US 5,615,933 A · Electric vehicle with regenerative and anti-lock braking

Abstract

A vehicle has an electric propulsion motor, a regenerative brake control and an anti-lock friction brake system which responds to excess wheel slip of a front wheel during braking to modulate friction braking torque to reduce the excess wheel slip. It further has a control responsive to activation of the anti-lock brake system to prevent the application of regenerative braking during such activation. The regenerative braking may be blended with the friction braking when anti-lock braking is not activated so that battery charge is conserved. When the anti-lock braking is activated, however, the regenerative braking is ramped down to preserve smoothness in the braking. The regenerative braking may be applied to create drag during vehicle coastdown. When anti-lock braking is activated, if it is sensed that the wheel is on a low friction (.mu.) surface, the regenerative braking is removed immediately. The low friction surface may be identified from the brake fluid pressure levels during the modulation process of the anti-lock brake system. The coastdown drag may be applied at more than one operator controlled level or, when cruise control is active, automatically at a higher level for more accurate vehicle speed control on downgrades.

Claims16

Dependent claims

A vehicle having an electric power supply, a front wheel, an electric propulsion motor mechanically coupled to the front wheel and electrically coupled to the electric power supply, a control for applying coastdown regenerative braking to the front wheel when the vehicle is in a coastdown mode, and a hydraulically activated friction brake system with an anti-lock apparatus which, when activated, responds to excess wheel slip of the front wheel during braking to modulate hydraulic pressure and thus control braking torque to reduce the excess wheel slip, the control comprising, in combination:

hydraulic pressure responsive means for determining when the front wheel is on a low friction road surface;
and
means for eliminating the coastdown regenerative braking when the anti-lock apparatus is active and the hydraulic pressure responsive means determines that the front wheel is on a low friction road surface but maintaining the coastdown regenerative braking when the anti-lock apparatus is active and the hydraulic pressure responsive means determines that the front wheel is not on a low friction road surface.

In an electric vehicle comprising a front wheel, an electric propulsion motor having a rotor coupled to the front wheel for rotation therewith, an electric power source, an inverter electrically connecting the electric propulsion motor and electric power source for motoring or regenerative braking operation, a friction braking system for the front wheel, and an anti-lock braking control for the friction braking system, a control comprising, in combination:

means for deriving a total motor torque signal from a requested accel torque signal and a coastdown regen decel torque signal;
means for, if the total motor torque signal represents a net decel torque, determining from the total motor torque signal an achieved blend regen decel torque signal and outputting the achieved blend regen decel torque signal to the inverter for regenerative braking operation;
means for determining if the front wheel is on a low friction road surface;
and
means for, when the anti-lock braking control is active and the front wheel is on a low friction road surface, changing the coastdown regen decel torque signal to zero but, when the anti-lock control is active and the front wheel is not on a low friction surface, maintaining the coastdown regen decel torque signal.

2 more elements

means for deriving a total motor torque signal from a requested accel torque signal, a coastdown regen decel torque signal, and a requested regen decel torque signal;
means for determining, if the total motor torque signal represents a net decel torque, an achieved blend regen decel torque signal and outputting the latter to the inverter for regenerative braking operation;
means for determining a friction brake decel torque signal and outputting the latter to the friction brake system for friction braking;
means for determining if there is a low friction road surface in contact with the front wheel;
means for, when the anti-lock braking control is active and there is not a low friction road surface in contact with the front wheel, ramping down the requested regen decel torque signal to zero but maintaining the coastdown regen torque signal;
and
means for, when the anti-lock braking control is active and there is a low friction road surface in contact with the front wheel, changing the requested regen decel torque signal and the coastdown regen decel torque signal to zero immediately.

4 more elements

Dependencies are inferred from the claim text.

Electric vehicle with regenerative and anti-lock braking

Life of this patent

Electric vehicle with regenerative and anti-lock braking

Life of this patent

Abstract

Claims16