Electro-hydraulic Braking System Research Articles

Finite-Time Adaptive Control for Electro-Hydraulic Braking Gear Transmission Mechanism with Unilateral Dead Zone Nonlinearity

Autonomous vehicles require more precise and reliable braking control, and electro-hydraulic braking (EHB) systems are better adapted to the development of autonomous driving. However, EHB systems inevitably suffer from unilateral dead zone nonlinearity, which adversely affects the position tracking control. Therefore, a finite-time adaptive control strategy was designed for unilateral dead zone nonlinearity. Initially, the unilateral dead zone nonlinearity was reformulated into a matched disturbance term and an unmatched disturbance term to reduce the adverse effects of disturbances, thereby enhancing system controllability. Then, the “complexity explosion” in the design of the control strategy was avoided by command filtering, and the design process of the controller was simplified. Furthermore, the finite-time control theory was employed to boost the system’s convergence speed, thereby enhancing control performance. In order to ensure the stability of the system under the dead zone disturbance, the unknown disturbance terms were estimated. The stability of the control strategy was validated through the finite-time stability theorem and the Lyapunov function. Eventually, simulations and hardware-in-the-loop (HIL) experiments validated the feasibility and availability of the finite-time adaptive control strategy.

An Economical Multilevel Backup Strategy for Electro-Hydraulic Braking System by Integrating Driving and Electronic Parking Brake Systems

An Economical Multilevel Backup Strategy for Electro-Hydraulic Braking System by Integrating Driving and Electronic Parking Brake Systems

Regenerative braking fault compensation control of distributed electric vehicle considering random wheel fault degree

Distributed drive electric vehicles can reduce range anxiety through regenerative braking. However, if the wheel motor torque output fails, it will form an additional yaw moment to the vehicle, causing instability, or deviation and threatening its safety. To solve this problem, the research object is an electric vehicle driven by a four-wheel hub motor. A braking force compensation distribution strategy for front and rear axles is proposed, which combines electronic hydraulic braking (EHB) system compensation control and deviation auxiliary control. Firstly, a fault detection module is established, and the motor’s output torque is estimated by designing a torque observer to obtain the fault degree information of the motor. Secondly, to fully use the motor’s regenerative braking force, the fault-free and faulty electro-hydraulic braking force distribution strategies are designed in the coordinated distribution layer of the electro-hydraulic braking system. The corresponding electro-hydraulic braking force compensation method is selected according to the fault degree of the regenerative braking function, the position of the faulty wheel, and the braking strength. Then, a deviation auxiliary controller is designed based on the model predictive control, and the intervention time of the auxiliary controller is determined according to the vehicle’s state. Finally, the control method is verified based on CarSim/Simulink co-simulation and hardware-in-the-loop (HIL) platform. The test results show that the designed control method can effectively compensate for the regenerative braking failure of random wheel and ensure the braking safety of the vehicle.

Cascade control algorithm for slip rate in a brake-by-wire system based on direct drive valve

To achieve a rapid response and precise control of braking hydraulic pressure, a brake-by-wire electro-hydraulic braking system based on a direct drive valve was designed. This system employs an electromagnetic linear actuator to drive the valve core directly, achieving swift adjustment of brake wheel cylinder hydraulic pressure. Given the strong coupling and non-linearity of the electromagnetic linear actuator, solely using a single-loop controller to control the slip rate can easily lead to weakened system performance. Hence, we proposed a cascade control algorithm for the brake-by-wire system, with an outer loop for slip rate control and an inner loop for direct drive valve position. The outer loop adopted a fuzzy PID control, while the inner loop adopted a model-free adaptive sliding mode control. By combining model-free adaptive control with a novel discrete exponential approach, we addressed the system’s non-linearity and unknown disturbances. A braking system test platform was constructed to verify the superior hydraulic tracking performance of this brake-by-wire system and to perform slip rate control performance analysis under different road conditions. Results demonstrated that compared to the fuzzy PID-MFAC algorithm, the proposed fuzzy PID-MFASMC control enhanced car slip rate control precision, and reduced both braking time and distance.

