The Abstract-- The
development of technologies affects the demands of industries at the present time. Thus, automatic control has played a vital role in the advance of engineering and science. In today’s industries, control of DC control is a common practice since DC motor has become an important drive configuration for many applications across wide range of powers and speeds. Therefore, the implementation of DC motor is required for the benefits of future generation. This project focused on the behavior of the motor based on the given value of the torque and the rise time of the system. The main objective is to design and develop P-Controller and PI controller that are able to run DC motor system efficiently. The controllers have been designed and the systems are simulated using MATLAB to analyze their performance as well as the system response. Finally, the characteristics of the systems are analyzed in the experiment to compare the differences from obtained results of MATLAB and practical. It will greatly help the student to visualize the performance of control system by experience compared compared to si mulation by the computer.
I.
II.
THE PURPOSE AND FUNCTION OF THE COMPONENTS.
A. Power Supply Unit PS150E The power supply provides electrical power of 24V DC 2A unregulated power supply for the motor and control system through the 8-way connector to the servo amplifier. It is shown in Figure 1.2. On the front panel, there are two sets of 4mm sockets to provide reference voltage. The ports on the left and right sides of the panel supply +15 and -15 DC volts relative to a zero volt ground. The ports in the center of the panel provide AC power. The needle at the top of the panel of the power supply indicates the current being sent to the motor or to the servo amplifier.
INTRODUCTION
In this project each station (MS150 System) is equipped with a DC motor, with a tachometer to measure angular velocity, turning potentiometer (designated as input pot and output pot ) to give and measure angular position, and power amplifier (also known as pre-amp and servo-amp) to drive the motor. The command signal can be provided by the function generator or input pot, and the output of angular position or velocity can be measured by the oscilloscope. Figure 1-1 shows the MS150 system.
Fig.2 Example of Power Supply Unit PS150E
B. Servo Amplifier SA150D
Fig.1 Example of MS 150 system
This unit contains two transistors, which drive the motor in either direction. To avoid overloading the motor, there is a motor current meter with a 2A overloading protection. Figure 1-3 shows the actual display of this unit. Current flow through the motor's armature is controlled by the servo amplifier unit (SA150D). Notice that in Figure 1-3 the motor is plugged directly into the servo amplifier with 8 way connector. The two ports labeled 1 and 2 on the servo amplifier are its inputs. If the voltage at port 1 equals the voltage at port 2 (V1 = V2), then the servo amplifier does not send any current to the motor. If V1 > V2, the
current to the motor travels in one direction, and if V2 > V1, the direction of the current is reversed. In general, the larger the difference of |V1 – V2|, the larger the current that will be send to the motor. However, circuitry prevents the armature current from exceeding 2A. On the panel of the servo amplifier, there is a port that allows one to measure the current being sent to the motor. Also, there are two ports which allow one to measure the voltage drop across the motor. For convenience there are three ports at the bottom of the servo amplifier panel which supply +15V, -15V, and a 0V ground reference.
Fig.4 Example of Attenuator Unit AU150B
D. The Pre-amplifier(PA150A): This provides the correct signals to drive the servo amplifiers in SA150D. A positive signal applied to either input causes the upper output (3) to go positive, the other output (4) staying near zero. A negative input causes the lower output (4) to go positive, the upper one staying near zero. Thus bi-directional motor drive is obtained when these outputs are linked to the SA150D inputs.
Fig.3 Example of Servo Amplifier SA150D
C. Attenuator Unit AU150B Fig.5 Example of Pre-amplifier(PA150A)
This unit contains of two variables of 10kΩ potentiometers. The proportion of the resistance being selected is indicated by a dial graduated from 0 to 10. Figure 1-4 shows the attenuator unit. This unit can either provide a reference voltage when connected to a DC source or can be used as a gain control when connected to the output of an amplifier. Two ways of schematically depicting potentiometers are shown in figure below. The potentiometer consists of a resistor between terminals A and C. In attenuator Unit (AU150B), the resistance is R = 10kΩ for each potentiometer. The potentiometer provides a means of “dividing” resistance.
