Odrive源码分析(七) Park逆变换
Odrive中FOC部分代码分散在各个对象中,并不是集中在某一块,所以试图在某一段代码就能得到FOC全貌是不现实的。
先看下FOC的整个流程:
控制变量到三相电流输出的关键部分分为Park逆变换和SVPWM。本文主要讨论逆park变换在odrive中的代码实现。、
代码主要在FieldOrientedController::get_alpha_beta_output函数中。
ODriveIntf::MotorIntf::Error FieldOrientedController::get_alpha_beta_output(uint32_t output_timestamp, std::optional<float2D>* mod_alpha_beta,std::optional<float>* ibus) {if (!vbus_voltage_measured_.has_value() || !Ialpha_beta_measured_.has_value()) {// FOC didn't receive a current measurement yet.return Motor::ERROR_CONTROLLER_INITIALIZING;} else if (abs((int32_t)(i_timestamp_ - ctrl_timestamp_)) > MAX_CONTROL_LOOP_UPDATE_TO_CURRENT_UPDATE_DELTA) {// Data from control loop and current measurement are too far apart.return Motor::ERROR_BAD_TIMING;}// TODO: improve efficiency in case PWM updates are requested at a higher// rate than current sensor updates. In this case we can reuse mod_d and// mod_q from a previous iteration.if (!Vdq_setpoint_.has_value()) {return Motor::ERROR_UNKNOWN_VOLTAGE_COMMAND;} else if (!phase_.has_value() || !phase_vel_.has_value()) {return Motor::ERROR_UNKNOWN_PHASE_ESTIMATE;} else if (!vbus_voltage_measured_.has_value()) {return Motor::ERROR_UNKNOWN_VBUS_VOLTAGE;}auto [Vd, Vq] = *Vdq_setpoint_;float phase = *phase_;float phase_vel = *phase_vel_;float vbus_voltage = *vbus_voltage_measured_;std::optional<float2D> Idq;// Park transformif (Ialpha_beta_measured_.has_value()) {auto [Ialpha, Ibeta] = *Ialpha_beta_measured_;float I_phase = phase + phase_vel * ((float)(int32_t)(i_timestamp_ - ctrl_timestamp_) / (float)TIM_1_8_CLOCK_HZ);float c_I = our_arm_cos_f32(I_phase);float s_I = our_arm_sin_f32(I_phase);Idq = {c_I * Ialpha + s_I * Ibeta,c_I * Ibeta - s_I * Ialpha};Id_measured_ += I_measured_report_filter_k_ * (Idq->first - Id_measured_);Iq_measured_ += I_measured_report_filter_k_ * (Idq->second - Iq_measured_);} else {Id_measured_ = 0.0f;Iq_measured_ = 0.0f;}float mod_to_V = (2.0f / 3.0f) * vbus_voltage;float V_to_mod = 1.0f / mod_to_V;float mod_d;float mod_q;if (enable_current_control_) {// Current control modeif (!pi_gains_.has_value()) {return Motor::ERROR_UNKNOWN_GAINS;} else if (!Idq.has_value()) {return Motor::ERROR_UNKNOWN_CURRENT_MEASUREMENT;} else if (!Idq_setpoint_.has_value()) {return Motor::ERROR_UNKNOWN_CURRENT_COMMAND;}auto [p_gain, i_gain] = *pi_gains_;auto [Id, Iq] = *Idq;auto [Id_setpoint, Iq_setpoint] = *Idq_setpoint_;float Ierr_d = Id_setpoint - Id;float Ierr_q = Iq_setpoint - Iq;// Apply PI control (V{d,q}_setpoint act as feed-forward terms in this mode)mod_d = V_to_mod * (Vd + v_current_control_integral_d_ + Ierr_d * p_gain);mod_q = V_to_mod * (Vq + v_current_control_integral_q_ + Ierr_q * p_gain);// Vector modulation saturation, lock integrator if saturated// TODO make maximum