Abstract：[Objective] Compared with the commercially available centralized motor drive systems, in-wheel drive motors are installed inside the wheels and provide high transmission efficiency, enhanced control flexibility, and ease of modular vehicle design. In mainstream configurations of in-wheel drive motors, the power and transmission devices are rigidly connected to the chassis, thereby increasing the unsprung mass of the vehicle and the rotational inertia of the wheels. This increase in unsprung mass and rotational inertia results in higher vertical acceleration of the vehicle body and increased dynamic loads on the wheels. Moreover, due to the lack of buffering effect from the centralized driving vehicle's half shaft, the rotational vibration of the wheels and the longitudinal vibration of the vehicle are more prominent. Electric wheels with suspended drive motors can not only extend motor life but also alleviate comfort problems as a result of excessive unsprung mass. Designing flexible coupling within limited wheel space in an electric wheel is a critical challenge.[Methods] In this paper, a flexible coupling was proposed for an electric wheel with a suspended drive motor. The coupling was a planar parallel mechanism composed of several connecting arms, each of which consisted of two parallelogram mechanisms linked in series. As only the rotational joints existed and the stiffness of the input and output disks were high, the analysis assumed that the connecting rod only experienced axial deformation and the input and output disks were treated as rigid bodies. Under these assumptions, kinematic and dynamic models were established for the coupling utilizing the geometric relationships between the rods with the principles of mechanical equilibrium. Coupling eccentricity and the static and dynamic loads of the components were then derived. To demonstrate, a set of parameters were selected for the coupling, and numerical calculations were performed for the eccentricity, static load, and dynamic load of the coupling.[Results] The results show that the coupling can transmit power with constant velocity and allows the transmission system to jump in vertical directions during power transmission. The total eccentric stroke of this coupling reaches 58.2 mm, which is sufficient for an in-wheel suspended drive motor. Application of 400 N·m torque and 1 000 r/min to the input shaft leads to a maximum static load on the connecting rod of approximately 1 300 N and a maximum dynamic load on the output disk of approximately 35 N. Under the same conditions, the dynamic load on the proposed coupling is only 1/10 of that on the Oldham coupling.[Conclusions] The coupling proposed in this paper can have a large eccentric stroke while occupying little axial space and imposing negligible dynamic load. This coupling can be helpful in developing electric wheels with suspended drive motors. The flexibility of the coupling allows the motor and transmission components to move independently from the wheel, which reduces the unsprung mass and solves the problem of vibration and noise. This coupling has significant advantages over previous solutions in terms of size, dynamic load, and mechanical efficiency. This work provides a reference for designing in-wheel suspended drive motors.
罗荣康, 俞志豪, 吴佩宝, 侯之超. 内悬置电动轮的柔性联轴器动力学性能分析[J]. 清华大学学报（自然科学版）, 2024, 64(1): 25-32.
LUO Rongkang, YU Zhihao, WU Peibao, HOU Zhichao. Dynamic analysis of flexible coupling for an electric wheel with a suspended drive motor. Journal of Tsinghua University(Science and Technology), 2024, 64(1): 25-32.
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2024, Vol. 64 
