TESTING
A DIFFERENT APPROACH Rototest is a Swedish company specialising in vehicle test systems that allow road testing to be moved indoors. This enables a higher eff iciency in the development process by providing a highly reproduceable, controlled laboratory testing environment. Rototest’s powertrain dynamometers off er many modes of operations, of which Road Load Simulation is the most used. The design features a unique
fl oating installation - it is not fi xed to the fl oor. This enables the system to accept steering manoeuvres that are being conducted while running in the dynamometer system. The steering angle is then connected to the dynamometer controller that controls wheel speeds to correlate with the steering radius. As the dynamometer units follow
steering very easily on the fl oor, this fulfi ls many applications where the use of steering is enough. For more
complex applications, the steering torque may be required, such as when replicating driving on the road. This could even be extended to fully autonomous driving. So, the steering torque can be used as a feedback signal for the vehicle’s internal model and supervision system. The company recently acquired a
new patent involving a solution that can replicate the self-aligning torque, meaning the torque that tends to steer the wheel while rotating around its vertical axis. This solution does not need any modifi cation to the test vehicle and it even works on vehicles with 4-wheel steering. It’s called Natural Steering, and it installs in minutes and adds a servo-assistance functionality to the dynamometer, thereby providing the vehicle with a representative steering torque. The dynamometer system, in
combination with the servo-assisted steering, can be operated and is fully supported through the system’s integrated 14-DoF vehicle model. For
customers wishing to utilise their own simulation experience with the dynamometer system, the systems support an open API to externally control the unit independently, meaning that it can connect to any simulation environment regardless of interface such as CAN, UDP or EtherCAT.
GOING VIRTUAL To simplify the step from HIL to Vehicle-in-the-Loop, Rototest has partnered with the German company IPG Automotive. Its simulation environment for light-duty vehicles is called CarMaker and the partners have implemented the EtherCAT API of the CarMaker TestBed to make it a ready-to-run interface. The benefi t of integrating this
way is that the whole environment for the vehicle can be simulated, like the image for the vehicle’s front-mounted camera, to recognise the road markings as in the ADAS example above.
Steering and driving can be tested together
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