RDE Plus - A Road to Rig Development Methodology for Complete RDE Compliance: Road to Chassis Perspective 2020-01-0378

To aid Original Equipment Manufacturers (OEM) in meeting future Real Driving Emissions (RDE) regulation criteria [1] across extended environmental conditions, a Road to Rig (R2R) whole vehicle development, calibration and verification approach, currently known as RDE Plus (RDE+), has been developed at HORIBA.

In this paper, the methodologies required for replicating real RDE road tests on a chassis dynamometer are discussed in depth. These include application of robot driver for successful cycle replication and repeatability and use of HORIBA’s Multi-function Efficient Dynamic Altitude Simulation (MEDAS) system in conjunction with a temperature and humidity controlled test cell to replicate the engine, vehicle and environmental conditions.

For RDE replication using a robot driver, two methods are presented. The first, is a speed matching method whereby a robot driver maintains the recorded vehicle speed via its own closed-loop control whilst road load is implemented via a Road Load Reconstruction (RLR) technique. The second is a “Torque Matching” (TM) method whereby robot driver pedal inputs are controlled in an open-loop mode and vehicle speed is implemented using Automatic Speed Regulation (ASR) of the chassis dynamometer. The former focuses on how robot driver controller tuning is used to successfully replicate real world driving if accurate road load components are known. The latter is presented as an elegant way to achieve a 1:1 road load match of a previously driven RDE test, or any other arbitrary road drive, with minimal prior information.

Considerations relating to vehicle preparation, robot driver tuning, and the application of HORIBA MEDAS will also be covered, including potential minor modifications to vehicles in pursuit of successful replication outcomes.

The RLR method showed good agreement in work done and CO₂ emissions for the real-world drives presented (approx. 2-3% difference). However, the TM method was able to demonstrate much less than 1% difference in these parameters when matching a previously driven test at the same conditions. This improved precision would be beneficial for minimizing the amount of back to back testing required to characterize the effect of powertrain calibration changes. NOx and PN emissions are also shown correlating well with the real road test values (< 10% difference).

This paper is the third in a series of ongoing technical reports from HORIBA on vehicle and engine development and calibration methodologies for RDE compliance. It is twinned with a concurrent SAE paper by the same authors covering Engine-in-Loop (EiL) methodologies and follows SAE Technical Paper 2019-01-0756 presented at WCX2019 [2, 3]. Additionally, there are patent applications arising from the techniques demonstrated [4].