Showing papers on "Dynamic braking published in 2014"

Increasing the Regenerative Braking Energy for Railway Vehicles

Abstract: Regenerative braking improves the energy efficiency of railway transportation by converting kinetic energy into electric energy. This paper proposes a method to apply the Bellman-Ford (BF) algorithm to search for the train braking speed trajectory to increase the total regenerative braking energy (RBE) in a blended braking mode with both electric and mechanical braking forces available. The BF algorithm is applied in a discretized train-state model. A typical suburban train has been modeled and studied under real engineering scenarios involving changing gradients, journey time, and speed limits. It is found that the searched braking speed trajectory is able to achieve a significant increase in the RBE, in comparison with the constant-braking-rate (CBR) method with only a minor difference in the total braking time. An RBE increment rate of 17.23% has been achieved. Verification of the proposed method using BF has been performed in a simplified scenario with zero gradient and without considering the constraints of braking time and speed limits. Linear programming (LP) is applied to search for a train trajectory with the maximum RBE and achieves solutions that can be used to verify the proposed method using BF. It is found that it is possible to achieve a near-optimal solution using BF and the solution can be further improved with a more complex search space. The proposed method takes advantage of robustness and simplicity of modeling in a complex engineering scenario, in which a number of nonlinear constraints are involved.

Extended-Kalman-filter-based regenerative and friction blended braking control for electric vehicle equipped with axle motor considering damping and elastic properties of electric powertrain

Abstract: Because of the damping and elastic properties of an electrified powertrain, the regenerative brake of an electric vehicle (EV) is very different from a conventional friction brake with respect to the system dynamics. The flexibility of an electric drivetrain would have a negative effect on the blended brake control performance. In this study, models of the powertrain system of an electric car equipped with an axle motor are developed. Based on these models, the transfer characteristics of the motor torque in the driveline and its effect on blended braking control performance are analysed. To further enhance a vehicle's brake performance and energy efficiency, blended braking control algorithms with compensation for the powertrain flexibility are proposed using an extended Kalman filter. These algorithms are simulated under normal deceleration braking. The results show that the brake performance and blended braking control accuracy of the vehicle are significantly enhanced by the newly proposed algorithms.

Hardware-in-the-loop simulation of pressure-difference-limiting modulation of the hydraulic brake for regenerative braking control of electric vehicles

Abstract: Because of its significant impact on the cooperative regenerative braking performance of electrified vehicles, the modulation effect of a hydraulic brake is of great importance. To improve the hydraulic brake control performance further, a novel pressure-difference-limiting control method for hydraulic pressure modulation based on on–off solenoid valves is proposed. The linear relationship between the coil current and the pressure difference across the valve is obtained. The characteristics of pressure-difference-limiting modulation are simulated and analysed. Then, a cooperative regenerative braking control algorithm based on the pressure-difference-limiting modulation of the hydraulic brake is designed. Hardware-in-the-loop tests of the algorithm under typical braking procedures are carried out. The test results demonstrate the validity and feasibility of the developed regenerative braking control algorithm and indicate that the proposed pressure-difference-limiting modulation method, which has an advantage over the conventional control based on a pulse-width-modulated signal with respect to the control accuracy of the hydraulic brake pressure, has great potential to improve the braking performance of a vehicle.

Realization of Anti-Lock Braking Strategy for Electric Scooters

Abstract: This research studies a novel method of realizing a nonmechanical antilock braking system (ABS) controller for electric scooters (ESs) based on regenerative, kinetic, and short-circuit braking mechanisms. In which, a boundary layer speed control is proposed for a guarantee of the optimal slip ratio between tires and road surface. The antilock braking controller, combined with this controller, drives a low-side driving circuit to induce either an open-circuit or a short-circuit loop on the motor stator's coil to a load; it thus produces braking actions analogous to those in the conventional ABS control. The proposed ABS controller is practically realized. Improvement of the braking performance for the ABS action is further addressed via real-world experiments.

