# The Structure Principle and Dynamic Characteristics of Mechanical-Electric-Hydraulic Dynamic Coupling Drive System and Its Application in Electric Vehicle

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## Abstract

**:**

## 1. Background and Significance

#### 1.1. Introduction

#### 1.2. Challenges of the MEH-DCDS

#### 1.3. Contribution of This Paper

- (1)
- In this paper, a new mechanical-electro-hydraulic dynamic coupling drive system (MEH-DCDS) is proposed, which consists of a permanent magnet synchronous motor and a swash plate plunger pump/motor. It can realize the mutual conversion between mechanical energy, hydraulic energy, and electrical energy.
- (2)
- The dynamic characteristics of MEH-DCDS are analyzed.
- (3)
- MEH-DCDS was applied to electric vehicles, and the feasibility of MEHPC-EV was verified by co-simulation.

#### 1.4. The Structure of the Paper

- (1)
- Section 2 illustrates the structure of MEH-DCDS.
- (2)
- Section 3 introduces the working principle of MEH-DCDS.
- (3)
- Section 4 completes the mathematical model of MEH-DCDS.
- (4)
- Section 5 analyzes the dynamic characteristics of MEH-DCDS.
- (5)
- Section 6 describes the application of MEH-DCDS in electric vehicles.
- (6)
- Section 7 realizes the simulation and analysis of MEHPC-EV.

## 2. The Structure of MEH-DCDS

#### 2.1. Supporting System

#### 2.2. Electric Energy Conversion System

#### 2.3. Mechanical Energy Conversion System

#### 2.4. Hydraulic Energy Conversion System

## 3. The Working Principle of MEH-DCDS

## 4. Mathematical Model of MEH-DCDS

#### 4.1. Hydraulic Power

_{p}is calculated as follows:

_{p}is the pressure difference between the high pressure accumulator and low pressure accumulator; V

_{p}is the displacement of hydraulic pump/motor; and η

_{p}is the mechanical efficiency of hydraulic pump/motor.

_{0}is the pre-charge pressure of the gas; v

_{0}is the accumulator charging volume; p

_{1}is the minimum working pressure of the accumulator; v

_{1}is the volume of gas before the accumulator works; p

_{2}is the maximum working pressure of the accumulator; and v

_{2}is the gas volume after the accumulator works.

_{gas}is the gas pressure; P

_{max}is the maximum pressure; V

_{gas}is the volume of gas; and V

_{0}is the volume of the accumulator.

_{out}is the output pressure of the accumulator.

#### 4.2. Electric Power

_{req}of the motor is confined by the limit torque T

_{lim}:

_{lim}is the minimum torque of the motor; and T

_{max}is the maximum torque of the motor.

_{m}is dictated by the limit torque T

_{lim}, which is calculated using first-order lag.

_{r}is the user-defined time constant.

_{mec}and power loss P

_{lost}of the motor are calculated as follows:

_{e}is the rotational speed of the motor shaft.

_{mec}and electrical power P

_{elec}is as follows:

_{elec}is the electric power; η

_{m}is the motor efficiency; and η

_{g}is the generator efficiency.

_{out}and SOC of the battery are calculated as follows:

_{oc}is the open-circuit voltage of the power battery; R is the internal resistance of the power battery; I is the current of the power battery; SOC is the state of charge of the power battery; SOC

_{0}is the initial state of charge of the power battery; and Q

_{0}is the capacity of the power battery.

## 5. The Dynamic Characteristics of MEH-DCDS

#### 5.1. Analysis of Pump in MEH-DCDS Hydraulic Module

#### 5.2. Analysis of Motor in the MEH-DCDS Hydraulic Module

## 6. Application of MEH-DCDS in Electric Vehicles

## 7. Simulation and Analysis of MEHPC-EV

#### 7.1. Whole Vehicle Simulation Model

#### 7.2. Results and Analysis

## 8. Conclusions

## Author Contributions

## Funding

## Conflicts of Interest

## References

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**Figure 1.**Four major system structures of the mechanical-electric-hydraulic dynamic coupling drive system (MEH-DCDS).

**Figure 4.**Diagram of low pressure accumulator (LPA) pressure and single plunger flow rate at low pressure oil port on pump analysis.

**Figure 5.**Diagram of high pressure accumulator (HPA) pressure and single plunger flow rate at high pressure oil port on pump analysis.

**Figure 7.**Diagram of HPA pressure and single plunger flow rate at high pressure oil port on motor analysis.

**Figure 8.**Diagram of LPA pressure and single plunger flow rate at low pressure oil port on motor analysis.

**Figure 9.**Diagram of Mechanical-Electric-Hydraulic Power Coupling Electric Vehicle (MEHPC-EV) structure and energy flow.

**Figure 11.**Diagram of MEHPC-EV simulation analysis. (

**a**) is the speed curve, (

**b**) is the accumulator pressure curve, (

**c**) is the motor torque curve, and (

**d**) is the battery SOC consumption rate curve.

Components | Main Parameters | Value |
---|---|---|

Loaded mass (m) | 1206 kg | |

Frontal area (A) | 2.28 m^{2} | |

Main parameters of the car | Rolling resistance coefficient (f) | 0.0135 |

Coefficient of air resistance (C_{D}) | 0.32 | |

Wheel width (R) | 290 mm | |

Transmission efficiency (η) | 0.85 | |

High pressure accumulator | Work pressure (P_{1}) | 240–350 Bar |

Volume (V) | 35 L | |

Low pressure accumulator | Work pressure (P_{2}) | 60–220 Bar |

Volume (V) | 35 L | |

Secondary component | Displacement (V_{p}) | 30 mL·r^{−1} |

Motor | Rated power (P_{e}) | 32 KW |

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**MDPI and ACS Style**

Sun, Y.; Zhang, H.; Yang, J.
The Structure Principle and Dynamic Characteristics of Mechanical-Electric-Hydraulic Dynamic Coupling Drive System and Its Application in Electric Vehicle. *Electronics* **2022**, *11*, 1601.
https://doi.org/10.3390/electronics11101601

**AMA Style**

Sun Y, Zhang H, Yang J.
The Structure Principle and Dynamic Characteristics of Mechanical-Electric-Hydraulic Dynamic Coupling Drive System and Its Application in Electric Vehicle. *Electronics*. 2022; 11(10):1601.
https://doi.org/10.3390/electronics11101601

**Chicago/Turabian Style**

Sun, Yue, Hongxin Zhang, and Jian Yang.
2022. "The Structure Principle and Dynamic Characteristics of Mechanical-Electric-Hydraulic Dynamic Coupling Drive System and Its Application in Electric Vehicle" *Electronics* 11, no. 10: 1601.
https://doi.org/10.3390/electronics11101601