Tankut Acarman

Stability and performance improvement of extremum seeking control with sliding mode

Extremum seeking control is an adaptive control strategy for a system to iteratively extremize a function in real-time. In this paper we investigate stability and performance improvement by using sliding mode concepts in extremum seeking controllers.

Nonlinear optimal integrated vehicle control using individual braking torque and steering angle with on-line control allocation by using state-dependent Riccati equation technique

This paper proposes the solution of state-dependent Riccati equation as a nonlinear optimal regulator to stabilise the motion dynamics of the vehicle model subjected to sudden disturbance inputs in the lateral direction. The proposed nonlinear regulator coordinates individually actuated wheel braking torque and steering wheel angle simultaneously in an optimal manner. Performance criteria are satisfied by solving the Riccati equation based on the given cost function subjected to the nonlinear vehicle dynamics. On-line control allocation in terms of optimal brake torque distribution enhanced by optimal wheel steering angle input is achieved. Furthermore, the proposed optimal nonlinear regulator is an active fault-tolerant control system against partial by-wire actuator failures while guaranteeing stability with good performance due to its capability to allocate the individual control inputs in an optimal way. The main aim is to stabilise the motion dynamics of the vehicle model during short-term emergency situations along the desired straight trajectory manageable by average drivers and to provide vehicle stability and handling predictability through the interaction of individual wheel braking and steering actuators. Simulation results are used to illustrate the effectiveness of the proposed methodology.

A robust nonlinear controller design for a pneumatic actuator

This paper presents a feedback linearization based variable structure controller for a pneumatically actuated system utilizing sliding mode observers. Using the robustness implications of the sliding mode control theory and the structural properties of pneumatically actuated systems, a nonlinear controller is designed to drive the output tracking error to zero in finite time. Strong robustness with respect to bounded modeling and parameter uncertainties is attained through compensation of the friction effect of the piston in the cylinder body. The controller and the observer are based on a third-order nonlinear state-space model of a pneumatic system which was developed, validated numerically with experimental data and presented by Acarman et al. (SAE, 2000-01). Simulation results are included to demonstrate the effectiveness of the designed observer and the good performance of the designed tracking controller.

A Control Authority Transition System for Collision and Accident Avoidance

Summary This paper addresses the problems ensuing with the human being who is controlling the technical system, especially problems related to his skill levels, driving habits, capabilities and decisions (especially when impaired by drugs, fatigue or physical handicaps). It may be possible to improve the ability of a driver to operate a vehicle safely if certain parameters in the control of the vehicle are adjusted according to the driver’s normal characteristics. Value has already been established for tailoring certain attributes such as seat, pedals, steering wheel position and mirrors to a given driver through memory functions. This research concentrates on assessing a driver’s operating characteristics and modifying the control to improve safe operation of the vehicle on a real-time basis.

Nash solution by extremum seeking control approach

In this paper, we propose an algorithm to solve the Nash equilibrium solution for an n-person noncooperative dynamic game by the extremum seeking control approach with sliding mode. For each player, a switching function is defined as the difference between the players cost function and a reference signal. The extremum seeking controller for each player is designed so that the system converges to a sliding boundary layer defined in the vicinity of a sliding mode corresponding to the switching function and inside the boundary layer, the cost function tracks the reference signal and converges it to the Nash equilibrium solution.

Relation of dynamic sliding surface design and high order sliding mode controllers

Dynamic sliding surface design is presented to avoid the chattering effects, which are always associated with practical implementations of variable structure control. We propose the use of compensator dynamics in sliding mode through a class of switching surfaces which has the interpretation of linear operators. This approach originally proposed by Young and Ozguner (1993) as dynamic sliding surface design is shown to be related to design of high order sliding mode controllers.

Non-standard safety technology

This paper explains the nonstandard safety technology which assists drivers to enhance drive safely when the driver is physiologically impaired, for example, drunk, fatigued, irritable, asleep, etc. When a driver operates a vehicle with some actions which may not result in an accident immediately but may reveal that the driver is drunk, fatigued, or asleep, the non-standard safety enhancement system makes a decision from the actions to determine whether the driver is physiologically impaired based on the available information of vehicle, road, and others before the driver causes an accident.

A robust controller design for drive by wire hydraulic power steering system

In this paper, a sliding mode controller cascaded by the frequency shaped optimal controller for drive by wire hydraulic power steering system utilizing sliding mode and exponentially convergent observers is presented. Using the robustness implications of the sliding mode control theory and the structural properties of the hydraulic power steering system, a nonlinear controller cascaded by an optimal linear controller is designed to stabilize the steering system dynamics and track the steering wheel reference. Lyapunov based controller design satisfies strong robustness with respect to bounded modeling and parameter uncertainties. The controller and the observer are based on an eight-order nonlinear state-space model of the hydraulic power steering system which is developed, validated numerically with experimental data. Simulation results are included to demonstrate the effectiveness of the observer and the performance of the tracking controller.

A control authority transition system for collision avoidance

Drivers differ significantly in their skill levels, driving habits, capabilities and decisions especially when impaired by drugs, fatigue or physical handicaps. Late or inadequate responses to hazards and dangers may cause severe results. It may be possible to improve the ability of a driver to operate a vehicle safely if certain parameters in the control of the vehicle axe adjusted according to the drivers normal characteristics. Value has already been established for tailoring certain attributes such as seat, pedals, steering wheel position and mirrors to a given driver through memory functions. This research concentrates on assessing a drivers operating characteristics and modifying the control of the vehicle to improve safe operation of the vehicle on a real-time basis.

FREQUENCY SHAPING COMPENSATION FOR BACKSTEPPING SLIDING MODE CONTROL

Abstract In this paper, dynamic sliding surface design combined with recursive backstepping algorithm is introduced. The high frequency, high amplitude chattering effects associated with high gain properties of the backstepping algorithm are eliminated by using compensator dynamics introduced in sliding mode through a class of switching surfaces which has the interpretation of linear operators.