Study on Emergency-Avoidance Braking for the Automatic Platooning of Trucks

Abstract: In developing automatic platooning of trucks as an energy-saving technology, the reliable driving of the platooned trucks is a primary objective for public implementation and future applications. At the same time, there is also an emergency requirement to ensure the safety of the driving experiment in the automatic platooning of trucks, including the conditions of a system failure. This paper presents a detailed experimental study on emergency avoidance braking for the automatic platooning of trucks using a driving simulator (DS) and an actual-vehicle experiment. In addition, a modification on the braking capability of the trucks of a platoon was applied for safety control. Therefore, human drivers can brake without risking a rear-end collision, in the case of an emergency for a failure in automatic platooning. Initially, an experimental platform was built to reproduce the automatic platooning of trucks in an advanced DS system. Assuming system failure and the emergency deceleration of the preceding truck without warning, the behavior of the driver in the following truck was studied in terms of emergency avoidance of a collision. In particular, with different settings for the mean maximum decelerations of the brake system of the following truck, the stopping gap distances and driver reaction times were analyzed in the driving experiment using the advanced DS and an actual vehicle. The experimental results indicated that emergency braking is an effective method for avoiding a rear-end collision when there is a system failure in the automatic platooning, resulting in the mean maximum deceleration for the following truck being higher than that for the preceding truck.

Optimization of nonlinear control strategy for anti-lock braking system with improvement of vehicle directional stability on split-μ roads

Abstract: In a hard braking on a split-μ road, the achievement of shorter stopping distance while maintaining the vehicle in the straight line are of great importance. In this paper, to achieve these conflicting aims, an optimal nonlinear algorithm based on the prediction of vehicle responses is presented to distribute the wheel braking forces properly. The base of this algorithm is reducing the maximum achievable braking forces of one side wheels, as low as possible, so that the minimum stabilizing yaw moment is produced. The optimal property of the proposed control method makes it possible to get a trade-off between the shorter stopping distance and the less deviation of the vehicle heading from the straight line. The special case of this algorithm leads to the conventional anti-lock braking system (ABS) which generates the maximum braking forces for all wheels to attain the minimum stopping distance. However, the ABS cannot control the vehicle directional stability directly. The simulation results carried out using a nonlinear 8-DOF vehicle model demonstrate that the designed control system has a suitable performance to attain the desired purposes compared with the convectional ABS.

A model predictive control allocation approach to hybrid braking of electric vehicles

Abstract: With the recent emergence of electric drivetrains, a faster and energy efficient braking actuator - the electric motor - has become available to complement the operation of the traditional friction brakes. The decision on how to split the braking torque among the friction brake and the electric motor is one of the main issues of such hybrid braking systems. With this challenge in mind, a new model predictive control allocation (MPCA) approach for hybrid braking is proposed. In comparison to state of the art torque blending solutions (daisy chain and dynamic control allocation) the MPCA offers faster transient response, without compromising the energy recuperation efficiency of the actuators. In addition, we also develop a linear wheel slip controller to regulate the braking force during emergency braking maneuvers. The tuning of this wheel slip controller is carried out using robust pole placement techniques, which ensures good operation in spite of uncertainties in the tire-road friction coefficient and the vertical load. Simulation results demonstrate the effectiveness of the proposed method.

Medium-Voltage Current-Source Converter Drives for Marine Propulsion System Using a Dual-Winding Synchronous Machine

Abstract: Medium-voltage (MV) drives are increasingly used in high-power marine applications for running thrusters and main propulsion motors. In this paper, an MV drive solution employing active front-end current-source converters is proposed for a synchronous-motor-based propulsion system. The proposed solution includes two independent drives, each to control one of the two sets of three-phase windings of the synchronous motor. A dedicated communication link between the drives allows continuous load sharing and robust system operation in a master-follower drive configuration. Field-oriented control with the use of an absolute encoder is implemented for providing high starting torque and smooth speed control over a wide speed range including a 30% overspeed region. The major advantages of the proposed solution include simple structure, increased system power rating, redundant operation, low-harmonic input/output waveforms, improved reliability, elimination of a bulky input isolation transformer, and parallel drive control without the need of a complex coordinated inverter gating system. In addition, the system offers input power factor compensation and dynamic braking to allow operation on a generator-based supply system. Field test results obtained on a 14-MW ship propulsion system are provided to demonstrate the system performance.

Development of an autonomous braking system using the predicted stopping distance

Abstract: An autonomous braking system is designed using the prediction of the stopping distance. The stopping distance needs to be determined by considering several factors such as the desired deceleration and the speed of the hydraulic brake actuator. In particular, the actuator speed is very critical because it affects the shape of the deceleration response and it determines the accuracy of the predicted stopping distance. The autonomous braking control algorithm is designed based on the predicted stopping distance. The proposed autonomous braking system has been validated in autonomous vehicle tests and demonstrates that the subject vehicle can avoid the collision effectively.

