For the development of the 4th generation of its famous hybrid, Toyota Motor Corporation first completely renovated its process for developing the software that controls the car’s electrical/electronic systems. This was revealed in a presentation by Shinichi Abe, General Manager of the Toyota HV System Control Development Division, at the dSPACE Japan User Conference 2016 held in Tokyo on June 3, 2016.
In front of a curious audience, Mr. Abe first explained the technological evolution of Toyota’s hybrid systems since the first models from 1997. He then continued that building the newest generation required not only more advanced control strategies to improve the fuel efficiency of the new Prius’ E-grade models to 40.8 km/liter (under the JC08 test cycle) and to enhance overall drivability. In addition, the general control for the system parts became more demanding because a new lithium-ion battery was added as a second battery in order to reduce charging times. At the same time, the batteries were moved below the backseat to increase the useable trunk space. Moreover, the new model also meets the other existing specifications of previous generations, like the four-wheel-drive.
To handle the increased requirements while maintaining Toyota’s established quality, the overall control system’s software underwent significant changes with a consolidation of inputs and processes, and a decrease in the combinatorial number of mode selections. The latter especially helped reduce complexity.
In order to safely achieve the general restructuring and also implement the new functional innovations in the control software, Toyota used model-based design (MBD) across the entire control software development process. However, this drastic change first required a substantial effort in man-hours – more than initially envisioned.
To complete the new process, the development teams then selected dSPACE’s production code generator, TargetLink, in combination with the test and validation tools EmbeddedTester and EmbeddedValidator by TargetLink’s strategic partner BTC Embedded Systems AG. Adopting this proven tool chain further increased the overall development efficiency and, in the end, allowed Toyota to produce all of the final control software’s code in-house – with TargetLink.
The new Toyota Prius successfully launched first in Japan in December 2015 and has reached other markets since early 2016.