Feedback and servo control for electric power steering systems

• US 6,370,459 B1
• Filed: 01/18/2001
• Issued: 04/09/2002
• Est. Priority Date: 07/21/1998
• Status: Expired due to Fees

• Current Assignee: Techco Corp.
• Original Assignee: Techco Corp.
• Inventors: Phillips, Edward H.
• Primary Examiner(s): Chin, Gary
• Application Number:
  US09/744,062
• Time in Patent Office: 446 Days
• Field of Search: 701/41, 701/42, 180/412, 180/413, 180/422, 180/443, 180/444, 180/446, 180/447
• US Class Current: 701/41
• CPC Class Codes: B62D 5/0436 the clutch being a controlled emergency clutch, e.g. for disconnecting at motor break-down
• CPC Class Codes: B62D 5/0463 calculating assisting torque from the motor based on driver input
• CPC Class Codes: B62D 5/065 characterised by specially adapted means for varying pressurised fluid supply based on need, e.g. on-demand, variable assist
• CPC Class Codes: B62D 6/008 Control of feed-back to the steering input member, e.g. simulating road feel in steer-by-wire applications

Abstract

Vehicle power steering systems (710, 760, 810 and 910) achieve substantially linear control relationships between and applied steering torque input Ts and a resulting steering force output, that is, a powered assist to vehicle steering. Impedance matching means utilized for coupling an electric motor (26) to the steering load respectively include speed reduction means (712), torque summing means (812) and force generating means (912) in the systems (710, 760, 810 and 910). The speed reduction means (712) comprises gear reduction means (722) and a supplemental pinion. The torque summing means (812) comprises steering column (814) coupled gear reduction means (822), and, the force generating means (912) comprises hydraulic transmission means including a power cylinder (18). The systems (710, 760, 810 and 910) are preferably regenerative. The systems (710, 716, 810 and 910) each utilize internal closed-loop servo control of the electric motor (26) to substantially eliminate stability control problems including, for example, a low frequency stability control problem which has typically not been overcome in prior EPS systems.

Claims

1. A power steering system (710) 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 (V_TT1) in response to at least an applied steering torque (T_S);

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 (32a) comprising torque calculation means responsive to input voltage and current input to the electric motor (26) which generates an assist torque signal (V_TT2) in response to assist torque (T_a) delivered via the output node (716), and to which the primary applied torque sensor (14) is operatively connected, and which controls actuation of the electric motor (26);

wherein the electronic control means (32a) establishes servo control (322a) over the powered assist to steering supplied by the speed reduction means (712) in dependence upon the assist torque signal (V_TT2) generated by the torque calculation means.

2. 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 (V_TT1) in response to at least an applied steering torque (T_s);

a primary assist torque sensor (762) which generates an assist torque signal (V_TT2′

) in response to assist torque (T_a) 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 (V_TT2′

) generated by the primary assist torque sensor (762).

3. 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 (V_TT1) in response to at least an applied steering torque (T_s);

a primary assisted output torque sensor (832) which generates an assisted output torque signal (V_TT6) in response to assisted output torque (T_ao) 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 (V_TT6) generated by the primary assisted output torque sensor (832).

4. 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 (V_TT1) in response to at least an applied steering torque (T_s);

a primary steering force sensor (914) which generates a steering force signal (V_FT1) in response to steering force (F_r) 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 (V_FT1) generated by the primary steering force sensor (914).