Importance

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Abstract

A vehicle supported for rolling movement on a track by a first set of wheels driven by an electric motor and a second unpowered set of wheels is provided with an improved braking system. The braking system includes a brake pedal which can be depressed to generate a brake demand signal, a regenerative braking system associated with the electric motor, and a friction braking system attached to the unpowered wheels. Control circuitry which regulates the operation of the two brake systems serves normally to actuate the regenerative braking system in response to the brake demand signal and to actuate the friction braking system only when the brake demand signal exceeds a predetermined level which corresponds normally to the maximum regenerative braking available. Under slippery rail conditions, a detector indicates slippage of the wheels relative to the rails during regenerative braking, and immediately actuates the friction braking system to produce additional braking in proportion to the brake demand signal. The braking system thus maximizes regeneration under optimal rail conditions and enhances braking under poor rail conditions.

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First Claim