# Energy Saving Performance of Agricultural Tractor Equipped with Mechanic-Electronic-Hydraulic Powertrain System

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## Abstract

**:**

## 1. Introduction

## 2. Principle of Powertrain Configuration

#### 2.1. Driving Mode Analysis

_{1}~i

_{3}are the transmission ratios of gear pairs, and e is the displacement ratio of the hydraulic system.

#### 2.2. Transmission Mode Analysis

## 3. Powertrain Modeling

#### 3.1. Engine Model

#### 3.2. Motor Model

#### 3.3. Battery Model

#### 3.4. Transmission Model

#### 3.5. Tractor Model

## 4. Tractor Control Strategy

#### 4.1. Overall Control Strategy

#### 4.2. HMT Transmission Ratio Control Strategy

#### 4.3. Mode Division of Rule-Based

_{opt}is the optimal engine torque; T

_{1}is the maximum torque of pure electric drive mode; T

_{2}is the maximum torque of driving charging; T

_{3}is the maximum torque of pure engine drive mode; T

_{4}is the maximum torque of speed coupling drive; n

_{e_max}is the rated speed of engine; SOC

_{h}is the higher limit of the SOC efficient region; SOC

_{l}is the lower limit of the SOC efficient region; v

_{sta}

_{1}is the start completion speed of start type 1; v

_{sta}

_{2}is the start completion speed of start type 2; i

_{g_min}is the minimum transmission ratio of HMT; s is the equivalence factor.

_{g}, T

_{req}, and v. Firstly, whether the tractor needs to start is judged, and if so, determine the start type according to the required torque; for example, if the tractor is in the ploughing or transport or other starting conditions that require it to provide a large torque, the starting type (1) can be selected; if the tractor is in the transit condition, the required torque is small and SOC is sufficient, the starting type (2) can be selected. After the tractor reaches the start completion speed that is to switch to the operating mode, when the transmission mode is mechanical transmission, if stepless speed change is required then only the pure electric drive mode can meet the requirements, otherwise stepless speed change can be achieved through the engine-driven hydro-mechanical transmission.

_{g}< i

_{g}

_{_min}reflects the tractor’s requirement for higher input speed. If so, the required speed is greater than the rated engine speed and SOC is high, it can be switched to the speed coupling drive mode to meet the requirement of higher speed; if SOC is low, the tractor can only be driven by the engine. If i

_{g}≥ i

_{g}

_{_min}, the tractor’s speed requirement is lower, according to the required torque, and SOC can choose the most appropriate driving mode in turn: pure electric drive, pure engine drive, torque coupling driving charging, and torque coupling motor assist.

#### 4.4. Optimization Strategy with Minimal Equivalent Fuel Consumption

## 5. Simulation and Experiment

#### 5.1. Simulation Modeling

#### 5.2. Test Bench and Principle

#### 5.3. Simulation and Test of Tractor Operation

#### 5.3.1. Ploughing Analysis

#### 5.3.2. Harvest Analysis

#### 5.3.3. Transport Analysis

## 6. Discussion

- In terms of structural design, compared to a typical hydro-mechanical transmission, this paper uses only a single planetary row for the merging of the hydraulic and mechanical power, which has fewer planetary gears compared to the structure mentioned in the paper [41]. Moreover, the advantages of hybrid power can be exploited without the need for more powerful electrical equipment.
- The speed ratio control strategy and energy management strategy are designed for the hybrid tractor, and three tractor operating conditions of the whole tractor is simulated. Moreda pointed out that there are no standard test conditions for hybrid tractors, however, the data from the actual tractor operation is reliable and can be a reference for the research of hybrid tractors [42].
- The feasibility of the MEH-PS scheme was confirmed by comparing the difference between bench test and simulation data within 5% and comparing the fuel consumption of PowerShift tractors and CVT tractors published by DLG under the corresponding operating conditions. It was found that the device has the lowest fuel consumption, which further confirms the reliability of the scheme, and the scheme has practical value for energy saving of agricultural machinery.

