Control Systems Laboratory (ELP800) (Semester-I, 2024-25)

In this experiment, students need to observe the transient and steady state responses of linear time invariant (LTI) systems by providing various test signals, such as step, square and triangular, as inputs to the linear simulator kit. The LTI systems are represented by first, second and third order transfer functions. The time responses of open loop and unity negative feedback closed loop system need to be observed, and their parameters such as time constants, maximum overshoot, settling time, rise time and steady-state errors needs to be tabulated. Further, the performance of the feddback loop, when subjected to added low frequency disturbance signals, needs to be observed. More details can be found out here.

In this experiment, students need to identify the AC servomotor and DC motor transfer functions, which characterize their dynamic behaviours. The AC servomotor is a two-phase induction motor, designed to have a perticular terque-speed characteristic (negative slope). The AC servomotor and DC motor dynamics are characterized by second order or first order (approximated) transfer functions G(s). It is required that the associated parameters, such as various time constants, inertia and friction coefficient need to be calculated to obtain the exact coefficients of polynomials in G(s). More details can be found out in document 1 and document 2.

In this experiment, students will study the control action required to maintain a set-valued temprature inside a long cylindrical tube through the Process Control Trainer kit. This kit has a centrifugal blower, which draws air from outside the tube, and passes it through a heater grid. The sensor measures the air temperature inside the tube, and then it compares with the desired set temprature. According to the error, the controller gives the command (ON-OFF) to the heater to maintain temperature. The long tube creates the transport-lag in the system. The behaviour of the controller ao address this property needs to be observed. Further, how the system behaves under disturbance also needs to be studied. More details can be found out in document 1.

The overall objectives of this experiment are devided into following three parts:

• System identification: Using the procedure followed in Exp-2, it is required to identify the given DC motor's transfer function. Once the transfer function is obtained, for the verfication purpose, the same transfer function needs to be simulated in MATLAB Simulink, by giving a step input, and then comparing the response with the response of actual DC motor in the Oscilloscope.

• Controller synthesis: Choose your own transient performance characterstics, such as damping and settling time. Then, design a PID controller to achieve these transient specifications using MATLAB sisotool available in Control System Toolbox with root-locus based design approach. You may use this page for reference.

• Active-Circuit Realization: Once the PID controller is designed, it needs to be implemented for controlling the DC motor speed. The PID controller needs to be realized through active circuits, such as using operational amplifiers, resistors and capacitors in the breadboard as shown in figure. This page may halp you for realizing the PID circuit.

• This experiment has same objectives as in Exp-4, and same procedures needs to be followed, except the last step (Active-Circuit Realization). Instead of the active circuit realization, it is required to implement the PID controller through an Arduino-Mega microcontroller with DC motor driver. In addition to speed of DC motor, the position control also needs to be carried out.

Following tasks are the broad objectives of this mini-project.

• Building a mobile robot: It is required to first build a mobile robot, as shown in the figure, using LEGO Mindstrom EV3 Kit. There is a MATLAB Simulink Support Package for LEGO Mindstrom EV3 hardware. Refer to page-1 and page-2 for more details on how to set the EV3 brick accordingly, and import Simulink blocks to EV3 brick and program them.

• Open-loop operation: In this part, there is no need to use and controller for the motors, attached with the wheels. Some speed reference is provided to both the motors, and the turn angle needs to set to zero. Then, observe the motion of the mobile robot. More details and step-wise procedures are available in this page.

• Closed-loop operation: In this operation, it is required to program the EV3 brick to drive the robot autonomously in a straight line. For this, following two different methods need to be followed. First, the motor encoders data are utilized to track wheel rotations for precise movement using PID controller. More details and step-wise procedures are available in this page In the second part, a gyro sensor need to be integrated to maintain the robot's orientation to ensure that it followed a straight path, even after giving a small disturbance.