Mathematical Modeling of DC Motors for the Construction of Prostheses

The article describes static and dynamic characteristics of a DC motor with independent excitation by mathematical modeling in MATLAB environment for the possibility of further construction of models of electric drive systems with this engine type. The tasks of designing bionic prostheses require solving the problem of developing a control system for this prosthesis. This complex system includes many different subsystems, in particular, DC drive systems. This study examines the control of the knee module of a bionic prosthesis based on a hydraulic cylinder, which is controlled by turning the spool, which in turn determines the moment of resistance. Therefore, the speed of the electric motor is a key factor in the operation of the bionic knee module. Inadequate assessment may result in personal injury. A brief theory describing the basic principles of calculating the electric and mechanical parts of a DC motor is presented. A basic structural diagram of a DC motor having an input effect, a transfer function and an output signal is constructed. Cases of structural schemes with a permanent and variable magnetic flux of the winding of the excitation and with variable anchor resistance are given. According to the above structural diagrams, a mathematical model of the DC motor in MATLAB/Simulink is compiled. The results of modeling a constant-current motor for direct starting with a constant and variable magnetic flux of the excitation winding are obtained. Using the special function linearization, the transfer function of the motor are obtained. Modeling of start-up modes at idle and under load was performed. A conclusion was made about the advisability of using direct-current motors in electric drive systems and the importance of the studies carried out for the further modeling of electric drive systems and real mechanisms.