The "Virtual Model" of the car is built in software known as Multi-Body Systems Software (MBS). In my view, the success of MBS modelling, and particularly the driver in the loop simulator, is affirmation that the nature of handling and the driver's task can be best understood with the application of some basic vehicle dynamics principles.
The motion and feel of the vehicle is governed by the forces generated between the tyres and the road. So, in order to "drive" the virtual model, engineers have developed mathematical models, the so-called "equations of motion". Tyre forces are calculated in cornering through an estimation of the vehicle sideslip angle and a related tyre model for the vehicle in question.
First up, we should highlight the difference between the algorithms used in high end racing computer games and virtual prototyping of real cars. The racing game only needs a life-like experience for the driver within the racing game. The virtual prototype represents the build and response of the real car. The driving experience in the simulator must transfer to the real car, for the virtual prototype to have value.
Design changes can be made to the virtual prototype then tested, either in a simulation shown directly on a computer screen, or in the driving simulator.
From its inception in the 1980s, MultiBody Systems (MBS) analysis has made a huge impact on road and race car development. Engineers can test and modify designs in the virtual world before the car is built. Initially running on main frame computers, before long, the simulations could run on PCs and simulate the manouvers performed in real world testing on the proving ground, or at the race track.
Emerging now, are vehicle simulators that can use the output from MBS to operate the simulator's movements and feel, to such a degree, that it replicates the driving experience and handling of the real car. Now we can have test drivers providing feedback on the design, way before the car is built.
For some time now, I have considered that the MBS experts have the best insights into how the car works. Vehicle Dynamics Engineers like Damien Harty, Paul Fickers and Greg Locock share their knowledge via books/websites and forum comment on the internet. With MBS, the engineers can carry out sensitivity studies to check the effect of a number of different setup possibilities, that could otherwise only be tested via fully instrumented vehicle…
Optimum G testing in Argentina
In this article, I want to look at what we know about the simulators, and how this can help us in understanding more about the basics of handling theory and its application directly to the racing driver’s task.
In the early days of motor cars and racing, there was no general theory of handling. The engineering for new cars was done by modifying and testing existing vehicles. Aeronautical engineering, on the other hand, had developed a theoretical base from it's inception, perhaps because of the need to limit the possibility of aeroplanes falling out of the sky! It is indeed appropriate that it was aircraft engineers who developed the "equation of motion" for ground vehicles.
The study of modern vehicle dynamics has its roots in the work of General Motors Research and Bill Milliken from Cornell Aeronautical Laboratory (CAL). CAL had a contract with GM Research, starting in 1952 and continuing for over ten years, including the period of the seminal racing collaboration between Chevrolet R&D and Chaparral in the 1960s. The history of the times is truly amazing – a great read – see Chapt 13 of “Race Car Vehicle Dynamics” by Bill and Doug Milliken. Bill Milliken himself placed great emphasis on physical as well as mathematical understanding. They built prototypes to test everything they were doing.
For the first time, it was possible to do calculations for car stability and control, but of course, only for the select few who had the mathematical skills. The reality was that those involved in car manufacturing and racing didn't pay much attention to the theories. One could reasonably assume that the simplified models used in the calculations would not correlate with real world cars, especially in relation to tyre behaviour at the limits of grip, where racing cars operate.
General utilization of vehicle dynamics theory in vehicle design had to wait for the common availability of digital computing and development of the computer programs and tools the engineers need.
This happened, starting in the 1980s, with the development of “MBS” (multibody systems software). MBS is used to study how loads and forces are distributed throughout mechanical systems that comprise interconnected rigid or flexible bodies. Just what the doctor ordered for vehicle dynamics. MBS now made possible “whole of car” modelling of the complete system. Engineers could try a lot of changes and verify the design before producing the first prototype, including ride and refinement considerations.
Major car manufacturers led the way in developing the software - mostly in partnership with the MSC Software Company, using their ADAMS™ software.
