Wheel Cylinder Research Articles

Linear Control of Switching Valve in Vehicle Hydraulic Control Unit Based on Sensorless Solenoid Position Estimation

Accurate linear brake-pressure control in a hydraulic control unit (HCU) of the vehicle dynamics control system, such as the electronic-stability control (ESC) system, can improve the control performance while significantly reduce noise and brake paddle vibration during the transient high-frequency brake-pressure control process. To minimize system cost, only simple switching solenoid valves and a master cylinder pressure (MCP) sensor are used in the ESC, thus an accurate real-time sensorless spool-position estimation is the key to the linear pressure controller. In this paper, a new sliding-mode controller (SMC) integrated with a nonlinear sliding-mode observer (SMO) is proposed to achieve a real-time linear controller for the switching valve in the HCU. First, a nonlinear SMO is used to observe the spool position based on the voltage and current values of the solenoid coil, from which the flow rate of brake fluid in the HCU of the ESC and the wheel cylinder pressure (WCP) can be deduced based on a specific hydraulic model of the solenoid valve and the braking system. Then an SMC is employed to adjust the spool position for accurate linear pressure control, taking into consideration the nonlinear characteristics of the electromagnetic force, the dynamic flow force, and the flow rate of the solenoid valve at different openings. Simulations and experiments were conducted, and the results supported the tracking ability of the sensorless linear pressure controller in different conditions. This study may provide a useful method to realize real-time linear control of high-frequency switching valve comparable to a high-performance proportional valve.

Co-Simulation of an Integrated Braking System Based on Dual-Motor Drive by Using ADAMS and SIMULINK

To improve the design efficiency of the Integrated braking system (IBS) based on dual-motor drive, the paper established a co-simulation model in ADAMS and Simulink. The 3D mechanical model which was set up in SolidWorks had been imported into the ADAMS software to build the retarding mechanism model, and build the motor model in Simulink, the established model was used to co-simulate the brake pressure regulation process. The results show, the system has a fast pressure response characteristics, and the single wheel cylinder pressure regulation frequency can reach 50Hz. The paper provides an effective method to design an IBS prototype.

Research on Control Strategies of Hydraulic ABS Wheel Cylinder Pressure Fine Regulation

In order to achieve fine regulation on wheel cylinder pressure of hydraulic ABS, the mathematical model of the solenoid valve and the wheel cylinder are built up through the analysis of the model of key components of hydraulic control unit solenoid valve and wheel cylinder.The relationship between the change rate of wheel cylinder pressure and the duty ratio of control signal is directly proportional. The frequency and effective duty ratio range of control signal of solenoid value is obtained through the simulation experiments. Oil pump is theoretically analyzed. The flow mathematical model of the oil pump is built up. The relationship between the speed of oil pump and the decompression rate of wheel cylinder is obtained. The wheel cylinder pressure fine regulation control strategy based on PID is presented. The control strategy is verified through simulation experiments. The Simulation results show that fine regulation of wheel cylinder pressure is achieved with the proposed control strategy, the vehicle braking effect is effectively improved and the vehicle braking stability is improved compared with the common logic threshold control strategy.

1A24 Wheel cylinder pressure estimation of EHB based brake-by-wire system(The 12th International Conference on Motion and Vibration Control)

1A24 Wheel cylinder pressure estimation of EHB based brake-by-wire system(The 12th International Conference on Motion and Vibration Control)

The Design of Regenerative Braking System with a Pedal Emulator

According to the regenerative braking system(RBS) with a pedal emulator as well as the control strategy. Design a hardware test platform of power regenerative system and the scheme of software experiment. Aim at the control strategy, braking safety and braking feeling of RBS with a braking pedal emulator is confirmed via hardware in loop (HIL) test. A high regenerative rate is obtained. From the result of simulation, the pedal force line from RBS with a pedal emulator is between the envelope curve of the pedal force from conventional vehicle. Actual wheel cylinder pressure can follow the change of target pressure very well. The regenerative braking rate reaches 53%.

