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Research on Motor Control Algorithm of Automotive Electric Brake Booster
DOI: 10.12677/MOS.2022.114112, PDF , HTML, XML, 下载: 145  浏览: 237  科研立项经费支持

Abstract: Electric brake booster is one of the key and difficult technologies of modern vehicles, which is directly related to the realization of vehicle system functions. The research on motor control strategy becomes very critical. At present, this technology is mainly controlled by foreign companies and research on this technology has become one of the urgent tasks of OEMs. First of all, the working mechanism of the electric brake booster is analyzed and compared, the PMSM and BLDC are compared, and the main reason for choosing the vector control strategy as the power motor control is clarified. Second, analyzing the characteristics of the vector control strategy and its control logic is described in detail, the project of the core part of the coordinate transformation and the SVPWM algorithm formula derivation and mathematical modeling, demonstrates the feasibility of this set of logic in theory, set up eight kinds of switch state, the corresponding relationship between phase voltage and line voltage sector which is used to describe the voltage space vector diagram. Then, the simulation model of vector control strategy is built by MATLAB/Simulink, and the position, speed and torque are taken as the target input, and the current loop, speed loop and position loop are respectively controlled by PI controller from inside to outside. Finally, the simulation model is used to verify the current loop, speed loop and position loop, and the control accuracy is 99%, 96% and 99%, respectively. The system delay is controlled within 0.02 seconds, and the amplitude fluctuation of the motor is less, which is within a reasonable range, thus proving the correctness and effectiveness of the simulation model.

1. 引言

2. 电动制动助力器及控制算法

2.1. 电动制动助力器工作机理

2.2. 制动电机控制算法

Table 1. The main differences between BLDC and PMSM

3. 电机矢量控制策略

3.1. 矢量控制算法

(a) 60˚受力 (b) 90˚受力

Figure 1. Six-step commutation method rotor force

(a) −120˚ (b) 120˚

Figure 2. Different angle FOC controls rotor force

Figure 3. Basic block diagram of vector control

1) 首先测量三相定子电流 ${i}_{A}、{i}_{B}、{i}_{C}$，由于在控制系统中 ${i}_{A}+{i}_{B}+{i}_{C}=0$，因此可以测量任两相的电流就可得到剩下一项的电流。

2) 测得三相电流后将三相电流经过Clarke变换得到具有变量 ${i}_{\alpha }、{i}_{\beta }$ 的两轴系统。从定子角度来看， ${i}_{\alpha }、{i}_{\beta }$ 是相互正交的时变电流值。

3) ${i}_{\alpha }、{i}_{\beta }$ 又经Park变换得到 ${i}_{q}、{i}_{d}$${i}_{q}、{i}_{d}$ 为变换到旋转坐标系下的正交电流。在稳态条件下， ${i}_{q}、{i}_{d}$ 是常量。

4) 误差信号由 ${i}_{q}、{i}_{d}$ 的实际值和各自的参考值(目标值) ${i}_{q}^{*}、{i}_{d}^{*}$ 进行比较而获得： ${i}_{d}$ 的参考值控制转子磁通； ${i}_{q}$ 的参考值控制电机的转矩；误差信号是PI控制器的输入；控制器的输出为 ${v}_{q}、{v}_{d}$，即要施加到电机上的电压矢量，一般FOC算法的控制器采用经典的PI线性控制器，这样可以使系统具有良好的线性特性。

5) 由旋转变压器获得转子位置信息，新的位置信息可告知FOC算法下一个电压矢量在何处，并且位置信息为位置环和转速环提供计算参数。

6) 通过使用新的角度，可将PI控制器的 ${v}_{q}、{v}_{d}$ 输出值逆变到静止参考坐标系。该计算将产生下一个正交电压值 ${v}_{\alpha }、{v}_{\beta }$

7) ${v}_{\alpha }、{v}_{\beta }$ 值经过SVPWM算法得到驱动逆变器的PWM信号，经过逆变器处理最终输出到三相电驱动电机。

3.2. 坐标变换与数学建模

Figure 4. Motor coordinate system

$\left\{\begin{array}{l}{i}_{a}={i}_{s}\mathrm{cos}\omega t\hfill \\ {i}_{b}={i}_{s}\mathrm{cos}\left(\omega t-\frac{2}{3}\text{π}\right)\hfill \\ {i}_{c}={i}_{s}\mathrm{cos}\left(\omega t+\frac{2}{3}\text{π}\right)\hfill \end{array}$ (1)

$\begin{array}{c}{i}_{\alpha }=\frac{3}{2}{i}_{a}\\ {i}_{\beta }=\frac{\sqrt{3}}{2}{i}_{a}+\sqrt{3}{i}_{b}\end{array}$ (2)

Figure 5. Diagram of Park transformation

$\left\{\begin{array}{l}{i}_{d}={i}_{\alpha }\mathrm{cos}{\theta }_{d}+{i}_{\beta }\mathrm{sin}{\theta }_{d}\hfill \\ {i}_{q}={i}_{\beta }\mathrm{cos}{\theta }_{d}-{i}_{\alpha }\mathrm{sin}{\theta }_{d}\hfill \end{array}$ (3)

$\left\{\begin{array}{l}{i}_{\alpha }={i}_{d}\mathrm{cos}{\theta }_{d}-{i}_{q}\mathrm{sin}{\theta }_{d}\hfill \\ {i}_{\beta }={i}_{q}\mathrm{cos}{\theta }_{d}+{i}_{d}\mathrm{sin}{\theta }_{d}\hfill \end{array}$ (4)

3.3. SVPWM控制策略

${S}_{x}x=a,b,c\left\{\begin{array}{l}1上桥臂导通\hfill \\ 0下桥臂导通\hfill \end{array}$ (5)

Figure 6. Schematic diagram of three-phase inverter

Table 2. Correspondence between phase voltage and line voltage

Figure 7. Sector division

3.4. 助力电机控制策略仿真与验证

Figure 8. Vector control algorithm model

${T}_{e}=\frac{3}{2}{p}_{n}{i}_{q}{\psi }_{f}$ (6)

3.4.1. 电流环仿真与验证

Figure 9. Three-phase current waveform

Figure 10. Current waveform after Clark transformation

3.4.2. 速度环仿真与验证

Figure 11. Current waveform after Park transformation

Figure 12. Speed waveform

3.4.3. 位置环仿真与验证

Figure 13. Position following waveform under the sinusoidal signal input

Figure 14. Position following waveform under step signal input

4. 结束语

1) 研究了矢量控制算法来控制助力电机矢量控制的相关策略，并从理论计算和坐标变换的推导，论证了控制策略的合理性和正确性。

2) 提出了电机助力空间矢量脉宽调制的控制策略，通过对相电压和线电压的三相互差120˚角度对比和分析，说明SVPWM具有谐波消除效果好和便于微控制的优点，适合解决系统控制和信号失真的问题。

NOTES

*通讯作者。

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