The active suspension has undoubtedly improved the performance of the vehicle, however, the trend of “low-carbonization, intelligence, and informationization” in the automotive industry has put forward higher and more urgent requirements for the suspension system. The automotive industry and researchers favor active energy regeneration suspension technology with safety, comfort, and high energy regenerative efficiency. In this paper, we review the research progress of the structure form, optimization method, and control strategy of electromagnetic energy regenerative suspension. Specifically, comparing the pros and cons of the existing technology in solving the contradiction between dynamic performance and energy regeneration. In addition, the development trend of electromagnetic energy regenerative suspension in the field of structure form, optimization method, and control technology prospects.

According to 2020 statistics from the International Energy Agency (IEA), the transport sector accounts for 26% of global carbon emissions [

As the automotive industry develops in the direction of “low-carbonization, intelligence, and informationization” [

The energy regenerative process of the existing air-type and hydraulic-type active suspensions is relatively complicated: the vibration energy needs to be converted into internal energy, and then converted into electrical energy using a motor [

This paper reviews the latest advances in dynamic performance and energy harvesting of electromagnetic energy regenerative suspensions. The main purpose of the research is to explore the structural form of the electromagnetic energy regenerative suspension according to the recovery effect of the suspension system on the vibration energy and the dynamic performance. On this basis, the multidisciplinary optimization design method of electromagnetic energy regenerative suspension system is further analyzed. In addition, the coordination of various control methods in the performance of electromagnetic energy regenerative suspension systems is discussed. And the existing problems and future development trends of the current electromagnetic energy regenerative suspension system and its key technologies are discussed, which will help to expand the development of the electromagnetic energy regenerative suspension optimization design method and control theory.

In the late 1980s, Karnopp verified the feasibility of combining permanent magnet motors with automotive suspension systems through theoretical analysis [

The rotating electromagnetic energy regenerative suspension generally consists of a set of motion conversion mechanisms and a rotating motor [

The ball-screw mechanism has the advantages of high efficiency, smooth motion, and accurate positioning, and can realize the mutual transformation of linear motion and rotary motion, which is now applied to the rotary electromagnetic energy regenerative suspension system.

The rotary electromagnetic energy regenerative suspension is easy to cause problems such as large fluctuation of electromagnetic output force and overload operation of the motor due to the addition of a motion conversion mechanism. Therefore, stability and safety are the first key issues to be considered in the design process of electromagnetic energy regenerative suspensions. Bose Corporation uses dual motors combined with ball-screws in a symmetrical arrangement, as shown in

The working efficiency of the rotary electromagnetic energy regenerative suspension cannot be ignored. Zhao et al. [

Due to the limited installation space of the rotary electromagnetic energy regenerative suspension system, there is a conflicting relationship between its structural size and its working performance. Galluzzi et al. [

According to the in-depth research of ball-screw type energy regenerative suspension by the above scholars, the ball-screw type energy regenerative suspension system has the advantages of good reliability, high transmission efficiency and compact structure, but the internal clearance between the mechanical mechanism is easy to cause its damping performance to be attenuated under the condition of the high road excitation frequency.

The rack-pinion mechanism has many advantages such as simple structure, high transmission efficiency, and conversion between circular motion and unidirectional motion, etc. It is now widely used in rotary electromagnetic energy regenerative suspension systems.

Since the 1990s, foreign scholars have begun to research the energy regenerative suspension based on the rack-pinion mechanism. Suda et al. [

The rack and pinion mechanism are the core component of the electromagnetic energy regenerative suspension, and its reliability will directly affect the driving safety of the vehicle. Papageorgiou [

The rack-pinion energy regenerative suspension has high transmission precision and good stability, but when the road impact is too large, the rack-pinion mechanism is easy to break, which affects the driving safety of the vehicle.

Compared with the ball-screw type and the rack-pinion type, the rotary motor combined with the rocker type electromagnetic energy regenerative suspension system has smaller inertia and faster response speed, but it is more difficult to install and more difficult to control.