Aerodynamic braking device for high-speed trains: Design, simulation, and experiment

Abstract: This paper proposes the design of an aerodynamic braking device for a high-speed train. The design is based on the parameters of the high-speed train and the working principles of airplane wings. T...

Braking control system and method for vehicle

Abstract: A braking control system and a method for a vehicle are provided The braking control method includes sensing, by a controller, a rear-side collision risk and a lane change and determining a lane change intention based on a steering change of a vehicle In addition, the controller is configured to determine a braking control for the vehicle and a magnitude of the braking control for the vehicle based on the rear-side collision risk and the lane change, and the lane change intention

Control allocation for regenerative braking of electric vehicles with an electric motor at the front axle using the state-dependent Riccati equation control technique

Abstract: In this paper the systematic development of an integrated braking controller for a vehicle driven by an electric motor on the front axle is presented. The objective is to engage the electric motor only during braking, up to the point at which the vehicle reaches its manoeuvrability and stability limit. The control challenges are to distribute the braking effort correctly between the hydraulic brakes at the four tyres and the electric motor, to handle the tyre saturation and motor constraints effectively and to adapt the control allocation based on the vehicle’s states. The controller is designed using the state-dependent Riccati equation control technique, the vehicle state estimation and the ‘magic formula’ tyre model. The state-dependent Riccati equation control technique is a suboptimal control design technique for non-linear systems. A novel method for constructing the state-dependent coefficient formulation of the system dynamics is proposed. Soft constraints in the state dynamics are described, while an augmented penalty approach is suggested for handling the system’s hard constraints. The performance of the controller was evaluated for different braking scenarios using simulations in a MATLAB/Simulink environment. An eight-degree-of-freedom non-linear vehicle model was utilized. The numerical results show that the controller suboptimizes the regenerative braking effort while considering the tyre force saturation, the motor torque limits, the vehicle yaw rate and the slip angle error. A comparison with a constrained linear quadratic regulator shows the advantages of the proposed controller.

Regenerative braking regulation in automotive vehicles

Abstract: The invention relates to a self-learning regenerative control system that adapts to the user's driving style. The system receives as input a signal that is indicative of the friction brake usage and adapts the degree of regenerative braking accordingly. When the friction brake usage is high, the system will make the regenerative braking more aggressive such that when the user lifts-off the foot from the accelerator pedal, the degree of regenerative braking will be higher, thus reducing the need to use friction brakes. The system continuously adapts the regenerative braking intensity based on driving style, road conditions, etc.

Longitudinal heavy haul train simulations and energy analysis for typical Australian track routes

Abstract: Computer simulations are utilised to study the energy used by heavy haul trains and the amount of energy that can be generated from dynamic braking of these trains; these studies allow the potential for the application of hybrid locomotives to be evaluated. An in-house written software package is used to perform simulations on the energy balance between energy usage and the energy generated from dynamic braking for heavy haul operations on two typical track routes in Australia. The simulation results show that the energy generated from dynamic braking can contribute up to 30% of the energy used in locomotive traction. Detailed analyses show that the locomotives can operate at an average power that is much less than full power, and an energy hybridisation potential factor is defined, with the maximum factor reaching a value of 63%. This factor indicates the considerable potential for using hybrid locomotive traction in heavy haul applications.

System and method for control of a hybrid vehicle with regenerative braking using location awareness

Abstract: A hybrid vehicle includes a location awareness module that determines an energy profile for a portion of a roadway or for a known route. The energy profile includes one or more measurements of regenerative braking operations for predicted braking events. The hybrid vehicle determines an efficient use of an electric motor and generator (EMG) based on the energy profile of the roadway portion or the route. When the energy profile includes a predicted braking event, the hybrid vehicle determines to engage the EMG to discharge the battery system prior to the regenerative braking operation for the predicted braking event.

Optimized Braking Torque Generation Capacity of an Eddy Current Brake With the Application of Time-Varying Magnetic Fields

Abstract: Unlike conventional hydraulic brakes (CHBs), eddy-current brakes (ECBs) are electrically controlled and noncontact-type actuators. Having such advantages makes ECBs a potential alternative to the conventional systems used in vehicles. However, the braking torque generation of ECBs at low speed is insufficient to stop the vehicle. Thus, such brakes are used for assistive braking. Our previous study showed that braking torque increases with an ac field application compared with the torque generated with a dc field application. To increase the braking torque generation to realize a stand-alone ECB, the braking torque generation of the ECB is optimized, using a stochastic search algorithm, with the consideration of comfort and skin effects, as well as geometric and field-dependent factors. The results show that the application of an ac field with varying frequency on a configuration with multiple pole projection areas (PPAs) results in a significant increase in the braking torque compared with the dc field application, and such optimum ECB configuration can generate a sufficient amount of braking torque comparable with those generated by CHBs.

