Control system for an all-wheel drive electric vehicle
First Claim
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1. 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;
an assist electric motor, said assist electric motor mechanically coupled to at least one wheel of a second vehicle axle, wherein said assist electric motor provides propulsion power to said at least one wheel of said second vehicle axle; and
a secondary power control module electrically connected to said assist electric motor, said secondary power control module configured to receive assist motor torque commands, and said secondary power control module configured to control said assist electric motor based on said assist motor torque commands;
a plurality of wheel speed sensors; and
a torque control system electrically connected to said primary and secondary 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 assist motor torque commands to said secondary 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 and a second slip error corresponding to 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 motor torque request;
a traction and stability control unit comprising;
a first stage feedback control system for minimizing said first slip error and said second slip error;
a first torque limiter 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; and
a second torque limiter for transforming said optimal assist motor torque request into said assist motor torque command in response to said output from said first stage feedback control system.
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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.
69 Citations
29 Claims
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1. An electric vehicle drive system, comprising:
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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; an assist electric motor, said assist electric motor mechanically coupled to at least one wheel of a second vehicle axle, wherein said assist electric motor provides propulsion power to said at least one wheel of said second vehicle axle; and a secondary power control module electrically connected to said assist electric motor, said secondary power control module configured to receive assist motor torque commands, and said secondary power control module configured to control said assist electric motor based on said assist motor torque commands; a plurality of wheel speed sensors; and a torque control system electrically connected to said primary and secondary 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 assist motor torque commands to said secondary 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 and a second slip error corresponding to 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 motor torque request; a traction and stability control unit comprising; a first stage feedback control system for minimizing said first slip error and said second slip error; a first torque limiter 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; and a second torque limiter for transforming said optimal assist motor torque request into said assist motor torque command in response to said output from said first stage feedback control system. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of enhancing traction of an electric vehicle, the electric vehicle having a primary electric motor coupled to a first axle and an assist electric motor coupled to a second axle, the method comprising the steps of:
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a) monitoring at least one first wheel speed sensor corresponding to said first axle and at least one second wheel speed sensor corresponding to said second axle, a primary motor speed sensor and an assist motor speed sensor, and computing a vehicle speed corresponding to said electric vehicle based on output from said at least one first wheel speed sensor, said at least one second wheel speed sensor, said primary motor speed sensor and said assist motor speed sensor, wherein said vehicle speed computing step is performed by a traction control command generation unit; b) monitoring a brake sensor and an accelerator sensor, and computing a total torque requirement request based on output from said brake sensor and said accelerator sensor and said vehicle speed, 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 motor torque request, wherein said total torque requirement request splitting step is performed by an optimal torque splitting unit; d) inputting a first wheel target slip ratio and computing a first slip error corresponding to said first axle based on output from said at least one first wheel speed sensor and said vehicle speed and said first wheel target slip ratio, wherein said first slip error computing step is performed by said traction control command generation unit; e) inputting a second wheel target slip ratio and computing a second slip error corresponding to said second axle based on output from said at least one second wheel speed sensor and said vehicle speed, wherein said second slip error computing step is performed by said traction control command generation unit; f) minimizing said first slip error and said second 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 assist motor torque request into an assist motor torque command based on said step of minimizing said first slip error and said second slip error; g) controlling said primary electric motor based on said primary motor torque command; h) controlling said assist electric motor based on said assist motor torque command; and i) repeating steps a)-h) throughout operation of said electric vehicle. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
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Specification