Dither magnitude control

#This invention relates generally to a control for a solenoid driver circuit, and more particularly, to a method and apparatus for controlling the dither signal of a solenoid driver circuit.

#Solenoid actuators convert electrical energy into mechanical motion. Such devices can be used in a wide range of devices and applications including household appliances and earthmoving equipment.

#Solenoid actuators often have problems with stiction and hystersis which lessen the effectiveness and responsiveness the system. In general, when current is applied to a linear-type solenoid, an armature moves into the solenoid, or an armature moves outward from the solenoid dependent upon the particular solenoid design. Stiction, or friction, is higher when the armature is at rest compared to when it is moving. Accordingly, when the armature is at rest, there is a certain delay from the time the solenoid command signal is received until there is actual mechanical motion because the magnetic forces must exceed the stiction before there is mechanical motion. Stiction produces an undesirable result known as hystersis.

#FIG. 1 is a schematic diagram of a preferred embodiment of a solenoid river circuit;

#FIG. 2 is a schematic diagram of one embodiment of a voltage controlled oscillator; and

#FIG. 3 is a schematic diagram of another embodiment of a voltage controlled oscillator.

#Referring first to FIGS. 1-3, a schematic diagram of a preferred embodiment of the solenoid driver circuit is shown. A current command signal of a preselected magnitude is controllably produced by a microprocessor 10. A dither parameter is measured and a dither parameter signal is delivered to the microprocessor 10 by a dither parameter means 9. The dither parameter signal is indicitive of the dither parameter. In response to the dither parameter signal, the microprocessor 10 delivers a dither command signal to a frequency producing means 14. Responsively, the frequency producing means 14 produces a frequency command signal.

#The current command and the frequency command signals are received and a solenoid actuator input signal is generated in response to said received signals. The actuator input signal's frequency is a function of the frequency of the received frequency command signal and the actuator input signal's magnitude is a function of the magnitude of the received current command signal. The solenoid actuator input signal is delivered to the solenoid actuator and the actuator is controlled in response to this received solenoid actuator input signal.

#Examples of the dither parameters that may be used for controlling the solenoid actuator are, for example, hydraulic oil temperature, solenoid actuator usage, an identification code which corresponds to a preselected type of solenoid actuator and other parameters as will be apparent to one skilled in the art.