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Technical Paper

Fault-Tolerant Control of Brake-by-Wire Systems Based on Control Allocation

Brake-by-wire (BBW) system has drawn a great attention in recent years as driven by rapidly increasing demands on both active brake controls for intelligent vehicles and regenerative braking controls for electric vehicles. However, unlike conversional brake systems, the reliability of the brake-by-wire systems remains to be challenging due to its lack of physical connection in case of system failure. There are various causes for the failure of a BBW system, such as failure of brake controller, loss of sensor signals, failure of communication or even power supply, to name a few. This paper presents a fault-tolerant control under novel control architecture. The proposed control architecture includes a driver command interpreter module, a command integration module, a control allocation module, a fault diagnosis module and state observers. The fault-tolerant control is designed based on a quadratic optimal control method with consideration of actuator constraints.
Technical Paper

Online Hierarchical Fault-Adaptive Control for Advanced Life Support Systems

This paper discusses a hierarchical online fault-adaptive control approach for Advanced Life Support (ALS) Systems. ALS systems contain a number of complex interacting subsystems. To avoid complexity in the models and online analysis, diagnosis and fault-adaptive control is achieved by local units. To maintain overall performance, the problem of resource management for contending concurrent subsystems has to be addressed. We implement a control structure, where predefined set-point specifications for system operation are used to derive optimizing utility functions for the subsystem controllers. We apply this approach in situations where a fault occurs in a system, and once the fault is isolated and identified, the controllers use the updated system model to derive new set point specifications and utility functions for the faulty system.
Journal Article

Allocation-Based Fault Tolerant Control for Electric Vehicles with X-by-Wire

This paper proposed a novel fault-tolerant control method based on control allocation via dynamic constrained optimization for electric vehicles with XBW systems. The total vehicle control command is first derived based on interpretation on driver's intention as a set of desired vehicle body forces, which is further dynamically distributed to the control command of each actuator among vehicle four corners. A dynamic constrained optimization method is proposed with the cost function set to be a linear combination of multiple control objectives, such that the control allocation problem is transformed into a linear programming formulation. An analytical yet explicit solution is then derived, which not only provides a systematic approach in handling the actuation faults, but also is efficient and real-time feasible for in-vehicle implementation. The simulation results show that the proposed method is valid and effective in maintaining vehicle operation as expected even with faults.
Technical Paper

Emergency Steering Evasion Torque Assistance Based on Optimized Trajectory

When automobile is at the threat of collisions, steering usually needs a shorter longitudinal distance than braking to avoid collision, especially at a high speed. In emergency steering evasion, the vehicle may be out of the road or colliding with obstacles ahead when the driver’s steering torque is excessive or insufficient. In view of the above problems, this paper presents an emergency steering evasion torque assistance system based on optimized trajectory. First, a feasible steering evasion area is established which treats the paths of excessive and insufficient steering as boundary conditions in this paper. An optimized trajectory is derived from the lateral acceleration of the vehicle and the time to the adjacent lane as optimization conditions. Second, a two degree of freedom vehicle model is used to represent dynamics of the vehicle.