Physics
Stepper Motors
Stepper motors are electromagnetic devices that convert digital pulses into precise mechanical motion. They move in discrete steps, making them ideal for applications requiring accurate positioning, such as 3D printers, CNC machines, and robotics. Stepper motors offer high torque at low speeds and are widely used in various industrial and consumer electronics applications.
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10 Key excerpts on "Stepper Motors"
eBook - PDFSensors and Actuators
Engineering System Instrumentation, Second Edition
- Clarence W. de Silva(Author)
- 2015(Publication Date)
- CRC Press(Publisher)
Each pulse received at the driver of a digital actuator causes the actuator to move by a predetermined, fixed increment of dis-placement. The stepwise rotation of the rotor can be synchronized with the pulses in a command-pulse train, assuming that no steps are missed, thereby making the motor respond faithfully to the input signal (pulse sequence) in an open-loop manner. Nevertheless, like a conventional continuous-drive motor, a stepper motor is also an electromagnetic actuator, in that it converts electromagnetic energy into mechanical energy to perform mechanical work. This chapter studies Stepper Motors. Chapter 9 discusses continuous-drive actuators. 576 Sensors and Actuators: Engineering System Instrumentation 8.1.2 Terminology The terms stepper motor , stepping motor , and step motor are synonymous and are often used inter-changeably. Actuators that can be classified as Stepper Motors have been in use for more than 70 years, but only after the discovery of effective magnetic and ferromagnetic material for them and incorpora-tion of solid-state circuitry and logic devices in their drive systems have Stepper Motors emerged as cost-effective alternatives for continuous-drive actuators (particularly, for dc servomotors) in engineering applications. Many kinds of actuators fall into the stepper motor category, but only those that are widely used in the industry and other engineering applications are discussed in this chapter. Note that even if the mechanism by which the incremental motion is generated differs from one type of stepper motor to the other, the same control techniques can be used in the associated control systems, making a general treatment of Stepper Motors possible, at least from the point of view of the drive system and control. There are three basic types of Stepper Motors: 1. Variable-reluctance (VR) Stepper Motors, which have soft-iron (ferromagnetic) rotors 2. Permanent-magnet (PM) Stepper Motors, which have magnetized rotors 3.
eBook - PDFMechatronics
An Integrated Approach
- Clarence W. de Silva(Author)
- 2004(Publication Date)
- CRC Press(Publisher)
675 8 Stepper Motors The actuator is the device that mechanically drives a mechatronic system. Proper selection of actuators and their drive systems for a particular application is of utmost importance in the instrumentation and design of mechatronic systems. There is another perspective to the significance of actuators in the field of mechatronics. A typical actuator contains mechanical components like rotors, shafts, cylinders, coils, bearings, and seals while the control and drive systems are primarily electronic in nature. Integrated design, manufac-ture, and operation of these two categories of components are crucial to efficient operation of an actuator. This is essentially a mechatronic problem. Stepper Motors are a popular type of actuators. Unlike continuous-drive actuators (see Chapter 9), Stepper Motors are driven in fixed angular steps (increments). Each step of rotation is the response of the motor rotor to an input pulse (or a digital command). In this manner, the stepwise rotation of the rotor can be synchronized with pulses in a command-pulse train, assuming of course that no steps are missed, thereby making the motor respond faithfully to the input signal (pulse sequence) in an open-loop manner. From this perspective, it is reasonable to treat Stepper Motors as digital actuators. Never-theless, like a conventional continuous-drive motor, a stepper motor is also an electro-magnetic actuator, in that it converts electromagnetic energy into mechanical energy to perform mechanical work. The present chapter studies Stepper Motors, which are incre-mental-drive actuators. The next chapter will discuss continuous-drive actuators. 8.1 Principle of Operation The terms stepper motor , stepping motor , and step motor are synonymous and are often used interchangeably.