ADAMS models in racing were also being developed from around the mid 90s. In 1997, Paul Fickers, an ADAMS expert with Ford, was seconded to work as Chassis and Dynamics Engineer with the just established Stewart Ford F1 team. And today, ADAMS is probably part of most specialist race car development programs.
The Rise and Rise of Vehicle Simulators in Racing and Road Car Development
In top level racing, the development process for the car is pretty clear cut – the race engineer and driver work together at the track to extract maximum performance, feeding all the data back to the factory to assist their work in developing the car.
On the other hand, road car manufacturers developing ride and handling for their new models, are more likely to have a disconnect between the design team and the physical testing and proving ground people.
The authors of “The Multibody Systems Approach to Vehicle Dynamics”, Mike Blundell and Damien Harty put it this way. “It seems to the authors that there are two camps for addressing the vehicle dynamics problem. In one is the practical ride and handling expert. The second camp contains theoretical vehicle dynamics experts.” It takes skill and experience to correctly use MBS programs like ADAMS. Only the theoretical camp can do this and analyse the results.
With ADAMS, there was the prospect that the designers could achieve most of the handling and refinement objectives for the car, before they have the first prototype car for test engineers to drive.
But now enter the vehicle simulator. It seems this physical addition to the virtual world of car development is a crushing innovation that brings the practical and theoretical development people ever closer together.
Test drivers and the engineers who work on the physical car can now be heavily involved in the virtual program. In racing car development, real drivers can test the virtual car from the very beginning.
However, there are limitations on the value of the simulator for race driver training - see videos and commentry below.
McLaren F1 have been at the forefront, having developed their simulator technology starting in the late 90’s and then from 2007, using it for road car development as well. Dick Glover, Technical Director for McLaren Automotive during development of the MP4-12C sports road car, appears in the video. He also led the team that designed and built their simulator.
Traditionally, lead engineers have always been involved in the testing of prototypes and engineering build vehicles. But Dick and his team were probably the first vehicle dynamics engineers who could drive in a "whole of vehicle" simulator, and try some alternative designs. Of course,they had data from their real world test drivers driving in the simulator as well. Apparently, they were in development and testing in the simulator fully twelve months before they had a physical car to test.
The next video is about developing the Alfa Romeo Giulia using the simulator. The Chief Technical Officer says the full development of the vehicle dynamics was done in the simulator, and that the physical car only required fine tuning. This is amazing given that the company has no rear wheel drive experience in modern times. Yet the real world dynamics of the car are favourably compared to competing models from BMW and Mercedes.
Volvo's V1-Grade Simulator
Volvo X 90 on the simulator. Dr Peter Mertens, Senior Vice President, Research and Development at Volvo, says they are getting a real world driving experience in the simulator.
Race Cars and Simulators
In this quote from his Facebook page, Jeff Braun is talking about race car development: (See https://www.facebook.com/AutoRacingTechTips/?fref=ts#)
"Today top race engineering companies like Multimatic design race cars in the virtual world first and build computer models of them rather than the actual car. Then they run the virtual models on the Driver in the Loop simulator and refine the design over and over. Suspension and aero and engine power curves are tested on the simulator. Then after 100's of combinations and days on the simulator they build the real car."
Here is Lars Ogilvie of Multimatic explaining how thats done:
Notice that they use MSC ADAMS™ multi-body systems software to develop the software model of the car. V1-Grade software can then assemble everything needed for the simulation and then output the result on a PC, or in a full blown simulator with a real driver driving the virtual car.
Triple 8 Racing in the BTCC...
In the following video, the Chief Designer at Triple 8 explains how they use simulation. Even with common front and rear suspension, including subframes, for all cars in the field, they can still extract small gains in performance. At the time of the video (2014) they had reached the stage of testing 100s and 100s of different setups prior to a race meeting. He says this work has been a big part of their success (eg locking out the front row 50% of races in 2013).
