1. INTRODUCTION Hybrid systems that combine multiple power sources have been developed and installed in a wide range of vehicles around the world as part of measures to help conserve the global environment from vehicle emissions and reduce consumption of fossil fuel energy sources. These systems include various different configurations. The Lexus Hybrid Drive (LHD) system, which was first adopted in Lexus vehicles in 2006, is a hybrid system comprising of an engine, an electrically-controlled continuously variable transmission (ECVT) that incorporates a power split device and two motor/generators, and a high-voltage battery that supplies power to the motor/generators via a power control unit (PCU) [ 1]. The characteristics of this system include high power performance, smooth and quiet drivability, and remarkable environmental performance including both fuel economy and emissions. The new LC500h hybrid luxury coupe was launched in 2017 to lead the next generation of Lexus vehicles. One role of the hybrid system in this vehicle is to contribute to the brand image and competitiveness of Lexus by enhancing the characteristics of the vehicle. The hybrid system in the LC500h features the newly-developed Multi Stage Hybrid System, which adds a multi stage shift device to the transmission from the previous hybrid system to maximize the potential of the ECVT in the LHD system. The construction of the system is shown in Fig. 1. Figure 1. Structure of hybrid system in the LC500h This paper describes the specifications of the Multi Stage Hybrid System in the LC500h and how this system helps to improve vehicle performance. It also details controls that were developed to help resolve the issues that arose due to adding the shift device, and to maximize the dynamic drivability of the vehicle.Development of Multi Stage Hybrid System for New Lexus Coupe Shunya Kato, Ikuo Ando, Koji Ohshima, Tooru Matsubara, and Yasuhiro Hiasa Toyota Motor Corporation Hideki Furuta and Yuma Mori AISIN AW CO., LTD. ABSTRACT Lexus launched the new hybrid luxury coupe LC500h in 2017 to help enhance its brand image and competitiveness for the new generation of Lexus. During the development of the LC500h, major improvements were made to the hybrid system by adopting the newly-developed Multi Stage Hybrid System, which combines a multi stage shift device with the transmission from the previous hybrid system to maximize the potential of the electrically-controlled continuously variable transmission. Optimum engine and electrical component specifications were designed for the new vehicle and transmission. As a result, the LC500h achieves a 0-to-60 mph acceleration time of 4.7 seconds, with a combined fuel economy of 30.0 mpg while satisfying SULEV emissions requirements. Two controls were constructed to help resolve the issues that arose due to adding the shift device. A model-based shift control that calculates the torque for the electrical components during shifts was established using an optimal control method. The power management control, which ensures the input and output power of the lithium-ion battery in the LC500h, was modified by applying compensators to reduce delays in detecting speeds of electrical components and providing torque request to the electrical components. Additionally, a control simulating a ten-speed transmission was established to enhance dynamic drivability in line with the intentions of the driver when accelerating, to eliminate the rubber band effect using the characteristics of the shift device. CITATION: Kato, S., Ando, I., Ohshima, K., Matsubara, T. et al., "Development of Multi Stage Hybrid System for New Lexus Coupe," SAE Int. J. Alt. Power. 6(1):2017, doi:10.4271/2017-01-1173.Published 03/28/2017 Copyright © 2017 SAE International doi:10.4271/2017-01-1173 saealtpow.saejournals.org2. OBJECTIVES OF DEVELOPMENT The development objectives adopting the Multi Stage Hybrid System were following A to D. A. T o de