Method and apparatus for controlling an electric assist steering system using an adaptive torque filter

An apparatus for controlling a steering assist system, said steering assist system providing 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 providing a torque signal indicative of applied steering torque;
• steering assist means for providing steering assist in response to a control signal;
• and
• control means operatively connected to said vehicle speed sensing means and to said torque sensing means for providing said control signal to said steering assist means in response to said vehicle speed and applied steering torque, said control means including torque filtering means for filtering said torque signal so as to maintain a selectable system bandwidth during system operation.

A method for controlling a steering assist system that provides steering assist in response to a steering control signal, said method comprising the steps of:

• measuring applied steering torque;
• providing steering assist in response to a steering control signal;
• filtering said torque signal so as to maintain a selectable steering assist system bandwidth during system operation;
• and
• providing the control signal in response to the filtered torque signal.

A method for controlling a steering assist system that provides 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;
• filtering said torque signal so as to maintain a selectable system bandwidth during system operation;
• and
• providing said control signal to said steering assist means in response to said vehicle speed and said filtered torque signal.

A method for designing an adaptive filter for an electric assist steering system having a torque sensor connected to a controller which is, in turn, connected to an electric assist motor, said method comprising the steps of:

• applying a command signal to an electric assist motor in an open loop configuration;
• measuring an open loop transfer function as a result of the applied command signal to the motor;
• determining the maximum assist curve gain;
• and
• designing a filter such that the open loop transfer function of the steering system has a predetermined (i) open loop crossover frequency, (ii) gain, and (iii) phase stability margin.

An apparatus for controlling a steering assist system, said steering assist system providing assist in response to a steering control signal, said apparatus comprising:

• torque sensing means operatively connected to a vehicle hand wheel for providing a torque signal indicative of applied steering torque;
• steering assist means for providing steering assist in response to a control signal;
• and
• control means operatively connected to said torque sensing means for providing said control signal to said steering assist means in response to said torque signal, said control means including torque filtering means for filtering said torque signal so as to maintain a selectable system bandwidth during system operation, and further including means for providing a desired output torque value as a function of applied input torque and for modifying said filtering means in response to a rate of change of desired output torque with respect to applied input torque.

An apparatus for controlling a steering assist system, said steering assist system providing 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 providing a torque signal indicative of applied steering torque;
• steering assist means for providing steering assist in response to a control signal;
• and
• control means operatively connected to said vehicle speed sensing means and to said torque sensing means for providing said control signal to said steering assist means in response to said vehicle speed and applied steering torque, said control means including torque filtering means for filtering said torque signal so as to maintain a selectable system bandwidth during system operation, and further including means for providing a desired output torque value as a function of applied input torque and for modifying said filtering means in response to a rate of change of desired output torque with respect to applied input torque.

An apparatus for controlling a steering assist system, said steering assist system providing 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 providing a torque signal indicative of applied steering torque;
• steering assist means for providing steering assist in response to a control signal;
• and
• control means operatively connected to said vehicle speed sensing means and to said torque sensing means for providing said control signal to said steering assist means in response to said vehicle speed and applied steering torque, said control means including torque filtering means for filtering said torque signal so as to maintain a selectable system bandwidth during system operation, said filter means including an adaptive filter defined by ##EQU17##

An apparatus for controlling a steering assist system, said steering assist system providing 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 providing a torque signal indicative of applied steering torque;
• steering assist means for providing steering assist in response to a control signal;
• and
• control means operatively connected to said vehicle speed sensing means and to said torque sensing means for providing said control signal to said steering assist means in response to said vehicle speed and applied steering torque, said control means including torque filtering means for filtering said torque signal so as to maintain a selectable system bandwidth during system operation, said filtering means being established by measuring an open loop system transfer function.

A method for controlling a steering assist system that provides steering assist in response to a steering control signal, said method comprising the steps of:

• measuring applied steering torque;
• providing steering assist in response to a steering control signal;
• filtering said torque signal so as to maintain a selectable steering assist system bandwidth during system operation;
• and
• providing the control signal in response to the filtered torque signal including providing a desired output torque value as a function of applied input torque and modifying said filtering step in response to a rate of change of desired output torque with respect to applied input torque.

A method for controlling a steering assist system that provides 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;
• filtering said torque signal so as to maintain a selectable system bandwidth during system operation;
• and
• providing said control signal to said steering assist means in response to said vehicle speed and said filtered torque signal including providing an output torque value as a function of applied input torque and modifying said filtering step in response to a rate of change of the output torque value with respect to the applied input torque.