Study on Improving Comfortable Turning Feel by Coordinated Control Between Steering and Suspension (i-LEED Technology)

Coordinated control (i-LEED: The trademark of Hitachi Astemo, Ltd.) provides performance evolution for vehicle dynamics response and stable steering feel. The system only adds a unique control logic module to the existing control logic and requires no additional hardware in the vehicle. A prominent aspect of innovation is that it uses the steering effort information from the EPS. This allows a very quick response for pre-conditioning the steering and shock absorbers at an earlier phase of the turning maneuver, enabling remarkably stable steering feel. First, the coordinated control for semi active shock absorber improve turning feel, which is response and feel of unity by optimizing the pitch movement in accordance with the roll motion at earlier timing using the steering effort from the EPS (Electric Power Steering) system. Then, the coordinated control for EPS improves stable steering effort by compensating the SAT (Self Aligning Torque), which is the cause of an unstable steering effort using the roll rate from the semi active shock absorber system. As a result, comfortable turning feel during turning transient is realized by applying both controls coordinated and in defined succession.　A welcome effect from not requiring additional hardware is the cost and weight saving, as well as the elimination of failure sources.