US 5,941,328 AGranted

Electric vehicle with variable efficiency regenerative braking depending upon battery charge state

AssigneeLockheed Martin Corporation

InventorsArthur Paull Lyons, Timothy Michael Grewe

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Abstract

An electric vehicle is controlled to conform its operation to that of a conventional internal-combustion-engine powered vehicle. In some embodiments, the charging of the batteries by the auxiliary source of electricity and from dynamic braking is ramped in magnitude when the batteries lie in a state of charge between partial charge and full charge, with the magnitude of the charging being related to the relative state of charge of the battery. The deficiency between traction motor demand and the energy available from the auxiliary electrical source is provided from the batteries in an amount which depends upon the state of the batteries, so that the full amount of the deficiency is provided when the batteries are near full charge, and little or no energy is provided by the batteries when they are near a discharged condition. At charge states of the batteries between near-full-charge and near-full-discharge, the batteries supply an amount of energy which depends monotonically upon the charge state. Charging of the batteries from the auxiliary source is reduced during dynamic braking when the batteries are near full charge. Control of the amount of energy returned during dynamic braking may be performed by control of the transducing efficiency of the traction motor operated as a generator.

Claims4

Dependent claims

A method for operating an electric vehicle which includes a traction motor connected for driving at least one drive wheel of said vehicle, and a control system for converting motion of said vehicle into electrical energy during braking, and for varying the amount of electrical energy produced by the traction motor during braking by adjusting the efficiency of the traction motor said method comprising the steps of:

returning substantially all of the energy from said traction motor to said batteries during braking, at a maximum efficiency of said traction motor operated as a generator, when said batteries are at a first charge condition which is less than a full charge condition;
adjusting the efficiency of said traction motor to a level intermediate said maximum efficiency and zero efficiency, for returning less than all of said energy from said traction motor to said batteries during braking when said batteries are at a charge level between said first charge condition and said full-charge condition;
and
adjusting the efficiency of said traction motor to a selected level of low efficiency, which is intermediate the zero efficiency and said intermediate level of efficiency when said batteries are at said first charge condition for returning a minimum amount of said energy from said traction motor to said batteries when said batteries are at said full-charge condition.

1 more element

Dependencies are inferred from the claim text.