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INTRODUCTION

In the 20th century, systems engineering methodology was developed so that a system could be decomposed into multiple sub-systems and each sub-system could be independently engineered, manufactured and serviced. The emphasis was laid  on defining requirement specifications such that the sub-systems and its interactions with other sub-systems were clearly defined. This method emphasized upfront planning, analysis and specification. Hence, the term Requirements  Driven Systems Engineering. In practice, it was always very  difficult to specify upfront with a high level of accuracy and to  resist changes to specifications during development. By and  large this methodology has been inadequate and has led to  delayed programs and last minute surprises; commonly referred to as the requirements-delay-surprise factor.

In the 21st century, iterative modeling and simulation play a crucial role in systems engineering. An operational model is  first developed to understand all usage conditions, including the surrounding environment; then systems models are built and simulated; finally, component models are developed.

Change is integral to this methodology and requirements, structure, and behavior are derived and finalized with the help of the models. In short, the model is the master!

The fidelity of the models is continuously improved during the development and it is possible to combine models and physical systems, also called, Hardware in the Loop (HiL). When the  physical systems are assembled, they are just a twin of the  model. Tests conducted on this physical prototype can be  continuously correlated against predicted behavior and be used  to improve the fidelity of models.

Using the Systems Engineering Methodology is very important for any Trophy Winning FSAE Car.

MODELS ARE EVERYWHERE

It’s fairly common today for FSAE participants to develop CAD models and subject them to structural, fluid and thermal simulation. Similarly, a number of models are built by students from other  disciplines: software engineers use models to specify the operating conditions and interactions between systems; control systems developers build block-based models and generate software code for  controllers; electrical engineers develop schematics and layouts of  their design; electronics engineers develop high level logic that is synthesized into physical design; hydraulic engineers define hydraulic  circuits. When interdisciplinary work is critical, multiple domains are combined. For example, the thermal and fluid dynamics models are simulated together to understand the performance of the climate  control systems.

Systems integration nightmare: Since each discipline is working on their own models, most often the first time  the FSAE participants witness how the systems function  together is when they finally assemble a physical  prototype. Its not uncommon that the physical prototypes require numerous build, test, fix iterations, before they work as intended. The net effect: projects are delayed and quality suffers.

In the era of autonomous systems - new types of sensors, complex control algorithms and the integration of on and off-board systems are the drivers of autonomous capabilities. This leads to an increase in software-based functionality and E/E complexity never seen before.

Coupled with ever-shorter time in FSAE, it can become the  perfect storm if complexity is not mastered starting from the early  phases of product definition.

Even though models are used by every engineer, they are siloed by  discipline, requiring  physical prototypes for integration and  validation.

MAKE YOUR VEHICLES DYNAMICS CAPABLE

FSAE participants can rapidly model and test their ideas in various operating conditions  before proceeding with detailed design. They can simulate the way multi-disciplinary features interact, enabling early detection of potential conflicts, if  discovered at a later stage, could delay projects and drive up costs. This  improves stakeholders’ agility and ability to rapidly choose concepts that  improve safety and comfort.

CATIA Dymola Behavior Modeling is part of this purpose-built solution for developing smart, safe and connected vehicles. The design and engineering of autonomous systems  requires a new model-based systems approach – it needs to be multi-disciplinary from the get go!

Make your vehicle models dynamics capable. If you are currently building  control systems models in a signal-flow oriented tool, higher fidelity and more  accurate control can be achieved by incorporating simulation of dynamic  physical systems with CATIA Dymola Behavior Modeling.

Signal-flow oriented control models typically don’t fully incorporate dynamic  effects caused by road, driving conditions and suspension design. These affect  driving comfort and safety, and if not incorporated in the models, may lead to  issues discovered only later during physical testing. Simulating dynamic  behavior under various road and driving conditions helps identify and fix issues in the early phases of product development.

DYNAMIC PHYSICAL MODELING - A CHECKLIST

If you want to incorporate dynamic behavior into you vehicle models, the following are some of the key capabilities of the modeling environment that you  may want to consider.

