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

• US 5,941,328 A
• Filed: 03/20/1998
• Issued: 08/24/1999
• Est. Priority Date: 11/21/1997
• Status: Expired due to Term

• Current Assignee: BAE Systems Controls Incorporated (BAE Systems Plc)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Grewe, Timothy Michael, Lyons, Arthur Paull
• Primary Examiner(s): Swann, J. J.
• Assistant Examiner(s): MAR, MICHAEL Y
• Application Number:
  US09/044,676
• Time in Patent Office: 522 Days
• Field of Search: 320/10, 320/22, 320/23, 318/139, 318/376, 180/65.1, 180/65.2, 180/65.3, 180/65.8, 180/65.4, 701/22
• US Class Current: 180/65.1
• CPC Class Codes: B60K 6/46 Series type
• CPC Class Codes: B60L 2220/12 Induction machines
• CPC Class Codes: B60L 2250/16 by display
• CPC Class Codes: B60L 50/61 by batteries charged by engine-driven generators, e.g. series hybrid electric vehicles
• CPC Class Codes: B60L 58/15 Preventing overcharging
• CPC Class Codes: B60L 58/40 for controlling a combination of batteries and fuel cells
• CPC Class Codes: B60L 7/14 for vehicles propelled by ac motors
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: B60W 10/18 including control of braking systems
• CPC Class Codes: B60W 10/26 for electrical energy, e.g. batteries or capacitors
• CPC Class Codes: B60W 20/00 Control systems specially adapted for hybrid vehicles hybrid vehicle design, B60K6/00; electric vehicles B60L
• CPC Class Codes: B60W 20/13 in order to stay within battery power input or output limits; in order to prevent overcharging or battery depletion
• CPC Class Codes: B64G 1/425 Power storage
• CPC Class Codes: B64G 1/428 Power distribution and management
• CPC Class Codes: Y02T 10/62 Hybrid vehicles
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility
• CPC Class Codes: Y02T 90/40 Application of hydrogen technology to transportation, e.g. using fuel cells
• CPC Class Codes: Y10S 903/903 having energy storing means, e.g. battery, capacitor
• CPC Class Codes: Y10S 903/947 : Characterized by control of braking, e.g. blending of regeneration, friction braking

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.

Claims

1. 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.

2. A method according to claim 1, wherein said steps of adjusting the efficiency of said traction motor operated as a generator includes the step of changing the slip frequency of said traction motor.

3. A method according to claim 1, wherein said steps of adjusting the efficiency of said traction motor operated as a generator includes the step of changing a level of the field current in said traction motor.

4. A method according to claim 1, wherein said traction motor is an AC motor, including a winding and said steps of adjusting the efficiency of said traction motor operated as a generator includes the step of passing a direct current through said winding of said traction motor.