## 7. Conclusions

## 8. Patents

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## Appendix A

Item | Parameter | Specification |
---|---|---|

Tractor | Mass | 8260 kg |

Radius of wheels | 750 mm | |

Engine | Rated power | 132 kW@2200 r/min |

Maximum torque | 750 Nm@1300 r/min | |

Minimum fuel consumption | 203 g/kW·h@1500 r/min | |

Motor | Rated power | 45 kW |

Rated speed | 3300 r/min | |

Maximum speed | 11,000 r/min | |

Battery | Capacity | 45 Ah |

Nominal voltage | 360 V | |

Driveline | Transmission ratio | 0.63~4.33 |

Gear ratio of main reducer | 6.4 | |

Gear ratio of wheel reducer | 3.7 |

Load Type | Test Cycle | Engine Speed (r/min) | Driving Speed (km/h) | Absolute Fuel Consumption (L/h) | BSFC (g/kWh) | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|

PowerShift | CVT | MEH-PS | PowerShift | CVT | MEH-PS | PowerShift | CVT | MEH-PS | PowerShift | CVT | MEH-PS | ||

Drawbar work | PL1 | 1407 | 1348 | 1684 | 7.1 | 6.7 | 7.0 | 37.8 | 34.2 | 26.9 | 247 | 251 | 208 |

PL2 | 1312 | 1393 | 1407 | 8.5 | 8.8 | 9.1 | 27.9 | 27.8 | 22.7 | 246 | 250 | 205 | |

Drawbar + PTO work | PTO1 | 1663 | 1622 | 1558 | 5.6 | 5.7 | 5.7 | 39.9 | 37.6 | 32.5 | 227 | 230 | 206 |

PTO2 | 1424 | 1664 | 1567 | 5.5 | 5.9 | 5.8 | 28.8 | 27.9 | 22.6 | 227 | 236 | 207 | |

PTO3 | 1433 | 1684 | 1574 | 5.5 | 5.9 | 5.8 | 18.1 | 18.1 | 15.7 | 249 | 266 | 207 | |

Transport work | TR60 | 1989 | 1448 | 2140 | 60.3 | 61.2 | 60.1 | 33.2 | 37.4 | 27.4 | 573 | 580 | 259 |

TR50 | 1908 | 1201 | 2135 | 51.1 | 50.4 | 50.0 | 30.0 | 28.4 | 12.6 | 539 | 610 | 266 | |

TR40 | 1478 | 1015 | 2079 | 40.8 | 40.2 | 40.0 | 20.3 | 21.0 | 7.09 | 266 | 643 | 236 |

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**Figure 6.**Power flow of powertrain system. (CM: coupling mechanism; ICE: internal combustion engine; VDP: variable displacement pump; FDM: fixed displacement motor; DA: drive axle; P

_{PTO}: power take-off power; P

_{H}: hydraulic system power; P

_{t}: traction power.).

**Figure 14.**Test bench: 1. Oil cooling system; 2. motor cooling system; 3. variable frequency motor; 4. driving motor and coupling mechanism; 5. HMT; 6. central transmission device; 7. power cabinet of dynamometer; 8. electrical dynamometer; 9. data acquisition cabinet.

**Figure 17.**Results of the ploughing operation: (

**a**) tractor speed, (

**b**) transmission ratio and efficiency, (

**c**) engine speed and BSFC, (

**d**) system efficiency and instant fuel consumption, (

**e**) SOC curve, (

**f**) simulation and test fuel consumption.

**Figure 19.**Results of the harvest operation: (

**a**) tractor speed, (

**b**) transmission ratio and efficiency, (

**c**) engine speed and BSFC, (

**d**) power of related components, (

**e**) system efficiency and instant fuel consumption, (

**f**) SOC curve, (

**g**) simulation and test fuel consumption.

**Figure 20.**Results of the transport operation: (

**a**) tractor speed, (

**b**) transmission ratio, (

**c**) engine and motor speed (

**d**) driving mode, (

**e**) SOC curve, (

**f**) simulation and test fuel consumption.

**Figure 22.**Fuel consumption of tractors equipped with different transmissions in different test cycles.

Driving Mode | C1 | C2 | C3 | B1 |
---|---|---|---|---|

Pure electric drive (1) | ▲ | ▲ | ||

Pure engine drive (2) | ▲ | ▲ | ||

Torque coupling drive (3) | ▲ | ▲ | ▲ | |

Speed coupling drive (4) | ▲ | ▲ |

Gear | C4 | C5 | B1 | B2 | B3 | B4 | B5 | i_{g} |
---|---|---|---|---|---|---|---|---|

