Proportional control of a permanent magnet brake.

摘要

A brake control apparatus for controlling the application of braking force to a permanent magnet brake (25) of the type wherein a permanent magnet (57) creates a magnetic flux path for applying a braking force and an electromagnet (55) provides a continuously variable flux in opposition to the permanent magnet (57). Braking force is controlled in response to a braking command signal from an operator controlled floor pedal or hand grip (150) which varies in relation to the amount of braking desired. A control circuit (50) responsive to the braking command signal causes braking force to be generated in direct proportion to the amount of braking desired. The control circuit (50) applies pulses of current to the electromagnet (55), the pulse width of which varies from a minimum pulse width representing maximum braking to a maximum pulse width representing no braking. The pulses are monitored to insure proper operation. The current in the pulses is used as an indication of brake temperature and is used to control the pulse width of any given desired brake torque. A tachometer (160) monitors the direction and speed of rota-tion of the braked wheel and an anti-skid algorithm modifies the pulses applied to prevent wheel lockup. The brake is fail safe since removal of current to the electromagnet (55) either by operation of the control circuit (50) or by an emergency removal of power will cause the permanent magnet to apply full braking torque. <IMAGE>