On the edge of reality

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Stratiform platform provides highly responsive motion profile
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Jonathan Newell visits Ansible Motion to see how it provides the means to put expert drivers on the edge of the performance envelope in a simulated environment.

We’re all familiar with simulators of various shapes and sizes, from PC software that emulates a flight deck to the large “War of the Worlds” type structures at amusement parks that bring the fantasies of “Star Wars” to a bumpy reality for a few thrilling minutes.

Outside of the world of entertainment, the automotive industry has been using similar technology in terms of software, graphics and hardware to assist in the development of vehicle ergonomics and, to some extent, performance and handling.

Aerospace heritage

These engineering design simulators have almost exclusively been based upon the “hexapod” structures originally designed in 1947 by Dr Eric Gough for aircraft simulation.

The ungainly looking hexapod is a platform sat on six computer-controlled rams which provide the motion in the six degrees of freedom needed to provide realistic motion in all vectors. Depending on the direction of motion needed, the movement of the rams can be highly complicated, with all six of them needing actuation to achieve a relatively simple movement along the X-Y plane.

Whilst entirely adequate for simulating the motion of high mass aircraft where the pilot has a long visual horizon and controls the vehicle in keeping with its inertial properties, the hexapod starts to demonstrate its inherent weaknesses when applied to the highly dynamic, lightweight environment of road vehicles.

Improving hardware response

The Stratiform hardware platform developed by Ansible Motion addresses this shortfall by simplifying the actuation requirements and placing the simulation pod on a table, itself mounted on a large X-Y stage, which provides front-to-back and side-to-side movements. The table which sits on it provides the yaw, pitch, roll and Z-plane “bounce” motions, and the pod itself can accommodate other internal motions, giving the pod a total of over 11 motion axes with much less inertia than a hexapod.

To complete the elimination of lag within the responses of the simulator to driver input or external environmental factors, computer system latency is minimised with an array of 16 custom-built computers with parallel processing.

Having developed motion systems that catered for the needs of dynamic automotive simulation, Ansible Motion understood that the motions themselves were not enough to fulfil the needs of a highly demanding industry and therefore went on to develop the full simulation suite that would provide automotive designers with the tools needed to simulate the performance of their products to the limits.

Simulation data

Large amounts of data are needed to be able to simulate both the vehicle and the driving environment as accurately as possible. Vehicle data in the form of parameterised physics models can be synchronised directly with the Ansible Motion simulator in real time from standard automotive software tools, such as Simpack from Dassault Systèmes.

Environmental models can be supplied by the vehicle manufacturer or can be loaded as standard test circuits and proving grounds from other standard automotive software tools, such as rFactor Pro.

Additionally, other factors influencing the performance and dynamics can be tied into the simulation as required. Ansible Motion’s Technical Director, Kia Cammaerts told me, “Virtual sensors can be used where necessary, for example you can take as many measurements as you want across the contact surface of the tyres, something you couldn’t possibly achieve in a real environment.”

Additionally, the system supports Hardware-in-the-Loop (HIL) testing so that a real Engine Control Unit (ECU) can be used as part of the simulation rather than a software version of it.

Putting the driver in the loop

Most importantly for such vehicle dynamics testing is the presence of a real driver. The driver is the most complex element of vehicle engineering and the most difficult to simulate. Driver-in-the-Loop (DIL) simulation is essential for assessing the subjective elements of vehicle dynamics.

Vehicle dynamics modelling provides advantages anywhere where driver behaviour is of interest and using DIL/HIL combinations enables co-dependencies to be established and for the behaviour of the driver to be assessed in different technical circumstances.

The first such DIL simulators from Ansible Motion were developed for the racing industry and filled the void in the simulation industry that would satisfy the needs of highly skilled drivers.

According to Cammaerts, “For such drivers, it’s important to get every detail as realistic as possible. The tiny stuff matters. Racing drivers need to be able to feel the cue for even very tiny rotational accelerations.”

Cueing is the key to successful DIL simulation and there are three elements to it. Environmental cues consist of the visual and acoustic elements, contact cues relate to what the driver feels such as vibration and inertial cues provide the driver with the sensation of motion.  Inertial cues are the most difficult to achieve with full realism and without inducing motion sickness.

Preparing for a virtual tour of Spa Francorchamps with Ian Haigh of Ansible MotionEverything has to match perfectly. When standing in the simulator control room watching the pod and with the ability to see the driving environment projected onto the 8m diameter wraparound screen, a slight motion sickness starts to be felt after a short time because you are not receiving the inertial cues that match the very realistic visual effects that you are partially immersed in.

If the driver feels such sickness, it means there’s inertial lag or network latency and is unacceptable for such high performance environments. Getting the inertial cues to the driver involves stimulating the vestibular system of the inner ear, something which Cammaerts likens to a system of accelerometers in the head. Perhaps this matching of technology to biology was the key to achieving such successful fidelity to real life.

Without this cueing by stimulating the human vestibular system, getting the full feeling of spinning out of control or accelerating consistently would require a vast area within the simulation chamber, which is neither practical nor affordable.

Ansible Motion has spent a lot of energy in getting the cueing right, so that the driver feels the way the car responds and can perceive the differences made by minor adjustments in vehicle parameters.

Driving the simulator

The “Delta Series” simulator in the Ansible Motion laboratories near Norwich is a very low-impact installation compared with many other professional simulators used in the automotive industry. It does not occupy cavernous amounts of space and its low inertia means it does not need a huge foundation to absorb the floor loading.

I tried it out on the Spa Francorchamps motor racing circuit and found the simulated car to be driveable and easy to handle. Spinning on entering the first corner too quickly resulted in a realistic sensation of losing control and haptic feedback relating to the vibrations and bumps of leaving the circuit into a grassy area.

The immersion was so complete that on returning to the pits, I had no idea in which direction I was facing until the lights came back on, the projection turned off and the simulator pod had returned to its neutral position.

These are professional simulators designed for expert drivers to test the dynamics of new vehicles to the limit, they’re not for entertainment and they aren’t designed for fun I was told…. Well maybe that’s true but it was great fun nonetheless!

Jonathan Newell

Jonathan Newell

Jonathan Newell is a graduate of Loughborough University and has three decades of experience in engineering as well as broadcast and technical journalism.
Jonathan Newell

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