Williams Formula One experience is helping to close the gap between objective and subjective vehicle simulator testing, often a contentious area for vehicle development engineers.
Automotive test systems’ supplier AB Dynamics is using Williams’ platform and proven motion control techniques for its next generation vehicle driving simulator. It has been designed with the aim of allowing far more vehicle development in advance of a prototype than previously possible.
The new aVDS (advanced Vehicle Driving Simulator) features reduced latency and increased frequency response to deliver what the company describes as “a high resolution, fully representative driving experience.”
Using the Williams platform, which has direct-drive linear actuators, the aVDS can provide up to 60 Hz response and capability in six axes. It is complemented by a vision system with mono or stereo projection. Such level of simulation is essential beyond just vehicle dynamics, explained Dr. Adrian Simms, AB Dynamics’ Business Manager for Laboratory Test Systems.
“The aVDS can be used for the development of features such as ADAS (Advanced Driver Assistance Systems), autonomous emergency braking, autonomous vehicle systems, and the integration of electric and hybrid systems.”
From sim to lab to track
Both the cost and duration of new product engineering programs have tended to increase in line with greater vehicle complexity and as more derivatives are required from global platforms. At the same time, consumer pressure is dictating shorter lead times between model facelifts.
OEMs have responded by replacing hard prototypes with virtual ones where possible, enabling faster progress at lower cost. But more was needed, said Simms. “The ultimate example of human interaction with a virtual vehicle is the driving simulator but, until now, the range of effective applications has been constrained by the physics of the motion platform," he explained.
This restriction has generally limited simulator use to the human-machine interface (HMI) and ergonomic studies. With the aVDS, the aim is to fully meet the demanding requirements of driver-in-the-loop (DIL) vehicle dynamic simulation, based on techniques developed in Williams' Formula One operations.
Simulators often fail to provide the driver with a high enough level of feedback and familiarity, resulting in driver behavior that may vary from on-road performance, explained Simms. He sees a wider potential role for the system in bridging the gap between objective and subjective testing—to provide a link between computer-based simulation, laboratory-based simulation, and whole-vehicle testing both in the laboratory and on the test track.
Simms regards the aVDS as not only as a stand-alone product, but also as the central tool in a suite of test and development systems that can increase correlation, reduce timescales and simplify development programs.
Unique motion platform
The Williams motion platform used by the AB Dynamics system mounts a vehicle cockpit on four identical “wedge” actuator modules mounted on two parallel rails. Quiet and lightweight linear motors control both the height of the platform on the wedge and the position of the wedge on the rail. With its angled sides, the platform can be moved backwards and forwards by changing the distance between the wedges on each rail. The comprehensive platform has a 500-kg (1102-lb) payload capacity.
Said Simms: “The range of surge [fore and aft] movement is +900/-320 mm (+35.4/-12.6 in) with a frequency response of 10Hz; lateral movement [sway] is +/- 1350 mm (+/-53.1 in) with a 35-Hz frequency response. The platform is turned by moving the front and rear actuator pairs in opposite directions along the rails.
Heave, pitch and roll are controlled by moving the wedges independently to lift or lower the platform at each corner. The range of movement available is: +/- 111 mm (4.4 in) at 35 Hz in heave; +/- 30° in yaw, +/-12° in pitch, both at up to 30Hz. The range of movement in roll is +/-8.6° at up to 60 Hz.
The arrangement of the motion platform, which Simms describes as being “unique,” means that consistently high frequency response is achieved throughout the full range of travel. Motion in one direction does not constrain motion in the others, ensuring accurate simulation of vehicle attributes, including ride quality and steering feel anywhere within the envelope of motion.
Other simulator architectures, such as the hexapod arrangement, impressive travel in one axis can hide limited excursion capability in combined directions, Simms noted. AB Dynamics has also kept the inertia of the platform to a minimum by mounting the graphics system remotely; a floor-standing 4-m (14.1-ft) radius screen, 3 m (9.8 ft) high, surrounds the installation.
To maximize dynamic performance, the company can also supply a lightweight, carbon- composite cockpit as an alternative to the full vehicle front-end module normally specified.
Wrapping such a large radius screen around the installation helps to provide an immersive driving environment, supported by high-fidelity, low-latency software from rFpro. The software provides high definition graphics and audio, including high frequency input to replicate measured road texture in real time at up to 5 kHz. A comprehensive library of rFpro proving- ground and public-road models already exists and can be supplemented with bespoke lidar scans of test routes.
The rFpro software plugs into mainstream vehicle modeling tools, such as SIMPACK, Dymola, CarMaker, CarSim, Simulink, VSM and VI-Grade. It also integrates programmable traffic modules, including additional robot or human drivers occupying the same environment.Continue reading »