Robust fixed-structure controller design of electric power steering systems

Robust multi-objective control for systems involving human-in-the-loop passivity constraints with application to electric power steering

“…21 shows [8,19] that unlike passive environments commonly encountered in tele-manipulated robots [5,16], the road-tires' selfaligning moments exhibit non-passive behavior over a large range of vx and road-surface adhesion condition. This shortage of passivity has to be accounted for, to realistically address the uncertainty involved in the EPS environment.…”

“…Parts (ii) and (iii) follow directly from part (i), see [8] for details. Finally, part (iv) is shown by noticing that Eq.…”

“…This transition is justified on the grounds of the following points [3,4,8], (1) ease of tunability: EPS systems are examples of mechatronic systems which employ programmable features making them easily adjustable to wider ranges of operation, (2) fuel economy: EPS systems are on-demand systems that operate only when the steering wheel is turned, (3) modularity: EPS systems are composed of more compact components that are easily packaged into separate subsystems. Nevertheless, the lack of analytical description of appropriate control design metrics, such as "feel", and the presence of the human-in-the-loop make control design tasks of EPS systems very challenging.…”

“…Moreover, the measured outputs are the torsion bar torque τ b , the rack displacement x rack and the rack velocityẋ rack . Assuming that the vehicle forward velocity vx is held constant and the road-tire steering angle is small, the force impedance for the self-aligning moment fSAM is given by the following 2 nd order transfer function [8]:…”

“…Steering systems are very common applications where man-machine interaction is inevitable [1,3,8,19]. This interaction places stringent requirements on the feedback design for EPS systems to ensure the safety of the human driver.…”