How does a Stepper Motor work ?


How does a robotic arm in a manufacturing facility repeat the exact same movements over and over? How does an automated milling machine move with such precision? It’s all because of the stepper motor What’s special about the stepper motor is that it can control the angular position of the rotor? Without a closed feedback loop it is a simple accurate and open-loop system Let’s first understand how the variable reluctance type of stepper motor works which is the simplest one? Later on we will move to a highly accurate and commonly used motor type This motor has six stator teeth and can be energized with three separate DC. Power sources The Rotor is made of a stack of steel laminations It has a different number of teeth than the rotor for in this case This is done. Intentionally, so that only one pair of rotor teeth is aligned with the stator at a time You can explain how the stepper motor works by yourself If you [de-energize] coil a and Energize B It becomes clear that the rotor will rotate as shown from the geometry it is clear that the one step size is 30 degrees to [get] the next step the energized coil B and energized [C] after [that] coil A becomes energized again in short the rotor moves to the position with the least reluctance the [step] size of this motor is 30 degrees. You can improve the accuracy to 15 degrees with a small trick When coil a is energized the rotor is in this position? We know that when coil B? Is energized it moves 30 degrees? What happens when coils A and B are energized together? The rotor will come to a position between these two cases Or it will move 15 degrees after this [de-energized] A then after reaching B Energized C as well this kind of operation is known as half stepping The motor we have been discussing is called a variable reluctance motor The most versatile and commonly used stepper motor is the hybrid motor type Let’s explore the functioning of a typical 1.8. Degree. Step size hybrid motor The Hybrid Motor has an actually magnetized rotor with toothed steel caps So one end of the rotor becomes the North pole and the [other] end becomes a south pole The accuracy of this motor lies in the clever arrangement of the rotor and [stator] teeth let’s understand it first The rotor has 50 teeth to understand the stator teeth arrangement first assume that the stator has 50 teeth as well However the stator actually has two fewer teeth than the rotor So we are left with 48 teeth Let’s arrange the 48 teeth into [four] group pairs as shown Now let’s realign these groups the green set moves so that it is half aligned with the rotor The teeth of the yellow group are completely unaligned with the rotor teeth The blue group is half aligned with the rotor the [red] group remains in place in Short the red set is completely aligned with the rotor while the yellow set is unaligned The other two sets are half aligned Please remember that the rotor and facing you acts like the south pole The stator coils are connected as shown They are two independent coil sets When set a is energized the stator forms a magnetized pattern as shown? one pair of stator pulls acts as the North pole and the other as the south pole as The opposite poles attract, they will be aligned the same polarity poles will be unaligned When the coil B. Is energized observe, what happens to the rotor? It has to rotate by a small angle in order to align with the new North Pole it Is clear [that] this angle is [1/4] of the angular pitch? in other words the rotor moves by 1.8 degrees Next set a is energized with the opposite polarity again the rotor moves by 1.8. Degrees This process is repeated and a highly accurate motion is achieved by the motor The step Angle Resolution can be further improved by half-stepping It is interesting to note that the north end cap teeth are placed in between the south end teeth This way the alignment of the opposite polarity poles are guaranteed again So this is how a hybrid stepper motor works They are ideal for applications where precise movements and simple control are desired at Learn engineering we are able to continue our educational video production service due to the support of our patrons your support at patreon.com Is Highly appreciated? Thank you