Electromechanical Brake Research Articles

Accurate State Estimation for Electro-Mechanical Brake Systems

Electro-mechanical brake (EMB) system is an electric motor based braking force generation module, and it requires various sensors such as motor position, motor current and clamping force sensor for stable vehicle deceleration control. Because fault in these sensors can lead to degradation of the system performance, system monitoring is essential. To build a model based state estimator for the braking system, there are some requirements: the mathematical model presenting the nonlinearity and disturbance of the real system, fast response time and the accurate estimation. To solve this problem, this paper proposes a new EMB model which clamping force term is divided into the linear and nonlinear compensation part, and Kalman filter algorithm is applied to design the state estimator. The proposed model is simple and linear, and Kalman filter algorithm is robust to system noise and guarantees the fast computation time. Additionally, the braking direction aware and contact point aware clamping force estimation techniques are introduced, and they help to improve the accuracy of the state estimation. Lastly, the proposed approach is verified through experiments on the EMB test bench.

Parameter matching and braking performance advantage study for all-electric independent driving and braking electric vehicle with four wheels

All-electric integrated brake system is the feature for all-electric independent driving and braking electric vehicle with four wheels (AEIDBEV). Based on its advantages, an integrated simulation platform for parameter matching and performance verification is built. The vehicle control strategy is given. The results of simulation show that all-electric integrated brake system can meet the driver's braking demand and has three advantages. The first is that its braking effectiveness is slightly better than pure mechanical brake system. The second is work time and torque capacity for electromechanical brake (EMB) can be reduced remarkably. This provides a basis for optimising EMB. The third is that it can improve vehicle economy obviously. AEIDBEV has obvious energy saving effect compared with no braking energy recovery scheme and coupled braking energy recovery scheme at three drive cycles of NEDC, Beijing and Changchun.

一种适用于电机械制动装置的电机设计

一种适用于电机械制动装置的电机设计

A Clamping Force Performance Evaluation of the Electro Mechanical Brake Using PMSM

This paper deals with clamping force simulation and experimental result of the Electro Mechanical Brake (EMB) for the High-Speed-Train (HST). Three phase Surface Permanent Magnet Synchronous Motor (SPMSM) is applied to the clamping force control of EMB. At the initial development stage, Proportional Integral (PI) current control under synchronous d-q axis frame was applied to the SPMSM torque control. In addition, an anti-windup controller, which is advantageous for fast current tracking, is proposed to improve the torque output. Matlab/Simulink simulation results were compared with the experimental results measured by the clamping force sensors of the EMB test rig. The experimental results were verified compared to the brake design specification of the High-Speed Electric Multiple Unit-430 Experimental (HEMU-430X) train.

Real-Time Longitudinal Location Estimation of Vehicle Center of Gravity

The longitudinal location of a vehicle’s center of gravity (CG) is used as an important parameter for vehicle safety control systems, and can change considerably according to various driving conditions. Accordingly, for the better performance of vehicle safety control systems, it is essential to obtain the accurate CG location. However, it is generally difficult to acquire the value of this parameter directly through sensors due to cost reasons. In this study, a practical algorithm for estimating vehicle’s longitudinal CG location in real time is proposed. This algorithm is derived based only on longitudinal motion of the vehicle, excluding excessive lateral, yaw and roll movements of the vehicle. Moreover, the proposed algorithm has main differences from previous studies in that it does not require information such as vehicle mass, vehicle moments of inertia, road grade or tire-road surface friction, which are difficult to acquire. In the proposed algorithm, the relationship between the ratio of rear-to-front tire longitudinal force and the corresponding wheel slips are used to determine the CG location. To demonstrate a practical use of the proposed algorithm, the ideal brake force distribution is tested. The proposed CG estimation algorithm and its practical use are verified via simulations and experiments using a test vehicle equipped with electro-mechanical brakes in the rear wheels. It is shown that the estimated CG locations are close to the actual ones, and that the deceleration can be maximized by the ideal brake force distribution.

