“…The objective functions are the requirements that certain parameters should be maximized, minimized, or within certain ranges. Some typical objective functions are force [2, 3, 9-11, 15-17, 19, 24-34], torque [4, 5, 7, 8, 12-14, 17-21, 34-42], torque density [43], yield stress [44], moment of inertia [13], mass [4-7, 18-20, 22, 23, 28, 39, 40, 42, 45-48], volume [24,29], temperature [7,12,14], magnetic flux density [25,29,49], acceleration [1,3], response time [4,6,9,15,16,[25][26][27][28]50], dynamic range [6, 9, 15, 16, 25-30, 32, 34, 37, 41, 51, 52], power consumption [8, 21-23, 26-28, 39, 50, 51], area of magnetic circuit [10], coil turns [52], pressure drop [50,51,53,54], and error [43], etc. Sometimes the cost function composed of several subobjective functions and constraints with respective weights is used as the objective function.…”