New prototype controller achieves over 2.6 million steps per revolution
Danish technology company, PCBMotor ApS, recently set a new performance record in printed circuit board (PCB) motors. In an experiment using its latest controller prototype, the company applied short micro-pulses (µpulses) to drive the motor and achieved a record 2.6 million equivalent steps per revolution.
“We’ve known for some time that PCBMotors are capable of realizing very high resolutions. And now we’ve proven it,” says Henrik Stæhr-Olsen, CEO of PCBMotor. “The driver sets the limit for what can be achieved and we can now show that resolutions over 2.5 Million µpulses per revolution are possible,” says Henrik Stæhr-Olsen.
More than your average experiment
The recently conducted experiment consisted of twenty 100 µpulse bursts, initiated manually via a USB connection to the motor controller, which resulted in the movement of a pointer, with a needle attached, against a linear code strip mounted on a ruler. “The resulting 2000 µpulses moved the needle seven ruler-lines which equates to 2 850 000 µpulses per revolution,” explains Henrik, referring to a video of the experiment that documents the results.
The prototype controller, built specifically for the experiment, is powered from the USB port and handles a wide range of settings for the motor such as pulse length and interval, drive voltage, and the number of µpulses and digital steps. Operating in open-loop mode it also has on-board memory (EEPROM) for storing the drive settings.
No noise. Ideal for high-precision applications
When in position, the PCBMotor and driver can be completely powered down, removing all mechanical and electrical interference (noise). “The experiment shows that the inherent holding torque of the motor is sufficient to stop and hold its position when the power is turned off―unlike a stepper motor. And this is very important for high-precision applications sensitive to even the smallest movement or vibration,” says Henrik Stæhr-Olsen.
The available holding torque depends on the size of the motor and is typically 35 Nmm for a standard 30 mm motor.
Innovators in the field of PCB motors
Based in North Zealand, Denmark, PCBMotor’s patented technology integrates highly accurate motors and the motor controller directly onto a printed circuit board. Their on-board innovation significantly reduces costs and introduces a host of new design possibilities while using standardized components and well-established assembly techniques. There are numerous applications that can utilize this technology, spanning the medico, telecom, aviation/aerospace, as well as the robotics and instrumentation industries.
Watch a video of the experiment…
Setup parameters for the 2.6M resolution experiment
- 25 mm PCBMotor with 265 mm long pointer with needle. Total weight of the rotating system is 67g.
- Moment of inertia for the pointer was calculated to 1 Ncm² (1/12 * m * l²).
- USB controller/motor driver with ON/OFF µpulses of 11 µs length and 2.7 ms interval between pulses.
- Motor driver supply (from 5V USB): 2.0V
- Ruler pattern for the needle pointer: 6 lines/mm equivalent to 10,000 lines/rev (radius 265 mm)
Note: Careful adjustment of the motor voltage is required to overcome the initial friction for eachµpulse without providing excessive power. This setting will depend on the individual motor and direction as well as the load, environment and temperature and must also be expected to change over time.
Note: The controller is open-loop, i.e. the µpulses are entirely “free-running”. No position sensor was used apart from visual inspection. The motor was also equipped with a 200 lines/rev digital codewheel, but this was only used for coarse adjustment of the needle pointer. In a practical application, some kind of external feedback is required to determine the position although the digital codewheel can be used for calibration of µpulses/step for each digital step.
Images from the experiment