Vehicle power antenna control with drive stress limiting

Claim 1

A power antenna control for a motor vehicle having antenna drive means effective to extend and retract the antenna relative to the vehicle, the antenna drive means including a DC motor having an armature, the control comprising, in combination: pulse signal means responsive to movement of the antenna drive means to generate pulses for equal predetermined increments of antenna travel; a first counter responsive to the pulse signal means while the antenna is extending to change its count in a first direction and while the antenna is retracting to change its count in the opposite direction to thereby maintain a count indicative of antenna position; a second counter responsive to the pulse signal to count in a first direction; means responsive to the first counter during antenna extension to deactivate the antenna drive means when the count of the first counter indicates a predetermined extended antenna position; means effective to periodically monitor the count of the second counter and reset the count to an initial value and, when said monitored count is less than a predetermined count indicating motor stall, to generate a stall signal; means responsive to the stall signal during antenna retraction to deactivate the antenna drive means and, if the count of the first counter is within a predetermined count of full retraction, to reset the count of the first counter to the count indicating full retraction; means activatable to limit the current in the motor armature to a predetermined maximum value; and means responsive to the first counter to activate the current limiting means only when the count of the first counter is within a range corresponding to a predetermined range of antenna position close to full retraction.