Continuously variable transmission and system and method of control based on a zeroed-out wheel slip

A transmission control system for controlling a continuously variable transmission (CVT) having a variator assembly, the transmission control system comprising an instruction set, the instruction set executable to:

• command an initial minimum clamping pressure to be applied to the variator assembly to achieve a desired torque capacity;
• determine a measured wheel speed of a first driven wheel;
• determine a measured wheel speed of a second driven wheel;
• determine a measured wheel speed of a first driving wheel;
• calculate a first driving wheel expected speed based on the measured wheel speeds of the first and second driven wheels, a track width, and a wheel base;
• calculate an actual wheel speed difference between the measured wheel speed of the first driving wheel and a measured wheel speed of an additional wheel, the additional wheel being one of the following:
• the first driven wheel, the second driven wheel, and a second driving wheel;
• calculate a theoretical wheel speed difference between the first driving wheel expected speed and the measured wheel speed of the additional wheel;
• calculate a zeroed-out wheel slip based on the difference between the actual wheel speed difference and the theoretical wheel speed difference;
• determine whether the zeroed-out wheel slip exceeds a predetermined threshold;
• and
• if the zeroed-out wheel slip exceeds the predetermined threshold, command an adjustment to the initial minimum clamping pressure applied to the variator assembly to compensate for the zeroed-out wheel slip.

A transmission controller for controlling a continuously variable transmission (CVT) having a variator assembly, the transmission controller comprising:

• a first control logic configured to determine a measured wheel speed of a first driven wheel, a measured wheel speed of a second driven wheel, and a measured wheel speed of a first driving wheel;
• a second control logic configured to calculate a first driving wheel expected speed based on the measured wheel speeds of the first and second driven wheels, a track width, and a wheel base;
• a third control logic configured to calculate an actual wheel speed difference between the measured wheel speed of the first driving wheel and a measured wheel speed of an additional wheel, the additional wheel being one of the following:
• the first driven wheel, the second driven wheel, and a second driving wheel;
• a fourth control logic configured to calculate a theoretical wheel speed difference between the first driving wheel expected speed and the measured wheel speed of the additional wheel;
• a fifth control logic configured to calculate a zeroed-out wheel slip based on the difference between the actual wheel speed difference and the theoretical wheel speed difference;
• a sixth control logic configured to determine whether the zeroed-out wheel slip exceeds a predetermined threshold;
• a seventh control logic configured to command an initial minimum clamping pressure to be applied to the variator assembly to achieve a desired torque capacity;
• and
• an eighth control logic configured to command an adjustment to the initial minimum clamping pressure to be applied to the variator assembly to compensate for the zeroed-out wheel slip if the zeroed-out wheel slip exceeds the predetermined threshold.

A continuously variable transmission (CVT) for a motor vehicle, comprising:

• a variator assembly including a first pulley and a second pulley, the first and second pulleys rotatably coupled by a continuous rotatable device, wherein the first pulley is rotatably coupled to an input member and the second pulley is rotatably coupled to an output member;
• the first pulley including a first moveable sheave that is translatable along a first axis relative to a first stationary sheave in response to urging of a first actuator;
• the second pulley including a second moveable sheave that is translatable along a second axis relative to a second stationary sheave in response to urging of a second actuator;
• and
• a control system having at least one controller and one or more sensors in communication with the controller, the control system including an instruction set, the instruction set executable to:
• determine a measured wheel speed of a first driven wheel;
• determine a measured wheel speed of a second driven wheel;
• determine a measured wheel speed of a first driving wheel;
• calculate a first driving wheel expected speed based on the measured wheel speeds of the first and second driven wheels, a track width, and a wheel base;
• calculate an actual wheel speed difference between the measured wheel speed of the first driving wheel and a measured wheel speed of an additional wheel, the additional wheel being one of the following:
• the first driven wheel, the second driven wheel, and a second driving wheel;
• calculate a theoretical wheel speed difference between the first driving wheel expected speed and the measured wheel speed of the additional wheel;
• calculate a zeroed-out wheel slip based on the difference between the actual wheel speed difference and the theoretical wheel speed difference;
• and
• determine whether the zeroed-out wheel slip exceeds a predetermined threshold.