State Feedback Control for Vehicle Electro-Hydraulic Braking Systems Based on Adaptive Genetic Algorithm Optimization

In traditional state feedback control, the difficulty in determining the coefficient matrix is a significant factor that prevents achieving optimal control. To address this issue, this paper proposes the integration of adaptive genetic algorithms with state feedback control. The effectiveness of the proposed algorithm is validated via an electro-hydraulic braking system. Firstly, a model of the electro-hydraulic braking system is introduced. Next, a state feedback controller optimized by parameter-adaptive genetic algorithm is designed. Additionally, a penalty term is introduced into the fitness function to suppress overshoots. Finally, simulations are conducted to compare the convergence speed of parameter-adaptive genetic algorithm with genetic algorithm, ant colony optimization, and particle swarm optimization. Furthermore, the performance of the proposed algorithm, the state feedback control, and the proportional-integral control are also compared. The comparison results show that the proposed algorithm effectively accelerates the settling time of the electro-hydraulic braking system and suppresses the overshoots.

A Review of One-Box Electro-Hydraulic Braking System: Architecture, Control, and Application

With the development of automobile electrification and intelligence, new requirements have been put forward for automotive braking technologies. Under this background, the One-box EHB (Electro-Hydraulic Braking system) brake-by-wire technology has emerged, which combines the electric booster and wheel-cylinder control module into one box and can realize vehicle stability and comfort functions such as service brake, pedal feel simulation, brake decoupling, failure backup, active braking, and wheel-cylinder pressure control. This article reviews the current research of key technologies of One-box EHB, including system architecture design and applications under high-level autonomous driving, master cylinder pressure control algorithm design, wheel-cylinder pressure control algorithm design, and electro-hydraulic composite braking control algorithm design. Finally, this article summarizes the current research status of One-box EHB key technologies and puts forward suggestions for future research directions.

Robust Braking Pressure Control for an Electrohydraulic Brake System under Friction and Disturbance Conditions

This paper addresses the challenges in hydraulic pressure control for an electrohydraulic brake (EHB), considering nonlinearities and uncertainties such as friction and parameter variations. The proposed solution is a robust integral backstepping control (IBC) strategy, which incorporates motor current dynamics and the LuGre friction model. A nonlinear observer is introduced to estimate the unmeasurable internal state of the LuGre model. The IBC is applied to pressure control for the EHB, resulting in improved steady-state behavior and robustness. The paper concludes with a global stability analysis using Lyapunov theory and performance validation through simulation using MATLAB/Simulink.

Adaptive Dual-loop Pressure Control for an Integrated Electro-hydraulic Brake System Considering Uncertain Nonlinear Characteristics

Adaptive Dual-loop Pressure Control for an Integrated Electro-hydraulic Brake System Considering Uncertain Nonlinear Characteristics

Anti-lock braking control using an interval type-2 fuzzy neural network scheme for electric vehicles

Control precision and robustness can be regarded as essential challenges of slip ratio control because of the external uncertainties of road conditions and the internal delay response of braking actuators. In addition, it is difficult to obtain a trade-off between braking energy recovery efficiency and braking safety under some extreme braking conditions. To synchronously improve both slip ratio control and braking energy recovery efficiency for different road conditions, an anti-lock braking system (ABS) using a novel interval type-2 fuzzy neural network (IT2FNN) control scheme is proposed for electrohydraulic braking systems. The novel IT2FNN control scheme with five layers is designed to calculate the commanded braking torque. The membership function layer utilizes type-2 fuzzy sets to describe the slip ratio error degree, which enhances the scheme’s anti-interference ability, and the enhanced Karnik-Mendel (EKM) algorithm is used in the type-reduction layer to accelerate computation. Additionally, the network adjusts the parameters of the membership function and rules by decreasing the performance function value corresponding to the braking torque error to improve slip ratio control and enhance the self-adaptation capacity. Simulations showed that IT2FNN control can not only improve slip ratio control performance and decrease the braking torque error but also enhance the energy recovery efficiency of regenerative braking on different road surfaces.

