Force and position control for active front steering
First Claim
1. A steering system comprising:
- a position overlay unit for applying one of an assist force to a rack and a motor command to a motor, wherein the position overlay unit includes a variable ratio gain, the steering system further comprising a position sensor for providing a position signal to the variable ratio gain and further comprising a position overlay command provided to output of the variable ratio gain;
a torque overlay unit for applying the other of the assist force to a rack or the motor command to a motor; and
,one of an electric power mechanism and a hydraulic power mechanism for providing the assist force to the rack, wherein a load torque is sent from a position loop of the position overlay unit to a force loop of the torque overlay unit, and wherein association between the position overlay unit and the torque overlay unit follows the equations;
τ
s=kTbar(θ
i−
θ
HW)θ
i=τ
s/kTbar+θ
HW
Δ
θ
=(τ
sc−
τ
s)/kTbarθ
ic=θ
i+Δ
θ
θ
o=θ
i+θ
mθ
mc=θ
o−
θ
ic where τ
s is hand wheel torque sensor signal, kTbar is torsion bar stiffness, θ
i is calculated input shaft position, θ
HW is hand wheel position sensor signal, Δ
θ
is calculated position correction, τ
sc is torque sensor command based on the load torque, θ
ic is commanded input shaft position, θ
o is output shaft position signal, θ
m is motor position, and θ
mc is commanded motor position.
9 Assignments
0 Petitions
Accused Products
Abstract
A steering system with reduced coupling between a position overlay unit and a torque overlay unit may include a remote valve assembly for controlling a hydraulic assist force or an electric motor for providing torque overlay and electric assist to a rack of a rack and pinion steering system. In one embodiment, the position overlay unit may provide the assist force and the torque overlay unit may provide a motor command signal to the motor of a differential positioned on a steering shaft. In another embodiment, the position overlay unit may provide the motor command signal and the torque overlay unit may provide the assist force. In either embodiment, the position overlay unit may include variable ratio gain that uses a position signal to output a variable ratio command.
50 Citations
9 Claims
-
1. A steering system comprising:
-
a position overlay unit for applying one of an assist force to a rack and a motor command to a motor, wherein the position overlay unit includes a variable ratio gain, the steering system further comprising a position sensor for providing a position signal to the variable ratio gain and further comprising a position overlay command provided to output of the variable ratio gain; a torque overlay unit for applying the other of the assist force to a rack or the motor command to a motor; and
,one of an electric power mechanism and a hydraulic power mechanism for providing the assist force to the rack, wherein a load torque is sent from a position loop of the position overlay unit to a force loop of the torque overlay unit, and wherein association between the position overlay unit and the torque overlay unit follows the equations;
τ
s=kTbar(θ
i−
θ
HW)θ
i=τ
s/kTbar+θ
HW
Δ
θ
=(τ
sc−
τ
s)/kTbarθ
ic=θ
i+Δ
θ
θ
o=θ
i+θ
mθ
mc=θ
o−
θ
icwhere τ
s is hand wheel torque sensor signal, kTbar is torsion bar stiffness, θ
i is calculated input shaft position, θ
HW is hand wheel position sensor signal, Δ
θ
is calculated position correction, τ
sc is torque sensor command based on the load torque, θ
ic is commanded input shaft position, θ
o is output shaft position signal, θ
m is motor position, and θ
mc is commanded motor position. - View Dependent Claims (2, 3, 4, 5)
-
-
6. A steering system comprising:
-
a position overlay unit for applying one of an assist force to a rack and a motor command a motor; a torque overlay unit for applying the other of the assist force to a rack or the motor command to a motor; one of an electric power mechanism and a hydraulic power mechanism for providing the assist force to the rack; and a hand wheel and further comprising a differential, the differential having an input shaft and an output shaft, the input shaft mechanically linked to the hand wheel and the output shaft mechanically linked to the rack, wherein an input angle at the input shaft is A*θ
input=θ
output−
B*θ
motor, where θ
output is the output angle at the output shaft, θ
motor is a rotor shaft angular position of a motor connected to the differential and A and B are constants, andwherein an input angle at the input shaft is θ
input=θ
output*(1−
VR gain), where θ
output is the t angle at the output shaft and VR gain is a variable ratio gain determined from within the position overlay unit using at least one of an output shaft angle signal and a vehicle speed signal. - View Dependent Claims (7, 8)
-
-
9. A steering system comprising:
-
a position overlay unit for applying one of an assist force to a rack and a motor command to a motor; a torque overlay unit for applying the other of the assist force to a rack or the motor command to a motor; one of an electric power mechanism and a hydraulic power mechanism for providing the assist force to the rack; and a hand wheel and further comprising a differential, the differential having an input shaft and an output shaft, the input shaft mechanically linked to the hand wheel and the output shaft mechanically linked to the rack, wherein an input angle at the input shaft is A*θ
input=θ
output−
B*θ
motor, where θ
output is the output angle at the output shaft, θ
motor is a rotor shaft angular position of a motor connected to the differential and A and B are constants, andwherein an output angle at the output shaft is θ
output=θ
input*(1+VR gain) where θ
input is the input angle at the input shaft and VR gain is a variable ratio gain determined from within the position overlay unit using at least one of a hand wheel position signal and a vehicle speed signal.
-
Specification