In digital motion control, the stepper motor is a particularly effective actuator, as it can faithfully execute commands given in digital form. This type of motor is currently widely used in the automation industry, especially the equipment that requires precise control. Stepper motors are widely used in machine tool such as CNC plasma cutting machine, wood machine, engraving machine, laser cutting machine ... In this report, we use 3D Printer for the example to stepper motor. Their downside is that their rotational accuracy is limited by the physical poles of the motor. This can be improved using micro-stepping. In summary, servos are great for some applications; but, for low cost situations like 3D printing, steppers are hard to beat. It is likely servos needed for milling CNCs because the cutting head is much more massive than an extruder or laser and the servo control loop is needed to provide accurate motion for the higher mass. From all reasons above, to build a 3D printer (especially in university, for a course project), Stepper motor is the best choice.
Trang 1HCMC UNIVERSITY OF TECHNOLOGY AND EDUCATION
FACULTY FOR HIGH QUALITY TRAINING
1 Lê Minh Huy ID: 17142019
2 Ngô Hữu Lâm ID: 17142029
Ho Chi Minh City December 2020
Trang 2CONTENT
CHAPTER 1: OVERVIEW 3
I PROBLEM VIEWING 3
II OBJECTIVE AND PURPOSE OF THIS PROJECT 3
1 Objective 3
2 Purpose of this project 4
III RESEARCH METHOD 4
1 Theoretical basic 4
2 Practical application 4
CHAPTER 2: THEORETICAL BASIC 5
I STEP MOTOR OVERVIEW 5
1 Stepper motor concept 5
2 Structure and working principle 5
2.1 Structure 5
2.2 Working principle 6
3 Types of step motor 6
4 Stepper motor torque 9
II STEP MOTOR CONTROL 13
1 Stepper motor applications 13
2 Stepper motor conrol method 14
2.1 Wave control (Wave drive) 14
2.2 Full step controller (Full step drive) 14
2.3 Half-stepping controller (Half-stepping drive) 15
2.4 MicroStepping controller (MicroStepping drive) 15
3 Stepper motor Driver 16
4 Stepper motor Driver types 17
CHAPTER 3: APPLICATIONS OF STEP MOTOR 20
I CHOICE OF ELECTRIC DRIVES 20
II 3D PRINTER PLAN DESIGN 21
III IMAGES OF 3D PRINTER 25
CHAPTER 4: COMMENTS AND EVALUATION 26
I COMMENTS 26
1 Advantage of the project 26
2 Disadvantage of the project 26
3 Practical applicability 27
II EVALUATION THE PROJECT’S RESULT 27
Trang 3III SUGGESTION FOR AUTOMATIC ELECTRIC DRIVE PROJECT 28 REFERENCE 29
Trang 4INSTRUCTOR COMMENT
HCMC, 28th, December 2020
Instructor
Trang 5THANK YOU
Our project team want to give our thanks to the teacher/professor in our Electronic falcuty for letting us study under your care all this time We would like to give our most heartful thanks to Mr Nguyen Phan Thanh has been supporting for the completion of this course project Automatic Electric Drive
Electrical-In the process of making this course project there has been some mistake that was make along the way, we hope that you can overlook it if possible Because our knowledge and practical experience are still short so our project may have been imperfect or lacking, we hope for you to give us some insight for our project to be more completed and for our team
to gain more experience and knowledge along the way
Thank You Very Much!