EHB Gear-Drive Symmetric Dead-Zone Finite-Time Adaptive Control

Intelligent driving vehicles require more accurate and stable braking control. Electrohydraulic braking (EHB) systems can better adapt to the development of autonomous driving technology. The gear transmission system plays a crucial role in EHB deceleration and torque increase mechanisms. However, its dead-zone nonlinearity poses challenges for EHB control. To address the position-control problem in the EHB gear transmission system, we propose a finite-time adaptive control method for the symmetrical dead zone. This approach combines adaptive control theory with finite-time control theory and designs parameter-updating laws for the unknown parameters in the system. Boundary estimates are introduced into the parameter-update laws and control laws to compensate for unknown disturbances. By adjusting the relevant parameters, the convergence rate can be improved, ensuring that errors converge within a specified range within a limited time. After modifying the parameter-updating laws and control laws, all closed-loop signals remain bounded. Finally, we validate the proposed control strategy through simulation and hardware-in-the-loop (HIL) testing. The results demonstrate that the control strategy developed in this study achieves high tracking accuracy and stability even in the presence of dead zones, unknown parameters, and unknown interferences in the EHB gear-drive servo system.

Adaptive fuzzy command–filtered control strategy for electro-hydraulic braking systems of winding hoist with prescribed performance

In the braking control of winding hoisting systems, proper braking strategy is of great significance in reducing the probability of significant hidden dangers and improving the safety and reliability of the system. However, as a typical elastic and variable stiffness system, the winding hoisting systems have large nonlinearity, parameter uncertainties, random disturbances, and so on, which severely restrict the improvement of braking performance. To this end, an adaptive fuzzy command–filtered controller with prescribed performance is developed for electro-hydraulic braking systems of winding hoist in this article. First, the dynamic model of the winding hoisting system is established with consideration of the elasticity of wire rope. Based on the established dynamic model, using the fuzzy logic system, the algebraic loop problem caused by non-strict feed structure is overcome, and the unknown nonlinearities arising from modeling error, parameter uncertainties, and system disturbances are also approximated for the subsequent active unknown nonlinearities compensation. Next, to enhance the convergence rate and guarantee the position tracking error within a prescribed region, a tracking error transformation method based on the prescribed performance function is utilized. Subsequently, the adaptive fuzzy control algorithm is developed with command filters, which can also avoid the complexity explosion issue due to the analytic calculation of the derivatives of stabilizing functions, and the rigorous stability of the close-loop system is proved by the Lyapunov theory. Finally, experimental results are utilized to illustrate the effectiveness of the developed controller.

Functional Model of an Automatic Vehicle Hold Based on an Electro-Hydraulic Braking System

The algorithm function designed in this paper can make a car maintain stability during automatic vehicle hold through the model input of multi-level target fluid pressure combined with slope judgment modules of different levels after the automatic vehicle hold software works. At the same time, a complete parking function module is designed, which can monitor the whole parking process in real time. Through the design of this function, the functional diversity of the electro-hydraulic braking system can be increased. When judging that the driver intends to start, the automatic vehicle hold system will automatically release the fluid pressure according to the opening of the accelerator pedal pressed by the driver so that the vehicle does not happen to brake when the vehicle starts in the slippery slope condition. Finally, real vehicle verification proves that the function can effectively meet the parking requirements and start on the flat and on a ramp. Also, it can effectively control the vehicle according to the driver’s driving intention.

Functional Safety for Automatic Emergency Braking based on ISO 26262

The popularity of electronic systems had increased in automobiles. A lot of ECUs, electronics sensors, bus are used in automobile systems which has made the system complex. Safety analysis should be done to ensure functional safety. IEC has introduced the standard, ISO 26262 for safety analysis of electrical/electronic/programmable systems in automobiles to reduce and control systematic faults. ISO 26262 give guidelines to define and follow the techniques strategically for the entire product life cycle of the vehicle. It does not explain how functional safety is done but it will guide us throughout the process. In this paper, we have analysed the Automatic Emergency Braking system as per the ISO 26262 guidelines. AEB is a significantly important active safety system which relies on electronic sensors, ECU and electronic actuators. The proper functioning of these electronic components could save the hazard from happening. We have determined the ASIL level, we determine safety goal and safety requirement, Fault Tree Analysis (FTA), Failure mode and Effect analysis. Also, we performed an HW safety analysis.
 Keywords: Electronic Sensors, functional safety, ISO 26262, Automatic Emergency Braking, Medini Analyze, Fault Tree analysis (FTA), Electro-Hydraulic Braking System, Failure Mode and Effect Analysis, Model-Based Safety Analysis, Safety Goals, HARA, FTA

