Nowadays, the use of asynchronous motors or also known as induction motors is the
most widespread in the field of factory automation and building service engineering, on the
grounds of their high reliability and low maintenance needs. Over the past decades, the
development of power electronics and decreasing prices of power electronic devices have
created new opportunities for controlling induction motors. For example, high quality drive can
be achieved by direct torque or field oriented control. The advancement of electric vehicles is
opening new, uncharted territories for the application of such motors, since loss mitigation can
be achieved through controlled magnetic flow at high rotational speed resulting in low working
Knowledge of the rotational speed, and the angle closed by the fixed and rotating
magnetic field, due to the slip, is essential for field oriented controlling. Such data can be
obtained by using expensive rotation speed measuring sensors, necessary because of the large
scale figures. To decrease the expenses, a functional method for estimating the rotational speed
can be applied based on the mathematic machine model. This method is one of the most
researched topics in the field of induction motors.
In this piece of work, a rotational speed estimation method has been tested, selected
after an in-depth review of corresponding academic literature and algorithms from various case
studies. Firstly, the chosen method has been tested in a simulation environment with and
without load. For the simulation, MATLAB Simulink software environment and the previously
measured electric parameters of a real induction motor have been used. The necessary devices
and parts have been selected in view of the measurement range, processing time and precision
requirement. The next step has been to design the printed circuit of the measuring device.
Having tested the designed device, the estimating algorithm has been implemented in a
STM32F4 microcontroller. After that, the testing and tuning of the implemented algorithm have
been carried out. The display of the measured values has been achieved by a computer sided,
MATLAB based user interface.
The simulation results of the chosen algorithm clearly show that in ideal circumstances
the rotational speed can be estimated with minimal errors.
The algorithm precision can be increased by constant rotor flux supply, due to the field
oriented supply. As a consequence, in real circumstances numerous factors can have an impacton the estimates, such as the fluctuating rotor flux, or changes in the motor parameters in
operation, which is proportional to the temperature variations.
The estimation can give rather precise results in real circumstances too, with the
compensation of the above mentioned errors and the online identification of the parameters.