Trang 6At present, there is a lot of motor types on the market like stepper motor, encoder motor, servo motor, a three-phase asynchronous motor etc… each type of motor have correctsponding of different advantangeous and disadvantangeous From those advantage and disadvantage that we will chose and use them in different areas in daily life and production
A system can consists a lot of motor, working together, do different task in that chain of production With the nonstop advancement of precision technology that has practical application for robot arm, 3D print machine, a lazer engraving machine, CNC…, the stepper motor has become more important and widespread The stepper motor has contributed in improving, research, educated our automatic electric drive course in our country to improve and increased the productivity based on the technological knowledge we gained, we have also save up the labor expense and still increased the production Because of that the act of creating a chain system that use stepper motor has been working favourably and controlling them easier is a worthwhile business
From the view and the practical application of the stepper motor our team has decied to choose the project “Studying about step motor and it application” to help other know more about step motor From here we can use our theoretical basic to apply in practical uses
II OBJECTIVE AND PURPOSE OF THIS PROJECT
1 Objectives
Trang 72 Purpose of this project
III RESEARCH METHOD
1 Theoretical basic
- Finding, summarize the study materials
- Research about types of stepper motor, how to control it and what it can be use for
2 Practical application
cutting machine, wood machine, engraving machine, laser cutting machine
In this report, we use 3D printer for the example to stepper motor
Trang 8CHAPTER 2: THEORETICAL BASIC
I STEPPER MOTOR OVERVIEW
1 Stepper motor concept
The Step motor is technically a synchronous motor that have the principle of turning discrete electrical impulse control signals into angular rotation
Figure 1: Step motor
A stepper motor is a particular type of DC motor that does not rotate continuously Instead, a full rotation is divided into a number of equal steps A stepper motor consists of phases, which are multiple coils that are organized into groups By applying the energy from the input voltage to each phase in a sequence, the stepper motor rotates by taking one step at
a time Thus a stepper motor converts electrical energy or an input digital pulse into mechanical shaft rotation
2 Structure and Working principle
2.1 Structure
Step Motor consist of 2 main part: Stator and Rotor
Figure 2 Step motor structure
Trang 9Like all electric motor, it has stator and rotor The rotor is the movable part which has
no windings, brushes and a commutator Usually the rotors are either variable reluctance or permanent magnet kind The stator is often constructed with multiploe and multiphase windings, usually of three or four phase windings wound for a required number of poles decided by desired angular displacement per input pulse
2.2 Working principle
A stepper motor works under the principle of electromagnetism A permanent magnet
or soft iron is used as the rotor and is surrounded by electromagnetic stators The poles of the rotor and stator may be teethed When voltage is applied at the terminals, the rotor aligns itself with the stator or moves to have a minimum gap with the stator due to the magnetic effect The stators are energized in a sequence and the rotor moves accordingly, giving a full rotation that is divided into a discrete number of steps with a particular step angle
• Advantage:
- A stepper motor is used in devices that need precise positioning and speed control Because it moves in precise repeatable steps, the stepper motor is used in devices like 3D printers, camera platforms, plotters, scanners, etc And because it has maximum torque at low speeds, the stepper motor is also used in devices that require a low speed
• Disadvantage:
- A stepper motor has low efficiency as its current consumption is independent of the load, and it consumes more energy than other DC motors Its torque is also reduced when used in high-speed applications Although a stepper motor can operate in open-loop control systems, it lacks an integrated feedback system for positioning and control
3 Types of step motor:
The four major types of stepper motor are as follows:
❖ Permanent magnet stepper
The Permanent Magnet Stepper Motor has a stator construction similar to that of the single stack variable reluctance motor The rotor consists of permanent magnet poles of high retentivity steel and is cylindrical in shape The concentrating windings on diametrically opposite poles are connected in series to form a two phase winding on the stator
The rotor poles align with the stator teeth depending on the excitation of the winding The two coils AA’ connected in series to form a winding of Phase A Similiarly the two coil BB’ is connected in series forming a phase B windings The figure below shows 4/2 Pole
Trang 10Permanent Magnet Stepper Motor.
The permanent magnet rotor with large number of poles is difficult to make, therefore, stepper motors of this type are restricted to large step size in the range of 30 to 90⁰ They have
higher inertia and therefore, lower acceleration than variable stepper motors The Permanent
Magnet stepper motor produces more torque than the Variable Reluctance Stepper Motor
❖ Hybrid synchronous stepper
The word Hybrid means combination or mixture The Hybrid Stepper Motor is a
combination of the features of the Variable Reluctance Stepper Motor and Permanent
Magnet Stepper Motor In the center of the rotor, an axial permanent magnet is provided It
is magnetized to produce a pair of poles as North (N) and South (S) as shown in the figure below
Trang 11One of the main advantages of the Hybrid stepper motor is that, if the excitation of the motor is removed the rotor continues to remain locked in the same position as before the
removal of the excitation This is because of the Detent Torque produced by the permanent
magnet
❖ Variable reluctance stepper
The principle of Variable Reluctance Stepper Motor is based on the property of the flux lines which capture the low reluctance path The stator and the rotor of the motor are aligned
in such a way that the magnetic reluctance is minimum There are two types of the Variable Reluctance Stepper Motor They are as follows:
+ Single stack variable reluctance motor
+ Multi stack variable reluctance motor
❖ Lavet-type stepping motor
