ODrive/Firmware/MotorControl/utils.cpp

#include <utils.hpp>
#include <math.h>
#include <float.h>
#include <cmsis_os.h>
#include <stm32f4xx_hal.h>


int SVM(float alpha, float beta, float* tA, float* tB, float* tC) {
    int Sextant;

    if (beta >= 0.0f) {
        if (alpha >= 0.0f) {
            //quadrant I
            if (one_by_sqrt3 * beta > alpha)
                Sextant = 2; //sextant v2-v3
            else
                Sextant = 1; //sextant v1-v2

        } else {
            //quadrant II
            if (-one_by_sqrt3 * beta > alpha)
                Sextant = 3; //sextant v3-v4
            else
                Sextant = 2; //sextant v2-v3
        }
    } else {
        if (alpha >= 0.0f) {
            //quadrant IV
            if (-one_by_sqrt3 * beta > alpha)
                Sextant = 5; //sextant v5-v6
            else
                Sextant = 6; //sextant v6-v1
        } else {
            //quadrant III
            if (one_by_sqrt3 * beta > alpha)
                Sextant = 4; //sextant v4-v5
            else
                Sextant = 5; //sextant v5-v6
        }
    }

    switch (Sextant) {
        // sextant v1-v2
        case 1: {
            // Vector on-times
            float t1 = alpha - one_by_sqrt3 * beta;
            float t2 = two_by_sqrt3 * beta;

            // PWM timings
            *tA = (1.0f - t1 - t2) * 0.5f;
            *tB = *tA + t1;
            *tC = *tB + t2;
        } break;

        // sextant v2-v3
        case 2: {
            // Vector on-times
            float t2 = alpha + one_by_sqrt3 * beta;
            float t3 = -alpha + one_by_sqrt3 * beta;

            // PWM timings
            *tB = (1.0f - t2 - t3) * 0.5f;
            *tA = *tB + t3;
            *tC = *tA + t2;
        } break;

        // sextant v3-v4
        case 3: {
            // Vector on-times
            float t3 = two_by_sqrt3 * beta;
            float t4 = -alpha - one_by_sqrt3 * beta;

            // PWM timings
            *tB = (1.0f - t3 - t4) * 0.5f;
            *tC = *tB + t3;
            *tA = *tC + t4;
        } break;

        // sextant v4-v5
        case 4: {
            // Vector on-times
            float t4 = -alpha + one_by_sqrt3 * beta;
            float t5 = -two_by_sqrt3 * beta;

            // PWM timings
            *tC = (1.0f - t4 - t5) * 0.5f;
            *tB = *tC + t5;
            *tA = *tB + t4;
        } break;

        // sextant v5-v6
        case 5: {
            // Vector on-times
            float t5 = -alpha - one_by_sqrt3 * beta;
            float t6 = alpha - one_by_sqrt3 * beta;

            // PWM timings
            *tC = (1.0f - t5 - t6) * 0.5f;
            *tA = *tC + t5;
            *tB = *tA + t6;
        } break;

        // sextant v6-v1
        case 6: {
            // Vector on-times
            float t6 = -two_by_sqrt3 * beta;
            float t1 = alpha + one_by_sqrt3 * beta;

            // PWM timings
            *tA = (1.0f - t6 - t1) * 0.5f;
            *tC = *tA + t1;
            *tB = *tC + t6;
        } break;
    }

    // if any of the results becomes NaN, result_valid will evaluate to false
    int result_valid =
            *tA >= 0.0f && *tA <= 1.0f
         && *tB >= 0.0f && *tB <= 1.0f
         && *tC >= 0.0f && *tC <= 1.0f;
    return result_valid ? 0 : -1;
}

// based on https://math.stackexchange.com/a/1105038/81278
float fast_atan2(float y, float x) {
    // a := min (|x|, |y|) / max (|x|, |y|)
    float abs_y = fabsf(y);
    float abs_x = fabsf(x);
    // inject FLT_MIN in denominator to avoid division by zero
    float a = MACRO_MIN(abs_x, abs_y) / (MACRO_MAX(abs_x, abs_y) + FLT_MIN);
    // s := a * a
    float s = a * a;
    // r := ((-0.0464964749 * s + 0.15931422) * s - 0.327622764) * s * a + a
    float r = ((-0.0464964749f * s + 0.15931422f) * s - 0.327622764f) * s * a + a;
    // if |y| > |x| then r := 1.57079637 - r
    if (abs_y > abs_x)
        r = 1.57079637f - r;
    // if x < 0 then r := 3.14159274 - r
    if (x < 0.0f)
        r = 3.14159274f - r;
    // if y < 0 then r := -r
    if (y < 0.0f)
        r = -r;

    return r;
}

// Evaluate polynomials using Fused Multiply Add intrisic instruction.
// coeffs[0] is highest order, as per numpy.polyfit
// p(x) = coeffs[0] * x^deg + ... + coeffs[deg], for some degree "deg"
float horner_fma(float x, const float *coeffs, size_t count) {
    float result = 0.0f;
    for (size_t idx = 0; idx < count; ++idx)
        result = fmaf(result, x, coeffs[idx]);
    return result;
}

// Modulo (as opposed to remainder), per https://stackoverflow.com/a/19288271
int mod(int dividend, int divisor){
    int r = dividend % divisor;
    return (r < 0) ? (r + divisor) : r;
}

// @brief: Returns how much time is left until the deadline is reached.
// If the deadline has already passed, the return value is 0 (except if
// the deadline is very far in the past)
uint32_t deadline_to_timeout(uint32_t deadline_ms) {
    uint32_t now_ms = (uint32_t)((1000ull * (uint64_t)osKernelSysTick()) / osKernelSysTickFrequency);
    uint32_t timeout_ms = deadline_ms - now_ms;
    return (timeout_ms & 0x80000000) ? 0 : timeout_ms;
}

// @brief: Converts a timeout to a deadline based on the current time.
uint32_t timeout_to_deadline(uint32_t timeout_ms) {
    uint32_t now_ms = (uint32_t)((1000ull * (uint64_t)osKernelSysTick()) / osKernelSysTickFrequency);
    return now_ms + timeout_ms;
}

// @brief: Returns a non-zero value if the specified system time (in ms)
// is in the future or 0 otherwise.
// If the time lies far in the past this may falsely return a non-zero value.
int is_in_the_future(uint32_t time_ms) {
    return deadline_to_timeout(time_ms);
}

// @brief: Returns number of microseconds since system startup
uint32_t micros(void) {
    register uint32_t ms, cycle_cnt;
    do {
        ms = HAL_GetTick();
        cycle_cnt = TIM_TIME_BASE->CNT;
     } while (ms != HAL_GetTick());

    return (ms * 1000) + cycle_cnt;
}

// @brief: Busy wait delay for given amount of microseconds (us)
void delay_us(uint32_t us)
{
    uint32_t start = micros();
    while (micros() - start < (uint32_t) us) {
        __ASM("nop");
    }
}