ITI is one of the world's leading systems simulation software and engineering companies. The SimulationX standard tool is used to evaluate the interaction of all components in a technical system and to support the Modelica language. ITI works with global subsidiaries, distributors and partners, and it is also a partner of the National Instruments Alliance.

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TraceTronic offers innovative solutions, services and software products for developing and validating complex embedded systems. The company's services range from software function development and testing of electronic control units (ECUs) to full development of HIL systems.

Development of a verification framework for multi-purpose vehicles

In order to equip the defense and police and security forces with more advanced mobility, modularity and protection technologies, Kraus-Maffei Wegmann (KMW) and other companies have been challenged to develop a new generation of armored multi-purpose vehicles (AMPV) that not only have Good mobility and the highest level of protection. They use armored steel and composite armor to create a self-supporting safety element that sets new standards for armored vehicles. Vehicles go beyond current protection standards and their weight is significantly reduced. The vehicle is easy to operate and its internal optimized human machine interface (HMI) allows the driver and other personnel to focus on completing the task, further enhancing the level of protection. The easier it is to drive AMPV, the safer the people and equipment. We work closely with experienced software and hardware manufacturers to develop a comprehensive validation strategy for in-vehicle systems.

Develop a combined HIL test platform

The project began with the implementation of the HIL test platform. First, we analyzed customer requirements and electronic controller units (ECUs). The results of the analysis laid the foundation for the technical concept and test platform specifications. Market research on existing HIL simulators shows that there are currently no standard solutions for specific project requirements in terms of flexibility, integration and price, so we have developed a custom system based on existing and dedicated components.

We chose NI VeriStand as a real-time platform. This NI solution is based on industry-standard hardware, enabling us to implement high-performance systems at very reasonable cost. In addition, we are able to expand the computing power of our systems based on growing testing needs in a flexible and cost-effective manner.

To quickly calculate the real-time model, we chose a standard server with two 2.53 GHz Intel Xeon processors. There are 8 cores in both processors. The relatively low load caused by the current real-time model provides sufficient scalability without even upgrading the hardware.

The I/O hardware is connected to the PC through a PXI expansion chassis. This occupies only one PCI Express slot, and the PXI backplane provides a sufficient number of slots for plugging in other I/O boards. The test platform uses NI PXI Controller Area Network (CAN) communication boards and analog and digital I/O. For the rigorous time requirements of analog speed sensor signals, we have added an NI PXI-7831R Field Programmable Gate Array (FPGA) module. We developed FPGA programs using NI LabVIEW FPGA software.

In addition, we have selected a signal conditioning unit with integrated fault simulation, which reduces the complicated wiring of the test bench and does not unreasonably reduce the signal quality. To meet the requirements of two onboard voltage level vehicles, we integrated two controllable power supplies in the test rig. The display shows the current load of the processor core and information about the real-time system and the real-time model.

Test platform hardware layout

All components and wiring of the combined HIL test rig are fully integrated into a 19-inch rack. In addition to validating the ECU software, we can also use the test bench layout to test small batches of module series, such as bays with ECUs. This has also proven to be feasible as we can connect the vehicle wiring harness directly to the test rig.

Real-time model

Claim

As controller functions become more complex, there is a growing demand for capabilities and detail modeling of real-time device models. In particular, the operation of the exciter in modern vehicles is increasingly restricted except for opening and closing. To this end, we choose ITI SimulationX.

Test system ECU interacts with model

In this project, we used SimulationX to model all the physical components interacting with the vehicle controller, including the following aspects:

engine

Gearbox with torque converter and two-stage shiftable gearbox

Drive system with lockable and self-locking differential, four-wheel drive, wheel speed for turning when connecting ABS and steering sensors

Steering model

Brake and ABS system

Tire pressure monitoring system

Ensure real-time performance

Compared to pre-configured black box solutions designed for real-time capabilities, physical models tailored to specific tasks or derived from other real-time models are generally not capable of performing real-time tasks. Their real-time performance is guaranteed by the modeler as they develop the model.

