Advanced PIV Compensator
In contrast to the more common PID compensator, the SSt servo drives employ a PIV compensator. The structure of this compensator is identical to a high performance analog positioning system (with some major updates). Teknic’s engineers have worked diligently to minimize all delays, quantization noise and numerical inaccuracies within the internal calculations to provide your application with the highest performance. Excellent tracking accuracy, fast settling time and ultra-smooth motion are the result.
A main advantage of this compensator is its ease of tuning. The nested control loop structure (embedded velocity loop inside of the position loop) allows the tuning procedure to be largely non-iterative (even for the feed-forward gains). This means that adjusting one gain doesn't affect the others, like in a PID system. A typical axis can be tuned to a high degree of performance in just a few minutes.
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- Figure 1: Structure of advanced PIV compensator (simplified)
The PIV structure of this compensator allows the internal algorithms to know the complete physical state of the axis without extra computation. This knowledge of the physical state is used to help implement several behind-the-scenes features that increase the robustness of control.
In addition to the base compensator structure, advanced features such as Adaptive Inertia Matching Technology™ (IMT) and AntiHunt™ assist in increasing the usability of SSt servo systems in demanding applications.
Tracking error can be minimized using velocity and acceleration feed-forward gains. The SSt servo drive’s feed-forward gains increase to the necessary values, ensuring the axis will still be smooth and quiet—unlike other servo systems where the use of acceleration or velocity feed-forward bring results in a noise penalty and a reduction in the RMS capability of the motor.