Components and Modules
Areas of use
Over 500 million stepper motors are installed worldwide each year. Although most of these motors are used in very simple applications, the trend is also continuing to grow in applications that were handled strictly by DC and BLDC motors in the past. High-performance controllers increasingly make it possible for more complex tasks to be solved. Many applications that were once handled using smaller servo motors can now be handled by a stepper motor outfitted with the corresponding electronics. Not only have the possibilities involving controllers advanced over the last few years, but the motors themselves are running considerably smoother and with higher torque thanks to improved technology. New, robust position feedback possibilities are becoming much less expensive and are also playing their part in opening up new areas of use for stepper motors. Of course, stepper motor solutions also have their limitations. Particularly high speeds, easily achieved by servos, often mean the end of implementation possibilities for a stepper motor. If implementing a geared solution, however, many opportunities present themselves by using a smaller gear ratio or even no gears at all. The reason for this is the high torque that can be achieved with stepper motors in the low to intermediate speed range.
Selecting the proper motor
The user faces many difficulties when it comes to choosing a motor. There are considerable differences between motors from different manufacturers or even between motor generations from the same manufacturer. The standard specifications listed in the datasheets often do not provide enough information to make a decision in this regard. Only detailed information can reliably indicate the possible areas of use. The more complex the application, the more important parameters such as concentricity, counter EMF, efficiency, resonance frequencies, etc. become. When chosen with care, stepper motors can be used for many more applications than is normally the case today. Special attention must be given to the characteristics that are particularly important for the respective application. These characteristics often cannot be achieved unless a drive is also used.
Concentricity and angular precision
A majority of the 2-phase hybrid stepper motors have a stepping angle of 1.8 degrees. In addition to this however, are the versions with 0.9 degrees and the even less common with 0.45 degrees. The smaller stepping angle often results in poorer torque characteristics. However, only stepper motor drivers that support micro-steps can achieve higher positioning accuracy. Moreover, a high step resolution produces excellent concentricity properties and reduces potential problems resulting from resonance effects.
The manner in which the desired position is ultimately reached depends on the applied load torque as well as how accurate the stepper motor is when it is manufactured. The position accuracy within one step is always dependent on the load and the resulting angular slip. However, this can never be higher than one full step because otherwise the motor gets out of sync and steps are lost. The best way to compensate for this load angle is via position feedback. This is why all B&R stepper motors are also available in affordable encoder variations, which achieve a resolution of up to 12 bits. Therefore, positioning precision is possible with an angular deviation of less than 0.1 degrees, even under considerable load torque.