Enhancement of electromechanical load-leveling suspensions for automotive applications using reversible transmission mechanisms

Abstract

This paper presents an electromechanical height adjustment system for vehicles. The proposed design acts on the spring holder of the automotive suspension by means of a reversible ball-screw transmission. This actuator falls within the load-leveling category of suspensions, which becomes relevant in instances where the vehicle enters different terrains, driving conditions, or travel speeds. Furthermore, it could ease accessibility for passengers and goods. To provide reversibility, the actuation system relies on a ball-screw mechanism. It increases the overall efficiency of the actuator, which in turn, implies faster actuation times and lower power consumption. To avoid back-drivability when not needed, a highly integrated and compact locking clutch is engaged. This component provides a fail-safe feature to the suspension, even in the absence of electricity. The clutch is controlled by means of an electromagnet, which is also used to estimate its locking state by measuring the inductance of its magnetic circuit. The proposed solution is compared to a very similar irreversible configuration, where the ball-screw is replaced by a power screw with trapezoidal profile. Experiments demonstrate the benefits of the reversible ball-screw transmission in terms of actuation time (two times faster) and average efficiency (three times more efficient) when compared to the irreversible alternative. The functionality and state estimation of the locking clutch is also validated.