This blog was a collaborative effort among a team of motion and automation experts here at Kollmorgen, including engineers, customer service and design experts. Our high-performance, brushless, maintenance-free stepper motors provide precise, extremely cost-effective motion control. You can also use our Application Sizing section to find the best solution that fits your application requirements. Stepper drives for both AC and DC power applications are ideal for high-performance indexing applications, offering microstepping capabilities up to 50, steps per revolution with no need for feedback systems.
How Does a Servo Drive Work? How Does a Servo Motor Work? How Does a Stepper Motor Work? Is Robotization Destroying or Creating Jobs? What does a Motion Controller Do? What is COTS? What is Mechatronics? What is SWAP? Size Weight and Power What is a Cobot? What is a Linear Actuator? What is a Robotic Cluster? Dynamic motion profiles. Control the applied force. Benefits of Servo.
Torque control. Can execute complex motion commands. Can adjust to changes in load. Lower power consumption. Specifics: Manufacturer looking to automate roller setup. The Goal: To reduce changeover time and increase repeatability between various production set ups. Integrate into existing PLC Control. Cycle time of under 1 minute.
Make micro adjustments on demand. Monitor position. Need to hold position at rest. Specifics: OEM builder of filling and bottling lines needs a linear and rotary actuator as part of an update to a capping operation. The Goal: To place the cap accurately and report any missing or misapplied caps. Very high throughput.
Cap on-torque limit. Multiple products. Torque limiting of the servo gives the system the ability to precisely apply the caps to correct cap on torque. Closed Loop : A system where the output is measured and compared to the input. The output is then adjusted to reach the desired condition. In a motion system a velocity or position or both sensor is used to generate the correction signals by comparison to desired parameters.
Holding Torque : The maximum external force or torque that can be applied to a stopped, energized motor without causing the motor to rotate continuously.
Open Loop : Refers to a motion system where no external sensors are used to provide velocity or position correction signals. For this reason stepper motors are ideal for short, quick moves. The diagram below shows a typical stepper motor based system. All of these parts must be present in one form or another. Each component's performance will have an effect on the others. The first component is the computer or PLC.
This is the brains behind the system. The computer not only control the stepper motor system but will also control the rest of the machine. It might raise an elevator or advance a conveyor. The second portion is the indexer or PLC card.
This tells the stepper motor what to do. It will output the correct number of pulses that motor will move and alters the frequency so the motor will accelerate, run at a speed, and then decelerate. The form is immaterial, but it must be present for the motor to move. The next four boxes make up the motor driver.
The logic for phase control takes the pulses from the indexer and determines which phase of the motor should be energized. The phases must be energized in a particular sequence, and the logic for phase control takes care of this. The logic power supply is a low level supply that powers the ICs in the driver. It depends on the chip set or application design, but most logic supplies are in the 5 volt range. The motor power supply is the supply voltage to power the motor. This voltage level is usually in the 24 VDC range but can be much higher.
Finally, the power amplifier is the transistor set that allows current to energize the phases. These are continuously turned on and off to move the motor through its correct sequence. All of these components will instruct the motor to move the load. The load may be a lead screw, a disk, or a conveyor. Variable reluctance step motors have teeth on the rotor and stator, but no magnet. Therefore it has no detent torque. The Permanent Magnet has a magnet for a rotor but no teeth.
Usually, the PM magnet has crude step angles, but it does have detent torque. Hybrid stepper motors combine the magnet from the permanent magnet and the teeth from the variable reluctance motors.
The magnet is axially magnetized meaning in the diagram to the right the top half is a north pole and the bottom half is a south pole. On the magnet are two toothed rotor cups with 50 teeth. The two cups are displaced 3. These motors are two phase construction, with 4 poles per phase. If the current in that phase were reversed, so would the polarity. This means that we can make any stator pole either a north pole or a south pole.
In the diagram, suppose the poles at 12 o'clock and 6 o'clock are north poles and the poles at 3 o'clock and 9 o'clock are south poles. When we energize phase A 12 and 6 would attract the south pole of the magnetic rotor, and 3 and 9 would attract the north pole of the rotor.
Looking from one end we would see the rotor teeth lining up with 12 and 6 while those at 3 and 9 would be right in the middle. If we looked from the opposite end, the rotor teeth of the north pole would be lined up exactly with the 3 and 9 while the teeth at 12 and 6 would be right in the middle. Depending on which direction we want to go, we would energize either the poles at 2 and 7 as north poles, or the poles at 11 and 5 as north poles.
This is where the driver is needed to determine the phase sequencing. Click image to start animation. Content on this page requires a newer version of Adobe Flash Player. There are 50 teeth on the rotor. The pitch between teeth is 7. Finally, torque and accuracy are dependent upon the pole tooth count. The greater the poles, the better the torque and accuracy. These motors have half the tooth pitch of our standard motor.
The rotor has teeth so the angle between the teeth is 3. The resolution of our "High Resolution" models is double that of the standard models, steps per revolution versus steps per revolution. The figure below shows a cross-section of a 5-phase stepper motor.
The stepper motor consists primarily of two parts: a stator and a rotor. The rotor in turn is made up of three components: rotor cup 1, rotor cup 2 and a permanent magnet. The rotor is magnetized in the axial direction so that, for example, if rotor cup 1 is polarized north, rotor cup 2 will be polarized south. Each winding is connected to the winding of the opposite pole so that both poles are magnetized in the same polarity when current is sent through the pair of windings.
Running a current through a given winding magnetizes the opposing pair of poles in the same polarity, i. The opposing pair of poles constitutes one phase. Since there are 10 magnetic poles, or five phases, in this particular motor called a 5-phase stepper motor. There are 50 teeth on the outer perimeter of each rotor, with the teeth of rotor cup 1 and rotor cup 2 being mechanically offset from each other by half a tooth pitch. It is very important the you know how to read a speed-torque curve since it will tell us what a motor can and cannot do.
Speed-torque curves represent a given motor and a given driver. Once the motor is running, its torque is dependent on the drive type and voltage.
The same motor can have a very different speed-torque curve when used with a different driver. If a motor is used with a similar drive, with similar voltage and similar current, you should get a similar performance. Refer to the interactive speed-torque curve below:.
The pulse rate is then increased until the desired speed is reached. To stop, the motor speed is then reduced until it is below the pull-in torque curve. Torque is proportional to the current and the number of turns of wire. No Comments. In this tutorial article you will learn how a stepper motor works. We will cover the basic working principles of stepper motors, their driving modes and the steppers types by construction. You can watch the following video or read the written article.
Stepper motor is a brushless DC motor that rotates in steps. This is very useful because it can be precisely positioned without any feedback sensor, which represents an open-loop controller. The stepper motor consists of a rotor that is generally a permanent magnet and it is surrounded by the windings of the stator. As we activate the windings step by step in a particular order and let a current flow through them they will magnetize the stator and make electromagnetic poles respectively that will cause propulsion to the motor.
There are several different ways of driving the stepper motor. In this mode we active just one coil at a time which means that for this example of motor with 4 coils, the rotor will make full cycle in 4 steps.
Next is the Full step drive mode which provides much higher torque output because we always have 2 active coils at a given time. For increasing the resolution of the stepper we use the Half Step Drive mode. This mode is actually a combination of the previous two modes. Here we have one active coil followed by 2 active coils and then again one active coil followed by 2 active coils and so on.
So with this mode we get double the resolution with the same construction. Now the rotor will make full cycle in 8 steps. However the most common method of controlling stepper motors nowadays is the Microstepping.
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