## 1 Introduction
Therefore, it is necessary to carry out multi-degree-of-freedom (MDOF) vibration-reduction research on vehicle seats. The traditional multi-dimensional vibration-reduction methods are mainly divided into two categories. One type uses elastic materials, such as rubber and sponge, to realize multi-dimensional vibration reduction via the elasticity of flexible materials. However, these materials have shortcomings, such as poor heat dissipation and rapid aging, which may lead to unstable vibration-damping performance and low service life [7]. Another multi-dimensional vibration-reduction method combines a mechanical structure with a damping element to reduce vibration. For example, [PERSON] developed a two-layer MDOF vehicle seat suspension that can simultaneously control vibration in the vertical direction and two rotational directions [8]. This suspension can effectively attenuate multi-dimensional vibration. However, it is necessary to adopt a multi-layer structure to realize multi-dimensional vibration reduction, and its structure is complex. A parallel mechanism can simultaneously move in different directions, and can attenuate vibrations in multiple degrees of freedom. This kind of mechanism has been in development for decades. In 1965, [PERSON] studied the mechanism that was designed by [PERSON], and invented the Stewart mechanism as a flight simulator [9]. In 2007, [PERSON] et al. [10] developed a six-axis vibration isolation system that used the Stewart platform, which demonstrated a strong damping effect. [PERSON] [11] developed a Stewart platform with a symmetric structure, and analyzed the dynamic characteristics of the platform. In 2015, [PERSON] [12] developed a 6 DOF vibration-reducing platform using [PERSON]'s mechanism, and showed that the platform had a strong damping effect on 6 degrees of freedom. In 2020, [PERSON] et al. [13] designed a Stewart platform-based parallel support bumper to alleviate the vibrations of inertially stabilized platforms. While the Stewart mechanism has many advantages in multi-dimensional vibration reduction, it still has some problems. Movement between the legs of a common Stewart mechanism is coupled, making its kinematic and kinetic analyses complex. In order to solve this problem, [PERSON] first proposed a special-house Stewart mechanism, which is a cubic Stewart mechanism. Any two adjacent legs of this mechanism are perpendicular to each other [14]. A cubic Stewart platform not only simplifies control algorithms and achieves controller decoupling, but also simplifies calculations of kinematics, and mechanical structural design. Due to the above-described structural characteristics, the sensors installed along each portion's axis have orthogonality, as do the vibration signals of each leg. That means that we can transform a multi-input, multi-output (MIMO) vibration control problem into a single-input, single-output control problem [15; 16]. The authors of this article propose a vehicle seat suspension that is based on a cubic configuration Stewart platform and an MRF damper. The main structure of the paper is described below. In the first section, we introduce the research background of the multi-dimensional damping of vehicle seats, establish the necessity of this research, and introduce the research scheme adopted in this study. In the second section, we establish a dynamic model of the MRF damper, carry out the kinematics analysis of the cubic configuration Stewart platform, and simplify the control measurement parameters according to the symmetrical characteristics of the platform. In the third section, we establish a virtual prototype model of the damping seat platform, and verify the feasibility of simplifying the control measurement. In the fourth section, we describe our experimental research on a multi-DOF seat damping suspension. In the fifth section, we consider semi-active vibration control, and show that the vibration-reduction effect in multiple directions could be effectively improved.