Steering System With A Differential For Additive Active Steering And Autonomous Operation

Ehsan Arasteh

Conventional electric power steering (EPS) uses a controlled motor to assist the driver with steering tasks. The motor is directly geared to the steering shaft and adds torque such that the torque feedback to the driver through the hand wheel is as desired. If such a steering system was used to steer the road wheels somewhat differently from that commanded by the driver, the motor would necessarily have to jerk the hand wheel from the driver’s hands.

In this thesis, it is proposed to use a differential in the steering system such that a steering motor can add or subtract from the driver command without affecting driver input. Such a setup has the advantage of allowing seamless additive active steering as well as allowing autonomous operation where the steering motor does all the steering.

Such a system has the disadvantage of perhaps feeling peculiar to the driver. To remedy this, it is proposed to have a second motor geared directly to the steering shaft that is used only to improve the feel of the hand wheel.

The desired target is generated using a model reference approach and different controllers such as PID, H2 and Hinf are developed and compared with each other in different test scenarios.

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