Different types of instability modes in tractor-trailer vehicles, including jackknifing and snaking, necessitate designing a fast and effective control strategy. In this paper, a model predictive ...controller (MPC) is developed to prevent these instability modes in a car-trailer vehicle as a specific form of tractor-trailer vehicles equipped with differential braking. The effectiveness of the control action when the differential braking is applied only to the tractor and only to the trailer is also studied comparatively. The developed MPC controller utilises an affine tyre force model, and the control actions are limited based on the capacity of the tyres. The aim of the controller is to ensure that the tractor and the trailer follow the desired yaw rate and the desired hitch angle, respectively. The controller performance is evaluated through experimental tests and simulations. Experimental tests are conducted on an all-wheel-drive electric Chevrolet Equinox and a student-built research trailer, both equipped with an independent braking module on each wheel. In the simulations, the controller is implemented in MATLAB/Simulink, and an experimentally validated CarSim model of the tested tractor-trailer vehicle is employed. The results show that the designed MPC controller effectively prevents both instability modes; however, differential braking has much more capacity when it is applied to the tractor.
Controlling the lateral dynamics of an autonomous vehicle confronting a sudden obstacle requires optimal use of tires' force capacities. In these situations, autonomous steering may not be able to ...respond fast enough to prevent collision or instability. This paper presents an integrated controller for autonomous vehicles, capable of suitably reacting to emergency situations when a sudden obstacle appears on the road. The proposed controller employs differential braking conservatively when needed, to produce an additional yaw moment, thereby improving a vehicle's lateral agility and responsiveness without endangering vehicle stability. A longitudinal controller is also designed to track a desired longitudinal velocity. Model predictive control (MPC) method is used for developing a combined path planning and tracking controller with a hierarchical structure that prioritizes (1) collision avoidance, (2) vehicle stability, and (3) path tracking. The effectiveness of the proposed integrated MPC controller is evaluated by simulating an experimentally validated CarSim model to demonstrate the controller's capability in preventing instability and collisions.
This paper presents a prioritization model predictive control for integrated lateral and roll stability control of all-wheel-drive vehicles. The vehicle's powertrain includes an electric motor and an ...open differential per axle, which enables generating a corrective yaw moment by front/rear torque shifting. In addition, the brakes can be used in differential mode to further enhance the corrective yaw moment when needed. To ensure vehicle stability, safety limits are defined on the vehicle's yaw rate, sideslip, and roll motions, considering road angle effects. The controller prioritizes the control actions and objectives based on, respectively, their advantages and their importance, and then combines the priorities such that differential braking, which is defined as the low priority actuation, will not kick in unless the stability limits are violated. The performance of the designed controller is thoroughly evaluated through numerical and full vehicle experimental studies in different driving scenarios on flat and non-flat roads.
This article presents a model predictive control design for improving the yaw stability of a rear-wheel-drive vehicle equipped with an electronic limited slip differential (ELSD) and differential ...braking capability. It first develops a model for an ELSD system for predicting its torque distribution dynamics, then uses the model in designing an intelligent ELSD control that prevents unwanted oversteering yaw moments through direct control of the ELSD clutch pressure. Since differential braking degrades the vehicle's longitudinal motion and driver comfort, two control actuations are prioritized: 1) ELSD clutch pressure and 2) differential braking. An appropriate stability limit is defined for the vehicle yaw rate, and two control objectives: 1) enforcing the yaw rate stability limit and 2) tracking the desired yaw rate are defined and prioritized. The actuation priorities and the objective priorities are combined within a model predictive control structure with particular soft constraints such that the low priority actuation is activated when the high priority objective demands it. Additionally, optimum corner braking forces are calculated by geometrically analyzing tire force vectors. The performance of the proposed controller, implemented in a Cadillac CTS vehicle, is experimentally evaluated for a variety of driving maneuvers.
This paper investigates the handling control and stability of an all-wheel-drive vehicle whose axles are individually equipped with an electric motor connected to an open differential. This could ...offer a potential configuration for the mass production of electric all-wheel-drive vehicles because of reduced cost and complexity. Although there is no torque vectoring or direct yaw moment control in this configuration, considerable handling improvement can be achieved by optimised front/rear torque distribution due to the longitudinal and lateral tire force coupling. In this study, a model predictive control design is presented with a coupled force prediction model for vehicle handling dynamics. The controller optimises the front/rear torque allocation to track the desired handling response and ensure vehicle stability. This study also compensates for actuator delay by incorporating the actuator dynamics into the control design. The performance of the proposed controller is evaluated through software simulations and experimental tests conducted on an electric all-wheel-drive Chevrolet Equinox.
