Potentialities of DTC strategies in position regulation: application to robotics
Purpose - This paper is devoted to the investigation of the potentialities of induction motor DTC strategies in position control applications. Design/methodology/approach - A comparison study is carried out between two DTC strategies dedicated to position control applications such as robotic: the Takahashi DTC strategy where the induction motor is fed by a two-level inverter and a new DTC strategy where the induction motor is fed by a three-level inverter. Special attention is paid to the synthesis of the vector selection table of the second strategy in an attempt to guarantee a high dynamic with reduced ripple of the torque. The comparison study is achieved considering four performance criteria: phase current total harmonic distortion; inverter switching loss factor; quality factor; and inverter commutation frequency. Findings - It has been found that the introduced DTC strategy offers higher performance than the Takahashi one. Of particular interest are: the reduction of both torque ripple and commutation frequency; the eradication of the demagnetization problem which is a vital requirement in position control applications; and the improvement of the power factor thanks to which a reduction of the inverter rating is gained. Research limitations/implications - This work should be extended considering the validation of the obtained simulation results through experiments. Originality/value - The paper proposes a new DTC strategy dedicated to position control applications. It allows the elimination of the demagnetization problem from which suffers the Takahashi DTC strategy at low speeds especially at zero speed in position control applications. It also offers a high power factor which opens up crucial cost benefits as far as the inverter rating is concerned.
induction motor position control comparison torque ripple demagnetization power factor direct torque control two- and three-level inverters