Question about motor resistance calibration

1

the code which perform motor phase resistance calibrate like

            actual_current_ = Ialpha_beta->first;
            test_voltage_ += (kI * current_meas_period) * (target_current_ - actual_current_);
            I_beta_ += (kIBetaFilt * current_meas_period) * (Ialpha_beta->second - I_beta_);

            float vfactor = 1.0f / ((2.0f / 3.0f) * *vbus_voltage);
            test_mod_ = test_voltage_ * vfactor;

             *mod_alpha_beta = {*test_mod_, 0.0f};
            *ibus = *test_mod_ * actual_current_;


    float get_resistance() {
        return test_voltage_ / target_current_;
    }

is there any reference to descripe how resistance and inductive calibration?

what test_mod_ mean ? why need to mul vbus_voltage?

2

The resistance measurement is a simple PI controller that outputs a set current, then measures the duty cycle required * the bus voltage:

V = IR
V_{bus} * DC \% = I R

The inductance measurement applies a 4kHz square wave and measures the rise/fall time.

1 Like
3

okk . I understand since i see the mainitude of the alpha-beta vector may not large than sqrt(3)/2 . It stand for the percentage of Vbus.

4

but for inductance measure , how can I know the 4kHz square wave from the following code?

struct InductanceMeasurementControlLaw : AlphaBetaFrameController {
    void reset() final {
        attached_ = false;
    }

    ODriveIntf::MotorIntf::Error on_measurement(
            std::optional<float> vbus_voltage,
            std::optional<float2D> Ialpha_beta,
            uint32_t input_timestamp) final
    {
        if (!Ialpha_beta.has_value()) {
            return {Motor::ERROR_UNKNOWN_CURRENT_MEASUREMENT};
        }

        float Ialpha = Ialpha_beta->first;

        if (attached_) {
            float sign = test_voltage_ >= 0.0f ? 1.0f : -1.0f;
            deltaI_ += -sign * (Ialpha - last_Ialpha_);
        } else {
            start_timestamp_ = input_timestamp;
            attached_ = true;
        }

        last_Ialpha_ = Ialpha;
        last_input_timestamp_ = input_timestamp;

        return Motor::ERROR_NONE;
    }

    ODriveIntf::MotorIntf::Error get_alpha_beta_output(
            uint32_t output_timestamp, std::optional<float2D>* mod_alpha_beta,
            std::optional<float>* ibus) final
    {
        test_voltage_ *= -1.0f;
        float vfactor = 1.0f / ((2.0f / 3.0f) * vbus_voltage);
        *mod_alpha_beta = {test_voltage_ * vfactor, 0.0f};
        *ibus = 0.0f;
        return Motor::ERROR_NONE;
    }