| 摘要 |
A self-calibrating linear actuator is configured to control a spring return valve with variable stroke. The actuator includes a motor, a spindle coupled to an output of the motor, a motor controller coupled to the motor, a microcontroller coupled to the motor controller, and a back electromotive force (BEMF) circuit, coupled to the motor, configured to provide to the microcontroller a BEMF value for each motor step. The microcontroller is configured to determine a difference of a number of motor steps during operation of the actuator and to store the difference as a calibrated touch point for the actuator. |
| 主权项 |
1. A self-calibrating linear actuator configured to control a spring return valve with variable stroke, wherein the actuator comprises:
a motor; a spindle coupled to an output of the motor; a motor controller coupled to the motor; a microcontroller coupled to the motor controller; a back electromotive force (BEMF) circuit, coupled to the motor, configured to provide to the microcontroller a BEMF value for each motor step, wherein the microcontroller is configured to cause the actuator to:
drive the spindle downward for a first predetermined number of motor steps at power on;drive the spindle upward until upper stall point is reached, wherein the spindle is determined to have reached the upper stall point when the BEMF value is measured to be zero;drive the spindle downward from the upper stall point until stroke end stall point is reached, wherein the spindle is determined to have reached the stroke end stall point when the BEMF value is measured to be zero;drive the spindle upward from the stroke end stall point to the upper stall point, wherein the microcontroller is configured to count a first number of motor steps from the stroke end stall point to the upper stall point, and store the first number of motor steps;drive the spindle downward from the upper stall point for a second predetermined number of motor steps, wherein the microcontroller is configured to measure a BEMF value for each of the second predetermined number of motor steps, and calculate and store a mean average of the BEMF values for the second predetermined number of motor steps;drive the spindle downward beyond the second predetermined number of motor steps, wherein the microcontroller is configured to measure BEMF value for each motor step and count a second number of motor steps until touch point is reached, wherein the spindle is determined to have reached the touch point when the BEMF value is measured to be lower than the stored average BEMF value by a predetermined threshold; and wherein the microcontroller is configured to subtract the second predetermined number of motor steps and the second number of motor steps from the first number of motor steps, and store the difference of number of motor steps, wherein the difference of number of motor steps is calibrated touch point for the actuator. |