The rocker-arm type electromagnetic energy regenerative suspension designed by Chen et al. [_{2} emissions by up to 3 grams per kilometer in daily driving conditions. Considering the limitation of installation space, scholars from all over the world have little research on rocker-arm electromagnetic energy regenerative suspension. With the continuous development of the automobile industry, the changes in the layout of the automobile chassis will promote the further development of the rocker-arm type electromagnetic energy regenerative suspension.

The rotating motor type energy regenerative suspension has been widely studied because of the reliability of the motion conversion mechanism and the high efficiency of the rotating motor. The simulation and test results in

Categories | Researchers | Motion speed/Excitation | Maximum output force (N) | Energy collection (W) | Equivalent damping coefficient (N⋅s/m) |
---|---|---|---|---|---|

Ball-screw type | Zuo et al. [ |
2 Hz | —— | 11.52 | 4425 |

Xie et al. [ |
1.2 Hz | —— | 135 | 540 | |

Xu et al. [ |
2–4 Hz | 240 | —— | 540 | |

Zhao et al. [ |
0.5 Hz | 1218 | 375 | —— | |

Zhang et al. [ |
2.5 Hz/5 mm | 500 | 270 | 369 | |

1 Hz/3 mm | 500/ |
Average |
10580 | ||

Amat et al. [ |
1 m/s | 1800 | —— | 12100 | |

Rack-pinion type | Zuo et al. |
3 Hz/5 mm | —— | 104.3 | 5000 |

Wang et al. [ |
0∼0.3 m/s | 982 | 8.56 | 600∼700 | |

Zhang et al. |
2.5 Hz | 240 | 4.302 | 1511.8 | |

2.5 Hz | 210 | 4.25 | 1839.27 | ||

Rocker-arm type | Chen et al. [ |
2 m/s | 3500 | —— | —— |

Audi Corporation [ |
Grade II rough pavement | —— | 613 W | —— |

The linear motor is the core component of the electromagnetic energy regenerative suspension, and its performance directly affects the dynamic performance and energy regenerative performance of the electromagnetic energy regenerative suspension [

Okada et al. [

The current research shows that Halbach arrays can generate ideal sinusoidal distributed magnetic fields inside electromagnetic linear actuators, and double-layer Halbach arrays can increase the internal magnetic flux density to ensure smooth electromagnetic force output and vibration energy conversion. However, the electromagnetic energy regenerative suspension has problems such as excessive mass, long displacement, and working dead zone in actual operation, and scholars from various countries have conducted corresponding research. To reduce the mass of the electromagnetic energy regenerative suspension system, the performance deterioration of the suspension system caused by excessive unsprung mass is avoided. Zuo et al. [

At present, scholars from various countries have carried out extensive and in-depth research on linear electromagnetic energy regenerative suspension. The simulation and test data are shown in

Researchers | Motion speed/excitation | Maximum output force (N) | Energy collection (W) | Equivalent damping coefficient (N⋅s/m) |
---|---|---|---|---|

Okada et al. [ |
15.6 Hz | —— | 0.8 | —— |

Gysen et al. [ |
1 m/s | 755 | 65 | —— |

Wang et al. [ |
1.2 m/s | 1354 | —— | —— |

Ye et al. [ |
1 m/s | 968 | —— | 762 |

Zuo et al. [ |
0.25∼0.5 m/s | —— | 26–33 | 1354 |

Lafarge et al. [ |
1 m/s | —— | 10 | —— |

Lai et al. [ |
5 Hz | 1562 | —— | —— |

In view of the fact that the rotary electromagnetic energy regenerative suspension adopts a mechanical mechanism for power transmission, the clearance of mechanical transmission is unavoidable, and the backlash seriously affects the reliability and durability of the energy recovery system. when received severe road impact will lead to gear cracking or even broken teeth. The hydraulic-electric composite design can effectively avoid such problems [

At the end of the 20th century, as PBW (Power-by-Wire) drive system came into people’s view [

To further promote the development of hydraulic-electric hybrid actuator technology, reducing losses is of great significance for saving suspension energy, improving system reliability, and improving power conversion efficiency [