eBook - PDFElectric Motors and Drives
Fundamentals, Types and Applications
- Austin Hughes(Author)
- 2005(Publication Date)
- Newnes(Publisher)
9 STEPPING MOTORS INTRODUCTION Stepping motors are attractive because they can be controlled directly by computers or microcontrollers. Their unique feature is that the output shaft rotates in a series of discrete angular intervals, or steps, one step being taken each time a command pulse is received. When a de W nite number of pulses has been supplied, the shaft will have turned through a known angle, and this makes the motor ideally suited for open-loop position control. The idea of a shaft progressing in a series of steps might conjure up visions of a ponderous device laboriously indexing until the target number of steps has been reached, but this would be quite wrong. Each step is completed very quickly, usually in a few milliseconds; and when a large number of steps is called for the step command pulses can be delivered rapidly, sometimes as fast as several thousand steps per second. At these high stepping rates the shaft rotation becomes smooth, and the behaviour resembles that of an ordinary motor. Typical applications include disc head drives, and small numerically controlled machine tool slides, where the motor would drive a lead screw; and print feeds, where the motor might drive directly, or via a belt. Most stepping motors look very much like conventional motors, and as a general guide we can assume that the torque and power of a stepping motor will be similar to the torque and power of a conventional totally enclosed motor of the same dimensions and speed range. Step angles are mostly in the range 1.8 8 –90 8 , with torques ranging from 1 m Nm (in a tiny wristwatch motor of 3 mm diameter) up to perhaps 40 Nm in a motor of 15 cm diameter suitable for a machine tool application where speeds of 500 rev/min might be called for. The ma-jority of applications fall between these limits, and use motors that can comfortably be held in the hand. Open-loop position control A basic stepping motor system is shown in Figure 9.1.
eBook - PDFElectromechanical Motion Devices
Rotating Magnetic Field-Based Analysis with Online Animations
- Paul C. Krause, Oleg Wasynczuk, Steven D. Pekarek, Timothy O'Connell(Authors)
- 2020(Publication Date)
- Wiley-IEEE Press(Publisher)
CHAPTER 9 Stepper Motors 9.1 INTRODUCTION Stepper Motors are electromechanical motion devices that are used primarily to convert information in digital form to mechanical motion. Although Stepper Motors were used as early as the 1920s, their use has skyrocketed with the advent of the digital computer. Whenever stepping from one position to another is required, whether the application is industrial, military, or medical, the stepper motor is often the motor of choice [1]. Stepper Motors come in various sizes and shapes but most fall into two types – the variable-reluctance stepper motor and the permanent-magnet stepper motor. Both types are considered in this chapter. We shall find that the operating principle of the variable-reluctance stepper motor is much the same as that of the reluctance machine that we have already discussed in earlier chapters, and the permanent-magnet stepper motor is similar in principle to the permanent-magnet synchronous machine. 9.2 BASIC CONFIGURATIONS OF MULTISTACK VARIABLE-RELUCTANCE Stepper Motors There are two general types of variable-reluctance Stepper Motors: single-stack and multistack. As a first approximation, the behavior of both types may be described from similar equations. Actually, the principle of operation of variable-reluctance Stepper Motors is the same as the reluctance machine that we considered in earlier chapters; only the mode of operation differs. There are, however, some new terms to define, and it is necessary for us to extend some of our previous definitions to fit the stepper motor. First, we will look at the multistack device in some detail, fol- lowed by a brief discussion of the single-stack, variable-reluctance stepper motor. In its most basic form, the multistack variable-reluctance stepper motor con- sists of three or more single-phase reluctance motors on a common shaft with their Electromechanical Motion Devices: Rotating Magnetic Field-Based Analysis and Online Animations, Third Edition.