Progress on Vehicle Dynamics Stability Control System

vehicle dynamics stability control system(DSC) is a key technology of vehicle active safety system, and it has been a hot research issue in vehicle field for a long time. The DSC system which is integrated with anti-lock braking system(ABS), traction control system(TCS) and active yaw control(AYC) can improve the stability and safety of vehicle significantly. The research progress of vehicle dynamics stability control system can be classified into modeling, state observation, control strategy and industrialization. The modeling includes the modeling in simulation and the modeling in control. ADAMS or Carsim can be adopted to build the vehicle model for simulation. Two wheels model or four wheels model usually are used in control. The state observation mainly focuses on the pressure estimation of the wheel cylinder, the estimation of road friction, the estimation of tire forces, the estimation of longitudinal and lateral velocity. After the realization of the basic function of vehicle stability control, the requirement for control is increasing gradually. A new AYC control strategy which is based on the predicted yaw rate is introduced to reduce the hysteresis of control. Meanwhile a new kind of TCS control strategy is introduced to reduce the vehicle vibration on uneven low-adhesion road. Through the unremitting exploration and research, the industrialization of DSC is gradual realizing.

A Realization Method for Wheel Cylinder Pressure Fine Regulation

To realize braking pressure fine regulation, the characteristics of hydraulic system should be well known, and there be a proper control method. By testing pressurization of braking circuit, the relationship between wheel cylinder pressure and current of the inlet valve was summarized, and the right rule of inlet valve current changing was found according to demands of pressurization. Finally, real car tests were carried out, and results prove the feasibility of this method. System can realize pressure fine regulation by this method, and get the goal pressure of control requirement.

Analysis of Effect on Change Rate of Wheel Cylinder Pressure for Electro-Hydraulic Brake System of Electric Vehicle

Based on a new type of electro-hydraulic brake system of electric vehicle, the operating principle was studied. A model of hydraulic brake system and corresponding control strategy were built with the co-simulation platform of AMESim and MATLAB. The impact factors of brake pressure change rate were analyzed theoretically. The influences of the main hydraulic parameters were analyzed through simulation, such as volume of brake fluid, type of pipe, ABS valve and brake clearance. The results provide a theoretical basis for the accurate control of wheel cylinder pressure.

Flow-valve modelling and wheel-slip control for an automotive hydraulic anti-lock braking system

Flow-valve modelling and wheel-slip control are investigated for an automotive hydraulic braking system which uses flow valves to supply brake fluid into the wheel cylinder and on/off valves to exhaust the brake fluid. First, the model of the flow valve is built using an experiment method, since its mechanism is difficult to analyse. Furthermore, because of the intrinsic difference between the two distinct valves, a special control problem is raised concerning how to realize wheel-slip control by using a unified strategy. Considering the essential characteristics of the two valves, a hybrid control approach, which contains an ordinary, continuous, state feedback function and a supervisory logic rule, is explored. Then, one feasible solution is obtained based on Lyapunov theory in the Filippov framework, so that the convergence of the control system is strictly guaranteed in theory. The controller has few tuning parameters and it is simple to tune. Illustrative hardware-in-the-loop simulation tests are carried out. The results show that both braking efficiency and ride quality are achieved, even if there are errors in the actuator control as well as in estimation of vehicle speed.

Expected Lengths of Minimum Spanning Trees for Non-identical Edge Distributions

An exact general formula for the expected length of the minimal spanning tree (MST) of a connected (possibly with loops and multiple edges) graph whose edges are assigned lengths according to independent (not necessarily identical) distributed random variables is developed in terms of the multivariate Tutte polynomial (alias Potts model). Our work was inspired by Steele's formula based on two-variable Tutte polynomial under the model of uniformly identically distributed edge lengths. Applications to wheel graphs and cylinder graphs are given under two types of edge distributions.

Modeling, Experimentation, and Simulation of an Air-Over-Hydraulic Brake System

This paper deals with the development and validation of an analytical dynamic model of an air-over-hydraulic (AOH) brake system that is widely used on loaders. The AOH system is broken into five simple and cascaded subsystems, pneumatic circuit, air-hydraulic actuator, brake line, wheel cylinder, and disk brake. Pneumatic, hydraulic, and mechanical dynamics are taken care of in each subsystem. The determination of model coefficients is introduced in detail. Many experiments are performed on an experimental setup of the real AOH system on a loader and the experimental data are compared with the simulation results. Preliminary analysis shows that the simulation results are in good agreement with the experimental data. Other researchers in the areas of brake systems in construction machinery would find the model useful for similar system modeling and analysis

Regenerative braking strategy for hybrid electric vehicles based on regenerative torque optimization control

A regenerative torque distribution (RTD) strategy is proposed to make maximum use of the braking energy to improve fuel economy for hybrid electric vehicles, in which the available regenerative braking force, the demand of the front wheel braking force, and the front wheel lock-up force are all explicitly taken into account. The actual front wheel cylinder pressure, which is reduced by the amount of the actual regenerative braking force, is supplied from the electronic hydraulic brake system. An emulated engine compression braking (EECB) is suggested during coasting, and the electric motor provides a negative torque to emulate the internal combustion engine drag torque to charge the ultracapacitor. In addition, a regenerative torque optimization strategy (RTO) is implemented to maximize the actual electric power recuperated by the ultracapacitor. The simulation results show that both the RTD with RTO and the EECB with RTO are able to offer improved ultracapacitor voltages.