The Lavet-type stepping motor has widespread use as a drive in electro-mechanical clocks and is a special kind of single-phase stepping motorand requires very little power, making a battery last for many years; the French engineer Marius Lavet is known as the inventor for this kind of drives and described it in 1936 in his patent application FR823395 Like other single-phase motors, the Lavet motor is only able to turn in one direction, which depends on the geometry of its stator; the rotor is a permanent magnet The motor can
Trang 12be built with a strong magnet and large stator to deliver high torque, but it is mostly built small, to drive the load through a low gear ratio
To make a Lavet motor turn, the current through its stator coil must change direction each step (bipolar) followed by an interval without current while the rotor moves to its reluctant position Aside from clock drives, there are many variations of Lavet's concept One example are types of dashboard instruments in cars
4 Stepper motor torque
When selecting a stepper motor, you try to pick a motor that meets your speed and torque requirements plus some safety margin But how do you compare motor performance between motor suppliers Most suppliers provide speed – torque characteristic curves to provide an idea of what performance can be expected from a motor Stepper motor speed - torque curves show how much torque is available from a stepper motor at a given speed when combined with a particular driver This means that depending on different motor and driver combinations, different performance can be expected from the stepper motor system This article will describe how a speed - torque curve for a stepper motor is generated and what are the important points to look for on a curve
A well defined speed – torque curve, such as the ones shown below, should include the following information
1 Power input: This is the voltage that is supplied to the driver For DC input voltage drivers, this same voltage is usually applied directly to the motor windings For AC input voltage drivers, the AC voltage is rectified to a DC voltage before being applied to the motor windings For example, for an 115VAC driver, the applied voltage to the motor windings is 162VDC
2 Driver type: This states what type of driver was used to create the curve Either a unipolar or bipolar driver should be shown The driver type will also states if the driver is of the constant current or constant voltage type
3 Damper use: While not required, a damper can help to create a more typical performance curve by representing an inertial load on the motor The curve should state if a damper was used and what its characteristics are
Trang 134 Step angle: This is the step angle the motor was driven at when creating the curve Curves will commonly show what the basic step angle (1.8°, 0.9°, 0.72°, 0.36°) of the motor or what driver resolution (full, half, microstep divisions) were used
5 Motor winding configuration: This describes how the motor was connected to the driver and what current was applied to the windings Motor connections could be unipolar, bipolar series, bipolar half coil and bipolar parallel
6 Torque units: The vertical axis shows the amount of torque and in what units (e.g oz-in, N.m, etc)
7 Speed: The horizontal axis shows the shaft speed of the motor and in what units (e.g rpm, pps, Hz, etc)
8 Maximum No-load starting speed: The maximum no-load starting speed is the maximum speed at which the motor can be started in synchronism with no load attached and no acceleration used It is usually shown as a tick mark labeled “fs” on the horizontal axis
9 Holding Torque: This is the torque that the motor will produce when the motor is at rest and rated current is applied to the windings
10 Pull-out Torque curve: This curve represents the maximum torque that the stepper motor can supply to a load at any given speed Any torque or speed required that exceeds (goes above) this curve will cause the motor to lose synchronism
11 Pull-in Torque curve (no load): This curve represents the maximum torque and speed combination that an unloaded stepper motor can start or stop without any acceleration or deceleration Since the pull-in torque curve for a stepper motor varies depends on the inertial load attached to the motor, the pull-in torque curves are not shown in the speed – torque curves shown in catalogs In order to operate above the
Trang 14pull-in torque curve, the motor must be accelerated into or decelerated out of the slew range
12 Pull-in Torque curve (inertial load): This curve represents the maximum torque and speed combination that a stepper motor with an inertial load (i.e damper) can supply
to a load and start or stop without any acceleration or deceleration In order to operate above the pull-in torque curve, the motor must be accelerated into or decelerated out of the slew range
13 Self start range (start/stop region): When in this area, the stepper motor can start, stop or change directions in synchronism with the input pulse without the need for acceleration or deceleration
14 Slew range: The slew range is where stepper motors are usually operated A stepper motor can not be started directly in the slew range After starting the motor somewhere in the self start range, the motor can be accelerated into or load applied into the slew range The motor must then be decelerated or load reduced back into the self start range before the motor can be stopped
15 Maximum response frequency: This is the maximum speed the motor can be operated when no load is applied to the shaft
Trang 15The speed – torque curves are created by spinning a step motor up to a known speed and then gradually applying torque to the output shaft with a brake and measured with a torque transducer The load is slowly applied until the motor loses synchronism (stops) At the moment that the motor loses synchronism, the torque that was applied to the motor shaft at that same moment is recorded This process is repeated three times at each speed point The average of the three torque values is then used as the value that will be displayed on the speed – torque curve This process is repeated at several speed points The torque points are then plotted at the various speed points to create the complete curve See figure below
Trang 16As was mentioned earlier, the speed – torque characteristics are determined by the stepper motor and driver combination In general, the higher the applied voltage to the motor windings, the faster the motor will rotate For example, in the curves below, the speed – torque curve for the CVK245AK/CVK245BK stepper driver indicates that 24VDC is applied to the motor windings, while the curve for the RKS545 stepper driver was created with 162VDC being applied to the windings As you can see, the torque at speed of the RKS545 stepper driver is held out to a much higher speed
II STEPPER MOTOR CONTROL
1 Stepper motor applications
Stepper motor are diverse in ther uses, but some of the most common includes:
• 3D printing equipment