Motor vehicle steering system with a control unit of redundant configuration

A redundant control device for a three-phase electric motor of a steering system of a motor vehicle, comprising:

• a primary control path comprising a primary processing unit, and
• a secondary control path comprising a secondary processing unit,
• wherein the primary control path is connected to a first phase winding of the electric motor, and the secondary control path is connected to a second and a third phase winding of the electric motor for actuating the electric motor, and
• wherein each phase winding is assigned an individual converter.

An electromechanical steering system for a motor vehicle, comprising:

• a steering pinion connected to a lower steering shaft and is in engagement with a toothed rack, mounted so as to be displaceable along a longitudinal axis in a housing, in order to steer wheels of the motor vehicle,
• a three-phase electric motor configured to provide power steering assistance,
• two torque sensors which are arranged between an upper steering shaft, connected to a steering wheel, and the lower steering shaft, and which are configured to sense a torque input, and
• an electronic control unit for calculating the power steering assistance, which comprises a redundant control device, the control device comprising:
• a primary control path and a secondary control path,
• wherein the primary control path has a primary processing unit, and the secondary control path has a secondary processing unit,
• wherein the primary control path is connected to a first phase winding of the electric motor, and the secondary control path is connected to a second and a third phase winding of the electric motor for actuating the electric motor, and
• wherein each phase winding is assigned an individual converter.

A method for providing a torque for a steering system of a motor vehicle, comprising a three-phase electric motor and an electronic control unit for calculating torque which is to be applied by the electric motor, wherein the electronic control unit comprises a redundant control device comprising a primary control path and a secondary control path, wherein the primary control path has a primary processing unit, and the secondary control path has a secondary processing unit, wherein the primary control path is connected to a first phase winding of the electric motor, and the secondary control path is connected to a second and a third phase winding of the electric motor for actuating the electric motor, and wherein each phase winding is assigned an individual converter, the method comprising:

• calculating, via the secondary processing unit, setpoint motor torques for actuating all the three phase windings,
• passing on the calculated setpoint motor torques to a primary motor regulating means of the primary processing unit,
• determining primary motor currents to operate the first phase winding in the primary motor regulating means,
• determining secondary motor currents to operate the second and third phase windings in a secondary motor regulating means of the secondary processing unit, and
• switching off, when a fault state is detected in one of the control paths, the power steering assistance of the control path with the detected fault state.