modulation configurablefloat mod_scalefactor = 0.80f * sqrt3_by_2 * 1.0f / std::sqrt(mod_d * mod_d + mod_q * mod_q);if (mod_scalefactor < 1.0f) {mod_d *= mod_scalefactor;mod_q *= mod_scalefactor;// TODO make decayfactor configurablev_current_control_integral_d_ *= 0.99f;v_current_control_integral_q_ *= 0.99f;} else {v_current_control_integral_d_ += Ierr_d * (i_gain * current_meas_period);v_current_control_integral_q_ += Ierr_q * (i_gain * current_meas_period);}} else {// Voltage control modemod_d = V_to_mod * Vd;mod_q = V_to_mod * Vq;}// Inverse park transformfloat pwm_phase = phase + phase_vel * ((float)(int32_t)(output_timestamp - ctrl_timestamp_) / (float)TIM_1_8_CLOCK_HZ);float c_p = our_arm_cos_f32(pwm_phase);float s_p = our_arm_sin_f32(pwm_phase);float mod_alpha = c_p * mod_d - s_p * mod_q;float mod_beta = c_p * mod_q + s_p * mod_d;// Report final applied voltage in stationary frame (for sensorless estimator)final_v_alpha_ = mod_to_V * mod_alpha;final_v_beta_ = mod_to_V * mod_beta;*mod_alpha_beta = {mod_alpha, mod_beta};if (Idq.has_value()) {auto [Id, Iq] = *Idq;*ibus = mod_d * Id + mod_q * Iq;power_ = vbus_voltage * (*ibus).value();}return Motor::ERROR_NONE;
}
下面主要分析上述函数的具体实现:
step1 在进入本函数计算之前,必须已经完成线电压的测量和相电流的测量,同时要保证时效性,如下所示:
//本函数调用前,在ControlLoop_IRQHandler函数中已经完成了测量。所以本条件必然满足。
if (!vbus_voltage_measured_.has_value() || !Ialpha_beta_measured_.has_value()) {// FOC didn't receive a current measurement yet.return Motor::ERROR_CONTROLLER_INITIALIZING;
}
//i_timestamp_和ctrl_timestamp_实际上是同一个值,因为都是外部传进来的
else if (abs((int32_t)(i_timestamp_ - ctrl_timestamp_)) > MAX_CONTROL_LOOP_UPDATE_TO_CURRENT_UPDATE_DELTA) {// Data from control loop and current measurement are too far apart.return Motor::ERROR_BAD_TIMING;
}
step2 相关控制数据检查,如下所示:
//判断是否已经计算出Vdq_setpoint(motor.cpp已通过PID计算得出)
if (!Vdq_setpoint_.has_value()) {return Motor::ERROR_UNKNOWN_VOLTAGE_COMMAND;
}
//判断是否已经得到电角度和电角速度(已经通过encode.cpp计算得出)
else if (!phase_.has_value() || !phase_vel_.has_value()) {return Motor::ERROR_UNKNOWN_PHASE_ESTIMATE;
}
//这里其实重复判断了...
else if (!vbus_voltage_measured_.has_value()) {return Motor::ERROR_UNKNOWN_VBUS_VOLTAGE;
}//变量提取
auto [Vd, Vq] = *Vdq_setpoint_;
float phase = *phase_;
float phase_vel = *phase_vel_;
float vbus_voltage = *vbus_voltage_measured_;
step3 通过测量到的电流进行Park变换转换到观察到的DQ,如下所示:
// 检查AB空间数据有效性,Ialpha_beta_measured_是通过FieldOrientedController父类 AlphaBetaFrameController::on_measurement计算得出。
if (Ialpha_beta_measured_.has_value()) {auto [Ialpha, Ibeta] = *Ialpha_beta_measured_;//这里得到电流测量时刻的电角度,这里很严谨,虽然i_timestamp_和 ctrl_timestamp_其实是相等的值,但是软件保留了拓展能力。float I_phase = phase + phase_vel * ((float)(int32_t)(i_timestamp_ - ctrl_timestamp_) / (float)TIM_1_8_CLOCK_HZ);//计算Park变换得到测量的DQ值用于后面的电流环闭环float c_I = our_arm_cos_f32(I_phase);float s_I = our_arm_sin_f32(I_phase);Idq = {c_I * Ialpha + s_I * Ibeta,c_I * Ibeta - s_I * Ialpha};Id_measured_ += I_measured_report_filter_k_ * (Idq->first - Id_measured_);Iq_measured_ += I_measured_report_filter_k_ * (Idq->second - Iq_measured_);