When the speed of the hydraulic motor-driven generator is lower than the minimum working speed of the generator, the hydraulic-electric composite energy regenerative suspension system will produce the phenomenon of a “power dead zone”. Zhou et al. [

To improve the ride comfort of the vehicle and realize the decoupling of various motion modes of the vehicle, the conflict between the dynamic reduction performance and energy recovery of the energy regenerative suspension system is avoided. Wang et al. developed a hydraulic-electric composite energy regenerative suspension system by designing a linear motor in parallel with a hydraulic system, as shown in

According to the characteristics of the hydraulic-electric composite energy regenerative suspension structure itself, researchers from various countries have carried out simulation and experimental verification on the comfort performance, safety performance, and energy-saving performance, as shown in

Researchers | Motion speed/Vehicle speed/Excitation | Maximum output force (N) | Energy collection (W) | Energy regenerative efficiency (%) |
---|---|---|---|---|

Levant Power [ |
—— | —— | 1000 | —— |

Kou et al. [ |
2 Hz | —— | —— | Around 50 |

Ding et al. [ |
5 m/s | 6350 | —— | —— |

Xu et al. [ |
Class C Pavement | —— | 400 | —— |

Fang et al. [ |
Class C Pavement | —— | 245.5763 | —— |

Jing et al. [ |
Class C Pavement | —— | 90.9 | 18 |

Zhang et al. [ |
1.67 Hz/50 mm | 2500 | 133.6 | —— |

Wang et al. [ |
20 m/s | −500 |
112 | —— |

Zhou et al. [ |
1.67 Hz/50 mm | 1115.6 | 223.5 | 38.3 |

Qin et al. [ |
2 Hz/15 mm | −1901–1510 | 258 | 36.1 |

Galluzzi et al. [ |
1 m/s, 1 Hz | —— | 33.5 W | 54 |

Miragli et al. [ |
0.5 m/s | 500–1000 N | 75 W | 11.7 |

This chapter mainly summarizes the structure of the electromagnetic energy regenerative suspension, as shown in

Title | Advantages | Limitations | |
---|---|---|---|

Linear type | High-frequency response, high precision, high power density, etc. | The end effect, bulky, etc. | |

Rotary type | Ball-screw type | High precision, large transmission ratio, low starting torque, etc. | High and low-frequency performance is poor, etc. |

Rack-pinion type | High precision, high power density, etc. | High friction loss, easy damage to parts, etc. | |

Rocker-arm type | Large transmission ratio, a wide range of applications, etc. | Difficult installation, poor impact resistance, etc. | |

Hydraulic-electric composite type | High-speed regulation ratio, high stability, high energy efficiency, etc. | Complex structure, easy to leak, low power density, etc. |

In the field of electromagnetic energy regenerative suspension research [

The disciplines are coupled with each other in the design process of electromagnetic energy regenerative suspension optimization [

The dynamic analysis of the suspension mainly studies the transmission characteristics of the suspension elastic elements and damping elements to the body of the road vibration excitation [

The coupling relationship between the electric and magnetic fields of the electromagnetic energy regenerative suspension is prone to its electromagnetic force fluctuations, and the effective output of electromagnetic damping directly affects the dynamic performance of the system. Yang et al. [

CFD and finite element methods developed in recent years occupy an important position in multi-body dynamics, electromagnetism, and fluid dynamics. They integrate multidisciplinary theories and high-precision algorithms to accurately calculate and analyze system performance and improve the efficiency of optimal design. CFD and finite element methods are based on geometric models, which need to be parameterized. During the optimization process, the geometric model can be automatically updated according to the optimization variables, thus finding the optimal design solution among the executable design solutions. Zhou et al. [

At present, researchers have carried out a variety of modeling methods to further deepen the dynamic, electromagnetic, and fluid mechanics analysis of the electromagnetic energy regenerative suspension system. The multidisciplinary coupled model is established under the support of single discipline theory and combined with finite element analysis software, the analysis efficiency of system performance is improved.

