Precision motors are usually quite expensive and inefficient when operating at slow speeds. A method was developed for controlling precise motion of a brushless DC (BLDC) motor using relatively inexpensive components.

Current motors are only capable of operating at approximately 15 RPM with a risk of excessive jitters. This technology reduces the responsive RPMs by several orders of magnitude to approximately 0.025 RPM. Its ability to operate at these ranges and with high precision provides an opportunity to integrate this technology into many applications and industries.

The technology is based on a precise current control loop and a high-fidelity velocity measurement algorithm. The precise current loop uses a mathematical model of the electrical dynamics of the motor, custom electronics, and a PI controller to maintain a rapid response and smooth current control. The velocity measurement algorithm is embedded in the velocity loop that is wrapped around the current loop to provide a smooth, low-velocity control.

The capability of the controller has been integral to the success of several NASA projects such as the OpTIIX telescope, the NASA Robonaut 2 robot, and the Modular Robotic Vehicle (MRV).

For more information, contact Johnson Space Center's Technology Transfer Office at This email address is being protected from spambots. You need JavaScript enabled to view it.; 281-483-3809.

Motion Design Magazine

This article first appeared in the December, 2019 issue of Motion Design Magazine.

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