Method and apparatus for controlling an electric assist steering system

Claim 1

An apparatus for controlling a steering assist system, said steering assist system providing steering assist in response to a steering control signal, said apparatus comprising: vehicle speed sensing means for sensing vehicle speed and for providing a speed signal having a value indicative of the sensed vehicle speed; torque sensing means operatively connected to a vehicle hand wheel for sensing applied steering torque and providing a torque signal indicative of applied steering torque; and control means operatively connected to said vehicle speed sensing means and to said torque sensing means and including a first set of torque-in vs. torque-out assist values associated with a first vehicle speed and a second set of torque-in vs. torque-out assist values associated with a second vehicle speed different from said first vehicle speed, said control means providing said steering control signal in response to said applied steering torque and having a value interpolated from values related to (i) said speed signal and (ii) both said first set and second set of assist values.

Claim 2

An apparatus for controlling a steering assist system, said steering assist system providing steering assist in response to a steering control signal, said apparatus comprising: vehicle speed sensing means for sensing vehicle speed and for providing a speed signal having a value indicative of the sensed vehicle speed; torque sensing means operatively connected to a vehicle hand wheel for sensing applied steering torque and providing a torque signal indicative of applied steering torque; and control means operatively connected to said vehicle speed sensing means and to said torque sensing means and including a first set of torque-in vs. torque-out assist values associated with a first vehicle speed and a second set of torque-in vs. torque-out assist values associated with a second vehicle speed different from said first vehicle speed, said control means providing said steering control signal in response to said applied steering torque and having a value interpolated from values related to (i) said speed signal and (ii) both said first set and second set of assist values.

Claim 6

An apparatus for controlling a steering assist system, said steering assist system providing steering assist in response to a steering control signal, said apparatus comprising: vehicle speed sensing means for sensing vehicle speed and for providing a speed signal having a value indicative of the sensed vehicle speed; torque sensing means operatively connected to a vehicle hand wheel for sensing applied steering torque and providing a torque signal indicative of applied steering torque; and control means operatively connected to said vehicle speed sensing means and to said torque sensing means and including a first set of torque-in vs. torque-out assist values associated with a first vehicle speed wherein said first vehicle speed is a relatively low vehicle speed and said torque-in vs. torque-out assist values associated with said first vehicle speed increases in accordance with a first monotonically increasing function after a first predetermined torque-in value is exceeded, said control means further including a second set of torque-in vs. torque-out assist values associated with a second vehicle speed different than said first vehicle speed wherein said second vehicle speed is a relatively high vehicle speed and wherein said torque-in vs. torque-out assist values associated with said second vehicle speed increases in accordance with a second monotonically increasing function after a second predetermined torque-in value is exceeded, said control means providing said steering control signal in response to said applied steering torque and having a value functionally related to (i) said speed signal and (ii) both said first set and second set of assist values wherein said steering control signal is functionally related to a requested torque assist value T ASSIST value determined according to T.sub.ASSIST =(K.sub.SP ×T.sub.LOW)+((K.sub.SPMAX -K.sub.SP)×T.sub.HIGH) where T LOW is the torque-out value in accordance with the first set of assist values, T HIGH is the torque-out value in accordance with the second set of assist values, K SP is a speed proportion value that decreases as vehicle speed increases, and K SPMAX is the maximum speed proportional value at low vehicle speed.

Claim 7

An apparatus for controlling a steering assist system, said steering assist system providing steering assist in response to a steering control signal, said apparatus comprising: vehicle speed sensing means for sensing vehicle speed and for providing a speed signal having a value indicative of the sensed vehicle speed; torque sensing means operatively connected to a vehicle hand wheel for sensing applied steering torque and providing a torque signal indicative of applied steering torque; and control means operatively connected to said vehicle speed sensing means and to said torque sensing means and including a first set of torque-in vs. torque-out assist values associated with a first vehicle speed wherein said first vehicle speed is a relatively low vehicle speed and said torque-in vs. torque-out assist values associated with said first vehicle speed increases in accordance with a first monotonically increasing function after a first predetermined torque-in value is exceeded, said control means further including a second set of torque-in vs. torque-out assist values associated with a second vehicle speed different than said first vehicle speed wherein said second vehicle speed is a relatively high vehicle speed and wherein said torque-in vs. torque-out assist values associated with said second vehicle speed increases in accordance with a second monotonically increasing function after a second predetermined torque-in value is exceeded, said control means providing said steering control signal in response to said applied steering torque and having a value functionally related to (i) said speed signal and (ii) both said first set and second set of assist values wherein said steering control signal is functionally related to a requested torque assist value T ASSIST value determined according to T.sub.ASSIST =(K.sub.SP ×T.sub.LOW)+((K.sub.SPMAX -K.sub.SP)×T.sub.HIGH) where T LOW is the torque-out value in accordance with the first set of assist values, T HIGH is the torque-out value in accordance with the second set of assist values, K SP is a speed proportion value that decreases as vehicle speed increases, and K SPMAX is the maximum speed proportional value at low vehicle speed.

