Adaptive Amplitude, Offset and Phase Control for Waveforms

Intro
Adaptive amplitude control is used for high-frequency repeating waveforms such as a sinusoid. The adaptive amplitude control changes the amplitude of the target signal (such as position of force), so that the actual amplitude reaches the desired amplitude. The is especially useful where the amplitude, offset, and possibly the phase are important, but there may be some change between each run, and it is not feasible to re-tune the system. High frequency waveforms that can be difficult to tune will also benefit from adaptive amplitude control.

Note that with adaptive amplitude control, a delay between the actual and target signals is expected. If you need the actual to follow the target exactly, adaptive amplitude will not work.

Implementation
This method makes tuning the system very easy, if the only objective is to get the correct amplitude and offset. The position tuning itself doesn’t need to be tuned very well (just proportional gain is often enough), and the adaptive part will bring the offset and amplitude right on! You may need to adjust the two adaptive gains, but the default values of 1 may work quite well.

For the phase control, a positive phase is leading, and a negative phase is lagging. Typically, one axis will run at 0 phase, and the others will be lagging by specified amounts (negative phases).

Real World Example
An OEM used adaptive amplitude control in an RMC200 to accelerate their gear testing.

Code Examples:
The code examples are configured to run in simulate mode. Downloading and running the examples is a good way to become more familiar with adaptive amplitude control.

  • Adaptive control of the amplitude and offset of a closed-loop sinusoidal wave, triangle wave, square wave, and trapezoid wave. The project includes user programs that generate a closed-loop sinusoidal, triangle, and square target profile and automatically adapt the target amplitude and offset such that the actual measured amplitude and offset match the requested amplitude and offset
    Adaptive Closed-Loop Sine Wave.rmcproj (106.2 KB)

  • Multi-axis adaptive control of amplitude, offset, and phase of a closed-loop sinusoidal wave 4 axes. The project includes a user program that generate a closed-loop sinusoidal target profile and automatically adapts the target amplitude, offset and phase such that the actual measured amplitude and offset match the requested amplitude and offset.
    Adaptive Closed-Loop Sine Wave with Phase 150.rmcproj (86.2 KB)

  • Adaptive control of the amplitude and offset of a closed-loop sinusoidal wave for force.
    Adaptive Closed-Loop Sine Wave Force.rmcproj (38 KB)