Fuzzy sliding mode control based on longitudinal force estimation for electro-mechanical braking systems using BLDC motor

This paper focuses on the controller design using fuzzy sliding mode control (FSMC) with application to electro-mechanical brake (EMB) systems using BLDC Motor. The EMB controller transmits the control signal to the motor driver to rotate the motor. The torque distribution of motors is studied in this paper actually. Firstly, the model of the EMB system is established. Then the state observer is developed to estimate the vehicle states including the vehicle velocity and longitudinal force. Due to the fact that the EMB system is nonlinear and uncertain, a FSMC strategy based on wheel slip ratio is proposed, where both the normal and emergency braking conditions are taken into account. The equivalent control law of sliding mode controller is designed on the basis of the variation of the front axle and rear axle load during the brake process, while the switching control law is adjusted by the fuzzy corrector. The simulation results illustrate that the FSMC strategy has the superior performance, better adaptability to various types of roads, and shorter braking distance, as compared to PID control and traditional sliding mode control technologies. Finally, the hardware-in-loop (NIL) experimental results have exemplified the validation of the developed methodology.

Braking Control for Improving Ride Comfort

While many vehicle control systems focus on vehicle safety and vehicle performance at high speeds, most driving conditions are very low risk situations. In such a driving situation, the ride comfort of the vehicle is the most important performance index of the vehicle. Electro mechanical brake (EMB) and other brake-by-wire (BBW) systems have been actively researched. As a result, braking actuators in vehicles are more freely controllable, and research on improving ride comfort is also possible. In this study, we develop a control algorithm that dramatically improves ride comfort in low risk braking situations. A method for minimizing the inconvenience of a passenger due to a suddenly changing acceleration at the moment when the vehicle is stopped is presented. For this purpose, an acceleration trajectory is generated that minimizes the discomfort index defined by the change in acceleration, jerk. A controller is also designed to track this trajectory. The algorithm that updates the trajectory is designed considering the error due to the phase lag occurring in the controller and the plant. In order to verify the performance of this controller, simulation verification is completed using a car simulator, Carsim. As a result, it is confirmed that the ride comfort is dramatically improved.

Backup Mechanical Brake System of the Wind Turbine

Paper clarifies the necessity of the emergency mechanical brake systems usage for wind turbines. We made a deep analysis of the wind turbine braking methods available on the market, identifying their strengths and weaknesses. The electromechanical braking appeared the most technically reasonable and economically attractive. We described the developed combined electromechanical brake system for vertical axis wind turbine driven from electric drive with variable torque enough to brake over the turbine even on the storm wind speed up to 45 m/s. The progress was made due to the development of specific kinematic brake system diagram and intelligent control system managed by special operation algorithm.

Дублирующая электромеханическая система торможения ветроэнергетической установки

The article presents data on Russian Federation regions with the highest average annual wind speeds and justifies the profitability of using wind power plants in these regions. Negative factors that can be encountered in the operation of wind power equipment in the zone of increased wind loads are considered. The necessity of application of duplicating braking systems in wind power plants is determined. Analytical comparison of existing methods of wind turbines braking is given, their advantages and disadvantages are revealed. The most reliable and efficient type is the electromechanical braking of a wind wheel, which combines the advantages of the considered analogues while lacking their shortcomings. A description of such electromechanical braking system for a vertically axial wind power plant is given using a computer 3D model created in the SolidWorks software package. The kinematic scheme of the braking system is illustrated, it describes the interconnection of the main components of the system: the electric drive, the reducer, the three-jaw brake unit and the brake drum on the wind turbine rotor. In addition, the article describes the suggested scheme and control algorithm for this braking system, based on the constant monitoring of the main components state and keeping it in acceptable operating ranges. The conclusion about the efficiency of the braking system application under consideration at wind power plants is made.

Hybrid Genetic Algorithm and Kalman Filter Approach to Estimate the Clamping Force of Electro-Mechanical Brake

In thispaper, a hybrid genetic algorithm (GA) and Kalman filter approach to combining motor encoder and current sensor models is presented to accurate estimate the clamping force of an electro-mechanical brake (EMB). Elimination of the clamping force sensor and measurement cables results in lower cost and increased reliability of an EMB system, including its electric motor.A Kalman filter is a special kind of observer that provides optimal filtering of the measurement noise and inside the system if the covariances of these noises are known. The proposed combined estimator is based on Kalman filter optimized by GA in which the motor encoder is used in a dynamic stiffness model and the motor current sensor is used to give measurement updates in a torque balance model. A real-coded GA is used to optimize the noise matrices and improve the performance of the Kalman filter. Experimental results show that, by using the proposed estimator, the virtual clamping force sensor can handle highly dynamic situations, making it suitable for possible use in sensorless fault-tolerant control. It is shown that the proposed combined estimator improves the root mean square error (RMSE) performance. The developed estimator can be used in real vehicle environments because it can adapt to parameter variations.