} else {Id_measured_ = 0.0f;Iq_measured_ = 0.0f;
}//相关中间变量计算
//这里mod_to_V是线电压的2/3.实际上这是相电压能达到的最大值,这里可以理解为SVPWM扇区的内接圆半径。
float mod_to_V = (2.0f / 3.0f) * vbus_voltage;
float V_to_mod = 1.0f / mod_to_V;
float mod_d;
float mod_q;
step4 电流环控制,如下所示:
//只有在开启了电流闭环控制时以下代码才会生效
//当motor_.config_.motor_type 为 Motor::MOTOR_TYPE_GIMBA 云台电机时,不使用电流控制模式而采用电压控制模式。
if (enable_current_control_) {//检查是否配置了PI参数if (!pi_gains_.has_value()) {return Motor::ERROR_UNKNOWN_GAINS;} //电流环控制必须已经得到了Idq(上面计算已经得出)else if (!Idq.has_value()) {return Motor::ERROR_UNKNOWN_CURRENT_MEASUREMENT;} //是否存在控制量Idq_setpoint_(该变量已经由motor.cpp中计算得出)else if (!Idq_setpoint_.has_value()) {return Motor::ERROR_UNKNOWN_CURRENT_COMMAND;}//语法糖auto [p_gain, i_gain] = *pi_gains_;auto [Id, Iq] = *Idq;auto [Id_setpoint, Iq_setpoint] = *Idq_setpoint_;//使用PI控制计算得出mod_q,mod_d,这里mod_q和mod_d可以理解为mod_to_V的倍数。float Ierr_d = Id_setpoint - Id;float Ierr_q = Iq_setpoint - Iq;//Vd/Vq作为前馈量加入到电流环PI控制中mod_d = V_to_mod * (Vd + v_current_control_integral_d_ + Ierr_d * p_gain);mod_q = V_to_mod * (Vq + v_current_control_integral_q_ + Ierr_q * p_gain);// Vector modulation saturation, lock integrator if saturated// TODO make maximum modulation configurablefloat mod_scalefactor = 0.80f * sqrt3_by_2 * 1.0f / std::sqrt(mod_d * mod_d + mod_q * mod_q);if (mod_scalefactor < 1.0f) {mod_d *= mod_scalefactor;mod_q *= mod_scalefactor;// TODO make decayfactor configurablev_current_control_integral_d_ *= 0.99f;v_current_control_integral_q_ *= 0.99f;} else {v_current_control_integral_d_ += Ierr_d * (i_gain * current_meas_period);v_current_control_integral_q_ += Ierr_q * (i_gain * current_meas_period);}} else {//直接使用Vd/Vq 电压控制,得到控制量为mod_to_V的倍数。mod_d = V_to_mod * Vd;mod_q = V_to_mod * Vq;
}
step5 正式完成park逆变换,如下所示:
//这里得到电角度,这里output_timestamp的时间会大于ctrl_timestamp_(理论上真好会大于一个控制周期),此时的电角度比测量电流时的电角度是不同的。
float pwm_phase = phase + phase_vel * ((float)(int32_t)(output_timestamp - ctrl_timestamp_) / (float)TIM_1_8_CLOCK_HZ);
float c_p = our_arm_cos_f32(pwm_phase);
float s_p = our_arm_sin_f32(pwm_phase);
float mod_alpha = c_p * mod_d - s_p * mod_q;
float mod_beta = c_p * mod_q + s_p * mod_d;// Report final applied voltage in stationary frame (for sensorless estimator)
final_v_alpha_ = mod_to_V * mod_alpha;
final_v_beta_ = mod_to_V * mod_beta;//得到最终计算出的AB控制量(后面会输入到SVPWM模块逆变出三相电流)
*mod_alpha_beta = {mod_alpha, mod_beta};//计算出相关数据
if (Idq.has_value()) {auto [Id, Iq] = *Idq;//计算出线电流*ibus = mod_d * Id + mod_q * Iq;//计算功率(电压和电流乘积)power_ = vbus_voltage * (*ibus).value();
}
完成Park逆变换后,下一步就直接送入了SVPWM模块了。