Automatic transmissions and methods therefor

A method of automatically controlling a continuously variable transmission (CVT) of a bicycle, the CVT having first and second rotatable traction rings, a shift rod, an electric actuator coupled to the shift rod, an electronic controller in communication with the electric actuator, and an electronic controller, the electronic controller configured to receive a first input associated with a target user pedaling speed and a second input associated with a speed of the bicycle, the method comprising the steps of:

• receiving an input associated with a target user pedaling speed;
• determining a speed of the bicycle;
• and
• based upon the target user pedaling speed and the determined speed of the bicycle, adjusting a speed ratio of the CVT to maintain a user pedaling speed within a band of the target user pedaling speed, wherein adjusting the speed ratio comprises adjusting the shift rod.

A method of automatically controlling a ball-planetary continuously variable transmission (CVT), the CVT having first and second rotatable traction rings, a shift rod, a servo coupled to the shift rod, and an electronic controller in communication with the servo, the electronic controller configured to receive a first input associated with a target user pedaling speed and a second input associated with a speed of the bicycle, the method comprising the steps of:

• providing an input associated with a target user pedaling speed;
• determining a speed of the bicycle;
• identifying a target encoder position associated with the speed of the bicycle;
• and
• actuating the servo to achieve the target encoder position.

A system for automatically shifting a bicycle continuously variable transmission (CVT), the CVT having first and second rotatable traction rings and a shift rod, the system comprising:

• a speed sensor configured to detect a speed of the bicycle;
• a control unit configured to receive input from the speed sensor;
• a data input interface configured to provide cadence data to the control unit, said cadence data indicative of a desired, constant input pedaling speed;
• a memory in communication with the control unit, the memory having stored therein one or more data structures correlating bicycle speeds with speed ratios of the CVT, wherein the control unit is configured to determine from said data structures a target speed ratio for the CVT based on the speed of the bicycle and the cadence data, and
• an actuator configured to selectively tilt a power transmitting ball of the CVT, the actuator in communication with the control unit, the actuator configured to adjust a speed ratio of the CVT to be substantially equal to the determined target speed ratio for the CVT.