There are a variety of ways to control a solenoid to improve performance depending on the application requirements.
Latching Solenoid Theory & Operation - Utilized for applications needing to maintain either an open or closed position for an extended period of time or require low power consumption as in a battery operated application.
Peak and Hold Solenoid Theory & Operation - Utilized in place of constant current solenoids when the application requires faster actuation times, lower average power consumption, lower heat generation or smaller package size.
Proportional Solenoid Theory & Operation - Utilized where precise positioning of a mechanism over a range of movement is required. Two critical design requirements that must be met for a proportional control solenoid are low hysteresis and a relatively flat force vs. stroke curve at a given applied current.
PWM Solenoid Theory & Operation - If the voltage steps are applied at a repeated frequency and the percentage "on time" (high voltage) is varied, the current applied to the solenoid will vary and the force created by the solenoid will vary from minimum to maximum. This type of voltage control, where the percent on time is varied, is called "pulse width modulation" control.