Shinjiro Saito

Improvement in Vehicle Agility and Stability by G-Vectoring Control

We extracted a trade-off strategy between longitudinal traction/braking force and cornering force by using jerk information through observing an expert drivers voluntary braking and turning action. Using the expert drivers strategy, we developed a new control concept, called ‘G-Vectoring control’, which is an automatic longitudinal acceleration control (No DYC) in accordance with the vehicles lateral jerk caused by the drivers steering manoeuvres. With the control, the direction of synthetic acceleration (G) changes seamlessly (i.e. vectoring). The improvements in vehicle agility and stability were evaluated by theoretical analysis and through computer simulation. We then introduced a ‘G-Vectoring’ equipped test vehicle realised by brake-by-wire technology and executed a detailed examination on a test track. We have confirmed that the vehicle motion in view of both handling and ride quality has improved dramatically.

A hybrid stability-control system: combining direct-yaw-moment control and G-Vectoring Control

In this study, a ‘hybrid stability-control’ system based on two concepts – G-Vectoring Control (GVC) and direct-yaw-moment control (DYC) – was developed. This system controls deceleration according to the information on vehicle lateral jerk and yaw moment according to the information on vehicle sideslip. It reduces the tendency to understeer by applying deceleration via GVC and reduces the tendency to oversteer by adding yaw moment via DYC. The tests with a vehicle fitted with this new GVC/DYC hybrid control confirmed that understeer can be reduced significantly more than that possible with conventional DYC only. It is concluded that this greater understeer reduction is a result of GVC preventing understeer prior to the skidding of the vehicle.

DYC and SMC Combined New Tracking Control Based on Nonholonomic Constraints for Skidding Cars

A car running on a low friction road skids off easily and falls into a spin. In general, it is technically difficult for normal drivers to recover a car into stable state. If the car obeys non-holonomic constraints, which corresponds to the case without side skidding, the steering controller based on exact linearization assures exponential stability to the desired trajectory. To keep these constraints, we have proposed a driving force controller based on the sliding mode control that drastically reduces the deviations from constraints. In this study, we combine “direct yaw moment control” and sliding mode control to show that our controller is effective to prevent undesired tracking errors. Additionally, the chattering phenomena caused by the driver’s and our controller’s inputs is smoothed by proper interior division of them related to transverse direction speeds of each tire. The advantage of our controller is verified through an interactive driving simulation.Copyright

Comparison and combination of direct yaw-moment control and G-Vectoring control

Previously, we developed a new control concept called ‘G-Vectoring control (GVC)’ to improve vehicle agility and stability. GVC is an automatic longitudinal acceleration control method that responds to vehicle lateral jerk caused by a drivers steering manoeuvres. In this paper, we compare GVC with the well-known direct yaw-moment control (DYC) method for daily driving ranges in particular. GVC shows good manoeuvrability (i.e. enhances both yawing and lateral acceleration) performance while maintaining a natural yaw and roll feeling in the early stage of cornering, while DYC is effective in improving vehicle stability during large lateral motions. We also re-review our previously proposed ‘hybrid control’ method that combines the strengths of GVC and DYC. A side-by-side test carried out for the hybrid control method and DYC only confirms the effectiveness of the hybrid control method.