Steering system for use in test driving of an autonomous vehicle and disengagement method

A steering system for use in test driving of an autonomous vehicle, comprising

• a manual steering means configured to manually steer the vehicle,
• a steering axle (20, 30, 50, 601, 70) attached to the manual steering means, and
• a direct drive motor (25, 35, 55, 655, 75) controllably affecting a torque on the steering axle (20, 30, 50, 601, 70), wherein the direct drive motor (25, 35, 55, 655, 75) has an axis (27, 37) of rotation being coaxial with the steering axle (20, 30, 50, 601, 70),
• characterized in that
• the steering system has at least two predefined states characterizing different driving conditions, wherein each predefined state has at least one predefined disengagement limit (82, 101, 102, 111, 112), and
• the steering system further comprises a controller assembly (56) operable based on a control parameter, the controller assembly (56) being configured to detect an actual predefined state of the vehicle, and the controller assembly (56) including
• a motion controller generating a command including a prescribed value of the control parameter to be reached,
• a motor drive unit for supplying power to the direct drive motor (25, 35, 55, 655, 75) based on the command received from the motion controller, and
• a feedback device for monitoring an actual value of the control parameter and determining a difference value between the prescribed value of the control parameter and the actual value of the control parameter, and initiating a disengagement of the direct drive motor (25, 35, 55, 655, 75) if, based on the difference value, the at least one predefined disengagement limit (82, 101, 102, 111, 112) corresponding to the actual predefined state is reached.