Dual Motor Drive and Control System for an Electric Vehicle
First Claim
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1. An electric vehicle drive system, comprising:
- a drive system, comprising;
a first electric motor, said first electric motor mechanically coupled to a vehicle drive axle, wherein said first electric motor provides propulsion power to at least one wheel of said vehicle drive axle;
a first power control module electrically connected to said first electric motor, said first power control module configured to receive first motor torque commands, and said first power control module configured to control said first electric motor based on said first motor torque commands;
a second electric motor, said second electric motor mechanically coupled to said vehicle drive axle, wherein said second electric motor provides propulsion power to said at least one wheel of said vehicle drive axle; and
a second power control module electrically connected to said second electric motor, said second power control module configured to receive second motor torque commands, and said second power control module configured to control said second electric motor based on said second motor torque commands;
at least one wheel speed sensor; and
a torque control system electrically connected to said first and second power control modules and to said at least one wheel speed sensor, wherein said torque control system outputs said first motor torque commands to said first power control module and outputs said second motor torque commands to said second 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 at least one wheel speed sensor, and a slip error corresponding to said vehicle drive axle;
a torque split unit for computing an optimal torque split between said first motor and said second motor based on said vehicle speed and a total required drive torque request, wherein said optimal torque split comprises an optimal first motor torque request and an optimal second motor torque request;
a traction control unit comprising;
a first stage feedback control system for minimizing said slip error;
a first torque limiter for transforming said optimal first motor torque request into said first motor torque command in response to an output from said first stage feedback control system; and
a second torque limiter for transforming said optimal second motor torque request into said second 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 by each motor of a dual motor drive system of an all-electric vehicle is provided, the torque adjustments taking into account wheel slip as well as other vehicular operating conditions.
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Citations
31 Claims
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1. An electric vehicle drive system, comprising:
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a drive system, comprising; a first electric motor, said first electric motor mechanically coupled to a vehicle drive axle, wherein said first electric motor provides propulsion power to at least one wheel of said vehicle drive axle; a first power control module electrically connected to said first electric motor, said first power control module configured to receive first motor torque commands, and said first power control module configured to control said first electric motor based on said first motor torque commands; a second electric motor, said second electric motor mechanically coupled to said vehicle drive axle, wherein said second electric motor provides propulsion power to said at least one wheel of said vehicle drive axle; and a second power control module electrically connected to said second electric motor, said second power control module configured to receive second motor torque commands, and said second power control module configured to control said second electric motor based on said second motor torque commands; at least one wheel speed sensor; and a torque control system electrically connected to said first and second power control modules and to said at least one wheel speed sensor, wherein said torque control system outputs said first motor torque commands to said first power control module and outputs said second motor torque commands to said second 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 at least one wheel speed sensor, and a slip error corresponding to said vehicle drive axle; a torque split unit for computing an optimal torque split between said first motor and said second motor based on said vehicle speed and a total required drive torque request, wherein said optimal torque split comprises an optimal first motor torque request and an optimal second motor torque request; a traction control unit comprising; a first stage feedback control system for minimizing said slip error; a first torque limiter for transforming said optimal first motor torque request into said first motor torque command in response to an output from said first stage feedback control system; and a second torque limiter for transforming said optimal second motor torque request into said second 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, 15, 16)
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17. A method of operating an electric vehicle, the electric vehicle having a first electric motor coupled to a vehicle drive axle and a second electric motor coupled to said vehicle drive axle, the method comprising the steps of:
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a) monitoring at least one wheel speed sensor corresponding to said vehicle drive axle, a first motor speed sensor and a second motor speed sensor, and computing a vehicle speed corresponding to said electric vehicle based on output from said at least one wheel speed sensor, said first motor speed sensor and said second 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 first motor torque request and an optimal second motor torque request, wherein said total torque requirement request splitting step is performed by an optimal torque splitting unit; d) inputting a wheel target slip ratio and computing a slip error corresponding to said vehicle drive axle based on output from said at least one wheel speed sensor and said vehicle speed and said wheel target slip ratio, wherein said first slip error computing step is performed by said traction control command generation unit; e) minimizing said slip error using a feedback control system implemented by a traction control unit, said traction control unit further performing the steps of transforming said optimal first motor torque request into a first motor torque command and transforming said optimal second motor torque request into a second motor torque command based on said step of minimizing said slip error; f) controlling said first electric motor based on said first motor torque command; g) controlling said second electric motor based on said second motor torque command; and h) repeating steps a)-g) throughout operation of said electric vehicle. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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Specification