Modeling of mechanical motions in a sewing machine

Abstract: To avoid high costs and delays, it is important to correct mistakes and to solve problems as early as possible in the development process. The aim for this master thesis is to develop dynamic models to describe the mechanical motions in an advanced sewing machine. The main purpose is to develop a mathematical model which can be connected with the development tools used by VSM Group. The starting point for the simulation of mechanical motions in the sewing machine has been that the in-signal to the model is the electric in-signal to the main motor [V] and that the out-signals are the arm shaft motions [position, velocity and acceleration]. There are significant friction variances depending on the arm shaft position during one cycle (one arm shaft revolution). The variation of the friction measurements have been implemented in two Simulink models, one that has been converted from the CAD model and one that is based on equations for an electric-motor. The model based on the electric-motor is the most accurate model because the model is less complex than the CAD converted model. The sewing machine contains several stepper motors. VSM Group wish to develop mathematical models also for the stepper motors. Two Simulink models have been developed, one with the aid of Matlab toolbox and one based on mathematical and physical relationships. The velocity of the sewing machine fluctuates from time to time depending on the temperature and lubrication. The temperature impact has not been included in these models. To compensate this, models for a warm and a cold machine have been developed.