# An Anti-Interference Control Method for an AGV-WPT System Based on UIO-SMC

^{1}

^{2}

^{*}

## Abstract

**:**

## 1. Introduction

^{13}and other observers of the same structure, it is necessary to consider the complexity of matching multiple parameters. Therefore, in the servo system, this type of observer is more popular. Considering that id and iq or torque and speed need to be controlled in the motor system, it is more appropriate to use an SMO

^{16}observer. The SMO has the feature of simultaneously observing two variables, but some noise will be introduced. In the WPT system, in order to avoid the complicated design of the observer from introducing difficulty to the system control, UIO

^{17}can be considered, which is simple in design and convenient to construct. In this paper, UIO is used in the WPT system, which is designed to observe mutual inductance disturbances, and reduces the initial observation error of UIO. The method proposed in this paper is suitable for use in WPT systems, where the mutual inductance changes and the output waveform is required to be stable.

## 2. System Topology

_{L}. L

_{p}and L

_{s}are the self-inductance of the primary and secondary coils, C

_{p}is the compensation capacitance of the primary coil, and M is the mutual inductance value between the primary and secondary coils.

_{in}, and $\omega =2\pi f$, and f is the resonant operating frequency (Hz) of the system. According to the SAEJ2954 international standard, the resonant operating frequency f of the system in this paper is set to 85 kHz.

_{in}of the output voltage of the high-frequency inverter is as follows:

_{in}and the secondary coil of current term I

_{P}is as follows:

_{s}of the secondary voltage is shown in Formula (4):

_{out}of the rectifier bridge output voltage can be equivalent to Formula (5):

_{out}can be expressed as follows:

## 3. Control System Design

#### 3.1. Sliding Mode Controller Design

#### 3.2. Unknown Input Observer Design

_{1}uses the exponential function to converge. $0<\sigma <1$, according to the system, selects $\sigma =0.99$, k = T/Ts, where k is the current time divided by the control period. The selection of filter time constant $\lambda $ was analyzed in [23], and $\lambda $ = 0.001 was selected here for better tracking.

_{L}and C

_{f}. In order to reduce the interference of system parameter deviation and load change on the control function, when selecting system control parameters, they should meet the following condition:

## 4. Verification and Discussion

#### 4.1. System Structure Design

_{f}and C

_{f}, and the parameters of L

_{f}and C

_{f}are smaller, for the dynamic response performance and stability of the system, the control parameters need to be enlarged by corresponding multiples. Based on these considerations, the sliding mode control parameters are selected as follows:

#### 4.2. Analysis of Simulation Result

#### 4.2.1. Controller Performance

#### 4.2.2. Observer Performance

^{13}and SMO

^{16}are used in this section to observe disturbance ${\phi}_{1}(t)$. The experimental results are shown in Figure 5. It can be found that the proposed UIO has better observation performance than ESO and SMO. Comparing the performance of UIO and ESO, it can be seen that although ESO can observe system disturbances, compared with UIO, it has a larger initial observation error.

#### 4.3. Analysis of Experimental Results

#### 4.3.1. Coil Offset Experiments

_{0}, load output current i

_{0}, and secondary rectifier current i

_{s}when the coil changes from a vertical distance of 7 to 4 cm and then back to 7 cm.

#### 4.3.2. Load Mutation Experiments

## 5. Conclusions

^{13}and SMO

^{16}is made. The experimental results show that the robustness and dynamic performance of the proposed control method in WPT systems are better than those of traditional PI and sliding mode control. This method can be used to solve the disturbance problem caused by coil offset and load change during wireless charging of AGVs. In this paper, an uncontrolled rectifier bridge is selected at the rectifier side. In order to better integrate battery BMS management in the future, it can be changed as a semi-controlled or controllable full bridge to realize the regulation of power and efficiency under the condition of original anti-disturbance stable voltage output.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

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**Figure 3.**Reference voltage tracking: (

**a**) sudden change of load resistance: 5 Ω → 20 Ω → 5 Ω; (

**b**) mutual inductance change: 17 μH → 32 μH → 17 μH.

**Figure 4.**Disturbance and value estimated by observer: (

**a**) estimated value of disturbance φ1; (

**b**) estimated value of disturbance φ2. In the graphs, a indicates estimated amount of disturbance, b indicates UIO without adding prediction equation, and c indicates UIO added to prediction equation.

Observer Type | ESO^{13} | SMO^{16} | UIO^{17} | Observer in this Paper |
---|---|---|---|---|

Number of parameters to be adjusted | 3 | 2 | 1 | 1 |

Whether to add wave filter | No | No | Yes | Yes |

Other features | Designed ESO can reduce control gain of SMC | Stability of SMC + SMO is proven; chattering caused by constant velocity approaching law in SMO is inevitable | Proposed and used in servo mechanism | Initial observation error is small; mutual inductance disturbance observed in WPT system, which can suppress controller chattering |

Description/Unit | Parameter | Value |
---|---|---|

Inverter input DC voltage (V) | E | 18 |

Inverter frequency (kHz) | f | 85 |

Primary side topological inductance (μH) | L1 | 31 |

Primary side coil inductance (μH) | Lp | 79 |

Primary sideline compensation capacitor (nF) | Cp | 33 |

Primary topology resonance capacitance (nF) | C1 | 47 |

Secondary side coil inductance (μH) | Ls | 70 |

secondary side resonant capacitance (nF) | Cs | 56 |

Filter inductance (μH) | Lf | 100 |

Filter capacitor (μF) | Cf | 470 |

Control Parameter | Value |
---|---|

λ | 0.001 |

σ | 0.99 |

α | 6.6 × 10^{6} |

β | 3 × 10^{13} |

η | 1 |

kp | 1.2 |

ki | 180 |

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**MDPI and ACS Style**

Hou, J.; Huang, W.; Huang, D.
An Anti-Interference Control Method for an AGV-WPT System Based on UIO-SMC. *World Electr. Veh. J.* **2021**, *12*, 220.
https://doi.org/10.3390/wevj12040220

**AMA Style**

Hou J, Huang W, Huang D.
An Anti-Interference Control Method for an AGV-WPT System Based on UIO-SMC. *World Electric Vehicle Journal*. 2021; 12(4):220.
https://doi.org/10.3390/wevj12040220

**Chicago/Turabian Style**

Hou, Jun, Weidong Huang, and Dongxiao Huang.
2021. "An Anti-Interference Control Method for an AGV-WPT System Based on UIO-SMC" *World Electric Vehicle Journal* 12, no. 4: 220.
https://doi.org/10.3390/wevj12040220