Dual data rate traction control system for a two wheel drive electric vehicle

A method of providing traction control in an electric vehicle, wherein the electric vehicle is comprised of a motor coupled to an axle via a locking differential, the method comprising:

• monitoring a torque value corresponding to said motor;
• monitoring a plurality of wheel speed sensors corresponding to a plurality of vehicle wheels;
• determining a maximum wheel speed corresponding to said plurality of vehicle wheels;
• determining a minimum wheel speed corresponding to said plurality of vehicle wheels;
• selecting a synchronized wheel speed from said maximum and minimum wheel speeds, wherein said maximum wheel speed is selected as said synchronized wheel speed if said torque value for said motor is positive, and wherein said minimum wheel speed is selected as said synchronized wheel speed if said torque value for said motor is negative;
• multiplying said synchronized wheel speed by a transmission ratio to yield a first synchronized motor speed, wherein said transmission ratio corresponds to said locking differential, and wherein said first synchronized motor speed is at a first sample frequency;
• translating said first synchronized motor speed to a second synchronized motor speed, wherein said second synchronized motor speed is at a second sample frequency, and wherein said second sample frequency is higher than said first sample frequency;
• defining a maximum motor speed and a minimum motor speed from said second synchronized motor speed and a slip speed map;
• inputting said maximum motor speed, said minimum motor speed, and a motor speed corresponding to said motor into a traction controller;
• determining a first motor speed error from said maximum motor speed and said motor speed;
• determining a second motor speed error from said minimum motor speed and said motor speed;
• saturating said first motor speed error to obtain a first motor speed error correction value;
• saturating said second motor speed error to obtain a second motor speed error correction value;
• selecting a particular motor speed error correction value from said first and second motor speed error correction values;
• feeding said particular motor speed error correction value to said traction controller;
• creating a torque correction command that brings said particular motor speed error correction value to zero, wherein said step of creating said torque correction command is performed by said traction controller;
• determining a current motor torque demand;
• and
• modifying said current motor torque demand by said torque correction command to yield a modified motor torque demand.