F(H) | ▲ | ▲ | ▲ | $-\frac{{i}_{1}{i}_{2}{k}_{4}(1+{k}_{2})}{e}$ | ||||

R(H1) | ▲ | ▲ | ▲ | $\frac{{i}_{1}{i}_{2}{k}_{4}(1+{k}_{2})(1+{k}_{3})}{e({k}_{3}{k}_{4}-1)}$ | ||||

R(H2) | ▲ | ▲ | ▲ | $\frac{{i}_{1}{i}_{2}(1+{k}_{2})}{e}$ | ||||

F (HM1) | ▲ | ▲ | ▲ | $\frac{{i}_{1}{i}_{2}{k}_{1}{k}_{4}(1+{k}_{2})(1+{k}_{3})}{\left[{k}_{1}e+{k}_{2}{i}_{1}{i}_{2}(1+{k}_{1})\right]({k}_{3}{k}_{4}-1)}$ | ||||

F (HM2) | ▲ | ▲ | ▲ | $\frac{{i}_{1}{i}_{2}{k}_{1}(1+{k}_{2})}{{k}_{1}e+{k}_{2}{i}_{1}{i}_{2}(1+{k}_{1})}$ | ||||

R(HM) | ▲ | ▲ | ▲ | $-\frac{{k}_{1}{k}_{4}(1+{k}_{2})}{{k}_{2}(1+{k}_{1})}$ | ||||

F (M1) | ▲ | ▲ | ▲ | $\frac{{k}_{1}{k}_{4}(1+{k}_{2})(1+{k}_{3})}{{k}_{2}(1+{k}_{1})({k}_{3}{k}_{4}-1)}$ | ||||

F (M2) | ▲ | ▲ | ▲ | $\frac{{k}_{1}(1+{k}_{2})}{{k}_{2}(1+{k}_{1})}$ | ||||

R(M) | ▲ | ▲ | ▲ | $-\frac{{k}_{1}{k}_{4}(1+{k}_{2})}{{k}_{2}(1+{k}_{1})}$ |

_{g}is the transmission ratio.

Parameters | k_{1} | k_{2} | k_{3} | k_{4} | i_{1} | i_{2} |
---|---|---|---|---|---|---|

Value | 1.80 | 1.60 | 1.65 | 1.65 | 0.62 | 1.00 |

Time (s) | Tractor Speed (km/h) | Ploughing Depth (m) |
---|---|---|

0~100 | 9.00 | 0.10 |

100~200 | 9.00 | 0.18 |

200~300 | 9.00 | 0.26 |

300~400 | 7.00 | 0.34 |

Parameter | Ploughing | Harvest | Transport |
---|---|---|---|

SOC initial value/final value (%) | 60.00/61.96 | 60.00/59.63 | 60.00/59.81 |

SOC difference (%) | +1.96 | −0.37 | −0.19 |

Simulation/test fuel consumption (L) | 2.59/2.72 | 6.56/6.80 | 1.69/1.77 |

Fuel consumption error (%) | 4.8 | 3.5 | 4.5 |

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## Share and Cite

**MDPI and ACS Style**

Zhu, Z.; Yang, Y.; Wang, D.; Cai, Y.; Lai, L.
Energy Saving Performance of Agricultural Tractor Equipped with Mechanic-Electronic-Hydraulic Powertrain System. *Agriculture* **2022**, *12*, 436.
https://doi.org/10.3390/agriculture12030436

**AMA Style**

Zhu Z, Yang Y, Wang D, Cai Y, Lai L.
Energy Saving Performance of Agricultural Tractor Equipped with Mechanic-Electronic-Hydraulic Powertrain System. *Agriculture*. 2022; 12(3):436.
https://doi.org/10.3390/agriculture12030436

**Chicago/Turabian Style**

Zhu, Zhen, Yanpeng Yang, Dongqing Wang, Yingfeng Cai, and Longhui Lai.
2022. "Energy Saving Performance of Agricultural Tractor Equipped with Mechanic-Electronic-Hydraulic Powertrain System" *Agriculture* 12, no. 3: 436.
https://doi.org/10.3390/agriculture12030436