The three outputs for Volts/Hz Controller are connected to the corresponding inputs of the induction motor block. Measured speed from the Rotary Encoder block is connected to the measured speed input of the Volts/Hz Controller block. A slider block, scaled between 30 and 400, is connected to the desired speed input of the Volts/Hz Controller block as RPM speed input. A plot block is wired to compare the desired and actual speeds. The actual speed is determined by converting load angular velocity to RPM. A const block set to 0 is connected to the load disturbance input of the rotational load model. wirePositioner and variable blocks are used to make the diagram legible.
Before simulating the model, click System > System Properties command and make the following selections:
•In the Start Time box, enter 0
•In the Step Size box, enter 0.0001
•In the End Time box, enter 10
Through minor exploration, the motor drive is found to have sufficient torque at all speeds to overcome maximum tool exertion.
Now with a working simulation, you have met the design requirements and can begin optimizing performance. For example, a fairly high-resolution encoder was used for estimating rate. How coarse can the resolution become before performance is degraded? Also, the motor may be oversized for the particular application. Surveys show that over 50% of the motors selected in the US are oversized for their application. Simulation provides a lower-cost alternative to performing extensive analysis or purchasing a variety of motors to empirically determine which is best suited for an application. This is true for any motion control application; not just limited to machine tools.