Cooperative regenerative braking control for front-wheel-drive hybrid electric vehicle based on adaptive regenerative brake torque optimization using under-steer index

Abstract: In this study, cooperative regenerative braking control of front-wheel-drive hybrid electric vehicle is proposed to recover optimal braking energy while guaranteeing the vehicle lateral stability. In front-wheel-drive hybrid electric vehicle, excessive regenerative braking for recuperation of the maximum braking energy can cause under-steer problem. This is due to the fact that the resultant lateral force on front tire saturates and starts to decrease. Therefore, cost function with constraints is newly defined to determine optimum distribution of brake torques including the regenerative brake torque for improving the braking energy recovery as well as the vehicle lateral stability. This cost function includes trade-off relation of two objectives. The physical meaning of first objective of cost function is to maximize the regenerative brake torque for improving the fuel economy and that of second objective is to increase the mechanical-friction brake torques at rear wheels rather than regenerative brake torque at front wheels for preventing front tire saturation. And weighting factor in cost function is also proposed as a function of under-steer index representing current state of the vehicle lateral motion in order to generalize the constrained optimization problem including both normal and severe cornering situation. For example, as the vehicle approaches its handling limits, adaptation of weighting factor is possible to prioritize front tire saturation over increasing the recuperation of braking energy for driver safety and vehicle lateral stability. Finally, computer simulation of closed loop driver-vehicle system based on Carsim™ performed to verify the effectiveness of adaptation method in proposed controller and the vehicle performance of the proposed controller in comparison with the conventional controller for only considering the vehicle lateral stability. Simulation results indicate that the proposed controller improved the performance of braking energy recovery as well as guaranteed the vehicle lateral stability similar to the conventional controller.

Instantaneous optimal regenerative braking control for a permanent-magnet synchronous motor in a four-wheel-drive electric vehicle:

Abstract: Recovering the kinetic energy of a vehicle is one inherent advantage of an electric vehicle. A permanent-magnet synchronous motor is widely adopted for the traction motor in an electric vehicle wit...

Normalizing deceleration of a vehicle having a regenerative braking system

Abstract: A method of operating a vehicle having a friction braking system and a regenerative braking system is presented here. The method determines a regenerative torque capacity, calculates a desired regenerative torque amount for the braking system, detects that the desired regenerative torque amount exceeds the regenerative torque capacity by at least a threshold amount, and controls actuation of the friction braking system in response to the detecting. Another operating method determines a coastdown torque capability of the vehicle, calculates a desired coastdown torque amount, detects that the desired coastdown torque amount exceeds the coastdown torque capability by at least a threshold amount, and controls actuation of the friction braking system in response to the detecting.

Hybrid vehicle braking limit determination system and method

Abstract: A vehicle includes a powertrain having an electric machine configured to selectively apply regenerative torque to cause deceleration in response to braking demand; the powertrain further including a torque converter configured to decouple the electric machine from wheels of the vehicle. The vehicle is also provided with a controller programmed to, during a regenerative braking event, receive a signal defining a regenerative torque limit, and in response to a fault condition associated with the regenerative torque limit, generate a replacement regenerative torque limit based upon a torque converter open speed to decrease roughness during transitions into and out of regenerative braking.

System and method for managing hybrid vehicle regenerative braking

Abstract: A vehicle includes a powertrain having an electric machine configured to selectively apply regenerative braking torque to decelerate the vehicle. The vehicle also includes a controller programmed to control a rate of change of a regenerative braking torque limit during a transmission downshift that occurs during a regenerative braking event based on a change in speed of an output shaft of the powertrain caused by the transmission downshift.

System and method for controlling a vehicle

Abstract: A control system for a vehicle comprises a control unit configured to be electrically coupled to a drive system of the vehicle. The drive system includes at least one traction motor for providing motive power to the vehicle. The control unit is configured to control a torque output of the traction motor to hold zero speed or near zero speed of the vehicle on a grade without knowing information, in at least one mode of operation, about the grade and/or a load of the vehicle, and without a service brake of the vehicle being activated.

