Feedback and servo control for electric power steering systems

A power steering system (760) for a vehicle having dirigible wheels (13), comprising:

• speed reduction means (712) having an input node (714) and an output node (716), the output node (716) being adapted to supply a powered assist to steering the dirigible wheels (13) of the vehicle upon the application of torque to the input node (714);
• a primary applied steering torque sensor (14) which generates an applied torque signal (VTT1) in response to at least an applied steering torque (Ts);
• a primary assist torque sensor (762) which generates an assist torque signal (VTT2′) in response to assist torque (Ta) delivered via the output node (716);
• an electric motor (26) operatively connected to the input node (714) and capable of reversibly driving the speed reduction means (712);
• and
• an electronic control means (32b) to which the primary assist torque sensor (762) and the primary applied steering torque sensor (14) are operatively connected, and which controls actuation of the electric motor (26);
• wherein the electronic control means (32b) establishes servo control (322b) over the powered assist to steering supplied by the speed reduction means (712) in dependence upon the assist torque signal (VTT2′) generated by the primary assist torque sensor (762).

A power steering system (810) for a vehicle having dirigible wheels (13), comprising:

• torque summing means (812) having an applied torque input node (816), an electric motor input node (818) and an output node (820), the output node (820) being adapted to supply an assisted output toque for steering the dirigible wheels (13) of the vehicle upon the application of torque to the applied torque input node (816);
• a primary applied steering torque sensor (14) which generates an applied torque signal (VTT1) in response to at least an applied steering torque (Ts);
• a primary assisted output torque sensor (832) which generates an assisted output torque signal (VTT6) in response to assisted output torque (Tao) delivered from the output node (820);
• an electric motor (26) operatively connected to the electric motor input node (818) and capable of reversibly driving the torque summing means (812);
• and
• an electronic control means (32c) to which the primary assisted output torque sensor (832) and the primary applied steering torque sensor (14) are operatively connected, and which controls actuation of the electric motor (26);
• wherein the electronic control means (32c) establishes servo control (322c) over the assisted output torque supplied by the torque summing means (812) in dependence upon the assisted output torque signal (VTT6) generated by the primary assisted output torque sensor (832).

A power steering system (910) for a vehicle having dirigible wheels (13), comprising:

• steering force generating means (912) having an applied torque input node (816), an electric motor input node (818) and a steering force output node (920), the steering force output node (920) being adapted to supply an assisted steering force for steering the dirigible wheels (13) of the vehicle upon the application of torque to the applied torque input node (816);
• a primary applied steering torque sensor (14) which generates an applied torque signal (VTT1) in response to at least an applied steering torque (Ts);
• a primary steering force sensor (914) which generates a steering force signal (VFT1) in response to steering force (Fr) delivered via the steering force output node (920);
• an electric motor (26) operatively connected to the electric motor input node (818) and capable of reversibly driving the steering force generating means (912);
• and
• an electronic control means (32d) to which the primary steering force sensor (914) and the primary applied steering torque sensor (14) are operatively connected, and which controls actuation of the electric motor (26);
• wherein the electronic control means (32d) establishes servo control (322d) over the steering force supplied by the steering force generating means (912) in dependence upon the steering force signal (VFT1) generated by the primary steering force sensor (914).