SERVOMOTOR MAGNETIC RESONANCE IMAGING (MRI)
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This project is titled servomotor Magnetic Resonance Imaging (MRI). A servomotor is a specific type of motor and rotary encoder combination, usually with a dedicated, that forms a servomechanism. This assembly may in turn form part of another servomechanism. The encoder provides position and usually speed feedback, which by the use of a PID controller allow more precise control of position and thus faster achievement of a stable position (for a given motor power).
Magnetic Resonance Imaging (MRI) was used to non-invasively measure velocity and concentration of granular flows in a partially filled, steadily rotating, long, horizontal cylinder. First, rigid body motion of a cylinder filled with granular material was studied to confirm the validity of this method. Then, the density variation and the depth of the flowing layer, where particles collide and dilate, and the flow velocity profile were obtained as a function of the cylinder rotation rate.
The aim of this work is to use a servomotor in magnetic resonance imaging to measure velocity and concentration of granular flows in a partially filled, steadily rotating, long, horizontal cylinder in industries.
TABLE OF CONTENT
Table of Content
1.1 definition of servo
1.2 servo motor basics
1.3 physical properties of servomotor
1.4 significance of the study
1.5 industrial applications of the study
1.6 advantages and disadvantages of servomotors
1.7 comparison between servomotors and stepper motors
2.0 literature review
2.1 Review of servomotors
2.2 History of servomotors
2.3 Components of servomotors
3.0 Description of servomotor
3.1 Principle of operation of servomotor
3.2 How to select a servo
3.3 Servo motor controlled
3.4 Servo feedback
4.0 Servomotor accessories
4.1 Servomotor mounting
4.2 Mounting, bonding and grounding
4.3 electrical safety
4.4 prevent EMI problem
4.5 possible effect of EMI in a servo motor and drive system
4.6 servo motor cost
A servo motor is a dc, ac, or brushless dc motor combined with a position sensing device (e.g. a digital decoder). In this work, our discussion will be focused on the three-wire DC servo motors that are often used for controlling surfaces on model airplanes. A three-wire DC servo motor incorporates a DC motor, a geartrain, limit stops beyond which the shaft cannot turn, a potentiometer for position feedback, and an integrated circuit for position control of the three wires protruding from the motor casig, one is for power, one is for ground, and one is a control input where a pulse-width signals to what position the motor should servo. As long as the coded signal exists on the input line, the servo will maintain the angular position of the shaft. As the coded signal changes, the angular position of the shaft changes.
Servos are extremely useful in robotics. The motors are small and are extremely powerful for their size. A standard servo such as the Futaba S-148 has 42 oz/inches of torque, which is pretty strong for its size. It also draws power proportional to the mechanical load. A lightly loaded servo, therefore, doesn’t consume much energy. The guts of a servo motor are shown in the picture below. You can see the control circuitry, the motor, a set of gears, and the case. You can also see the 3 wires that connect to the outside world. One is for power (+5volts), ground, and the white wire is the control wire.
1.2 DEFINITION OF SERVO MOTOR
A Servo Motor is a motor which is part of a servomechanism. It is typically paired with some type of encoder to provide positioning and speed feedback.
1.3 SERVO MOTOR BASICS
A Servo Motor is defined as an automatic device that uses an error-correction routine to correct its motion. The term servo can be applied to systems other than a Servo Motor; systems that use a feedback mechanism such as an encoder or other feedback device to control the motion parameters. Typically when the term servo is used it applies to a ‘Servo Motor’ but is also used as a general control term, meaning that a feedback loop is used to position an item.
A servomechanism may or may not use a servo motor. For example, a household furnace is a servomechanism that is controlled by a thermostat. Once a set temperature is reached, there is feedback signaling it to shut off; making it a “servo” in nature. The term “servo” describes more of a function or task, than it does a specific product line. For this guide, we will discuss servo motors specifically.
A servo motor can be a DC, AC, or brushless DC motor, combined with a position sensor; in most cases, a digital encoder. A servo motor is typically the motor selected when it is essential that there is a high degree of confidence that the servo motor and drive system will closely track what is asked of it. There is typically a higher cost to a servo motor system than a stepper motor system, due to the servo motor’s feedback sensor and processing electronics.
1.4 PHYSICAL PROPERTIES OF A SERVO MOTOR
A Servo Motor consists of three major parts: a motor, control board, and potentiometer (variable resistor) connected to the output shaft. The motor utilizes a set of gears to rotate the potentiometer and the output shaft at the same time. The potentiometer, which controls the angle of the servo motor, allows the control circuitry to monitor the current angle of the servo motor. The motor, through a series of gears, turns the output shaft and the potentiometer simultaneously. The potentiometer is fed into the servo control circuit and when the control circuit detects that the position is correct, it stops the servo motor. If the control circuit detects that the angle is not correct, it will turn the servo motor the correct direction until the angle is correct. Normally a servo motor is used to control an angular motion of between 0 and 180 degrees. It is not mechanically capable (unless modified) of turning any farther due to the mechanical stop build on to the main output gear.
1.4 SIGNIFICANCE OF THE PROJECT
Servos are extremely useful in robotics and automation. Servo motors are used across various automation fields specifically where the motor must be able to operate at a range of speeds without overheating, operate at zero speed while being able to retain its load in a set position, as well as operate at low speeds. Servo motors are utilized in industrial machine tools, CNC manufacturing machines and processes, and packaging applications. Robots utilize servo motors because of their smooth commutation and accurate positioning. The aerospace industry makes use of servo motors in their hydraulic systems to contain system hydraulic fluid. The servo motor is relatively small in size, yet very powerful. A servo motor also draws power proportional to the mechanical load.
1.6 INDUSTRIAL APPLICATION OF THE STUDY
Servo motors are seen in applications such as factory automation, robotics, CNC machinery, and packaging. The feedback lets the drive know its position, speed, and torque to detect unwanted motion. Pharmaceutical industries are driven be the need to create smaller devices; ones that are easier to operate and function more efficiently.
1.7 ADVANTAGES AND DISADVANTAGES OF SERVO MOTORS
Servo motors are used in many robotics applications, due to many reasons:
- Servo motors usually have a small size
- Servo motors have a large angular force (torque) comparing to their size
- Servo motors operate in a closed loop, and therefore are very accurate
- Servo motors have an internal control circuit
- Servo motors are electrically efficient – they required current is proportional to the weight of the load they carry.