Control method and apparatus for two-wire motor actuator
First Claim
1. An apparatus comprising:
- an actuator including a DC motor for positioning an output element, the actuator having only two wires;
a variable resistance in the actuator connected across the two wires and controlled by the output element over a resistance range to produce a resistance value dependent on the position of the output element;
a motor controller remote from the actuator and connected to the two wires for supplying current to the actuator and reading voltage developed across the actuator;
control means in the actuator responsive to the actuator voltage for applying driving current to the motor only for voltage above a threshold value to position the actuator, and for blocking current through the motor for voltage below the threshold value;
the controller having a current source for alternatively producing current in a first mode which yields actuator voltage above the threshold value over the variable resistance range, and producing current in a second mode which yields actuator voltage below the threshold value over the variable resistance range whereby in the second mode the voltage across the wires is dependent on the position of the output element;
and means in the controller responsive to the voltage across the wires during the second mode to determine the position of the output element.
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Accused Products
Abstract
An actuator for automotive HVAC control is coupled to a remote controller by two wires. The controller applies power to the actuator in a high current or a low current mode. A variable resistance driven by the actuator generates a voltage proportional to position in the low current mode. Zener diodes in the actuator circuit prevent motor operation in the low current mode and permit motor operation in the high current mode. A microprocessor in the controller selects the mode and reads the voltage in low mode to determine position. It controls the motor for a duration required to reach a desired position and then checks the new position to verify that the target has been reached. If not, another iteration is employed to reach the target.
22 Citations
10 Claims
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1. An apparatus comprising:
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an actuator including a DC motor for positioning an output element, the actuator having only two wires; a variable resistance in the actuator connected across the two wires and controlled by the output element over a resistance range to produce a resistance value dependent on the position of the output element; a motor controller remote from the actuator and connected to the two wires for supplying current to the actuator and reading voltage developed across the actuator; control means in the actuator responsive to the actuator voltage for applying driving current to the motor only for voltage above a threshold value to position the actuator, and for blocking current through the motor for voltage below the threshold value; the controller having a current source for alternatively producing current in a first mode which yields actuator voltage above the threshold value over the variable resistance range, and producing current in a second mode which yields actuator voltage below the threshold value over the variable resistance range whereby in the second mode the voltage across the wires is dependent on the position of the output element; and means in the controller responsive to the voltage across the wires during the second mode to determine the position of the output element. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. In an actuator apparatus having a controller connected by only two wires to a motor which drives an output element, the controller including a dual mode current source alternatively providing a high current for driving the motor and a low current for sensing position of the output element, the method of positioning the output element comprising the steps of:
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during a low current mode inhibiting motor operation and producing a voltage across the wires as a function of the position of the output element; determining the present initial position from the voltage; receiving a desired position command; estimating the duration of motor operation required to reach the desired position; driving the motor by supplying high current for the estimated duration; then supplying low current and determining the new position to verify the attainment of the desired position. - View Dependent Claims (9, 10)
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Specification