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01 理论原理

见arm_cos_f32.c 代码分析文章Odrive0.5.1-FOC电机控制 arm_cos_f32.cpp arm_sin_f32.cpp代码实现（一）-CSDN博客

02 float32_t our_arm_sin_f32(float32_t x)

float32_t our_arm_sin_f32(float32_t x)
{float32_t sinVal, fract, in;                           /* Temporary variables for input, output */uint16_t index;                                        /* Index variable */float32_t a, b;                                        /* Two nearest output values */int32_t n;float32_t findex;/* input x is in radians *//* Scale the input to [0 1] range from [0 2*PI] , divide input by 2*pi */in = x * 0.159154943092f;/* Calculation of floor value of input */n = (int32_t) in;/* Make negative values towards -infinity */if (x < 0.0f){n--;}/* Map input value to [0 1] */in = in - (float32_t) n;/* Calculation of index of the table */findex = (float32_t)FAST_MATH_TABLE_SIZE * in;index = (uint16_t)findex;/* when "in" is exactly 1, we need to rotate the index down to 0 */if (index >= FAST_MATH_TABLE_SIZE) {index = 0;findex -= (float32_t)FAST_MATH_TABLE_SIZE;}/* fractional value calculation */fract = findex - (float32_t) index;/* Read two nearest values of input value from the sin table */a = sinTable_f32[index];b = sinTable_f32[index+1];/* Linear interpolation process */sinVal = (1.0f-fract)*a + fract*b;/* Return the output value */return (sinVal);
}/*** @} end of sin group*/