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Original Authors: Chris Thoroughgood, Austin Consultants
Edited by Cyth Systems
The Challenge
Developing a deterministic, easy-to-use, automatable, and easily maintained platform for open- and closed-loop testing on multiple linked electronic control modules (ECMs) and electronic control units (ECUs), that can also be configured to support a number of different product lines.
The Solution
Creating a generic hardware platform for the customer to perform ECM/ECU integration testing and a software solution that allows a highly configurable setup and automated configuration to suit multiple product lines and variants.
Introduction
The Caterpillar Advanced Components and Systems Division handle full system integration testing for many of Caterpillar’s popular product lines. This system integration activity involves linking up multiple ECUs and ECMs, alongside real displays, technician tools, and other connected systems that form part of the internal infrastructure of a vehicle.
As the vehicles themselves get more and more complex, the full system tests become more time consuming and a manual approach becomes less viable due to reliance on human resources and differences in how these tests are performed (timing and interpretation). The previous testing process was very manual as many of the tests involved setting an indicator and looking for a result either on a separate CAN tool or perhaps on a display.
Austin Consultants took a Windows-based system with custom conditioning electronics (developed by Caterpillar) and migrated it to a custom full-featured, hardware-in-the-loop (HIL) platform. The platform runs a real-time OS and real-time testing engine. It features simulated instrumentation, custom FPGA signals, deterministic I/O, and is driven by a highly configurable system setup and user-definable interface.
Key Business Benefits
A new standardized HIL test bench that Caterpillar can deploy across multiple departments
Standard software interface for automation and custom plug-ins
Easy-to-use intuitive interface that reduces the requirement for in-house training
Reuse of customer’s bespoke PCBs to reduce development and build costs
Simplified maintenance by:
Consolidated power supply and distribution eliminate multiple, distributed mains AC connections
Swapping fuses previously used for mini circuit breakers (MCBs), all quickly accessible from a removable panel
Repackaging PCBs into dedicated rack mount enclosures for a plug-and-play system
Pull out fault insertion unit (FIU) drawers for product-specific customization by the customer
Increased safety thanks to a new safety relay and emergency stop button
Left: Front of Main Rack (ECU/ECM connections at top), Right: Side of Main Rack (DC power and signal distribution)
Our Approach
We worked alongside the Caterpillar team to create a real-time hardware platform based on a PXI real-time controller. In addition, Caterpillar designed conditioning electronics (to bring signal levels to a suitable format) to directly interface with the ECUs/ECMs and a custom-built hardware platform.
Our hardware design involved a review of the existing Caterpillar hardware and understanding the day-to-day challenges that the operators faced, such as maintenance and servicing. The result was a double 24u floor standing rack. On one side was all the NI hardware and the signal conditioning PCBs/modules developed by the customer, including all power supplies and safety circuits. We focused on making these aspects easily maintainable with the following features:
§Using pull-out slides/trays for faster access to components
§Relocating interface connectors on the customer’s signal conditioning modules to allow quicker replacement
§Swapping fuses to MCBs and making these easily accessible by having them all behind an easily removable panel
§Removing all switch-mode PSUs from the signal conditioning modules and creating a low-voltage distribution around the system, which not only increased safety but also reduced electrical noise
§Integrating a safety system within the enclosure that interfaces with the customer’s existing safety systems
§Keeping all wiring and cabling within the rack when possible, which resulted in a much clearer finish
We dedicated the second rack to FIUs. In this rack, we supplied and fitted an FIU controller and the rest of the rack allowed for the customer to fit in product-specific FIUs and load trays. This makes the system very versatile and means that one asset can be used to test a wide range of products.
From a hardware point of view, this project was largely a refresh and repackage of existing Caterpillar systems. We added value with the software aspects of the rig. By fitting a PXI real-time controller and using our extensive knowledge of VeriStand, we could offer a real-time test (HIL) engine to give the customer a very flexible solution. We provided the hardware and software expertise to integrate this into a solution for the customer.
Our Solution
By exploiting the power of VeriStand and embedded real-time hardware, we delivered a system with many benefits. The system has deterministic communications and simulated behavior. It also has the flexibility of using deterministic targetable FPGAs for customizable measurements synchronized with the primary control-loop rate. This gives the customer great flexibility and the capability to meet more complex design requirements in the future, such as missing tooth cam/crank signals.
We took advantage of the VeriStand framework to concentrate on customer-specific components, such as the integration of hardware and other interfaces not supported off the shelf, as well as custom devices to talk to the ECM/ECUs via CAN bus.
The benefits of using VeriStand and some of the reasons behind its utilization in this project include:
Configurability: As we introduce new variants, the user can just update the configuration with ease (or programmatically from Excel using Austin’s automation code).
Standard interfacing: VeriStand includes plug-ins (custom devices) for standard interfaces such as NI switching hardware or Lambda low-noise power supplies.
Ease of FPGA integration: This gives direct access to FPGA variables from within the VeriStand configuration tool.
Comes with a built-in test framework: The Stimulus Profile Editor (part of VeriStand) allows automated testing and pushes results to an automatic test mark-up language (ATML) report file out of the box.
VeriStand runs a real-time engine on the PXI real-time devices allowing deterministic testing, stimulation, and logging.
Dynamic user interface: The client can build extra features on the fly whilst running (such as adding in extra graphs or more controls for different variants). This also allows the client to add to the UI without any programming experience (drag and drop controls).
We have also provided custom functionality to translate Excel-based configuration files to specific system configurations, allowing easy selection of multiple types of products, which then configures the system to test on the same hardware platform. This configuration-based approach helps the customer to easily extend the capability of the equipment on their own.
Caterpillar can run automated testing in a much more controlled manner and with much less operator input because of the built-in stimulus profile and real-time sequence editors, along with custom additions and training.
The hardware platform worked with Caterpillar to realize (on top of NI equipment): FIU/FIU with load/frequency generation/PWM generation (optical isolation) CAN. Use different harnesses rather than complete matrix channel switching.
We have a vast knowledge of HIL test applications. Caterpillar extensively uses HIL testing throughout its business. The company approached us to help migrate an existing HIL test bench into a standardized platform that can be expanded to support current and future ECU products.
Caterpillar’s Advanced Technologies and Solutions team is responsible for the electronic systems on a wide range of Caterpillar products. Integration verification involves testing the entire electronic control system for a particular product as a system. We designed this bench specifically for the material handler product, but we want the hardware to be generic enough to be replicated and used for other product lines with simple reconfiguration.
Original Authors:
Chris Thoroughgood, Austin Consultants
Edited by Cyth Systems