Description

15MH302J – LINEAR AND DIGITAL CONTROL SYSTEMS
EXERCISE 9
COMPARISON OF REAL TIME AND MODELING OF QUBE SERVO DC MOTOR
LAB PREREQUISITES:
Exercise 1 to 3
PREREQUISITE KNOWLEDGE:
Fundamentals of MATLAB programming and Simulink.
OBJECTIVES:
The objective of this exercise is to compare the speed of the Qube Servo for both real time and modeling systems.
QUBE SERVO DC MOTOR MODELING AND SPECIFICATIONS:
The Quanser QUBE-Servo 2 is a direct-drive rotary servo system. Its motor armature circuit schematic
is shown in Figure 1. and the electrical and mechanical parameters are given in Table 1. The DC motor shaft is connected to the load hub. The hub is a metal disk used to mount the disk or rotary pendulum and has a moment of inertia of Jh. A disk load is attached to the output shaft with a moment of inertia of Jd.

Figure.1. Qube servo DC motor with load
The back-emf (electromotive) voltage eb(t) depends on the speed of the motor shaft, wm, and the back-emf constant of the motor, km. It opposes the current flow. The back emf voltage is given by:
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Table 1. Qube servo 2 system parameters

Using Kirchoff’s Voltage Law, we can write the following equation

Since the motor inductance Lm is much less than its resistance, it can be ignored. Then, the equation becomes

Solving for im(t), the motor current can be found as:

The motor shaft equation is expressed as
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Where, Jeq is total moment of inertia acting on the motor shaft and τm is the applied torque from the DC motor. Based on the current applied, the torque is

The moment of inertia of a disk about its pivot, with mass m and radius r, is

PROGRAMS, OBSERVATIONS AND INFERENCES
1. Draw the modelling of the Qube servo 2.0 DC motor by assuming the inputs and output are the voltage and speed.
2. Compare the modelling results with real time output of the Qube servo 2.0 DC motor.
PROGRAM

15MH302J
D E P A R T M E N T O F M E C H A T R O N I C S E N G I N E E R I N G EXERCISE 9
RESULTS & INFERENCES:
Evaluation
Component Maximum Marks Marks Obtained
Pre-lab Tasks 10
In-Lab Tasks 20
Post-lab Tasks 10
Bonus Tasks 10
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