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Moving autonomous driving to the lab


Traditional roller-type dynos are facing a challenging future. Using direct drive from the hubs offers more flexibility, as Teo Stort explains

The automotive industry is gradually picking up from a global standstill. Not many harbour much short term optimism. In the long term though, most agree that the transition to new propulsion systems will continue, if not with increased pace. This as governments are working on consumer incentives to support the industry that is likely to be targeted towards electrification. These disruptive challenges put the focus on organisational flexibility to turn challenges into opportunities.

While flexibility may be applied to an organisation’s structure and the human mindset, it can equally well be applied to testing methods and equipment. Rototest has been working in the powertrain testing field for more than thirty years. Over the last ten years the company has focused on providing hub-coupled powertrain dynamometers with flexibility to support the OEMs and the Tier 1s in their pursuit of development efficiency and cost reduction. Moving powertrain calibration into the lab (road-to-lab), makes vast cost and time savings as the testing environment becomes stable and repeatable.

Even though this new decade has had a rough start with global production stops, the development of new drive systems such as electrified powertrains has continued. Not only is there an ongoing global transition in the way we propel the vehicles but also how our vehicles are controlled with more Advanced Driver Assistance Systems (ADAS) functionality being implemented. With the rapid introduction of new powertrain configurations in combination with a growing number of derivatives to meet wider customer segments, the number of vehicle variants to be calibrated, tested, and validated continues to increase. However, as consumers are not expected to accept a higher price tag on their next car, the increased volume of development must become more efficient to reduce costs.

Autonomous driving meets the lab

One of the megatrends in the global automotive industry is development towards autonomous driving, although it may now take some additional time until we see many vehicles being fully self-driving. Meanwhile, ADAS plays a crucial role for the medium-term reality of cars taking over more control from drivers. Calibration and validation in this area is growing rapidly and Rototest is involved in multiple innovative projects globally.

Customers report that time savings of up to 80% are achievable by moving calibration manoeuvres from road testing into the lab environment. The powertrain dynamometer systems from Rototest provide an efficient testing environment for ADAS functionality calibration and validation thanks to its modular use structure.

Apart from ADAS, Rototest’s dynamometers are additionally applicable on demanding high dynamic manoeuvres. A typical such manoeuvre is a WOT (Wide-Open-Throttle) standing start with maximum acceleration from standstill through the gears. Even with a medium powered vehicle, trying to conduct such a manoeuvre on a traditional roller type dynamometer commonly results in unrealistic and excessive tyre slippage. As Rototest’s dynamometers connect directly to the vehicle’s wheel hubs the relationship between tyre and surface can, for each wheel independently, be defined such that it can realistically represent dry, wet, snow or icy road conditions.

Rototest’s high dynamic control technology, the HDC, is included as a standard feature on many of the models in the powertrain dynamometer series. The HDC furthermore includes an integrated 14 DOF (Degrees-Of-Freedom) vehicle model. The integrated model is easily parameterised by only a few physical properties of the vehicle. Reducing the number of parameters required and keeping them to commonly published physical properties makes the process of setting up a new vehicle in the dynamometer system not only quick and effortless but also enables swift setup of vehicles of unknown detailed specification, such as competitor vehicles.

The integrated 14 DOF vehicle model comprises 6 DOF for the vehicle chassis, ie x, y, z movement and yaw, pitch and roll rotation, and 2 DOF for each wheel, ie rotational speed and steering angle. The capability of simulating individual wheel steering angles works well with Rototest’s dynamometer solution that provides a fully floating test environment enabling all wheels to physically provide steering angles, all the way up to full steering (+/- 45 degrees).

Increase in automotive modelling and simulation

Modelling and simulation are increasingly being used within the automotive industry to reduce development time and costs. With models, capabilities of a future vehicle can be simulated before it physically exists. This increases the speed of development and major mistakes can be avoided prior to production.

Rototest fully supports this trend with its dual interface, one with an integrated vehicle model and one open for any external model. All standard communication interfaces are supported such as CAN, Ethernet and EtherCAT. Rototest has together with one of its technology partners, IPG Automotive, added a connection through Rototest’s open interface to the IPG Xpack4 real-time system to be run in combination with IPG’s simulation software CarMaker. This allows OEMs and Tier 1s that use CarMaker earlier in the development phases to further utilise their resource investment in modelling in the powertrain phase with potential savings.

The system only requires a hard floor to be installed. As there are no horizontal forces acting on the vehicle during testing, full accelerations or emergency braking are of no concern and this ensures a stable testing environment with an unmatched vehicle installation time.

The unique capability of physical steering has proven to be very valuable for certain ADAS functionality as well as in Automated/Autonomous Driving (AD) testing. The steering functionality can be further improved with Rototest’s newly introduced steering force feedback system. The patented system together with the powertrain dynamometers presents a testing environment that gives the driver (or the AD control system) a natural steering feeling while driving, all without modification or connections to the test vehicle.