E. Output Potentiometer (OP150K) This is rotary potentiometer used for position control. The output potentiometer is connected to the GT150X low-speed shaft by using the push-on coupling. The OP150K output potentiometer has no mechanical stops and so cannot be changed by continuous rotation. The unit has a buffer amplifier with a gain of one so that even if the output is shorted to a power supply or ground, the potentiometer will not be damaged by overloading. The buffer also ensures that the potentiometer wiper does not have to carry any current load during normal use.
Fig.6 Example of Output Potentiometer (OP150K)
F. Reduction Gear and Tacho Unit (GT 150X) This equipment serves three purposes. First, notice that it has three shafts sticking out. All are mechanically connected through a series of gears. Furthermore, the sizes of the gears are chosen so that shafts rotate at dramatically different speeds. The speed reduction in the gearbox will be 30/1 from high speed input shaft to the low speed output shaft. The second use of the reduction gear tacho unit is it is used as digital volt meter. To use the volt meter, we first need to supply power to the unit. The -15V, +15V, and 0V ports at the top of the GT150X unit need to be connected to the corresponding ports on the power supply. When the switch on the panel is in the “dc volts" position, the digital read-out indicates the voltage at port 4 relative to ground. Finally, unit GT150X can be used as a tachometer. As one of the shafts rotates, it spins a wire coil within a magnetic field and generates a voltage between ports 1 and 2. If we connect port 1 to ground, then one can measure this voltage by connecting port 2 to port 4 and keep the switch set to “dc volts”. However, if we connect port 2 to port 3 and set the switch to “tacho rpm”, then the unit make the conversion from voltage to shaft revolutions per minute (rpm)as shown in the figure 1-7 below.
Fig.7 Example of Reduction Gear and Tacho Unit (GT 150X)
Note that the output voltage of the potentiometer is proportional to the input shaft speed, if the tachometer dynamics is neglected the relation between the input speed and the output voltage can be written as Vs = Ksω. Here Vs is the tachometer output voltage and ω is the shaft speed in terms of revolution per minute. G. Operational Amplifier OA150A It is an op-amp that normally connected as a unity-gain summing-inverter by means of the 3-position switch mounted on it. It is used as the angular-position-error detector. Since the unit is a summing amplifier, the feedback signal polarity must be reversed with respect to the reference signal, in order that the output will represent the error. The unit has three summing input terminals, and the output is available at two (or three) output sockets. The unit also has a zero-set control and a selector switch, which selects the feedback (normally resistive) within the unit. The selector switch is normally switched to the leftmost position indicating resistive feedback with unity gain. The op-amp must be zeroed before use.
Fig.8 Example of Operational Amplifier OA150A
H. Input potentiometer module(IP150H) These are rotary potentiometers, used in experiments on position control. The input potentiometer has ±150° of motion while the output potentiometer has no mechanical stops and so it cannot be damaged by continuous rotation. The input potentiometer is used to set up a reference voltage and the output potentiometer is connected to the motor low-speed shaft to obtain an output voltage proportional to the motion.
III.
MATHEMATICAL MODEL DERIVATIONS
Vin = 2.85v Vout = 4.85 Vin / Vout = 0.59 @ 57/ 97 A. P Controler
=
Assume (57/97)Kp >1 (ignore) =[
Kp ] /
= = Fig.9 Input potentiometer module(IP150H)
I.DC motor (DCM150F)
τ=
This motor is driven by a servo amplifier and the combination of the two being called a 'Servomotor„. As given in figure 1-10. The overall transfer function can be written as follows :
τ=
Gp(s) =
=
=
Kp =
= 54.55 ms
=
= 3.48
B. PD Control Where ωm is the output angular velocity, Vm is the servomotor input voltage, Km is the servomotor gain constant and τ m is an equivalent electro-mechanical time constant.
=
=
=
[
=
Fig.10 Example of DC motor (DCM150F)
τ n1 =
τ n1 =
]/0.022 Kp
= 0.12 / 2.2 = 0.055
Kd = 0.001 - 0.01, assumed Kd = 0.005 0.055 =
Kp = 92.65 IV.
CONTROLLERS DESIGN
A. P Controller
Fig.11 Block diagram of P Controller
B. PD Controller
Fig.12 Block diagram of PD Controller
