A method checks the plausibility of a measurement of an actuator current by use of an actuator two-terminal network. The actuator two-terminal network contains an inductive load and a resistive load. A first pole of the actuator two-terminal network is connected to a supply voltage via a pulse-width-modulated switch and is connected to earth via a freewheeling diode arranged in the reverse direction, and wherein a second pole of the actuator two-terminal network is connected to earth.

Embodiments of the present disclosure provide method, controller and system for regulating a current of a coil. The method comprises: obtaining a first sample value of the current of the coil at a first moment, the first sample value being associated with a duty cycle of a PWM signal applied to a control end of a switch and the switch being coupled in series with the coil; obtaining a second sample value of the current of the coil at a second moment; determining a difference value between the first and the second sample values; and updating the duty cycle of the PWM signal based on the difference value to regulate the current of the coil. According to embodiments of the present disclosure, the inrush current of the coil generated at the moment of closing the contactor can be limited to a target current value, so as to increase the service life of the contactor.

Provided are embodiments for operating an autonomous mode change circuit for solenoid drivers. The embodiments include initiating an operation of a solenoid, and receiving a command to control the operation of the solenoid. The embodiments also include controlling, by a drive circuit, a switch coupled to the solenoid based at least in part on the command, and detecting at least one of a current or voltage of the solenoid, and subsequently controlling the operation of the solenoid based at least in part on the detection.

A sprayer control system includes a plurality of smart nozzles each having at least one control valve with a valve operator, an electronic control unit for the valve operator, and one or more spray nozzles. The at least one control valve and the ECU control a flow rate of liquid agricultural product through the nozzles. A duty cycle modulator is in communication with the ECU and generates an applied duty cycle for the at least one control valve. The duty cycle modulator includes a specified duty cycle input having a specified duty cycle and a pressure monitor associated with the at least one control valve. A pressure comparator compares the valve pressure determined with the pressure monitor with a system pressure and generates a pressure error. An applied duty cycle generator generates the applied duty cycle based on the specified duty cycle modified by the pressure error.

A controller for a linear solenoid valve is configured to: calculate an average value of an exciting current within a period including a natural number multiple of the dither cycle as an average current value; execute a feedback control on a control value of the pulse width modulation signal such that a target value of the exciting current and the average current value match; and calculate a dither correction amount by multiplying a ratio between the control value of the pulse width modulation signal obtained by the feedback control and the average current value by a dither current value that is a current value corresponding to the dither correction amount and calculating the dither correction amount such that an increase in the exciting current due to the dither correction amount is canceled out by a decrease in the exciting current due to the dither correction amount within one dither cycle.

A method checks the plausibility of a measurement of an actuator current by use of an actuator two-terminal network. The actuator two-terminal network contains an inductive load and a resistive load. A first pole of the actuator two-terminal network is connected to a supply voltage via a pulse-width-modulated switch and is connected to earth via a freewheeling diode arranged in the reverse direction, and wherein a second pole of the actuator two-terminal network is connected to earth.

Methods and systems for operating an on-off valve coupled to a system for regulating a system parameter are described herein. The method comprises setting an upper limit on a duty cycle of a pulse width modulation (PWM) signal for controlling the valve, generating the PWM signal with the duty cycle less than or equal to the upper limit and applying the PWM signal to the valve, monitoring the system parameter as the PWM signal is applied, and increasing the upper limit on the duty cycle over time until the system parameter reaches a target.

Improved solenoid controllers and control methods. One illustrative solenoid control method embodiment includes: supplying a drive signal to a solenoid, the drive signal having: an average current corresponding to a desired position of an armature, and a dither current having a dither amplitude that produces an associated solenoid voltage variation; varying the dither amplitude in a region insufficient to overcome static friction of the armature; determining a linear relationship between the dither amplitude and the associated solenoid voltage variation in said region; increasing the dither amplitude while monitoring the associated solenoid voltage variation for a deviation below the voltage variation indicated by the linear relationship; and upon detecting said deviation, employing a corresponding dither amplitude to maintain mobility of the armature.

A circuit for controlling current in an inductive load is provided. The circuit includes a driver circuit for driving a load current in the inductive load. The driver circuit includes a switch, which is switched on to increase the load current and a recirculation diode, which re-circulates the load current when the switch is off. The circuit includes a control module that generates a control signal to switch on and off the switch. The control module includes a PWM current controller comprising a negative feedback closed loop implementing at least a proportional control and an integral control. The PWM current controller receives a target current value and an estimated current flowing in the load during a measurement PWM cycle. The PWM current controller generates the control signal for a control input of the switch based on an error between the target current and the estimated current.

In an example, a system for applying an agricultural product includes a valve and a solenoid. For instance, the valve includes a coil that generates a magnetic flux. The system includes a valve controller. The valve controller is configured to measure one or more electrical characteristics of at least one of the coil or a dissipation element. In some examples, the valve controller determines an actual duty cycle of a valve operator of the valve using the measured electrical characteristics. The valve controller determines a magnetic flux correction, for instance based on a difference between the actual duty cycle and a specified duty cycle. The valve controller operates the valve operator according to the specified magnetic flux and the magnetic flux correction to guide the actual duty cycle toward the specified duty cycle.