Conventional Antilock Braking System Research Articles

Full-scale testing of a novel slip control braking system for heavy vehicles

This paper summarises the measured emergency braking performance of a tri-axle heavy goods vehicle semitrailer fitted with a novel pneumatic slip control braking system developed by the Cambridge Vehicle Dynamics Consortium. Straight-line braking tests were carried out from 40 km/h in order to compare a commercially electro-pneumatic available anti-lock braking system and the Cambridge Vehicle Dynamics Consortium system, which has bi-stable valves coupled with a sliding-mode slip controller. On average, the Cambridge Vehicle Dynamics Consortium system reduced the stopping distance and the air use by 15% and 22% respectively compared with those for the conventional anti-lock braking system. The most significant improvements were seen on a wet basalt-tile surface (with similar friction properties to ice) where the stopping distance and the air use were improved by 17% and 30% respectively. A third performance metric, namely the mean absolute slip error, is introduced to quantify the ability of each braking system to track a wheel slip demand. Using this metric, the bi-stable valve system is shown to improve the wheel slip demand tracking by 62% compared with that of the conventional anti-lock braking system. This improvement potentially allows more accurate control of the wheel forces during extreme manoeuvres, providing scope for the future development of advanced stability control systems.

A Survey of Traction Control and Antilock Braking Systems of Full Electric Vehicles With Individually Controlled Electric Motors

Wheel slip control for ground vehicles with individually controlled electric motors can be realized with strategies that can significantly differ from the conventional antilock braking system (ABS) and traction control (TC) system. This paper provides a review of state-of-the-art technology and recent developments in TC and ABSs using the actuation of electric motors. Particular attention is paid to the realization of slip estimators, the formalization of torque demand, and the control methods applied for the implementation of TC and ABSs. The performed analysis allowed for the differentiation of several most elaborated methods for slip and torque control and defining still imperfectly investigated problems to be covered by the further development of TC and ABSs for full electric vehicles.

Slip-based regenerative ABS control for in-wheel-motor drive EV

Research on regenerative brake systems on electric vehicles (EVs) has progressed considerably, but anti-slip functions have not been practical due to the difficulty in coordinating with conventional hydraulic brake systems. This paper takes advantage of the features of driving electric motors to derive an allowable torque according to the expected relation between the vehicle and wheel acceleration. Then, an innovative saturation control in a regenerative antilock braking system (ABS), which adopts logic threshold control, is presented. The control system realizes lock prevention on a wheel by constraining the motor reference torque directly with the derived allowable value. By theoretical analyses and simulation studies, including a comparison with conventional ABS control, the resulting control design is shown to be effective in anti-slip performance.

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

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.

Designing and testing an advanced pneumatic braking system for heavy vehicles

Heavy goods vehicles exhibit poor braking performance in emergency situations when compared to other vehicles. Part of the problem is caused by sluggish pneumatic brake actuators, which limit the control bandwidth of their antilock braking systems. In addition, heuristic control algorithms are used that do not achieve the maximum braking force throughout the stop. In this article, a novel braking system is introduced for pneumatically braked heavy goods vehicles. The conventional brake actuators are improved by placing high-bandwidth, binary-actuated valves directly on the brake chambers. A made-for-purpose valve is described. It achieves a switching delay of 3–4 ms in tests, which is an order of magnitude faster than solenoids in conventional anti-lock braking systems. The heuristic braking control algorithms are replaced with a wheel slip regulator based on sliding mode control. The combined actuator and slip controller are shown to reduce stopping distances on smooth and rough, high friction ( μ = 0.9) surfaces by 10% and 27% respectively in hardware-in-the-loop tests compared with conventional ABS. On smooth and rough, low friction ( μ = 0.2) surfaces, stopping distances are reduced by 23% and 25%, respectively. Moreover, the overall air reservoir size required on a heavy goods vehicle is governed by its air usage during an anti-lock braking stop on a low friction, smooth surface. The 37% reduction in air usage observed in hardware-in-the-loop tests on this surface therefore represents the potential reduction in reservoir size that could be achieved by the new system.

