DS-15-1379: Virtual Vehicle Control Concept for Hydrostatic Dynamometer Control ⇤† Zhekang Du, Tan Cheng, Perry Y. Li, Kai Loon Cheong and Thomas R. Chase Center of Compact and Efficient Fluid Power Department of Mechanical Engineering University of Minnesota Minneapolis, MN 55455. Email: {duxxx139,cheng164, lixxx099, cheo0013, trchase}@umn.edu. Please send all correspondence to Perry Y. Li. ABSTRACT An approach for controlling a hydrostatic dynamometer for the Hardware-In-the-Loop (HIL) testing of hybrid vehicles is proposed and experimentally evaluated. The hydrostatic dynamometer, which is capable of absorbing and regenerating power, was specifically designed and built in-house to evaluate the fuel economy and control strategy of a hydraulic hybrid vehicle being developed. Unlike a chassis dynamometer whose inertia is similar to the inertia of the vehicle being tested, the inertia of this hydro-static dynamometer is only 3% of the actual vehicle. While this makes the system low cost, compact and flexible for testing vehicles with different weights and drag characteristics, control challenges result. In particular, the dynamometer must apply, in addition to the torques to mimic the wind and road drag, also the torques to mimic the acceleration and deceleration of the missing inertia. To avoid estimating the acceleration and deceleration, which would be a non-causal operation, a virtual vehicle concept is introduced. The virtual vehicle model generates, in response to the applied vehicle torque, a reference speed profile which represents the behavior of the actual vehicle if driven on the road. This reformulates the dynamometer control problem into one of enabling the actual vehicle-dynamometer shaft to track the speed of the virtual vehicle, instead of directly applying a desired torque. To track the virtual vehicle speed, a controller with feedforward and feedback components is designed using an experimentally validated dynamic model of the dynamometer. The approach has been successfully tested on a power-split hydraulic hybrid vehicle with acceptable virtual vehicle speed and dynamometer torque tracking performance. 1 Introduction Hardware-In-the-Loop (HIL) simulation is an efficient technique to develop and test complex real-time embedded sys- tems. A HIL system reduces testing complexity by using only part of the hardware which needs to be tested, while the remaining hardware is simulated on the computer. HIL is widely used in the automotive industry to verify the performance of production powertrain controller modules (PCM) [1]. A prototype hydraulic hybrid passenger vehicle test-bed is being developed within the Center for Compact and Efficient Fluid Power (CCEFP) to advance hydraulic hybrid technologies. While simulations can predict fuel economy and perfor- mance of the vehicle, experimental validation is still necessary. Outdoor road tests require a test track and results may not be repeatable due to variable environmental conditions such as wind, rain, snow, and road and traffic conditions. A reliable HIL system, such as a dynamometer (or dyno in short), can enable reliable and consistent measurements in the laboratory and not be influenced by environmental factors. Furthermore, a dynamometer allows the comparison, development, and tuning of various control strategies for different vehicle characteristics and driving conditions. To this end, a hydrostatic dynamometer capable of both absorbing and regenerating energy (a necessity for testing hybrid vehicles) has recently been developed in our group [2]. ⇤ To appear in the ASME Journal of Dynamic Systems Measurement and Control. Original submission: August 16, 2015. Revised: May 23, 2016 and July 20, 2016 † A preliminary version of this paper was presented at the 2014 ASME Dynamic Systems and Control Conference, San Antonio, TX.