MODERN AIRCRAFT BRAKING SYSTEMS

This paper presents some problems concerning the present trends in the field of aircraft braking systems. New solutions like electro-mechanical or electro-hydrostatic actuators are considered the future, but some big aircraft producers do not renounce yet to classical electro-hydraulic braking systems. New solutions are not generally accepted, they have to prove their reliability and that they bring considerable more advantages than penalties.

Brake-by-wire architecture design and analysis in accordance with functional safety standard

The brake-by-wire (BBW) system is one of the safety-critical components of intelligent vehicle chassis, and ensuring its reliability requires a comprehensive functional safety design process. Although many studies have been conducted on electro-mechanical braking (EMB), there is a lack of relevant content on electro-hydraulic braking (EHB), another scheme of BBW system. And the key components affecting EHB system reliability need to be further explored. To address these issues, a system-architecture for EHB with fail-operational capabilities based on ISO 26262 is proposed. Additionally, Fault tree analysis (FTA) and Bayesian network (BN) are used for assessing its reliability. Fault tree (FT) is established to quantitatively calculate the Automotive Safety Integration Level (ASIL). Then FT is mapped into BN, and the conditional probability table is modified to express the polymorphic and uncertain logical relationship of events. To mitigate the dimensional disaster caused by numerous risk factors in the joint probability distribution, a Noisy-or gate method is applied in the BN to address this problem. Finally, the crucial events of system reliability are analyzed. The results indicate that the proposed EHB architecture can meet the safety and reliability requirements of ASIL D and can provide essential reference for the design of EHB related fail-operational system.

Regenerative braking torque compensation control based on improved ADRC

Electro-hydraulic braking (EHB) compensation is an effective method to solve the insufficient regenerative braking of electric vehicles, but the accuracy and speed of executive pressure response are still insufficient. In order to solve this problem, a brake pressure compensation control method based on EHB system is proposed and verified. Firstly, adaptive LuGre friction model and braking dead time compensation are introduced to obtain a more accurate friction model. Then, an electro-hydraulic braking control strategy based on Improved Active Disturbance Rejection Control (IADRC) is proposed. Finally, the effectiveness of the proposed method is verified by simulation experiments and hardware-in-the-loop (HIL) simulation experiments. The test results show that the proposed control method can achieve accurate control of brake pressure compensation in time. The research results promote the research and application of EHB system to a certain extent.

Research on Adaptive Distribution Control Strategy of Braking Force for Pure Electric Vehicles

The actual driving conditions of electric vehicles (EVs) are complex and changeable. Limited by road adhesion conditions, it is necessary to give priority to ensuring safety, taking into account the energy recovery ratio of the vehicle during braking to obtain better braking quality. In this work, an electric vehicle with an EHB (electro-hydraulic braking) system whose braking force adaptive distribution control strategy is studied. Firstly, the vehicle dynamics model, including seven degrees of freedom, tire, drive motor, main reducer, battery pack, and braking system, was constructed, which is attributed to the vehicle configuration and braking system scheme. Second, based on curve I and ECE regulations, the adaptive braking force distribution control strategy was formulated by taking the maximum regenerative braking torque as the inflection point, the synchronous adhesion coefficient as the desired point, and the battery SOC, road adhesion coefficient, and braking strength as the threshold. Finally, the vehicle dynamics simulation model was built on the Matlab/Simulink platform, and the simulation results verified the feasibility of the proposed braking force adaptive allocation control strategy. The research shows that the adaptive distribution control strategy can better adapt to the complex and variable driving conditions of the vehicle by combining the inflection point and the desired point. The braking energy recovery ratios of the vehicle under the NEDC and NYCC cycle conditions on a high adhesion road are 52.62% and 47.45%. The braking force distribution curve is close to curve I under the low adhesion extreme road.