This Institution in Italy, Quattroruote Academy, offers a Masters Degree in Vehicle Dynamics. The key learning is in protyping using the V1-Grade simulator followed by hands on vehicle testing. This should greatly enhance the usual vehicle dynamics theory taught at University level. The course integrates the study of vehicle dynamics with simulator and practical testing.
Race Car Development using the Simulator and Driver Training
Porsche Motor Sport Video- the LMP1 Porsche Development Program
From a technical perspective with the race car, the simulator accurately represents how the vehicle behaves. The race engineers are looking to develop an optimised set up for each race track.
From a driver perspective, Timo Bernard, Porsche factory driver for LMP1, explains:
"It's never quite 100% the same because the way the driver feels everything in the race car on the track, cannot really be compared 1 to 1 in the simulator - it's not the same feeling. But you can judge the setups for the development of the vehicle." The way I interpret what they are saying in this video, the driver must use his intimate knowledge of driving the real car, to be able to get his race face on and drive the simulator car accordingly, so as to extract every ounce of performance, so that the engineers can properly compare the data, and so improve the vehicle.
It is clear that the simulator is very good for car development. Every company in the videos has gained extremely valuable insights.
On the hand, there is strong evidence suggesting the simulator has limited use for racing driver training.
However, the car companies do claim they are getting a real world driving experience in the simulator that relates to the DNA and feel of their brand.
Note the comments below from Nico Rosberg and Lewis Hamilton. In 2016, Mercedes F1 had some issues with the simulator...
Lewis Hamilton on Simulators and F1 driving (Autosport.com, June 2016):
Simulators have become an almost ubiquitous tool in F1 in recent times, as the rules have increasingly limited on-track testing.
Mercedes team-mate Nico Rosberg recently described parts of Mercedes' simulation of the new Baku street circuit as "weird", and Hamilton said he drove just eight laps in the sim ahead of this weekend's European Grand Prix because of the tool's limitations.
"I don't drive the simulator a lot because it's not at its best at the moment - we're working on trying to make it better," Hamilton said.
"I don't do a lot of time in simulators. When I was at McLaren we did way too much. I could spend £100 on a PlayStation and learn the same amount."
Hamilton said the simulator was more use to engineers than drivers, because the sensations of driving a real car cannot be replicated correctly in a sim.
"There's a difference between driving a simulator and driving the real thing - you have no emotion," Hamilton added.
"When you get into the simulator you have to adjust yourself to the simulator, and when you get in the car you don't adjust to it, you drive. In the simulator, you have to adjust all your feelings - you don't get the same movements, the same bumps.
"You drive the same track the day before and on Monday you drive the simulator and the bumps aren't there, the kerbs are different, and the speed is different."... (I think he means the sensation of speed rather than the speed as shown on the data from the simulator.) You don't feel the speed, you don't feel the physicality of it. The engineers learn more from the fuel usage, the power usage and aerodynamics."
Hamilton also revealed that he does not walk circuits anymore, something that is common practice among many drivers during a race weekend.
"I've walked around circuits since Formula Renault to probably my third or fourth year in F1 and it made zero difference to my weekend," Hamilton said.
"I've not walked a track since 2010 and it’s made zero difference. It might work for others, but for me it doesn't."
A lot of car development can be done without the simulator, by running the simulation on the computer. (eg Triple 8 does this in the video above.)
Whether driving simulator or simulation on computer, it is MBS software, and particularly ADAMS, using the mathematics of classical vehicle dynamics, that is driving the system.
The success of MBS modelling,and particularly the driver in the loop simulator, is affirmation that the nature of handling and the driver's task can be best understood with the application of vehicle dynamics principles.
Our biggest take-away? From a control aspect, the driver-car interaction can be much less complicated than we are inclined to think. In these advanced simulators, it works just fine to give the driver the feel of the car, based on the driver sensing and controlling the Body Slip Angle * as per the mathematics of classical vehicle dynamics. The same mathematics is at the heart of the control software behind Electronic Stability Control (ESC) systems.
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