Methods and apparatus for flexure-based torque sensor in a bicycle

Apparatus comprising a radial flexure, one or more sensors and a controller, wherein:

• (a) the radial flexure is configured to be part of a drivetrain in a bicycle, which drivetrain includes pedals, an RTFC and the flexure, and which drivetrain is configured to transmit torque from a human rider of the bicycle through at least the pedals, RTFC and radial flexure to a wheel of the bicycle;
• (b) the bike has a frame;
• a part of the bicycle has a fixed position relative to the frame;
• the wheel has a first rotational angle relative to the part;
• and the RTFC has a second rotational angle relative to the part;
• (c) the first and second rotational angles may each vary as the wheel and the RTFC, respectively, rotate;
• (d) the radial flexure is configured to undergo elastic deformation due to a difference between the first and second rotational angles;
• (e) the one or more sensors are configured to measure the elastic deformation;
• and
• (f) the controller is configured to seek to cause the elastic deformation to be equal to a constant, by controlling torque imparted on the wheel by a motor.

A method comprising, in combination:

• (a) using a drivetrain in a bicycle, which drivetrain includes pedals, an RTFC and a radial flexure, to transmit torque from a human rider of the bicycle through at least the pedals, RTFC and flexure to a wheel of the bicycle;
• (b) using one or more sensors to measure elastic deformation of the flexure, which elastic deformation is due to a difference between rotational displacement of the wheel and of the RTFC, respectively;
• and
• (c) using a controller to seek to cause the difference to be equal to a constant, by controlling torque contributed to the wheel by a motor.