eBook - PDFElectric Motors and Drives
Fundamentals, types and applications
- Austin Hughes(Author)
- 2013(Publication Date)
- Newnes(Publisher)
8 STEPPING MOTOR SYSTEMS INTRODUCTION Stepping motors have become very popular because they can be controlled directly by computers, microprocessors or programmable controllers. Their unique feature is that the output shaft rotates in a series of discrete angular intervals, or steps, one step being taken each time a command pulse is received. When a definite number of pulses has been supplied, the shaft will have turned through a known angle, and this makes the motor ideally suited for open-loop pos-ition control. The idea of a shaft progressing in a series of steps could easily conjure up visions of a ponderous device laboriously indexing until the target number of steps has been reached, but this would be quite wrong. Each step is completed very quickly, usually in a few milliseconds; and when a large number of steps is called for the step command pulses can be delivered rapidly, sometimes as fast as several thousand steps per second. At these high stepping rates the shaft rot-ation becomes smooth, and the behaviour resembles that of an ordinary motor. Typical applications include floppy-disc head drives, and small numerically-controlled machine tool slides, where the motor would drive a lead screw; and daisy-wheel print heads, where the motor might drive the head directly, or via a belt. 230 Electric Motors and Drives Most stepping motors look very much like conventional motors, and as a general guide we can assume that the torque and power of a stepping motor will be similar to the torque and power of a conventional motor of the same dimensions. Step angles are mostly in the range 1.8°-90°, with torque ranging from 1//Nm (in a tiny wristwatch motor of 3 mm diameter) up to perhaps 40 Nm in a motor of 15 cm diameter suitable for a machine tool application where speeds of 500 rev/min might be called for. The majority of applications fall between these limits, and use motors which can com-fortably be held in the hand.
- Paul C. Krause, Thomas C. Krause(Authors)
- 2022(Publication Date)
- Wiley-IEEE Press(Publisher)
8 Stepper Motors8.1 Introduction
Stepper Motors are electromechanical motion devices which are used primarily to convert information in digital form to mechanical motion. Although Stepper Motors were used as early as the 1920s, their use has skyrocketed with the advent of the digital computer. Whenever stepping from one position to another is required, whether the application is industrial, military, or medical, the stepper motor is often the motor of choice. Stepper Motors come in various sizes and shapes but most fall into two types − the variable‐reluctance stepper motor and the permanent‐magnet stepper motor. Both types are considered in this chapter. We shall find that the operating principle of the variable‐reluctance stepper motor is much the same as that of the salient‐pole (reluctance) machine, and the permanent‐magnet stepper motor is similar in principle to the permanent‐magnet synchronous or ac machine.8.2 Basic Configurations of Multistack Variable‐Reluctance Stepper Motors
There are two general types of variable‐reluctance Stepper Motors: single‐ and multistack. As a first approximation, the behavior of both types may be described from similar equations. Actually, the principle of operation of variable‐reluctance Stepper Motors is similar to the reluctance torque which we considered in Chapter 4 ; only the mode of operation differs. There are, however, some new terms to define, and it is necessary for us to extend some of our previous definitions to fit the stepper motor. First, we will look at the multistack device in some detail, followed by a brief discussion of the single‐stack variable‐reluctance stepper motor.Rotor of an elementary two‐pole, three‐stack, variable‐reluctance stepper motor.Figure 8.2-1In its most basic form, the multistack variable‐reluctance stepper motor consists of three or more single‐phase reluctance motors on a common shaft with their stator magnetic axes displaced from each other. The rotor of an elementary three‐stack device is shown in Fig. 8.2-1 . It has three cascaded two‐pole rotors with a minimum‐reluctance path of each aligned at the angular displacement θrm. In stepper motor language, each of the two‐pole rotors is said to have two teeth. Now, visualize that each of these rotors has its own, separate, single‐phase stator with the magnetic axes of the stators displaced from each other. In Fig. 8.2-1 , we have labeled the individual rotors a, b, and c. The corresponding stators are shown in Fig. 8.2-2 ; the stator with the as winding is associated with the a