Analytical study, design, and optimization of radial-flux PM limited-angle torque motors

Document Type : Article


Department of Electrical Engineering, University of Larestan, Lar, Iran


This paper presents an analytical study of the radial-flux slotless limited-angle torque motors. The modelling is based on the magnetic equivalent circuit of the actuators and uses the electromagnetic equations to calculate the air-gap flux as well as the produced torque. This model is then used for designing the actuators both in outer-rotor and inner-rotor structures, considering the design constraints and desired characteristics. As the objectives in design stage usually conflict with each other, an intelligent multi-objective optimization algorithm is required to design the best fit actuators. Analytical and simulation results are presented and compared to show the accuracy of the model and verify the design equations as well as the design approach. As this type of actuators is a key element in industrial control, the contributions of this paper are focused on new analytical field solution based on magnetic equivalent circuit, design and optimization approach for radial-flux structure and introducing a general procedure that could be extended to similar structures and actuators.


1. Chen, S., Kamaldin, N., Teo, T., et al. "Toward comprehensive modeling and large-angle tracking control of a limited-angle torque actuator with cylindrical Halbach", IEEE/ASME Trans. Mechatronics, 21(1), pp. 431-442 (2016).
2. Hekmati, P., Yazdanpanah, R., Mirsalim, M., et al. "Radial- flux permanent-magnet limited-angle torque motors", IEEE Trans. Ind. Electron., 64(3), pp. 1884- 1892 (2017).
3. Guodong, Y., Yongxiang, X., Jibin, Z., et al. "Analysis and experimental validation of dynamic performance for slotted limited-angle torque motor", IEEE Trans. Magn., 53(11) (2017).
4. Zhang, Y., Smith, I.R., and Kettleborough, J.G. "Accurate tracking control of a limited angle torque motor", Electric Machines & Power Systems, 27(11), pp. 1191-1199 (1999).
5. Yu, G., Yongxiang, X., Zou, J., et al. "Development of a radial- flux slotted limited-angle torque motor with asymmetrical teeth for torque performance improvement", IEEE Trans. Magn., 55(7) (2019).
6. Hekmati, P. and Mirsalim, M. "Design and analysis of a novel axial-flux slotless limited-angle torque motor with trapezoidal cross section for the stator", IEEE Trans. Energy Convers., 28(4) (2013).
7. Tsai, C.C., Lin, S.C., Huang, H.C., et al. "Design and control of a brushless DC limited-angle torque motor with its application to fuel control of small-scale gas turbine engines", Mechatronics, 19(1), pp. 29-41 (2009).
8. Nasiri-Zarandi, R., Mirsalim, M., and Cavagnino, A. "Analysis, optimization, and prototyping of a brushless DC limited-angle torque-motor with segmented rotor pole tip structure", IEEE Trans. Ind. Electron., 62(8), pp. 4985-4993 (2015).
9. Roohnavazfar, M., Houshmand, M, Zarandi, R.N., et al. "Optimization of design parameters of a limited angle torque motor using analytical hierarchy process and axiomatic design theory", Production & Manufacturing Research, 2(1), pp. 400-414 (2014).
10. Xue, Z., Li, H., Zhou, Y., et al. "Analytical prediction and optimization of cogging torque in surface-mounted permanent magnet machines with modified particle swarm optimization", IEEE Trans. Ind. Electron., 64(12), pp. 9795-9805 (2017).
11. Arehpanahi, M. and Kashefi, H. "Cogging torque reduction of Interior permanent magnet synchronous motor (IPMSM)", Scientia Iranica, 25(3), pp. 1471- 1477 (2018).
12. Yamazaki, K. and Ishigami, H. "Rotor-shape optimization of interior permanent-magnet motors to reduce harmonic iron losses", IEEE Trans. Ind. Electron., 57(1), pp. 61-69 (2010).
13. Ibtissam, B., Mourad, M., Medoued, A., et al. "Multi-objective optimization design and performance evaluation of slotted Halbach PMSM using Monte Carlo method", Scientia Iranica, 25(3), pp. 1533-1544 (2018).
14. Yazdanpanah, R. and Mirsalim, M. "Hybrid electromagnetic brakes: design and performance evaluation", IEEE Trans. Energy Convers., 30(1), pp. 60-69 (2015).
15. Chen Xing, Deng Zhaoxue, Hu Jibin, et al. "An analytical model of unbalanced magnetic pull for PMSM used in electric vehicle: numerical and experimental validation", International Journal of Applied Electromagnetics and Mechanics, 54(4), pp. 583-596 (2017).
16. Mohammadi Ajamloo, A., Abbaszadeh, K., and Nasiri-Zarandi, R. "A novel transverse  flux permanent magnet generator for small-scale direct drive wind turbine application: design and analysis", Scientia Iranica, 28(6), pp. 3363-3378 (2021).
17. Liu, Y., Zhang, M., Zhu, Y., et al. "Optimization of voice coil motor to enhance dynamic response based on an improved magnetic equivalent circuit model", IEEE Trans. Magn., 47(9), pp. 2247-2251 (2011).
18. Wurtz, F., Richomme, M., Bigeon, J., et al. "A few results for using genetic algorithms in the design of electrical machines", IEEE Trans. Magn., 33(2), pp. 1892-1895 (1997).
19. Konaka, A., Coitb, D.W., and Smithc, A.E. "Multiobjective optimization using genetic algorithms: a tutorial", Reliability Engineering and System Safety, 91(9), pp. 992-1007 (2006).