulation model of the sensorless vector control system is established using MATLAB. Simulation results verify that the proposed sensorless vector control system possesses good dynamic and static performance. Keywords: Induction motor, Sensorless vector control, Speed ​​estimation Abstract: Based on the synchronous reference frame, the voltage equations in terms of flux linkage of induction motor were deduced in this paper. A vector-controlled approach based on rotor field orientation control was also proposed. The error signal of the stator q-axis current in the synchronous reference frame was utilized to obtain the induction motor speed. Because classical PI controllers were used, the structure of the sensorless vector control was very simple. Simulation results based on MATLAB 6.1 demonstrate that the proposed vector control scheme is valid, and the dynamic and static performance are excellent. Keywords: Induction motor, Sensorless vector control, Speed ​​estimation 1 Introduction In closed-loop speed control of induction motors, the motor speed information is generally required. However, using a speed sensor not only increases the cost but also causes installation inconvenience and reduces reliability. Theoretically, the speed can be calculated in real time using the voltage and current of the asynchronous motor, thus eliminating the need for a speed sensor. Sensorless control brings the following advantages: reduced system cost, enhanced system anti-interference and reliability, and reduced motor shaft dimensions, etc. Therefore, sensorless control of asynchronous motors has become an important research direction in the field of electrical drives in recent years. Many speed estimation methods have been proposed for sensorless asynchronous motor vector control [1,2,3]. Currently, the main methods used include direct estimation, model reference adaptive method, sliding mode variable structure method, and artificial neural network-based adaptive method for speed identification. Some of these methods rely on motor parameters, resulting in large speed estimation errors, while others are computationally complex and difficult to implement. This paper proposes a rotor field-oriented vector control method for induction motors based on the fundamental principle of rotor field orientation and the voltage flux linkage equation of the induction motor under synchronous shaft system. The method utilizes the error signal of the q-axis current in the synchronous shaft system to estimate the motor speed. In this sensorless vector control system, the use of a classic PI controller instead of a traditional flux linkage observer simplifies the control system. MATLAB dynamic simulation verifies the correctness of the proposed sensorless vector control method, demonstrating its simplicity, ease of implementation, and good dynamic and static performance. For details, please click: Research on a Sensorless Vector Control System