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Original Authors: G. Paviglianiti - Whirlpool Fabric Care, Advanced Development
Edited by Cyth Systems
Increasing reliability standards and testing capabilities of our washing machine electronic control boards and implementing an automatic system for embedded firmware validation to save time and resources.
Using NI VeriStand real-time testing software and NI PXI hardware to create a stand-alone system that tests and validates electronic control boards and automatically tests, calibrates, and validates smart algorithms that support Whirlpool 6th Sense Advanced Technology in domestic washing machines.
Hardware-In-The-Loop simulation is a technique used for testing complex control systems. It is a system that can simulate scenarios for the testing of an electronic control board. HIL must be able to perform a test with high-speed analog and digital I/O data acquisition to ensure a boards proper function before deployment.
We developed the 6th Sense smart control algorithms using rapid control prototyping systems based on the NI LabVIEW Real-Time Module and the LabVIEW Simulation Interface Toolkit. With our company-wide use of this system, we can test new concepts developed with simulation tools directly on a real washing machine.
The development process also requires validating engineered control algorithm firmware on the production control board. Algorithm complexity is growing exponentially due to higher quality requirements and challenging cost targets associated with energy label, washing performance, low noise, and advanced features. To handle these new requirements, we designed and implemented a hardware-in-the-loop (HIL) system.
Our system serves two main purposes: fast, automatic testing of the low-level signals processed and provided by the production control board for algorithm functionality and minimizing calibration and validation effort with considerable time and resource savings.
We developed a washing machine mathematical model to simulate the main control loops inside the home appliance, such as mechanical, hydraulic, and thermodynamic subsystems.
We adapted the I/O interfaces of the model to comply with production control boards. In conjunction with the mathematical model, we designed an external I/O board to act as a bridge and signal processor between the control mainboard and the PXI I/O interfaces.
Simulating a whole washing machine requires real-time performance. To achieve this determinism, we chose a 2.2 GHz NI PXI-8110 Intel Core 2 Quad controller combined with an NI R Series Virtex-II multifunction reconfigurable I/O (RIO) module for high I/O capabilities and flexibility.
We used NI VeriStand software to integrate our washing machine model. We developed the main part with MathWorks, Inc. MATLAB® and Simulink® software so it is possible to compile, deploy, and run the model on the PXI real-time controller. NI VeriStand performs all I/O mapping. Due to special requirements such as time constraints and numeric integration issues, we designed a specific part of the model directly on the field-programmable gate array (FPGA) RIO module using the LabVIEW FPGA Module.
We used NI VeriStand to see and log all low-level signals coming from the control board. With the model inline parameters, we can simulate the behavior of different washing machine models with various external conditions.
Beyond Rapid Prototyping
As our next step, we integrated the HIL test system in our previously developed algorithm calibration system. This system, developed with LabVIEW, automatically drives the washing machine to perform specific tests and prompts the user with instructions to configure the washer load condition. Moreover, it performs defined test plans and automatically computes algorithm calibration parameters.
To integrate the two systems, we implemented a LabVIEW application that remotely configures the NI VeriStand environment according to the test plan executed by the calibration system. This way, we can use plug and play architectures to integrate our HIL system with actual algorithm calibrations set up to rapidly scope how different sources of noise affect algorithm calibration.
We designed our system using LabVIEW and NI VeriStand for several reasons. First, Whirlpool and NI have a long history of more than 10 years that has successfully delivered high-performance features to customers. NI instrumentation and technology are flexible, so we can use the development environment in other product categories.
Whirlpool used NI VeriStand for the first time with this project and found it modular and intuitive. Even nonsoftware-expert resources agreed. Furthermore, the backward compatibility and easy customization of NI VeriStand helped us reuse VIs already developed for algorithm calibration applications.
With LabVIEW software and NI hardware, we can store technical data in an easy, suitable way, such as the Technical Data Management Streaming (TDMS) format. In addition, laboratory resources can preliminarily manage test data files thanks to user-friendly NI DIAdem software. This has a big impact on the day-by-day task scheduling between engineers and lab tech resources, resulting in overall team efficiency. The MATLAB and Simulink environments can also process the TDMS format, which facilitates synergy between company departments and easy, quick, specific data analysis.
The powerful combination of the NI VeriStand platform, LabVIEW FPGA, the real-time PXI module, and years of fast prototype development and experience with NI products helped us quickly and easily design and develop the whole HIL system.
G. Paviglianiti - Whirlpool Fabric Care, Advanced Development
Edited by Cyth Systems