Principles of PID Controllers

The digital implementation makes it possible to embed multiple PID controllers on the same instrument, whose inputs and outputs can be either cascaded in a sequential fashion or used in a parallel configuration, that is, independently of one another.

Thanks to the type of architecture depicted in Figure 6, the PID option embedded in lock-in amplifiers enhances the versatility of the instruments, making them benefit a large variety of applications – even though the specific application needs might significantly differ from one another.

As previously mentioned, determining appropriate starting conditions for a PID controller and its optimization can be a challenging task. LabOne® control software, the software of Zurich Instruments interfacing with the hardware, offers a kit of several tools to streamline the process of setting up and optimizing a PID controller, making the task more efficient and straightforward.

LabOne tools like the Sweeper, the PID Advisor and Autotune can help the user with the implementation of PID control loops, providing intuitive adjustability of the bandwidth, speed and initial tuning parameters, according to the desired performance.

For example, the Sweeper can be used to obtain the open-loop response of the device under test (DUT) through signal sweeping, then the PID Advisor selects initial feedback gain parameters based on predefined transfer functions and the DUT open-loop parameters obtained with the Sweeper measurement. After closing the loop, to minimize residual error signal and enhance control performance, the Auto Tune feature can be applied to the feedback signal to dynamically adjusts feedback gain parameters.

Additionally, thanks to LabOne’s support for the most popular programming languages (Python, C/C++, MATLAB®, LabVIEW™ and .NET), maximum versatility is ensured when setting up a control loop and its successive optimization and refinement.