Machines can only function optimally if their drives are perfectly adapted to the drive train. Only then can high-quality products be produced at the highest cycle rate of the machine with a minimum error rate. To achieve this, the control in the inverter must be set specifically for the machine. With the usual procedure, a drive expert often needs several hours for this manual task in the commissioning phase - depending on the complexity of the controlled system. But with Lenze's Auto-Tuning, the adjustment is now faster - and more accurate.
High-precision tuning of the closed-loop control in the drive is the basic prerequisite for competitive machine performance in many machine applications - especially in assembly robots, storage and retrieval machines (SRM) or packaging machines. Currently, however, a drive expert has to invest a lot of time during commissioning in order to achieve this exact and high-performance tuning. The automation specialist Lenze has now developed an auto-tuning function that significantly reduces commissioning times for customers in a wide range of applications.
The physical models commonly used today for mapping the controlled system of a machine are only of limited use in practical applications for optimum controller setting of the drive axis. This is due to significant deviations in the behaviour between the physical model of a machine and the real machine. This is why today's drive specialists still "feel their way" to the optimal control setting on the real machine in several tests. This is done using the oscillation method developed by Ziegler and Nichols in 1943. The drive is brought to its - audible - stability limit and the controller setting used is multiplied by a safety factor. The method is easy to use, not model-based and produces a robust control result. However, manual adjustment takes a lot of time.
With the auto-tuning function, Lenze has now automated and significantly simplified the setting of control parameters for its i-series servo inverters. The procedure from Ziegler and Nichols is integrated into it. No additional measuring components are required apart from the servo inverter. The drive itself becomes the sensor with the current variables of the position encoder and the motor current. After completion of the auto-tuning, the settings of the control parameters are calculated and stored in the configuration of the drive.
The existing physical controlled system is automatically measured in a short time and an exact adaptation to the real machine takes place. Errors that previously occurred due to model deviations or during manual adjustment can be avoided with the new function. This procedure saves commissioning time, is robust, delivers reproducible results and optimum performance for the machine. Even with complex control challenges such as "gear backlash" or "variable loads", the auto-tuning function works reliably and safely.
The Auto-Tuning function can be executed with the Lenze tools EASY Starter and PLC Designer. The developers paid attention to the simplest operation and clear, informative feedback, so that even commissioning engineers without expert knowledge can execute the function virtually at the push of a button.
The feedback from Lenze customers who have already used this method in their machines is consistently positive. In particular, the simple, robust principle and the enormous speed of optimisation were cited as major advantages over the previous manual procedure. The fact that the cycle times and thus the output of the machine could also be improved also provided a high level of satisfaction. Lenze's developers were able to achieve up to 10 percent higher cycle rates in on-site tests with plant operators by optimising the inverter parameterisation.
The auto-tuning function has been available since the Hanover Fair in April 2021. Auto-tuning can already be carried out with all i950 and i700 servo inverters purchased since then. Units sold before then can be upgraded with the auto-tuning function via a firmware update.