# Strategy Design and Performance Analysis of an Electromechanical Flywheel Hybrid Scheme for Electric Vehicles

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Topological Scheme and Working Principle of Electromechanical Flywheel Hybrid Systems

#### 2.1. Topological Scheme of Electromechanical Flywheel Hybrid Systems

#### 2.2. Design of Working Mode of Electromechanical Flywheel Hybrid Systems

#### 2.2.1. Initial Acceleration Stage

#### 2.2.2. Constant Speed Driving Stage

#### 2.2.3. Braking Deceleration Stage

#### 2.2.4. Re-Acceleration Stage

## 3. Design of Energy Management Strategies for Driving Mode

## 4. Design of Energy Management Strategies in Braking Mode

#### 4.1. Design of a Braking Force Distribution Strategy for Front and Rear Axles

_{f}. Among them, the domain of flywheel SOE is [0 1], and the fuzzy set of input quantities is SOE = {L M B}. The domain of braking severity is [0 1], and the fuzzy set of input quantities is z = {L M B}. The domain of controlling the motor torque distribution coefficient K

_{f}is [0 1], and the fuzzy set of output quantities is K = {L ML MB B}. As shown in Table 2, the braking force distribution coefficient K

_{f}is controlled by the flywheel SOE and braking severity z. It can be clearly seen that in most cases, the braking force distribution coefficient K

_{f}is MB and above, so when the vehicle brakes, more braking torque can be distributed to the front axle, so that the electromechanical flywheel can participate more in the recovery of braking energy. Only when the flywheel SOE is large and the severity of braking z is low, is the braking force distribution coefficient K

_{f}set at ML and below. On the one hand, this is to allow the drive motor to recover more braking energy, and at the same time, to prevent the flywheel from reaching the maximum design speed; on the other hand, in the case of a high severity of braking, no matter what the flywheel SOE is, the braking safety of the vehicle should be considered as the first factor. The front axle of the vehicle needs to allocate more braking torque, so the braking force distribution coefficient K

_{f}in this case is MB and above.

#### 4.2. Design of Fuzzy Controller for Regenerative Braking Torque Distribution

_{r}. Among them, the domain of battery SOC is [0 1], and the fuzzy set of input quantities is SOC = {L M B}. The domain of flywheel SOE is [0 1], and the fuzzy set of input quantities is SOE = {L ML MB B}. The domain of vehicle speed V is [0 150], and the fuzzy set of input quantities is V = {L M B}. The domain of regenerative braking force distribution coefficient K

_{r}is [0 1], and the fuzzy set of output quantities is K = {L ML M MB B}. Among them, L, ML, M, MB, and B represent small, medium-small, medium, medium-large, and large, respectively. In order to control the regenerative braking force more accurately, the fuzzy set of flywheel SOE and regenerative braking force output is divided in more detail, as shown in Table 3.

