A PID and state space approach for the position control of an electric power steering
The steering system is one of the primary controls for a vehicle. With the increase in driver assistance the demands of this subsystem have drastically increased. This has brought along much greater control intelligence. As with some assistance functions, autonomous driving requests a front steer angle for the vehicle to conduct a manoeuvre. The front steer angle is realized through the position control of the electric power steering (EPS). Thus far, the control of EPS systems in literature has focused heavily on generating a desired driver hand torque as is shown in works by Mehrabi et al. (2011), Fankem et al. (2014) and Dannöhl et al. (2011). The absence of a driver in the loop yields new challenges for control of an EPS. For instance, autonomous driving means that the steering wheel is free moving without the hands of the driver to control it. The resonance frequency caused by the free motion dynamics has an adverse effect on the position control. Moreover, both internal and external disturbances which are normally compensated by the driver have to be regulated by the EPS controller. Work by von Groll et al. (2006) shows that the most of the relevant frequencies for driver’s inputs are below 4Hz. This is the frequency range where the controller should perform well in order to achieve all the relevant manoeuvres. Additionally, the steering wheel should move in a smooth and non-erratic way.
KeywordsPosition Control Steering System Pole Placement Front Axle State Space Approach
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