Clamping force control based on dynamic model estimation for electromechanical brakes

The electromechanical brake (EMB) is expected to be utilized for future brake systems due to its many advantages. In this paper, keeping commercialization of the EMB in mind, a new EMB clamping force controller is proposed to overcome the limitations of the existing controller, namely, the extra cost for sensor installation and response delay. To design the controller, both mechanical parts and electrical parts in the EMB have to be mathematically analyzed. Also, dynamic models, clamping force, and friction torque are estimated to generate some feed-forward terms of the controller. With an estimation of the contact point where brake pads start to come into contact with a disk wheel, the clamping force is expressed as a polynomial curve versus the motor angle. The estimated clamping force is evaluated in comparison with measured values by a load cell. The proposed controller is based on an adaptive sliding mode control method with an adaptive law reducing errors of the friction torque model. Lastly, the performance of the entire control system is compared with that of the existing controller on a test bench.

Path Following With Authority Sharing Between Humans and Passive Robotic Walkers Equipped With Low-Cost Actuators

A promising way to offset the reduced mobility of a large number of older adults is using robotic systems providing physical and cognitive support for the navigation in large and crowded public spaces. In this letter, we study a possible solution for guidance based on the action of electromechanical brakes mounted on the rear wheels. The solution does not require sophisticated sensing devices and aims to share the control authority between the user and the robotic platform: the system kicks in with quick corrections only in presence of deviations from the path or of dangerous situations. The level of the shared authority is controlled by means of a simple parameter. The control paradigm is based on an all-or-nothing policy relying on very rough actuators. In our experimental validation, all the users have been proficient in the use of the device after a short learning time.

Clamping force estimation based on hysteresis modeling for electro-mechanical brakes

The Electro-Mechanical Brake (EMB) is anticipated by research communities and car manufacturers to be the future adopted brake system due to its advantages. However, to be competitively priced, the high cost load cell of EMB, which measures the clamping force to a disk, should be replaced by a clamping force estimation algorithm. For this purpose, a new clamping force estimator, compatible with readily available sensors, is proposed in this paper. This estimator determines the kissing point where the brake pads start to come into contact with the disk, and generates the characteristic curve of the polynomial function between the clamping force and the motor angle. Periodically updating the characteristic curve can enhance robustness to the pad’s changing thickness. Also, the model includes a description of the hysteresis of the clamping force in the overall algorithm, which prevents the estimation performance from decreasing in the transient state. The performance of the propose algorithm was validated by comparison with measured values on a developed EMB test bench.

Design and optimization of a cam-actuated electrohydraulic brake system

Although different types of brake-by-wire mechanism including electrohydraulic brakes, electromechanical brakes, electronic wedge brakes and distributed electrohydraulic brakes have been developed in the past two decades, there is still an increasing demand for further improvement and also for development of new brake mechanisms in the automotive industry because of the escalating requirements for higher safety and better performance. This paper proposes a novel brake-by-wire system based on the cam actuation mechanism. The proposed cam-actuated electrohydraulic brake system is a combination of an electrical component, a mechanical component and a hydraulic component. The unique feature of the proposed cam-actuated electrohydraulic brake system is that the characteristics of the motor torque amplification can be optimized by careful design of the cam shape. The overall structure of the cam-actuated electrohydraulic brake system is described, and the dynamic model of the system is developed. Optimum design of the cam-actuated electrohydraulic brake system is obtained by multi-objective optimization, and the obtained simulation results are discussed. The compactness and the self-contained characteristics of the design enable the brake system to be installed on each wheel, allowing fully independent control of each wheel for better stability control.

Robust Clamping Force Control of an Electro-Mechanical Brake System for Application to Commercial City Buses

This paper proposes a sensor-less robust force control method for improving the control performance of an electro-mechanical brake (EMB) which is applicable to commercial city buses. The EMB generates the accurate clamping force commanded by a driver through an independent motor control at each wheel instead of using existing mechanical components. In general, an EMB undergoes parameter variation and a backdrivability problem. For this reason, the cascade control strategy (e.g., force-position cascade control structure) is proposed and the disturbance observer is employed to enhance control robustness against model variations. Additionally, this paper proposed the clamping force estimation method for a sensor-less control, i.e., the clamping force observer (CFO). Finally, in order to confirm the performance and effectiveness of a proposed robust control method, several experiments are performed and analyzed.