## 5. Hardware in the Loop Test and Performance Analysis

#### 5.1. Test Platform Design

#### 5.2. Analysis of Speed and Torque Laws in Electromechanical Flywheel Hybrid Systems

#### 5.3. Economic Analysis of Electromechanical Flywheel Hybrid Electric Vehicles

## 6. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 13.**Battery current and efficiency for two schemes: (

**a**) battery current change and (

**b**) battery efficiency.

**Figure 14.**Comparison of front and rear motor efficiency of two schemes: (

**a**) efficiency of control motor and front motor and (

**b**) efficiency of drive motor.

**Figure 15.**Electromechanical flywheel with total brake recovery energy: (

**a**) energy storage of the flywheel in each brake and (

**b**) the total brake energy recovered by the two schemes.

Serial Number | Fuzzy Control Rules |
---|---|

1 | If (SOE is L) and (V is L) then (K is MB) |

2 | If (SOE is L) and (V is M) then (K is ML) |

3 | If (SOE is L) and (V is B) then (K is ML) |

4 | If (SOE is M) and (V is L) then (K is B) |

5 | If (SOE is M) and (V is M) then (K is MB) |

6 | If (SOE is M) and (V is B) then (K is MB) |

7 | If (SOE is B) and (V is L) then (K is B) |

8 | If (SOE is B) and (V is M) then (K is B) |

9 | If (SOE is B) and (V is B) then (K is B) |

Serial Number | Fuzzy Control Rules |
---|---|

1 | If (FWSOE is L) and (Z is L) then (K_{f} is B) |

2 | If (FWSOE is L) and (Z is M) then (K_{f} is MB) |

3 | If (FWSOE is L) and (Z is B) then (K_{f} is MB) |

4 | If (FWSOE is M) and (Z is L) then (K_{f} is MB) |

5 | If (FWSOE is M) and (Z is M) then (K_{f} is MB) |

6 | If (FWSOE is M) and (Z is B) then (K_{f} is MB) |

7 | If (FWSOE is B) and (Z is L) then (K_{f} is L) |

8 | If (FWSOE is B) and (Z is M) then (K_{f} is ML) |

9 | If (FWSOE is B) and (Z is B) then (K_{f} is B) |

Serial Number | Fuzzy Control Rules |
---|---|

1 | If (SOC is L) and (SOE is L) and (V is L) then (K_{r} is B) |

2 | If (SOC is L) and (SOE is L) and (V is M) then (K_{r} is B) |

3 | If (SOC is L) and (SOE is L) and (V is B) then (K_{r} is B) |

4 | If (SOC is L) and (SOE is ML) and (V is L) then (K_{r} is B) |

5 | If (SOC is L) and (SOE is ML) and (V is M) then (K_{r} is B) |

6 | If (SOC is L) and (SOE is ML) and (V is B) then (K_{r} is MB) |

7 | If (SOC is L) and (SOE is MB) and (V is L) then (K_{r} is B) |

8 | If (SOC is L) and (SOE is MB) and (V is M) then (K_{r} is MB) |

9 | If (SOC is L) and (SOE is MB) and (V is B) then (K_{r} is M) |

10 | If (SOC is L) and (SOE is B) and (V is L) then (K_{r} is M) |

11 | If (SOC is L) and (SOE is B) and (V is M) then (K_{r} is ML) |

12 | If (SOC is L) and (SOE is B) and (V is M) then (K_{r} is ML) |

13 | If (SOC is M) and (SOE is L) and (V is L) then (K_{r} is B) |

14 | If (SOC is M) and (SOE is L) and (V is M) then (K_{r} is B) |

15 | If (SOC is M) and (SOE is L) and (V is B) then (K_{r} is B) |

16 | If (SOC is M) and (SOE is ML) and (V is L) then (K_{r} is B) |

17 | If (SOC is M) and (SOE is ML) and (V is M) then (K_{r} is MB) |

18 | If (SOC is M) and (SOE is ML) and (V is B) then (K_{r} is MB) |

19 | If (SOC is M) and (SOE is MB) and (V is L) then (K_{r} is MB) |

20 | If (SOC is M) and (SOE is MB) and (V is M) then (K_{r} is M) |

21 | If (SOC is M) and (SOE is MB) and (V is B) then (K_{r} is ML) |

22 | If (SOC is M) and (SOE is B) and (V is L) then (K_{r} is ML) |

23 | If (SOC is M) and (SOE is B) and (V is M) then (K_{r} is ML) |

24 | If (SOC is M) and (SOE is B) and (V is B) then (K_{r} is L) |

25 | If (SOC is B) and (SOE is L) and (V is L) then (K_{r} is B) |

26 | If (SOC is B) and (SOE is L) and (V is M) then (K_{r} is B) |

27 | If (SOC is B) and (SOE is L) and (V is B) then (K_{r} is MB) |

28 | If (SOC is B) and (SOE is ML) and (V is L) then (K_{r} is MB) |

29 | If (SOC is B) and (SOE is ML) and (V is M) then (K_{r} is MB) |

30 | If (SOC is B) and (SOE is ML) and (V is B) then (K_{r} is M) |

31 | If (SOC is B) and (SOE is MB) and (V is L) then (K_{r} is M) |

32 | If (SOC is B) and (SOE is MB) and (V is M) then (K_{r} is M) |

33 | If (SOC is B) and (SOE is MB) and (V is B) then (K_{r} is ML) |

34 | If (SOC is B) and (SOE is B) and (V is L) then (K_{r} is ML) |

35 | If (SOC is B) and (SOE is B) and (V is M) then (K_{r} is L) |

36 | If (SOC is B) and (SOE is B) and (V is B) then (K_{r} is L) |

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

Complete vehicle kerb mass (Scheme 1) | 1580 kg |

Radius of tire (both) | 300 mm |

Rolling resistance coefficient (both) | 0.015 |

Air resistance coefficient (both) | 0.3 |

Windward area (both) | 2 m^{2} |

Type of drive motor | Permanent magnet motor |

Rated speed of drive motor (both) | 3000 rpm |

Rated torque of drive motor (both) | 64 N·m |

Rated power of drive motor (both) | 20 kW |

Peak speed of drive motor (both) | 8000 rpm |

Peak torque of drive motor (both) | 130 N·m |

Peak power of drive motor (both) | 40 kW |

Mass of flywheel (Scheme 2) | 8.8 kg |

Height of flywheel (Scheme 2) | 100 mm |

Inner radius of flywheel (Scheme 2) | 100 mm |

Outer radius of flywheel (Scheme 2) | 150 mm |

Speed range of flywheel (Scheme 2) | 0~20,000 rpm |

Rotational inertia of flywheel (Scheme 2) | 0.08 kg·m^{2} |

Type of control motor of flywheel | AC induction motor |

Rated speed of control motor (Scheme 2) | 4000 rpm |

Rated torque of control motor (Scheme 2) | 35 N·m |

Rated power of control motor (Scheme 2) | 15 kW |

Peak speed of control motor (Scheme 2) | 10,000 rpm |

Peak torque of control motor (Scheme 2) | 95 N·m |

Peak power of control motor (Scheme 2) | 40 kW |

Type of battery pack | Ternary lithium battery |

Rated voltage (both) | 320 V |

Rated capacity (both) | 130 Ah |

Rated power (both) | 100 kW |

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## Share and Cite

**MDPI and ACS Style**

Sun, B.; Gu, T.; Xie, M.; Wang, P.; Gao, S.; Zhang, X.
Strategy Design and Performance Analysis of an Electromechanical Flywheel Hybrid Scheme for Electric Vehicles. *Sustainability* **2022**, *14*, 11017.
https://doi.org/10.3390/su141711017

**AMA Style**

Sun B, Gu T, Xie M, Wang P, Gao S, Zhang X.
Strategy Design and Performance Analysis of an Electromechanical Flywheel Hybrid Scheme for Electric Vehicles. *Sustainability*. 2022; 14(17):11017.
https://doi.org/10.3390/su141711017

**Chicago/Turabian Style**

Sun, Binbin, Tianqi Gu, Mengxue Xie, Pengwei Wang, Song Gao, and Xi Zhang.
2022. "Strategy Design and Performance Analysis of an Electromechanical Flywheel Hybrid Scheme for Electric Vehicles" *Sustainability* 14, no. 17: 11017.
https://doi.org/10.3390/su141711017