rotor, the bs winding with the b rotor, etc. There are several things to note. First, we see that each of the single‐phase stators has two poles, with the stator winding wound around both poles. In particular, positive current flows into as1 and out , which is then connected to as2 so that positive current flows into as2 and out . Although we have shown only one circle for , we realize that each would represent several turns, and that the number of turns from as1 to (indicated by Ns/2 in Fig. 8.2-2 ) is the same as from as2 to . Let us note one more thing; heretofore, we have referenced θrm(or θr) from the as axis to the maximum‐reluctance path of a salient‐pole rotor as shown in Fig. 4.3‐1 . In Fig. 8.2-2 , θrm
eBook - PDFElectric Motors and Drives
Fundamentals, Types and Applications
- Austin Hughes(Author)
- 2013(Publication Date)
- Newnes(Publisher)
8 STEPPING MOTOR SYSTEMS INTRODUCTION Stepping motors have become very popular because they can be controlled directly by computers, microprocessors or pro-grammable controllers. Their unique feature is that the output shaft rotates in a series of discrete angular intervals, or steps, one step being taken each time a command pulse is received. When a definite number of pulses has been supplied, the shaft will have turned through a known angle, and this makes the motor ideally suited for open-loop position control. The idea of a shaft progressing in a series of steps could easily conjure up visions of a ponderous device laboriously indexing until the target number of steps has been reached, but this would be quite wrong. Each step is completed very quickly, usually in a few milliseconds; and when a large number of steps is called for the step command pulses can be delivered rapidly, sometimes as fast as several thousand steps per second. At these high stepping rates the shaft rotation becomes smooth, and the behaviour resembles that of an ordinary motor. Typical applications include disc head drives, and small numerically-controlled machine tool slides, where the motor would drive a lead screw; and print heads, where the motor might drive a character disc directly, or via a belt. Most stepping motors look very much like conventional motors, and as a general guide we can assume that the torque 258 Electric Motors and Drives Figure 8.1 Open-loop position control using a stepping motor Direction and power of a stepping motor will be similar to the torque and power of a conventional motor of the same dimensions and speed range. Step angles are mostly in the range 1.8°-90°, with torques ranging from 1 μΝιη (in a tiny wrist-watch motor of 3 mm diameter) up to perhaps 40 Nm in a motor of 15 cm diameter suitable for a machine tool application where speeds of 500 rev/min might be called for.
- Jack Smith(Author)
- 2005(Publication Date)
- Newnes(Publisher)
120 C H A P T E R 8 Introductory Stepper Motors Stepper Motors, as the name implies, rotate in discrete steps. Most conventional motors are continuous; if we make a mark on the shaft of a conventional motor and if we were able to precisely control the motor’s excitation, we could make the shaft move to any angle. 123.456 degrees from the starting mark is just as achievable as 321.765 degrees. Of course, practical considerations make this degree of precision unlikely in a real motor. A stepper motor’s shaft, in contrast, is moveable to only certain, pre-defined angles. A 48-step stepper motor, for example, may be positioned only in increments of 7.5 degrees (360°/48). Hence, we may command the shaft to go to 7.5° (one step) or 15° (two steps) but not to 8.432°. (Later in this chapter, and in Chapter 19, we’ll see ways to step the shaft rotation one-half or a smaller fraction of the motor’s normal step size, so the difference between conventional and Stepper Motors blurs.) Why would we want a motor that only moves in steps? Suppose we wish to move an ink jet printer’s print head across the paper, and that we must position the print head with an accuracy of 0.001. We’ll assume the print head is attached to a nonslip, no stretch toothed belt and that the belt is driven through a toothed pulley system attached to a positioning motor. Let’s attach a 200-step stepper motor to the pulley, through 5:1 step down gears, and pick the pulley size so that 1,000 steps of the motor moves the printing head 1.000 inch. Each motor step therefore corresponds to 0.001 and we may position the print head to 4.567 by initializing the print head at the start position and then advancing the motor by 4,567 steps. This “open loop” solution is much cheaper than a “closed loop” design that continuously monitors the position of the print head and stops the advance when the target position is reached.