The electromagnetic energy regenerative suspension system is a multi-disciplinary strong coupling nonlinear uncertainty system, and its uncertainty is divided into parameter uncertainty and model structure uncertainty [

Title | Features | Typical methods | Advantages | Limitations |
---|---|---|---|---|

Reliability analysis | Quantitative analysis of the influence of uncertainty factors on structural performance | Fault tree analysis; |
Simple, intuitive, |
Heavy workload, tedious analysis process, poor generality |

Robust analysis | Comprehensive analysis of the influence of uncertainty factors on structural performance and sensitivity | The minimum sensitivity method. |
Stable, reliable, and easy to operate, |
High theoretical requirements, complex model solutions |

Reliability analysis can obtain the failure probability of the system. In the research of electromagnetic energy regenerative suspension systems, reliability analysis ensures the driving safety of the vehicle; robustness analysis estimates the sensitivity of uncertainties to the system response and achieves controllable product quality characteristics [

The Taguchi method was first proposed by Taguchi Genichi, and the basic idea is to determine the output response by adjusting the control factor and considering the effect of uncertainty factors while the input response is constant [

The Monte Carlo method can determine the correlation between random variables in the suspension system to ensure high confidence in the system analysis results. Hamid et al. established a dynamic model of the commercial vehicle suspension system and used Monte Carlo analysis to obtain the correlation between the energy regenerative power and driving conditions under different suspension and road conditions [

The uncertainty analysis method can further clarify the correlation of the performance parameters of the electromagnetic energy regenerative suspension system, which helps to make trade-offs among the performance parameters and then coordinate the performance requirements of the electromagnetic energy regenerative suspension system to meet the researchers’ requirements on the damping performance, energy regenerative performance and safety performance of the electromagnetic energy regenerative suspension system.

In the optimization process, advanced optimization algorithms are the key to improving the efficiency of optimal design and promoting multidisciplinary and multi-objective optimization to practical applications. The objects of multidisciplinary optimization are generally nonlinear systems. Therefore, the optimization algorithms are mainly nonlinear programming methods. The commonly used optimization algorithms are shown in

Algorithm | Advantages | Limitations | |
---|---|---|---|

Classical optimization algorithms | Direct search method | Easy to implement, simple and practical | Inefficiency and slow convergence |

Penalty function method | Convertible to unconstrained optimization, simple to execute | Affected by the penalty coefficient, the convergence effect shows a polarized trend | |

Conjugate gradient method | Fast running speed, high precision, good stability | Low linear convergence, slow convergence | |

Quasi-Newton method | Good second-order convergence speed | Localized convergence | |

Intelligent optimization algorithm | Simulated annealing algorithm | High initial value robustness, good generality, easy to implement | Difficult to select control parameters and difficult to control |

Genetic algorithm | High robustness, wide applicability, self-organizing, self-adaptive and self-learning properties | Poor local searchability, prone to early maturity | |

Ant colony algorithm | Parallel search, robustness | Slow convergence, easy to fall into local optimum | |

Particle swarm algorithm | Easy to implement, small code size | Easy to fall into local optimum and low search accuracy |

In the optimization design process of the electromagnetic energy regenerative suspension, the parameters involved in the genetic algorithm are random. This stochastic search characteristic makes the genetic algorithm has strong robustness in the operation process, and the search mode is not limited to a certain point, expanding the search range and easy to obtain the global optimal solution. Li et al. [

Compared with the genetic algorithm, the particle swarm algorithm contains fewer parameters, runs faster, and is easy to implement, but like a genetic algorithm, it is easy to fall into local optimum. Yu et al. [

By using the optimization algorithm, the loop nesting problem existing in the system optimization design process is solved, and the sensitivity to uncertain factors and the optimization efficiency is improved. The current optimization algorithm still has the problems of premature convergence and insufficient diversity when solving the multidisciplinary optimization design problem of the electromagnetic energy regenerative suspension system.