Modelling and analysis of an air-over-hydraulic brake system

This study presents the development and validation of an analytical dynamic model of an air-over-hydraulic (AOH) brake system for a commercial vehicle (CV). The brake system model includes the controller, intensifier, brake lines, wheel cylinder, and foundational drum brake, which are presented for the interaction with the application system. A generalized AOH brake system, based on systems analysis level for the components, is formulated in detail. The pipeline hysteresis and fluid fluctuation of the brake system have been investigated in detail. Many experiments were performed on a bench setup of the AOH brake system and real vehicles. The experimental data is compared with the model simulation results. Preliminary results show that the simulation matches the experimental data closely. The models, which are developed from physical laws, are intended for use in the design and analysis of vehicle control systems for CVs.

Development of vehicle dynamics management system for hybrid vehicles: ECB system for improved environmental and vehicle dynamic performance

In anticipation of the increased needs to further reduce exhaust gas emissions and improve fuel consumption, a new brake-by-wire system called an “electronically controlled brake” system (hereafter referred to as “ECB”) has been developed. With this brake system, which is able to smoothly control the hydraulic pressure that is applied to each of the four wheel cylinders on an individual basis, functional enhancements can be added by appropriately modifying its software. This paper discusses the necessity of the ECB, the system configuration and the results of its application on hybrid vehicles.

Boiling Point Measurement of a Small Amount of Brake Fluid by Thermocouple and Its Application

This study describes a new method for measuring the boiling point of a small amount of brake fluid using a thermocouple and a pear shaped flask. The boiling point of brake fluid was directly measured with an accuracy that was within approximately 3 C of that determined by the Japanese Industrial Standards method, even though the sample volume was only a few milliliters. The method was applied to measure the boiling points of brake fluid samples from automobiles. It was clear that the boiling points of brake fluid from some automobiles dropped to approximately 140 C from about 230 C, and that one of the samples from the wheel cylinder was approximately 45 C lower than brake fluid from the reserve tank. It is essential to take samples from the wheel cylinder, as this is most easily subjected to heating.

Electronic control of braking force distribution for vehicles using a Direct adaptive fuzzy controller

In brake systems, a proportioning valve(P. V), which reduces the brake line pressure on each wheel cylinder for the anti-locking of rear wheels, is closely related to the safety of vehicles. However, it is impossible for current P. V. s to completely control brake line pressure because, mechanically, it is an open loop control system. In this paper we describe an electronic brake force distribution system using a direct adaptive fuzzy controller in order to completely control brake line pressure using a closed loop control system. The objective of the electronic brake force distribution system is to change the cut-in-pressure and the valve slop of the P. V in order to obtain better performance of the brake system than with mechanical systems.

Automatic breaking apparatus with ultrasonic detector

An automatic braking apparatus includes: an ultrasonic wave emitter provided in a front portion of an automatic braking car producing and emitting ultrasonic waves frontwardly in a predetermined distance in front of the car, an ultrasonic receiver also formed in a front portion of the car operatively receiving a reflective ultrasonic wave signal as reflected by another car positioned within the pre-determined distance in front of the automatic braking car for actuating a driving motor to intermittently drive a brake master cylinder to boost brake oil towards two wheel cylinders of front and rear wheels to brake the car intermittently for automatically braking the car for a safe braking purpose.

Noise attenuated anti-lock brake system

A noise sensor for supplying a central processing unit of an anti-lock brake system with a noise signal corresponding to vibrations produced during braking. The central processing unit responds to the noise signal by supplying a control valve assembly with an operational signal which modulates the fluid pressure supplied to a wheel cylinder to create a predetermined fluid pressure frequency therein to nullify vibrations and correspondingly attenuate noise produced thereby.

Effect of Brake Lining Friction Coefffcient upon Ideal Braking Force Distribution : Report 1, Optimum Braking

It is said to be difficult even for a bus to secure the directional stability and shorten the braking distance by means of the ideal braking force distribution, since it is affected significantly by the friction coefficient between brake linings and drums. It, however, becomes clear through the theoretical analyses and many experiments that the optimum control of braking force distribution is achieved successfully by using a new device which consists of disc brakes at rear and drum brakes at front. The latter are equipted with specially designed wheel cylinders to mitigate self-energizing action.