Method and apparatus for controlling an electric assist steering system using two-dimensional interpolation for current commands
First 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 steering assist system including a variable reluctance motor, said apparatus comprising:
- motor position sensing means for sensing the relative position between the motor'"'"'s rotor and stator;
first and second torque look-up tables, each of said first and second torque look-up tables having motor current values that vary as a function of motor position;
control means operatively connected to said motor position sensing means, said control means (i) determining a first motor current value by interpolating between two current values corresponding to the two motor positions stored in the first look-up table closest to the sensed motor position, (ii) determining a second motor current value by interpolating between two current values corresponding to the two motor positions stored in the second look-up table closest to the sensed motor position, and (iii) determining a final motor current value by interpolating between the first and second determined motor current values; and
providing a motor control signal in response to said determined final motor current value.
2 Assignments
0 Petitions
Accused Products
Abstract
A control arrangement for an electric assist steering system having a variable reluctance motor (26) includes sensing (54) motor position and sensing (110) applied steering torque. A controller determines a desired motor torque assist value in response to the applied steering torque. A plurality of look-up tables are provided having a plurality of motor current values versus motor position values stored therein. The stored motor current values are functionally related to motor position values. The controller selects a first (T1) and second (T2) torque look-up table from the plurality of look-up tables. The first look-up table corresponds to a torque value less than the desired motor torque assist value. The second look-up table corresponds to a torque value greater than the desired motor torque assist value. A first motor current value (I1) is determined by interpolating between two current values corresponding to two motor positions stored in the first look-up table closest to the sensed motor position. A second motor current value (I2) is determined by interpolating between two current values corresponding to two motor positions stored in the second look-up table closest to the sensed motor position. A final motor current value (ICMD) is determined by interpolating between the first and second determined motor current values. A motor control signal is provided in response to the determined final motor current value.
71 Citations
10 Claims
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1. An apparatus for controlling a steering assist system, said steering assist system providing steering assist in response to a steering control signal, said steering assist system including a variable reluctance motor, said apparatus comprising:
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motor position sensing means for sensing the relative position between the motor'"'"'s rotor and stator; first and second torque look-up tables, each of said first and second torque look-up tables having motor current values that vary as a function of motor position; control means operatively connected to said motor position sensing means, said control means (i) determining a first motor current value by interpolating between two current values corresponding to the two motor positions stored in the first look-up table closest to the sensed motor position, (ii) determining a second motor current value by interpolating between two current values corresponding to the two motor positions stored in the second look-up table closest to the sensed motor position, and (iii) determining a final motor current value by interpolating between the first and second determined motor current values; and providing a motor control signal in response to said determined final motor current value. - View Dependent Claims (2, 7)
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3. An apparatus for controlling a steering assist system, said steering assist system providing steering assist in response to a steering control signal, said steering assist system including a variable reluctance motor, said apparatus comprising:
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motor position sensing means for sensing the relative position between the motor'"'"'s rotor and stator; torque sensing means operatively connected to a vehicle hand wheel for sensing applied steering torque; motor torque assist determining means for determining a desired motor torque assist value in response to the sensed applied steering torque; a plurality of motor torque look-up tables, each of said motor torque look-up tables having a plurality of motor current values that vary as a function of motor position; control means operatively connected to said motor torque assist determining means and to said motor position sensing means, said control means (i) selecting a first and second torque look-up table from said plurality of look-up tables wherein said first look-up table corresponds to a torque value less than the desired motor torque assist value and said second look-up table corresponds to a torque value greater than the desired motor torque assist value, (ii) determining a first motor current value by interpolating between two current values associated with the two motor positions stored in the first look-up table closest to the sensed motor position, (iii) determining a second motor current value by interpolating between two current values associated with the two motor positions stored in the second look-up table closest to the sensed motor position, and (iv) determining a final motor current value by interpolating between the first and second determined motor current values; and providing a motor control signal in response to said determined final motor current value. - View Dependent Claims (4, 5)
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6. A method for controlling a steering assist system, said steering assist system providing steering assist in response to a steering control signal, said steering assist system including a variable reluctance motor, said method comprising the steps of:
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sensing motor position by sensing the relative position between the motor'"'"'s rotor and stator; providing first and second torque look-up tables, each of said first and second torque look-up tables having a plurality of motor current values that vary as a function of motor position; determining a first motor current value by interpolating between two current values corresponding to the two motor positions stored in the first look-up table closest to said sensed motor position; determining a second motor current value by interpolating between two current values corresponding to the two motor positions stored in the second look-up table closest to said sensed motor position; determining a final motor current value by interpolating between the first and second determined motor current values; and providing a motor control signal in response to said determined final motor current value.
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8. A method for controlling a steering assist system, said steering assist system providing steering assist in response to a steering control signal, said steering assist system including a variable reluctance motor, said method comprising the steps of:
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sensing motor position by sensing the relative position between the motor'"'"'s rotor and stator; sensing applied steering torque; determining a desired motor torque assist value in response to the sensed applied steering torque; providing a plurality of motor torque look-up tables, each of said motor torque look-up tables having a plurality of motor current values that vary as a function of motor position; selecting a first and second torque look-up table from said plurality of look-up tables wherein said first look-up table corresponds to a torque value less than the determined desired motor torque assist value and said second look-up table corresponds to a torque value greater than the determined desired motor torque assist value; determining a first motor current value by interpolating between two current values corresponding with two motor positions stored in the first look-up table closest to the sensed motor position; determining a second motor current value by interpolating between two current values corresponding with two motor positions stored in the second look-up table closest to the sensed motor position; determining a final motor current value by interpolating between the first and second determined motor current values; and providing a motor control signal in response to said determined final motor current value. - View Dependent Claims (9, 10)
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Specification