VP21-06 Integration Design of MR Fluid Brake-Based External Rotor PMSM For Robotic Arm Application
Creators: Youkang Hu
Publisher: name: IEEE
Year: 2025

1.Introduction Due to the high efficiency, high torque density, and fast dynamic response, the external rotor permanent magnet synchronous motor (PMSM) is prone in robotic arms [1]-[2]. With the increasing use of robotic arms in human-robotic interaction, it is desirable to minimize the risk of impulsive force injury when an unexpected impact occurs. Faced with this demand, magnetorheological (MR) fluid-based brakes are a novel passive way of compliance that has been widely applied in robotic interaction tasks to provide adjustable brake torque [3]. In [4], the design of MR fluid-based human-friendly manipulator is proposed to balance safety and performance. The common connection type between the MR fluid brake and PMSM is cascaded through an additional transmission unit, resulting in a low integration and space utilization. This article proposes an integration design of MR fluid brake-based external rotor PMSM (MRFB-B-ERPMSM) for robotic arm application. By adding the inner braking teeth to the stator with outer armature teeth, the MR fluid brake is integrated into the interior of the external rotor PMSM. The multimode stator design can allow the proposed machine to operate in both rotation and brake modes while improving space utilization in a relatively simple structure. 2.Machine topology and FE analysis Fig.1(a) shows the detailed integration topology of the proposed machine. The detailed design parameters of the proposed MRFB-B-ERPMSM are shown in Fig.1(b). Fig. 2(a) shows the flux density and magnetic field distribution in the open-circuit field. A small amount of magnetic leakage enters the inner braking tooth area of the stator under the open circuit field. Fig. 2(b) further illustrates the impact of this magnetic leakage on the back electromotive force (EMF) of the proposed machine under 1200 rpm. Fig.2(c) shows the flux density of the MR fluid in the inner air-gap under two operation states. Fig.2(d) compares the torque versus different current densities under rotation state and brake state. It can be observed that the built-in integration of the MRFB does not have a significant impact on the performances of the ERPMSM.References: [1] C. Ma et al., “Analytical calculation of no-load magnetic field of external rotor permanent magnet brushless direct current motor used as in-wheel motor of electric vehicle,” IEEE Trans. Magn., vol. 54, no. 4, pp. 1-6, Apr. 2018. [2] S. Zuo, F. Lin, and X. Wu, “Noise analysis, calculation, and reduc-tion of external rotor permanent-magnet synchronous motor,” IEEE Trans. Ind. Electron., vol. 62, no. 10, pp. 6204-6212, Oct. 2015. [3] P. Fauteux, M. Lauria, M. A. Legault, B. Heintz, and F. Michaud, “Dual differential rheological actuator for robotic interaction tasks,” IEEE/ASME Int. Conf. Adv. Intell. Mechatronics, AIM, pp. 47-52, 2009. [4] A. S. Shafer and M. R. Kermani, “On the feasibility and suitability of MR fluid clutches in human-friendly manipulators,” IEEE/ASME Trans. Mechatronics, vol. 16, no. 6, pp. 1073-1082, Dec. 2011.
1.Introduction Due to the high efficiency, high torque density, and fast dynamic response, the external rotor permanent magnet synchronous motor (PMSM) is prone in robotic arms [1]-[2]. With the increasing use of robotic arms in human-robotic interaction, it is desirable to minimize the risk of impulsive force injury when an unexpected impact occurs. Faced with this demand, magnetorheological (MR) fluid-based brakes are a novel passive way of compliance that has been widely applied in robotic interaction tasks to provide adjustable brake torque [3]. In [4], the design of MR fluid-based human-friendly manipulator is proposed to balance safety and performance. The common connection type between the MR fluid brake and PMSM is cascaded through an additional transmission unit, resulting in a low integration and space utilization. This article proposes an integration design of MR fluid brake-based external rotor PMSM (MRFB-B-ERPMSM) for robotic arm application. By adding the inner braking teeth to the stator with outer armature teeth, the MR fluid brake is integrated into the interior of the external rotor PMSM. The multimode stator design can allow the proposed machine to operate in both rotation and brake modes while improving space utilization in a relatively simple structure. 2.Machine topology and FE analysis Fig.1(a) shows the detailed integration topology of the proposed machine. The detailed design parameters of the proposed MRFB-B-ERPMSM are shown in Fig.1(b). Fig. 2(a) shows the flux density and magnetic field distribution in the open-circuit field. A small amount of magnetic leakage enters the inner braking tooth area of the stator under the open circuit field. Fig. 2(b) further illustrates the impact of this magnetic leakage on the back electromotive force (EMF) of the proposed machine under 1200 rpm. Fig.2(c) shows the flux density of the MR fluid in the inner air-gap under two operation states. Fig.2(d) compares the torque versus different current densities under rotation state and brake state. It can be observed that the built-in integration of the MRFB does not have a significant impact on the performances of the ERPMSM.References: [1] C. Ma et al., “Analytical calculation of no-load magnetic field of external rotor permanent magnet brushless direct current motor used as in-wheel motor of electric vehicle,” IEEE Trans. Magn., vol. 54, no. 4, pp. 1-6, Apr. 2018. [2] S. Zuo, F. Lin, and X. Wu, “Noise analysis, calculation, and reduc-tion of external rotor permanent-magnet synchronous motor,” IEEE Trans. Ind. Electron., vol. 62, no. 10, pp. 6204-6212, Oct. 2015. [3] P. Fauteux, M. Lauria, M. A. Legault, B. Heintz, and F. Michaud, “Dual differential rheological actuator for robotic interaction tasks,” IEEE/ASME Int. Conf. Adv. Intell. Mechatronics, AIM, pp. 47-52, 2009. [4] A. S. Shafer and M. R. Kermani, “On the feasibility and suitability of MR fluid clutches in human-friendly manipulators,” IEEE/ASME Trans. Mechatronics, vol. 16, no. 6, pp. 1073-1082, Dec. 2011.