Speed tracking of induced armature field in electric power assisted steering
First Claim
1. A motor driven power assisted steering system for a motor vehicle comprising:
- an electric motor with a controllable induced armature field;
a coupler mechanism for coupling an output shaft of said electric motor to steering gear of a motor vehicle;
a vehicle speed sensor coupled to said motor vehicle for detecting the operating speed of said motor vehicle and for generating representative speed signals; and
a motor controller responsive to said speed signals for controlling the induced armature field of said electric motor as a function of the operating speed of said motor vehicle, said motor controller operating along a flux versus vehicle velocity curve to reduce power consumed by said electric motor, said flux versus vehicle velocity curve having a maximum value for a range of low vehicle speeds, a minimum value for a range of high vehicle speeds and a smooth transition between said range of low vehicle speeds and said range of high vehicle speeds.
2 Assignments
0 Petitions
Accused Products
Abstract
Electric motors having controllable induced armature fields, such as induction motors and synchronous reluctance motors, are used in power assisted steering systems for motor vehicles. Power is conserved by tailoring induced armature fields or rotor flux in accordance with the speeds of motor vehicles including the power assisted steering system. In particular, one or more flux programs or maps are provided for the power assisted steering system with the flux map or program being accessed or addressed by means of the vehicle speed. During low speed operation of the motor vehicle, for example to perform parking maneuvers where speeds are near zero and steering forces are near or at maximum, the rotor flux is programmed to maximum. For high speed operation, such as highway and rural motor vehicle operation, the rotor flux is programmed to a low value so that internal loss mechanisms in the power assist motor and motor controller are minimized yet provide sufficient rotor flux to meet steering needs such as lane changes, obstacle avoidance and the like. Various transition speeds and flux transition curves provide smooth transitions between high flux levels and low flux levels.
50 Citations
34 Claims
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1. A motor driven power assisted steering system for a motor vehicle comprising:
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an electric motor with a controllable induced armature field; a coupler mechanism for coupling an output shaft of said electric motor to steering gear of a motor vehicle; a vehicle speed sensor coupled to said motor vehicle for detecting the operating speed of said motor vehicle and for generating representative speed signals; and a motor controller responsive to said speed signals for controlling the induced armature field of said electric motor as a function of the operating speed of said motor vehicle, said motor controller operating along a flux versus vehicle velocity curve to reduce power consumed by said electric motor, said flux versus vehicle velocity curve having a maximum value for a range of low vehicle speeds, a minimum value for a range of high vehicle speeds and a smooth transition between said range of low vehicle speeds and said range of high vehicle speeds. - View Dependent Claims (2, 3)
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4. A motor driven power assisted steering system for a motor vehicle comprising:
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an electric motor with a controllable induced armature field; a coupler mechanism for coupling an output shaft of said electric motor to steering gear of a motor vehicle; a vehicle speed sensor coupled to said motor vehicle for detecting the operating speed of said motor vehicle and for generating representative speed signals; and a motor controller responsive to said speed signals for controlling the induced armature field of said electric motor as a function of the operating speed of said motor vehicle, said motor controller including a flux versus velocity curve comprising at least two piecewise continuous portions wherein the velocity of said flux versus velocity curve is the velocity of said motor vehicle. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A method for operating a power assisted steering system for a motor vehicle, said power assisted steering system including an electric motor having an output shaft coupled to steering gear of said motor vehicle and a controllable induced armature field, said method comprising the steps of:
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detecting the operating speed of said motor vehicle; generating speed signals representative of the operating speed of said motor vehicle; and controlling the induced armature field of said electric motor in response to said speed signals as a function of the operating speed of said motor vehicle by operating along a flux versus vehicle velocity curve to reduce power consumed by said electric motor, said step of controlling the induced armature field comprising the steps of; moving along a low speed portion of said flux versus vehicle velocity curve extending from zero velocity to a first velocity and passing through a maximum point of flux; moving along an intermediate portion of said flux versus vehicle velocity curve extending from said first velocity to a third velocity which intermediate portion of said curve provides a smooth transition between said low speed portion of said curve and a high speed portion of said curve; and moving along said high speed portion of said flux versus vehicle velocity curve extending upward from said third velocity and passing through a minimum point of flux.
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20. A method for operating a power assisted steering system for a motor vehicle, said power assisted steering system including an electric motor having an output shaft coupled to steering gear of said motor vehicle and a controllable induced armature field, said method comprising the steps of:
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detecting the operating speed of said motor vehicle; generating speed signals representative of the speed of said motor vehicle; and controlling the induced armature field of said electric motor in response to said speed signals as a function of a flux versus velocity curve comprising at least two piecewise continuous portions wherein said velocity of said flux versus velocity curve is the velocity of said motor vehicle. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34)
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Specification