Positioning servo instability is one of the most common performance limits in motion systems.
It typically appears as:
These issues become more severe in:
Traditional fixes (PID tuning, filters, damping) help—but that’s not the whole story.
Most servo systems use a cascaded control structure:
Servo stability is strongly affected by torque control
The current loop generates motor torque. If it is inaccurate or noisy:
Accurate current regulation is therefore foundational to stable motion control.
Many systems rely on basic commutation or limited current control.
This leads to:
Even with careful tuning:
It will be more difficult to stabilize a system built on unstable torque control.
Field-Oriented Control (FOC) is an advanced BLDC motor control technique that precisely controls motor current.
FOC works by:
Smooth, continuous, and highly accurate torque generation
FOC improves stability at the source: torque production
Torque ripple is a key driver of instability.
FOC reduces ripple by generating smooth current waveforms.
Impact:
FOC enables high-bandwidth current regulation.
This provides:
Accurate current control is critical for stable servo behavior.
Improved current regulation over the entire motor speed range reduces vibration.
System-level benefits:
More accurate current waveforms are directly linked to quieter motor operation.
Stable torque allows more aggressive position & velocity loop tuning.
With FOC:
Without FOC: tuning is limited by instability
With FOC: tuning becomes a performance tool
FOC strengthens other control strategies by improving torque accuracy.
Feedforward can improve tracking accuracy:
Feedforward builds on the core control loop to improve accuracy.
Today’s machines require:
These demands reduce stability margins.
FOC enables:
FOC improves performance by generating smooth, accurate torque, reducing ripple, and stabilizing control loops.
Yes. For modern high-precision and high-dynamic systems, FOC is typically required to achieve stable, predictable motion.
Yes. By smoothing current waveforms, FOC reduces vibration and significantly lowers audible motor noise.
Servo instability is not just a tuning issue—it is a control architecture issue.
Field-Oriented Control reduces instability at the source by:
FOC transforms servo stability from a tuning challenge into a design advantage
PMD has been producing ICs that provide advanced motion control of DC Brush, Brushless DC, and stepper motors for more than twenty-five years. Since that time, we have also embedded these ICs into plug and play modules and motion control boards. While different in packaging, all of these products are controlled by C-Motion, PMD's easy to use motion control language and are ideal for use in medical, laboratory, semiconductor, robotic, and industrial motion control applications.
ION®/CME N-Series Drives are high performance intelligent drives in an ultra-compact PCB-mountable package. In addition to advanced servo and stepper motor control, N-Series IONs provide s-curve point to point profiling, field oriented control, downloadable user code, general purpose digital and analog I/O, and much more. These all-in-one devices make building your next machine controller a snap.
The MC58113 series of ICs are part of PMD's popular Magellan Motion Control IC Family and provide advanced position control for stepper, Brushless DC, and DC Brush motors alike. Standard features include FOC (Field Oriented Control), trapezoidal & s-curve profiling, direct encoder and pulse & direction input, and much more. The MC58113 family of ICs are an ideal solution for your next machine design project.
ION 500 and 3000 Drives are high performance intelligent drives in a compact cable-connected package. In addition to advanced servo motor control, IONs provide s-curve point to point moves, i2T power management, downloadable user code, and a range of safety functions including over current, over voltage, and over temperature detect. IONs are easy to use plug and play devices that will get your application up and running in a snap.
Prodigy®/CME Machine Controller boards provide high-performance motion control for medical, scientific, automation, industrial, and robotic applications. Available in 1, 2, 3, and 4-axis configurations, these boards support DC Brush, Brushless DC, and stepper motors and allow user-written C-language code to be downloaded and run directly on the board. The Prodigy/CME Machine-Controller has on-board Atlas amplifiers that eliminate the need for external amplifiers.