An iterative compensation method for production tolerances in electric drive systems

Like all industrially manufactured products, interior permanent magnet synchronous machines are subject to deviations due to production tolerances. In particular, deviations in the permanent magnet flux and the air gap thickness cause considerably high torque errors and influence efficiency. Especially for traction drives in hybrid or electric vehicles this is not acceptable. In this paper, the impact of deviations caused by tolerances is first discussed. Second, a way to determine the deviation of an individual system is given. Finally, a method for compensation is presented that significantly increases torque accuracy with optimum efficiency: Based on a conventional open-loop torque controller, an iterative torque compensation (ITC) is introduced. Therewith, the commanded torque is adapted based on a torque estimation. The aim of the paper is to reduce torque error by changing the control method. The concept is proven by test bench measurements with machines deviating in their permanent magnet flux. Therewith, the torque error is reduced from 12 % to 2 % with respect to maximum torque.

[2]  Ho-Gi Kim,et al.  A MTPA control scheme for an IPM synchronous motor considering magnet flux variation caused by temperature , 2004, Nineteenth Annual IEEE Applied Power Electronics Conference and Exposition, 2004. APEC '04..

[3]  G. Ombach,et al.  Design of PM Brushless Motor Taking into Account Tolerances of Mass Production - Six Sigma Design Method , 2007, 2007 IEEE Industry Applications Annual Meeting.

[4]  Joachim Bocker,et al.  Sensitivity analysis on production tolerances for electric drive systems in automotive application , 2016, 2016 18th European Conference on Power Electronics and Applications (EPE'16 ECCE Europe).

[5]  Benedikt Schmuelling,et al.  A novel online PMSM parameter identification method for electric and hybrid electric vehicles based on cluster technique , 2015, 2015 IEEE International Electric Machines & Drives Conference (IEMDC).

[6]  Benedikt Schmuelling,et al.  Sensitivity analysis on electrical parameters for Permanent Magnet Synchronous Machine manufacturing tolerances in EV and HEV , 2016, 2016 IEEE Transportation Electrification Conference and Expo (ITEC).

[7]  E. G. Strangas,et al.  Parametric sensitivity in the analysis and control of permanent magnet synchronous machines , 2012, 2012 XXth International Conference on Electrical Machines.

[8]  Balluff Markus,et al.  Sensitivity analysis on tolerance induced torque fluctuation of a synchronous machine , 2016 .

[9]  Joachim Bocker,et al.  Optimum Control for Interior Permanent Magnet Synchronous Motors (IPMSM) in Constant Torque and Flux Weakening Range , 2006, 2006 12th International Power Electronics and Motion Control Conference.

[10]  Jin Hur,et al.  Torque characteristics analysis considering the tolerance of electric machine by stochastic response surface method , 2002, Conference Record of the 2002 IEEE Industry Applications Conference. 37th IAS Annual Meeting (Cat. No.02CH37344).