Integrated Pressure Estimation and Control for Electro-hydraulic Brake Systems of Electric Vehicles Considering Actuator Characteristics and Vehicle Longitudinal Dynamics

In the automotive field, electro-hydraulic brake systems (EHB) has been developed to take place of the vacuum booster, having the advantage of faster pressure built-up and continuously pressure regulation. Pressure control, one of the most crucial issues to be solved for EHB, is influenced by the system nonlinearities (e.g., pressure-position, friction). Recently, there are a series of studies that focus on this issue. However, the pressure control based on pressure estimation is rarely investigated in the previous literatures. In order to achieve cost-effective and highly integrated, the pressure is regulated without any add-in sensors, making it very difficult to achieve a satisfactory performance. A pressure control system based on pressure joint estimation is developed in this article according to a requirement-oriented model. The pressure joint estimation is designed considering actuator characteristics and vehicle dynamics. The wheel speed feedback is used for modification via a proportional-integral observer. A pressure control combining feedforward, torque-adaptive friction compensation with feedback controller is employed to improve the pressure-tracking performance. The constraint of feedback gain of controller is derived based on the small-gain theorem to remain the input–output stability of the overall control system. Superior to the estimation method based on actuator characteristics, the joint estimation method improves the accuracy by more than 10%. The pressure-tracking performance and robustness of system are validated by vehicle experiments under the typical common braking situations.

Master Cylinder Pressure Estimation of the Electro-Hydraulic Brake System Based on Modeling and Fusion of the Friction Character and the Pressure-Position Character

To estimate the master cylinder pressure of the electro-hydraulic brake system (EHB) accurately and robustly, this paper proposes a master cylinder pressure estimation method (MCPE) based on modeling and fusion of the friction character and the pressure-position character of EHB. First, the kinetic equation of EHB is established based on Newton's Law. Second, the sliding friction in EHB is theoretically analyzed and tested under multi conditions (e.g., rack speed, individual difference, wear and temperature). Test results show that the sliding friction is stable except for conditions below −25 °C. The static friction in EHB is derived from EHB's kinetic equation. Based on the above, a novel robust Karnopp friction model is established. Third, the pressure-position relationship of EHB is tested under multi conditions (e.g., rack speed, brake circuit, parking brake state, brake pair wear and temperature). Test results show that the pressure-position relationship is susceptible to all the tested conditions. The influence of rack speed on pressure-position relationship is further analyzed and a novel dynamic pressure-position model is established, which incorporates a static term and a dynamic term. Vehicle test verifies the superiority of the dynamic pressure-position model in terms of response speed and accuracy. Furthermore, a robust MCPE is proposed by combining the kinetic equation of EHB, which incorporates the proposed novel friction model, and the dynamic pressure-position model based on recursive least square algorithm with a forgetting factor. Finally, the accuracy and robustness of the proposed MCPE is demonstrated by vehicle test under multi braking conditions.

A Model Predictive Control Approach for Electro-Hydraulic Braking by Wire

In this article, based on a novel electro-hydraulic braking system for full self-driving vehicles, a model predictive control approach is designed for precisely tracking of braking pressure. Concerning electric motor, reduction mechanism, and hydraulic system, a new braking system model is formulated. Due to the nonlinear hydraulic characteristic of the master cylinder piston, a quadratic polynomial is utilized to fit a relationship between piston position and cylinder pressure, by which a desired pressure of master cylinder is transformed into a desired position of the piston. A recursive least square with forgetting factor is developed to find the optimal parameters of pressure–position relationship. A system friction model is established to calculate the equivalent friction torque, which is regarded as the compensation of the desired torque. A vehicle test bench of full self-driving is established to validate the designed approach. According to the accurate tracking and the quick response of braking pressure from experimental results, it can be concluded that the model predictive control approach is a good candidate for the pressure demand control of electro-hydraulic braking by wire.