This paper investigates the problem of improving vehicle stability using an electronic limited slip differential (ELSD). Unlike brake-based vehicle stability control systems, electronic limited slip ...differentials have the potential to control a vehicle's yaw stability without slowing down its speed. In this study, first, an ELSD model is designed to properly predict ELSD torque distribution. The model's accuracy is evaluated using experimental test data. Then, an intelligent ELSD control design is proposed using the developed ELSD model, capable of working in both off-throttle and on-throttle scenarios. The proposed design, which is based on a model predictive control approach, offers control of the ELSD differential by directly controlling the ELSD clutch pressure. This control design enables the controller to prevent unwanted oversteering yaw moments and avoid chattering in the ELSD clutch. The controller is implemented in a Cadillac CTS vehicle to evaluate its performance experimentally in various driving maneuvers.
This paper proposes a novel prioritisation model predictive control for improving the handling and stability of all-wheel-drive vehicles configured with an electric motor and an open differential per ...axle with differential braking capability. The configuration of the powertrain provides a significant handling improvement by optimising front/rear torque distribution. The controller gives a high priority to front/rear torque distribution and, if needed, activates the differential braking. A coupled force prediction model of the vehicle handling dynamics is developed to capture the interaction of longitudinal and lateral tyre forces. Since differential braking causes speed drop, energy waste, and noise, two control actuations are prioritised: (1) front/rear torque shifting, (2) differential braking. Appropriate stability constraints are defined for the vehicle yaw rate and sideslip, dividing the sideslip-yaw rate phase plane into three regions - stable, marginal, unstable - based on which three control objectives are defined. Then, the priorities of the control actuations and the control objectives are combined, and a model predictive control structure is developed for this multi-objective multi-actuation control problem. The predictive controller prioritises the objectives and actuations through the prediction horizon. The performance of the proposed controller is thoroughly evaluated through numerical and full vehicle experimental studies.
The effect of some important testing conditions including test specimen (SCB and ENDB), fracture mode (I and II), loading rate (0.5, 1.0, and 5.0 mm/min), and temperature (−5°C, −15°C, and −25°C) is ...evaluated on fracture toughness of asphalt material containing different percentages of fibers (0%, 0.025%, 0.05%, and 0.1% of unit weight). The experimental and numerical results show that the addition of 0.025%, 0.05%, and 0.1% of the polyolefin–aramid fiber in asphalt mixture increases the fracture toughness of the control mixture by about 8%, 17%, and 23% in pure mode I and 7%, 16%, and 24% in pure mode II, respectively; which are among the most promising enhancements compared to other fibers. Results also reveal that fracture toughness at mode I obtained from the SCB and ENDB specimens is similar. However, the mode II fracture toughness obtained from the ENDB specimen is about 12% higher than the corresponding value obtained from the SCB specimen.
HIGHLIGHTS
The ability of ENDB was examined by comparing the result with the SCB specimen.
Tests were performed using HMA asphalt concrete containing fiber content.
Fracture toughness was measured for both pure mode I and II.
The strengthening ability of used fiber was evaluated in comparison to other researches.
This article presents an adaptive nonlinear delayed feedback control scheme for stabilizing the unstable periodic orbit of unknown fractional-order chaotic systems. The proposed control framework ...uses the Lyapunov approach and sliding mode control technique to guarantee that the closed-loop system is asymptotically stable on a periodic trajectory sufficiently close to the unstable periodic orbit of the system. The proposed method has two significant advantages. First, it employs a direct adaptive control method, making it easy to implement this method on systems with unknown parameters. Second, the framework requires only the period of the unstable periodic orbit. The robustness of the closed-loop system against system uncertainties and external disturbances with unknown bounds is guaranteed. Simulations on fractional-order duffing and gyro systems are used to illustrate the effectiveness of the theoretical results. The simulation results demonstrate that our approach outperforms the previously developed linear feedback control method for stabilizing unstable periodic orbits in fractional-order chaotic systems, particularly in reducing steady-state error and achieving faster convergence of tracking error.