Breadth of Library Models: Are there pre-built libraries for the sub-systems that  are included in your system? If your systems are multi-disciplinary in nature,  look for libraries across multiple domains containing models for mechanical, electrical, control, thermal, pneumatic, hydraulic, power train, thermodynamics, vehicle dynamics, air conditioning, etc.

Object Oriented: Can you directly instantiate the library models and build your  systems with ease? Typically, look for a drag and drop interface. Also, look for  the ability to abstract sub-systems in a single model. If necessary can you  modify the library models and create your own derivatives of the models? Model  management capabilities are a key requirement if you are working in a team.

Equation Based: Can the dynamic behavior of systems be described by  differential and algebraic equations? Does it support the concept of flow and  across variables?

Acausal: Does the environment support the definition of equations in a  declarative form, without considering the sequence? This reduces the effort to  describe behavior in comparison with procedural languages like C and other  block-based tools, where signal flow direction needs to be considered.

LEVERAGE LIBRARIES TO MODEL YOUR VEHICLE

While it's good to know that all of this is possible with CATIA Dymola Behavior Modeling, it is also important to realize that you don't need to start from scratch. Many of the specialized libraries that come with CATIA Dymola Behavior Modeling include not only high quality component and subsystem models but also the interfaces and architectures that give you a head start in building models of your system. You  can also import your legacy models into CATIA Dymola Behavior Modeling, either using direct interfaces, or by adopting the standard FMI interface.

It includes Engine, Electrified Powertrain, Suspensions, Battery, Cooling libraries, etc. that work in conjunction with the Modelica Standard Library.

USING END TO END MODEL BASED SYSTEMS ENGINEERING SUITE

Systems engineering in its current approach has really been a reactive change process with ineffective traceability back to the requirements given the multiple heterogenous software tools, as well as little to no connected validation of the sub-systems. There has been no ability to test what happens to the whole when a single part malfunctions, and make adjustments within context of all the involved systems.

A Requirement, Functional, Logical, and Physical (RFLP) data model has evolved to help counteract this fragmentation and guide the vehicle architects chartered with the overall design. RFLP provides a collaborative engineering methodology that can capture, manage and track product requirements with full traceability, all from one engineering desktop window. Based upon a single, open, and scalable service oriented architecture platform, RFLP provides a unified infrastructure to share whole data across the specific discipline. With this approach, changing the product and/or requirements is completely traceable as to how it impacts the other systems.

WHAT CAN YOU MODEL AND SIMULATE USING THE 3DEXPERIENCE PLATFORM?

1. Range Simulation

Model an electrified powertrain to perform an energy consumption simulation which could for example lead to a range simulation.

2. Battery Management System

Model and Simulate battery management models that provide information about the performance of the cells in a battery pack.

3. Cooling System

Model and simulate an external pump causing a volume flow through the inverter first and the machine subsequently.

4. Suspension System

Plot full kinematic suspension variables against bump input and plot full kinematic suspension variables against steering input run scripts to plot variables from the sensor pack.

5. Tyre

Model and simulate a spin roll test, that allows free longitudinal movement while defining the torque applied to the spin axis of the wheel. The torque is defined by a single output source block.

6. Brakes

Simulate the action of a hydraulic braking system within a vehicle equipped with an Electronic Stability Programme (ESP).

7. Steering

Model and simulate Rack and Pinion steering that has friction both in the column and the rack, and uses a transfer function with a quasi-static filter based power steering applied to the column.

8. Skidpad Test

Model and simulate your vehicle's response to skid.

9. Drivecycle Test

Model and simulate a Drivecycle Test using existing drive-cycle templates. For example - test an NEDC drive cycle featuring an electric car.

10. Slalom Test

Model and simulate a Slalom Test. The performance is evaluated by measuring the driving time between the start and finish gates. The test is performed on dry asphalt where the test vehicle engages a sequence of turning at the maximum allowed speed following a line defined by 12 cones

11. Brake Test

Model and simulate a Brake Test to measure the vehicle braking.

12. Acceleration Test

Utilizing an open loop driver model, the vehicle will start from rest, apply the brake to hold the vehicle then accelerate at wide open throttle through the gears throughout the duration of the test.

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