Valve calibration routine
A method for calibrating a proportional solenoid valve used in the propulsion system of a windrower, wherein a programmable control module in connection with a valve and a sensor is programmed as part of an automatic calibration routine for directing test control signals to the valve for causing a predetermined displacement of the hydraulic cylinder, the test control signals having values which vary based on the actual displacement of the hydraulic cylinder as compared with a predetermined value of displacement, and operating the hydraulic cylinder using the test control signal that causes the predetermined displacement of the element. The predetermined displacements correspond to the crack points, or the electrical signal levels at which two ports of interest are just beginning to open to one another from a closed position. Of particular interest are the crack points from the supply pressure port to each of the work ports and from the tank port to each of the work ports.
1. A method for calibrating a proportional solenoid valve operable for controlling a device for changing a displacement, comprising steps of:
providing a proportional solenoid controlled valve, the valve including a supply pressure port, at least one work port, and a tank port, the valve being controllably operable responsive to a control signal input for moving through a predetermined range of positions, including a range of positions wherein hydraulic fluid will be directed through the valve between at least the supply pressure port and the at least one work port;
providing a hydraulic cylinder in fluid communication with the at least one work port, the hydraulic cylinder being operable to move an element to various positions within a range of positions responsive to delivery of hydraulic fluid thereto from the at least one work port;
providing a sensor operable for detecting displacements of the element and outputting displacement signals including information representative of detected displacements;
providing a programmable control module in connection with the valve and the sensor, the control module being operable for outputting control signals to the valve and receiving the displacement signals from the sensor; and
wherein the control module is programmed for automatically calibrating the control signals, including steps of:
i. outputting a test control signal having a predetermined value to the valve for causing a predetermined displacement of the element, and comparing information representative of an actual displacement caused by the test control signal to information representative of the predetermined displacement;
ii. if the actual displacement is greater than the predetermined displacement, then incrementing a first counter and calculating a new test control signal as an average of the predetermined value of the test control signal and a first predetermined value; and
iii. if the actual displacement is less than the predetermined displacement, then incrementing a second counter and calculating a new test control signal as an average of the predetermined value of the test control signal and a second predetermined value, and
iv. repeating steps i through iii a predetermined number of times;
storing the value for the test control signal; and
operating the hydraulic cylinder using the stored value for determining displacements of the element.
2. The method of claim 1 , wherein the control signal values comprise electrical currents.
3. The method of claim 1 , wherein the predetermined displacement includes a tolerance range.
4. The method of claim 1 , wherein when the actual displacement is less than the predetermined displacement, the new test control signal is calculated as an average of the test value and a historical high test value.
5. The method of claim 4 , wherein the historical high test value is initialized to an upper control signal test limit and updated to the value of the test control signal when the actual displacement is greater than the predetermined displacement.
6. The method of claim 1 , wherein when the actual displacement is greater than the predetermined displacement, the new test control signal is calculated as an average of the test value and a historical low test value.
7. The method of claim 6 , wherein the historical low test value is initialized to a lower control signal test limit and updated to the value of the test control signal when the actual displacement is less than the predetermined displacement.
8. The method of claim 1 , wherein the proportional solenoid valve is used in a propulsion system of an agricultural windrower.
9. The method of claim 1 , wherein the information representative of the predetermined displacement is related to the position of the element that corresponds to an initiation of hydraulic fluid flow through the valve between the supply pressure port and the at least one work port.
10. The method of claim 1 , wherein the information representative of the predetermined displacement is related to the position of the element that corresponds to an initiation of hydraulic fluid flow through the valve between the at least one work port and the tank port.