Stability Control on Tractor Semi-Trailer during Split-Mu Braking

Handling behaviour of articulated vehicles combination is more complex and less predictable than that of non-articulated vehicles. It is usually difficult for drivers to maneuver a tractor semi-trailer during high speed emergency braking on split-mu road surface. Braking on this type of road surface, the conventional anti-lock braking systems will cause the vehicle deviate from the desired direction, or overmuch stopping distance. In this paper, a 3-dof of tractor semi-trailer model was used to produce desired yaw rates which were compared with actual yaw rates. An active front steering control and four-channel ABS were integrated to improve the tractor semi-trailer lateral stability while braking on split-mu road surface, which will produce maximum braking force. A full function tractor semi-trailer model was built and assembled in multi-body dynamics software, and the dynamic analysis was performed on split-mu road surface. The simulation results show that the integrated system can improve the tractor semi-trailer lateral stability under braking on split-mu road surface.

Study of Acceleration Slip Regulation Strategy for Four Wheel Drive Hybrid Electric Car

The use of multiple power sources not only increases the modulation means of driving wheel torque,but also brings a new challenge to the acceleration slip regulation(ASR) realized by relying on conventional anti-lock braking system(ABS).Aiming at four wheel drive hybrid electric car,a powertrain forward simulation model is built with consideration of the nonlinear seven degree-of-freedom vehicle longitudinal dynamics.Using the electric motor characterized by the accurate control and rapid response of torque to adjust the torque of slipping wheel,and based on the existing energy management strategy validated in the real vehicle,ASR control algorithms of logic threshold and P-Fuzzy-PI having the qualities of multi-mode and time-sharing are respectively developed,offline simulation is conducted under the two running cases of pure electric launching and hybrid propulsion emergence acceleration at the low adhesion coefficient road.Afterwards,front wheel speed sensor signals are acquired by the hybrid control unit(HCU)and ASR is integrated into HCU,real vehicle anti-slip test is performed on the snow/ice road.Simulation and test results indicate that the proposed two kinds of anti-slip strategies can effectively prohibit the driven wheel from transient slipping,so the scheme that ASR strategy can be integrated into the energy management strategy and be carried out in the HCU is feasible and effective.

Design concept for an alternative heavy vehicle ABS system

This paper investigates the use of slip control on heavy vehicles to reduce stopping distances and compressed air usage in an emergency stop. A hardware-in-the-loop (HiL) rig has been developed to investigate slip control. The hardware includes an air receiver, anti-lock braking system (ABS) or slip-control modulator, brake actuator and brake calliper. The braked wheel and vehicle dynamics are simulated on a micro-processor. A gain-scheduled slip controller using the same pneumatic actuation as used by conventional ABS is developed. The slip control strategy increases the mean fully developed deceleration by 6% and halves the air usage compared to the ABS strategy on the HiL rig. The transient performance of the slip controller is poor due to the sluggish response of the ABS valves, causing a 10% increase in stopping distance. A novel fast-acting brake actuator design is described. Simulations of the new actuator implementing slip control show an improvement of 10% in stopping distance performance and 30% in air usage.

Iterative Learning Control of Antilock Braking of Electric and Hybrid Vehicles

Hybrid electric vehicles (HEVs) use multiple sources of power for propulsion which provides great ease and flexibility to achieve advanced controllability and additional driving performance. In this paper, the electric motor in HEV and electric vehicle (EV) propulsion systems is used to achieve antilock braking performance without a conventional antilock braking system (ABS). The paper illustrates that the antilock braking of HEV can be easily achieved using iterative learning control for various road conditions. A vehicle model, a slip ratio model, and a vehicle speed observer were developed to control the antilock performance of HEV during braking. Through iterative learning process, the motor torque is optimized to keep the tire slip ratio corresponding to the peak traction coefficient during braking. Simulations were performed on a compact size vehicle to validate the proposed control method. The control algorithm proposed in this paper may also be used for the ABS control of conventional vehicles.

Automotive Steering Control in a Split-µ Manoeuvre Using an Observer-Based Sliding Mode Controller

Summary In this paper a sliding mode integral action controller and sliding mode observer are used to enhance vehicle stability in a split- µ manoeuvre. Anti-lock braking systems (ABS) have become an integral part of modern cars, and they have dramatically improved vehicle handling in braking manoeuvres. However, when a vehicle attempts to brake on a surface with uneven friction coefficient such as on wet or icy roads, a so-called split- µ scenario, the yaw moment generated by the asymmetric braking can prove demanding for an inexperienced driver. The controller presented hereworks in conjunction with a conventional ABS system to provide safe and effective braking through steer-by-wire. This paper extends previous state-feedback work by only using certain measurable quantities in the controller, estimating further signals by employing an observer.