An emergency braking controller based on extremum seeking with experimental implementation

An extremum seeking scheme is developed for maximizing the longitudinal tire forces of the road vehicles during emergency braking situations. If the road condition is known, then a conventional braking controller could generate required braking moment to track the slip set point which belongs to that road condition. However, estimating the road condition is not an easy task and it brings additional computation effort. Rather than that, a self optimization algorithm is presented in this paper without relying on road condition estimation. The developed controller searches optimum operation point for getting maximum friction force. Computer simulations show the effectiveness of the self optimization routine. To validate the real time applicability of the algorithm, an electromechanical braking test system is used for the experiments. Due to the limited measurements from the experimental system, force and moment observers are designed to calculate necessary control inputs for maximizing the friction potential, i.e. the braking force. Via the experimental study, it has been shown that the developed self optimizing controller is fast, accurate, and operable on a real braking system.

Adaptive Model Predictive Control Research on Regenerative Braking for Electric Bus Cruising Downhill

To use regenerative brake and mechanical brake co-operatively to maintain the constant speed and the braking energy can be regenerated as much as possible when vehicles travel downhill, the mathematical model of the braking system is established, and the adaptive model predictive control method is adopted to control the speed of vehicles. The recursive least square algorithm with the forgetting factor is used to identify the road gradient online. And then the control results of the adaptive model predictive control are compared with the results of PID control, simulation results show that the robustness and the stability of the adaptive model predictive control method are better. The speed can be maintained basic stability with the coordinated use of the regenerative braking and the mechanical braking. Meanwhile, the braking energy can be regenerated as much as possible as the regenerative braking system can be used as much as possible. Moreover, as the charge acceptance ability of the battery is restricted, the brake mode switching model is designed. The braking mode can be switched between the electro-mechanical braking system and mechanical braking system according to the SOC of the batteries.

Fault-tolerant braking control with integerated EMBs and regenerative in-wheel motors

This paper presents a fault-tolerant brake torque controller for four-wheel-distributed braking systems with in-wheel motors and Electro-Mechanical Brakes (EMB). Mechanical and electrical faults can degrade the performance of the EMB actuators and, thus, their effects need to be compensated in vehicle dynamics level. In this study, the faults are identified as performance degradation and expressed by the gains of each actuator. Assuming the brake force distribution and the regenerative braking ratios, the over-actuated braking system is simplified into a two-input system. A sliding mode controller is designed to track the driver’s braking and steering commands, even if there exist faults in EMBs. In addition, adaptive schemes are constructed to achieve the fault-tolerant control in braking. The proposed controller and strategies are verified in the EMB HILS (Hardware-in-loop-simulation) unit for various conditions.

전동식 브레이크 시스템의 클램핑력 센서 교정 및 클램핑력 추정 알고리즘 개발

The electromechanical brake (EMB) is one of future brake systems due to its many advantages. For imple- mentation of the EMB, the correct feed back about clamping force is necessary. Keeping commercialization of the EMB in mind, it is strongly demanded that an expensive load cell measuring the clamping force is replaced with an estimation algorithm. In addition, an estimation of the kissing point where the brake pads start to come into contact with a disk wheel is proposed in this paper. With these estimation algorithms, the clamping force can be expressed as a polynomial characteristic curve versus the motor angle. Also, a method for calibration of measured values by the load cell is proposed and used for an actual characteristic curve. Lastly, the performance of the proposed algorithms is evaluated in comparison with the actual curve on a developed EMB test bench.

An Integrated Vehicle Dynamic Controller

This paper proposes a new multivariable linear parameter varying $(\mbox{LPV})/\mathcal{H}_\infty$ control strategy for global chassis control. The main objective is to handle critical driving situations by activating several subsystems (semi-active suspensions, active steering, and electromechanical braking actuators) in a hierarchical way. The main idea is to schedule the three control actions (braking, steering, and suspension) according to the driving situation evaluated by a specific monitor. Indeed, on one hand, rear braking and front steering are used to enhance the vehicle yaw stability and lateral dynamics, and on the other hand, the semi-active suspensions are used to improve comfort and car handling performance. Due to the $\mbox{LPV}/\mathcal{H}_\infty$ framework, this new approach allows a smooth coordination to be reached between the various actuators, to ensure robustness and stability of the proposed solution, and to significantly improve the vehicle dynamical behavior. Simulations have been performed on a complex full vehicle model, which has been validated using data obtained from experimental tests on a real Renault Megane Coupe. Moreover, the suspension system uses magnetorheological dampers whose characteristics have been obtained through experimental identification tests. A comparison between the proposed $\mbox{LPV}/\mathcal{H}_\infty$ control strategy and a classical linear time-invariant/ $\mathcal{H}_\infty$ controller is performed using the same simulation scenarios and confirms the effectiveness of this approach.