Autotuning capabilities in TwinCAT software can optimize motion control and compensate for application challenges without requiring specialized understanding of Bode plot
The reasons why servomotors and servo drives require tuning vary. Sometimes key metrics change or are unknown before the drive technology is specified. Without knowing what’s needed in terms of speed, torque, inertia and mass, it’s difficult to select the right motor-drive combo that will work well in an application without advanced tuning.
Specifying your servos based simply on horsepower is one infamous cause for unwanted oscillation. Other times, the problem lies in a machine’s mechanics. Structural components could be loose or misaligned, or resonant frequencies could impede performance. Whatever the cause, these challenges wreak havoc on your motion capabilities.
More and more, engineers are turning to specialized tuning tools to eliminate oscillation and ensure top performance. Beckhoff has integrated this powerful functionality into our TwinCAT 3 automation software. Let’s explore how tuning works, how the TwinCAT Autotuning package further streamlines this process and what you could avoid tuning altogether.
Understand the role of Bode plot in servo tuning
In the past, engineers would turn to a Bode plot to analyze and tune out any issues. This graph of the system’s frequency domain behavior shows the overall conditions of the motion control – that is, the stability and quality of the axis. To do so, it examines specific factors, such as:
overall gain
gain margin
amplitude
phase margin
phase reserve
Take that gain margin and that phase margin, analyze it with a complex application, and compare it to three decibel frequencies, which simulate machine resonance. Based on that analysis, you implement the correct filters.
Because of the complexity of the process – and the rise of software-based tools to simplify it – creating and interpreting a Bode plot has become a dying art. Recent graduates often have no idea what it is, and the skill set is reserved for Ph.D.-level engineers. Even for engineers with expertise in this area, the process remains time-intensive and requires some trial and error. But that’s not to say you can’t do it.
Beckhoff has offered the TwinCAT 3 Bode Plot package for many years to help engineers find the right parameters for current, speed and position control as quickly as possible using frequency analysis. The tool’s speed control is a standout feature that highlights the mechanical influences of the application.
Boost servomotor applications with TwinCAT 3 Autotuning
Along with the Bode plot utility, Beckhoff has long offered an Advanced Tuning tool. This senses the inertia of the system to automatically configure the Velocity Observer. Now, we’ve combined these two pieces to create the next level in servo tuning: TwinCAT 3 Autotuning.
With the TE5960 Autotuning functionality, engineers can seriously streamline servo axis commissioning. This software automates the interpretation of phase, amplitude and other stability criteria. As a result, the iterative tuning procedure pinpoints the application’s mechanics, load inertia, controller parameters and filter settings. The calculated parameters can be loaded directly into the servo drives via the TwinCAT 3 Drive Manager 2. While making the process faster, you still get the transparency of a manual process. The software generates a Bode plot graphic to visualize the optimization results.
Engineers can harness the advantages of autotuning in a wide range of applications. These range from basic PTP and camming to NCI, CNC and more. That means you can enhance even a complex machine’s motion system in a minute or less. Even with zero knowledge of Bode plot, you can easily determine the parameters needed to deliver smooth motion control.
TwinCAT 3 Autotuning will work on all Beckhoff motors and drives, including servos, steppers and linear motors. In the near future, it will also apply to our mechatronics technologies, XTS and XPlanar. This software will only grow in importance, especially when combatting issues with mechanics and resonant frequencies. But avoiding this situation is possible as well through proper selection of motors and drives.
Pick the right industrial servomotors, steppers and drives
Beckhoff has always worked to set up engineers for success when tuning systems – even complex systems. We’ve done that by offering the Motion Designer (TE5910) tool to help you select the right motor and drive combination for the application. Motion Designer can ensure you have the right fit, but it does require some homework on the user’s part.
To spec your motion systems accurately, you need to know the speed, torque and inertias of each axis. The Velocity Observer uses this information to feed forward acceleration. As a result, you can precisely control motor behaviors right out of the box.
Beyond that, ensure best practices on the mechanical side. Make sure everything is tightened, lubricated and maintained to standard. If your servo system was working properly before but starts to go haywire after months of service, there’s a good chance the issue isn’t related to drive technology and the root cause is elsewhere.
Still, things change in any application, whether it’s during the design phase, commissioning or operation. The power of TwinCAT 3 Autotuning is that you can filter out those unknowns to deliver smooth motion every time.
Want to enhance the drive technology in your industrial automation applications? Contact your local Beckhoff sales engineer today!
Matt Prellwitz is the Drive Technology Product Manager for Beckhoff Automation LLC.
Comments