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US 7,742,852 B1Granted
Control system for an all-wheel drive electric vehicle
AssigneeTesla Motors, Inc.
InventorYifan Tang
Life of this patent
Estimating the term…
Abstract
A method and apparatus for optimizing the torque applied to the primary and assist drive systems of an all-electric vehicle is provided, the torque adjustments taking into account wheel slip as well as other vehicular operating conditions.
Claims30
An electric vehicle drive system, comprising:
- a primary drive system, comprising:
- a primary electric motor, said primary electric motor mechanically coupled to at least one wheel of a first vehicle axle, wherein said primary electric motor provides propulsion power to said at least one wheel of said first vehicle axle;
- and
- a primary power control module electrically connected to said primary electric motor, said primary power control module configured to receive primary motor torque commands, and said primary power control module configured to control said primary electric motor based on said primary motor torque commands;
- an assist drive system, comprising:
- a first assist electric motor, said first assist electric motor mechanically coupled to a first wheel of a second vehicle axle, wherein said first assist electric motor provides propulsion power to said first wheel of said second vehicle axle;
- and
- a first assist power control module electrically connected to said first assist electric motor, said first assist power control module configured to receive first assist motor torque commands, and said first assist power control module configured to control said first assist electric motor based on said first assist motor torque commands;
- a second assist electric motor, said second assist electric motor mechanically coupled to a second wheel of said second vehicle axle, wherein said second assist electric motor provides propulsion power to said second wheel of said second vehicle axle;
- and
- a second assist power control module electrically connected to said second assist electric motor, said second assist power control module configured to receive second assist motor torque commands, and said second assist power control module configured to control said second assist electric motor based on said second assist motor torque commands;
- a plurality of wheel speed sensors;
- and
- a torque control system electrically connected to said primary, first assist and second assist power control modules and to said plurality of wheel speed sensors, wherein said torque control system outputs said primary motor torque commands to said primary power control module and outputs said first assist motor torque commands to said first assist power control module and outputs said second assist motor torque commands to said second assist power control module, wherein said torque control system further comprises:
- a traction control command generation unit for computing vehicle speed, wheel slip ratios corresponding to said plurality of wheel speed sensors, a first slip error corresponding to said first vehicle axle, a second slip error corresponding to said first wheel of said second vehicle axle, and a third slip error corresponding to said second wheel of said second vehicle axle;
- a torque split unit for computing an optimal torque split between said primary drive system and said assist drive system based on said vehicle speed and a total required drive torque request, wherein said optimal torque split comprises an optimal primary motor torque request and an optimal assist drive system torque request, wherein said torque split unit further splits said optimal assist drive system torque request into an optimal first assist motor torque request and an optimal second assist motor torque request;
- a traction and stability control unit comprising:
- a first stage feedback control system for minimizing said first slip error, said second slip error, and said third slip error;
- means for transforming said optimal primary motor torque request into said primary motor torque command in response to an output from said first stage feedback control system;
- means for transforming said optimal first assist motor torque request into said first assist motor torque command in response to said output from said first stage feedback control system;
- and
- means for transforming said optimal second assist motor torque request into said second assist motor torque command in response to said output from said first stage feedback control system.
19 more elements
A method of enhancing traction of an electric vehicle, the electric vehicle having a primary electric motor coupled to a first axle, a first assist electric motor coupled to a first wheel of a second axle, and a second assist electric motor coupled to a second wheel of said second axle, the method comprising the steps of:
- a) computing a vehicle speed corresponding to said electric vehicle, wherein said vehicle speed computing step is performed by a traction control command generation unit;
- b) computing a total torque requirement request, wherein said total torque requirement request computing step is performed by a vehicle torque command generation unit;
- c) splitting said total torque requirement request into an optimal primary motor torque request and an optimal assist drive system torque request, wherein said total torque requirement request splitting step is performed by an optimal torque splitting unit;
- d) splitting said optimal assist drive system torque request into an optimal first assist motor torque request and an optimal second assist motor torque request, wherein said optimal assist drive system torque request splitting step is performed by said optimal torque splitting unit;
- e) monitoring at least one first axle wheel speed sensor corresponding to said first axle, and a second wheel speed sensor corresponding to said first wheel of said second axle, and a third wheel speed sensor corresponding to said second wheel of said second axle;
- f) computing a first slip error corresponding to said first axle, wherein said first slip error computing step is performed by said traction control command generation unit;
- g) computing a second slip error corresponding to said first wheel of said second axle, wherein said second slip error computing step is performed by said traction control command generation unit;
- h) computing a third slip error corresponding to said second wheel of said second axle, wherein said third slip error computing step is performed by said traction control command generation unit;
- i) minimizing said first slip error and said second slip error and said third slip error using a feedback control system implemented by a traction and stability control unit, said traction and stability control unit further performing the steps of transforming said optimal primary motor torque request into a primary motor torque command and transforming said optimal first assist motor torque request into a first assist motor torque command and transforming said optimal second assist motor torque request into a second assist motor torque command based on said step of minimizing said first slip error, said second slip error and said third slip error;
- j) controlling said primary electric motor based on said primary motor torque command;
- k) controlling said first assist electric motor based on said first assist motor torque command;
- l) controlling said second assist electric motor based on said second assist motor torque command;
- and
- m) repeating steps a)-l) throughout operation of said electric vehicle.
11 more elements
Dependencies are inferred from the claim text.