6. This cascaded control-loop diagram shows how the motion controller works to keep the platen level while it follows the motion of the platen and monitors the force exerted.
Custom Feedback
These mathematical computations done by the motion controller on the raw feedback from the position and pressure transducers are performed using a feature that Delta Computer Systems calls custom feedback. “By doing math on the raw transducer data before that feedback is provided to the control loop algorithm, the control algorithm itself can be much more straightforward and simple to implement and tune,” says Dennis Ritola, an applications engineer with the company.
The cascaded-loop architecture, custom feedback, and multi-axis synchronization functions used in this application are standard features supported by Delta motion controllers. These features are easy to set up using RMCTools, Delta’s development software package provided free by the company to its motion control customers. “A complex hydraulic control application such as this one can be accomplished with very few lines of code,” continues Ritola. “Programming a conventional motion controller to perform the nested control function would be extremely difficult.”
Tuning for Optimal Results
Once the motion steps are programmed, the system must be tuned for optimal operation. For this step in the development process, the RMCTools package provides tools for analyzing the motion and adjusting control-loop parameters. Motion analysis is simplified using Delta’s Plot Manager, which produces a graphical representation of actual versus target motion profiles, the goal being for the designer to adjust control-loop gain values to make the actual motion match the target profile.
Adjusting the gains is made easier using the Tuning Wizard, which Delta provides as part of the package. To help resolve any issues that Wuxi Forever engineers had during the design process, Ritola and the author were available for late night phone calls, as well as online exchanges of computer screens displaying tuning status, between China and Washington state.
“The completed press has met or exceeded all of the design goals for the project,” says Xie. “The development of the LANLI press was made easy using Delta Computer Systems motion controller and development tools, and Delta’s technical support was excellent.”
“The customer that ordered the press is very pleased with the results,” adds Ruhong Liu, technical director and an engineer at LANLI. “The press has been in production since July, running 24 hr./day for four months making auto body panels for a German auto maker’s Chinese plant. Because of the good performance of the press, we have gotten more orders from other foreign-China joint-venture auto makers. So we will build three more presses to fulfill increased demand.”
“The future prospects for the LANLI press design are excellent,” echoes Xie. “The trend in the automotive industry for ‘green’ lightweight vehicles and EVs has increased the demand for composite material automotive parts. This trend will likely continue for the foreseeable future.”
Gan Li, is director of business development-Asia Pacific Rim, Delta Computer Systems Inc., Battle Ground, Wash.