Claim 10

An method of controlling a steering assist system, said steering assist system providing steering assist in response to a steering control signal, said method comprising the steps of: sensing vehicle speed and providing a speed signal having a value indicative of the sensed vehicle speed; sensing applied steering torque and providing a torque signal indicative of applied steering torque; providing a first set of torque-in vs. torque-out assist values associated with a first vehicle speed; providing a second set of torque-in vs. torque-out assist values associated with a second vehicle speed different from said first vehicle speed; and providing said steering control signal in response to said applied steering torque by interpolating from values related to (i) said vehicle speed signal and (ii) both said first set and second set of torque-in vs. torque-out assist values.

Claim 11

An method of controlling a steering assist system, said steering assist system providing steering assist in response to a steering control signal, said method comprising the steps of: sensing vehicle speed and providing a speed signal having a value indicative of the sensed vehicle speed; sensing applied steering torque and providing a torque signal indicative of applied steering torque; providing a first set of torque-in vs. torque-out assist values associated with a first vehicle speed; providing a second set of torque-in vs. torque-out assist values associated with a second vehicle speed different from said first vehicle speed; and providing said steering control signal in response to said applied steering torque by interpolating from values related to (i) said vehicle speed signal and (ii) both said first set and second set of torque-in vs. torque-out assist values.

Claim 12

An method of controlling a steering assist system, said steering assist system providing steering assist in response to a steering control signal, said method comprising the steps of: sensing vehicle speed and providing a speed signal having a value indicative of the sensed vehicle speed; sensing applied steering torque and providing a torque signal indicative of applied steering torque; providing a first set of torque-in vs. torque-out assist values associated with a first vehicle speed; providing a second set of torque-in vs. torque-out assist values associated with a second vehicle speed different from said first vehicle speed; and providing said steering control signal in response to said applied steering torque and having a value functionally related to (i) said vehicle speed signal and (ii) both said first set and second set of torque-in vso torque-out assist values wherein said step of providing said steering control signal includes determining a requested torque assist value T ASSIST value determined according to T.sub.ASSIST =(K.sub.SP ×T.sub.LOW)+((K.sub.SPMAX -K.sub.SP)×T.sub.HIGH) where T LOW is the torque-out value in accordance with the first set of assist values, T HIGH is the torque-out value in accordance with the second set of assist values, K SP is a speed proportion value that decreases as vehicle speed increases, and K SPMAX is the maximum speed proportional value at low vehicle speed.

Claim 13

An method of controlling a steering assist system, said steering assist system providing steering assist in response to a steering control signal, said method comprising the steps of: sensing vehicle speed and providing a speed signal having a value indicative of the sensed vehicle speed; sensing applied steering torque and providing a torque signal indicative of applied steering torque; providing a first set of torque-in vs. torque-out assist values associated with a first vehicle speed; providing a second set of torque-in vs. torque-out assist values associated with a second vehicle speed different from said first vehicle speed; and providing said steering control signal in response to said applied steering torque and having a value functionally related to (i) said vehicle speed signal and (ii) both said first set and second set of torque-in vso torque-out assist values wherein said step of providing said steering control signal includes determining a requested torque assist value T ASSIST value determined according to T.sub.ASSIST =(K.sub.SP ×T.sub.LOW)+((K.sub.SPMAX -K.sub.SP)×T.sub.HIGH) where T LOW is the torque-out value in accordance with the first set of assist values, T HIGH is the torque-out value in accordance with the second set of assist values, K SP is a speed proportion value that decreases as vehicle speed increases, and K SPMAX is the maximum speed proportional value at low vehicle speed.