At present, researchers at home and abroad have achieved certain results in the optimization design of electromagnetic energy regenerative suspension. The optimization process is shown in

In the design and research process of the electromagnetic energy regenerative suspension at this stage, the electromagnetic energy regenerative suspension structure and the system controller are the key contents of the research. A good structure can ensure the dynamic performance of the electromagnetic energy regenerative suspension, and the system controller is responsible for calculating the control rate to optimize the vehicle’s motion posture [

Classical control theory is a theory based on the frequency response method and the root trajectory method, using the Laplace transform as a mathematical tool, and has significant results for linear time-invariant systems with a single input and a single output [

The skyhook control algorithm was first proposed by Karnopp in the United States and was originally used for the control of semi-active suspension [

To improve the practicality and effectiveness of semi-active control of energy regenerative suspensions, Chen et al. [

The control principle of groundhook control is the same as that of skyhook control [

LQG (Linear Quadratic Guass) optimal control is a classic optimal control algorithm [

There are three main performance evaluation indexes for energy regenerative suspensions, which are body acceleration representing ride comfort, suspension dynamic deflection representing safety, and average energy regenerative efficiency representing energy regenerative characteristics [

Traditional control methods are simple, reliable, and easy to implement. However, traditional control methods require high precision system models. They are difficult to meet the high-performance requirements of the electromagnetic energy regenerative suspension system, when solving the performance coordination problem of the electromagnetic energy regenerative suspension system. With the continuous development of theories in various disciplines, the combination of advanced algorithms can improve the adaptability of traditional control methods to complex coupled systems.

Modern control methods do not require parameter identification, but need to define the variation law of adaptive parameters to reduce system errors and ensure system stability. They are suitable for complex systems such as multi-input multi-output systems and nonlinear systems. They are the characteristics of clear theory and convenient operation. Modern control methods mainly include: adaptive control, sliding mode control, robust control, etc.

In the 1960s, the concept of adaptive control was proposed by Aseltine, and it was first used for control problems in the aerospace field [

In recent years, researchers have adopted adaptive control for the electromagnetic energy regenerative suspension system, which improves the dynamic performance and energy regenerative performance of the electromagnetic energy regenerative suspension system and ensures its safety performance. Li et al. [

Sliding mode control, also known as variable structure control, is essentially discontinuous nonlinear control and was first proposed by Utkin [

Due to the different working characteristics of the electromagnetic energy regenerative suspension modes, the mode switching is prone to generate thrust fluctuations, and it is difficult to achieve smooth dynamic control of the switching process. Shi et al. [

In 1978, Davison of the University of Toronto first proposed robust control [

Electromagnetic energy regenerative suspension systems are nonlinear systems with bounded uncertain parameters, which can be transformed into robust problems with linear intervals. Thereby, the control performance of the electromagnetic energy regenerative suspension system is improved. Joo et al. [

Modern control methods have better suppression of nonlinear effects, uncertainty factors and environmental disturbances in electromagnetic energy regenerative suspension systems. They can realize the closed-loop stable control of the system, which makes up for the shortcomings of traditional control. And they have obvious advantages in improving the dynamic performance, energy regenerative performance and safety performance of the electromagnetic energy regenerative suspension system.

The intelligent control method is a control method spanning multiple disciplines that have been continuously developed based on “classical control” and “modern control”, combined with advanced technologies in different fields [

Neural network control has strong nonlinear approximation capability, self-learning capability, and the ability to obtain the corresponding neural network model according to the input and output characteristics of the controlled system. In the process of engineering application, there are uncertain factors in the complex model of the electromagnetic energy regenerative suspension system. Neural network control has strong fitting ability to uncertainty functions, especially for uncertain nonlinear systems, which ensures that the system has strong adaptability.

Liu et al. [

Fuzzy control is an intelligent control algorithm developed based on Zade’s fuzzy set theory [

Su et al. [

Model-free control is not limited by the specific mathematical model of the system, and only uses the input and output data of the nonlinear system to be controlled to complete the real-time control of the system, improving the robustness of the controller in the energy regenerative suspension system [

Yonezawa et al. [

Researchers using intelligent control technology can abstract the control problem of the electromagnetic energy regenerative suspension system, combined with artificial intelligence technology, coordinate the relationship between its system performance, and improve the comprehensive performance of the electromagnetic energy regenerative suspension system.