- Stuart Ball(Author)
- 2003(Publication Date)
- Newnes(Publisher)
Motors 7 Motors are key components of many embedded systems because they provide a means to control the real world. Motors are used for everything from the vibrator in a vibrating pager to moving the arm of a large industrial robot. All motors work on the same principles of electromagnetism, and all function by applying power to an electromagnet in some form or another. We won’t spend our time on magnetic theory here. Instead, we will look at the basic motor types and their applications in embedded systems. Stepper Motors Stepper Motors come in three flavors: permanent-magnet, variable-reluctance, and hybrid. Figure 7.1 shows a cross-sectional view of a variable-reluctance (VR) stepper motor. The VR stepper has a soft iron rotor with teeth and a wound stator. As current is applied to two opposing stator coils (the two ‘‘B’’ coils in the figure), the rotor is pulled into alignment with these two coils. As the next pair of coils is energized, the rotor advances to the next position. The permanent magnet (PM) stepper has a rotor with alternating north and south poles (Figure 7.2). As the coils are energized, the rotor is pulled around. This figure shows a single coil to illustrate the concept, but a real stepper would have stator windings surrounding the rotor. The PM stepper has more torque than an equivalent VR stepper. The hybrid stepper essentially adds teeth to a permanent magnet motor, resulting in better coupling of the magnetic field into the rotor and more precise movement. In a hybrid stepper, the rotor is split into two parts, an upper and lower (Figure 7.3). One half is the north side of the magnet and one is the south. The teeth are offset so that when the teeth of one magnet are lining up with the mating teeth on the stator, the teeth on the other magnet are lining up with the 171 A A B B C C D D 1 2 3 4 5 6 SOFT IRON CORE Figure 7.1 Variable-reluctance stepper.
eBook - ePubSensors and Actuators in Mechatronics
Design and Applications
- Andrzej M Pawlak(Author)
- 2017(Publication Date)
- CRC Press(Publisher)
5 Stepper MotorsStepper Motors and, in particular, claw pole Stepper Motors are widely applied in industrial controls (Chirikjian et al. 1999, Floresta 1990, Kenjo 1990, Pawlak 1984, Rajagopal et al. 2003, Singh 1974). In the automotive industry, these Stepper Motors, often called tincan or can-stack motors, have found a variety of applications, such as in the timing of fuel injectors or to adjust the amount of fuel going to the engine. Claw pole or interdigitated construction is used for this type of electrical machine, similar to the Lundell construction used in automotive alternators. Because this type of machine has a very complex 3D magnetic circuit, it is difficult to analyze using closed-form solutions. A 3D computer program for numerical solutions is necessary.5.1 Principles of Operation
Figure 5.1 shows the various motor components necessary to produce a torque. There are two stators, each consisting of a north and a south lamination, with a coil enclosed between them and one PM rotor having P poles along the periphery. Each lamination has P/2 teeth which, when assembled, mesh with each other, as shown in Figure 5.1 and in a developed view in Figure 5.2 having the same number of teeth and number of magnet poles. When the coil is energized with, say, a positive current, all the teeth of the north lamination will become north poles and all the teeth of the south lamination south poles. Thus, a torque will be exerted on the rotor to align its south poles with the teeth of the north lamination and its north poles with the teeth of the south lamination, as presented in Figure 5.2 . Reversing the direction of the current reverses the polarity of the stator teeth and the resultant torque moves the rotor one step. With only one stator, however, the rotor is as likely to turn backward as forward and so the second stator is introduced, physically displaced by 90 electrical degrees (one fourth of the pole pitch), as shown in Figure 5.3 . It can be readily seen that positive and negative rotation can be obtained by exciting the stators in the sequence shown in Table 5.1
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