A Study of Triple Skyhook Control for Semi-Active Suspension System 2019-01-0168
It is said that a vertical vibration from 4 to 8 Hz (the mid-frequency range) particularly affects ride comfort. In order to suppress the mid-frequency range vibration, a number of control methods using a semi-active suspension system have been proposed. Skyhook damper control (SH) is a well-known strategy to suppress the vibration around the sprung mass resonance frequency about 1-2 Hz (the low-frequency range). However, the mid-frequency range vibration can’t be suppressed by SH. Therefore, dampers of the semi-active suspensions adopting SH are usually set soft to balance the low- and mid-frequency vibration. However, the soft dampers increase unsprung vibration opposite ride comfort.
H-infinity and gain-scheduled approaches also have been proposed to achieve these multiple objectives. However, those controls have many tuning parameters and require information of unsprung vibration from sensors or accurate estimations.
To solve those problems, the triple skyhook control (tSH) hooked by a virtual spring, inerter, and damper was proposed. This strategy has advantages of suppressing vibration from under 1 Hz to the mid-frequency without changing the hardware, and it requires no unsprung information. The effectiveness was verified by experiments using a full-active suspension vehicle.
The aim of this paper is to verify the effectiveness of tSH with semi-active suspensions.
As a result of experiments, the following were obtained:
1. tSH can widely suppress the sprung vibration from low- to mid-frequency compared with passive suspensions.
2. tSH is compatible with hard dampers and therefore it can suppress unsprung vibration compared with SH.
From the above, tSH set hard dampers has the ability of improving ride comfort and road holding simultaneously.