The real-time capabilities of the model are achieved through two main mechanisms. On the one hand, a unique, thorough symbolic pretreatment is used. During code generation, SimulationX automatically preprocesses the physical and mathematical equations of the entire system model. Simplify the system by solving and substituting equations to simplify expressions that occur multiple times in a single calculation and to completely remove calculations that do not affect the number of signals on the specified interface (such as internal result variables). All of this does not require user involvement; by working with other code optimizations, very efficient real-time code is available. On the other hand, several analytical methods such as natural frequency and vibration modes, as well as energy distribution and performance analysis, provide assistance to the user in the model-performance optimization process to meet all computational time requirements.

In general, the SimulationX model developed for this project has excellent performance. For example, on a processor core, even if the model achieves a relatively high sampling rate, the entire drivetrain model requires only 20% of the computational power.

Drivetrain model example

The component models in the drive train are implemented with different levels of detail in accordance with the I/O requirements of the relevant ECU. From an engine perspective, a map-based model is sufficient to accurately describe the behavior of the engine. However, fuel injection system actuators require accurate equipment modeling from control inputs to position sensors as well as parameterization.

In this project, we validated this part of the model with the actual fuel injection control system. The gearbox and torque converter are physically modeled, including clutch and brake models, and the friction characteristics of these models are parameterized. This makes it possible to model gear changes and transition behavior during shifting, such as speed gradients and gear change times. This step makes sense because, with different brake and clutch torques, the gearbox actuator can be operated not only in the on/off mode but also in the intermediate step. The residual drivetrain model includes the flexibility of the drive shaft so it can perform typical drive train vibrations. Depending on the steering angle, the curve radius of each wheel is different, so during the turn, the sensor can detect the individual wheel speeds.

In addition to the controller output signal, the drivetrain model also handles the braking torque provided by the brake system model and applies it to the wheels. The speed sensor output of the drive system supports each ECU, but because of their high signal frequency, it is difficult to generate from the real-time model, but instead generated by the FPGA. The model can only provide the pulse frequency of the teeth passing through the sensor

The model shown runs on a processor core of a real-time system with a period of 0.1 ms. Therefore, the model occupies less than 20% of the processor core computing resources.

Test automation

In order to take full advantage of the HIL test bench, we need a flexible test automation environment. Since KMW internal development requires multiple regression tests, automated testing is essential for quality and cost reasons.

For this application, we use the test automation environment of TraceTronic ECU-TEST. This tool is used to specify, implement, execute, and document test results.

By changing the signal mapping at different stages of development in the relevant test environment, the reusability of the test case saves the user's valuable time. The test uses a visual design without editing the source code.

The regression test implemented in ECU-TEST covers the entire bandwidth of the required verification level, ranging from low-level tests such as analog ECU input and observation of relevant responses on CAN, to interactions and complex functions such as fault management and fault identification. This helps reduce the test effort to 15% of the previous workload and the test depth is significantly improved.

benefit

Production of advanced, highly protected, relatively lightweight, multi-purpose vehicles with a variety of new features is only produced by complex networked ECUs. The vehicle manufacturer is responsible for the entire system, including the vehicle, the internal development ECU, and the ECU obtained from an external supplier. In order to complete the task well, the manufacturer will integrate and jointly test all ECUs to ensure they are properly installed in the vehicle from the beginning.

The new HIL test platform is a unique combination of international standard hardware and software components. As a result, customers receive a pricing-optimized, highly scalable verification framework consisting of a HIL test platform, a custom real-time model, and a highly automated test environment. This combination helps manufacturers integrate different vehicle ECUs in a cost-effective and optimized manner. This allows customers to take advantage of scalability and I/O flexibility. With a real-time model in the loop, AMPV's ECU network can quickly verify and provide an integrated approach to optimizing the entire system. In this project, compared with the non-HIL test method, the test workload was reduced by 85%, and the test depth was significantly improved.

result

Using NI Real-Time hardware and NI VeriStand software, we have successfully completed model development and HIL test bed integration. We use parallel interfaces between the model, test bed software and hardware to perform development activities in all three areas in parallel. The short learning curve of NI VeriStand helps us quickly build and run HIL test systems. The scalable environment ensures that we can extend the HIL test system to meet future needs. The reconfiguration of NI VeriStand is very simple so that when the test requirements change, for example, when the signal and model need to be rerouted for debugging, the configuration can be changed. The inherent integration of NI VeriStand with real-time and FPGA hardware enables the test system to meet the required timing requirements and can be extended for future trials.

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