A robust wheel slip control design for in-wheel-motor-driven electric vehicles with hydraulic and regenerative braking systems

Abstract: A robust wheel slip ratio controller for in-wheel-motor-driven electric vehicles equipped with both hydraulic anti-lock braking systems (ABS) and regenerative braking (RB) systems is designed in this paper. Based on an integration of optimal predictive control design and Lyapunov theory, the issue of uncertain vehicle parameters is addressed. The corresponding braking torque distribution strategy between the RB and hydraulic braking (HB) is also introduced to achieve smooth regulation of the brake torque, such that the pedal pulsating effect of the traditional ABS system can be relieved. By utilizing the larger working range of the HB system and the higher bandwidth of the RB system, a better wheel slip ratio control performance can be obtained. The effectiveness of the proposed control system has been validated in Matlab/Simulink simulations.

Control unit for a recuperative brake system of a vehicle and method for braking a vehicle

Abstract: A control device for a recuperative braking system of a vehicle includes: an actuating device configured to (i) select the maximum value of a front axle generator braking torque and of a rear axle generator braking torque, taking into account at least one provided default variable concerning a setpoint total braking torque which is predefined by a driver, (ii) control an electric motor, and (iii) control a hydraulic front axle brake circuit component and a hydraulic rear axle brake circuit component in such a way that a front axle brake pressure and a rear axle brake pressure are settable in such a way that a difference between a predefined setpoint braking torque distribution and an actual braking torque distribution present between the front axle and the rear axle is minimized.

Advanced Emergency Braking Controller Design for Pedestrian Protection Oriented Automotive Collision Avoidance System

Abstract: Automotive collision avoidance system, which aims to enhance the active safety of the vehicle, has become a hot research topic in recent years. However, most of the current systems ignore the active protection of pedestrian and other vulnerable groups in the transportation system. An advanced emergency braking control system is studied by taking into account the pedestrians and the vehicles. Three typical braking scenarios are defined and the safety situations are assessed by comparing the current distance between the host vehicle and the obstacle with the critical braking distance. To reflect the nonlinear time-varying characteristics and control effect of the longitudinal dynamics, the vehicle longitudinal dynamics model is established in CarSim. Then the braking controller with the structure of upper and lower layers is designed based on sliding mode control and the single neuron PID control when confronting deceleration or emergency braking conditions. Cosimulations utilizing CarSim and Simulink are finally carried out on a CarSim intelligent vehicle model to explore the effectiveness of the proposed controller. Results display that the designed controller has a good response in preventing colliding with the front vehicle or pedestrian.

Maximise the Regenerative Braking Energy using Linear Programming

Abstract: Regenerative braking improves the energy efficiency of railway transportation by converting the kinetic energy into the electrical energy. In this paper, Linear Programming (LP) is applied to search for the train braking trajectory with the maximum Regenerative Braking Energy (RBE). LP takes the advantages of simplicity in modelling, efficiency in computation, flexibility in applications. Compared with a previously proposed model, the proposed LP optimisation model takes into account the speed limit constraints during the braking operation. Four case studies have been performed with different speed limits and initial braking speeds. While the maximum allowed braking time takes a key role for the RBE recovery, a threshold exists when the impact of maximum allowed braking time starts to become negligible. It has been demonstrated in this paper that LP is a robust and effective method to locate the optimal braking trajectory with the maximum RBE. The results of the optimisation are of significant interest for urban transportation systems where the regenerative braking is frequently applied. Future work of this paper is to investigate the optimisation of RBE in a more complicated scenario where the gradients are present and the motoring operation of train is allowed.

PMSM-driven satellite reaction wheel system with adjustable DC-link voltage

Abstract: This paper presents a digital signal processor-based permanent magnet synchronous motor (PMSM)-driven satellite reaction wheel with DC-link voltage adjustable according to speed and photovoltaic voltage. After the PMSM-driven reaction wheel is established, an improved current-controlled pulse-width modulation scheme is designed to yield precise sinusoidal winding current command tracking, and a simple, robust, model-following control scheme is designed to yield good dynamic speed response. To provide an adjustable and well-regulated DC-link voltage, DC/DC boost and DC/DC buck-boost front-end converters are established and compared. The stable chopping-controlled dynamic braking mechanism is also established.