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Stepper Motor
Published in Hossam Fattah, LTE™ Cellular Narrowband Internet of Things (NB-IoT), 2021
A stepper motor is an electromechanical device which converts electrical pulses into discrete mechanical movements. The shaft or spindle of a stepper motor rotates in discrete and precise step increments when electrical pulses are applied to it in the proper sequence. The motors rotation has several direct relationships to these applied input pulses. The sequence of the applied pulses is directly related to the direction of motor shafts rotation. The speed of the motor shafts rotation is directly related to the frequency of the input pulses and the length of rotation is directly related to the number of input pulses applied. One of the most significant advantages of a stepper motor is its ability to be accurately controlled in an open loop system. Open loop control means no feedback information about position is needed. This type of control eliminates the need for expensive sensing and feedback devices such as optical encoders. The stepper motor position is known simply by keeping track of the input step pulses. The stepper motor position is known simply by keeping track of the input step pulses.
Applications of Technology
Published in Roger Timings, Basic Manufacturing, 2006
Control systems can be open-loop or closed-loop as shown in Fig. 4.15. In the open-loop system, Fig. 4.15(a) the machine slides are moved according to information loaded from the part program into the control system, without any feedback signal to monitor the slide positions. The most common method of moving the slides is by a lead screw driven by a stepper motor either directly or via a toothed belt drive. A stepper motor is an electric motor energized by a train of electrical pulses rather than a continuous electrical signal. Each pulse causes the motor to rotate through a small discrete angle. Thus the motor rotates in a series of steps according to the number of pulses supplied to it from the controller. Stepper motors have only limited torque and are usually found on small machines where the loads are limited, for example, small machine tools used in teaching, knitting machines, computer printers and scanners, etc. Although open-loop systems are lower in cost than closed-loop systems, they are intrinsically less accurate since, if the load on the motor causes it to stall, the controller continues to supply pulses to the motor unaware that no movement is taking place.
Force-System Resultants and Equilibrium
Published in Richard C. Dorf, The Engineering Handbook, 2018
The stepper motor is an electromagnetic actuator used for positioning of the rotor without any feedback. The motor converts digital pulse inputs designating a certain degree of rotation to an actual rotation of the rotor shaft. The machines have zero steady-state error and high torque density. The stepper motors develop a holding torque rather than a rotating torque when one phase is activated, thereby accurately retaining the position with load. Typical applications of stepper motors are printers, plotters, machine tools, and robotics.
Pneumatic piston hydrostatic bioreactor for cartilage tissue engineering
Published in Instrumentation Science & Technology, 2023
J. Hallas, A. J. Janvier, K. F. Hoettges, J. R. Henstock
The motor and driver module were selected based on calculations that the motor must be able to withstand up to 9.93 N m of torque (Table 1). Servo motors offered the required properties, but due to their relatively high cost, other solutions were investigated.[22] A brushless, closed-loop electric bipolar stepper motor was chosen which combined accurately controlled speed and positioning. Bipolar wiring of the stepper motor offered greater torque due to the single larger coil per winding than the unipolar wiring, which allowed for a stronger magnetic field to be generated, hence greater torque.[23] The closed-loop stepper motor included in-built feedback from an encoder to the driver which in turn reduced the chance of ‘dropping’ steps under loading, and helped to increase running efficiency, therefore reducing the temperature increase of the motor whilst active.
Virtual commissioning for an Overhead Hoist Transporter in a semiconductor FAB
Published in International Journal of Production Research, 2020
Joo Y. Lee, Kwanwoo Lee, Sangchul Park
The main mission of an OHT is to move a FOUP from a starting point to a destination point, and it consists of four major steps; (1) Move to the starting point in an empty state, (2) Load a FOUP at the starting point, (3) Move to the destination point with the FOUP, and (4) Unload the FOUP at the destination point. Among the four steps, the FOUP loading and unloading steps require many tasks from shutter, slide, hoist and gripper. An OHT device has multiple motions requiring actuators such as ‘servo motors’ and ‘stepper motors’. While servo motors are used for precise control requiring feedback sensors (closed-loop control), stepper motors are suitable for less precise control without feedback sensors (open-loop control). Typically, an OHT has four servo motors (two for driving, one for slide, and one for hoist) and two stepper motors (one for shutter and one for gripper). Each motor has corresponding tasks. By analysing those tasks, we identify nine tasks, as shown in Table 1.