# Research on the Decoupling of the Parallel Vehicle Tilting and Steering Mechanism
###### Abstract  
Active tilting vehicles tilt to the inside of the corner when the vehicle is steering. The tilting motion improves the steering and roll stability of the vehicle. The steering mechanism and the tilting mechanism of the vehicle are connected in parallel. The transmission of the steering mechanism is influenced by the movements of the tilting mechanism. In order to solve this problem, a parallel mechanism is proposed in this paper. It consists of a spatial steering mechanism and a tilting mechanism in parallel. A mathematical model of the parallel mechanism with the wheel alignment parameters has been established. The model calculates the decoupling conditions of the parallel mechanism. In this study, a decoupling method for the parallel mechanism is proposed. A prototype of the parallel mechanism was designed according to the proposed method. The prototype was found to reduce the influence of vehicle tilting on the outer and inner wheel steering angles by up to 0.64% and 0.78%, respectively. The steering geometry correction rate of the prototype is between 1.198 and 0.961. The correctness of the model was verified by experimentation on the prototype. The proposed method can effectively decouple the tilting motion and steering motion of the vehicle and make the wheels on both sides satisfy the Ackerman steering condition. p 2022 25 July 2022 26 July  
mechanism of the vehicle are connected in parallel. Some design methods for a tilting and steering mechanism have been proposed [10; 11]. When the tilting mechanism drives the vehicle tilting to the left, all of the wheels of the vehicle on the left side move up and the wheels on the right side move down in relation to the position of the vehicle [11]. When the vehicle tilts to the right, the movement of the wheels is reversed. The swingarm connecting the kingpin in the tilting mechanism is longer than that which is found in typical wishbone suspension. It has a broader range of movement that allows it to tilt the vehicle at a greater angle [10]. The steering mechanism also has to direct the wheels on the left and right sides by use of the swingarm and steering rod. As such, the movements of the tilting mechanism will influence the transmission of the steering mechanism. One option to solve this problem is to split the tilting mechanism and the steering mechanism into two independent mechanisms [1]. [PERSON] and [PERSON] designed tilting mechanisms that steer by the use of an independent wheel [1; 12]. [PERSON] et al. connected two mechanisms in series. This tandem mechanism used separate actuators to control the tilting motion and steering motion of the vehicle [13]. These methods add a lot of costs. Connecting the steering mechanism and the tilting mechanism in parallel is a low-cost method that can realize two-wheel steering [11]. [PERSON] et al. and [PERSON] et al. used planar four-bar linkage as the steering mechanism. The mechanism parameters which realize the Ackerman steering condition (ASC) were obtained [14; 15]. [PERSON] et al. designed a vehicle steering mechanism with incomplete non-circular gears [16]. The mechanism can reduce the deviation between the actual steering angle of the wheel and the steering angle that satisfies the ASC. These two mechanisms are planar. These mechanisms will generate coupling when they are paralleled with the tilting mechanism. A spatial steering mechanism is required to be in parallel with the tilting mechanism due to the nature of the coupling. [PERSON] and [PERSON] et al. have provided theoretical methods for parallel mechanism decoupling [17; 18; 19]. [PERSON] and [PERSON] have proposed design methods for tilting and steering mechanisms without considering the wheel alignment parameters [8; 11]. The method can decouple the vehicle's tilting and steering motion. The steering angles of the wheels on both sides are equal, which cannot satisfy the ASC.