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### An Electro-mechanical System Model by MATLAB SIMULINK: Part 3

This is the last part from the part 1

Observation 9: Step input (10 V) & Square Wave (1 V, 1 HZ)
From observations 9 to 12, only the step input voltage will be varied keeping the square wave source parameters to 1 V and 1 HZ. From figure 14, it is observed that the cart displacement is periodic, more specifically complex periodic which again reminds the non-linearity. The motor velocity is increased which is approximately 9 rad/s at steady state. This seems very reasonable as the input voltage to the motor increases. The flow in the tank and the current flow in the circuit decrease with the increase in time.

Observation 10: Step input (20 V) & Square Wave (1 V, 1 HZ)
The step input is increased to 20 V. No significant change in the cart displacement except the curve shape. With the increase in the input voltage, the system starts oscillating. From the figure 15, the motor, flow in tank and the current through the circuit oscillates with higher value and show instability.

Observation 11: Step input (30 V) & Square Wave (1 V, 1 HZ)
From figure 16, the cart displacement profile is almost identical with the previous observation. The motor angular velocity, flow rate and the current flow throughout the circuit oscillates with higher magnitude than the previous observation.

Observation 12: Step input (50 V) & Square Wave (1 V, 1 HZ)
Here also with the increase in the step input, the oscillations in the motor, flow in tank and current in the circuit increased with increased magnitude. However, the cart displacement again remains same.

Observation 13: Step input (1 V) & Square Wave (10 V, 1 HZ)
This is the last criteria of this experiment’s observation. From observations 13 to 15, only the voltage of the square wave source will be increased gradually keeping the frequency 1 HZ and the step input is set to 1 V for rest of the observations. The cart displacement is now in the negative region keeping the periodic shape. There is noticeable decrease in the angular speed of the motor that oscillates with time. There is also slight decrease in current flow and flow in the tank. The probable cause for this behavior might be the increment of the voltage of the pneumatic source that acts backward with respect to the overall system flow.

Observation 14: Step input (1 V) & Square Wave (20 V, 1 HZ)
Observation 14 reflects the system non-linearity once again. From figure 19, the cart displacement is increased with the complex periodic wave form. The motor reaches steady state in previous fashion and there is also decrements in flow rate and current flow in the circuit with time.

Observation 15: Step input (1 V) & Square Wave (40 V, 1 HZ)
This is the last observation of this lab. The cart displacement again in the negative region which is almost identical to the observation 13. The motor velocity, flow in the water tank and current flow throughout the circuit resemblance the same characteristics as observed also in observation 13.

Concluding Remarks:
Due to the complexity and nonlinearity of the system, the dynamics of the system is hard to predict. Slight changes in the initial conditions or changes in the input sources affect the dynamics which eventually creates instability in the system. The properties (mass, stiffness, damping effect) of the system also play very crucial role in the system response.

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