This chapter summarizes the research status at home and abroad related to the electromagnetic energy regenerative suspension control system, and classifies the control methods. As shown in

Category | Control methods | Features |
---|---|---|

Classical control methods | Skyhook control | Suppression of body vibration, poor high-frequency control |

Groundhook control | Good road adaptability and operational stability of the vehicle | |

LQG control | Reduces vehicle vertical acceleration, tire dynamic load, and relative body displacement | |

Modern control methods | Adaptive control | Enables multi-objective control and provides dynamic system response |

Sliding mode control | High control accuracy, fast convergence, easy to implement | |

Robust control | Anti-jamming to improve the vehicle’s road holding and low-frequency performance of the suspension | |

Intelligent control methods | Neural network control | Strong nonlinear approximation ability, self-learning ability |

Fuzzy control | Strong logic capability, suitable for control systems with complex features such as strong coupling, nonlinearity, and large inertia | |

Model-free control | Robustness, fast convergence, good tracking performance, and no jitter |

This paper provides a comprehensive review of the structure, optimization methods, and control strategies of electromagnetic energy regenerative suspensions, according to the research status of the electromagnetic energy regenerative suspension by researchers from various countries. Driven by low carbonization, intelligence and informatization, the researchers gradually realize the transition from passive energy consumption to energy harvesting in the suspension system of the vehicle. However, there are still many key technical problems in the development process of the energy regenerative technology of electromagnetic suspensions, such as the contradiction between energy regeneration and dynamic performance, lightweight problem, motor dead zone and so on. These will play a key role in promoting the development of electromagnetic energy regenerative suspensions in the future. In the author’s view, a more reliable and energy-efficient structural solution is the basis for the research of electromagnetic energy regenerative suspension. A more realistic and optimized design method is an effective way to improve the reliability of electromagnetic energy regenerative suspension. And a more effective control method is the key to improving the comprehensive performance of electromagnetic energy regenerative suspension. Therefore, by reviewing the structural form, optimization method, and control strategy of the electromagnetic energy regenerative suspension, it is found that the electromagnetic energy regenerative suspension system has the following development laws:

The damping performance and energy regeneration of the rotary motor regenerative suspensions are remarkable, but the wear problem of its own mechanical structure cannot be ignored. The maximum output force of the hydraulic-electric electromagnetic energy regenerative suspensions is higher than that of the rotary and linear structures, but the hydraulic systems have problems such as easy leakage and low power density. The linear motor regenerative suspensions have high-performance requirements such as compact structure, high-frequency response, high accuracy, and high power-to-weight ratio compared with the rotary motor type and hydraulic-electric regenerative suspension. Therefore, the linear motor regenerative suspensions meet the development requirements of the electromagnetic energy regenerative suspension system in the future.

The electromagnetic energy regenerative suspension is a multi-disciplinary strong coupling complex system, which has the characteristics of multi-function and parameter uncertainty. It increases the design difficulty. In the optimization design process of electromagnetic energy regenerative suspension, the establishment of a multidisciplinary coupling model is the basis of system performance analysis. The correlation of performance parameters can be further clarified through uncertainty analysis, and the optimization design efficiency can be improved by combining optimization algorithms. In future research, it is necessary to establish a more accurate system dynamic model, and improve the stability of the algorithm operation and overcome the problems of local convergence and optimization distortion.

For the research of the control methods of the electromagnetic energy regenerative suspension systems, researchers have established a certain research foundation about the traditional control methods and the modern control methods. On the basis of this research, intelligent control methods are gradually applied to the electromagnetic energy regenerative suspension systems, and the system control performance is significantly improved, but there are still some limitations. Therefore, future related research should utilize the advantages of traditional control methods and modern control methods, and combine the adaptability of intelligent control methods in complex models. We also need to combine research with practical applications, take more consideration of the actual working conditions of the electromagnetic energy regenerative suspension systems, and gradually realize the improvement in the performance of the electromagnetic energy regenerative suspension system in the actual operating environment.