Dc motor speed control
...ed (lab_5.smf) that interfaced the motor and tachometer for control. The model in Simulink outputted a step function to a power amplifier. This powered signal drove the motor for a set time. The tachometer output was then inputted into the computer to create a response of the system. This graph was used to calculate the transfer function. Once the transfer function of the system was found a model system could be built in Simulink. In order for the system response to be correct a gain would have to be added into the model. To find the exact gain of the modeled system a function called ‘rlocus’ was used in Matlab. This function takes a known transfer function and plots the polls of the system. The rendered plot shows a poll at the origin. This point represents the gain of the system. In this case it was found to be 5.31. Now that all the variables are known the Simulink model is completed and run to reveal the response of the system. This model represents the system with out the disturbance. Next a disturbance was added at the input of the of the transfer function. The disturbance was made of a step input. This would just increase the voltage going into the transfer function by adding the constant voltage input with the disturbance voltage. The reason this disturbance was added at this juncture was because the system included an integrator block. If the disturbance was added after the transfer function the spike would have been incorporated with the input function and then integrated causing the wrong input to the transfer function. By adding it in between the integrator and the transfer function the disturbance could be varied where as if it was outside this point it would have to be fixed value. Now that the modeled system works it is now time to build a circuit that will control the speed of the motor. The circuit will compare the tachometer voltage and reference voltage of the system and compensate these by adjusting a gain to make the motor speed constant. If the circuit sees a higher tachometer voltage compared with the reference voltage the motor speed will increase but when the gain is adjusted by the circuit it will return to its original constant speed. If the disturbance causes a negative drop in the tachometer voltage the motor speed will slow down and the gain will be decreased by the circuit causing the motor speed to return to constant. Using the analog computer the speed control circuit was constructed and interconnected with the motor and power amplifier. For functional tests a potentiometer was used on the analog computer for a disturbance. The pot would increase or decrease the disturbance voltage into the system. This was disturbance was used for testing of the control circuit only. For the actual test the disturbance was added by way of the Simulink program used to model the motor. To make this measurement using a physical increase or decrease was impossible. The response time between the human and computer was inadequate. There was also a ground leakage problem when the computer and the circuit were connected. This caused the system to bypass the control circuit and saturate the motor with voltage making it run at maximum rpm. Finally when the system was all connected the computer program was run a few different times with different disturbance voltages. From these test trials the response plots were compiled in Matlab. These plots were then compared with the ones rendered in the system model in Simulink. Some trails were also done in both Simulink and in the physical system with different system gains. One was done with an undershoot gain and the other with an overshoot gain. The purpose was to show that the system will not operate correctly unless the right gain is in the system. Task List Peter Jette • Design of system circuit o Circuit design • Layout of circuit design o Construction of circuit on the analog computer • Testing of circuit o Test of analog computer circuit • Documentation – Final report and presentation o Speaking during final presentation o Construction of Power point o Writing of final report Ryan Kearns • Analysis of equations o Motor equations and system equations • Design of system circuit o Circuit design and testing using Multisim 8 • Testing of circuit o Test of analog computer circuit • Simulink simulation o Transfer of block diagram to Simulink o Simulation using Simulink using various gains • Documentation – Final report and presentation o Speaking during final presentation o Construction of Power point o Writing of final report Florian Behme • Modeling o ...